Manufacturing Process of H3PO4 (wet process) Guided by : Prof. Sejal solanki Chemical department Prepared by : 140150105020 140150105029 140150105030 Chemical engineering department Government engineering college Bhuj-370001
Wet Process (Strong acid): The wet process is according to the acids (sulfuric acid, nitric acid or hydrochloric acid) used to decompose the phosphate rock. The process using sulfuric acid is the most common among all particularly for producing fertilizer grade phosphoric acid. The wet process phosphoric acid, also called as green acid.
Contents to be included Properties Raw Materials Quantitative requirements Chemical reaction Flow sheet Major engineering problems uses
Properties: Phosphoric Acid: Molecular formula : H3PO4 Molecular weight : 98 gm/mole Melting point : 42.4ºC Boiling point : 213ºC
Raw Materials: The high grade of imported ore is necessary to avoid solubilization of mined rock impurities such as aluminium, silicon, iron oxide, and alkali minerals. The only other raw material required is strong sulphuric acid which comes from a contact sulphuric acid plant located at or near the phosphoric acid plant.
Quantitative requirements: Basis: 1 ton of phosphoric acid (100%) Phosphate rock(32% P2O5) = 2.5 tons Sulfuric acid(93-98%) = 2 tons Plant capacity: 100-150 tons/day of 100% H3PO4
Chemical Reaction: Ca10F2(PO4)6 + 10H2SO4 + 20H2O → 10CaSO4.2H2O + 2HF + 6H3PO4
Flow Sheet:
Process Description: Sulfuric acid on reaction with phosphate rock along with precipitation of calcium sulfate results into the formation of phosphoric acid. The process is simple and requires grinding of phosphate rock reacting with dilute phosphoric acid. so that, melt is produced which in a reactor as mixed with concentrated sulfuric acid for 4 to 8hrs in the temperature range of 75-80°C. Lot of air is required to control the temperature.
The gypsum-phosphoric acid slurry goes to a travelling pan vacuum filter where the 40% acid is removed and the cake washes the water. The gypsum can either be dried for use in plaster, paints, and cements, or reacted with ammonium carbonates to give ammonium sulphate and calcium carbonate. The dilute acid is concentrated in a single effect evaporator to any grades >50% acid. gypsum and phosphoric acid are separated and after minor purification the phosphoric acid is concentrated into the evaporator.
Major Engg. Problems: Process design: Material of construction: Fineness of grind Temperature Control of sulphuric acid Material of construction: Reaction tank constructed of steel and lined with acid-proof brick. All air vent systems are PVC coated steel. Storage tanks of rubber-lined steel.
Uses: Used for preparation of hydrogen halides Used as a "rust converter”. Food-grade phosphoric acid is used to acidify foods and beverages such as various colas. Used in many teeth whiteners to eliminate plaque. As a chemical oxidizing agent for activated carbon production As a cleaner by construction trades to remove mineral deposits, cementitious smears, and hard water stains. As a pH adjuster in cosmetics and skin-care products. As a dispersing agent in detergents and leather treatment.