Phosphoric acid is a basic chemical raw material, widely used in phosphate, fertilizer, food additive, feed, washing, electronics, flame retardant and other industries. Pure phosphoric acid is colorless crystal, with a melting point of 42.3 ℃, high boiling point acid, and easily soluble in water. Phosphoric acid is a ternary medium strong acid, which is ionized step by step, is not easy to volatilize, decompose, and has almost no oxidation. It has the general property of acid. In industry, concentrated sulfuric acid is often used to react with calcium phosphate to produce phosphoric acid. The calcium sulfate precipitate that is slightly soluble in water is filtered out, and the filtrate obtained is the phosphoric acid solution.
Phosphoric acid is a basic chemical raw material, widely used in phosphate, fertilizer, food additive, feed, washing, electronics, flame retardant and other industries. Pure phosphoric acid is colorless crystal, with a melting point of 42.3 ℃, high boiling point acid, and easily soluble in water. Phosphoric acid is a ternary medium strong acid, which is ionized step by step, is not easy to volatilize, decompose, and has almost no oxidation. It has the general property of acid. In industry, concentrated sulfuric acid is often used to react with calcium phosphate to produce phosphoric acid. The calcium sulfate precipitate that is slightly soluble in water is filtered out, and the filtrate obtained is the phosphoric acid solution.
A method for producing crystalline phosphoric acid by concentrating phosphoric acid with phosphoric anhydride, the steps are as follows:
The purity is 99.95% and the arsenic content is 152 × 10-6 yellow phosphorus is fully melted at 70 ℃. According to the ratio of 1kg yellow phosphorus to 6.3-6.6m3 air, the yellow phosphorus is pumped to the yellow phosphorus combustion nozzle and mixed with 0.7MPa compressed air, and then injected into the phosphorus burning boiler, where the yellow phosphorus is rapidly atomized and burned violently.
P2O5 generated from combustion is introduced to the top of the hydration tower, and the tower top is sprayed with deionized water. After getting dilute acid, dilute acid is sprayed. Dilute phosphoric acid is sprayed continuously from the top and overflows evenly from the inner wall. P2O5 is absorbed circularly. After 100% H3PO4 is obtained, a proper amount of deionized water is added to the tower top to spray continuously, and 100% H3PO4 is sent to the arsenic removal device. HCl gas 0.5% of the total weight of phosphoric acid is introduced, the temperature is 130 ℃, and the time is 120 minutes, Cool to 32 ℃, send to crystallizer, add 0.4% phosphoric acid seed by weight of total phosphoric acid, stir, send to centrifugation for separation, and obtain crystalline phosphoric acid product. Its components are: P2O5 72.42%, SO42 - 25 × 10-6，Fe 8 × 10-6，As 0.5 × 10-6，Cl-2 × 10-6，Pb 2 × 10-6。
A process for producing phosphoric acid by direct reduction of phosphate rock with double-layer composite pellets is as follows:
Chemical composition of raw materials used: phosphate rock contains 525% P2O5, silica contains 298% SiO, and coke powder contains 75% fixed carbon. According to the CaO/SiO2mol ratio of 0.4, the carbon content of the three raw materials is 1.5 times of the theoretical amount of P2O5 in the phosphate rock. After mixing and grinding to the particle size of - 200 mesh ＞ 80%, and then mixing 2% sodium humate binder, water is added to make the pellets. The water content of the pellets is 12%, and the pellet size is 10~16mm. The above pellets are pelletized for the second time and coated with a layer of coke powder with - 200 mesh size 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 ℃, and then delivered φ Within 0.8 × For a 10m radial ventilated rotary kiln, the reduction temperature of pellets in the kiln is controlled to 1300 ℃, the materials stay in the kiln for 1.5 hours, and the volatilization rate of phosphorus in the pellets is more than 80%. The produced kiln gas containing P2O5 is hydrated and absorbed to produce phosphoric acid with a concentration of 485% H3PO.
Raw materials: The raw materials of phosphoric acid are mainly phosphate rock (mainly composed of calcium fluorophosphate Ca10F2 (PO4) 6) and inorganic acid mainly composed of sulfuric acid.
Principle: 3H+ PO4 = H3PO4 (principle: strong acid makes weak acid)
Wet process: In industry, concentrated sulfuric acid reacts with calcium phosphate and phosphate rock to produce phosphoric acid, and then filter out calcium sulfate precipitation that is slightly soluble in water to obtain phosphoric acid solution. Or let white phosphorus react with nitric acid to obtain pure phosphoric acid solution.
3P4 + 20HNO3 + 8H2O = 12H3PO4 + 20NO↑
Thermal method: white phosphorus burns in the air to produce phosphorus pentoxide, which is then made by hydration. Note that hot water must be used, because phosphorus pentoxide will react with cold water to form highly toxic metaphosphoric acid.
Production of polyphosphoric acid: the production of polyphosphoric acid is mainly made by dehydration of orthophosphoric acid under appropriate conditions.
Recrystallization method: Dissolve industrial phosphoric acid in distilled water, purify the solution, remove impurities such as arsenic and heavy metals, and filter it to make the filtrate meet food grade requirements, then concentrate it to prepare finished edible phosphoric acid.
Use:
Agriculture: phosphoric acid is the raw material for the production of important phosphate fertilizer (calcium superphosphate, potassium dihydrogen phosphate, etc.), and also the raw material for the production of feed nutrient (calcium dihydrogen phosphate).
Industry: Phosphoric acid is an important chemical raw material, and its main functions are as follows:
The metal surface is treated to generate insoluble phosphate film on the metal surface to protect the metal from corrosion.
It is mixed with nitric acid as a chemical polishing agent to improve the smoothness of metal surface.
Phosphate ester, the raw material for the production of washing products and pesticides.
Raw materials for production of phosphorus containing flame retardants.