Ozone producing system

Abstract

In an ozone producing electrolytic cell for producing ozone gas by water electrolysis, said anode compartment 1, said cathode compartment 2, said anode compartment frame 6, said anode 8, said ion exchange membrane 9, said cathode 10, said current collector 11, and said cathode compartment frame 12 constituting the electrolytic cell for ozone production 3 are all in the same shape of square or rectangular; and multiple numbers of grooves 13 are formed on the internal surfaces of said anode compartment frame 6 and said cathode compartment frame 12, thereby reducing current density to suppress load on the electrolytic cell for ozone production, even under a given current value supplied to the electrolytic cells for producing ozone.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ozone producing system to produce ozone gas by means of water electrolysis in which the current density is kept smaller for a given electric current value applied to the electrolytic cell for ozone production, thus the load imposed on the electrolytic cell for ozone production being suppressed and the temperature in the electrolytic cell is kept lower in order to achieve ozone production at a higher efficiency and longer lives of structural members of the electrolytic cell for ozone production.

2. Description of the Related Art

The method of producing ozone gas by means of water electrolysis is among those of publicly known technology, in which a conventional way has been the method by the electrolytic cell for ozone production with an anode supported with ozone generation catalyst on an electrically conductive porous material and a cathode supported with platinum catalyst, being tightly attached to each side of an ion exchange membrane of perfluorocarbon group, where pure water is supplied to the anode compartment to generate ozone gas.

The shape of the conventional types of electrolytic cell for ozone production is mostly round, as shown in JP 9-095791 A, so that the uniform pressure to compress the anode and the cathode against each side of the perfluorocarbon sulfuric acid group ion exchange membrane is easily available.

The system described in JP 9-095791 A, however, has a weak point in that the size of the ozone producing system becomes large because the round shape of the electrolytic cell for ozone production presents a large volume in the ozone producing system to be installed. On the other hand, if the electrolytic area is reduced, the cell must be operated at a higher current density to compensate for the reduced area, possibly leading to a lower current efficiency of ozone production or shorter lives of various structural members of the system. Whereas, in order to avoid the operation at a higher current density, the electrolytic area must be enlarged, leading to an enlarged electrolytic cell, and eventually to the whole installation area being enlarged.

Generally speaking, in order to obtain high concentration ozone gas at a high current efficiency, the electrolytic cells are operated at around 30 degrees Celsius. Whereas, since electrolytic cells for ozone gas generation heat up to a temperature significantly over 30 degrees Celsius during electrolysis, the electrolytic cells must be cooled down to lower the internal temperature. For cooling the electrolytic cells, such methods have been conventionally known as the one, like JP 11-315389 A, in which anolyte is circulated between the anode compartment of the electrolytic cell and the anolyte gas-liquid separation tower to lower the temperature through heat release from the circulation line, or the one in which cooling jackets are provided on the external of the anode compartment and the cathode compartment constituting the electrolytic cell.

In the system described in JP 11-315389 A, the temperature rise in the anode compartment can be suppressed and the temperature of the electrolytic cells can be reduced, but as no cathode cooling is applied, the temperature remains high, and then, lowering temperatures inside the electrolytic cells, especially at the interfaces between the ion exchange membrane and the anode and between the ion exchange membrane and the cathode, where electrolysis reaction is being performed, is not sufficient. Because of these reasons, temperature distribution occurs within the electrolytic. cell; ozone gas concentration or current efficiency tend to be deteriorated due to degraded structural members with lapse of time; and frequent replacement of structural members is required to maintain satisfactory performance level, which are problematic to this system.

SUMMARY OF THE INVENTION

Then, the subject of the present invention to solve said problems is to provide an ozone producing system to generate ozone gas by water electrolysis wherein the shape of the electrolytic cells is discussed to enlarge electrolytic area through effective utilization of the volume shared by electrolytic cell for ozone production, so that ozone can be obtained at a high current efficiency under a small current density operation and lives of various structural members of the electrolytic cell for ozone production are prolonged; ozone is produced at a high efficiency in an economical space area; and ozone gas is generated at a high efficiency through uniform temperature within the electrolytic cell; and lives of various structural members of the electrolytic cell for ozone production are prolonged.

In order to solve said problems, the present invention relates to 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 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, characterized in that in an electrolytic cell for ozone production cell 3 for producing ozone gas from pure water supplied to said anode compartment 1, said anode compartment 1, said cathode compartment 2, said anode compartment frame 6, said anode 8, said ion exchange membrane 9, said cathode 10, said current collector 11, and said cathode compartment frame 12, constituting said electrolytic cell for ozone production 3 are all in the same shape of square or rectangular; and that multiple numbers of grooves 13 are formed on the internal surfaces of said anode compartment frame 6 and said cathode compartment frame 12.

In addition, as a special embodiment of the present invention, cooling jackets 16, 16 are installed to attach tightly to the external surface of said anode compartment frame 6 and said cathode compartment frame 12.

Furthermore, as another special embodiment of the present invention, an anolyte gas-liquid separation tower 4 to separate anolyte from ozone-containing gas generated at said anode compartment 1 and a catholyte gas-liquid separation tower 5 to separate catholyte from hydrogen gas generated at said cathode compartment 2 are installed outside of said electrolytic cell for ozone production 3, being connected to said anode compartment 1 and said cathode compartment 2, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1-a] Detailed drawing, viewed from the upper part, of the electrolytic cell 3 by the present invention

[FIG. 1-b] Detailed drawing, viewed from the side, of the electrolytic cell 3 by the present invention

[FIG. 2-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

[FIG. 2-b] A-A Cross-section Drawing of [FIG. 2-a]

[FIG. 3-a] Overall view of the ozone producing system by the present invention

[FIG. 3-b] A-A Cross-section Drawing of [FIG. 3-a]

[FIG. 4] Electrolytic cell 3 cited in the comparative example.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The following explains the mode of working of the present invention. FIG. 1-a is a detailed drawing, viewed from the upper part, of the electrolytic cell 3 by the present invention, FIG. 1-b is a detailed drawing, viewed from the side, of the electrolytic cell 3 by the present invention, FIG. 2 show the shapes of the anode compartment frame 6 and the cathode compartment frame 12 and a detailed drawing of multiple grooves 13 formed on the respective internal surfaces thereof by the present invention and FIG. 3 are an overall view of the ozone producing system by the present invention.

The electrolytic cell for ozone production 3 to be used in the ozone producing system by the present invention comprises, as shown in FIG. 1-a and FIG. 1-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 part 7 is an O-ring and the parts 16, 16 are cooling jackets installed so as to tightly attach to the external surface of said anode compartment frame 6 and said cathode compartment frame 12.

The anode compartment 1, cathode compartment 2, anode compartment frame 6, anode 8, ion exchange membrane 9, cathode 10, current collector 11, and cathode compartment frame 12 constituting the electrolytic cell for ozone production 3 are all in the same shape of square or rectangular; and multiple numbers of grooves 13 are formed in vertical direction (refer to FIG. 2) on the internal surfaces of said anode compartment frame 6 and said cathode compartment frame 12, to increase the area for heat exchange and thus to enhance cooling efficiency. These multiple numbers of grooves 13, configurable in any shape without restriction intend to facilitate circulation of each solution of anolyte and catholyte.

The ozone producing system by the present invention is, as shown in FIG. 3, composed of an electrolytic cell 3 which electrolyzes pure 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 to which the fluoroplastic piping A is connected to carry ozone bubble-contained water from the electrolytic cell 3 to said anolyte gas-liquid separation tower and the fluoroplastic piping B to 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 to which the piping C which supplies hydrogen bubble-contained water from the electrolytic cell 3 to the catholyte gas-liquid separator 5 and the piping D which returns water from the catholyte gas-liquid separation tower 5 to the cathode compartment 2 are attached, having the hydrogen gas outlet 15.

According to the present invention, pure water supplied into the anode compartment 1 of the electrolytic cell 3 is electrolyzed to produce ozone-contained gas within the anode compartment 1, 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.

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 is 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.

According to the present invention, anolyte and catholyte are circulated between the anolyte gas-liquid separation tower 4 and the anode compartment 1 of the electrolytic cell 3 and between the catholyte gas-liquid separation tower 5 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, thus cooling down being promoted, enabling to achieve a higher cooling efficiency of the electrolytic cell 3. Besides, multiple numbers of grooves 13 are formed vertically, 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 within the electrolytic cell 3, resulting in further promoted catholyte and anolyte circulations by airlift effect.

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 higher current density with concomitant larger heat generation.

Furthermore, according to the present invention, the cooling jackets 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 higher current density in order 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.

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 lives of structural 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 descended, in spite that the part is electrolytically heat generated area. 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 a reduced space area, electrolytic heat is generated more; and in such case, the temperature descending effect by the present invention proves quite effective.

EXAMPLE

The following explain examples of the present invention. The present invention, however, is not limited to these examples.

As Examples 1 and 2 of the present invention, electrolysis was conducted at a current density 200 A/dm² using the ozone producing system shown in FIGS. 1-3. In this. experiment, the anode 8 is that supported with ozone generation catalyst on the electrically conductive porous material, the membrane 9 is a perfluorocarbon sulfuric acid polymer ion exchange membrane, the cathode 10 is that supported with platinum catalyst. The applied anode and cathode in Example 1 were 112.5 mm square or rectangular type electrodes and those in Example 2 were 100 mm square or rectangular type electrodes.

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. The externals of the anode compartment frame 6 and the cathode compartment frame 12 are provided with the cooling jackets 16, 16 for cooling of the anode compartment 1 and the cathode compartment 2.

As a comparative example, the round type electrolytic cell was used. FIG. 4 shows the shapes of the anode compartment frame 6 and the cathode compartment frame 12 used in the round type electrolytic cell.

For comparative example, a round type electrolytic cell with 1 dm² of electrolytic area, same as Example 2, was used, and electrolysis was conducted at the cell current of 200 A, using the ozone producing system as shown in Examples 1 and 2.

Table 1 shows the results of Examples 1 and 2 and said comparative example. These results show that by using a square or rectangular type cell, performance equivalent to or higher than that by a round type electrolytic cell can be obtained and the required installation area of electrolytic cells can be reduced by about 10%.

In Examples 1 and 2 and the comparative example, performance effect was able to be improved by circulating anolyte and catholyte 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, which led to lowered temperatures over the entire cells, smaller temperature distribution, and ozone production at a higher current efficiency; and by providing the cooling jackets 16, 16, the anode compartment 1 and the cathode compartment 2 were cooled down, also leading to enhanced performance.

	TABLE 1
					Catholyte	Anolyte	O3 Gas
		Electrolysis	Cell	Current	In/Out	In/Out	Current	O3
	Installation	Area	Current	Density	Temperature	Temperature	Efficiency	Output
	Area	(dm2)	(A)	(A/dm2)	Difference (° C.)	Difference (° C.)	(%)	(g/hr)
Square or rectangular-type	1.00	1.26	200	159	3	5	18.5	11.0
Electrolytic Cells
(Example 1)
Square or rectangular-type	0.89	1.00	200	200	5	7	18.0	10.7
Electrolytic Cells
(Example 2)
Round-type Electrolytic Cells	1.00	1.00	200	200	8	7	17.5	10.4
(Comparative Example)

As a notable fact, it has been proved that without circulation of anolyte and catholyte, or without provision of the cooling jackets 16, 16, the square or rectangular-type electrolytic cell by the present invention was able to achieve the performance equivalent to or higher than that by the round-type electrolytic cell, and the installation area was able to be reduced about 10%.

According to the present invention, in the ozone producing system to generate ozone gas by water electrolysis, the shape of the electrolytic cells is discussed to enlarge electrolytic area through effective utilization of the volume shared by electrolytic cell for ozone production, so that ozone can be obtained at a high current efficiency under a small current density operation and lives of various structural members of the electrolytic cell for ozone production are prolonged; ozone is produced at a high efficiency in an economical space area; and lives of various structural members of the electrolytic cell for ozone production are prolonged.

Moreover, according to the ozone producing system by the present invention, the anode compartment and the cathode compartment are cooled down by the cooling jacket, which is further promoted by heat release through the circulation of the anolyte and catholyte of the electrolytic cell. In addition, the application of the anode compartment and the cathode compartment with multiple numbers of grooves engraved vertically, horizontally or radially enhances circulation of catholyte and anolyte by air-lift effect, resulting in higher cooling efficiency, suppressing temperature rise in the cells by generated heat during electrolysis, making temperatures within the electrolytic cells uniform to obtain ozone gas at a high efficiency and prolonged various structural members of the electrolytic cell.

This application claims the priorities of Japanese Patent Application 2006-242152 filed Sep. 6, 2006, the teachings of which are incorporated herein by reference in their entirety.

Claims

1. 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 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), characterized in that in an electrolytic cell for ozone production (3) for producing ozone gas from pure water supplied to said anode compartment (1), said anode compartment (1), said cathode compartment (2), said anode compartment frame (6), said anode (8), said ion exchange membrane (9), said cathode (10), said current collector (11), and said cathode compartment frame (12) constituting said electrolytic cell for ozone production (3) are all in the same shape of square or rectangular; and multiple numbers of grooves (13) are formed on the internal surfaces of said anode compartment frame (6) and said cathode compartment frame (12).

2. An ozone producing system according to claim 1, wherein cooling jackets (16, 16) are installed to attach tightly to the external surfaces of said anode compartment frame (6) and said cathode compartment frame (12).

3. An ozone producing system according to claims 1 and 2, wherein an anolyte gas-liquid separation tower (4) to separate anolyte from ozone-containing gas generated in 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 in said cathode compartment (2), being connected to said cathode compartment (2) are installed outside of said electrolytic cell for ozone production (3).