A fuel cell system includes a first fuel cell having a first anode and a first cathode, wherein the first anode is configured to output a first anode exhaust gas. The system further includes a first oxidizer configured to receive the first anode exhaust gas and air from a first air supply, to react the first anode exhaust gas and the air in a preferential oxidation reaction, and to output an oxidized gas. The system further includes a second fuel cell configured to act as an electrochemical hydrogen separator. The second fuel cell includes a second anode configured to receive the oxidized gas from the first oxidizer and to output a second anode exhaust gas, and a second cathode configured to output a hydrogen stream. The system further includes a condenser configured to receive the second anode exhaust gas and to separate water and CO.sub.2.

A fuel cell system includes a first fuel cell having a first anode and a first cathode, wherein the first anode is configured to output a first anode exhaust gas. The system further includes a first oxidizer configured to receive the first anode exhaust gas and air from a first air supply, to react the first anode exhaust gas and the air in a preferential oxidation reaction, and to output an oxidized gas. The system further includes a second fuel cell configured to act as an electrochemical hydrogen separator. The second fuel cell includes a second anode configured to receive the oxidized gas from the first oxidizer and to output a second anode exhaust gas, and a second cathode configured to output a hydrogen stream. The system further includes a condenser configured to receive the second anode exhaust gas and to separate water and CO.sub.2.

A fuel cell system including a fuel cell, an off-gas reprocessing unit that is provided downstream of the fuel cell and that at least partially removes at least one of steam or carbon dioxide from an off-gas discharged from the fuel cell, a flow passage that is provided downstream of the off-gas reprocessing unit and that allows a reprocessed off-gas discharged from the off-gas reprocessing unit to flow therethrough, and a controlling unit that modulates the reaction constant K.sub.pa of a reaction A with respect to the reprocessed off-gas discharged from the off-gas reprocessing unit, to 1.22 or more.

A fuel cell system including a fuel cell, an off-gas reprocessing unit that is provided downstream of the fuel cell and that at least partially removes at least one of steam or carbon dioxide from an off-gas discharged from the fuel cell, a flow passage that is provided downstream of the off-gas reprocessing unit and that allows a reprocessed off-gas discharged from the off-gas reprocessing unit to flow therethrough, and a controlling unit that modulates the reaction constant K.sub.pa of a reaction A with respect to the reprocessed off-gas discharged from the off-gas reprocessing unit, to 1.22 or more.

A hydrogen system includes a compressor that causes hydrogen in hydrogen-containing gas supplied to an anode to move to a cathode and produces compressed hydrogen by applying a voltage across the anode and the cathode disposed with an electrolyte membrane interposed therebetween; an anode gas supply channel through which the hydrogen-containing gas flows; a recycle channel through which anode off-gas flows; a drainage channel provided at a position of the recycle channel or anode gas supply channel on a downstream side relative to a position where the recycle channel merges and draining liquid water out of the recycle channel or anode gas supply channel; a pump provided in the recycle channel or the anode gas supply channel on the downstream side relative to the position; and a controller causing the pump to operate in a state where the applied voltage has been decreased when operation of the compressor is stopped.

A hydrogen system includes a compressor that causes hydrogen in hydrogen-containing gas supplied to an anode to move to a cathode and produces compressed hydrogen by applying a voltage across the anode and the cathode disposed with an electrolyte membrane interposed therebetween; an anode gas supply channel through which the hydrogen-containing gas flows; a recycle channel through which anode off-gas flows; a drainage channel provided at a position of the recycle channel or anode gas supply channel on a downstream side relative to a position where the recycle channel merges and draining liquid water out of the recycle channel or anode gas supply channel; a pump provided in the recycle channel or the anode gas supply channel on the downstream side relative to the position; and a controller causing the pump to operate in a state where the applied voltage has been decreased when operation of the compressor is stopped.

A fuel cell system includes an anode configured to output an anode exhaust stream comprising hydrogen, carbon dioxide, and water; and a membrane dryer configured to receive the anode exhaust stream, remove water from the anode exhaust stream, and output a membrane dryer outlet stream. The membrane dryer includes a first chamber configured to receive the anode exhaust stream; a second chamber configured to receive a purge gas; and a semi-permeable membrane separating the first chamber and the second chamber. The semi-permeable membrane is configured to allow water to diffuse therethrough, thereby removing water from the anode exhaust stream. The membrane dryer may further be configured to remove hydrogen from the anode exhaust stream.

A fuel cell system includes an anode configured to output an anode exhaust stream comprising hydrogen, carbon dioxide, and water; and a membrane dryer configured to receive the anode exhaust stream, remove water from the anode exhaust stream, and output a membrane dryer outlet stream. The membrane dryer includes a first chamber configured to receive the anode exhaust stream; a second chamber configured to receive a purge gas; and a semi-permeable membrane separating the first chamber and the second chamber. The semi-permeable membrane is configured to allow water to diffuse therethrough, thereby removing water from the anode exhaust stream. The membrane dryer may further be configured to remove hydrogen from the anode exhaust stream.

An apparatus for purifying impure hydrogen fuel is described that includes a first chamber and a second chamber. The first chamber is configured to receive impure hydrogen fuel in the form of a first mixture of gases with hydrogen gas and carbon monoxide at the first concentration while the second chamber is configured to receive a second mixture of gases with hydrogen gas at the second concentration. The apparatus also includes a solid-state electrolyte that separates the first chamber and the second chamber and includes an adsorbing catalyst. The apparatus also includes a pair of electrodes installed each in the first chamber and the second chamber to create a potential difference is created across the solid-state electrolyte.

An apparatus for purifying impure hydrogen fuel is described that includes a first chamber and a second chamber. The first chamber is configured to receive impure hydrogen fuel in the form of a first mixture of gases with hydrogen gas and carbon monoxide at the first concentration while the second chamber is configured to receive a second mixture of gases with hydrogen gas at the second concentration. The apparatus also includes a solid-state electrolyte that separates the first chamber and the second chamber and includes an adsorbing catalyst. The apparatus also includes a pair of electrodes installed each in the first chamber and the second chamber to create a potential difference is created across the solid-state electrolyte.