Compared with conventional evaporative drying processes

microwave drying technology realizes simultaneous and rapid heating of both the inside and outside through microwave radiation

and has the advantages of low energy consumption

high efficiency

and no pollution in the lignite drying and upgrading process. However

overheating and thermal runaway tend to occur during microwave drying of lignite

which may cause spontaneous combustion of lignite or even explosion

thus resulting in great loss to the production line. In order to realize optimal control of lignite temperature during microwave drying

a lignite moisture content based method for dynamic adjustment of target temperature range was proposed in this paper. Based on this method

an active coordinated microwave power control system for multistage microwave drying chambers on the production line was established through modeling and simulation of the microwave drying chambers and analysis of on-site sampling data. Taking temperature and reflection coefficient as its input parameters

the system can dynamically adjust the output power of microwave sources through a PID control model. The system was installed and tested on the microwave lignite drying production line built by Nanjing Sanle Corporation in Hailar

Inner Mongolia. The results show that the system can accurately control the temperature range of lignite at each stage of microwave chambers

guarantee production safety

and keep the lignite moisture content under 10%.