modelling of biomass combustion in fluidised beds tai...

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BIOMODELLING

Modelling of Biomass Combustion in

Fluidised Beds

Timo Hyppänen

Lappeenranta University of Technology

14.1.2010

14.1.20101

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Content of the presentation

• ERA-NET Project Background

– Goals, benefits

– Organisation

– Work plan

• CFB modeling

14.1.20102

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Background

• Need to develop environmentally sound ways to

increase utilization of biomass in energy production

• ERA-NET Bioenergy is a network of national R&D

programmes focusing on bioenergy

– Joint call on clean biomass combustion

– Modeling of the combustion process

14.1.20103

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Project goals

• Goal is to develop and improve the modelling methods

for biomass combustion in circulating fluidised bed

(CFB) boilers

– fluidization behavior

– combustion properties

– emissions formation

– heat transfer

• Improved models for biomass combustion

• Models enable more accurate development, design and

analysis of CFB boilers utilizing biomass.

14.1.20104

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Benefits

• Increased

– capability of using renewable energy

– boiler performance

– efficiency

– availability

• Reduced emissions

14.1.20105

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ERANET PROJECT PARTNERS

14.1.20106

• Czestochowa University of Technology, Faculty of

Environmental Engineering and Protection

• Chalmers University of Technology, Department of Energy

and Environment, Division of Energy Technology

• VTT Technical Research Centre of Finland

• Foster Wheeler Energia Oy

• PGE Turow Power Plant

• Lappeenranta University of Technology, LUT Energy

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PGE Elektrownia Turów S.A.

( Polish Energy Group, Turow Power Plant)

3 x 235 MW CFB hot cyclone

3 x 261 MW CFB compact

Lignite & biomass

BIOMODELLING

•TUROW is a largest CFB utility company

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ERANET PROJECT WORK PLAN

14.1.20108

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Modelling CFB Fluid Dynamics and

Thermal Behaviour

•Flow of solids and gases

•Fractional material

balances

•Combustion of fuel

•drying

•devolatilization

•char combustion

•Heat transfer

•Gaseous reactions

•Emissions (SOx, NOx)

Reh, L. (2003). China Particuology Vol. 1, No. 5, 185-200.

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O2

Sec.

air

CO

Fuel

TemperatureReh, L. (2003). China Particuology Vol. 1, No. 5, 185-200.

Min

Max

Modelling CFB Fluid Dynamics and

Thermal Behaviour

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Modelling of CFB fluid dynamics

•CFD multiphase modelling challenging for CFB

combustion cases (reliability/speed)

•Mass balances must be valid

•Semiempirical model used for averaged flow profiles

– Gas: Momentum equation with drag force

dominating

– Solids: First order model to produce experimental

profiles, potential flow principle

•Mixing of solids and gases is due to nonstationary

and small scale flow structures => Dispersion model

•CFD getting closer to be utilised

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3-D Model Description

• Steady-state combustion model for CFB furnace.

• Fractional material balances of solids.

• 3-D flow modelling of solid and gaseous species.

• 3-D modelling of energy balance.

• Submodels required in balance models.

• fluid dynamics of solid materials and gases

• combustion (drying, devolatilization, char

combustion)

• gaseous reactions

• comminution of solids

• heat transfer

• emission models for SOx and NOx

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CFB3D Model Frame

Fuel, limestone,

make-up

Secondary airs

Gas and solids from outlets

Separator(s)Flue gas, fly ash

Solids

External heat

exchanger(s)

Solids to return leg(s)

Flue gas / fly ash recirculation

Solids,

gas

Furnace outlets

Heat transfer

to wallsCombustion

& other reactions

Heat transfer

within bed

Bottom ash

Primary air

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Three dimensional furnace model

14.1.201014

Example of CFB3D model results.

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Methods – laboratory equipment

Fuel particle conversion Cold models

Pilot-scale

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nc Xkm

t

mr O2c

c

d

d

COefCO Ykt

Y

d

d

)/1/(1 mCOef kk

nrefv ddTAb )/)(/exp(

Model

analyses

CO combustion

Mixing

Char combustion

Volatile,

moist

ure re

lease

Different scales of experiments

and modelling

1D-MODELflue gas

1

n n+1

to stack

Primary airSecondary air

2

n-1

3

n-2

Bench scale Pilot scale Boiler scale

EXPERIMENTAL

SCALES

Models for

phenomena

1-D process

models

3-D process

models

MODELS AND

DESIGN TOOLS

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THANK YOU FOR YOUR ATTENTION!