Systems and methods for actively controlling steam-to-carbon ratio in hydrogen-producing fuel processing systems

A hydrogen-producing fuel processing system including a reactant delivery system, the reactant delivery system comprising:

• a water source adapted to supply water;
• a water flow-regulating device adapted to accept the water from the water source and produce a water stream;
• a water vaporizer adapted to vaporize the water stream to produce a steam stream;
• a carbon-containing feedstock source adapted to supply a carbon-containing feedstock;
• a carbon-containing feedstock flow-regulating device adapted to accept the carbon-containing feedstock from the carbon-containing feedstock source and produce a carbon-containing feedstock stream;
• a mixing device adapted to combine the steam stream and the carbon-containing feedstock stream to produce a combined feedstock stream;
• a hydrogen-producing region adapted to accept the combined feedstock stream and produce a mixed gas stream including hydrogen gas therefrom;
• a sensor assembly including a steam stream temperature sensor adapted to detect a temperature of the steam stream, a carbon-containing feedstock stream temperature sensor adapted to detect a temperature of the carbon-containing feedstock stream, and a combined feedstock stream temperature sensor adapted to detect a temperature of the combined feedstock stream;
• and
• a controller configured to control a flow rate of the combined feedstock stream and a steam-to-carbon ratio in the combined feedstock stream based at least in part on a desired flow rate of the mixed gas stream, a desired steam-to-carbon ratio in the combined feedstock stream, the temperature of the steam stream, the temperature of the carbon-containing feedstock stream, and the temperature of the combined feedstock stream.

A method of controlling the operation of a hydrogen-producing fuel processing system that includes a reactant delivery system, the method comprising:

• providing a carbon-containing feedstock stream from a carbon-containing feedstock source;
• supplying a steam stream from a steam source;
• combining the carbon-containing feedstock stream and the steam stream in a velocity pump to produce a combined feedstock stream, wherein the supplying includes supplying the steam stream to a primary inlet of the velocity pump and the providing includes providing the carbon-containing feedstock stream to a secondary inlet of the velocity pump;
• measuring a pressure of the carbon-containing feedstock stream associated with the secondary inlet of the velocity pump;
• maintaining the pressure of the carbon-containing feedstock stream associated with the secondary inlet of the velocity pump at a desired pressure;
• applying the combined feedstock stream to a hydrogen-producing region to produce a mixed gas stream that includes hydrogen gas as a majority component;
• controlling a flow rate of the steam stream to the primary inlet of the velocity pump based at least in part on a desired mixed gas stream flow rate;
• purifying at least a portion of the mixed gas stream in a separation assembly to produce a product hydrogen stream and a byproduct stream;
• and
• regulating a pressure of the product hydrogen stream at an exit from the separation assembly to control the pressure of the product hydrogen stream within the separation assembly.

A hydrogen-producing fuel processing system including a reactant delivery system, the reactant delivery system comprising:

• a water source adapted to supply water;
• a water flow-regulating device adapted to accept the water from the water source and produce a water stream;
• a water vaporizer adapted to vaporize the water stream to produce a steam stream;
• a carbon-containing feedstock source adapted to supply a carbon-containing feedstock;
• a carbon-containing feedstock flow-regulating device adapted to accept the carbon-containing feedstock from the carbon-containing feedstock source and produce a carbon-containing feedstock stream;
• a velocity pump adapted to combine the steam stream and the carbon-containing feedstock stream to produce a combined feedstock stream, wherein the steam stream is supplied to a primary inlet of the velocity pump and the carbon-containing feedstock stream is supplied to a secondary inlet of the velocity pump;
• a hydrogen-producing region adapted to accept the combined feedstock stream and produce a mixed gas stream including hydrogen gas as a majority component therefrom;
• a separation assembly adapted to accept at least a portion of the mixed gas stream and to separate the portion of the mixed gas stream into a product hydrogen stream and a byproduct stream;
• a fuel cell stack adapted to accept at least a portion of the product hydrogen stream and an oxidant stream and produce an electrical output therefrom;
• a back pressure regulator between the separation assembly and the fuel cell stack that is adapted to control the pressure upstream of the back pressure regulator;
• a sensor assembly including a carbon-containing feedstock pressure sensor adapted to detect a pressure of the carbon-containing feedstock stream;
• and
• a controller configured to control a flow rate of the combined feedstock stream and a steam-to-carbon ratio in the combined feedstock stream based at least in part on the pressure of the carbon-containing feedstock stream and a desired flow rate of the mixed gas stream.