1: Add 28% ammonia slowly to dilute phosphoric acid, this reaction is exothermic, when the reaction is completed and cooled, determine the pH of the solution in the range of 3.8 to 4.5, cool, precipitate crystals, filter, wash with cold water, and then recrystallise in hot water to obtain monoammonium phosphate. In the reaction between phosphoric acid and ammonia, when the reaction temperature is in the range of 0 to 75°C, NH4H5(PO4)2-H2O, NH4H5(PO4)2, NH4H2PO4, (NH4)2HPO4- 2(NH4)2HPO4, (NH4)3PO4, (NH4)3PO4-3H2O and other phosphates may be produced, so it is important to control the pH of the solution. It is important to control the pH of the solution.
Method 2: A method for the production of monoammonium phosphate using a direct complexation reaction between high purity urea phosphate and ammonia to prepare monoammonium phosphate with a reaction equation of
The reaction temperature is controlled at 40-80°C, the reaction is stirred for 20-60 min, the end-point pH is 4.2-4.6 and the monoammonium phosphate product is obtained by cooling and crystallisation and centrifugal separation and drying steps. Specifically the following steps are included.
1) Preparation of urea phosphate solution: adding water to the solid urea phosphate of 98% purity in the dissolution tank and metering, raising the temperature to 40-80°C and then stirring to dissolve and mix evenly, and controlling the stirring speed of 30-50r/min to obtain urea phosphate solution.
(2) Synthesis of mono-ammonium phosphate: feed the urea phosphate solution into the synthesis tank using a transfer pump, control the temperature to 40-80°C, and add ammonia at a molar ratio of urea phosphate to ammonia of (0.99-1.05):1 to carry out the reaction; take to add ammonia while stirring, stirring speed of 60-70r/min, stir the reaction for 20-60min, detect the pH value of 4.2- 4.6, then the reaction is terminated. 4.6, the reaction is terminated and monoammonium phosphate slurry is obtained.
(3) Crystallization and centrifugal separation: the monoammonium phosphate slurry is transferred to the crystallizer for cooling to ≤40°C to precipitate crystals, and the crystals are transferred to the centrifuge for centrifugal separation to obtain filtrate and filter cake, the filtrate is urea slurry, which is transferred to the urea phosphate production process for urea phosphate raw material production; the filter cake is monoammonium phosphate, which is placed in the dryer at a drying temperature of 80°C and dried for 3-5min to obtain monoammonium phosphate product. Monoammonium phosphate product.