Partial Condensation Process and Liquid Methane Wash
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
Example
Partial Condensation Process and Liquid Methane Wash
Customer:
Idemitsu Petrochemical Co., Ltd.
Plant location:
Chiba / Japan
Process:
Partial condensation of Calcor gas, purification of CO by distillation, refrigeration by liquid N2
Capacity:
150 Nm3/h (0.135 MMSCFD) CO
99.7 mol% purity, 10 ppm CH4
Scope of work:
Process design, engineering, procurement and supervision of construction and start-up
Cryogenic carbon monoxide separation
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 feedgas 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 operated with methane supplied through the process gas.
Basic Flow Diagram: Partial Condensation and Liquid Methane Wash
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. Only 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.
References:
Rainer Zeller, Cryogenic gas separation, Handout brochure to be received through Linde
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