In recent years CDS Engineering has performed a series of upgrades of the Feed Gas Scrubber and 2nd Stage Recompressor Scrubber upstream of the Amine Contactors on a North Sea Production Platform.

The gas stream from both scrubbers are combined together prior to entering the Amine Absorbers for CO2 removal. The thought behind the design was that in order to avoid liquid entering the absorbers due to condensation in the piping, the gas from the Feed Gas Scrubber would be mixed with the relatively hot gas from the compressor, which would result in superheated gas entering the absorbers. However, due to liquid carry over from the scrubbers, a superheated state of the gas was not achieved. This meant that liquid was entering the absorbers, which resulted in poor CO2 removal performance and operational difficulties.

In order to tackle this problem the 2nd Stage Recompressor Scrubber went through a series of retrofits in order to reduce liquid carryover.

The original internals in the vessel comprised a proprietary half open pipe type inlet device and a vane pack. Due to shutdown time limitations, initially only the inlet device was replaced by a Vane Type Inlet Device, which resulted in improvement in the performance of the vessel (13 to 20%).

In 1998, the vane pack was replaced by Axiflow cyclones, the forerunner of the SpiraFlowTM cyclone that showed a further improvement (43 to 44%).

The problem with the operation of the Amine Absorber as described above was finally tackled in 1999 by replacing the Axiflow cyclones with SpiraFlowTM cyclones. The SpiraFlowTM cyclone was developed from the Axiflow cyclone during an extensive test period. In effect, the SpiraFlowTM cyclone is has improved characteristics compared to the Axiflow cyclone, specifically with respect to liquid and gas handling capacity. The installation of the SpiraFlowTM cyclones resulted in substantial improvement in performance of the vessel (67 to 68%) with respect to the performance with Axiflow cyclones.

The table below shows the summary of these retrofits. Taking a sample on the gas outlet side of the vessel and performing a gas chromatography analysis determined the carry over. The measured amount of C6+ combined with the theoretical amount of C6+ in the gas gives a measure for the amount of liquid carryover from the vessel.