JP2004073934A - Method of removing adherent matter to equipment to be disassembled - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost method of removing an adherent matter to equipment to be disassembled excellent in mobility and small in scale. <P>SOLUTION: In a method of treating washing wastewater generated when foreign matter adhering to an equipment to be disassembled is washed off by spraying washing water to the equipment to be disassembled at the time of disassembling of waste incineration equipment, the washing wastewater is collected in a raw water tank and led out of the raw water tank to be introduced into a membrane filter and a part of the introduced washing wastewater is filtered by the membrane filter to obtain treated water substantially containing no harmful matter. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for removing substances containing dioxins adhered to equipment by water washing before or during the demolition work of a waste incineration facility.
[0002]
[Prior art]
When dismantling aging waste incineration facilities, it is necessary to sufficiently remove dioxins and other organic chlorine-containing deposits from the equipment before dismantling work (Occupational Safety and Health Regulations) Article 592-3). Removal of deposits is often performed by high-pressure water washing, which is relatively easy to perform and can remove the deposits even in places that are not accessible.
[0003]
Generally, tap water or industrial water is used for the washing water. In addition, the wastewater after washing may be contaminated with dioxins. Therefore, the wastewater is drained to the outside after being treated to a level below the legally regulated wastewater (10 pg-TEQ / L) with existing wastewater treatment equipment. I was
[0004]
[Problems to be solved by the invention]
However, the conventional method requires a large amount of water for cleaning when the adhered substance is adhered to a wide area or when the adhered substance is not easily separated from the material to be dismantled. Since it is huge, the cost of dismantling work becomes excessive.
[0005]
Also, depending on the site, it is very difficult to secure a large amount of water itself, and the above method may not be adopted.
[0006]
Furthermore, the existing wastewater treatment facilities cannot be used when dismantling the entire waste incineration facility, so the wastewater must be disposed of as industrial waste or provided by a method other than water washing that does not generate wastewater. The kimono had to be removed.
[0007]
On the other hand, as a method for decomposing dioxins in water, for example, Japanese Patent Application Laid-Open No. 11-33570 describes a water treatment method that enhances the efficiency of generating hydroxy radicals to accelerate the decomposition reaction of dioxin and suppresses the pH adjustment cost. Have been. In this conventional method, hydrogen peroxide is added, and the reaction between ultraviolet rays and hydrogen peroxide, and the reaction between ozone and hydrogen peroxide activates the reaction of generating hydroxyl radicals, thereby efficiently decomposing dioxin.
[0008]
However, in the above-mentioned conventional method, a large-scale and highly complicated processing apparatus is brought to the site, and the cost becomes excessively large.
[0009]
The present invention has been made to solve the above-mentioned problems, and has as its object to provide a small-scale, highly maneuverable, low-cost method for removing deposits on demolition equipment.
[0010]
[Means for Solving the Problems]
The method for removing deposits on demolition facilities according to the present invention is directed to spraying cleaning water onto the demolition facilities when dismantling a waste incineration facility, and treating cleaning wastewater generated when cleaning and removing foreign substances attached to the demolition facilities. In the method, the washing wastewater is collected in a raw water tank, the washing wastewater is led out from the raw water tank, introduced into a membrane filtration device, and a part of the introduced washing wastewater is subjected to membrane filtration to substantially remove harmful substances. Characterized in that treated water containing no is obtained.
[0011]
Various filtration membranes can be used in the membrane filtration device used in the method of the present invention. For example, any one of a microfiltration membrane (MF membrane), an ultrafiltration membrane (UF membrane), and a reverse osmosis membrane can be used. Harmful substances such as dioxins can be separated and removed.
[0012]
The microfiltration membrane (MF membrane) is made of a polymer compound having a pore size of submicron (for example, 0.2 μm or less), and can have a module structure for mass processing. The ultrafiltration membrane (UF membrane) is composed of a high molecular compound having a pore size of double submicron (for example, 0.05 μm or less) and has a separation function having a molecular weight cutoff ranging from several hundred to several hundred thousand. Reverse osmosis membranes mainly use cellulose acetate membranes for desalination and can also be used to remove harmful low-molecular compounds in wastewater.
[0013]
It is preferable to employ a so-called cross flow method for the membrane filtration device of the present invention. In the cross-flow method, as shown in FIG. 3, the water flow 42 is parallel to the membrane 37a, so that clogging due to the adhesion of the foreign matter 41 is unlikely to occur in a short time use, and it can withstand a certain degree of continuous use. This is because the treated water 43 can be obtained with high stability. Such a cross-flow method is suitable for treating dismantled washing water having a high degree of contamination. The cross-flow method is also suitable for treating a large amount of wastewater.
[0014]
In addition, even if the cross-flow method is adopted, clogging occurs during continuous use. Therefore, it is desirable to perform backwashing of the membrane filtration device every predetermined time.
[0015]
The interval between the backwash operations is determined, for example, as follows. The pressure difference before and after the membrane is recorded at regular intervals, and the time interval of the backwash operation is determined so that this pressure difference is below the allowable value.
[0016]
By the way, it is not desirable to employ the total filtration method in the membrane filtration device of the present invention. The reason is that the total filtration method is apt to cause clogging since the water flow is orthogonal to the membrane, and is not suitable for treating wastewater from a dismantling facility containing a large amount of foreign matter. Incidentally, the total filtration method is a method suitable for finishing treatment of a relatively clean fluid or for treating a small amount of fluid.
[0017]
In addition, it is preferable to return the remainder of the washing wastewater introduced into the membrane filtration device to the raw water tank. This is because the treatment can be efficiently performed by returning the rest of the washing wastewater from the membrane filtration device to the raw water tank and circulating a part of the washing wastewater between the membrane filtration device and the raw water tank.
[0018]
Further, it is preferable that part or all of the treated water subjected to membrane filtration be reused as washing water used for removing adhered foreign matter inside the dismantling facility. This is because in a site where it is difficult to obtain a large amount of water, an amount of water necessary for cleaning can be secured.
[0019]
Further, it is preferable that the membrane filtration device is mounted on a vehicle so as to be movable. The period required for dismantling the facility is several days to several months, and high mobility is advantageous in order to quickly install or remove the device.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[0021]
A high-pressure jet water washing device (not shown) is disposed at the demolition site of the waste incineration facility, and a high-pressure jet water stream is sprayed on the demolition facility to wash and remove surface deposits. This washing operation generates a large amount of washing wastewater.
[0022]
FIG. 1 is a block diagram showing an outline of a water treatment facility used in a method for removing deposits on a dismantled facility according to an embodiment of the present invention. The water collecting port of the raw water tank 1 communicates with a drainage ditch of an existing building (not shown) or a pipe newly provided in a temporary construction, and most of the cleaning drainage is collected in the raw water tank 1 via these.
[0023]
The raw water tank 1 is a large-capacity storage tank capable of temporarily storing a large amount of washing wastewater. When an existing concrete water tank or the like exists at the site, it can be used as the raw water tank 1. If there is no suitable existing equipment at the site, the raw water tank 1 may be newly provided. When there are a plurality of locations where drainage occurs, the location may be once received in a tank or the like for each location and then transferred to the raw water tank 1.
[0024]
An appropriate place of the raw water tank 1 communicates with a lower part of the membrane module 3 via a line L1. The line L1 is provided with a raw water supply pump 2 so that the cleaning drainage is continuously or intermittently sent from the raw water tank 1 to the membrane module 3. If the raw water tank 1 is used as a sedimentation tank and the supernatant water is introduced into the membrane module 3, the operation load of the membrane module 3 is reduced, and a more preferable water treatment system is obtained.
[0025]
A discharge port of a compressor 6 is connected to a lower portion of the membrane module 3 via a line L2, so that compressed air having a predetermined pressure and a flow rate is supplied into the membrane module 3. A control valve V1 is provided in the air supply line L2 so that the amount of air supply to the membrane module 3 is adjusted.
[0026]
A treated water tank 4 is connected to the upper part of the membrane module 3 via a line L3, and the concentrated water filtered by the membrane module 3 is sent to the treated water tank 4.
[0027]
The treatment water tank 4 is also used as a backwash tank. An appropriate part of the treatment water tank 4 is connected to an upper part of the membrane module 3 via a backwash line L5. A backwash water pump 5 and a valve V2 are attached to the backwash line L5. The valve V2 is closed during normal operation, but during backwashing operation, the valve V2 is opened and the pump 5 allows the washing water to flow back to the membrane module 3 to backwash the filtration membrane incorporated in the membrane module 3. It has become.
[0028]
Further, a chemical solution line L6 is inserted in the backwash line L5 between the backwash water pump 5 and the valve V2. A pump 8 and a valve V3 are attached to the chemical solution line L6, and communicate with the chemical solution tank 7. The chemical solution tank 7 contains a sodium zinc chlorate solution. When the pump 8 is driven by opening the valve V3, the chemical liquid flows into the backwash water line L5 through the chemical liquid line L6, and the chemical liquid is injected into the backwash water.
[0029]
The side peripheral portion of the membrane module 3 communicates with two branch lines L4 and L7 which are divided into two by a three-way switching valve V4. One branch line L <b> 4 is connected to the raw water tank 1. The other branch line L7 is connected to the backwash water distribution tank 9. During the steady operation, the three-way switching valve V4 opens the line L4 and keeps the line L7 closed. During the backwashing operation, the three-way switching valve V4 is switched to close the line L4 and open the line L7.
[0030]
Next, the membrane module 3 will be described in detail with reference to FIGS.
[0031]
As the filtration membrane of the membrane module 3, either a microfiltration (MF) membrane or an ultrafiltration (UF) can be used. This is because these membranes can reliably remove suspended substances, microorganisms, polymer colloids, and the like having a size larger than the separation pore diameter.
[0032]
The membrane module 3 of the present embodiment includes a cross-flow type microfiltration membrane (MF membrane). A large number of hollow fiber membranes 37 are loaded in the case 31 as microfiltration membranes (MF membranes). The hollow fiber membrane 37 is made of polyvinylidene fluoride (PVDF), and has an inner diameter of 0.7 mm, an outer diameter of 1.3 mm, a nominal pore diameter of 0.1 μm, and a standard design filtration water volume of 0.3 to 8 m ³ / hr. Such a hollow fiber membrane 37 is strong enough to withstand a maximum pressure of 300 kPa. Incidentally, the case 31 is made of hard polyvinyl chloride, has a length of 1100 to 2400 mm, and an outer diameter of 90 to 170 mm.
[0033]
A water inlet 34 is provided at the lower end of the case 31, and washing drainage and compressed air are sent into the hollow fiber membrane 37 through the water inlet 34. One end of the hollow fiber membrane 37 is adhered to the inner surface of the case 31 with an epoxy resin adhesive at the flange 32 to form an adhesive portion 38, and the other end is held by a channel 39 having a number of guide holes or guide grooves. ing.
[0034]
A concentrated water outlet 35 is provided at the upper end of the case 31, and the concentrated water 42 after filtration exits from the membrane module 3. This concentrated water outlet 35 communicates with the treated water tank 4 via the line L3.
[0035]
A filtered water outlet 36 is provided in the upper peripheral portion of the case 31 so that the filtered water 43 filtered by the hollow fiber membrane 37 exits from the membrane module 3. A part of the filtered water 43 is returned to the raw water tank 1 and is again supplied from the raw water tank 1 to the membrane module 3, while another part is supplied to a jet cleaning water line (not shown) to be used as cleaning water. It is being reused.
[0036]
Next, an embodiment in the case where the method of the present invention is actually used for removing deposits on the dismantling facility will be described.
[0037]
(Example 1)
A hollow fiber MF membrane having a pore diameter of 0.1 μm and a pencil module UF membrane having a molecular weight cut off of 13,000 daltons were used as the filtration membrane in the membrane treatment device. Most of the organic chlorine compounds such as dioxins, which are particularly harmful substances that may be contained in the washing wastewater, exist in a state of being adsorbed by suspended substances, and this is treated by a membrane treatment device. Most of them are eliminated. For this reason, even if it is reused as washing water, there is no safety problem. Further, the membrane processing apparatus is composed of a membrane module and a pump attached to the membrane module, but is more compact than other dioxin removal apparatuses.
[0038]
A sample was collected from water treated using the method of Example 1, and the results of the analysis are shown in (1) to (3) below.
[0039]
(1) Raw water dioxin concentration: 1.6 pg-TEQ / L
(2) Dioxin concentration after treatment with membrane: 0.00021 pg-TEQ / L
(3) Dioxin concentration after treatment with UF membrane: 0.009 pg-TEQ / L
(Example 2)
As in Example 1 above, a hollow fiber MF membrane having a pore diameter of 0.1 μm was used as a filtration membrane in the membrane treatment device.
[0040]
A sample was collected from water treated using the method of Example 2, and the analysis results are shown in (4) and (5) below.
[0041]
(4) Raw water dioxin concentration: 50 pg-TEQ / L
(5) Dioxin concentration after treatment with MF membrane: 0.058 pg-TEQ / L
In the method of the present invention, the cross-flow filtration system shown in FIG. The cross-flow filtration method has the advantage of increasing the flow velocity on the primary filtration surface of the membrane, generating turbulence on the raw suspension water side, generating a shear flow on the membrane surface, and preventing deposition and adhesion of suspended solids. There is.
[0042]
Nevertheless, if the membrane is used for a long period of time, the filtration surface of the membrane may be clogged. This can prevent a decrease in the filtration capacity.
[0043]
At the time of the backwashing operation, if a chemical such as sodium hypochlorite solution is injected from the tank 7 and the compressed air from the compressor 6 is mixed and bubbled, the effect of the backwashing is further enhanced. Since the amount of concentrated water generated by this backwashing water is as small as about 5 to 10% of treated water, it is separately treated as high-concentration wastewater or returned to the raw water tank 1.
[0044]
The treated water after the membrane treatment is temporarily stored in the treated water tank 4 or the like, and is reused as washing water in the dismantling operation.
[0045]
【The invention's effect】
According to the present invention, the water once used for washing can be reused as washing water again, so that the consumption of new water such as clean water is reduced, and it is economical.
[0046]
Further, according to the present invention, the amount of washing wastewater can be significantly reduced, or the washing wastewater can be completely eliminated.
[0047]
Further, according to the present invention, since dioxins are highly removed from the treated water, there is no problem in terms of safety and health for workers even if the treated water is reused as washing water.
[0048]
Further, according to the present invention, since the membrane processing apparatus is compact, it can be easily transported by truck or the like. Since it can be used in the state of being mounted on a vehicle, there is an advantage that the wastewater treatment equipment can be installed in a very short time.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an outline of a water treatment facility used for a method for removing deposits on a dismantled facility according to an embodiment of the present invention.
FIG. 2 is a perspective sectional view showing the internal structure of the membrane module.
FIG. 3 is a schematic diagram illustrating a cross flow method.
[Explanation of symbols]
1 ... raw water tank,
2. Raw water supply pump
3 ... membrane module,
31 case, 32, 33 flange, 34 water inlet, 35 concentrated water outlet, 36 filtered water outlet, 37 hollow fiber membrane, 37a membrane wall, 38 adhesive part, 39 channel
4: Treatment tank
5. Backwash water pump
6 ... Compressor,
7 ... Chemical liquid tank,
8. Chemical pump
9 ... backwash water tank,
40: washing drainage, 41: sludge particles (foreign matter),
42: water flow, 43: treated water (filtered water),
L1 to L7 ... line,
V1 to V4: valves.

Claims (5)

A method of spraying cleaning water onto demolition facilities when dismantling a waste incineration facility and treating cleaning wastewater generated when cleaning and removing foreign substances attached to the demolition facilities,
The washing wastewater is collected in a raw water tank, the washing wastewater is led out from the raw water tank, introduced into a membrane filtration device, and a part of the introduced washing wastewater is subjected to membrane filtration to substantially eliminate harmful substances. A method for removing deposits on demolition equipment, characterized by obtaining water. The method according to claim 1, wherein the remaining portion of the washing wastewater introduced into the membrane filtration device is returned to the raw water tank. The method according to claim 1, wherein the membrane filtration device is backwashed at predetermined time intervals. 2. The method according to claim 1, wherein a part or all of the treated water is reused as cleaning water used for removing adhered foreign matter inside the dismantling facility. The method according to any one of claims 1 to 4, wherein the membrane filtration device is mounted on a vehicle and is movable.

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