Hydrogen generation apparatus, fuel cell system including the same, and method of operating hydrogen generation apparatus

A hydrogen generation apparatus comprising:

• a first desulfurizer configured to remove a sulfur component from a raw material gas at a normal temperature;
• a second desulfurizer configured to remove the sulfur component from the raw material gas by hydrogenating the sulfur component;
• a reformer configured to generate a hydrogen-containing reformed gas from the raw material gas from which the sulfur component has been removed by at least one of the first desulfurizer and the second desulfurizer;
• and
• a recycle passage through which a part of the reformed gas generated by the reformer is mixed into the raw material gas that is to be supplied to the second desulfurizer, wherein
• the hydrogen generation apparatus is configured such that
• after installation or maintenance of the hydrogen generation apparatus, the raw material gas is supplied to the reformer through the first desulfurizer until a catalyst in the second desulfurizer is activated by a mixed gas of the reformed gas supplied through the recycle passage and the raw material gas, and
• after the catalyst in the second desulfurizer is reduced by the reformed gas supplied through the recycle passage, the raw material gas is supplied to the reformer through the second desulfurizer.