JPH0235986A - Regeneration of ion exchange apparatus for making pure water - Google Patents

Abstract

PURPOSE:To well perform regeneration by recirculating treated water to a raw water storage tank through a recirculation line and regenerating an ion exchange apparatus using treated water. CONSTITUTION:Raw water is preliminarily stored in a raw water storage tank 9 in an amount necessary for regeneration and a valve 12 is closed while a valve 13 is opened and the raw water in the raw water storage tank 1 is continuously passed through an ion exchange apparatus 2 reaching the finish of the passage of water by a raw water pump 4 to perform ion exchange treatment. The obtained treated water is recirculated to the raw water storage tank 1 through the valve 13 and a recirculation line 11. The raw water in the raw water storage tank 1 is reduced in Ca<2+> and Mg<2+> by this recirculation to approach almost pure water. By this method, cost concerned can be reduced.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for regenerating an ion exchange device for producing pure water,
In particular, the present invention relates to a regeneration method most suitable for an ion exchange device when producing pure water using raw water containing a large amount of hardness components such as Ca'' and MgZ'' as water to be treated.

<Conventional technology Ion exchange equipment for producing pure water is a hot bed type ion exchange equipment in which a column is filled with a mixed ion exchange resin of a cation exchange resin and an anion exchange resin, or a hot bed type ion exchange equipment in which a tower is filled with a mixed ion exchange resin of a cation exchange resin and an anion exchange resin, or A multi-bed ion exchange apparatus in which an exchange column and an anion exchange column are each packed separately is well known.

FIG. 2 is an explanatory diagram showing the flow of a conventional pure water production device using such an ion exchange device. In the figure, 1 is a raw water storage tank, 2 is an ion exchange device, and 3 is water obtained from the ion exchange device 2. Each figure shows a pure water storage tank for storing pure water.

When producing pure water using a pure water producing apparatus having the flow shown in FIG.
This is done by passing water through the ion exchange device 2 through the ion exchanger 2. In the ion exchange device 2, Ca2+ and Mgz' contained in raw water are removed by a cation exchange resin that has been made into H-form in advance.
Cation components such as ", Na" are adsorbed and removed, and Cl-18 is
Anion components such as 04'- are adsorbed and removed to obtain treated water from which these impurity ions have been removed, that is, pure water.

The obtained pure water is passed through the treated water outflow line 6 to the pure water storage tank 3.
and then supplied to the point of use via the pure water supply line 7.

As this type of pure water production continues, the capacity of the ion exchange resin used in the ion exchange device 2, and the capacity of the cation exchange resin used for boat fishing, decreases, making it impossible to obtain treated water of the specified purity. (or when the so-called water flow end point is reached, such as when a predetermined treatment amount (constant volume treatment amount) is reached, etc., the cation exchange resin is treated with a mineral acid such as hydrochloric acid.
The anion exchange resin is also regenerated using an alkaline agent such as caustic soda. The regeneration process is roughly as follows. In other words, (1) a step of backwashing the ion exchange resin in the tower, (2) a step of passing a regenerating agent through each ion exchange resin layer, and (2) a step of removing the regenerating agent remaining in each ion exchange resin layer after the completion of the drug passing step. Extrusion process, ■After the extrusion process,
It consists of a step of washing away a small amount of regenerant remaining in each ion exchange resin layer.

Each process requires so-called regenerating water, such as water for backwashing, water for diluting the regenerant during drug delivery, water for extrusion, and water for washing. Normally, raw water, which is the water to be treated by the ion exchange device, is used as the regeneration water, and in that case, the raw water is supplied to the ion exchange device by a raw water pump.

However, if the raw water contains a large amount of hardness components such as Ca2' and MgZ-, the raw water cannot be used as water for regeneration for the reasons described below. In other words, when an ion exchange device is regenerated using such raw water, the hardness components in the raw water may react with an alkaline regenerant such as caustic soda, or the anion Ca(OH)2, M
g(OH)2, CaCO3, MgCO2, calcium silicate, etc. are generated and precipitated in the anion exchange resin layer, and even after the precipitated solids are regenerated, they remain in the mixed bed type ion exchange tower or double bed type ion exchange tower. This is because it will remain in the anion exchange column of the exchange device. the result,
In the water passage step after completion of regeneration, the residual solids gradually dissolve and leak into the treated water, making it impossible to obtain treated water of a predetermined purity.

Therefore, in a pure water production apparatus that processes raw water with a large amount of hardness components, pure water, which is usually treated water of the apparatus, is used as water for regeneration. That is, as shown in FIG. 2, the pure water stored in the pure water storage tank 3 is supplied to the ion exchange device 2 by the regeneration water pump 8 for regeneration.

In FIG. 2, reference numeral 9 indicates a raw water supply line for supplying raw water to the raw water storage tank 1, and reference numeral 10 indicates a discharge line for recycled waste liquid discharged when the ion exchange device 2 is regenerated.

<Problems to be Solved by the Invention> As described above, in a pure water production apparatus that uses raw water containing relatively large amounts of hardness components such as Ca2° and Mg2° as water to be treated, it is difficult to use pure water as reclaimed water as described above. In this case, in addition to the raw water pump 4, it is necessary to provide an expensive regeneration water pump 8, which is usually made of SUS or the like and is dedicated for regeneration. Therefore, there is a problem in that the cost of the entire pure water production apparatus is higher than in the case of so-called raw water regeneration, in which raw water is used as water for regeneration and a raw water pump is also used during regeneration. In addition, if the suction side of the raw water pump 4 and the pure water storage tank 3 are connected through piping in FIG. 2, the pure water in the pure water storage tank 3 can be supplied to the ion exchange device 2 using the raw water pump 4 during regeneration. However, with such a structure, there is a risk that the raw water in the raw water storage tank 1 will flow back through the pipe and mix into the pure water storage tank 3 due to an operational error or equipment trouble. It's not actually done.

Further, when using pure water as water for regeneration, the capacity of the pure water storage tank 3 must be made large enough to secure the amount of water necessary for regeneration. However, the storage tank 3
Since the storage tank 3 is for storing pure water, it is necessary to apply expensive inner coatings and linings, or to make the tank body from expensive materials such as SUS. Increasing the value also increases the cost of the device.

The present invention has been made to solve the above-mentioned problems in water purification equipment that uses raw water containing relatively large amounts of hardness components such as Ca"° and MgZ- as water to be treated. It is an object of the present invention to provide a method for regenerating an ion exchange device that can perform good regeneration even in such a case using almost the same equipment as in the case of raw water regeneration.

Means for Solving the Problems> The present invention provides a pure water production device in which raw water once stored in a raw water storage tank is passed through an ion exchange device to obtain pure water. A circulation line is provided to return the raw water to the raw water storage tank, and when regenerating the ion exchange device, the raw water in the raw water storage tank is continuously treated using the ion exchange device that has reached the end point of water flow, and the resulting treated water is returned to the circulation line. After the raw water is circulated to the raw water storage tank via a line, and the raw water in the raw water storage tank is replaced with the treated water through the circulation process, the ion exchange device is regenerated using the treated water obtained in the storage tank. It is characterized by:

Effect of cation exchange resin at the end point of water flow when raw water containing ions such as Ca g + and M gZ-1Na is passed through a mixed bed ion exchange device or a double bed ion exchange device in a downward flow. The distribution of ion types in the cation exchange resin is schematically shown in Figure 3.In other words, an adsorption layer of Ca'' (Ca type layer), which has the strongest adsorption power to the cation exchange resin, is formed at the top of the resin layer. and then an adsorption layer of MgZ- (Mg
layer) is formed, and below that is Na, which has the weakest adsorption force.
An adsorption layer (Na-type layer) is formed, and unreacted H-type cation exchange resin remains at the bottom of the resin layer. This distribution is caused by the fact that when water is passed through, the cation exchange resin This is because the Na+ adsorbed on the resin is desorbed by Ca and MgZ-, which have stronger adsorption power than the Na, and is driven to the bottom of the resin layer. The fastest leaks into the process water.

When raw water continues to flow through the cation exchange resin in the state shown in Figure 3, the amount of Na+ glue gradually increases, but Ca2° and Mg'', which have stronger adsorption power than Na+, are Because they are adsorbed by the Na-type cation exchange resin in the Na-type layer shown in the figure, a state in which Ca" and Mg" do not leak into the treated water continues for a while. In other words, the ability of the cation exchange resin has decreased and the water flow end point If the raw water is subsequently passed through the ion exchange device that has reached this level, it is possible to obtain a certain amount of treated water that does not contain hard components such as Ca2' and MgZ-, although the purity is low.

In addition, although neither the cation exchange resin nor the anion exchange resin used in the ion exchange equipment has deteriorated in capacity, in the case of an ion exchange equipment where the water flow has ended because a constant volume throughput has been reached, Naturally, pure water can be obtained by continuing to pass the raw water through.

As described above, in any case, if raw water is continued to flow through the ion exchange device that has reached the water flow end point, it is possible to obtain treated water that does not contain hard components such as Ca'' and Mg2+. The present invention has been made focusing on this fact.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is an explanatory diagram of the flow of a pure water production apparatus showing an example of an embodiment of the present invention. In the figure, 1 is a raw water storage tank, and 2 is a flowchart for processing the raw water in the storage tank 1 to obtain pure water. An ion exchange device, 3 a pure water storage tank for storing pure water that is treated water of the ion exchange device 2, 4 a raw water pump for supplying raw water to the ion exchange device 2, and 5 a raw water pump. Reference numeral 6 indicates an inflow line, 6 indicates a treated water outflow line, 7 indicates a pure water supply line, and 9 indicates a raw water supply line, which are the same as in the case of the conventional pure water production apparatus.

In the above configuration, the device feature of the present invention is that a circulation line is provided for circulating the treated water of the ion exchange device 2 to the raw water storage tank 1, and in FIG. This is a circulation line that branches off from 6 and reaches the raw water storage tank 1.

In FIG. 1, reference numerals 12 and 13 indicate switching valves for switching the flow path of treated water to the pure water storage tank 3 side and the raw water storage tank 1 side, respectively.

When producing pure water using a pure water producing apparatus having the flow shown in FIG. The raw water in the raw water storage tank 1 may be passed through the ion exchange device 2 by the raw water pump 4, and the water passing process is exactly the same as the conventional one.

If such a water flow process is continued and treated water of a predetermined purity cannot be obtained from the ion exchange device 2, or if the throughput of the ion exchange device 2 reaches a constant volume throughput, the so-called water flow When the end point is reached, the ion exchange device 2 is regenerated, but in the present invention, the following processing is performed prior to the regeneration.

That is, the amount of raw water necessary for regeneration is stored in advance in the raw water storage tank 9, the valve 12 is closed and the valve 13 is opened, and the raw water in the raw water storage tank 1 is continuously passed through the raw water pump 4 until the water reaches the end point for ion exchange. Water is passed through the device 2 to perform ion exchange treatment. As mentioned above, in the ion exchange treatment, hard components such as Ca'' and Mg2° in the raw water can be continuously removed. In some cases, it was possible to obtain treated water that contained Na but did not contain the above-mentioned hardness components, and even though the capacity of both cation and anion exchange resins had not decreased, a constant volume throughput was reached. If the water is used as the end point, pure water can be obtained as the treated water.The obtained treated water is circulated to the raw water storage tank 1 via the valve 13 and the circulation line 11. By performing this process for a predetermined period of time, the raw water in the raw water storage tank 1 is purified to
The circulating treatment can be stopped at an appropriate time and the ion exchanger 2 can be regenerated. to move to.

In the regeneration of the ion exchange device 2, the treated water obtained in the raw water storage tank 1 as described above is used as regeneration water, and this is supplied to the ion exchange device 2 by the raw water pump 4 and regenerated in a conventional manner. The waste liquid is discharged out of the system via the recycled waste liquid discharge line 10. In this regeneration, Ca24
Since water with low hardness components such as , MgZ-, etc. is used as regeneration water, it is natural that solid matter derived from the hardness components does not precipitate in the anion exchange resin layer. It is possible to obtain high quality treated water.

In addition, when carrying out the method of the present invention, it is necessary to consider equipment so that the raw water in the raw water storage tank 1 does not flow back to the treated water side via the circulation line 11 under any circumstances. 11 to the raw water storage tank 1 is located near the top of the raw water storage tank 1, and by providing an overflow line for raw water in the raw water storage tank I below the connection part, backflow of the raw water can be reliably prevented.

In addition, as mentioned above, if the water flow is terminated when the ion exchange resin used in the ion exchange device has a certain amount of capacity remaining, and the method of the present invention is then carried out, the raw water will be almost pure in the raw water storage tank l. Since it is possible to obtain treated water that is close to water, the present invention is not limited to the case of ion exchange equipment that processes raw water that contains a large amount of hardness components such as Ca 2 + and yl g2°. It can be applied in any case where it is desired to perform regeneration using fresh water.

Ion exchange apparatuses to which the method of the present invention can be applied include, for example, the hot bed type ion exchange apparatus, a two-bed type, a two-bed three-column type, a three-column type, and a three-column type, which are formed by appropriately combining a cation exchange tower, an anion exchange tower, and a decarboxylation tower. A double bed type ion exchange device such as a bed type ion exchange device, and a double bed type ion exchange tower in which the same type of gate type ion exchange resin and strong type ion exchange resin are stacked and packed in the same column are used. An example is a multi-bed ion exchange device.

<Effects> According to the present invention, by using the ion exchange device that has reached the end point of water flow, Ca2' and Mg are stored in the raw water storage tank although the purity is not good.
It is possible to obtain treated water with a reduced concentration of hardness components such as 2°, or treated water that is almost pure water. Therefore, in regenerating the ion exchange device, it is sufficient to use the treated water obtained in the raw water storage tank as regeneration water and supply it to the ion exchange device using a raw water pump. Not only can it prevent the precipitation of solids derived from hardness components, but it can also omit the regeneration water pump that was required in the conventional method of regeneration using pure water, making the equipment easier to use than before. The overall cost can be reduced.

In addition, the conventional method requires expensive internal coatings, linings, etc., and therefore the capacity of the expensive pure water storage tank must be increased to the extent that it can secure the amount of water necessary for regeneration. On the other hand, in the present invention, it is only necessary to increase the capacity of the raw water storage tank, which does not require particularly expensive internal coatings or linings, and can be manufactured at low cost.Instead, the capacity of the expensive pure water storage tank can be reduced compared to the conventional method. Therefore, the cost of the entire device can be further reduced than in the past.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a flow showing an example of an embodiment of the present invention, Fig. 2 is an explanatory diagram of a flow of a conventional pure water production apparatus, and Fig. 3 is an explanatory diagram of a flow of a conventional pure water production apparatus. FIG. 2 is a schematic diagram showing the ion distribution in the cation exchange resin in the device. ■...Raw water storage tank 2...Ion exchange device 3
...Pure water storage tank 4...Raw water pump 5...
Raw water inflow line 6... Treated water outflow line 7...
Pure water supply line 8...Regeneration water pump 9...Raw water supply line 10...Regeneration waste liquid discharge line 11...Circulation line 12.13...Switching valve Figure 1 Figure 3 Figure 2

Claims (1)

[Claims] In a pure water production device in which raw water once stored in a raw water storage tank is passed through an ion exchange device to obtain pure water, a circulation line is provided to return treated water from the ion exchange device to the raw water storage tank, and the ion exchange In order to regenerate the equipment, the raw water in the raw water storage tank is continuously treated using the ion exchange equipment that has reached the end point of water flow, and the resulting treated water is circulated to the raw water storage tank via the circulation line. A method for regenerating an ion exchange device for producing pure water, comprising replacing raw water in a raw water storage tank with the treated water through treatment, and then regenerating the ion exchange device using the treated water obtained in the storage tank. .