WO2015054035A1

WO2015054035A1 - System, method, and apparatus for oxygen removal

Info

Publication number: WO2015054035A1
Application number: PCT/US2014/058931
Authority: WO
Inventors: Daniel SCHERSON; Srinivasan Sarangapani
Original assignee: Scherson Daniel; Srinivasan Sarangapani
Priority date: 2013-10-07
Filing date: 2014-10-03
Publication date: 2015-04-16

Abstract

An apparatus (10) for removing oxygen from an enclosed environment (E) includes an electrolyzer (60) operable to remove oxygen from the environment and a zinc-air battery (20) for powering the electrolyzer and removing oxygen from the environment.

Description

SYSTEM, METHOD. AND APPARATUS FOR OXYGEN

REMOVAL

Related Application

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 61/887,523, filed October 7, 2013, the disclosure of which is hereby incorporated by reference in its entirety.

Technical Field

[0002] The invention relates generally to controlling atmospheric conditions in a closed environment. More particularly, the invention relates to a system and method for removing oxygen from an environment, such as a completely or partially sealed enclosure.

[0003] There are many scenarios in which it may be desirable to remove oxygen from an environment in which its presence can be detrimental to materials known to degrade in the presence of this highly reactive gas. These scenarios, for example, can be industrial, commercial, experimental, consumer, or other such scenarios. One such scenario involves the storage of fresh produce, i.e., fresh fruits and vegetables. Another such scenario involves the storage of drugs and medicines whose shelf-life or effectiveness can be reduced by exposure to oxygen.

[0004] During storage, fresh produce undergoes respiration. During respiration, sugars and other compounds are broken down within the cells of the stored produce. This releases energy, carbon dioxide, water and heat. The energy is needed by the living cells of the stored product.

[0005] Several factors regulate respiration. In general, the higher the temperature, within normal ranges, the faster the respiration rate. Thus, it is important to refrigerate produce in order to prolong its shelf life. The presence of soluble sugars in cells also influences the rate of respiration. For example, at 70° F, the respiration rate of sweet corn is 3.6 times as fast as it is at 41° F. Thus, adequate cooling is essential. The rate of respiration also varies directly with water content. At a given temperature, succulent plant parts, such as head lettuce, respire more rapidly than non-succulent products, such as sweet or Irish potatoes. Immature vegetables respire more rapidly than mature vegetables.

[0006] The respiration rate is also influenced by the amount of oxygen in the storage environment. During respiration, oxygen is absorbed and carbon dioxide is released. Consequently, an airtight area will allow a decrease in oxygen and an increase in carbon dioxide. As a result, the respiration rate gradually decreases and freshness is prolonged. Accordingly, it can be desirable to maintain the rate of respiration in fresh produce at low levels in order maintain its freshness.

Summary of the Invention

[0007] The present invention relates to an apparatus for removing oxygen from an enclosed environment. According to one aspect, the apparatus includes an electrolyzer operable to remove oxygen from the environment, and a zinc-air battery for powering the electrolyzer and removing oxygen from the environment.

[0008] According to another aspect, alone or in combination with any of the preceding aspects, the electrolyzer comprises an anode and a cathode, and the cathode is exposed to the enclosed environment.

[0009] According to another aspect, alone or in combination with any of the preceding aspects, the zinc-air battery comprises a zinc electrode and an air electrode, and the air electrode is exposed to the enclosed environment.

[0010] According to another aspect of this invention, alone or in combination with any of the preceding aspects, the electrolyzer is adapted to allow the cathode to reduce oxygen present within the enclosure via the redox reaction

4e + 2HsO + Os→ 40H- Alkaline Media

O2 + 4e + 4h⁺→ 2H2O Acid Media instead of generating hydrogen gas.

[0011] According to another aspect, alone or in combination with any of the preceding aspects, the electrolyzer includes an anode and a cathode, the cathode being exposed to the enclosed environment. The zinc-air battery includes a zinc electrode and an air electrode. The air electrode is exposed to the enclosed environment. The apparatus also includes a device for blocking exposure to the enclosed environment of the zinc-air battery. [0012] According to another aspect, alone or in combination with any of the preceding aspects, the apparatus includes a seal for sealing the enclosure.

[00131 According to another aspect, alone or in combination with any of the preceding aspects, the apparatus includes circuitry for controlling the power supplied to the electrolyzer.

[0014] According to another aspect, alone or in combination with any of the preceding aspects, the apparatus is adapted to be self-regulating due to the oxygen supply for the zinc-air battery being the enclosed environment.

[0015] According to another aspect, alone or in combination with any of the preceding aspects, the apparatus includes means for deactivating the electrolyzer in response to the enclosed environment being exposed to the surrounding atmosphere, and means for reactivating the electrolyzer in response to the enclosed environment being sealed from the surrounding atmosphere.

[0016] According to another aspect, alone or in combination with any of the preceding aspects, the zinc-air battery is configured as a removable element that can be replaced upon expiration.

[0017] According to another aspect, alone or in combination with any of the preceding aspects, the electrolyzer is configured as a removable element that can be replaced upon expiration.

[0018] According to another aspect, alone or in combination with any of the preceding aspects, the apparatus includes means, such as a sensor, for indicating at least one of the available residual oxygen consuming capacity of the apparatus and a warning signal that the zinc-air battery needs replaced. [0019] According to another aspect, alone or in combination with any of the preceding aspects, the electrolyzer can be an acid electrolyzer.

[0020] According to another aspect, alone or in combination with any of the preceding aspects, the electrolyzer can be an alkaline electrolyzer.

[0021] According to another aspect, alone or in combination with any of the preceding aspects, a system for storing products that are sensitive to exposure to oxygen includes an enclosure for storing the products, an electrolyzer for removing oxygen from the enclosure, and an electrical power source for powering the electrolyzer. The power source is adapted to consume oxygen in order to produce the electrical power. According to yet another aspect, the power source comprises a zinc-air battery having an air electrode exposed to the enclosure.

[00221 According to further aspect, alone or in combination with any of the preceding aspects, a method for removing oxygen from an enclosed environment includes providing an electrolyzer with a cathode exposed to the enclosed environment, providing a zinc-air battery for powering the electrolyzer and exposing an air electrode of the zinc-air battery to the enclosed environment, which will also remove oxygen from the enclosure,

Brief Description of the Drawings

[0023] The foregoing and other features of the invention will become apparent to those skilled in the art to which the invention relates upon reading the following description with reference to the accompanying drawings, in which:

[0024] Fig. 1 illustrates a system and apparatus for reducing oxygen levels. [0025] Fig. 2 illustrates an example configuration of a zinc-air battery component of the system and apparatus of Fig. 1.

[0026] Fig. 3 illustrates a conventional use of an electrolyzer.

[0027] Fig. 4 illustrates the use of an electrolyzer component of the system and apparatus of Fig. 1.

[0028] Fig. 5 is a block diagram illustrating a method performed by the system and apparatus of Fig. 1.

Description

[0029] The invention relates generally to controlling atmospheric conditions in a closed environment. More particularly, the invention relates to a system and method for removing oxygen from, an environment, such as a completely or partially sealed enclosure. According to the invention, and referring to Fig. 1, a system includes an apparatus 10 for removing oxygen from an environment, indicated generally at E. The apparatus 10 includes a zinc-air (Zn/Oa) battery 20 and an electrolyzer 60.

[0030] Zinc-air batteries are a type of metal-air batteries that produce electrical energy by oxidizing zinc at one electrode and reducing oxygen from the air at the other. Zinc-air batteries have high energy densities and are relatively inexpensive to produce. Zinc-air batteries range in size from small button cells {e.g., for hearing aids) to larger batteries {e.g., for cameras) and very large batteries {e.g., for electric vehicle propulsion). An example of a button cell zinc-air battery is illustrated in Fig. 2, and serves as an example of the construction of the battery 20 in Fig. 1.

[0031] Zinc-air batteries include zinc anode, typically formed by a mass of porous zinc particles saturated with an electrolyte to form a paste/gel/emulsion, and a cathode typically formed from catalyzed carbon. One or more holes in the battery can/container allow oxygen from the air to enter the cathode and be reduced on the carbon surface. During discharge, the oxygen reacts at the cathode and forms hydroxyl ions which migrate into the zinc anode, forming zincate Zn(OH)^² and releasing electrons to travel to the cathode:

2Zn + 80H→ 2[Zn(OH) iP~ + 4e

0₂ + 4e + 2HsO→ 40H-

2Zn + 2H2O + 40H→ 2[Zn(OH)₄]² Net Reaction

[0032] Electrolysis involves the use of electric current to stimulate a non-spontaneous reaction typically to separate a substance into its original components/elements. For instance, a typical use of electrolysis is water electrolysis, where water is separated into its components - ¾ and O2. Polymer electrolyte membrane (PEM) electrolyzers are a type of water electrolyzer.

[0033] The fundamental components of an electrolyzer are illustrated in Fig. 3. Referring to Fig. 3, the electrolyzer 100 includes an anode 110 and a cathode 120 separated by a membrane 130. In Fig. 3, the PEM electrolyzer 100 is illustrated performing its primary conventional use - extracting hydrogen from water. The reactions that take place during the conventional PEM electrolysis illustrated in Fig. 3 are shown below:

H₂0 > 2H⁺ + 2 °2 + 2e^_ Anode

2H⁺ + 2e^~— * H2 Cathode H₂0 > H2 + 2 °2 Net Reaction

The electrolyzer 100 illustrated in Fig. 3 is an acid electrolyzer that performs electrolysis according to the above -listed reaction equations for acid media. Those skilled in the art will appreciate that the electrolyzer 100 could be an alkaline electrolyzer that performs electrolysis in a known manner according to reaction equations for alkaline media that are analogous to those listed above.

[0034] Operation of the PEM electrolyzer shown in Fig. 3 depends upon a sufficiently high voltage being supplied to the electrolyzer to stimulate the desired reactions to take place at the anode and cathode. If the voltage supplied to the electrolyzer is less than required, the reactions shown above will not take place.

[0035] Referring to Fig. 4, the electrolyzer 100, operating in the presence of air, and at a voltage less than required for electrolysis of water, consumes oxygen in a reduction reaction that produces water. The reactions that take place during this operation of the PEM electrolyzer 100 illustrated in Fig. 4 are shown below:

0₂ + 4e + 4H⁺ > 2H₂0 Cathode

2H₂ O > 0₂ + 4e + 4H⁺ Anode

The electrolyzer 100 illustrated in Fig. 4 is an acid electrolyzer that performs electrolysis according to the above-listed reaction equations for acid media. Those skilled in the art will appreciate that the electrolyzer 100 could be an alkaline electrolyzer that performs electrolysis in a known manner according to reaction equations for alkaline media that are analogous to those listed above.

[0036] Referring to Fig. 1, the environment E is defined by an enclosure 14. The enclosure 14 can have any desired configuration designed to provide a particular environment commensurate with the purpose for which the O2 removal is desired. For example, in a consumer application for removing O2 from an environment where fresh produce is stored, the enclosure 14 may be a refrigerator crisper drawer. Similarly, in a commercial produce storage application, the enclosure 14 may be a shipping container or a walk-in cooler. In a medical application, the enclosure 14 may be a container or cooler in which drugs or medicine are stored or transported.

[0037] Since the environment E is one in which it is desired to remove oxygen, the enclosure 14 is sealed in a manner suitable under the circumstances to help prevent outside air from entering the enclosure 14 and environment E. Of course, no seal can be perfect. But, through careful and sound design, the seal of the enclosure 14 can be optimized within the confines of limitations such as cost, size, materials, etc.

[0038] As shown in Fig. 1, the enclosure 14 supports the zinc-air battery 20 and the electrolyzer 60. The enclosure 14 itself could have portions adapted to receive and support zinc-air battery 20 and the electrolyzer 60. Alternatively, the zinc-air battery 20 and the electrolyzer 60 could be housed in a separate structure or housing that itself is mounted in the enclosure 14. The specific structure of the enclosure 14 and any structure 12 that houses the battery 20 and/or the electrolyzer 60 can vary depending on the application in which the apparatus 10 is implemented.

[0039] For example, in one particular configuration of the system and apparatus 10, the zinc-air battery 20 and the electrolyzer 60 could be separate components formed as units or cartridges that can be removed and replaced as they expire. In this instance, the structure 12 supporting the battery 20 and electrolyzer 60 could be a separate component that is installed in the enclosure 14. Alternatively, the structure 12 supporting the battery 20 and electrolyzer 60 could be an integral portion of the enclosure 14, with the battery and electrolyzer cartridges being installed directly therein.

[0040] Electrically, the anode 62 of the electrolyzer 60 is connected to the electrode 24 of the battery 20. The cathode 64 of the electrolyzer 60 is connected to the zinc electrode 22 of the zinc-air battery 20. The electrolyzer cathode 64 and the air electrode 24 are exposed to the environment E via air ducts or passages 26, 66 in the zinc-air battery 20 and electrolyzer 60, respectively. The electrolyzer anode 62 is exposed outside the environment E, e.g., to the atmosphere, via air ducts or passages 68 in the electrolyzer 60.

[0041] In operation, the zinc-air battery 20 and electrolyzer 60 work in concert to remove oxygen from the environment E. The zinc-air battery 20 consumes oxygen when it generates electrical current. This current is supplied to the electrolyzer 60 at a level such that it also consumes oxygen in the reduction reaction described above. To this end, the apparatus 10 may include electronics/circuitry, illustrated schematically at 50, that regulates the power supplied to the electrolyzer 60 by the zinc-air battery 20. The electronic circuitry 50 will maintain the voltage of the electrolyzer 60 below that required for hydrogen evolution.

[0042] As the oxygen partial pressure within the enclosure 14 is reduced, the voltage of the Zn-air battery 20 will decrease to values below those required to power the electrolyzer 60. The apparatus 10 could thus be adapted to shut down automatically when the oxygen level falls to a certain level. This self-limiting feature serves to extend the life of the battery 20. To this end, the circuitry 50 could also be adapted to shut down (i.e., break the circuit) when the voltage generated by the battery 20 falls below a certain level.

[0043] The enclosure 14 can also be adapted to extend the life of the zinc-air battery 20 through the inclusion of a mechanical device, illustrated schematically at 52 in Fig. 1, installed adjacent to the air passages 26 through which oxygen is supplied to the air electrode 24 of the zinc-air battery 20. The device 52 is adapted to expose the air electrode 24 to the environment E when the enclosure 14 is closed and block exposure of the air electrode to the environment when the enclosure is opened. This will prevent direct contact of the air electrode 24 battery to the atmosphere when the enclosure 14 is opened, e.g., to remove an item stored therein.

[0044] The device 52 can be, for example, a door or gasket that is adapted to move {e.g., through a mechanical or electro-mechanical actuating mechanism) in response to opening the enclosure 14 to access the environment E. For instance, the device 52 can be as simple as a lid or cover adjacent to which the battery 20 slides when the enclosure is opened. This would be convenient, for example, in the case of a refrigerator crisper drawer that is opened routinely— the battery 20 could slide adjacent the device 52 (cover) when the drawer is slid, open.

[0045] Further, the electronics/circuitry 50 can be adapted to perform additional monitoring and control functions of the apparatus 10 to optimize the overall operation of the zinc-air battery 20 and electrolyzer 60. For instance, the electronics/circuitry 50 can be adapted to, in certain cases, allow for an external power source to power the electrolyzer 60 in the event of a power failure or expiration of the zinc-air battery 20. The external power source can, for example, be a conventional (e.g., alkaline) battery source or system power from the environment of the enclosure 14 (e.g., refrigerator power). It will thus be envisioned that the electrolyzer 60 could operate in this mode without using the zinc-air battery 20, although the self- re ulating features described above would not be realized.

As another example, the electronics/circuitry 50 can include a mechanism or means, such as a switch, that is adapted to activate and deactivate the electrolyzer when the enclosure 14 is opened, exposing the environment E to the surrounding atmosphere. As an additional example, the electronics/circuitry 50 can include a monitoring circuit including means, such as a sensor, that can indicate a residual oxygen consuming capacity of the apparatus 10 and also provide a warning signal to the user that the battery or electrolyzer cartridge needs to be changed. As a further example, the electronics/circuitry 50 can include sensor electronics including means, such as a sensor, for monitoring the oxygen level in the environment E.

[0046J Still further, the electronics/circuitry 50 can be adapted to control operation of the apparatus 1.0 to maintain a desired level of oxygen within the enclosure 14. For example, for a given configuration of the zinc-air battery 20, a given level of oxygen in the enclosure 14 can be associated with a certain voltage or power output of the battery. The battery voltage/power can thus be used as an oxygen sensor of sorts. This being the case, the electronics/circuitry 50 can be configured to monitor oxygen content in the enclosure 14 via the battery power/voltage and switch or otherwise control power supplied to the electrolyzer 60 based on the monitored oxygen content.

[0047] Referring to Fig. 5, the system and apparatus 10 is adapted to perform a process or method 150 for removing oxygen from an enclosed environment. The method 150 begins at step 160, where an electrolyzer is provided with a cathode exposed to the enclosed environment. At step 170, a zinc-air battery is provided to power the electrolyzer. At step 180, the air electrode of the zinc-air battery is exposed to the enclosed environment. Through this process, the zinc- air battery provides power for operating the electrolyzer. The zinc-air battery consumes oxygen in the enclosed environment to power the electrolyzer. The electrolyzer functions to remove oxygen from the enclosed environment. 48] From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.

Claims

Having described the invention, the following is claimed:

1. An apparatus for removing oxygen from an enclosed environment, comprising:

an electrolyzer operable to remove oxygen from the environment; and

a zinc-air battery for powering the electrolyzer and removing oxygen from the environment.

2. The apparatus recited in claim 1, wherein the electrolyzer comprises an anode and a cathode, the cathode being exposed to the enclosed environment.

3. The apparatus recited in claims 1 or 2, wherein the zinc- air battery comprises a zinc electrode and an air electrode, the air electrode being exposed to the enclosed environment.

4. The apparatus recited in any of the preceding claims, wherein to remove oxygen from the enclosed environment, the electrolyzer reduces oxygen from within the enclosure and evolve oxygen on the outside of the enclosure serving as an oxygen pump.

5. The apparatus recited in any of the preceding claims, wherein:

the electrolyzer comprises an anode and a cathode, the cathode being exposed to the enclosed environment; and

the zinc-air battery comprises a zinc electrode and an air electrode, the air electrode being exposed to the enclosed environment, the apparatus further comprising a device for blocking exposure to the enclosed environment of the zinc-air battery.

6. The apparatus recited in any of the preceding claims, further comprising a seal for sealing the enclosure.

7. The apparatus recited in any of the preceding claims, further comprising circuitry for controlling the power supplied to the electrolyzer.

8. The apparatus recited in any of the preceding claims, wherein the apparatus is adapted to be self-regulating due to the oxygen supply for the zinc-air battery being the enclosed environment.

9. The apparatus recited in any of the preceding claims, further comprising means for deactivating the electrolyzer in response to the enclosed environment being exposed to the surrounding atmosphere, and means for reactivating the electrolyzer in response to the enclosed environment being sealed from the surrounding atmosphere.

10. The apparatus recited in any of the preceding claims, wherein the zinc-air battery is configured as a removable element that can be replaced upon expiration.

11. The apparatus recited in any of the preceding claims, wherein the electrolyzer is configured as a removable element that can be replaced upon expiration.

12. The apparatus recited in any of the preceding claims, further comprising means for indicating at least one of the available residual oxygen consuming capacity of the apparatus and a warning signal that the zinc-air battery needs replaced.

13. The apparatus recited in any of the preceding claims, further comprising means for monitoring the level of oxygen in the environment.

14. The apparatus recited in any of the preceding claims, wherein the electrolyzer is an acid electrolyzer.

15. The apparatus recited in any of the preceding claims, wherein the electrolyzer is an alkaline electrolyzer.

16. A system for storing products that are sensitive to exposure to oxygen, comprising:

an enclosure for storing the products;

an electrolyzer for removing oxygen from the enclosure; and

an electrical power source for powering the electrolyzer, wherein the power source is adapted to consume oxygen in order to produce the electrical power.

17. The system recited in claim 16, wherein the power source comprises a zinc-air battery having an air electrode exposed to the enclosure.

18. A method for removing oxygen from an enclosed environment, comprising:

providing an electrolyzer with a cathode exposed to the enclosed environment;

providing a zinc-air battery for powering the electrolyzer; and

exposing an air electrode of the zinc-air battery to the enclosed environment.