JP2567300B2 - Solvent recovery equipment using dry air - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to equipment for efficiently recovering an organic solvent having a low vapor pressure and a hygroscopic organic solvent from the exhaust gas.

[0002]

2. Description of the Related Art In many cases, the use of organic solvents is indispensable in the process of manufacturing various industrial products, and the solvent used for the treatment of semi-finished products and intermediate products does not need to remain in products. The product is heated and dried to separate the solvent as vapor. In this case, a solvent with a high vapor pressure is relatively easy to recover, but a solvent with a low vapor pressure and a hygroscopic property absorbs a large amount of moisture in the air, resulting in a high concentration and a high concentration. It is extremely difficult to collect efficiently. An example of such a solvent is N-methyl-2-
There is pyrrolidone. This N-methyl-2-pyrrolidone is used in the battery manufacturing process. In this case, in order to remove the solvent remaining in the battery intermediate product, the intermediate product is charged into a heated processing furnace and the solvent is evaporated as vapor.

[0003]

In order to evaporate and separate the hygroscopic solvent having a low vapor pressure from the intermediate product as described above, a large amount of the solvent can be used in the air atmosphere in view of productivity by using a processing furnace equipped with a heating means. When processing, it is most convenient to recover the liquid solvent by cooling the solvent-containing exhaust gas of this processing furnace to a temperature at which the solvent is liquefied. However, in such cooling liquefaction, the water content in the exhaust gas is also condensed at the same time, The recovered liquid has a very high water content. For this reason, since it cannot be reused as it is, a regenerating operation such as distillation is required, and as a result, the cost of the regenerating equipment is increased, the economic merit of recovering the solvent is reduced, and the exhaust may be performed as it is. there were. This not only wastes resources, but also causes environmental problems. The present invention is intended to solve such a problem.

[0004]

According to the present invention, a processing furnace in which vapor of an organic solvent is generated, a dehumidifying device for supplying dry air to the processing furnace, and an atmospheric gas in the processing furnace are forced. An exhaust duct for exhausting the gas, a solvent recovery device connected to the exhaust duct, and an air supply duct for supplying the gas after the solvent is separated by the solvent recovery device to the processing furnace. The recovery device is equipped with a heat exchanger and an exhaust gas cooler, and the dry air is used for liquefying the solvent in the exhaust gas cooler and performing heat exchange between gases before and after passing through the exhaust gas cooler in the heat exchanger. The solvent recovery equipment that was used. The solvent recovery device may be equipped with a reheater and / or a high performance filter,
The gas that has passed through the exhaust gas cooler and heat exchanger is guided to the reheater, and the exhaust gas that has passed through the high-performance filter is sent to the heat exchanger and exhaust gas cooler. Further, the solvent liquefied by the exhaust gas cooler is introduced into the solvent tank, and a part of the dry air dehumidified by the dehumidifier is introduced into the solvent tank. The dehumidifying device is a dry dehumidifier in which a dehumidifying agent-impregnated rotor is arranged across a dehumidifying path and a regenerating path. An air cooler is provided upstream of the rotor in the dehumidifying path and an upstream of the rotor is provided in the regenerating path. Use the one with an air heater on the side. INDUSTRIAL APPLICABILITY The facility of the present invention is suitable as a facility for recovering the solvent in a battery manufacturing process using N-methyl-2-pyrrolidone as a solvent.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the entire solvent recovery equipment according to the present invention. Reference numeral 1 denotes a processing furnace, and products 2 containing a solvent are continuously conveyed in the processing furnace 1 by a conveyor belt 3. The inside of the processing furnace 1 is controlled to a predetermined temperature, but this can be performed by controlling the temperature of the air supplied into the furnace. Moreover, a separate heating means may be provided. In any case, the ambient temperature is controlled to an appropriate ambient temperature according to the type of solvent used and the product, and the ambient gas containing the solvent vapor in the furnace is exhausted from the exhaust duct 5 through the exhaust hood 4. Reference numeral 7 is an exhaust fan for performing forced exhaust. Air, which almost corresponds to the amount of air discharged from the furnace (or is slightly larger in consideration of leakage), is supplied from the air supply port 8 into the furnace. Reference numeral 9 is an air supply fan for this purpose. When the processing furnace 1 is applied to a battery manufacturing process using N-methyl-2-pyrrolidone as a solvent, the temperature of the introduced air is controlled to about 60 ° C. In the equipment of the present invention, a solvent recovery device 10 for recovering the solvent from the solvent-containing exhaust gas discharged by the exhaust duct 5 and the dry air are supplied to the processing furnace 1 in the processing furnace 1 in which the vapor of the organic solvent is generated. A dehumidifying device 11 for doing so is attached.

The solvent recovery device 10 has a heat exchanger 13 and an exhaust gas cooler 14 housed in one casing 12,
In some cases, a high performance filter 15 and a reheater 16 are provided (this example is shown in the illustrated example). The exhaust gas cooler 14 is for cooling the solvent-containing exhaust gas to a temperature sufficient for the solvent to condense, and a normal fin-equipped heat exchange coil is used in this coil, and cold water produced by a refrigerator is used. Or brine is passed. The cooling capacity is controlled by a three-way valve 17 provided in the liquid passage. The heat exchanger 13 is
It is a heat exchanger that indirectly exchanges sensible heat between gases. The heat exchanger 13 is installed so as to exchange sensible heat between the exhaust gas before passing through the exhaust gas cooler 14 and the exhaust gas after passing through the cooler 14. In the illustrated example, the inside of the casing 1 is divided into a forward path A and a return path B by a partition plate 18, and the exhaust gas introduced from the exhaust gas inlet 19 to the forward path A is returned to the return path through an opening 20 provided at the back of the partition plate 18. Enter B and flow in the return path B in a counter-current manner with the outgoing path, and the outlet 21 provided on the same side as the intake 19
The exhaust gas cooler 14 is installed on the outward path A side, and the heat exchanger 13 is installed across the upstream path A on the upstream side of the cooler 14 and the return path B. Is installed. The return path A is arranged below the return path B, and the solvent liquid condensed in the exhaust gas cooler 14 present in the return path A is collected in the receiver 22. Further, the solvent liquid which may be condensed in the heat exchanger 13 is also collected in the receiver 22. On the outward route A, a high-performance filter 15 is attached near the intake port 19 and removes dust entrained in the exhaust gas. Further, a reheater 16 is installed near the outlet 21 of the return path B, and reheats the gas flowing out from the device 10. The reheater 16 uses a finned heat exchanger through which hot water flows or an electric heater.

A part or all of the solvent-containing exhaust gas in the exhaust duct 5 is introduced into the intake port 19 of the solvent recovery apparatus 10 constructed in this way through a branch duct 24 branching from the exhaust duct 5 leading to the exhaust port 23. Is taken in. The control of the intake amount of exhaust gas is performed by the motor damper 25. Further, the solvent is separated from the outlet 21 of the solvent recovery device 10 and the heated gas (air) is taken out by the heat exchanger 13.
This is sent to the processing furnace 1 through the air supply duct 26 together with the dry air described later.

On the other hand, the new air introduced into the processing furnace 1 is dehumidified by the dehumidifier 11 and used as dry air. This dehumidifying device 11 divides the inside of one casing 27 into a dehumidifying path C and a regenerating path D by a partition plate 28,
The moisture absorbent impregnated rotor 29 is rotatably installed across the dehumidification route C and the regeneration route D, and the air cooler 30 and the rotor 29 are provided in the dehumidification route C upstream of the rotor 29. An air heater 31 is arranged on the regeneration path D on the upstream side of the air heater 31. 32 indicates a dehumidifying side blower, and 33 indicates a regenerating side blower. In the illustrated example, the dehumidifying path C and the regenerating path D are formed in a counterflow type. The outside air is taken into the inlet 34 of the dehumidification path C, passes through the filter 35, is cooled to below the dew point temperature in the air cooler 30, the moisture in the air is separated as drain, and further passes through the rotor 29 to absorb moisture. Moisture is adsorbed on the agent to form dry air. Then, this dry air is taken out from the outlet 36 and blown out into the furnace from the air supply port 8 of the processing path 1 through the air supply path 37. Also, the entrance 38 of the reproduction path D
The outside air is also taken in, and after passing through the filter 39, it is heated by the air heater 31, and when this heated air passes through the rotor 29, it absorbs the moisture adsorbed by the hygroscopic agent, regenerates it, and accompanies it. The exhaust gas is exhausted from the exhaust port 40 to the outside of the system. In the rotor 29, not only the moisture moves from the air in the dehumidifying path to the air in the regenerating path, but also the sensible heat of both air is heat-exchanged, so that the dry air coming out of the dehumidifying path passes through the air cooler 30. The temperature is higher than the temperature. As the air heater 31, a heat exchanger with fins or an electric heater for flowing steam or a heat medium is used.

The air cooler 30 is a finned heat exchanger through which cold water or brine passes. The cold water or brine is manufactured by the refrigerator unit 42 and is circulated and supplied by the pump 43. The cold water or brine produced in the refrigerator unit 42 can also be used in the exhaust gas cooler 14 of the solvent recovery device 10 described above. Reference numeral 44 is a three-way valve for controlling the cooling capacity of the air cooler 30.

The solvent recovered by the solvent recovery device 10 is a receiver.
It is led from 22 to the solvent tank 46 and stored there. At this time, a part of the dry air produced by the dehumidifier 11 is sent to the solvent tank 46 through the small-diameter duct 47, and the atmosphere in the tank is made a dry atmosphere to prevent water from adsorbing to the solvent.

In the equipment of the present invention having the above structure, dry air from which moisture has been removed by the dehumidifier 11 and air from which solvent has been separated by the solvent recovery device 10 are introduced into the processing furnace 1. Does not substantially contain moisture, and the former receives sensible heat from the hot air for regeneration at the rotor 29, and the latter also has a heat exchanger.
Since the heat is received at 13, the temperature is raised, and the heated dry air is supplied to the processing furnace 1. Therefore, the solvent generated in the processing furnace 1 is exhausted to the exhaust duct 5 by the low-humidity air, and this exhaust gas is guided to the solvent recovery device 10, so that the solvent recovery device 10 also converts the solvent with low humidity into liquid. Recovered in a state. The amount of dry air blown to the processing furnace should be controlled to the minimum necessary considering the explosion limit of the solvent used.

[0012]

EFFECTS OF THE INVENTION According to the equipment of the present invention, even if an organic solvent having a low vapor pressure and a hygroscopic property is used, a highly concentrated solvent liquid having a low water content can be recovered from the zone where it is generated. It can be reused as it is without undergoing operations such as distillation. The gas (air) after the solvent is recovered is also heated and has a low humidity, so that it can be recycled to the processing furnace. This can reduce the load on the dehumidifier (reduce both the heating load and the dehumidifying load). Furthermore, the adoption of a dehumidifier that combines an air cooler and a regenerative dry dehumidifier (hygroscopic agent impregnated rotor) makes it possible to generate dry air that has been heated at extremely low humidity using outside air, and is relatively large. Even in the above processing furnace, the heated dry air can be supplied at a low cost. By installing a high-performance filter in the solvent recovery device, impurities are prevented from mixing into the solvent, and a solvent with high purity can be collected.

[Brief description of drawings]

FIG. 1 is a device arrangement system diagram showing, in a schematic cross-section, devices that compose the facility of the present invention.

[Explanation of symbols]

 1 Processing furnace 2 Product containing solvent 4 Exhaust hood 5 Exhaust duct 7 Exhaust fan 9 Air supply fan 10 Solvent recovery device 11 Dehumidifier 13 Heat exchanger 14 Exhaust gas cooler 15 High performance filter 16 Reheater 29 Hygroscopic agent impregnated rotor 30 Air Cooler 31 Air heater 37 Dry air air supply duct 42 Refrigerator unit 46 Solvent tank

Claims (6)

(57) [Claims] 1. A processing furnace in which vapor of an organic solvent is generated, a dehumidifying device for supplying dry air to the processing furnace, an exhaust duct for forcibly exhausting atmospheric gas in the processing furnace, and this exhaust. It comprises a solvent recovery device connected to the duct and an air supply duct for supplying the gas after the solvent is separated by the solvent recovery device to the processing furnace. The solvent recovery device includes a heat exchanger and exhaust gas cooling. And a solvent recovery device for liquefying the solvent in the exhaust gas cooler and performing heat exchange between gases before and after passing through the exhaust gas cooler in the heat exchanger. 2. The solvent recovery equipment according to claim 1, wherein the solvent recovery device includes a reheater, and gas passing through the exhaust gas cooler and the heat exchanger passes through the reheater. 3. The solvent recovery device comprises a high performance filter,
The solvent recovery equipment according to claim 1 or 2, wherein the gas that has passed through the high-performance filter passes through a heat exchanger and an exhaust gas cooler. 4. The solvent liquefied by the exhaust gas cooler is introduced into a solvent tank, and part of the dry air dehumidified by the dehumidifier is introduced into the solvent tank. Solvent recovery equipment. 5. The dehumidifying device comprises a dry dehumidifier in which a dehumidifying agent-impregnated rotor is arranged across a dehumidifying path and a regenerating path,
The solvent recovery equipment according to claim 1, 2, 3 or 4, wherein an air cooler is arranged on the upstream side of the rotor in the dehumidification path, and an air heater is arranged on the upstream side of the rotor in the regeneration path. . 6. The solvent recovery facility according to claim 1, 2, 3, 4, or 5, wherein the organic solvent is N-methyl-2-pyrrolidone.