JP2012139657A - Solvent-recovering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solvent-recovering system which reduces a cost required for recovering the vapor of a solvent in a gas to be fed again to a dryer.SOLUTION: The solvent-recovering system 1 feeds exhaust, which is emitted from the drying chambers 17A-G of a dryer 16, to the drying chambers 17A-G. In addition, the system includes: a first solvent-recovering part 2 which recovers the vapor of a solvent contained in the exhaust emitted from the drying chambers 17A-G; a second solvent-recovering part 3 which recovers the vapor of the solvent, which remains in the exhaust which passes through the first solvent-recovering part 2, and then feeds the vapor concerned, as a drying gas, to the drying chambers 17A-G; and a gas-feeding route 19H which feeds the exhaust, as a preliminary drying gas, to the drying chambers 17A-G, just after the exhaust passes through the first solvent-recovering part 2, so that the exhaust may contact an object to be coated, just after the exhaust passes through the first solvent-recovering part 2, before the drying gas fed by the second solvent-recovering part 3 contacts the object concerned, the vapor of the solvent remaining more in the exhaust just after the exhaust passes through the first solvent-recovering part 2 than in the drying gas fed to the drying chambers 17A-G by the second solvent-recovering part 3.

Description

  The present invention relates to a solvent recovery system.

  In production facilities involving chemical treatment, solvent vapor is included in the exhausted gas. As a technique for recovering such solvent vapor, for example, a technique in which the solvent vapor is condensed and adsorbed on an adsorbent has been proposed (see Patent Document 1).

JP 2010-69435 A Japanese Patent Laid-Open No. 5-15725 JP 2008-180459 A JP 2009-66578 A JP-A-2005-103378 JP 2005-152762 A JP 2009-162404 A

  For example, when a treatment for drying an object to be coated with various solvents, such as an electrode for a lithium ion battery to which an NMP solvent is applied, is effective in drying the applied solvent and the cost required for the drying process. In order to achieve a balance with the reduction, solvent vapor is recovered from the exhaust of a dryer (drying furnace) for drying an object to be dried to be dried and supplied to the dryer again. At this time, the dry air supplied to the dryer is required to have a relatively high dryness so that the applied solvent is surely dried, although it depends on the specifications required for the product to be processed.

  However, if the dryer is large, the cost required to maintain the dryness of the gas supplied to the dryer again is great. This invention is made | formed in view of such a problem, and makes it a subject to provide the solvent collection | recovery system which suppresses the cost required in collection | recovery of the gaseous solvent vapor | steam supplied again to a dryer.

  In order to solve the above-mentioned problems, the present invention includes at least two or more solvent recovery sections that recover and process solvent vapor in the exhaust of a dryer in stages, and a first stage solvent recovery section that has a relatively large amount of residual solvent vapor. Was exhausted before the exhaust of the second-stage solvent recovery part with relatively little residual solvent vapor.

Specifically, the solvent recovery system supplies air to the drying chamber of a dryer that dries an object to which the solvent is applied and recovers the vapor of the solvent vaporized in the drying chamber. A first solvent recovery section for recovering the solvent vapor contained in the exhaust of the chamber; and the solvent vapor remaining in the exhaust gas that has passed through the first solvent recovery section is recovered and supplied to the drying chamber as dry air And the exhaust immediately after passing through the first solvent recovery section, wherein more solvent vapor remains than the dry air supplied to the drying chamber by the second solvent recovery section. However, the exhaust immediately after passing through the first solvent recovery unit is used as pre-dry air so that the second solvent recovery unit hits the object to be coated before the dry air supplied by the second solvent recovery unit. An air supply path for supplying air to

  Although it is preferable from the aspect of promoting drying that the dryness of the dry air applied to the object to be coated is as high as possible, from the viewpoint of reducing the cost required for the drying treatment, the equipment that recovers the solvent is the most efficient operating point. It is preferable to be operated at. In other words, it is preferable that any object to be coated in the drying chamber of the dryer is dried at a substantially uniform drying rate.

  Therefore, in the solvent recovery system, paying attention to the fact that the drying air for drying the coating immediately after the start of drying may have a higher degree of drying than the drying air for drying the coating immediately before the end of drying, By sending a relatively high concentration exhaust gas from the first solvent recovery section, which is the first stage of the solvent recovery section having a two-stage configuration, to the dryer, and mainly using it as the dry air of the coating object immediately after the start of drying, The capacity of the second solvent recovery section corresponding to the second and subsequent stages is reduced. Thereby, the initial cost and running cost of the equipment required for solvent recovery can be suppressed, and the cost for solvent recovery can be reduced.

  In addition, the object to be coated passes so as to flow in the drying chamber of the dryer, and the air supply path is a material to be coated which is supplied with air from the second solvent recovery unit in the drying chamber. The pre-drying air may be supplied to the drying chamber so as to hit an object to be coated on the upstream side. In the case where the drying process is performed by continuously passing the coating object through the drying chamber of the dryer, the degree of drying of the coating object differs between the upstream side and the downstream side. In this way, if the solvent recovery system is applied to the drying chamber of a dryer in which objects to be coated with different degrees of drying coexist, the cost reduction effect due to the multistage of the solvent recovery unit, that is, the second and subsequent stages. The cost reduction effect due to the fact that the capacity of the second solvent recovery unit can be reduced is more effectively exhibited.

  In addition, the first solvent recovery unit brings the exhaust into contact with a coil in which a cooling medium cooled in a refrigeration facility flows in a pipe, and condenses and recovers the solvent vapor contained in the exhaust, and the second solvent The recovery unit is configured to bring the exhaust gas that has passed through the first solvent recovery unit into contact with an adsorbent, so that the solvent vapor remaining in the exhaust gas is adsorbed and recovered and supplied to the drying chamber as dry air. Also good. When recovering the solvent vapor, the adsorption recovery method can lower the concentration of the solvent vapor in the gas than the condensation recovery method. Therefore, if the first solvent recovery unit is based on the condensation recovery method and the second solvent recovery unit is based on the adsorption recovery method, the solvent concentration in the exhaust gas of each solvent recovery unit can be differentiated in stages. Thus, the cost reduction effect due to the multi-stage solvent recovery unit, that is, the cost reduction effect due to the capacity of the second solvent recovery unit corresponding to the second and subsequent stages being more effectively exhibited.

  If it is the said solvent collection | recovery system, it is possible to suppress the cost required for collection | recovery of the solvent vapor | steam in the gas supplied again to a dryer.

It is a block diagram of a solvent collection | recovery system. It is a block diagram of a dryer. It is the graph which showed NMP saturation concentration. The graph which showed the solvent density | concentration of the air supply of each drying chamber. It is a block diagram of the solvent collection | recovery system which concerns on a modification. It is a block diagram of the dryer which concerns on a modification.

A configuration of a solvent recovery system according to an embodiment of the present invention is shown in FIG. As shown in FIG. 1, the solvent recovery system 1 includes a solvent recovery device 2 that condenses and recovers a solvent by cooling a predetermined gas containing solvent vapor (hereinafter simply referred to as gas) with a coil, and a solvent recovery device 2. And a concentrating device 3 for adsorbing and recovering a solvent remaining in the gas passed by an adsorbent such as zeolite or activated carbon. The solvent recovery system 1 includes various fans for supplying gas and a coil for performing heat exchange.

  The solvent recovery system 1 is an apparatus that recovers solvent vapor in exhaust gas exhausted from production facilities that perform various chemical treatments with an organic solvent. In the present embodiment, description will be made on the assumption that NMP is recovered from production exhaust gas containing solvent vapor of N-methylpyrrolidone (hereinafter referred to as NMP) used in a lithium ion battery factory. Also good. In lithium ion battery factories, NMP is used when manufacturing electrodes. The NMP applied to the electrode is evaporated and exhausted by a dryer for drying the applied NMP. FIG. 2 shows a dryer provided with the solvent recovery system 1 according to this embodiment.

  As shown in FIG. 2, the dryer 16 is divided into a plurality of drying chambers 17 </ b> A to 17 </ b> G, and electrodes in which the NMP solvent is applied to the surface sequentially pass through the drying chambers 17 </ b> A to 17 </ b> G. The dryer 16 is semi-hermetic and is provided with an entrance through which an electrode passes. In order to prevent gas containing solvent vapor from leaking, the supply / exhaust is adjusted so that the inlet / outlet has a negative pressure. A high temperature gas is introduced into each of the drying chambers 17 </ b> A to 17 </ b> G, and the NMP solvent applied to the surface of the electrode evaporates as the electrode passes through the inside. In order to save energy, most of the high-temperature gas introduced into the drying chambers 17A to 17G is exhausted from the drying chambers 17A to 17G and is recirculated from the fan 15S through the heating coil and the particulate filter (HEPA filter). A part of the gas is returned to the drying chambers 17A to 17G after being purified by the solvent recovery system 1 according to the present embodiment.

  The solvent recovery system 1 according to the present embodiment is an apparatus attached to the dryer 16 and recovers the solvent vapor in the exhaust of the dryer 16. In this embodiment, the assumed concentration of solvent vapor exhausted from the dryer 16 is 2000 ppm. The exhaust of the dryer 16 is assumed to be about 80 to 100 ° C. The cooling water used in the solvent recovery system 1 is that of an air conditioning facility generated by a cooling tower that cools the heat generating part of the production apparatus in a building where the production facility is installed. This cooling water is prepared in two types of temperature bands, cooling water cooled by a cooling tower installed outdoors, and cooling water cooled by a refrigerator (may be called cold water) There is. Although the former depends on the outside air temperature, the design temperature is set to 32 ° C., and hence the cooling water cooled by the cooling tower is hereinafter referred to as 32 ° C. cooling water. On the other hand, since the latter is cooling water cooled to 7 ° C. by the refrigerator, the cooling water cooled by the refrigerator is hereinafter referred to as 7 ° C. cooling water. The power required for producing the 32 ° C. cooling water is much smaller than that required for producing the 7 ° C. cooling water using the heat pump. Therefore, it is possible to treat the heat load with the 32 ° C. cooling water as much as possible. It is effective in reducing the power consumed by the whole.

  As shown in FIG. 1, the solvent recovery device 2 has four heat exchange coils (reference numerals 4 to 7) arranged in series. Hereinafter, the pre-cooler 4, the pre-cooler 5, the main cooler 6, and the post-heater 7 will be referred to in order from the upstream side.

  The precooler 4 is connected to preheaters 8H and 8L provided on the downstream side of the fans 15AH and 15AL for supplying air to the dryer 16 via a water circulation system 9. In addition, the solvent recovery system 1 includes a fan 15 </ b> B that feeds the gas mixed with the remaining solvent vapor cooled and condensed to the adsorption rotor 13, which will be described later, and a fan 15 </ b> C for regenerating the adsorption function of the adsorption rotor 13. The precooler 4 cools the gas sent from the dryer 16. The heat of the gas removed by the precooler 4 is transferred to the preheaters 8H and 8L by water circulating in the water circulation system 9, purified by the solvent recovery device 2 and the concentration device 3, and sent to the dryer again. Heat. The gas of about 100 ° C. flowing into the precooler 4 reaches 63 ° C. and is sent to the precooler 5.

  In the water circulation system 9, the pressure in the circulation system is higher than atmospheric pressure (for example, if the gauge pressure is 0.2 MPa, the saturated steam temperature is 133.7 ° C., and if it is below this temperature, it will not boil), Even if the temperature of the gas sent from the dryer becomes high, the water in the system does not boil. The pressure in the water circulation system 9 is kept constant by the accumulator.

  The precooler 5 further cools the gas cooled by the precooler 4. The precooler 4 cools the gas with the cooling water of the 32 ° C. cooling water circulation system 11 having a cooling tower in the path. The 63 ° C. gas flowing into the precooler 5 reaches 27 ° C. and is sent to the main cooler 6.

  The main cooler 6 further cools the gas cooled by the pre-cooler 5. The main cooler 6 cools the gas with the cooling water of the 7 ° C. cooling water circulation system 12 having a refrigerator in the path. The main cooler 6 cools the 27 ° C. gas sent from the precooler 5 to 12 ° C. The flow rate of the cooling water passing through the main cooler 6 is adjusted by the flow rate adjusting valve 10 that controls the temperature so that the temperature of the gas on the downstream side of the main cooler 6 becomes 12 ° C. When the gas sent from the dryer is cooled to 12 ° C. by the main cooler 6, NMP vapor is condensed on the surface of the cooling coil of the main cooler 6.

  FIG. 3 is a graph showing the NMP saturation concentration. In the solvent recovery device 2, when the gas containing the solvent vapor passes through the precooler 4 and reaches 63 ° C., the concentration of the solvent vapor reaches about 2000 ppm, and when the gas passes through the precooler 5 and reaches 27 ° C. The concentration of the solvent vapor becomes about 800 ppm, and when it passes through the main cooler 6 and reaches 12 ° C., the concentration of the solvent vapor becomes about 270 ppm.

  The post heater 7 heats the gas cooled by the main cooler 6. The post heater 7 heats the gas with the cooling water of the 32 ° C. cooling water circulation system 11 that requires a cooling tower in the path. The post heater 7 heats the 12 ° C. gas sent from the main cooler 6 to 27 ° C.

  Here, the cooling water of the 32 ° C. cooling water circulation system 11 follows the following path. That is, the cooling water cooled in the cooling tower passes through the post heater 7 after leaving the cooling tower, and then returns to the cooling tower through the pre cooler 5 again. Since the temperature of the gas flowing into the post heater 7 is 12 ° C., the 32 ° C. cooling water flowing into the post heater 7 becomes 17 ° C. after passing through the post heater 7 and flows into the pre cooler 5. To do. Since the temperature of the gas flowing into the precooler 5 is 63 ° C., the cooling water flowing into the precooler 5 becomes 53 ° C. after passing through the precooler 5 and is sent again to the cooling tower. In addition, since the cooling tower provided in the 32 degreeC cooling water circulation system 11 is integrated and operated with the cooling tower of another production facility, the 53 degreeC cooling water sent to the cooling tower again cools the other production equipment. By mixing with water, the return temperature of the cooling water returning to the cooling tower is lower than 53 ° C.

  For this reason, in the solvent recovery apparatus 2, most of the heat is processed by the 32 ° C. cooling water circulation system 11. That is, when the cooling water of the 32 ° C. cooling water circulation system 11 is flowed to the pre-cooler 5 without passing through the post-heater 7, the gas that has passed through the pre-cooler 5 does not decrease to 27 ° C. The load of the refrigerator of the 7 degreeC cooling water circulation system 12 will increase. However, in the case of the solvent recovery apparatus 2 according to the present embodiment, the post heater 7 is made to flow by flowing the cooling water of the 32 ° C. cooling water circulation system 11 to the pre cooler 5 through the post heater 7. Since the cooling water cooled to 17 ° C. by passing through the pre-cooler 5, the gas flowing into the main cooler 6 can be cooled to 27 ° C. in advance.

  A certain amount of solvent is recovered by the solvent recovery device 2, and the gas heated at the most downstream side thereof is sent to the concentration device 3 for further purification. As shown in FIG. 1, the concentrating device 3 has an adsorption rotor 13 and a steam heating coil 14 and is configured as follows.

The adsorption rotor 13 carries an adsorbent such as zeolite inside a cylindrical member. A section division cassette (not shown) is arranged on both end faces of the adsorption rotor 13, and the gas passage area of the adsorption rotor 13 is divided into three sections by this cassette. The suction rotor 13 is rotatable relative to the section division cassette, and a processing region R1, a regeneration region R2, and a purge region R3 are formed in the suction rotor 13 by this cassette.

  The 27 ° C. gas exiting the solvent recovery device 2 sent by the fan 15B passes through the processing region R1. The processing region R1 adsorbs NMP in the gas to be vented and discharges the purified gas. Most of the gas exiting the processing region R1 exits the solvent recovery system 1 and is sent to the dryer. Further, part of the gas exiting the processing region R1 is sent to the purge region R3. Note that part or all of the gas exiting the processing region R1 may be exhausted outdoors.

  The purge region R3 is a region formed in the middle of the transition of the suction rotor 13 from the regeneration region R2 to the processing region R1 as the suction rotor 13 rotates relative to the section division cassette. The purge region R3 is a region for cooling the adsorbent that is in a high-temperature state immediately after regeneration and before in-service, and is cooled by passing a part of the gas exiting the processing region R1. As the suction rotor 13 rotates in the direction indicated by the arrow in FIG. 1, one point of the suction rotor 13 repeatedly changes in the order of the processing region R1, the regeneration region R2, and the purge region R3.

  The gas exiting the purge region R3 is heated by the steam heating coil 14 and then sent to the regeneration region R2. The steam heating coil 14 heats the gas with the steam of the boiler supplied from the utility pipe of the building where the solvent recovery system 1 is installed. Condensate in the steam heating coil 14 is returned again to the boiler water supply tank via the drain trap. The gas at 68 ° C. discharged from the purge region R3 becomes 130 ° C. by heating by the steam heating coil 14, and is sent to the regeneration region R2. As a result, the regeneration region R2 becomes high temperature, and the adsorbed solvent is released. The gas exiting the regeneration region R2 is sent again to the solvent recovery device 2. As a result, most of the solvent detached from the adsorption rotor 13 by regenerative heating is condensed and recovered by the main cooler 6 of the solvent recovery device 2. As described above, the heat exchange of the cooling water exiting the cooling tower of the 32 ° C. cooling water circulation system 11 with the gas exiting the main cooler 6 at the same temperature is the boiler that supplies the steam heating coil 14 with high heat. This contributes to a reduction in the load.

  By the way, in the drying chambers 17A to 17G, since the NMP solvent is vaporized, the NMP concentration in the air becomes very high (for example, about 2000 ppm). The NMP concentration of the gas introduced into G needs to be lower than this (for example, about 300 to 500 ppm). For this reason, the NMP concentration of the gas exhausted from the solvent recovery system 1 that purifies part of the gas exhausted from the drying chambers 17A to 17G and returned to the drying chambers 17A to 17G is purified to about 10 to 200 ppm. Although it is necessary, the concentration differs depending on the drying chamber of the destination. That is, in the upstream process of the dryer 16 immediately after the start of drying, a large amount of NMP solvent adheres to the electrode, so that the NMP concentration in the drying chamber is high. The NMP concentration in the drying chamber is low because most of the NMP solvent adhering to is already dried.

Therefore, in the solvent recovery system 1 according to the present embodiment, the drying chambers 17A to 17G of the dryer 16 are conceptually divided into two regions, and the drying chambers 17A to 17E belonging to the region 18H on the upstream side of the dryer 16 are divided. The exhaust of the solvent recovery device 2 having a relatively high NMP concentration is sent through the air supply path 19H, and the concentrating device having a relatively low NMP concentration is supplied to the drying chambers 17F to G belonging to the region 18L on the downstream side of the dryer 16. 3 exhaust gas is sent through the air supply path 19L. That is, a part of the gas flowing from the fan 15B of the solvent recovery device 2 to the adsorption rotor 13 of the concentration device 3 is sent from the fan 15AH to the region 18H. This gas is called a high concentration dryer air supply. Further, a part of the gas exiting the processing region R1 of the adsorption rotor 13 is sent from the fan 15AL to the region 18L. This gas is called a low-concentration dryer air supply.

  In the case of this solvent recovery system 1, there is an air supply path 19 </ b> H for supplying the dryer 16 with pre-drying gas having a higher NMP concentration than that of the gas exiting the concentration device 3 and having just passed through the solvent recovery device 2. Since it is equipped, the capacity | capacitance of the concentration apparatus 3 can be small, and the cost concerning solvent collection | recovery can be reduced.

  FIG. 4 shows the solvent concentration of the supply air sent from the solvent recovery system 1 to each drying chamber and that of the present embodiment (example) and that of the prior art (that is, the entire drying chamber 17A without the supply passage 19H). It is the graph which compared with what flowed the gas of 19 L of supply path | routes to ~ G). As can be seen from this graph, in the present embodiment, the supply air having a relatively high NMP concentration is sent to the drying chambers 17A to 17E belonging to the region 18H. For this reason, according to the present embodiment, it can be seen that the capacity of the concentrating device 3 can be significantly reduced as compared with the prior art, and the operation efficiency of the entire system can be improved.

  In this embodiment, since the solvent recovery system can operate at an efficient operating point as described above, the concentrator and the like can be downsized, and the initial cost and running cost can be suppressed.

  In addition, the said solvent collection | recovery system 1 may perform solvent collection | recovery in three or more steps, and may make it supply the exhaust of each step to a dryer. For example, in the case of three stages, as shown in FIG. 5, the solvent vapor remaining in the gas discharged from the solvent recovery apparatus 2 is removed in two stages of the concentrator 3A and the concentrator 3B. In the case of this modification, an air supply path 19M is added in addition to the air supply paths 19H and 19L. Then, each of the drying chambers 17A to 17G constituting the dryer 16 has a medium concentration supply that is sent via an air supply path 19H, an area 18H where a high concentration supply air is sent via an air supply path 19H, and an air supply path 19M. This is conceptually divided into three areas: an area 18M where air is sent and an area 18L where air with a low concentration sent via the air supply path 19L is sent.

  The vapor solvent recovery system 1 may adopt any system as long as the solvent vapor can be removed step by step. For example, a high-concentration dryer air supply is processed by a condensing solvent recovery device. However, the combined use of a wet apparatus that absorbs and removes an NMP solvent such as a scrubber in water can significantly reduce the capacity of the wet apparatus.

1. Solvent recovery system 2. Solvent recovery device 3. Concentration device 16. Dryers 17A to G ... Drying chambers 18H, 18L ... Areas 19H, 19L ... Air supply path

Claims (3)

A solvent recovery system for supplying an exhaust of the drying chamber in which a solvent vapor evaporated in the drying chamber is recovered to a drying chamber of a dryer for drying an object to be coated with a solvent,
A first solvent recovery section for recovering the solvent vapor contained in the exhaust of the drying chamber;
A second solvent recovery unit that recovers the solvent vapor remaining in the exhaust gas that has passed through the first solvent recovery unit and supplies the dry vapor to the drying chamber;
The exhaust gas immediately after passing through the first solvent recovery section, in which more solvent vapor remains than the dry air supplied to the drying chamber by the second solvent recovery section is the second solvent recovery section. An air supply path for supplying the exhaust immediately after passing through the first solvent recovery section as pre-dry air to the drying chamber so as to hit the coating object before the dry air supplied by Comprising
Solvent recovery system. The coating object passes so as to flow in the drying chamber of the dryer,
The air supply path supplies the pre-drying air to the drying chamber so as to hit an object to be coated on the upstream side of the object to be coated with air supplied from the second solvent recovery unit. Care
The solvent recovery system according to claim 1. The first solvent recovery unit brings the exhaust into contact with a coil in which a cooling medium cooled in a refrigeration facility flows in a pipe, and condenses and recovers the solvent vapor contained in the exhaust,
The second solvent recovery unit brings the exhaust gas that has passed through the first solvent recovery unit into contact with an adsorbent, adsorbs and recovers the solvent vapor remaining in the exhaust gas, and supplies the drying chamber with dry air. To
The solvent recovery system according to claim 1 or 2.

Images