Detailed analysis of sewage sludge pyrolysis gas: Effect of pyrolysis temperature

Abstract

Conventional methods of sewage sludge disposal are often limited by their environmental impact and economic demands. Pyrolysis has been studied as a viable method for sewage sludge disposal and transformation into usable products. Pyrolytic products may have various uses, and their complex characteristics shall be described to assess their potential for safe utilization. Here, we studied slow pyrolysis of stabilized sewage sludge in a fixed bed reactor at 400-800 °C to describe the composition of the pyrolysis gas and the condensate fraction. We found that condensate elemental composition was practically independent of pyrolysis temperature. On the other hand, the composition of the pyrolysis gas was strongly temperature-dependent regarding both the share of major components (H2, CO, CO2, CH4) and C2-C6 hydrocarbons speciation (which as a sum attributed to 7-9 vol. % of the gas). The increase in pyrolysis temperature also resulted in increasing the N2 content of the gas, whereas the sulfur containing gas compounds were substantially diluted in the increasing gas volume.