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

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℃ and 600℃, 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. © All Right Reserved.