Study On Performance Of Hydrothermal Liquefaction Of Sludge And Its Product Characteristics

Biomass is a kind of renewable organic resource, and it has been regarded as an alternative energy for fossil fuels. It can be transformed into bio-oil, hydrogen and other clean energy sources by hydrothermal liquefaction using hot-compressed water, attracting much attention from researchers.In this study, performances of hydrothermal liquefaction using sludge, water plants, corn stover and lignite as raw materials were compared at first. It was found that the sludge showed the best performance for hydrothermal liquefaction. Then, the hydrothermal liquefaction process of sludge and the physicochemical properties of its product bio-oil were investigated. The main results were summarized as follows:① The effects of temperature, retention time and the initial pressure on noncatalytic hydrothermal liquefaction of sludge were investigated using a high pressure autoclave. It was found that the best temperature was 340 ℃, retention time was 30 min, and the initial pressure is 4 MPa.② The effects of temperature, atmospheres and the initial pressure on catalytic hydrothermal liquefaction of sludge were also investigated using a high pressure autoclave. that Results showed that the best temperature was 340 ℃, the initial pressure was 4 MPa. Reducing atmospheres(especially CO) could signifieantly promote the hydrothermal liquefaction convesion of sludge and improve the qualities of liquid products.③ The effeets of homogeneous catalysts on the hydrothermal liquefaction of sludge under CO atmosphere were investigated. It was found that the conversion of sludge and the yield of liquid products under different catalysts were ordered as Na2CO3> K2CO3 > Na OH >KOH. The effects of heterogeneous catalysts on the hydrothermal liquefaction of sludge under CO atmosphere were studied. Results showed that both the conversion of sludge and the yield of liquid products under different catalysts were ordered as Ni/Mo>Co/Mo.④ The physicochemical properties of liquid products were investigated. Results showed that the density is 0.9508 g/ml at 25 ℃,the viscosity 19.1 m Pa﹒s at 60℃, the acid value 44.94 mg KOH/g,flash point 108.9 ℃. The content of C, H, O, N and S were 75.60, 11.39, 10.39, 2.10 and 0.52, respectively, and heating value is 35.84 MJ/Kg.