Recovery apparatus and recovery method for volatile organic compounds

Abstract

To provide a recovery device and recovery method of VOC which can efficiently recover VOC generated in a drying furnace, and are excellent in cost and environment.SOLUTION: A recovery device of VOC is a device where workpiece coated using an electro-deposition coating material is carried in, and which recovers VOC in a coating and drying furnace in an electro-deposition coating line having a dip washing tank and a coating and drying furnace, wherein the coating and drying furnace includes an evaporation zone where moisture of the workpiece is evaporated at a furnace temperature of 80°C or higher and 120°C or lower, and a curing zone arranged on the downstream side of the evaporation zone, where the coating film is cured at the furnace temperature of 150°C or higher and 200°C or lower, weight absolute humidity of second furnace air in the curing zone is lower than weight absolute humidity of first furnace air in the evaporation zone, and a take-out passage for taking out the furnace air in the coating and drying furnace, and a cooling and recovering part for cooling the furnace air containing the first furnace air, and recovering VOC contained in the furnace air as a condensate together with moisture contained in the furnace air are provided.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a recovery device and a recovery method for volatile organic compounds in a painting drying furnace.

Background Art

[0002] Conventionally, in the painting process of a vehicle body or the like, in order to reduce paint loss, surplus paint has been recovered (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the drying process of carrying a painted workpiece into a drying furnace to dry the paint film (bake or flash off), it is known that a large amount of volatile organic compounds (Volatile Organic Compounds, hereinafter sometimes referred to as "VOC") contained in the paint film evaporates.

[0005] This VOC has conventionally been incinerated, but there are problems in terms of cost, and there are also problems in terms of the environment such as a large amount of CO2 being generated by the incineration of VOC.

[0006] Therefore, an object of the present disclosure is to provide a VOC recovery device and a recovery method that can efficiently recover VOC generated in a drying furnace and are excellent in terms of cost and the environment.

Means for Solving the Problems

[0007] To solve the above problems, the first volatile organic compound recovery apparatus disclosed herein is an apparatus for recovering volatile organic compounds in a paint drying furnace in an electrodeposition coating line, which comprises a dip washing tank into which workpieces coated with electrodeposition paint are brought and for dipping the workpieces, and a paint drying furnace located downstream of the dip washing tank for drying the coating film of the workpieces, wherein the paint drying furnace into which the workpieces are brought and for evaporating the moisture of the workpieces at a furnace temperature of 80°C to 120°C The paint drying oven is characterized by comprising an evaporation zone and a curing zone located downstream of the evaporation zone, where the coating film is cured at a furnace temperature of 150°C to 200°C, wherein the absolute humidity by weight of the second furnace air in the curing zone is lower than the absolute humidity by weight of the first furnace air in the evaporation zone, an extraction passage for extracting the furnace air from the paint drying oven, and a cooling and recovery unit for cooling the furnace air, including the first furnace air, and recovering the volatile organic compounds contained in the furnace air as condensates together with the moisture contained in the furnace air.

[0008] The coating film of workpieces painted with water-soluble paints contains large amounts of water and volatile organic compounds. In particular, in electrodeposition coating lines equipped with a dip water washing tank where workpieces painted with electrodeposition paints are immersed in washing water for cleaning, the coating film of workpieces transported to the paint drying oven contains a large amount of water derived from the washing water. In the low-temperature evaporation zone, the water contained in the coating film mainly evaporates, and the air in the first furnace contains a large amount of water vapor. In the high-temperature curing zone, the VOCs contained in the coating film mainly evaporate, and the air in the second furnace contains a large amount of VOCs. That is, the absolute humidity by weight of the air in the second furnace in the curing zone is lower than the absolute humidity by weight of the air in the first furnace in the evaporation zone. In this technology, by cooling the furnace air, including the air in the first furnace, VOCs can be dissolved in the water and condensed. In this way, VOCs in the paint drying oven can be efficiently recovered. Furthermore, since this technology recovers VOCs as condensates, it eliminates the need for exhaust gases and catalytic oxidation equipment used in conventional VOC incineration treatments, or, even if catalytic oxidation equipment is required, it can be miniaturized and its exhaust volume reduced.

[0009] The second technology disclosed herein is a volatile organic compound recovery apparatus for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought and the paint film of the workpiece is dried. The paint drying oven comprises an evaporation zone into which the workpiece is brought and the internal temperature of the oven is 80°C to 120°C to evaporate the moisture from the workpiece, and a curing zone located downstream of the evaporation zone and the internal temperature of the oven is 150°C to 200°C to cure the paint film. The absolute humidity by weight of the second oven air in the curing zone is lower than the absolute humidity by weight of the first oven air in the evaporation zone. The apparatus comprises an extraction passage for taking out the oven air from the paint drying oven, and a cooling and recovery unit for cooling the oven air, including the second oven air, and recovering the volatile organic compounds contained in the second oven air as condensates together with the moisture contained in the oven air. The cooling and recovery unit is equipped with a moisture supply unit for replenishing additional moisture within the cooling and recovery unit.

[0010] The coating film of a workpiece painted with water-soluble paint contains a large amount of water and volatile organic compounds (VOCs). In the low-temperature evaporation zone, the water contained in the coating film mainly evaporates, and the air in the first furnace contains a large amount of water vapor. In the high-temperature curing zone, the VOCs contained in the coating film mainly evaporate, and the air in the second furnace contains a large amount of VOCs. That is, the absolute humidity by weight of the air in the second furnace in the curing zone is lower than the absolute humidity by weight of the air in the first furnace in the evaporation zone. If the amount of water in the second furnace air is small, it may be difficult to secure enough water to adequately recover VOCs in the cooling and recovery section. In this technology, by adding water to the furnace air, including the second furnace air, and cooling the furnace air, VOCs can be dissolved in the water and condensed. In this way, VOCs in the paint drying furnace can be efficiently recovered. Furthermore, since this technology recovers VOCs as condensates, it eliminates the need for exhaust gases and catalytic oxidation equipment used in conventional VOC incineration treatments, or, even if catalytic oxidation equipment is required, it can be miniaturized and its exhaust volume reduced.

[0011] The third technology is characterized in that, in the first or second technology, the cooling and recovery unit comprises a cooler for cooling the furnace air, a heater into which the residual air cooled by the cooler and from which the condensate has been removed is introduced and which heats the residual air, a return passage for returning the heated residual air to the evaporation zone of the paint drying oven, and a heat pump connecting the cooler and the heater, which supplies cold energy to the cooler for cooling the furnace air by heat exchange and heat energy to the heater for heating the residual air by heat exchange.

[0012] According to this technology, the air inside the furnace is cooled, and the dry air, after condensing and removing moisture and VOCs, is heated and returned to the evaporation zone of the paint drying furnace. This suppresses the rise in vapor pressure inside the paint drying furnace. As a result, the evaporation rate of moisture and VOCs in the paint film in the paint drying furnace increases, allowing the paint film on the workpiece to be dried quickly and efficiently in the paint drying furnace, which is advantageous for improving quality. Furthermore, since a heat pump is used for cooling and heating the air inside the furnace, energy loss is reduced, which is advantageous for energy saving.

[0013] The fourth technology is, 1st technique In the procedure, the above-mentioned extraction passage communicates with the above-mentioned evaporation zone. do 1st takeout street road It is characterized by being equipped with.

[0014] The fifth technology is characterized in that, in the second technology, the extraction passage comprises a second extraction passage that communicates with the hardening zone.

[0015] The following disclosure 6The method for recovering volatile organic compounds related to the technology is for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought and the paint film of the workpiece is dried, wherein the paint drying oven comprises an evaporation zone into which the workpiece is brought and the internal temperature of the oven is 80°C to 120°C to evaporate the moisture from the workpiece, and a curing zone located downstream of the evaporation zone and the internal temperature of the oven is 150°C to 200°C to cure the paint film, and the absolute humidity by weight of the second oven air in the curing zone is above The invention comprises a removal step of removing the oven air from the paint drying oven at a temperature lower than the absolute humidity by weight of the first oven air in the evaporation zone, and a cooling and recovery step of cooling the oven air, including the first oven air, to recover the volatile organic compounds contained in the oven air as condensates together with the moisture contained in the oven air, wherein the water-soluble paint is an electrodeposition paint, and the workpiece is transported to the paint drying oven after undergoing a washing step in which it is immersed in washing water after an electrodeposition step using the electrodeposition paint.

[0016] The coating film of a workpiece painted with water-soluble paint contains a large amount of water and volatile organic compounds. In particular, when a washing process is performed after the electrodeposition process, in which the workpiece is immersed in washing water, the coating film of the workpiece brought into the paint drying oven contains a large amount of water derived from the washing water. In the low-temperature evaporation zone, the water contained in the coating film mainly evaporates, and the air in the first furnace contains a large amount of water vapor. In the high-temperature curing zone, the VOCs contained in the coating film mainly evaporate, and the air in the second furnace contains a large amount of VOCs. That is, the absolute humidity by weight of the air in the second furnace in the curing zone is lower than the absolute humidity by weight of the air in the first furnace in the evaporation zone. According to this technology, by cooling the furnace air, including the air in the first furnace, VOCs can be dissolved in the water and condensed. In this way, the VOCs evaporated in the paint drying oven can be efficiently recovered. Furthermore, the exhaust gas and catalytic oxidation equipment for conventional VOC incineration treatment become unnecessary, or even if catalytic oxidation equipment is installed, it can be miniaturized and the amount of exhaust gas reduced.

[0017] The following disclosure 7The method for recovering volatile organic compounds related to the technology is a method for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought and the paint film of the workpiece is dried, wherein the paint drying oven comprises an evaporation zone into which the workpiece is brought and the internal temperature of the oven evaporates the moisture of the workpiece at 80°C to 120°C, and a curing zone located downstream of the evaporation zone and the internal temperature of the oven curing the paint film at 150°C to 200°C, wherein the absolute humidity by weight of the second oven air in the curing zone is lower than the absolute humidity by weight of the first oven air in the evaporation zone, and comprises a removal step for taking out the oven air from the paint drying oven, and a cooling recovery step for replenishing the oven air, including the second oven air, with additional moisture and cooling the oven air to recover the volatile organic compounds contained in the oven air as condensates together with the moisture contained in the oven air.

[0018] The coating film of a workpiece painted with water-soluble paint contains a large amount of water and volatile organic compounds. In the low-temperature evaporation zone, the water contained in the coating film mainly evaporates, and the air in the first furnace contains a large amount of water vapor. In the high-temperature curing zone, the VOCs contained in the coating film mainly evaporate, and the air in the second furnace contains a large amount of VOCs. That is, the absolute humidity by weight of the air in the second furnace in the curing zone is lower than the absolute humidity by weight of the air in the first furnace in the evaporation zone. If the amount of water contained in the second furnace air is small, it may be difficult to secure enough water to adequately recover VOCs in the cooling and recovery process. According to this technology, by adding additional water to the furnace air, including the second furnace air, and cooling the furnace air, VOCs can be dissolved in the water and condensed. In this way, the VOCs evaporated in the paint drying furnace can be efficiently recovered. Furthermore, the exhaust gas and catalytic oxidation equipment for conventional VOC incineration treatment become unnecessary, or even if catalytic oxidation equipment is installed, it can be miniaturized and the amount of exhaust gas reduced.

[0019] The 8 The technology is, 6 or the 7The technology is characterized by comprising a return step in which the remaining air from which the condensate has been removed after the cooling and recovery step is heated and returned to the evaporation zone of the paint drying oven, and using a heat pump that uses the oven air as an absorption source and the remaining air as a heat dissipation source to cool the oven air and heat the remaining air.

[0020] According to this technology, the air inside the furnace is cooled, and the dry air, after condensing and removing moisture and VOCs, is heated and returned to the evaporation zone of the paint drying furnace. This suppresses the rise in vapor pressure inside the paint drying furnace. As a result, the evaporation rate of moisture and VOCs in the paint film in the paint drying furnace increases, allowing the paint film on the workpiece to be dried quickly and efficiently in the paint drying furnace, which is advantageous for improving quality. Furthermore, since a heat pump is used for cooling and heating the air inside the furnace, energy loss is reduced, which is advantageous for energy saving.

[0021] A volatile organic compound recovery apparatus according to one embodiment is an apparatus for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought and the paint film of the workpiece is dried. The paint drying oven comprises an evaporation zone into which the workpiece is brought and the internal temperature of the oven is 80°C to 120°C to evaporate the moisture from the workpiece, and a curing zone located downstream of the evaporation zone and the internal temperature of the oven is 150°C to 200°C to cure the paint film. The apparatus comprises a first extraction passage communicating with the evaporation zone for extracting first internal air from the evaporation zone, a second extraction passage communicating with the curing zone for extracting second internal air from the curing zone, a mixing chamber for mixing the first internal air and the second internal air to obtain mixed air, and a cooling and recovery unit for cooling the mixed air and recovering the volatile organic compounds contained in the mixed air as condensates together with the moisture. The cooling and recovery unit comprises a moisture supply unit for replenishing additional moisture within the cooling and recovery unit. The coating film of a workpiece coated with a water-soluble paint contains a large amount of moisture and volatile organic compounds. In the low-temperature evaporation zone, the moisture contained in the coating film mainly evaporates, and the air inside the first furnace contains a large amount of water vapor. On the other hand, in the high-temperature curing zone provided downstream of the evaporation zone, the VOCs contained in the coating film mainly evaporate, and the air inside the second furnace contains a large amount of VOCs. In this technology, the air inside the first furnace in the evaporation zone and the air inside the second furnace in the curing zone are taken out, mixed, and cooled, so that the VOCs can be condensed while being dissolved in the moisture. Thus, the VOCs inside the coating drying furnace can be efficiently recovered. Also, according to this technology, since the VOCs are recovered as condensates, the exhaust gas for the conventional VOC incineration treatment and the installation of a catalytic oxidation device are not required, or even when a catalytic oxidation device is provided, its miniaturization and reduction of the exhaust gas volume are possible. Furthermore, when the moisture contained in the mixed air is low, it may be difficult to ensure a sufficient amount of moisture for efficiently recovering the VOCs in the cooling and recovery section. According to this technology, in the cooling and recovery section, by supplementing additional moisture, the VOCs can be efficiently recovered.

[0022] A method for recovering volatile organic compounds according to an embodiment is a method for recovering volatile organic compounds in a coating drying furnace in which a workpiece coated with a water-soluble paint is carried in and the coating film of the workpiece is dried. The coating drying furnace includes an evaporation zone in which the workpiece is carried in and the moisture of the workpiece is evaporated at a furnace internal temperature of 80°C or higher and 120°C or lower, and a curing zone disposed downstream of the evaporation zone and in which the coating film is cured at a furnace internal temperature of 150°C or higher and 200°C or lower. The method comprises a first extraction step of extracting the air inside the first furnace in the evaporation zone, a second extraction step of extracting the air inside the second furnace in the curing zone, a mixing step of mixing the air inside the first furnace and the air inside the second furnace to obtain mixed air, and a cooling and recovery step of supplementing the mixed air with additional moisture and cooling the mixed air to recover the volatile organic compounds contained in the mixed air as condensates together with the moisture and the additional moisture. According to the present technology, by taking out and mixing the first in-furnace air and the second in-furnace air and cooling them, it is possible to condense while dissolving VOC in moisture. Thus, it is possible to efficiently recover the VOC evaporated in the painting drying furnace. In addition, exhaust for conventional VOC incineration treatment and installation of a catalytic oxidation device become unnecessary, or even when a catalytic oxidation device is provided, its miniaturization and reduction of the exhaust volume become possible. Furthermore, when the moisture contained in the mixed air is low, it may become difficult to secure a moisture amount sufficient to recover VOC in the cooling and recovery process. According to the present technology, in the cooling and recovery process, by replenishing additional moisture, it is possible to efficiently recover VOC.

[0023] An additional cooler for preliminarily cooling the in-furnace air may be provided upstream of the cooler. The in-furnace air may be preliminarily cooled before being cooled by the heat pump. Thereby, since the in-furnace air can be cooled to some extent by preliminary cooling, it becomes easy to cool the in-furnace air to a predetermined temperature by the heat pump.

[0024] In the return process, the remaining air heated by the heat pump may be further heated and returned to the painting drying furnace. Thereby, it becomes easy to adjust the temperature of the remaining air returned to the painting drying furnace. In addition, it is possible to accelerate the temperature rise of the painting drying furnace at the start of operation.

[0025] Preferably, the weight absolute humidity of the moisture contained in the in-furnace air is 21 g / kg or more, the concentration of the volatile organic compound contained in the in-furnace air is 500 ppmC or more, the weight absolute humidity of the moisture contained in the remaining air is 18 g / kg or less, and the concentration of the volatile organic compound contained in the remaining air is 80 ppmC or less.

[0026] According to the present technology, in the cooling and recovery process, since VOC can be efficiently recovered together with moisture, it is possible to provide a method for recovering volatile organic compounds that is excellent in terms of cost and environment.

Effects of the Invention

[0027] As described above, according to this disclosure, VOCs can be condensed while dissolving them in moisture by cooling the air inside the furnace. In this way, VOCs in the paint drying furnace can be efficiently recovered. Furthermore, since this technology recovers VOCs as condensates, it eliminates the need for exhaust gases and catalytic oxidation devices used in conventional VOC incineration treatments, or, even if a catalytic oxidation device is installed, it can be miniaturized and its exhaust volume reduced. [Brief explanation of the drawing]

[0028] [Figure 1] This figure shows an example of an electrodeposition coating line. [Figure 2] This is a schematic cross-sectional view along line AA in Figure 1. [Figure 3] This figure shows a paint drying oven equipped with a recovery device according to Embodiment 1. [Figure 4] This figure corresponds to Figure 3, showing a paint drying oven equipped with a recovery device according to Embodiment 2. [Modes for carrying out the invention]

[0029] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The following description of preferred embodiments is illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses in any way.

[0030] (Embodiment 1) <Configuration of the electrodeposition coating line> The workpiece 2 in the electrodeposition coating line 900 shown in Figure 1 is an automobile body. This electrodeposition coating line 900 includes an electrodeposition station 910, a washing station 920, and a drying station 930, arranged in order from the upstream side, and a hanger-type conveying device 90 that guides the workpiece 2 sequentially to each station 910, 920, and 930.

[0031] In this specification, "upstream" and "downstream" refer to the direction in which the workpiece 2 flows in the electrodeposition coating line 900, and the direction in which the air flows in the circulation path 6, which will be described later.

[0032] <Hanger-type conveying device> Figure 2 is a schematic cross-sectional view of the paint drying oven 100, which will be described later, at the drying station 930. As shown in Figures 1 and 2, the hanger-type conveying device 90 is an overhead conveyor and includes a guide rail 11 that extends along the electrodeposition coating line 900, and front and rear trolleys 13 that engage with the guide rail 11 by rollers 12 and move along the guide rail 11, with hangers 10 suspended from the trolleys 13. The hangers 10 are equipped with front and rear gantry frames 15 suspended from the trolleys 13 via C-necks 14 for supporting the workpiece 2 from both sides. Workpiece holders 16 are provided at the lower ends of the gantry frames 15. The workpiece 2 is suspended from the hangers 10 and transported sequentially to each station 910, 920, and 930. Then, the electrodeposition coating of the workpiece 2 is completed through the electrodeposition process, washing process, and drying process at each station 910, 920, and 930.

[0033] <Electrode Plating Station> The electrodeposition station 910 is equipped with an electrodeposition tank 911 that stores electrodeposition paint 912. The workpiece 2 is immersed in this electrodeposition tank 911 after, for example, undergoing a chemical conversion treatment. Cationic electrodeposition coating is then performed with the workpiece 2 as the cathode and a counter electrode (not shown) provided in the electrodeposition tank 911 as the anode (electrodeposition process).

[0034] <Flush toilet station> At the washing station 920, the workpiece 2 on which the electrodeposited paint 912 has been electrodeposited is dipped in UF filtrate 923 (washing water), followed by spray washing, and then dipped in industrial water 927 (washing water), followed by spray washing (washing process).

[0035] To this end, the washing station 920 includes, arranged in order from upstream, a UF dip washing tank 921 in which UF filtrate 923 is stored and a UF spray nozzle 922 for spraying UF filtrate 923, an industrial water dip washing tank 925 in which industrial water 927 is stored and an industrial water spray nozzle 926 for spraying industrial water 927. The workpiece 2 is washed by immersion in the UF filtrate 923 or industrial water 927 stored in each dip washing tank 921, 925, and then further washed with UF filtrate 923 or industrial water 927 sprayed through each spray nozzle 922, 926.

[0036] The UF filtrate 923 is a filtrate obtained by ultrafiltration (sometimes referred to as "UF") of the electrodeposited paint 912 in the electrodeposited tank 911. For this purpose, the electrodeposited tank 911 is equipped with a UF device and a UF tank (not shown). The electrodeposited paint 912 in the electrodeposited tank 911 is ultrafiltered by the UF device to reduce its loss, and the resulting UF filtrate 923 is stored in the UF tank. The UF filtrate 923 stored in the UF tank is supplied to the UF spray nozzle 922, and the sprayed UF filtrate 923 is collected in the UF dip rinsing tank 921. Then, the overflow water from the UF dip rinsing tank 921 is collected in the electrodeposited tank 911.

[0037] <Drying Station> As shown in Figure 3, the drying station 930 includes a paint drying oven 100 and a volatile organic compound (VOC) recovery device 200 installed in the paint drying oven 100 according to this embodiment.

[0038] <Paint drying oven> The paint drying oven 100 receives the workpiece 2 that has undergone the electrodeposition process and the water washing process, and dries the paint film on the workpiece 2 (drying process). The paint drying oven 100 is equipped with an inlet 110, an evaporation zone 120, a hardening zone 130, and an outlet 140, in order from the upstream side. The evaporation zone 120 is a zone mainly for evaporating the moisture contained in the paint film. The hardening zone 130 is a zone mainly for evaporating the VOCs contained in the paint film to harden the paint film. The workpiece 2 that has passed through the water washing station 920 is brought into the inlet 110 of the paint drying oven 100, passes through the evaporation zone 120 and the hardening zone 130 in order, and is discharged out of the paint drying oven 100 from the outlet 140.

[0039] As shown in Figure 2, nozzle boxes 18 are provided on the opposing inner walls 17 of the evaporation zone 120 and curing zone 130 of the paint drying oven 100 to blow hot air supplied from the circulation path 6 (described later) toward the workpiece 2 mounted on the hanger 10. An air intake port 19 is opened at the top of the inner wall 17 to discharge the air inside the paint drying oven 100 into the circulation path 6 by the operation of a circulation fan (not shown). Insulation material 8 is provided on the walls of the paint drying oven 100.

[0040] Here, the furnace temperature in the evaporation zone 120 is maintained, for example, between 80°C and 120°C. On the other hand, the furnace temperature in the curing zone 130 is maintained, for example, between 150°C and 200°C. That is, the furnace temperature in the curing zone 130 is maintained at a temperature near the boiling point of VOCs in order to promote the curing of the coating film. Furthermore, the furnace temperature in the evaporation zone 120, which is located upstream of the curing zone 130, is lower than the furnace temperature in the curing zone 130 and is maintained at a temperature near the boiling point of water.

[0041] The coating on workpiece 2 after the electrodeposition and washing processes contains a large amount of VOCs from the electrodeposition paint 912, as well as a large amount of water. In the low-temperature evaporation zone 120 located upstream, the water contained in the coating on workpiece 2 is mainly evaporated beforehand. After the water has been sufficiently evaporated in the evaporation zone 120, the coating is cured in the high-temperature curing zone 130 located downstream of the evaporation zone 120, where the VOCs contained in the coating are mainly evaporated.

[0042] If workpiece 2, which has undergone the water washing process, is directly transported to the curing zone 130, the water and VOCs contained in the coating film will evaporate all at once. This could lead to an excessive amount of evaporated components from the coating film, potentially resulting in a decrease in coating film quality, such as the formation of voids in the coating film.

[0043] By providing an evaporation zone 120 and a curing zone 130, moisture and VOCs can be evaporated in stages, resulting in a high-quality coating. In this configuration, the first furnace air 121 in the evaporation zone 120 contains a large amount of water vapor, while the second furnace air 131 contains a large amount of VOCs.

[0044] The absolute humidity by weight (hereinafter sometimes simply referred to as "humidity") of the first furnace air 121 in the evaporation zone 120 is, for example, 20 g / kg or more and 25 g / kg or less. On the other hand, the humidity of the second furnace air 131 in the hardening zone 130 is lower than the humidity of the first furnace air 121, for example, 15 g / kg or more and 20 g / kg or less.

[0045] Furthermore, the concentration of VOCs in the first reactor air 121 is, for example, between 60 ppmC and 100 ppmC. On the other hand, the concentration of VOCs in the second reactor air 131 is higher than that of the first reactor air 121, for example, between 600 ppmC and 1000 ppmC.

[0046] <Recovery device> The recovery device 200 is a device for recovering VOCs from within the paint drying oven 100.

[0047] As shown in Figure 3, the recovery device 200 includes a circulation path 6 for taking out and circulating air from the paint drying oven 100, a mixing chamber 230, a cooling and recovery unit 300, a heat pump 600, a second heater 210, a third heater 220, and a cooling tower 400 and a tank 500 connected to the cooling and recovery unit 300, all of which are arranged on the circulation path 6.

[0048] The circulation path 6 includes a first outlet passage 202, a second outlet passage 203, an evaporation zone outlet passage 201, a first connecting passage 204, a second connecting passage 205, an evaporation zone return passage 207, and a hardening zone circulation passage 209.

[0049] VOCs are recovered using the recovery device 200 through the following steps: a first extraction step of extracting the first furnace air 121 from the evaporation zone 120; a second extraction step of extracting the second furnace air 131 from the curing zone 130; a mixing step of mixing the first furnace air 121 and the second furnace air 131 in the mixing chamber 230 to obtain mixed air 231; a cooling and recovery step of cooling the mixed air 231 in the cooling and recovery unit 300 to recover the VOCs contained in the mixed air 231 as condensate 501 along with moisture; and a return step of heating the remaining air 301 from which the condensate 501 has been removed after the cooling and recovery step and returning it to the paint drying oven 100. In addition, the recovery device 200 according to this embodiment can also perform a curing zone circulation step in conjunction with or separately from VOC recovery, in which the second furnace air 131 from the curing zone 130 is extracted, heated by the third heater 220, and returned to the curing zone 130 as is. The following describes the VOC recovery method using the above-mentioned steps, corresponding to the description of each part of the recovery device 200.

[0050] -1st extraction passage- The first extraction passage 202 is in communication with the evaporation zone 120 via an air intake port 19 provided in the evaporation zone 120. As indicated by the arrow labeled G12, the first furnace air 121 in the evaporation zone 120 is extracted through the first extraction passage 202 (first extraction process). The first extraction passage 202 is provided with a flow rate adjustment valve 202A, which can adjust the flow rate of the first furnace air 121.

[0051] -Second extraction passage- The second extraction passage 203 is connected to the hardening zone 130 via an air intake port 19 provided in the hardening zone 130. As indicated by the arrow labeled G21, the second furnace air 131 in the hardening zone 130 is extracted through the second extraction passage 203 (second extraction process). The second extraction passage 203 is also provided with a flow rate adjustment valve 203A, which allows the flow rate of the second furnace air 131 to be adjusted.

[0052] -Mixing Chamber- The first furnace air 121, introduced from the evaporation zone 120 through the first extraction passage 202, and the second furnace air 131, introduced from the hardening zone 130 through the second extraction passage 203, are introduced into the mixing chamber 230 and mixed (mixing process). The mixed air 231 generated in the mixing chamber 230 is then sent to the cooling and recovery unit 300 through the first connecting passage 204, as indicated by the arrow labeled G31.

[0053] -Cooling and Recovery Unit- The cooling and recovery unit 300 is for cooling the mixed air 231 and recovering the VOCs contained in the mixed air 231 as condensates 501 along with moisture (cooling and recovery process). The cooling and recovery unit 300 includes a first cooler 320 (additional cooler) and a second cooler 330 (cooler).

[0054] The first cooler 320 is, for example, a cooling coil made of metal and is connected to a cooling tower 400 located outside the electrodeposition coating line 900. It pre-cools the mixed air 231 using cooling water W21 as a refrigerant. This allows the mixed air 231 to be cooled to a certain extent by pre-cooling before being cooled by the second cooler 330, making it easier for the mixed air 231 to be cooled to a predetermined temperature by the second cooler 330.

[0055] The mixed air 231, pre-cooled by the first cooler 320, is further cooled by the second cooler 330. The second cooler 330, like the first cooler 320, is, for example, a cooling coil made of metal, and constitutes the evaporator of the heat pump 600, which will be described later. When the mixed air 231 is cooled by the second cooler 330, some of the VOCs contained in the mixed air 231 condense together with the moisture. The resulting condensate 501 is then removed from the mixed air 231 and collected in the tank 500, as shown by the dashed arrow labeled V11 in Figure 3. Then, for example, VOCs are separated from the condensate 501 in the tank 500 and reused.

[0056] The mixed air 231 may contain resin components produced by the oxidative decomposition of paint components, etc. Some of the resin components can also be removed from the mixed air 231 as condensates 501. In addition, a filter or the like may be placed in the cooling and recovery unit 300 to remove resin components from the mixed air 231.

[0057] The remaining air 301 after cooling, from which the condensate 501 has been removed, is sent to the first heater 240 through the second communication passage 205, as indicated by the arrow labeled G32, and heated (return process).

[0058] Here, the second cooler 330 and the first heater 240 are connected by a heat pump 600. Specifically, the heat pump 600 is a vapor compression type that uses a refrigerant such as CO2, a fluorocarbon-based medium, or water, and circulates the refrigerant in the order of compressor → condenser → expansion valve → evaporator. The evaporator of the heat pump 600 constitutes the second cooler 330, which cools the mixed air 231 by heat exchange. On the other hand, the condenser of the heat pump 600 constitutes the first heater 240, which heats the residual air 301 by heat exchange. Thus, the heat pump 600 supplies cold energy to the second cooler 330 to cool the mixed air 231 by heat exchange, while supplying warm energy to the first heater 240 to heat the residual air 301 by heat exchange. In other words, the heat pump 600 is a heat pump that uses the mixed air 231 as an absorption source and the residual air 301 as a heat dissipation source. Note that in Figure 3, the symbol W22 indicates the flow of the refrigerant.

[0059] The residual air 301 heated by the first heater 240 is returned to the evaporation zone 120 through the evaporation zone return passage 207, as indicated by the arrows labeled G33, G41, and G42 (return process). The evaporation zone return passage 207 is connected to the evaporation zone 120 via the nozzle box 18. In other words, the warm air of the residual air 301 is blown into the evaporation zone 120 via the nozzle box 18.

[0060] A second heater 210 is located in the middle of the evaporation zone return passage 207, and can further heat the residual air 301 heated by the first heater 240 as needed. A gas burner is used as the second heater 210, and gas fuel and outside air are supplied to the second heater 210.

[0061] In addition, the evaporation zone 120 is provided with an evaporation zone extraction passage 201 for extracting the first furnace air 121, separate from the first extraction passage 202. This evaporation zone extraction passage 201 communicates with the evaporation zone return passage 207 upstream of the second heater 210. The evaporation zone extraction passage 201 is equipped with a flow rate adjustment valve 201A, and by opening and closing this flow rate adjustment valve 201A, as indicated by the arrow labeled G11, a portion of the first furnace air 121 can be sent directly to the second heater 210 for heating as needed and then returned to the evaporation zone 120. In this way, the second heater 210 can be used for rapid heating of the air in the evaporation zone 120 at the start of operation and for temperature control within the evaporation zone 120.

[0062] Furthermore, the curing zone 130 is also provided with a curing zone circulation passage 209, separate from the second extraction passage 203, and a third heater 220 is installed along this passage. As indicated by the arrows labeled G22 and G43, the curing zone circulation passage 209 is a passage that extracts a portion of the second furnace air 131 from the curing zone 130, heats it using the third heater 220, and returns it to the curing zone 130. With this configuration, the third heater 220 can be used to rapidly raise the temperature of the air in the curing zone 130 at the start of operation and to adjust the temperature within the curing zone 130 (curing zone circulation process).

[0063] -Temperature, humidity, and VOC concentration of the air in the circulating system- In the mixing chamber 230, the first furnace air 121 and the second furnace air 131 are mixed such that, for example, the humidity and VOC concentration of the mixed air 231 are 21 g / kg or more and 500 ppmC or more, preferably 21 g / kg to 23 g / kg and 500 ppmC to 700 ppmC, respectively. This allows a portion of the VOCs in the mixed air 231 to be dissolved in water and efficiently removed as condensate 501 when the mixed air 231 is cooled in the cooling and recovery unit 300. The temperature of the mixed air 231 in the mixing chamber 230 is, for example, around 100°C to 120°C.

[0064] The mixed air 231 is cooled by the first cooler 320 to, for example, 40°C to 60°C. Then, the mixed air 231 cooled by the first cooler 320 is cooled by the second cooler 330, which uses a heat pump 600, to a temperature at which the moisture and VOCs in the mixed air 231 condense, for example, 10°C to 30°C. In this way, some of the VOCs in the mixed air 231 condense together with some of the moisture and are removed as condensate 501.

[0065] The humidity and VOC concentration of the residual air 301 remaining after the removal of the condensate 501 are, for example, 18 g / kg or less and 80 ppmC or less, respectively, preferably 13 g / kg to 18 g / kg and 30 ppmC to 80 ppmC.

[0066] Subsequently, the remaining air 301 is gradually heated by the first heater 240 and the second heater 210 of the heat pump 600 and returned to the evaporation zone 120. Specifically, for example, it is heated to about 50°C to 80°C by the first heater 240, and then heated to about 80°C to 100°C by the second heater 210 before being returned to the evaporation zone 120.

[0067] <Effects and Effects> As described above, in the recovery device 200 according to this embodiment, the first furnace air 121 from the evaporation zone 120 and the second furnace air 131 from the curing zone 130 are taken out, mixed, and cooled, allowing VOCs to be dissolved in moisture and condensed. In this way, VOCs in the paint drying oven 100 can be efficiently recovered, and the conventional exhaust equipment that takes out the air from the paint drying oven 100 and burns off the VOCs with a catalytic combustion device can be eliminated or simplified.

[0068] Furthermore, the residual air 301 returned to the evaporation zone 120 has reduced humidity due to cooling and removal of condensates 501 in the cooling and recovery unit 300, so dry warm air is supplied to the evaporation zone 120. This suppresses the rise in vapor pressure inside the paint drying oven 100, and increases the evaporation rate of moisture and VOCs in the paint film inside the paint drying oven 100. As a result, the paint film of the workpiece 2 can be dried quickly and efficiently in the paint drying oven 100, which is advantageous for improving the quality of the paint film. In addition, since the heat pump 600 is used to cool the mixed air 231 and heat the residual air 301, energy loss is reduced, which is advantageous for saving energy. Also, the surface temperature of the hanger 10 that is brought into the paint drying oven 100 is about 27-28°C, but when dry residual air 301 is supplied to the paint drying oven 100, the dew point temperature of the air in the paint drying oven 100 becomes lower than the surface temperature of the hanger 10. Therefore, condensation on the hanger 10 is avoided, and for example, deterioration of the coating quality due to condensation water falling onto the workpiece 2 is avoided.

[0069] (Embodiment 2) Other embodiments relating to this disclosure will be described in detail below. In the description of these embodiments, the same reference numerals are used for parts that are the same as in Embodiment 1, and detailed descriptions will be omitted.

[0070] The recovery device 200 can also be applied to painting processes that have a washing step that does not involve dip washing, for example, only spray washing, or to drying ovens in painting processes that do not have a washing step. In this case, the humidity of the mixed air 231 may be less than 20 g / kg. If this occurs, the humidity of the mixed air 231 may be insufficient, making efficient recovery of VOCs difficult. For this reason, as shown in Figure 4, the cooling and recovery unit 300 may be equipped with a water supply device 310, for example, a spray nozzle type, to replenish additional moisture within the cooling and recovery unit 300. Industrial water or the like is supplied to the water supply device 310 from outside the recovery device 200, as indicated by the arrow labeled W11. In this way, the moisture necessary for efficient VOC recovery can be replenished in the mixed air 231.

[0071] (Other embodiments) The recovery device 200 can be applied not only to paint drying ovens in electrodeposition coating lines, but also to paint drying ovens in other coating lines that use water-soluble paints. Furthermore, it can be applied not only to paint drying ovens for baking, but also to paint drying ovens for flash-off. Specifically, for example, it can be used in paint drying ovens for intermediate and top coat coatings using water-soluble paints after electrodeposition coating.

[0072] Alternatively, multiple coolers for preliminary cooling may be installed in the cooling and recovery unit 300 to perform multi-stage cooling of the mixed air 231.

[0073] Furthermore, multiple heat pumps 600 may be installed in the circulation path 6 to perform multi-stage cooling of the mixed air 231 and heating of the residual air 301. In this case, heat pumps with different refrigerants may be arranged according to the temperature of the mixed air 231. Specifically, for cooling the hotter mixed air 231, a heat pump using CO2 as the refrigerant, which is suitable for heat absorption and release on the high-temperature side, may be used, and for cooling the colder mixed air 231, a heat pump using a fluorocarbon-based medium as the refrigerant, which is suitable for heat absorption and release on the low-temperature side, may be used. This makes it possible to efficiently cool and heat the mixed air 231.

[0074] The circulation path 6 may be configured to include only one of the evaporation zone extraction passage 201 and the hardening zone circulation passage 209, or it may not include either of them.

[0075] Furthermore, the second cooler 330 of the cooling and recovery unit 300 may be another cooler, such as a chiller (cooling water circulation device), instead of the evaporator of the heat pump 600. Also, the first heater 240 may be another heater, such as a gas burner, instead of the condenser of the heat pump 600. In addition, the recovery device 200 may be configured without a return process for residual air 301.

[0076] Workpiece 2 is not limited to automobile bodies, but may also be painted automobile parts such as bumpers (plastic), filler lids (fuel filler caps), door mirrors, antennas, spoilers, and other non-automobile parts made of metal and resin. [Explanation of Symbols]

[0077] 2 Work 6 Circulation route 100 Paint drying oven 120 Evaporation Zone 121 First reactor internal air 130 Hardening Zones 131 Second reactor internal air 200 Recovery device 201 Evaporation Zone Removal Passage 202 1st extraction passage 203 2nd extraction passage 204 1st communication passage 205 2nd communication passage 207 Evaporation Zone Return Passage 209 Hardening Zone Circulation Passage 210 Second heater 220 Third heater 230 Mixing Chamber 231 Mixed air 240 1st heater 300 Cooling and Recovery Unit 301 Remaining air 310 Moisture supply device 320 1st cooler 330 Second cooler 501 Condensates 600 Heat Pump 900 Electrodeposition Coating Line 910 Electroplating Station 920 Flush Station 930 Drying Station

Claims

1. An apparatus for recovering volatile organic compounds in a paint drying oven in an electrodeposition coating line, which includes a dip washing tank for receiving workpieces coated with electrodeposition paint and for dipping the workpieces, and a paint drying oven located downstream of the dip washing tank for drying the paint film on the workpieces, The above paint drying oven is The above workpiece is brought in, and an evaporation zone is set up in the furnace at a temperature of 80°C to 120°C to evaporate the moisture from the workpiece. The system comprises a curing zone located downstream of the evaporation zone, which cures the coating film at a furnace temperature of 150°C to 200°C. The absolute humidity by weight of the second furnace air in the hardening zone is lower than the absolute humidity by weight of the first furnace air in the evaporation zone. An outlet passage for removing the air inside the paint drying oven, The system includes a cooling and recovery unit that cools the furnace air, including the first furnace air, and recovers the volatile organic compounds contained in the furnace air as condensates together with the moisture contained in the furnace air. A recovery apparatus for volatile organic compounds, characterized by the following features.

2. A device for receiving workpieces painted with water-soluble paints and recovering volatile organic compounds in a paint drying oven used to dry the paint film on the workpieces, The above paint drying oven is The above workpiece is brought in, and an evaporation zone is set up in the furnace at a temperature of 80°C to 120°C to evaporate the moisture from the workpiece. The system comprises a curing zone located downstream of the evaporation zone, which cures the coating film at a furnace temperature of 150°C to 200°C. The absolute humidity by weight of the second furnace air in the hardening zone is lower than the absolute humidity by weight of the first furnace air in the evaporation zone. An outlet passage for removing the air inside the paint drying oven, The system includes a cooling and recovery unit that cools the furnace air, including the second furnace air, and recovers the volatile organic compounds contained in the furnace air as condensates together with the moisture contained in the furnace air. The above-mentioned cooling and recovery unit is equipped with a water supply device for replenishing additional moisture within the cooling and recovery unit. A recovery apparatus for volatile organic compounds, characterized by the following features.

3. In claim 1 or claim 2, The above cooling and recovery unit is, A cooler for cooling the air inside the furnace, A heater is provided to which the residual air, cooled by the above-mentioned cooler and from which the above-mentioned condensate has been removed, is introduced and the residual air is heated. A return passage for returning the heated residual air to the evaporation zone of the paint drying oven, The system includes a heat pump that connects the cooler and the heater, supplying cold energy to the cooler to cool the furnace air through heat exchange, and supplying warm energy to the heater to heat the remaining air through heat exchange. A recovery apparatus for volatile organic compounds, characterized by the following features.

4. In claim 1, The above-mentioned extraction passage includes a first extraction passage that communicates with the above-mentioned evaporation zone. A recovery apparatus for volatile organic compounds, characterized by the following features.

5. In Claim 2, The above-mentioned extraction passage includes a second extraction passage that communicates with the above-mentioned curing zone. A recovery apparatus for volatile organic compounds, characterized by the following features.

6. A method for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought in and the paint film of the workpiece is dried, The above paint drying oven is The above workpiece is brought in, and an evaporation zone is set up in the furnace at a temperature of 80°C to 120°C to evaporate the moisture from the workpiece. The system comprises a curing zone located downstream of the evaporation zone, which cures the coating film at a furnace temperature of 150°C to 200°C. The absolute humidity by weight of the second furnace air in the hardening zone is lower than the absolute humidity by weight of the first furnace air in the evaporation zone. The above painting drying oven includes a removal process for removing the air inside the oven, The system includes a cooling and recovery step in which the furnace air, including the first furnace air described above, is cooled to recover the volatile organic compounds contained in the furnace air as condensates together with the moisture contained in the furnace air. The above water-soluble paint is an electrodeposition paint. The above workpiece is transported to the above-mentioned paint drying oven after undergoing a water washing process in which it is immersed in washing water following the electrodeposition process using the above-mentioned electrodeposition paint. A method for recovering volatile organic compounds, characterized by the features described above.

7. A method for recovering volatile organic compounds in a paint drying oven into which a workpiece painted with a water-soluble paint is brought in and the paint film of the workpiece is dried, The above paint drying oven is The above workpiece is brought in, and an evaporation zone is set up in the furnace at a temperature of 80°C to 120°C to evaporate the moisture from the workpiece. The system comprises a curing zone located downstream of the evaporation zone, which cures the coating film at a furnace temperature of 150°C to 200°C. The absolute humidity by weight of the second furnace air in the hardening zone is lower than the absolute humidity by weight of the first furnace air in the evaporation zone. The above painting drying oven includes a removal process for removing the air inside the oven, The process includes a cooling and recovery step in which additional moisture is added to the furnace air, including the second furnace air mentioned above, and the furnace air is cooled to recover the volatile organic compounds contained in the furnace air as condensates together with the moisture contained in the furnace air. A method for recovering volatile organic compounds, characterized by the features described above.

8. In claim 6 or claim 7, The system includes a return step in which the remaining air from which the condensate has been removed after the above-mentioned cooling and recovery step is heated and returned to the evaporation zone of the above-mentioned paint drying oven, A heat pump is used that uses the furnace air as a heat absorption source and the remaining air as a heat dissipation source to cool the furnace air and heat the remaining air. A method for recovering volatile organic compounds, characterized by the features described above.

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