Process for the production of hydrogen with intermediate-pressure purging

Process for the production of hydrogen from a hydrocarbon feedstock and water vapor that comprises:

• A stage for the production of a synthetic gas in a vapor reforming unit of the hydrocarbon feedstock in the presence of water vapor, with a fuel that provides the heat that is necessary to the reaction,
• A stage for conversion to vapor of the synthetic gas that is obtained in the preceding stage producing a hydrogen stream that contains methane and carbon dioxide,
• A stage for recovering carbon dioxide that is present in the stream that is obtained in the stage for conversion to vapor, making it possible to separate the carbon dioxide from the hydrogen stream,
• A stage for recovery and recycling to the vapor reforming of impurities that are present in the hydrogen stream, comprising a decompression phase that is carried out at a pressure of between 0.2 MPa and 1.4 MPa 1.4 MPa;
• and wherein the phase for decompression and regeneration of the adsorber is produced in the following way:
• Isolation of the first adsorber and putting the second adsorber on line,
• Decompression of the first adsorber, recompression and flushing of the first adsorber, with a hydrocarbon feedstock stream that is designed to serve as feedstock in the vapor reforming unit, and heated by exchange with the water vapor that is also intended for the vapor reforming unit, up to a temperature that is greater by at least 20° C. than the condensation temperature of the water vapor,
• Regeneration of the reheated adsorber and desorption of impurities by circulation of water vapor that is superheated by at least 20° C. intended for the vapor reforming unit,
• Elimination of the water vapor that is present in the adsorber that is regenerated by a flushing of the adsorber with a pure and hot hydrogen stream,
• Flushing of the adsorber from which water vapor is removed by a pure and cold hydrogen stream.