Study On New Technology Of Preparation Of Potassium Dihydrogen Phosphate With Wet Process Phosphoric Acid

Potassium dihydrogen phosphate is a highly efficient fertilizer with phosphorus and potassium elements bearing,which has advantages of high nutrient composition,stable chemical properties,high solubility and out of agglomeration,the virtue of which has been widely used to agricultural production.At present,The production technologys of the potassium dihydrogen phosphate can be various in the industry,in which have generally many defects such as large investment and equipment corrosion and so on.The research on a new technology for the production of potassium dihydrogen phosphate with wet process phosphoric acid and potassium chloride is carried out based on analyzingand summarying the traditional technology of the production of potassium dihydrogen phosphate.This process has the advantages of shorter flow circuit,more simple facilities,lower energy consumption and less investmentso that ithas awidespread prospect of application.The method on manufacturing potassium dihydrogen phosphate and compound fertilizer with the raw materials of wet-process phosphoric acid and potassium chloride is carried out.An organic solvent should be added in the process.In the specific conditions,potassium dihydrogen phosphate and compound fertilizer were precipitated and crystaled by a kind of solvent.The potassium dihydrogen phosphate and compound fertilizer products’ quality were better than before.The potassium dihydrogen phosphate and compound fertilizer made can be deposited and crystallized with adding organic solvent that could attain high quality production under the specific condition.Over the process stage of potassium dihydrogen phosphate,the paper reseaches the effect of the purity of potassium dihydrogen phosphate on the ratio of raw materials,reaction temperature,reaction time,solvent dosage as well as crystallization temperature and so on.The experimental results show that:The purity of potassium dihydrogen phosphate is more than 95% that reaches the qualified requirement（refer to HG 2321-1992）on agricultural utility under the condition of the molar ratio of H₃PO₄ to HCl of 1.2:1,the reaction temperature of 170℃,the reaction time of 180 min,the amount of solvent of 200 ml,as well as the crystallization temperatureof 45℃.When the purity of potassium dihydrogen phosphate refindedwith recrystallization could be up to above 99.3%,meeting with the standard（refer to HG 2321-1992）of industrial potassium dihydrogen phosphate.This product is up to the requirements of premium grades by refering to the of HG 2321-1992.The filter liquor can be used to preparae compound fertilizer in the process of recoverying of materials.In the process of preparation of compound fertilizer,the effect of the quality of compound fertilizer is carried out on the pH,reaction temperatureand reaction time.The experimental results present that:when the condition of pH of5.25,the reaction temperature of 40 ℃ as well as the reaction time of 45 min,the recovery of N,P,K elements is higher,mean while,the content of chlorine bearing in the compound fertilizer is less than 0.2%.Secondly,a large amount of organic solvent was used in the process of the production of potassium dihydrogen phosphate and compound fertilizer.So it is necessary to recycle the organic solvent after the end of production.The study shows that:The higher above 98% the recovery of the solvent is,the lower the loss rate of the solvent is,which significantly improves the feasibility of the process in the production practice.Finally,did economic benefit analysis of the process,contains material balance and energy balance.The balance on materials and economy is worked out to the process.The results indicate that: the high quality production of potassium dihydrogen phosphate with the purity of 99.3% are produced per ton,that can be gain the profit of approximately 1000.The material unreacted are recovered in the process,that’s why the utilization rate of raw materials is greatly improved.so that the cost of production is reduced obviously in the process.