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Fertilizer Production

TSP COMPLEX LIMITED, CHITTAGONG (AN ENTERPRISE OF BCIC)

INTRODUCTIONTriple Super Phosphate Complex Limited (TSPCL) is a Public Sector enterpriseregistered as a Private Limited Co. Situated at Patenga, Chittagong having its registered office at BCIC Bhaban, 30-31. Dilkusha C/Area, Dhaka-1000, It is under the administrative control of Bangladesh Chemical Industries Corporation (6C1C), one of the Largest public sector corporation of the country having big and medium sized Industries covering at present Nitrogenous and Phosphatic Fertilizer, Paper Cement Chemical. Sanitary Ware-etc.

TSP Complex was established with the objective of producing TSP Fertilizer. Accordingly 2 (Two) units viz TSP-I and TSP-II-1,20,000 MT respectively). Among the units TSP-II was commissioned earlier. TSP-I unit went into commercial production in April 1977 and TSP-II in September, 1974. TSP Complex is the only Phosphatic Fertilizer Factory of the country. Initially the factory started with production of TSP. Later on since 1990 manufacturing of SSP Fertilizer was started and his already established itself as a major fertilizer of the country. On account of technical problem in TSP-I unit, the Phosphoric Acid (PA) Plant of the unit was abandoned and closed. Due to increasing demand of SSP Fertilizer in the country, the facilities of TSP-I were then converted to produce SSP. In TSP-II Unit, necessary TSP-I and TSP-II plants are now known as Unit-I and Unit-II respectively. Production of this factory is increasing day by day and in 2002-2003 total production of 2,00,528 MT Phosphatic Fertilizer was achieved. The basic raw materials are Phosphate Rock (PR) and Element Sulphur (S) which are imported.

Basic Data About the location of the projects and raw materials of TSPCL:

01. Location of the Project:It is located on the bank of the river Karnaphuli at Patenga which is about 4

km from Chittagong Airport an 1km to the south of Chittagong City. This location is in Patenga Industrial Area having communication facilities by rail, road and river.

02. Product Name:a) Main Product: Triple Super Phosphate (TSP) Fertilizer, Single Super

Phosphate (SSP) Fertilizer and Mixed Fertilizer (NPKS).b) Intermediate Product: Sulphuric Acid, Phosphoric Acid.c) By-Product: Gypsum.

03. Plant Capacity Unit-I Unit-II a) Sulphuric Acid Present-100MTD Installed-400MTD

Present-60 MTD Present-320 MTDb) Phosphoric Acid Dismantled & Closed Installed-270MTD(50% P2O5) Present- 135 MTDc) TSP/SSP 50,000MTY(SSP) 500MTD (1,50,000MTY)Capacity Basis: On 300 Stream (TSP 70,000 MT and

Days per year SSP 80,000 MT)

04. Design/Erection Technical Enterprise Hitachi Zosen (Japan)Incorporation (USA)

05. Type of Contract FOB Contract Turn Key Contract06. Com. Production April, 1977 September, 197407. Capital Investment Tk. 274 Lac Tk. 2374 Lacs

Additional for Fertilizer Industries Rehabilitation Project of Tk. 5562.72 Lacs (1980-87). Part MBRE Tk. 972.43 lacs (as on 30-06-98 TSP-I & TSP-II combined).

08. Plant Process:a) Sulphuric Acid Monsanto Contact Process Monsanto contact processb) Phosphoric Acid Nissan (Hemi Di-Hydrate)c) Reaction Den Process Den Proecessd) Granulation Stami Carbon

09. Auxiliary/Ancillary/Special facilities:a) Jetty for raw material unloading facility having maximum length of ship 535 ft. Mooring to Mooring 665 ft. and draft 8 meters.(Unloading Capacity-2,500 MTD)d) Raw material storage capacity- Rock Phosphate : 50,000 MT- Rock Sulphur : 23,000 MT- Phosphoric Acid : 10,000 MT- Sulphuric Acid : 7,000 MT

c) 300 MT per hour capacity Water Treatment Plant with tow Demineralization Units each having capacity 35 MT per hour

d) 3 tracks Railway siding for dispatch of products.e) Polythne Bag Manufacturing plant (10,000 pcs. per day).f) Bagging Machine (2) units for TSP-I and 3 units for TSP-II).g) 2 Nos. Weighing Bridge Scale having capacity of 20 MT. and 30 MT.

10. Factory Area (Acre)a) Plant Site : 37.25b) Gypsum filed : 11.98c) Housing area : 16.69d) Jetty & adjoining area : 9.90e) Others : 4.69

Total : 80.50

11. Main Raw Materials and Source:a) Rock Sulphur from : Iraq, Iran, Canada, Morocco, Saudi

Arabia, Poland,b) Rock Phosphate from : Jordan, Morocco, Egypt, China, Algeria,

Syria.c) Phosphoric Acid from : Tunisia, Poland, Iran, Morocco, India.

RESEARCH AND DEVELOPMENT

The factory is equipped with a modern laboratory and testing facilities for controlling quality of raw materials, finished products as well as control of pollution. Continuous research & development is conducted in its laboratory for the purpose of process improvement and product diversification including search for new source of Phosphate Rock at lower cost.

01. RS/BMR Executed:In TSP Complex during 1974-79, the capacity utilization had been very poor,

maximum 40%. The main reason for low production had been teething problems, electrical/mechanical breakdown, power failure and shortage of raw materials. An improvement Program under the name of Fertilizer Industries Rehabilitation Program (FIRP) was taken up and the scheme was started in July 1980. The scheme envisaged setting up a granulation plant of 1,50,000 MT/yr, facilities for use of imported phosphoric acid and replacement and modification in different sections to improve the operating capacity, setting up of a power generator of 5 MW capacity. The FIRP was completed in June, 1987 at a cost of Tk. 55.62 crore. After completion of the program, TSPCL's production capacity was restored at 1,50,000 MT TSP per year (1,00,000 MT/yr. by own Phosphoric Acid and 50,000 MT/yr. by imported phosphoric Acid).

02. BMR Project:Another BMRE program of Tk. 972.43 Lacs Undertaken in may, 95 was

completed in June 98 for enhancing production capacity from 1,52,000 MT to 2,00,000 MT (TSP 70,000 MT + SSP 1,30,000 MT),ORGANOGRAM :Manpower :

Total Labour Staff Officer604 294 165 145

NAME & DESIGNATION OF THE DEPARTMENTAL HEADS

Dept. Depastmental Heads Name Designation1. Administration Md. Saquee Hussain Manager (Administration)

Head of Administration2. Accounts Md. Abul Kashem Deputy Chief Accountant

Head of Accounts3. Commercial Md. Golam Rasul Khan General Manager

(Commercial)

4. Maintenance & Technical Services (MTS)

A.U.M Zubair Genaral Manager (MTS)

5.Technical Division Md. Hossain Additional Chief Chemist Acting General Manager

6. Opposition Md. Zulfiquar Ali Additional Chief Chemist Acting General Manager

1. Sulphuric Acid Plant:

Sulphuric acid required for manufacture of phosphoric acid is produced by Monsanto Contact Process in both the units.

In this process, rock sulphur is melted in a melter and burnt in a furnace in presence of dried air where sulphur is oxidized to sulphur dioxide (SO2) gas. This gas is then converted into sulphur trioxide (SO3) gas in a converter in presence of catalyst, V2O5 under optimum conditions. SO3 gas is then absorbed in 98.5% H2SO4

in an Absorbing Tower. Strength of the absorbing acid is thereby raised which in turn is diluted by adding demineralised water to maintain the desired strength. The quantity of acid in Absorbing Tower is thus continuously increased and the increased portion is sent to the storage tanks as 98.5% H2SO4.Reactions: S + O2 = SO2, SO2 + ½ O2 = SO3, SO3 + H2O = H2SO4

2. Phosphoric Acid Plant:

Phosphoric Acid required for production of TSP is manufactured by Hemihydrate- Dihydrate process.

In this process, rock phosphate ground to the fineness of 70% passing through 200 Tyler mesh is mixed thoroughly with Sulphuric Acid (70%) and dilute Phosphoric Acid (19-21%) in a tank to acidulate. The reacted slurry is passed into a series of tanks successively to effect decomposition of rock, crystallization of Gypsum and completion of reaction. Slurry in each reacting vessel is constantly agitated with agitators. Temperature and solid-liquid ratio and acid concentration are kept at standard levels designed for the process. From the last reacting vessel, the slurry is pumped into a Vacuum Filter to separate the acid form the Gypsum. The first filtrate is the product acid of 30% P2O5. The residue is the filter cake (Gypsum) which is sent to Gypsum Yard after final washing with hot water. This residue is the by-product Gypsum (CaSO4, 2H2O).

Reaction: Ca3 (PO4)2 + 3H2SO4 + 6H2O = 2H3PO4 + 3CaSO4.2H2O

The product acid of 30% P2O5 is then concentrated to 50% P2O5 acid in a concentrator (Calendria) by heating the material with steam under forced vacuum circulation system as 50% P2O5 acid is required to manufacture TSP of 46% P2O5.

3. TSP Plant:

Triple Super Phosphate is manufactured by decomposition of rock phosphate ground to the fineness of 80% pass through 200 Tyler mesh in an air swept Ball Mill, with phosphoric acid (50%) P2O5 in a Reaction Den under standard conditions of temperature and flow are. The Den product is koown as Green TSP. Green TSP is fed in a Granulator through conveying system, where granules are formed through the principle of agglomeration with steam and process water. Granular TSP is then dried with hot air generated by combustion of natural gas and then bagged to get finished product of granular TSP.

Reaction: Ca3 (PO4)2 + 4H3PO4 + 3H2O=3CaH4 (PO4)2.H2O

4. SSP Plant:

SSP is manufactured by acidulating finely ground phosphate rock with 70-75% sulphuric acid in Reaction Den under standard conditions of temperature and flow rate. The outlet Den product known as Green SSP is kept in a curing house for about three weeks for completion of the reactions. The cured SSP is then dried by natural air and bagged to get finished product of powder SSP.

Production of SSP in powder form started since 1988 in Unit No. 1. But with the rising trend of use of SSP in agriculture, arrangement was made to produce SSP through Unit No. 2 also.

Reaction: Ca3 (PO4)2 + 2H2SO4+5H2O = 2CaSO4.2H2O + CaH4(PO4)2.H2O

5. Gypsum:

Gypsum (CaSO4.2H2O) a by-product of Phosphoric acid manufacturing process has use as a supplementary fertilizer for soil treatment. It is generally used in sulphur deficient areas.

6. Mixed fertilizer (NPKS):

From the year 2002, TSPC is experimentally producing one grade of mixed fertilizer for paddy grade as per recommendation of Bangladesh Agricultural Research Council (BARC). Marketing of this fertilizer has already been started for use at farmer's end. We are also working for production of NPKS suitable for tea production. This fertilizer will increase the fertility of land and also production. The basic raw materials are TSP, SSP, Ammonium Sulfate (AS), Di-ammonium Phosphate (DAP) and Murate of Potash (MOP).

Raw materials for sulphuric acid production :-1. Rock Sulphur2. Air (O2)3. Deme Water (H2O)

Raw materials for Phosphoric acid production:1.Higher grade rock Phosphate2.Sulphuric acid

Raw materials for TSP plant:1.Low grade rock phosphate2.Phosphoric acid

Raw materials for SSP plant:1. Low grade rock phosphate2. Sulphuric acid

Rock Sulphur

Source : Iran, Canada, USA, Soudi Arabia

Chemical Ingredients:i. Sulphure Content : 99.50% (Min) w/wii. Moisture : 0.5% (Max) w/wiii. Organic Matter : 0.10% (Max) w/wiv. Ash Content : 0.06% (Max) w/wv. Water Soluble Chloride : 10 PPM (Max) w/wvi. Acidity as H2SO4 : 0.025% (Max) w/wvii. Colour : Yellowviii. AST (Arsenic Salemium : Nil

Tellariumix. Particle Size : 30-50 mm 10% Max.

Above 0.2 mm and below30 mm 89% Min.Below 0-0.2 mm 1% Max.

ROCK PHOSPHATE

low grade rock phosphate:

Source :Jordan,Morocco,Egypt,China,Algeria

Specification of lower grade rock phosphate (65.5% BPL Min.)A. Chemical Ingredientsi. Moisture 2.00 (Max) % w/w ii. Total Phosphate (P2O5) 30(Min) % w/wiii. Calcium Oxide (CaO) 45-52 % w/wiv. Sulphate (SO3) 0.5 - 2.0 % w/wv. Silica (SiO2) 5 - 8 % w/wvi. Carbon-di-Oxide (CO2) 5 - 6 % w/wvii. Cluoride (F) 4 (Max) % w/wviii. Iron (Fe2O3) 1.0 (Max) % w/wix. Iron and Aluminum (R2O3) 2.0 (Max) % w/wx. Water Soluble Chloride (Cl) 0.2 (Max) % w/wxi. Sodium Oxide (Na2O) 0.8 (Max) % w/wxii. Potassium Oxide (K2O) 0.3 (Max) % w/wxiii. Magnesium Oxide (MgO) 0.5 (Max) % w/wxiv. Organic Matter with 2.4 (Max) % w/w

Crystalline Waterxv. BPL 65.5 % Min.

B. Physical Ingredientsi. Fluidity Free Flowingii. Particle size distribution

a. + 4 mesh (4.75 mm) 0 - 2 % w/wd. -4+100mesh (4.75mm-0.15mm) 65-80% w/wc. -100 +200mesh (0.15mm-0.075mm) 15-25 % w/wd. -200 + 270mesh (0.075 mm- 0.053mm) 1-3 % w/we. -270mesh (0.53mm) 2-3 % w/w

C. Colour : Whitish /Off - White (Blackish not acceptable)

HIGHER GRADE ROCK PHOSPHATE

Source:Jordan, Morocco, China (Wong-fu mine)

Specification of Higher Grade Rock Phosphate (72% BPL min.)

A. Chemical Ingredientsi. Moisture 2.00 (Max) % w/w ii. Total Phosphate (P2O5) 32.95(Min) % w/wiii. Calcium Oxide (CaO) 48-52 % w/wiv. Sulphate (SO3) 0.7-1.9 % w/wv. Silica (SiO2) 2.5-5 % w/wvi. Carrbon-di-Oxide (CO2) 5 (Max) % w/wvii. Cluoride (F) 4 (Max) % w/wviii. Iron (Fe2O3) 1.0 (Max) % w/wix. Iron and Aluminum (R2O3) 2.0 (Max) % w/wx. Water Soluble Chloride (Cl) 0.04 (Max) % w/wxi. Sodium Oxide (Na2O) 0.2-0.8 (Max) % w/wxii. Potassium Oxide (K2O) 0.1-0.3 (Max) % w/wxiii. Magnesium Oxide (MgO) 0.5 (Max) % w/wxiv. Organic Matter with 2.4 (Max) % w/w

Crystalline Waterxv. BPL 72 % Min.

B. Physical Ingredientsi. Fluidity Free Flowingii. Particle size distribution

a. + 4 mesh (4.75 mm) 0 - 2 % w/wd. -4+100mesh (4.75mm-0.15mm) 65-80% w/wc. -100 +200mesh (0.15mm-0.075mm) 15-25 % w/wd. -200 + 270mesh (0.075 mm- 0.053mm) 1-3 % w/we. -270mesh (0.53mm) 2-3 % w/w

SULPHURIC ACID

CHEMICAL FORMULA : H2SO4

ANNUAL PRODUCTION : 62704 MT (uni-1 in 2007-2008)

SPECIFICATION : Specific gravity (at 20oC) : 1.830H2SO4 : 98.5%Iron (Fe ++) : 0.004%SO2 : 0.0001%Ignition reside : 0.005%Color : Turbid White

USES :sulfuric acid is an intermediate product. It is mainly used for manufacturing SSP and for production of phosphoric Acid, required for manufacturing TSP, Sulphuric acid is an essential item for all kinds of chemical factory small or big in size. About 5000-6000 MT Sulphuric acid per year is sold to the Industrial organization of the country. This Sulphuric acid plays an important role towards country’s industrial development.

PHOSPHORIC ACID

Chemical formula : H3PO4

Production capacity : 17884MT (2007-08)Product specification:

Specific gravity (at 20oC) : 1.830H2SO4 : 98.5%Iron (Fe ++) : 0.004%SO2 : 0.0001%Ignition residue : 0.005%Colour : Turbid White

Use & application: it is an intermediate product and used for manufacture of TSP.Entire qantity of phosphoric acid produced,is used in the process.

By-product : Gypsum

TRIPLE SUPER PHOSPHATE (TSP)

Chemical formula : 3CaH4 (PO4)2.H2O

SPECIFICATION OF TSP: Moisture : 5% (Max)Total P2O5 : 46% (Min)Water soluble P2O5 : 40% (Min)Free P2O5 : 3% (Max)Physical appearance : GranularSize : 85% (Between 6& 16 mesh)

i.e. Between 3.3 mm & 1 mm).

SINGLE SUPER PHOSPHATE (SSP) PLANT:

Chemical Formula : CaH4(PO4)2H2OAnnual production: 55,014 MT (2007-2008)Specification :

Moisture : 8% (Max)Total P2O5 : 18-20%Available P2O5: 16% (Min)Free P2O5 : 3% (Max)

Sulphur : 10% (Min)Calcium : 18% (Min)

Physical appearance : Powder.

Use & application :

Single Super phosphate commonly known as SSP contains (a) phosphorus, (b) Sulphur and (c) Calcium nutrients and as such it is called mixed fertilizer. Sulphur has been established as the fourth primary plant nutrient and is necessary for all kinds of crops. It is also proved that without correction Sulphur deficiency of the land, the remaining three nutrients (NPK) can only be utilizer by the plants to a limited extent and hence the product quantity but also improves the product quality in helping to add more vitamin and protein value. To provide both phosphorus and Sulphur nutrients to the lands, use of SSP is rapidly increasing. As pre Govt/s instruction SSP is produced in powder form.

GYPSUM (a by product)

Chemical formula : CaSO4. 2H2O

Uses of Application:Gypsum is obtained as a by product during phosphoric acid manufacturing.

For a long time, use of gypsum except in Cement factories as retarder was not known. Ultimately with the help of BARC this Sulphur enriched gypsum has been established as a fertilizer. About 70-80% of the country's soils are deficient in Sulphur which causes significant yield reduction. As such gypsum is being used at large quantities in Bangladesh to Compensate the deficiencies of Sulphur specially in the northern districts.

This gypsum contains 18% Sulphur and 30% calcium, So, for 20kg Sulphur for a land of one hectre 112kg gypsum is to be applied.

Annual Production: 41,575 MT (2007-2008)

Analytical report on a Particular sample:- Total P2O5 : 0.47%- Water Soluble P2O5 : 0.15%- CaO : 31.69%- Total SO3 : 45.32%- Total SiO2 : 0.70%- Fe2O3 : 0.011%-Al2O3 : 0.007%- Fluorine : 0.32%- Moisture : 15-20%- Water of Crystallization : 19.29%- Acidity as CO2 : 0.26%-Organic matter : 0.02%- Water soluble chloride : 0.13%

Packing: Lose delivery through Track/ wagon as arranged by the Customers.

Process Outline:Gypsum (CaSO4.2H2O) a by- product of phosphoric acid manufacturing

process has use as a supplementary fertilizer for soil treatment. It is generally used is Sulphur deficient areas.

Comparative Specification of Products

Specification of Products : TSP SSP1. Total P2O5 : 46% (Min) 18-20%2. Free P2O5 : 03% (Max) 3% (Max)3. Sulphure : - 10% (Min)4. Available P2O5 : 43-44% 16-17%5. Moisture : 05% (Max) 08% (Max)6. Physical Character : Granular Powder

WATER TREATMENT PLANT

1.1 AIM of the Plant:This plant has been planed to supply process water to the chemical complex of

chittagong (Bangladesh Chemical Industries Corporation.)

1.2 Characteristics of Raw Water:The water to be treated is river water.Its main characteristics are as follow:

Physical -chemical analysis (contractual analysis) Turbidity .................................................. 1500 kaolin pH ............................................................... 7.4 Total hardness (ppm CaCO3) .................... 128.41 Calcium hardness (ppm CaCO3) ............... 38.52 magnesium hardness (ppm CaCO3) .......... 89.89 m-alkalinity (ppm CaCO3) .................... 43.66 Strong acid salts (ppm CaCO3) .............. Sulphate (ppm CaCO3) .......................... Chloride (ppm CaCO3) .......................... 39.18 Iron .........................................................0.25 mg/l Silica ...................................................... 40 mg/l Nitrite .................................................... None

Nitrate ................................................... traces

Table : showing approximate calculation of ion content

Cations meq/l mg/l Anions meq/l mg/lCa++ 0.769 15.40 HCO3

- 0.873 43.66Mg++ 1.774 21.57 CO3

-- 0 -Na+ 6.13 141.00 SO4

-- 0.816 39.18K+ 0.180 7.05 NO3

- - -Na+ + K+ 6.21 148.05 Cl- 7.102 251.80Fe+++ 0.012 0.23 SiO3

- 0.67 40.00

1.3 Treated water Characteristics1.3.1 Filtered water before demineralization

o Turbidity .......................................... max. 20 (kaolin)o Free chlorine ................................... max. 0.2 mg/l

1.3.2 Dematerialized watero Conductivity ............................ max. 10 micromhos/cmat 250

o Silica residual ......................... max. 0.2 mg/l

1.4. Plant Flow Rateo Clarified water ............................ 300 m3/houro Filtered water ............................. 55 m3/houro Demineralized water ................. 40 m3/hour

1.5 Treatment Principle1.5.1 Pretreatment Coagulation - Flocculation - SettlingWater contains very fine, colloidal or pseudocolloidal suspended solids which

must be gathered into a bulky and heavy floc to allow settling and help retention in the filters.

The interfaces of colloids are electrically charged, which prevents nearby particles from coming close together.

The action takes place in three steps: Coagulation, which destabilizes the colloids to give rise to a

precipitate. Flocculation, which destabilizes the colloids to give rise to a

precipitate, Flocculation, which is intended to increase the volume and

cohesion of the floc formed by coagulation, Settling, which is intended to permit particles to settle out.

A/CoagulationUse is made of a metal salt such as aluminum sulphate.

It is determined at plant start-up after jar tests have been conducted.

The greater a water's colloid content, particularly matter of vegetable origin, the higher the amount of reagent required for clarification,

The nature of organic matter has an influence on coagulation. The pH of the medium is of paramount importance in

coagulation and in the dosage of chemical.The hydrolysis, and thus the efficiency, of aluminum sulphate is maximum

when the pH is close to 6.1 and organic matter removal is maximum when the pH is between 6 and 7. Therefore, the pH must range within these limits. However, aluminum sulphate is a strong acid salt and causes the pH to decrease, which may render the water aggressive.

Neutralization is applied before treatment so as to adjust the flocculation pH to its optimum value.

B/ FlocculationFlocculation is promoted by constant speed, slow mechanical stirring which

increases likelihood of collision between destabilized colloidal particles without breaking the floc.

Flocculation is further improved by the addition of a flocculant aid (a polyelectrolyte which will not always be necessary).

C/ SettlingSettling is designed to allow the particles in suspension in the water to settle,

under the effect of gravity, to improve water quality.

To ensure that settling takes place, the settling rate of the particles must be higher than the water's rising velocity, Va, in the units:

These particles exist in the raw water and are precipitated into larger (and thus heavier) floccules by adding chemical agents during flocculation.

OPERATING PRINCIPLE

Pretreatment :The pretreatment is carried out in three steps : injection and mixing of reagents, flocculation, settling.

Reagent Injection :It takes place in the mixing chamber in the following order : caustic soda and aluminium sulphate. When it is used, the polyelectrolyte is added at the outlet from the mixing chamber.Mixing is achieved by a stirrer at a speed of 70 rpm.

Flocculation :The flocculator is a tank which provides a significant contact time between the water and the flocculation reagents (30 min).

The unit is equipped with a mixing device with vertical paddles with a specially designed propeller which rotates relatively slowly, but rapidly enough to prevent sedimentation on the bottom of the flocculator.

The rotation speed is slow in order not to break up the floc. There will be a large weir so that the flocculated water flows slowly into the following treatment unit with no sudden surges which could result in floc break up.

Settling:The static settling tank is a rectangular basin in which water is continually.The bottom of this settling tank is sloped for maximum sludge concentration in the low point of the static settling tank will be emptied periodically in order to eliminate settled sludge.

This system must operate in a regular manner. Variations in flow rate cause stirring which lifts the sludge to the surface.

DEMINERALIZATION:Demineralization is designed to remove dissolved salts from the raw water. These salts are essentially bicarbonanates, sulphates, chlorides and silica.

Two types of ion exchangers are available :1. Cation exchangers, featured by the presence of acid, sulphonic functional radicals in

the molecule.

They exchange their cations (H+ or any other cation) bound with the active radicals for the cations in the liquid with which they are in contact (Ca, Mg, Na, etc.), and this in a reversible menner.They are regenerated with an acid solution.

Strong acid cation exchangers (sulphonic function) can take up all cations. Including those in equilibhrium with strong anions : sulphates, chlorides, nitrates.

2. Anion exchangers, featurd by the presence of basic functional radicals in the molecule.

They exchange their anions (OH or any other anion) bound with the active radicals for the anions in the liquid with which they are in contact (Cl -, SO4 --, NO3

-, SiO2), and this in a reversible menner.

They are regenerated with an a alkaline solution.

Weak-base anion exchangers can only take up the anions from strong acids (HCl, HNO3, H2SO4).

Strong-base anion exchangers can take up the anions from strong acids and the anions from weak acids such as carnbonic acid and silica.The feed water successively passes through one H+ cycle cation exchanger and two OH- cycle anion exchangers.

After passing through the strong acid cation exchanger, all the cations in the water are replaced by the hydrogen ion, H, of the resin; then, the treated water only contains the acids of the initial salts.

The decationized water next passes through the weak-base anion exchanger and the strong-base anion exchanger. All of its anions are replaced by the hydroxyl ion, OH-; then, the demineralized water only contains traces of caustic soda corresponding to the cation leakage.

The treated water is highly pure and has a constant quality at a pH close to neutral.

SULPHURIC ACID PLANTS (SA- 1 & SA- 2)

There are two sulphuric plants namely SA-1 (Capacity: 100 NT/Day) and SA-2 (Capacity: 400 MT/Day). In both the plants, sulphuric acid is manufactured by the Monsa to designed single contact single absorption process with Rock sulphur imported at 99.5% (Min) purity.

SA-1 was commissioned in 1967 and SA 2 in 1974.

The manufacturing process of sulphuric acid consists of the following principal steps :

1. Melting of sulphur.2. Production of sullphur dioxide (SO2)3. Conversion of sulphur dioxide to sulphur Trioxide (SO3)4. Cooling of SO3 gas and absorption of SO3 in water to produce 98.5% sulphuric acid.

SA-1 PLANT

PROCESS OUTLINE :

1. MELTING OF SULPHUR :-

Rock sulphur is charged into the charging chamber of a melter and melted by steam coils installed in it. Steam is supplied to the steam coil to maintain the temperature at 132-1350C. The molten to the flows out to the settling chamber of the melter where the heavy impurities settle at the bottom and the light impurities rises on the upper layer as scum. The charging chamber and the settling chamber are provided with agitators to make a satisfactory contact between sulphur and steam coil. The molten sulphur from the settling chamber is pumped to the pumping chamber of the melter through a pre-coated sulphur filter which separates the impurities present in molten sulphur.

2. PRODUCTION OF SULPHUR DIOXIDE :-

The clear molten sulphur from the pumping chamber of the molten is pumped through the sulphur burners into a sulphur which as preheated to a temperature of about 8000C by the combustion of natural gas. In the sulphur Furnace, Sulphur starts to burn with oxygen from dried air that has passed through the Drying Tower and produces sulphur dioxide as per following reaction :-

S + O2 = SO2

A steady supply of dry air is made available to the burner. Atmospheric air is sucked and pressurized by Blower, passed through Drying Tower to eliminate moisture and forced into the burner. The burning of sulphur evolves a large amount of heat which rises the temperature of the burner gas at around 10000C where strength of 2% SO2 is maintained. The exit temperature of the Furnace should never be allowed to exceed 10250C in order to ensure long life of brick lining. The hot combustion gas (i.e.SO2) coming out of the sulphur furnace at around 10000C is cooled down to a temperature of 420-4300C suitable for conversation reaction in the converter, by passing through state host boiler waste heat boiler generates steam which is mainly used in the boiler melter and phosphoric acid plant. From the waste heat boiler, the gases (SO2 +O2 + other) pass to a hot gas filter where impurities like ash, dust, etc are filtered out by graded layers of crushed bricks. This protects the catalyst of the converter from contamination and prevents build up of A pressure across the catalyst beds of the converter.

3. CONVRSION OF SULPHUR DIOXIDE TO SULPHUR TRTOXIDE :-

The purified SO2 gas leaving the hot gas filter is passed into converter containing V2O5

catalyst. 4 (four) beds of catalysts are placed inside the converter at different positions. SO2

gas is allowed to pass through each bed of the converter and optimum conditions (of temperature/ pressure/ flow rate/ air supply) are maintained to favor the conversion of SO2 to SO3 in the converter. As conversion of SO2 to SO3 is exothermic reaction, temperature rises in each bed and is controlled by supplying dry air in the 1st bed and 2nd bed and by circulating the gases of the 3rd bed through a air cooled heat exchanger. The reaction that takes place in the converter in presence of catalyst is represented below :-

SO2 + ½-O2 = SO3

1. COOLING OF SO3 AND ABSORPTION OF SO3

IN WATER TO PRODUCE SULPURIC ACID :-

After converter, the temperature of SO3 gas is around 4300C, heat of which is made available for the following purpose in order to get the SO3 gas at a suitable temperature for absorption in 98.5% sulphuric acid.

a) To preheat a part of the dried air leaving the Drying Tower required for combustion of molten sulphur in the sulphur furnace. This type of equipment is called SO3 cooler and is installed in SA-1 Plant.

b) To heat the deaerated dematerialized boiler feed water, which has a temperature of 100-1500C. This type of equipment is called Economizer and is installed in SA-2 plant.

In SA-1, SO3 gas from the converter is cooled to 2300C in the SO3 cooler and introduced to the Absorption Tower.

In SA-2, SO3 gas from the converter is cooled to 2300C in the 1st Economizer and further cooled to 1700C in the 2nd Economizer (Formerly, 2nd Heat Exchanger using air cooling) before the SO3 gas is entering the Absorption Tower.

The cooled SO3 gas (along with gaseous components) is passed into Absorbing Tower from the bottom and a stream of sulphuric acid (98.5% strength) is circulated from top and mixed counter currently to effect absorption of SO3, strength of absorber acid is thereby raised which in turn is diluted by adding water to maintain the desired strength of 98.5%. The quantity of acid in Absorbing Tower is thus, continuously increasing and the increased portion is cooled by passing through irrigation cooler and finally sent to storage. The unabsorbed gas leaving the Absorbing Tower is discharged to atmosphere.

The reaction that takes place in the Absorbing Tower is represented below: SO3 + H2O = H2SO4

SA-2 PLANT

3. Detailed description of process :

3.1. Sulfur melting1) Equipment

V -1202 1. Sulfur PitE-1202 2. Sulfur Melting CoilJ- 1201 A, B3. Sulfur PumpM- 1202 A, B4. Agitator

2) Standard of operation(a) Stamard feed rate of sulfur to melter 5,610 kg/hr.(b) Standard temperature

Molten sulfur 132-1350C Heating steam 7 kg/cm2G (abt. 1690C)

3) Purpose To melt solid elemental sulfur and pump up molten suflur to the sufur furnace.

4) Description

(a) Sulfur melter

Best results will usually be obtained by maintaining the molten sulfur in the melter at approximately 132-1350C. Higher temperature entering the furnace are sometimes beneficial, but never in excess of approximately 1490C. Materially higher or lower temperatures than those stated should not be used because of the increased viscosity of molten sulfur. It is necessary to keep the level of molten sulfur at normal level. Sulfur itself is no corrosive. Any corrosive properties result form contaminants, and most corrosion results form sulfurous and sulfuric ac id generated by the reaction of sulfur, moisture, and air. Most corrosion occurs in liquid-handling equipments at sulfur-air interface. On the part of these equipments at the interface, some protectors are provided, then if the liquid level is not kept normally, corrosion occurs in the other part of them having no protectors.

When it becomes necessary to clean sulfur pit, it should first be pumped as low as possible. In order to do this, the pump should be taken out of the melter, for the extension of the inlet piping as required and the pump then installed again. This change in the inlet piping makes it possible for the pump to draw form a greater depth than would otherwise be the case.

After removing as much of the molten sulfur as possible, cleaning may start immediately by adding the small portion of the water at the corner where the work is to be started.

It is advantageous to start cleaning before the mixture of sulfur and dirt has become cold, as the immediate addition of water will often give mixture a “much” c consistency which is readily shoveled. Water should be added however only at the spot where the man is working. Since there are two settling sections, this cleaning can be handled for one setting section while the other is operating.

(b) Sulfur pumpThe burner feed pump is mounted in the sulfur pit located near the furnace.

When installing a sulfur pump, be sure that it is perfectly plumb and that it turns freely by hand. Piping should be connected, and held firmly, so that no starains are ever put on the pump.

For further information, any instructions about the pump and pump drive should be consulted.

The sulfur pump drive is interlocked with the blower driving unit so that whenever the blower stops, the sulfur pump simultaneously stops. Nevertheless, when evern the blower is stopped the operator should always make sure at once that the sulfur pump has actually stopped. If the sulfur pump should remain in operation while the blower is stopped, the system would soon become filled with sublimed sulfur and much damage may occur to the sulfur furnace and other equipment.

In order to test a sulfur pump while the blower is stopped, provision has been made so that it is possible to operate the pump, even though the blower be stopped. Before testing a pump in this manner, however, the blind flange on the end of the jacketed tee in the discharge piping nearest this pump should be removed and a pail should be placed under the end of the tee. The jacketed valves should be turned so

that the pump to be tested will deliver sulfur to the pail instead of the furnace. When starting the pump always be sure that there is at least 3.0 kg/cm2 steam pressure in the jacketed discharge line.

It is very clear by Monsanto’s experience that many troubles with sulfur pumps are due to misalignment. It is to be emphasized that spare pumps or pumps out of service for repaid should be properly maintained while in storage or while being handled so that they cannot become sprung or distorted. All parts must b e carefully aligned with one another and also the pump with the drive.

The usual warning to the operator that plugging is occurring at some point is that the furnace temperature, as shown on the temperature recorder, gradually decreases. It has been found that tripping the pump and allowing the sulfur in the discharge line to drain back for a minute or so, often cures the trouble. This procedure often saves the trouble and expense of removing a pump for inspection and repair, when actually no repairs are needed.

It should be emphasized that under any conditions sulfur flow should be in creased by only small steps and the operator should make sure of the result of each change on gas strength before making further adjustment.

(c) Steam-jackted molten sulfur piping.The sulfur in this line may freeze, if an adequate amount of steam is not

supplied to all parts of it, and if condensate is not kept drained. Only rarely, however, will this line become scaled or plugged with foreign matter.

The sulfur nozzle at the end of the sulfur inlet pipe of the furnace may rarely become scaled or plugged. It has been found that the scale may be burned off the nozzle and the nozzle reused. It is recommended, there fore, that a few spare nozzles be stocked.

3.2. Sulfur burning.1) Equipment

D-1201 Sulfur FurnaceD-1202 Sulfur BurnerD-1203 Oil BurnerD-1204 Oil Burning Unit

2) Standard of operation (a) Standard flow rate

Molten sulfur to furnace 5,610 kg/Hr.Dry air to furnace 34,987 Nm3/HrGenerated gas from furnace 34,900 Nm3/Hr

(b) Standard concentration Generated gas

SO2 11 vol %O2 10 vol %N2 79 vol %

Total 100 vol %

3) Purpose

The sulfur furnace is the combustions chamber where molten sulfur from the sulfur pumps is combined with combustion air from blower to form SO2 gas.

4) Description Care must be taken to avoid overheating the brickwork adjacent to the burner.

There must be a substantial flow of combustion air around the burner at all times to lower the temperature at this point and especially to carry heat to remote parts of the furnace more rapidly. A large volume of combustion gases at a reasonable temperature will achieve the desired results much faster than a small volume at an excessive temperature. Note also that a substantial flow of combustion gases is required to obtain a representative temperature reading on the thermocouple adjacent to the combustion gas outlet.

Frequent observations must be made of the color of the brick in the combustion zone. To avoid damage, the brickwork should not be heated beyond full red heat. Heating the brickwork to a color of orange, yellow, or white must be avoided.

When the furnace is at normal operating temperature there should never be more than a small pool of molten sulfur in the bottom of the furnace, so that when the blower and sulfur pump are stopped simultaneously, there will be substantially no unburned sulfur left in the furnace.

When the blower stops, any sulfur left in the furnace would sublime; if small in amount it would cause no damage, but large amounts would be harmful. When shutting down the plant deliberately, the sulfur pump should be stopped, and the blower a few minutes later so as to eliminate all possibility of any unburned sulfur being left in the furnace.

There is a close correspondence between the furnace outlet temperature and gas strength. Accordingly, with experience the gas strength can be checked approximately from the furnace outlet temperature. The theoretical flame temperature corresponding to various percentages of SO2 in the burner gas are as follows :

% S02

by VolumeApprox. Theoretical Flame Temperatures

5.06.07.08.09.010.011.012.0

540C-10100F6210C-11500F6990C-12900F7770C-14300F8600C-15800F9430C-17300F10240C-18750F11040C-20200F

It should be noted that the above temperatures are not exactly those which will prevail at the stated gas-strengths. Actually, the are increased in proportion to the amount of heat in the combustion air and decreased in proportion to the amount of heat lost form furnace shell by radiation, convection, etc.

The protecting well and thermocouple in the gas outlet should be inspected and checked occasionally to sure that it is in good condition and is giving an accurate reading.

3.3 Heat recovery 1) Equipment

E- 1201 Waste Heat Boiler Flush Tank Sampling Cooler

V-1203 Deaerator J- 1202, A, B Boiler Feed Water Pump

2) Purpose To recovery of excess heat of combustion gas-

3) Description a) Boiler food water treatment.Experience has shown that any troubles whit the waste heat boilers are almost

invariably due to internal scaling of the boiler. In many cases such scaling has been due to inadequate attention to the supply and maintenance of suitable treated feed water of uniform Quality. Because of the great variations in the water supplies available in different locations, it is impossible for a standard treatment to be prescribed. Thus, it is most desirable that competent advice be obtained form specialist in this field, and preferably from those with experience of this type of waste heat boiler.

b) Boiler water testing Acid plant operators, because of their frequent lack of familiarity with boilers,

often negalect faithful routine testing of the boiler water and consistent maintenance of boiler water of the proper analysis. These comments apply also to feedwater treating equipment when such comes under the jurisdiction of the acid plant. Both the feed water and the boiler water must be consistently kept of the composition specified by us and within the limits instructed in the boiler manual.

Attention is particularly required while starting the plant as well as immediately after and during a shutdown.

After the method of treatment and a control procedure has been established, the simple routine tests any be run by the operators. The number and nature of the tests depend entirely upon local conditions. Whenever suitable feedwater is provided and the boiler water is carefully kept within prescribed limits of composition, scaling of tubes is rarely encountered.

Boiler water samples for tests should be taken form the continuous blow down at times to be posted by the supervisor. Each sample should consist of 230 g. These samples are to be tested by the operator according to posted instructions. Frequently, an additional sample should be taken and sent to the laboratory.

The procedure for taking a boiler water sample is a follows:

Case 1: When the conductivity indicator (Al-1001) is operated;The sample is taken form the conductivity indicator outlet pipe.

Case 2. When the conductivity indicator (Al-1001) is not in good condition;

i) Open the cooling water valve of the sampling cooler on the continuous blowdown line.

ii) Do not disturb the setting of the needle valve. Open the sample valve and let the boiler water escape for a few seconds before taking the sample.The sample must be sufficiently cold as drawn that none of it flashes into steam.

iii) Rinse the sample bottle twice with the boiler water before collecting the sample for test.

iv) Close the sample valve and the sampling cooler cooling water inlet v alve.

c) Boiler water level.To avoid completely the entrainment of the water from the boiler into the

steam lines, it is important that the water level in the boiler be maintained at a point close to the standard line of the gauge glass. The remote water level indicator should be checked against the gauge glass on the boiler at least daily.

The low-level alarm on the water column of the boiler should sound in case that the water level reaches about 60 mm below the standard level. The liquid level indicator should be set at such an elevation that it stops the mover of the blower when the level in the water column is about 100mm below the standard level. The purpose of this setting is to give the operator sufficient time after the low-level alarm sounds to put more water into the boiler, otherwise the plant is shut down automatically when the water level drops below this point.

Regarding the adjustment or operation of other steam of feedwater accessories, the other instructions by us should be consulted. Operators must be thoroughly familiar with all such instructions before operating any of the equipment.

d) Manual blowdown The boiler should be blown down manually at least once each day at times to

be specified by the supervisor Where two seat and disc type blow down valves are installed in the same line,

the valve nearest nearest the boiler should be opened first and closed last. This valve nearest the boiler, when opened, should be opened completely. The other value should be opened as much as possible without blowing down more than specified by the supervisor. If the sliding plunger type valves are used, the valve nearest the boiler should be opened last and closed first.

These blowdown valves many be opened rapidly, but they should be closed gradually to avoid the dangerous effects of possible water hammer if closed too rapidly. Care must be taken to close these valves tightly as even a minute amount of leakage may upset the boiler water analysis and will also quickly ruin the valve.

The water column and its gauge glass should be blow down each day. These should not be given a hard blowdown. The water column should be blow down before the gauge glass in order to prevent etching or the glass.

The reliance level unit need be blown down only periodically. This unit shuts down the blower on very low boiler water level. A by pass switch is provided on the control panel for use during blowdown to prevent shut down of the blower. At all other times this by pass switch should be off.

The automatic feedwater regulator should be blown down only periodically and after a shutdown, in order to speed up the action of the regulator.

e) Continuous blowdown.The continuous blowdown valve must be so regulated as to hold the total

solids in the boiler water within specified limits. Cooling water must be used in the condenser around the continuous blowdown only while taking boiler water samples. At all other times the cooling water should be shut off and the condenser drain valve left open. If the drain valve is not kept open, the jacket may soon become plugged with sediment.

When the total solids in the boiler water are high, the continuous blowdown valve should be opened a little so that the next test will be within prescribed limits. When the total solids are low the continuous blowdown valve should be closed a little.

f) Supplementary boiler water treatment.Equipment is provided for the addition of supplementary treating, chemicals

directly to the boiler. Usually, such supplementary treatment is essential regardless of the suitability of the boiler feedwater, and whether or not it has been softened or had othr preliminary treatment. Cases have been rare in which better results were obtained by introducing the supplementary treating chemicals into the feedwater heater or into the inlet of the feedwater pump. Introduction at the later points sometimes results in scaling of piping and corrosion of the feedwater pump.

The solution of supplementary treating chemicals is to be prepared according to directions furnished by the supervisor.

3.4 Gas Filter 1) Equipment

P-1201 Gas Filert

2) Purpose The function of the gas filter is to remove ash and dust from the gas stream

ahead of the converter when burning sulfur.

The sulfur commonly used in sulfuric acid manufacture contains a small amount of ash. In addition, a small amount of dirt may be picked up in shipping and handling. The sulfur settling pit is not 100% efficient in removing this ash and dirt. Hence, at all times, there are minute amounts of ash entering the sulfur furnace along with molten sulfur.

While the gas filter also is not 100% efficient, if it were not provided most of the dust and ash would be carried into the converter and caught by the catalyst. This would increase the pressure drop through the converter. If enough of the catalyst surface becomes covered, conversion efficiency decreases. The increased pressure drop and reduced conversion efficiency would necessitate cleaning of the catalyst by screening. Use of the filter lessens the frequency of cleaning the catalyst.

3) Description The pressure drop across the gas filter should be recorded at regular intervals

and at least once a month. The pressure drop through a clean filter at rated gas volume will be approximately 150 mm water column. The filter medium should be rescreened when the resistance increases to the point of decreasing the blower capacity and the acid production rate or when the blower power consumption becomes excessive.

Nozzles are provided on side top, and under the grids of the filter, so that the filter medium may be raked out and prescreened, or replaced with spare clean material.

While cleaning the filter, some dirt always falls through the cast iron grids into the bottom of the filter. The space under the grids should be carefully cleaned after installation of the clean filter medium. The use of a vacum cleaner is suggested, if available. Care should be taken that the layers of ½” to 1” pebbles and the layer of 1/8” to 3/8” crushed firebrick are perfectly level as thin spots will affect the efficiency of the filter.

Rescreening of direct filter medium should be done promptly, preferably while still warm and dry. The dust in the filter while still warm and dry. The dust in the filter mass may contain some acid sulfates which will absorb atmospheric moisture in the time become sticky.

The porcelain pebbles are separated rfrom the crushed firebrick by the use of a ½” screen. A screen with openings not more than 3/32” square is used to separate the dust form the crushed firebrick, so as to retain the 1/8” size material. Loss of the small material will materially affect the efficiency of the filter.

The crushed firebrick used in the gas filter must be free of dust and must not spall or disintegrate at 6000C. Size specifications are:

Screen with Square Openings % By VolumeThrough 1/16”Through 1/8”On 11/8” and through ¼”On ¼” and through 3/8”On 3/8”

0-0.58-1540-6030-400-5

3.5 Converter 1) Equipment

F-1301 Converter

E-1301 1st Heat Exchanger

2) Standard of operation a) Standard gas volume (Nm3/h) 34,900b) Inlet gas concentration SO2 11.0 ±0.2%

O2 10.0 ±0.2%c) Standard gas temperature and conversion rate

Temperature(OC)

ConversionEfficiency (%)

1 C Intlet 430 ±5Outlet 603 ± 0 55 Note:

2. C Intlet 491 ± 5Outlet 562 ± 5 84

10- No. 1 layer 20- No. 3 layer

3.C Intlet 453 ±5Outlet 475 ± 5 95.5

30-No.3 layer 40-No. 4 layer

more than 98

d) Volume of air introduced 1 C Outlet (Nm3/h) 10,0282 C Outlet (Nm3/h) 13,379

3) Purpose Oxidation of SO2 to SO3.

5) Description :

a) Converter inlet gas concentrationControl the gas concentration within the standard values. Carry out the control

by adjusting the burner pump so that the gas concentration does not vary in normal operation.

Variations of the gas concentration have direct harmful effect on the conversion rate, leading to its declines. The temperature distribution of each layer is changed by fluctuations of the gas concentration. As a result, it becomes necessary to adjust the air volume introduced at the 10, and 20 outlet. The magnitude of variations of the gas concentration and the frequency of such variations should be reduced as small as possible.

b) Gas temperatureIn order to achieve sufficient conversion, the gas temperature must be

controlled at the standard level, especially not to let the temperature at the 10 outlet exceed 6200C, it will sometimes cause difficulties, for example, the warpage of catalyst shelf plate at 10.

In case that the temperature approaches to 6200C, reduce the 1C inlet temperature for control. Particularly the 4C inlet temperature should be rigidly controlled. If this temperature rises too high, the conversion rate will be reduced.

Also where the temperature is too low, the conversion rate will decline. Do not let the 4C inlet gas temperature fall below 4100C. At such low temperatures the catalyst may not act as a medium for conversion reaction. Since the 1 st heat exchanger is installed for this particular purpose, carry out the through control of this heat exchanger.

C) Air volumeThe SO2 incoming to the converter accounts for 11% by volume. Therefore air

is introduced to ensure the optimum conversion rate and also to control the temperature on each layer. Assumed that design amount of air in introduced at the converter inlet, the SO2 concentration will be about 6.6%. Since this air introduction aimes temperature control the air volume which is obtained by deducting the burning air volume form total air at outlet of the drying tower, is only for standard of operation, and will be changed in actual operation. d) Control of concentration and temperature at converter inlet.

Where the concentration and temperature at the converter inlet are too high, control them by introducing air to the converter inlet flue form the duct expending form the drying tower. Also this temperature can be adjusted by the bypass valve of waste heat boiler.

e) Conversion rate To obtain the most satisfactory conversion rate, control the gas temperature

and concentration, and the air volume introduced.

Although the standard values have already been indicated for the conversion rate on each layer, some deviations from these values are allowable. Because, our real purpose is to keep the overall conversion rate maximum. The conversion rate declines with the progress of time. Be sure to note these progress of declines, because occasionally the conversion rate might sharply drop.

Considerable causes are as follows:i) Any abnormality of raw gases.ii) Sudden changes in gas volume and concentration.iii) Increased quantities of impurities in the gas.iv) Abnormality of converter interior construction.v) Abnormality of catalyst.vi) Abnormality of gas filter.

However, it is advisable to be familiar with data or routine operation and note the operating characteristics of each equipment involved so that proper measures can be taken at all times. Particularly to prevent large quantities of impurities from being carried into the gas, it is necessary to study the results of analyzing the quality of raw sulfur and that of the sulfur supplied to the sulfur burner and the water and mist content of the gas leaving the drying tower.

f) Draft resistance The draft resistance rises progressively higher. Keep a close watch over the

range of increases in this resistance. Sharp increases may be attributable to the same

causes as listed in the preceding paragraph (e). As a rule, the resistance will never decline so. However, if considerable decreases occur, it is often due to the abnormality of the interior of the converter.

g) Screening and recharge of catalyst.With progress of time, the conversion rate falls and the draft resistance rises.

In case that there will be no more possibility to carry out normal operation, the catalyst should be taken out, screened and recharged. In this cases, it is also necessary to replace fresh catalyst partially.

h) 1st Heat exchangerThe 1st heat exchanger is provided to reduce the 4C inlet gas temperature to

the standard level. For this purpose, the quantity of cooling air should be properly controlled. It is necessary to note the range of variations in temperature.

Draft resistance at inside of the tubes gradually increases as a rule. If such increases reach the point where normal operation is impossible, cleaning of the exchanger system is required. Where pressure abnormally builds up inside and outside the tubes due to damaged tubes, this condition can be easily detected by white fumes of SO3 observed by opening sample value at the outlet piping of air

In this case, it is of course necessary to repair these tubes.

i) Other abnormalitiesIt is important to control the quantity of introduced air into the converter as

mentioned before article.

Improper quantity of air causes abnormal distribution of the temperature and pressure of each layer.

Operators should check the air flow rate, the related valves, blast ring pipes and baffle plates.

J) Recording and checkingOperating data on the items given below should be recorded in Log Sheet

form at the prescribed intervals.i) SO2 gas concentrations ii) SO2 gas volumesiii) Temperatures of SO2 and SO2, conversion rates and gas pressure.

3.6 Cooling of SO3 gas.1) Equipment

E-1302 EconomizerE-1303 2nd Heat Exchanger

2) Standard of operation a) Standard gas temperature

Inlet of E-1302 4300C±2Outlet of E-1302 2300C±2

Inlet of E-1303 2300C±2Outlet of E-1303 1700C±2

b) Standard gas flow rate 56,469 Nm3/Hr.

3) Purpose To reduce the SO3 gas at the cooling system inlet and outlet should be

maintained at the standard levels. This temperature control is carried out be adjusting the volumes of cooling air introduced. Experience in actual operation indicates that appreciable deviations (± 50C) of the inlet gas temperature of 2nd heat exchanger from the above-mentioned standard are permissible.

The outlet gas temperature should be kept at the standard level in principle, however there is some exception, that is, in case the volumes and temperatures of circulating acid through the absorption tower are off the standard values due to unavoidable causes, such as star-up, shut-down and etc. the SO3 temperature at the heat exchanger out let should be controlled judging by the white fumes in the exhaust form the stack. In such case, said SO3 temperature may deviate from the standard level.

b) Draft resistance The draft resistance progressively increases on the gas side (inside the tubes)

in the heat exchanger and in the economizer. Keep a close watch over this increasing rate. In case there is any sharp rise in said resistance, the cause should be traced at once.

The increased resistance inside the tubes of the 2nd heat exchanger is mainly due to the abnormally high content of moisture and SO3 mist in the gas passing through the tubes. In other words, these high contents of moisture and SO 3 mist lead to the tube corrosion, and the resultant formation of FeSO4 plugs the tubes.

The inclusion of H2O and SO3 mist in said gas result from the insufficient purification of air in the drying tower, or excess hydrocarbon content in raw sulfur etc. If normal operation fails due to increased draft resistance, cleaning should be carried out by adequate means.

Besides the foregoing, a damage on the tubes may cause troubles in draft resistance. In such a case, white smoke will be seen by opening sample value at the outlet piping of air. Then it is necessary to repair the tube by a suitable method. In other words, minor damage could be repaired by placing plugs above and below the damaged tube; if so many tubes are damaged as to hamper the required performance, they will have to be replace. In case that the boiler feed water is not treated well, it causes the damage of the economizer tubes often. So, the certain precautions shall be paid to keep the boiler feed water at the standard level specified in boiler instruction.

C) Volume of drainsMeasurement should be made once a day (in the morning) as to the volumes

discharged from the drain piping. Note variations in these drain volumes. In case the volume suddenly increases, trace the cause. The following are deemed such causes:

i) Insufficient purification of air in the drying tower.ii) Steam leaks form the waste heat boiler and e economizer.iii) Damaged tubes.iv) Excess hydrocarbon content in raw sulfur

The concentration and specific gravity of the drains should be checked at the prescribed intervals. The determination of variations in these contents may sometimes lead to the discovery of damaged tubes in the waste heat boiler and economizer.

It is better to analyze the concentration and contents of drain form time to time (twice a year or so). The date obtained from such analysis may enable you to anticipate or detect abnormal phenomena in the operation of that part of equipment before 2nd heat exchanger.

d) Recording and checking The gas temperature, draft resistance, etc. must be recorded at fixed interval in

Log Sheet, and operator must be familiar with those tendency.

3.7 Absorbing of SO3 gas1) Equipment

F-1401 Absorbing TowerF-1401 A.T. Pump TankJ-1405 Waste Acid PumpJ-1401 A, B A.T. Circulation PumpE-1401 A.T. Acid Cooler

2) Standard of operation a) Absorbing tower i) Standard gas temperature (OC).

Inlet 170 ±5Outlet 70 ± 5

ii) Standard gas volume (Nm3/h)Inlet 56,469Outlet 52,641

iii) Gas concentration (%)SO3 SO2

Inlet 6.82 0.136Outlet 0.037 0.146

iv) Quantities, temperature and concentration of sulfuric acid.

kg/h m3/h OC H2SO4%Inlet 885,001 494 65 98.5±0.1Outlet 898,677 82.5 98.86

b) Pump tank Sulfuric acid and water

Kg/h OC %

The inlet of pump tank H2SO4 898,677 82.5 98.86 (from F-1401)pump tank H2SO4 35,566 82.5 40.0 94.0 (from F-1402)pump tank H2O 1,690 20.0 0

The outlet of pump tank H2SO4 935,933 83.5 98.5

c) Circulation pump (J-1401 A, B)H2SO4

Kg/h OC %inlet 935,933 83.5 98.5out let 935,933 83.5 98.5

d) A. T. Acid cooler (E-1401)

H2SO4

Kg/h OC %inlet 918,943 83.5 98.5out let 918,943 65.0 98.5

3) Purpose To absorb the SO3 gas cooled to an appropriate temperature by the 2nd heat

exchanger.

4) Description :

a) Gas temperature The gas temperature must be kept within the range of standard values. The

SO3 gas absorption rate at the absorbing tower largely depends on the gas temperature and the volume and temperature of circulating acid. How little the exhaust gas makes white smoke out of the stack depends, as a matter of course, on whether the absorptin rate at the absorbing tower is good or not, but it is relative much to the atmospheric temperature, humidity, wind velocity, etc. It is therefore permissible to adjust so as to obtain the best absorption rate, even they deviate from the standard values. Operators must be careful that in case the inlet gas temperature is lowered extremely or lowered quickly, the SO3 contained in the inlet gas turns to (SO3)n.

b) Flow rate of circulation of sulfuric acid The flow rate of circulating sulfuric acid must not decrease to smaller than the

standard value. When it, is too little, the rate of absorption decreases. The volume must be examined by a method instructed separately. In normal operation, checking is carried out by the measurement of electrical current with ammeter. But it is also necessary to watch, through the sight glass of the tower at the time of routine inspection patrol, and if the acid is dropping abnormally, make necessary adjustment. The temperature of circulating sulfuric acid at the inlet of the tower must be

controlled at the standard level. When it is too high or too low, SO3 gas can be hardly absorbed efficiently. This temperature can be adjusted by acid cooler.

Operators shall pay the attention to keep sulfuric acid concentration at the tower inlet within the range of standard values. In cases you find the fluctuation of this concentration too much, you must examine and adjust it by checking other various conditions. Such other various conditions mean the flow rate and concentration of sulfuric aid coming form the drying tower, the flow rate of process- water being fed to the pump tank, the flow rate of circulating acid, the sulfuric acid concentration at the outlet of the tower. and so forth.

The sulfuric acid conductivity meter must be twisted from time to time in accordance with the instructions provided separately. The acid cooler should be adjusted in such a way than the water will be sprayed as even as possible. If you neglect this adjustment, you may not be able to avoid undue corrosion of acid tube.

c) Pump tank and Product The pump tank must usually be operated keeping its liquid level at half the

total height of the tank. This is necessary because the sulfuric acid should not overflow out of the tank in cases of power failure or emergency. part of sulfuric acid sent form the outlet of the pump (J-1401 A, B.) is led to the product cooler mentioned in the next section, and finally the product is stored in the storage tank.

d) Under-load operation and emergency shut-down.It is sometimes allowable that the aforementioned standard values deviates at

the time of under-load operation.

But such allowance for deviation from standards must be limited to the gas temperature and the temperature and concentration of circulating acid at the inlet of the tower.

It must be avoided to decrease the total volume of circulating acid less than the standard value. There fore, proper control must be made referring to the condition of gas put out from the stack. In such occasions as the damage of acid cooler, actions must be taken as instructed separately. The sulfuric acid staying in the damaged acid cooler must be drained into the storage tank by the waste acid pump (J-1405).

e) Recording and Checking Specified data must be recorded as the daily report and their tendency must be

kept in mind.

3.8 Product acid system1) Equipment

E-1403 Product Cooler J-1403 A, B Product Transfer PumpV-1403, A, B Storage Tank

2) Standard of operation Flow rate, temperature and concentration of sulfuric acid

kg/H TemperatureOC H2SO4 %

The inlet ofproduct cooler 16,990 83.5 98.5

The inlet ofStorage tank 16,990 45.0 98.5

3) PurposeTo cool the still hot product manufactured in the absorbing tower, and store it

in the storage tank.

4) Description a) Temperature

The temperature of the sulfuric acid produced in the absorbing tower is 83.50C. It is too hot as the product to be stored in the storage tank. Therefore it must be cooler down to 450C by the product cooler. The sulfuric acid thus cooler goes to the storage tank.

b) Measuring and storageThe product sulfuric acid sent through product cooler is stored in storage tank

and then pumped form storage tank to respective destinations.

The daily output of sulfuric acid must be checked by calculating the incoming and outgoing of sulfuric acid of storage tank through the reading of sulfuric acid liquid level.

3.9. Air drying1) Equipment

F-1402 Drying TowerV-1402 D.T. Pump TankJ-1402 A, B D.T. Circulation PumpE-1402 D. T. Acid Cooler

2) Standard of operationa) Drying tower

i) Standard gas temperature (0C)Intel 50 5Out let 41 1

ii) Standard gas volume (Nm3/h)Inlet 60,416outlet 58,395

iii) Volume, temperature and concentration of sulfuric acid.kg/h m3/h 0C H2SO4 %

inlet 894,634 494 400.5 94.00.5outlet 896,258 45.0 93.83

b) Pump tankH2SO4

kg/h m3/h 0C %inlet 896,258 45.0 93.83 (from drying tower)inlet 33,942 65.0 98.50 (from A.T. pump tank)

outlet 930,200 46.1 94.0c) Circulation pump (J-1402 A, B)

kg/h 0C %inlet 930,200 46.1 94.0outlet 930,200 46.1 94.0

d) D. T. acid coolerH2SO4

kg/h 0C %inlet 930,200 46.1 94.0outlet 930,200 46.1 94.0

3) Purpose To dry the air to be used for process, i.e. for sulfur burning and for the air

introduced into the converter, and to remove dust and other unnecessary substances out of the air. The drying is carried out by contacting air with concentrated sulfuric acid.

4) Descriptiona) Air temperature

Air form the air blower comes into the drying tower. Through the air at the inlet varies in temperature according to seasons, the air temperature at the outlet of the drying tower must be kept within the air temperature at the outlet should become higher than the standard value. Should the air temperature at the outlet be too high, the water content in the gas will increases, giving troubles at various parts of the equipment. The water content in the air at the outlet of the tower ranges form 0.05 g to 0.1 g/Nm3. The air discharged from the drying tower is let to the sulfur furnace and converter.

b) Circulation of Sulfuric acidKeep the standard amount of sulfuric acid circulating. Deficiency of

circulating sulfuric acid will degrade the drying. The amount of the sulfuric acid circulating must be checked by a method specified separately. In regular operation, it must be checked by the measurement of electric current with ammeters. It is also necessary to watch, through the sight glass of the tower at the time of routine inspection patrol, and if the acid is dropping abnormally, make necessary adjustments. The temperature of the circulating acid at the inlet of the tower should not be higher than the standard temperature. If it is high, the drying of air will become bad. This temperature can be adjusted by the acid cooler.

Keep the sulfuric acid concentration at the inlet of the tower within the range of the standard values. If the fluctuation of this concentration is found too much, operators must adjust it by looking into various ambient conditions. Such ambient conditions mean the quantity of sulfuric acid coming from the absorption tower, its concentration, the condition of sulfuric acid density meter, the quantity and outlet concentration of circulating acid, and so on. The acid cooler must be so adjusted as to be able to spray water as even as possible.

c) Pump tankThe pump tank must keep the liquid level at half its total height. This is

necessary because the sulfuric acid should be prevented from overflowing out the tank in case of power failure or emergency.

d) Other requirementsIt is desirable to maintain to quantity of the circulating acid over the standard

value even in the case of under load operation. The actions to be taken in the case of damage on acid cooler, and the matters concerning recording and checking are the same as already stated as for the absorbing tower system.

3.10. Air blower and air fan1) Equipment

K-1301 Air FanK- 1201 Air Blower

2) Standard of operation a) Air blower i) Standard air Volume (Nm3/h)

inlet 58,395 (Dry base)outlet 58,395 (Dry base)

ii) Standard air temperature inlet 33

outlet 33 + xb) Air Fani) Standard air volume (Nm3/h)

inlet 52,712 (Dry base)outlet 52,712 (Dry base)

ii) Standard air temperature inlet 33

outlet 33 + x

3) Description:

a) Air blowerThe air blower is coupled with the motor and steam turbine on the same axis.

In starting up, the blower is first driven by the motor and when generated steam is available for the turbine is driven by the steam turbine and motor. And so, the load on the motor decrease gradually.

After no load, of motor is required the electric source of motor is cut off and the blower is driven only by the steam turbine.

After no load of motor is required the electric source of motor is cut off and the blower is driven only by the steam turbine.

As regards the methods of starting up, and its normal operation, follow the specified instructions presented by us. In any event af an abnormal phenomenon, the blower will, as a matter of course, stop operating as its interlocking protective device works. However, if operators find any other abnormality in the course of patrol, they

should report it to their supervisor at once or if they determine the case is urgent, they will have to take emergency action to stop the operation.

Failure of air blower has so much serious effects on the entire production process that operators should most carefully keep watching on the condition of the blower. The air pressure at the inlet and outlet of air blower must be recorded as specified, and the tendency of its increase must be kept in mind. The decrease of the air pressure at the blower inlet is a result of plugging of the filter installed at the blower suction. In case the pressure decreases so badly as to prevent the proper operation of blower, the filter must be cleaned or renewed. The delivery pressure of the blower will gradually increase. In this connection, operators must always have a complete knowledge of the location of the increase and for what cause it has increased. The purpose of this air blower is to feed the air into the drying tower.

b) Air fanThe air fan functions to send air to the 1st and 2nd heat exchanger. As regards

the methods and notes of operation, follow the specific instructions presented by the manufacturer of the equipment. A filter is installed at the suction of the fan, and it must be cleaned or renewed when it becomes no longer able to pass sufficient air.

PHOSPHORIC ACID PLANT (PA-1 & PA-2)111. DETAILED DESCRIPTION OF THE PROCESS

1. Feeding of Raw Materials

1.1 DescriptionPhosphate rook ground to specifications is fed to the ROCK WEIGHER (M-2304) VIA The Ground Rcck Bin (V-2204).

The feed rates of 98% sulfuric acid and dilution water are controlled in conjunction with the free H2SO4 concentration of the product acid.

In the Dilution cooler (E-2301), the excess heat is removed with cooling water.

The P205 concentration of weak phosphoric acid returned to the reaction system from the FILTER (M-2401) is regulated as required and metered before feeding the PREMIXER (V-2302).

1.2. Operating Condition

1.2.1. Ground Rock Feeding (1) Requirements

(a) Particle size of ground rock minimum 90% thru 100 Tyler mesh minimum70% thru 200 Tyler mesh.

(b) Rock analysis Prior to feeding of the ground rock, analyses of the following components

should be made: moisture CaoP2O5

SO3

(c) Weighing accuracy 0.5% integral 2% instantaneous

(d) Rock feeding method The feeding of the rock should be continuous and at a constant rate, consistent

with the feeding of the acid. This is necessary to prevent an imbalance of the rock/acid ratio taking place locally or of short duration, as the rock is fed into the PREMIXER (V-2302).

(2) Outline of Operation: The ground rock is conveyed from the grinding system and fed into the

GROUND ROCK BIN (V-2204). The level of ground rock in the GROUND ROCK

BIN (V-2204) is kept constant by the over flow system and the ground rock is fed to the ROCK WEIGHER (M-2304).

The ground rock is weighed by the ROCK WEIGHER (M-2304) to the accuracy specified above, maintaining continuous and constant rate feeding. It is desirable to check the accuracy of the integrating mechanism of the ROCK WEIGHER (M-2304) every day periodically.

1.2.2. Sulfuric Acid and Return Acid(1) Requirements (a) Concentration of sulfuric acid feed

Standard 75% H2SO4

Permissible deviation of concentration from the actual operation design

0.4% range

(b) Concentration of return acidPermissible deviation of concentration from the actual operating design

0.5% range (c) Metering accuracy

For the 98% H2SO4, dilution water and return acid each

0.5% integral 2% instantaneous

(d) Mixed acid Prior to feeding to the PREMIXER (V-2302), the return acid and the sulfuric acid should be mixed.

(e) Temperature control The temperature of diluted sulfuric acid is controlled by adjustment of flow rate of cooling water to the DILUTION COLLER (E-2301) automatically, and the index set of the temperature controller (TRC-2301) should be adjusted so as to maintain the temperature of the PREMIXER (V-2302) at the designed level.

(2) Outline of operation98% sulfuric acid is diluted to 75% H2SO4.98% sulfuric acid and dilution water are metered and mixed, and the dilution

heat generated is transferred to cooling water in the DILUTION COOLER (E0-2301).

After cooling, the temperature of the diluted acid is usually about 70-80c. This temperature is variable depending on the ambient temperature, the rate of rock decomposition in the PREEIXER (V-2302), condition of air suction and on any heat into or out of the PREMIXER (V-2302). The flow rate of the cooling water is regulated by a value controlled by the diluted sulfuric acid temperature recording controller (TRC-2301).

The return phosphoric acid is adjusted to a designated level of P2O5

concentration and metered within an accuracy of 0.5% before feeding to the PREMIXER (V-2302) through the MIXING BOX (V-2306).

The concentration of the return acid is normally set at certain concentration within the range of 19-20% P2O5, but the concentration to be fixed is varied depending on the P2O5 content of phosphate rock, the level of free H2So4 in the product phosphoric acid, the H2So4 concentration of the raw material sulfuric acid, and on other conditions.

The concentration of return acid is of course closely related to the P2o5 content of the resulting product acid. If the P2o5 concentration of the product phosphoric acid is found to be too low, the P2o5 concentration of the return acid should be raised. In the reverse situation, if the concentration of product acid is too high, the return acid concentration should be lowered.

The diluted sulfuric acid and the return acid are mixed in the MIXING BOX (v-2306).

Occasionally, it becomes necessary to remove gypsum sales from this MIXING BOX (V-2306). Sealing occurs in the following manner:

The return acid contains dissolved or super-saturated CaSO4. 2H2O and the temperature of this acid is about 45-50C under normal condition. When this return acid is mixed with hot sulfuric acid (about 70C), the temperature of the resultant mixed acid becomes much higher than the initial temperature of the return acid. (The temperature of the mixed acid is higher than the arithmetic mean of the temperatures calculated from the enthalpies of two acids.) The actual temperature of this mixed acid is between 60 and 75C. The solubility of CaSO4. 2H2O in the return acid decreases under higher temperature and consequently solid CaSO4. 2H2O is separated from the mixed acid.

At the same time, the So4 concentration in the mixed acid is very much higher than the SO4 content in the return acid, because of the addition of large amount of H2SO4. As a result of the common on effect of SO4, the solubility of CaSO4. 2H2O in the mixed acid decreases, and precipitation of CaSO4. 2H2O immediately takes place on the surface of the MIXING BOX (V-2306). As far as the acid feeds are concerned, it is necessary to check periodically:

(a) The concentration of the feed sulfuric acid using a hydrometer, and (b) The P2O5 and the SO3 contents in the return acid by analyses.

2. Digestion Stage

2.1 Description Ground phosphate rock is first decomposed with a mixture of sulfuric acid

and recycled weak phosphoric acid (return acid), to form phosphoric acid and semis table hemihydrates of calcium sulfate. This reaction takes place in the PREMIXER (V-2302) and the DIGESTERS (V-2303), under carefully controlled conditions of

reaction. These conditions are associated with the following factors. individually and in combination:

Reaction temperature Combined H2SO4 and P2O5 concentration of the acid mixture. Percentage decomposition of phosphate rock attained under this stage. So3/CaO ratio of the slurry. Total retention time in this stage, i.e. the reaction time.

Factors (1) and (2), individually and in combination, have a significant effect on the proper formation of hemihydrates calcium sulfate. The total concentration of acid mixture is dictated by: the product acid concentration, the permissible solid concentration of the phosphoric acid-gypsum slurry, the heat balance, and the water balance of the reaction. Conditions are selected so as to allow the decomposed rock to form hemihydrates of calcium sulfate only.

The relationship between the reaction temperature and the acid concentration was originally investigated by seven Nordengren. Studies made by Nissan have cleared that the acids concentration required for the formation of hemihydrates in the Nissan Process is defined properly to the combined P2O5 and H2SO4 concentration as shown in Figure 2, rather than P2O5 concentration alone as has been conventionally understood. Contrary to the conventional approaches, in Nissan Process the temperature under this decomposition stage is so selected that if falls in certain range of 3-20C higher than the transition temperature shown as a transition curve in Figure 2, in order to prevent direct formation of dehydrate gypsum. Such optimum operating conditions have been established in the Nissan Process as a result of extensive laboratory researches.

Factor (3), the percentage of decomposition, has also an important bearing on the application of the Nissan Process. Under the decomposition state, a certain minimum percentage of P2O5 in the phosphate rock must become water soluble. This percentage is defined by a formula:

% decomposition =

Where A = Total P2O5 in gypsum cake B = Water sol. P2O5 in gypsum cake C = Total Cao in gypsum cake X = Total P2O5 in phosphate rock Y = Total Cao in phosphate rock.

It has been found that in practice, the percentage of decomposition should be in a certain range as dictated by the rock type at the end of this stage. At a percentage of decomposition much lower than the permissible minimum limit, the phosphate rock either unattached or partially attacked by the acid mixture reacts with the acid to form dehydrate gypsum directly in the subsequent crystallization stage. That is, inadequate decomposition stage would result in incomplete final decomposition at the end of the crystallization stage, and the dehydrate gypsum cannot be grown to sufficiently large size. The objectives of the process-high P2O5 recovery and production of quality gypsum-would be impaired.

On the other hand; a percentage of decomposition much above the permissible maximum limit implied possible formation of the hemihydrates in its stable form immediately after feeding. If this occurs, hydration in the crystallization stage could proceed only very slowly, and the result would be formation of fine gypsum crystals of varying size possessing poor filtering properties. Factor (4), the So3/CaO ratio of the slurry, also influence the final decomposition and particularly the formation of large, well-shaped crystals crystals of gypsum.

Even if H2SO4 is deficient, when a sufficient quantity, when a sufficient quantity of ortho-phosphoric acid is present to attack the phosphate rock, the percentage of rock decomposition can be expected to reach to a level desirable under this stage, however, in the following crystallization stage, satisfactory results could not be expected. It is assumed that the formation of monocalcium phosphate and particularly declaim phosphate as a result of insufficient H2SO4 present plays a role in inhibiting the formation of gypsum crystals free from declaim phosphate (in solid solution with the gypsum), during crystallization of the hemihydrates calcium sulfate to dihydrate gypsum.

Factor (5), the total retention time in the decomposition state, is associated with the stability of hemihydrates calcium sulfate. The Nissan Process requires hemihydrates calcium sulfate to the formed in this stage. The hemihydrates state should be a transient stage which is followed by formation of dehydrate gypsum through hydration and recrystallization. Limiting and securing the retention time of the slurry under this stage as required—just sufficient to effect the necessary reaction a hemihydrates calcium sulfate is produced which has an active surface of easily soluble, and of accelerated hydration and recrystallization in the recrystallization stage which follows.

In summary, the important process conditions which are required to the decomposition stage are as follows:

(1) Optimum reaction conditions must be maintained to form hemihydrates of calcium sulfate and exclusively the hemihydrate.

(2) The minimum percentage of rock decomposition must be attained as required with adequate supply of H2SO4.

(3) Finance The fineness of the ground rock has a definite influence on the decomposition

percentage of rock under the limited time and temperature of the decomposition. Therefore a specification on the fineness of the rock is clearly stated to maintain the minimum requirement of the process. Namely the required fineness is 90% through 100 mesh and 70u% through 200 mesh.

If the fineness of the feed rock is coarser than the standard conditions as specified, the proper decomposition of the rock may not be reached in this stage, consequently the unrecompensed rock with hemihydrates is placed under the reaction conditions of forming of dehydrate of gypsum that is quite undesirable and reduces the advantage of the hemi-dehydrate method.

On the other hand, if it is finer, then this naturally means the waste of an electric power for the surplus grinding of the rock, concurrently this might, result in the extraordinarily high decomposition of the ground rock which is possibly correlated with a stabilization of the hemihydrates of calcium sulfate under high temperature. Hence the maintenance of the proper performance of grinding is one of most important practices.

(4) Decomposition of rock must be carried out in the possible shortest time to prevent the hemihydrates from stabilizing.

(5) The retention time must be as short as possible but sufficient to get the proper decomposition percentage.

2.2. Operating Condition

2.2.1 Requirements (1) Temperature of slurry in PREMIXER (V-2302)

Standard - 90CAccuracy of temperature control - 2C

(2) Temperature of slurry in DIGESTERS (V-2303) Standard - 90 -98CMaximum - 100Minimum - 85

(3) Decomposition percentage of rock standard - 80-90%

(4) Hydration ratio of CaSO4

Standard 0.5-0.7

2.2.2 Outline of Operation: Instantaneous and complete mixing of the ground rock and the mixed acid,

under vigorous agitation, is effected in the PREMIXER (V-2302).

As the slurry from the PREMIXER (V2302) flows through the decomposer, and semi-stable CaSO4. 1/2H2O is formed. The slurry overflows from the LAST DIGESTER (V-23033) into the CRYSTALLIZER No. 1 (V-2304A).

The temperature of the PREMIXER (V-2302) is controlled, by aid of a temperature recording controller (TRC-2301), by varying the temperature of the feed sulfuric acid.

The temperature of the DIGESTERS (V-2303) should be kept about 90-98C by regulating the volume of draught air effecting surface cooling of the slurry in these tanks.

In the course of operation, care should be taken to avoid the following troubles:

(1) Rock dusting from the PREMIXER (V-2302) out through the duct. (2) Choking of the rock chute (by building-up of wetted ground rock).

(3) Accumulation of the ground rock along the baffle plate, deposit of rock on the baffle plate, or formation of blocks of damp unrecompensed ground rock in the PREMIXEER (V-2302).

(4) Clogging of exhaust gas duct. (5) Overload of agitator motors (especially of PREMIXER) caused by

accumulation of heterogeneous ingredients in the feed rock or lf small particles of siliceous materials formed at the bottom of tanks by acidulation of the rock.

If any of these troubles are found, remedial measures should be taken. It is necessary to periodically check the decomposition percentage of the rock, hydration ratio of CaSO4, SO3 and solid contents of the slurry.

3. Crystallization Stage:

3.1 DescriptionIn the crystallization stage, the slurry proceeding from the decomposition

stage, containing hemihydrates of calcium sulfate, is recrystallized and thereby hydrated to form gypasum (CaSO4. 2H2O).

The slurry of decomposed phosphate rock is introduced in to the three CRYSTALLIZERS (V-2304). Near the point of entry, the slurry is mixed with the seed slurry recycled from the CRYSTALLIZER No.3 (V-2304C). As the slurry flows along the trains of the CRYSTALLIZERS (V-2304), it is gradually cooled to maintain an optimum declining temperature gradient for recrystalization and hydration.

The solubility of calcium sulfate in its hemihydrates state rises rapidly with a drop in temperature. The solubility of dihydrate calcium sulfate with the maximum at about 50C is far less then that of the hemihydrates. In the crystallization stage, the slurry of relatively high-temperature containing hemihydrate calcium sulfate is cooled to a temperature below the hemihydrate dihydrate transition point. See Figure-2. At this point, the solubility of the hemihydrates increases considerably. Generally, the difference in solubility serves to accelerate the crystallization of the hemihydrate to dihydrate gypsum, and the solubility difference is mainly a function of temperature. In the actual operation of the Nissan Process, however, the solubility difference does not directly act as a motive force. The recrystallization of the hemihydrate to the dihydrate is dependent not only on the temperature but also on the ratio of the recycled seed slurry and the ratio of the new slurry feed respectively to the slurry retained in the CRYSTALLIZERS (V-2304). The actual motive force promoting the recrystallization is subject to the degree of super saturation of dehydrates gypsum.

The hydration of hemihydrates calcium sulfate and the crystallization of the dihydrate are frequently influenced by minor constituents of the phosphate rock, such as metallic sesquioxides, SiO2, fluorine and organic matter. These minor constituents also affect the crystalline form of the recrystallized gypsum.

As it is apparent, considerable hydration heat is generated in this stage, necessitating a fairly large quantity of heat to be removed. This is accomplished in practice by air cooling.

In the crystallization stage, the following factors are to be considered:

(1) Retention time (2) Hydration temperature(3) Recycle ratio of seed slurry (4) Free H2SO4 content in filtrate acid.

The most important in the Nissan Process can be said to be the factor (1).

In this case where certain amount and varied amount of recycle of the reactant substances is consistently applied, the term “retention time” is defined as the average retained time of the slurry in series of reaction vessels ignoring the effect of such recycle. This is expressed as;

Q = V/F Where Q = Retention time

V = Effective volume of CRYSTALLIZERS (V-2304).F = Feed rate of slurry from the decomposition stage to the CRYSTALLIZER

No.1 (V-2304A).

In the crystallization stage, sufficient retention time must be allowed in order to complete; further decomposition of phosphate rock, conversion of the hemihydrates to form dihydrate gypsum, formation and growth of new gypsum crystals, recrystallization of the hydrated gypsum on seed crystals present in the recycle slurry. The necessary retention time in the crystallisation stage is determined based on the information of the reactivity of the rocks to be used, or if required, on laboratory studies using specially developed beaker-test facilities or a pilot plant.

If hydration is not sufficiently completed in this stage, it would continue during the filtration stage, resulting in too quick blinding of the filter cloth.

If crystallization is not adequate, a slurry containing mixture of fine and coarse crystals would be produced, impairing filtrated after a short time as a result of blinded filter cloth.

Factor (2), the hydration temperature, is also important in the Nissan Process. As previously mentioned, at a low temperature, dihydrate gypsum would be formed under the same condition that the P2O5 +H2SO4 concentration is held constant. Referring to P2O5+H2SO4 concentration, the temperature required for the formation of dihydrate gypsum from hemihydrate calcium sulfate can be found on the transition temperature curve. For instance, when the product phosphoric acid is to contain 30 percent P2O5 and 3.5 percent H2SO4 (total acid 33.5 percent), the temperature required for the formation of the dehydrate gypsum is below 80c approximately. This temperature taken from this diagram, however, is somewhat higher than the actual temperature applied in the Nissan Process. This difference is due to the fact that the rate of hydration of the hemihydrate calcium sulfate is

accelerated at a temperature lower than the conversion point. On the other hand, for ideal crystallization of gypsum, enabling effective filtration, the degree of super saturation of the hemihydrate calcium sulfate should be held at a low level. As it is well known, when the degree of super saturation is too high, numerous crystals of very fine size are formed--- a tendency undesirable for manufacture of phosphoric acid. The actual process conditions applied to the crystallization stage have been established on consideration of the above two factors. That is, in the CRYSTALLIZER No.1 (V2304A), in order to minimize hemihydrate super saturation and to prevent formation of fine crystal nuclei, a higher temperature than optimum is applied. In the CRYSTALLIZER No.3 (V-2304C), a temperature necessary for quick and complete hydration is selected.

With respect to the Factor (3), the ratio of the recycle slurry to the new feed slurry is between 1: 1 and 2:1. The slurry recycled from the CRYSTALLIZER No.3 (V-2304C) accelerates crystallization by supplying seed crystals. Recycling of mature slurry is effective in accelerating the hydration and crystallization of the hemihydrates calcium sulfate. When a proper recycle ratio is selected, hydration can be easily promoted two times or quicker, as compared with conditions of no seed recycle or improper recycle. The degree of calcium sulfate super saturation is actually dictated by the ratio of the recycle slurry to the new feed slurry to a large extent. Therefore, the control of crystallization also can be said to be dependent on this ratio.

It is to be noted incidentally that the recycle ratio is related to the presentation time of the newly fed slurry. In other words, if no recycles is made, all the slurry fed to the CRYSTALLIZERS (V-2304) should have uniform designed retention time. On the other hand, if the recycle ratio is very high, some amount of the new slurry is liable to pass through the reaction vessels without having been remained for sufficient time in the crystallization stage. In the latter case, the result would be the continued hydration during the filtering stage. Accordingly, on the recycle ratio, a proper balance between the desired effects of the seed crystal land the adverse effect of increased discharge of immature slurry must be maintained.

Factor (4), Free H2SO4 content in the filtrate acid, is important for the ideal growth of gypsum crystals and for the ultimate high percentage decomposition of the rock. In addition, a high percentage decomposition of the rock. In addition, a moderate degree of excess free H2SO4 in the filtrate acid provides a buffering effect when operational turbulence occurs. Such excess free H2SO4 can, in particular, absorb imbalances in raw material feeding.

In Summary, the important conditions applying to the crystallization stage are:

(1) As far as possible, to effect quick and complete hydration of hemihydrates calcium sulfate.

(2) To form dihydrate gypsum crystals, permitting quick and clean separation of the filtrate acid.

3.2. Operating Condition: 3.2.1 Requirements:

(1) Temperature of CRYSTALLIZERS (V-2304). Standard 68-50C Maximum 70CTypical temperature gradient CRYSTALLIZER No. 1 (V-2304A) 67CCRYSTALLIZER No. 2 (V-2304B) 59CCRYSTALLIZER No. (V-2304C) 55C

(2) Decomposition percentageMinimum 98.0%

(3) Hydration ratio Minimum 1.90

(4) Slurry recycle ratioRecycle/New feed = 1:1 to 2:1

3.2.2 Outline of Operation: The hot slurry from the DIGESTER No. (V-2303B) is fed to the CRYSTALLIZER No.1 (V-2304A) through an overflow trough. The slurry in the CRYSTALIZER No.3 (V2304C) is pumped to the SLURRY DISTRIBUTOR (V-2401), and an appropriate portion of the slurry in metered and recycled to the CRYSTALLIZER No.1 (V-2304A). As the slurry flow through the three CRYSTALLIZERS (V-2304) in steps, air cooling is affected.

The total volume and the distribution of air to each CRYSTALLIZER (V-2304) are controlled by dampers on the air lines.

The exhaust gas is drown by the CRYSTALLIZER EXHAUST FAN (K-2303) and the pressure in each CRYSTALLIZER (V-2304) is kept slightly negative. The suction volume of the exhaust gas from each CRYSTALLIZER (V-2304) is regulated by a damper in the exhaust gas ducts. It will be necessary occasionally to clean out the ducts.

4. Filtration Stage

4.1. Description: The slurry discharged from the CRYSTALLIZER No.3 (V-2304C) is fed into

the FILTER (M-2401), and after separation of the 1st filtrate, the filter cake is given two counter-current washes.

The wash water is usually preheated to about 50-60c. The 2nd filtrate is returned to the digestion stage to be used for the

decomposition of rock. The P2O5 concentration of this 2nd filtrate, called as the return acid, is regulated by adding a portion of the 1st filtrate.

4.1.1 Washing of Filter Cake: Generally discussing, washing of filter cake on the vacuum filter is usually

well simulated by batch wise washing. That is; the soluble matter contained in wet filter cake is displaced by washing medium, stepwise, off the filter cake. And the washing effect is dependent mainly on two factors below, under the condition of the

cake thickness and the vacuum applied being considered to be constant. These factors are E; displacement efficiency, and n; washing ratio. Washing ratio is defined as

And displacement efficiency, E is defined as the percentage of soluble matter washed off the filter cake to the total soluble matter before washing when washing ratio n = 1 is assumed to be applied. And this factor E is characteristic to the filter cake itself--- in gypsum cake washing, this is depending on the crystal size, uniformity of crystal size distribution, etc.

Taking a remaining ratio of soluble matter in the cake, expressed as R, then R is given as follows:

R = (1 – E/100)N.

The value of R becomes less when the values of E and n get higher. As the value of E is usually characteristic to the gypsum cake of which physical properties are definitely influenced by the digestion and crystallization conditions, it remains unvaried in filtrating stage, hence measures shall be taken to increase the value of n to improve the extraction percentage of acid.

Experimentally this relationship can be easily tested, however some difference is always observed between the theoretically calculated figure and the actual performance figure in the range of higher n value.

At the same time, it must be particularly noted that R means the remaining ratio of soluble matter to the initial content of such matter. Accordingly, the important point is to keep the soluble matter content as low as possible prior to washing of the cake.

As would be clear from the above discussion, low water soluble P2O5 in ex-filter gypsum can be achieved through the following steps:

(1) Effecting of utmost liquor separation of cake on the 1st section of the FILTER (M-2401).

This means the substantial decrease of water soluble P2O5 in the cake prior to the washing of it, and at the same time, the washing ratio, not the second section is increased because of the eventual decrease of the volume of liquor in the cake even the volume of wash acid is constant.

(2) Effecting of maximum liquor separation from the cake on the 2nd

section. First washing is definitely predominating the washing effect. If the

washing is poor under this stage, even though thorough washing could be expected in the following stage, then the overall wash effect is far inferior to the contrary case. The good separation of liquid under this stage means the low water soluble P 2O5

content on which the washing effect of the second wash is subject to.

4.1.2 Thickness of Filter Cake On the other hand, the cake thickness has significant meaning on the washing

effect. Cake washing time is the required period from the time of pouring of wash liquor on the cake to the time of disappearing of wash liquor from the surface of the cake. Further appropriate cake drying time (drainage of the cake), which is characteristic to the filter cake and correlating with the thickness of such cake, is also necessary subsequent to the cake washing time and prior to the further washing of it.

As is clarified in the above paragraph, minimizing of remain water soluble P2O5 is subject to the lowering of liquor content in the filter cake prior to its washing. Under the production requirement that certain amount of dry solid must be separated within certain limited time, the optimum cake thickness must be determined as a result of the adequate combination of

Cake formation time 1st filtration section Cake drying time Cake washing time 2nd filtration section Cake drying time Cake washing time 3rd filtration section Cake drying time

Cake thickness is of course inversely proportional to the time required for one cycle of the FILTER (M-2401).

Based on the observed results, in practice;

(1) The actual cake washing time gets longer than the time calculated as proportional to the cake thickness, particularly if the cake thickness gets more.

(2) the cake drying time is proportional to the cake thickness or gets a little longer than the time proportional to the cake thickness.

Accordingly, the above results indicate the direction that the filter rotation speed is to be high. Or it means that the cake thickness is thinner, the liquor content in the filter cake gets less, within the allocated time-calculated from the required amount of solid to be separated within required time.

However a consideration is to be made for a time required for the mechanical removal of the filtrate from the filter leaf.

4.2. Operating Condition:

4.2.1 Requirements(1) Temperature of wash water

Standard 50-60C(2) Accuracy of flow meter

For slurry, wash acid and wash water 2%

(3) Accuracy of level indicator

2%(4) Density meter for return acid

Sensitivity 0.001 Accuracy 0.002

(5) Thickness of filter cakeMinimum 30 mm

(6) Vacuum required Maximum 160 mm Hg abs.

4.2.2. Outline of OperationMature slurry is pumped, in excess flow rate, to the SLURRY

DISTRIBUTOR (V-2401) located above the FILTER (M-2401).

The slurry to the FILTER (M-2401) is metered and the feed rate is controlled by the FRC -2304, and the flow rate index is altered automatically according to the level change in the CRYSTALIZER No.3 (V-2304C).

The hot water from the HOT WATER TANK (V-2402) is metered by the FI-2306 fed to the 3rd section of the FILTER (M-2401).

The distribution of the hot water on the filter cake should be checked periodically for uniformity. The flow rate of the hot water is altered by the LICA-2307 automatically. This adjustment is necessary for maintaining the water balance in the process. The excess or shortage of wash water flow rate can also be judged by checking the specific gravity of the second and third filtrates.

The third filtrate flows down into the 3rd SEAL TANK (V-2410), where the specific gravity is measured. This third filtrate pumped up to the 2nd section of the FILTER (M-2401) is metered with the FI-2305, and the flow rate of the wash acid should be adjusted periodically according to the level change in the RETURN ACID TANK (V-2409).

The return acid is prepared by mixing a portion of the product acid with the second filtrate, to adjust the P2O5 concentration of the return acid, and is sent to the RETURN ACID TANK (V-2409). The concentration of the return acid is measured and controlled by the DRCA-2301.

The gypsum cake from the FILTER (M-2401) is repulsed with water in the GYPSUM SLURRY TANK (V-2414) and discarded by the GYPSUM SLURRY PUMP (J-2405).

5. The whole Process

5.1 P2O5 Yield In the Nissan Process, the overall P2O5 yield can be maintained to 97-98% for

long periods continuously. But, to do this, it is necessary to secure the fundamental operational conditions described relevant to each stage. and moreover to take effective and proper measures in the actual operations.

The overall P2O5 yield fluctuates over day, so that it is advisable to calculate the yield on the basis of actual measurements at regular intervals for the purpose of determining the production. In doing so, the P2O5 in slurry should be calculated on the basis of analytical value for operational control, and the P2O5 in acid on the basis of P2O5 concentration found from measurement of specific gravity using ANNEXED DATA Fig. 1 “Relationship between specific gravity and P2O5 concentration of phosphoric acid.”

Today’s production = today’s stock –yesterday’s stock + today’s carry over

Today’s production Yield (%) = 100

P2O5 in ground rock used today

5.2. Regular Shutdown for Kaintenance:The normal on-stream days through a year of the Nissan Process planet are

340 days. The recommended practice of scheduled plant shutdown for maintenance is 3 days shutdown every other month and 5 days shutdown every half a year at minimum.

Planned and regular shutdowns for maintenance are indispensable to preserve the production capacity and to expect the long trouble free production time and the high P2O5 recovery.

REACTION-I & REACTION -II PLANTReaction Plant-I (RA-I):

In this plant, only TSP is produced. Triple Super Phosphate is manufactured by decomposition of rock phosphate ground to fineness (50% pass through 200 Tyler mesh in an air swept ball mill, phosphoric acid (50% P2O5) in Reaction Den under standard conditions of temperature and flow rate. The Den product is known as green TSP. Green TSP is fed in a Granulator through conveying system, where granules are formed through the principle of agglomeration with steam and process water. Granulated TSP is then dried with hot air generated by combustion of natural gas and then bagged to get finished product of Granular TSP.

Reaction: Ca3 (PO4)2 + H3PO4 + 4H2O = 3CaH4 (PO4)2.H2O

Reaction Plant-II (RA-II):In this plant both TSP and SSP age produced. Same process is followed

producing TSP. However, to produce SSP the following process is followed:

SSP is manufactured by acidulating finely ground phosphate rock with 70-75% Sulphuric acid in Reaction Den under standard conditions of temperature and flow rate. The out let Den product known as green SSP is kept in a curing house for about three weeks for completion of the reaction. The cured SSP is then dried by natural air and bagged to get finished product of powder SSP.

Production of SS in powder form started since 1988 in Unit no. 1, however, with the rising trend of use of SSP in agriculture, Arrangement was made to produce SSP through Unit No.2 also.

Reaction:

TRIPLE SUPER PHOSPHATE (TSP) & SINGLE SUPER PHOSPHATE (SSP) PLANT

TRIPLE SUPER PHOSPHATE (TSP) PLANT

PROCESS DESCRIPTION:

TSP is manufactured by the Board Field Den process. In this process ground rock phosphate approximately 80% passing through 200 mesh is mixed with 48 to 50% P2O5

content phosphoric acid in a Cone Mixer (Formerly in a paddle ribbon type mixer).

The amounts of rock phosphate and phosphoric acid fed are designed depending on the Chemical analysis of the two raw materials and the quality of TSP and temperature of reacting slurry to react and solidify.

The slurry gets increasingly porous solid as it proceeds to the outlet of the Den. Sliding boards go back and forth along the both side walls around the inlet of the Den. This is intended for preventing adhering of slurry which cloggs on the side walls and does not move toward the outlet of the Den.

The reaction product is cut into small pieces at the tip of the Den outlet by a rotary cutter.

The retention time of the reaction product in the Den is generally about 20 minutes, the velocity of the Den conveyor is regulated in accordance with the changes in the reactor velocity.

The reaction proceeds in the Den at about 90% (A.P2O5/ T.P2O5) and the adhering moisture amounts to 10-12%. The Den product (Green TSP) is passed to curing pile of to the Granulator directly by means of a series of conveyor belts. Green of Semi-cured TSP having moisture content about 8% is granulated in the Granulation plant with process water and steam by the process of agglomeration and then bagged in polythene inserted polypropylene bag, each of 50 kg.

REATIONS:-The basic reaction governing the process may be written as follows :-

1. Ca3 (PO4)2 + 4H3PO4 + 3H2O = 3CaH4 (PO4)2.H2O(Mono calcium (phosphoric Acid) Tri calcium phosphate (TSP)Phosphate)

The mono calcium phosphate produced is soluble in water and therefore, the main nutrient ‘P2O5’ is readily available to the plants when applied to the soil.

Several side reactions take place during manufacture of TSP, as represented by the following reactions:-2) Ca3(PO4)2+H3PO4+6H2O = 3CaHPO4. 2H2O

(Di-calcium phosphate)3) Ca3(PO4)2+2H2SO4+ H2O = CaH4(PO4)2. H2O +2 CaSO4.4) 2CaF2+4H3PO4+SiO2 = SiF4+ 2CaH4 (PO4)2.H2O5) Al2O3(or Fe2O3)+2H3PO4 = 2 AlPO4. H2O (or 2FePO4.H2O) + H2O

Eqn. No. (2) mentioned above produces di-calcuum phosphate which is the desirable product. However, equation no (5), produces Aluminum of Ferric phosphates which are undesirable compounds, as they cause bad physical properties in the resulting product such as, stickiness, bard mass formation etc.

SINGLE SUPER PHOSPHATE (SSP) PLANT

Process Description:Single Super Phosphate (SSP), also called normal or ordinary super phosphate is the oldest source of phosphate for fertilizer. It has a P2O5 equivalent of 16-20%.SSP is manufactured by the same Broad Field Den process like TSP. There is no intrinsic difference between the manufacturing processes of TSP and SSP. The only difference is in the raw materials used. TSP is manufactured by acidulating finely ground Rock phosphate with 48-50% P2O5 content phosphoric acid where as SSP is manufactured by acidulating finely ground Rock phosphate with 70-72% Sulphuric acid. As sulphuric acid of 98.5% strength is produced in the sulphuric acid plant, it is required to dilute this acid is maintained at 70-72 0 C.The basic reaction governing the process may be written as follows :-Ca3(PO4)2 + 2H2SO4 + 3H2O = CaH4(PO4)2.H2O + 2CaSO4 + 2H2O

GRANULATION PLANT

Cured TSP from the curing pile is transported with a shovel truck to a hopper. This hopper is equipped with a grid to prevent too big lumps from being introduced into the system and disturbing the proper operation of the extraction belt conveyor located below the hopper.

Via a belt conveyor the cured TSP is transported to a bucket elevator. To prevent metal particles from entering the granulation plant, where they will remain in circulation, a magnet is installed above the belt conveyor.

At the bottom of the elevator a double cage mill type crusher is installed to ensure the TSP powder fed to the granulating plant is of the proper size. The TSP powder from the bucket elevator is fed, via a weighing belt, to the granulator. This weighing belt is equipped with a weighing device, which controls the speed of the extraction belt conveyor below the hopper, which controls the speed of the extraction belt conveyor below the hopper, to ensure a constant feed to the granulating plant.

The fine material recycled from the screens, together with dust from the several cyclones, is also weighed and fed to, the granulator. In this granulator, some LP steam and process water are added.

The LP steam is required to increase the temperature of the TSP, while some additional water is required to provide the liquid phase/solid phase ratio necessary for satisfactory granulation.

Granulation results in a decrease in the specific surface area of the TSP. The ratio of recycled product to cured TSP product fed to the granulator is about 1.

By means of a fan vapours from the granulator are removed via the granulator scrubber, and sent to the dryer scrubber. Directly after the granulator hood, a sprayer is installed in the vapour line to prevent blocking of the line by dust and water vapour.

The granules leaving the granulator are dried in a rotating drying drum (existing) in which they are contacted with hot air of about 4250C. Suring the drying stage the moisture content of the granulated TSP decreases from about 12% to about 4$. The product flow and the hot air flow are co-current.

The air temperature about 900C after the dryer controls the fuel oil feed to the burner of the dryer.

After drying, the granules are transported by a belt conveyor to a bucket elevator. This bucket elevator provides the feed to the coarse screen. The oversize product is screened off and sent to the double cage mill type crusher, located at the bottom of the bucket elevator.

The remaining product is dosed to a fine screen. The undersize product is separated off and recycled to the granulator by the recycle belt conveyor. The on-size product is sent to the storage via a belt conveyor. The on-size product is sent to the storage via a belt conveyor.

This belt conveyor is equipped with a weighing device to measure the amount of final product leaving the plant.

The off-gases from the drying drum pass the cyclones and are sent by a fan to the dryer scrubber.

In the cyclones, the bulk of the dust entrained with the air from the drying drum is removed and discharged to the recycle belt conveyor.

Before entering the dryer scrubber, this air is wetted by a sprayer to promote dust removal in this scrubber, which is equipped with one wash-tray.

On top of this plate is a water layer, while at the bottom side sprayers are spraying water to prevent blockages. The required wash water is circulated by a circulation pump.

The screens, crushers and all discharge points are working under a slight vacuum to prevent dust emission in the plant. The air from this general dedusting

system is sent through a cyclone. A fan discharges the cleaned air to the dryer scrubber.

The dust removed in the dedusting cyclone is recycled to the granulator by the recycle belt conveyor.All dust suction points are equipped with a hot air injection to prevent blocking of the dedusting lines due to condensation.The hot air for the hot air injection is provided by an air heater and an air blower. Bagging System

The operations conducted in this system is as follows.

The dried T.S.P. can be the final product in terms of its chemical composition, but it is necessary to sieve and finely grind the lumps containing therein so as to bring the product into fine power.

In the course of this system, a large quantity of TSP dust is dispersed and, if it is left untreated, a loss will be caused in its production. Furthermore, it is undesirable for environmental health. It will be therefore required to collect these dusts.

Firstly, the heaped up stocks of TSP in the bulk storage are scraped with a shovel loader and put into the feed hopper.

From the feed hopper, the TSP thus scraped is fed divided to two TSP screens via product TSP conveyor.

The TSP is sieved on the screens. The undersize is stored in 2 hoppers and bagged with two bagging machines under them.

Packing is conducted in 25kg as well as 50kg jute bags containing each a polyethylene bag in their inside.

The jute bags thus packaged are sealed by two sewing machines their mouth and are transported to final product store house by the bag transfer conveyor and fork truck.

On the other hand, the over-side of TSP on the screen in transferred to the over-size crusher via over side TSP feed conveyor where it is finely ground.

Two crushers are installed here for alternate operation; the crusher in stoppage is cleaned of materials clogging to its inside.

The crushed TSP coming out of the crusher is again returned to the screen along with the dry TSP newly supplied to it by conveyors such as the over size return conveyor the above mentioned product conveyor and product TSP elevator.

TSP dust dispersing from these apparatus is suctioned by the exhaust fan and collected into the bag filter.

The suctioning parts for each bag filter are as follows:

TSP elevatorProduct TSPTSP screenBagging machine

The dust thus formed is suctioned by the exhaust fan for TSP screen and is collected on the halfway of its duct into the bag filter for TSP screen.

The dust formed in the over size crusher is suctioned by the exhaust fan for crusher and collected into the bag filter for crusher on the half way of the duct.

The dust thus collected is dropped on the product conveyor by the screw conveyor under the bag filter and conveyed to the screen through the above mentioned pass way.

The above mentioned reaction and the drying system are designed and installed in a function of 20 hrs/day operation, but the packaging system is designed and installed for operation of 12 hrs/day although the packaging quantity is 430 MT/day as with the prior process.

STORAGE CAPACITY

1. Raw Materials

1.1 Rock Phosphate godown capacity, length breadth:

Details Cap. Length breadtha) Rock phosphate godown capacity, No-1 20,000 MT 110M x 30.50Mb) Rock phosphate godown capacity, No-2 20,000 MT 42M x 85.25Mc) Rock phosphate godown capacity, No-3 20,000 MT 70M x 50Md) Rock phosphate godown capacity, No-4 12,000 MT 45M x 30MTotal = 72,000 MT

1.2 Rock Sulphate godown capacityDetails Cap. Length breadtha) Rock phosphate godown capacity, No-1 8,000 MT 30.50M x 45.70Mb) Rock phosphate godown capacity, No-2 15,000 MT 71.46M x 25.00MTotal = 23,000 MT

2. INTERMEDIATE PRODUCTS :

2.1 Sulphuric Acid Tank Cap.

Details Cap.a) SA Tank, No-1 (In SA-2) 2,000 MTb) SA Tank, No-2 (In SA-2) 2,000 MTc) SA Tank, No-3 (In SA-2) 2,000 MTd) SA Tank, No-4 (In SA-1) 1,000 MT

Total = 7,000 MT

2.2 Own Phosphoric Acid (48.5% P2O5)

Details Cap.a) CPA Tank, No-1 (In SA-2) 280 MTb) CPA Tank, No-2 (In SA-2) 280 MTc) CPA Tank, No-3 (In SA-2) 280 MTd) CPA Tank, No-4 (In SA-1) 800 MTTotal = 1640 MT

2.3 Imorted phosphoric Acid (52-54% P2O5) Tank cap.- 10,000 MT

3. Finished for ducts (TSP of SSP)

Bag Godown Cap.

Details Cap.a) Bag Gowown No.-1 1400 MTb) Bag Gowown No.2 1600 MTc) Bag Gowown No.-3 5200 MTd) Bag Gowown No.-4 6400 MTe) Bag Gowown No.-5 3400 MTf) Bag Gowown No.-6 7000 MTTotal = 25,000 MT POWER MANAGEMENT

1. TSP complex is 100% dependent on PDB power.2. There're two 33KV lines from PDB

One from Halishahar line (primary line) & one from Patenga line.There is another alternate 11 KV Halishahar line.

3. Main PDB incoming substation (transformer) line: 33 KV Outlet : 11 KV

4. Used transformer: 10 MVA (Power factor 0.8, 8MW capacity receiving & Transmission)

5. Total motor: 303, there're thee 3.3KV high tension motora. Ball-mill drive motor- 750 KWb. AA-II air blower motor - 500 KWc. Ball-mill circulation fan - 350 KW

One of them is 220v three phase motor. It is used in sections such as Electrical, workshop, grinding m/c.The rest of the motors are 222-400V three phase motors.6. Emergency diesel generator 400 KW for lighting load & emergency motor

supply.Emergency Diesel Generator ensures uninterrupted power supply in some of

the key sections like-

Boiler feed pumpPA-2 (Crystallizer agitator)Water Treatment (Sanitary pump, low pressure pump)

Specifications of the Emergency Diesel Generator-

Type P500 Volts 380KVA 500 Amp 759kw 400 pf 0.8Hz 50 Phase -3RPM 1500 Amp. Temp-410

Maximum demand of the factory is 4 MW & average load is 2.5-3 MW.

Instrumentation & Maintenance of Instrument

Different categories of instruments are used they are:1. Measuring & indicating instruments.2. Measuring & recording instruments.3. Controller.

The measuring devices measure different parameter. They are generally divided as follows:1. Pressure.2. Flow3. Level4. Temperature5. pH

6. Conductivity

The measuring instruments used to measure these parameter are:1. For measuring pressure:

Pressure gauge, Pressure transmitter, differential pressure gauge.I. Electronic- These are operated by using electricity 110V/24V-30vII. Pneumatic- These are operated by using fluid. Generally, these

pneumatic devices are computer controlled. It specification is 1.4 kg/cm2

air supply.

Electronic Signal - Control room(Output Signal)The signal varies from 4 mA to 20mA, where 4mA corresponds to O kg and 20A Corresponds to 40 kg.Pneumatic signal- Control room(output signal)It varies from 0.2 kg to 1 kg where 0.2 kg represents 0 kg and 1 kg represent 40 kg respectively.

2. To measure flow:* Differential pressure transmitter [It is used with orifice meter and high

accuracy].

* Electromagnetic flow meter (mostly used)

The parameters that are fed in EM flow meter are: Length Conductivity of fluid Sp. Gravity of fluid

This device generally consists of 3 parts: Detector Conductor IndicatorHowever, it has one problem when the device is out of order it is beyond repairing capacity are the components are replaced.

3. To measure level:Differential transmitter is used. It has two sides:

High side: It is attached to the side where level is indicated. Low side: It is attached to the atmosphere.

This device is capable of indicating the level of fluid directly

4. To measure temperature: Simple thermometer Thermocouple: Chromel-Alumel K-type is used. It can measure up to 2000.

Platinum- Iridium (P1). It has a measuring range up to 17000C.

Chromel-Alumel:The chromel-Alumel thermocouple, with a positive chromel wire and a

negative alumel wire, is recommended for use in clean oxidizing atmospheres. The operating range for this allow is 126020C for the largest wire sizes. Smaller wires should operate in correspondingly lower temperatures. Resistance Temperature Detector (RTD): It is used for lower range. Platinum

is used in the device whose accuracy is higher than that of thermocouple. It is used in PA-2 Plant.

5. To measure pH.It is flow-throw type device. It is used at cooling water lines and acid leakage

lines to determine contaminations and leakage.

6. Measurement of conductivity:Non- conductive Element/System is used. It is based on Faraday's law of EM

induction A. Coil is emerged in the acid and an emf is produced at both ends of the coil.Therefore, Emf is proportional strength of acid.

Control System:After measuring the process parameters signal is transmitter to controller,

which control valves, and thus controls the process parameter.JETTY & UNLOADING

Imported raw materials such as Rock Sulphur and Rock Phosphate are unloaded from ships in Jetty. From there they are directly carried by conveyer belts to the go downs and from which they are carried to the milling plant using the same mechanism.

Conveyer belts of different sizes and length, driven by motors, are used to transfer the raw materials and product sequentially from jetty.

Jetty Rock phosphate Go down (1,2,3) Rock Sulphur Go Down(1,2)

The whole mechanism can be understood by following the flow chart thoroughly.

JETTY FACILITY

1. Jm-1 A/E grab for ship Derrick.2. JO-1 Belt Conveyor on Jetty3. JV-1 A/D moving Hoppper

Client- East Pakistan Industrial Development corp.Manufacture No.-1-56-6-740Name of Plant- Jetty FAcilityItem No.-JM-1 A/EName of Unit - crab fro ship DerrickUnit Required - Five (5)Type - Signal role pull openigMaterial Handled sulfure/phosphate rockCapacity- 1.2m3

Weight: Grab-1350 kgBalance Weight-200 kgLoad (s.g.=1.3) 1560kgTotal - 3.110 kg

Principal dimensions : width - 1300mmOpening - 2370mmWorking height (bottom to hanger) max. 4700mm

Wire rope- JISG 3525 No.6Class B Dia. 16mm

UNLOADING SECTION EQUIPMENT

List of machines1. Crawlign Crane

Milling I

Milling II

2. Merrick Scale3. Transfer conveyor4. Distribution conveyor for rock storage (TSP-II)5. Distribution conveyor for rock storage (TSP-I)6. Distribution conveyor for sulphur storage (TSP-I)7. Distribution conveyor for sulphur storage (TSP-II)

Operating ConditionMaterial handled Sulphur/ Phosphate RockBulk Density 1.34 / 1.29Grain Size max.50mm / max. 12mmAngle of Repose 350 / 350

Temperature Ambient / AmbientPurpose Unloading of shlphur and phosphaterock from barge to moving hopper at Jetty.

Type SpecificationDiesel engine drive, full revolving, crowding mounted ISHIKAWAJIMA- KOEHRING clamshell crane, model 605-2A.

Engine Manufacturer model. Caterpillar- MITSUBISHI D 333A-T Water cooled, 4 cycles, pre combustion type, super charged.

Continuous Rated Output 137 PS/2200 rpmBucket Capacity 2.8m3

Lifting Speed 50.8 m/minRevolving Speed 3.4 rpmTravelling Sped 1.48 km/hrBoom Length 15.24mMax. Loading capacity 40 T at 3.7 m (as crane)Net weight (including bucket) 55,970 kgName of Unit MERRICK SCALEUnit required Operating ConditionMaterial Handled Sulphur / Phosphate RockBulk Density 1.34 / 1.29Angle of Repose 350 / 350

Grain Size Max. 50 mm/ Max. 12mmTemperature Ambient / AmbientWeighing Capacity 250 T/hrLocation Outdoors

Type SpecificationsBelt Scale

Weighing Range Max. 300 T/hrMin. 60 T/hr

Minimum Graduation 20 kgMax. Indication of Totalizer 9999.8 TWeight Length 2400 mmBelt Speed 85 m/minBelt Width 750 mmConveyor Slope 8.54'

Transportation Garage & Shovel Loader

1. Transport garage:Personnel involved in this garage:

Executive Engineer 1 Technician 6

There are total 8 transports that Transport Garage handles:

9 Cars

Bus 1Microbus 2Pickup 1Ambulance 1VIP Pazero 2VIP Car

2. Shovel loader garage:Personnel involved in this garage:Executive Engineer 1Asst. Mechanical Engineer 1Technician 16

There are:7-Shovel loader3-Cranes 1-Fork lifter

The shovel loaders are directly related with rate of production. The shovel loaders were at first imported from Japan but bow these are rented yearly basis from China. Although the life of all these machines are less due to the hazardous environment and heavy duty working and need to be serviced almost everyday.

The shovel loader handles per day:Raw materials 400 metric tons for TSP and 500 metric tons for SSP. A total of

900 metric tons per day.

Total handling per day is *900+700) metric tons 1600 metric tons.Therefore, 24 hr handling is 1600 metric tons. There are three shifts and each shifts handles 533 metric tons by 5-6 shovel loaders.

Shovel Loader/wheel loader withHard Top Cabin & Spare PartsTechnical Specification of Shovel Loader (Wheel Loader)1.0 Name of Item : Shovel Loader (Wheel Loader)2.0 Quantity : 2 (Two) Nos complete.3.0 Service : Transportation of Rock Sulfur/Phosphate TSP/SSP4.0 Bucket:1) Bucket Capacity : 2.0 M3 to 2.3 M3

(2) Bucket width : 2400mm to 2750mm(3) Bucket type : Heavy duty with both on tecth(4) Static tipping load straight : 7.0 MT to 12.0 MT(5) Operating weight : 10 MT to 15 MT5.0 Bulk density of handling materials:(1) TSP : 0.95-1.00 gm/cc(2) SSP : 0.85-90gm/cc(3) Rock Sulfur : 1.32 gm/cc(4) Rock Hpospate : 1.63 gm/cc6.0 Overall dimension :(1) Overall length (Bucket on ground position) : 6.8M3 to 7.5 M3

(2) Overall height:a. Ground to cabin top : 3.0 M to 3.5 M

d. Ground to exhaust pipe : Must be below from the top of cabin.c. Dumping height : 2.5M to 3.0M

(3) Overall width (Width over Tires) : 2.4M to 2.8M

7.0 Operating Specification:(1) Steering system : Articulated frame with hydraulic power steering.(2) Turning radius

(Center of the out side tire) : Maximum 5.9 meter.(3) Transmission Control system : Mechanical(4) Hydraulic control system : Mechanical8.0 Brake system:(1) Service brake : 4(Four) wheel hydraulic wet disc brake(2) Parking brake : Mechanical type hand operated

9.0 Bucket Operation:(1) Bucket lifting system : Hydraulic operated.(2) Hydraulic cycle time : Lifting at full load : 6.5 Sec. to 6.5 Sec.

: Lowering(empty) : 2.5 Sec to 4.5 Sec.: Dumping : 1.0 Sec to 2.0 Sec.

10. Engine Details :(1) Engine type : Water cooled, 4 cycle, 6 cylinder, Diesel engine,

Direct injection type without turbocharger.(2) i. Net available power at

fly wheel (B.H.P). : 125 KW to 140 KW at Maxm. Engine Speed 2500 RPM.

ii. Indicating Power : To be mentioned by the bidder.(3) Total displacement : Minimum 8000 cc.(4) Fuel injection pump type : Plunger/Bosch type

PAINTING, INSULATION & LUBRICATION

Painting is a coating which protects corrosion. It is done by scraping followed by finishing.Painting

First Cost (PbO + FeO) Enamel Coat

Process of Painting:1. Scraping the scraper2. Smoothing by the emery cloth (metallic)3. Cleaning by the thinner (adhesive material)4. Red oxide by the brush or spray gun5. Enamel paint (BERGER paints are chosen)

Insulation:Insulation

Inner (refractory acid proof rubber) Thermal Insulation(outer side- for getting sudden temp.)

Refractory Material:- AI2O3

- SiO2

- Fe2O3

Lubrication

It is used to resist friction.

Lubricant states - LiquidSolidGaseous

Sources of Lubricants:Crude oil can be of 2 types-1. Paraffinic2. Nepthanic

According to Basic Oil classification Basic oil classification-1. HVI 2. MVI oils 3. LVI oils(V. Index > 80) (45 < VI <80) (VI < 45)

According to state of lubricants.Lubricants are of 4 types-1. Liquid2. Semi-solid3. Solid4. Gaseous

Additives are used:1. To maintain existing quality2. To reduce unexpected events

Factors affecting life of additives-1. Temperature 2. Contamination3. Water4. Shear stress

This department is involved in controlling the quality of Rock phosphate, Phosphoric acid, Sulphuric acid, which are the ingredients of producing TSP and SSP. The quality of SSP and TSP is also observed.

Sulphuric acid is an intermediate product of this plant. The produced Sulphuric acid should have the strength 98.5%. They assess the sample Sulphuric acid to see if it has the required strength to avoid any undesirable situation.

Similarly, this department measures the strength of Phosphoric acid. The quality of TSP and SSP is also observed.

Several equipments are used for various purposed by this department. Their names and functions are given below:Name Function1. Moisture Oven Heating the material and remove moisture.2. Centrifugal Machine Separating solid and liquid part of mixture.3. Balance Measuring the weight of material accurately4. PH Meter Measuring the PH of material5. Spectrophotometer Measuring the percentage of phosphate, silicate by

using their color6. Electrical heater Heating u material for various purpose7. Dryer Drying up material8. Stirrer Mixing up matrials

9. Digital Balance Measuring the weight of material more accurately10. Muffle Furnace Burning materials at 10000C to 10500C11. Flame Photometer Identifying material by flame detection12. Desiccating Jar Removing water particles from material

QUALITY CONTROL & LABORATORY ASSESSMENT :

ANALYSIS OF SULFUR ORE

A. DETERMINATION OF MOISTURE IN SULFUR ORE(Gravimetric Method)

Procedure :

1. Weight 20 g or the sample into a weighing bottle which has been dried and weighed in advance.

2. Dry it in a dryer controlled at 60o to 70oC.3. Dry it for 5 hours and then weigh it after cooling in a desiccators for 30 minutes.

4. Calculation :

Moisture % = x 100

Where :W1= Weight of weighing bottle plus sample.W2= Weight of the weighing bottle.W3= (W1) after 5 hours drying at 60o-70oC.

B. DETERMINATION OF ORGANIC MATTER, ASH IN SULFUR ORE(Gravimetric Method)

Process:

1. Weight 20 g of the sample into a porcelain crucible which has been ignited and weighed.

2. Heat it on a sand bath for melting in order to evaporate sulfur.3. Perfectly evaporate sulfur are to stick ness of sulfur in side of porcelain crucible, and

weigh it after cooling in a desiccator. This weight is to be A (g).4. Then ignite the crucible to 850-900oC in a electric furnace for 30 minutes and weigh it

after cooling in a desiccator. This weight is to be B (g).5. Porcelain crucible weight is to be C (g).6. Sample weight is to be D (g).7. Calculation

Organic matter % = x 100

Ash % = x 100

Note : Take care not to do fire in the vicinity of

C. DETERMINATION OF SULFUR IN SULFUR

Calculation Sulfur % = 100 – (Organic Matter % + Ash %)

ANALYSIS OF SULFURIC ACID

DETERMINATION OF SULFURIC ACID CNTENT IN SULFURIC ACID(Volumetric Method – Sodium Hydroxide)

Titrate the sample with sodium hydroxide solution using mixed indicator of methyl red-methylene blue and calculate the content of sulfuric acid.

Reagent and Chemicals :1. Methyl red2. Methylene blue 3. Ethyl alcohol (95%)4. Sodium hydroxide5. Sulfuric acid

6. Mixed indicator of methyl red-methylene blue :

a. Dissolve 0.1 g of methyl red in 90 ml of ethyl alcohol and dilute with water to 100 ml.

b. Dissolve 0.1 g of methylene blue into water and dilute with water to 100 ml.c. Mix methyl red solution and methylene blue solution by the ratio of 2:1 every day

of the test and keep in a brown colored bottle.d. The methylene blue solution should be stored in a brown colored bottle.

7. Sodium bydroxide solution (N/2)a) Dissolve 230 gm of sodium hydroxide in 400 ml of water, keep it in a 10 liter glass

bottle with rubber stopper and leave it for several days in the cool place to prepare the saturated solution.(Then sodium cabonate as impurity and excess quantity of sodium hydroxide will crystallize out).

b) Measure previously the concentration of the saturated solution, take the supernatant solution corresponding to 20 g of sodium hydroxide into a 1,000 ml measuring flask, and dilute it with water into 1,000 ml.

c) Standardization of the solution.Weight accurately 1 g of sulfamic acid which has been dried for more than 24 hours in a desiccator, dissolve it in water and dilute it into approx. 25 ml. Add one or two drops of the mixed indicator of methyl red-methylene blue and titrate it with N/2 sodium hydroxide solution. It is the end point at the moment when the color of the solution changes to pale green.

d)Calculation:

F =

Where

F = factor of sodium hydroxide solution (N/2)W= weight of sulfamic acid (g)A= amount of sodium hydroxide solution (N/2) to be titrated (ml)0.04855 : sulfamic acid (g) per 1 ml of sodium hydroxide solution (N/2)

Procedure :

1. Weigh accurately approx. 0.5 g of sample to mg order into a weighing bottle which has been weighed in advance.

2. Transfuse the above weighing bottle itself into a 500 ml beaker containing approx. 200 ml water.

3. After adding one or two drops of mixed indicator of methyl red-methylene blue, titrate it with sodium hydroxide solution (N/2) until color of the solution changes to palo green.

4. Calculation :

H2SO4 % = x 100

Where 0.02452 = H2SO4 (g) per 1 ml of sodium hydroxide solution (N/2)A = Amount of sodium hydroxide solution (N/2) to be titrated (ml)

Accounting, Finance & Commercial

Commercial

Administration:GMACM/DGMMANAGERASSISTANT MANAGERASSISTANT OFFICER/JUNIOR OFFICER

Purchase Law:Purchase is drawn by two types of tenders: Local tender & Press tender. These are very restricted and followed by public Procurement Regulation 2003 (PPR 2003).

Store Sales MPIC Purchase

Foreign Purchase(Raw Material)

Local Purchase

Another is direct procurement method, which is followed by material planning & accounts.

PROFIT D (2011) DURING THE LAST ELEVEN YEAR

Unit : Lac Taka

Year Profit / C Loss1998- 1999 1318.761999-2000 2097.772000-2001 985.922001-2002 1382.382002-2003 2600.062003-2004 1390.972004-2005 1900.662005-2006 1131.582006-2007 709.202007-2008 3575.982008-2009 4587.00 (Provisional)

YEAR WISE SALE

Unit : MT

SALE

Fiscal Year TSP SSP Total1999-2000 65,510.85 1,38,422.65 2,09,33.502000-2001 67,993.10 1,22,367.60 1,90,360.702001-2002 71,201.55 1,24,613.90 1,95,815.452002-2003 61,052.60 1,29,721.75 1,90,774.352003-2004 66,534.90 1,47,682.05 2,14,216.952004-2005 59,314.65 1,70,931.30 2,30,245.952005-2006 59,660.15 1,30,393.15 1,90,053.302006-2007 50,192.80 1,25,401,85 1,75,594.652007-2008 26,929.15 57,948.50 84,877.652008-2009 35,880.80 24,293.80 60,174.60

YEAR WISE PRODUCTION AGAINST TARGET

Unit : MT

TARGET

Fiscal Year

Target Actual ProductionTSP SSP TOTAL TSP SSP TOTAL

(July-June)1999-2000

65,000 1,25,000 1,90,000 65,144 1,27,224 1,92,368

2000-2001

70,000 1,20,000 1,90,000 71,339 1,21,107 1,92,446

2001-2002

60,000 1,35,000 1,95,000 64,552 1,35,978 2,00,530

2002-2003

55,000 1,35,000 1,90,000 65,049 1,35,489 2,00,538

2003-2004

65,000 1,25,000 1,90,000 66,002 1,41,003 2,07,005

2004-2005

50,000 1,40,000 1,90,000 53,848 1,62,531 2,16,379

2005-2006

55,000 1,35,000 1,90,000 56,392 1,35,147 1,91,539

2006-2007

50,000 1,25,000 1,75,000 50,430 1,17,641 1,68,071

2007-2008

45,000 55,000 1,00,000 41,167 55,014 1,02,181

2008-2009

50,000 60,000 1,10,000 24,144 36,756 60,900

Safety Features of TSPCL:

Safety features of an industry are of almost importance. So, its mandatory to ensure safety of all the personnel's especially working on it different plants.

Possibility of accident in any industry is not negligible at all. Accidents may occur at any moment. Being an industry under BCIC. TSPCL deals with chemicals like sulphuric acid, phosphoric acid, rock sulphur etc. Both these acids are really corrosive and very harmful to health. Besides, sulphur ging a chemical used in making explosives, can produce explosions. So, proper safety measures have to be taken.

There are-In TSPCL, to ensure safety of the personnel's, there is a small medical centre

to provide primary aid.

There is a fine office equipped with instruments capable of extinguishing fire. The office holds.i. There types of fire extinguisher-a. Air foam type fire extinguisherb. CO2 fire extinguisherc. Dry powder fire extinguisherii. Fire bucketsiii. Helmetsiv. Hose pipes.

With the help of a fire engine room, it is ensured that water is supplied in case of an emergency at 23 key points of the industry using fire hydrants. If there is

any powder failure, there is a diesel engine to run the motors and pumps as backup. Besides these, the authority has ensured to make the factory compound a non-smoking zone.

So, it can be said that the factory is well prepared to handle any accidents or mishaps.

Comments and Recommendation

Our four-week training in TSPCL taught us many things, which we could not have learnt otherwise. We were very careful, concentrated and deep into the industrial process and plants and observed it very closely. From our scope of knowledge, we would like to highlight and recommend some of the following features:

TSPCL is one of the most profiting corporations under the administrational control of Bangladesh Chemical Industries Corporation (BCIC). Its administrational, financial and commercial activities have been framed in line with the rules and regulations of the government Bangladesh. It fulfils the aims and objectives of BCIC by advance planning in respect of production, marketing, development, expansion and investment development with due regard to national need, interest and overall policy of the government.

Four important elements such as N, P, K and S are essential for our agricultural land. TSPCL provided P&S by producing TSP and SSP fertilizer, which are most important for the growth of the plants. Although the instruments and machinery of TSPCL are backdated, is can take part in national and agricultural development by producing phosphatic fertilizer (TSP & SSP). They also produce H2SO4, which is important and auxiliary chemical of many industries and research. Therefore every year TSPCL earn a lot of profit.

From engineering point of view, TSPCL is well known opportunity for an engineer. It is a developing industry, which is increasing its production each year, but it remains in the profit zone largely owed to the contribution of its by- product Gypsum.

The peak load in TSPCL is 4 MW and it is completely dependent on PDB power supply. TSPCL should have its own power generation system. Gas Turbine Generator manufactured by Siemens (capacity, 5MW), it had been disabled for many years. It could not supply power service since 1996. This GTG has not been operated for almost thirteen years due to flow in its rotor balancing. Even the manufacturer’s experts failed to solve this problem. This GTG has now become a liability for TSPCL and will be sold as salvage.

The facility is developed in this industry for 900 personnel, but now it is lacking its manpower. Now TSPCL has only 604 personnel, which is hampering its production efficiency.

Despite of its old machineries and technologies, it is the highest profitable company. Government should take primitive care in running its production successively. Corrosion in pipelines, converter, and reformer and reaction vessels must be repaired to hinder pollution problems.

Because of lack of metallurgical research in our country, special composite materials required to construct pumps and piping for handling acid cannot be made in our country. So these

pumps and pipes are exported from abroad, which increases annual expense of TSPCL. So the associated administration should take an intensive care of TSPCL, so that it can cheer up the economy of the country by its utmost profiting production.