Исследование процесса получения фосфата карбамида

Abstract

В статье рассмотрено получение азотно-фосфорного удобрения (фосфат карбамида) из карбамида и ортофосфорных кислот различной чистоты. Определены особенности растворения карбамида в ортофосфорной кислоте и кристаллизации фосфата карбамида в зависимости от концентрации ортофосфорной кислоты. Представлены рентгенограммы и дериватограммы полученных образцов фосфата карбамида (CO(NH₂)₂∙H₃PO₄). Показана зависимость изменения массы фосфата карбамида от времени взаимодействия и температуры процесса. Установлена оптимальная концентрация ортофосфорной кислоты для получения фосфата карбамида.

The purpose of the article is to study the process of obtaining fertilizer in the systems urea-orthophosphoric acid-water. A typical example of such a fertilizer can be carbamide phosphate. In connection with this, it is of interest to obtain urea phosphates depending on the concentration of orthophosphoric acid. The following methods were used in the studies: X-ray phase analysis, visual-polythermal, differential-thermal analysis. As a result of the studies, the characteristics of carbamide dissolution in orthophosphoric acid and the crystallization of carbamide phosphate were determined depending on the concentration of orthophosphoric acid, X-ray diffraction patterns and thermograms of carbamide phosphates were obtained. The general procedure for the preparation of urea phosphate from orthophosphoric acid and urea. As a result, a solid fraction was obtained - crystals of carbamide phosphate. X-ray analysis showed that the composition of carbamide phosphate obtained from orthophosphoric acid (analytically pure) is identical to the composition of carbamide phosphate obtained from orthophosphoric acid (commercially pure). Differential thermal analysis (thermographic studies) showed that the endothermic effect for orthophosphoric acid (analytically pure) and orthophosphoric acid (commercially pure), respectively, at 110 °C and 115.1 °C, characterizes the fusion of carbamide phosphate followed by the formation of ammonium pyro- and metaphosphate. It was established that irrespective of the purity of the phosphoric acid used, the product of the interaction is carbamide phosphate. The optimal concentration of phosphoric acid (CH₃PO₄) for the production of carbamide phosphate is 80 %. Since at this concentration the loss of moisture is faster than with CH3PO4 = 86%, and the yield of the product is almost the same, while at phosphoric acid concentrations of 75 and 60 %, the yield of the product is much lower.