Study On The New Technology Of Potassium Dihydrogen Phosphate With Sulfuric Acid

Potassium dihydrogen phosphate is widely used as food additives,feed additives and efficient chlorine-free phosphorus and potassium compound fertilizer.At present,the main method of producing potassium dihydrogen phosphate is the neutralization method.Because the raw material price of phosphoric acid and potassium hydroxide is too expensive,neutral method is difficult to be popularized and widely applied in agriculture.In addition,a large quantity of waste sulfuric acid treatment and emissions has become a serious environmental problem with the rapid development of domestic industry.In view of the above problems,a new process has been proposed in the paper that is we prepare potassium dihydrogen phosphate with potassium chloride,sulfuric acid and calcium hydrogen phosphate as raw materials.The key point is that the whole reaction process is controlled below 80?,which can overcome the traditional Mannheim method of high temperature(600-800?)synthesis reaction conditions and the fundamental shortcomings of the serious corrosion of equipment(sulfuric acid and hydrochloric acid).This process can also solve the shortcoming that is high cost of traditional neutralization method to phosphoric acid,potassium hydroxide as raw material.The results showed that the total recoveries of potassium and phosphorus were 99% and 95%.The cost of raw materials for the production of one ton of potassium dihydrogen phosphate is about 3100-3500 yuan,which was significantly lower than the existing raw materials with potassium hydroxide and phosphoric acid as raw materials(about 6,000 yuan / ton).The cost of raw materials is reduced by 35-45%.The new process optimization process conditions are:(1)Potassium chloride and sulfuric acid were used to prepare potassium hydrogen sulfate.The optimum conditions were as follows: the initial mass concentration of potassium chloride was 50%,the reaction temperature was 80 ?,the molar ratio of potassium chloride and sulfuric acid was 1: 1.2,the reaction time was 12 min.(2)In the experiment we use calcium hydrogen phosphate and potassium hydrogen sulfate as raw materials to prepare potassium dihydrogen phosphate.And through single factor experiments and orthogonal test,this paper gives the following optimal combination of processes: the reaction time was 120 min,the reaction temperature was 60?,the ratio of liquid to solid was 4.5,and the ratio of potassium to phosphorus was 1.3.The effect of various factors on the yield of phosphorus in the preparation of potassium dihydrogen phosphate: reaction temperature > liquid to solid ratio > phosphorus and potassium ratio > reaction time.(3)Through the mother liquor evaporation and crystallization experiments,we got the result that the purity of potassium dihydrogen phosphate can be 96% when the amount of evaporated water is 70%.And the products can meet the national agricultural grade first-class standards.