JPH10230249A - Activated carbon treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of slime on the surface of an activated carbon. SOLUTION: An introducing direction of a solution to be treated to an activated carbon column 10 with a built-in an activated carbon packed layer 12 is switched regularly. After being made to flow in the downward flow for a fixed time, the solution is made to flow in the upward flow for a fixed time and the process is repeated. As a result, the whole activated carbon in the activated carbon packed column 12 is exposed to hydrogen peroxide contained in the solution to be treated to prevent the generation of a slime.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for introducing a liquid to be treated containing an oxidizing agent such as hydrogen peroxide, ozone or sodium hypochlorite into an activated carbon column filled with activated carbon, and bringing the liquid to be treated into contact with activated carbon. Activated carbon treatment apparatus for decomposing an oxidizing agent.

[0002]

2. Description of the Related Art In many cases, hydrogen peroxide is contained in wastewater discharged from a process of manufacturing electronic components such as various semiconductor devices and liquid crystal displays. This is because a cleaning liquid containing hydrogen peroxide is used in a semiconductor wafer cleaning step or the like. Usually, the concentration of hydrogen peroxide in these wastewaters is about several tens to several hundreds mg / L,
As it is, it cannot be released into public waters or reused. Therefore, it is necessary to decompose and remove hydrogen peroxide in wastewater, and a method of decomposing hydrogen peroxide into oxygen and water by bringing the liquid to be treated into contact with granular activated carbon has been widely adopted.

[0003] Here, it is expected that an oxidizing agent such as hydrogen peroxide has a bactericidal action, and slime or the like will not be generated much on the activated carbon surface in contact therewith. However, even in the activated carbon treatment of water that originally contains an oxidizing agent such as hydrogen peroxide in the liquid to be treated, for example, in the case of a downward flow, bacterial slime is generated on the activated carbon surface below the upper layer, There is a problem that the pressure loss increases and the cells flow out to the subsequent stage.

[0004] That is, by the bactericidal action of hydrogen peroxide,
No slime is generated on the surface of the activated carbon in the portion that first comes into contact with the liquid to be treated. However, since the removal of hydrogen peroxide ends at the surface layer portion of the activated carbon packed bed, slime is generated in the activated carbon packed bed at the subsequent stage (in the case of a downward flow, from the middle lower layer to the lower layer).

As a method for solving this problem, Japanese Patent Publication No. 7-1
No. 2471 discloses a method of immersing activated carbon in an acid solution during treatment to remove slime (first conventional method). Japanese Patent Publication No. 2520206 discloses a method (second conventional method) of backwashing an activated carbon packed bed with water containing a chlorine-based oxidizing agent.

[0006]

However, in the first conventional method, the activated carbon packed bed is once immersed in an acid solution. Therefore, a step of neutralization after that becomes indispensable, and the activated carbon packed bed that has been immersed must be sufficiently washed. For this reason, there is a problem that the process for removing the slime takes time and the process is complicated.

[0007] In the second conventional method, water containing an oxidizing agent is introduced from below the activated carbon packed bed to perform reverse washing and sterilization. However, in the case of this back washing, since the period of the back washing is very short, sufficient sterilization treatment cannot be performed at that time, and there has been a problem that the slime generation of the activated carbon located below cannot be sufficiently prevented.

The present invention has been made in view of the above-mentioned problems, and is directed to a method of treating activated carbon, which can effectively prevent slime from being generated when a liquid to be treated containing an oxidizing agent is passed through an activated carbon packed bed for treatment. And an apparatus thereof.

[0009]

SUMMARY OF THE INVENTION The present invention relates to an activated carbon processing apparatus for introducing a liquid to be treated containing an oxidizing agent such as hydrogen peroxide into an activated carbon tower filled with activated carbon to decompose the oxidizing agent in the liquid to be treated. The liquid flowing direction to the activated carbon tower can be reversed, and the liquid flowing direction is periodically reversed to bring the liquid to be treated into contact with the activated carbon.

For example, when a liquid to be treated containing hydrogen peroxide as an oxidizing agent is brought into contact with activated carbon, the hydrogen peroxide is decomposed into oxygen gas and water, and the hydrogen peroxide is removed. Since hydrogen peroxide has a bactericidal activity, no slime is generated on the surface of the activated carbon that is brought into contact with the hydrogen peroxide. However, since hydrogen peroxide is removed by contact with activated carbon, a large amount of hydrogen peroxide is present at the inlet side of the liquid to be treated in the activated carbon tower.
Hydrogen peroxide hardly exists at the treatment liquid outlet side of the activated carbon tower. Therefore, slime is easily generated in the activated carbon on the outlet side of the activated carbon tower.

However, according to the present invention, the flowing direction of the liquid to be treated to the activated carbon tower is periodically switched. Therefore, the activated carbon that has been on the outlet side for a predetermined period will be located on the inlet side in the next predetermined period. Therefore, the activated carbon is regularly located on the entrance side and is exposed to hydrogen peroxide, and the generation of slime in the entire activated carbon in the activated carbon tower can be prevented.

[0012] In particular, since the activated carbon is brought into contact with hydrogen peroxide by continuous water flow, sufficient sterilization can be performed by contact for a sufficient time, and the generation of slime can be effectively prevented.

Further, the present invention has two activated carbon towers, one of the two activated carbon towers having a liquid flowing direction of an upward flow, the other having a flowing liquid of a downward flow, and both activated carbon towers being connected in series. The method is characterized in that the liquid to be treated is first introduced into one activated carbon tower in an upward flow, and the treatment liquid in one activated carbon tower is introduced into the other activated carbon tower in a downward flow.

As described above, the activated carbon tower is divided into two columns, and most of the oxidizing agent can be removed in the activated carbon tower located on the inflow side, and the remaining oxidizing agent can be sufficiently removed in the activated carbon tower on the outflow side. Therefore, generation of slime in the activated carbon in the activated carbon tower on the inflow side can be prevented. Then, by periodically changing the flow direction, any activated carbon tower is periodically disposed on the inflow side where the liquid to be treated is first introduced. This can effectively prevent slime from being generated in all of the activated carbons in both activated carbon towers. In particular, when treating a liquid to be treated containing hydrogen peroxide as an oxidizing agent,
By setting the liquid flow direction in the activated carbon tower located on the inflow side to be the upward flow, the oxygen gas generated by the decomposition can be easily discharged upward, and the occurrence of channeling can be prevented and effective treatment can be performed. .

[0015]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 shows the configuration of an activated carbon processing apparatus according to one embodiment of the present invention. Inside the activated carbon tower 10, granular activated carbon is filled to form an activated carbon filled layer 12. At the bottom of the activated carbon tower 10, the liquid to be treated is placed on the activated carbon tower 10.
A lower pipe 14 for introducing or discharging the processing liquid is connected to the inside, and an upper pipe 16 for discharging the processing liquid or flowing the liquid to be processed is connected to the upper part of the activated carbon tower 10.

The lower pipe 14 is connected to a liquid inflow pipe 22 through a first inflow pipe 20 provided with a valve 18 at an intermediate portion, and connected to a valve 24 at an intermediate portion.
Through the first outflow pipe 26 provided with the processing solution outflow pipe 2
8 is connected. On the other hand, the upper pipe 16 is connected to the liquid to be treated inflow pipe 22 through a second inflow pipe 32 in which a valve 30 is provided in an intermediate portion, and a second outflow in which a valve 34 is provided in an intermediate portion. It is connected to the processing liquid outlet pipe 28 via a pipe 36.

In such an apparatus, the valves 18, 2
By switching 4, 30, and 34, the activated carbon tower 1
The introduction direction of the liquid to be treated at 0 is switched. That is, by opening the valves 18 and 34 and closing the valves 24 and 30, the liquid to be treated flows into the liquid inflow pipe 22 and the first liquid.
Is introduced into the activated carbon tower 10 from the lower portion thereof through the inflow pipe 20 of the above, passes through the activated carbon packed bed 12 in an upward flow, and the processing liquid
Through the outflow pipe 36 and the processing liquid outflow pipe 28. On the other hand, by opening the valves 30 and 24 and closing the valves 18 and 34, the liquid to be treated is
Is introduced into the activated carbon tower 10 from the upper portion thereof through the inflow pipe 32, passes through the activated carbon packed bed 12 in a downward flow, and the processing liquid
Through the outflow pipe 26 and the processing liquid outflow pipe 28.

Here, the liquid to be treated is, for example, wastewater from a semiconductor device manufacturing process and contains hydrogen peroxide. Although not shown, the liquid to be treated is usually once stored in a drainage storage tank and pumped by a pump.

Then, when the liquid to be treated is introduced into the activated carbon tower 10 and flows through the activated carbon packed bed 12, hydrogen peroxide is decomposed and removed into oxygen and water by the catalytic action of the activated carbon. Therefore, the activated carbon on the introduction side of the liquid to be treated is always exposed to hydrogen peroxide. And because hydrogen peroxide has a bactericidal action, the surface of the activated carbon exposed to hydrogen peroxide
Slime is less likely to occur.

On the other hand, the processing solution after the decomposition of hydrogen peroxide has no germicidal action. In addition, a mixed solution of an acid and hydrogen peroxide is often used in an etching step of a semiconductor wafer or the like, and an alcohol is used in subsequent rinsing. For this reason, the wastewater contains organic substances such as isopropyl alcohol in addition to hydrogen peroxide, and the organic substances often remain in the treatment liquid after the hydrogen peroxide is removed. Therefore, slime is easily generated from the middle layer of the activated carbon packed bed 12 to the outflow side.

Here, in the present embodiment, the direction of passage of the liquid to be treated into the activated carbon tower 10 is periodically switched by operating the valves 18, 24, 30, and 34 as described above. For example, the flow direction is switched every two days such as upward flow and downward flow. Thereby, the entire activated carbon in the activated carbon packed bed 12 is reliably exposed to hydrogen peroxide, and generation of slime can be prevented as a whole.

FIG. 2 shows another embodiment, in which two activated carbon towers are connected in series. In this example, the first and second activated carbon towers 70 and 76 are formed in an inverted conical shape having the same shape, and the liquid to be treated is supplied in order from the first activated carbon tower 70 to the second activated carbon tower 76. Or vice versa, from the second activated carbon tower 76 to the first activated carbon tower 7
0 so that the activated carbon tower through which the liquid to be treated first flows can be used as the upward flowing liquid, and the activated carbon tower at the subsequent stage can be used as the downward flowing liquid. The distribution channel can be switched.

That is, the liquid to be treated can be supplied to the lower part of the first activated carbon tower 70 via the valve 40 or to the lower part of the second activated carbon tower 76 via the valve 42, respectively. Further, the final treatment liquid by the series flow from the first activated carbon tower 70 to the second activated carbon tower 76 can be discharged from the lower part of the second activated carbon tower 76 through the valve 44, and vice versa. The treated final treatment liquid can be discharged from the lower part of the first activated carbon tower 70 via the valve 46. Further, from the upper part of the first activated carbon tower 70, a valve 5
0, the primary treatment liquid treated in the first activated carbon tower 70 can be discharged to the storage tank 72, and the second activated carbon tower is supplied from the storage tank 72 to the upper part of the activated carbon tower 70 via the pump 74 and the valve 52. The primary processing liquid in the storage tank 72 processed at 76 can be supplied. In addition, the second activated carbon tower 76
The primary treatment liquid in the storage tank 72 treated in the first activated carbon tower 70 can be supplied from a storage tank 72 via a pump 74 and a valve 54 to the upper part of the second activated carbon tower 76. From the storage tank 72 via the valve 56
The primary treatment liquid treated in the activated carbon tower 76 can be discharged.

Therefore, by opening the valves 40, 50, 54 and 44 and closing the valves 42, 52, 56 and 46, the liquid to be treated is discharged through the valve 40 and the pipe 58 to the first liquid.
From the lower part of the activated carbon tower 70
Is discharged from the top of the tower through a pipe 60 as a primary treatment liquid through a pipe 60, and is introduced into a storage tank 72 via a valve 50. Thereafter, a pump 74 and a valve 54
And is supplied to the upper part of the second activated carbon tower 76 via the pipe 62, passes through the second activated carbon tower 76 in a downward flow, and the processing liquid is supplied as a final processing liquid from the lower part of the pipe 64, the valve 44, and the pipe 6.
Exhausted through 6. On the other hand, valves 40, 50, 5
By closing the valves 4, 44, and opening the valves 42, 52, 56, 46, the liquid to be treated flows through the second activated carbon tower 76 in an upward flow, and then flows through the storage tank 72 to the first activated carbon tower. 70
Through a downward flow.

As described above, the first and second activated carbon towers 70,
By changing the order of passing the liquid through 76, it is possible to effectively prevent the generation of slime on the surface of the granular activated carbon in the activated carbon packed bed in the first and second activated carbon towers 70 and 76.
That is, the liquid to be treated containing the oxidizing agent such as hydrogen peroxide in a high concentration is supplied to the activated carbon tower 70 or 76 used as the previous stage. By passing the liquid to be treated at a flow rate at which a small amount of the oxidizing agent remains, almost all of the granular activated carbon in the activated carbon tower 70 or 76 is exposed to the oxidizing agent. Therefore, the generation of slime is suppressed by the bactericidal action of the oxidizing agent. On the other hand, most of the oxidizing agent is decomposed in the former activated carbon tower and the primary treatment liquid having a reduced oxidizing agent concentration is supplied to the activated carbon tower 70 or 76 in the latter stage. The oxidizing agent is almost completely decomposed in the portion, and the activated carbon present below the intermediate layer is not exposed to the oxidizing agent. Therefore, slime is easily generated below the intermediate layer. However, in this embodiment, since the flow order of the liquid to be treated is periodically switched, the activated carbon in both the activated carbon packed beds of the activated carbon towers 70 and 76 is surely sterilized even if intermittent, and slime is generated. It is suppressed as a whole.

When slime is generated, there are problems such as the outflow of the slime into the processing solution, the formation of a dead space, the occurrence of a short circuit in the processing solution, and an increase in pressure loss in flowing water. Generation can be suppressed.

Here, each of the two activated carbon towers 70 and 76 has an inverted conical shape, and has a larger diameter upward. And the activated carbon tower 70 used as the previous stage
Or 76 flows upward, and the activated carbon tower 70 or 76 used as a subsequent stage flows downflow.

The apparatus having such a configuration is particularly effective for treating a liquid containing a relatively high concentration of an oxidizing agent such as hydrogen peroxide which generates a gas such as oxygen by decomposition. That is, the first-stage activated carbon tower 70 or 76 through which the liquid to be treated is first passed is formed in an inverted conical shape having a large diameter upward, and the liquid to be treated is passed through this tower in an upward flow. By liquefying, oxygen gas generated in the tower can be effectively discharged upward. On the other hand, in the activated carbon tower 70 or 76 of the second stage, the flow velocity of the liquid flowing in the activated carbon tower 70 or 76 is higher at the outlet side (lower side) of the tower.
Therefore, the granular activated carbon and the liquid to be treated come into contact with each other at a high flow rate in a portion where the concentration of hydrogen peroxide is low.
If the flow rate is high, the Reynolds number of the liquid to be treated flowing through the activated carbon packed bed increases, and the surface of the activated carbon and the liquid to be treated are more easily contacted. Therefore, hydrogen peroxide having a low concentration can be effectively removed.

In FIG. 2, inverted-cone-shaped towers are used as the first and second activated carbon towers. However, as the first and second activated carbon towers, cylindrical columns as shown in FIG. 1 are used. Of course, a tower may be used.

[0031]

[Example] Hydrogen peroxide concentration 3 mg / L, TOC 50 mg
FIG. 2 shows a change in pressure loss when wastewater from a semiconductor device manufacturing process of about / L is treated by the apparatus shown in FIG. In this example, the activated carbon tower 10 switched the flow direction every two days.

From the figure, it can be seen that the apparatus of the present invention can prevent the generation of slime and can stably suppress the increase in pressure loss for a long period of time. On the other hand, in the comparative example, the direction of liquid passage was not switched, and normal backwashing was performed for a sufficient time using water containing no oxidizing agent.
As described above, the pressure loss can be reduced to some extent by the backwashing, but it can be seen that the pressure loss cannot be sufficiently reduced due to the generation of slime due to long-term operation.

[0033]

As described above, according to the present invention,
By periodically switching the flowing direction, all the activated carbons forming the activated carbon packed bed come into contact with the oxidizing agent in the liquid to be treated. That is, the activated carbon packed bed from the lower part to the middle part during the upward flow and the upper part to the middle part during the downward flow is exposed to the oxidizing agent contained in the liquid to be treated. Therefore, the generation of slime over the entire activated carbon packed bed can be effectively prevented by passing the water to be treated. Further, in the present invention, since the activated carbon packed bed is sterilized using an oxidizing agent such as hydrogen peroxide contained in the liquid to be treated, it is not necessary to newly add a sterilizing agent.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an embodiment.

FIG. 2 is a diagram illustrating a configuration of another embodiment.

FIG. 3 is a diagram showing the relationship between the number of operating days and pressure loss.

[Description of Signs] 10 activated carbon tower, 12 activated carbon packed bed, 14 lower piping, 16 upper piping, 18, 24, 30, 34, 40,
42,44,46,50,52,54,56 valves,
20 first inflow pipe, 22 liquid inflow pipe to be treated, 26 first outflow pipe, 28 processing liquid outflow pipe, 32 second inflow pipe,
36 second outlet pipe, 70 first activated carbon tower, 72 storage tank, 74 pump, 76 second activated carbon tower.

Claims (2)

[Claims] 1. An activated carbon treatment apparatus for introducing a liquid to be treated containing an oxidizing agent such as hydrogen peroxide into an activated carbon tower filled with activated carbon to decompose the oxidizing agent in the liquid to be treated. An activated carbon treatment apparatus, characterized in that the liquid flowing direction of the liquid to be treated can be reversed, and the liquid flowing direction is periodically reversed to bring the liquid to be treated into contact with activated carbon. 2. The activated carbon treatment apparatus according to claim 1, comprising two activated carbon towers, wherein one of the two activated carbon towers has a liquid flowing direction upward, and the other has a liquid flowing direction falling downward. In addition to using both activated carbon towers connected in series, the liquid to be treated is first introduced into one activated carbon tower in an upward flow, and the treatment liquid in one activated carbon tower is introduced into the other activated carbon tower in a downward flow Activated carbon processing equipment.