Revamp of HP mono reactor, ammonia based purification plants.

Key features

  • Energy saving
  • Waterfree off-gas
  • “debottlenecking effect” for urea production

Several melamine plants have one HP melamine reactor and an ammonia-based purification section.

This arrangement has some drawbacks, namely:

  • low pressure (25 bar g) and high-water content in the off-gas sent to the Urea Plant
  • High energy consumption for the recovery and recycle of ammonia in the purification section.

Taking advantage from some unique features of the Casale LEM™ technology, Casale has devised a revamping scheme, which basically consist is adding an HP scrubber fof the off-gas, upstream the HP reactor, and a secondary reactor just downstream. The main benefits of the revamped plant are as follows:

  • Higher urea conversion to melamine, due to enhanced OATs conversion to melamine and reduced melam formation
  • Production of CO2-free melamine melt
  • Increased heat recovery.

Part of the heat is recovered from the off gas in the new scrubber by directly preheating the molten urea feed. Furthermore, heat is also recovered by cooling the circulating urea melt in the scrubber thus generating steam that can be used within the plant.

The off-gas recycled to the urea plant is available at high-pressure and water-free.

This has a beneficial effect on urea plant since, being water no longer added to the urea synthesis section as in unmodified scheme, it creates room for additional urea production.