Systems and methods for reliable feedstock delivery at variable delivery rates

A hydrogen-producing fuel processing assembly, comprising:

• a hydrogen-producing region adapted to receive at least a feed stream containing at least a carbon-containing feedstock and to produce a mixed gas stream containing hydrogen gas as a majority component therefrom, the hydrogen-producing region further adapted to operate within a hydrogen-producing pressure range;
• and
• a feedstock delivery system adapted to deliver at least a portion of the feed stream to the hydrogen-producing region, wherein the feedstock delivery system is in communication with a liquid supply containing at least the carbon-containing feedstock, wherein the feedstock delivery system includes:
• a pump assembly adapted to draw from the liquid supply a liquid inlet stream containing at least the carbon-containing feedstock and to emit a liquid outlet stream at least intermittently within or above the hydrogen-producing pressure range, the pump assembly having an inlet for receiving the liquid inlet stream and an outlet for emitting the liquid outlet stream;
• an inlet conduit through which the liquid inlet stream is drawn to the pump assembly;
• an outlet conduit through which the liquid outlet stream is emitted from the pump assembly;
• a delivery conduit in fluid communication with the outlet conduit and the hydrogen-producing region and through which a delivery stream is delivered to the hydrogen-producing region;
• and
• a stall prevention mechanism, the stall prevention mechanism including:
• a check valve positioned between the outlet conduit and the hydrogen-producing region and adapted to isolate pressure in the outlet conduit from pressure in the hydrogen-producing region during periods in which the pump assembly is not emitting the liquid outlet stream within or above the hydrogen-producing pressure range;
• and
• a bleed conduit in fluid communication between the outlet conduit and at least one of the liquid supply, the inlet conduit, the pump assembly, and a burner associated with the hydrogen-producing fuel processing assembly, and through which a bleed stream at least intermittently flows;
• wherein the stall prevention mechanism is adapted to reduce pressure in the outlet conduit during periods in which the pump assembly is not emitting the liquid outlet stream within or above the hydrogen-producing pressure range.