Polyphosphate press, also known as ammonium polyphosphate, is a mixture of ammonium orthophosphate and a variety of ammonium polyphosphates. The ammonium polyphosphate contained is mainly ammonium pyrophosphate, ammonium tripolyphosphate, and ammonium tetraphosphate, and only a small amount of ammonium polyphosphate with a longer chain exists. Easily soluble in water, solubility greater than ammonium orthophosphate, and can also chelate metal cations so that they remain in solution. In addition to being used as an ingredient in various fertilizers, ammonium polyphosphate is also used as an important chemical for fighting forest and mountain fires, and as a fireproof impregnating agent for wood. Ammonium polyphosphate solution containing 11% nitrogen and 37% phosphorus pentoxide made from thermal superphosphate can be used as a basic chemical for extinguishing forest and mountain fires, and as a fireproof impregnating agent for construction wood. Ammonium polyphosphate base solution containing 10% nitrogen and 34% phosphorus pentoxide made from wet phosphoric acid can be used as a raw material for preparing liquid compound fertilizers of various specifications.