Background and overview[1]
Phosphoric acid is a basic chemical raw material and is widely used in phosphate, fertilizer, food additives, feed, washing, electronics, flame retardant and other industries. Pure phosphoric acid is a colorless crystal with a melting point of 42.3 degrees Celsius, a high boiling point acid, and is easily soluble in water. Phosphoric acid is a ternary medium-strong acid that ionizes step by step, is not easy to volatilize, is not easy to decompose, and has almost no oxidizing properties. Has acidic properties. In industry, phosphoric acid is commonly produced by reacting concentrated sulfuric acid with calcium phosphate. The calcium sulfate precipitate that is slightly soluble in water is filtered out. The resulting filtrate is a phosphoric acid solution.
Preparation[2-3]
Report 1,
A method for producing crystalline phosphoric acid by concentrating phosphoric acid anhydride, the steps are as follows:
Fully melt yellow phosphorus with a purity of 99.95% and containing arsenic 152×10-6 at 70°C. According to the ratio of 1kg yellow phosphorus to 6.3-6.6m3 air According to the proportion, use a pump to send yellow phosphorus to the yellow phosphorus burner and mix it with 0 thixotropic agent. 7MPa compressed air, and spray it into the phosphorus-fired boiler. The yellow phosphorus is rapidly atomized and burned violently in the phosphorus-fired boiler.
The P2O5 produced by combustion is introduced into the top of the hydration tower, and the top of the tower is sprayed with deionized water. After dilute acid is obtained, dilute acid spray is used instead. Dilute phosphoric acid is continuously sprayed from the top and overflows evenly from the inner wall, recycling P2O5 to obtain 100% H3PO After 4, add an appropriate amount of deionized water to the top of the tower to continue spraying, and send 100% H3PO4 to the arsenic removal device , introduce 0.5% HCl gas based on the total weight of phosphoric acid, temperature 130°C, time 120 minutes, cool to 32°C, send to the crystallizer, add 0.4% phosphoric acid seed crystal based on the total weight of phosphoric acid, stir, and send to centrifugal separation, The crystalline phosphoric acid product is obtained, its composition 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 directly reducing phosphate rock to produce phosphoric acid using double-layer composite pellets. The method is as follows:
Chemical composition of the raw materials used: phosphate rock contains P2O525%, silica contains SiO298%, coke powder It contains 75% fixed carbon. The CaO/SiO2mol ratio of the three raw materials is 0.4, and the carbon content is P2O5 Reduce the ingredients to 1.5 times the theoretical amount, mix and grind until the particle size reaches -200 mesh > 80%, then mix 2% sodium humate binder and add water to make pellets. The pellet moisture content is 12% and the pellet size is 10~ 16mm. The above-mentioned pellets are pelletized twice and coated with a layer of coke powder of -200 mesh greater than 80%. The weight of coke powder is 10% of the weight of pellets. The pellets with the above chemical composition and physical specifications are dried and solidified at 100°C, and then sent to a radial ventilation rotary kiln with a diameter of 0.8 × 10 meters. The pellet reduction temperature in the kiln is controlled to 1300°C, and the materials stay in the kiln. After 1.5 hours, the volatilization rate of phosphorus in the pellets is greater than 80%. The generated kiln gas containing P2O5 is hydrated and absorbed to obtain a concentration of H3PO485% phosphoric acid.
