BACKGROUND OF THE INVENTION
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1. Field of the Invention
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This invention relates to an ozone producing system which can achieve prolonged lives of various members composing an electrolytic cell, and can produce ozone gas at a higher efficiency, as well, by lowering temperatures inside the electrolytic cell when producing ozone gas by water electrolysis.
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2. Description of the Related Art
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The methods to produce ozone gas by means of water electrolysis are publicly known, where the applied electrolytic temperature is commonly around 30 degrees Celsius in order to manufacturing high concentration ozone gas at a high electric current efficiency.
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However, electrolytic cells used for ozone gas generation are heated by electrolysis to a temperature substantially in excess of 30 degrees Celsius and therefore, the internal temperature must be lowered by cooling the electrolytic cells. As a cooling method of electrolytic cells, such methods are known that as shown in FIG. 4, for instance, the temperature is lowered by heat release from the circulation line through which anolyte is circulated between the anode compartment 1 of the electrolytic cell 3 and the anolyte gas-liquid separation tower 4, or the temperature of the electrolytic cell 3 is lowered by proving cooling jackets (not illustrated) on the externals of the anode compartment 2 and the cathode compartment 1 composing the electrolytic cell 3. (JP 11-315389 A)
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However, the system disclosed by JP 11-315389 A demonstrated insufficient temperature lowering; it enabled to suppress temperature rise inside the anode compartment and lower the electrolytic cell temperature, but still allowed a high temperature to remain due to the lack of cathode cooling and thus showed inadequate temperature lowering inside the electrolytic cell, especially at the interfaces between the ion exchange membrane and the anode, and the ion exchange membrane and the cathode, where electrolytic reaction is being performed. Because of these reasons, uneven temperature distribution occurs inside the electrolytic cell, causing deterioration of structural members, leading to lowered ozone gas concentrations or electric current efficiency with time lapse and eventually resulting in necessity for frequent replacement of structural members to maintain satisfactory performance.
SUMMARY OF THE INVENTION
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Therefore, the object of the present invention is to solve the problems of said conventional methods, by enhancing cooling effect, suppressing temperature rise in the electrolytic cell caused by heat generation during electrolysis, and further, maintaining uniform temperature in the electrolytic cells at the time when ozone gas is produced by water electrolysis, so as to obtain ozone gas at a high efficiency and to prolong various members composing the electrolytic cells.
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In order to solve said problems, the present invention constitutes an ozone producing system, comprising a perfluorocarbon polymer ion exchange membrane 9, an anode 8 supported with ozone generation catalyst on an electrically conductive porous material and a cathode 10 supported with platinum catalyst tightly installed on each side of said ion exchange membrane 9, an anode compartment frame 6 installed on the back face of said anode 8, an anode compartment 1 formed between the internal surface of said anode compartment frame 6 and the back of said anode 8, a cathode compartment frame 12 installed on the back of said cathode 10 via a current collector 11, a cathode compartment 2 formed between the internal surface of said cathode compartment frame 12 and the back of said current collector 11, and cooling jackets 16, 16 installed so as to tightly attach to the external surface of said anode compartment frame 6 and said cathode compartment frame 12, characterized in that in an ozone producing electrolytic cell 3 for producing ozone gas from pure water supplied to said anode compartment 1; multiple numbers of grooves 13 are formed on the internal surfaces of said anode compartment frame 6 and said cathode compartment frame 12; an anolyte gas-liquid separation tower 4 to separate anolyte from ozone-containing gas generated from said anode compartment 1, being connected to said anode compartment 1 and a catholyte gas-liquid separation tower 5 to separate catholyte from hydrogen gas generated from said cathode compartment 2, being connected to said cathode compartment 2 are installed outside of said electrolytic cell 3 for ozone producing; achieving enhanced cooling effect of anolyte and catholyte and producing ozone gas at a high efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
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[FIG. 1] Overall view of the ozone producing system by the present invention
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[FIG. 2-a] Detailed drawing viewed from the upper part of the electrolytic cell 3 by the present invention
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[FIG. 2-b] Detailed drawing, viewed from the side, of the electrolytic cell 3 by the present invention
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[FIG. 3] Detailed drawing of multiple grooves 13 formed on the internal surface of the anode compartment frame 6 and the cathode compartment frame 12 by the present invention
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[FIG. 4] Drawing of ozone producing system by a conventional system
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
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The following explains the mode of working of the invention. FIG. 1 is the overall view of the ozone producing system by the present invention, FIG. 2-a is a detailed drawing viewed from the upper part of the electrolytic cell 3 by the present invention, FIG. 2-b is a detailed drawing, viewed from the side, of the electrolytic cell 3 by the present invention, and FIG. 3 is a detailed drawing of multiple grooves 13 formed on the internal surface of the anode compartment frame 6 and the cathode compartment frame 12 by the present invention.
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The ozone producing system by the present invention is, as shown in FIG. 1, composed of an electrolytic cell 3 which electrolyzes purified water to generate ozone containing gas and two gas- liquid separation towers 4, 5 provided in the upper space of the electrolytic cell 3. One gas-liquid separation tower is the anolyte gas-liquid separation tower 4 which is connected to the fluoroplastic piping A which supplies ozone gas bubble-contained water from the anode compartment 1 of the electrolytic cell 3 and the fluoroplastic piping B which return water from the anolyte gas-liquid separation tower 4 to the anode compartment 1, having the ozone-contained gas outlet 14. The other gas-liquid separation tower is the catholyte gas-liquid separation tower 5 which is connected to the piping C which supplies hydrogen bubble-contained water from the cathode compartment 2 of the electrolytic cell 3 and the piping D which returns water from the catholyte gas-liquid separation tower 5 to the cathode compartment 2, having the hydrogen gas outlet 15.
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The electrolytic cell 3 comprises, as shown in FIG. 2-a and FIG. 2-b, a perfluorocarbon polymer ion exchange membrane 9, an anode 8 supported with ozone generation catalyst on an electrically conductive porous material and a cathode 10 supported with platinum catalyst tightly installed on each side of said ion exchange membrane 9, an anode compartment frame 6 installed on the back of said anode 8, an anode compartment 1 formed between the internal surface of said anode compartment frame 6 and the back of said anode 8, a cathode compartment frame 12 installed on the back of said cathode 10 via a current collector 11, and a cathode compartment 2 formed between the internal surface of said cathode compartment frame 12 and the back of said current collector 11. The component 7 is an O-ring and the components 16, 16 are the cooling jackets installed so as to tightly attach to the external surface of said anode compartment frame 6 and said cathode compartment frame 12.
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Multiple numbers of grooves 13 are plurally formed vertically and horizontally, as shown in FIG. 3, to increase heat-exchange area for a higher cooling efficiency. In other words, these multiple numbers of grooves 13 attempt at facilitating circulation of each anolyte and catholyte solution, formable in any shape without restriction, including radial pattern or others.
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According to the present invention, purified gas supplied into the anode compartment 1 of the electrolytic cell 3 is electrolyzed to produce ozone-contained gas, which is sent to the anolyte gas-liquid separation tower 4 together with anolyte via the piping A and is separated into gas and liquid in the anolyte gas-liquid separation tower 4, from which ozone-contained gas is vented from the ozone-contained gas outlet 14 and anolyte is circulated to the anode compartment 1 via the piping B.
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On the other hand, hydrogen gas generated in the cathode compartment 2 is supplied, together with catholyte, via the piping C to the catholyte gas-liquid separation tower 5, where separated into gas and liquid in the catholyte gas-liquid separation tower 5, from which hydrogen gas is vented through the hydrogen gas outlet 15 and catholyte is circulated to the cathode compartment 2 via the piping D.
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According to the present invention, anolyte and catholyte are circulated between the anolyte gas-liquid separation tower 4 and the catholyte gas-liquid separation tower 5 and the anode compartment 1 and the cathode compartment 2 of the electrolytic cell 3, respectively; therefore, heat is radiated from the piping A, B, C, and D and the gas- liquid separation towers 4 and 5; and thus cooling is promoted, enabling to achieve a higher cooling efficiency of the electrolytic cell 3. Besides, multiple numbers of grooves 13 are formed vertically and horizontally or radially on the internal surfaces of the anode compartment frame 6 and the cathode compartment frame 12, contributing to increased areas for heat exchange and decreased solution resistance of electrolyte passage in the electrolytic cell 3, resulting in further promoted catholyte and anolyte circulations by airlift effect.
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According to the present invention, a lower temperature is achieved both in the anode compartment 1 and the cathode compartment 2, compared with the case in which circulation system is not provided on the cathode side of the electrolytic cell 3, and also a smaller temperature distribution in the electrolytic cell 3 is achieved. This temperature descending effect becomes more significant when electrolysis is carried out at a high current density with concomitant large heat generation.
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Furthermore, according to the present invention, the cooling jacket 16, 16 are provided so as to tightly attach to the external surfaces of the anode compartment frame 6 and the cathode compartment frame 12. Given the electrolytic area of the electrolytic cell 3 is constant, electrolysis operation is carried out at a high current density to increase the amount of ozone gas output, which, however, results in increased electrolytic heat generation, causing the temperature rise in the cell, especially at the contact part between ion exchange membranes and electrodes, eventually leading to decreased current efficiency.
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According to the present invention, a higher current efficiency can be maintained by suppressing the temperature rise in the electrolytic cell 3 and at the same time, the life of construction members of the electrolytic cell 3 can be prolonged. Namely, according to the present invention, the temperature in the electrolytic cell 3 did not rise; in particular, the temperature in the vicinity of ion exchange membrane 9, where is electrolytic heat generation part, was lower than the case of operation by the conventional system as shown in FIG. 4. In addition, the temperature distribution in the whole electrolytic cell 3 is minimized. When the electrolytic cell 3 is operated at a high current density to obtain a large amount of ozone gas from less areas, more electrolytic heat is generated; and in such case, the temperature descending effect by the present invention proves quite effective.
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The following explain examples of the present invention. The present invention, however, is not limited to these examples.
EXAMPLE
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As an example of the present invention, electrolysis was conducted at a current density 200 A/dm2 using the ozone producing system shown in FIG. 1. In this experiment, the water electrolysis cell for ozone production, shown as 3 in FIG. 1 employed the cell shown in FIG. 2-a and FIG. 2-b. In FIG. 2-a and FIG. 2-b, 8 is the anode supported with ozone generation catalyst on the electrically conductive porous material, 9 is a perfluorocarbon sulfuric acid polymer ion exchange membrane, 10 is a cathode supported with platinum catalyst. Whereas, 6 is an anode compartment frame, and 12 is a cathode compartment frame, on which multiple numbers of grooves 13 as explained in FIG. 3 are formed. Anolyte and catholyte were circulated between the anode compartment 1 and the anolyte gas-liquid separation tower 4, and the cathode compartment 2 and the catholyte gas-liquid separation tower 5, respectively. The externals of the anode compartment frame 6 and the cathode compartment frame 12 are provided with the cooling jackets 16, 16 for cooling.
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On the other hand, as a comparative example, electrolysis was conducted at a current density 200 A/dm2 using the ozone producing system, as shown in FIG. 4, in which only anolyte was circulated between the anode compartment 1 and the anolyte gas-liquid separation tower 4, having no circulation system on the cathode side. In this comparative example also, the cooling jackets 16, 16 are provided for cooling the anode compartment 1 and the cathode compartment 2.
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Table 1 shows the results of said example and said comparative example. These results show that the case in which anolyte and catholyte were circulated between the anode compartment 1 and the anolyte gas-liquid separation tower 4 and between the cathode compartment 2 and the catholyte gas-liquid separation tower 5, respectively gives a lower temperature of the entire cell, a smaller temperature distribution, and a higher current efficiency in terms of ozone production than the case in which only anolyte was circulated between the anode compartment 1 and the anolyte gas-liquid separation tower 4.
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TABLE 1 |
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Catholyte mean |
Anolyte mean |
Temperature |
Temperature |
Ozone gas |
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temperature |
temperature |
Distribution Δ |
Distribution Δ |
current |
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(° C.) |
(° C.) |
(° C.) (Cathode) |
(° C.) (Anode) |
efficiency (%) |
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|
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| Example |
35 |
39 |
7 |
6 |
18.3 |
| Comparative |
38 |
39 |
10 |
10 |
18.0 |
| Example |
| |
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The ozone producing system by the present invention allows the anode compartment and the cathode compartment to be cooled by the cooling jacket and also such cooling is further promoted by heat release brought about through circulating anolyte and catholyte of the electrolytic cell. Also, the anode compartment and the cathode compartment which have vertically and horizontally or radially formed grooves allow enhanced circulation of catholyte and anolyte by airlift effect, suppress temperature rise of the cell by heat generation during electrolysis operation, achieve ozone gas generation at a high efficiency through uniform temperature within the electrolytic cell, and prolong lives of various structural members constituting the electrolytic cell.
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This application claims the priorities of Japanese Patent Application 2006-215500 filed Aug. 8, 2006, the teachings of which are incorporated herein by reference in their entirety.
