N2O EMISSIONS FROM THE FLUIDIZED-BED COMBUSTION OF SEWAGE SLUDGES

Emissions of N2O were measured during the incineration of sewage sludg es, originating from various municipal waste-water treatment plants, i n stationary and circulating fluidised-bed combustors. The mechanicall y de-watered sludges had a solids content of 20-30% wt dm, and the pre -dried sludges had 87-94% wt dm. Bituminous and brown coals were also investigated, for purposes of comparison. Measurements from both combu stors showed that the sludges yield much higher N2O than the coals, in comparable combustion conditions. Wet sludges emitted higher N2O than pre-dried sludges. Staged combustion proved effective for lowering th e emissions of N2O during the combustion of the pre-dried sludge. Incr easing the freeboard temperature was shown to be the most effective wa y of reducing N2O.