JPH0143031B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Application of the Invention) The present invention relates to a liquid flow type electrolytic cell that holds a liquid permeable porous electrode in an electrode chamber. (Background of the Invention) Electrolytic cells can be classified into batch type and flow type in terms of the flow of electrolyte. The former is a type in which the electrolyte is stirred in the tank and the electrolyte is not refreshed until the electrolytic reaction is completed, while the latter is a type in which the liquid is circulated through the electrolytic tank and constantly refreshed during electrolysis. An electrolytic cell that renews the liquid is usually called a "liquid flow type electrolytic cell." The structure of this type of electrolytic cell is generally a laminated structure consisting of a repeating bipolar partition plate/electrode (positive)/diaphragm/electrode (negative)/bipolar partition plate/, and the electrode is a porous material that allows liquid to pass through. (liquid-permeable porous electrode), and the electrode is housed within a frame having a liquid flow path or is formed integrally with the frame. Here, it is desirable that the electrolytic solution flowing from the liquid flow path of the frame into the electrode is equally distributed to each electrode (electrode chamber made of a porous material) and evenly distributed within the electrode chamber. Therefore, the structure and shape of the porous electrode are extremely important, and directly affect not only the electrolytic voltage and efficiency but also the liquid feeding power and the like. Specifically, as shown in Fig. 1, this type of electrolytic cell is a single electrolytic cell in which a chamber frame 3 holding a liquid-permeable porous electrode 1 is arranged on both sides of a diaphragm, and further partitioned by a partition plate. An electrolytic cell was constructed by stacking a large number of (single cells). In the figure, 4 is an electrolytic solution manifold, and 5 is a slit provided in the chamber frame 3 through which the electrolytic solution passes. Conventional electrolytic cells of this type have mainly been configured vertically, with a ratio b/a of electrode width a to electrode height b of 1 or more, taking into consideration the equidistribution of electrolyte within the electrode chamber. Note that the electrode height refers to the length of the electrode in the electrolyte flow direction (vertical direction), and the electrode width refers to the length of the electrode width in the direction perpendicular to the electrode height (horizontal direction). However, in the case of an electrolytic cell with such a vertically elongated electrode, if the electrode is made of a network of carbon or the like, and the area weight (apparent density) must be increased, the permeation of the electrolyte may be difficult. As a result, the required power of the liquid pump increases and the liquid tends to mix through the diaphragm between the cathode chamber and the anode chamber (or the anode chamber and the cathode chamber in the case of batteries). Furthermore, there is a problem in that there is an increased risk of liquid leakage from the cell stack or the like to the outside. For this reason, for example, in the case of an electrolytic cell using a porous carbon electrode, b/a
For those with a value of about 1, the electrode chamber thickness must be increased to 10 mm or more. If the electrode chamber thickness is increased in this way, the potential distribution will become uneven, and the amount of electrodes used will increase, so the electrolytic cell The disadvantage is that the cost increases. (Objective of the Invention) The object of the present invention is to provide an electrolytic cell having a liquid flow type electrolytic cell, in which the thickness of the electrode is 5 mm or less, yet the loss of permeation pressure of the solution is small, and the liquid is excellent in isodistribution. There is a particular thing. (Summary of the Invention) The present invention provides a liquid flow type electrolytic cell (or battery, hereinafter the same) that holds a liquid permeable porous electrode in an electrode chamber.
, the electrode thickness is 5 mm or less, and the ratio a/b of the width b to the height a of the electrode is 0.8 to 0.1.
It is characterized by: The liquid-permeable porous electrode used in the present invention includes:
A material with a thickness of 1.5 mm or less, made of porous carbon such as carbon felt or carbon cloth, or porous metal such as sintered nickel, is used. In addition, the ratio a/b of the width to the height of the electrode in the present invention
The value of is in the range 0.8 to 0.1. If this value exceeds 0.8, the reduction in permeation pressure loss will not be sufficient, and if it does not reach 0.1, the width will be too wide, resulting in insufficient isotropy of the electrode liquid. Hereinafter, the present invention will be explained in more detail with reference to the drawings. FIG. 1 is an elevational view showing the configuration of an electrode chamber of an electrolytic cell showing an embodiment of the present invention. This electrode chamber is
It consists of an electrode chamber frame 3 having an electrolyte manifold 4 and an electrolyte distribution slit 5, and a liquid permeable porous electrode (carbon cloth in this case) 1 held in the electrode chamber frame. The ratio of height b to width a, a/b, is smaller than 0.8. Note that 2 is a gap in the frame of the electrode chamber. (Effect of the invention) With the above configuration, the electrode 1 is arranged horizontally, so that when the electrode liquid flows from the bottom to the top (or vice versa), a uniform potential distribution is achieved over the entire area inside the electrode. Since it is easy to obtain and the pressure loss due to solution permeation is small, the occurrence of side reactions, mixing of the two electrode liquids through the diaphragm, leakage, etc. is suppressed, and it is possible to construct a highly efficient electrolytic cell. can.
Furthermore, by reducing the height, the power for pumping liquid is also reduced, so the efficiency of the entire system can be significantly improved. The electrolytic cell of the present invention can also be used as a battery cell for a secondary battery such as a redox battery. (Examples of the Invention) Examples 1 to 4, Comparative Example 1 The sizes of the electrodes shown in FIG. 1 (Example) and FIG. 2 (Comparative Example) are a=0.75 m and b=1, respectively.
m, thickness 1.5 mm (Example 1), a=0.2 m, b=1
m, thickness 1.5 mm (Example 2), a=1 m, b=0.75
m, thickness 1.5mm (comparative example 1), a=0.75m, b=1
m, thickness 2 mm (Example 3) and a = 0.05 m, b
= 1m, thickness 1.5mm (comparative example 2) single electrolytic cell,
Electrolysis experiments were conducted using an aqueous solution of ethylenediaminetetracarbonate iron complex (a mixture of divalent and trivalent iron) using a carbon cloth electrode (flow rate 500ml/min). A cation exchange membrane was used to separate the cathode and anode chambers. Table 1 shows the results of galvanostatic electrolysis experiments at a current density of 12 mA/cm ² .

[Table] However, the reaction amount was measured using a polarograph.
Examples 4 and 5, Comparative Examples 3 to 5 In a single electrolytic cell with an area within the electrode frame of 50 cm in height (vertical) and 30 cm in width (horizontal), electrode heights of 10 cm, 20 cm,
Insert 30cm and 40cm carbon cloth electrodes with a thickness of 5mm (electrodes made of 3 layers of carbon cloth), chlorine,
The hydrogen gas generation reaction was investigated. The electrolyte solution was approximately 1 mol/aqueous sodium chloride solution for both the catholyte and the anolyte, and the flow rate was approximately 1/min. Electrolytic cell voltage when performing constant current electrolysis at 10A, pressure loss of electrolytic solution permeating the electrolytic cell, hydrogen gas collection efficiency (ratio of the amount of hydrogen released and recovered outside the electrolytic cell to the amount of current applied,
(can be regarded as current efficiency). Furthermore, an electrolytic experiment was conducted under the same conditions in an electrolytic cell (the size inside the electrode frame was the same) having electrodes of 6 layers of carbon cloth with a thickness of 10 mm and an electrode height of 20 cm. These results are shown in Table 2.

[Table] In the above table, allowable electrolytic voltage
A voltage of about 4.5V or less was achieved except for Comparative Example 5.
However, in Comparative Examples 3 and 4, the electrolyte permeation pressure loss was large, so that the gas was mixed between the cathode and the anode through the diaphragm to a large extent, and the gas compensation efficiency was significantly reduced. Therefore,
The double disadvantages of increased pump power and decreased current efficiency occurred.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are elevational views showing the structure of an electrode chamber forming an electrolytic cell of the present invention and a conventional electrolytic cell. 1... Liquid permeable porous electrode, 3... Electrode chamber frame,
4... Electrolyte manifold, 5... Slit, a
... Width of the electrode, b ... Height of the electrode.

Claims (1)

[Claims] 1. In a liquid flow type electrolytic cell that holds a liquid permeable porous electrode in an electrode chamber, the electrode is made of carbon felt, carbon cloth, porous carbon, or sintered nickel, and the thickness of the electrode is 5 mm or less. A liquid flow type electrolytic cell characterized in that a ratio a/b of width b to height a is 0.8 to 0.1.