| China is a large agricultural country,and the steady development of agriculture depends on rational fertilization.Potash is one of the more important fertilizer.As the most important of a chlorinefree high-quality potash fertilizer,potassium sulphate is widely used and its price is lower than the potassium nitrate,and it’s one of the important sources of elemental sulfur for most crops.Potassium bisulfate is a kind of potash fertilizer,which not only can be used as intermediate products of many N,P,K compound fertilize,but also is a kind of pesticides.With the growing progress of science and technology,the application of potassium hydrogen sulfate is slowly extension.Yuntianhua Co.Ltd.as an important domestic phosphorus and compound fertilizer production enterprises,the current proposed potassium bisulfate and phosphate reaction preparation of agricultural potassium dihydrogen phosphate compound fertilizer.In the present study,based on the two-step reaction mechanism of potassium sulfate prepared by Mannheim method,the first step of the Mannheim method is studied in the low temperature reaction,which is the process study of potassium chloride reaction with sulfuric acid to produce potassium bisulfate.This study will provide more suitable raw materials for the company subsequent using hydrogen sulfate potassium and phosphate reaction preparation of potassium dihydrogen phosphate,and it also provide important basic data for improving their own interests and saving raw material costs.This study investigated the reaction of potassium chloride with industrial sulfuric acid in the aqueous phase and the dry phase condition.The effects of temperature,molar ratio,time,concentration and strring rate intermediate product,potassium bisulfate are systematically studied.In addition,the products were characterized by XRD,FT-IR,Raman and SEM.(1)Research conducted under the conditions of the aqueous phase.The single factor experimental results showed that the conversion is 98.99%and the solid phase composition was 98.77%KHSO4,0.29%KCl and 0.94%H2SO4 under the following conditions:85℃,molar ratio of 1.2:1,60 min,H2SO4 concentration of 80%and stirring rate of 300r/min.From the orthogonal experiments,the results demonstrated that temperature and the molar ratios of raw materials is the main influence factors,and the temperature effect is the most obvious.And other influencing factors as follows:reaction time>mixing rate>concentration of sulfuric acid.And the optimal production conditions are 90℃,molar ratio of 1.2:1,reaction time 60min,H2SO4 concentration of 80%,stirring rate of 250r/min.Then the experiment was repeated under the optimal process conditions which inferred the process was relatively stable and can be amplified,and the conversion was about 98.6%.The solid phase composition is about 98.4%KHSO4,0.6%KCl and 1%H2SO4 in the product.By crystals precipitated experiments of reaction liquid and filtrate,the results showed that adding a small amount of finely milled potassium bisulfate seed in the reaction mixture can make products faster precipitation,and Fe impurities in industrial acid for precipitation of crystal has some auxiliary function.For by-product hydrochloric acid in the process of experiment and filtrate,recycling suggestions are put forward combined with the company advantage Finally,the characterization of XRD,FT-IR,Raman and SEM showed that the potassium hydrogen sulfate product is high purity which can meet the industry standards.(2)Research conducted under the condition of the dry phase.The single factor experimental results showed that the optimum conditions of industrial acid were 80℃,molar ratio of 1.2:1,50min,stirring rate of 300r/min.Its conversion was 92.64%and the solid phase consists of 97.42%KHSO4,2.04%KC1 and 0.54%H2SO4.By the orthogonal experiments,the results demonstrated that temperature and the molar ratios of raw materials is the main influence factors,and reaction time and stirring speed to the secondary influence factors which the stirring rate is the least.And the optimal production conditions were the temperature of 80℃,molar ratio of 1.1:1,reaction time 60min,stirring rate of 250r/min.Then the experiment was repeated under the optimal conditions which inferred that the process was relatively stable.Its conversion was about 92%and the solid phase consists about of 98%KHSO4,2%KCl and 0.1%H2SO4.When the experiment was repeated under the optimal conditions,the escape amount of hydrogen chloride gas was corresponding studied.The gas absorption effect is good,and meet the industrial emissions standard.In this paper,the mannheim method was improved and the high temperature reaction was tried to investigate the effect of high temperature on the reaction conversion rate.Finally,the characterization of XRD,FT-IR,Raman and SEM showed that the potassium hydrogen sulfate product is high purity which can meet the industry standards.From the study of the process of preparing potassium hydrogen sulfate from industrial sulfuric acid and potassium chloride under the two experimental conditions showed that the aqueous phase can produce higher quality of products,higher conversion rates and better utilization of raw materials compared to the dry phase conditions.In addition,the reactants are viscous under the dry phase condition,and the resulting potassium bisulfate is encapsulated on the unreacted potassium chloride which prevent contact between the reactants,so that the reaction conversion rate is low and the solid phase product is easy into small spherical particles.Therefore,the proposed industrial production using aqueous phase production of potassium hydrogen sulfate is better,adding a small amount of seed in crystal precipitation reaction solution is better,the filtrate and the reaction water can also be a good recycling. |
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