Urea-formaldehyde slow-release compound fertilizer is formed by the reaction of urea and formaldehyde in a certain environment. The methylol urea solution continues to shrink in an acidic environment, producing partially or mostly water-insoluble methylol urea and polymethyl urea solutions; these solutions of different contents are mixed together and are generally referred to as urea-formaldehyde solutions.
The npk fertilizer production line mainly includes feeder, disc mixer, chain crusher, granulator, drum dryer, drum cooler, drum screener, finished product warehouse, automatic packaging machine, belt conveyor, dust settling chamber, heat exchanger, etc. The granulator is an important link in the production of granular npk compound fertilizers. Common granulators include double roller granulator, rotary drum granulators, disc granulators, etc.
Add urea and water into the urea-formaldehyde reaction tank, mix and dissolve the urea, then pour into the sodium hydroxide solution, adjust the pH value to 7.5, heat to 60°C, and then add a certain amount of formaldehyde to the reaction tank at a constant temperature of 60°C. Most of the urea and formaldehyde solution react within a certain period of time to produce methylol urea solution, then add industrial sulfuric acid or phosphoric acid, adjust the pH value to about 3.5, keep the temperature at 50 °C, and fully react for a certain period of time to generate urea-formaldehyde solution. Then the regulating valve and the solution enter the buffer tank, and then are sprayed into the solid material bed of the drum granulator through the pump, electromagnetic flowmeter, and granulation nozzle, and then poured into the powdered solids such as urea, ammonium phosphate, and potassium chloride transported by the seasoning post. The material is then rolled and agglomerated in a rotary drum granulator or disc granulator to form granules. The material and waste gas emission treatment produced by the granulator are the same as those of general compound fertilizers.