Taking a 420t/h tangentially coal-fired boiler as the object

numerical simulation using eddy-dissipation model(EDM)was carried out to evaluate the combustion characteristics of pure coal and mixtures of coal and sludge with different moisture contents and mass ratios.Several parameters under various operation conditions were investigated

such as the flow field

combustion

pollutants emission characteristics

total fuel burn out rate and coal particle burnout rate during the gas phase turbulent co-combustion.The results show that

the EDM can reasonably simulate the effects of mass ratio and moisture content of sludge on the combustion characteristics and pollutants emissions after co-firing.With the increasing mass ratio and moisture content of sludge

the vapor absorbed the heat

causing a decrease in furnace temperature

thus the total fuel burn out rate decreased.After the sludge was co-fired

the formation of fuel-NOx reduced

leading to an significant reduction in total NOx emission.The SO2 emission characteristics were obviously different in co-combustion of different kinds of sludge.This is mainly because the sulfur content in different kinds of sludge varies from each other.