Pollutant emissions of semi-dried sewage sludge combustion in a 1MW circulating fluidized bed combustor

The semi-dried sewage sludge was combusted in a 1MW CFB furnace. The emission characteristics of CO, NO and N₂O at different temperatures and excess air ratios were studied. The heavy metals distribution was also investigated. With 30% moisture content, the net heating value of sewage sludge is sufficient for auto-thermal combustion without supplementary fuel. The CO concentration in flue gas was reduced by 70% with excess air ratio rising from 1.18 to 1.75. The NO and N₂O concentrations in flue gas were 255 mg/m and 89 mg/m with excess air ratio of 1.75 at 800 °C which can meet the emission standard of MSW incineration in China. The heavy metals content in fly ash was low enough for use in alkaline soil.