CHEC Annual Day, 2009

Ash Deposition and Shedding in Biomass Suspension-Fired Boilers

Muhammad S. BashirPhD Student (01-09-2008 to 31-08-2011)

Supervisors: Kim Dam-JohansenPeter A. JensenFlemming FrandsenStig Wedel

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Project Objectives

“Optimal use of Biomass in large suspension-fired boilers.”

• Ash deposition and removal behavior in the boiler chamber and superheater region (convective pass).

• Transient model based description of key processes responsible for ash deposition and shedding.

• Influence of load, operation conditions and fuel mixing on ash deposition and shedding.

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Ash Deposition during Biomass Combustion

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

L. Tobiasen et al; Fuel Processing Technology, 88 (2007) 1108-1117.

Biomass (straw) K, Cl, S

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Initial Experiments on Amagerværket Unit 2: Co-firing straw and wood

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

80% Straw

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Deposit Probe Weight and Heat Uptake

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

Test No. 1 (SH) 2 (SH) 3 (SH) 4 (SH) 5 (TB)

Straw (%) 35 65 80 100 0

Wood (%) 65 35 20 0 100

Flue Gas Temp. (oC) 846 841 851 821 586

Weight Uptake (g/m2) 1080 1410 1480 1700 (20)

Heat Uptake (kW/m2) 22 23 22 24 10

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Deposit Characterization for different straw shares

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

80 %

100 %

35 %

65 %

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Ash Enrichment

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

Ca K Si S Cl0

5

10

15

20

25

30

35

40

45

Fuel Ash Fly ash (Suspension-firing, 80% straw)Fly ash (Grate-firing, 100% straw)

Wt

%

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Front Deposits Elemental Composition

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

Ca K Si S Cl0

5

10

15

20

25

30

35% Straw 100 % Straw

wt

%

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Conclusion

• Deposition rate increases for increase in straw share.

• Deposit layers differ in terms of color, thickness, hardness and composition for change in fuel composition.

• Deposits are more sintered in the upper layer for 100% straw-firing.

• Deposits and fly ash contains significant amounts of Ca and Si during suspension-firing.

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Future Work• Final design of vertical probe for ash deposition/shedding

in the furnace region.

• Modeling of ash deposition/shedding in the furnace region.

• Ash deposition/shedding tests at Amagerværket Unit 1 (co-fired with coal) using horizontal sootblowing probe.

• Ash deposition/shedding tests at Amagerværket Unit 1 (co-fired with coal) using vertical probe.

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

DTU Chemical Engineering, Technical University of Denmark

CHEC Annual Day, 2009CHEC Annual Day, 2009

Acknowledgment

• Dr. Johan Wadenbäck/Søren Thaaning., Vattenfall A/S

• Energinet.dk for PSO project funding

Objectives Background Experiments Results and Discussion Conclusions Future Work Acknowledgment

Tak for opmærksomheden/

Thanks for the Attention !