Process to prepare a diluted hydrogen gas mixture

1. A process to prepare a diluted hydrogen gas mixture starting from a gas mixture comprising hydrogen and carbon monoxide by

(i) converting part of the carbon monoxide in said gas mixture to hydrogen and carbon dioxide by means of a catalyzed water gas shift reaction to obtain a shifted gas;

(ii) separating hydrogen from said shifted gas by means of a membrane to obtain the hydrogen comprising gas at the permeate side of the membrane and a carbon dioxide comprising gas at the retentate side of the membrane, wherein at the permeate side of the membrane a sweep gas comprising nitrogen, steam or natural gas or a mixture thereof is provided;

(iii) cooling the carbon dioxide comprising gas to obtain liquid carbon dioxide and a gas mixture of non-condensable gasses; and

(iv) separating the liquid carbon dioxide from the non-condensable gasses;

wherein the non-condensable gasses are used to supplement the sweep gas at the permeate side of the membrane in step (ii).

2. The process according to claim 1 , wherein the membrane is a H2-selective membrane having a permselectivity of H2 over CO2 of at least 30.

3. The process according to claim 1 , wherein the membrane is a silica, organic-inorganic silica hybrid membrane, a blend of silica and organic-inorganic silica hybrid, PBI, PBI/PI membranes or a combination of two or more of the above.

4. The process according to claim 1 , wherein the membrane is comprised of a hydrogen-permeable and hydrogen-selective metal.

5. The process according to claim 4 , wherein the hydrogen-selective metal is one of the following metals or alloys Pt, Ni, Au, Pd, Pd—V, Pd—Ta, Pd—Nb, Pd—Ag, Pd—Cu and Pd—Au, Pd—Rh, Pd—Ru.

6. The process according to claim 1 , wherein the shifted gas as obtained in step (i) is subjected to a further water gas shift in step (ii) in a membrane water gas shift reactor.

7. The process according to claim 1 , wherein step (i) is performed by feeding a gas mixture comprising hydrogen and carbon monoxide and having a steam to carbon monoxide molar ratio of between 0.2:1 and 0.9:1 to a water gas shift reaction wherein part or all of the carbon monoxide is converted with the steam to hydrogen and carbon dioxide in the presence of a catalyst as present in one fixed bed reactor or in a series of more than one fixed bed reactors and wherein the temperature of the gas mixture as it enters the reactor or reactors is between 190 and 230° C.

8. The process according to claim 1 , wherein the gas mixture comprising hydrogen and carbon monoxide is obtained by gasification, auto thermal reforming or steam reforming of a gaseous hydrocarbon feedstock or by gasification of a liquid or solid carbonaceous feedstock.

9. The process according to claim 1 , wherein the non-condensable gasses are subjected to a CO2 recovery step prior to being fed into the hydrogen comprising gas.

10. The process according to claim 9 , wherein a CO2-rich gas is recovered from the non-condensable gasses by the use of a polymeric gas separation membrane operating at temperatures between −55° C. and −10° C., and said CO2-rich gas is recompressed and recycled to step (iii).

11. The process according to claim 10 , in which the membrane comprises a polymeric membrane.

12. A process to generate power from a gaseous hydrocarbon or a liquid or solid carbonaceous feedstock by preparing a diluted hydrogen gas mixture according to the process of claim 1 and providing said diluted hydrogen gas mixture as fuel to a gas turbine to generate power.

13. A process to operate more than one furnace, which furnaces run on a fuel as provided by a common fuel delivery system, wherein to said fuel delivery system the diluted hydrogen gas mixture is provided as prepared by the process of claim 1 .