Process steps of Snamprogetti urea fertilizer manufacturing
Sequence of operations:
Urea formation and High-pressure unit:
- CO2 and NH3 are primary inputs, urea is formed in this unit at 158-160 kg/cm2 pressure.
- Passivation air is added to carbon dioxide stream to prevent corrosion of reactor.
- Compressed CO2 and high pressure NH3, both fed to urea reactor.
- Product from urea reactor is sent to stripper for H.P.decomposition, and released gases recycled.
- Solution from stripper fed to medium pressure unit.
Medium pressure unit:
- Ammonia sent by feed pump to urea reactor and to carbamate condenser.
- Liquid ammonia enters into the top section of the absorber.
- Solution from M.P. decomposer fed to low pressure section.
Low-pressure unit:
- L.P decomposition and vacuum preconcentrator gives urea solution.
- Ammonia preheating and low pressure condensing is done.
- Urea solution from preconcentrator sent to vacuum concentration.
Vacuum preconcentrator:
- To concentrate urea solution to 70% by removing water from solution.
- Heat provided by the heat content of MP and LP decomposer overheads.
- Operates under vacuum vapor escapes from top. Solution let out from bottom.
Vacuum concentration:
- Urea solution from L.P section is input, water removed from solution in this section.
- Water from the solution is separated in two vacuum concentrators.
- Vacuum system creates vacuum draws in and condenses water vapor.
- Urea melt from the second concentrator is sent to the Prilling section.
Prilling:
- Vacuum concentrated urea melt sent to prilling tower.
- Urea melt sprayed from prill bucket to form prills.
- Urea prills collected and sent to the bagging plant.
Process flowsheet design of urea manufacturing:
Conceptual process flowsheet is shown with main unit operations.
Chemical process flowsheet drawing of urea industry
Equipments used in urea fertilizer manufacturing process flowsheet design:
- Autoclave reactor
- absorber
- evaporator
- prilling tower