2.4 solid fuel handling system

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PROCESS DESCRIPTION CFBT-582-1 0

Osasto - Department Kohde - Subject Sivu - Page

Power Generation Systems

RAPP PB3 PROJECT CFB MULTIFUEL BOILER

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0 2005 - 03 - 00 T. Anttonen

Muut. Rev.

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Tarkastanut Reviewed by

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KLY-1 1997-05 P:\582-RAPP-PB3\int\Kayttoonotto\koulutus\Training Manuals\Folder 1\2.4 Solid fuel handling system.doThis document is the exclusive intellectual property of Kvaerner Power Oy and is furnished for the sole purpose of operating and maintaining of the specific project, and re-use of the document for any other project

TABLE OF CONTENTS 2.4 SOLID FUEL HANDLING SYSTEM.............................................................. 3

2.4.1 Purpose of the system ................................................................................ 4

2.4.2 General description of the system............................................................. 4

2.4.3 Fuel feeding regulation ............................................................................. 11

2.4.4 Design criteria............................................................................................ 12

2.4.5 Equipment specification ........................................................................... 13

2.4.5.1 Coal feeding silos ........................................................................................ 13

2.4.5.2 Coal silo reclaimer ....................................................................................... 14

2.4.5.3 Bio fuel silos ................................................................................................ 15

2.4.5.4 Bio fuel silo reclaimer .................................................................................. 17

2.4.5.5 Bark chain conveyor .................................................................................... 19

2.4.5.6 Metering screw 10 ....................................................................................... 20

2.4.5.7 Mixing screw (front wall) .............................................................................. 20

2.4.5.8 Mixing screw (rear wall) ............................................................................... 21

2.4.5.9 Fuel conveyor (front wall) ............................................................................ 22

2.4.5.10 Fuel conveyor (rear wall) ............................................................................. 22

2.4.5.11 Motor operated slide gate ............................................................................ 23

2.4.5.12 Balancing pocket ......................................................................................... 24

2.4.5.13 Metering screw ............................................................................................ 24

2.4.5.14 Rotary feeder............................................................................................... 25

or purpose is prohibited. The document or the information shall not be reproduced or copied, or disclosed to a third party without prior written consent of Kvaerner Power Oy. Kvaerner Power Oy, Tampere, Finland 2005






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This document is the exclusive intellectual property of Kvaerner Power Oy and is furnished for the sole purpose of operating and maintaining of the specific project, and re-use of the document for any other project

2.4.5.15 Fuel chute.................................................................................................... 27

2.4.5.16 Wall screw ................................................................................................... 28







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2.4 SOLID FUEL HANDLING SYSTEM







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Flowsheets: T582-00022 Fuel silos, front wall T582-00023 Fuel feeding, front wall T582-00025 Fuel feeding, rear wall

2.4.1 Purpose of the system

− serve as a short-term fuel storage − supply solid fuel flow at required capacity from the silos to

the boiler

2.4.2 General description of the system From the coal storage (not in scope) crushed coal is fed by belt conveyor (not in scope) to dividing drag conveyor (not in scope) which transfer fuel to two coal silos located by the furnace left side wall. Biofuel is fed from the bark yard (not in scope) by a belt conveyor (not in scope) to dividing drag conveyor (not in scope) located above the biofuel feeding silos. The fuel silos, 2 for coal and 2 for biofuel, are located to the left side wall of the furnace. There are three feeding lines from silos to the furnace, two at front wall and one at rear wall. Coal is primary fuel and bark secondary fuel. Coal and bark can be fed to the boiler separately or they can be mixed. Fuel from coal silo 1 (283T011) and bark silo 1 (283T012) is fed to the boiler front wall and fuel from coal silo 2 (283T013) and bark silo 2 (283T014) is fed to the boiler rear wall.







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Boiler automation controls the conveying line capacity/speed according the capacity need of the boiler. Round shaped bark silos are equipped with slewing screw dischargers (Picture 1). Dischargers drop biofuel to drag conveyors, which furthermore take biofuel to mixing screws, where biofuel and coal are mixed. After that biofuel is fed to the combustion chamber through the same conveyor system and feeding points as coal.







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Picture 1. Biosilo slewing screw discharger Biosilo screw reclaimer has three separate drive units, one for screw and two for slewing. The screw of the reclaimer turns slowly around the centre circle and unloads material through the centre point to the underlying bark conveyor. The capacity of the screw reclaimer can be regulated between 35-500 m3/h. Regulation can be done by changing the rotation speed of the screw motor. The primary speed control for the screw is coming from the boiler automation, but the level regulating of the balance pocket corrects the speed command, if the fuel level in balance pocket is not on the desired area. The slewing motor torque is regulated by the frequency converter. Screw reclaimer is equipped with the automatic lubrication unit which lubricates all particles needed to lubricate on slewing part of the reclaimer except the slewing rings tooth and slipring units bearing which must be lubricated manually.







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Coal is discharged from the feeding silos by variable frequency controlled chain dischargers (Picture 2), two pieces on each silo.

Picture 2. Coal discharger underneath the coal silo Dischargers carry coal to the mixing screws where it is mixed to the fuel coming from biofuel silos. After mixing screws fuel (or fuel mixture) goes to drag chain type feeding conveyors. On the furnace front wall fuel is divided to two parallel drag conveyors from which the fuel is divided to the six feeding points, so that each drag conveyor is feeding three separate feeding points. On the rear wall side there is only one drag conveyor. Each of the three conveyors is equipped with variable frequency drive.







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The even distribution of fuel to all feeding points is controlled by metering screws on each feeding points. Also these screws are variable frequency controlled.

Picture 3. Opened rotary feeder Each fuel feeding chute is equipped with rotary lock feeders (Picture 3) in order to prevent any backflows from the furnace. The lower part of each fuel feed chutes on the front wall is equipped with constant speed feeding screw (Picture 4). These screws are equipped with a feed/purge air system that improves the fuel injection and distribution while also cooling the feeding system. On the rear wall fuel is fed from the rotary feeders directly to loop seals.







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Picture 4. Feeding screw (looked from inside the boiler) Bark flow is controlled by variable frequency controlled electric motor drives of the silo discharger, drag conveyor and metering screw.







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The design allows also use of smaller amount of sludge (reservation made for sludge silo and feeding equipment).







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2.4.3 Fuel feeding regulation

Coal + bark feeding If using coal and bark or only bark for boiler feeding, all the motor operated slide gates are fully open. At the third outlet point there is a balancing pocket between fuel conveyor and metering screw. To guarantee that also the third outlet point gets fuel there must be fuel level all the time in the balancing pocket. To make that possible the balancing pocket is equipped with the continuous level measuring system. If the fuel level on the pocket is under or above the set point, the level regulation corrects the speed of the fuel conveyor for getting the fuel level to the set point. Coal feeding It is important that fuel feeding to the boiler via fuel conveyors each three outlet points are as even as possible. When using only coal the fuel dividing is regulated with the motor operated slide gates. All slide gates are equipped with positioning detectors. Slide gates are positioned so, that the first slide gate is 1/3 open and second 2/3 open. If boiler automation notices that the fuel feeding is not even the correction is made by changing the rotation speed of the metering screw(s). Respectively to coal + bark feeding the balancing pocket has a certain fuel level in the coal feeding also.







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2.4.4 Design criteria

Coal system Coal particle size when entering feeding silos shall be as follows

100% mm < 890% mm < 6max. 10% mm < 0,1

Coal volume weight is 850 kg/m3. Bark system Bark particle size (measured as side+side+side) when entering feeding silos shall be as follows

100% mm < 50

Bark volume weight is 300 - 400 kg/m3. Note! Due to bark chlorine content and high superheating temperature bark shall be fired together with coal. It is estimated that about 10% of fuel heat input shall be from the coal. Sludge system (reservation) Sludge volume weight is 700 - 900 kg/m3. Note! Due to sludge chlorine and alkaline content and high superheating temperature sludge shall not be fired with bark only. It is estimated that about 30% of fuel heat input shall be from the coal when firing sludge.







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2.4.5 Equipment specification 2.4.5.1 Coal feeding silos

Equipment numbers 283T011 (1) and 283T013 (2)Number pcs 2Manufacturer RAPP (Raumaster design)Gross volume / each m3 1500Diameter m 10Height m 22,5Materials: − cover carbon steel− side wall carbon steel− bottom cone carbon steel− lining for bottom cone stainless steelEquipment: − manhole − support − fasteners for level indicators − explosion doors and connection for extinguishing − handrails on the cover − filter A = 10 m², pneumatic cleaning − standard service doors

Pneumatic cleaning system removes coal dust which appears when feeding the coal silo 1 (283E127) and coal silo 2 (283E128). Pneumatic cleaning system (motor 1,5 kW + cleaning) is started at the same time when starting the conveyor which is feeding the silo.







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Cleaning system has a control system of its own which controls the magnetic valves of cleaning. The motor of the cleaning system is stopped with 5 minutes delay after the silo feeding conveyor is stopped. The cleaning is stopped with 2 minutes delay after the motor of the cleaning system is stopped.

2.4.5.2 Coal silo reclaimer

Equipment numbers 283C003 (1) and 283C004 (2) (front wall)

283C008 (3) and 283C009 (4) (rear wall)

Number / silo 2Manufacturer RAPP (Raumaster design)Reclaimer type Chain conveyorSilo opening mm 950 x 4000, with needle

gateCapacity / each m3/h 4 ... 40Inclination º 0Chain speed m/s 0,008 ... 0,08Chain width mm 1250Lenghts m 14 (283C003) m 11,5 (283C004) m 10 (283C008 and

283C009)Chains 2 pcs M450-A-200, pins

and bushes AISI 420Spacing of flights mm 400Motor kW 11, with thermistorsControl variable frequency drive

(supplied by RAPP)







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Materials: − bottom 15 mm carbon steel− intermediate bottom 12 mm carbon steel− side walls 8 mm carbon steel− cover 4 mm carbon steel Reclaimers are equipped with fuel weight measurement connections

2.4.5.3 Bio fuel silos

Equipment numbers 283T012 (1)and 283T014 (2)Number pcs 2Manufacturer RAPP (Raumaster design)Gross volume / each m3 300Diameter m 7Height m 8Materials: − cover carbon steel− side wall stainless steel − bottom stainless steel− other parts carbon steelEquipment: − manhole − service door − support L ~ 4 m − fasteners for level indicators − explosion doors and connection for extinguishing − handrails on the cover − fuel speader (283A004 and 283A005) for silo’s inlet opening,

motor 1,5 kW







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Picture 5. Slewing screw reclaimer







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2.4.5.4 Bio fuel silo reclaimer

Equipment numbers 283C001 (silo1), 283C007 (silo2)Number / silo pcs 1Manufacturer Raumaster OyManufacturer’s type CSR-4 SReclaimer type Slewing screw reclaimerCapacity / each m3/h 35 ... 500Screw rotation speed rpm 3,5 ... 50Screw flight diameter mm 800Main motor kW 90, with thermistors 3 pcs− variable frequency drives (1+1 pcs, supplied by RAPP) Slewing motors (2+2 pcs) kW 3, with thermistors 3 pcs− variable frequency drives (2+2 pcs, supplied by RAPP) Power supply with collector slip ring unitLubrication unit manufacturer LincolnLubrication unit motors (2 pcs) kW 0,09Materials: − screw flight 15 mm stainless steel + hard metal

welding− shaft lining 6 mm stainless steel− screw part is bolted − fall chute stainless steel− other parts carbon steel







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Picture 6. Drag chain conveyor







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2.4.5.5 Bark chain conveyor

Equipment numbers 283C002 (1)and 283C010 (2)Number pcs 2Manufacturer Raumaster OyConveyor type Chain conveyorCapacity / each m3/h 35 ... 500Conveyor width mm 1500Conveyor length − front wall (283C002) m 34− rear wall (283C010) m 22Chain speed m/s 0,02 ... 0,3Chains 2 pcs M450-A-200, pins

and bushes SS 420Motor kW 30, with thermistors− variable frequency drive (supplied by RAPP) Materials: − bottom 8 mm stainless steel− side walls 6 mm stainless steel − slide bars for chains 30 mm polyethene HD2000− other parts carbon steel

Bark coming from the screw reclaimer is falling to the balance pocket of chain conveyor. The meaning of the balance pocket is to guarantee even material flow from screw reclaimer to the chain conveyor. Conveyor is also equipped with extinguishing steam connections and with fuel weight measurement connections.







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Chain conveyor 1 (283C002) has two outlet points. First outlet point is equipped with metering screw 10 (283C055). The speed of the metering screw is regulated so that it takes 50% of the bark coming to the chain conveyor.

2.4.5.6 Metering screw 10

Equipment number 283C055Number pcs 1Manufacturer Raumaster OyCapacity m3/h 17 ... 250Screw rotation speed rpm 1,7 ... 25Screw flight diameter mm 800Screw length m 3Motor kW 18,5, with thermistors− variable frequency drive (supplied by RAPP) Materials: − trough 6 mm stainless steel− thread 10 mm stainless steel− shaft pipe lining 4 mm stainless steel− other parts carbon steel

2.4.5.7 Mixing screw (front wall)

Equipment numbers 283C005 (1) and 283C006 (2)Number pcs 2Manufacturer Raumaster OyCapacity m3/h 50 ... 300Screw rotation speed rpm 8 ... 48Screw flight diameter mm 800Screw length m 9







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Motor kW 37, thermistors (3 pcs)− variable frequency drive (supplied by RAPP) Materials: − trough 6 mm stainless steel− thread 10 mm stainless steel, top

hard welded− shaft pipe lining 4 mm stainless steel− other parts carbon steel

2.4.5.8 Mixing screw (rear wall)

Equipment number 283C011 (3)Number pcs 1Manufacturer Raumaster OyCapacity m3/h 80 ... 500Screw rotation speed rpm 6 ... 36Screw flight diameter mm 1000Screw length m 10Motor kW 37, thermistors (3 pcs)− variable frequency drive (supplied by RAPP) Materials: − trough 6 mm stainless steel− thread 10 mm stainless steel, top








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2.4.5.9 Fuel conveyor (front wall)

Equipment numbers 283C012 (1) and 283C016 (2)Number pcs 2Manufacturer Raumaster OyConveyor type Chain conveyorCapacity / each m3/h 20 ... 300Conveyor width mm 1200Conveyor length − 283C012 (1) m 24− 283C016 (2) m 21Chain speed m/s 0,017 ... 0,25Chains 2 pcs M315-A-200, pins

and bushes SS 420Motor kW 18,5, with thermistors− variable frequency drive (supplied by RAPP) Materials: − bottom 8 mm stainless steel− side walls 6 mm stainless steel− slide bars for chain 30 mm polyethene HD2000− other parts carbon steel Conveyor is equipped with extinguishing steam connections and two first outlets are equipped with slide gates

2.4.5.10 Fuel conveyor (rear wall)

Equipment number 283C028 (3)Number pcs 1Manufacturer Raumaster OyConveyor type Chain conveyor







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Capacity m3/h 35 ... 500Conveyor width mm 1500Conveyor length m 25Chain speed m/s 0,02 ... 0,3Chains 2 pcs M450-A-200, pins

and bushes AISI 420Motor kW 30, thermistors (3 pcs)− variable frequency drive (supplied by RAPP) Materials: − bottom 8 mm stainless steel− side walls 6 mm stainless steel− slide bars for chain 30 mm polyethene HD2000− other parts carbon steel Conveyor is equipped with extinguishing steam connections and two first outlets are equipped with slide gates

2.4.5.11 Motor operated slide gate

Equipment numbers 283-HV-1572 (1), 283-HV-1573 (2)283-HV-1546 (4), 283-HV-1549 (5)283-HV-1585 (7), 283-HV-1588 (8)

Number pcs 6Manufacturer Raumaster OyMotor kW 2,2Materials: − gate plate stainless steel− frame carbon steel The slide gate is equipped with positioning detector.







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2.4.5.12 Balancing pocket

Equipment numbers (above screws)

283C015 (3), 283C019 (6)and 283C031 (9)

Number pcs 3Manufacturer Raumaster OyVolume / each m3 2Size (L x W x H) m 1,5 x 1 x 1,5Materials: − side walls and cover 4 mm stainless steel− other parts carbon steel The balancing pocket is equipped with continuous level measurement (radioactive) (supplied by RAPP).

2.4.5.13 Metering screw

Equipment numbers 283C013 (1), 283C014 (2)283C015 (3), 283C017 (4)283C018 (5), 283C019 (6)283C029 (7), 283C030 (8)

and 283C031 (9)Number pcs 9 Manufacturer Raumaster OyCapacity / each m3/h 12 ... 170Screw rotation speed rpm 2,3 ... 35Screw flight diameter mm 630Screw length m 3 (5 pcs), 4 (2 pcs) 5 (2pcs)







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Motor kW 15, 1000 rpm, thermistors

(3 pcs)− variable frequency drive (supplied by RAPP) Materials: − trough 6 mm stainless steel− thread 10 mm stainless steel,


2.4.5.14 Rotary feeder

Equipment numbers 283E082 (1), 283E083 (2)283E084 (3), 283E085 (4)283E086 (5), 283E087 (6)283E089 (7), 283E090 (8)

and 283E091 (9)Number pcs 9Manufacturer Raumaster OyManufacturer’s type ALF 63/80 CCapacity / each m3/h 170Rotation speed rpm 29Filling grade % 34Motor kW 15Overload clutch ball couplingZero speed swith manufacturer TelemecaniqueMaterials: − parts in contact with fuel stainless steel − other parts carbon steel







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Picture 7. Rotary feeder







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2.4.5.15 Fuel chute

Number pcs 9Manufacturer Raumaster OyOpening size diameter mm 500Height m 4Material: 4 mm stainless steel The fuel chute is equipped with air heat jacket. Equipment:

Expansion bellow Opening size mm 630 x 800Height (approx.) mm 800Movements − vertical mm 0 - 220− horizontal mm 0 - 40Materials: − internal chute 4 mm stainless steel − other parts carbon steel− elastic part stainless steel

Hand operated slide gate Opening size mm 670 x 800Materials: − frame carbon steel− slide gate stainless steel







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2.4.5.16 Wall screw

Equipment numbers 283C020 (1), 283C021 (2)283C022 (3), 283C023 (4)283C024 (5), 283C025 (6)

Number pcs 6Manufacturer Raumaster OyCapacity / each m3/h 170Screw rotation speed rpm 70Screw flight diameter mm 500Screw length m 3Motor kW 7,5Materials: − screw flight stainless steel − shaft lining stainless steel− trough and thread stainless steel − hot part of screw heat resistant steel Screws are equipped with air cooled jacket.







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This document is the exclusive intellectual property of Kvaerner Power Oy and is furnished for the sole purpose of operating and maintaining of the specific project, and re-use of the document for any other project or purpose is prohibited. The document or the information shall not be reproduced or copied, or disclosed to a third party without prior written consent of Kvaerner Power Oy. Kvaerner Power Oy, Tampere, Finland 2005

Picture 8. Wall screw

2.4 solid fuel handling system

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