Method for producing phosphoric acid by utilizing tunnel kiln

The invention discloses a method for producing phosphoric acid by utilizing a tunnel kiln and relates to a method of phosphoric acid production; the phosphoric acid is produced by adopting an improved tunnel kiln; the materials are pulverized and molded after mixing according to proportion, the mixture passes through pre-heating, sintering and cooling sections, in the pre-heating section, at about 400 DEG C, gases containing volatile substances such as tar oil and the like are removed, and the tar oil is collected after heat exchange and cooling. The reduction rate of phosphorus in the production process of phosphoric acid is promoted to 85 percent from 60 percent by optimal silico-calcium ratio, and in the sintering section, the reductive phosphorus is oxidized into phosphorus pentoxide,the gases containing the phosphorus pentoxide are respectively prepared into crude phosphoric acid and high-purity phosphoric acid through two-stage adsorption, wherein the high-purity phosphoric acid reaches the requirements