KR100498234B1 - Electrolytic Hydrogen-Oxygen generator - Google Patents

Abstract

The present invention provides a hydrogen-oxygen generator having an anode cell, a cathode chamber, and an electrolytic cell composed of a membrane-electrode assembly that separates the anode chamber and the cathode chamber and serves as a conductor. And an electrolyte discharge line and a gas discharge line shorter in length than the electrolyte discharge line and having a larger cross-sectional area than the electrolyte discharge line.

Description

Electrochemical Hydrogen-Oxygen Generator

High purity hydrogen and oxygen gas are used in many fields such as silicon oxide film, CVD film, single crystal growth film, heat treatment process such as semiconductor process, piping of water for nuclear power plant refrigerant, corrosion prevention and ceramic firing. Hydrogen gas is generally obtained by purifying hydrogen generated as a by-product from a petrochemical plant or caustic soda plant, pressurized or liquefied, stored in a cylinder, and transferred to a cylinder where hydrogen is needed. Cylinders filled with high pressure hydrogen gas are very dangerous in themselves and there is a risk of gas explosion due to leakage during transport and storage. In addition, when the hydrogen gas is compressed by the gas compressor, impurities such as compressor lubricating oil or hydrocarbon may be introduced.

Oxygen gas, on the other hand, can obtain liquid oxygen by cooling air at low temperature. The liquid oxygen is moved to the place where oxygen is needed such as semiconductor process and vaporized when used. Unlike hydrogen gas, oxygen gas itself is not explosive or flammable, but reacts rapidly with metals, so oxygen gas, like hydrogen gas, can be dangerous during transportation, storage and use. Therefore, many problems may arise regarding the storage and transportation of cylinders filled with hydrogen or oxygen at high pressure.

The above mentioned problems can be solved by using a system that generates hydrogen and oxygen by electrolyzing water where hydrogen and oxygen are needed alone or simultaneously. In other words, by installing a hydrogen and oxygen generating system can solve the safety problems associated with the transport and storage of high-pressure hydrogen and oxygen gas.

The method of producing hydrogen and oxygen by electrolysis of water is widely known, and the gas generating system should have high purity, high pressure, low use of electric energy in terms of operation, and convenient operation. It must be durable and have the characteristics of a compact system in terms of equipment.

In the case of electrolyzing pure water instead of using an electrolyte (caustic soda or sulfuric acid), the operation of the electrolysis device can be operated at high current density (current density of 0.5 A / m 2 or more) and at high pressure. The design of high current density operation enables compact device design, and the high pressure operation design enables the production of high purity gas at high pressure without hydrogen and oxygen to be used where the customer wants.

1 is a view showing the basic configuration of the pure electrolysis device for hydrogen-oxygen generation. The electrolytic cell is largely divided into a cathode catalyst 31 that generates oxygen, a cathode catalyst 21 that generates hydrogen, and a membrane 10 that separates and serves as a conductor, and is a membrane-electrode assembly in a combined form. (1) becomes a basic configuration.

When pure water 90 is supplied to the anode catalyst 31 and current is applied to the anode catalyst 31, the pure water 90 is formed by oxygen (the anode catalyst 31 of the membrane-electrode assembly 1) by the following equation (1). 72) and cations (80, hydrogen ions, protons), electrons (62). The cation 80 moves toward the cathode and the electron 62 moves to the power supply 900.

The negative electrode catalyst of the membrane-electrode assembly 1 meets the positive electrode 80 moving from the positive electrode catalyst 31 to the negative electrode catalyst 21 and the electrons 62 moving from the power supply 900. Hydrogen 82 is generated at 21.

As shown in FIG. 1, the method of supplying pure water only to the anode has a very small concentration gradient of water passing through, so that the electrical resistance of the membrane 10 is hardly influenced by the current supplied to the electrolytic cell. Therefore, the anode chamber supply electrolytic system can obtain a current density of up to 3.2 A / m 2. 90a is pure water to which pure water 90 has not reacted.

However, as the current density increases, more gas is generated in the electrolytic cell, and as shown in FIG. 2, the electrolyte and the gas do not smoothly discharge to the restricted outlets 10 and 20, and the gas and the liquid are alternately discharged. When pressure gauges (Pa, Pc) are installed in the anode and cathode chambers to observe the pressure fluctuations in the electrolytic cell, the pressures in the anode and cathode chambers are combined (PT = Pa-Pc) as shown in FIG. In this way, the pressure fluctuations generated in the anode chamber and the cathode chamber may be damaged as the electrode-membrane assembly 1 rubs against the porous conductors 32 and 22, resulting in pinholes. Oxygen is mixed with hydrogen gas, which can threaten safety of product and safety such as gas explosion, thus limiting current density operation.

There is no example that solves the above problem to date, there are a number of patents on the structure that can only withstand the pressure in the electrolytic cell according to the high pressure operation. Methods for preventing membrane damage and leakage of electrolytes and gases associated with high pressure operation are generally well known and have been improved in two ways.

One method is to specially design the gasket by surface treatment of the gasket in the cell to protect the electrolyte and gas leakage and the membrane. Related patents include US Pat. No. 6,365,032B1, US Pat. No. 6,270,636B1, US Pat. No. 6,099,716, and the like.

Another method is to install an electrolytic stack in a separate high-pressure water tank to eliminate pressure in the cell and pressure outside the cell, reducing the pressure differential between the electrolytic stack and preventing electrolyte damage and reducing electrolyte and gas leakage. This is how you do it. Related patents include U.S. Patent 5,665,211, U.S. Patent 5,690,297, U.S. Patent 5,888,361, U.S. Patent 5,783,051, and the like.

However, this prior art does not eliminate the pressure fluctuations in the electrolytic cell and thus has limitations in high current density operation and high pressure operation. Typically, the maximum current densities of these systems are 7kA / m2 and 9bar.

High current density and high pressure operation reduces the investment cost and operating cost of the hydrogen generation system and enables the system design to be compact. However, under high current density and high pressure operating conditions, the pressure fluctuations inside the electrolytic cell are very large, causing damage to the membrane-electrode assembly, thus reducing the purity of the product and the risk of explosion due to the mixing of generated hydrogen and oxygen gas. The system has very limited current density and pressure conditions. Accordingly, there is a need for developing an electrolysis cell that minimizes pressure fluctuations inside the electrolysis cell under high current density and high pressure operating conditions.

The present invention relates to an electrolytic cell operable at a current density of 20 kA / m 2 or more and an operating pressure of 20 bar or more. One of the key techniques of the present invention relates to a cell structure that minimizes the pressure fluctuation inside the electrolytic cell under high current density and high pressure operating conditions.

Hereinafter, the present invention will be described in more detail with reference to FIGS. 5 to 8 as an embodiment.

5 is an exploded perspective view of an electrolysis cell 210 of a pure hydrogen electrolysis device for hydrogen-oxygen generation. The electrolytic cell 210 is composed of an anode chamber (A) in which oxygen is generated, a cathode chamber (B) in which hydrogen is generated, and a membrane-electrode assembly (1) that separates them and serves as a conductor.

The anode chamber (A) has a function of supplying an electrolyte such as water and a function of supplying electrical energy to the anode catalyst.

The method of supplying and discharging the electrolyte and the reactant during the function of the anode chamber (A) is as follows.

One side of the anode chamber (A) has a supply passage 35 for supplying water, and the other side of the anode chamber (A) has a double discharge line for moving oxygen generated by the electrode reaction to the outside of the electrolytic cell 210 ( 37a) and 37b. The discharge lines 37a and 37b discharge the gas and the electrolyte in the electrolytic cell 210 to the outside through different paths, and in this way, when the gas and the electrolyte are simultaneously discharged through one line (the existing prior art) Pressure fluctuations in the anode cell of the electrolytic cell were eliminated due to the competition between the gas and the liquid. At this time, the pressure discharge line 37a is a discharge line of the electrolyte, and the other discharge line 37b is a gas discharge line. The length of the electrolyte discharge line 37a and the gas discharge line 37b is generally 1.2 times longer than the electrolyte discharge line and preferably 3 mm long. The cross-sectional area of the electrolyte discharge line 37a and the gas discharge line 37b is generally 1.2 times larger than the gas discharge line 37b and preferably 1.5 times larger. The material of the electrolyte discharge line 37a and the gas discharge line 37b is made of the same plastic as that of the anode chamber, and preferably Teflon or polypropylene is preferable. The double discharge lines 37a and 37b may be configured as separate lines as shown in the drawing, and although not shown in the figure, a discharge area having a large area may be inserted into a discharge area having a large area. It is desirable to have a separate line on the side.

The method of supplying electric energy, which is another function of the anode chamber, to the electrode catalyst is as follows.

The supplied electrical energy passes through the porous conductor 32 in contact with the bipolar electrode plate 40 in the anode chamber A and moves to the surface of the anode catalyst 31 to induce an electrolysis reaction.

As the anode catalyst 31 of the membrane-electrode assembly 1 of the present invention, an electrochemical catalyst of a noble metal group which is an electrode catalyst having a low oxygen overvoltage is preferable. Particularly suitable as an oxygen generating electrode catalyst for water electrolysis, a metal or oxide of platinum group such as iridium is preferable.

The porous conductor 32 of the anode chamber (A) having the function of an electrical conductor is preferably made of titanium, and is preferably a metal coated with an electrochemical catalyst of a noble metal group which is an electrode catalyst having a low oxygen overvoltage. Particularly, it is preferable that the tin and iridium are coated on the titanium base material.

The cathode chamber B has a function of supplying electrical energy to the cathode catalyst 21 and a function of discharging hydrogen generated by electrolysis and water moved from the anode chamber A to the outside of the electrolysis cell 210.

In the cathode chamber B, there is no supply path for supplying water, and there are double discharge lines 27a and 27b for moving hydrogen and water generated by the electrode reaction to the outside of the electrolytic cell. The double discharge lines 27a and 27b eliminated pressure fluctuations in the electrolytic cell cathode chamber B in the same manner as in the anode chamber A. The discharge line 27a is a discharge line of the electrolyte, the other discharge line 27b is a gas discharge line, and the size and length are the same as in the case of the anode chamber A.

The pressure variation of the electrolytic cell 210 having the double discharge line of the present invention is shown in FIG. 7 is a case of decomposing pure water under a current density of 20 kA / m 2 operating conditions, and the pressure fluctuations are greatly reduced even at a high current density operation than the pressure fluctuations in a conventional electrolytic cell under a 6 kA / m 2 operating condition of FIG. 3.

A method of supplying electrical energy, which is another function of the cathode chamber B, to the cathode catalyst 21 is as follows. The supplied electrical energy passes through the porous conductor 22 in contact with the bipolar electrode plate 40 in the cathode chamber B and moves to the surface of the anode catalyst 21 to induce an electrolysis reaction.

As the cathode catalyst 21 of the membrane-electrode assembly 1 of the present invention, an electrochemical catalyst of the platinum group group, which is an electrode catalyst having a low hydrogen overvoltage, is preferable. Most suitable electrocatalyst is platinum or its oxide. The porous conductor 22 of the cathode chamber B has titanium as a base material, and is preferably coated with platinum, an electrode catalyst having a low hydrogen overvoltage.

In addition, while maintaining a constant gap between the anode chamber (A) and the cathode chamber (B) and the membrane-electrode assembly 1 and between the anode chamber (A) and the cathode chamber (B) and the bipolar electrode plate 40, Gaskets 25 and 36 are provided for performing a sealing role therebetween. The gaskets 25 and 36 are most preferably high ethylene propylene (EPDM) rubbers having high coefficient of resistance and high temperature resistance.

The membrane 10 of the membrane-electrode assembly 1 is composed of 300 series of cation exchange membranes (eg, Nafion) made of fluoropolymers having sulfonic acid groups. Dupont de Nemours (Wilmington, Del.) Is known to be most suitable. The cathode chamber frame 24 holds the porous conductors 22 and the gasket 25 and the movement of the product in the cathode chamber B. do. The anode chamber frame 34 maintains the movement of reactants (eg, water) and products (eg, oxygen) and porous conductors 32 and gaskets 36.

In the present invention, the bipolar electrode plate 40 is preferably plated with platinum on titanium.

6, the anode chamber A, the gaskets 36 and 25, the membrane-electrode assembly 1, and the cathode chamber B are combined to form one unit of an electrolysis cell. FIG. 6 illustrates one typical electrolytic cell, and is continuously coupled according to capacity to form an electrolytic stack 500 (electrolyzer) as shown in FIG. Therefore, the amount of oxygen and hydrogen generated depends on the number of these electrolytic cells.

The configuration electrolytic stack 500 is formed of a stainless steel structure to withstand the electrolytic cell at the final outer side as shown in FIG. 8 to 300 psi, or to reduce the weight of the overall device high strength It may be made of a plastic material. At this time, the frames 98a and 98b are fixed by the bolts 92 and the nuts 93. In addition, when power is applied to both sides of the frame through the connection part of the anode and cathode of the power supply 900, it serves as a conductor for supplying current to each electrolytic cell.

In addition, the electrolytic stack 500 supplies water to all the electrolytic cells 210 configured through the fluid supply passage 330, and collects hydrogen gas generated in each of the electrolytic cells 210 and discharges the hydrogen gas to the outside ( It has a 290, and at the same time has an oxygen gas discharge path 390 for collecting the oxygen gas generated at the anode at the same time and discharged to the outside.

The configuration electrolytic stack 500 is put into a constant pressure vessel 600, as shown in FIG. 9 shows an example of a process for producing high pressure and high purity hydrogen. Hydrogen collected at one side of the frame of the electrolytic stack 500 is partially cooled in the heat exchanger 200 and then moved to a hydrogen-water phase separator 700 outside the high-pressure pressure vessel 600 to phase-separate water and hydrogen. After phase separation, the hydrogen moves to a dehumidifier 800 to remove fine moisture in hydrogen. The moisture is removed from the dehumidifier 800 and then stored in the hydrogen storage tank 910. At this time, the water removed from the phase separator is collected in the pure water storage tank (100).

Oxygen is generated on the other side of the praim to rise to the upper side of the pressure vessel 600. The gas raised to the upper side is moved to the dehumidifier 810 to remove the moisture present in the gas via the pressure vessel 600, and the moisture is removed and then stored in the oxygen storage tank 920.

At this time, the high pressure pump 120 is installed between the pure water storage tank 100 and the pressure vessel 600 in order to continuously supply water to the oxygen and hydrogen generator.

Currently, the gas used is used to purify hydrogen generated as a by-product from chemical plants and steel mills and fill it with a high-pressure container and move it to a cylinder. This hydrogen distribution environment is exposed to the explosion risk from the time of movement to use. Industrially produced hydrogen is difficult to continuously receive high-purity quality, and the efficiency is inferior because of insufficient use of gas in the cylinder. Therefore, the present invention can stably produce high purity, high pressure hydrogen with only pure water without the risk of explosion, and it may be helpful for the overseas market as well as the import substitution effect for the present device imported at 100%.

1 is a view showing the electrochemical hydrogen-oxygen generation principle,

2 is a view showing a gas-liquid discharge phenomenon in the electrolytic cell,

3 is a view showing a pressure fluctuation phenomenon in an existing electrolytic cell,

4 is a view showing the fluctuation of the membrane-electrode assembly,

5 is a diagram illustrating decomposition of a unit cell of the present invention.

6 is a view showing a unit cell of the present invention,

7 is a view showing the pressure variation in the electrolytic cell of the present invention,

8 is a view showing the assembly of the electrolytic stack,

9 shows a hydrogen-oxygen generator.

Claims (3)

A hydrogen-oxygen generator having an anode chamber, a cathode chamber, and an electrolytic cell composed of a membrane-electrode assembly separating the anode chamber and the cathode chamber and acting as a conductor, And an electrolyte discharge line and a gas discharge line having a length shorter than that of the electrolyte discharge line and having a larger cross-sectional area than the electrolyte discharge line in each of the anode chamber and the cathode chamber. The method of claim 1, The length of the electrolyte discharge line is an electrochemical hydrogen-oxygen generator, characterized in that more than 1.2 times longer than the length of the gas discharge line. The method of claim 1, The cross-sectional area of the gas discharge line is more than 1.2 times larger than the cross-sectional area of the electrolyte discharge line electrochemical hydrogen-oxygen generator.