Co-combustion Characteristics of Raw Sewage Sludge and RDF in a Fluidized Bed Reactor

摘要

Refuse Derived Fuel (RDF) was used as an auxiliary fuel for the combustion of sewage sludge with high moisture. The experiments were performed in a lab scale and a pilot scale bubbling fluidized bed reactor to study co-combustion characteristics of sewage sludge and RDF. The temperature distributions in a reactor and the emission of major gaseous pollutants including CO, NO, SO_2 and HCl were investigated according to the air supply ratio and the mixing ratio of RDF. In a lab scale reactor as the mixing ratio of sludge increased, temperature and CO concentration decreased, but NO and SO_2 concentrations increased gradually. In case of sludge only combustion, CO, NO and SO_2 concentrations were very high. In a pilot scale reactor bed temperature in the reactor decreased with the mixing ratio of sludge. When sludge mixing ratio was over 70%, bed temperature was dramatically dropped. CO concentration decreased with air supply ratio and air supply ratio needed for co-combustion with sludge was lower than for RDF only combustion (sludge 0%). NO concentration increased with air supply ratio and it was slightly low to 50 ～ 150 ppm regardless of the mixing ratio. As the mixing ratio of sludge increased and air supply ratio decreased, SO_2 concentration increased. HCl emission level for a mono-combustion of RDF was 52ppm. HCl concentration increased with the increase of mixing ratio of sludge although Cl content of sewage sludge is low. This result may be due to the high moisture and the drop of bed temperature. It was confirmed that RDF could be used as an auxiliary fuel for the combustion of raw sewage sludge and then co-combustion with sludge of 70% performed successfully in a fluidized bed reactor.