- MP Absorber debottleneck
- No CO2 carry-over in the overhead vapour line
The MP absorber column separates the carbamate condensed in the MP carbamate condenser from ammonia and inert gases. It is crucial that the uncondensed CO2 is thoroughly scrubbed below the upper section of the column to avoid crystallization of carbamate in the overhead lines, which might upset the ammonia pumps or even force a shutdown of the plant. The operating range of any standard MP absorber is quite narrow and small deviations are enough to trigger significant upsets.
Casale has redesigned the whole section to improve its stability and thus the operability of the entire plant.
In Casale's new scheme, the gas/liquid phases are separated in a dedicated item and the carbon dioxide recovery is improved thanks to a few modifications in the column internals.
The carbamate mix from the MP condenser is fed to a new separator, where the carbamate solution is split from the uncondensed gases. The carbamate is then pumped back to the HP synthesis section. The gases are washed in the MP absorber column by means of a carbonate solution taken from the LP section. New dedicated pumps take the solution from the column bottom to the MP condenser.
This new arrangement improves significantly both the reliability and flexibility of the operation with the additional benefit, provided the new separator is adequately sized, that a higher plant load can be achieved.