Electrochemical oxygen consumption system

Abstract

The present disclosure proposes an electrochemical oxygen consumption system configured to consume oxygen in air in a confined space, the electrochemical oxygen consumption system comprising a stack comprising a plurality of elementary constituent units, each elementary constituent unit comprising a cathode and an anode, the electrochemical oxygen consumption system is configured to introduce air in the confined space into the cathode such that oxygen in the air is reduced at the cathode to consume oxygen in the air, and wherein the electrochemical oxygen consumption system is configured to discharge deoxygenated air into the confined space. The electrochemical oxygen consumption system disclosed by the utility model is relatively low in cost, relatively small in size and capable of realizing rapid oxygen consumption.

Description

Technical Field

[0001] The present disclosure relates to the field of fire prevention and firefighting in confined spaces, and more particularly to an electrochemical oxygen consumption system for fire prevention. Background Art

[0002] In modern life, for various reasons, it may be necessary to store materials in confined spaces such as warehouses. It is well known that the volume concentration (i.e. volume percentage) of oxygen in the air is about 21%. At this concentration, combustible materials will ignite and then burn as long as they reach the ignition point. For most combustible materials, when the oxygen concentration in the air is less than 10%, it can be prevented from ignition and subsequent combustion. For spaces where people enter and exit, a design oxygen concentration level of 14-15% is usually used for fire prevention to ensure that the oxygen concentration in the air is sufficient to maintain the normal physiological needs of the human body.

[0003] Conventional fire protection systems usually dilute the oxygen in the air by producing inert gas, such as nitrogen, to achieve a target oxygen concentration in the air. However, the equipment used to produce inert gas is expensive, bulky, and occupies a large space. Utility Model Content

[0004] The utility model aims to propose a new solution for reducing the oxygen concentration in the air, that is, an electrochemical oxygen consumption system is proposed to reduce the oxygen concentration in the air by consuming oxygen in the air. The electrochemical oxygen consumption system has low cost, small volume, and can achieve rapid oxygen consumption. In addition, the electrochemical oxygen consumption system uses deionized water as a raw material for oxygen consumption, and the products are only water and oxygen, so it does not pollute the environment.

[0005] According to one embodiment of the present disclosure, an electrochemical oxygen consumption system is proposed, which is configured to consume oxygen in the air in a confined space, and the electrochemical oxygen consumption system includes a fuel cell stack, which includes a plurality of basic component units, each of which includes a cathode and an anode, wherein the electrochemical oxygen consumption system is configured to introduce air in the confined space into the cathode so that the oxygen in the air is reduced at the cathode to consume the oxygen in the air, and wherein the electrochemical oxygen consumption system is configured to discharge deoxygenated air into the confined space.

[0006] In one embodiment, each of the basic constituent units includes: an ion exchange membrane located in the middle; an anode catalyst layer located on one side of the ion exchange membrane; a cathode catalyst layer located on the other side of the ion exchange membrane; an anode diffusion layer located outside the anode catalyst layer; and a cathode diffusion layer located outside the cathode catalyst layer, wherein the anode catalyst layer and the anode diffusion layer constitute the anode, and the cathode catalyst layer and the cathode diffusion layer constitute the cathode.

[0007] In one embodiment, the ion exchange membrane is a proton exchange membrane, and wherein the electrochemical reactions occurring at the anode and the cathode are respectively: anode: 2H2O→4H++O2+4e-; cathode: O2+4H++4e-→2H2O.

[0008] In one embodiment, the electrochemical oxygen consumption system further includes a water tank, a water pump and a first gas-liquid separator, wherein the water tank is used to store water, the water pump is configured to pump the water in the water tank to the anode for reaction, the oxygen generated by the reaction and the unreacted water flow from the battery stack into the first gas-liquid separator, the first gas-liquid separator is configured to separate the oxygen and the unreacted water, the oxygen is then discharged outside the enclosed space, and the unreacted water is sent back to the water tank.

[0009] In one embodiment, the electrochemical oxygen consumption system also includes an air pump and a second gas-liquid separator, wherein the air pump is configured to pump the air in the enclosed space to the cathode for reaction, and the water and deoxygenated air generated by the reaction flow from the battery stack into the second gas-liquid separator, and the second gas-liquid separator is configured to separate the water generated by the reaction from the deoxygenated air, and the deoxygenated air is subsequently discharged into the enclosed space.

[0010] In one embodiment, the ion exchange membrane is an anion exchange membrane, and wherein the electrochemical reactions occurring at the anode and the cathode are: anode: 4OH-→O2+2H2O+4e-; cathode: O2+2H2O+4e-→4OH-.

[0011] In one embodiment, the electrochemical oxygen consumption system also includes a water tank, a water pump, a first gas-liquid separator, an air pump, and a second gas-liquid separator. The water tank is used to store water. The water pump is configured to pump the water in the water tank to the cathode for reaction. The air pump is configured to pump the air in the enclosed space to the cathode for reaction. Unreacted water and deoxygenated air flow into the second gas-liquid separator. The second gas-liquid separator is configured to separate the unreacted water and the deoxygenated air. The unreacted water is then returned to the water tank, and the deoxygenated air is then discharged into the enclosed space. The first gas-liquid separator is configured to separate the oxygen and water generated by the anode reaction, and the oxygen is then discharged outside the enclosed space.

[0012] In one embodiment, the electrochemical oxygen consumption system further includes an oxygen concentration sensor, which is disposed on a pipeline between the air pump and the fuel cell stack.

[0013] In one embodiment, the electrochemical oxygen consumption system further includes an additional oxygen concentration sensor, which is disposed in the enclosed space at a location far away from the oxygen concentration sensor.

[0014] In one embodiment, the electrochemical oxygen consumption system further includes a control unit, which communicates with the fuel cell stack, the water pump, the air pump, and the oxygen concentration sensor.

[0015] In general, the various embodiments of the present disclosure may be combined and coupled in any possible manner within the scope of the present disclosure. These and other aspects, features and / or advantages of the present disclosure will be apparent and elucidated with reference to the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present disclosure will be described by way of example with reference to the following drawings, in which:

[0017] Figure 1 Schematically shows an electrochemical oxygen consumption system according to one embodiment of the present disclosure;

[0018] Figure 2 Schematically shows an electrochemical oxygen consumption system according to another embodiment of the present disclosure;

[0019] Figure 3 The structure of the basic component unit of the stack of the electrochemical oxygen consumption system is schematically shown; and

[0020] Figure 4 The performance curve of the battery stack of the electrochemical oxygen consumption system is shown.

[0021] It should be understood that the drawings only illustrate several ways of implementing the present disclosure and should not be construed as limiting other possible embodiments within the scope of protection of the appended claims. The scope of protection of the present disclosure is limited only by the appended claims. DETAILED DESCRIPTION

[0022] In order to reduce the oxygen concentration in the air in a confined space, the utility model proposes several electrochemical oxygen consumption systems by way of example. These electrochemical oxygen consumption systems are based on electrochemical principles and continuously consume oxygen in the air by reducing the oxygen in the air at the cathode, thereby achieving the purpose of reducing the oxygen concentration in the air. Figure 1-Figure 4 The utility model is described in detail.

[0023] Figure 1 The electrochemical oxygen consumption system according to one embodiment of the present disclosure is schematically shown. Figure 1 As shown, the electrochemical oxygen consumption system includes a fuel cell stack 1, a water tank 2, a water pump 3, a first gas-liquid separator 4, an anode oxygen exhaust pipe 5, an air pump 6, an oxygen concentration sensor 7, a second gas-liquid separator 8, a cathode deoxygenated air exhaust pipe 9, a cathode drain pipe 10 and a control unit 11.

[0024] The fuel cell stack 1 is the core component of the electrochemical oxygen consumption system, which can be formed by stacking multiple basic component units. Figure 3 The structure of the basic component unit is schematically shown. Figure 3 As shown, the basic component unit includes: an ion exchange membrane 101 located in the middle; an anode catalyst layer 102 located on one side of the ion exchange membrane 101 (the left side in the figure); a cathode catalyst layer 103 located on the other side of the ion exchange membrane 101 (the right side in the figure); an anode diffusion layer 104 located on the outside of the anode catalyst layer 102 (the left side in the figure); and a cathode diffusion layer 105 located on the outside of the cathode catalyst layer 103 (the right side in the figure). Among them, the anode catalyst layer 102 and the anode diffusion layer 104 constitute the anode of the basic component unit, and the cathode catalyst layer 103 and the cathode diffusion layer 105 constitute the cathode of the basic component unit. The anode diffusion layer 104, the anode catalyst layer 102, the ion exchange membrane 101, the cathode catalyst layer 103 and the cathode diffusion layer 105 are stacked on each other and fixed together by fasteners to form a complete basic component unit. Multiple basic component units are stacked together by bipolar plates inserted between them to form a stack 1. The bipolar plate is used to separate the basic component units and has anode reactant flow channels and cathode reactant flow channels spaced apart from each other. The bipolar plate located on the anode side of a basic component unit can supply the anode reactant to the anode of the basic component unit so that the anode reactant is oxidized at the anode. Figure 3The arrow A in the figure shows the flow of the anode reactant; the bipolar plate located on the cathode side of the basic component unit can supply the cathode reactant to the cathode of the basic component unit, so that the cathode reactant is reduced at the cathode, Figure 3 Arrow B in shows the cathode reactant flow. In the present invention, the cathode reactant used for reduction at the cathode includes oxygen, or air (which contains oxygen). In addition, the present invention does not limit the anode reactant.

[0025] The water tank 2 is used to store water. The water in the water tank 2 is pumped to the anode of the battery stack 1 by the water pump 3 and is oxidized at the anode as an anode reactant. In a preferred embodiment, the water in the water tank 2 is deionized water, and most or all of the ionic impurities have been removed, thereby avoiding interference with the electrochemical reaction and corrosion of the battery stack components, which affects the life of the battery stack 1.

[0026] On the other hand, the air pump 6 is configured to pump the air in the enclosed space S (roughly shown in the box in the figure) to the cathode of the stack 1, so that the oxygen therein is reduced at the cathode as a cathode reactant. The enclosed space S is a space to be deoxygenated. For example, the enclosed space S is a warehouse for storing combustible materials. It will be understood that an air filter (not shown in the figure) can be provided upstream of the air pump 6 to filter out impurities in the air, thereby avoiding contamination of the stack 1.

[0027] exist Figure 1 In the embodiment of the present invention, the ion exchange membrane 101 used in the basic component unit of the stack 1 is a proton exchange membrane. In this case, the electrochemical reactions occurring at the anode and cathode of the stack 1 are:

[0028] Anode: 2H2O→4H + +O2+4e -

[0029] Cathode: O2+4H + +4e - →2H2O

[0030] As shown in the above electrochemical reaction formula, water reacts at the anode to generate hydrogen ions (i.e., protons), oxygen, and electrons. Hydrogen ions pass through the proton exchange membrane to reach the cathode, and electrons pass through the external circuit to reach the cathode, thereby reacting with oxygen at the cathode to generate water. The oxygen generated by the anode reaction and the unreacted water flow out of the anode together and enter the first gas-liquid separator 4. In the first gas-liquid separator 4, water and oxygen are separated, and the oxygen therein can be discharged into the atmosphere outside the enclosed space S through the anode oxygen exhaust pipe 5. Alternatively, the oxygen can be recovered, stored, and reused. The water separated by the first gas-liquid separator 4 can be sent back to the water tank 2 for recycling. The water generated by the cathode reaction and the remaining air (most of which has been removed) flow out of the cathode together and enter the second gas-liquid separator 8. In the second gas-liquid separator 8, water and deoxygenated air (i.e., air in which most of the oxygen has been consumed) are separated, and the deoxygenated air therein can be directly discharged into the enclosed space S through the cathode deoxygenated air exhaust pipe 9, and the water therein can be discharged through the cathode drain pipe 10. Alternatively, the cathode drain pipe 10 may be connected to the water tank 2 so that the water generated by the cathode reaction can be recycled.

[0031] The first gas-liquid separator 4 and the second gas-liquid separator 8 are configured to separate gas from liquid. They can be gas-liquid separators of the same type or gas-liquid separators of different types. As an example, the first gas-liquid separator 4 and the second gas-liquid separator 8 can simply utilize the different densities of gas and liquid to achieve the purpose of separation.

[0032] Although not listed one by one, those skilled in the art will understand that adjacent components of the electrochemical oxygen consumption system are connected via gas / liquid pipelines to achieve gas / liquid transmission.

[0033] The electrochemical reaction will continue to consume oxygen in the enclosed space S, thereby reducing the oxygen concentration in the enclosed space S. Further, as described above, Figure 1 The electrochemical oxygen consumption system shown further includes an oxygen concentration sensor 7 and a control unit 11 .

[0034] The oxygen concentration sensor 7 is configured to measure the oxygen concentration in the closed space S. In order to provide a high-precision and high-stability sensor to ensure safe and reliable measurement results, the oxygen concentration sensor 7 can preferably be: an electrochemical oxygen sensor that converts oxygen components into electrical signals through electrochemical reactions; a galvanic oxygen sensor; a multiphase oxygen sensor; a zirconium oxide oxygen sensor; etc. In order to measure the actual oxygen concentration in the closed space S as accurately as possible, the oxygen concentration sensor 7 should be set at a position away from the outlet of the cathode deoxygenation air exhaust pipe 9. In a preferred embodiment, and as Figure 1As shown, the oxygen concentration sensor 7 can be arranged on the pipeline between the air pump 6 and the cathode inlet of the stack 1. Here, the deoxygenated air discharged from the cathode deoxygenated air exhaust pipe 9 and the original air in the enclosed space S have been fully mixed by the suction of the air pump 6, so the oxygen concentration here will be roughly the actual oxygen concentration in the enclosed space S. It will be understood that the above-mentioned oxygen concentration sensor 7 is particularly suitable for measuring the oxygen concentration during the operation of the electrochemical oxygen consumption system. During the shutdown of the electrochemical oxygen consumption system, due to the poor gas flow in the pipeline between the air pump 6 and the cathode inlet of the stack 1, the measurement result of the oxygen concentration sensor 7 may not be able to reflect the change (e.g., increase) of the oxygen concentration in the enclosed space S in a timely manner. Therefore, the electrochemical oxygen consumption system may also include an additional oxygen concentration sensor (not shown in the figure). The additional oxygen concentration sensor can be arranged at a position away from the oxygen concentration sensor 7, for example, at the door of the enclosed space. Through the measurement results of both the oxygen concentration sensor 7 and the additional oxygen concentration sensor, the accurate control of the oxygen concentration of the air in the enclosed space S is achieved in a safer way, which will be further described below in conjunction with the control unit.

[0035] The control unit 11 communicates with at least the battery stack 1, the water pump 3, the air pump 6, the oxygen concentration sensor 7, and the additional oxygen concentration sensor. The communication can be wired communication or wireless communication. When the oxygen concentration measured by the oxygen concentration sensor 7 or the additional oxygen concentration sensor is higher than the first threshold value (for example, 16%), the control unit 11 applies current to the battery stack 1, and starts the water pump 3 and the air pump 6, so that the above-mentioned electrochemical reaction can be carried out to continuously consume the oxygen concentration in the confined space S. In this process, the oxygen concentration sensor 7 and the additional oxygen concentration sensor continuously measure the oxygen concentration in the confined space S. When the oxygen concentration measured by both is lower than the second threshold value (for example, 15%), the control unit 11 stops applying current to the battery stack 1, and turns off the water pump 3 and the air pump 6 to stop the above-mentioned electrochemical reaction. It will be understood that the second threshold value is less than the first threshold value. In addition, the first threshold value and the second threshold value are not limited to the specific values ​​given above, and the second threshold value and the first threshold value can be set to different values ​​according to actual conditions.

[0036] Figure 2 The electrochemical oxygen consumption system according to another embodiment of the present disclosure is schematically shown. Figure 1 The electrochemical oxygen consumption system shown is similar. Figure 2 The electrochemical oxygen consumption system shown includes a battery stack 1', a water tank 2', a water pump 3', a first gas-liquid separator 4', an anode oxygen exhaust pipe 5', an air pump 6', an oxygen concentration sensor 7', a second gas-liquid separator 8', a cathode deoxygenated air exhaust pipe 9', an anode drain pipe 10' and a control unit 11'. The above components are Figure 1The components of the electrochemical oxygen consumption system shown are basically the same, but they are arranged differently. Figure 2 In the stack 1' of the electrochemical oxygen consumption system, the ion exchange membrane 101 used is an anion exchange membrane. In this case, the electrochemical reactions occurring at the anode and cathode of the stack 1 are:

[0037] Anode: 4OH - →O2+2H2O+4e -

[0038] Cathode: O2+2H2O+4e - →4OH -

[0039] As shown in the above electrochemical reaction formula, and reference Figure 2 The air pump 6' pumps the air in the enclosed space S to the cathode of the stack 1', and the water pump 3' pumps the water in the water tank 2' to the cathode of the stack 1', so that the oxygen, water and electrons in the air react at the cathode to generate OH - . Then, OH - It enters the anode through the anion exchange membrane and is oxidized at the anode to generate oxygen, water and electrons. Electrons can flow into the cathode through an external circuit for the above-mentioned cathode reaction. The oxygen and water generated at the anode are separated at the first gas-liquid separator 4', and the oxygen therein can be discharged into the atmosphere outside the enclosed space S through the anode oxygen exhaust pipe 5'. Or as mentioned above, the oxygen can be recovered, stored and reused. The water generated by the anode reaction can be discharged through the anode drain pipe 10'. In a preferred embodiment, the anode drain pipe 10' can be connected to the water tank 2' so that the water generated by the anode reaction can be recycled. The remaining water and air (most of which have been removed from the cathode reaction) flow into the second gas-liquid separator 8' together and are separated here. The separated deoxygenated air is discharged into the enclosed space S through the cathode deoxygenated air exhaust pipe 9', and the separated water is introduced into the water tank 2' for recycling.

[0040] Figure 2 The oxygen concentration sensor 7' and the control unit 11' of the electrochemical oxygen consumption system shown in the figure play the same role as Figure 1 The same, will not be repeated here. In addition, Figure 2 The electrochemical oxygen consumption system shown may also include the additional oxygen concentration sensor described above. Figure 1 and Figure 2 The electrochemical oxygen consumption system shown is basically arranged in the enclosed space S, but it should be understood that the above-mentioned electrochemical oxygen consumption system can also be basically arranged outside the enclosed space S (except for the oxygen concentration sensor), and the specific installation position can be arranged according to actual needs.

[0041] Figure 1 and Figure 2 The electrochemical oxygen consumption system shown consumes oxygen in the air by performing an oxygen reduction reaction at the cathode, which has low cost, small size, and can achieve rapid oxygen consumption.

[0042] Figure 4 The performance curve of the stack of the electrochemical oxygen consumption system is shown, which shows the voltage of the stack at different current densities. Figure 4 As shown, when the current density of the battery stack is 2A / cm 2 The voltage is about 2.8 V. The effective area of ​​each basic component unit is 300 cm 2 For example, when the stack is 2A / cm 2 When the current density is 20000, the oxygen consumption rate can reach 12500L / h. Considering the general application scenario of reducing the oxygen concentration in the air from 21% to 15%, the air treatment rate of the stack is greater than 200m 3 / h. For an area of ​​100m 2 In a confined space with a height of 3m, the electrochemical oxygen consumption system only needs to be turned on for less than 1.5 hours to reduce the oxygen concentration from 21% to 15%.

[0043] In addition, the reactants and products of the above-mentioned electrochemical oxygen consumption system are only water and air, so it does not pollute the environment and will not pose a threat to the storage of combustible materials in a confined space. It is an environmentally friendly solution.

[0044] Although the present disclosure has been described in conjunction with the above-mentioned specific embodiments, it should not be understood as being limited to the examples presented in any way. The scope of the present disclosure is defined by the appended claims. In the context of the claims, the term "comprising" does not exclude other possible elements or steps. In addition, references such as "one" or "an" should not be interpreted as excluding multiple. The use of reference symbols for elements shown in the figures in the claims should not be interpreted as limiting the scope of the present disclosure. In addition, the various features mentioned in different claims may be advantageously combined, and the mention of these features in different claims does not exclude that the combination of these features is impossible and advantageous. In addition, the "first", "second", etc. used in the present disclosure are only used to distinguish the relevant components, and are not intended to give them any priority attributes.

Claims

1. An electrochemical oxygen consumption system, the electrochemical oxygen consumption system is configured to consume oxygen in the air in a closed space (S), characterized in that: The electrochemical oxygen consumption system comprises a battery stack (1, 1'), wherein the battery stack (1, 1') comprises a plurality of basic component units, each of which comprises a cathode and an anode. wherein the electrochemical oxygen consumption system is configured to introduce air in the enclosed space (S) into the cathode so that oxygen in the air is reduced at the cathode to consume the oxygen in the air, and wherein the electrochemical oxygen consumption system is configured to discharge deoxygenated air into the enclosed space (S).

2. The electrochemical oxygen consumption system according to claim 1, characterized in that: Each of the basic components comprises: an ion exchange membrane (101) located in the middle; an anode catalyst layer (102) located on one side of the ion exchange membrane (101); a cathode catalyst layer (103) located on the other side of the ion exchange membrane (101); an anode diffusion layer (104) located outside the anode catalyst layer (102); and a cathode diffusion layer (105) located outside the cathode catalyst layer (103), The anode catalyst layer (102) and the anode diffusion layer (104) constitute the anode, and the cathode catalyst layer (103) and the cathode diffusion layer (105) constitute the cathode.

3. The electrochemical oxygen consumption system according to claim 2, characterized in that: The ion exchange membrane (101) is a proton exchange membrane, and the electrochemical reactions occurring at the anode and the cathode are respectively: Anode: 2H2O→4H + +O2+4e - Cathode: O2+4H + +4e - →2H2O.

4. The electrochemical oxygen consumption system according to claim 3, characterized in that: The electrochemical oxygen consumption system further comprises a water tank (2), a water pump (3) and a first gas-liquid separator (4), wherein the water tank (2) is used to store water, the water pump (3) is configured to pump the water in the water tank (2) to the anode for reaction, the oxygen generated by the reaction and the unreacted water flow from the fuel cell stack (1) into the first gas-liquid separator (4), the first gas-liquid separator (4) is configured to separate the oxygen and the unreacted water, the oxygen is then discharged outside the enclosed space (S), and the unreacted water is sent back to the water tank (2).

5. The electrochemical oxygen consumption system according to claim 4, characterized in that: The electrochemical oxygen consumption system also includes an air pump (6) and a second gas-liquid separator (8), wherein the air pump (6) is configured to pump the air in the enclosed space (S) to the cathode for reaction, and the water and deoxygenated air generated by the reaction flow from the fuel cell stack (1) into the second gas-liquid separator (8), and the second gas-liquid separator (8) is configured to separate the water generated by the reaction from the deoxygenated air, and the deoxygenated air is subsequently discharged into the enclosed space (S).

6. The electrochemical oxygen consumption system according to claim 2, characterized in that: The ion exchange membrane (101) is an anion exchange membrane, and the electrochemical reactions occurring at the anode and the cathode are respectively: Anode: 4OH - →O2+2H2O+4e - Cathode: O2+2H2O+4e - →4OH - .

7. The electrochemical oxygen consumption system according to claim 6, characterized in that: The electrochemical oxygen consumption system also includes a water tank (2'), a water pump (3'), a first gas-liquid separator (4'), an air pump (6'), and a second gas-liquid separator (8'), wherein the water tank (2') is used to store water, the water pump (3') is configured to pump the water in the water tank (2') to the cathode for reaction, the air pump (6') is configured to pump the air in the closed space (S) to the cathode for reaction, unreacted water and deoxygenated air flow into the second gas-liquid separator (8'), the second gas-liquid separator (8') is configured to separate the unreacted water from the deoxygenated air, the unreacted water is then returned to the water tank (2'), and the deoxygenated air is then discharged into the closed space (S), the first gas-liquid separator (4') is configured to separate the oxygen and water generated by the anode reaction, and the oxygen is then discharged outside the closed space (S).

8. The electrochemical oxygen consumption system according to claim 5 or 7, characterized in that: The electrochemical oxygen consumption system further comprises an oxygen concentration sensor (7, 7'), wherein the oxygen concentration sensor (7, 7') is arranged on a pipeline between the air pump (6, 6') and the fuel cell stack (1, 1').

9. The electrochemical oxygen consumption system according to claim 8, characterized in that: The electrochemical oxygen consumption system further comprises an additional oxygen concentration sensor, which is arranged in the closed space (S) at a position far away from the oxygen concentration sensor (7, 7').

10. The electrochemical oxygen consumption system according to claim 8, characterized in that: The electrochemical oxygen consumption system further comprises a control unit (11, 11'), wherein the control unit (11, 11') communicates with the battery stack (1, 1'), the water pump (3, 3'), the air pump (6, 6') and the oxygen concentration sensor (7, 7').

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