Physical properties :
- Molecular formula : CH4N2O
- Molecular weight :60.06 gm/mole
- Appearance :White granules,Odourless
- Melting point :132–135 ºC
- Solubility :Soluble in water, ethanol, glycerol, Moisture :1% by wt. (Max.) ,Dissolved in water, it is neither acidic nor alkaline.
- CO2 + 2NH3 → NH2COONH4 ΔH = -37,021 Kcals
- NH2COONH4 → NH2CONH2 + H2O ΔH = +6.3 kcals
- Liquid ammonia, gaseous carbon dioxide and recycle materials charged in the reaction chamber at the pressure of 14 MPs at 170–190ºC to form carbamate.
- The carbamate decomposition reaction is both slow and endothermic.
- The mixture of unreacted reactants and carbamate flows to the decomposer.
- The stoichiometric ratio of CO2/NH3 conversion to urea is essentially about 55%, but by using an excess of CO2 (or NH3) the equilibrium can be driven as high as 85%.
- The reactor must be heated to force the reaction to proceed.
- CO2 is introduced at process pressure followed by stripper
- All the unreacted gases and undecomposed carbamate to be removed from the product, the urea must be heated at lower pressure (400 kPa).
- The reagents are reacted and pumped back into the system.
- Evaporation and prilling or granulating produces the final product.
- Overall, over 99% of both CO2 and NH3 are converted to urea, making environmental problems to minimum.
- Carbamate is highly corrosive to both ordinary and stainless steel, but with oxygen present,stainless steel resist it very well.
- Granular urea minimize air pollution and granules has higher strength.