JPH059647Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention promptly detects abnormalities in electrolyzer operation by monitoring the concentration and flow rate of return salt water in ion-exchange membrane method alkaline chloride aqueous electrolysis. This invention relates to a monitoring device for returning salt water for alkali chloride electrolysis that issues an alarm when

[Conventional technology]

In the ion-exchange membrane method for electrolysis of aqueous alkali chloride solutions, when the concentration of the aqueous alkali chloride solution drops below a certain value, deterioration such as the formation of blisters occurs in the ion-exchange membrane, and as a result, hydroxyl flowing from the cathode chamber Ion blocking ability decreases.

Furthermore, deterioration of the ion exchange membrane sometimes causes chlorine ions to diffuse into the cathode chamber, causing problems such as an increase in salt content in the catholyte.

In extreme cases, the coating layer of the anode, whose active material is mainly a platinum group metal, may peel off.

In order to prevent such troubles, it is necessary to sufficiently control the concentration of the aqueous alkali chloride solution, and at the same time, it is also necessary to control the flow rate.

The general method for controlling the concentration of the alkali chloride aqueous solution is to control the flow rate of the alkali chloride aqueous solution supplied to the electrolytic cell, but this method alone is still not sufficient and sometimes causes the problems described above. There is a possibility that this may occur.

However, the flow rate management of aqueous alkali chloride solution is
A rotameter or the like is generally used for each electrolytic cell.

[Problem that the invention attempts to solve]

However, when the rotameter is used, the following troubles are likely to occur.

For example, in rare cases, the concentration of alkali chloride to be supplied decreases for some reason, and as a result, even if the flow rate is appropriate, the concentration of alkali chloride in the electrolytic cell may decrease.

On the other hand, an electrolytic cell is usually composed of multiple pairs of anode chambers and cathode chambers, but when the flow of alkali chloride aqueous solution to each anode chamber becomes unbalanced, the flow rate may change. Problems arise in anode chambers with reduced .

Furthermore, if a liquid leak occurs in the device behind the rotameter, similar troubles will occur if the leakage is delayed.

Furthermore, in addition to the above, when adjusting power during the day and night, for example, the current fluctuates, so it is necessary to carefully adjust the flow rate of each electrolytic cell.
If this adjustment is insufficient, the electrolytic cell with reduced flow rate will be affected.

As described above, when operating an ion-exchange membrane method aqueous alkali chloride electrolyzer, it is essential to promptly detect abnormalities in the concentration and flow rate of the aqueous alkali chloride solution and to maintain these conditions appropriately.

For this purpose, it is rational in all respects to detect abnormalities in the concentration and flow rate of the return salt water leaving the alkaline chloride aqueous electrolytic cell.

[Means for solving problems]

In order to achieve the above object, the returned salt water monitoring device for alkali chloride electrolysis of this invention monitors the concentration of the internal return salt water and/or A transparent cylindrical body that floats or sinks with changes in flow rate and has a detection body that blocks or reflects light is connected in an upright state, and the return salt water that has passed through the cylindrical body is drained through an outflow pipe. The salt water is returned to the main return pipe, and an optical sensor connected to an alarm that detects the floating or sinking of the detection object at the upper limit setting position or the lower limit setting position and issues an alarm is arranged on the outside of the cylindrical body. It is characterized by this.

In this invention, the cylindrical body constituting the returned salt water monitoring device has an internal shape that accommodates the detection object and allows the detection object to rise and fall, and is made of a transparent body that allows light to pass through from the outside. It is connected upright to one end of a branch pipe branching from the main return salt water pipe.

On the other hand, the detection body installed in the cylindrical body has an excellent light blocking effect or light reflection effect, and has a good effect against the normal concentration and normal flow rate of the return salt water flowing inside the cylindrical body. It floats in the returned salt water, but it responds quickly to changes in the concentration of the returned salt water, in other words, to changes in specific gravity, and when the specific gravity exceeds the set value, it floats, and conversely, it floats to the lower limit of the set value. Subsidence occurs when the amount is below.

On the other hand, in response to changes in the flow rate of the return salt water, it will float below the set lower limit (as shown in Figure 1 below) or sink (as shown in Figure 1 below). (If the return salt water is circulated as an upward flow as shown in Figure 2). However, when the flow rate of the returned salt water exceeds the set upper limit value, the movement of the detection body is opposite to that described above.

This detection object has corrosion resistance to aqueous alkali chloride solution and heat resistance.

Materials constituting such a detection body include various materials such as plastic, glass, ceramic, and metal.

The specific gravity of the detection body is set to correspond to the appropriate concentration of the returned salt water, and under normal conditions, the detection body floats in the returned salt water.

In order to adjust the specific gravity of the detection body, it can be made of a hollow body or a foam body having excellent light blocking effect or light reflection effect as described above, but in particular, polyvinylidene fluoride resin colored black can be used. A hollow body made of is preferable in many respects, such as durability, ease of adjusting specific gravity, and reliable detectability with an optical sensor.

The optical sensor to which the alarm is connected has a light blocking function by capturing the object that floats or sinks due to changes in the specific gravity or flow rate of the returning salt water using the light that passes through the transparent cylindrical body. Alternatively, there is no particular restriction as long as it is equipped with a mechanism that detects floating or sinking by a light reflection function and issues an alarm.

This optical sensor is located on one side or/and the outside of the cylindrical body.
and placed at both ends.

Specifically, the return salt water can be supplied to the transparent cylindrical body by connecting a branch pipe to the upper end of the upright cylindrical body and allowing the return salt water to flow in from above. There is a method of connecting to the lower end surface of the body and allowing return salt water to flow in from below.

It is preferable that the return salt water is allowed to flow in the cylindrical body in a full state, and the return salt water that has left the cylindrical body is returned to the return salt water main pipe from below or above the cylindrical body through an outflow pipe.

[Function] The concentration of aqueous alkali chloride solution can be determined from specific gravity and temperature.

In a general electrolytic cell, the temperature of the electrolytic cell (more precisely, the temperature of the liquid inside the electrolytic cell) fluctuates to some extent.

For example, using the example of saline solution, the concentration
The specific gravity of NaCl at 220g/at a temperature of 90℃ is 1.107, the specific gravity of NaCl at a concentration of 200g/at a temperature of 90℃ is 1.092, and the specific gravity at a temperature of 80℃ is
It is 1.099.

Also, the specific gravity of NaCl with a concentration of 150g/at a temperature of 90°C is 1.063, and the specific gravity at a temperature of 80°C is
It is 1.070.

The detection object used in this invention can detect changes in concentration as specific gravity, and can be determined based on ups and downs.Furthermore, it also rises and falls with changes in the flow rate of the returned salt water in the cylindrical body, so it can detect changes in electrolyzer temperature. The detection object can be selected so as to rise and fall in response to a predetermined change.

〔Example〕

Hereinafter, the returned salt water monitoring device for alkali chloride electrolysis of this invention and its usage will be specifically explained based on the attached drawings.

FIG. 1 shows an embodiment of the returned salt water monitoring device for alkali chloride electrolysis of this invention, and shows the monitoring device and the flow of the liquid when the returned salt water is used as a downward flow.

In the figure, the return salt water that has left the anode chamber of the ion-exchange membrane method aqueous alkaline chloride electrolyzer 10 is stored in a transparent cylindrical body 1 that is connected upright to one end of a branch pipe 12 provided in the middle of the return salt water main pipe 11. flows from above.

The returned salt water flows downward in the transparent cylindrical body 1 in a full state, and passes through an outflow pipe 13 connected to the lower end surface and a fixed or variable flow rate adjustment valve 14 provided in the middle of the outflow pipe 13. The salt water is configured to return to the main salt water pipe 11 through the water.

Inside the transparent cylindrical body 1 constituting the monitoring device, a detection body 2 made of a hollow body with a light blocking function is installed, and on the outside near the bottom of the cylindrical body 1, A light sensor 3 having a light emitting part and a light receiving part is arranged, and an alarm 4 is connected to this.

In addition, for convenience of explanation, the optical sensor 3 is shown in FIG.
Although the alarm 4 is provided at a position where it is activated only when the detection object 2 sinks, it can also be provided at a position where it is activated when the detection object 2 floats up.

FIG. 2 shows another embodiment of the returned salt water monitoring device for alkali chloride electrolysis of this invention, and shows the monitoring device and the flow of the liquid when the returned salt water is used as an upward flow.

In the figure, one end of a branch pipe 12 branched off from a main return saltwater pipe 11 is connected to the lower end surface of a transparent cylindrical body 1 held upright, and the return saltwater is fed to the main return saltwater pipe 11 via an outlet pipe 13 provided on the upper end surface.
The system is designed to return

A bypass pipe 15 is provided between the branch pipe 12 and the outflow pipe 13, and a fixed or variable flow rate regulating valve 14 is provided in the middle of the bypass pipe 15.
The cylindrical body 1 constituting the monitoring device has the same configuration as in the embodiment, and the optical sensor 3 and the alarm 4 are installed in positions where they are activated only when the detection object 2 sinks, but when the detection object rises to the surface. It can also be provided at a position where it is activated.

Note that in FIG. 2, the same reference numerals as in FIG. 1 indicate the same parts.

In such a monitoring device, the return salt water that has flowed from the return salt water main pipe 11 through the branch pipe 12 into the transparent cylindrical body 1 is restricted in its outflow amount by the flow rate regulating valve 14, and The fluid circulates through the body 1 while maintaining a fluid-filled state at all times.

Then, when the salt water is returned to the cylindrical body 1 containing the detection body 2 inside, the detection body 2 is suspended in the transparent cylindrical body 1 when the specific gravity of the returned salt water is in a normal state. When the specific gravity of the returned salt water reaches the set lower limit value or falls below the set lower limit value, the detection object 2
sinks and is located at the bottom of the cylindrical body 1.

In this state, the detection body 2 blocks the light emitted from the light emitting part of the optical sensor 3 placed outside the cylindrical body 1, and the attached alarm 4 issues an alarm to determine the concentration and flow rate of the returning salt water. This is to notify the decrease.

In the above configuration, the branch pipe 12 is connected to the electrolytic cell 10
It may be branched directly from a manifold provided at the anode chamber outlet.

Note that in the configurations shown in FIGS. 1 and 2,
It is desirable to change the type of detection body 2 depending on the flow direction of the liquid flowing inside the cylindrical body 1.

For example, in the case of the downward flow shown in Fig. 1, it is necessary to float the detection object 2 against the downward flow of liquid, so the buoyancy is greater than in the case of the upward flow shown in Fig. 2. The use of detectors is advantageous.

Furthermore, in the downward flow method shown in FIG. 1, when the return salt water flow to the branch pipe 12 is cut off due to some kind of accident such as a failure of the electrolytic cell 10, the liquid in the cylindrical body 1 quickly flows out. This is advantageous because the detecting body 2 sinks and an alarm can be issued immediately. However, in the upward flow method shown in FIG. may remain, resulting in a time delay in issuing an alarm until this liquid pool is discharged through the flow rate regulating valve 14.

Therefore, it is difficult to expect that the accuracy of detecting the flow rate due to a drop in the liquid level will be as high as in the case of downward flow.

Next, the concentration and flow rate of the returned salt water were monitored using the monitoring device of this invention according to the downward flow method shown in FIG. 1 as follows.

Implementation conditions Type of returned brine: Returned brine containing sodium chloride Returned brine temperature: 61 to 63°C Liquid flow rate: 530/h Detector: Black-colored vinyldene fluoride resin 25 mmφ, weight 9.174 g Transparent cylindrical body: Glass tube 50mmφ Return salt water flow direction: downward flow As a result of testing under the above conditions, the detection object was floating at a sodium chloride concentration of 220 g/in the return salt water, but when water was added to lower the return salt water concentration,
It settled at 187g/, and the alarm was definitely activated.

Furthermore, when the liquid flow rate was reduced from the normal flow rate of 530/h to 0, the detection object sank down and the alarm was activated similarly.

[Effect of idea]

The returned salt water monitoring device for alkali chloride electrolysis of this invention is connected upright to a branch pipe branching from the main return salt water pipe, and floats or sinks depending on the concentration and/or flow rate of the returning salt water, and The concentration or concentration of the returned salt water can be determined by an extremely simple method of flowing the returned salt water into the transparent cylindrical body provided with a detection element that blocks or reflects light, and causing it to flow upward or downward into the cylindrical body and out. /If there is an abnormality in the flow rate, an optical sensor placed outside the cylindrical body will reliably detect the rising or sinking of the object at the upper limit setting position or lower limit setting position, and an alarm connected to the optical sensor will alert the user. This is to issue a warning.

Therefore, it is possible to maintain the normal operation of the ion-exchange membrane method alkaline chloride aqueous electrolyzer and to take appropriate measures against abnormal situations, while also eliminating the troublesome work that was previously required in terms of maintenance. It can be eliminated.

In particular, the monitoring device for return brine for alkali chloride electrolysis of this invention is installed in a route branching from the return brine piping of the electrolyzer, so it can be easily separated from the main route for electrolyzer operation for inspection and maintenance of the monitoring device. can be carried out simply, easily, and safely, and since the returned salt water required for detection is returned to the electrolytic cell, there is no unnecessary consumption of the electrolytic solution.

Furthermore, the returned salt water monitoring device for alkali chloride electrolysis of this invention includes a transparent cylindrical body, a detector mounted inside the cylindrical body, and an optical sensor with an alarm that detects an abnormality by the vertical movement of the detector. Because of its extremely simple configuration, it can be manufactured at low cost and easily, and the maintenance costs required during use are virtually non-existent, and it can be easily installed in existing ion-exchange membrane method alkaline chloride aqueous solution electrolysis. It has many practical advantages, such as the ability to

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the returned salt water monitoring device for alkali chloride electrolysis of this invention, and FIG. 2 is an explanatory diagram showing another embodiment. 1... Cylindrical body, 2... Detection body, 3... Optical sensor, 4... Alarm, 10... Electrolytic cell, 11... Return salt water main pipe, 12... Branch pipe, 13... Outflow pipe,
14...Flow rate adjustment valve, 15...Bypass pipe.

Claims (1)

[Scope of utility model registration request] In an ion-exchange membrane method alkaline chloride aqueous electrolyzer, a branch pipe branching from the main return salt water pipe is provided with a detection body that floats or sinks depending on the concentration and/or flow rate of the returning salt water and blocks or reflects light. In addition to connecting transparent cylindrical bodies in an upright position,
The return salt water that has passed through the cylindrical body is returned to the return salt water main pipe through an outflow pipe, and the rising or sinking of the detection body is detected outside the cylindrical body at an upper limit setting position or a lower limit setting position. A monitoring device for return brine for alkali chloride electrolysis, characterized in that a light sensor connected to an alarm that issues an alarm is installed.