JPH043630B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a redox battery in which one or two of the redox systems constituting the redox battery contain an active substance with low solubility, in which the active substance is crystallized, This invention relates to a redox battery that is designed to be separated.

Electricity is easy to convert into various forms of energy, easy to control, and does not pollute the environment when consumed, so its share in energy consumption is increasing every year. A unique feature of electricity supply is that production and consumption occur simultaneously. Within this constraint, the environment for power technology is to reliably transmit high-quality power at a constant frequency and constant voltage while responding quickly to fluctuations in power consumption. In reality, nuclear power generation and new thermal power generation, whose output is difficult to change but are highly efficient, are operated at the highest efficiency rating possible, while hydropower generation, etc., are suitable for generating power in response to fluctuations in power consumption. The current situation is that they are meeting the large increase in demand for electricity during the day.

For this reason, surplus electricity at night is stored through pumped-storage power generation using economically efficient nuclear power generation and cutting-edge thermal power generation, but the location conditions for pumped-storage power generation are becoming increasingly difficult.

Due to the above-mentioned circumstances, various types of secondary batteries have been researched as a method of storing electric power, which is a highly versatile energy that does not pollute the environment. Redox batteries are attracting attention.

An overview of this principle will be explained using FIG. 1. FIG. 1 shows a power storage system using a two-tank redox battery.

In these figures, 1 is a power plant, 2 is substation equipment, 3 is a load, 4 is an inverter, and 5 is a redox battery.

The flow-through electrolytic cell 8 is partitioned by a diaphragm 9, and has a positive electrode liquid chamber 10a and a negative electrode liquid chamber 10b inside, and the positive electrode liquid chamber 10a houses a positive electrode 11 and a positive electrode liquid such as a hydrochloric acid solution containing Fe ions. , while the negative electrode liquid chamber 10
b accommodates the negative electrode 12 and a negative electrode liquid such as a hydrochloric acid solution containing Cr ions, and a pump 13a is provided between the tank 6 and the positive electrode liquid chamber 10a. A positive electrode liquid circulation path 14 is formed, a pump 13b is provided between the tank 7 and the negative electrode liquid chamber 10b, and a negative electrode liquid circulation path 15 is formed between the tank 7 and the negative electrode liquid chamber 10b.

In the above configuration, the power generated in the power plant 1 and transmitted to the substation equipment 2 is transformed to an appropriate voltage and supplied to the load 3.

On the other hand, when surplus power is generated at night, the inverter 4 performs AC/DC conversion and charges the redox battery 5.

In this case, charging is performed while the pumps 13a and 13b circulate the positive and negative electrode liquids through the positive and negative electrode chambers 10a and 10b. to catholyte
When using Fe ions and Cr ions in the negative electrode liquid,
The reactions that occur in the flow-through electrolytic cell 8 are reactions on the charging side in equations (1) to (3) below.

Positive electrode side: Fe ³⁺ +e discharge ---→ ← --- Charging Fe ²⁺ ......(1) Negative electrode side: Cr ²⁺ discharge ---→ ← --- Charging Cr ³⁺ +e ......(2) Total reaction: Fe ³⁺ + Cr ²⁺ discharge ---→ ← --- Charge Fe ²⁺ + Cr ³⁺ ...(3) In this way, electric power is accumulated in the positive and negative electrode solutions.

Next, when the supplied power is less than the demanded power, the pumps 13a and 13b circulate the positive and negative electrode liquids through the positive and negative liquid chambers 10a and 10b, and the discharge in equations (1) to (3) is performed. A discharge occurs due to the side reaction, orthogonal conversion is performed by the inverter 4, and power is supplied to the load 3 via the transformer equipment 2.

The power storage system using a redox battery is as described above, but in this redox battery, an active substance with low solubility is contained in one or both of the redox solution, that is, the positive electrode solution and the negative electrode solution, which are in contact with each other through a diaphragm. There are cases.

In the above-mentioned (Cr ²⁺ /Cr ³⁺ )-(Fe ³⁺ /Fe ²⁺ ) redox battery, Cr ²⁺ and Fe ²⁺ are active substances with low solubility. When the amount of these active substances with low solubility increases during discharge or charging, they precipitate in the redox solution to which they belong, so these precipitates must be separated from the redox solution.

Also, after sedimentation, the lost amount of active substance must be replenished into the original redox solution.

On the other hand, as a diaphragm for separating two different redox solutions, a homogeneous cation exchange diaphragm made of polystyrene sulfonic acid or the like has higher conductivity than anion exchange diaphragms, heterogeneous cation exchange diaphragms, etc., and is an extremely superior material. However, on the other hand, this diaphragm is (Cr ²⁺ /Cr ³⁺ )−
When used as a diaphragm in a (Fe ³⁺ /Fe ²⁺ )-based redox battery, a problem arises in that Fe ²⁺ mixes into the Cr redox solution through the diaphragm and precipitates.

As mentioned above, one way to prevent the sedimentation of an active substance with low solubility in the redox solution to which it belongs or in a redox solution of a different type is to increase the volume of the electrolytic cell to prevent the active substance with low solubility from settling. It is conceivable to dilute the redox solution to a concentration that does not saturate it, but this is not preferable because it increases the size of the apparatus.

In view of the above circumstances, the present invention aims to effectively separate active substances that have low solubility and tend to settle without increasing the size of the device.
The feature is that the redox battery is equipped with a crystallization tank for the above-mentioned active substances, which crystallizes and separates the active substances that tend to settle.The crystallization tank is used to store the positive and negative electrode liquids of the redox battery. It may be provided in the tank or may be interposed in the electrolyte circulation path.

The present invention will be explained below based on the illustrated embodiments. FIG. 2 shows the (Cr ²⁺ /Cr ³⁺ )− shown in FIG.
(Fe ³⁺ /Fe ²⁺ ) system redox battery with crystallizer 1
6 and 17, and the same reference numerals are used for the same components as in FIG. 1 in this figure, and the explanation thereof will be omitted.

In FIG. 2, the crystallizer 16 is a positive electrode liquid chamber 10.
The crystallizer 17 is interposed in the circulation path 14 between the tank 7 and the anode liquid chamber 10b, and the crystallizer 17 is interposed in the circulation path 15 between the tank 7 and the negative electrode liquid chamber 10b. A heat pump 18 is provided.

In the above configuration, during charging, the reaction progresses as described above: positive electrode side: Fe ³⁺ +e←Fe ²⁺ negative electrode side: Cr ²⁺ ←Cr ³⁺ +e.

Here, Cr ²⁺ generated on the negative electrode side has a lower solubility than Cr ³⁺ and tends to precipitate particularly at low temperatures. Therefore, in this embodiment, Cr ²⁺ generated on the negative electrode side is crystallized and separated in a crystallizer 16.

On the other hand, during discharge, as mentioned above, the reaction progresses on the positive electrode side: Fe ³⁺ + e → Fe ²⁺ On the negative electrode side: Cr ²⁺ → Cr ³⁺ + e, but at this point, the reaction generated on the positive electrode side
Since Fe ²⁺ has a lower solubility than Fe ³⁺ or Cr ³⁺ and is easily precipitated, in the present invention, Fe ²⁺ generated on the positive electrode side is transferred to the negative electrode side through the crystallizer 16 and through the diaphragm 9. The Fe ²⁺ mixed in is crystallized in the crystallizer 17,
To separate.

Cr ²⁺ or Cr 2+ crystallized and separated as described above
Fe ²⁺ may be returned to the negative or positive electrode solution as is or by adjusting its concentration.

As is clear from the above explanation, in the (Cr ²⁺ /Cr ³⁺ )-(Fe ³⁺ /Fe ²⁺ ) redox battery shown in FIG. 2, the crystallizer 17 is mainly discharged during charging. If the crystallizer 16 is cooled at times, effective crystallization can be performed.For this reason, in this embodiment, a heat pump 18 is provided between the crystallizers 16 and 17, and the crystallizer 17 is cooled during charging. The crystallizer 16 is cooled during discharge.

In addition, FIG. 3 shows the anode liquid chamber 1 in the above embodiment.
This shows an example of the crystallizer 17 interposed in the circulation path 15 between the tank 7 and the crystallizer 17.
At its bottom, a heat exchanger 19 with a built-in heat pump 18 is exposed.

On the other hand, the tip of the pipe 15a on the negative electrode liquid chamber 10b side forming the circulation path 15 is inserted into the upper part of the crystallizer 17, and the passage 15b on the tank 7 side forming the circulation path 15 has a pipe 20 provided at its tip.
is inserted into the crystallizer 17 in a meandering manner, and the tip opening of the pipe 20 is positioned below the crystallizer 16, and a valve 21 is provided at the opening.

In this embodiment, the pipe 20 is made of a resin such as silicone resin or fluorine resin that has a relatively low affinity with crystallized substances, and has pleated grooves 20a along the longitudinal direction on its circumferential surface. form...

By configuring the crystallizer 17 as described above, the negative electrode liquid in the negative electrode liquid chamber 10b is supplied into the crystallizer 17 through the pipe 15a during charging or charging. The temperature of this negative electrode liquid is maintained at about 50°C by the electrode reaction and internal resistance in the negative electrode liquid chamber 10b during charging or discharging. Since the liquid flows down in contact with the meandering pipe 20 through which the liquid passes, it is gradually cooled, and at the bottom of the device 17, it is cooled in contact with the heat exchanger 19.

Therefore, during charging, the negative electrode liquid contains
During Cr ²⁺ and Fe ²⁺ discharge, Fe ²⁺ is in the crystallizer 1.
7, and these crystallized substances can be easily separated from the negative electrode liquid.

Note that, especially during discharge, the heat pump 18 is operated in reverse to connect the bottom of the crystallizer 17 to the heat exchanger 19.
The precipitated Cr ²⁺ can be redissolved and returned to the negative electrode solution by heating at .

In addition, the negative electrode liquid after crystallizing and separating active substances with low solubility such as Cr ²⁺ or Fe ²⁺ in the crystallizer 17 is
The tip opening passes through a pipe 20 provided below in the crystallizer 16, and is further supplied into the tank 7 through a passage 15b. Crystallization does not occur in the tank 7 because it is heated in contact with the warm negative electrode liquid that has been sent.

In the crystallizer 17, crystallization may occur on the surface of the pipe 20 through which the cooled negative electrode liquid passes.
However, in this embodiment, since the pipe 20 is made of a resin such as a silicone resin or a fluororesin that has a relatively low affinity for crystals, crystallization is less likely to adhere to the surface of the pipe 20.

Moreover, in the case where crystallization adheres to the surface of the pipe 20, in this embodiment, since the resin pipe 20 has pleated grooves 20a formed along the longitudinal direction on its peripheral surface, the tip of the resin pipe 20 is When the valve 21 provided at the opening is closed, the pipe 20 shrinks along the grooves 20a, . . . by the liquid feeding pressure of the pump 13b, so that crystals attached to the surface of the pipe 20 can be easily peeled off.

In addition, although the crystallizer 17 was described in the above embodiment, the crystallizer 16 can also be configured in exactly the same manner.

In addition, in this example, an example in which a crystallizer is provided on both the positive electrode liquid side and the negative electrode liquid side was explained.
The crystallizer may be provided in either one, and although an example has been described in which the crystallizer is interposed in the circulation path of the positive electrode liquid or the negative electrode liquid, it may be provided in the storage tank.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a power storage system using a redox battery, Fig. 2 is a schematic diagram when the present invention is applied to the above-mentioned power storage system, and Fig. 3 is an example of a crystallizer of the present invention. FIG. 4 is a perspective view of a pipe constituting the same crystallizer. In the figure, 16 and 17 are crystallizers.

Claims (1)

[Scope of Claims] 1. A flow-through type electrolytic cell in which a positive electrode liquid chamber and a negative electrode liquid chamber are exposed through a diaphragm, a tank containing a positive electrode electrolyte to be supplied to the positive electrode liquid chamber, and a tank for storing a positive electrode electrolyte to be supplied to the negative electrode liquid chamber. A tank for accommodating the negative electrode electrolyte to be supplied, a circulation path for circulating the positive electrode electrolyte between the positive electrode liquid chamber and the tank for the positive electrode electrolyte by a pump provided in the middle of the path, and a circulation path provided in the middle of the path. a circulation path for circulating the anode electrolyte between the anode electrolyte chamber and the anode electrolyte tank by a pump provided with the anode electrolyte; a positive electrode inserted into the cathode electrolyte chamber; and a negative electrode inserted into the anode electrolyte chamber. A redox battery comprising: In the positive electrode electrolyte and the negative electrode electrolyte, an active substance whose solubility in the electrolyte becomes lower during charging or discharging than in the state before charging or discharging is contained. A redox battery characterized in that the circulation path through which the electrolytic solution is circulated or the tank containing the electrolytic solution is provided with a crystallization tank that crystallizes the active substance by cooling the electrolytic solution. 2. The active substance is ferrous chloride, which has lower solubility in the positive electrode electrolyte during discharge than in the state before discharge; The redox battery according to claim 1, wherein the redox battery is provided in a tank for electrolyte. 3. The active substance is chromium chloride, which has lower solubility in the negative electrode electrolyte during charging than in the state before charging; The redox battery according to claim 1 or 2, wherein the redox battery is provided in a tank for electrolyte solution. 4. A crystallization tank is provided in either the positive electrode electrolyte circulation path and the positive electrode electrolyte tank, and in the negative electrode electrolyte circulation path and either the negative electrode electrolyte tank. The redox battery according to claim 1, characterized in that: 5 The above-mentioned active substance is ferrous chloride, which has a lower solubility in the positive electrode electrolyte during discharging than in the state before discharging, and ferrous chloride, which has lower solubility in the negative electrode electrolyte during charging than in the state before charging. Chromium chloride; A crystallization tank provided in either the circulation path for the negative electrolyte or the tank for the negative electrolyte allows the crystallization tank to pass through the diaphragm of the flow-through type electrolytic tank into the negative electrolyte. The redox battery according to claim 4, characterized in that the ferrous chloride mixed in the ferrous chloride is also crystallized.