According to the manufacturing process, the production method of urea phosphate can be divided into batch type and continuous type. It can be classified into wet -process phosphoric acid method, thermal phosphoric acid method and polymerization phosphoric acid method according to the source of raw materials. The production process of intermittent method is short, investment is low, but the scale is small and the operation is inconvenient. The production process of continuous type is long, one-time investment is large, which is suitable for large-scale production. The polymeric phosphoric acid method is limited by raw materials. Thermal phosphoric acid has higher concentration and less impurity, but the production cost is higher. Wet-process phosphoric acid has lower concentration, more impurity, the production process is long, but the production cost is lower.
Thermal Phosphoric Acid Method
Add the measured thermal phosphoric acid containing more than 85% orthophosphoric acid and urea into the reactor, raise the temperature to dissolve the urea in the acid. Then make them reaction for 10-30 minutes at 75-85℃. After cooling, there will be crystal precipitation. Then after filtration, dehydration, drying, we can get the product urea phosphate. When the molar ration of pyrophosphoric acid to urea is 1:1-1.05, raw thermal phosphoric acid contains 50%-60% P2O5, the reaction temperature is 75-85℃, the reaction time is 25-30 minutes, the content os nitrogen, phosphorus and melting point of urea phosphate is the best.
Wet-process Phosphoric Acid Method
There is 55%-80% of fluorine in phosphate rock enter wet-process phosphoric acid, and fluorine has very big harm to animals. So if using wet-process phosphoric acid to produce urea phosphate, defluorination purification must be carried out first. The fluorine enters the phosphoric acid is generally present in the form of fluorosilicic acid, and sodium salt is usually used to make it form sodium fluorosilicate precipitates and then can be removed. After defluoridation purification, the wet-process phosphoric acid containing 25% of P2O5 react under normal pressure and 80℃. Then it will be concentrated at 60℃ and the pressure is lower than 13.3kpa. And then crystallization is precipitated at 20 degrees. Finally, it is separated by centrifugation and dried to obtain urea phosphate product. The mother liquor can be recycled. For preparing feed grade urea phosphate, secondary crystallization can be carried out.