Abstract: Production of urea phosphate by ordinary crystallization has shortcomings,such as long crystallization time and low heat transfer efficiency. In allusion to the shortcomings of ordinary crystallization,the application of vacuum crystallization in production of urea phosphate was studied.Major steps and optimum conditions of the production of urea phosphate by vacuum crystallization were as follows:phosphoric acid by wet process and urea were added into a three-neck flask with heating,stirring and vacuum devices in accordance with the amount-of-substance ratio of 1∶1,then add the laboratory-made activator,whose dosage accounted for 0.05%~0.25% (mass fraction) of the total feed;start the stirring device,stirring speed should be set to 200 r/ min;raise the temperature to 80 ℃ at the rate of 4 ℃/min;react at this temperature for 45 min;then close the heating device;open the vacuum device and regulate the vacuum degree to 0.08 MPa;vacuum concentration for 45 min;when the temperature dropped to 30~40 ℃,close the vacuum device;the material was centrifuged and then dried to obtain urea phosphate products.Results showed that the quality of urea phosphate product produced by vacuum crystallization was similar with that of produced by ordinary crystallization,but the yield of the former increased by 19.5%.

Key words: urea phosphate, vacuum crystallization, phosphoric acid by wet process, urea