CHAPTER-1RAW MATERIAL HANDLING

Introduction:

In general, a right amount of input for an industry is necessary in order to

produce an effective output. In our pellet plant we are getting the iron ore fines as the input

from National Mineral Development Corporation (NMDC), we need an effective handling

system for the passage of the raw material from NMDC to our plant, hence we are making

use of Conveyors for serving that purpose.

Fig: Stockpile Area

Generally during mining different sizes of iron ore are being produced with

different quantities of iron content. In this aspect large amount of run-off mines are

produced during mining. These are –10 mm fines and these fines comes from screening

plant of NMDC through their conveyors then with the help of stacker these fines are being

dumped at their stockpile.

Belt Conveyors System:-

A Conveyor belt or belt conveyor consist of two end pulleys, with a continuous loop of

material that rotates about them. The pulleys are powered, moving the belt and the material

on the forward. Conveyor belts are extensively used to transport industrial and agricultural

materials, such as grain, coal, ores, etc. Conveyor belts with regularly spaced partitions are

often called elevator belts. Conveyor belts are used in self-unloading bulk freighters and

in live bottom trucks. This technology is also used in conveyor transport such as

moving sidewalks or escalators, as well as on many manufacturing assembly lines.

Stores often have conveyor belts at the checkout counter to move shopping items. Ski

areas also use conveyor belts to transport skiers up the hill.

In contrast, the moving floor system is a technology that used reciprocating slats to

move cargo through the floor. Also in contrast is a roller conveyor system, which uses a

series of rotating rollers to convey boxes or pallets.

Conveyor mechanisms are used as components in automated distribution and

warehousing. In combination with computer controlled pallet-handling equipment this

allows for more efficient retail, wholesale, and manufacturing distribution. It is

considered a labor saving system that allows large volumes to move rapidly through a

process, allowing companies to ship or receive higher volumes to move rapidly through

a process, allowing companies to ship or receive higher volumes with smaller storage

space and with less labour expense.

Fig: -Basic Arrangement of Conveyors

2

Drive pulley Snub

Pulley

Take up pulley

Bend pulley

Tail pulley

Basic Terminology:-1. Head Pulley: It is the pulley towards which the carrying side of belt approach.

2. Snub Pulley: It is the pulley, which is used to increase the contact surface of the

belt with the pulley, generally it is placed near the head pulley, and snub pulley

increases the angle of contact, there by increasing the tension.

3. Bend Pulley: It is the pulley, which is helpful in changing the direction from the

actual line of movement; it is generally used in coincidence with the take-up

pulley.

4. Take-Up Pulley: It is the pulley, which is helpful in increasing the tension of the

belt, having some load, so as to keep belt always under tension, does this.

5. Tail Pulley: It is the pulley towards which the return side of the belt approaches.

Belt Supports:

The carrying side of the belt is supported on three rollers, one of which is parallel

to the belt and the other two are inclined so as to form a trough of the belt. Two rollers

support the return side.

The gripping of one belt with that of pulley can be increased by having a rubber

structure around the pulley, this structure has different design grooves, which aid in the

gripping action.

Belt Construction:

Belt is a rubberized material, which consists of layers, the top and bottom

layers are made of rubber. The intermediate layer can be either fabric or steel

chords, which are called plies. The number of layers determines the strength of the

belt.

3

CHAPTER-2

IRON ORE GRINDING

Introduction to Grinding:

The term Grinding refers to the size reduction of a material by tumbling it

in a revolving cylinder. There are two types of grinding processes (1) Vertical and (2)

Horizontal. But we are using Horizontal Ball mill Iron Ore grinding process. This occurs

when the ore and a grinding media are tumbled together usually is a long horizontal

cylinder called “BALL MILL”. The grinding media used are steel balls. These steel balls

are may be of different diameters as grinding media.

Fig: Grinding Media

The media method of size reduction depends primarily on impact or compression

fracture of the ore caused by the impact action of heavier steel balls. Such impacts caused

by the impacts or point-to-point contacts occur between the ore and the balls or between

the balls and the mill shell liners. It is important that the balls are large enough so that as

many points of contacts as possible occur and sufficient impacting action is provided

which will result in the proper breaking of the ore particle.

The grinding mill liners are provided with lifters. As the mill cylinder is rotated

the lifters lift the balls to give them a proper cascade pattern and the energy to do

breaking. The cascade pattern is determined by the rotating speed of the mill cylinder and

4

the mill diameter. The energy consumed in grinding is therefore proportional to the

weight of media, the diameter and rotational speed of the mill.

The size of the ball media is determined by the size of the ball media is

determined by the size of the incoming feed particles. Larger sized ore requires a larger

ball size for good impact efficiency. As the ore is gradually reduced size, the media itself

wears out and the balls are reduced in size. These smaller balls are also necessary, as

these balls are still adequate in size to cause fracture because many more points of

contact occur and many more balls are present per unit volume. It is imperative to add

bigger size balls for two reasons.

1. To keep up the number of bigger size balls to break the large ore particles.

2. To maintain the required number of balls in the mill to provide the power

required for grinding. The media should be added as and when required as the

balls are continuously being worn away.

Another mechanism of size reduction that occurs in the mill together with impact

grinding is abrasive grinding or attrition grinding or grinding by rubbing as the ore

particles and media slide and rub against each other as the ball mill rotates.

Fig : Ball mill input and output

The size of the ore up to a certain extent, it is best to make the ball mill diameter

as large as possible. However mill length is also important. If the mill is too short, Ore

particles could flow through the mill and may never come into the point contact with

5

media. This is known as “short circuiting”. Many mills are provided with a classifier at

the discharge end (like cyclones) where the oversized particles are returned back to the

feed end of the mill. Mills grinding in closed circuit can be shorter than those grinding in

open circuit. Mills grinding in open circuit, which means the designed size reduction has

to be done in one pass, are usually about twice in the size as compared to those in closed

circuit. Closed circuit was selected for this facility in our case because iron ore fines are

procured from different sources and have a wide range of particle size distribution and

tests showed that they would give best balling and induration results.

Fig : Ball Mill Discharge

All the remaining processes are mainly dependant on the successful grinding of

the iron ore particles i.e. The ball mills must grind the particles to a specific size range for

the success of all the other operations that follow. If the grind is too coarse the material

will not ball easily. If the grind is too fine it may inhibit the drying action of the filters

and thereby substantially decrease their output.

Generally wet grinding process will be preferred for the grinding of iron ore i.e.

water will be added to the raw material at feed end of the mill and this will be removed in

subsequent operations like thickening and filtration. We have 3 mills in total namely:

Primary Mill, Regrind Mill and Single Mill. We have an option of running both primary

and single mills as open circuits and also as closed circuits and as also as closed circuits

by connecting another pump to the regrind mill.

The ball mills must grind the particles to a specific size range, as over size results

in poor balling and undersize leads to reduction of throughput of filters. We are using a

wet grinding process at both Vizag and Kirandul. In this process water is

6

added to the raw material at the feed end of the mill and this will be removed in

subsequent operations like filtration and induration to make pellets.

The speed at which the balls in the mill are lifted up to 1800 with the help of lifter bars is

known as critical speed of the mill. Practically we run the mill at 70% of critical speed.

CRITICAL SPEED OF BALL MILLS:-CRITICAL SPEED OF BALL MILLS:-

CRITICAL SPEED: IT IS THE LOWEST RPM WHICH WILL CAUSE AN INFINITELY SMALL CRITICAL SPEED: IT IS THE LOWEST RPM WHICH WILL CAUSE AN INFINITELY SMALL PARTICLE ON THE SHELL LINER TO CENTRIFUGE.PARTICLE ON THE SHELL LINER TO CENTRIFUGE.

BALL MILLS ARE NORMALLY OPERATED AT BALL MILLS ARE NORMALLY OPERATED AT 70 – 75%70 – 75% CRITICAL SPEED. CRITICAL SPEED.

CRITICAL SPEED: [RPM] = 76.63 / √ DCRITICAL SPEED: [RPM] = 76.63 / √ D Where D is the Internal Diameter of mill in feet, measured inside shell linersWhere D is the Internal Diameter of mill in feet, measured inside shell liners

Types of circuits used in the Mills: -1. Single Mill2. Primary as Single Mill3. Primary as Twin Circuit4. Single as Twin circuit

Types of Grinding Media : Steel Balls Rods Pebbles

Types of Grinding Mills : 1. Rod Mills2. Ball Mills3. Pebble Mills

The Pebble Mills are predominantly for secondary Grinding.

The advantages of wet grinding over dry grinding are as follows:

Very less amount of dust, there by reducing air pollution

Less power requirement per ton as compared to dry grinding

7

Factors controlling the ball mill:

1. Mill feed

2. Feed water

3. Mill discharge density

4. Cyclone pressure

5. Cyclone feed density

The patterns, which generally exist, are: -

a) Cascade Pattern – Here the lifters lifts the balls giving them the proper cascading

energy for breaking up the ore initially.

b) Impact Pattern - Once the balls lifted up and after attaining a definite height it falls

down on the ore creating fractures. More the intensity of the balls finer be the size

reduction.

c) Attrition Pattern – This takes place along with the impact grinding, here due to

rubbing / sliding of the ore particles and the media against each other, size reduction

takes place on the mill rotation.

The discharge of the ball mill (through the Trommel) passed through the hydro

cyclones to separate the fines particles from coarse particles, it acts as a classifier.

The details of a hydro cyclones given below:-

HYDRO CYCLONES:-

The hydro-cyclones are a cluster of cyclones used in order to classify the various

materials using the principle of Cyclones. Just as in a cyclone the lighter particle whirl

around and rise up to the air and the coarser particles gets concentrated to the center, the

same phenomenon guides the separation of a denser and a lighter slurry. The Krebs

hydro-cyclones are used in our plant in order to differentiate the slurry and to obtain a

finer material.

8

Fig: Hydro-Cyclones

The main parts of the cyclone are:

Inlet orifice: The inlet orifice governs the velocity of the materials. The inlet is

generally an in volute orifice, which orients the particle thereby, creating a lesser

turbulent inflow and thus reducing the probability of flow of coarser particles to

the vortex finder.

Vortex finder: This has a critical impact on the quality of the product obtained. A

larger vortex finder creates a coarser cut thus allowing the coarser particles to

reach the overflow and vice-versa. This is because a higher pressure produces a

better quality of the product.

Cylinder/body extension: This is the cylindrical part of the cyclone. The larger

the cylinder length the higher will be the handling capacity of the cyclone. This is

an optional part of the cyclone that just enhances the quantity of the material to be

classified.

Long body/cone: The conical part is used to converge the flow of the material

and create a cyclonic effect. This is another critical part of the cyclone next to the

vortex finder as it is the part that creates the cyclonic effect. The angle of the cone

is a valuable factor that affects output. Any change in the angle can create

threading effect that pulls down even the finer particle to the underflow.

Apex orifice: The size of the orifice controls the roping effect of the underflow.

The orifice must be large enough to allow the material to flow freely and thus

reducing the choking of the material

9

Spray reducer: This is used just to reduce the spray of the coarse materials flow.

The spray reducer creates a small pressure difference and thus constricts the

materials to the apex of the cyclone.

The cyclone is completely rubber lined in order to reduce the wear of the metal as

it comes in contact with some of the most abrasive materials.

The performance of the cyclone is not only depended upon the physical parts of

the cyclone but also depends on the various process parameters. These parameters are the

only factors to control the product quality, as the physical parameters are not flexible.

The various process parameters that govern the cyclones effective output are:

Particle size: the finer the particles the probability of getting a right throughput

decreases and vice versa.

Specific gravity of the solids: The higher the specific gravity higher would be

the weight of the material thus leading to an improper quality of product.

Pulp density: The material must be properly mixed or have a uniform density.

The more the material the density will be uniform the higher is the quality of

classification

Inlet pressure: a higher inlet pressure would create a better cyclonic effect, thus

improving the classification of the material.

Feed quantity: the higher feed quantity supports a better classification, as the

velocity will have a uniform impact on the materials.

Ball Mill Lubrication SystemThe Ball mill is operated at very high power nearly; so during its operation enormous

amount of heat is liberated at ball mill main bearings, pinion bearings, gearbox, girth gear

and pinion. Hence proper amount of lubrication should be given in order to run the ball mill

efficiently.

10

ADDITIVE GRINDING :

Limestone, Dolomite, Bentonite and Coke are the additives we use in the pellatization process. Limestone and dolomite are used as additives and Bentonite is used as a binder. Coke is used to reduce the fuel consumption in the induration process.

Additive grinding unit totally consists of three activities. Those are 1] Raw material loading to day bins. 2] Grinding

1] Raw material loading: The raw materials are loaded to respective bins by conveyor system. This consists of conveyors AC1, AC2 and Shuttle conveyor. Front-end loader loads the material in to the hopper provided on the conveyor AC1. Shuttle conveyor direction can be selected by selecting the raw material to be loaded. Bentonite is loaded to B5002 bin.Lime stone or dolomite either singly or in combination of specified ratio is loaded to B5003 bin. Coke is loaded to B5OO4 bin.

2] Additive Grinding And Pumping: The raw material is ground in a roller mill (Raymond mill) to the required size. Lime stone or dolomite is either ground singly or in combination with coke in the desired ratio (L: C=3:1) and bentonite is always ground alone

11

CHAPTER-2-1THICKENER

Thickening is a process of reducing the liquid content and thereby increasing the

solid density within the slurry. The mechanism is all based on the settling rate. The

settling is even controlled by the rotation of the rake arms. The rotation of the rake arms

makes the denser particles to be dragged to the central portion and the light particles

move to the periphery. Almost clear water is taken as the overflow.

Construction of thickener:

Fig : Parts of a Conventional Thickener

Figure shows the different parts of a thickener,

1. Drive unit 2.Hydraulic unit 3. Local control unit 4. Rake assembly

5.Bridge and walkway 6.Way to launder 7.Understructures

Thickener is essentially a conical tank like structure. It has a central shaft at the

axis of the conical tank. The rake arms are attached to a sprocket that rotates about the

central shaft. There are four arms, two long and two short, all 900 apart. The longer arms

are responsible for the settling action. The shorter arms mainly deal with the central

portion. But the central area is a denser portion subjecting more torque on the arms. The

shorter arms handle such denser matter reducing the torque on longer arms.

12

Fig 5.2: Overall Mechanism of Thickeners

There are two motors, which rotate the central sprocket. There is also hydraulic

lifting mechanism, which is used for lifting the rake arms. Whenever the production is

stopped, the denser material slowly settles down and thereby the rake arms experience

high torque when started again. So the rake arms are lifted such that they are above the

high-density slurry and experience less torque during subsequent start up. When the

process is engaged, slowly the rake arms are lowered.

The inlet for the thickener is at the central portion where the slurry passes by a

launder or a pipe. There is a pass way to walk to the central portion of the thickener in

order to meet the maintenance of the drive and lifting unit.

13

CHAPTER-3FILTRATION

Process Descript ion:

Thickening Process :

The thickener is installed to handle a turbid liquid from which coarser granular materials have been removed by other means such as classifier.Feed to thickener comprises of

(1) Cyclone overflow slurry from iron ore grinding(2) Slurry from de dusting system(3) Slurry from filters overflow(4) Filtrate from filter plant

The iron ore slurry supplied from the grinding plant through a slurry line is directly fed into the feed well of thickener, with a density of approximately 1.25t/m 3 . Here there is a 50mts diameter thickener, equipped with 2 long and 2 short rake arms that scrape the settled solids to the central discharge well. The raking mechanism collects the solids as fast as they settle. The rake blades roll and squeeze liquids from the solids as fast as they settle. The rake blades roll and squeeze liquids from the solids during their travel to the center of the thickener. The rake drive mechanism will lift automatically step by step until the normal operating torque is restored. After a preset interval, the rakes will be lowered again step by step. The thickener has two products underflow and overflow, the major parts of the feed i.e. water flows over at the periphery into the process water basin via a corresponding launder. The under flow, which is a thickener slurry with approximately 70% solids by weight will be taken out from the central discharge well through a variable speed pump. The pressure lines of the pumps are connected to the slurry distributor. The slurry density is indicated by in the control room. If the slurry density has not reached a preset value, the slurry can be circulated to the thickener by opening relevant valves. From the thickener the final slurry is pumped to one of the two slurry storage tanks via distributor cone. Operation of the corresponding shut off valves of the distributor cone is remote controlled. The slurry tanks are equipped with agitators to maintain the solid particles in suspension and to assist in homogenization. The slurry tanks are interconnected by across flow pipes to give increased operational flexibility. Both tanks can be emptied separately and independently, if the valves of the connecting pipe between pipe between the tanks are closed. One of the tanks is filled from thickener, while the other one can be used for filtration. There is a possibility of operating the

14

tanks in such a way that the thickened slurry, to be pumped to filters, is fed from the thickener into one tank and flows through the connecting pipes with opened valves into the second tank, from which slurry is supplied to the filters.

Filtration Process:

The filtration section serves to dewater the thickened slurry to residual moisture of approximately 9.5% by weight. For producing the necessary vacuum, each filter is equipped with a vacuum pump, each filter is equipped with a vacuum pump, sucking a mixture of air and filtrate water from the filters via double stage vacuum receiver system, where air and filtrate water are separated. The filter cake from the filters is separated and is collected on to a belt conveyor and fed into filter cake bin, which is having an effective volume of 450cu.mts. The moisture content of the filter cake depends on the fineness of the material, speed of the discs, the feed slurry density, the cake thickness and the suction vacuum, in addition to the mechanical performance of the filter. As the speed of rotation of the discs is increased, production rate increases. However, since the filter cake is subject to drying vacuum for a shorter time, the moisture content could increase. The disc filters are therefore provided with variable speed drives in order to provide a control over speed so that optimum capacity can be achieved. While the moisture content is held with in the required limit. Level control of the filter boot is provided to ensure that the filter may be run at near maximum level to obtain optimum capacity with less chances of vacuum leakages and less chances of boot overflow.

Major equipment Used: The following are the major equipment involved in the Filtering section:

1. Thickener rake mechanism2. Vacuum disc filters 3. Ceramic filters4. Slurry pumps 5. Slurry Tank and Agitators6. Belt Conveyors7. Compressors

15

CHAPTER-3-1

MIXING AND BALLING

Process Description: The production of filter cake is followed by a through mixing of the filter cake with the ground additives namely, limestone, coke and bentonite. This activity is accomplished in an intensive mixer. The output of the mixer is a homogenously mixed material, which is used to produce green balls on the pelletizing discs. Filter cake is drawn from its storage bin by a variable speed weigh feeder. The weigh feeder is provided with a load cell, which senses the weight of the conveyor. The weigh feeder belt speed is varied to feed the desired quantity of material to the mixer. The filter cake is conveyed from the weigh feeder to the mixer by a belt conveyor, which discharges the filter cake into the mixer through a chute. Bentonite and limestone + coke are drawn from the day bins by gravitimetric weigh feeders called loss-in-weigh feeders. The loss-in-weigh feeders control the addition of additives and are provided with hooper mounted on load cells. The weigh loss of the hooper in a given time indicated the amount of material discharged from the hopper. At the bottom of each hooper is located a screw which conveys the additives into the mixed feed chute.

MIXER: Mixer is provided for mixing of iron ore concentrate, bentonite and dolomite on continuous basis. The maximum throughput of the mixer is 460 t/hr and material retention time is approximately 68 seconds.

Mixed consists of following subunits:1. Central pan-holds the material being mixed.2. Agitators (rotor tools) – 3 nos for mixing material.3. Discharge gate assembly with hydraulic power pack.4. Central lube system for bearings and girth gear.5. Lube oil-cooling circuit for agitator 1.

Effective mixing of filter cake and additives depends upon their retention time in the mixer. In other words, the gate opening determines the retention time of the material in the mixer. The mixer is provided with a load cell, which indicates the weight of the material in the mixer. As mixing is continuous process, the above procedure facilitates in the production of mixed material of homogenous quality. The mixed material is than conveyed to storage bins by a series of conveyors colloquially. This series consists of four conveyors. This series is also includes a conveyor that is used for collecting the rejected green balls after screening. The material through conveyor falls into the storage bins whenever corresponding plough is lowered onto the belt surface to plough the material off the sides of the belt.

16

The mixed material is withdrawn from the storage bins by weigh feeders, which discharge the material onto the discs through a chute. The material that is fed to the discs should be in a powder form. In order to break any large lumps of the mixed ore oversized green balls, feed chutes of the discs are provided with motor driven fluffers. A fluffer consists of a horizontal shaft mounted with a number of blades, which rotated at a high speed, breaks the material falling on it.

GREEN BALLING : The pelletizing discs consist of a flat circular base with a wall perpendicular to the plane of the base along the circumferences. Scrapers are provided on the base and side wall for deflecting the material. The disc is inclined at angle greater than the angle of response of the feed material and is rotated in this plane with a variable speed drive. The scrapers are fixed 1 position and do not rotate with the disc.Agglomeration: As the material is fed to the disc, it gets lifted upwards due to the rotation of the disc. The material gets lifted up as long as the friction between the ore particles and the disc bed is more than the gravitational force. Once the gravitation force on the ore particles is more than the frictional force, the particles roll down. As the particles roll down, they agglomerate. The agglomeration of the particles and the continues as long as the rolling movement is sustained, resulting in formation of the balls.

The scrapers provided defect the material, limiting the distance to which ore particles are lifted, there by facilitating rolling action. The smaller the particle, the greater is the distance to which it is carried by the disc rotation. Once the particles attain sufficient size, they escape from the disc by virtue of their higher centrifugal force. The balls have certain moisture content (9.0 to 9.5) and hence are called green balls. The green balls, which escape from the disc, are guided onto a conveyor, which transports the green balls to the reciprocating conveyor.

Major equipment Used:

The following are the major equipment involved in the Mixing and Balling section:

1. Intensive mixer2. Pelletizing Discs3. Belt Conveyors4. Loss-in-weigh feeders5. Dosing belt weigh feeders

17

CHAPTER-4 INDURATION

Process Description: Initially machine has to be filled with 300mm hearth layer pellets and to be moved up to cooling zone-2. For this purpose hearth layer series conveyors have to be started and filling activity has to be completed. Cooling air fan connected wind boxes and updraft-drying fan connected wind box doors are to be closed. Atomizing air fan has to be started and all the burners have to be kept in their respective positions. Heating up the furnace activity has to be separated. For this pilot burners have to be made ON in CZ and temperature has to be raised slowly. Fuel oil transfer pump has to be started for the oil re-circulation from the tank to the oil header and back to the tank. Oil preheating system has to be started and increase the oil temperature to the required value for firing the oil in the burners. Once the hood temperature reaches 50o c, hood exhaust fan has to be started and updraft hood pressure to be maintained negative and the main burners start up to be initiated. Initially 2 burners in CZ opposite side of the furnace have to be started and hood temperature has to be raised slowly. If required, 2 more burners in a zigzag fashion have to be made ON in CZ for temperature increase. Temperature gradient of 50o c/hr should be attempted. Once the hood temperature reaches 100o c. Operator at the burner area should give clearance for the lintel & seal box cooling water pump and ensure water flow at all the outlets. Once the hood temperature reaches 400o c. Start up of conveyor systems and process fans can be initiated. Fan lube systems and cooling systems to be started. All the dedusting systems are to be started (i.e. feed and discharge end & hearth layer separation area systems). Hearth layer and product conveyor systems are to be started. Once all the conveyor system and dedusting systems are through. Process fans startup can be initiated.

The sequences of start up of process fans are1. Wind box exhaust fan2. Wind box recuperation fan3. Cooling air fan4. Up draft drying fan

Before starting of the respective fans the corresponding wind box doors are to be Closed.(Cooling air fan connecting wind boxes will be in closed condition from the beginning of the heat up). Control room engineer will control the process fan dampers as per the temperature profile. Machine lube system and grease system are to be started and machine is to be moved at a slow speed (0.8-1.0 m/min) with the 300 mm hearth layer. Once M/c stats moving, temperature can be raised at a rate of 75o c/hr and remaining burners in CZ are to be ignited. Once CZ burners are on, control room clearance has to be taken for lighting the

18

remaining zone burners. During the temperature raising time, the M/c will be running with the 300 mm hearth layer in recirculation. Once the hood temperature reaches 1200o c, start up of feed circuit for the green feed can be initiated. (Refer Table 3 for temperature Gradient) Feed end sequence/system i.e. conveyor for undersize/oversize, double deck screener, reciprocating conveyor, wide belt and hydraulic device can be initiated. Initially 3 discs to be started after taking clearance from shift-in-charge. Once the green balls start discharging, the hearth layer height from 300 mm to be reduced slowly as per the control room instruction. CCR will set the pellet bed height to get the required M/C speed. Once the green balls start discharging on to the reciprocating conveyor, hydraulic device stroke to be adjusted to the required pressure. Once the green feed enters into the furnace the sequence of operations like drying, preheating, firing and cooling will takes places. Control room engineers will control the process fan dampers to attain the wind box temperature profile, pressure ratio and hood pressure profile. Once the pellets start discharging 4th and 5th disc can be initiated. Once the pellet production is through equipment checking- physical inspection & checklist updating to be carried out.

19