Rotary drum granulator is still widely used in the production of compound fertilizers. Its granulation production process is to send each basic fertilizer raw material into its own storage hopper, according to the requirements of formula proportions, through the computer-controlled metering and conveying equipment, and sent into the raw material crushing or secondary remixing or storage hopper, each basic fertilizer, fine material and crushed coarse granules are returned to the granulation equipment through belts for granulation.