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 a colorless crystal with a melting point of 42.3 degrees Celsius, a high-boiling acid, and is easily soluble in water. Phosphoric acid is a ternary medium strong acid, which is ionized step by step, not easily volatile, not easily decomposed, and has almost no oxidizing properties. Has acidity. In industry, concentrated sulfuric acid is commonly reacted with calcium phosphate to prepare phosphoric acid, and the calcium sulfate precipitate that is slightly soluble in water is filtered off, and the obtained filtrate is phosphoric acid solution.

　　Report 1.

　　A method for producing crystalline phosphoric acid by concentrating phosphoric acid with phosphoric anhydride, the steps are as follows:

　　Fully melt yellow phosphorus with a purity of 99.95% and arsenic content of 152 × 10-6 at 70 °C. According to the ratio of 1kg yellow phosphorus to 6.3-6.6m3 air, pump the yellow phosphorus to the yellow phosphorus burner and mix it with 0.7MPa. The compressed air is mixed and injected into the phosphorus-fired boiler, and the yellow phosphorus is rapidly atomized and burnt violently in the phosphorus-fired boiler.

　　The P2O5 produced by the combustion is introduced into the top of the hydration tower, and the top of the tower is sprayed with deionized water. After the dilute acid is obtained, the dilute acid is used for spraying. After obtaining 100% H3PO4, the top of the tower is supplemented with deionized water to continue spraying, and the 100% H3PO4 is sent to the dearsenic device, and 0.5% of the total weight of phosphoric acid is introduced into the HCl gas, the temperature is 130 ° C, and the time is 120 minutes. Cool to 32°C, send it to the crystallizer, add 0.4% phosphoric acid seed crystals based on the total weight of phosphoric acid, stir, and send to centrifugal separation to obtain a 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 2.

　　A process for producing phosphoric acid by directly reducing phosphate rock with double-layer composite pellets, the method is as follows:

　　The chemical composition of the raw materials used: phosphate rock contains P2O525%, silica contains SiO298%, coke powder contains fixed carbon 75%, the three raw materials are based on the CaO/SiO2mol ratio of 0.4, and the carbon content is the theoretical amount of P2O5 reduction in the phosphate rock. 1.5 times of the ingredients, mixed and milled until the particle size reaches -200 mesh> 80%, then mixed with 2% sodium humate binder, and then added water to make pellets, the pellet moisture content is 12%, and the pellet size is 10-16mm. The above-mentioned pellets are pelleted for a second time, and coated with a layer of coke powder with a -200 mesh greater than 80%. The coke powder weight is 10% of the pellet weight. The pellets with the above chemical composition and physical specifications are dried and consolidated at 100 °C, and sent to a radial ventilation rotary kiln with a diameter of 0.8 × 10 meters. After 1.5 hours, the phosphorus volatilization rate in the pellets is greater than 80%, and the generated kiln gas containing P2O5 is hydrated and absorbed to obtain phosphoric acid with a concentration of 85% H3PO4.