Study On The Purification Process Of Hydrochloric Acid Wet-process Phosphoric Acid

Phosphorus is one of the essential elements in national production and life,especially in crop growth.The raw material of phosphate fertilizer comes from phosphate ore.China's reserves of phosphate ore are the second largest in the world.However,with the excessive exploitation of phosphate ore,phosphorus resources have tended to be depleted.About the phosphoric acid production methods are mainly thermal method,the method and wet method kiln.The production process of hot process phosphoric acid has strict requirements for phosphorous ore,high power consumption,and the method is easy to cause environmental pollution.The production technology of cellar-process phosphoric acid has made great achievements,but there are still many restricting factors affecting its progress.Wet process phosphoric acid is currently the most widely used method of phosphoric acid production in the world.The advantage of hydrochloric acid wet process phosphoric acid is that hydrochloric acid is a by-product of many processes with a wide source of raw materials,and it does not have high requirements for the taste of phosphate ore.The calcium chloride by-product of hydrochloric acid decomposition of phosphate ore has many USES,and because hydrochloric acid is good in solubility,it is conducive to the recovery of rare earth elements associated with phosphate ore.In general,the hydrochloric acid method has relatively small pollution to the environment,and is applicable to low-and medium-grade phosphate ore,suitable for China's national conditions,so the hydrochloric acid method has certain development advantages.This paper from the western tang industrial hydrochloric acid to dissolve the rock phosphate guiyang map of xifeng,?1?hydrochloric acid dissolving phosphate rock is studied the optimal condition;?2?respectively with MIBK and the TBP extracting was made of thick phosphate,explores the suitable extraction conditions,;?3?the metal impurity ions was studied on the influence of different extraction system of extraction crude phosphoric acid,;?4?the melamine crystallization to remove calcium chloride.?1?The leaching rate of phosphate rock P₂O₅ dissolved by hydrochloric acid is high,up to 100%,but at the same time,the leaching rates of Ca²⁺and Cl^-are also high,and a large amount of CaCl₂ needs to be further separated in the future.For hydrochloric acid method dissolving guiyang map of xifeng phosphate rock experiments show that the experiments the optimum conditions for hydrochloric acid concentration was 25%,the mole ratio 2.2 response:1,the reaction time for 30 min,the reaction temperature is 20?,the mechanical stirring speed of 200 r/min.?2?When for MIBK extraction agent,the optimum extraction conditions is compared is 4:1,oscillation frequency is 200 times/min,the extraction temperature of30?,the extraction time is 10 min,phosphoric acid extraction rate can reach 7%,extraction of phosphoric acid concentration is 0.35%.The concentration of purified acid was 8%.When the extractant is the TBP,the optimum extraction conditions is compared is 4:1,oscillation frequency is 200 times/min,the extraction temperature is20?,and extraction time for 10 min,phosphoric acid extraction rate can reach 36%.?3?When the extraction system is TBP+kerosene?volume ratio is 1:1?,the presence of Ca²⁺and Mg²⁺is conducive to the extraction of phosphoric acid.When the concentration of Fe³⁺is within a certain range,the phosphoric acid extraction is beneficial,but the phosphoric acid extraction rate decreases after exceeding this range.When the extraction system was n-pentanol+isopentanol?volume ratio:60:40%?,the presence of Ca²⁺and Mg²⁺was favorable for phosphoric acid extraction.The presence of Fe³⁺is detrimental to phosphate extraction.When the extractant is n-butanol,the presence of Ca²⁺and Fe³⁺is not conducive to the extraction of phosphoric acid,while the presence of Mg²⁺is conducive to the extraction of phosphoric acid.?4?In the extraction systems of TBP+kerosene,n-pentanol+isopentanol and n-butanol,when the content of Ca²⁺in the aqueous phase is 5%-20%,the distribution coefficient of Ca²⁺gradually decreases,and when the content of Mg²⁺and Fe³⁺in the aqueous phase is 1%-5%,the distribution coefficient of Mg²⁺and Fe³⁺also gradually decreases.?5?The optimum reaction conditions of melamine phosphate as the reaction temperature 25?,the reaction molar ratio of 2.2:1,the reaction time 60 min,points three times to join,melamine phosphate precipitation rate can reach 98.84%.In the process of washing melamine phosphate,when the solid-liquid washing ratio was 1:4,the content of CaCl₂ dropped significantly,to 0.23%,the loss rate of phosphoric acid was 4.3%,and the recovery rate of phosphoric acid reached 90%.At room temperature,a certain amount of concentrated ammonia water is added to melamine phosphate and stirred magnetically for 20 min.When the ammonia-hydrolysis ratio is2.0:1,the phosphoric acid leaching rate can reach 88%.After separating the ammonia-lysate from melamine,the obtained melamine could be recycled,and the recovery rate of melamine was 94%.The filtrate is heated and concentrated,and then cooled and crystallized to produce monoammonium phosphate and diammonium phosphate solid products respectively.