Method for preparing ammonium dihydrogen phosphate and preparing special composite fertilizer for grapefruit trees as byproduct

[0033] Example one

[0034] a. Preparation of raw materials: first mix phosphoric acid and urea at a molar ratio of 2:1.4, and the concentration of phosphoric acid is 70%. The temperature rise rate is 6°C / min to 90°C, and the reaction is stirred for 28 minutes to prepare slurry and separate. Urea phosphate is obtained, and the reaction of phosphoric acid and urea is the reaction of phosphoric acid solution and urea solid;

[0035] b. Preparation of ammonium dihydrogen phosphate: slowly add ammonia water to the slurry containing urea phosphate to control the PH value of 3.6 and fully stir to obtain a slurry containing nitrogen and phosphorus. The slurry is cooled to 24°C in a cooling crystallizer, filtered, Separate and obtain ammonium dihydrogen phosphate;

[0036] c. Filtrate element addition: Add potassium element and the trace element compound required by grapefruit tree to the separated filtrate to obtain the mother liquor of special compound fertilizer for grapefruit tree. The t

[0038] Example two

[0039] a. Preparation of raw materials: first mix phosphoric acid and urea at a molar ratio of 2:1.5, the concentration of phosphoric acid is 71%, and the temperature rises at a rate of 6°C / min to 95°C, stirring and reacting for 28 minutes to prepare a slurry, and separate Urea phosphate is obtained, and the reaction of phosphoric acid and urea is the reaction of phosphoric acid solution and urea solid;

[0040] b. Preparation of ammonium dihydrogen phosphate: slowly add ammonia water to the slurry containing urea phosphate to control the PH value of 3.5 and fully stir to obtain a slurry containing nitrogen and phosphorus. The slurry is cooled to 24°C in a cooling crystallizer, filtered, Separate and obtain ammonium dihydrogen phosphate;

[0041] c. Filtrate element addition: Add potassium element and the trace element compound required by grapefruit tree to the separated filtrate to obtain the mother liquor of special compound fertilizer for grapefruit tree. The

[0043] Example three

[0044] a. Preparation of raw materials: first mix phosphoric acid and urea at a molar ratio of 2:1.6, and the concentration of phosphoric acid is 73%. The temperature rise rate is 6°C / min to 90-120°C, and the mixture is stirred and reacted for 28 minutes to prepare a slurry. , The urea phosphate is separated, and the reaction of phosphoric acid and urea is the reaction of phosphoric acid solution and urea solid;

[0045] b. Preparation of ammonium dihydrogen phosphate: slowly add ammonia water to the slurry containing urea phosphate to control the PH value of 3.4 and fully stir to obtain a slurry containing nitrogen and phosphorus. The slurry is cooled to 24°C in a cooling crystallizer, filtered, Separate and obtain ammonium dihydrogen phosphate;

[0046] c. Filtrate element addition: Add potassium element and the trace element compound required by grapefruit tree to the separated filtrate to obtain the mother liquor of special compound fertilizer for grapefrui