A study of fluidized bed combustion of propane and methyl chloride mixtures

Abstract

A study of the fluidized bed combustion of methyl chloride/propane mixtures was conducted to examine what processes may be important when FBCs are used to incinerate hazardous wastes. Methyl chloride represents a model hazardous waste, while propane represents a model auxiliary fuel. Although methyl chloride has been studied extensively in the past in fundamental experiments, methyl chloride combustion in FBCs has only been studied to a limited extent. The reactor used in the experiments was a 12.5 cm I. D., 152 cm long, stainless steel FBC, operated in the atmospheric, bubbling mode. The bed used was 500 μm sand with a slumped height of 8 cm. Inlet air temperature, equivalence ratio, and chlorine loading (Cl/H, molar) were varied to study their effects on combustor temperatures and emission of CO, CO2, NO, NOx, hydrocarbons, and chlorinated hydrocarbons. The data suggests a dramatic change in the overall performance of an FBC as the combustion moves from within the bed to the bed surface (overbed ignitions). Overbed ignitions were found to increase as equivalence ratio and/or chlorine loading increased. Combustion occurred later in the bed as chlorine loading increased because of the inhibition effect of increased chlorine content in the system. The overbed ignition phenomena caused a decrease in the destruction efficiency of methyl chloride, an increase in NOx levels, an increase in the number of volatile byproducts detected, and an increase in the concentrations of these byproducts. Methane was the most abundant of the hydrocarbon and chlorinated hydrocarbon species detected at all conditions; acetylene became an important byproduct when chlorine was added to the system. Comparison with the work of other investigators suggests that the use of an auxiliary fuel is important to obtain high destruction efficiencies (measured in the range 94.65–99.99% in this study).