Flash pyrolysis of sewage sludge

Abstract

A dry mixture of raw and activated sewage sludge was pyrolyzed in a bench-scale fluidized-bed reactor at residence times of less than 1s over the temperature range 400-700°C. Organic liquid yields of up to 52% maf were obtained at the optimum temperature of 450°C and 0.55-s residence time. Shorter reaction times gave slightly higher liquid yields. The effects of reaction athmosphere, char accumulation, and deashing on liquid yields were also investigated. A test in a larger unit at a feed rate of 2kg/h duplicated the bench-scale result. From elemental analyses, the char appears to be aromatic in character, while the liquid tar product has a H/C atomic ratio of about 1.77. A certain amount of water-soluble alcohols, ketones, etc., appear to be present also.