Some Combustion Characteristics of Biomass and Coal Cofiring under Oxy-Fuel Conditions in a Pilot-Scale Circulating Fluidized Combustor

A series of tests were conducted using CanmetENERGY's pilot-scale, oxy-fuel firing capable circulating fluidized bed (CFB) combustor. These tests were done with a variety of coals, ranging from lignite to bituminous, that were cofired with biomass, specifically wood pellets. The amount of cofired wood pellets varied from 20 to 50% by weight. The objectives of these tests were to measure the combustion characteristics of oxy-fuel cofiring with coal and biomass, including flue gas composition, emissions of volatile organic compounds, and emissions of trace metals. Test results showed that stable combustion conditions could be obtained with a CO2 concentration in the flue gas of >90% and that the addition of wood pellets did not appreciably affect combustion conditions. These results provided support for the claim that cofiring solid fossil fuels such as coal and coke with carbon-neutral biomass under oxy-fuel conditions with CO2 capture is a sound approach for achieving negative CO2 emissions.