Study On Synthesis Of Zeolites From Fly Ash And CO₂ Performance

With the rapid development of economy and industry,on the one hand,a large number of coal ash production and accumulation in coal-fired power plants;On the other hand,the disordered excess emissions of CO2 from key industries such as coal-fired power plants and chemical industry all cause serious environmental pollution.In view of the high-value resource utilization of fly ash and the degradation of CO2,this paper uses the alkali fusion of fly ash-hydrothermal synthesis of zeolite,and the application of it in the treatment of CO2,to achieve the coal industry to fly ash "waste control waste,comprehensive utilization" value.In this paper,fly ash synthesis of zeolite pretreatment conditions,synthesis process were studied,and comparative analysis of the zeolite in different adsorption temperature and pressure conditions on the adsorption performance of CO2.The main research results are as follows:(1)In this paper,fly ash from a power plant in Shaanxi Province was used as raw material,and it was found that the content of impurities such as alkaline oxides and organic carbon in fly ash was high.Considering the factors of economy and convenience,high temperature roasting and acid treatment were used to pretreat fly ash to remove impurities.Through single factor experiment,the best impurity removal conditions were obtained:calcination temperature is 800?,hydrochloric acid concentration is 6mol/L,reaction temperature is 75?,reaction time is 2h,liquid solid ratio is 4:1.Under these conditions,the removal rates of Fe2O3,CaO and organic carbon can reach 55.6%,53.9%and 100%,respectively.(2)The process parameters for the synthesis of zeolite were optimized by alkali fusion and hydrothermal synthesis method.The optimal process parameters of NaA and NaX zeolite were determined by BET,XRD,SEM and FT-IR characterization analysis.The specific surface areas were 27.3671m2/g and 608.1947m2/g,respectively,with a lime-base ratio of 1:1.2,solid-liquid ratio of 1:6,crystallization time of 5h(NaA)and crystallization time of 6h(NaX).CaA zeolite was prepared by using the synthesized NaA zeolite,and its specific surface area was 471.8638m2/g.(3)Taking CO2 as the target adsorbate,the adsorption capacity of three zeolites for CO2 and the selective adsorption of CO2/N2 were studied.The effects of the types of zeolite,the adsorption pressure and temperature on the adsorption capacity of CO2 were mainly investigated.The results show that:The CO2 adsorption capacity of NaX zeolite is significantly higher than that of NaA and CaA zeolite,and the CO2 adsorption capacity of NaX zeolite reaches the highest(4.32mmol/L)when the adsorption temperature and pressure are 0? and lbar,respectively,and the N2 adsorption capacity of NaX zeolite is only 0.35 mmol/L under these conditions.It has good selective adsorption of CO2/N2.(4)Through economic calculation and analysis of NaX zeolite,it can be seen that 0.9t NaX zeolite can be obtained by experimental treatment of It fly ash without considering the fixed assets and labor costs in the early stage.The operating cost is about 3314 yuan,and the net profit is 2086 yuan,which has good social and environmental benefits.