Study On Drying Characteristics And Drying Device In Moving Bed Of Coking Coal

Coke is an important raw material of iron and steel technology,its production process not only consumes a lot of energy,but also discharges a lot of pollutants.It is of great significance to reduce the moisture content of coal in the furnace for controlling coking cost,improving coke quality and reducing pollutant discharge.Based on the problems existing in the existing drying methods and devices,this paper present a new type of gravity moving bed dryer with double steam solid shunting.Coking coal moves downward from top to bottom by gravity and is indirectly heated in contact with a hollow heating plate with steam as the heat source;in the process of passing through each layer of heating plate,the interface between the coal layer and the heating plate is renewed by its shunting effect,which realizes the efficient heating.Through the outlet channel of evaporation steam set in the dryer,the generated evaporation steam can be exported out of the system in time to achieve efficient drying.Through the pilot test of 2t/h coal handling capacity,the influence of the retention time and initial moisture content of coal in the drying device on its drying effect was explored.It was determined that the retention time of coal in the device was 40 min,which could achieve the target moisture content of 8%.The secondary drying of coal could achieve the continuous reduction of the moisture content of coal to 6.26%.Through simulating the heat and mass transfer process of porous media in the gravity moving bed,it was found that the particle size and heat source temperature of coal material had a great influence on the drying process,the particle refinement and the increase of heat source temperature could effectively improve the drying rate,and the full contact between coal material and heat source could increase the drying rate of coal material.The pilot test modeling and drying process simulation were carried out by fluent.The simulation results showed that the coal was in a turbulent and orderly flow state in the device.As the coal moved down,the temperature increased gradually.The coke was diverged downward at an angle of 25° from the vertical and entrainment occurred between the falling and the air flow.Some fine particles formed eddy current at the top of the splint due to the air back impact,which could effectively reduce the dust.In addition,the experiment of moisture transferred between different particle sizes showed that the moisture absorption capacity of fine coal was stronger and its moisture was difficult to transfer to coarse particles.In practice,the drying effect of coal can be evaluated as a whole by controlling the moisture content of fine particles.In this paper,a new type of gravity moving bed dryer with double flow separation of gas and solid was proposed,which can effectively improve the drying efficiency and plays a positive role in energy saving and emission reduction of coking industry.