JPS5919993B2 - How to tighten a filter press type electrolytic cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for tightening a filter press type electrolytic cell.

This method is particularly suitable for tightening ion exchange membrane electrolysis equipment. A hydraulic machine (
The general term for machines that use liquid as a medium for pressure transmission, such as water pressure and hydraulic pressure, is commonly used.

In this case, there is a problem in that the clamping pressure decreases due to leakage of pressure oil, which in turn causes leakage of liquid or gas from between the units of the filter press type electrolytic cell. When electrolyzing an aqueous alkali metal salt solution using the ion-exchange membrane method, toxic substances such as chlorine gas and caustic soda are generated, so leakage of the contents is extremely dangerous and can also cause electrical leakage. The contents must not be leaked to anyone. On the other hand, in order to maintain the pressurized state of a hydraulic machine, a method is known in which a pin or a lock nut is used in combination with a mechanical lock mechanism that prevents the piston from retreating.

However, especially when electrolyzing an aqueous alkali metal salt solution using an ion exchange membrane method, the operating temperature is relatively high (70 to 100°C), so the thermal expansion of the filter press type electrolytic cell frame cannot be ignored. . That is, there is a risk of overtightening during operation, which not only promotes creep of the packing but also may cause rupture of the ion exchange membrane that is in close contact with the packing. Furthermore, when the position of the piston of a hydraulic machine is fixed, the tightening pressure decreases due to the creep property of the packing material. In particular, the elastic recovery power of rubber used for packing decreases under the action of alkali and chlorine at high temperatures, resulting in a noticeable decrease in tightening pressure. In order to compensate for the above drawbacks, the present invention uses a hydraulic machine in combination with a mechanical retreat prevention mechanism, and also interposes a plurality of disc springs between the thrust mechanism of the hydraulic machine and the object to be clamped (usually a clamping plate). It is characterized by compression. Disc springs are springs with very characteristic spring constants, especially in certain regions of deformation, where the spring constant is approximately o, and this characteristic is used to maintain a constant axial load or gasket pressure. It is often used as a washer when tightening bolts. There are also examples where it is used to buffer the pressure of pressurizing devices. As seen in these examples, disc springs differ from coil springs, some types of leaf springs, etc. in that their deformation range is extremely small, and they achieve a cushioning effect against minute pressure applied to washers and pressurization. In general, when it is necessary to tighten a filter press consisting of a large number of unit electrolytic cell frames as in the present invention, for example, 20 or more pairs of frames at once, the condition of the packing interposed between each unit electrolytic cell will depend on the condition of the packing interposed between each unit electrolytic cell. There is a thickness variation of several millimeters or more.

For this reason, there is usually a method in which the tightening pressure of the hydraulic machine is monitored and the tightening pressure is manually sequentially tightened or loosened, or the drive device is automatically started in response to changes in the tightening pressure to control the tightening pressure. It had been taken. Such methods, especially the former, require manpower, and the latter not only increases the cost of equipment, but also leads to constant tightness, which in turn promotes cleaving during packing. Also, springs such as disc springs whose spring constant approaches 0 in a certain range are known, and there are methods to keep the pressure approximately constant within a certain range of deformation, but as mentioned above, the effective range is narrow. Therefore, the idea of using it as a washer for tightening and buffering in devices whose overall length fluctuates, such as filter press type electrolytic cells that require heating, never occurred. In a filter press type electrolytic cell, particularly an ion exchange membrane type electrolytic cell, the present invention not only deals with the creep of packing between each unit electrolytic cell frame, but also deals with dimensional changes due to thermal expansion of the electrolytic cell, and packing hardness due to heat. To provide an extremely simple tightening method that can always cope with complex dimensional changes such as deformation due to lowering, can follow a considerable dimensional change range with a constant pressure without always applying overpressure. That is, in order to achieve these objects, the present invention is characterized by interposing a plurality of disc springs between the thrust mechanism of the hydraulic machine and the object to be tightened, and by interposing the thrust mechanism (in this case, the piston rod of the hydraulic machine). A lock mechanism is also used to prevent the vehicle from moving backward. Furthermore,
In order to fully demonstrate the effects of the present invention, the apparent spring constant of a plurality of disc springs [when the load is scaled on the vertical axis and the amount of deformation (scouring/plate thickness) is scaled on the horizontal axis] It is desirable to maintain the strain of the disc spring in a deformed state approximately at the center of the region where the gradient in the graph of the relationship between the total deformation and load becomes approximately O. In addition, in the present invention, a plurality of disk springs are used in series in accordance with the expected dimensional changes of the electrolytic cell, and in order to increase the tightening pressure, a plurality of these disc springs are connected in parallel. It can also be used. To show an example of a disc spring used in the present invention, spring free height/plate thickness (ratio) = 1.25 to 1.75 and deflection/plate thickness (ratio) =
It is desirable to use it in the range of 0.75 to 1.25.

Moreover, a plurality of disc springs are stacked and used so that the range in which the apparent spring constant becomes approximately 0 is several millimeters to several tens of millimeters. Note that the combination direction of the disc springs used in series is set to the direction shown in FIG. 1 and FIG. 2 described below, or any other appropriate direction. The present invention will be explained below with reference to the drawings.

FIG. 1 is a schematic diagram of a filter press type ion exchange membrane type electrolytic cell using the tightening method of the present invention. 1 is a unit electrolytic cell frame, and packing 2 is interposed between each unit electrolytic cell.

These unit electrolytic cells may be suspended on the side bar 3. A piston rod 5 is moved forward or backward by a thrust mechanism consisting of a hydraulic cylinder 4 and a piston to move a clamping plate 6, and each unit electrolytic cell frame is pressed against a fixing plate 7 and clamped. In the present invention, a lock nut shown at 8 is used to prevent the piston rod from retreating. Furthermore, a disc spring as detailed in FIG. 2 is interposed at the portion indicated by 'A7. That is, FIG. 2 is a sectional view of part A, and in this example, there are three disc springs 9 and two disc springs.
The piston rods 5 are stacked on top of each other, and are the thrust mechanism.
It is housed so as to be interposed between the spring seat 10 at the tip of the spring seat 10 and the tightening plate 6. Of course, the number and installation direction of disc springs are
It is not limited to this example. The effects of the present invention will be further explained using the examples shown in FIGS. 3 and 4.

In a typical filter press type ion exchange membrane type electrolytic cell, when the piston rod is moved in the direction of arrow P as shown in FIG. 3, each unit electrolytic cell frame reaches a position where they are in contact with each other. This is the position O on the displacement axis of the piston in FIG. The piston moves further forward, compressing the packing 2 until a point in FIG. 4, and the load W is applied at point a. It reaches a point where no liquid leakage occurs. Up to this point, the relationship between the displacement of the piston and the load is normally almost a straight line. Next, when further compressed, the load increases rapidly as shown by the broken line when a disc spring is not used. In this state, so-called overtightening occurs, causing the packing of the filter press to protrude and damage to the ion exchange membrane. In the present invention, a plurality of disc springs are interposed, and the disc springs are deformed until the displacement of the piston advances to point b in Figs. 3 and 4, but during this time, the load is reduced due to the deformation of the disc springs. It increases and becomes W1. As the displacement of the piston further progresses, the increase in the load with respect to the displacement becomes small between c and d, and for example, at point d, as at W2, the load does not substantially change with respect to the displacement of the piston. Further, beyond point d, the disc spring characteristics are already lost and the load increases again as the piston is displaced. Therefore, in the present invention, a plurality of disc springs are used so that b-d is several millimeters or more, and normally b-d is several millimeters or more.
By keeping the displacement of the piston within the range d, it is possible to tighten without worrying about liquid leakage and without applying excessive tightening pressure to the packing. Particularly preferably, it should be kept in the range from the middle of b-d to c. It should be noted that FIG. 4 is an example, and it goes without saying that the shape is not always the same as that of the graph, and that various shapes are possible, such as when point a and point b overlap, for example.

Furthermore, in the case of an ion exchange membrane type filter press type electrolytic cell, it is necessary to maintain the clamped state for a long period of time, and in this case, the clamping pressure inevitably decreases due to leakage of pressure oil.

It is difficult for the disc spring to absorb this reduced tightening pressure. Therefore, in the present invention, it is necessary to use a mechanism for preventing the clamping plate from retreating in combination with the characteristics of a disc spring. By doing so, it is possible to prevent fluctuations in the clamping pressure due to thermal expansion of the filter press type electrolytic cell and cleaving of the packing. The filter press type electrolyzer to which the present invention can be applied is not limited to membrane electrolysis of alkali metal salts, but also filter press type electrolysis, such as diaphragmless electrolysis, dimerization of acrylonitrile, salt concentration or desalination using an ion exchange membrane, etc. It is particularly effective when applied to electrolytic cells, particularly electrolytic cells operated at temperatures of 50° C. or higher.

[Brief explanation of the drawing]

FIG. 1 is an example of a plan view of a filter press type electrolytic cell, and FIG. 2 is an enlarged explanatory view of portion A in FIG. 1.

Claims (1)

[Scope of Claims] 1. A method for tightening a filter press type electrolytic cell, which uses a hydraulic machine having a retreat prevention mechanism and compresses via a plurality of disc springs. 2. The method according to claim 1, characterized in that the disc spring is tightened in a range where the spring constant of the disc spring is approximately 0. 3. The method according to claim 1, wherein the electrolytic cell is heated to 50° C. or higher. 4. The method according to claim 1, wherein the electrolytic cell is a diaphragm method alkali metal salt water electrolytic cell using an ion exchange membrane.