Method for separating calcium, magnesium and phosphorus in chemical mineral separation byproduct

The invention relates to a method for separating calcium, magnesium and phosphorus in a chemical mineral separation byproduct, which comprises the following steps: by using medium-low-grade phosphorite as a raw material, crushing, calcining, digesting, leaching, carrying out filter pressing separation to obtain a calcium-magnesium-containing leaching solution, and concentrating the calcium-magnesium-containing leaching solution to obtain a calcium-magnesium ammonium nitrate concentrated solution of which the mass concentration is greater than 25%; preparing a potassium sulfate solution with the concentration of 20-50%; reacting the calcium magnesium ammonium nitrate concentrated solution with a potassium sulfate solution to perform decalcification and filtration, performing centrifugal separation on the decalcified and filtered filtrate to obtain potassium nitrate, and performing concentration and granulation on the centrifugally separated crystallization mother solution to obtain magnesium potassium nitrate/