Abstract:

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%.

摘要：

与传统的蒸发干燥工艺相比，微波干燥技术采用微波辐射的方式，具有内外同时加热、加热速度快等特点，使得褐煤干燥提质的过程耗能小、效率高、无污染。但是，在微波干燥褐煤的过程中易出现热过度和热失控的情况，会导致褐煤自燃，甚至爆炸，给生产线带来极大损失。为了实现微波干燥过程中褐煤温度的最佳控制，提出了一种基于褐煤含水率的目标温度范围动态调节方法。在该方法的基础上结合微波干燥腔的建模仿真及现场取样数据的分析，构建了一套生产线中多级微波腔的微波功率主动协调控制系统，以温度和反射系数作为输入参数，通过PID控制模型来动态调节微波源的输出功率。将该系统安装于南京三乐公司在内蒙古海拉尔建立的微波干燥褐煤生产线上进行测试，结果表明，该系统能够对各级微波腔内褐煤的温度范围精准控制，保证生产的安全性，并且将褐煤的含水率控制在10%以内。