JP2010246830A - Anesthetic gas recovery method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently recover the anesthetic gas used in an euthanizing treatment of an animal, by applying a new carbon dioxide gas system using anesthetic gas together, and reduce the scale of the recovery device, thereby improving the entire economic efficiency of euthanizing treatment. <P>SOLUTION: The mixed gasses of anesthetic gas and air discharged from a treatment chamber 10 are guided to a membrane separator 30. The membrane separator 30 has a membrane module 33 in the shape of a columnar bundle of many hollow threads made of nonporous homogeneous polymer membranes.The membrane module 33 separates the anesthetic gas by passing it alone among the mixed gases flowing through the hollow threads. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an anesthetic gas recovery method and a recovery device for efficiently and economically recovering an anesthetic gas after being used for euthanasia of an animal.

  In related facilities such as animal protection management centers and health centers established throughout the country, small animals such as stray dogs and stray cats captured are protected for a certain period of time, but if the owner or taker is not found during the protection period, The small animal is killed. This small animal is generally killed by suffocation due to carbon dioxide. However, in the suffocation killing with carbon dioxide gas, there are indications that it is not euthanized because there is little anesthetic effect and it takes time to death and it may cause pain to the animal at the time of killing. It has become.

  Under these circumstances, recently, the adoption of a new carbon dioxide gas method using an anesthetic gas is gradually increasing. In the new carbon dioxide gas system, for example, as described in Patent Document 1, an animal to be killed is put into a sleep state with an anesthetic gas, and in that state, carbon dioxide is used to suffocate and die. In the method presented by Patent Document 1, an animal that is subject to euthanasia is accommodated in a processing chamber, an anesthetic gas is supplied into the processing chamber, the anesthesia gas is inhaled, and the treatment is performed in an anesthetized state. Carbon dioxide is supplied into the room from below.

  Carbon dioxide has a greater specific gravity than air, and as the carbon dioxide gas is supplied from below into the processing chamber, the gas in the processing chamber, that is, the mixed gas of anesthetic gas and air, is discharged upward in the processing chamber, and the processing chamber is filled with carbon dioxide. The Incidentally, the concentration of the anesthetic gas is 2-3% when the anesthetic gas is isoflurane.

  In the euthanasia disposal by such a new carbon dioxide gas method combined with anesthetic gas, the mixed gas of anesthetic gas and air discharged from the processing chamber with the supply of carbon dioxide gas into the processing chamber was discarded to the atmosphere. . However, anesthetic gas is expensive. The global warming potential of anesthetic gas reaches 300 times that of carbon dioxide. For this reason, there has been a great demand for a technique for separating and recovering the anesthetic gas from the gas discharged from the processing chamber.

  As techniques for separating and recovering a specific component from a mixed gas, a cryogenic separation method, a pressure swing adsorption method, and the like are well known. The cryogenic separation method is effective when the concentration of the recovered components in the mixed gas is high, but the concentration of the anesthetic gas in the mixed gas generated by euthanasia of small animals is as low as 2-3% as described above. Concentration. For this reason, in order to liquefy and recover the anesthetic gas from the mixed gas, it is necessary to cool the mixed gas to an ultra-low temperature (−70 ° C. or lower), which is practical from the viewpoint of running cost, handling of the apparatus, maintenance, and the like. Absent. Moreover, the recovery efficiency is not as high as expected even with such very low temperature cooling.

  On the other hand, the pressure swing adsorption method has high recovery efficiency even when the concentration of components to be recovered is low, and is used to recover excess anesthetic gas discharged from hospital operating rooms. Can be diverted for anesthesia gas recovery, but an adsorber and a regenerator are required, the equipment becomes large, the price is high, and there is a problem from the viewpoint of energy saving. In addition, since a regeneration operation is required, it takes time to separate and collect, and it is not suitable from this viewpoint for use in animal euthanasia disposal where anesthetic gas needs to be separated from a large amount of mixed gas in a short time.

  Under these circumstances, development of anesthetic gas recovery technology that is suitable for use in animal euthanasia using the new carbon dioxide gas method combined with anesthetic gas, has high recovery efficiency, is small in scale, and has good economic efficiency. Is waiting.

JP 2007-60925 A

  An object of the present invention is to provide an anesthetic gas recovery method and recovery apparatus suitable for use in animal euthanasia disposal using a new carbon dioxide gas system in combination with an anesthetic gas, having a high recovery efficiency, a small apparatus scale, and good economic efficiency. Is to provide.

  In order to achieve the above object, the present inventor has paid attention to the composition of a mixed gas generated in animal euthanasia disposal by a new carbon dioxide gas method using an anesthetic gas together. The composition of the mixed gas is mostly air, with some anesthetic gas added. On the other hand, the present inventor has paid attention to a membrane permeation separation system which is one of techniques for separating a specific component in a fluid. This is a technique for separating a specific component by utilizing a difference in transmission coefficient with respect to a thin film of a polymer resin such as silicon.

  In the process of trial and error, the present inventor applied this membrane permeation separation method to the separation of anesthetic gas from the mixed gas generated in animal euthanasia by the new carbon dioxide method as one attempt. As a result, it has been found that there is a large difference in the permeability coefficient between anesthetic gas and air, and that anesthetic gas can be efficiently separated and recovered. And according to this membrane permeation separation system, a large facility is unnecessary, and the energy used is suppressed to the level of household power.

  The present invention has been completed on the basis of such knowledge, and the method for recovering anesthetic gas includes a mixed gas containing anesthetic gas used for animal euthanasia disposed in a hollow fiber formed of a homogeneous polymer membrane. The anesthetic gas that is circulated and permeates out of the hollow fiber is collected.

  The anesthetic gas recovery device of the present invention is an anesthetic gas recovery device for recovering an anesthetic gas from a mixed gas containing an anesthetic gas used for euthanasia of an animal. A membrane module configured by bundling hollow fibers, a gas supply system that pressurizes the mixed gas and supplies the mixed gas to the membrane module, and a gas recovery system that recovers anesthesia gas that has permeated the hollow fiber constituent membrane in the membrane module is doing.

  Specifically, the mixed gas referred to in the present invention is a gas in the processing chamber when the anesthetic gas is supplied at a predetermined concentration into the processing chamber containing the animal to be killed. It is a mixed gas. After the anesthetic gas is supplied, carbon dioxide for lethality is supplied into the processing chamber, so that the carbon dioxide gas is excessively mixed with the mixed gas, and the carbon dioxide concentration may be higher than the carbon dioxide concentration in the air.

  In the anesthetic gas recovery method and recovery apparatus of the present invention, the anesthetic gas in the mixed gas permeates the hollow fiber constituent membrane by circulating the mixed gas containing the anesthetic gas used for euthanasia of the animal through the hollow fiber. While passing through this, the other gas (mainly air) passes through the hollow fiber as it is. As a result, the anesthetic gas in the mixed gas is separated and recovered with a small amount of energy with high efficiency.

  For high-efficiency separation of anesthetic gas, it is preferable to pressurize the inside of the hollow fiber and reduce the pressure outside the hollow fiber. For the same purpose, it is preferable to dehumidify the mixed gas containing the anesthetic gas before feeding it into the hollow fiber. Moisture in the air is removed by dehumidification, and the mixed gas supplied to the hollow fiber becomes a mixed gas of dry air and anesthetic gas, and the anesthetic gas separation efficiency in the hollow fiber increases. The anesthetic gas thus separated is preferably liquefied and collected for handling.

  The material of the homogeneous polymer membrane constituting the hollow fiber is not particularly limited as long as it can separate the anesthetic gas from the air, but when the inventor conducted a test, silicon showed a difference in permeability coefficient. The size is preferable, and then polyimide is preferable.

  The anesthetic gas recovery method and recovery apparatus of the present invention uses a hollow fiber formed of a homogeneous polymer membrane when recovering an anesthetic gas from a mixed gas containing an anesthetic gas used for euthanasia of an animal. Since the anesthetic gas can be separated from the air in the mixed gas with extremely low energy by circulating the mixed gas through the gas mixture, the mixed gas used for the animal euthanasia disposal by the new carbon dioxide gas method combined with the anesthetic gas is used. When applied to the separation and recovery of anesthetic gas, the recovery efficiency is high, the apparatus scale is small, and the economy is good.

  Therefore, the anesthetic gas recovery method and recovery apparatus of the present invention are particularly suitable for the separation and recovery of anesthetic gas from the mixed gas used for animal euthanasia by the new carbon dioxide gas method using anesthetic gas.

It is a block diagram of the anesthetic gas collection | recovery apparatus which shows one Embodiment of this invention. It is a detailed block diagram of the membrane separator currently used for the anesthetic gas separation apparatus. It is a schematic diagram which shows the image of anesthesia gas permeation | transmission.

  Embodiments of the present invention will be described below with reference to the drawings.

  As shown in FIG. 1, the anesthesia gas recovery apparatus of the present embodiment separates and recovers anesthesia gas from a mixed gas of anesthesia gas and air discharged from a processing chamber 10 that houses an animal to be euthanized. used. This anesthetic gas recovery device is separated from air by a membrane separator 30 which is a main part of the recovery device, a gas supply system 20 for supplying the mixed gas in the processing chamber 10 to the membrane separator 30, and the membrane separator 30. A gas recovery system 40 for liquefying and recovering the anesthetic gas and a gas discharge system 50 for discharging the remaining gas (mainly air) from which the anesthetic gas has been separated by the membrane separator 30 are provided.

  The processing chamber 10 is, for example, a processing chamber of an animal euthanasia apparatus disclosed in Patent Document 1, and is configured to be supplied with anesthesia gas and carbon dioxide gas from the lower part and discharge the indoor gas from the upper part.

  The gas supply system 20 includes a three-way valve 21, a recovery pump 22, a storage tank 23, a flow rate adjustment valve 24, a dehumidifier 25, and the like that are sequentially provided on the downstream side of the processing chamber 10. The mixed gas of anesthetic gas and air in the processing chamber 10 is temporarily stored in the storage tank 23 in a pressurized state via the three-way valve 21 and the recovery pump 22. The pressurized mixed gas in the storage tank 23 is supplied to the membrane separator 30 via the dehumidifier 25 in a state where the flow rate is adjusted by the flow rate adjusting valve 24. The recovery pump 22 also serves as a pressure pump for the mixed gas.

  As shown in FIG. 2, the membrane separator 30 includes a cylindrical container 31 closed at both ends, and a membrane module 33 supported by end plates 32 a and 32 b at both ends of the container 31 excluding both ends. have. Both end portions in the container 31 are header portions 34a and 34b. The membrane module 33 is formed by bundling a large number of hollow fibers formed of a homogeneous polymer membrane having no holes, here a silicon thin film, into a cylindrical shape, and an annular outer circumferential space between the inner circumferential surface of the container 31. 35 is supported and fixed concentrically at the central portion in the container 31 with 35 remaining. The membrane module 33 is configured to distribute only the anesthetic gas in the mixed gas in the process of circulating the mixed gas of anesthetic gas and air introduced from the header portion 34a on the one end side to the header portion 34b on the other end side. The light is transmitted through the space 35.

  A gas introduction port 36 communicating with the header portion 34a is provided at an end portion on the gas introduction side of the container 31, a passing gas exhaust port 37 communicating with the header portion 34b is provided at an end portion on the gas discharge side, and an outer peripheral space is provided in the body portion. A separation gas discharge port 38 communicating with 35 is provided. The gas supply system 20 described above is connected to the gas inlet 36 of the container 31.

  The gas recovery system 40 is connected to the separation gas discharge port 38 of the container 31, and includes a vacuum pump 41 and a condenser 42 that are sequentially provided downstream of the separation gas discharge port 38. By operating the vacuum pump 41, the outer peripheral space 35 in the container 31 is depressurized, the permeation of the anesthetic gas into the outer peripheral space 35 is promoted, and the anesthetic gas in the outer peripheral space 35 is forcibly sent to the condenser 42. The condenser 42 includes a cooling device 43, liquefies the anesthetic gas sent from the membrane separator 30 and stores it in the collection container 44.

  The gas discharge system 50 is connected to the passage gas discharge port 37 of the container 31 in order to discharge the gas that has passed through the membrane separator 30. The gas discharge system 50 includes an anesthetic gas concentration sensor 51 and a three-way valve 52, and controls the three-way valve 52 according to the anesthetic gas concentration in the gas passing through the anesthetic gas concentration sensor 51. Specifically, when the anesthetic gas concentration in the gas passing through the anesthetic gas concentration sensor 51 is equal to or lower than a predetermined value, the three-way valve 52 is operated to discharge the gas to the atmosphere, and passes through the anesthetic gas concentration sensor 51. When the anesthetic gas concentration in the gas exceeds a predetermined value, the three-way valve 52 is operated to return the gas to the three-way valve 21 in the gas supply system 20 through the reflux path 53.

  Next, the overall operation and function of the anesthetic gas recovery apparatus of this embodiment will be described as an embodiment of the anesthetic gas recovery method of the present invention.

  Animals to be euthanized are housed in the processing chamber 10. Isoflurane is vaporized and supplied as an anesthetic gas into the room from the lower part of the processing chamber 10, and the anesthetic gas concentration in the room is controlled to 2-3%, which is the minimum effective concentration of isoflurane. The reason why the anesthetic gas concentration in the processing chamber 10 is controlled to the minimum effective concentration is as follows.

  Since anesthesia is maintained while leaving the animal's spontaneous breathing, the respiratory state is related to the anesthetic gas concentration. As anesthesia deepens, respiratory volume and respiratory rate decrease. This reduces the degree of inhalation of anesthetic gas into the body. The depth of anesthesia is reduced by reducing the inhalation of anesthetic gas. As the depth of anesthesia decreases, the respiration rate and respiration rate increase. As a result, the amount of anesthetic gas inhaled increases. As the amount of inhalation of anesthetic gas increases, the depth of anesthesia increases. Since the depth of anesthesia is controlled by the animal's own respiratory rhythm, it is desirable to maintain the anesthetic gas concentration at a minimum effective concentration.

  In this way, the treatment chamber 10 is filled with anesthesia gas having a predetermined concentration, so that an animal in the room is inhaled and anesthetized, and then carbon dioxide gas is supplied into the treatment chamber 10 from below. By supplying carbon dioxide from the lower part into the processing chamber 10, carbon dioxide having a large specific gravity accumulates from below in the chamber, and accordingly, air containing a predetermined concentration of anesthetic gas, that is, a mixed gas of anesthetic gas and air, It is discharged from the upper part of the processing chamber 10. At this time, the recovery pump 22 in the gas supply system 20 and the vacuum pump 41 in the gas recovery system 40 are operated.

  By operating the recovery pump 22 in the gas supply system 20, the discharge of the mixed gas of anesthetic gas and air from the processing chamber 10 is promoted, and the mixed gas is pressurized and stored in the storage tank 23. The The mixed gas stored in the storage tank 23 is supplied to the membrane separator 30 through the dehumidifier 25 in a state where the flow rate is adjusted to a predetermined value by the flow rate adjusting valve 24. The dehumidifier 25 is filled with calcium chloride. When the mixed gas passes through the dehumidifier 25, moisture in the air is mainly removed, and the mixed gas of dry air and anesthetic gas is supplied to the membrane separator 30. .

  In the membrane separator 30, a mixed gas of dry air and anesthetic gas is supplied in a pressurized state from the gas inlet 36 of the container 31 to the membrane module 33 in the container 31 through the header portion 34 a. Here, the inside and outside of the individual hollow fibers constituting the membrane module 33 are in a state as shown in FIG. That is, inside the silicon thin film 39 as a polymer membrane constituting the hollow fiber, a mixed gas of dry air and anesthetic gas flows in a pressurized state, and on the outside, the vacuum pump 41 in the gas recovery system 40 operates. When the annular outer peripheral space 35 in the container 31 is sucked, the pressure is reduced.

  Thereby, only the anesthetic gas in the mixed gas flowing in the hollow fiber permeates the silicon thin film 39 constituting the hollow fiber and enters the annular outer peripheral space 35 in the container 31, and the separation gas discharge port 38 of the container 31. To the condenser 42 in the gas recovery system 40. The pressure difference inside and outside the hollow fiber promotes permeation of anesthetic gas. Thus, in the process in which the mixed gas of dry air and anesthetic gas supplied to the membrane module 33 passes through the membrane module 33, the anesthetic gas is separated from the dry air and discharged out of the membrane module 33. The anesthetic gas discharged out of the membrane module 33 is sent from the separation gas discharge port 38 of the container 31 to the condenser 42 in the gas recovery system 40, where it is cooled to about −40 ° C. or less, which is the liquefaction temperature of the anesthetic gas. Then, it becomes liquid and is collected in the collection container 44.

  The membrane module 33 does not separate and collect the anesthetic gas in the mixed gas. For this reason, the gas that has passed through the membrane module 33 becomes dry air containing a small amount of anesthetic gas. This dry air containing a small amount of anesthetic gas flows into the gas discharge system 50 from the passage gas discharge port 37 of the container 31, the residual anesthetic gas concentration is measured by the anesthetic gas concentration sensor 51 in the gas discharge system 50, and the measured value. When is below a predetermined value, it is released into the atmosphere. Since the released gas is substantially dry air, there is no problem in releasing into the atmosphere.

  When the measured value exceeds a predetermined value, the dry air is returned from the three-way valve 52 to the three-way valve 21 disposed upstream of the gas supply system 20 via the reflux path 53 and again subjected to an anesthetic gas separation process. . This prevents the anesthetic gas exceeding the predetermined concentration from being released into the atmosphere.

  Thus, according to the anesthesia gas recovery method and recovery apparatus of the present embodiment, the anesthesia gas from the mixed gas of anesthesia gas and air used for animal euthanasia by the new carbon dioxide gas method using the anesthesia gas is small and economical. This makes it possible to collect with high efficiency by using a typical facility.

  This is because the main components in the anesthetic gas recovery device of this embodiment are the recovery pump 22 in the gas supply system 20, the membrane separator 30, and the vacuum pump 41 and the condenser 42 in the gas recovery system 40. The membrane separator 30 as a member is small and does not require motive energy itself, and the motive energy is required by the recovery pump 22, the vacuum pump 41 and the condenser 42, all of which are small and inexpensive. This is because it can be driven by energy as low as household power.

In order to confirm the effect of the present invention, the following experiment was conducted. A sealed container was prepared assuming a processing chamber. The size of the sealed container is about 250 liters that can handle four small dogs. In order to fill the sealed container with anesthetic gas having a concentration of 3%, 38.5 cc of isoflurane as an anesthetic was vaporized in the container. The membrane module in the membrane separator is a bundle of hollow fibers made of silicon rubber, and the total surface area of the silicon thin film constituting the hollow fibers is 8 m ² .

  A mixed gas of anesthetic gas and air in an airtight container is pressurized and recovered to a storage tank with a recovery pump, and the pressurized mixed gas in the tank is adjusted to 5 liters per minute by a flow adjustment valve. Supplied to. The outside of the membrane module was depressurized to 10 kPa by a vacuum pump. The anesthetic gas collected by the vacuum pump was cooled to −40 ° C. with a condenser and liquefied. Moreover, the water | moisture content in mixed gas was removed with the dehumidifier filled with the calcium chloride just before supplying to a membrane separator.

  By continuing to supply the mixed gas in the pressurized tank to the membrane separator at a flow rate of 5 liters per minute for 50 minutes, the anesthetic gas was separated and recovered for the total amount (250 liters) of the mixed gas in the sealed container. As a result, 32 cc of anesthetic (isoflurane) could be recovered. The recovery rate was 32 / 38.5≈83%.

  The above experiment is an example, and when it is desired to increase the throughput per unit time, the surface area of the membrane module may be increased. In addition, since the permeability coefficient of the anesthetic gas to the polymer membrane increases at a low temperature, cooling the mixed gas before supplying it to the membrane module is also effective in increasing the recovery efficiency. Although silicon was used as the film material, it may be slightly inferior to silicon or polyimide.

  As anesthetics, sevoflutilan, halothane, enflurane, desflurane and the like are preferable in addition to isoflurane. Both are volatile anesthetics and easily generate anesthetic gas in the processing chamber. Moreover, the separation efficiency from the air by a membrane permeation separation system is high.

DESCRIPTION OF SYMBOLS 10 Processing chamber 20 Gas supply system 21 Three-way valve 22 Recovery pump 23 Storage tank 24 Flow regulating valve 25 Dehumidifier 30 Membrane separator 31 Container 32a, 32b End plate 33 Membrane module 34a, 34b Header part 35 Outer space 36 Gas inlet 37 Passing gas outlet 38 Separating gas outlet 39 Silicon thin film (polymer film)
40 Gas recovery system 41 Vacuum pump 42 Condenser 43 Cooling device 44 Recovery container 50 Gas discharge system 51 Anesthetic gas concentration sensor 52 Three-way valve 53 Reflux path

Claims (8)

  Anesthesia gas recovery, characterized in that a mixed gas containing anesthesia gas used for animal euthanasia is circulated through a hollow fiber formed of a homogeneous polymer membrane and anesthesia gas permeating out of the hollow fiber is recovered. Method.   The anesthetic gas recovery method according to claim 1, wherein the inside of the hollow fiber is pressurized and the outside of the hollow fiber is depressurized.   3. The anesthetic gas recovery method according to claim 1, wherein the mixed gas containing the anesthetic gas is dehumidified before being supplied into the hollow fiber.   4. The anesthetic gas recovery method according to claim 1, wherein the anesthetic gas permeated out of the hollow fiber is liquefied and recovered.   An anesthetic gas recovery device for recovering an anesthetic gas from a mixed gas containing an anesthetic gas used for euthanasia of an animal, comprising a membrane module configured by bundling a plurality of hollow fibers formed of a homogeneous polymer membrane; An anesthetic gas recovery apparatus comprising: a gas supply system that pressurizes the mixed gas and supplies the gas to the membrane module; and a gas recovery system that recovers the anesthetic gas that has permeated the hollow fiber constituting membrane in the membrane module.   6. The anesthetic gas recovery apparatus according to claim 5, wherein the gas supply system includes a pressurizing pump, and the gas recovery system includes a vacuum pump.   The anesthetic gas recovery apparatus according to claim 5 or 6, wherein the gas supply system includes a dehumidifier.   The anesthetic gas recovery device according to any one of claims 5 to 7, wherein the gas recovery system includes a condenser for liquefying the recovered anesthetic gas.

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