Systems and methods for reliable feedstock delivery at variable delivery rates
View Patent ↗Hydrogen-producing fuel processing assemblies and methods for delivering feedstock to a hydrogen-producing region of a hydrogen-producing fuel processing assembly. In some embodiments, the fuel processing assemblies include a feedstock delivery system that includes a pump assembly and a stall prevention mechanism that is adapted to reduce pressure in an outlet conduit during periods in which the pump assembly is not emitting a liquid outlet stream within or above a hydrogen-producing pressure range. In some embodiments, pressure in the outlet conduit is isolated from pressure in the hydrogen-producing region of the fuel processing assembly and is reduced during periods in which a liquid stream is not being pumped within or above a hydrogen-producing pressure range.
1. A method for delivering feedstock within a hydrogen-producing pressure range to a hydrogen-producing region of a hydrogen-producing fuel processing assembly that is adapted to produce a mixed gas stream containing hydrogen gas as a majority component therefrom, the method comprising:
drawing a liquid stream from a liquid supply containing at least one carbon-containing feedstock;
pumping the liquid stream at least intermittently within or above the hydrogen-producing pressure range into an outlet conduit;
delivering a delivery stream comprising at least a portion of the liquid stream from the outlet conduit to the hydrogen-producing region;
isolating pressure in the outlet conduit from pressure in the hydrogen-producing region during periods in which the liquid stream is not being pumped within or above the hydrogen-producing pressure range;
reducing pressure in the outlet conduit during periods in which the liquid stream is not being pumped within or above the hydrogen-producing pressure range; and
wherein the reducing pressure in the outlet conduit includes diverting a bleed stream comprising at least a portion of the liquid stream from the outlet conduit through a bleed conduit during periods in which the liquid stream is not being pumped within or above the hydrogen-producing pressure range.
2. The method of claim 1 , further comprising:
delivering the bleed stream to at least one of the liquid supply, the liquid stream upstream of the outlet conduit, and a burner associated with the hydrogen-producing fuel processing assembly.
3. The method of claim 1 , further comprising:
restricting flow of the bleed stream through the bleed conduit during periods in which the liquid stream is being pumped within or above the hydrogen-producing pressure range.
4. The method of claim 1 , further comprising:
restricting flow of the bleed stream through the bleed conduit during periods in which pressure in the outlet conduit is within or above the hydrogen-producing pressure range.
5. The method of claim 1 ,
wherein the pumping the liquid stream is facilitated by a pump assembly including a positive displacement pump having an internal chamber and that is adapted to receive the liquid stream into the internal chamber during a refill stroke and to discharge the delivery stream from the internal chamber to the outlet conduit within or above the hydrogen-producing pressure range during a discharge stroke; and
wherein the method further comprises:
delivering the bleed stream to the internal chamber of the positive displacement pump during the refill stroke of the positive displacement pump.
6. The method of claim 5 , wherein the bleed conduit is integral to the pump assembly.
7. The method of claim 1 , further comprising producing, in the hydrogen-producing region, the mixed gas stream from the feed stream.
8. The method of claim 1 , wherein the isolating pressure is performed during periods in which the liquid stream is not being pumped within or above the hydrogen-producing pressure range and in which the hydrogen-producing region is producing the mixed gas stream from the feed stream.
9. The method of claim 1 , wherein the reducing pressure is performed during periods in which the liquid stream is not being pumped within or above the hydrogen-producing pressure range and in which the hydrogen-producing region is producing the mixed gas stream from the feed stream.