Experimental Study On Extraction Of Urea Phosphate And Phosphorus Magnesium Fertilizer By Means Of Extraction Of Succinic Acid By Wet - Process Phosphoric Acid

According to the national energy conservation technology promotion directory (5th), by 2020, in China,50% of industrial phosphoric acid will replaced by wet process phosphoric acid solvent extraction purification process. The core technology of purifying wet phosphoric acid with solvent extraction method is separating the high impurity content wet phosphoric acid industrial grade phosphoric acid by organic solvent extraction to obtain industrial phosphoric acid, P2O5 extraction rate of solvent extraction purification of wet-process phosphoric acid is 50%～70% by-product extraction residual acid containing 35%～40% of P2O5. Because of the concentration of extraction residual acid by-product is low, and the output is large, which need to configure high concentration, low impurity of wet process phosphoric acid to produce high-quality MAP fertilizer products, otherwise only can produce low standard MAP fertilizer. Therefore, the efficient use of P2O5 in by-product residual acid has become a balance phosphate fertilizer production technical problem that enterprises must solve.This research used by-product residual acid which from wet process phosphoric acid solvent extraction purification and urea as raw material, to produce high value urea phosphate, recovering P2O5 in residual acid, the mother liquor which contain Fe, Al, Mg impurities direct processed into Magnesium phosphate fertilizer, to satisfy the demand of trace element fertilizer in agriculture. The experiment used phosphoric acid which in residual acid to react with urea, adapting two step crystallization separation method to obtain urea phosphate, achieving the separation of phosphoric acid between with Fe, Al, Mg impurities; through researched on the ratio of reaction materials, reaction temperature, reaction time, crystallization control and other technology contions, obtained qualified urea phosphate product, the mother liquor which from urea phosphate crystallization separation reacted with magnesium oxide to produce magnesium phosphate fertilizer. Through experiment research obtained conclusion as follows:(1) Measured the chemical composition and physical and chemical properties of residual acid which from wet process phosphoric acid solvent extraction purification, determined the technology development route of the pretreatment of residual acid and the preparation of urea phosphate.(2) Through pretreated the raffinate acid with Settlement separation experiment extraction acid pretreatment, removed the sediment in raffinate acid.(3) Through pretreatd raffinate acid synthesis urea phosphate experiment, inspected the effect of residual acid concentration, material ratio, reaction time, reaction temperature, crystallization time on the recovery rate of phosphate in residual acid and urea phosphate product quality, obtained the optimal technological conditions, namely residual acid concentration was 36%(count by P2O5), material ratio of phosphoric acid and urea was 1:1, reaction time was 60 min, reaction temperature was 50℃, crystallization time was 8 h, after once crystallization, the recovery rate of phosphate in residual acid reached 57.33%. Carried on the mother liquor concentration, cooling crystallization experiment, to improve the yield of urea phosphate, the recovery rate of phosphate in raffinate acid increased by 16% at the same time.(4) Analyzed the chemical composition and physical property of second separation mother liquor of urea phosphate, determined adapting industrial grade magnesium oxide to carry out solid-liquid mixing and maturation reaction, obtained a new type phosphate magnesium products which contain magnesium ammonium phosphate.(5) Through carried on the second urea phosphate mother liquor and magnesium oxide synthesis phosphorus magnesium fertilizer experiment, inspected the effect of material ratio, reaction temperature, reaction time and stirring speed on the quality of the final product, obtained the optimum technological conditions, namely the material quality of magnesium oxide and mother liquor was 14%, reaction temperature was 90℃, reaction time for 30 min, stirring speed was 450 r/min.