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At present, the research on Zhundong coal is mainly focused on the ash melting characteristics, the occurrence and migration of alkali metal elements, the ash deposition and slagging characteristics of Zhundong coal. There is no case that only Zhundong coal ash is used to produce alumina and silica. Therefore, this paper takes the coal ash of Zhundong coal in high temperature combustion atmosphere as the research object, and optimizes the laboratory to produce alumina and silica The preparation conditions and process plan provide technical support for the cascade utilization of Zhundong coal.
author
Wang Min 1, Wang Hui 1, Yang Hai Rui 2, Liu Hanhui 1, sun Jianwei 1
Author unit
1. School of energy science and engineering, Harbin University of Technology
2. Department of energy and power engineering, Tsinghua University
abstract
In order to realize the green comprehensive utilization of Zhundong coal ash, the author studied and designed the technological process of preparing alumina and silica from Zhundong coal ash, determined the best technological conditions, and compared the influence degree of different factors on the extraction rate by SPSS. In the experiment, Zhundong coal, jiangjunmiao raw coal, was crushed and the ash sample was made by muffle furnace simulating the static combustion of pulverized coal furnace. The composition analysis and element analysis of Zhundong coal ash show that SiO2 accounts for 48.84% and Al2O3 accounts for 31.26%. According to the standard, the ash samples were prepared and analyzed by SEM. It was found that the viscosity of the ash samples was serious, so the mechanical grinding was carried out before the test. Alumina is prepared by calcination of coal ash and ammonium sulfate. The process is divided into calcination process and acid leaching process. Because the filtrate contains a lot of impurities such as iron and calcium, the pH adjustment method is used to remove impurities and the effect of impurity removal is tested. The test result shows that the impurity removal rate is close to 100%. The preparation of silica from aluminum residue is divided into alkali leaching process and multiple carbon separation process. In the roasting process of aluminum extraction process, the best test conditions of various factors are determined by the change curve of aluminum extraction rate and the angle of energy saving: the roasting temperature is 600 ℃, the roasting time is 60 minutes, and the ratio of roasting ingredients is 1:6; in the acid leaching process of aluminum extraction process, the best test conditions are: the acid leaching temperature is 60 ℃, the acid leaching time is 20 minutes, the concentration of H2SO4 is 0.2 mol / L, and the ratio of acid leaching liquid to solid is 50. In the study on the preparation of silica from aluminum residue, it is found by SEM that the aluminum residue is porous, which is conducive to further silicon extraction test. Through XRD analysis, it is found that there are a lot of silicon and calcium elements in the slag; the content of Si in the slag and the loss rate of Si after aluminum extraction are 7.64% by the method of RIR. The results show that the best conditions of alkali leaching are: temperature 60 ℃, time 30 min, NaOH concentration 3 mol / L, solid ratio 70, and the extraction rate of Si is 99%. The method of multiple carbon separation can meet the purity requirements of different silicon content. The optimum conditions of alkali leaching are pH = 9.5, aeration rate of CO2 24 ml / min, NaOH concentration of carbon 0.2 mol / L and liquid-solid ratio of carbon 80. Through the correlation analysis of two variables, the influence degree of each factor on the extraction rate of aluminum, the extraction rate of SiO2 and the precipitation rate of H2SiO3 are obtained as follows: roasting temperature & gt; roasting time & gt; roasting ratio, acid leaching time & gt; acid leaching temperature & gt; H2SO4 concentration & gt; acid leaching liquid-solid ratio, alkali leaching liquid-solid ratio & gt; alkali leaching temperature & gt; NaOH concentration & gt; alkali leaching time, carbon pH & gt; carbon liquid-solid ratio & gt; Carbon NaOH concentration & gt; CO2 ventilation rate. Through the analysis of economy and feasibility, it shows that the technology can effectively realize the green comprehensive utilization of Zhundong coal ash. The (NH4) 2SO4 is re extracted from the filtrate after aluminum extraction to realize the reuse of production raw materials; the Na2CO3 solution after carbon separation process can be recycled in the extraction process by adding lime causticization; in addition to the production of alumina and silica, the process can also obtain Na2SO4 and other additional products.
Illustrations in the text
　
Figure 1 appearance of high temperature coal ash sample
Figure 2 phase analysis of high temperature coal ash
Figure 3 process flow of extracting alumina and silica from Zhundong coal ash
Fig. 4 optimum test conditions for aluminum extraction from Zhundong coal ash and ammonium sulfate by roasting
Fig. 5 the best test conditions of acid leaching aluminum from roasted clinker
Figure 6 iron removal and inspection of aluminum containing filtrate
Fig. 7 test of Ca 2 + removal by mixed indicator method of calcein phenolphthalein
Figure 8 alumina sample prepared
Figure 9 appearance of roasted clinker and aluminum slag
Figure 10 appearance of Zhundong coal ash and aluminum slag
Figure 11 XRD analysis of aluminum extraction slag
Fig. 12 the best test conditions for extracting silica by alkali leaching
Fig. 13 process flow of preparing silica by multiple carbon separation
Fig. 14 the best test conditions for preparing silica by multiple carbon separation
Figure 15 preparation of white carbon black sample
Figure 16 technological process of extracting alumina and silica from Zhundong coal ash
conclusion
1) The best test conditions of roasting process are: temperature 600 ℃, time 60 min, ratio of ingredients 1:6. The best experimental conditions of acid leaching process: acid leaching temperature 60 ℃, acid leaching time 20 min, H2SO4 concentration 0.2 mol / L, acid leaching liquid solid ratio 50; extraction of aluminum elements with high purity, need to remove impurities such as Fe, CA, etc. in the filtrate, the pH adjustment method is used to remove impurities, and the effect is good. The best conditions of alkali leaching were 60 ℃, 30 min, 3 mol / L NaOH concentration, 70 solid-liquid ratio, and the extraction rate of SiO2 was 99%. The best carbon separation process conditions are pH = 9.5, aeration rate of CO2 24 ml / min, NaOH concentration of carbon 0.2 mol / L and liquid-solid ratio of carbon 80.
2) By correlation analysis, the influence of various factors on aluminum extraction rate, SiO2 extraction rate and H2SiO3 precipitation rate are as follows: roasting temperature & gt; roasting time & gt; roasting ratio, acid leaching time & gt; acid leaching temperature & gt; H2SO4 concentration & gt; acid leaching liquid-solid ratio, alkali leaching liquid-solid ratio & gt; alkali leaching temperature & gt; NaOH concentration & gt; alkali leaching time, carbon pH & gt; carbon liquid-solid ratio & gt; carbon NaOH concentration & gt; CO2 ventilation rate.
3) The technology designed in this paper can realize the green comprehensive utilization of Zhundong coal ash and has the production feasibility. It can re extract (NH4) 2SO4 from the filtrate after aluminum extraction, realize the reuse of raw materials and save production cost. After the carbon separation process, Na2CO3 solution can be causticized by adding lime to obtain CaCO3 products and NaOH. NaOH can be recycled in the extraction process to avoid the loss of caustic soda. In addition to the normal production of alumina and silica, additional products such as Na2SO4 can also be obtained.
Citation Style
Wang Min, Wang Hui, Yang Hai Rui, et al. Study on Extraction of alumina and silica from Zhundong coal ash [J]. Clean coal technology, 2020, 26 (1): 194-206
WANG Min,WANG Hui,YANG Hairui,et al.Study on the technology of extracting Al2O3 and SiO2 from Zhundong coal ash[J].Clean Coal Technology，2020，26(1):194-206.
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