Phosphoric Acid Replenishment

Abstract

The invention of the current application is directed to a cooling spray system and method for a high temperature proton exchange membrane (HTPEM) fuel cell including a HTPEM fuel cell including a cathode and an anode, a liquid sprayer, and a storage vessel containing a mixture of water and electrolyte. The storage vessel is in fluid communication with the liquid sprayer and the liquid sprayer is positioned to spray the mixture of water and electrolyte into the air supply of the cathode.

Claims

1. A cooling spray system for a high temperature proton exchange membrane (HTPEM) fuel cell comprising: an HTPEM fuel cell comprising a cathode and an anode; a sprayer; and a storage vessel containing a water and electrolyte mixture, wherein the storage vessel is in fluid communication with the sprayer and wherein the sprayer is positioned to spray the mixture of water and electrolyte into the air supplied to the cathode.

2. The cooling spray system of claim 1, wherein electrolyte concentration in the mixture of water and electrolyte is 10-15 Mol/L.

3. The cooling spray system of claim 1, wherein the electrolyte is phosphoric acid.

4. The cooling spray system of claim 1, wherein an electrolyte concentration in the mixture of water and electrolyte is less than or equal to an electrolyte concentration in the cathode.

5. The cooling spray system of claim 4, wherein the electrolyte concentration in the mixture of water and electrolyte is regulated by a control system to maintain a constant level of electrolyte in a fuel cell membrane.

6. The cooling spray system of claim 5, wherein the electrolyte concentration is measured in the fuel cell membrane.

7. The cooling spray system of claim 6, wherein the measurement is provided by at least one of DC conductance, AC impedance, and/or spectroscopic analysis.

8. The cooling spray system of claim 1, additionally comprising an anode tail oxidizer (ATO) wherein the ATO is in fluid communication with the cathode.

9. The cooling spray system of claim 1, additionally comprising a separator wherein the separator is positioned downstream from the cathode and collects electrolyte from the cathode exhaust.

10. The cooling spray system of claim 9, wherein the separator is a centrifugal separator.

11. The cooling spray system of claim 1, additionally comprising a compressor in gas communication with the sprayer.

12. A method for cooling a high temperature proton exchange membrane (HTPEM) fuel cell comprising: spraying into the air supply of a cathode of the HTPEM fuel cell with a mixture of water and electrolyte.

13. The method of claim 12 wherein the electrolyte is phosphoric acid.

14. The method of claim 12 wherein an electrolyte concentration in the water and electrolyte mixture is regulated by a controller to control the amount of electrolyte in the fuel cell membranes.

15. The method of claim 12 additionally comprising combusting the cathode exhaust with the anode exhaust.

16. The method of claim 12 additionally comprising separating a mixture of liquid water and electrolyte from air and recycling the mixture of liquid water and electrolyte to a storage vessel which is in fluid communication with the sprayer.

17. The method of claim 12 wherein the electrolyte concentration in the mixture of water and electrolyte is 10-15 Mol/L.

18. The method of claim 12 wherein 2 kg of water is passed through the cathode along with air for each kilowatt-hour of electricity produced.

19. The method of claim 15 wherein heated exhaust from combusting the cathode exhaust with the anode exhaust is delivered to a turbine which recovers energy from the heated exhaust.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 depicts an electrolyte incorporated water spray stream in accordance with the present disclosure.

[0047] FIG. 2 depicts an anode tail oxidizer reclamation stream for electrolyte where air exits from the center of a separator flow while liquid water and electrolyte exit from the perimeter.

[0048] FIG. 3 depicts an HTPEM fuel cell system that includes a cooling water spray and sensors.

[0049] FIG. 4 depicts a flowchart for operation of an HTPEM fuel cell system with electrolyte replenishment in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE DRAWINGS

[0050] FIG. 1 shows a simplified example of how an electrolyte is incorporated into a cooling spray system in which a water spray stream is used to cool a cathode in an HTPEM fuel cell 112. The water and electrolyte mixture 100 is combined and then input into a sprayer 104 along with compressed air. The sprayer 104 distributes the water and electrolyte mixture into the cathode supply air. The air with entrained water and electrolyte passes through the cathode 110, supplying oxygen, absorbing heat, and replenishing any electrolyte that might be carried away in the cathode exhaust air. Wet air with electrolyte 116 exits the cathode 110 on the other side. Additionally, hydrogen 108 enters the anode 114 from a hydrogen storage tank 106 and the anode's 114 hydrogen exhaust 118 exits the other side.

[0051] FIG. 2 shows an anode tail oxidizer reclamation stream for electrolyte where air 124 exits from the center of a separator 126 flow while liquid water and electrolyte 122 exit from the perimeter. Specifically, water and electrolyte mixture 100 (FIG. 1) is provided to a sprayer 104 from a storage vessel 120, for example a tank. Compressed air 102 is also provided to the sprayer 104 via, for example a compressor 130. The sprayer 104 then delivers the electrolyte and water mixture 100 over the surface of the cathode 110 and wet air with electrolyte 116 exits the cathode 110 on the other side. Additionally, hydrogen 108 enters the anode 114 from a hydrogen storage tank 106, and the anode's 114 hydrogen exhaust 118 exits the other side.

[0052] Upon their exit from the cathode, the wet air with electrolytes is collected by separator 126. The liquid 122 containing a mixture of water and electrolyte is delivered to tank 120. The exhaust air 124 is delivered to an anode tail oxidizer (ATO) 128, along with hydrogen 118 from anode 114. The ATO combusts the hydrogen and air. The heated exhaust from the ATO can be then delivered to a turbine 132 to recover some of the energy from the heated exhaust. A separator 126 then extracts the remaining liquid water droplets from the water/electrolyte-air mixture, and the extracted water/electrolyte 122 is recycled to the storage vessel 120.

[0053] FIG. 3 depicts an HTPEM fuel cell system that includes a cooling water spray 104 and sensors 136 which monitor electrolyte concentrations in the fuel cell cathode 110, and optionally in the fuel cell exhaust. A controller 130 is configured to control the addition of electrolyte, typically H.sub.3PO.sub.4, from storage vessel 140 and water from storage vessel 142 to the cooling water spray 104. Compressed air 102 may also be provided to the sprayer 104. Water may also be added as needed to control the fuel cell temperature. Electrolyte is added as needed to control the electrolyte concentration in the fuel cell. The controller 130 regulates the mixing and spray by control of pumps and/or valves 134.

[0054] FIG. 4 depicts a typical operating method for adding electrolyte to an operating HTPEM FC. A series of steps is repeated. In step 200, the electrolyte concentration is measured. This can include direct measurement of the electrolyte concentration within the fuel cell membrane, or indirect measurement such as a measurement of the amount of electrolyte removed with the cathode exhaust. In step 202 an amount of electrolyte is determined for addition to the fuel cell. The electrolyte is dispensed in step 203 and directed to the fuel cell via the sprayer in step 204.

[0055] Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The preceding referenced specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

[0056] From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.