Study On Characteristics Of Coking Coal Drying In Moving Bed And Dense Phase Continuous Flow Charging

Coke is the main raw material for iron makin,and coking is an important process in the upper reaches of the iron and steel industry chain.In the process of coking,the moisture content of coking coal has an important effect on the production of coking wastewater,energy consumption and coke quality.In order to save water and reduce consumption,Japan Nippon Steel has developed coal moisture control technology such as fluidized bed and rotary pipe,which has become an important technology of energy saving and efficiency increasing in coking industry.However,the escape of coal charging dust and high drying cost hinder the popularization of application.According to the current research status and background significance,a new process model of coal moisture control and dried coal charging in top-charged coke oven was established.Theoretical and technical innovation were carried out in the process of coal moisture control and charging.Firstly,in the process of coal moisture control,a vapor-solid double split moving bed dryer was proposed based on the updating of coal dry and wet interface.The drying characteristics of the moving heating surface and moisture transfer in the fixed heating surface were simulated by the indirect drying platform built in the laboratory.Then the characteristics of coal particles after drying were tested and analyzed to evaluate the influence of these changes,environmental temperature and humidity on moisture readsorption of dried coal in constant temperature and humidity box.The results indicate that the updating of dry-wet interface increased the drying rate of coal.Compared with static drying,the average moisture content of interfacial renewal drying can be reduced by 1.6% under the same drying temperature and time.Compared with the third generation coal moisture control technology in Japan,the water saving rate and energy saving of the new moving bed dryer were increased by49.0% and 3.4%,and there was no dust during drying.In addition,when the drying temperature exceeds 110℃,the shrinkage and collapse of large and medium pores of particles will occur,thus the moisture absorption rate of dry coal stored in bunker was reduced later.Secondly,a certain amount of alkali slag additive was added into coal blending,and it was found that the drying rate of coal in the moving bed was improved,and the coke products made could meet the demand of industrial production.When the temperature was 110℃,adding 2%,5% and 10% alkali slag,the drying rate increased by 11.5%,25.3% and 37.3%,respectively.The dry distillation experiment of coal mixed with alkali slag shows that when the mass addition ratio of alkali slag was less than 5%,the increase of carbon loss was less than 10% compared with raw coal.In addition,alkali slag can increase the active point of carbon dissolution reaction and inhibit the internal dissolution of coke.Subsequently,the fine coal after drying in moving bed was treated with humidification and agglomeration.The coal particles were fluidized by the air flow of fan through a special fine particle humidifier and agglomerating device,and then the compound soap solution was used as agglomerating accelerator to humidify and increase viscosity of fine particles.During the experiment,the effects of equipment operation parameters,particle characteristics and soap components ratio on fine particle agglomeration were analyzed.By establishing agglomeration and mechanical models,the force and velocity distributions of particles during agglomeration were studied based on CFD.The results indicate that soap solution has a strong agglomeration effect on particles with particle size less than 0.5 mm,and the adsorption and flocculation of polymer chain in soap solution can promote its agglomeration.The coating efficiency of fine particles increased from 82% to 96%with the increase of the mass addition ratio of soap powder from 5% to 15% in the vortex region.For the soap component,the wettability and agglomeration efficiency of coal particles can be obviously improved by increasing the proportion of non-ionic surfactant fatty acid methyl ester ethanol and fatty alcohol polyoxyethylene ether.Compared with carboxymethyl starch,using hydrophilic organosilicon as antifouling redeposition agent can increase the adsorption capacity of raw coal to surfactant by5%;compared with the traditional polymer aqueous solution,the coating efficiency of the compound soap solution was increased by 10%.Finally,it was the coal charging.Based on the related equipment parameters of6 m top-loading coke oven,a matching telescopic sleeve coal-charging device was designed to realize the dense phase continuous flow mode of coal powder into the coking chamber.The characteristics of coal transportation,dust emission and accumulation during coal charging were studied by cold state.The influence of temperature gradient on the force and motion of coal particles during coal charging were studied by means of theoretical analysis,calculation and numerical simulation in the hot state.The results show that when the moisture content was 5%-6%,the sleeve lifting speed was 0.02m/s,and the distribution range of spiral feeding speed was[0.31m/s,0.50m/s].The dust emissions per square metre reduced by 90% compared with the traditional coal loading method.The dust escape was mainly affected by thermal force and airflow disturbance through simulation of coal charging in the hot state.In non-uniform temperature field,radiation heat transfer reduces the deposition rate of coal particles.The dust escape velocity can be controlled below 0.4m/s by the dense phase transportation mode of coal powder(traditional coal charging was1.1m/s).