HYDROGEN PURIFICATION PROCESS AND SYSTEM

Abstract

A hydrogen generation system is disclosed that includes a fuel reforming reactor generating a hydrogen-rich reformate gas at a temperature greater than 150 C, a pressure swing adsorption (PSA) hydrogen purification unit that separates the reformate gas into a relatively pure hydrogen stream and an off-gas stream, and a catalytic reactor down stream of the PSA unit that converts carbon monoxide (CO) and hydrogen (H2) contained in the relatively pure hydrogen stream into methane (CH4) and water vapor (H2O). The method of purification involves generating a hydrogen-rich reformate gas at a temperature greater than 150 C in a fuel reforming reactor, separating the reformate gas into a relatively pure hydrogen stream and an off-gas stream in a pressure swing adsorption (PSA) hydrogen purification unit, and converting carbon monoxide (CO) and hydrogen (H2) contained in the relatively pure hydrogen stream into methane (CH4) and water vapor (H2O) in a catalytic reactor down stream of the PSA unit. The hydrogen can be further purified by including a secondary purification stage downstream of the PSA unit and the catalytic reactor wherein the secondary purification stage has a water adsorbent material bed that adsorbs the water vapor H2O and a hydrogen absorbent material downstream of the water absorbent material that absorbs hydrogen gas preferentially, thus concentrating the non-hydrogen components, such as CH4, into an exhaust stream that exits the bed, wherein the absorbed hydrogen gas is then desorbed to create an exiting very pure hydrogen stream.

Description

DRAWINGS

FIG. 1 illustrates one embodiment of a system of the disclosure in which thermal energy of the reformate stream is used to maintain the catalyst at optimum conditions.

FIG. 2 illustrates a second embodiment of the system in which thermal energy of the combustion exhaust gas is used to maintain the catalyst at optimum conditions.

FIG. 3 is a graph that illustrates test data collected on a hydrogen generation unit shown in FIG. 1.

FIG. 4 illustrates an exemplary system in which a secondary hydrogen purification process is added downstream of the methanation reactor in either of the systems shown in FIG. 1 or 2.

FIG. 5 is a set of tables showing predicted hydrogen production levels at various stages in the systems shown in FIGS. 1, 2, and 4.

FIG. 6 is a graph of critical CO conversion and hydrogen purity in the purification process shown in FIG. 4.

Claims

1. A hydrogen generation method comprising: generating a hydrogen-rich reformate gas at a temperature greater than 150 C in a fuel reforming reactor;separating the reformate gas into a relatively pure hydrogen stream and an off-gas stream in a pressure swing adsorption (PSA) hydrogen purification unit, andconverting carbon monoxide (CO) and hydrogen (H2) contained in the relatively pure hydrogen stream into methane (CH4) and water vapor (H2O) in a catalytic reactor down stream of the PSA unit.

2. The hydrogen generation method of claim 1 further comprising: positioning the catalytic reactor such that the temperature of the hydrogen-rich reformate gas maintains the temperature of the catalytic reactor.

3. The hydrogen generation method of claim 1 further comprising: integrating the fuel reforming reactor with a combustion reactor that uses the off-gas stream to provide thermal energy to the fuel reforming reactor, the combustion reactor having a combustion exhaust gas at a temperature greater than 150 C; andpositioning the catalytic reactor such that the temperature of the exhaust gas maintains the temperature of the catalytic reactor.

4. The hydrogen generation method of claim 1 further comprising: providing a secondary purification stage downstream of the PSA unit and the catalytic reactor, the secondary purification stage having a water adsorbent material bed that adsorbs the H2O; andconcentrating non-hydrogen components into an exhaust stream exiting the bed by providing a hydrogen absorbent (or adsorbent) material downstream of the water absorbent material bed; anddesorbing the absorbed hydrogen gas to generate a very pure hydrogen stream.

5. A hydrogen generation system comprising: a fuel reforming reactor generating a hydrogen-rich reformate gas at a temperature greater than 150 C;a pressure swing adsorption (PSA) hydrogen purification unit that separates the reformate gas into a relatively pure hydrogen stream and an off-gas stream, anda catalytic reactor down stream of the PSA unit that converts carbon monoxide (CO) and hydrogen (H2) contained in the relatively pure hydrogen stream into methane (CH4) and water vapor (H2O).

6. The hydrogen generation system of claim 5 further comprising: the catalytic reactor being positioned such that the temperature of the hydrogen-rich reformate gas maintains the temperature of the catalytic reactor.

7. The hydrogen generation system of claim 5 further comprising: a combustion reactor integrated with the fuel reforming reactor that uses the off-gas stream to provide thermal energy to the fuel reforming reactor;the combustion reactor having a combustion exhaust gas at a temperature greater than 150 C exiting the combustion reactor; andwherein the catalytic reactor is positioned such that the temperature of the exhaust gas maintains the temperature of the catalytic reactor.

8. The hydrogen generation system of claim 5 further comprising: a secondary purification stage downstream of the PSA unit and the catalytic reactor wherein the secondary purification stage has a water adsorbent material bed that adsorbs the water vapor H2O; anda hydrogen absorbent material downstream of the water absorbent material that absorbs hydrogen gas preferentially, thus concentrating the non-hydrogen components, such as CH4, into an exhaust stream that exits the bed, wherein the absorbed hydrogen gas is then desorbed to create an exiting very pure hydrogen stream.

9. The hydrogen generation system of claim 5 further comprising: a secondary purification stage downstream of the PSA unit and the catalytic reactor wherein the secondary purification stage has a water adsorbent material bed that adsorbs the water vapor H2O; anda hydrogen absorbent material downstream of the water absorbent material that absorbs hydrogen gas preferentially, thus concentrating the non-hydrogen components, such as CH4, into an exhaust stream that exits the bed, wherein the adsorbed hydrogen gas is then desorbed to create an exiting very pure hydrogen stream.