Method for preparing potassium nitrate by direct method

The invention discloses a method for preparing potassium nitrate by a direct method. The method comprises the following steps of (1) adding potassium chloride, nitric acid and a salting-out agent intowater, and stirring to react; after reaction is finished, cooling, crystallizing, and fully separating out the potassium nitrate; separating soilsolid and liquid, wherein the obtained solid is potassium nitrate, and the obtained liquid is a mother liquid; (2) enabling the mother liquid and deionized water to simultaneously flow through a diffusion dialyzerdiffusing and dialyzing device to diffuseand dialyzediffusion dialysis, so as to obtain an acid liquid and a salt liquid, wherein the salt liquid is used for replacing the water and the salting-out agent in the step (1) for the preparationof the potassium nitrate in the next step; the acid liquid is concentrated to obtain hydrochloric acid. The method has the advantages that the traditional production technology is changed, the production efficiency is improved,