OIL SEPARATION BY DISTILLATION IN THERMOCHEMICAL LIQUEFACTION OF SEWAGE-SLUDGE

Steam distillation was studied as a means of oil separation from the reaction product of the direct thermochemical liquefaction of sewage sludge. The authors looked for any influence of liqufaction conditions on the distillable oil yield. It was found that the yield increased with increase in the liquefaction temperature. Holding time and catalyst loading had some bearing on the yield when considered in conjunction with the liquefaction temperature, but the kind of catalyst used for the liquefaction had little effect on the yield. Under the same liquefaction conditions, the distillable oil yield exponentially increased with rising distillation temperature. The distillable oils were similar to petroleum fuel oil in terms of heat value and viscosity. The reaction heat of the sewage sludge liquefaction was also observed by high-pressure DTA (differential thermal analysis). The result of this DTA study revealed that the liquefaction of sewage sludge was an exothermic reaction with a peak at about 550 K. On the basis of foregoing data, the heat balance of the liquefaction process coupled with distillation was evaluated, and it was confirmed that the sewage sludge liquefaction process is a net energy producer.