1.2 mptpapp

PLANTPROCESS OPERATION& CONTROL

AREA:INDURATION

PROJECT: 1.2 MTPA PELLET PLANT

FOR

Client:

M/s:- JAYASWAL NECO INDUSTRIES LIMITED

Consultant:

M/s GANG ENGINEERING PVT LTD

RAIPUR , C.G

Revision 0.

Dated Jan. 3rd .2013

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Table of Contents

1. Introduction............................................................................................................................1

2. Induration Process Review...................................................................................................2

2.1 The Indurating machine..................................................................................................22.2 Process Areas, Process Fans.........................................................................................22.3 Material flow through the machine..................................................................................3

2.3.1 Drying.....................................................................................................................32.3.2 Preheating..............................................................................................................32.3.3 Firing......................................................................................................................32.3.4 After-firing...............................................................................................................42.3.5 Cooling in the 1st cooling zone..............................................................................42.3.6 Cooling in the 2nd cooling zone.............................................................................42.3.7 Machine Discharge................................................................................................4

2.4 Gas flow through the machine........................................................................................42.4.1 Overview................................................................................................................42.4.2 Primary Process Gas Stream.................................................................................52.4.3 Secondary Process Gas Stream............................................................................52.4.4 Other Features of the Process Gas System..........................................................5

3. Control Review.......................................................................................................................5

3.1 Operating Modes.............................................................................................................53.1.1 Local Mode.............................................................................................................53.1.2 Remote Mode.........................................................................................................63.1.3 Manual Mode.........................................................................................................63.1.4 Automatic Mode.....................................................................................................63.1.5 Cascade Mode.......................................................................................................6

3.2 Principal Control Mechanisms in the Induration machine...............................................63.2.1 Grate Speed and Bed Depth..................................................................................63.2.2 Hood Temperature Profile......................................................................................73.2.3 Burn-through Control..............................................................................................8

3.3 Secondary Control Mechanisms in the Induration machine............................................83.3.1 Cooling Air Flow.....................................................................................................83.3.2 Updraft Drying Windbox Pressure..........................................................................83.3.3 Updraft Drying Temperature..................................................................................83.3.4 Downdraft Drying Temperature..............................................................................93.3.5 Windbox Exhaust Fan Flow...................................................................................93.3.6 Downdraft Drying Hood Pressure..........................................................................93.3.7 Updraft Drying Hood Pressure...............................................................................9

4. Operational Review................................................................................................................9

4.1 Starting Up the Plant after a Planned Shutdown............................................................94.1.1 Routine Checks......................................................................................................94.1.2 Utilities....................................................................................................................94.1.3 Heating-up of the Firing Hood..............................................................................104.1.4 Starting the Main Burners....................................................................................114.1.5 Heating Up and Starting the Plant........................................................................11

4.2 Cold Shutdown of the Induration System......................................................................144.3 Interruptions and Failures.............................................................................................16

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4.3.1 Interruption of the Indurating Machine.................................................................164.3.2 Interruption Less Than 7 Minutes.........................................................................164.3.3 Interruption More Than 7 Minutes........................................................................164.3.4 Power Failure.......................................................................................................174.3.5 Emergency Diesel Generator Failure...................................................................17

4.4 Faults during Operation................................................................................................18

4.4.2 Breakdown 0f Vibrating Feeders .........................................................................194.4.3 Breakdown for Belt Conveyor .............................................................................194.4.4 Breakdown of the Hearth Layer Feeding System................................................194.4.5 Breakdown of the Travelling Grate. .....................................................................194.4.6 Breakdown of the Green Pellet Conveyor System...............................................194.4.7 Breakdown of the Green Pellet Undersize System..............................................194.4.8 Breakdown of the Double Deck Roller Screen.....................................................194.4.9 Breakdown of Cooling Air Fan.............................................................................194.4.10 Breakdown of Windbox Recuperating Fan. (This option should be authorized

by Senior Manager PP)........................................................................................204.4.11 Breakdown of Updraft Drying Fan........................................................................204.4.12 Breakdown of Windbox Exhaust Fan...................................................................204.4.13 Breakdown of Hood Exhaust Fan........................................................................204.4.14 Breakdown of Burner cooling (Cooling) Air Fan...................................................204.4.15 Unsatisfactory Permeability of Pellet Bed............................................................204.4.16 Too Much Charge Supplied to Travelling Grate...................................................204.4.17 Windbox Temperature Profile Too High...............................................................214.4.18 Pellet Temperature at Travelling Grate Discharge Too High...............................214.4.19 Firing Hood Pressure Too High............................................................................214.4.20 Breakdown of Cooling Water System for the Travelling Grate.............................21

5. Interlocks and Alarms.........................................................................................................22

5.1 Interlocks.......................................................................................................................225.1.1 Travelling Grate....................................................................................................225.1.2 Hood exhaust air fan ...........................................................................................225.1.3 Updraft Drying Fan, Windbox Recuperation Fan , Windbox Exhaust Fan ..........235.1.4 Cooling Air Fan....................................................................................................245.1.6 Associated Ancillary Systems..............................................................................25

6. Alarms...................................................................................................................................27

7. Required Logic and Instrumentation................................................................................28

7.1 Bed Level and Grate Speed..........................................................................................287.2 Pallet Change Facility...................................................................................................287.3 Pallet Car Identification.................................................................................................29

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1. Introduction

The purpose of the induration section is to dry, heat harden and cool the green pellets to produce a fired pellet with properties suitable for processing into sponge iron in the Direct Reduction plant.

The pellets are hardened on a 3-meter wide Straight Grate induration machine. The machine has a Parea of 189m2. Green pellets are dried in two stages, updraft followed by downdraft drying gas flow. The dried pellets are preheated to a progressively higher temperature. The pellets are then fired at approx. 1300oC to provide the recrystallisation and slag bonding which will give the pellets adequate strength. A short section designated as after-firing allows the heat front to completely penetrate to the bottom of the bed without the application of additional high temperature heat.

Cooling is accomplished on the travelling grate in two stages by updraft passage of ambient air supplied by a cooling air fan. The cooled pellets leave the induration machine at 100oC or less.

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2. Induration Process Review

2.1 The Indurating machine

The pellet induration machine consists of a continuous strand of cast steel pallets which carry and contain the green pellets and which conveys the pellets in a layer in continuous motion through the machine. The strand comprises of 108 rail mounted pallet cars and gas-sealed at the hood and windbox sides. The bottom of the pallet car (the suction area) consists of narrow spaced separate grate-bars, which allow passage of the gaswhile preventing the pellets from falling through.

The pallet cars are drawn from the return strand and pushed along the upper strand by a toothed sprocket wheel driven by a variable speed motor at the feed end of the machine. Pallets are lowered from the top strand to the return strand by a similar non-driven sprocket at the discharge end. The expansion in the strand, which varies according to temperature of the components, is provided by a counter weight tensioning unit which controls the horizontal position of the lowering wheel.

The grate is provided with a refractory-lined hood above the machine and windboxes below the machine. The hood is provided with water-cooled side and transverse lintels. Separation of the zones in the hood is provided by internal dividing baffle walls and in the windboxes by movable shell-shaped dead plates. Two false windboxes are connected to the exhaust gas system to provide clean and cool conditions at the feed end of the machine.

Below the induration machine is a dribble conveyor which collects spillage from the tail (drive) pulley of the machine, pellets dislocated from the return strand pallets and dust and spillage from windboxes, which pass through a series of air-operated double pendulum valves.

The speed of the strand, temperatures, gas volumes and pressures can be varied to obtain optimal process conditions.

2.2 Process Areas and Process Fans

There are 7 process areas in the indurating machine, divided as follow:

Updraft Drying area 9 meters, corresponding towindbox 1 to 3.

Down Draft Drying area 6 meters “ to “ 4 to 5.

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Pre heat area 9 meters “ to “ 6 to 9.

Firing area 16 meters “ to “ 10 to 13

After Firing area 2 meters “to “ 14.

Primary cooling 16.5 meters “to “ 15 to 201/2

Secondary Cooling 4.5 meters “ to “ 201/2 and 21.

Total process area 63 m. in length X 3 m. in width. or 189 meters Square.

There are five Fans which transport process gas (essentially air) through the induration machine. These are:

Cooling Air Fan (G5002)

Updraft Drying Fan (G5012)

Windbox Recuperation Fan (G5022)

Windbox Exhaust Fan (G5032)

Hood Exhaust Fan (G5042)

In addition, a Hood Sealing Air Fan (G5045 046) is provided.

All fans are centrifugal design and the flow through them is controlled by VVVFD.

2.3 Material flow through the machine

Prior to the green pellet feed a hearth layer of 100-125 mm is laid on the grates of the pellet cars. At the same time, a 50mm wide side layer is placed against the inside each of the vertical sides of the pellet cars. The hearth layer level is controlled by 3 ultrasonic probes (G3L111,112,113).

The hearth layer and side layer consist of already fired pellets to protect the grate bars (or sides as the case may be) from the high temperature of the process gas. The green pellets are then deposited on the hearth layer from the roller screen in a layer of approx. 400mm.

The total bed height (approx. 500mm) is detected by ultrasonic probes. The speed of the grate is varied automatically from this signal to maintain a constant bed height (loop No.G3L106) . This ensures that the gas can flow through uniformly at all points.

The pellets then undergo the following operations: drying, firing and cooling.

2.3.1 Drying

The first zone is the updraft drying zoneand covers windboxes Nos. 1 to 3. In this zone hot gas (approx.280C) from the second cooling zone flow from bottom to top through the pellet bed. The gas absorbs the moisture present in the pellets and leaves the pellet bed saturated and at a low temperature (80C) and high moisture content.

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The second zone is the downdraft drying zone extending from windbox no. 4 to 5. Here, gas with 280 to 300°C is used to dry the pellets from top to bottom. The remaining moisture in the upper layer is thus removed.

The gases used for downdraft drying come from the induration zone windboxes (10 to 13). After they have passed through the pellet bed they contain much moisture and little heat; they are now no longer useful and are discharged via a ESP to the stack.

2.3.2 Preheating

After drying, the pellet temperature has to be gradually raised to the required firing temperature otherwise thermal shock may damage the pellets (spaalling). In this zone the gas temperature is progressively raisedto approx. 650-750C. This takes place in the preheating zone which covers windboxes Nos.6 to 9. The gas in this zone comes mainly from the 1st cooling zone and flows through the bed in downdraft. The temperature profile of the gas above the bed is controlled either by tempering air from the windbox recuperation fan or by F/O burners. After flowing through the preheating bed, the process gas is discharged together with waste gas from the downdraft drying zone via a ESP collector and with the Windbox Exhaust Fan to the stack.

2.3.3 Firing

In this zone there is a downward gas flow which is raised to a peak temperature of approx. 1260 to 1310C by the burners (depending on % carbon addition). The firing section extends from windbox No.10 to 13.As the material flow of pellets passes through this zone, the hot gas cause the heat front to descend progressively through the pellet bed. The temperature of the gas in the hood and the quantity of F/O burned in each group of burners is not uniform, but conforms to a thermal profile selected and adjusted by the operator based on the raw materials used for pelletizing and the physical and metallurgical properties of the product pellets, as indicated by laboratory quality control test results.

2.3.4 After-firing

When the end of the firing zone has been reached, the approx. 1260 to 1310 C heat front has still not reached the lowest layer of pellets, The material now enters the after-firing zone, which extends for windboxe No. 14)where the gas temperature is immediately lowered to approx. 1230-1280C without the use of burners. This lower gas temperature is boosted sufficiently by the hot top layer, and thus the very lowest layer of pellets is brought to the correct induration temperature.The exhaust gas from the firing zone and after-firing zone are partly discharged to the stack and partly used again for downdraft drying and preheating. The exhaust gas of the preheat zone and the first parts of the firing zone contain moisture and are low in temperature and are thus discharged to the stack.

2.3.5 Cooling in the 1st cooling zone

If the machine is properly set up, the 1260 to 1310C heat front – after leaving the after-firing zone – will have passed completely through the full green pellet layer. The 100 to 125 mm thick hearth layer, however, still protects the grate bars against the heat front.

When all the pellets have been brought to the correct temperature by the heat front, the gas flow is reversed and cold air is now blown in to cool the grate bars and the pellets on them. This prevents overheating of the grate bars. Tha gases leaving the top of the

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pellet bed range from about 1230-1280°C to about 650-700°C .The first cooling zone extends from windbox No. 15 to half of windbox No.20 (Partial).

2.3.6 Cooling in the 2nd cooling zone

In the second cooling zone the pellets are cooled still further.Gas heated during the process are used in Updraft drying. The second cooling zone extends from half of windbox20,towindbox No. 21.

2.3.7 Machine Discharge

The lowest layer is taken closeto the ambient temperature, while the topmost layer is 200 to 300C. As a result the average layer temperature becomes 80 - 100C. The hotgas from the second cooling zone hood are used for the UpdraftDrying zone.

The pellets, sufficiently cooled to be transported on rubber conveyor are discharged from the pallets at the tipping wheel into a discharge hopper mounted on load cells. Pellets are fed out of the discharge hopper at a controlled rate onto two vibrating feeders which feeds the product belt G7002A.

2.4 Gas flow through the machine

2.4.1 Overview

All process gas (essentially air) used in the machine is derived from the Cooling Air Fan (G5.002) and by in-leakage of ambient air into the sides and ends of the induration machine.

The cooling air fan (G5002) draws in ambient air and forces it up through the cooling zones at a pressure of up to500 mm WC.The air flows through the pellet bed and cools the fired pellets. The air, which is now hot, enters the hood of the 1st and 2nd cooling zones. The process gas derived from the cooling zones can be considered as two separate streams designated as primary and secondary process gas streams.

2.4.2 Primary Process Gas Stream

The larger part of the cold air which passes through the hot pellet layer has, after cooling these pellets reach an average temperature of about 800-950ºC (in 1st cooling zone) and is conveyed into the preheat and firing zone via the direct recuperation header and through downcomers to the burner chambers arranged on each side of the grate. .

In the hood of the firing zone, F/O burners heat up the gas from 800-950ºC to a peak temperature of approx. 1310ºC. The temperature to which the gases is raised in each section of the firing zone is set by the Control Room Operator depending on the raw material conditions and the quality results from the product pellets.

The windboxes under the latter part of the firing zone and the after-firing zone(windboxes Nos. 10 to14) are drawn through the bed by the Windbox Recuperation Fan (G5.022), which conveys the approx. 280-300º C gases to the Downdraft drying zone. Here the gases finally dries the green pellets.

The waste gas from Downdraft Drying, Preheating and the first part of Firing zones (windbox Nos.4 to 9) is then pulled through ESP by the Windbox Exhaust Fan (G5.032) and forced to the stack.

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2.4.3 Secondary Process Gas Stream

Part of the cooling air is drawn from above the second cooling zone by the Updraft Drying Fan (G5.012) is fed to the updraft drying zone at approximately 280-300OC.. This air is discharged to atmosphere, after passing through the bed, by the Hood Exhaust Fan (G5.042).

2.4.4 Other Features of the Process Gas System

The primary and secondary process gas streams are interconnected at two points: Interconnecting ducts from the discharge of the Windbox Recuperation Fan to the

inlet of the Updraft Drying Fan (G5.012) through dampers G5H.102(G5.025) Bleed off from Windbox Recuperation Fan to the Updraft Drying hood through

damper G5H.110

Because there is an over-pressure in the entire 1st cooling zone, the seal between the hood of this zone and the pellet cars is provided by sealing air supplied by the hood seal fan (G5045)).

3. Control Review

3.1 Operating Modes

3.1.1 Local Mode

Equipment is started, stopped or adjusted in the field. Related equipment is:

a) Burner systems – always started and normally stopped from Local Panel. Burning rate is set by at the Control Room Workstation (HMI/ MIMIC)

b) Travelling Grate – May be started, stopped and speed controlled from the Local Panel. Permission to switch between Local and Remote Control is granted at the Control Room Workstation.

c) All other equipment which can be run in “TEST” mode.

3.1.2 Remote Mode

Equipment is started or stopped from the D C S at Central Control Room Workstation

This applies to all equipment in the Induration section, with the exception of the burners and optionally the travelling grate..

3.1.3 Manual Mode

The output of an instrumentation loop controller is directly set by the Control Room Operator from the Central Control Room Workstation, irrespective of the relative values of the process variable and the set-point.

3.1.4 Automatic Mode

The output of an instrumentation loop controller is directly set by the DCS depending on the relative values of the process variable and the set-point.

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3.1.5 Cascade Mode xx

a) The setpoint of an instrumentation loop controller (slave) is set by the output from another (master) instrument.

b) When the Expert System is implemented, this will be the nominated mode when instructions and set-points are determined by the Expert System and acted on by the DCS.

3.2 Principal Control Mechanisms in the Induration machine

Control of the process is achieved by varying the temperature and flows of process gas through the machine. Some operating parameters, such as bed height, Hood temperature Profile in thePreheat and Firing Zones and Burn-through are adjusted by the Control Room Operator according to the production schedule and the quality of the product pellets.

Other parameters, such as drying zone temperatures, are set by the operator based on operating procedures and Process section instruction and are not frequently adjusted.

Process gas flow is not measured directly and the balance of the gas is obtained by maintaining pressure set-points in various points of the hoods and windboxes of the furnace. These set-points are rarely adjusted by the operator unless otherwise instructed in normal operation.

3.2.1 Grate Speed and Bed Depth

The grate is a volumetric conveying device and at a constant total bed height, the speed of the travelling grate is directly related to the quantity of green pellets fed to it. If green pellet production (after screening) increases, the grate speed increases to maintain a preset bed height as detected by the ultrasonic probes at the feed of the machine (loop No._G3L106_). The converse is true. The normal setpoint for bed height will be 500mm The normal grate speed is 1.5 m/min or lower. If production rate rises to such an extent that a grate speed reaches 1.65 m/s, the bed height may be raised further, provided that green pellet quality provides sufficient bed permeability, as determined by pressure in the windboxes of the Cooling zone (PI G5P121 to G5P126B).

3.2.2 Hood Temperature Profile

The principal process control is the attainment of the correct temperature profile of the gas entering the bed from the hood in the preheating and firing zones. The burners are divided into ten control groups along the length of the machine in the preheat and firing zones. The first two of the down comersactually contain no burners.. The temperature for each zone is set manually by the Control Room Operator. Deviation from the setpoint for a burner pair causes the quantity of Fuel oil to be burned to be automatically varied. The atomizing air and cooling air is supplied to all burners by a Air Fan G4.041 & G4.042.

In the case of the first two pair of down comer (in the preheat area), process gas to this zone is provided by the direct recuperation header and also, at a lower temperature, by the Windbox Recuperation Fan through additional ducts into the preheat zone down comers. Control valves G4.033 &G4.034 in this “spider” are indicating the temperature detected above the bed in the preheat zone. The PH 1 and PH 2 temperature are set to control the valves G4.033 & 034. For wet feed and/or high tonnages these should be set as low as possible to avoid spalling.

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First 2Down comers- No burners

Typical hood profiles are indicated in the table below:

Burner No. (pairs)Typical Set

Point No coke

Typical Setpoint with

1.4% coke

No burner Zone 450°C 425°C or less

Burner Zone 1/1 650°C 625°C or less

Burner Zone 2/2 855°C 800°C








Burner Zone 10/10 1310°C 1275°C

Burner Zone 11/11 1280°C 1230°C

3.2.3 Burn-through Control

3.2.4 The most important controls in the machine is “burn-through”. This determines the point at which the heat front reaches the bottom of the bed and the intensity of this heat front and has a direct influence on pellet quality, particularly Abrasion Index and is varied by adjusting the quantity of process gas drawn through last part of the firing zone and the after-firing zone by the Windbox Recuperation Fan. The burn-through control loop modulates the motor speed of the Windbox Recuperation Fan (G5022)according to the average temperature of the penultimate two windboxes (windbox number 12 (2 T/C),13 ( 1 T/C) in the firing zone (TIR G5T111,G5T112). If this average temperature falls below set-point, the motor speed of fan G5022 increased until setpoint is restored. The normal setpoint for burn-through is approximately 400OC without carbon addition and 370OC with carbon addition at arate of about 1.4 %. The last windbox in firing (windbox no 13) has only one (1) thermocouple included in the burn-through control because this temperature is usually lower (on one side) than actual, due to the leakage of cold air from the cooling air windboxesThis burn-thru control loop must be correctly tuned and used at all times for automatic control. It controls the tumble index and affect the compression strength. Manual operation of this loop is only for starting the machine and under exceptional conditions.

3.3 Secondary Control Mechanisms in the Induration machine

These controls are used to balance the process gas flow through the machine and maintain the required pressure differentials between process zones. In normal operation, these conditions change as a consequence of adjustments in the principle control mechanisms

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outlined above. Once established the set-points of these loops are rarely changed by the operator during normal operation.

3.3.1 Cooling Air Flow

The flow through Cooling Air Fan G5002 is controlled by maintaining a slightly negative pressure of 3 - 5mm WG in the firing zone hood (loop no. G4P305). If the Windbox Recuperation Fan VVVFD CONTROLLED (possibly due to low burn-through temperature), the above-bed pressure will become more negative and Cooling Air flow will increase (by VVVFD) until the setpoint is restored.

3.3.2 Updraft Drying Windbox Pressure

The speed of the Updraft Drying Fan G5012 is controlled to maintain a set pressure of approximately -25mm WCin the hood above the second cooling zone (loop no. G4P306).

If the windbox pressure in the Updraft Drying zone exceeds a maximum setpoint of 500mm WC, process gas is directed around the bed by a bypass duct containing damper G5015 (loop no.G5H106to the inlet of the ESPH1002, rather than through the bed.

3.3.3 Updraft Drying Temperature

1. If Updraft Drying temperature is too high, it can be tempered by air drawn in from atmosphere into the duct from 2nd cooling zone through bleed-in damper G5016 (loop G4T303). This is very unlikely as the grate absorbs 70% of the heat and the bottom of the bed sees lower temperatures.

2. If the UDD temperature is too low, at start up for instance, it can be boosted by bleeding process gas from the outlet of the Windbox Recuperation Fan G5022 to the suction side of the Updraft Drying Fan by damper G5025 and Loop No.- G5T125.

3.3.4 Downdraft Drying Temperature

If the temperature of the process gas for Downdraft Drying is too high(maximum 320°C)it can be controlled at the inlet duct of the Windbox Recuperation Fan by bleeding-in cold air from atmosphere through Tempering Air Dampers G5021 (loop G5T124).

3.3.5 Windbox Exhaust Fan Flow

Flow through the Windbox Exhaust Fan, which draws process gas from windbox Nos. 4 to9 and includes downdraft drying, preheating and the first part of the firing zones, is controlled by the temperature of windboxes Nos.7 or 8, as selected by the operator (loop no G5T117).

3.3.6 Downdraft Drying Hood Pressure

This pressure, typically -15mm WG, is set by the operator(loop no.G5P115) and is controlled by damper G5PH110.

G5H110- Bleed off from Downdraft Drying Hood to Updraft Drying Hood controlled by P/T G5P 115.

3.3.7 Updraft Drying Hood Pressure

Typically -25mm WG, this pressure is set by the operator and controls the speed of the Hood Exhaust Fan G5042 through loop no. G5P114.

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4. Operational Review

4.1 Starting Up the Plant after a Planned Shutdown

4.1.1 Routine Checks

1) Once the operation department, process department, electrical department, repairs and maintenance department, instrumentation and control department, utilities department (water/compressed air/instrument air/fuel oil) have given clearance for the plant to start operating, it can be started up from the control room.

2) All belt conveyors and material transfer points must be checked to make sure they are free from foreign matter.

3) All interlock equipment must be set for interlock operation, so that starting can be done from the control room.

4) All safety trip cords and safety switches must be set in the correct position for starting up.

5) All inspection ports must be closed and secured.

6) All process control dampers must be closed

4.1.2 Utilities

1) A check must be made that the cooling water circulation system is operating and that sufficient cooling water is available to the individual users.

2) The following users must be checked:

Cooling water system for the lintels of the travelling grate.

Coolingwater for the shuttle belt conveyor hydraulic system.

Cooling water for the hydraulic system of the mixer.

3) The travelling grate operator must check the lintels water discharge points to ensure that the correct water flow rates are set to water compartments (lintels) along the travelling grate and cross beams (lintels) between the individual zones.

4) LPG must be available at the correct pressure, temperature and supply rate to start up the plant.

5) Compressed air must be available in sufficient quantities and at a pressure of 5 bars for the following users:

Double flaps valves under the windboxes.

RAV’S under the ESP. H1.001,002

Ploughs on conveyor G1.016 to feed mixed bins.

Lubricating systems for the balling disc.

Lubricating system for the travelling grate,air supply to indurating machine burners.

6) The entire length of the travelling grate must be filled up to a depth of 350 mm with hearth/side layer. The hearth layer bin should be full.

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7) Instrument air must be available at a pressure of 5 bar.

8) Process fans:

a) Start hood exhaust fan G5.042 to provide a slight negative pressure in the furnace hood

b) Start one of the Burner Atomizing air fans ./ G4.042 from the control room.

c) Start UDD process fan G5012

d) The motor speed of the process fans are adjusted such that a slight negative pressure develops in the firing hood.

4.1.3 Heating-up of the Firing Hood

In the temperature range below approx. 700OC, the firing hood is heated up with the temperature controllers in manual mode. In this case, it is essential that the operating staff pay special attention to monitoring the individual burners. When the temperature in the firing hood reaches about 700OC, the temperature controllers can now be switched over to automatic mode.

From ambient temperature to 700OC, pilot burner are required to maintain F/O combustion, above 700OC self ignition of F/O is ensure and pilot burners have to be removed and stored properly.

At the start of heating-up, four LPG gas burners (2 on each side of the firing hood, but not opposite each other) are ignited. To ensure a gradual increase in temperature, the gas flow rate is kept to a minimum. As higher temperatures are required, more burners are ignited one after another, and the gas flow rate at the burners already running is slightly increased.

Heating up must be done in line with the heating-up curve. After each major shutdown heating curve and instruction are given by pellet plant management to control room operator and shift in charge.

4.1.4 Starting the Main Burners see bloomxxxxx

Provided that all conditions for starting are fulfilled and that natural gas is on line up to the safety shutoff valve, the individual burners can be started once the following conditions are fulfilled:

1) That one of the cooling water pumps is in operation. G6.014 OR G6.015

2) The hood exhaust fan G5.042must be in operation.

3) The updraft drying fanG5.012must be in operation. (Optional, not required below 250OC).

4) No emergency switch may be actuated.

5) One of the Burner cooling air fans G4.041orG4.042must be in operation.

6) Burner cooling air must be available at the correct pressure.

7) The LPG gas temperature and pressure may be correctly adjusted.

8) The instrument air pressure must be available.

9) Once these conditions are fulfilled, the burners can be started.

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4.1.5 Heating Up and Starting the Plant

After a planned shutdown where some refractory repairs/installation had been done, the firing hood should be heated up from ambient to 800°C at a rate of 40°C/h. From 800°C on, a rate of 70 °C/h is used.

Heating up too fast, with an excessive number of burners and with long flames must be avoided to protect the refractory lining from thermal shocks (which shorten its service life). During heating up, the travelling grate must be covered with a fired pellet, hearth/side wall protection layer of 350 mm minimum.

As already described, the hood exhaust fan and the updraft drying fan are operating. One Burner atomizing air fan is also in operation. Bleed-out damper G5015 is closed.

1) The first pilot gas burners are ignited; two burners on either side are normally sufficient.

2) Until temperature reaches at around 350 to 400 °C, no further burners are required.

3) The E S P andDust conveying system are started.

4) The conveyor system for hearth layer and product is checked and started.

5) The process gas flow rate is checked and set with slightly negative pressure in the firing hood.

6) The lubrication system for lubricating the drive and driven sprocket and travellinggrate seal bars is started.

7) The travelling grate is started up every hour locally in manual control at minimumspeed. Two pallet cars are then moved in the machine every hour.

8) When the temperature reaches about 750°C, pilot burners are removed.

9) At this stage, several burners should be in operation ( on each side of the firing hood).

10) Once all burners which are not yet running and installed in the machine, the shutoff devices for atomizing air to the burners must be opened to get sufficient air for cooling.

11) Once the temperature reaches approx. 900°C, the following pressures should be set:

Table 1

Zone PressureUp-draft drying hood -25 mm WCDowndraft drying hood -15 mm WCPreheating and firing zone -3 / -5 mm WCSecond cooling zone -15 mm WC

Those pressure adjustments are possible by modulating the motor speed on HE fan G5.042 and UDD fanG5.012. Over-pressure damper G5P114,G4.306.

12) When temperature reaches approx. 950°C to 1000°C, nearly all burners should be ignited.

13) The operating staff should take care of the following rules:

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Reducing the process gas flow rate raises the temperature in firing and cooling zones. Increasing the process gas flow rate lowers the temperature in the firing and cooling zones. HEF fan G5.042, exhaust temperature should be followed closely, if temperature rise above 200°C, HEF fan G5.042, inlet damper will close automatically.

14) WBE G5.032, WBR G5.022 and CAFG5.002 Fans are now started.

15) Once enough air is being circulated through the direct recuperation line (indicated by pressure in cooling zone I) the burner control system can be switched from manual to automatic mode. This means that all interlock conditions in the burner safety system now apply.

16) When the temperature reaches approx. 1200 °C or when the temperatures in the windboxes rise above the intended operating levels, the depth of the hearth layer is reduced to 125 mm, and possibly three balling disc (roughly 200 t/h) are started. The depth of pellets of 500 mm is regulated by means of varying the speed of the travelling grate.

17) Once the green pellets have reached the up-draft drying zone, all the firing zones temperatures must be adjusted to their normal operation temperature. Hood pressure in up-draft drying zone must be set to - 3 mm WC PIC G5P.114

18) Once the green pellets have reached windbox3, the control vanes of the WBE fan G5G113 is opened approx. 25%.

19) Once the green pellets reach windbox6, the SPEEDon the WBR fan G5.022 also is increase by approx. 25 - 30%.The temperature in firing zone should reach normal , 1250 to 1300°C at the peak.

20) Once the green pellets have reached cooling zone I, a check must be made of whether the windbox temperature profile has settled down right. The temperature in windbox14 should now be approx. 360 to 370 °C. (assuming no coke addition)

21) If the temperature there is lower, the gas flow rate of WBE G5.032 and WBR G5.022 fans must be increased; if the temperature is higher, the gas flow rate of both fans must be reduced, by adjusting fan motor speed accordingly.

22) Approx. 1 hour later, when the correct windbox temperature have developed, the discharge material from an another balling disc is diverted to the travelling grate.

23) As already described, once green pellets are reaching the various zones, the gas flow rate of fans WBE G5.032 and WBR G5022 must be adjusted, so that the correct windbox temperature profile is maintained.

24) The cooling airflow rate of CAF G5.002 is adjusted automatically, by means of controller PCR G4P305. so that a negative pressure of approx. -3 mm WG develops in the firing zone.

25) The UDD Fan G5.012 must be set, so that a negative pressure of approx. -3 mm WC develops in cooling zone II (PIC G5P306).

26) This procedure is now repeated, until (possibly) 3 balling discs are feeding to the travelling grate with an inlet feed of 160 T/H.

27) Once the travelling grate has been operating at design capacity for approx. 1 - 2 hours, all process conditions must have settled down correctly. All control Systems now get switched over to automatic control from D C S .

28) It must be remembered that as the green pellet volume increases step by step, the

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travelling grate speed is increased, which can lead to the pellet temperature at the travelling grate discharge rising for a short time. If the pellet temperature is too high, the water sprinkling system (G7T.101 at product belt conveyor G7.002 or G7.002A is started/ opened automatically.

29) As the green pellet volume increases. To protect the green pellets in the heating and firing zone, it is advisable to adjust pressure in windboxes 6 to 14.xxxx

When the plant is operating at design capacity, the following pressure profile should be established:

Windbox No.6 to 8 G5T105 to 107. - 400 mm WGWindbox No. 10 to 14 G5T109 to 113. - 400 mm WG

30) Approximate set points for the process fans and motor speed, with the plant operating at design capacity:

Table 2

Item Instrument Set pointCA Fan G5002 G4P305 - 3 mm WGHE Fan G5042 G5P114 - 25 mm WGWBR Fan G5022 G5T115 300° CWBE Fan G5032 G5T117 180 deg CUDD Fan G5012 G4P306 - 15mm WG

4.2 Cold Shutdown of the Induration System

The description assumes that:a) The plant is operating normally

b) All control systems are in automatic control. D C S

c) Inspection or repair work on the refractory lining makes it necessary to cool the hoods down.

1) The depth of the hearth layer is increased to 350 mm. The supply of green pellets is cut off. The travelling grate speed control system is switched over from automatic to manual control.

2) The green pellet conveying system to the travelling grate is emptied; it can then be stopped.

Note:During shutdowns, the mixed material bins above the balling discs should not stay filled otherwise bridges of material will form around the bin outlets. It is therefore advisable to empty the bins or, at the very least, to keep the bin level below 20%.

If the bins at the weighting belt scales are required to be empty for shutdown work, the supply of mixed material should be stopped earlier, and the supply of green pellets to the travelling grate be stopped as soon as every single bin gets empty.

3) The undersize green pellet conveying system is emptied and then stopped.

4) The fans WBE G5.032 and WBR G5.022 are switched over to manual control, and motor speed adjusted.

5) The travelling grate speed is manually adjusted at maximum 1.6 m/min.

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6) The over pressure damperG5.021 gets opened to 100%.

7) The firing curve is adjusted as follows with no coke addition.

.

8 A negative pressure of - 3 mm WG is kept in the updraft drying zone.

9) The temperatures in windboxes 10 to 14 are controlled by the motor speed of fan WBR G5022. The damper G5021 gets opened to 100% if required. Maximum temperature should not exceed 400°C.

10) When full hearth layer reach end of windbox14. All burners are stopped; WBR G5022, WBE G5032 and CA G5002 Fans are stopped. Burner cooling air must be available to cool the burners.

All burners are removed for general inspection and maintenance.

11) Vent door are opened on suction duct of fans WBE G5032 and WBR G5022.

Thus it is not absolutely required; inspection door can be open on windboxes number 15 to 21.

12) All dampers are put in manual mode and closed and fan speed on HE G5.042 and UDD G5.012 fans and damper G5G.114. Damper G5G111 is kept at 100 % open in manual mode. Only motor speed is adjusted accordingly.

13) Temperature of HE fanG5.042 should be followed closely, if temperature exceeds 200OC, inlet damper will close automatically.

14) Machine should be cooled down at a rate of 70OC/hr. by adjusting both fan motor speed.

15) Once the hood temperature has dropped below 250 °C:

a) In the case of major repairs to the refractory lining, the gate valves for hearth/side layer get closed and the travelling grate gets emptied. The hearth layer bin is filled up by means of the hearth layer conveying system. As soon as the travelling grate is empty, the grate and the conveyor systems are stopped. The greasing system for the travelling grate is stopped.

b) In the case of inspections and minor repairs to the refractory lining, the

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Zone no burner 450°C

Burner Zone 1/1 650°CBurner Zone 2/2 855°CBurner Zone 3/3 1000°CBurner Zone 4/4 1150°CBurner Zone 5/5 1250°CBurner Zone 6/6 1310°CBurner Zone 7/7 1310°CBurner Zone 8/8 1310°CBurner Zone 9/9 1310°CBurner Zone 10/10 1310°CBurner Zone 11/11 1280°C

travelling grate is stopped. Once the conveyor systems beyond are empty, they are stopped.

c) The greasing system for the travelling grate gets switched off.

16) At this point, if faster cooling is required, WBE fan G5.032 can be started and motor speed adjusted accordingly.

17) The dust collection systems for the plant are switched off.

18) As-soon as the refractory lining has cooled down far enough (below 50 °C); the remaining fans can be stopped. When WBE fan G5032 the auxiliary oil pumps is starting automatically. After a preset time, that pumps automatically stop.

The damper of HE fan G5042 to be opened, so that the flue effect causes a slight draft.

19) The cooling water system for the travelling grate should stay in operation, until the inspection of the hoods (lintels and cross lintels) has been done.

4.3 Interruptions and Failures

4.3.1 Interruption of the Indurating Machine

The firing hood temperature to be set up for an interruption mainly depends on the following conditions:

a) The length of the interruptionb) The reason for the interruption

It is perfectly possible to maintain the firing hood temperature at 900°C for few hours, provided that the travelling grate can be operated should the temperature raise for some reason.

However, it is not advisable to keep the temperature above 900°C, if the indurating machine will not start soon. In this case, either the travelling grate must be capable of moving again after a few hours or the temperature in the firing hood must be lowered further.

4.3.2 Interruption Less Than 7 Minutes

A stoppage of the travelling grate is one of the most dangerous emergencies that can occur. The control room staff must take action at once.

1) The burners are switched to "Low fire". Automatically until they reach the hold temperature the F/O flows to each burner group is reduced to minimum.

2) All fan motor speed and controllers are kept in automatic mode. If the control system of WBE G5.032 and WBR G5.022 fans were switched over to manual control. It is not advisable to operate the indurating machine in manual mode for long period of time, since; during stoppage this can produce very hazardous and dangerous conditions. (Overheating of pallet car, fan, etc.).

3) Bleed-in damper on WBE G5.032 and WBR G5.022 fans are opened at 100%.

4) With the fans and burners in operation, the firing hood temperature should stay same while running. If hood temperature rises excessively, burner should be tripped. If

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windboxes temperatures rise excessively, WBE G5032 and WBR G5022 fans speed should be reduce.

5) As soon indurating machine can be started again, green pellet feed system should be put in operation and all other operating conditions resume on the indurating machine.

6) If travelling grate is stopped for more than 7 minutes WBE G5.032, WBR G5.022 and put on turning gear (automatically)CAF G5.002fans must be stopped.

4.3.3 Interruption More Than 7 Minutes

1) If travelling grate is stopped for more than 7 minutes WBE G5.032, WBR G5022 and CAF G5002fans must stop. Burner cooling air must be available to cool the burners.

2) All the burners are put on hold condition, 900°C.(low fire followed by temperature hold).

3)All motor speed control are put in manual mode except HEG5.042, UDD G5.012 and bleed-in dampers G5.019 and G5.016.

4) Bleed-in damper are opened on suction duct of fan WBR G5.022. This it is not absolutely required; inspection door can be opened on windboxes number 6 to 13.

5) Temperature of HE fan G5042 should be followed closely. If this temperature exceeds 200 deg. °C inlet damper will close automatically.

6) Hood temperature will drop to 900°C. At that time a few burners must be started (if required) to maintain this level of temperature.

7) As soon it is confirmed when plant will be available for start-up, the ramp system must start on the control room and indurating machine and pellet plant start accordingly.

4.3.4 Power Failure

If the power supply fails, the entire plant operation is interrupted and all motor drives are stopped.

To avoid damage to the mechanical equipment, a separate emergency power supply is provided so that certain machines can be operated.

As soon as the power supply fails, the emergency power supply starts up supplying electricity for the control panel and the intercommunication equipment. The staff in the control room must now clarify with the electrical department, whether the power failure is the result of a short voltage fluctuation or of a complete breakdown of the main power supply over a considerable period:

a) If the power failure is the result of a short voltage fluctuation, the plant can be started up again as soon as the main power supply functions again.

b) If a complete breakdown over a considerable period occurs, the appropriate drives are started automatically or local.

c) Following drives are to be started immediately as soon emergency power is made available.

Description ItemCooling Water Pumps (automatically G6.014

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after 10 sec.)Cooling Water Pumps (automatically after 10 sec.)

G6.008

Burner cooling Air Fan (automatically after 10 sec.)

G4.041/.042

Air Compressor (automatically after 10 sec.)

G6.020

Air Compressor (automatically after 20 sec.)

G6.025

d) Doors are manually opened on windboxes4to14.

e) Ensure that firewater (1 of 2) is running.

f) All indurating machine burners should be purged and removed.

4.3.5 Emergency (Diesel) Generator Failure

If the power supply fails, the entire plant operation is interrupted and all motor drives are stopped.

To avoid damage to the mechanical equipment, a separate emergency power supply is provided so that certain machines can be operated. If for some reason it cannot be operated, following action should be taken on top priority.

As soon as the power supply fails, the staff in the control room must now clarify with the electrical department, whether the power failure is the result of a short voltage fluctuation or of a complete breakdown of the main power supply over a considerable period and ask about status of emergency power supply. All possible action should be taken urgently to start the diesel generator.

a) The emergency water supply on the head tank outlet valve and adjust valves position in such a way that lintelsare getting enough water. (Steam formation at the lintel discharge end should be avoided).The cross lintel at the beginning of the Pre-heat and the end of firing are the most important ones. The water flow can be reduce in UDD and second cooling in such a way that it will provide more flow to the hot section of the furnace.

b) All indurating machine burners should be removed immediately.

c) Doors are manually opened on windboxes 6 to 14.

d) This is a TOP PRIORITY EMERGENCY, power should be restored, normal or emergency, as soon as possible, lintel-cooling water will be available from the emergency system for a maximum period of 1 hour if water consumption is restricted to the minimum. If lintels run out of water, severe damage can happen to the lintels, refractory and machine structure.

4.4 Faults during Operation.

The following directives apply to faults in the operation of plant equipment. In the case of some faults, pellet production can be kept going, though at a reduced rate.

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The plant management should decide whether to stop pellet production or to carry on at a reduced rate. Possibilities of keeping pellet production going are listed below. The following cases are dealt with:

1) Breakdown of vibrating feeders. G7.003 or G7.0042) Breakdown of windboxes belt conveyor. G7.0023) Breakdown of the hearth layer feeding system.

(G8.002,G8.003,G8.004,G8.001)4) Breakdown of the travelling grate. G3.0075) Breakdown of the green pellet conveyor system—G2.0506) Breakdown of the green pellet undersize/oversize system-- G3.105/G3.0047) Breakdown of double deck roller screen.-- G3.003/M01,M028) Breakdown of the cooling air fan.-G5.0029) Breakdown of the windbox recuperating. –G5.02210) Breakdown of the updraft drying fan. -G5.01211) Breakdown of the windbox exhaust fan.- G5.03212) Breakdown of the hood exhaust fan.- G5.04213) Breakdown of the Burner Cooling air fans- G4.041/04214) Unsatisfactory permeability of pellet charge15) Too much charge supplied to travelling grate16) Windbox temperature profile too high17) Pellet temperature at travelling grate discharge too high18) Pressure in firing hood too high19) Breakdown of the lintel cooling water system for the travelling grate

4.4.1 Breakdown of Vibrating Feeders G8.001and G7.006.

If the vibrating feeders break down, the conveyor system keeps on running. All attempts must be made to keep the pellets flowing in the emergency chute of the bin . If the discharge bin G7.005 fills up and stops conveyor G7.002A and vibrating feeders G7.003 and G7.004 thetravelling grate will stop when machine discharge hopper reach 100% level reaching the maximum level.Proceed with shutdown accordingly.

4.4.2 Breakdown for Belt Conveyor G7.001

If belt conveyor G7.001 breaks down.Production can continue, since vibrating.feederG7.003, G7.004 and belt conveyor G7.002Ais in operation. The fault should be found as soon as possible, because dust and spillage will collect in the hoppers above the double pendulum valves, could result in an overload when restarting the belt conveyors, G7.001 and G7.002A. The tail end of Conveyor G7.001 will have to be inspected before any attempt to restart it. During stoppage, pellets from indurating machine drive station will get accumulated on the conveyor tail end.

4.4.3 Breakdown of the Hearth Layer Feeding System

If this conveying system breaks down, no hearth/side layer gets re-circulated. If the stoppage only lasts a few minutes (e.g. if the trip cord at belt conveyor G8003 gets pulled), there is no problem, as bin G8005 is normally kept at 80 to 85 % bin level, which means enough heath/side layer is available for approx. 15 minutes. If it is expected to last more than 20 minutes, it is better to go for an emergency shutdown.

4.4.4 Breakdown of the Travelling Grate.G3.007

Proceed with shutdown according to Section 4.3.1 or 4.3.2

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4.4.5 Breakdown of the Green Pellet Conveyor System G2.050


4.4.6 Breakdown of the Green Pellet Undersize/Oversize System G3.105


4.4.7 Breakdown of the Double Deck Roller Screen. G3.003


4.4.8 Breakdown of Cooling Air Fan.G5.002

If the cooling air fan breaks down, the travelling grate must be stopped immediately; otherwise excessively hot pellets will be discharged. If the fan can be restarted immediately, burners should be switched on low fire, otherwise if the fan is not started immediately, the burners must be extinguished and the process fans switched off. A supply of air must be available to cool the burners. The vent door must be opened on fan WBEG5.032 and WBR G5.022. This is not strictly necessary, the doors of windboxes 6 to 14 can alsobe opened to cool the grate to avoid sagging of pallet car.

4.4.9 Breakdown of Windbox Recuperating Fan G5.022.

Indurating machine is stopped. Proceed with shutdown according to section 4.3.1. or 4.3.2.

4.4.10.Breakdown of Updraft Drying Fan G5012.

Indurating machine is stopped. Proceed with shutdown according to section 4.3.1.or 4.3.2.

4.4.11.Breakdown of Windbox Exhaust Fan G5032

Indurating machine is stopped. Proceed with shutdown according to Section 4.3.1 or 4.3.2

4.4.12.Breakdown of Hood Exhaust Fan G5042

Indurating machine is stopped. Proceed with shutdown according to section 4.3..1. or 4.3.2.

4.4.10 Breakdown of Burner Cooling Air Fan G1.041, G1.042

One of the two fans is always running, one fan is a standby. If one of the fans in operation breaks down, the shutoff damper closes and the standby fan automatically starts. The shutoff damper opens automatically. During the same period the burners will go off due to lack of atomizing air and the grate will stop, purging will take place automatically and the burner will be relit. Once the temperature is back to normal the grate can be restarted.

4.4.11 Unsatisfactory Permeability of Pellet Bed

Unsatisfactory permeability is usually caused by inferior green pellets quality. The supply of green pellets to the travelling grate should therefore be reduced, until normal conditions are re-established. The first symptom of a decline in green pellet quality is a drop in windboxtemperature plus increase in pressure in the windboxes of the preheating and firing zone.Unsatisfactory permeability can also be caused by:

a) Excessively high firing temperatures;

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This may be the result of incorrect temperature set points or of faulty temperature indication.

b) Pellets bursting in the drying zones or preheating zone;This can occur, if the moisture is too high or the volume of green pellets is too large and the capacity of the drying and preheating zones is therefore inadequate. In this case, the moisture content of the green pellets or the degree of fineness in grinding may be the cause; also the binder addition should be checked for adequate drop number of the green pellets. Appropriate action should be taken to adjust the operating parameters correctly.

c) Crushing of green pellet due to indurating machine low speed.This can occur, if the ultrasonic bed level detector is not working properly at the machine feed end or if the travelling grate speed is controlled via volumetric mode and/or manual mode.

4.4.12 Excessive supply of green balls to Travelling Grate

If the quality of the green pellets is normal and they still do not burn through (abrasion index increases, compression strength decreases), this is usually caused by too much charge getting supplied to the travelling grate. In this case, the supply of green pellets must be reduced. A downward trend in the windbox pressure profile and high travelling grate speed are symptoms of this situation.

4.4.13 Windbox Temperature Profile Too High

This indicates that the supply of green pellets to the travelling grate can be increased or the gas flow rates at WBE G5.032 and WBR G5.022 fans reduced.

1) The instrumentation circuits should be checked.

2) The speed control instruments of WBE G5.032 and WBR G5.022 fans should also be checked.

4.4.14 Pellet Temperature at Travelling Grate Discharge Too High

Belt conveyors G7.002, G7.002A, G8.002, G8.003, G8.004 have to be protected by activating the sprinkling water system.

Possible causes:1) Good anticipation from control room operator while playing with process parameters

will avoid any kind of hot discharge.

2) The permeability of the pellets is unsatisfactory, and action taken to correct this (as described above) has no effect or was started too late.

3) The upper layer of pellets has burst or been crushed. Hi temperature in PHbed level too high.

4) The cooling airflow rate is too low as a result of faults in the instrumentation or the damper/ motor speed adjustment system on the cooling air fan, not functioning properly.

5) Too high rate of green pellets feed to the indurating machine, when dampers on fans WBE G5.032 and WBR G5.022 are already adjusted at the maximum efficiency level for those fans curves. (Machine operated above actual process possible capability).

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4.4.15 Firing Hood Pressure Too High

If the firing hood pressure is too high (positive), hot gases are forced through the hood seal, and thus structural parts get overheated. CAF G5002 will stop.

Possible causes:1) The set point for the firing hood pressure is not set correctly.G4P301,305,G4H304.

2) The speed control instruments on the cooling air fan G5002 is defective.

3) There is a fault in the instrumentation system.

4.4.16 Breakdown of Cooling Water System for the Travelling Grate

If the cooling water system for the travelling grate breaks down, the appropriate non-return valve for the emergency water supply will open automatically. Make sure that there is really emergency water supply. If neither water system is available, this constitutes anmajor emergency. The travelling grate must be stopped and the hood temperatures lowered, meanwhile, the pressure in the firing hood must be negative. The water systems must be investigated/corrected immediately (flow rate, temperature, etc.)

5. Interlocks and Alarms

5.1 Interlocks

With some exceptions there are few interlocks between equipment in this area. Generally, the interlocks are concerned with protecting the equipment itself.

5.1.1 Travelling Grate

The travelling grate can be started and controlled either from the local panel or from the central control room. A selector feedback from the field LCSto control room determines the position of start/stop control for this equipment.

In sequence mode, the following conditions are required to be satisfied in order to start the grate drive mechanism

1. Lintels cooling water flow

2. Machine lubrication system is switched on

3. Discharge hopper level is not Hi-Hi (G3L011)

4. Hearth Layer Bin level is not Lo-Lo.(G8L005)

5. Expansion limit switches not actuated (G3G101A/B)

6. No emergency pushbutton are actuated on the machine .

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Grate Speed and Bed Depth

If green pellet production (after screening) increases, the grate speed increases to maintain a preset bed height as detected by the ultrasonic probes at the feed of the machine(G3L101,G3L102,G3L103) (loop No.-G3L106). The converse is true. The normal setpoint for bed height will be 500mm The normal grate speed is 1.5 m/min or lower. If production rate rises to such an extent that a grate speed reaches 1.65 m/s

5.1.2.Hood exhaust fanG5.042

The hood exhaust fan can only be started if the following conditions are fulfilled:

1. The inlet dampers louvers are closed

2. The temperature of the fan bearings is belowpermissible level. 60°C

3. The temperature of motor bearing is below permissible level. 60°C

4. The motor winding temperature is belowpermissible level. 70°C

5. No emergency button are actuated.

During normal operation the fan stops automatically when:

1. The temperature of the fan bearings rises above permissible level 60°C. 2. The vibration level exceeds the permissible level. 130µm.

During normal operation

HEF control (G5042), is controlled by the hood suction (G5P114) at -5mm to -25mm. Inlet damper(G5G110) is at 100% open and the (VFD) controls motor speed. If HEF (G5042) fan temperature reaches at maximum operating temperature (180°C)

inlet damper(G5G110) will close to protect the fan.

At machine emergency stop, the inlet damper closes and the VFD goes to minimum speed.

5.1.3.Updraft Drying Fan G5.012, Windbox Recuperation Fan G5.022, Windbox Exhaust Fan G5.032,

The interlocks are identical for these three fans. For themto start, the following conditions must befulfilled:

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1. The temperatures of the fan bearings must not be above permissible level 60°C

2. The control dampermust be closed

3. The temperature of the motor winding must be abovethe maximum permissible level

4. The temperature of the motor bearings must be above themaximum permissible level

Windbox Exhaust Fan : 80µm alarm, 130µm shutdownWindbox Recuperation Fan: 80µm alarm, 130, µm shutdown

Updraft Drying Fan: 80µm alarm, 130µm shutdown

During normal operation the fan stops automatically when:

1. The temperature of the fan bearings rises above permissible level 60°C.2. The vibration level exceeds the permissible level. 130µm.


1. UDDF control (G5012) , Controlled by the UDD pressure (G4P306) at -15mmWC. Inlet damper(G5G111) is at 100% open and the (VFD) controls motor speed. If UDD fan (G5012) temperature reaches maximum operating

temperature(400°C) the inlet damper(G5G111) will close to protect the fan.

At machine emergency stop, the inlet damper(G5G111) closes, the bleed-in damper (G5.016) opens 100% and the VFD goes to minimum speed.If UDD fan (G5012) main motor stops auxiliary drive(G5012M06) will start to keep it running at minimum speed.

2. WBEF control (G5032), Controlled by an average temperature set point of 180OC in Wind box No. 7, 8

(G5T117). Inlet damper(G5G113) is at 100% open and the (VFD) controls motor speed. A Stand by signal for WBEF controls (G5032) and/or shut-off damper (G5G113),

An optional method of control is a Ratio Control of average pressure in wind box 5, 6, 7, 8 (G5P104, G5P105, G5P106, G5P107)and in wind box 10, 11, 12, 13, 14 (G5P109, G5P117, G5P118, G5P119).This option can be used but it is not recommended by the process designer.

If WBE fan(G5032) temperature reaches maximum operating temperature (280°C) the inlet damper(G5G113) will close to protect the fan.

At machine emergency stop, the inlet damper(G5G113) closes and the VFD goes to minimum speed.

3. WBRF control (G5022),

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Controlled by an average temperature average Wind box No. 12 2 t/c, 13 1 t/c (G5T115). If this average temperature falls below set-point, the motor speed of fan G5022 increased until set point is restored. The normal set point for burn-through is approximately 400OC without carbon addition and 370OC with carbon addition at a rate of about 1.4 %.

Inlet damper(G5G112)is at 100% open and the VFD controls motor speed. If WBR fan (G5022) temperature reaches maximum operating temperature(400°C)

the inlet damper(G5G112) will close to protect the fan. The bleed-in damper opens !00%.

At machine emergency stop, the inletdamper(G5G112) closes and the VFD goes to minimum speed.At that point the bleed in damper will open at 100%.If WBR fan (G5022) main motor stops auxiliary drive(G5022M06) will start to keep it running at minimum speed

5.1.4.CoolingAir Fan G5.002

The cooling air Fan can only be started when the followingconditions are fulfilled:

1. The hood sealing air fan G5045 must be operating

2. The adjustable dampers must be in closed position

3. The temperatures of the motor windings must be below themaximum permissible level

4. The temperatures of the motor bearings must be below themaximum permissible level

5. The temperatures of the fan bearings must be below themaximum permissible level

An alarm is given in the process control centerDCS whenthe fan bearing temperature exceeds 70OC.


CAF control (G5002), is controlled by the suction in the firing zone at -3mm to -5mmWC (G4P305).

Inlet damper(G5G110) is open at 100% and the VFD is controls the motor speed.

At machine stop, the inlet damper remains fully open and the VFD goes to minimum speed.

Other loops

1. Control damper (G5H110), WBRF (G5022) to HEF (G5042) duct, for control of the dew-point (ESP requirement) in the HEF exhaust gases (G5T123). Controlled at around 85 ºC.

2. Control dampers (G4H101, G4H102), WBRF (G5022) to Preheat (spider). Controls the temperature of the first Preheat zone at about 400ºC if required to lower the temperature to prevent spalling. (G4T201, G4T202, G4T304, and G4T305). This damper to close upon machine stop.

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3. Control damper (G5H106), UDD (G5012) bleed-off UDD gases to exhaust gas chimney. Controlled at set point of 500mmWC (G5P102).

4. Control damper (G5H101), UDDF (G5012) bleed-in for control of UDD gases temperature in UDD wind boxes and fan protection, located in duct above the second cooling zone. Controlled at about 400ºC (G4T303). To maintain Fan manufacturers advised max operating temperature (400ºC).The bleed-in Damper opens fully in case of emergency stoppage of the fan.

5. Control damper (G5H102), If the UDD(G5012) outlet temperature G5T125 is too low, at start up for instance, it can be boosted by bleeding process gas from the outlet of the Wind box Recuperation Fan G5022 to the suction side of the Updraft Drying Fan by damper.(to operate at start-up only)

6. Control damper (G5H103), WBRF (G5022) bleed-in for fan protection, located in end of the long WBR manifold. Controlled at about 400 ºC (G5T124). To maintain Fan manufacturers advised max operating temperature (400ºC). This damper to open fully in case of emergency stoppage of the fan.

7. Control Damper (G5H107), HEF (G5042) bleed in damper for ESP, located at inlet. Controlled at about 110 ºC temperature (G5T123). It also maintains Fan Manufacturer recommended limit of operating temperature(120ºC).This damper to open upon power failure.

8. Emergency Shut off Damper G4U101 (G4032) located at PH zone in WBRF(G5022) duct. This will operate in case of power failure or if grate stops. Normally it is fully open, on emergency it shuts off to prevent HEF G5042. It is pneumatically operated Fail Close damper.

9. Expansion switches(non contact type) (G4G101A/B) on each side of the discharge end to limit the grate expansion. If expansion exceeds to set point it will trip the grate.

10. At 20% level of Discharge bin G3011 the vibratory feeders G7003 & G7004 will start, controlling range will be between 20-40%. HiHi level will be at 50 % level. At this level the vibrating feeders will operate on its maximum and grate will stop.

11. Two temperaturesensors G7T101,G7T102are installed on discharge conveyor G7002AIfthe pellet discharge temperature exceeds more than set point (105ºC) then the water spray valveG7U101will open. Iftemperature does not decrease below (90ºC) second water spray valve G7U102 will open to control the temperature.

12. At 40% HLSB bin G7005 level the vibro feeder G7006 will start and after that it will adjust the speed to control the bin level. Bin level controlling range will be 40-60%.

13. At 40% HLSB bin G7005 level thevibro feeder G8001 will start. It will control the Hearth layer bin G8005 level between 30-60% by adjusting the speed. At bin G8005 level reaches HIHI (85%) feeding conveyor G8003,G8004 and the vibro feeder G8001 will trip immediately.

14. There is a product overflow if HLSB bin G7005 level reaches more than 80%. If overflow chute chokes and level goes high then discharge conveyor G7002A and vibro feeders on discharge bin G7003,G7004 will trip immediately.

5.1.5.Associated Ancillary Systems

The following systems have association with the induration area

1. Grate feed

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2. Hearth Layer

3. Dribble Conveyor

4. Double Pendulum Dust Valves (windboxes)

5. Product Handling

6. ESP Dust Handling

7. Lintel Cooling Water

8. Burner Management System

9. Fuel Oil supply and heating

10. Burner Purging (plant air)

11. Burner Cooling Air fan.

12. Instrument Air compressor(s)

13. Plant air compressor(s)

Refer to the appropriate Process Operation & Control document

6. Alarms

No.

Detection Condition Description

1. Fan bearing >60°C Bearing Hi Temperature D/E2. “ “ >60°C “ “ ND/E3. “ “ >100µ Bearing Vibrations D/E4. “ “ >100µ “ “ ND/E5.6. Fan motor >90°C Motor winding temperature7. “ “ >60°C Motor bearing temperature8. “ “ >xxxµ Motor Vibrations9. “ “ Above set value Motor high current10. “ “ Above set value Motor winding temperature High.11. Travelling grate <xxxbar Lubrication pressure low 12. “ “ < xxx L/M Lintel water flow low13. “ “ Level abnormal Lintel water emergency tank level 14. “ “ <400mm Bed level low15. “ “ >500mm Bed level Hi16. “ “ >1.6 m/m Grate speed Hi17. “ “ Below set value Grate speed low18. “ “ >xxx A Motor current Hi19. “ “ Motor torque Hi20. “ “ >90% Discharge hopper Hi level21. “ “ Stopped Dust collector not operating H3.00122.23. Burners <80°C Fuel oil low temperature

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No.

Detection Condition Description

24. “ <xxxbar Fuel oil pressure low25. “ <xxxbar L P G pressure low26. “ <xxxbar Plant air pressure low27. Burners <xxxbar Instrument air pressure low28. “ <xxx mm Atomizing air pressure low29.30.31. Balling bins >set value x 6 Bin level Hi32. “ “ <set value x 6 Bin level low33. Balling disc feed < set value x 6 Feed rate low34. “ “ >set value x 6 Feed rate Hi35. Balling disc motor >Set value x6 Motor current high36. Green ball production <70% yield Green production Low37.38.39.40. Filter cake <set value Feed rate low41. “ “ >set value Feed rate Hi42. Bentonite feeder <set value Feed rate low43. “ “ >set value Feed rate Hi44. Limestone feeder <set value Feed rate low45. “ “ >set value Feed rate Hi46. Carbon feeder <set value Feed rate low47. “ “ >set value Feed rate Hi48. Dust collector (bentonite) Stopped Dust collector not operating49. “ “ (limestone) Stopped “ “ “50. “ “ (carbon) Stopped “ “ “51. “ “ Ash bin Stopped “ “ “ 52. Conveyors current (all) >set value Motor current Hi53. “ Side travel Conveyor side travel 54.55.56. Plant air receiver <set value Air receiver pressure low57. Instrument air <set value “ “58. Water basin <set value Water basin low level (X Section)59.60. Product discharge >set value Product discharge temperature Hi.61. Product bin G7.005 >90% Product bin level Hi62. “ “ “ < 25% Product bin low level63. Dust collector Stopped Dust collector not operating H4.00164.65.66.67.

7. Required Logic and Instrumentation

7.1 Bed Level and Grate Speed

Number of green bed level detectors are three in quantity.(G3L101,G3L102,G3L103)

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Number of Hearth layer bed level detectors are also three in quantity.(G3L111,G3L112,G3L113)

Range of level detectors is 0 – 600mm

Install Grate Speed Hi Hi alarm (setting at 1.6m/min).

Display 3-D graph of bed height (requires logging of last 15 minutes data)

7.2 Pallet Change Facility

Local panel for “Pallet Change” at Change-out station. Mode selection (local panel activation) from Central Control Room Workstation.

Local panel selector switch to “Pallet Change” stops travelling grate through DCS (grate fault).

Fault Cleared by switching to “Normal” on Local Panel.

Signal may eventually be used as command for pallet change, burner control(at a later date)

7.3 Pallet Car Identification

Add heat resistance tagging to the pallet cars and detector

Pallet cars in the machine to be identified by number on the Workstation display

7.4 Windbox Exhaust Fan Control :

temperatureof wind box 7 and wind box 8 ratioed ( i.e., G5T106 & G5T107 )to operate wind box exhaust fan.

Add pressure tapping and PT (H1P101, H1P201) into duct between ESP-2 dust collector and inlet of WBE Fan G5032.

END

R.C.12/01.2012

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1.2 mptpapp

Documents

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breakdown of cooling

hood exhaust air fan

cooling zone42

windbox recuperation

windbox exhaust fan

cooling air fan245

cooling air flow83