Paper details

Title:

Laboratory Research on Co-firing Wooden Biomass with Bosnian Brown Coal and Lignite for Large Utility

Author(s):

Kazagic, A., Smajevic, I.

Document(s):

Abstract:

Paper presents an experimental research into ash-related problems and emissions during co-firing wooden biomass with Bosnian brown coal and lignite. The research is aimed to optimize percentage of the switching coal by wooden biomass in two large Bosnian coal-based power stations; the Kakanj power station (2x110 MWe, 1x230 MWe) supplied by brown coal and the Tuzla power station (1x100 MWe, 2x200 MWe, 1x215MWe) supplied by lignite. For purpose of the research, an electrically heated entrained pulverized-fuel flow reactor was used. Co­firing trials were running under different conditions in the reactor; varying the process temperature, excess air ratio, and air distribution. The co-firing tests used spruce sawdust in combination with Kakanj brown coal and a lignite blend consisted of Dubrave and Sikulje lignite. Coal/biomass mixtures at 93:7%wt and 80:20%wt were tested. During the tests, the temperature in the experimental facility varied between 880 ºC and 1550 ºC, while the excess air ratio varied between 0.95 and 1.4. Both for lignite-wooden biomass and brown coal-wooden biomass co-firing, there were no significant ash-related problems if the blend with 7%wt of wooden biomass was used and if the process temperature did not exceed 1250 oC. From the other side, adding biomass to the brown coal for the co-firing at temperature 1550 oC, which is actual temperature in the boilers with slag tap furnaces in the Kakanj power station, slag flow over ceramic surface was improved. Much lower NOx emissions were measured at the lower process temperatures and the lower excess air ratio used in all co-firing regimes. It was identified that not only nitrogen content in the co-firing blend but also volatile content and particle size distribution of the coal-wooden biomass mixture influenced on NOx emissions. Reduction of SO2 emission was detected for all co-firing regimes. In addition to the reduction of SO2 due to the lower sulfur content in the coal/biomass blends tested, the brown coal-sawdust co­firing generated a further reduction of SO2 due to the higher sulfur capture rate than for coal alone. Finally, significant reductions of CO2 found by calculation for the blends tested, due to the low ranking of Bosnian coals. It was found that 7%wt of wooden biomass can be used in combination with coal in both power stations without risk to the combustion process and with benefits through emissions reductions. For the first time in Western Balkan a trial run of co-firing on a large-scale utility is going to be realized (at the Kakanj unit 5 – 110 MWe) – the preparation for this pilot project is ongoing at the moment and co-firing trial run is scheduled for the summer time of 2010.

Keywords:

biomass, coal, co-firing

Topic:

Thermochemical conversion - Combustion and co-combustion

Subtopic:

Combustion and co-combustion for large utility and industrial scale applications

Event:

18th European Biomass Conference and Exhibition

Session:

VP2.4.11

Pages:

1145 - 1155

ISBN-13:

978-88-89407-56-1

ISBN-10:

88-89407-56-5

Paper DOI:

10.5071/18thEUBCE2010-VP2.4.11

Price:

FREE