2.7 Limestone 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 - 09 T. Anttonen

Muut. Rev.

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Laatinut Prepared by

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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\2.7 Limestone system.doc 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

TABLE OF CONTENTS 2.7 LIMESTONE SYSTEM.................................................................................. 3

2.7.1 Purpose of the system ................................................................................ 3

2.7.2 General description of the system............................................................. 4

2.7.3 Design criteria.............................................................................................. 7

2.7.4 Equipment specification ............................................................................. 8

2.7.4.1 Limestone receiving hopper .......................................................................... 8

2.7.4.2 Limestone hopper vibratory feeder ................................................................ 8

2.7.4.3 Limestone intake belt..................................................................................... 9

2.7.4.4 Magnet .......................................................................................................... 9

2.7.4.5 Limestone mill feed hopper ......................................................................... 10

2.7.4.6 Limestone mill vibratory feeder.................................................................... 10

2.7.4.7 Limestone mill and separator ...................................................................... 11

2.7.4.8 Limestone mill fan........................................................................................ 14

2.7.4.9 Limestone drying unit burner ....................................................................... 14

2.7.4.10 Limestone air heater fan.............................................................................. 15

2.7.4.11 Limestone cyclone....................................................................................... 15

2.7.4.12 Limestone cyclone rotary feeder.................................................................. 16

2.7.4.13 Limestone bag filter ..................................................................................... 16

2.7.4.14 Limestone bucket elevator........................................................................... 18

2.7.4.15 Limestone feeding silo ................................................................................. 19

2.7.4.16 Limestone feeding screw ............................................................................. 20

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

2.7.4.17 Limestone rotary feeder............................................................................... 21

2.7.4.18 Limestone injection piping ........................................................................... 22

2.7.4.19 Limestone injection air blower ..................................................................... 23







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2.7 LIMESTONE SYSTEM

Flowsheets: T582-00030 Limestone drying T582-00031 Limestone feeding

2.7.1 Purpose of the system

The purpose of the limestone system is to supply to the boiler limestone needed for sulphur removal from the flue gas. Big and moist limestone particles are first crushed and dried in a separate limestone prehandling factory.







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2.7.2 General description of the system

Limestone is delivered to the intake hopper, and a vibratory feeder discharges onto the inclined belt conveyor, which discharges into the mill feed hopper. The feed is extracted from the feed hopper by a vibratory feeder, automatically keeping the mill at constant load. In the mill plows throw the material between the rollers and the die ring for grinding. The rollers are forced against the die ring by centrifugal action, creating great grinding pressure and automatically compensating for wear. Hot air is drawn into the mill, to dry the material being ground and to carry the powder from the mill to the separator, which allows only the correct particles size to pass. The ground product is blown to the (limestone) cyclone, where it is separated from the air stream and discharged to the bucket elevator, which feeds the limestone storage (or feeding) silo.







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Air from the cyclone passes through the mill fan and returns to the mill. Part of the air is vented through a bag filter, and this is replaced by hot air from the heater. The heater firing rate is automatically controlled to keep the product moisture constant. Collected dust from the filter is also discharged to the bucket elevator and furthermore conveyed to the limestone storage (or feeding) silo. From limestone silo material falls through the hand operated slide gate to the variable frequency controlled dosing screw feeder. Above screw feeder there is an intermediate hopper. On the intermediate hopper there is a low level detector which controls the fluidising valves (3pcs) near the discharge chute of the silo. If low level detector gives alarm fluidising is started as long as the material level is under low level. On the screw feeder pocket there are three screw feeders which discharge material to the rotary feeder. Rotary feeder rotor is divided to three separate blocks so that each screw feeds material to its own section. After rotary feeder there are three separate pneumatic feeding lines, one for each section of the rotary valve, where the material is falling from the rotary feeder. Pneumatic line pressure is controlled by the magnetic valves. Limestone feeding capacity is controlled by the speed regulated screw feeders.







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Furthermore pneumatic feeding is divided to six feeding points at furnace front wall. Feeding openings are located close to the fuel feeding points. The pneumatic conveying air comes from a separate high pressure blower. Amount of dosed limestone is adjusted according to fuel sulphur content and boiler load and fine tuning is carried out based on flue gas SO2-measurement.







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2.7.3 Design criteria

Limestone

Requirement for limestone is the following: Particle size before crushing: 100 % mm < 25

Reactivity TGA index based on Kvaerner Power analysis method

% >50

Limestone properties according to report dated February 09, 2001 and laboratory test in Finland 19.06.2003:

CaCO3 % 96,6 – 97,1MgCO3 % 1,5 - 3,0

Assumed maximum moisture content % 3

Limestone prehandling factory

Equipment is capable to handle 40t/h limestone when having properties as explained above. The expected maximum end moisture of the limestone is 0,5%. The expected limestone size distribution after the prehandling is: 99 % mm < 250 % mm < 0,220 % mm < 0,045







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2.7.4 Equipment specification 2.7.4.1 Limestone receiving hopper

Equipment number 283T018Number pcs 1Manufacturer RAPP (Bradley Pulverizer

Company design)Volume m3 20Dimensions m 4 x 3Feed height m 5Material steelEquipment − weather cover − supports to ground

2.7.4.2 Limestone hopper vibratory feeder

Equipment number 283C032Number pcs 1Manufacturer Bradley Pulverizer CoCapacity (max) t/h 60Drive Magnetic motor with variable

amplitude from manual thyristor drive

Accessories − thyristor in local panel







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2.7.4.3 Limestone intake belt

Equipment number 283C033Number pcs 1Manufacturer Bradley Pulverizer CoCapacity (max) t/h 40Lenght m 26Drive kW 4Materials: − 2 ply nylon − 3 mm rubber face − 1,5 mm rubber reverse Accessories − dust covers − supports to ground − foundation bolts

2.7.4.4 Magnet

Equipment number 283E095Number pcs 1Manufacturer Type permanent magnetMotor kW 2Accessories − suspension chains − draw plate to remove tramp iron







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2.7.4.5 Limestone mill feed hopper

Equipment number 283T027Number pcs 1Manufacturer RAPP (Bradley Pulverizer

Company design)Dimensions m 5 x 3Feed height m 8,5Material steelEquipment − weather cover − isolating slide gate at exit Level probes Type Magnetrol VSH-S2BA-00Size 235 insertion lenghtQuantity 3 off

2.7.4.6 Limestone mill vibratory feeder

Equipment number 283C035Number pcs 1Manufacturer Bradley Pulverizer CoCapacity (max) t/h 60Drive 2 kW with variable amplitude from

automatic thyristor driveAccessories − local panel houses controls to keep mill amps contstant







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2.7.4.7 Limestone mill and separator

Figure 1 Grinding chamber of the limestone mill

Limestone mill Equipment number 283E099Number pcs 1Manufacturer Bradley Pulverizer CoManufacturer’s type BM20 Pendulum 3 rollerCapacity t/h 40Materials − cast iron base − cast steel gearbox, grinding chamber and roll carrier − wear resistant cast alloy die ring and rollheads







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Accessories − foundation bolts − four large spanners (special tools) Drive Type Bradley supply belt drive

and pulleys with slide railsMotor (supplied by RAPP) kW 250 (6 pole) Limestone mill lubrication pump Equipment number 283P030Type Lubricator for gearbox with

low pressure switchMotor kW 0,25 Limestone mill purge air fan Equipment number 283K018Type Air fan for mill rollsFlow at design point m3/h 400Motor kW 1,1

The airswept mill system grinds, classifies and dries material simultaneously. Pulverized material from the grinding zone is carried by air stream to a separator, mounted directly above the mill. Product-size material is carried to the collection cyclone while oversize particles are rejected and recycled for further grinding.







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Figure 2 Limestone separator above the mill

Limestone separator Equipment number 283E099Number pcs 1Manufacturer Bradley Pulverizer CoType Inverted cone separatorAdjustment hand winch to raise or lower

inner coneCapacity t/h 40Material steelAccessories − antivibration mountings − isolating rubber sleeve at base







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2.7.4.8 Limestone mill fan

Equipment number 283K017Number pcs 1Manufacturer Bradley Pulverizer CoType centrifugalCapacity m3/h 50000Material steelDrive Vee belt drive, guard and

base frame with slide railsMotor (supplied by RAPP) kW 250 (4 pole)Accessories − rubber sleeve on inlet (anti-vibration) − foundation bolts

2.7.4.9 Limestone drying unit burner

Equipment number 283E126Number pcs 1Manufacturer Type Fully modulating diesel

burner, sideplate mounted in duct packaged heater.

Capacity kW 1500 (5 x 106 kJ/h)Motor kW 0,2Materials − cast iron manifold − stainless steel diffuser plate and end wings − mil steel housing







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Accessories − panel with controls and temperature indicator direct mounted on

duct − flame monitoring − ignition system − foundation bolts

Burner is automatically adjusted to keep mill exit temperature constant.

2.7.4.10 Limestone air heater fan

Equipment number 283K011Number pcs 1Manufacturer Bradley Pulverizer CoFlow at design point m3/h 1745Motor kW 2,2 (2 pole)

2.7.4.11 Limestone cyclone

Equipment number 283E124Number pcs 1Manufacturer RAPP (Bradley Pulverizer

Company design)Type Standard mill cycloneCapacity m3/h 50000Dimensions, diameter mm 3600Efficiency % 90 – 92Material steelAccessories − fixing bolts to steelwork − support to ground level







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2.7.4.12 Limestone cyclone rotary feeder

Equipment number 283E124Number pcs 1Manufacturer Bradley Pulverizer CoType rotary airlockSize, diameter mm 450Drive Geared motor with chain

set and guardMotor kW 2,2

2.7.4.13 Limestone bag filter

Equipment number 283E097Number pcs 1Manufacturer Bradley Pulverizer CoType Reverse jet, top bag

removal, tubular bagsCapacity m3/h 15000Filter bag area m2 150Controls Timer for compressed air

pulsesConsumption, pressurized air m3/h 15Materials steel− bags polyester needle felt cloth− casing steelAccessories − fixing bolts to steelwork − access platform for valves − ladder to filter top







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Figure 3 Limestone bag filter







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Limestone filter fan Equipment number 283K012Number pcs 1Manufacturer Bradley Pulverizer CoFlow at design point m3/h 15300Type Belt driveMotor kW 15 Limestone filter rotary feeder and screw Equipment number 283E098Number pcs 1Manufacturer Bradley Pulverizer CoType Combined drive with

chainsetDiameter mm 200Motor kW 2,2

2.7.4.14 Limestone bucket elevator

Equipment number 283C038Number pcs 1Manufacturer Raumaster OyCapacity t/h 40Accessories steel− feed chute from cyclone and filter − discharge chute to silo







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2.7.4.15 Limestone feeding silo

Equipment number 283T019Number pcs 1Manufacturer RAPP (Raumaster design)Gross volume m3 300Diameter m 6,5Height (total) m 18Equipment: − legs and support steel construction − fluidizing air ring − filter A = 10 m², pneumatic cleaning − standard service doors Hand operated slide gate (below the silo) Opening size mm 400 x 400Materials: − frame carbon steel− slide gate stainless steel

Pneumatic cleaning system removes limestone dust which appears when feeding the limestone silo. Pneumatic cleaning system (motor 1,5 kW + cleaning) is started at the same time when starting the conveyor which is feeding the silo. 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.







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Intermediate hopper (above the feeding screw) Volume (about) l 120Material stainless steelLevel switch Drexelbrook or equivalent

2.7.4.16 Limestone feeding screw

Equipment number 283C039Number pcs 1 (3 separate screws)Manufacturer Raumaster OyCapacity (total) m3/h 2,6 ... 25Screw rotation speed rpm 4 ... 42Screw flight diameter mm 219Screw length m 1,2Motors kW x 2,2 with thermistors (3 pcs)− variable frequency drive (supplied by RAPP) Accessories: − ventilation pipeline connection DN80 in the discharge chute and in

intermediate hopper − pipeline to the upper part of the limestone silo


Figure 4 Limestone feeding screw






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2.7.4.17 Limestone rotary feeder

Equipment number 283E101Number pcs 1 (3 separate sections)Manufacturer Raumaster OyManufacturer’s type ALF 30/60 PCapacity (total) m3/h 25Rotation speed rpm 24Motor kW 5,5Zero speed swith manufacturer TelemecaniqueMaterials: − inner lining of cells stainless steel− inner surface of frame hard crome plating− other parts carbon steel







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2.7.4.18 Limestone injection piping

Manufacturer Kvaerner Power OyPipe from the feeding air blower DN400Piping from rotary feeder 3 x DN250Piping to boiler 6 x DN150Injection nozzle location Furnace front wallInjection nozzle height m 2,5 from furnace bottomNozzle inclination 30° downwards







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2.7.4.19 Limestone injection air blower

Equipment number 283K014Manufacturer Oy Ekstrom Flow Ab /

DresserNumber of blowers 1Model XLP408Type Three-bladed roots blowerMotor (supplied by RAPP) kW 355 Performance at maximum pressure difference Differential pressure kPa 73Air flow Nm3/s 2,6Temperature increase °C 80Rotary blower speed rpm 1924 Accessories: − pressure relief valve − acoustic enclosure (about 4m x 2,2m x 3,6m) − suction side silencer − ventilation air fan for the acoustic enclosure (fan motor rated

power 0,55 kW – 0,75 kW, manufacturer WEG, CMG or equal) − flexible connection (either a stainless steel bellows type with mild

steel flanges or a silicon tube type with mild steel flanges)

Figure 5 shows Limestone injection air blower curve and figures 6 and 7 the structure of the blower.







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DRESSER ROOTSHOLMES OPERATIONPO BOX B7 TURNBRIDGEHUDDERSFIELD HD1 6RB

PERFORMANCE BASED ON AIR, INLET PRESSURE = 1013

MBAR INLET TEMPERATURE = 20 0C

0.000

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500 1000 1500 2000 2500SPEED - RPM

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200 MBAR400 MBAR600 MBAR800 MBAR

800 MBAR

PRESSURE PERFORMANCEFRAME XLP 408

MAX. PRESSURE RISE = 800 MBARMAX. SPEED = 2000 RPM

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200 MBAR

Figure 5 Limestone injection air blower curve







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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

Figure 6 Limestone injection air blower (type XLP)

Figure 7 Three-bladed rotor of the blower

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2.7 Limestone System