FLUIDIZED BED COMBUSTION­ TESTING,CHARACTERIZATION

AND RESEARCH SERVICES

Fluidised Bed Combustion research in VTT aims at promoting technological development ofheating­ and power plants in order to secure high level of plant availability and reliability. Inmultifuel applications our research activities focus on solving problems related to ashbehaviour such as fouling of heat transfer surfaces and hot corrosion. As the legislation onemission levels of heating and power plants is continuously tightening, we can offer ourclients expertise on emission control­ and reduction techniques. In process development areawe promote the development of high efficiency CFB processes. Our aim is to develop processmeasurement­ and modelling methods in order to deepen knowledge on CFB process in all itscomplexity. Majority of the activities is experimental research work, which takes advantage ofour unique test facilities, strong experience and contacts covering the whole researchcommunity of Europe.

We conform to the Quality Management System Standard ISO 9001:2000.

FLUIDIZED BED COMBUSTION­ TESTING,CHARACTERIZATION

AND RESEARCH SERVICES

Tools and facilities

2D & 3D

Bench scale reactors(cold and hot)

Pilot scale reactors50 kW, 20 kW

Commercial CFBboilers

0D

Experimental facilities, scale up

1D

Modeling tools, modeling of processes in multiple scales

VTT have a pilot CFB reactor, a pilot BFB reactor, a bench scale BFB reactor and afluidized bed erosion tester. Depending on the objectives and requirements thesedevices can be applied for the combustion and material testing.

Pilot Scale test rig &Bench Scale test rig

Full Scale units

Stationary andDynamic models

Population balanceCombustion

EmissionsSteam cycle Controlsystem

Boiler simulatorInformation gained data

•3D­models, 1D­models

Secondarycyclone

Fuel container 1 and 2Zone 1

Zone 2

Gas coolig

Primarycyclone

Observation port Sampling port/Deposit probe

Zone 3

Zone 4To stack

Sampling port

Sampling port

Observation and Sampling port/Deposit probe

Additivecontainer

Air

Secondary air(preheated)

Primary gas heating

Nitrogen

PC control and data logging system

Sampling port

Sampling port

Bag filter

CFB and BFB reactors are equipped with several separately controlledelectrically heated and water/air­cooled zones in order to control the processconditions (for example oxygen level, temperature and load) almostindependently. There are several ports in the freeboard area for gas and solidmaterial sampling. Typically the aim is to carry out a pilot size test burn tocharacterize the fuel in terms of the combustion properties for a CFB or a BFBpower plant. Combustion conditions can be adjusted to correspond with thoseprevailing in full­scale boilers. The test rigs are applied in research workrelating to the formation of pollutants, ash property characterisation andcombustion behaviour characterisations of problematic fuels. Depositformation can be studied by inserting air­cooled probes into the reactors'furnace and flue gas paths. It is also excellent environment for characterisingfine fly ash emissions in multifuel and waste combustion. Development ofcombustion process includes analysis of experimental results applying steadystate and dynamic process models and also testing of advanced process controlmethods can be carried out.

Comparison of methods to control flue gasoxygen concentration.

Measured SO2 emissions

Fuel 1

Fuel 2

0 %

20 %

40 %

60 %

80 %

100 %

120 %

0 1 2 3 4 5Ca/S­ratio

Calculated SO2 for 100% conversion

Measured SO2 concentration in flue gas asa function of Ca/Stratio.

FB REACTORS

TEST FACILITIES

ash properties, ash split (bottomash vs.fly ash)

Typical issues studied with pilot CFB and BFB reactors:

fuel and limestone reactivity

advanced combustion control

bed agglomerationcombustion profiles (gas, solidmaterial, temperature, heat transfer)

limestone dosage

emissions

deposit formation

Comparison of controllers

0

20

40

60

80

100

120

140

0 50 100 150 200 250 300 350Time (s)

Set point

PID

Smith

GPC

flue gas

1

n n+1

to stack

2

n­1

3

n­2

Primary air

To stack

Samplingport

Samplingport

Samplingport

Gas cooling

Bagfi lter

Gas probe

Observationport

Cyclone

Gassample

Temperaturecontrol

Tertiary air optional

Tertiary air optional

Tertiary air (preheated)

Fuel container 2Fuel container 1

Secondary air(preheated)

Nitrogen

Air

Additivecontainer

Primary gas heating

Heating zone 2/Cooling zone 2

Heating zone 3

Heating zone 4

Heating zone 1/Cooling zone 1

BEDmade of quarz

PC control and data logging system

Obervation port

Obervation port

Obervation port

Obervation port/Deposit probe

Depositprobe

Co­combustion of biomass and REF: distribution ofchlorine between HCl and particulate matter (alkalichlorides) in 870°C BFB furnace.

Pre­heated primary air is fed to the furnace through the grid. Oxygen concentration in the furnace is set to desired level with nitrogen.Alsodifferent kind of gas mixtures can be used e.g. O , CO , SO , CO, NO in addition to air and nitrogen. Temperature and pressure profilesalong the riser are measured. Temperature is controlled inside the reactor tube with surrounding electric heaters.

2 2 2

Air

Nitrogen

Secondary air

Continuousfuel feed

Fuel batch feed

Cooler/heater

Cooler

Primary gas heatingPC control anddata logging system

Cyclone

FilterTo Stack

Air

Nitrogen

Secondary air

Continuousfuel feed

Fuel batch feed

Cooler/heater

Cooler

Primary gas heatingPC control anddata logging system

Cyclone

FilterTo Stack

Characterization offuels and sorbents

Comminution

bed agglomeration

NOx formation

Typical issues studied with bench scale reactor:

Agglomeration of bed material

Sub­process foremission formation

Reactivity

5

10

15

20

25

0 50 100 150 200

Brown coal (A)

Bituminous coal (B)

Anthracite (C)

A

B

C

Reactivity test ­ Fuel batch experiments

250

BENCH SCALE CFB/BFB REACTOR

0

2

4

6

8

10

12

14

0,01 0,1 1 10 100 1000 10000Particle size (

Time[s]

m)

Calcination

Sulfur capture

Changes in PSDduring sulfur capture

Typical operational parameters for CFB and BFB pilots

Dimensions of furnace: CFB BFBHight (m) 8 4

Diameter (m) 0.17 0.23

Feeds:Fuel (g/s) 1.5­6 0.9­1.3

Fuel power (kW) 25­50 12­16Fuel particle size (mm) 0­5 1

Limestone (g/s) 0­1.5 0­1Limestone particle size (ξm) 0­500 0­500

Total combustion air (Nl/min) 600­1100 278Secondary air (Nl/min) 0­500 83

Tertiary air (Nl/min) 0­200 56Additional gases N2, CO2, O2, H2O can be mixed with combustion airAdditive feeders liquid spraying system with gas atomising, solid powder additive feeder

Option for oxyfuel combustion in CFB fuel power up to 100 kW, additional bed heat exchanger

Conditions: CFB BFBTemperature (oC) 700­950 870­1100

Bed pressure (Pa) 2000­3500 2000Fluidization velocity (m/s) 1­2.5 0.5

Total gas velocity (m/s) 2.5­4 0.6Gas recidence time (s) 2­4 8

Circulation (kg/m2s) 1­6 ­

Measurements for CFB and BFB:Flue gas composition O2 (0­100%), CO2 (0­100%), CO (0­5000ppm), NO (0­1000ppm), SO2 (0­5000ppm)

FTIR spectrometer H2O, CO2, CO, NO, NO2, N2O, NH3, SO2, HCl, CH4, C2H2, C2H4, C2H6

Ash samples bottom ash, fly ash and circulation in CFBHeat transfer probes (number) 3

Quenched gas­solid sampling probe (number) 1Deposit probe (number) 2, tubular rings (L = 35­40 mm, D in = 10 mm, Dout = 16 mm)

Additional measurements fine particles (DLPI, ELPI), heavy metals

Typical operational parameters for Bench scale (CFB­BFB)

Dimensions of furnace:Height (mm) 610

Diameter (mm) 32.8Feeds:

Continuous fuel/additive feed (g/min) 1­2.5Fuel batch feed (g) 0.5­2

Fuel power (kW) 0.25­2PSD for continuous fuel/additive feed (mm) 0.25­1

PSD for batch fuel/additive feed (mm) 0­2Total combustion air (Nl/min) 0­120

Secondary air (Nl/min) 0­6Additional gases N2 and bottle gases: e.g. CO2, O2, SO2, NO, CO can be mixed with combustion air

Conditions:Temperature ( oC) 750­1050

Bed pressure (Pa) 150­3000Fluidization velocity (m/s) 0.5­5

Total gas velocity (m/s) 0.5­5Gas recidence time (s) 0.12­1.2

Measurements:Flue gas composition O2 (0­100%), CO2 (0­100%), CO (0­5000ppm), NO (0­1000ppm), SO2 (0­5000ppm)

FTIR spectrometer H2O, CO2, CO, NO, NO2, N2O, NH3, SO2, HCl, CH4, C2H2, C2H4, C2H6

Ash samples bottom ash, fly ash, circulation

Schematic diagram of the laboratoryscale bubbling fluidized bed reactor

Additional information

Dr Jouni Hämäläinen,jouni.hamalainen@vtt.fiTel. +358 20 722 2529http://www.vtt.fi

Dr Martti Aho,martti.aho@vtt.fiTel. +358 20 722 2545

Mr. Pasi Vainikka,pasi.vainikka@vtt.fiTel. +358 20 722 2514

Mr. Antti Tourunen,antti.tourunen@vtt.fiTel. +358 20 722 2718

CFB and Bench scale reactors BFB reactor

The fluidised bed erosion tester has been build from a commercial electrically heated fluidised bed having a total height of 950 mm andinner diameter of about 400 mm. The actual test rig consists of two horizontal arms rotated by two concentric vertical axe counter­wisewithin the fluidised bed.

FLUIDISED BED EROSION TESTER

The mass loss behaviour of AISI 316 samples testedat two different temperatures at identical upper­armsample placement "A”

Erosion of AISI 316 samples (Location A)

00.050.1

0.150.2

0.25

0 50 100 150

Exposure time [h]

T= 500 CT=400 C

Typical operational parameters for FB ErosionTester

Dimensions of furnace:Hight (mm) 950

Diameter (mm) 400Sample material tubular rings (L =15 mm, D in = 15 mm, Dout = 25 mm), max number 16

Conditions:Bed temperature (oC) 400­500

Bed material aluminium oxide, mean grain size 0.22 mmFixed bed height (mm) 660

Fluidized bed height (mm) 40Rotation speed (1/min) 270

Relative velocity of sand particles (m/s) 1.2­3.5Typical test run time (h) 100

Analyses:Mass loss curves

SEM/EDSAtomic force microscopy

Schematic view of the fluidised bed erosion tester.

Motor

Gearbox

Cover