Co-Combustion of dried sewage sludge and coal/wood in CFB-A Search for Factors Influencing Emissions

Co-combustion of sewage sludge with either coal or wood as base fuels was investigated in two CFB units, one laboratory scale combustor and one pilot scale boiler of industrial size. The investigation was focused on general combustion performance and flue gas emissions. It was found that cocombustion with dry sewage sludge can be carried out within the range investigated (a sludge fraction of less than 50% of the energy supply) without any problems. The NO emission could be high because of the high nitrogen content of the sludge, but it was shown that the reduction in the CFB is also high and the resulting emission is only moderate. The same is the case with the other emissions recorded (CO, N2O). Sulphur emissions from combustion of the sludge is a consequence of sulphur components originating from the organic part of the sludge (sulphur-containing proteins for example)