The investigation of availability of torrified dry sewage sludge
2017
Gödekmerdan, E.
Sewage sludge has great potential for renewable energy production due to its large amounts and high organic matter content and may be a source for high quality solid fuel such as biochar, when the torrefaction process is applied. Sewage sludge is used to produce energy by thermal conversion methods such as pyrolysis, gasification, incineration and co-incineration. Torrefaction, also known as mild-pyrolysis, is a thermal treatment carried out at temperatures between 200 and 300 oC in the absence of oxygen. In the experiments that were carried out, 75%, 50% and 25% of the total feedstock was mixed with the sewage sludge and the remaining part was completed with pine chips. Experiments were carried out at temperatures of 250 oC, 280 oC, 310 oC for 20, 40, 60 minute, respectively. In this thesis, it is aimed to obtain biofuel with low ash and sulfur contents, high calorific value and maximum sludge mixing ratio. In the experiments of the torrefaction of sludge and pine chips together; the effects of temperature, residence time and mixing ratio, on calorific value, ash and sulfur content were investigated by Box-Behnken experimental design. According to the optimization result; 298.5 oC / 33,15 minutes / 30% mixture ratio was chosen as the optimum point. If the torrefaction process takes place under these conditions, the calorific value of the biochar to be obtained was determined as 4942,1 kal/g as well as the ash content and sulfur content of the biochar to be obtained were determined as 25% and 0,23%, respectively.
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