JP5083777B2 - Volatile organic solvent recovery equipment and method - Google Patents

Description

  The present invention adsorbs a volatile organic solvent from a solvent gas containing a volatile organic solvent generated in a production facility using an adsorbent, and desorbs the volatile organic solvent from the adsorbent using steam. The present invention relates to an organic solvent recovery facility and method.

  Polymer films (hereinafter referred to as “films”) have excellent light transmittance and flexibility, and can be reduced in thickness and are widely used as optical functional films. Among these, the cellulose ester film using cellulose acylate has toughness and low birefringence in addition to the above-described properties. This cellulose ester film is used as a protective film and an optical compensation film for polarizing plates, which are constituent members of liquid crystal display devices (LCDs) whose market has been expanding in recent years, including photographic photosensitive films.

  One method for producing this film is a solution casting method. In the solution casting method, a dope containing a polymer and a solvent is cast on a support from a casting die to form a casting film, and after the casting film has a self-supporting property, The film is peeled off from the support to form a wet film, and dried while the wet film is conveyed in a tenter to obtain a film. Thereafter, the film is wound by a winding device through a drying device.

  In the film forming process, the solvent evaporates from the cast film, the wet film, and the film by drying in the casting chamber, drying by a drying device such as a tenter, and other natural drying. The gas containing the evaporated solvent (hereinafter referred to as “solvent gas”) is sent to the adsorption tower. A plurality of adsorption towers are provided, and the adsorption process and the desorption process are alternately performed in each adsorption tower. In the adsorption step, the solvent gas is passed through the adsorbent in the adsorption tower to adsorb the solvent to the adsorbent, and the gas from which the solvent component has been removed from the solvent gas is discharged to the atmosphere. In the desorption process, vapor is sent to the adsorption tower to desorb the solvent adsorbed on the adsorbent. The vapor from which the solvent has been desorbed is liquefied by a condenser such as a condenser, and fractionated into a solvent and water in a distillation column. The fractionated solvent is used again in the film forming process.

  The timing for switching from the adsorption process to the desorption process is preferably before the adsorbent can adsorb the solvent and the solvent remains in the solvent gas discharged from the adsorption tower. As for the timing for switching, those disclosed in Patent Documents 1 and 2 have been proposed. In Patent Document 1, the temperature change of the adsorbent is continuously measured, and when the differential value of the temperature reaches a predetermined value, the adsorption process is switched to the desorption process. Further, in Patent Document 2, a time during which the adsorbent cannot adsorb the solvent is calculated based on an adsorption model that models the adsorption step and the desorption step, and switching to the desorption step is performed based on the calculated time. ing.

JP-A-5-155603 Japanese Patent Laid-Open No. 11-71584

  However, the invention of the above patent document has the following problems. Regarding the invention of Patent Document 1, the differential value of the temperature becomes a predetermined value, and when switching to the desorption process, the solvent may remain in the solvent gas discharged from the adsorption tower to the atmosphere by 100 ppm or more. The main component of the solvent is composed of volatile organic substances, and among these volatile organic substances, methylene chloride, in particular, is required to have an emission concentration of 50 ppm or less by the government. Therefore, it is necessary to avoid discharging the solvent gas exceeding the discharge concentration into the atmosphere. Thus, until now, even if there was still room for the adsorbent to adsorb the solvent, the adsorbent was switched to the desorption process early. However, since the cycle of the adsorption process and the desorption process is accelerated, the life of the adsorbent is shortened, and the amount of steam in the desorption process is used excessively.

  In the invention of Patent Document 2, the adsorption model may not match the actual phenomenon due to environmental changes or the like.

  It is an object of the present invention to provide a volatile organic solvent recovery facility and method that does not use an excessive amount of vapor in the desorption process.

In order to solve the above problems, the present invention provides a plurality of adsorption devices including first and second adsorption devices that pass a solvent gas containing a volatile organic solvent through an adsorbent and adsorb the volatile organic solvent to the adsorbent. When an apparatus is provided in parallel and adsorption is performed on one side, vapor is supplied to the adsorbent on the other side, and the volatile organic solvent is desorbed from the adsorbent to adsorb the volatile organic solvent. In a continuously performing volatile organic solvent recovery facility, for each adsorber, among the solvent gas inside the adsorber, a mass spectrometer that measures the solvent component concentration of the solvent gas after passing through the adsorbent ; In the first adsorption device that is adsorbing the volatile organic solvent, when the solvent component concentration exceeds a reference value based on the solvent discharge allowable concentration, the supply of the solvent gas is already desorbed from the first adsorption device. Second adsorbent The first operation for starting desorption by the first adsorption device and the solvent component concentration measured by the first adsorption device during desorption by switching to the adsorption device and supplying the vapor to the first adsorption device. And a switching control device for performing a second operation for stopping the supply of the steam to the first adsorption device .

  The volatile organic solvent is methylene chloride, and the mass spectrometer is an apparatus that ionizes a sample and separates and detects the sample based on the ratio between the mass number and the charge, and the reference value is preferably 1 ppm.

Method for recovering a volatile organic solvent of the present invention, the each adsorber, of the solvent gas inside the adsorption apparatus, said measured by the solvent component concentration of the solvent gas after the adsorbent pass through the mass spectrometer, the In the first adsorption device that is adsorbing the volatile organic solvent, when the solvent component concentration exceeds a reference value based on the allowable solvent discharge concentration, the supply of the solvent gas is desorbed from the first adsorption device. The solvent component is measured by the first adsorption device during desorption by switching to the second adsorption device having an adsorbent and supplying the vapor to the first adsorption device to start desorption by the first adsorption device. The supply of the vapor to the first adsorption device is stopped based on the concentration .

  According to the present invention, the solvent component concentration in the solvent gas that has passed through the adsorption device is measured by a mass spectrometer, the solvent component concentration measured by the mass spectrometer is compared with a reference value based on a solvent discharge allowable concentration, When the solvent component concentration exceeds the reference value, the flow path is switched to allow the solvent gas to pass through the adsorption device having the adsorbed adsorbent, so the adsorbent should be used until the reference value is almost reached. And the adsorbent can be used effectively. Moreover, since the adsorbent used effectively is desorbed, the amount of steam used can be reduced.

It is the schematic which shows the solution casting apparatus, boiler, the 1st-3rd adsorption tower, capacitor | condenser, distillation tower, mass spectrometer, and controller which are one Embodiment of this invention.

  FIG. 1 is a schematic view showing an embodiment of the present invention, in which a solution casting apparatus 10, a boiler 11, first to third adsorption towers 12, 13, and 14, a mass spectrometer 15, a controller 16, a condenser 17, and a distillation are shown. Tower 18 is shown.

  In the solution casting apparatus 10, first, a dope 23 including a polymer 20 and a solvent 22 is cast from a casting die 26 to a traveling casting band 25. Thereby, the casting film 28 is formed on the casting band 25. The formed casting film 28 is dried by a dryer 30 provided above the casting band 25. The solvent evaporates from the casting film 28 by this drying. When the casting film 28 has self-supporting properties, the casting film 28 is peeled off from the casting band 25 as a wet film and sent to the tenter 31. In the tenter 31, the wet film is stretched in the width direction and dried to obtain a film. The film exiting the tenter 31 is dried in the drying device 32. The film exiting the drying device 32 is taken up by the take-up device 34. The main component of the solvent is a volatile organic solvent such as methylene chloride.

  The solution casting equipment 10 is installed so that the casting film, the wet film, and the solvent evaporated from the film do not come out of the equipment by drying or natural drying by the dryer 30, the tenter 31, and the drying device 32 described above. The entire structure is hermetically sealed. A gas 35 containing evaporated solvent (hereinafter referred to as “solvent gas”) is sent to one of the first to third adsorption towers 12, 13, and 14 through pipes 36, 37, 38, and 39. The pipe 36 connected to the solution casting apparatus 10 branches into a pipe 37 connected to the first adsorption tower 12, a pipe 38 connected to the second adsorption tower 13, and a pipe 39 connected to the third adsorption tower 14. Is done. Solenoid valves 37a, 38a, 39a are installed in the pipes 37, 38, 39, respectively. The opening / closing operation of the solenoid valves 37a, 38a, 39a is controlled by the controller 16 via a driver (not shown).

  The boiler 11 heats the water 43 to generate steam 44. The generated steam 46 is sent to one of the first to third adsorption towers 12, 13, and 14 through pipes 46, 47, 48, and 49. The pipe 46 connected to the boiler 11 is branched into a pipe 47 connected to the first adsorption tower 12, a pipe 48 connected to the second adsorption tower 13, and a pipe 49 connected to the third adsorption tower 14. Solenoid valves 47a, 48a and 49a are installed in the pipes 47, 48 and 49, respectively. The opening / closing operation of the solenoid valves 47a, 48a, 49a is controlled by the controller 16 via a driver (not shown).

  The first to third adsorption towers 12, 13, and 14 include adsorbents 12a, 13a, and 14a therein. Examples of the adsorbent include activated carbon. The first to third adsorption towers 12, 13, and 14 are provided with supply units 12b, 13b, and 14b and discharge units 12c, 13c, and 14c. Pipes 37, 38, 39 from the solution casting apparatus 10 and a pipe 60 connected to the capacitor 17 are attached to the supply units 12 b, 13 b, 14 b. Discharge ports 12d, 13d, and 14d are formed in the discharge portions 12c, 13c, and 14c, and pipes 47, 48, and 49 from the above-described boiler 11 are attached. Gas intake devices 61, 62, and 63 are installed in the vicinity of the discharge ports 12d, 13d, and 14d.

  The solvent in the solvent gas 35 is adsorbed by the adsorbents 12a, 13a, and 14a in the first to third adsorption towers 12, 13, and 14. The solvent gas 35 that has passed through the adsorbents 12a, 13a, and 14a is discharged into the atmosphere from the discharge ports 12d, 13d, and 14d. The gas take-in devices 61, 62, 63 take in the solvent gas 35 that has passed through the adsorbents 12 a, 13 a, 14 a and send it to the ionization unit 70 in the mass spectrometer 15. On the other hand, the solvent adsorbed on the adsorbents 12a, 13a, and 14a is desorbed from the adsorbents 12a, 13a, and 14a by the steam from the boiler 11. The vapor 65 from which the solvent is desorbed (hereinafter referred to as “desorption vapor”) is sent to the capacitor 17 through the pipe 60.

  The capacitor 17 includes a capacitor main body 17a and a cooling pipe 17b provided inside the capacitor main body 17a. The cooling pipe 17 b is connected to the cooler 67. The desorption steam 65 from the first to third adsorption towers 12, 13, and 14 is fed into the capacitor body 17a. A heat transfer medium (not shown) such as water flows inside the cooling pipe 17b, and this heat transfer medium cools the desorption steam 65 in the capacitor body 17a. Thereby, the desorption steam 65 is condensed and liquefied on the surface of the cooling pipe 17b. This liquid is sent to the distillation column 18. On the other hand, since the temperature of the heat transfer medium that has cooled the desorption steam rises, it is sent to the cooler 67 and cooled. The heat transfer medium cooled by the cooler 67 is sent again to the cooling pipe 17b.

  In the distillation tower 18, the liquid sent from the condenser 17 is fractionated into a solvent and water. The fractionated solvent is reused as the solvent 22 as a raw material. The water is disposed as drainage 68. In addition, when a solvent consists of a several component, since it fractionates for every component, after prescribing | solving a solvent to a predetermined | prescribed mixing | blending, it reuses.

  The mass spectrometer 15 includes an ionization unit 70, a mass separation unit 71, a detection unit 72, and a concentration calculation unit 73. The ionization unit 70 includes a hot filament (not shown), generates thermoelectrons from the hot filament, and collides the thermoelectrons with the solvent gas 35 taken in from the gas intake devices 61, 62, and 63. The solvent gas 35 is ionized by the collision of the thermal electrons. The mass separation unit 71 includes a variable magnetic field that is separated according to the ratio between the mass number and the charge, and allows ions of the solvent gas 35 to pass through the variable magnetic field. The detection unit 72 includes an ion detector (not shown), and detects ions that have passed through the variable magnetic field by the ion detector. The detected signal is sent to the concentration calculation unit 73. The concentration calculation unit 73 calculates the component concentration of the solvent gas 35 based on the detection signal from the detection unit 72. The component concentration of the solvent gas 35 is preferably calculated from 5000 ppm to 50000 ppm. Data on the calculated component concentration of the solvent gas 35 is transmitted to the controller 16. Since few ions reach the ion detector, an amplifier for amplifying the detection signal is preferably provided in the ion detector. Further, instead of providing the ionization unit, the mass separation unit, and the detection unit on the mass spectrometer side, they may be provided on each gas intake side. In this case, the signal detected by the detection unit is sent to the concentration calculation unit, and the component concentration of the solvent gas is calculated.

  The controller 16 includes a memory (not shown), in which a reference value determined based on the allowable discharge concentration of the solvent that can be discharged into the atmosphere is stored in advance. For example, when the allowable discharge concentration of methylene chloride to the atmosphere is 50 ppm and the discharge allowable concentration based on the establishment is 1 ppm, the reference value is stored in the memory as 1 ppm. Based on the component concentration of the solvent gas 35 calculated by the mass spectrometer 15, the controller 16 determines whether the component concentration of the solvent contained in the solvent gas 35 exceeds the reference value of 1 ppm. When it is determined that the reference value exceeds 1 ppm, the adsorption towers 12 to 14 are switched by the controller 16. For example, when the solvent gas 35 is adsorbed in the first adsorption tower 12 and the component concentration of the solvent gas 35 reaches 1 ppm, the adsorbent 13a desorbed from the first adsorption tower 12 is provided. The piping path is switched to the second adsorption tower 13 and the solvent gas 35 is sent to the second adsorption tower 13. Further, the vapor 44 is fed into the first adsorption tower 12 which has been switched after the adsorption is completed, and desorption is started.

  Next, the operation of the present invention will be described. First, the controller 16 opens the electromagnetic valve 37a. A solvent gas 35 is sent from the solution casting apparatus 10 to the first adsorption tower 12 through pipes 36 and 37. As the solvent gas 35 passes through the adsorbent 12a in the first adsorption tower 12, the solvent in the solvent gas 35 is adsorbed by the adsorbent 12a. A part of the solvent gas 35 that has passed through the adsorbent 12a is sent to the ionization unit 70 of the mass spectrometer 15 by the gas intake device 61, and most of the other is discharged from the discharge port 12d. The solvent gas 35 sent to the mass spectrometer 15 is ionized by the ionization unit 70. The ions of the solvent gas 35 pass through the variable magnetic field of the mass separator 71 and are detected by the ion detector of the detector 72. The detection signal of the ion detector is sent to the concentration calculation unit 73. The concentration calculation unit 73 calculates the component concentration of the solvent gas 35. Data on the calculated component concentration of the solvent gas 35 is sent to the controller 16.

When the controller 16 determines that the component concentration of the solvent in the solvent gas 35 exceeds the reference value of 1 ppm, the controller 16 closes the solenoid valve 37a and opens the solenoid valve 38a. As a result, the solvent gas 35 sent to the first adsorption tower 12 is sent to the second adsorption tower 13 through the pipes 36 and 38. Further, the controller 16 opens the electromagnetic valve 47 a and sends the vapor 44 to the first adsorption tower 12 through the pipes 46 and 47. The vapor 44 desorbs the solvent adsorbed on the adsorbent 12 a of the first adsorption tower 12. The desorption vapor 65 from which the solvent has been desorbed is sent to the condenser 17 through the pipe 60. The condenser 17 condenses and liquefies the desorption vapor 65. This liquid is sent to the distillation column 18 and fractionated into a solvent and water. The solvent is recovered and reused as the raw material solvent 22. When the desorption of the solvent in the first adsorption tower 12 is completed, the electromagnetic valve 47a is closed by the controller 16.

  On the other hand, in the second adsorption tower 13, like the first adsorption tower 12, the solvent gas 35 passes through the adsorbent 13a in the second adsorption tower 13, whereby the solvent in the solvent gas 35 is adsorbed on the adsorbent 13a. Is done. The mass spectrometer 15 calculates the component concentration of the solvent gas 35 based on the solvent gas 35 from the gas intake device 62. Data on the calculated component concentration of the solvent gas 35 is sent to the controller 16.

  When the controller 16 determines that the component concentration of the solvent in the solvent gas 35 exceeds the reference value of 1 ppm, the controller 16 closes the solenoid valve 38a and opens the solenoid valve 39a. As a result, the solvent gas 35 that has been sent to the second adsorption tower 13 is sent to the third adsorption tower 14 through the pipes 36 and 39. Further, the controller 16 opens the electromagnetic valve 48 a and sends the vapor 44 to the second adsorption tower 13 through the pipes 46 and 48. The vapor 44 desorbs the solvent adsorbed on the adsorbent 13 a of the second adsorption tower 13. As described above, the desorption vapor 65 from which the solvent has been desorbed is fractionated into the solvent and water. The fractionated solvent is reused as the raw material solvent 22. When the desorption of the solvent in the second adsorption tower 13 is completed, the controller 16 closes the electromagnetic valve 48a.

  On the other hand, in the third adsorption tower 14, similarly to the first and second adsorption towers 12 and 13, the solvent gas 35 passes through the adsorbent 14 a in the third adsorption tower 14, whereby the solvent in the solvent gas 35 is changed. Adsorbed on the adsorbent 14a. The mass spectrometer 15 calculates the component concentration of the solvent gas 35 based on the solvent gas 35 from the gas intake unit 63. Data on the calculated component concentration of the solvent gas 35 is sent to the controller 16.

  When the controller 16 determines that the component concentration of the solvent in the solvent gas 35 exceeds the reference value of 1 ppm, the controller 16 closes the electromagnetic valve 39a and opens the electromagnetic valve 37a. Thus, the solvent gas 35 that has been sent to the third adsorption tower 14 is sent to the first adsorption tower 12 through the pipes 36 and 37. Further, the electromagnetic valve 49 a is opened by the controller 16, and the vapor 44 is sent into the third adsorption tower 14 through the pipes 46 and 49. The vapor 44 desorbs the solvent adsorbed on the adsorbent 13 a of the second adsorption tower 13. As described above, the desorption vapor 65 from which the solvent has been desorbed is fractionated into the solvent and water. The fractionated solvent is reused as the raw material solvent 22. When the desorption of the solvent in the third adsorption tower 14 is completed, the controller 10 closes the electromagnetic valve 49a.

  In this way, solvent is adsorbed in one of the three adsorption towers, and solvent is desorbed in other adsorption towers at the same time, so that the solvent is continuously recovered from the solvent gas. can do. Moreover, the component concentration of the solvent in the solvent gas discharged from the adsorption tower by the mass spectrometer 15 can be suppressed to 1 ppm or less. This can limit the amount of solvent discharged to the atmosphere to a minimum. Furthermore, compared to the conventional case where the adsorbent is switched early with a margin, the adsorbent can be used close to the adsorption limit and the adsorption / desorption cycle of the adsorbent can be lengthened. Can do. As a result, the vapor used for desorption of the solvent can be reduced by about 10% as compared with the case where the mass spectrometer is not used. The number of adsorption towers may be two or four or more.

  In this embodiment, the solvent is recovered from the solvent gas generated in the solution casting equipment. However, the present invention is not limited thereto, and the solvent may be recovered from the solvent gas generated in other manufacturing equipment.

DESCRIPTION OF SYMBOLS 10 Solution film forming equipment 12 1st adsorption tower 12a Adsorbent 13 2nd adsorption tower 13a Adsorbent 14 3rd adsorption tower 14a Adsorbent 15 Mass spectrometer 16 Controller 22 Solvent 35 Solvent gas 44 Vapor

Claims (4)

A plurality of adsorption devices including a first and a second adsorption device for supplying a solvent gas containing a volatile organic solvent to the adsorbent and adsorbing the volatile organic solvent to the adsorbent are provided in parallel, while performing adsorption. The volatile organic solvent is recovered continuously by supplying vapor to the adsorbent and desorbing the volatile organic solvent from the adsorbent and continuously adsorbing the volatile organic solvent. In
For each adsorption device, among the solvent gas inside the adsorption device, a mass spectrometer that measures the solvent component concentration of the solvent gas after passing through the adsorbent , and
In the first adsorption device that is adsorbing the volatile organic solvent, when the solvent component concentration exceeds a reference value based on the solvent discharge allowable concentration, the supply of the solvent gas is already desorbed from the first adsorption device. A first operation for starting desorption by the first adsorption device by supplying the vapor to the first adsorption device, and a first adsorption device during desorption. A volatile organic solvent recovery facility comprising: a switching control device for performing a second operation for stopping the supply of the vapor to the first adsorption device based on the solvent component concentration measured in (1) . The volatile organic solvent is methylene chloride;
The mass spectrometer is a mass spectrometer that ionizes a sample and separates / detects it by a ratio of mass number and charge,
The volatile organic solvent recovery facility according to claim 1, wherein the reference value is 1 ppm. A plurality of adsorption devices including a first and a second adsorption device for supplying a solvent gas containing a volatile organic solvent to the adsorbent and adsorbing the volatile organic solvent to the adsorbent are provided in parallel, while performing adsorption. The volatile organic solvent is continuously adsorbed on the other side by supplying vapor to the adsorbent and desorbing the volatile organic solvent from the adsorbent. In
For each adsorber, among the solvent gas inside the adsorber, measure the solvent component concentration of the solvent gas after passing through the adsorbent, using a mass spectrometer,
In the first adsorption device that is adsorbing the volatile organic solvent, when the solvent component concentration exceeds a reference value based on the solvent discharge allowable concentration, the supply of the solvent gas is already desorbed from the first adsorption device. A first operation for starting desorption by the first adsorption device by supplying the vapor to the first adsorption device, and a first adsorption device during desorption. A method for recovering a volatile organic solvent, comprising performing a second operation for stopping the supply of the vapor to the first adsorption device based on the concentration of the solvent component measured in (1) . The volatile organic solvent is methylene chloride;
The mass spectrometer is a mass spectrometer that ionizes a sample and separates / detects it by a ratio of mass number and charge,
4. The method for recovering a volatile organic solvent according to claim 3, wherein the reference value is 1 ppm.

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