Patent ID: 8021464

Claim:
A method for the combined production of hydrogen and carbon dioxide from a mixture of hydrocarbons, comprising at least: (a) generating a syngas containing at least carbon dioxide, hydrogen, carbon monoxide, methane, and water vapor, from said hydrocarbon mixture; (b) cooling the syngas issuing from (a) with recovery of the available waste heat; (c) back-converting, to steam, all or part of the cooled syngas issuing from (b) in order to oxidize most of the carbon monoxide it contains to carbon dioxide, with the corresponding production of hydrogen; (d) cooling the mixture issuing from step (c), with condensation of the steam, by heat exchange with various boiler feedwater and/or deionized water circuits; (e) purifying the cooled mixture issuing from (d) in a pressure swing adsorption (PSA) unit to obtain a hydrogen-enriched stream having a purity at least equal to 98% and an offgas called “PSA offgas” containing carbon dioxide, at a pressure of about 1 to 3 bar abs; and steps of treating said PSA offgas to obtain a carbon dioxide-enriched fluid, comprising at least: (f) compressing the PSA offgas to a pressure higher than the reforming pressure and such that the partial pressure of the CO 2 therein is between about 15 and 40 bar; (g) drying the compressed PSA offgas by removing the water therein to obtain a dry gas; and (h) two or more successive steps (hn) of condensation/separation, such that each of the steps (hn) itself comprises: a step of condensing all or part of the CO 2 present in the gas issuing from the preceding step, followed by a step of separating the CO 2 -rich condensate issuing from the separation from the gas phase containing incondensable compounds and constitutes an incondensables purge; the step(s) (hn) are implemented at temperatures tn of between ambient temperature and −56° C., with, for any n tn lower than tn-1; the gas phase issuing from step (hn-1) feeds the step (hn), the gas phase issuing from the final step (hn) constituting the incondensables purge; and using the incondensables purge.