Lecture 4: Fluidised Bed

Oxyfuel Boilers and CCS

Monica Lupion

CO2 Capture Programme

CIUDEN

Second APP Oxy-fuel Capacity Building Course

Beijing, 15th March 2010

Introduction to OxyCFB

Features of CFB

Supercritical CFB

CIUDEN and OxyCFB technology

• Combustion technologies Overview

• Comparison PC-FB Boilers

• Comparison CFB-BFB Boilers

• Historical Perspective

• CFB Hydrodinamics

• Combustion in CFB Boilers

Content

OxyCFB

• Supercritical Steam Parameters

• Lagisza OTU Supercritical CFB Plant

• Introduction

• Challenges

• Emissions in OxyCFB

• CIUDEN OxyCFB Boiler

• OXYCFB300 Project

Combustion technologies

Coal

Combustion

Fixed Bed

Pulverised Coal-PC

Fluidized Bed

PressurisedFluidized Bed

BubblingBFBC

CirculatingCFBC

Supercritical

Subcritical

Ultra-Supercritical

Combustion technologies

SUBCRITICAL PC SUPERCRITICAL PC ULTRASUPERCRITICAL PC

SUBCRITICAL CFB

Performance WOC WC WOC WC WOC WC WOC WC

Efficiency (HHV)

34.3 25.1 38.5 29.3 43.3 34.1 34.8 25.5

CO2 emited (g/KWh)

931 127 830 109 738 94 1030 141

COE 4.84 8.16 4.78 7.69 4.69 7.34 4.68 7.79

Performance and economics for air-blown PC generating

technologies

Basis net output: 500 MWe, 61.2% wt C, HHV=25350 kJ/kg

Adapted from The Future of Coal, Massachussetts Institute of Technology

45%

PC / FB Boilers

Characteristics Bubbling Circulating Pulverized

Height of the bed (m) 1-2 10-30 27-45

Superficial velocity (m/s) 1.5-2.5 3-5 4-6

Excess air (%) 20-25 10-20 15-30

Coal size (mm) 6-0 6-0 <0.1

Combustion efficiency (%) 90-96 95-99.5 99-99.5

NOx (ppm) 300-400 50-200 400-600

SO2 capture in furnace (%) 80-90 80-90 None

Comparison of PC and FB Boilers

Advantages of FB Boilers

• Low average heat flux: furnace tubes safer and more resilient to operational upsets

• Lower peak heat flux, different locationIn PC near the most vulnerable point (water to steam)In CFB where the water is just heated

Advantages of FB Boilers

Height (%Total)

Heat F

lux (

% P

C m

ax)

CFB

Fuel Flexibility

Better gas-solid mixing and higher burning rateHigh Combustion

Efficiency

• Staged addition of comburantLower NOx Emissions

• Higher sulfur capture capability of CFB: larger specific area of sorbents and longer residence time

In Situ Sulfur Removal

Smaller Grate Area

Good load-following capability

• Higher sugerficial gas velocity: Smaller grate area (furnacegrate area 2 to 3 times smaller than BFB)

• High fluidizing velocity and easy control: Quick response

CFB / BFB BoilersAdvantages of CFB Boilers

BFB needs to adjust heat absorption by number of tubesinmersed in the bed: LIMITED FLEXIBILITY

Historical Perspective of CFB

Beginning of FB

Firstexperiences

with CFB

CFB at Commercial

scale

- 1921. Fritz Winkler: Fluidization

- 1938. W Lewis & E Gilliland: CFB

- 60’s. Lurgi: cementindustry

- 80’s. 1st CFBB: 84 MW (9MW electricity)

- Ahlstrom.15 MW

- 2005. AirCFB Lagisza

- 1986. Berry and WolskyFirst OxyCFB with FGR

- 2015. OXYCFB300

In South East Asia

No. of UnitsTotal Capacity

(MW)

Historical Perspective of CFBCFB Plants by Manufacturer

In the World

No. of UnitsTotal Capacity

(MW)

Foster Wheeler

Alstom

21324,526

647,760

12010,193

243,076

About 500 CFB units around the world

•Over 170 CFB units in the US

•Over 350 CFB units in China

Unit Capacity (MWe)

0

100

200

300

400

500

600

1970 1975 1980 1985 1990 1995 2000 2005 2010

Start-Up Year

Pilot PlantOriental Chem

Lagisza

JEA

Turow 1

Vaskiluodon

Nova ScotiaTri-State

General Motors

2015

CIUDEN TDP

Jamestown

CompostillaAIR-FIRED

OXY-FIRED

Pilot Plant

Historical Perspective of CFBEvolution of CFB Unit Capacities

CFB Hydrodinamics

Property Packed bed Fluidizedbed

Fast bed PneumaticTransport

Application in boilers Stoker Fired BFB CFB PC

Mean particle diameter(mm)

<300 0.03-3 0.05-0.5 0.02-0.08

Gas velocity (m/s) 1-3 0.5-2.5 4-6 15-30

Solid-solid mixing Negligible Near perfect Near perfect Small

Overall voidage 0.4-0.5 0.5-0.85 0.85-0.99 0.98-0.998

Temperature gradient Large Very small Small Maybesignicant

Comparison of Gas-Solid Contacting Processes

Component Regime

Furnace (below secondary air level) Turbulent of BFB

Furnace (above secondary air level) Fast fluidized bed

Cyclone Swirl flow

Return leg (Standpipe) Moving packed bed

Loope seal/external heat exchanger BFB

Back-pass Pneumatic transport

Flow regimes in the components of a CFB

CFB Hydrodinamics

Supercritical CFB TechnologySteam Parameter

Steam Parameter

Change in boiler cost (%)

Change in Investment

cost (%)

Efficiency increase (%)

Change in CoE (%)

265 bar, 535ºC/571ºC

Reference Reference Reference Reference

265 bar, 583ºC/601ºC

+4.6 +0.2 1.9 -0.7

290 bar, 603ºC/621ºC

+9.5 +1.6 3.5 -0.7

Adapted from Laffont et al, PowerGen-Europe

At Lagizsa the SC-CFB firing option was found to be 20% cheaper in capital cost and 0.3% higher in net efficiency than SC-PC

Supercritical CFB TechnologyLagizsa OTU CFB Plant

• Location: Poland (PKE)• 460 MWe (gross) supercritical OTU-CFB

World’s largest single CFB UnitWorld’s first supercritical CFB

• NTP: Dec 05• Hand over: June 09• FW providing boiler island

Design Parameters

Fuel Bituminous coal

Plant efficiency

45.3% Gross43.3% Net

Design Steam Parameters at 100% load

SH Flow 361 kg/s

SH Pressure 275 bar

SH Temperature 560 ºC

RH Flow 306 kg/s

RH Pressure 54.8 bar

Cold RH Temperature 315 ºC

Hot RH Temperature 580 ºC

Emission (6% O2, dry)

SO2 200 mg/Nm3

NOx 200 mg/Nm3

Particulates 30 mg/Nm3

•BENSON vertical OTU tech licensed by Siemens AG (GE)

•Integrated steam cooled solids separators

•INTREXTM superheaters

•Furnace dimensions

- 27.6m x 10.6m

- 48 m height

Oxy-CFB

Oxyfuel

CFB

Technicallyviable

Challenges!

OxyCFB Technology

The established CFB advantages also exist in oxy

• Fuel Flexibitily

• Low NOx

• In bed SO2 capture

• Efficient heat transfer and uniform heat flux

Further potential

• CO2 capture

• Reduce boiler size

OxyCFB Technology

Coal and

limestone

OxyCFB TechnologySimplified diagram

Cooling – 53.5%

Auxiliaries

2.4%

Air Separation

7.0%

CO2 Compression

3.7%

Output

33.4%

OxyCFB TechnologyPenalty from Oxycombustion

Adapted from Andersson, Univeristy of Chalmers

Fuel input

100%

OxyCFB TechnologiesChallenges

Boiler and burner

development “Design issues”

ASU

“Cost of oxygen

production”

CPU

“Removal of impurities”

Demonstration in 10s of MW and large scale needed to prove design, performance and economics

Design

Construct

Learn

Operate

2000 2005 2010 2015 2020 2025 2030 2035

D C A O

COMMERCIAL

400-1600 MW

to 2070

D C A ODEMOSTRATOR 2

400-800 MWTo 2070

DEMOSTRATOR 1

400-800 MWD C A O To 2035

D C A O

PILOT

1-30 MW

D C A

LAB

0.1-0.5 MW

Year

Adapted from R. S. Haszeldine Science 325, 1647-1652 (2009). Published by AAAS

OxyCFB TechnologiesChallenges

Source: Near Zero CO2 Emissions in Coal Firing with Oxy-fuel Circulating Fluidized-Bed Boiler. Chem. Eng. Technol. 2009, 32, No.3, 355-363

OxyCFB TechnologyDifferences of Combustion in O2/CO2

compared to Air-firing

Emissions of OxyCFB BoilersSO2 and Calcium utilisation (Bituminous)

Adapted from A Hotta,: Oxycombustion Development by Foster Wheeler. Clean coal in the future. March. 2009

Emissions of air- and oxy- firing tests at VTT CFB-pilot (30-100 kW)

Emissions of OxyCFB BoilersNO Emissions (Bituminous)

Emissions of air- and oxy- firing tests at VTT CFB-pilot (30-100 kW)

Adapted from A Hotta,: Oxycombustion Development by Foster Wheeler. Clean coal in the future. March. 2009

Dimensions (m) 21x2.7x2.4

Power (MWth) 30 max

O2 (kg/h) 8775

Flue gas recycle (kg/h) 25532

Flue gas (kg/h) 28800

Coal feed (kg/h) 5469

Limestone feed (kg/h) 720

Steam (t/h) 44.6

P(bar) / T (°C) 30 / 250

CIUDEN OxyCFB Boiler

CIUDEN OxyCFB BoilerFlexiburn Project

OxyCFB300 Project

Source: Foster Wheeler

Concluding remarks

OxyCFB technically feasible and cost competitive when majorreduction of CO2 emissions are required

• The established CFB advantages also exist in oxy

• Fuel Flexibitily

• Low NOx

• In bed SO2 capture

• Adapting an existing CFB boiler for oxy technically feasible(24-30 % O2 input)

• Integration of components: ASU, CPU, Combustion island

• Demonstration at large scale are neccesary for theimplementation of the technology at fully commercial size