PRODUCTION OF UREA
Urea is a white dry organic compound and a crystalline substance and has minimum of 46% Nitrogen calculated in dry state. M.P: 132 deg C. Urea is made by reacting carbon dioxide (CO2) with anhydrous ammonia (NH3) under pressure of 208 atm and temperatures of around C. Water is removed during processing and the molten matter is either converted to prills or into granules. Urea can be produced as prills, granules, flakes, pellets, crystals and solutions.
USES 1. Urea is highly soluble in water and is therefore also very suitable for use in fertilizer solutions (in combination with ammonium nitrate: UAN) and as animal feed. 2. For the manufacture of plastics specifically, urea-formaldehyde resin(Plywood adhesive- Fevicol) 3. For the manufacture of various glues (urea- formaldehyde or urea-melamine-formaldehyde). The latter is waterproof and is used for marine plywood
Specifications for Prilled Urea 46%N: Nitrogen:46.0% min. Moisture:0.3% max. Biuret:1.0% max. Granulation:1 – 4 mm 90-94% min. Melting Point: 132 Degrees Celsius Colour: Pure White Prilled Free Flowing, Treated against caking, 100% free from harmful substances.
Specifications for Granular Urea 46%N: Nitrogen:46.0% min. Moisture:0.5 % max. Biuret:1.4% max. Granulation:2 – 4 mm 90-94% min. MeltingPoint:132DegreesCelsius Colour: Standard White or Pure. Free Flowing, Treated against caking, 100% free from harmful substances.
Market grades 1. Technical grade: 46% Nitrogen 2. Fertilizer grade: Coated with Non- hygroscopic dust such as Phosphate rock/Lime stone, containing 40-42% Nitrogen 3. Liquor: Mixtures of Urea in Ammonia Solution
Principle raw materials: 1) CO2 from synthesis gas 2) NH3 Process description: 1. Ammonia and CO2 are compressed separately and added to the high pressure autoclave. 2. The Reactor is water-cooled due to the highly exothermic nature of the reaction. 3. The Reactor is operated on a continuous basis; A mixture of Urea, Ammonium Carbamate, Water and unreacted NH3+ CO2 results.
Process description This liquid effluent is let down to 27 atms. and fed to a flash-evaporator containing a gas-liquid separator and condenser. Unreacted NH3, CO2 and H2O as a solution are thus removed and recycled (in case of partial recycle option). An aqueous solution of carbamate-urea is passed to the atmospheric flash drum, where further decomposition of carbamate takes place.
Process description The off-gases from this step can either be recycled or sent to NH3 processes for making chemical fertilizer. The 80% aqueous Urea solution can be used as is, or sent to a vacuum evaporator to obtain molten Urea containing less than 1% water. The molten mass is then sprayed into a prillng or granular solidification tower.
Process description To avoid formation of bi-uret in percentages greater than1%, the temp. must be kept just above the Melting Point for processing times of 1-2 sec. in this phase of the operation.