H2/CO Separation
Cryogenic processes like partial condensation and liquid methane wash are used for the recovery of pure carbon monoxide and pure hydrogen from gases resulting from partial oxidation or catalytic reforming processes. Carbon monoxide is mainly used for the production of acetic acid, formic acid, polyurethane, polycarbonates and methylacrylates. The desired purity of carbon monoxide depends on the prevailing requirements and can be adjusted into the ppm range with respect to the residual contents of hydrogen and methane.
To separate carbon monoxide from synthesis gas there are basically two main cryogenic process types:
Condensation process
Methane scrubbing process
For both cases it is mandatory that the feed gas to the process is absolutely free from water, CO2 and other components which could freeze at the low operation temperatures. Therefore process gas is initially purified in a molecular sieve adsorber station.
Feed gas from partial oxidation is normally supplied with high pressure, high CO and low CH4 content. In this case the condensation process is used. Alternatively, gases from steam reforming have lower pressure, lower CO and elevated CH4 content. In this case preferably methane wash is used and operated with methane supplied through the process gas.
General Scheme: Condensation process
Condensation process and methane wash process exist in several alternative configurations depending on required product purity, recovery rate, presence of other impurities like N2 and Ar in feed. The most simple configuration of a condensation process is depicted above. It includes an adsorber station, a coldbox containing the plate fin heat exchangers to precool feed gas against product streams, the hydrogen separator and stripping column. As carbon monoxide compressor mostly a dry piston or integrally geared centrifugal compressor is used.
The cryogenic equipment is manufactured and assembled in Linde's workshops and supplied as one package unit. Adsorber station and other machinery like carbon monoxide compressor, liquid methane pump or expansion turbine are supplied separately and interconnected on site. The cold box is insulated with perlite on site.
Example:
HyCO plant with condensation process in Mai Liao, Taiwan
Client:
Formosa BP Chemicals Corp.
Process:
Partial oxidation, CO2 wash, condensation process. PSA
Feedstock:
Naphtha
Product:
20,000 Nm3/h H2 99.9%, 25,400 Nm3/h CO 99.8%
Linde-Scope:
Engineering, procurement, erection and start-up supervision
Start-up:
2005
