technical considerations on biomass fired boilers for heat and power - research in chec, dtu weigang...

Technical considerations on biomass fired boilers for heat and power - Research in CHEC, DTU

Weigang Lin

CHEC Research CenterDepartment of Chemical and Biochemical EngineeringTechnical University of Denmark

2 DTU Chemical Engineering, Technical University of Denmark

Outline

• Brief introduction of DTU Chemical Engineering and CHEC research center

• Problems in biomass fired boilers• Fundamental studies

–Deposit–Corrosion–Aerosol emissions–Counter measures–Gasification

• Concluding remarks

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DTU Chemical Engineering:

Lyngby

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CHEC Research Center

• New and Fundamental knowledge on• High Temperature Processes• Formation and Reduction of Harmful Components and

Particulates• Catalysis and Chemical Product Design

• To assist enterprises and governmental organisations

• To train engineers and researchers

• To catalyze international cooperation

Combustion and Harmful Emission Control (CHEC)

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Development of CHEC

2000

Time

2010

Acidification Debate

1990

Coal

Fluid Bed

SO2

NOx

Bio-mass

Alkali

Corrosion-depositions

Models

Cement

Waste

Products

Coatings

Catalysis

Gasification

Pharma

Minerals

Merger Risø

Systematic development of experimental methods and modeling tools

Focus on Reaction Engineering, Transport processes

New pilot

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CHECKDJ

CombustionPGl

GasificationUBH

Fuel Pretreatment

JA

DiognosticsSC

InorganicsFF

CatalysisAJ

Products and Pharma

SK

Project coordination

JBI

Technique, Pilot facilities

PAJ

SDC CoordinationWL

CHEC Organization

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New MSc Programme Started in China

A full MSc programme on chemical and Biochemical Engineering, with focus on Biomass, is launched in Beijing, China. The programme offers Danish and Chinese students the possibility of obtaining a dual degree from DTU and the University of Chinese Academy of Sciences (UCAS).

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Problems in firing of biomass

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Main reason for the problems

KCl Ash deposition

Bed agglomeration

Corrosion

SCR deactivation

PM2.5

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K-S-Cl Chemistry in Straw-Fired Systems:

K in straw

KCl/KOH (g)

K-Ca-silicates in bottom ash

KCl/K2SO4 nucleation/

heterogeneous condensation

K2SO4 (g)

SO2

Cl in straw

HCl (g)

Cl in bottom ash

HCl emission

KCl (g) SO2

K2SO4 (g)

S in straw

SO2 (g)

S in bottom ash

SO2 emission

K2SO4 (g) (+

HCl)

KCl / KOH

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Deposit Formation:Layered structure:

cm

> 0.7

100% KCl

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Measuring Campaigns at Grate Boilers:Fly Ash and Deposit Chemistry• Haslev and Slagelse CHPs (probe), 1994 • Rudkøbing CHP (probe + mature), 1995• Masnedø CHP (probe + mature), 1996-1997, 2000-2002

• Maribo-Sakskøbing CHP (mature), 2001, 2004

• Probe deposits: short term [~ 2-10 hours] exposure of cooled probes (finger print chemistry)

• Mature deposits: In-boiler, long term [~ 103 hours] exposed deposits (real chemistry, including chemical reaction sintering)

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Measuring Campaigns at Grate Boilers

Maribo-Sakskøbing boiler Rudkøbing boiler

Haslev boiler Slagelse boiler

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Deposit Chemistry

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Boiler wall

Probe

Superheaters

CCD camera

Flue gas flow

New, advanced probe:

- Heat transfer

- Mass of deposits

- Temperatures (flue gas and probe)

- Video – visible and IRAfter 3 hr

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Corrosion

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Corrosion induced by Deposit

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Selective Cl-Corrosion: Influence of Methal Temperature

Metal temperature

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Aerosol (PM2.5) emissions

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Main mechanisms for formation of aerosols during biomass combustion

From van Loo and Koopejan (2002).

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Aerosol in a Straw-Fired Boiler

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Effect of Additives on Aerosol Mass Loading in a Straw-Fired Boiler:

mg/Nm3

mg/Nm3

dAero, nm

dAero, nm

Ca-P

S

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• Aerosol sampling: before SCR unit, T=350oC

• Deposit probe measurement: location B, T= 780±20 oC

• Deposit probe measurement: location A, T= 1275±50 oC

Aerosol emission in Avedøre unit 2

Damø et al. (2014), Wu et al. (2013)

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Mass-based particle size distribution of aerosols

• Significant reduction of submicron aerosol formation with addition of coal fly ash

• Similar effect for the addition of 6 ton/h and 3 ton/h coal fly ash Damø et al. (2014)

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Possible counter measures to reduce the risk of the problems

+

Co-combustion

Pretreatment

Boiler modification

Boiler SCR ESP

Boiler ESP SCR

Additives

+

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Gasification

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Two Stage Pilot Plant at Weiss A/S

1:1 1:10

DTU Chemical Engineering, Technical University of Denmark

(LT-CFB) PyroneerDONG Energy Asnæsværket

Low Temperature Circulating Fluid Bed (LT-CFB)

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Concluding remarks

• Cl, K and S cause severe operational problems in biomass fired boilers for heat and power production, especially deposition, corrosion, agglomeration and aerosol emissions

• Co-firing biomass and coal can significantly reduce the operational problems

• Application of right additives may be the other solution

• Biomass to power through gasification

Thanks for the Attention