Method for preparing columnar large-particle monopotassium phosphate through wet-process phosphoric acid chelation

The invention discloses a method for preparing columnar large-particle monopotassium phosphate by wet-process phosphoric acid chelation, which comprises the following steps: adding a chelating agent into wet-process phosphoric acid, a potassium hydroxide solution, a mixture of the wet-process phosphoric acid and the potassium hydroxide solution or a monopotassium phosphate crystallization mother liquor, and after the reaction is finished, performing primary filtration and concentration to obtain a concentrated solution; and performing cooling crystallization, secondary filtration and drying to obtain the product. The chelating agent is a mixture of one or more than two of diethylene triamine pentaacetic acid, nitrilotriacetic acid and sodium gluconate in any proportion, and the addition amount of the chelating agent is 0.15%-5% of the mass of the concentrated solution. The produced monopotassium phosphate product is in a uniform columnar large particle shape, reaches the fertilizer-grade monopotassium phospha