Parameter study on the incineration of municipal solid waste fuels in packed beds

A parameter study on the incineration of municipal solid waste fuels has been carried out in both a bench-top fixed-bed reactor and a full-scale moving bed. Temperature and gas composition (including NOx) profiles inside the bed and the burning rate were measured in the bench-top reactor under different conditions. Effects of primary air flow rate, preheated temperature and moisture level in the waste have been investigated. For the large-scale moving bed, a unique in-house prototype instrument was introduced into the incinerator with the waste feed so that it tumbled along with the burning waste while recording temperatures, gas composition and bed motion on its thermally insulated electronic chip. For mathematical modelling, governing equations for mass, momentum and heat transfer for both solid and gaseous phases in the packed bed of solid wastes are described and relevant sub-models are presented. For the bench-top reactor, the maximum temperature inside the waste bed was 900-950degreesC and the maximum burning rate obtained was 135 kg m(-2) h(-1) with 49% of moisture in the waste. The depth of the burning layer was five times larger than the particle size of the waste. Preheating air to below 100degreesC produced no effect on the burning rate. Peak VOC and NOx concentrations measured near the bed top were 1.5% and 60 ppm, respectively. For the large-scale moving bed, the maximum temperature was 1000-1128degreesC but strong fluctuations in temperature as high as 800 C were recorded by the electronic device inside the bed. It is also shown that the waste feed on the bed was ignited at a distance of 1.8 to 2.0 m from the waste entrance. O-2 concentration was 2-4.5% for a large part of the bed length, although sharp fluctuations were observed in the early period of combustion (ignition zone).