Reducing Emissions from Biomass Fuel Combustion

Biomass combustion can make use of many waste products found in the timber, manufactured wood products, and agricultural industries. It not only provides a source of essentially free fuel, but can also eliminate many of the disposal problems associated with these by-products. The environmental regulations faced by industry are one of the primary governing factors that must be addressed when designing a new system. The associated costs to comply with mandated NOx emissions limits can be significant, especially if it requires the addition of costly flue gas treatment equipment. In these cases, the ability to reduce NOx emissions significantly through changes to the combustion equipment can make the difference as to whether a system can meet required NOx levels in a cost effective manner. In order to make significant reductions in the NOx emissions from biomass combustion, without the use of flue gas treatment, a method must be found to reduce the conversion of fuel bound nitrogen (FBN) to NOx. In this paper we will deal primarily with our experiences in firing sanderdust fuels that are a by-product of the manufactured wood products industry, although the results are applicable to many other biomass fuels. Through the use of air staging, it has been possible to reduce the total NOx emissions by more than 50 percent over that of an un-staged system. New analysis tools and increasing data from the operation of these staged systems is allowing new burners to be designed with even more ambitious emission levels. This paper reviews two case studies where low emissions technologies are used to reduce emissions from suspension fired and grate fired biomass fired systems.