Modeling and simulation of coupled pyrolysis and gasification of oily sludge in a rotary kiln

[Display omitted] •The coupled pyrolysis and gasification of oily sludge model was conducted.•The successive and simultaneous reactions were investigated, respectively.•A peak of 525 kJ was observed at solid heat carrier of 1187 K in successive reaction.•The highest heat value was 517 kJ at 1400 K in simultaneous reaction. Oily sludge is considered as hazardous material which has a negative impact on environment and human health. Pyrolysis and gasification are effective technologies for the utilization of oily sludge. In this work, the coupled pyrolysis and gasification process of oily sludge in a rotary kiln was simulated. The material motion equations, heat transfer equations and kinetics equations were used to model the pyrolysis process, while the mass equations and energy equations were used to model the gasification process. The successive and simultaneous reactions were investigated. In the successive reaction, CH4 yield has a peak of 3.25% at the initial temperature of solid heat carrier of 1167 K. At higher temperatures, CH4 yield decreased and CO and H2 became the dominant fuel gases, with the yields of 7.49% and 1.81% at 1400 K, respectively. A heat value peak of 525 kJ was observed at 1187 K. In the simultaneous reactions, high temperature promoted the yields of gaseous products. The yields of gaseous products (CH4, C2H4, C2H6, CO and H2) increased rapidly with increasing temperature (3.65%, 0.035%, 4.01%, 0.76% and 0.66% at 1400 K). The highest heat value was 517 kJ at the initial temperature of solid heat carrier of 1400 K.