Aaem Removal From Xinjiang High-alkali Coal Through Water Leaching Enhanced By Flue Gas

Recently,high quality steam coal reserves are extensively discovered in Xinjiang province.However,it is prone to cause serious fouling and slagging problems during combustion due to the high content of alkali metal and alkali soil metal,thus endangering the safety and stability of power plants.Based on the water leaching method enhanced by flue gas,this work explored the influence of key process parameters on the effect of AAEM removal.A correlation model was establishesd,and the influence of enhanced water washing on the ash formation characteristics and thermal conversion characteristics of high alkali coal was investigated.The results shows that the feasibility and advantages of this method when inhibiting the fouling and slagging of high alkali coal combustion was confirmed.In addition,the process simulation and life cycle analysis of water leaching enhanced by flue gas were carried out,and the feasibility of industrial application and environmental impact were evaluated.The results show that water leaching enhanced by flue gas evidently reduced the content of AAEM and some heavy metals in high-alkali coal.The removal rate of Na,K,Ca,and Mg reached 86.8%,62.7%,44.7%,35.4%,respectively.The AAEM removal efficiency increased with the increase of the leaching time and the decrease of the raw material particle size,and the influence of time is more significant than the particle size.With the increase of leachate cycles,the salt in it concentrated correspondingly,resulting in decreased AAEM removal efficiency.Therefore,the circulating leachate needs to be purified before circulation to ensure the efficiency of AAEM removal.Water leaching enhanced by flue gas significantly enhanced the melting temperature of high-alkali coal ash,thereby increasing the average melting temperature of high alkali coal ash to 107℃.Meanwhile,this leaching method decreased the ignition temperature,increased the burn-out temperature and reduced thegasification rate of coal slightly.Finally,the simulation results of Aspen Plus and e Balance show that water leaching enhanced by flue gas could reduce CO₂ emissions by 4 tons/100 tons coal.At the same time,0.083 t of diesel oil,12 t of water and 507 k W·h of electricity were consumed per 100 tons coal for the water leaching by enhanced flue gas,and the cost was about 950 yuan.The greatest environmental problem during this process was the pollution caused by dust and fly ash.Compared with the stages of feedstock preparation and water treatment,the leaching stage had the greatest impact on the environment,accounting for 48.7%,which implicated that more attention needed to be paid on this stage during process optimization.