Calcor cleans up carbon monoxide production

Carbon monoxide is the feedstock for the production of many chemicals, such as carbonic acids and phosgene. The quality of the products depends largely on that of the raw material.

To boost the purity of CO, the German company Caloric, of Munich, has developed the Calcor process - a reforming process combined with CO2 recovery and CO purification. The raw material, natural or liquid petroleum gas, is mixed with hydrogen, heated prior to catalytic/adsorptive hydration and desulphurisation, then mixed with CO2.

While passing over the catalyst in the reformer tubes, the mixture of CO2 and feedstock is converted into a synthesis gas comprising CO, H2, CO2 and CH4. Heat for this endothermic reaction is generated by a high-velocity burner firing into the reformer plenum.

The main problem that the Calcor process had to overcome was controlling both temperature and reaction kinetics to avoid the formation of carbon (by the Bou-douard reaction or by feedstock cracking). Caloric achieved this with its combination of catalysts and their orientation in the reformer tube.

Leaving the reformers, the syngas is cooled to ambient temperature prior to CO2 removal and recovery. The CO2 from the raw gas is absorbed in a packed tower at ambient temperature by a caustic. With the recovery of CO2 from the reformer flue gas as well as from the syngas, the standard Calcor process generates a CO molecule from almost every carbon atom imported into the process as feed and fuel. Thus, a carbon yield of 97-99 per cent volume nearly reaches the theoretical maximum. The production of one tonne of CO requires either 816m3 of natural gas or 531kg of LPG.

Deleting the CO2 recovery section and using imported CO2 can simplify the process. In some situations, CO2 may be available as a low cost by-product. Or, buying in the CO2 can cut investment costs.

With decreasing plant capacity, the cost for utilities and energy become less and less significant. Eventually CO production costs are dominated by the costs of depreciation and interest on the investment. For a requirement of 200kg/h CO or less, the use of purchased CO2 may become attractive, Caloric estimates.

The maximum purity of the CO product is obtainable by combining the standard Calcor process with a low-temperature purification. This can yield a CO purity of 99.98 per cent volume, with CH4 or CO2 impurities below 1ppm.

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