Fuel unit, refillable hydrogen generator and fuel cell system
A packaged fuel unit and a refillable hydrogen generator that uses the fuel unit to produce hydrogen gas are disclosed. The fuel unit includes a reactant that can undergo a thermal decomposition reaction that produces hydrogen gas when heated to at least a minimum initiation temperature. The reactant is contained within a package that includes a poor thermal conductor with one or more thermal conductor sections for conducting heat from outside the package to the reactant. The hydrogen generator includes a holder with a cavity in which the fuel unit can be removably disposed and a heating system for heating the fuel unit when disposed therein. The hydrogen generator can be part of a fuel cell system including a fuel cell battery that is provided with hydrogen gas from the hydrogen generator.
1. A hydrogen generator comprising:
a base having a cavity therein;
a plurality of replaceable segregated fuel units placed in the cavity, each comprising a single or a plurality of reactant pellets, each reactant pellet comprising a reactant that can undergo thermal decomposition to produce hydrogen gas when heated to at least a minimum initiation temperature;
a plurality of compartments, each containing at least one of the plurality of replaceable, segregated fuel units, each compartment comprising a covering layer that retains the reactant in the compartment;
at least one hydrogen outlet through which hydrogen gas can escape;
at least one replaceable hydrogen purification unit located upstream of the hydrogen outlet;
a lid comprising:
a layer of material with a poor thermal conductivity of less than 5 watts/meter·Kelvin, the layer having a plurality of apertures therethrough, and
a plurality of separate thermal conductor sections, wherein the layer of material with a poor thermal conductivity is configured to provide thermal insulation between the separate thermal conductor sections,
wherein each thermal conductor section is in contact with at least one of the plurality of replaceable, segregated fuel units;
wherein the apertures are covered by the plurality of thermal conductor sections, with each of the thermal conductor sections bonded to the corresponding aperture with a bond around the peripheral portion of the thermal conductor section; and
wherein the cavity is covered by the lid; and
a heating system comprising a plurality of heaters, each heater in thermal communication with at least one of the plurality of thermal conductor sections.
2. The hydrogen generator of claim 1 , wherein the hydrogen purification unit comprises at least one of silica, silicon dioxide, a silicon nitride, silicon carbide, silica aerogel, alumina, aluminum oxide, glass, glass wool, mineral wool, cellular glass, microfiber glass, perlite or a polymer.
3. The hydrogen generator of claim 2 , wherein the polymer is a polyimide, polyetheretherketone, or epoxy-amine composite.
4. The hydrogen generator of claim 1 , wherein the plurality of replaceable, segregated fuel units further comprises an exothermic ignition material to provide heat to initiate the hydrogen-producing reaction of the reactant.
5. The hydrogen generator of claim 4 , wherein the ignition material is disposed proximate to the surface of the plurality of replaceable, segregated fuel units.
6. The hydrogen generator of claim 4 , wherein the ignition material comprises at least one of TiH 2 plus KClO 4 , MnO 2 plus LiAlH 4 , Ni plus Al, Zr plus PbCrO 4 , Fe 2 O 3 plus Al (thermite), or LiAlH 4 plus NH 4 Cl.
7. The hydrogen generator of claim 1 , wherein the plurality of replaceable, segregated fuel units comprises a single reactant pellet.
8. The hydrogen generator of claim 1 , wherein the plurality of replaceable, segregated fuel units comprises a plurality of reactant pellets.
9. The hydrogen generator of claim 8 , wherein porous thermal insulation is disposed between adjacent pellets.
10. The hydrogen generator of claim 1 further comprising a fuel gauge element to determine at least one of the amount of hydrogen gas produced, the amount of hydrogen gas remaining, the amount of reactant consumed, the amount of reactant remaining, the number of segregated quantities of fuel, or the number of segregated quantities of fuel remaining.
11. The hydrogen generator of claim 1 , wherein the bond around the peripheral portion of each of the thermal conductor sections is continuous.
12. The hydrogen generator of claim 1 , wherein the bond around the peripheral portion of each of the thermal conductor sections is discontinuous.