Background and Overview[1]

　　Phosphoric acid is a basic chemical raw material, widely used in phosphate, fertilizer, food additives, feed, washing, electronics, flame retardants and other industries. Pure phosphoric acid is colorless crystals with a melting point of 42.3 degrees Celsius, a high boiling point acid, easily soluble in water. Phosphoric acid is a strong acid in ternary, step-by-step ionization, non-volatile, not easy to decompose, almost no oxidation. It has the generality of acid. Industry commonly used concentrated sulfuric acid and calcium phosphate reaction to produce phosphoric acid, filtered off slightly soluble in water calcium sulfate precipitate, the resulting filtrate is phosphoric acid solution.

　　Report I,

　　A method of producing crystalline phosphoric acid by concentrating phosphoric acid with phosphoric anhydride in the following steps:

　　Put the purity of 99.95%, containing arsenic 152 × 10-6 of yellow phosphorus at 70 ℃ fully melted, according to the ratio of 1kg yellow phosphorus and 6.3-6.6m3 of air, with a pump to send the yellow phosphorus to yellow phosphorus combustion nozzle and mixed with 0.7MPa compressed air, sprayed into the phosphorus-fired boiler, the yellow phosphorus in the phosphorus-fired boiler rapid atomization and intense combustion.

　　The P2O5 produced by combustion is introduced into the top of hydration tower, the top of the tower starts to spray with deionized water, and then change to spray with dilute acid after obtaining dilute acid, and dilute phosphoric acid is constantly sprayed from the top and overflowed uniformly from the inner wall, and then the P2O5 is absorbed by circulation, and then 100% H3PO4 is obtained, the top of the tower is supplemented with appropriate amount of deionized water to continue to spray, and 100% H3PO4 is sent to the arsenic removal device, and 0.5% HCl gas is passed into the phosphoric acid by the weight of phosphoric acid. 0.5% of the total weight of phosphoric acid HCl gas, temperature 130 ℃, time 120 minutes, cooled to 32 ℃, sent to the crystallizer, add 0.4% of the total weight of phosphoric acid phosphoric acid crystal seed, stirring, sent to the centrifugal separation, to obtain the crystalline phosphoric acid product, the composition of which is: P2O5 72.42%, SO42- 25 × 10-6, Fe 8 × 10-6, As 0.5 × 10-6, Cl-2 × 10-6, Pb 2×10-6.

　　Report II,

　　A process for the production of phosphoric acid by direct reduction of phosphorus ore with double-layer composite pellets by the following method:

　　The chemical composition of the raw materials used: phosphate rock containing P2O525%, silica containing SiO298%, coke powder containing 75% of fixed carbon, the three raw materials according to the CaO/SiO2mol ratio of 0.4, the amount of carbon for the reduction of phosphorus ore in the theoretical amount of 1.5 times the amount of P2O5 dosage, by mixing and grinding to the size to reach -200 mesh > 80% and then mixed with 2% of the binder of sodium humate and then added to the ball of water production, pellet moisture The water content of the pellet is 12%, and the particle size of the pellet is 10～16mm. the above pellet is made into ball for the second time, and coated with a layer of coke powder with a mesh of -200 >80%. The weight of coke powder is 10% of the weight of the pellet. The above chemical composition and physical specifications of the pellets in 100 ℃ drying and solidification, sent to φ0.8 within the × 10 m radial ventilation rotary kiln, control the kiln pellet reduction temperature of 1300 ℃, the material stays in the kiln for 1.5 hours, the volatility of phosphorus in the pellet is greater than 80%, the production of the kiln gas containing P2O5 hydration absorption, the concentration of phosphoric acid containing H3PO485% of the system.