JP3810342B2 - Electrodeposition paint recovery method and recovery device - Google Patents

Description

【００４０】
次に第１の膜濾過装置Ｃを停止した後、第１の濾過膜モジュール10を新品と交換し、上記１次濃縮タンク６の濃縮液５７０Ｌ（リットル）を２次濃縮タンク８に移して該２次濃縮タンク８の液量を７７０Ｌ（リットル）とした。
【００４１】
その後、濾過液の抜き出し量の積算値が７２０Ｌ（リットル）になるまで、第２の膜濾過装置Ｄにより再度濃縮（２次濃縮）を行った。第２の膜濾過装置Ｄの操作条件は入口圧力を２５０ｋＰａ、出口圧力を５０ｋＰａに調整した。
【００４２】
濾過液量の変化及び上記した測定条件で測定した濃縮液の固形分濃度、ｐＨ測定結果を以下の表２に示す。
【００４３】
尚、第２の膜濾過装置Ｄにより再度濃縮（２次濃縮）を開始した直後の２次濃縮タンク８内の濃縮液の固形分濃度は０．９２ｗｔ％であり、濃縮過程での濾過液の固形分濃度は０．０３ｗｔ％〜０．０４ｗｔ％であった。
【００４４】
【表２】

【００４５】
上記構成によれば、カチオン電着塗装工程の条件変動があっても、濃度変動に伴う第１、第２の膜濾過装置Ｃ，Ｄの能力低下が無く、必要な濾過液の確保が出来る。また、返送可能な量が変わっても濃縮液の量をカチオン電着塗装工程に合わすことが出来る。
【００４６】
即ち、第１の膜濾過装置Ｃの濃縮液の濃縮度を低く抑えることが出来、濾過能力を高く維持することが出来る。また、第２の膜濾過装置Ｄで任意の量まで２次濃縮出来る。また、第１、第２の膜濾過装置Ｃ，Ｄの１次、２次濃縮タンク６，８の容量を小さく出来る。
【００４７】
【発明の効果】
本発明は、上述の如き構成と作用とを有するので、第１の膜濾過装置（Ｃ）の１次濃縮液の全量を適宜、第２の膜濾過装置（Ｄ）の２次濃縮タンク（８）に抜き出すことにより、第１の膜濾過装置（Ｃ）の処理能力を高く発揮させることが出来、且つ、第２の膜濾過装置（Ｄ）で電着槽（１）に返送可能な量まで任意に２次濃縮することが出来る。
【００４８】
更に第１の膜濾過装置（Ｃ）及び第２の膜濾過装置（Ｄ）の１次、２次濃縮タンク（６，８）の容量をより小さくすることが出来、第１の膜濾過装置（Ｃ）は停止の必要がないため、常時、最終水洗槽（５）に濾過液を供給することが出来、カチオン電着塗装工程に影響することもない。
【図面の簡単な説明】
【図１】 本発明に係る電着塗料の回収装置の構成を示す概略図である。
【符号の説明】
Ａ…ＵＦ（限外濾過）濾過液回収水洗工程
Ｂ…最終水洗工程
Ｃ，Ｄ…第１、第２の膜濾過装置
１…電着槽
２〜４…第１〜第３水洗槽
５…最終水洗槽
６…１次濃縮タンク
７…濾過液タンク
８…２次濃縮タンク
９…ＵＦ膜モジュール
10，11…第１、第２の濾過膜モジュール
12…循環ポンプ
13…濾過液回収ポンプ
14，15…循環ポンプ
16…濾過液回収ポンプ
17…２次濃縮液回収ポンプ
18…２次濃縮液返送ライン
19…濾過液回収ライン
20…純水供給ライン
21…濾過液排出ライン
22…被塗物
23…コンベア[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrodeposition paint recovery method and a recovery device for concentrating and recovering wastewater from a final washing tank in cationic electrodeposition coating with a membrane filtration device.
[0002]
[Prior art]
Conventionally, cationic electrodeposition coating has been widely used for painting automobile bodies, automobile parts, electrical products, building materials and the like. The electrodeposition coating system consists of an electrodeposition process for electrochemically forming a coating film on an object to be coated, a cleaning process for washing off non-electrodeposited paint, and a drying-baking process for curing the coating film. In general, the water washing process is roughly divided into a UF (ultrafiltration) filtrate recovery water washing process and a final water washing process.
[0003]
In the UF (ultrafiltration) filtrate recovery water washing step, the object to be coated is washed with the UF filtrate obtained by filtering the paint in the electrodeposition tank with a UF (ultrafiltration) membrane. This is a step of washing away the paint component physically adhered to the electrode and collecting it in the electrodeposition tank.
[0004]
In addition, the final water washing step is a step of performing final washing using pure water or industrial water, and trace amounts of paint components and impurities that could not be washed out in the UF filtrate recovery water washing step are washed away. The water after being used for is discharged out of the process as waste water.
[0005]
A large amount of water is required for the final water washing, which is the final washing, and when the object to be coated is an automobile body, water of 100 L (liter) / min or more is newly supplied as the washing water. It is discharged as waste water.
[0006]
Although this wastewater contains a small amount of paint components and impurities, not only does it have to be treated in some way, but it also results in the loss of paint. The loss of paint is equivalent to 5% of the paint physically taken out from the electrodeposition tank by the object to be coated.
[0007]
In recent years, a membrane separation method has been proposed as a method for treating such waste water, and the filtrate and concentrate are separated in one stage by a membrane filtration device, and the filtrate is circulated and used as washing water and the concentrate is used as an electrodeposition tank. A method of returning and collecting and reusing as paint has been put into practical use.
[0008]
[Problems to be solved by the invention]
However, in the above-described conventional example, the amount of liquid that can be returned to the electrodeposition tank is limited, and this amount is the amount of evaporation from the electrodeposition tank and the water washing system, the water brought in from the pretreatment process of the coating, and the UF recovery water washing system. Depending on the balance of water taken out from the water, the amount of evaporation decreases when the humidity is high, such as in summer, and the amount of liquid that can be returned is limited. The same problem occurs when there is a large amount of water brought in.
[0009]
In such a case and when the shape of the object to be coated is changed and the concentration of waste water in the final washing tank is increased, or when the operating time of the coating process is extended, the concentration of the concentrated solution concentrated in the membrane filtration device As a result, the capability of the membrane filtration device is lowered, and there is a problem that it is impossible to secure the amount of filtrate necessary for water washing. In addition, a larger tank for storing the concentrate was necessary in preparation for the situation where the amount of the concentrate was too large to be returned.
[0010]
In addition, when concentrating in one-step concentration and batch operation as in the past, install a larger receiving tank or increase the number of times the concentrate is dispensed in order to suppress an increase in the concentration of the concentrate during the concentration process. Therefore, it was necessary to mitigate the increase in concentration.
[0011]
However, it is necessary to substantially stop the membrane filtration device during the dispensing of the concentrate, and during this time, the filtrate cannot be returned to the washing tank, so the return timing of the concentrate is adjusted to the pause time of the painting process. Such a complicated response was indispensable.
[0012]
These problems can also be solved by increasing the scale of the membrane filtration device and increasing the processing capacity, but it is not only economically disadvantageous, but also has a large installation area and is compact and fits the actual conditions of the painting process. There has been a long-awaited need for an electrodeposition paint recovery method and recovery device.
[0013]
The present invention solves the above-mentioned problems, and the object is to treat the waste water of the final washing tank of the cationic electrodeposition coating with a membrane filtration device, collect the concentrated solution as a paint, and wash the filtrate with washing water. As a recycling system, it is not possible to provide a method and equipment for collecting electrodeposition paint that can be efficiently concentrated even if there are fluctuations in the concentration of wastewater, operating conditions in the painting process, and fluctuations in the liquid level of the electrodeposition tank. Is.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the electrodeposition coating material recovery method according to the present invention includes a UF (ultrafiltration) filtrate recovery water washing step (A) and a final water washing step (B) . The waste water discharged from the final washing tank (5) is primarily concentrated while being received in the primary concentration tank (6) of the first membrane filtration device (C) , and the total amount of the concentrated liquid in the primary concentration tank (6) is obtained. a second lead to membrane filtering device secondary concentrate tank (8) of (D), after secondarily concentrated in the second membrane filtration unit (D), the concentrated solution of the secondary concentrate tank (8) While returning to an electrodeposition tank (1) , the filtrate from the said 1st and 2nd membrane filtration apparatus (C, D ) is returned to the said last water washing tank (5) , It is characterized by the above-mentioned.
[0015]
In addition, the electrodeposition coating material recovery device according to the present invention includes a final water rinsing tank (5 ) of a cationic electrodeposition coating process having a UF (ultrafiltration) filtrate recovery water washing process (A) and a final water washing process (B). ) Obtained by a first membrane filtration device (C) having a primary concentration tank (6) for primary concentration while receiving wastewater discharged from the wastewater ), and the first membrane filtration device (C) . electrodeposition and second membrane filtration apparatus provided with a secondary concentrate tank (8) for secondary concentrated accept the total amount of the primary concentrated liquid (D), the concentrated solution of the secondary concentrate tank (8) A first pipe for returning to the tank (1) and a second pipe for returning the filtrate from the first and second membrane filtration devices (C, D) to the final water washing tank (5). It is characterized by having.
[0016]
Since the present invention is configured as described above, the total amount of the primary concentrated liquid from the first membrane filtration device (C) is appropriately led to the secondary concentration tank (8) of the second membrane filtration device (D). by, it is possible to suppress the first membrane filtration unit a primary enrichment of (C) to the extent that the filtration capability can be exhibited high of the first membrane filtration unit (C), and, second membrane filtration unit In (D) , the concentrated solution can be optionally subjected to secondary concentration up to the amount that can be returned to the electrodeposition tank (1) , and the primary and secondary of the first and second membrane filtration devices (C, D) , respectively. The capacity of the secondary concentration tank (6, 8) can be further reduced.
[0017]
And since it is not necessary to stop a 1st membrane filtration apparatus (C) , a filtrate can always be supplied to the last washing tank (5), and it does not affect a coating process.
[0018]
In the present invention, the concentrated liquid in the secondary concentration tank (8) can be returned to the electrodeposition tank (1) directly by batch operation. However, after the secondary concentrated liquid is once stored, the electrodeposition tank (1 it is more preferable to return in accordance with the state of the liquid surface of).
[0019]
The scale of the first membrane filtration device (C) and the scale of the second membrane filtration device (D) are in the mass balance (liquid amount and concentration ) within the range of the filtrate amount that needs to be returned to the final washing tank (5) . Can be set arbitrarily in consideration of the balance between the balance and the balance, but the concentration of the concentrate in the primary concentration tank (6) of the first membrane filtration device (C) should be set to 1% or less. Preferably, when the scale of the first membrane filter (C) is determined, the scale of the second membrane filter (D) is automatically determined from the mass balance.
[0020]
Here, since the density | concentration of the last washing tank (5) is 0.1% or less normally, the concentration of the concentrate in a 1st membrane filtration apparatus (C) becomes 10 times or more. That is, on average, the primary concentrated liquid having an amount of 1/10 or less of the amount of waste water discharged from the final washing tank (5) received in the primary concentration tank (6) of the first membrane filtration device (C). Will be led to the secondary concentration tank (8) of the second membrane filtration device (D) . Then, it is secondarily concentrated by the second membrane filtration device (D) to an amount that can be returned to the electrodeposition tank (1) .
[0021]
Moreover, the capacity of the secondary concentrate tank (8) of the first film primary concentrate tank of the filter (C) (6) and a second membrane filtration apparatus of the present invention (D) is not particularly limited, too small And the frequency of extracting the concentrate increases. Further, if it is too large, not only will the installation area be increased, but also the amount of hold-up (storage amount) will increase, and in the case of stopping for a long period of time, it will take time to drain the liquid and will be difficult to clean.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of an electrodeposition coating material recovery method and recovery device according to the present invention will be specifically described with reference to the drawings. FIG. 1 is a schematic view showing a configuration of an electrodeposition paint recovery apparatus according to the present invention.
[0023]
As shown in FIG. 1, the water-washing process of the electrodeposition paint in the cationic electrodeposition coating process includes a UF (ultrafiltration) filtrate recovery water-washing process indicated by A and a final water-washing process indicated by B. ing.
[0024]
In the UF (ultrafiltration) filtrate recovery water washing step A, the object 22 conveyed by the conveyor 23 is immersed in the electrodeposition tank 1 and is electrodeposited, then the first water washing tank 2 and the second water washing tank 3. And it wash | cleans in order in the 3rd water-washing tank 4. The paint washed away by each of the water washing layers 2 to 4 is returned to the electrodeposition tank 1 from the third water washing tank 4 through the second water washing tank 3 and the first water washing tank 2 in this order.
[0025]
The electrodeposition liquid in the electrodeposition tank 1 is supplied to the UF (ultrafiltration) membrane module 9 by the circulation pump 12, and the UF filtrate obtained by filtering with the UF membrane module 9 is recovered by the filtrate recovery pump 13. Then, the coating object 22 is washed, the paint component physically adhered to the coating object 22 is washed away, and the concentrated solution concentrated in the UF membrane module 9 is collected in the electrodeposition tank 1.
[0026]
In addition, the final water washing step B is a step of performing final washing using pure water or industrial water, and trace amounts of paint components and contaminating ions that could not be washed out in the UF filtrate recovery water washing step A are washed away.
[0027]
The object to be coated 22 conveyed by the conveyor 23 is guided to the UF filtrate recovery water washing step A and washed in the order of the first water washing tank 2, the second water washing tank 3, and the third water washing tank 4, and then the final water washing step B. Then, after entering the final water washing tank 5 and dip-cleaning, finally, it is cleaned with pure water supplied from the pure water supply line 20 as necessary, such as removal of contaminant ions.
[0028]
The waste water discharged from the final rinsing tank 5 is separated into a concentrate and a filtrate by the first membrane filtration device C and the second membrane filtration device D, and each filtrate is stored in the filtrate tank 7. Although it is mainly recycled to the final rinsing tank 5, in order to maintain the balance of the amount of water in the final rinsing system when the final rinsing is performed, the secondary concentration from the second membrane filter D is used from the amount of pure water used. It is necessary to discard the filtrate corresponding to the amount obtained by subtracting the liquid, and the filtrate is discarded out of the system from the filtrate discharge line 21.
[0029]
It should be noted that such a partial disposal of the filtrate can prevent the accumulation of contaminating ions in the final washing system.
[0030]
The first membrane filtration device C and the second membrane filtration device D are respectively from the primary and secondary concentration tanks 6 and 8, the circulation pumps 14 and 15, the first and second filtration membrane modules 10 and 11, and the like. Composed.
[0031]
First, the waste water discharged from the final water washing tank 5 is passed through a first filtration membrane module 10 through a circulation pump 14 on the co If accepted the primary concentrating tank 6 of the first membrane filtration device C 1 Next concentrated.
[0032]
The total amount of the primary concentrated liquid in the primary concentration tank 6 is guided to the secondary concentration tank 8 of the second membrane filtration device D as appropriate. On the other hand, the filtrate filtered by the first and second filtration membrane modules 10 and 11 of the first and second membrane filtration devices C and D is stored in the filtrate tank 7 and then filtered by the filtrate collection pump 16. The filtrate is returned to the final rinsing tank 5 through the filtrate recovery line 19 serving as the second pipe and recycled.
[0033]
The primary concentrated liquid received from the primary concentration tank 6 of the first membrane filtration device C and stored in the secondary concentration tank 8 of the second membrane filtration device D is second filtered through the circulation pump 15. After being passed through the membrane module 11 and secondarily concentrated to an amount that can be returned to the electrodeposition tank 1, the concentrated liquid in the secondary concentration tank 8 becomes a first pipe by the secondary concentrated liquid recovery pump 17. It returns to the electrodeposition tank 1 through the concentrate return line 18.
[0034]
<Example 1>
Filtration membrane modules 10 and 11 (for example, Asahi Kasei Co., Ltd.) having a membrane area of 1000 L (liter) primary and secondary concentration tanks 6 and 8 and 4.7 m ² in the final water washing step B of the cationic electrodeposition coating of the automobile body The first and second membrane filtration devices C and D each having a single ECS-3010 were installed, and the following tests were performed.
[0035]
First, 200 L (liters) of waste water from the final rinsing tank 5 is received in the primary concentration tank 6. Thereafter, the liquid level controller maintains this liquid level and the pH of the filtrate is adjusted by a pH sensor provided in the filtrate line. When the pH of the filtrate rises to 5.7 so that it can always be detected, acetic acid with a solid content concentration of 10 wt% is automatically added to the primary concentration tank 6, and acetic acid is added when the pH drops to 5.5 The first concentration was performed by the first membrane filtration device C while adjusting the pH.
[0036]
Filtrate once, after accumulated into the filtration tank 7, to return a final water washing tank 5, the concentrate without withdrawal until 10 hours concentrated time, once after 20 minutes, 1000 4L (L) L It was treated continuously for 58 hours while being taken out into another tank (liter).
[0037]
The operating conditions of the first membrane filtration device C were adjusted such that the inlet pressure was 250 kPa and the outlet pressure was 50 kPa. Table 1 below shows the change in the amount of the filtrate, the measurement results of the solid content concentration of the concentrate, and the pH measurement results.
[0038]
In addition, the solid content concentration of the concentrate and the filtrate was appropriately measured by collecting 10 g samples from the primary concentration tank 6 and the filtrate tank 7 and drying at 105 ° C. for 3 hours. The solid content concentration of the waste water received at the beginning was 0.04 wt%, and the solid content concentration of the filtrate was changed from 0.01 wt% to 0.03 wt%.
[0039]
[Table 1]

[0040]
Next, after the first membrane filtration device C is stopped, the first filtration membrane module 10 is replaced with a new one, and the concentrated liquid 570L (liter) of the primary concentration tank 6 is transferred to the secondary concentration tank 8 to The amount of liquid in the secondary concentration tank 8 was 770 L (liter).
[0041]
Thereafter, concentration (secondary concentration) was performed again by the second membrane filtration device D until the integrated value of the amount of the filtrate extracted reached 720 L (liter). The operating conditions of the second membrane filtration device D were adjusted such that the inlet pressure was 250 kPa and the outlet pressure was 50 kPa.
[0042]
Table 2 below shows the change in the amount of the filtrate, the solid content concentration of the concentrate measured under the above-described measurement conditions, and the pH measurement results.
[0043]
It should be noted that the concentration of the solid in the secondary concentration tank 8 immediately after the concentration (secondary concentration) is started again by the second membrane filtration device D is 0.92 wt%, and the concentration of the filtrate in the concentration process is 0.92 wt%. The solid content concentration was 0.03 wt% to 0.04 wt%.
[0044]
[Table 2]

[0045]
According to the said structure, even if there exists a fluctuation | variation of the conditions of a cation electrodeposition coating process, there is no capability fall of the 1st, 2nd membrane filtration apparatus C and D accompanying a density | concentration fluctuation | variation, and a required filtrate can be ensured. Moreover, even if the amount which can be returned changes, the quantity of a concentrate can be match | combined with a cationic electrodeposition coating process.
[0046]
That is, the concentration of the concentrate of the first membrane filtration device C can be kept low, and the filtration capacity can be maintained high. Further, the second membrane filtration device D can perform secondary concentration to an arbitrary amount. Further, the capacity of the primary and secondary concentration tanks 6 and 8 of the first and second membrane filtration devices C and D can be reduced.
[0047]
【The invention's effect】
Since the present invention has the above-described configuration and operation, the total amount of the primary concentrated liquid in the first membrane filtration device (C) is appropriately adjusted to the secondary concentration tank (8 in the second membrane filtration device (D). by withdrawing the), it is possible to highly exhibit the processing capability of the first membrane filtration unit (C), and, to an amount that can be returned to the electrodeposition bath in the second membrane filtration unit (D) (1) Secondary concentration can be optionally performed.
[0048]
Furthermore, the capacity | capacitance of the primary and secondary concentration tank (6, 8) of a 1st membrane filtration apparatus (C) and a 2nd membrane filtration apparatus (D) can be made smaller, and the 1st membrane filtration apparatus ( Since C) does not need to be stopped, the filtrate can be always supplied to the final washing tank (5) and does not affect the cationic electrodeposition coating process.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the configuration of an electrodeposition paint recovery apparatus according to the present invention.
[Explanation of symbols]
A ... UF (ultrafiltration) filtrate recovery water washing process B ... Final water washing process C, D ... 1st, 2nd membrane filtration apparatus 1 ... Electrodeposition tank 2-4 ... 1st-3rd water washing tank 5 ... Final Washing tank 6 ... Primary concentration tank 7 ... Filtrate tank 8 ... Secondary concentration tank 9 ... UF membrane module
10, 11 ... 1st and 2nd filtration membrane module
12 ... circulation pump
13 ... Filtrate recovery pump
14, 15 ... Circulation pump
16 ... Filtrate recovery pump
17 ... Secondary concentrate recovery pump
18 ... Secondary concentrate return line
19 ... Filtrate recovery line
20 ... Pure water supply line
21 ... Filtrate discharge line
22 ... Coating
23 ... conveyor

Claims (2)

Waste water discharged from the final rinsing tank (5) of the cationic electrodeposition coating process having a UF (ultrafiltration) filtrate recovery rinsing step (A) and a final rinsing step (B) is removed from the first membrane filtration device ( and primary concentrated while receiving the primary concentrating tank (6) in C), the concentrated solution of the primary concentrating tank (6) the total amount, the secondary concentrate tank of the second membrane filtration unit (D) (8) Then, after secondarily concentrating with the second membrane filtration device (D) , the concentrated solution in the secondary concentration tank (8 ) is returned to the electrodeposition tank (1) and the first and second membrane filtration devices A method of recovering an electrodeposition paint, wherein the filtrate from (C, D) is returned to the final washing tank (5) . In order to perform primary concentration while receiving waste water discharged from the final washing tank (5) of the cationic electrodeposition coating process including the UF (ultrafiltration) filtrate recovery washing process (A) and the final washing process (B). A first membrane filtration device (C) comprising a primary concentration tank (6) of
A second membrane filtration device (D) comprising a secondary concentration tank (8) for receiving and secondary-concentrating the total amount of the primary concentrate obtained by the first membrane filtration device (C) ;
A first pipe for returning the concentrate of the secondary concentration tank (8) to the electrodeposition tank (1) ;
A second pipe for returning the filtrate from the first and second membrane filtration devices (C, D) to the final washing tank (5) ;
An electrodeposition coating material recovery apparatus comprising:

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