The effect of high temperature on syngas production by immediate pyrolysis of wet sewage sludge with sawdust

In this paper, the co-pyrolysis characteristic of wet sewage sludge (60 mass%) with sawdust (40 mass%) at high temperature was investigated by Py–GC/MS and a bench-scale screw moving bed reactor. The Py–GC/MS analysis indicated that the main pyrolysis process has nearly accomplished below 700 °C, and the decomposition at high-temperature range of 800–1000 °C was the secondary cracking of macromolecule with the generation of non-condensable gas. According to the laboratory experimental results, it was found that the gas fraction increased with temperature increasing, especially H2 and CO, and the solid and liquid had an opposite tendency. Moreover, the moisture in raw material played an important role in the increase in gas fraction with temperature increasing. From the view of industrial application, a pilot-scale screw moving bed reactor with the handling capacity of 100 kg/h was designed and tested in a proper temperature range of 800–950 °C for syngas production. The exergy analysis of the pilot system was conducted, and the exergy values of gas took a large proportion in the output exergy and the exergy efficiency of gas increased from 50.58 to 57.38 mass%. The proposed intermediate pyrolysis of wet sewage sludge with additive, like sawdust, in screw moving bed reactor for syngas production would provide a promising method for wet sewage sludge treatment.