城市污水污泥催化快速热解制备芳香烃和烯烃

Fast catalytic pyrolysis of sewage sludge to produce aromatic hydrocarbons and olefins

将城市污水污泥干燥处理,在小型热解分析系统中使用沸石分子筛进行催化快速热解实验,研究热解条件对芳香烃和烯烃产率及选择性的影响。结果表明:污泥快速热解产物中,烃类物质和含氮化合物较多,这些组分主要源自污泥中的蛋白质和油脂成分;添加催化剂后,芳香烃和烯烃的产率明显提高;在热解温度500℃、催化温度600℃条件下芳香烃和烯烃的产率分别为24%和19%。另外,污泥中大部分的N、P、Na和K等元素依然保留在炭粉中。

In this study, ex-situ catalytic pyrolysis using HZSM-5 zeolite catalyst was studied to obtain aromatic hydrocarbons, olefins and nutrition rich bio-char from sewage sludge. The experiments were applied in the pyrolyzer-gas chromatography-mass spectrometer/flame ionization detector/thermal conductivity detector system（Py-GC-MS/FID/TCD）. The sewage sludge was dried and grinded for pyrolysis experiment. Pyrolysis temperature and catalysis temperature were investigated to obtain an optimal condition in terms of hydrocarbon（aromatic hydrocarbons and olefins） production. The optimal pyrolysis and catalysis temperatures were 500°C and 600°C, respectively. Carbon yields of olefins and aromatic hydrocarbons were 24% and 19%, respectively. The main olefins produced from sewage sludge were ethylene and propene, accounting for more than 95% of the total olefins. The main aromatic hydrocarbons produced from sewage sludge were benzene, toluene, and xylene, accounting for more than 75% of the total hydrocarbons production. The N and C migration experiment showed that 32% of the C and 51% of the N were kept in the bio-char. The fate of inorganic minerals during the process was also investigated. Negligible amounts of metals volatilized during pyrolysis, suggesting that the catalyst poisoning during pyrolysis of sewage sludge may not be a major problem so that the catalyst can be reused and the bio-car can be collected from the reactor. Most of the nutritious elements were still kept in the bio-char, and then the char can be used as potential agriculture application. This study suggested that the catalytic pyrolysis can be used to convert sewage sludge into value-added chemicals and nutrient-rich bio-char.