Structure Effect on Heating Performance of Microwave Inductive Waste Lubricating Oil Pyrolysis

Abstract

Microwave has been widely used in pyrolysis of waste lubricating oil, but the uneven electromagnetic field distribution seriously affects the product distribution and even aggravates coking in pyrolysis process, where the pyrolizer structure plays a dominant role. Four structures were simulated in the continuous pyrolysis of waste lubricating oil under microwave irradiation, including single circular tube, parallel tubes, pulse type spherical tube as well as circular tube equipped with baffles. The temperature distribution and pressure drop were calculated to evaluate the performance of heat transfer and flow behavior. The simulation indicates that there exists several “hot spots” in continuous circular structure due to the maldistribution of electromagnetic field, which may cause coke in industry. The baffles can enhance the turbulence of oil flow in the reactor but cause several stagnant zones, which hinder local liquid renewal. The parallel tube-type pyrolizer shows highly efficient heating performance but large temperature difference among each tube as well as large pressure drop due to the decrease of effective flow area for high viscous oil. Among those structures, the spherical tube can accelerate the renewal process of liquid and thus make the temperature more uniform, which is a durable and available strategy for microwave-inductive pyrolysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge financial support from the National Nature Science Foundation of China (No. 21878219) and the National Key R&D Program of China (2018YFB0604900).

Notes on contributors

Zhenyu Zhao

Zhenyu Zhao is a Ph.D. student in the School of Chemical Engineering and Technology, Tianjin University, under the supervision of Prof. Hong Li. He received the degree of Bachelor of Engineering for Chemical Engineering from Tianjin University in 2017. He is currently working on the development of microwave-assisted chemicals separation process.

Xinhui Tang

Xinhui Tang is a Bachelor student in the School of Chemical Engineering and Technology, Tianjin University, who was admitted in 2017. He is currently participating in the Campus Student Research Training Program about waste oil recycle assisted by microwave technology.

Borui Jiang

Borui Jiang is a Bachelor student in the School of Chemical Engineering and Technology, Tianjin University, who was admitted in 2017. He is currently participating in the Campus Student Research Training Program about waste oil recycle assisted by microwave technology.

Hong Li

Hong Li is a professor in the School of Chemical Engineering and Technology, Tianjin University, China. She received her Ph.D. in the School of Chemical Engineering and Technology, Tianjin University in 2007. Her main research interests include separation process intensification, energy engineering and coal chemical industry.

Xingang Li

Xingang Li is a professor in the School of Chemical Engineering and Technology, Tianjin University, China. He received his Ph.D. in the School of Chemical Engineering and Technology, Tianjin University in 1992. His main research interests include mass transfer and separation engineering, scale-up of distillation, energy saving, and process intensification of chemical engineering.

Xin Gao

Xin Gao received his Ph.D. degree in Chemical Engineering from Tianjin University in 2011, China. He is currently working as an Associate Professor in Tianjin University. He has published more than 120 peer-reviewed scientific journal papers. He is the member of Editorial Board for Journal of Engineering Thermophysics. His research focuses on process intensification and application of microwave energy in chemical engineering.