JP2013086024A - Organic solvent desorption method and organic solvent desorbing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate work for removing an organic solvent mixed in concentrated water by securing a high desorption rate and reducing the quantity of concentrated water generated after desorption when desorbing the organic solvent from an adsorbent having adsorbed organic solvent.SOLUTION: An organic solvent desorbing device includes; a desorption tank 1 filled with adsorbents having adsorbed organic solvents; a blower 2 and a heater 3 for supplying heated dry gas to the desorption tank 1; and a superheated steam generator 6 which supplies superheated steam to the desorption tank 1. An organic solvent desorption method carries out a first desorbing step in which the organic solvents are desorbed by supplying the dry gas to the adsorbents, and thereafter, a second desorbing step in which the organic solvents are further desorbed by supplying superheated steam to the adsorbents.

Description

  The present invention relates to a technical field of an organic solvent desorption method and an organic solvent desorption apparatus for desorbing and recovering an organic solvent adsorbed on an adsorbent such as activated carbon or zeolite.

In general, organic solvents with high volatility such as toluene, ethyl acetate, methyl ethyl ketone, dichloromethane, chlorobenzene, normal propyl alcohol, isopropyl alcohol, chemical factories, painting factories, printing factories, chemical factories, semiconductor manufacturing factories, precision machinery manufacturing factories, etc. Are widely used as solvents in various processes such as reaction, extraction, coating, and degreasing. When such a highly volatile organic solvent is gasified and discharged into the atmosphere, it becomes a factor of photochemical oxidants and suspended particulate matter, and there is a recovery system for recovering (removing) the gasified organic solvent. Is needed.
Conventionally, as the recovery system, the gasified organic solvent is adsorbed on an adsorbent such as activated carbon or zeolite, and the adsorbent is repeated by desorbing the organic solvent from the adsorbent on which the organic solvent is adsorbed. What is made available is known. Furthermore, in such a recovery system, when desorbing the organic solvent from the adsorbent, a method is known in which dry gas such as heated air or nitrogen gas is supplied to the adsorbent as a carrier gas and desorbed. Desorption using a dry gas has a problem that the desorption rate, that is, the removal rate of the organic solvent from the adsorbent is not so high. For this reason, in the desorption using dry gas, the non-desorbed organic solvent remains in the adsorbent, and the adsorption amount decreases when trying to adsorb again using the adsorbent after desorption. There's a problem.
Therefore, conventionally, a method for desorbing an organic solvent from an adsorbent by supplying superheated steam as a carrier gas to a desorption tank instead of dry gas is known (for example, see Patent Document 1). It has been confirmed that desorption using superheated steam can achieve a high desorption rate by appropriately setting the temperature, pressure, flow rate, etc. of superheated steam.

JP 2011-125800 A

  However, in desorption using superheated steam, the desorbed organic solvent gas and a large amount of water vapor used as a carrier are mixed gas and discharged from the desorption tank. Then, when the mixed gas of the organic solvent gas and water vapor is condensed and separated into the organic solvent and condensed water by specific gravity separation or the like, the organic solvent is mixed in the collected condensed water. For this reason, the recovered condensed water cannot be discharged to the outside without performing a removal process for separating and removing the organic solvent further mixed from the recovered condensed water. The removal treatment for removing the organic solvent from the condensed water has a problem that the larger the amount of condensed water, that is, the larger the amount of superheated steam used for desorption, the larger the removal treatment becomes and the more difficult it is. There is a problem to be solved by the present invention.

The present invention has been made in view of the above-mentioned circumstances and has been created for the purpose of solving these problems. The invention of claim 1 is for desorbing the organic solvent from the adsorbent adsorbing the organic solvent. The desorption method includes a first desorption step in which a dry gas is supplied to the adsorbent for desorption, and superheated steam is supplied to the adsorbent desorbed in the first desorption step for further desorption. And a second desorption step. The method of desorbing an organic solvent.
The invention of claim 2 is a desorption device for desorbing the organic solvent from the adsorbent adsorbing the organic solvent, the desorption device comprising a desorption tank filled with the adsorbent adsorbing the organic solvent; Dry gas supply means for supplying dry gas to the desorption tank, superheated steam supply means for supplying superheated steam to the desorption tank, and superheated steam after the first desorption step of supplying and desorbing the dry gas. An organic solvent desorption apparatus comprising a switching means for switching the supply of dry gas and superheated steam to a desorption tank so as to perform a second desorption step of desorption.
According to a third aspect of the present invention, in the second aspect, the dry gas supply means includes a heater for heating the dry gas supplied to the desorption tank, and the heater uses the superheated steam generated by the superheated steam supply means. An organic solvent desorption apparatus having a configuration in which dry gas is heated as a heat medium.

According to the invention of claim 1 or 2, the organic solvent remaining in the adsorbent without being desorbed in the first desorption process using dry gas is surely desorbed in the second desorption process using superheated steam. As a result, a high desorption rate can be secured. And since the 2nd desorption process using superheated steam is performed with respect to the activated carbon after desorption using dry gas, the usage-amount of superheated steam can be reduced significantly. As a result, the condensed water generated when the mixed gas of the organic solvent gas and water vapor after desorption is condensed is greatly reduced, and the removal process for removing the organic solvent mixed in the condensed water can be made small scale. Thus, the removal process can be facilitated and the cost can be greatly reduced.
According to the invention of claim 3, the dry gas used in the first desorption step can be heated by effectively using the superheated steam used in the second desorption step, and a separate heat source for heating the dry gas is required. Therefore, the device can be shared and energy can be saved.

It is a figure which shows the flow of a desorption apparatus. It is a table | surface figure which shows the experimental result of a preliminary experiment example. It is a table | surface figure which shows the experimental result of an Example. It is a table | surface figure which shows the experimental result of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a flow of a desorption apparatus. In FIG. 1, 1 is a desorption tank, and the desorption tank 1 has activated carbon adsorbed with an organic solvent (corresponding to the adsorbent of the present invention). Is filled).

  Reference numeral 2 denotes a blower provided on the upstream side of the desorption tank 1, and the dry gas (air in the present embodiment) fed from the blower 2 is heated by the heater 3 and then the desorption tank 1. To be supplied. In this case, a first open / close valve 5 is arranged in the pipe 4 extending from the heater 3 to the desorption tank 1, and the first open / close valve 5 can open and close the supply of dry gas to the desorption tank 1. It is like that. The temperature and flow rate of the dry gas supplied to the desorption tank 1 are appropriately set according to the characteristics of the organic solvent adsorbed on the activated carbon, the adsorption amount, and the like. The blower 2 and the heater 3 constitute dry gas supply means of the present invention. Furthermore, the dry gas of the present invention refers to a low moisture state gas such as air, air from which moisture has been removed, inert gas such as nitrogen, or a mixed gas of air and inert gas.

  Furthermore, 6 is a superheated steam generator (corresponding to the superheated steam supply means of the present invention) provided upstream of the desorption tank 1 in parallel with the blower 2, and the superheated steam generator 6 is 100 Superheated steam exceeding 200C (for example, steam at 200C to 350C) is generated and supplied to the desorption tank 1. In this case, a second opening / closing valve 8 capable of adjusting the opening degree is provided in the pipe 7 extending from the superheated steam generator 6 to the desorption tank 1, and the second opening / closing valve 8 allows the superheated steam generator 6 to The superheated steam supply to the desorption tank 1 can be opened and closed, and the pressure of the supplied superheated steam can be adjusted. The temperature and flow rate of the superheated steam supplied to the desorption tank 1 are appropriately set according to the characteristics of the organic solvent adsorbed on the activated carbon, the adsorption amount, and the like.

  Here, the heater 3 is configured to heat the dry gas fed from the blower 2 using the superheated steam generated by the superheated steam generator 6 as a heat medium. In this case, a third opening / closing valve 10 capable of adjusting the opening degree is provided in the pipe 9 extending from the superheated steam generator 6 to the heater 3, and the third open / close valve 10 allows the superheated steam generator 6 to The supply of superheated steam to the heater 3 can be opened and closed, and the pressure of the supplied heated steam can be adjusted.

  Then, when desorbing the activated carbon filled in the desorption tank 1, first, as a first desorption process, dry gas fed from the blower 2 and heated by the heater 3 is supplied to the desorption tank 1 as a carrier gas. Desorb organic solvent adsorbed on activated carbon. In the first desorption step using the dry gas, the concentration of the organic solvent measured by the concentration sensor 11 (for example, gas chromatography) connected to the outlet side of the desorption tank 1 is lowered to a preset concentration or less. It ends when it does. Alternatively, the process is terminated after a preset time has elapsed. The set time or set concentration for ending the first desorption step is set according to the characteristics of the organic solvent adsorbed on the activated carbon, the adsorption amount, etc., but in this embodiment, the adsorption amount before desorption is Thus, the set time or set concentration is set so that about 70% to 90% of desorption is performed in the first desorption step.

  Subsequently, as the second desorption process, the superheated steam generated by the superheated steam generator 6 is supplied to the desorption tank 1, and the organic solvent is further desorbed from the activated carbon desorbed by the dry gas in the first desorption process. The second desorption process using superheated steam is terminated when the gas temperature measured by the temperature sensor 12 connected to the outlet side of the desorption tank 1 exceeds a preset temperature. The set temperature for ending the second desorption step is set to a temperature higher than the boiling point (for example, a temperature 10 ° C. higher than the boiling point of the organic solvent) according to the boiling point of the organic solvent adsorbed on the activated carbon. This is inferred that during the desorption, the outlet side temperature of the desorption tank 1 is maintained near the boiling point of the organic solvent (during desorption, the temperature of the superheated steam is lowered and balanced by the heat of vaporization of the organic solvent). On the other hand, after completion of the desorption, it has been confirmed by experiments that the temperature on the outlet side of the desorption tank 1 rapidly rises to near the supply temperature of the superheated steam.

  Thus, as a desorption process for desorbing the organic solvent from the activated carbon, first, a first desorption process using dry gas is performed, and then a second desorption process using superheated steam is performed. And by the 1st desorption process using dry gas, most organic solvents (for example, 70%-90% of adsorption amount) are desorbed from activated carbon, and the 2nd desorption process using superheated steam performed continuously is performed. In addition, most of the organic solvent remaining on the activated carbon without being desorbed in the first desorption step (for example, 99% to about 100% of the adsorption amount including the desorption amount in the first desorption step) is surely desorbed. It is like that. During the first desorption process, the first on-off valve 5 provided in the pipe 4 extending from the heater 3 to the desorption tank 1 is opened, and the first open / close valve 5 provided in the pipe 7 extending from the superheated steam generator 6 to the desorption tank 1 is opened. The two on-off valves 8 are controlled to be closed, and during the second desorption process, the first on-off valve 5 is controlled to be closed and the second on-off valve 8 is opened. The superheated steam is supplied to the desorption tank 1 in the second desorption process, and the first on-off valve 5 and the second on-off valve 8 are connected to the desorption tank of the present invention. This corresponds to switching means for switching the supply of dry gas and superheated steam. The desorption tank 1, blower 2 and heater 3 (dry gas supply means), superheated steam generator 6 (superheated steam supply means), first on-off valve 5 and second on-off valve 8 (switching means) The desorption apparatus of the invention is configured.

  On the other hand, 13 is a precooling condenser provided on the downstream side of the desorption tank 1, and the precooling condenser 13 cools the mixed gas discharged from the desorption tank 1 using industrial water as a refrigerant. The mixed gas discharged from the desorption tank 1 is a mixed gas of an organic solvent gas and dry gas desorbed from activated carbon in the first desorption step, and an organic desorbed from activated carbon in the second desorption step. Although it is a mixed gas of solvent gas and water vapor, when these mixed gases are cooled by the precooling condenser 13, the organic solvent gas and a part of the water vapor are liquefied. The liquefied organic solvent and condensed water are trapped in the condensate tank 14 and then separated into an organic solvent and condensed water by a separator 15 such as a specific gravity separator and a distillation separator, respectively. It is recovered in the tank 16 and the condensed water recovery tank 17.

  Further, 18 is a low-temperature condenser provided on the downstream side of the condensate tank 14, and the low-temperature condenser 18 has cooled the mixed gas that has not been liquefied by the pre-cooling condenser 13 by a cooler 19. It cools and liquefies using a low temperature (for example, -5 degreeC-5 degreeC) refrigerant | coolant. The condensate liquefied by the low-temperature condenser 18 is separated from the organic solvent and condensed water, and is recovered in the organic solvent recovery tank 20 and the condensed water recovery tank 21, respectively. In addition, as a condenser, it replaces with the said low temperature condenser 18, and a pressurized deep-cooling type | mold condenser etc. can also be used.

  Here, the condensed water recovered in the condensed water recovery tanks 17 and 21 contains some organic solvent. The condensed water containing the organic solvent is drained after performing a removal treatment for removing the organic solvent. The gas discharged from the low temperature condenser 18 is adsorbed by an adsorbent such as activated carbon as necessary to remove the organic solvent, and then exhausted to the outside.

  In the present embodiment configured as described above, the desorption apparatus includes a desorption tank 1 filled with activated carbon that has adsorbed an organic solvent, a blower 2 that supplies heated dry gas to the desorption tank 1, and a heater 3. And a superheated steam generator 6 for supplying superheated steam to the desorption tank 1, and first and second on-off valves 5 and 8 for switching the supply of dry gas and superheated steam to the desorption tank 1. When the activated carbon filled in the desorption tank 1 is desorbed, first, a first desorption step is performed in which the activated gas is supplied to the activated carbon and desorbed, and then desorbed in the first step. A second desorption step is performed in which superheated steam is supplied to the activated carbon for further desorption.

  Thus, after the first desorption step using the dry gas, the second desorption step using the superheated steam is performed, so that the activated carbon is not desorbed in the first desorption step using the dry gas. The organic solvent remaining in the substrate can be surely desorbed by the second desorption step using superheated steam, and a high desorption rate can be secured. Moreover, since the second desorption step using superheated steam is performed on the activated carbon after desorption using dry gas, only desorption using superheated steam is performed without performing desorption using dry gas. Compared with the case, the usage-amount of superheated steam can be reduced significantly. As a result, the condensed water generated when the mixed gas of the organic solvent gas and water vapor after desorption is condensed can be greatly reduced, and thus the removal process for removing the organic solvent from the condensed water can be reduced on a small scale. This can greatly contribute to the simplification of removal processing and cost reduction.

  In addition, in this apparatus, the heater 3 for heating the dry gas used in the first desorption process uses the superheated steam generated by the superheated steam generator 6 as a heat medium, so the superheated steam used in the second desorption process. It is possible to heat the dry gas used in the first desorption process by effectively utilizing the above, so that a separate heat source for heating the dry gas is not required, and the apparatus can be shared and energy can be saved.

Next, preliminary experiments, examples and comparative examples for confirming the usefulness of the present invention will be specifically described below. The devices used in the experiments of these preliminary experimental examples, examples, and comparative examples are the above-described desorption devices downsized from the practical level, and are given the same reference numerals, and the description of each device is as follows. Omitted. In these experiments, activated carbon was used as the adsorbent filled in the desorption tank 1, and 2.90 kg of toluene (C ₆ H ₅ CH ₃ ) as an organic solvent was adsorbed to 13.8 kg of the activated carbon. An experiment was conducted in which toluene was desorbed from the activated carbon adsorbed with.

<Example of preliminary experiment>
As a preliminary experiment, in order to examine the conditions for increasing the desorption rate in the first desorption process of the present invention, desorption was performed only with dry gas using the temperature and air volume of the dry gas as parameters. In this case, the blower 2 and the heater 3 were set so as to supply heated air having a temperature and an air volume shown in Experiments No. 1-1 to No. 1-6 in FIG. This desorption with heated air was completed after a desorption time of 1 hour. The results are shown in FIG. 2, and the highest desorption rate in this preliminary experiment is Experiment No. 1-3 (desorption amount 2.66 kg, desorption rate 91%). An air temperature of 207 ° C. and an air volume of 800 L / min) were adopted as conditions for the first desorption process of the examples described later. In addition, even if the desorption time was 1 hour or more under the conditions of Experiment No1-3, it was confirmed by experiments that the desorption amount of toluene hardly increased.

<Example>
As an example of the present invention, a second step using superheated steam was performed after the first desorption step using dry gas. In this case, in the first desorption step, the blower 2 and the heater 3 are set so as to supply heated air of 207 ° C. and 800 L / min (conditions of the preliminary experiment No. 1-3) to the desorption tank 1. The first desorption step was completed with a desorption time of 1 hour. From the result of the preliminary experiment described above, the desorption amount of toluene at the time when the first desorption step is completed is 2.66 kg, and the desorption rate is 91%. In the second desorption process, the superheated steam generator 6 is set so as to supply the superheated steam having the temperature and the amount of steam shown in the experiments No2-1 to No2-3 in FIG. The desorption process was terminated when the outlet side temperature of the desorption tank 1 exceeded 120 ° C. (temperature higher by 10 ° C. than the boiling point of toluene 110 ° C.). The results are shown in FIG. 3, and the desorption time required in the second desorption step is 35 minutes for Experiment No2-1, 31 minutes for Experiment No2-2, and 25 minutes for Experiment No2-3. Moreover, in any of Experiment No2-1 to No2-3, the desorption amount of toluene (including the amount desorbed in the first desorption step) at the time when the second desorption step is completed is 2.90 kg, The rate was 100%.
Thereby, it was confirmed that the desorption can be performed with a high desorption rate (100% in the example) by performing the second desorption step using superheated steam after the first desorption step using heated air (dry gas). . In the calculation, the total amount of superheated steam used in this example is 25 kg ((43 kg / hour) × 35 minutes = 25 kg) in Experiment No2-1, and 22 kg ((43 kg / hour) × 31 minutes in Experiment No2-2). 22 kg) and 20 kg in Experiment No2-3 ((47 kg / hour) × 25 minutes = 20 kg).

<Comparative example>
As a comparative example, only desorption with superheated steam was performed without desorption with dry gas. In this case, the superheated steam generator 6 was set to supply the superheated steam having the temperature and the amount of steam shown in Experiments No. 3-1 to No. 3-3 in FIG. The temperature and the amount of steam of the superheated steam set in No3-3 are the same as the temperature and the amount of steam of the superheated steam set in Experiments No2-1 to No2-3 of the above embodiment. The desorption with superheated steam was terminated when the outlet side temperature of the desorption tank 1 exceeded 120 ° C. (temperature higher by 10 ° C. than the boiling point of toluene 110 ° C.), as in the example. The results are shown in FIG. 4, and the desorption time required for the comparative example is 91 minutes for Experiment No3-1, 80 minutes for Experiment No3-2, and 65 minutes for Experiment No3-3. Moreover, in any of Experiment No3-1 to No3-3, the desorption amount of toluene (including the amount desorbed in the first desorption step) was 2.9 kg, and the desorption rate was 100%. In addition, the total amount of superheated steam used in this comparative example was calculated to be 65 kg ((43 kg / hour) × 91 minutes = 65 kg) in Experiment No3-1 and 57 kg ((43 kg / hour) × 57 in Experiment No3-2. Min = 57 kg) and in Experiment No3-3, it is 51 kg ((47 kg / hour) × 65 min = 51 kg).
Therefore, in the comparative example in which only desorption with superheated steam is performed, desorption can be performed at a high desorption rate as in the above-described example, but a large amount (about 2.6 times) of overheating as compared with the example. It was confirmed that water vapor was required, and thus it was confirmed that the amount of superheated water vapor used can be significantly reduced in the examples in which the present invention is implemented as compared with the comparative example.

  In the above example, the first desorption process was set to desorb up to the maximum amount that can be desorbed in the first desorption process, and the remaining desorption was desorbed in the second desorption process. In this case, since the remaining desorption amount to be desorbed in the second desorption step is minimized, the amount of superheated steam used can be reduced to the maximum, but the first, The ratio of the desorption amount desorbed in each of the second steps can be appropriately set in consideration of the energy used in each of the first and second desorption steps, the cost for water treatment, and the like.

  For example, the first desorption step with dry gas can be set to be terminated at a time when the desorption efficiency is relatively high. That is, the desorption efficiency (desorption amount per hour) of the first desorption step is high immediately after the start of desorption, but decreases as the desorption time elapses. For this reason, if the maximum amount that can be desorbed in the first desorption step is desorbed, the desorption time in a state where the desorption efficiency is low becomes long, which may be contrary to energy saving. Therefore, the first desorption step may be set to be terminated when the desorption efficiency is relatively high (for example, when desorption is performed up to 70% of the adsorption amount) and the rest is desorbed in the second desorption step. Even in this case, it is a matter of course that the amount of superheated steam used can be greatly reduced as compared with the case where only desorption using superheated steam is performed without performing desorption using dry gas.

  The present invention can be used when desorbing an organic solvent adsorbed on an adsorbent such as activated carbon or zeolite.

DESCRIPTION OF SYMBOLS 1 Desorption tank 2 Blower 3 Heater 5 First on-off valve 6 Superheated steam generator 8 Second on-off valve

Claims (3)

  A desorption method for desorbing the organic solvent from an adsorbent adsorbing an organic solvent, the desorption method comprising a first desorption step of desorbing by supplying a dry gas to the adsorbent, and the first desorption step And a second desorption step of further desorption by supplying superheated steam to the adsorbent desorbed in step (b).   A desorption device for desorbing the organic solvent from an adsorbent adsorbing an organic solvent, the desorption device comprising: a desorption tank filled with an adsorbent adsorbing the organic solvent; and a dry gas in the desorption tank A dry gas supply means for supplying; a superheated steam supply means for supplying superheated steam to the desorption tank; and a second desorption process for supplying and desorbing superheated steam after the first desorption process of supplying and desorbing said dry gas. An organic solvent desorption apparatus comprising: a switching means for switching the supply of dry gas and superheated steam to the desorption tank.   3. The dry gas supply means according to claim 2, wherein the dry gas supply means includes a heater that heats the dry gas supplied to the desorption tank, and the heater heats the dry gas using the superheated steam generated by the superheated steam supply means as a heat medium. An organic solvent desorption apparatus characterized by comprising:

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