2.9 Flue gas system

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Asiakirjan nimi - Name of Document Tunniste - Identification Rev.

PROCESS DESCRIPTION CFBT-582-1 0

Osasto - Department Kohde Subject Sivu - Page

Power GenerationSystems

RAPP PB3 PROJECTCFB MULTIFUEL BOILER

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0 2005 - 03 - 09 T. AnttonenMuut.Rev.

PvmDate

LaatinutPrepared by

PvmDate

TarkastanutReviewed by

PvmDate

HyvksynytApproved by

KLY-1 1997-05 P:\582-RAPP-PB3\int\Kayttoonotto\koulutus\Training Manuals\Folder 1\2.9 Flue gas system.docThis 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

2.9 FLUE GAS SYSTEM..................................................................................... 22.9.1 Purpose of the system................................................................................32.9.2 General description of the system............................................................. 32.9.3 Design criteria..............................................................................................62.9.4 Equipment specification .............................................................................72.9.4.1 Flue gas fans ................................................................................................. 72.9.4.2 Electrostatic Precipitator (not in scope) .......................................................112.9.4.3 Stack ........................................................................................................... 122.9.4.4 Recirculation gas nozzles ............................................................................ 12

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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Osasto - Department Kohde - Subject Sivu - Page



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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

2.9 FLUE GAS SYSTEM

Flowsheets: T582-00017 Combustion air

T582-00019 Flue gas

T582-00039 Oil lubrication units of the ID

fans

T582-00040 Oil lubrication unit of the

recirculation fan




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2.9.1 Purpose of the system

The purpose of the flue gas system is to:

supply flue gas from the boiler to the stack

control flue gas pressure inside the furnace

control combustion temperature by means of flue gas

recirculation

clean the flue gas from particulates

purge the boiler before starting the combustion

2.9.2 General description of the system

The flue gas system consists of:

furnace

cyclones

second and third pass flue gas ducts and dampers

electrostatic precipitator (not in scope)

flue gas fans

flue gas recirculation fan

stack (not in scope)

FurnaceThe boiler furnace is a combustion chamber where the thermal

energy bound in the fuel is released. The flue gas amount and

properties generated in the combustion process depend on the

fuels used.




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Cyclones

In three parallel cyclones most of particles conveyed with flue

gas from the combustion chamber are separated and returned

back to the furnace.

Second and third pass

The walls of the 2nd pass are cooled by superheated steam

flowing in the wall tubes. After plain tube economizer flue gas is

led to third pass where walls are constructed with a plate casing.

In the second and third pass flue gas cools down when it flows

across superheater, economizer and air preheater sections.

Electrostatic precipitator (not in scope)Fly ash is removed from the flue gas in electrostatic precipitator

(not in scope), which comprises two parallel chambers and three

fields. Both ESP chambers are designed for 60% boiler capacity.

Flue gas ducts before the ESP chambers are equipped with

guillotine dampers.

Dust-laden flue gas from the boiler is sucked by means of a flue

gas fan into the inlet funnel of the electrostatic precipitator andfurther to the precipitator casing where dust collection takes

place. The cleaned gas is led from the precipitator casing

through the outlet funnel via the flue gas fan and the flue gas

ducts to the stack.

The collected dust falls down to the precipitator bottom cones

and is led via ash conveyors to the ash silo.




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Flue gas fans

The two parallel operated radial-type induced draft (ID) fans,

located after the electrostatic precipitator, provide the draft

required to keep flue gas pressure in upper part of the furnace at

about -0,1 ... -0,2 kPa. The draft is controlled by the variable

frequency drives of the fans. The ID fans also discharge flue gas

into the stack.

Recirculating gas system

When needed, part of the flue gas can be recirculated after the

ID fans through recirculation flue gas fan to the lower part of the

furnace. Flue gas recirculation system is used to lower

combustion temperature in the furnace and it can also be used

to increase full superheating range. Recirculation flue gaspressure in controlled by inlet vanes of the fan and flow to

separate sections is adjusted by dampers. Recirculation gas

nozzles are divided into two separately controlled sections.

Recirculation flue gas duct before and after the fan is equipped

with guillotine dampers.




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2.9.3 Design criteria

Flue gas paths, electrostatic precipitators and flue gas fans are

designed to transfer combustion process products in a controlled

way from the furnace to the stack when fired design fuels at

specified boiler operation range.

Both flue gas fans are able to generate required draft up to 60%

boiler load.

Dimensioning basis for ESP at 100% boiler load when both

chambers are in service and design fuels are fired is dust

content of 135 mg/Nm3(converted to dry gas @ 7% O2) after the

ESP. It is possible also to run 60% boiler load through one ESP

chamber, then dust emission is 150 mg/Nm

3

.

Dimensioning basis for recirculation flue gas fan is to produce

together with fluidizing air fans such a high fluidizing velocity

inside the furnace that combustion temperature during coal firing

remains at an acceptable level.




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2.9.4 Equipment specification

2.9.4.1 Flue gas fans

Flue gas (I.D.) fans

Equipment number 283K002 (1) and 283K003 (2)

Supplier Flkt Woods OyNumber of fans 2

Model HACP-224-285-cc-d-e

Type radial fan

Control (supplied by RAPP) variable frequency control

Bearings oil lubricated

Motor (supplied by RAPP) kW 1800

Performance at design pointGas flow / fan Nm

3/s 122,2

Gas flow / fan m3/s 202,4

Inlet density kg/m3 0,786

Total pressure rise Pa 5900

Inlet temperature C 155

Fan efficiency % 74,2

Impeller power demand kW 1580

Figure 1 shows Flue gas fan curve. Both of the fans are

equipped with an oil lubrication unit.




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Figure 1 Flue Gas Fan Curve




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Recirculation flue gas fan

Equipment number 283K004

Supplier Flkt Woods Oy

Number of fans 1

Model HACP-090-205-cc-d-e

Type radial fan

Control inlet vane controlBearings oil lubricated

Motor (supplied by RAPP) kW 710

Performance at design point

Gas flow Nm3/s 25,1

Gas flow m3/s 39,8

Inlet density kg/m3 0,821

Total pressure rise Pa 12300Inlet temperature C 155

Fan efficiency % 81,1

Impeller power demand kW 581

Figure 2 shows Recirculation gas fan curve. The fan is equipped

with an oil lubrication unit.




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Figure 2 Recirculation Gas Fan Curve




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2.9.4.2 Electrostatic Precipitator (not in scope)

Equipment numbers 283E071 (1) and 283E072 (2)

Supplier F.L.Smidth Airtech

Suppliers type 1E400/H2P1/3*45-

104125/C/C/6P/6A

Number of precipitators one (1)

Number of parallel chambers two (2)

Number of fields / chamber three (3)

Process design

design flow / chamber 115,6 Nm3/s

design flow / chamber 183,6 m3/s

flue gas temperature 136 C

flue gas pressure -2000 Pa

O2-content 2,82 % vol wet

H2O-content 11,86 % vol

SO2-content 157 ppm

inlet dust contents (in wet flue gas) 31,0 g/Nm3

outlet dust content (wet gas; O2=3 %) 50 mg/Nm3

collecting efficiency 99,458 %

The mechanical operating range of the precipitator

the maximum flue gas temperature 200 C

static pressure max / min +6 / - 6 kPa

Pressure drop between the inlet and the outlet

flanges at boiler MCR load with 2 chambers


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-

stainless steel AISI316

2.9.4.4 Recirculation gas nozzles

AVESTA 253 MA

enings

16

eight from furnace bottom mm 500

Nozzles inclined 10 downwards

2.9.4.3 Stack

Equipment number 283E122

Delivery by the Purchaser (Kvaerner design)

Height 100 m

Inner liner diameter 4100 mm

- made of 5 mm Cor-Ten B steel

upper 5 m made of 4 mm

Material

Number of op front wall pcs 12

rear wall pcs 12

Diameter of openigs mm 8,3

H

2.9 Flue gas system

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