WANG Min;WANG Hui;YANG Hairui;LIU Hanhui;SUN Jianwei;

• 1:College of Energy Science and Engineering
• 2:Harbin Institute of Technology
• 3:Department of Energy and Power Engineering
• 4:Tsinghua University

Abstract：

In order to realize the green utilization of Zhundong coal ash,the process of preparing Al_2O_3 and SiO_2 from Zhundong coal ash was designed. The optimal process conditions was determined,and the degree of different factors on the extraction rate were carrieed out by SPSS bivariate analysis. Zhundong coal—Jiangjunmiao was used as raw coal,and ash samples was prepared using a muffle furnace to simulate the static combustion of a pulverized coal furnace after crushing.. Through the composition analysis and elemental analysis of the coal ash,it is found that SiO_2 accountes for 48.84%,and Al_2O_3 accounted for 31.26%. The coal ash sample was prepared according to the standard,and the sample was analyzed by SEM. The stickiness is serious,so mechanical grinding is performed before experiment.The Al_2O_3 was prepared from coal ash by ammonium sulfate roasting method which was divided into roasting process and acid leaching process.Because the filtrate contained a large amount of impurities such as iron and calcium,impurities were removed by using the pH adjustment method and the effect of removing impurities was checked. The impurity removal rate is almost 100%. Alkali leaching process and multiple CO_2 separation process were used to prepare SiO_2 from the aluminum slag. In the calcination process of aluminum extraction,the optimum experimental conditions of various factors were determined by the change curve. The results show that the calcination temperature is 600 ℃,the calcination time is 60 min,and the roasting ratio is 1 ∶ 6. In the acid leaching process of aluminum extraction process,the best experimental conditions are temperature 60 ℃,time 20 min,H_2SO_4 0.2 mol/L,and liquid-solid ratio 50. The slag was analyzed by SEM and XRD. It is found that aluminum extraction slag contains a large amount of silicon and calcium elements,and the Si loss after aluminum extracting is 7.64% by the RIR method.The optimum experimental conditions for the alkali leaching process are temperature 60℃,time 30 min,NaOH_3 mol/L,liquid-solid ratio 70,and the SiO_2 extraction rate is 99%. Multiple CO_2 separation method can meet the requirements of different SiO_2 content purity. The optimum alkali leaching conditions are p H = 9. 5,CO_2 aeration rate 24 m L/min,NaOH 0.2 mol/L,and liquid-solid ratio 80. Through the bivariate correlation analysis,the effects of various factors on the Al_2O_3 extraction rate,SiO_2 extraction rate and H_2SiO_3 precipitation rate are obtained which are roasting temperature > roasting time > roasting ratio,acid leaching time>acid leaching temperature>H_2SO_4 concentration>acid leaching liquid-solid ratio,alkali immersion liquid-solid ratio>alkali leaching temperature>NaOH concentration> alkali leaching time,pH> liquid-solid ratio> Na OH concentration>CO_2 aeration rate.Through the economy and feasibility analysis,the research can effectively realize the green utilization of Zhundong coal ash.( NH_4)_2SO_4 is re-extracted from the filtrate after aluminum extraction to realize the reuse of production raw materials. The Na_2CO_3 solution after the CO_2 separation process can be causticized by adding lime to realize the recycling of Na OH in the extraction process. In addition to the production of Al_2O_3 and SiO_2,additional products such as Na_2SO_4 can also be obtained.

Key Words： Zhundong coal ash;Al2O3;SiO2;bivariate correlation;feasibility analysis

Abstract:

Keywords:

Foundation: 国家重点研发计划资助项目(2016YFB0600203)

Authors: WANG Min;WANG Hui;YANG Hairui;LIU Hanhui;SUN Jianwei;

DOI: 10.13226/j.issn.1006-6772.20022702

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