Co-firing Biomass in Coal-fired Boilers - Hot Topic March 17, 2011

Dr. Desmond Smith, Ph.D. Vice-President at BRUKS Rockwood, Inc, discussed biomass handling and preparation prior to co-firing. Co-firing wood and biomass with coal in a suspension burning boiler requires that the fuel be prepared in specific ways to be effective in the way it performs.  Conventional coal preparation machinery does not process biomass. It is necessary to control moisture to allow the machinery that grinds the organic fuel to produce a finely ground product that can be transported and injected pneumatically. The potential of using a gas to gas reheater such as Mitsubishi and Hitachi are using to reduce precipitator temperatures was discussed. A good way to extract heat from the system without paying an energy penalty would be quite attractive.

Dr. Fernando Preto, Senior Scientist and Group Leader for Biomass Conversion at CANMET Energy Technology Centre, discussed the co-firing of lignite with wood (pine) residues and peat focusing on emissions and ash deposition. His presentation reviewed the effects of fuel blending ratios, excess air, and moisture content on air emissions (CO, SO₂ and NO_x) from co-combustion of wood residues and peat with lignite. Co-firing leads to significant differences in the concentrations of some major inorganic compounds (e.g. SiO₂, CaO, MgO, SO₃) in deposited ashes.

There was a discussion of the combustion of municipal waste (MSW). Fernando made a very important point. Their research shows that the presence of sulfur reduces dioxin formation. So burning MSW in a coal-fired boiler has a beneficial impact on emissions. McIlvaine pointed out the advantages of using the chlorine in the waste to convert mercury to a soluble form. It was further observed that with the new Utility MACT rules power plants will have the air pollution controls to deal with MSW.

Kevin Toupin Director, Boiler Equipment at Babcock Power, Inc. / Riley Power, Inc., discussed conversion of coal-fired power plants to biomass-fired ones and the emission and combustion ramifications. He pointed out that a tail end SCR system using the concept similar to regenerative thermal oxidizers has solved the NO_x problem. These RSCR systems are operating on four plants and are reducing 80 percent of the NO_x and 60 percent of the CO, when the catalyst is operating at 400°F-500°F.

The Bios, Photo and Abstracts are linked below.
BIOS, PHOTOS, ABSTRACTS - March 17, 2011.htm