Research on low temperature thermo-chemical conversion to oil process for sewage sludge

The process of low temperature thermo-chemical conversion of municipal sewage sludge to oil is a new developing technology in developed countries, which is developed based on some poor fuels processing process in recent years. The process has the advantages of reasonable thermal energy recovery (the whole process is a net thermal energy exporting process), suitable cost and less secondary pollutants. This research included the reaction conditions versus the converted products distributions, the reaction conditions versus the ratio of the process thermal energy input and output, exploring of reaction mechanisms, creating of reaction kinetics models. These results contribute not only to having a clear understanding about the technological features and evaluating the prospectives of technological development, but also provide a sound basis for the technological development on a larger scale. It is concluded that: 1) the sludge treatment process is a net thermal energy producer. 2) The optimal conversion temperature is 270°C, referring to making energy recovery ratio maximum. 3) The parameters of simple conversion reaction kinetics are n=2, A=8.5 S-1 and E=37.9 KJ/mol. 4) The secondary pollutants of the process can be effectively controlled. 5) The investment intensity of the process could be similar to that of the sewage sludge incineration process, and the operational economics of the process are obviously superior to those of the sewage sludge incineration process. The research results show that the technical-economic feasibility of low temperature thermo-chemical conversion process is favorable, because the reaction conditions are more moderate and the separation process of the products is more easily realized.