Hydrogen system and method for starting up a hydrogen system

A method for starting up a hydrogen system which includes

• a reformer in which a vaporized hydrocarbon fuel is reformed to yield a reformate gas comprising hydrogen, the reformer including a mixing space and a reforming space, the mixing space comprising a vaporizer for the vaporization of liquid hydrocarbon fuel, water and air inlet or inlets for the supply of steam and air and a glow plug, the reforming space comprising a catalyst for the reforming process and an outlet for the reformate gas,
• a hydrogen consumer arranged in fluid communication with the reformer such that the reformate gas is fed to the hydrogen consumer, the hydrogen consumer consuming at least a part of the hydrogen produced by the reformer,
• an offgas burner which is arranged in fluid communication with the hydrogen consumer and receives offgas exhausted from the hydrogen consumer, the offgas burner combusting remaining reformate gas in the offgas from the hydrogen consumer,
• a first heat exchanger which is in fluid communication with the offgas burner and receives exhaust gas from the offgas burner,
• an air pump which is arranged in fluid communication with the reformer and the offgas burner, the air pump supplying air to said reformer and offgas burner, and
• a water pump which is arranged in fluid communication with the first heat exchanger and, thereafter, the reformer, the water pump feeding water to the first heat exchanger wherein the heat energy contained in the exhaust gas from the offgas burner is used to produce steam, wherein the steam produced by the first heat exchanger is fed to the reformer,
• the method comprising:
• passing the liquid hydrocarbon fuel through the vaporizer and mixing a resulting hydrocarbon vapor with air in the mixing space;
• turning on the glow plug when the hydrocarbon fuel vaporizer has reached a predetermined temperature and thereby starting a combustion of the mixture of hydrocarbon vapor and air;
• continuing said combustion until the reformer catalyst inlet temperature has reached a predefined value;
• after the reformer catalyst inlet temperature has reached the predefined value, terminating said combustion by turning off the supply of liquid hydrocarbon fuel and the glow plug;
• cooling down the mixing space in which said combustion has taken place until a predetermined temperature has been reached at which self-ignition of the mixture of hydrocarbon vapor and air will not take place;
• turning on the glow plug in the offgas burner and the supply of liquid hydrocarbon fuel to the reformer, whereby the reformer starts producing the reformate gas by catalytic partial oxidation;
• passing the reformate gas to the offgas burner wherein the reformate gas is burned off to produce heat;
• using the heat produced by the offgas burner to preheat the air being fed to the reforming, the preheating taking place in a third heat exchanger;
• turning on the water pump when the temperature of the first heat exchanger reaches a predetermined temperature whereby heat energy contained in the exhaust from the offgas burner is used to produce steam;
• feeding the reformer with the mixture of steam and air so that a steam reforming process starts;
• and
• after said steam reforming process starts, gradually increasing the amount of steam being fed into the reformer such that the reforming process is gradually converted to auto thermal reforming.