Preparation method and production device of phosphorus-potassium nitrate compound fertilizer

The invention discloses a preparation method and a production device of a phosphorus-potassium nitrate compound fertilizer. The preparation method mainly comprises the following steps: fully mixing powdery potassium salt, monoammonium phosphate, nitrophosphate and an additive to generate flowing melt slurry, and preparing a spherical granular finished product through a compound fertilizer granulation tower, wherein the finished product comprises the following components in parts by weight: 12-22 parts of nitrogen fertilizer in terms of N, 6-18 parts of phosphate fertilizer in terms of P2O5 and9-21 parts of potassium fertilizer in terms of K2O; the device comprises a raw material hopper, a vibrating screen, a melting tank, a mixing tank, a reaction tank, a prilling tower and the like whichare sequentially connected through pipelines, a feeding metering scale is arranged at a feeding port of the melting tank, a bag-type dust collector is arranged at a waste gas emission position of thecooling machine, a particl