Improved HP loop for NH3 Stripping plants.

Key features

  • Revamping scheme for large capacity increase of NH3 Stripping plants
  • Addtional section to handle extra capacity with no modifications of HP loop and plant back-end

The medium-high pressure section (MHP) is a process scheme particularly suitable to revamp ammonia stripping plants when significant capacity increase is desired. It involves installing a new plant section operated at an intermediate pressure between that of the synthesis and MP sections. The urea-containing solution from the stripper outlet is further purified in the new MHP decomposer upstream of the MP decomposer. Thanks to this intermediate decomposition, the amount of vapours from the MP decomposer is so significantly reduced that no modifications are necessary in the MP section (including the ammonia recovery section) or to the HP carbamate pumps and ammonia pumps. The intermediate operating pressure is sufficient for the resulting vapours to be condensed generating LP steam.

The benefits are a higher CO2 conversion and consequent reduced steam consumption in the stripper, due to the reduced water content in the carbamate solution from the new condenser that is recycled back to the converter.

Figure: Process flow diagram of Medium-High Pressure section in NH3 stripping plants Process flow diagram of Medium-High Pressure section in NH3 stripping plants