Method for extracting hydrogen from a gas that contains methane, especially natural gas, and system for carrying out said method
The invention relates to a method for extracting hydrogen from a gas containing methane, especially natural gas. Hydrocarbons contained in the gas are catalytically broken down in a reformer ( 4 ) by steam in order to form hydrogen, carbon monoxide and carbon dioxide. Catalytic conversion of the obtained carbon monoxide with steam occurs in a downstream conversion step in order to form carbon monoxide and water. Carbon dioxide is removed from the converted gas flow ( 8 ) by gas washing ( 7 ), and the washed hydrogen-rich gas flow ( 10 ) is subsequently divided in a pressure-swing adsorption system ( 11 ) into a product gas flow ( 12 ) made of hydrogen and a waste gas flow ( 13 ). The waste gas flow ( 13 ) is introduced with hydrogen ( 14 ), which is separated from the gas flow ( 10 ) after gas washing, into a reformer ( 4 ) which is essentially a carbon-free combustible gas, and is combusted there. The invention also relates to a system for carrying out the method.
1. A method for extracting hydrogen from a gas that contains methane comprising:
catalytically splitting hydrocarbons contained in the gas into hydrogen, carbon monoxide, and carbon dioxide in a reformer, by means of steam;
performing catalytic conversion of the carbon monoxide that was formed to carbon dioxide and hydrogen in a subsequent conversion stage, with steam;
removing the carbon dioxide after the step of catalytic conversion by means of a gas scrubber;
subsequently separating the remaining gas stream into a product gas stream that consists of hydrogen, and a waste gas stream, in a pressure swing adsorption system;
passing the entire waste gas stream to a combustion chamber of the reformer, together with a partial hydrogen stream that is branched off from the gas behind the gas scrubber, as a combustion gas that is extensively free of carbon, and
burning the waste gas stream and said partial hydrogen stream in the reformer;
wherein during the production of hydrogen in a steady-state operation the amount of the partial hydrogen stream is adjusted so that the partial hydrogen stream meets an energy demand of the reformer during common combustion with the waste gas stream.
2. The method according to claim 1 , wherein a conversion reactor operating at temperatures between 360 and 500° C. and a subsequent conversion reactor operating at temperatures between 210 and 270° C. are used for the conversion stage.
3. The method according to claim 1 , wherein the carbon dioxide separated in the gas scrubber is used for technical applications or processed further to produce a product having a quality that can be used in the foods industry.