Study On The Production Technology Of Urea Phosphate

Urea phosphate as a useful refined chemical product, is mainly used for cattle,sheep category ruminant as feed additives, in addition, it's also used for silagepreservation, the high concentration of nitrogen and phosphorus compound fertilizer,ammonium polyphosphate intermediate, flame retardant and so on. Its applicationsspread from stock raising, industry, agriculture to other fields with broad marketprospects. At present, basic data of urea phosphate (such as phase diagram, themetastable zone width, and the crystal growth rate, etc.) is also lacking. Domesticproduction of urea phosphate remains in batch production with thermal phosphoricacid as the raw material. The research on the cystallization process and thecontinuous production method is scarce. Therefore, this paper further discussed thesynthesis method and developed the device of continuous production method withwet-process phosphoric acid as the raw material, completing the basic data tests ofurea phosphate and the research on the suitable conditions of thermal phosphoricacid as the raw material.First, the basic data about urea phosphate was tested, which provided guidancefor the follow-up experiment. The phase diagrams of 20℃and 40℃were drawn, themetastable zone width was tested, and the effect of common impurities in acid wasalso studied. It was found that Fe³⁺, Al³⁺ increased the metastable zone width, whileSO₄^2-and EDTA made it smaller, and impurities could affect the appearance ofcrystal urea phosphate. Furthermore, the quality growth-rate of urea phosphate wasmeasured under the saturate temperature of 16℃and 20℃, which showed a upward trend with the increase of the supersaturation, the additive EDTA could also increasethe growth rate.Then the optimum conditions with thermal phosphoric acid as the raw materialwere explored via orthogonal experiment: Urea and phosphate acid in the molarratio of 1:1; Concentration of phosphoric acid was 70%; Reaction temperature was80^C; Reaction time was 20min; The crystallization time was 12h.Moreover, theeffect of common impurities in wet-process phosphoric acid on the yield of ureaphosphate was studied. The results showed that the yield declined with Fe³⁺, Al³⁺,Mg²⁺, SO₄^2-content increasing, and the yield rose with the increasing of F^-.Finally, the technical conditions of pre-treatment for wet-process phosphoricacid were discussed: Reaction temperature was room temperature; Reaction timewas 100min; Stirring speed was 400 R·P·M; BC-activated carbon content was 0.3%(acid); Phosphorite and sodium carbonate were 1.20 times the theoretical quantity.Then, conditions of crystallization control in batch production with wet-processphosphoric acid as the raw material was studied: Cooling rate was 10℃per hour;The seed adding temperature was 56℃; Mother liquor circulation was half thephosphoric acid quantity. Continuous experimental device was developed too, itsoptimum operating conditions were determined: Preparation of feed-in liquid (ureaand phosphate molar ratio was 1:1, the reaction temperature was 80℃, the reactiontime was 20min); Feed-in liquid temperature was 90℃; The volume of circulatingmother liquor was 2500ml; Feed-in rate was 5ml/min; Mother liquor temperaturewas 25℃; Stay time of crystal inside the device was 3h. In this device, we hadobtained a high-quality and granular urea phosphate product.