Emerging Technology for Multi-Pollutant Control on the Emissions of a Biomass Fired Boiler

Proposed modifications to the laws governing the emissions from biomass fired boilers require more stringent control on emissions. During biomass combustion there are several pollutants produced which require advanced pollution control measures to maintain environmental compliance. These pollutants include Particulate Matter, Hydrogen Chloride, Sulfur Dioxide, Sulfuric Acid Mist, and Oxides of Nitrogen. To ensure operational compliance of the boiler’s stack emissions both now and in the future, proper pollution control technology is paramount. This presentation will address an emerging air pollution control technology that embodies all of these removal steps in a single device specifically designed to meet the needs of biomass fired boilers. Historically, the control strategy for stack emissions from such boilers has included the use of various standalone systems. For example, Dry Electrostatic Precipitators have been used for PM reduction, Selective Non-Catalytic Reduction systems for NOx control, Flue Gas Desulphurization for SO2 removal, and single pass Wet Electrostatic Precipitators for H2SO4 abatement. The consolidation of these multiple, standalone systems into a smaller, less costly alternative tailored specifically for biomass fired boilers can address the new requirements. EISENMANN’s recently patented multi-pollutant control system includes the use of a pre-scrubbing chamber for large PM, SO2, and water soluble NO2 removal. Following the quench and pre-scrubbing region, a specially tuned downflow wet ESP field is responsible for finer PM and Sulfuric Acid aerosol removal, as well as an important Ozone producing stage that oxidizes non-water soluble NO. As the gas continues to travel through the system, a secondary scrubbing chamber is used to further reduce NOx by scrubbing the newly formed NO2 that has been formed from the oxidation of NO through the use of Ozone produced by the electrostatic precipitator. The final polishing stage of the system includes an upflow wet electrostatic precipitator field for the removal of newly oxidized material such as mercury. Research and testing on the aforementioned system took place through the development of a pilot sized unit. Expected performance was validated proving high removal efficiencies for pollutants specifically addressed earlier. Implementation of the technology within the biomass fired area is underway and is currently viewed as an acceptable solution to the environmental regulations associated with a biomass fired boiler because of the smaller footprint, lower operating costs, and overall condensed solution when compared to previously used technologies.