An industrialized fuel cell

Abstract

The system comprises a fuel cell including electrodes, a fuel inlet for introducing a non-carbon binding fuel into the fuel cell, an air inlet, an electrolyte inlet, and an outlet for outlet of deplenished electrolyte.

Description

[0001]An industrialized fuel cell The present disclosure is directed to an industrialized fuel cell system running on a non-carbon binding fuel and air. 5 It is contemplated that in an industrialized fuel cell the carbon in the air is reacts with the electrolyte. This causes the electrolyte to precipitate reducing the efficiency of the fuel cell. Replenished electrolyte may be introduced into the fuel cell for compensating for the pre- cipitation. 10 An example of a system replenishing electrolyte in a fuel cell is disclosed in WO2011073621. In this system there is a large consumption / precipitation of electrolyte, because it is run 15 on a carbon fuel, which means that there is a high rate of precipitation / degradation of the electrolyte. It is an object of the present disclosure to achieve a more efficient fuel cell as well as a more cost efficient fuel cell for medium scale production of electricity, and for small scale 20 such as for compact vehicles. A first aspect of the present disclosure is: A system for generating electricity, said system comprising: 25 a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel 30 cell for oxidization at said anode, - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, 35 - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, - an outlet for outlet of said product from said fuel cell. A second aspect of the present disclosure is: A method for generating electricity, said method comprising: 5 - providing a fuel cell including a pair of electrodes including an anode and a cathode separated by an electrolyte, 10 a first inlet for introducing a non-carbon binding fuel into said fuel cell for oxidizing said non-carbon binding fuel at said anode, a second inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product. 15 The product constitutes precipitated electrolyte, e.g. electrolyte that can no longer maintain a desired efficiency of the fuel cell. The “fuel cell” part of the system is to be understood as the pair of electrodes and the 20 space between the pair of electrodes where ions flow from one electrode to the other through the electrolyte. At the same time electrons move between the pair of electrodes in an electric circuit including a load. The term “replenished or new electrolyte” is to be understood as electrolyte that has been 25 produced in the chemical reaction in the reactor between a product comprising hydroxide and the product from the fuel cell. In the present context replenishing refers to substituting the electrolyte that has reacted with the CO2 in the air and can therefore not function as electrolyte for the generation of electric current / electric energy. It should be understood as a loop where the “degraded” electrolyte comes out of the fuel cell and into the reactor 30 where it reacts and the degraded electrolyte is “transformed” back to usable electrolyte. The term “pipe” is to be understood as a passageway for conveying. It may include several pipe sections connected to each other and it may have corners or bends. It may also in- clude a pump for example for pumping fluid in the pipe. 35 The hydroxide may be bound to a metal as it is let into the reactor and inside the reactor exist as a hydroxide ion. A third aspect of the present disclosure is: An electrochemical cell comprising at least one cathode and one anode separated by a shared alkaline electrolyte, wherein at least one electrode surface is geometrically struc- 5 tured to induce triple phase boundary (TPB) formation at discrete breakthrough zones. In the following specific examples according to aspects of the present disclosure will be explained in more detail with reference to the accompanying drawings. The present dis- closure may, however, be embodied in different forms than depicted below, and should 10 not be construed as limited to any examples set forth herein. Rather, any examples are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. 15 For example, hydrogen is mentioned in the following as a specific example of a non-car- bon binding fuel, e.g. an inorganic fuel, because it is a fuel that does not comprise carbon and therefore does not emit carbon dioxide. However, other non-carbon binding fuels than hydrogen are contemplated as long as the fuel match the oxidizing agent (and the electro- 20 lyte) so that the redox reaction of the fuel cell can take place. Fig.1 illustrates a schematic example of a fuel cell for generating electricity for small or medium scale. 25 The fuel cell 10 is part of a first loop (contactor loop) including a reactor 12. Kalium may circulate in the first loop, and alternate between binding carbon and hydroxide. In the reactor, the carbon is transferred from kalium to calcium and hydroxide is transferred 30 from calcium to kalium. The fuel cell comprises a pair of electrodes including an anode and a cathode (not shown). The pair of electrodes are separated by a distance and a fuel cell space is thus defined be- 35 tween the pair of electrodes. A pair of wires (not shown) are connected to the electrodes such that an electric current can flow between the pair of electrodes through a load. The space between the two electrodes is filled with an electrolyte / aqueous alkaline solu- 5 tion. In the specific example the electrolyte is potassium hydroxide (KOH). However, in general, the idea is that carbon dioxide (CO2) from the air is captured in the fuel cell. Thus, an electrolyte reacting with CO2 may be contemplated such as sodium hydroxide (NaOH) or another compound where a hydroxide is present in the electrolyte, i.e. another metal such as an alkali metal may be used for binding the hydroxide. 10 A non-carbon binding fuel such as hydrogen (H2) is introduced into the fuel cell at a (hy- drogen) inlet for oxidizing the hydrogen at the anode, and air including oxygen (O2) is in- troduced at an (oxygen / air) inlet at the cathode, and the fuel cell produces power through a redox reaction between the hydrogen and the oxygen. 15 The non-carbon binding fuel may be stored in a first tank 14. The first tank may have an opening 15 for filling hydrogen on the first tank. The CO2 in the air reacts with the electrolyte, e.g. there is a carbonate precipitation of the 20 electrolyte whereby the fuel cell loses its effect over time - the electrolyte reacts with the CO2 and a compound containing carbonate ion is produced such as potassium carbonate (K2CO3) and / or potassium bicarbonate (KHCO3). The product produced in the reaction between the CO2 and the electrolyte is a carbonate 25 product characterized by the presence of the carbonate ion such as potassium carbonate (K2CO3) and / or potassium bicarbonate (KHCO3) as mentioned above. The product result- ing from the chemical reaction in the electrolyte (electrolyte reaction) in the fuel cell may be in solid state and form small particles or pellets. 30 The fuel cell has an outlet for outlet of (precipitated electrolyte, e.g. the product). The outlet is closer to the bottom of the fuel cell than the top of the fuel cell. 35 The product (the small particles or pellets) from the fuel cell is transported to the reactor, e.g. the precipitated electrolyte is transported to the reactor. The product may have a high temperature and a heat exchanger may be arranged be- tween the fuel cell and reactor for heating liquid flowing in for example a district heating system. 5 Hydroxide (for example included in calcium hydroxide (Ca(OH)2)) is added to a reactor for reacting with the product from the fuel cell, and the reaction produces new electrolyte (re- actor product), e.g. the potassium carbonate product from the fuel cell reacts with the cal- cium hydroxide and the reaction produces potassium hydroxide as well as a byproduct. 10 The reactor has a reactor inlet for adding the hydroxide. The hydroxide may be stored in a second tank 16. The tank may have an opening 18 preferably arranged closer to the top of the tank than 15 the bottom of the tank for adding the hydroxide to the second tank. As an example the second tank may comprise calcium hydroxide. Alternatively, the second tank may comprise calcium oxide (commonly known as quicklime). 20 When storing the hydroxide as calcium oxide a slaking process may be performed before the hydroxide is added to the reactor, e.g. a slaker 17 may be provided between the sec- ond tank and the reactor. The slaker may comprise an inlet for the calcium oxide and an 25 inlet 19 for water. The calcium oxide and the water is mixed and heated in the slaker and calcium hydroxide is produced. Fig.2 illustrates the example with a slaker. 30 In the reactor a byproduct is produced as mentioned above, specifically a carbonate such as limestone (CaCO3), e.g. a carbonatation process takes place in the reactor. 35 The byproduct may be stored in a third tank 18. The tank may have an opening 20 prefera- bly arranged closer to the bottom of the tank than the top of the tank for emptying the third tank. The new electrolyte that has been produced in the reactor may then be added to the fuel cell, i.e. there is a first loop comprising the fuel cell and the reactor. Potassium K circulates in the first loop and transfers from being bound to hydroxide to car- 5 bonate (the chemical reaction in the fuel cell = electrolyte reaction) and back again from being bound to carbonate to hydroxide (the chemical reaction in the reactor). As mentioned above another metal may be used and circulate in the first loop. With re- spect to the metal the loop is considered a closed loop in that metal is not added into the 10 loop except for compensating for any leakage that may occur. A first pipe or conduit is arranged between the fuel cell and the reactor for transporting the product resulting from the electrolyte reaction to the reactor. 15 A second pipe or conduit is arranged between the fuel cell and the reactor for transporting the reactor product to the fuel cell. 20 Fig.3 illustrates a schematic example of a fuel cell for generating electricity for a vehi- cle. The vehicle may be a truck or a compact vehicle such as an automobile or a vessel or an aircraft. 25 The vehicle 30 comprises a fuel cell 32 such as the fuel cell 10 described in the example illustrated in fig.1. The non-carbon binding fuel may be stored in a first tank 14 (fuel tank). The first tank has a 30 first volume defining the range of the vehicle. Typically, the tank should be large enough to contain up to 5 kg of hydrogen. This may achieve a range of about 500 km for a compact vehicle such as an automobile. A large tank may be contemplated for larger vehicles or a greater range. 35 The electrolyte cycle in a loop. However, as opposed to the fuel cell described in the ex- ample illustrated in fig.1 the loop does not comprise a reactor. Instead, the fuel cell has an outlet for outlet of (precipitated electrolyte). The outlet is at the bottom of the fuel cell, e.g. closer to the bottom of the fuel cell than the top of the fuel cell. A (electrolyte) pipe 34 or conduit transports the electrolyte around in the loop, e.g. out from 5 the outlet and back again to the fuel cell and inlet via an inlet. The inlet is at the top of the fuel cell, e.g. closer to the top of the fuel cell than the bottom of the fuel cell. 10 The fuel cell and pipe define a space for containing a volume of electrolyte. It is contemplated that the volume should be large enough in order not to reduce the range, e.g. if the fuel tank has a capacity resulting in a certain range, the volume of electro- lyte should preferably not be so low that the vehicle would not be able to achieve the 15 range. Said in other words, there is a precipitation of electrolyte per kilometer (driven, flown or sailed) and there is a consumption of fuel per kilometer. The precipitation of electrolyte re- duces the efficiency of the fuel cell. At a point the efficiency has been reduced so much 20 that the fuel cell in effect cannot provide adequate propulsion for the vehicle. It is contemplated that the volume of electrolyte in the fuel cell and the electrolyte pipe is in the range 5 L to 65 L. 25 The fuel cell or the electrolyte pipe may comprise an opening 36 for removing the elec- trolyte from the system, and replacing it with new electrolyte. It is contemplated that this procedure may take place when filling the fuel tank with fuel. Alternative, the filling of fuel and replacement of electrolyte may take place at different times depending on the need and availability. 30 Figure 4 At least one of the electrodes (or both of them) may have at one of the sides have a surface geometrically structured to induce triple phase boundary (TPB) formation at 35 discrete breakthrough zones. For example, a surface having protrusions comprising serrated, undulating, pyramidal, or otherwise non-planar topographies for regulating electrolyte flow paths. An example of such a geometry is shown in fig.4 and explained in greater detail in the following. Specifically, this non planar topography may have a prominence or relative height (height difference between a “valley floor” / bottom of pro- trusion and a “mountain summit” / top of protrusion) of more than 0.1 cm, such as more than 0.13 cm. 5 Historically, the Bacon fuel cell used a two-layer sintered nickel structure with small pores near the electrolyte and larger ones near the gas side to establish TPBs. Mod- ern approaches often involve precise pressure control and hydrophobic barriers to pre- vent flooding. 10 This invention deliberately inverts that principle: by applying a slight overpressure to the electrolyte side and using geometrically patterned electrode surfaces, it forces electrolyte through selected paths, thereby forming controlled TPBs at the surface-gas interface. This allows for simplified system architecture, more reliable performance, 15 and potential elimination of hydrophobic layers or membranes. The invention provides an electrochemical cell comprising at least one cathode and one anode separated by a shared alkaline electrolyte. At least one electrode is config- ured with a non-planar or patterned geometry designed to regulate the flow path of the 20 electrolyte. The surface features may include serrated, undulating, pyramidal, striped, or otherwise spatially variable topographies that define where the electrolyte pene- trates through the electrode. The pressurized electrolyte is directed outward through the electrode toward a lower- 25 pressure gas compartment. By engineering the electrode geometry, localized wetting occurs at geometrically defined breakthrough zones while adjacent regions remain dry, enabling robust formation of triple phase boundaries. In contrast to traditional systems where flooding of the gas side is detrimental, this in- 30 vention introduces controlled "micro-flooding" at specific points, enabling sustained gas-liquid-solid contact for reaction, while preserving gas transport through surround- ing dry areas. This system extends principles previously employed in sintered nickel electrodes by35 using modern geometric modulation to create self-regulating flow patterns under con- trolled electrolyte overpressure. The term "modern" here refers to advanced manufacturing techniques such as 3D printing, sinter molding, or etching, which allow highly customizable electrode shapes—including features for internal fluid routing be- tween stacked cells. This capability includes the formation of transport recesses and channels that eliminate the need for separate conductive diffusion layers, which are 5 traditionally required to conduct electrons while allowing gas flow. Furthermore, the design enables stacking of multiple cells separated by planar bipolar plates, which may be made of conductive and corrosion-resistant materials such as nickel-coated steel, titanium, stainless steel, or equivalent metals. The structured elec-10 trodes incorporate integrated channels that allow gas to flow laterally, thereby eliminat- ing the need for separate conductive gas diffusion layers. These conventional layers typically add cost and complexity due to the need to conduct electricity, allow gas pas- sage, tolerate caustic environments, and avoid clogging. The present invention avoids such layers by directing gas through embedded electrode recesses—simplifying stack 15 assembly and increasing durability. In addition, the geometry of the electrode is configured to induce controlled micro- flooding at discrete breakthrough zones, thereby forming stable triple phase bounda- ries without the need for hydrophobic coatings or membranes. 20 The electrochemical cell includes: • A first electrode with non-planar or selectively patterned geometry facing a low- pressure gas compartment. • A second electrode, optionally patterned, facing an opposite gas compartment. 25 • A flowing alkaline electrolyte (e.g., 6–10 M KOH) pumped between the elec- trodes. • A pressure differential between electrolyte and gas side (typically 0.1–0.5 bar). The non-planar surface features act as flow directors, concentrating electrolyte pene- 30 tration at geometrically or chemically defined zones. These features may be fabricated via molding, etching, or additive manufacturing. Alternative embodiments include flat electrodes with surface-applied patterns (e.g., PTFE dots, stripes, or zones) to modu- late wetting and gas access. 35 As illustrated in Figure 4, both the anode (1) and cathode (2) are made from porous materials and are oblongly shaped, vertically oriented in their longitudinal direction. The higher-pressure area (3) comprises the alkaline electrolyte, which is introduced through the inlet area (5). A slight pressure difference drives the electrolyte through the porous electrodes into the adjacent lower-pressure gas areas (4), where oxygen (8) and hydrogen (9) are produced or consumed depending on operational mode. 5 Gas evolution (in electrolysis mode) or gas consumption (in fuel cell mode) occurs pri- marily at the triple phase line (6), where gas, liquid, and solid meet. This configuration avoids significant gas bubble formation within the bulk electrolyte, leading to higher ef- ficiency compared to conventional systems. The main purpose of the serrated geome-10 try is to reduce electrolyte leakage into the gas compartments, while allowing any mi- nor leakage to collect in recessed areas (7) where the porous path is shortest. Both electrolyzers and fuel cells are operated at elevated temperatures, preferably be- tween 90°C and 150°C, to improve reaction kinetics and efficiency. These tempera-15 tures exceed the limitations of traditional systems and may eliminate the need for addi- tional heating or cooling if thermal balance is achieved. In embodiments where the electrochemical cell is operated in electrolysis mode, the inner surface of the electrode—facing the pressurized electrolyte—may optionally be 20 coated with a thin, electrically insulating but hydroxide-permeable oxide layer, such as titanium dioxide (TiO₂). In theory, the overpressure and preferential formation of triple phase boundaries on the gas-facing side are sufficient to prevent electrolysis from oc- curring on the inner (electrolyte-facing (5)) side of the electrode. However, under cer- tain conditions, the electrolyte flow rate may not be high enough to fully displace gas 25 bubbles or inhibit unwanted gas evolution on the inner side. To provide an additional safeguard, the oxide layer suppresses electron transfer while still allowing OH⁻ transport. This prevents unintended gas production on the electrolyte side, thus avoid- ing crossover or formation of explosive gas mixtures. In reversible systems, the coat- ing remains present during fuel cell operation without hindering performance. 30 Figure 4 shows a top view of two electrodes in an electrolyzer or fuel cell. Both elec- trodes (1 and 2) are oblongly shaped and vertically oriented. A higher-pressure area (3) containing alkaline electrolyte forces the fluid through the porous electrodes toward the lower-pressure gas compartments (4). Electrolyte enters at the inlet zone (5). Tri- 35 ple phase boundaries form along line (6), where gas, liquid, and solid meet. Minor electrolyte leakage, if any, accumulates at recessed zones (7). Oxygen (8) and hydro- gen (9) are respectively produced or consumed in the surrounding gas areas. In fig.4 the electrochemical cell is illustrated as operating as a fuel cell, e.g. A hydro- 5 gen fueled proton-exchange membrane fuel cell using hydrogen gas and oxygen to produce electricity and water. However, it may also be operated as a regenerative hy- drogen fuel cell uses electricity and water to produce hydrogen and oxygen. When the fuel cell is operated in regenerative mode, the anode for the electricity production mode (fuel cell mode) becomes the cathode in the hydrogen generation mode (reverse10 fuel cell mode), and vice versa. When an external voltage is applied, water at the an- ode side will undergo electrolysis to form oxygen and protons; protons will be trans- ported through the solid electrolyte to the cathode where they can be reduced to form hydrogen. In this reverse mode, the polarity of the cell is opposite to that for the fuel cell mode. 15 The following description is a summary of the features of the present disclosure ar- ranged according to subject. 1. A system for generating electricity, said system comprising: 20 a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel 25 cell for oxidization at said anode, - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, 30 - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, - an outlet for outlet of said product from said fuel cell. 2. The system according to any of the preceding items, comprising: 35 a first pipe connected to said outlet for transporting said product away from said fuel cell. 3. The system according to any of the preceding items, comprising: a second pipe connected to said third inlet for transporting electrolyte to said fuel cell. 4. The system according to any of the preceding items, comprising: a first tank for storing said non-carbon binding fuel. 5 5. The system according to any of the preceding items, comprising: a reactor for reacting with said product for producing replenished electrolyte and a byprod- 10 uct. 6. The system according to any of the preceding items, said reactor having a reactor inlet for introducing said product into said reactor. 15 7. The system according to any of the preceding items, said reactor having a reactor outlet for outlet of said replenished electrolyte from said reac- tor. 8. The system according to any of the preceding items, 20 said reactor having a fourth inlet constituting a reactor inlet for introducing hydroxide to said reactor. 9. The system according to any of the preceding items, said first pipe connected to said reactor inlet for transporting said product from said fuel 25 cell to said reactor. 10. The system according to any of the preceding items, said second pipe connected to said reactor outlet for transporting said replenished electro- lyte from said reactor to said fuel cell. 30 11. The system according to any of the preceding items, said reactor having a second outlet for outlet of said byproduct from said reactor. 35 12. The system according to any of the preceding items, said first pipe connected to said electrolyte inlet for recycling said product into said fuel cell. 13. The system according to any of the preceding items, 5 said fuel cell and said first pipe defining a space for containing a volume of electrolyte in the range 5 L to 65 L. 14. The system according to any of the preceding items, comprising: an opening into said fuel cell or said first pipe for removing said volume of electrolyte 10 from said system, and replacing with new electrolyte. 15. The system according to any of the preceding items, comprising: 15 a second tank for storing hydroxide. 16. The system according to any of the preceding items, said second tank having an opening for introducing said hydroxide into said third tank. 20 17. The system according to any of the preceding items, comprising: a third tank for storing said byproduct. 18. The system according to any of the preceding items, said third tank having an opening for emptying said third tank. 25 19. The system according to any of the preceding items, comprising: a first loop for circulating a metal for binding hydroxide in said electrolyte from said fuel cell 30 through said reactor and back to said fuel. 20. The system according to any of the preceding items, said metal being an alkali metal such as potassium. 35 21. The system according to any of the preceding items, said electrolyte comprising an aqueous alkaline solution. 22. The system according to any of the preceding items, said fuel cell being an alkaline fuel cell. 23. A vehicle comprising the system according to any of the preceding items. 5 Geometric configuration of electrode plate 24. An electrochemical cell comprising at least one cathode and one anode separated by a shared alkaline electrolyte, wherein at least one electrode surface is geometrically struc- 10 tured to induce triple phase boundary (TPB) formation at discrete breakthrough zones. 25. The electrochemical cell of any of the preceding claims, wherein said structured sur- face comprises serrated, undulating, pyramidal, or otherwise non-planar topographies that regulate electrolyte flow paths. 15 26. The electrochemical cell of any of the preceding claims, wherein electrolyte is deliv- ered under slight overpressure to force breakthrough through the porous electrode at geo- metrically defined points. 20 27. The electrochemical cell of any of the preceding claims, wherein gases are transported laterally across the electrode surface through dedicated recesses, eliminating the need for a separate conductive gas diffusion layer. 28. The electrochemical cell of any of the preceding claims, wherein the triple phase 25 boundary is established without the use of hydrophobic coatings or membranes. 29. The electrochemical cell of any of the preceding claims, wherein the electrode is man- ufactured from sintered metal or a composite thereof, optionally featuring a porosity gradi- ent. 30 30. The electrochemical cell of any of the preceding claims, wherein the operating temper- ature lies between 90°C and 150°C. 31. The electrochemical cell of any of the preceding claims, configured for reversible oper- 35 ation as both a fuel cell and an electrolyzer. 32. The electrochemical cell of any of the preceding claims, wherein multiple cells are stacked with planar bipolar plates in between. 33. The electrochemical cell of any of the preceding claims, wherein controlled micro-5 flooding occurs at the breakthrough zones to sustain gas-liquid-solid interface while main- taining gas transport in surrounding dry regions.

Claims

1 Claims 1. A system for generating electricity, said system comprising: 5 a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel cell for oxidization at said anode, 10 - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, 15 - an outlet for outlet of said product from said fuel cell, - a reactor for reacting with said product for producing replenished electrolyte and a by- product, 20 said reactor having a fourth inlet for introducing hydroxide to said reactor, and a second outlet for outlet of said byproduct from said reactor, - a second tank for storing hydroxide, said second tank having an opening for introducing said hydroxide into said second tank, 25 - a third tank for storing said byproduct, said third tank having an opening for emptying said third tank.

2. The system according to any of the preceding items, comprising: 30 a first pipe connected to said outlet for transporting said product away from said fuel cell.

3. The system according to any of the preceding items, said first pipe connected to said fourth inlet for transporting said product from said fuel cell to said reactor. 35 4. The system according to any of the preceding items, comprising: a second pipe connected to said third inlet for transporting said replenished electrolyte to said fuel cell.2 5. The system according to any of the preceding items, comprising: a first loop for circulating a metal for binding hydroxide in said electrolyte from said fuel cell through said reactor and back to said fuel. 5 6. The system according to any of the preceding items, said metal being an alkali metal such as potassium.

7. The system according to any of the preceding items, 10 said electrolyte comprising an aqueous alkaline solution.

8. The system according to any of the preceding items, said fuel cell being an alkaline fuel cell. 15 9. The system according to any of the preceding items, said second tank having an opening arranged closer to the top of said second tank than the bottom of said second tank.

10. The system according to any of the preceding items, 20 said third tank having an opening arranged closer to the bottom of said third tank than the top of said third tank.

Images