Systems and methods of securing immunity to air CO;in alkaline fuel cells

• US 9,214,691 B2
• Filed: 11/25/2014
• Issued: 12/15/2015
• Est. Priority Date: 08/24/2009
• Status: Active Grant

• Current Assignee: Hydrolite Limited
• Original Assignee: Elbit Systems Land and C4I - Tadiran Limited (Elbit Systems Limited)
• Inventors: Gottesfeld, Shimshon
• Primary Examiner(s): HARRIS, GARY D
• Application Number:
  US14/552,700
• Publication Number:
  US 20150155580A1
• Time in Patent Office: 385 Days
• Field of Search: 429/410
• US Class Current: 1/1
• CPC Class Codes: H01M 10/46 Accumulators structurally combined with charging apparatus circuits for charging H02J7/00
• CPC Class Codes: H01M 2300/0014 Alkaline electrolytes
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 8/0668 Removal of carbon monoxide or carbon dioxide
• CPC Class Codes: H01M 8/0693 Treatment of the electrolyte residue, e.g. reconcentrating
• CPC Class Codes: H01M 8/083 Alkaline fuel cells
• CPC Class Codes: H01M 8/1007 with both reactants being gaseous or vaporised H01M8/12 takes precedence
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02E 60/50 Fuel cells

Abstract

An air CO₂ filtration assembly or system is provided that includes CO₂ filters or traps designed and configured with a limited, but high capacity, volume to maximize filtration/absorption of CO₂ from an air stream supplied to an alkaline fuel cell to thereby minimize the CO₂ level in the air stream fed into the fuel cell cathode. The CO₂ filters or traps include at least one thermally regenerative CO₂ chemical filter or trap arranged in a tandem configuration with a strongly bonding CO₂ chemical filter or trap. The combination of the two types of filters or traps sequentially filter/absorb CO₂ from the air stream and reduce the level of CO₂ in the air stream fed into the cathode. The air CO₂ filtration assembly or system may be used in conjunction with electrochemical purging of the alkaline fuel cell that enables removal of CO₂ from the fuel cell by anodic decomposition of accumulated carbonate ions in the fuel cell anode and release of CO₂ through the anode exhaust stream.

Claims

1. An alkaline fuel cell comprising:

an air inlet operatively coupled with a three-trap air filter assembly;

the three-trap air filter assembly including a first thermally regenerative chemical CO2 trap and

a second thermally regenerative chemical CO2 trap;

and a third disposable CO2 chemical trap;

each of the first and second thermally regenerative chemical traps being arranged parallel to one another upstream from and in a tandem configuration with the third disposable CO2 chemical trap, the first and second thermally regenerative chemical traps and the third disposable chemical CO2 trap all being disposed downstream from the inlet, the third disposable chemical CO2 trap disposed upstream from an inlet to the cathode of the alkaline fuel cell;

each of the first and second thermally regenerative chemical traps being configured to reduce the level of CO2 in an air stream passing through a thermally regenerative chemical trap by a first predetermined amount, and the third disposable chemical CO2 trap being configured to reduce the level of CO2 in an air stream passing through the third disposable chemical CO2 trap by a second predetermined amount; and

each of the first and second thermally regenerative chemical traps being switchable to different modes to switch one thermally regenerative chemical trap to actively trap CO2 in an air stream passing through the one thermally regenerative chemical trap while the other thermally regenerative chemical trap undergoes thermal regeneration, wherein the alkaline fuel cell includes an alkaline aqueous electrolyte or an OH-ion conducting polymeric membrane without liquid electrolyte.

2. The alkaline fuel cell of claim 1, wherein each of the first and second thermally regenerative chemical CO2 traps is configured to switch from a CO2 trapping mode to a thermal rejuvenation mode and back to a CO2 trapping mode after a preset period of operation of the fuel cell at a given fuel cell power output.

3. The alkaline fuel cell of claim 2, wherein each of the first and second thermally regenerative chemical CO2 traps is configured to switch from a CO2 trapping mode to a thermal rejuvenation mode by redirection of inlet air and cathode exhaust air streams, wherein cathode exhaust air is redirected to each thermally regenerative chemical CO2 trap for thermal rejuvenation.

4. The alkaline fuel cell of claim 1, wherein the predetermined amount includes a factor of 10, and the second predetermined amount includes a reduction by a factor of 10.

5. The alkaline fuel cell of claim 1, wherein the first and the second thermally regenerative chemical CO2 traps are configured for thermal regeneration by passing a rejuvenating air stream through the thermally regenerative chemical CO2 traps wherein the rejuvenating air stream includes cathode exhaust air supplied to the thermally regenerative chemical CO2 traps with or without additional heating.

6. The alkaline fuel cell of claim 5, wherein any additional heating includes heating provided by an electric heater or a catalytic heater operatively coupled with the fuel cell.

7. The alkaline fuel cell of claim 1, wherein the disposable chemical CO2 trap includes an active material of inorganic hydroxide or hydroxide mixtures, and wherein the active material includes one or more of:

soda lime, lithium hydroxide, potassium hydroxide or sodium hydroxide.