Construction Of A New Type Of Coal Moisture Control Technology Based On The Characteristics Of Indirect Heat And Mass Transfer Process In Coking Coal

The technology of coal moisture control taking the dry dehydration technology as the prototype is an important part of energy conservation and emission reduction in the coking industry and sustainable development.The traditional multi-tube rotating drum technology is more advantageous in reducing the dust pollution and the operation safety,but the indirect heat transfer mode leads to low efficiency of heat and mass transfer.Although the heat and mass transfer efficiency of fluidized bed technology is higher,it is difficult to control the dust pollution,and the oxygen content in the device should be strictly controlled,which has a great potential safety hazard.Both technologies have their own obvious technical defects.Based on pollution control,a new indirect heat transfer technology for coal moisture control is proposed in this paper,in order to improve drying efficiency and reduce energy consumption of indirect heating,Through the experiment,the basic research of this new type of coal moisture control technology was carried out,and the initial design parameters are optimized.Through the sidewall heat transfer experiment,it was found that the coking coal with 12% water content was 8 times the heating rate of pure coking coal,it is proved that the moisture transfer caused by phase change can accelerate the heat transfer process of coal,however,because the coal seam is too thick,the repeated phase change process leads to low drying rate.In order to reduce the mass transfer resistance,the coal material is stirred at a constant speed,so that the contact surface of the coking coal and the heat source is constantly updated,and the contact surface between the coal material and the wetted body is also constantly updated.It was found that the heating rate at this time was 9 times of the static state and the drying rate was 7.5 times of the static state.It was proved that the interface update was an effective way to enhance the indirect heat and mass transfer rate.At the same time,through thin layer plane heat transfer experiment,it is found that thin layer drying has positive effect on indirect heat and mass transfer rate.Therefore,a new type of device design is proposed.The hollow inclined plate with hot steam is used as the heat source,and the coal particles form thin layer flow on the multi layer inclined plate with their own gravitational potential energy,which can reduce the energy consumption of the interface renewal while maintaining the interface update effect.The moisture content is controlled by the number of inclined plates and the residence time of the coal in the device.Based on the experimental data of heat transfer at the resting layer,the device was preliminarily determined to be dried at 160°C with a thickness of 2 cm and the moisture content was reduced from 12% to 5% in 15.9 min.Fluent software is used to model and simulate the running process of 4.8 t/h production.The results show that the interface update can increase the heat transfer rate twice,and the number of inclined plate can be reduced from 7 to 4 in pilot plant.Based on the investigation of the indirect heat and mass transfer characteristics of coal,the new type of coal moisture control technology and its technical parameters are put forward,which has certain reference value for further promoting energy saving and emission reduction work in coking industry.