PROJECT REPORT ON BENZOL RECOVERY PLANT

Submitted in partial fulfilment of the requirements for the award of degree of

BACHELOR OF TECHNOLOGYIN

CHEMICAL ENGINEERING

Submitted By:

KUMARCHAND BEHERA

112CH0070

N I T ROURKELA

(2ND JUNE 2014 – 28TH JUNE 2014)

COKE OVENS AND COAL CHEMICAL PLANT

SUBMITTED BY:

KUMARCHAND BEHERA

112CH0070

CERTIFICATE

I hereby certify that Kumar chand behera, (112CH0070) of National Institute of Technology, Rourkela (Odisha), has undergone Project from 02-06-2014 to 28-06-2014 at our organisation to fulfil the requirements for the award of degree of B.Tech. Of branch Chemical Engineering. He worked on Optimization of Benzol Plant project during this period under the supervision of Mr. G.Venkata Rao, AGM (Operation). During his tenure with us we found him sincere and hard working. We wish him a great success in the future.

Dated: Project In-charge:

ACKNOWLEDGEMENTS

A summer project is a golden opportunity for learning and self development. I consider myself very lucky and honoured to have so many wonderful people lead me through in completion of this project.

My grateful thanks to Mr. G.VENKATA RAO, AGM (Operation) who in spite of being extraordinarily busy with his duties, took time out to hear, guide and keep me on the correct path. I do not know where I would have been without him. A humble ‘Thank you’ Sir.

Mr. M. GANESH BABU, HR Department monitored my progress and arranged all facilities to make life easier. I choose this moment to acknowledge his contribution gratefully.

Prof. R.K.SINGH, HOD (Chemical department, NIT Rourkela) whose patience I have probably tested to the limit. He was always so involved in the entire process, shared his knowledge, and encouraged me to think. Thank you, Dear Sir.

I would like to thanks for his efforts and help provided to me to get such an excellent opportunity.

Last but not the least there were so many who shared valuable information that helped in the successful completion of this project.

KUMAR CHAND BEHERA

ABSTRACT

Iron and steel making technology, including the

preparation of raw materials and utilisation of wastes, has undergone marked changes over the last years. The hand mining of ores/minerals has almost completely been replaced by mechanised mining. The role of mineral beneficiation and sizing has therefore increased. The current emphasis is on maximising the use of mined materials through multiple beneficiation stages and agglomeration of fines.

Whilst emerging technologies for producing liquid iron are making their advent, blast furnaces continue to be the unchallenged source of hot metal production. However, the efficiency of iron making, both in terms of productivity and quality of hot metal has improved markedly.

Gone are the days of open hearth furnaces and Bessemer converters. LD steelmaking has incorporated in it a number of improvements, namely combined blowing, dynamic control along with the use of the sub lance, improved refractory’s for lining and ladle treatment of liquid steel.

Trends emerging in the area of steel-casting include, horizontal casting, thin strip casting and hot charging of con-cast products without soaking/re-heating.

The paper deals with some of these areas including the advances in Benzol plant in the recovery section.

CONTENTS

I. INTRODUCTION VISAKHAPATNAM STEEL PLANT VSP’S FRUITFUL ACHIEVEMENTS

II. MODERN TECHNOLOGY AND MAJOR PLANT FACILITIES THE MODERN TECHNOLOGY THE MAJOR PLANT FACILITIES

III. PROFILE ON “VSP” VARIOUS DEPARTMENTS IN BRIEF

IV. COKE OVENS AND COAL CHEMICAL PLANT COAL AND ITS ORIGIN, TYPES, PROPERTIES NEED FOR MANUFACTURE OF COAL FROM COKE COAL CHEMICAL PLANT

V. IMPROVEMENTS IN CO & CCD SINCE INCEPTIONVI. BENZOL PLANT

BENZOL DISTILLATION PLANT HYDRO-REFINING UNIT EXTRACTIVE DISTILLATION UNIT CRUDE AND FINISHED PRODUCT STORAGE UNIT

VII. QUALITY PRODUCTS COMPOSITIONVIII. USES OF BY-PRODUCTS

IX. UTILITIESX. CENTRAL LAB

DETERMINATION OF FOLLOWING COMPONENTS: FREE AMMONIA TOTAL AMMONIA(KJELDAL’S METHOD) VOLATILE PHENOLS CHEMICAL OXYGEN DEMAND BOILOGICAL OXYGEN DEMAND MIXED LIQUOR SUSPENDED PARTICLES

INTRODUCTION

The role of ferrous metals in general and of steel in particular in national economy is enormous. One cannot name an economic branch where ferrous metals find no applications. The economic power of country is determined by its output of steel, since it determines the progress in the principle economic branches, be it mining, transport, manufacture engineering or agriculture implements is unthinkable without steel.

An additional impetus for increasing the scope of steel manufacturers had been the vigorous progress in chemical engineering. It has turned out that steel can be very profitable combined with certain novel materials for instance plastic combined with stainless steel are excellent materials fore making furniture, decorating automobiles internal lining of houses and building purposes. As a result the manufacture of stainless steel has been appreciably increased in order to cover these new demands in recent years. The world for the steel rises continuously and is expected to reach the level of thousand million tons per year by the end of this century. The steel will obviously remains the principle structural material in for seeable.

To meet the above requirements the following iron and steel companies were established:

Tata iron and steel company is the first ever-integrated steel plant in India in 1908 at Jamshedpur.

TISCO in Bihar IISCO in Burnapur Bhadravathi steel in Karnataka Hindustan steel plant at Bhilai, Rourkela and Durgapur Visakhapatnam steel plant at Visakhapatnam

VISAKHAPATNAM STEEL PLANT

In order to increase the steel production reasonably high in the nation and remove the regional imbalances in industrial developments, the government of India took a great step in setting up the coastal-based steel plant of India is Visakhapatnam steel plant in Andhra Pradesh. This plant is located 16km south west of the city limits. A great emphasis has been made on total automation, seamless integration and efficient up gradiation at Visakhapatnam steel plant. This has resulted in a great demand for Visakhapatnam steel plant product in India and abroad which are having international standards. Visakhapatnam steel plant is considered to be the first integrated steel plant in India to become fully ISO-9002 certified company. This certificate covers quality systems of training and marketing functions over four regional marketing functions and 22 stock yards located all over the country. The decision of the government of India to set up an integrated steel plant at Visakhapatnam was announced by the Prime Minister Smt.Indira Gandhi. The plant was inaugurated formally on 20th January 1971 by the prime minister.

The project was estimated to the cost of rupees 3,897.28 crores based on process on 4th quarter of 1981 but during the implementation of VSP is has been on served that the project cost as increased substantially over the sanctioned coast mainly due to this and the approved concept were studied in 1986 the rationalization has basically been from the point of view of obtaining maximum output from the equipment already installed panelled for procurement, achieving the higher level of operation efficiency and procurement over what was envisaged earlier under the rationalized concept. 3.0 million tons of liquid steel is to be produced in a year and the project is estimated to cost 5,822 crores based on 4 th

quarter of 1987.

VSP’S FRUITFUL ACHIVEMENTS

It has crossed many milestones in the fields of production, productivity and exports.

Coke rate at an order of 543kg/ton hot metal

Average converter life of 649 heats.

An average of 11.5 heats per sequence in continuous bloom caster.

Specific energy consumption of 7.51 Kcal/ton of liquid steel.

Specific refractory consumption of 15.2kg.

A labour productivity of 192-ton/man yr.

MODERN TECHNOLOGY & MAJOR PLANT FACILITIES

THE MODERN TECHNOLOGY

Visakhapatnam steel plant is the most sophisticated and modern integrated steel plant in the country. Modern technology has been adopted in many areas of production, some of them for the first time in the country.

Among these are:

Selective crushing of coal Dry quenching of coke On ground blending of sinter base mix Conveyor charging and bell less top blast furnace Cast house slag granulation for blast furnace 100% continuous casting of liquid steel Gas expansion turbine for power generation utilization blast furnace top

gas pressure Computerization for process control

THE MAJOR PLANT FACILITIES

Coke oven batteries of 67 ovens each having 41.6 cu.m volumes. Sinter machines of 312 m2 area. Blast furnace of 3200m3 useful volume. Steel melt shop with three L.D converters of 150 ton capacity each and 6

nos. of 4 strand continuous bloom casters Light and medium merchant mill of 710,000 tonnes per year capacity Wire rod mill of 850,000 tons per year capacity Medium merchant and structural mill of 850,000 tons per year capacity

Extensive facilities have been provided for repair and maintenance as well as manufacture of spare parts. A power plant, oxygen plant, compressed air plant also form part of the plant facilities. The steel plant is getting its supply of iron ore-lumps and fines from the Bailadilla deposits in Madhya Pradesh.

Blast furnace grade limestone comes from jaggayyapeta in Andhra Pradesh, SMS grade limestone from Jaisalmer and Goton in Rajasthan. Blast furnace and SMS grade dolomite from Birmitrapur (Orrisa) the Khammam deposits in Andhra Pradesh. 70% of the coking coal requirements are met by imports through the harbor while the balance come from the Bengal Bihar area. Coal for Power generation comes from Anantha deposits of Talcher region in Orissa.

The plant has in-plant power generation from a power plant having 3 nos. of 60MW sets installed. Additional requirements of operational power, around 150MVA is being met from the APSEB grid. Operational power supply is initially at 220 KV, which is subsequently stepped down to 400 KV.

PROFILE ON “VSP”

MAJOR DEPARTMENTS IN VSP

1. Raw materials handling plant2. Coke ovens and coal chemical division3. Sinter plant4. Blast furnaces5. Steel melt shop6. Rolling mills

a. LMMM (Light and medium merchant mill)b. WRM (Wire rod mill)c. MMSM (Medium merchant and structure mill)

VARIOUS DEPARTMENTS IN BRIEF

1. Raw material handling plant: VSP annually requires quality raw materials like iron ore, fluxes

(dolomite, limestone) coking coal and non-coking coal. It requires 12-13 million tonnes of raw materials, which produce three million tonnes of liquid steel. It is provided with unloading, stacking and reclaiming facilities, which include wagon , tippler , ground and track hoppers. The various features are:

Peripheral unloading system for railway wagons Blender reclaimed for blending of ores and fluxes Storage yards to facilitate comfortable storage and supply of raw

materials Ring granulators for crushing of boiler coals PLC control of all systems Mixer for mixing lime is purchased and generated fines Cone crushers for the crushing of lump ore.

2. Coke ovens and coal chemical division:

Coke is manufactured by heating of crushed coking coal in absence of air at a temperature of 1000c and for about 16-18 hrs. a coke oven comprises of two hallow chambers namely coal chamber and heating chamber. In heating chamber a gaseous fuel such as gas, coke oven gas is burnt. The heat so generated is conducted through the common wall to heat & carbonize the coking coal placed in the adjacent coal chamber. Various features of coke oven are:

7 mts tall coke oven batteries. Coke dry cooling or quenching using Nitrogen. Recovery of BY-Product from coke oven gas by Distillation process. Twin fuel gas regenerative system for power generation from coke

oven gas. Back pressure turbine station for power generation from coke oven

gas. Selective coal crushing. High productivity. High capacity of coke ovens.

1. SINTER PLANT:

Sinter is hard, porous ferrous material obtained by agglomeration of iron fines, coke breeze, lime stone fines, metallurgical waste like dust, mill scale, LD slag. Usage of sinter in B.F increase productivity by decrease in the coke rate and imposing the quality of hot metal produced. Parameters of the machines are:

Effective area 312 m2

Sintering area 276 m2

Capacity 450 m2

Sinter bed height 300mm

2. BLAST FURNACE: Hot metal is produced in blast furnace, which are tall and vertical. Raw

materials are Iron Ore, Coke, Dolomite, and Limestone. It is charged from the top and hot blast at 1100c-1300c. there are two B.F’s each with a volume of 3200m3, each with 4 tap holes and with a daily production of 9720 tons of liquid steel. The technical parameters are:

Effective volume 3200m3

Capacity 4860TPD Height 33.1m Number of tap holes 4

Each furnace is facilitated with two Cast Houses, Slag Granulation Plants. There are 4 Pig Casting Machines to handle the pig iron to cast into PIGS.

3. STEEL MELT SHOP:

Steel is an alloy of iron with carbon up to 18%. Hot metal produced in B.Fcontains impurities such as carbon (3.5-4.25%), silicon (0.4-0.5%, manganese (0.3-0.4%), sulphur(0.04%max) and phosphorous(0.14%max). to improve the quality of steel, the impurities have to be removed by oxidation process which is done in converter shop having 3 LD converters. Operational parameters are:

Useful volume 133m3

Capacity 150 tons Temporary Lining Tarred Dolomite Permanent lining Chrome magnesite Oxygen working pressure 16kg/cm2

4. ROLLING MILLS:Blooms produced in SMS-CCD do not have much application as they are.

So they are shaped into Billets, Rounds, Squares, Angles, Channels, Wire Rods, Rein Forced Bars etc. by rolling them in 3 sophisticated high capacity, high speed, fully automated rolling mills namely LMMM, WRM, MMSM.

A) LIGHT AND MEDIUM MERCHANT MILL:

It is unique rolling mill; it consists of Billet Mill and Bar Mill. It is facilitated with 2 walking beam furnaces of 200 TPH heating capacity and 2 stand roller hearth furnaces. The roller hearth furnace connects the billet with bar mill.

B) WIRE ROD MILL:

It is a 4-stand mill and is fully automated. The mill has 4 zone combination type pre heating furnace of 2100 TPH capacity. The mill products include rounds and ribbed wire in size of 5.5mm-12.7mm dia. Wire rods are made in coil from having maximum weight of 1200kg. The mill is equipped with retarded still more lines for improving the quality of wire rods.

C) MEDIUM MERCHANT & STRUCTURE MILL:

This mill is installed at ground level and has the capacity of roll 8,50,000 ton of medium merchant products per annum. The feed materials to mill are 250mm x 250mm blooms. MMSM is a high capacity continuous rolling mill consists of 20 stands arranged in 3 train i.e. roughing, intermediate and finishing trains.

COKE OVENS & COAL CHEMICAL PLANT

ORIGIN OF COAL

Coal originated from the arrested decay of the remains of trees, bushes, mosses, vines and other forms of plant life, which flourished in huge swamps and bogs millions of years ago, during prolonged periods of humid, tropical climate and abundant rainfall. Streams into the swamps and lake basins to form the coal beds carried an enormous amount of vegetations. Owing to pressure, the streams have generally been crushed to an elliptical section and formed coal.

USE OF COAL IN VSP

Coal is used in the form of coke to serve the purpose of iron ore reduction in blast furnace. It also serves as a heat source.

TYPES OF COAL

There are 2 types of coal:

(1) Coking Coal. (2) Non-Coking Coal.

The different coking coals used in VSP are:

1) M.C.C - Medium coking coal - BENGAL, BIHAR2) I.C.C - Imported coking coal - AUSTRALIA3) I.S.S.A.C - Imported coking coal - AUSTRALIA4) SOFT - Imported coking coal - AUSTRALIA

In VSP coking coal is used for producing metallurgical coke where as non-coking coal is used for producing thermal power (in boilers).

TYPES OF COAL AND PROPERTIES

S.NO. TYPE OF COAL % MOISTURE % ASH MEAN MAXIMUM

REFLUTANCE

1. M.C.C 25-28 17-22 0.9

2. I.C.C 24-26 8-10 1.10-1.3

3. I.S.S.A.C 23-25 8-10 1.16-1.3

4. SOFT 30-34 8-10 0.9-1.0

COKE

It is a strong porous hard mass that is obtained by heating of the coal in the absence of air at high temperature. It is a reactive fuel and satisfies the need for blast furnace.

FUNCTIONS OF COKE

1. It acts as heat producer in blast furnace2. It acts as reducing agent by carbon reduction in blast furnace with oxygen

reaction.3. It gives a permeable bed and also as a slag carrier.

CARBONIZATION OF COAL

Heating of coal in the absence of air at high temperatures to produce residue coke, coke oven gas is called “CARBONISATION OF COAL” or “DESTRUCTIVE DISTILLATION”. Its main purpose is to produce coke and the by-product known as coke oven gas from which various products are obtained and this is used as fuel of high calorific value.

NEED FOR MANUFACTURE OF COKE FROM COAL

1. Natural coal is too dense and fragile to be used as a fuel in the furnace.2. Coal is not strong enough to withstand nearly 25 mts of burden lying on it

inside the furnace.3. Coal is nearly “VOLATILE MATTER FREE” so it does not create problems of

hot shortness and coal shortness.4. As compared to coal coke is of high quality and is highly reactive.5. Coke is highly porous mass and it equalizes the blast coming from the

bottom of the charge.6. As coke is a rigid hard mass it does not create the problems of dust

nuscence.7. The ASH CONTENT in coke is very low i.e.) around 10%. So it does not arise

problems of striking on the grates.

The coke oven and coal chemical plant is mainly divided into the following department:

1. Coal Preparation Plant (C.P.P) 2. Coke Oven Batteries3. Coke Dry Cooling Plant (C.D.C.P)4. Coke Sorting Plant (C.S.P)5. Coal Chemical Plant (C.C.P)

IMPROVEMENTS IN CO&CCD SINCE INCEPTION

COAL PREPARATION PLANT:

1. Polymer lining done for 14 silos and chutes to prevent jamming/sticking of coal.

2. Coal receiving conveyors to mixing bins speed increased to avoid stoppage of conveyor on overload etc.

3. Additional small conveyors installed to blend pitch and sludge to feeding coal track to coal towers.

4. Y5 & Y5a conveyors drive drums changed with higher diameter to avoid off-centering and stoppage on load (jamming).

5. Y5, Y51, Y16 and Y16 return idlers modified to avoid jamming and off-centering.

6. Conveyor Y12 gear box internal were changed to stop belt reversal.

7. All inclined conveyors were provided with back skirt to avoid spillage.

8. All chutes were narrowed to avoid spillage & off- centering.

BATTERY:

1. Lid catcher flange bolts provided and mounting structures modified in Charging Cars to avoid off- centering.

2. Pusher Cars and Charging Cars provided with BCH brakes to avoid sliding of Cars.

3. In all DEs’ door extractor and guide coupling replaced with tie rod and spring assembly to avoid detachment.

4. Pusher Car 4,5 leveler bar plat form extended to facilitate door/window regulation.

5. EB1, 4, 5 & 7 brick and dust collecting bunkers provided.

6. Catenary system installed for Charging Cars in all Batteries.

7. DETL support brackets provided for all anchor columns.

8. Cable reeling drums installed in DEs’ to continue DETL, GCM work without stopping production.

COKE DRY COOLING PLANT:

1. Operators cabin shifted out of lifter for safety and better visibility.

2. Falls post erected in all charging devices to eliminate lowering of hot bucket if lid is not opened properly.

3. Bucket liner plates design changed to eliminate plates falling from bucket to to chamber and also to increase the life of liners.

4. Rotary discharging device installed in Chamber-12.

5. CDCP 1&2 discharging devices controls changed to PLC.

6. Introduction of Lifter ground control operation while closing and opening of hooks to avoid single side gripping.

7. Monitoring of all HT drives running horns.

8. Pre-chamber modification to reduce charging device damage.

9. 5 Chambers complete refractory lining changed.

COKE SORTING PLANT:

1. Delayed stopping of K1, K2, K3, K4, K25 & K26 conveyors for emptying the coke from belt in case of track stoppage.

2. Usage of BF bunker for storing of nut coke by modifying K21receiving chute.

3. Transportation of Nut coke to BF by modifying P3-1 receiving chute from K22.

4. Introduction of level sensors in all sludge pump houses for monitoring overflows.

5. Vibrating screen modification for increasing mesh life and reducing slipping of belts.

6. Installation of high capacity pumps for 100% recycling of service water in CSP.

BENZOL PLANT:

1. Up gradation of HRED instrument control to PLC.

2. Reactor catalyst regeneration.

3. CB1 & CB2 columns taken into line to improve quality of Crude Benzol.

4. New products HC Benzol, Still bottoms, Polymers were introduced and sales of HCB started from Jan’04.

5. 100% recycling of distillation effluents in Benzol unit to MBC.

6. Catch pit introduced in Benzol Distillation Unit for removal of Traces of oil.

7. In CFPS unit two CB tanks roof replaced.

8. Wall constructed along the boundary of Benzol plant HRED, CFPS unit and entire area inside boundary wall PCC flooring done.

9. Expansion of Fire Fighting Pump House of BRP.

10. Benzol distillation unit muck is being recycled.

COAL CHEMICAL PLANT

Many by products are extracted from the coke oven gas at this department. It consists of the following sections:

1. Exhauster house.2. Ammonium sulphate plant.3. M.B.C plant.4. Tar distillation plant.5. P.C.L.A 6. Naphthalene fraction crystallization.7. Benzol plant.

Benzol distillation plant. Hydro refining. Extractive distillation.

BENZOL RECOVERY

PLANT

(PROCESS DESCRIPTION)

BENZOL PLANT

Benzol plant is provided in order to produce pure benzene, toluene, and solvent naphtha. Benzol plant consists of three sections:

Benzol distillation plant. Hydro refining unit. Extractive distillation unit. Crude & Finished Products Storage.

Crude benzol recovered from the coke gas is fed to the benzol distillation plant. Various chemicals in the benzol are recovered by distillation.

OBJECTIVE (BENZOL PLANT):

• To recover Crude Benzol from Benzolised Oil.

• To produce Pure Products from Crude Benzol

In the benzol distillation plant, the Benzolised oil from final absorption is pumped to the storage tanks of the benzol distillation. The BO is then stripped of with steam to get the crude benzol and debenzolised oil. This DBO is again pumped to the benzol recovery section. Makeup solar oil is added continuously to compensate for the losses in the equipment. The Benzolised oil is initially pre-heated in three pre-heaters, which are shell and tube heat exchangers. Pre heating is first done in oil dephelegmators, then oil-oil heat exchanger and finally in steam pre heaters. The temperature is slowly in order

to prevent chemical decomposition of benzolised oil. The temperature of the BO fed to the stripping column is about 130-135˚c.

The Recovery & Distillation unit has two streams each consisting of one final gas cooler two scrubbers connected in series. In scrubber the Solar Oil and CO-Gas is subjected to counter current flow and thus Solar Oil absorbs and Benzol from CO-Gas and becomes Benzolised oil. This Benzolised oil is taken to a stripping column, where with the help of direct steam, the benzol is stripped, removed and cooled. The de-Benzolised oil is the bottom product, which is reused for scrubbing the CO Gas.

Tube side Shell side

Oil dephlegmator vapours of stripping column BO

Oil-oil exchangers DBO from stripping column BO

Steam pre-heaters medium pressure steam BO

SALEABLE CHEMICALS:

• Ammonium Sulphate (PUSHKALA)

• Crude Coal Tar

• Hard Pitch

• HP Naphthalene

• Drained Naphthalene Oil (DNO)

• Phenol Fraction

• CG Benzene

• NG Toluene

• Light Solvent Naphtha

• SOL 110

• Coal Tar Wash Oil

• Anthracite Oil

• Coal Tar Fuel / PCM

EQUIPMENT:

• Two streams.

• Each Stream consisting of

- Stripping column -1No.

- Steam pre-heater -2Nos.

-DBO Coolers -6Nos.

-Oil Heat Exchangers -3Nos.

- Oil Dephelegmators -2Nos.

- Water Dephelegmators-1No.

- Decanter -1No.

• Common for both streams-

-CB-1 Condensers -2Nos

-CB-1 Column -1No.

-CB-2 Column -1No.

OBJECTIVE (BENZOL DISTILLATION SECTION:

• To separate Crude Benzol from Benzolised Oil.

• To separate HCB from Crude Benzol.

OVER ALL PROCESS OF BENZOL DISTILLATION :

Benzol distillation plant receives Benzolised oil from benzol recovery plant and the Benzolised oil is treated to produce crude Benzol.

Benzol distillation plant comprises of Benzolised oil stripping and fractionation of crude benzol as CB-I, and heavy crudebenzol as CB-II.

The Benzolised oil received from Benzol recovery plant is heated to 118-125 degrees and CB is stripped from Benzolised oil by steam in Stripping Column and crude Benzol vapour is produced. The vapours are passed through Oil & Water Dephlegmators for separating phlegma condensate. Then Crude Benzol vapours are fed into a fractionating column to produce Crude Benzol-I and Heavy Crude Benzol CB-II.

The stripped oil is called De-benzodised oil. De-benzodised oil is cooled and sent to Decanter where the oil is separated from emulsion. Then De-benzodised oil is pumped to Benzol recovery plant.

Emulsion from decanter is periodically transferred to emulsion breaker for the separation of oil and muck by heating. Muck is semi solid mass, generating during the circulating of oil in process of Benzol recovery due to absorption of tar fog. Muck is transferred to muck beds for disposal.

The regeneration of oil is done by feeding a small portion of hot Benzodised oil to regenerator. The bottom from the regenerator containing polymers called high boiling fraction is collected in high boiling fraction tank.

Steam condensate generated of direct stream stripping is separated in Phlegm separator, CB-II control separator and collected in a settling tank and then directed to separated water tank. Water from separated water tank is pumped to final gas cooling condensed water circuits. Water used in the decanters for the separation of sludge and other contaminated water is pumped to final gas cooling condensed water circuit.

Crude Benzol is present in range of 25-40g per Nm3i n coke oven gas & it yields on recovery varied from 6-11L petrol of coal carbonized. The unrefined product is chiefly a complex mixture of hydrocarbons. But sulphur, Oxygen & nitrogen compounds are also present in trace amounts.

At VSP solar oil, a petroleum fraction boiling from 270-370 degree is used for scrubbing coke oven gas. In Benzol scrubber to recover crude Benzol, coke oven gas consists of 27-34 g of Benzol hydrocarbons per Nm3/gas. In a continuous process the benzolised oil thus generated is stripped in Benzol from the solar oil. & The DBO (debenzolised oil) is sent back to Benzol scrubber for subsequent absorption.

STRIPPING COLUMN:

Pre-heated BO from the exchangers is fed to the 17 th tray of the stripping column. The column consists of bubble cap trays. Low pressure of steam at a temperature of 180°c and 3.8kg/cm2 is injected through DBO at the bottom of the column.

Crude Benzol in the BO is recovered by steam distillation. Steam distillation is done so that the partial pressure of the Benzol decreases and easily get vaporized. LP steam injected at the bottom not only maintains temperature of the column but also decrease the partial pressure of the crude

Benzol. The crude Benzol vapours along with steam from the top of the column are fed to the oil dephlegrmators. The DBO from the bottom in which crude Benzol is recovered is pumped to the decanter through oil-oil heat exchangers.

The crude Benzol vapours are partially condensed in the oil dephlegrmators. The partial condensation removes any higher fractions present in the vapours which further increases the purity of the vapours. Three sets of dephlegrmators are provided, two sets for oil and one for water. The vapours are cooled to 92-95°c in oil dephlegmator by pre-heating the feed to the stripping column and further cooled to 84 °c in water dephlegmator. The condensate collected in the heat exchanger is called PHLEGMA. The phlegm from the exchangers, which contains water, is collected in a separator. Water is separated and phlegma over flows to the phlegma collecting tank from this tank phlegma is sent to stripping column as reflux.

REGENERATOR:

The continuous circulation of DBO forms some polymer due to heating and cooling. This polymer must be removed from the DBO by regeneration. Regeneration is a hollow tank in which steam coils are arranged MP steam is circulated through these coils. Part of the stripping column is fed to the regenerator. Due to the pressure CB vapors are collected at the top, which are in turn to the stripping column. The bottom liquid from the regenerator is pumped out and stored in Crude and Finished Product Storage.

Top temperature 110-115°c

Bottom temperature 120-130°c

No. of trays 23

Feed tray 17 th tray

Pressure in the column 0.3-0.35

CRUDE BENZOL COLUMN I:

The vapors containing crude benzol from the top of the stripping column is fed to the crude benzol column I through water dephlegmator where the crude benzol is separated to heavy crude benzol and light crude benzol. Crude benzol mainly consists of LCB, HCB and polymer. Lighter fractions like benzene, toluene, and xylene are present in LCB and HCB is similar to that of heavy polymer, which is used as furnace oil.

The column consists of 16 bubble cap trays. Simple distillation is carried out in this column. A reboiler provided at the bottom of the column supplies the necessary heat. MP steam is used as heating media.

A CB vapour at a temperature of 80-85°c is fed to the 6 th tray of the column. The lighter components are vaporized and these are collected at top of the column, which are then condensed in a condenser by water. The condensed vapours are then fed to the separator where the moisture present in the vapours is separated and the LCB obtained is stored in CB1 tanks. Part of the LCB is fed as reflux to the CB1 column. The bottom product obtained from CB1 column is fed to the CB II.

Top temperature 70-80°c

Bottom temperature 115-120°c

CRUDE BENZOL COLUMN II:

CB II consists of 6 bubble cap trays. The bottom product of the CB I which mainly contains HCB with small amount of LCB is fed to the CB II column. To recover the LCB the liquid is to be distilled. The LCB vapours obtained from the top of CB II is fed to the CB I column as reflux. The bottom product obtained from the CB II is called as Heavy Crude Benzol (HCB).

Top temperature 120°C

Bottom temperature 140°C

DEBENZOLISED OIL:

The DBO from the bottom of the stripping column is pumped through oil-oil heat exchanger to DBO cooler. In DBO cooler it is cooled to 45-50°C. Due to high temperature exposure, part of the solar oil may get decomposed. This decreases the absorption efficiency of the solar oil. To remove this decomposed matter DBO is fed to the decanter.

DECANTER:

It is a horizontal cylindrical tank unlike mechanical decanters DBO is fed to the decanter at a temperature of 45-50°C. Small amount of water is fed to the decanter which provides better removal of sludge or muck form of oil. Water settles at the bottom carrying sludge with it. Muck or sludge layer is formed the water layer. Oil layer is formed above the muck layer. The residence time in the decanter is three to four hours. Water is continuously drained from the decanter. Oil after 3-4 hours is fed to the DBO tank. Muck from the decanter is drained and sent to the emulsion beaker. Due to contact of oil, water and muck oil-water emulsions and muck-water emulsions are formed. These emulsions float on the surface of the water, which is fed to the emulsion beaker along with muck.

EMULSION BEAKER:

This is a horizontal cylindrical vessel provided with insulation. Medium pressure steam is fed through a coil into the beaker. Residence time for setting the oil, muck and water in the beaker is 2 hours. Due to heating of emulsion, oil and water get separated which is called as De-emulsification. Emulsion thus formed is broken and muck will float on water. This muck is fed to the muck tank and the water is drained. The temperature inside the beaker is 80-90°C.

HYDRO REFINING

In this unit using hydrogen gas purifies the light crude Benzol. Hydrogen is recovered from coke oven gas and LCB from Benzol distillation plant.

OBJECTIVE:

• To remove Sulphur, oxygen and nitrogen from Crude Benzol.

• To produce BTXS Raffinate for processing in Extractive Distillation Unit.

LCB consists of benzene, toluene, xylene, solvent naphtha, non-aromatics and residue. Initially, the LCB is purified from sulphur, non-aromatics and other compounds. This consists the following sections. They are,

De-fronting section Reaction section Purification section

DE FRONTING SECTION:

In this section, carbon disulphide is removed from the crude Benzol and this is called as de-fronted crude Benzol. LCB from the storage tank is pumped to a surge tank, which is meant for intermediate storage. The LCB from surge tank is pumped to the distillation column through feed pre-heater. The feed enters the column at a rate of 3 T/hr and at 70°c. Pressure in the column will be 0.5 kg/cm2. Sulphur content in the feed is 2000-1800 ppm. This is decreased to about 1200 ppm in the column.

Distillation column consists of 30 bubble cap trays of which 17th tray is the feed tray. Steam is fed into the reboiler, which heats the bottom product recycled to the column. The remaining bottom called de-fronted crude Benzol is fed to the reaction section through feed pre-heater. The sulphur is removed in the form of CS2. Simple distillation is carried out and due to heating CS2

vapours rise in the top and these are condensed in a water condenser. Condensed CS2 is collected in CS2 vaporizer. Part of it is fed to the column as reflux and the other part is stored. The DCB obtained is at 70°c and this is fed to the intermediate storage.

Feed rate to the column 3T/hr

Pressure in the column 0.5 kg/cm2

Sulphur content in the feed 2000-1800 ppm

Sulphur content in DCB 1200 ppm

No. of bubble cap trays 30

Boiling point of CS2 45

Temperature at the top of the column 55-65°c

Column bottom temperature 105°c.

REACTION SECTION:

This section consists of reactors and evaporators. Here the hydro refining takes place in the reactors provided which removes the oxygen, nitrogen and sulphur content in DCB.

PROCESS:

The de-fronted crude Benzol is pumped to the de-fronted storage tank (V-401) through a filter. The filter is provided to remove the solid particles and polymers, which may be present in the crude Benzol. The Benzol filter is an edge type filter and consists of a slotted tube inside a shell with a specified filter fineness, which is determined by the slots and scrappers. This is agitated by a hard crank.

HYDROREFINING UNIT(FLOW SCHEME)

De-Fronting agent(For removal of CS2)

CB-1

STAGE EVAPORATOR

Heating by thermal oil.

Recycle gas mixing

Evaporation in stage.

PER-REACTOR Ni-Mo Catalyst

Styrene Ethyl Benzene

H2

MAIN-REACTOR Co-mo Catalyst

Thiophene Butane+H2S

Condensation &seperation of RC gas

H2

STRIPPER COLUMN THERMAL TREATMENTREMOVAL OF H2S

BTXS REFINATE

The particles are retained at the edges of the slots and must be scrapped off. If the pressure difference between the inlet and the outlet streams is too high the concerned filter must be opened and cleaned. The filtered DCB is stored in the surge drum (V-401). The drum is set to approximately two bars split range controlled by feeding N2and venting gases. From surge drum, the DCB is fed to pre-vaporizer at a pressure of 30 bars using 32 stage centrifugal pumps.

PRE-VAPORIZER:

It is nothing but a vertically mounted shell and tube heat exchanger. The feed is mixed with a part of cycle gas (containing H2 approximately 15% of the total gas) before it is fed to the vaporizer. This feed is pre-vaporized to about 160-165°C by means of the main reactor effluent passing through shell side. The feed at a temperature of 160-165°C is fed to the third mixing nozzle of stage evaporator.

This vertical heat exchanger is provided with turbulence promoters in the tube side to achieve high turbulence so that more heat exchange will occur and no scale formation is attained. This arrangement is provided as the feedstock is in partial vapour stage (gas-liquid stage) and so fouling of the tubes will occur rapidly. This arrangement also provides easy cleaning of tubes by simply pulling the turbulence promoters.

STAGE EVAPORATOR:

The stage evaporator is a long cylindrical vessel provided with three stages, which are separated by two plates. Demister pads are provided at the top of the evaporator. Each stage is provided with a mixing nozzle. Two reboiler E-402 and E-403 are provided for second and first stage respectively. A gas pre-heater E-404 is also provided in which the rectangle gas (85% of the

total gas) is pre-heated to 210°C by the main reactor effluent. E-402 and E-403 are heated by hot oil through tubes at a temperature of 250°C. Rectangle gas mixed with feed is passed through the shell side.

Down comers are placed so that the liquid in the third stage will enter the second and from second to first. Pressure inside is about 20kg/cmm.

The DCB mixed with 15% of rectangle gas is fed at the third mixing nozzle of the evaporator. The vapours coming from the second stage and the feed are mixed thoroughly and fed to the third stage. Lighter vapours are passed through the demister pads and to the pre-reactor. The liquid containing lighter and heavier substance is passed

through down comers to the second stage. Here the fed is mixed with the vapours from first stage in the mixing nozzle II and heated in reboiler E-402. This is fed to the top of the second stage.

Similarly liquid from second stage flows to first stage. This liquid is pre-heated in E-403 and mixed with 85% of the rectangle gas in first mixing nozzle and again fed to the first stage. The temperature at the bottom of the evaporator is 210°C. Due to heating of the feed the vapours are sent to the top and any residue or polymers in the feed are collected at the bottom. Part of the liquid from the first stage is fed to the residue flash drum (V-406) from where they are recycled to Benzol distillation plant. The lighter vapours from the flash drum are fed to the surge drum (V-401) nearly this residue would be 3-4% if total feed.

The vaporization of feed (DCB) in the evaporator is done by reduction of partial pressure of DCB, which is manipulated by addition of the rectangle gas. This results in lower operating temperature even at higher pressures. Vaporization of feed in heat exchanger should be avoided to reduce fouling of surfaces.

PRE-REACTOR:

The vapours from the top of the evaporator at 180°C are heated in a heat exchanger E-406 to 190-225°C by passing main reactor effluent through shell side. The reactor is provided with a bed of catalyst i.e. NICKEL MOLYBDEBUM. In this pre-reactor such as diolefins, styrene and CS2 are removed by hydrogenation. Feed enters from the bottom of the reactors through catalyst bed. Hydrogenation of diolefins, styrene takes place in the presence of catalyst.

The temperature at the inlet of the reactor is 190-225°C and this depends on the life cycle of the catalyst. Due to the exothermic reaction the outlet temperatures increases to 200-235°C. Due to continuous operation of the catalyst bed coke like polymerization products deposit on the catalyst bed resulting in the lower efficiency. This can be overcome by increasing the inlet temperature of the reactor. Catalyst activity can be determined by the temperature difference between inlet and outlet, which should be more than 10°C. Catalyst can be regenerated by heating the bed with steam and air. The reactions in the pre-reactor are

Diolefins + H2 mono olefins

CnH2n-2 CnH2n

Cyclopentadiene + H2 cyclopentane

C5H6 C5H8

Styrene + H2 ethyl benzene

C8H8 C9H10

Carbon disulphide + H2 methane + H2S

CS2 CH4

MAIN REACTOR:

In main reactor treated pre-reactor effluent is hydrogenated on special sulphide molybdenum catalyst. The main reactor consists of two beds of catalyst makeup gas i.e. pure H2 gas from the compressor at pressure of 18 bars provided more hydrogenation and hence complete saturation of olefin hydrocarbons. The inlet temperature is about 270°C and the outlet temperature is 330°C due to exothermic reaction. Mainly desulphurization, densification and olefin saturation feed stock occurs in main reactor. The hydrogen is fed through a distributor below first bed of catalyst oxygen content in H2 gas should be very low so that no polymerization occurs in the reactor.

Hydrogenation of aromatics should be prevented. Catalyst deactivation can be determined by the amount of thyophene content at the outlet of the reactor. If this increases hydrogenation of aromatics, coke formation increases. So the temperature of the reactor should be increased or other regenerations should be done.

Main reactions are:

Mono olefins + H2 Paraffin

Ethyl mercaptans + H2 Ethane + H2S

Thyopene + H2 Butane + H2S

Coumarone + H2 Ethyl benzene + H2

Pyridine + H2 Pentene + H2

Pyridine + H2 Butane + H2

Benzene + H2 Cyclohexane

Toluene + H2 Methyl cyclo hexane

Hence required to maintain a heater to which part of the effluent is passed, Heated and fed to the main reactor supplies the temperature. Coke oven gas is used as fuel in the heater.

The effluent from the main reactor collected at the bottom, which is at 330оc. This effluent is passed through E-407, E-406, E-404, E-401 and finally cooled in water cooler E-408.

This condenser effluent is fed to the separator. Before water cooler hot water is dosed into the effluent. This dissolves the deposits of salts such as NH4HS2 and NH4Cl. The cooled effluent at 50 оc is fed to the separator. A water leg provided separates the dosed water. The water free effluent is fed to the stripping column. The gases i.e. un reacted hydrogen gas and other gasses are sucked by recycle gas compressor and are recycled part of the gas is purged out through vent provided.

HOT OIL SYSTEM:

The heat demand of the process is supplied by a separate hot oil system. The hot oil is used as a heating medium for several heat exchangers in hydro refining unit and extractive distillation unit. A horizontal furnace is used to heat the oil; the furnace is fired using coke oven gas. Hot oil is pumped in to the coils into the furnace. The temperature of the oil increases to about 340-350 оc. The hot oil is pumped by P-404 pump. The oil at temperature of 340 оc is fed to the HR unit by using another pump. This is again recycled to the suction side of P-404.

PRESSURE SWING ADSORPTION UNIT:

The required hydrogen gas to HR units is supplied from this section. The clean coke oven gas after Benzol recovery is fed to a filter at a pressure of 800mm WC. Moisture and carbon particles present in the gas are filtered and the filtered coke oven gas is fed to a reciprocating compressor, which compresses the gas to about 2.5 kg/cm2. The compressed gas is again fed to the other compressor where the pressure of the gas increases to 6.5 kg/cm2. The gas is then fed to another filter, which removes the moisture in the gas. From the filter the gas is fed to the pressure swing adsorption unit. It consists of 4 cylindrical vessels in a bed of molecular sieves is placed. The coke oven gas is passed from the bottom of the bed and the molecular sieves absorb the hydrogen present in the gas. The hydrogen thus collected is fed to the makeup gas compressor. The gas is passed through one catalyst bed only. At this time, the remaining beds are in regeneration. This is because catalyst for 180 seconds only. Then it has to be regenerated. This is done by using pure H2 gas. The regeneration of then bed is done automatically.

The H2 gas is collected from the top of the bed and is fed to the makeup gas compressor. This is a vertical reciprocating compressor of double stage. The H2 gas is compressed to about 30 bar. The recycle gas from the gas separator is fed to the recycle gas compressor, which is a horizontal single stage compressor.

PURIFICATION:

This section consists of a stripping column in which the sulphur content as H2S and any dissolved gases in the DCB are removed.

PROCESS:

The liquid part from the separator is fed to the stripping column through a pre-heater, which is heated by BTX solvent from the stripping column. The fed at a temperature of 135 оc is fed to the column. The column consists of sieve trays. Top temperature is 125-135 оc and bottom temperature is 150 оc. Pressure is about 4.3 kg/cm2. Re boiler is provided which supplies the required heat to the column. MP steam is fed to the shell side of the re boiler. The gas from the column contains H2S. These are condensed in the condenser where water issued. This condensate (70 оc) is fed to the reflux drum. Part of the condensate is refluxed to the column. Moisture present in the gas is removed from the water leg and the off gasses are fed to the off gas mains.

The bottom product called BTX solvent raffinate is passed through the pre heater where it is cooled and finally raffinate is cooled in the raffinate cooler which is cooled by water. This is stored in intermediate storage.

EXTRACTIVE DISTILLATION UNIT

In this unit, the BTX raffinate is processed to separate benzene, toluene and xylene solvent. Further benzene and toluene are also separated. Using ‘Extractive Distillation’ in which N-formylmoropholine (NFM) is used as solvent does separation of BTX into BT and X. Non aromatic compounds present in BTX are removed by pressure distillation solvent is recovered in solvent recovery column. Benzene and toluene are separated in BT separation column.

The total heat required for the unit is supplied from various means pressure distillation receives heat from hot oil. Aromatic separation column and solvent recovery column receives heat from the vapours of the pressure distillation column. The BT column receives heat from the LP steam.

OBJECTIVE:

• To separate non aromatics from benzene & toluene.

• To produce pure benzene, pure toluene, Light solvent oil &still bottom oil from BTXS Raffinate.

The unit consists of the following sections:

Pressure distillation section Extractive distillation section Solvent recovery section Aromatic stripper BT separation section Batch Distillation section

PRESSURE DISTILLATION SECTION:

This section consists of a distillation column in which the BT & X solvent are separated by simple distillation from raffinate.

PROCESS:

The BTX solvents raffinate from the IPS is pumped to the feed surge drum (V-513). The drum is a horizontal tank provided with a vane and line from reflux drum (V-501) that carries vapours to this drum. The BTX solvents raffinate from the surge drum is pumped to pressure distillation column through four heat exchangers I series E-502, E-503, E-504 & E-505respectively. E-502 and E-505 are heated by bottom product i.e. Xs fraction. E-503 and E-504 are heated by BT fraction. The column consists of 50 bubble cap trays of which 25th trays is the feed tray. Column pressure is about 15 kg/cm2.

A re boiler is provided to the column through which hot oil passes through shell side. These supplies the heat required for the column. The BT vapours from the top of the column a collected in reflux drum before which they are condensed in E-504 and E-509. This condensed BT fraction is collected in reflux drum. Some of it is reflux to the column and the remaining is passed to E-503 and cooled in BT condensed in E-501 by using water.

EXTRACTIVE DISTILLATION COLUMN (C502):

The BT surplus is conveyed by steam pressure from V-501 via heat exchangerE-503 and cooler E-501 as feed to extractive distillation column C-502. The feed is introduced on the 31st tray at the middle of the column. The N-formylropholine (NFM) solvent is introduced on the top tray of the ED Column at the physically required conditions at the flow ratio of 56 kg NFM per kg of feed at 92оc. The NFM temperature is regulated for the achievement of the low level of aromatics in the non-aromatics.

ED column serves for the separation of non-aromatics contained in the feed, which is not possible under normal distillation conditions. This means that non-aromatics originally with boiling points higher than aromatics, becomes low boiling non-aromatics which can be withdrawn at the top of the ED column while the aromatic substances dissolve in the NFM is yielded at the bottom of the ED column.

ED column is supplied by the reboiler E-507 (LP Steam), E-508 (Hot NFM) and partially via vapour heated reboiler E-509. The NFM at the top of the column promotes the scrubbing of aromatics out of ascending vapours; where as non –aromatic vapours are dissolved only to a slight extent.

ED column trays 60-bubble cap

Feed plate 31 tray

Top temperature 110оc

Bottom temperature 150 оc

Top pressure 0.8kg/cm2

Bottom pressure 0.4kg/cm2

SOLVENT RECOVERY COLUMN:

The column is used for separation of non- aromatics yielded at the top of ED column from the residual carried over solvent contents. For this purpose the top vapour of the ED column are fed at the point below at the pall rings packing in the column. Bottom heating to the column is affected using reboilerE-510, also by means of hot NFM from the solvent circulation. The top phase in the column, consisting principally of non-aromatics is condensed in condenser E-511 and the liquid phase yielded is routed to the reflux vessel V-502. A portion of the non-aromatics is routed as reflux to the column. While bottom product is discharged through a level controller to CFPS.

NFM recovered at the bottom of the column is returned to the ED column. The solvent recovery column minimizes the NFM losses by means of extensive recalculation of NFM flow inevitably leaving the top of the extraction column. The basic difference as compared to the normal hydrocarbon distillation and ED column is that its bottom section must be operated in the phase occurs in V-509. The bottom contains large quantities of non-aromatics due to the reflux required for scrubbing. In contrast to an ED column, the recovery column is operated under normal circumstances with a two-phase bottom product.

Packing Pall rings

Bottom pressure 0.25 kg/cm2

Top pressure 0.2 kg/cm2

Top temperature 100оc

Bottom temperature 125 оc

STRIPPING COLUMN:

The product yielded at the bottom of the ED column consists of NFM in which the extracted aromatic substances are dissolved. The non-aromatic content will be in low PPM due to the existing pressure drop. This flow is conveyed into the aromatics column, which is operated under vacuum. In this column the pure aromatics are separated from the NFM, which is yielded as the bottom product and cooled in the heat exchanger system of the equipment prior to be being returned to the ED column.

Before feeding NFM to the ED column, it is passed through the following equipment:

1. Centre re boiler E-508 on ED column C-502.2. Re boiler E-512 on solvent recovery column.

3. NFM re boiler E-514 on the stripper column and then fed to the ED column.

Solvent cooler E-522 serves as a trim cooler for NFM. The bottom of the stripper column is heated by means of the two continuous re boilers E-512 and E-513, which are heated by BT vapours and E-514 heated by means of NFM.

The reflux to the stripping column serves to remove the solvent in the lower section of the column. The vapour liquid mixture discharges from the re boiler E-514 is fed below the chimney tray in the stripping column. Traces of the solvent flash are washed back by the aromatics reflux and directed into the lower part of the column.

Total trays 30

Feed tray 5 th

Top temperature 56 оc

Bottom temperature 119 оc

Pressure 0.36-kg/cm3 vacuums

BENZENE TOLUENE SEPERATION COLUMN:

BT separator is a normal two-phase distillation for pure aromatics. The BT fraction is routed using a reflux pump from reflux drum via exchanger E-517 to separation column C-505. The heat required for distillation is supplied to the system via re boilers E-518 by means of LP steam. Overheads are pure benzene, bottom are pure toluene as specified.

Total trays 65 Bubble capFeed tray 30 th

Pressure 1.2 bars

Benzene purity 99.97%

Toluene purity 99.95%

CRUDE &FINISHED PRODUCT

STORAGE UNIT

OBJECTIVES:

• To store crude Benzol, HCB and pure products.

• To Despatch HCB and pure products to customers by road tankers.

EQUIPMENT:

Total Storage capacity

• CB Tanks 4Nos 2800kl.

• PB Tanks 4Nos 2000kl.

• PT Tanks 2Nos 400kl.

• LSO Tanks 5 Nos 250kl.

• NA Tanks 2Nos 100kl.

• HCB Tanks 2Nos 200kl.

QUALITY PRODUCTS (Composition)TOLUENE (Industrial Grade)

Distillation Range

Up to 1050C 5 ml

Up to 1200C 90 ml

• Specific Gravity at 15/150C 0.860 - 0.875

• Residue on Evaporation 10 mg/100 ml (max)

• H2S & Mercaptanes Negative

• Purity (by GLC method) 92.0 % (min)

TOLUENE (Nitration Grade)

• Distillation Range 0.6 (Including 110.60C)(1 - 96%)

• Specific Gravity at 15/150C 0.870 - 0.874

• Residue on Evaporation 5 mg/100 ml (max)

• H2S & Mercaptanes Negative

• Purity (by GLC method) 99.2 % (min)

CG BENZENE

• Distillation Range 0.6 (Including 80.10C)(1 - 96%)

• Specific Gravity at 0.879 - 0.886

• Residue on Evaporation 5 mg/100 ml (max)

• H2S & Mercaptanes Negative

• Total Sulphur (ppm max.) 2.0

• Non Aromatics (ppm max) 500

USES OF BY-PRODUCTS

TOLUENE

• Solvents, TNT, Paint ,Rubber Industries, & Varnishes

• Printing Ink, Benzoic Acid, Sodium Benzoates

• Synthetic Fibers, Adhesives, Benzyl Chloride, Thinners

HP NAPHTHALENE

• Dye intermediates, Insecticides

• Dispersing & Tanning Agents

• Beta Naphthol, Refined Naphthalene

• Naphthalene balls

BENZENE

• Raw material for various Drugs, Dye-stuff, Synthetic Rubber, Styrene.

• Pesticides, Monochlorobenzene

• Caprolactum, Phenol, DDT

• LAB Nitro Benzene, Aniline, Maletic Anhydride

• Cumene, Cyclo-Hexane

• Nylon-6, Styrene

• Resin, Nylon Intermediates

HARD PITCH

Used by Aluminium Industries requiring Pitch Carbon for Electrodes. Used for manufacturing graphite and in BF ladle repair.

AMMONIUM SULPHATE

As Fertilizer due to its Nitrogen content. As a Nitrogen bearing material in mixed Fertilizer in Fertilizer

plant.

ANTHRACENE OIL

Feed stock for Carbon Black.

DRAINED NAPHTHALENE OIL

Naphthalene balls Naphthalene bearing feed stocks

COAL TAR WASH OIL

Preservation of Wooden Sleepers Carbon Black Feed Stocks, Disinfectant

LIGHT SOLVENT NAPHTHA

Solvents, Starting material for Dyes, Printing Ink, Thinner

UTILITIES

Utilities department supplies other utilities required for various department such as oxygen, nitrogen, chilled water, compressed air & instrument air.

DIFFERENT SECTIONS IN UTILITIES: Air separation plant. Compressor house. Acetylene plant. Chilled water plant.

QUALITY ASSURANCE & TECHNOLOGY DEVELOPMENT

(CENTRAL LAB)

DETERMINATION OF FREE AMMONIA: (DISTILLATION METHOD)

1) 50 ml of sample is taken into a kjeldal flask.2) The sample is arranged into a conical flask containing into a 2% Boric acid

solution i.e. 50 ml of 2% Boric acid + 50 ml of DM water + mixed indicator.3) After 30 min4) Distillation, the set up is removed and the condensate is titrated against

N/10 H2SO4.

CALCULATION: ml of N/10 H2SO4 consumed × 34

DETERMINATION OF TOTAL AMMONIA (OR) AMMONICAL N2 (KJELDAL METHOD):

1) Take 10 ml of filtrate sample into a kjeldal flask.2) Add 10 ml of 6N NaOH and 10 ml of Borate Buffer and 100-150 ml of Dm

water.3) Take 100 ml of 2% Boric Acid in a beaker, add 2-3 drops of mixed indicator,

and keep the beaker, below the water condenser to absorb the ammonia.4) Arrange the distillation unit and switch on. Boil the contents till the volume

reduced to 1/3rd.

5) Now remove the beaker in which ammonia is absorbed. Titrate it with 1N OR N/10 H2SO4 colour changes from green to red.

CALCULATION:

Total NH3= (T.V ×Normality ×17×1000 ) / vol.of sample taken

DETERMINATION OF VOLATILE PHENOLS:

PRINCIPLE:

Steam distiable phenolic compounds react with 4-Amino anti pyrine at Ph 7.9 in the presence of potassium ferric cyanide to form a coloured Antipyrine dye. This is measured at 510 nm wave length in Spectrophotometer.

PROCEDURE:

1) Take 50(or) 100 ml of sample, add 10 ml of 10% Cuso4 solution to this add 10 ml OF 1:3 H2SO4 and few drops of methyl orange indicator.

2) Take them all into a kjeldal distillation flask. 3) The distillation as to be conducted by using steam. And collect 500 ml of

distillate.4) From this take 50 ml of distillate and add 1 ml of ammonia buffer, 2 ml of

8% potassium ferric cyanide and 2 ml 2% 4 amino anti pyrine in a 100 ml volumetric flask.

5) Now make up the volume to 100 ml with the distillate what we collected.6) Keep it for 15 min and measure absorbance at 510 nm wave length. Run

the blank simultaneously.

CALCULATION:

Vol. of Distillate collected / vol. of.sample×k×absorbance

K=Calibration factor=7.4

DETERMINATION OF CHEMICAL OXYGEN DEMAND:

1) 50 ml of sample is taken into a round mouthed 500 ml conical flask and 50 ml of water is added in it.

2) Then 25 ml of 0.25 N K2Cr2O7 and 75ml of conc.H2SO4 is added and kept for cooling in the water bath.

3) After cooling, 1 gm of silver sulphate and 1 gm of Mercuric sulphate and few glass pieces are added to control the bubbling.

4) After all additions the conical flask is placed on a heater for refluxing for 4 hours using condenser. After reflux the flask is cooled and washing of condenser is Collected in the flask.

5) The refluxed sample is titrated against 0.25 N Mohr’s solution (FAS) using Ferroin indicator.

6) The COD in ppm is calculated as

Normality of Mohr’s (0.25) × Y× 8000

Amount of sample taken in ml.

Y= ml of 0.25 N K2Cr2O7 added – ml of Mohr’s solution consumed for titration.

DETERMINATION OF OILS&GREASES:

1) Take 100 ml of sample is taken in a separating funnel and add 200ml of Petroleum ether is added as successive separations.

2) Then the funnel containing sample is shaken vigorously for 5 min with intimately releasing the vapour pressure and allowed for settling for 15 min.

3) The aqueous layer is drained from bottom of the separating funnel and petroleum ether is transferred to the tared porcelain dish.

4) The porcelain dish is kept in over the water bath. It is kept always in water bath. It is kept always in water bath because if you dry it directly on flame it catches fire.

5) After the evaporation of ether the dish is cooled in a desiccators and weighed.

The oils & greases is calculated as:

Final – Initial wt of dish ×106

Sample taken

DETERMINATION OF BIOLOGICAL OXYGEN DEMAND (BOD) :

1) Two sets of BOD bottles, each set containing two bottles labelled as blank and sample are taken.

2) Twenty ml of sample is pipetted into BOD bottles labelled as sample.3) 10ml of seed prepared as per work procedure. 4) The BOD bottles are filled up to the mark with dilution with DM water.5) 10ml sample is taken in a blank BOD bottle.6) Dissolved oxygen content is measured immediately for one set of BOD

bottles by Membrane Electrode Method. (Blank & sample) 7) The other set of BOD bottles are incubated at 200c for 5 days in BOD

incubator. And the temperature of incubator is monitored frequently.

8) The BOD bottles are taken out from incubation after 5 days and dissolved oxygen content is measured immediately by Membrane Electrode Method for Blank (B2)& sample(S2)

CALCULATION:

BOD= (S1-S2) – (B1-B2) × 15

S1= Initial dissolved oxygen in the sample.

S2= Dissolved oxygen left out in the sample after 5 days incubation.

B1= Initial dissolved oxygen in the blank.

B2= Dissolved oxygen left out in the sample after 5 days incubation.

DETERMINATION OF MIXED LIQUOR SUSPENDED SOLIDS:

1) 10 to 25 ml of sample is taken in a beaker.2) The sample is filtered in a free weighed GFC filter paper under suction by

the set up provided for this purpose 3) The filter paper is removed and dried in a drying oven. Then filter paper

with the residue is weighed.4) The MLSS is calculated in ppm as

(X-Y) ×10 6

Z

X= Final weight of filter paper in mg

Y= Initial weight of filter paper in mg

Z= Volume of sample taken in ml

CONCLUSION

The above describes the main features of the majority of coke oven by-products plants around the world. Coal properties and plant design and operation influence the actual quantities.

Blast Furnaces, the mother units of any Steel plant require huge quantities of strong, hard and porous solid fuel in the form of hard metallurgical coke for supplying necessary heat for carrying out the reduction and refining reactions besides acting as a reducing agent. At VSP there are Four Coke Oven Batteries, 7 Metre tall and having 67 Ovens each. Each oven is having a volume of 41.6 cu. metre & can hold upto 31.6 Tonnes of dry coal charge. There are 4 Coke Dry Cooling Plants (CDCP) each having 4 cooling chambers. Nitrogen gas is used as the Cooling medium. The heat recovery from nitrogen is done by generating steam and expanding in two back pressure turbines to produce 7.5 MW each.

The Coal chemicals such as Benzole (& its products), Tar (& its products), Ammonium Sulphate etc. are extracted in Coal Chemical Plant from C.O. Gas. After recovering the Coal chemicals the gas is used as a by product fuel by mixing it with gases such as BF Gas, LD Gas etc. A mechanical,Biological & chemical treatment plant takes care of the effluents.

REFERENCES

1) en.wikipedia.org/

2) Data from the in charge officers

3) VSP website: https://www.vizagsteel.com/index.asp

4) www.google.com