Simple and efficient removal of the water and CO2 from synthesis gas.
Energy saving up to 0.1÷0.15 Gcal/MT.
The Ammonia Washing Unit is working as a drying unit and therefore is going to remove the oxygenated compounds (water and CO2 in particular) from the fresh make up synthesis gas fed to the ammonia synthesis loop.
Carbon oxides presents in synthesis gas are almost completely removed by Shift, CO2 Removal and Methanation sections, while some moles (especially) of water still remains in the make-up gas and they could poison ammonia converters catalyst decreasing the ammonia converter performances. Ammonia wash system takes advantage from ammonia-water reciprocal solubility to completely remove water from make-up gas.
Also the CO2 still present in the MUG would be washed due to the solubility in liquid ammonia.
The new equipment required for the installation of the Ammonia Washing Unit are:
- Casale Ejector
- Feed/effluent exchanger
- Start up Ammonia Pump (optional)
- Liquid Ammonia Separator
- Coalescent Oil Filter
The Casale ejector is used to intimately mix the synthesis gas with the liquid sprayed ammonia, the feed/effluent exchanger is viceversa used to limit the liquid ammonia evaporation.
The ammonia washing unit allows a direct feeding of the make up gas and of the recycle gas to the ammonia synthesis converter, for this reason it is usually required the installation of an oil filter to remove the seal oil leaked by the synthesis gas compressor inside of the syngas.
In general the AWU is providing the following benefits:
- energy saving (up to 0.15 Gcal/MTNH3 on LHV)
- operational easiness
- robust deisgn
For the plant limited by the synthesis gas compressor the installation of the AWU allows also a small capacity increase.