JPH10215764A - Adsorption separation system for low temperature ca - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a system capable of managing the concentration of nitrogen and oxygen, etc., inside a container fixed so as to maintain freshness at the time of the storage and transportation of fruits and vegetables by constituting a nitrogen replacing means by a one-through type PSA device for nitrogen generation capable of alternately switching and using two tower type adsorption/ desorption towers filled with an MSC adsorption material and continuously manufacturing the nitrogen. SOLUTION: For instance, this system is constituted of a CA refrigerator 10, the refrigeration device 11 of the refrigerator 10, an air pressure source part 12, an intra-container air supply part 13, a cooling part 14, a PSA adsorption/desorption part 15 or a VSA adsorption/desorption part 16, a gas lead-out part 17 and a suction discharge part 23. The PSA adsorption/desorption part 15 or the VSA adsorption/desorption part 16 is constituted of the two adsorption/desorption towers 18 and 19 and an accompanying switching valve group, the gas lead-out part 17 is constituted of a product gas tower 20, a check valve 21 and a switching part 22, etc., and the target system is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the concentration of nitrogen, oxygen, carbon dioxide, and ethylene gas in a refrigerator to keep the freshness of the fruits and vegetables during storage and transportation. , Especially MSC
(Molecular sieves carbon) using adsorbent,
The present invention relates to an adsorption / separation system for low-temperature CA, in which air in a refrigerator is replaced with nitrogen gas, and concentration of carbon dioxide and ethylene gas in the refrigerator after the replacement is controlled to maintain an atmosphere gas having an optimum composition.

[0002]

2. Description of the Related Art It is a well-known fact that foods that are susceptible to deterioration can be extended in storage by refrigeration rather than simply stored at room temperature. However, CA is a powerful means for further extending the storage life. The refrigeration method is recommended, especially among fruits and vegetables, which is the best method for storing apples.

Generally, in CA refrigeration, the refrigerator is refrigerated in an atmosphere in which the oxygen concentration of the air in the refrigerator is reduced and the concentration of carbon dioxide gas is increased. In that case, the foods to be refrigerated, especially the fruits and vegetables to be refrigerated, have their own optimal CA gas composition, and in view of the prolonged storage period and the accompanying effects by refrigerated storage under the optimal composition atmosphere. I have.

Incidentally, the CA method used in the above-mentioned CA system includes: 1, a normal CA method; a method utilizing the respiration of fruits and vegetables, 2, a combustion method 1: a method of previously preparing an optimum composition air, and a method of (CA composition gas). Is usually produced by burning pure propane together with air.) 3. Combustion formula 2: Correcting the fluctuation component of the air in the refrigerator without rejecting all the CA composition air produced by the combustion formula 1, and recirculating it. Method 4, non-combustion method; method of adjusting the CA composition optimally using a nitrogen generator to lower the oxygen concentration in the refrigerator, and then maintaining the optimal composition air with the CA controller, covering the above items 1-4. There is a method, but currently there is a tendency to shift to a non-combustion type. The above-mentioned nitrogen generator includes a membrane separation type normal pressure type and a pressurization type PSA.

Recently used low temperature CA systems include:
A nitrogen generator (PSA), which is also the oxygen reducing device;
It is composed of an adsorption device for removing carbon dioxide and an adsorption device for removing ethylene gas. That is, after reducing the oxygen concentration in the storage to a predetermined oxygen concentration by using a nitrogen generator at the same time as the storage of the stored goods, the outside air is periodically introduced to maintain the concentration, and by the respiratory action. The carbon dioxide gas newly generated and accumulated in the storage is removed by the carbon dioxide gas removal adsorption device to prevent deterioration of the stored fruit, and the ethylene gas generated from the storage product is removed by the ethylene gas adsorption device. In the case of fruits, for example, ripening, softening, detachment, settling, and storage diseases of fruits are prevented.

[0006]

In the storage of fruits and vegetables by the low-temperature CA system, in the case of apples mainly using CA storage, low oxygen (2-3%) and high carbon dioxide (1-8 %), The respiratory volume of the apples is reduced by 30-60% when refrigerated in an atmosphere composition combining (%). It has also been proposed that the relative humidity in the CA storage chamber may be kept as high as about 95%. That is, the optimal conditions of the temperature and atmosphere composition of the CA refrigeration slightly change depending on the variety, cultivation, and harvesting conditions, so that the functions of the corresponding carbon dioxide gas-removing adsorption device and ethylene gas-removing adsorption device, especially The adsorption function of the adsorbent requires a delicate and accurate control function.

As the above-mentioned industrial adsorbent, activated carbon, silica gel, activated alumina, activated clay and the like have been used for a long time for the purpose of purification and separation, and as shown in the utilization area shown in FIG. Other adsorbents selectively adsorb polar molecules, while selectively adsorb polar molecules. For example, silica gel is widely used as a desiccant or dehydrating agent for the purpose of selectively adsorbing water, a representative of polar molecules, and activated carbon is used for solvent recovery from humid air and air purification. .

[0008] Silica gel and other adsorbents selectively adsorb molecules having unsaturated bonds, and all adsorbents adsorb molecules having higher molecular weight in the same family. However, any of the above adsorbents has a pore involved in adsorption of 50 to 200 n.
m or less, and those having a molecular diameter larger than the pore size distribution range of each adsorbent are hardly adsorbed. Also,
Molecular sieves, which appeared in 1954,
-4A, MSZ-5A, MSZ-10X, MSZ-13
X, etc., each of about 3.5 nm, 4.2 n
m, a synthetic zeolite having an effective pore size of 9.0 nm and 10.0 nm, which adsorbs only those having a molecular size smaller than the above pore size, and enables a selection principle based on the molecular size. However, different separation and high-precision adsorption / separation constitute polar molecules, and high-precision adsorption / separation is possible for molecules having a saturated bond.

However, in a region where the selective adsorption characteristics of activated carbon are effectively used for non-polar molecules and molecules having a saturated bond, an adsorbent having the above-described molecular sieve selection principle has not yet been put to practical use. However, as shown in FIG. 8 described above, a molecular sieve carbon as an MSA adsorbent capable of responding to the above matters has been recently developed and proposed.

The present inventors have conducted various studies on the above-mentioned conventional CA system. As a result, when a system based on the non-combustion type CA system is adopted, it takes a short time to completely replace the atmosphere in the chamber with nitrogen. Since it is necessary to supply a large amount of nitrogen gas with high efficiency, the invention according to claim 1 requires the nitrogen replacement means to have a large oxygen gas adsorption capacity per unit mass of adsorbent and to continuously increase a large amount of nitrogen generated. MSC which can operate at low temperature (0 to 13 ° C) and high pressure (7 atm or less), has a speed separation function, and can selectively adsorb oxygen gas. It is an object of the present invention to provide an adsorption / separation system for low-temperature CA comprising a one-through type two-column switching type PSA apparatus for nitrogen generation using molecular sieves (carbon) as an adsorbent.

Further, in the invention according to claim 2, in order to efficiently and continuously carry out adsorption separation of carbon dioxide gas and ethylene gas in the atmosphere gas, the atmosphere gas optimum composition control means includes a low-temperature low-pressure Carbon dioxide gas and ethylene gas removal that can be continuously and selectively removed by switching between two-column adsorption towers that operate below and are filled with MSC (Molecular Sieves Carbon) adsorbent that has a molecular sieve function and can be selectively adsorbed The purpose of the present invention is to provide an adsorption / separation system for low-temperature CA composed of a circulation type VSA device for use. In particular, since the MSC adsorbent has a function of adsorbing and separating a multicomponent gas based on the difference in adsorption speed, a plurality of components (in this case, carbon dioxide gas and ethylene gas contained in nitrogen gas) In the prior art, a separate removal device using each removal adsorbent was required for the separation of (a), but a single removal device using a single adsorbent can be used for both removal. b) It is obtained by thermal decomposition of organic polymer, etc., and the pores are formed in a slit shape, so the molecular diameter to be fractionated is very small, so for adsorption separation where high fractionation accuracy is required Optimal. c. For the above reasons, the use of MSC adsorbents allows for the provision of a simple and efficient low temperature CA adsorption separation system.

Another object of the present invention is to provide a more efficient adsorption / separation system for low-temperature CA by using the inventions of the first and second aspects together.

The invention according to claim 4 provides a one-through type PSA for nitrogen generation in addition to the object of the invention according to claim 3.
It is an object of the present invention to provide a low-temperature CA adsorption / separation system in which the configuration of the apparatus is continuously operated under low temperature and high pressure and is specified as one-way supply.

According to a fifth aspect of the present invention, in addition to the object of the third aspect, a configuration of a circulating VSA device for removing carbon dioxide and ethylene gas is specified so as to be operable at a low temperature and a low pressure. It is intended to provide a CA adsorption separation system.

Further, the invention according to claim 6 is based on claim 4,
Another object of the present invention is to provide a low-temperature CA adsorption / separation system in which the configuration of a dehumidifying cooling unit is specified so that brine / chiller water for a refrigerator can be effectively used.

[0016]

According to the first aspect of the present invention,
An adsorption / separation system for CA, wherein a nitrogen purging means for forming the system is alternately switched between a two-column adsorption tower filled with MSC (molecular sieves carbon) adsorbent, thereby enabling continuous production of nitrogen. PSA (Pressure S) for one-through type nitrogen generation operated at low temperature and high pressure
wing Adsorption) device.

According to a second aspect of the present invention, there is provided an adsorption / separation system for CA, wherein the atmosphere gas optimum composition control means for forming the system is a two-column system filled with an MSC (molecular sieves carbon) adsorbent. A circulating type VSA for removing carbon dioxide and ethylene gas operated at low temperature and low pressure, which enables continuous removal of carbon dioxide gas and ethylene gas from circulating atmosphere gas by alternately using and using adsorption towers
(Vacuume Swing Adsorption) device.

Further, the invention according to claim 3 is the adsorption separation system for CA, wherein the CA refrigerator, the refrigerator of the refrigerator and the air in the refrigerator are collectively replaced with nitrogen gas.
The one-through type PSA device for nitrogen generation described above and the circulating VSA device for removing carbon dioxide and ethylene gas according to claim 2 for controlling the concentration of carbon dioxide gas and ethylene gas in the internal atmosphere gas after replacement with nitrogen gas. And a main configuration.

According to a fourth aspect of the present invention, there is provided a PSA device according to the third aspect, wherein a high-pressure low-temperature air supply unit for supplying compressed air via a dehumidifying cooling unit and a P-type unit capable of continuous switching use.
It is characterized by comprising a two-tower type adsorption / desorption section for SA, a desorption suction / discharge section, and a nitrogen gas discharge section with a check valve.

According to a fifth aspect of the present invention, there is provided a VSA device according to the third aspect, wherein an in-compartment air supply section for circulating the in-compartment air via a dehumidifying cooling section, and a V which can be continuously switched.
It is characterized in that it has a configuration including a two-tower type adsorption / desorption section for SA and a desorption suction / discharge section.

The invention according to claim 6 is the invention according to claim 4,
A dehumidification cooling section according to a fifth aspect is characterized in that it is configured to use the brine / chiller water for a refrigerator in combination with the third aspect.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
This will be described together with the illustrated example. However, unless otherwise specified, the dimensions, shapes, relative positions, and the like of the components described in this embodiment are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent. FIG.
2 is a process flowchart showing a schematic configuration of the adsorption / separation system for low-temperature CA of the present invention. FIG. 2 is a view showing a situation in which the nitrogen replacement means is operated in the flowchart of FIG. 1, and FIG. It is a figure showing the situation where the atmosphere gas optimal composition control means was operated.

The adsorption / separation system for low-temperature CA of the present invention comprises:
A system in which air in a refrigerator of a CA refrigerator is replaced at a time by nitrogen replacement means, and carbon dioxide and ethylene gas in the air after replacement are removed by an atmosphere gas optimum composition control means after replacement and controlled to an optimum state. The nitrogen purging means is constituted by a one-through type PSA device for nitrogen generation which operates under low temperature and high pressure, and the atmosphere gas optimum composition control means is controlled by a circulation type VSA device for removing carbon dioxide and ethylene gas which operates under low temperature and low pressure. It is composed. The adsorption / separation system for low-temperature CA of the present invention shown in FIG. 1 having the above-described configuration includes a CA refrigerator 10 and a refrigerator 11 of the refrigerator 10.
, An air pressure source section 12, an internal air supply section 13, a cooling section 14, a PSA adsorption / desorption section 15 to a VSA adsorption / desorption section 16,
And a gas outlet 17 and a suction / discharge unit 23. The CA refrigerator 10 is provided with an in-compartment air exhaust unit 10a, an in-compartment air pressure adjusting unit 10b, an in-compartment gas composition analyzer 10c, and the like so that the in-compartment gas composition and the air pressure can be optimally maintained and adjusted. The refrigerator 11 supplies the brine / chiller water obtained by the refrigerator 11a to the cooler 11b of the CA refrigerator 10 and the brine cooler 14a of the cooling unit 14 to cool the refrigerator 10 and adsorb nitrogen gas, respectively. It is possible to cool the high-pressure dehumidified air for separation and the air in the circulation chamber for controlling atmospheric gas. At the time of starting to cool the refrigerator temperature to a required low temperature, the refrigerating load of the refrigerator 11a becomes the maximum, but becomes light after the internal temperature is lowered to the required low temperature. However, with the above configuration, the brine / chiller water for the cooler 11b can be effectively used.

The air pressure source section 12 is provided for obtaining high-pressure dehumidified air used in the one-through type nitrogen generating PSA apparatus constituting the nitrogen replacing means, and includes a compressor 12a, an aftercooler 12b, a drain separator 12
d and the like, and the high-pressure and high-temperature air discharged from the compressor 12a (about 200 ° C. at 7 bar (G)) is supplied to the aftercooler 12b and the drain separator 1
Through 2d, high-pressure dehumidified air cooled to about 60 ° C. or lower is obtained. In addition, the circulating internal air used in the circulating VSA apparatus for removing carbon dioxide gas and ethylene gas constituting the post-atmosphere gas optimal composition control means is supplied through a blower 13 a provided in the internal air supply unit 13, The air is introduced into a stage preceding the drain separator 12d and dehumidified by the drain separator 12d to obtain dehumidified air in the circulation storage.

The cooling unit 14 includes the refrigerator 1 as described above.
A brine cooler 14a is provided which receives a supply of brine / chiller water from 1a and enables required cooling.
Then, the high-pressure dehumidified air cooled to about 60 ° C. or less is converted into high-pressure and low-temperature dehumidified air by passing through the Blind cooler 14a and injected into the PSA adsorption / desorption section 15 of the downstream one-through type PSA for nitrogen generation. I have to do it. Further, the dehumidified air in the circulation chamber is converted into low-pressure low-temperature dehumidified air by passing through the Blind cooler 14a, and is supplied to the VSA adsorption / desorption section 16 of the circulating VSA apparatus for removing carbon dioxide gas and ethylene gas downstream. It is like that.

The PSA adsorption / desorption section 15 to the VSA adsorption / desorption section 16 are composed of two adsorption / desorption towers 18 and 19 and an associated switching valve group. When it is replaced with, it is operated as a PSA adsorption / desorption section. In addition, when maintaining the optimum composition by circulating the air in the storage by the atmosphere gas optimum composition control means after the nitrogen replacement and appropriately removing carbon dioxide gas and ethylene gas,
Operate as a VSA adsorption / desorption section. Thus, the two adsorption / desorption columns 18 and 19 are filled with MSC (molecular sieves carbon) adsorbent and the switching valves 18a and 1
By switching between 8b, 18c, 19a, 19b, and 19c, the device functions as appropriate for adsorption or desorption reproduction.

The gas outlet section 17 includes a product gas tower 20, a check valve 21, a switching section 22, and a nitrogen gas stop valve 21.
C, etc., and the product gas tower 20 stores the nitrogen gas generated through the PSA adsorption / desorption section 15, and passes through each of the downstream CAs via the downstream check valve 21 and the nitrogen gas stop valve 21 c. It can be supplied to the refrigerator as appropriate. Also,
The switching unit 22 incorporates switching valves 21a and 21b. When circulating and adjusting the internal air by the atmosphere gas optimal composition control means, the switching unit 22 closes the valve 21a, opens the switching valve 21b, and sets the VSA adsorption / desorption unit 16 The optimum atmospheric gas from which the carbon dioxide gas and ethylene gas have been removed is supplied directly to the CA refrigerator 10 without supplying the product gas tower 20.
It is designed to be switched to and supplied to.

The suction / discharge unit 23 includes a vacuum pump 23a and a silencer 23b, and includes a PSA suction / desorption unit 15 and a VS.
In the A adsorption / desorption section 16, when one of the adsorption / desorption towers 18 and 19 is switched to perform desorption / regeneration, the adsorbed gas is desorbed / absorbed, and when the PSA adsorption / desorption section 15 is activated, oxygen is used. When the gas is desorbed and sucked and the VSA adsorption and desorption section 16 is operated, the carbon dioxide gas and the ethylene gas are desorbed and sucked and discharged. The discharged oxygen gas can be effectively used as the oxygen-added combustion gas of the diesel engine.

The MSC is a recently developed industrial adsorbent. As shown in the schematic diagram of FIG. 7 showing the use area divided according to the selection principle and FIG.
Whereas 5A selectively adsorbs small molecules of polar molecules or molecules having unsaturated bonds, MSC selectively adsorbs small molecules of non-polar molecules or molecules having saturated bonds. . With respect to the characteristics, refer to FIG. 4 for selectivity to polar molecules, to FIG. 5 for selectivity to molecules having unsaturated bonds, and to FIG. 6 for selectivity to multi-component mixed gas. This will be described below.

FIG. 4 shows the isothermal adsorption lines for comparing the selectivity of water as a polar molecule and nitrogen as a non-polar molecule. As shown in FIG. 4, M is opposite to that of MSZ-5A.
SC indicates a non-polar adsorbent. FIG. 5 shows an isotherm adsorption line of ethane and ethylene, which shows that although ethylene has a lower boiling point, MSZ-5A adsorbs a lot and has high selectivity.
C is more adsorbed by ethane, similar to the case of ordinary activated carbon.

FIG. 6 shows a gas phase separation of activated carbon, MS, for a binary system of n-paraffin n-hexane and isooctane, which is a chain structure of saturated hydrocarbon in nitrogen gas.
C shows the results obtained using MSZ-5A.
As shown in (A) of the figure, in the case of activated carbon having no molecular sieving function, both of the above two components are adsorbed, and once adsorbed n-hexane is extruded, isooctane is adsorbed. The breakthrough concentration of hexane rises above the incoming gas. As can be seen in FIGS.
And MSZ-5A, isooctane breaks through from the beginning and only n-hexane is adsorbed. Note that the slope indicating the rise of the breakthrough curve of the MSC is steeper than that of the MSZ-5A, and the MSC has a larger overall mass transfer coefficient.
This indicates that the separation is performed more efficiently than -5A.
As described above, the MSC adsorbent has a multi-component adsorption / separation function in which a plurality of components (in this case, carbon dioxide contained in nitrogen gas and ethylene Conventionally, when removing gas), separate removing devices using respective removing adsorbents are required, but on the other hand, a single removing device using a single adsorbent (MSC adsorbent) can be used for both removal. b) It is obtained by thermal decomposition of organic polymer, etc., and the pores are formed in a slit shape, so the molecular size to be fractionated is very small, so it is optimal for adsorption separation where high fractionation accuracy is required To be possible.

FIG. 2 shows a situation in which the nitrogen purging means is operated in the flow chart of FIG. 1, and FIG. 3 shows a situation in which the atmosphere gas optimum composition control means is operated in the flow chart of FIG. The open / closed state of each valve according to the open / closed state is shown in the figure. In the figure, white outlines indicate open valves, and closed valves are illustrated in black. In addition,
The switching valve groups 18a, 18c, 19a, 19c of the PSA adsorption / desorption section 15 and the VSA adsorption / desorption section 16 are opened and closed when the adsorption / desorption towers 18, 19 are in the adsorption state, and in the desorption / regeneration state. When in the closed state.
The switching valve groups 18b and 19b are closed when the adsorption / desorption towers 8 and 19 to which they are connected are in the adsorption state, and are opened when the adsorption / desorption tower is in the desorption / regeneration state.

Referring to FIG. 2, the situation of the operation for replacing the inside air with nitrogen gas will be described. First, the internal air valve 13b of the internal air supply unit 13 and the switching unit 2 of the gas outlet unit 17
2, the switching valve 21b is closed, the compressed air valve 12c is opened in the air pressure source unit 12, and the compressor 12a is operated to obtain a high-pressure high-temperature air of about 7 atm and about 200 ° C. Further, the aftercooler 12b and the drain separator 1
High pressure dehumidified air of about 60 ° C. or less is obtained via 2d.

Next, the high-pressure dehumidified air is sent to the cooling unit 14, converted into high-pressure, low-temperature dehumidified air at about 0 to 13 ° C. via the bunk roller 14 a, and supplied to the PSA adsorption / desorption unit 15. Next, the switching valves 18b, 19a, 19c
Is closed, the high-pressure low-temperature dehumidified air is supplied to the adsorption / desorption tower 18 via the switching valve 18a in the open state, and oxygen gas is adsorbed in the adsorption / desorption tower 18, and nitrogen gas generated by the adsorption is removed. Switching valves 18c, 19d, 21a
To the product gas tower 20 via Next, the switching valves 18a, 19b, 18c are closed, and 18b, 1
9a and 19c are opened, and the high-pressure and low-temperature dehumidified air is adsorbed and desorbed through the switching valve 19a which is in the open state.
To allow oxygen gas to be adsorbed in the adsorption / desorption tower 19, and through a switching valve 19c in which the nitrogen gas generated by the adsorption is opened, the switching valve 19d,
The product gas is supplied to the product gas column 20 via 21a. On the other hand, the switching valve 18b is opened and the adsorption / desorption tower 18 which has previously adsorbed oxygen gas is connected to the suction / discharge unit 23, and the desorbed oxygen gas is desorbed under reduced pressure via the vacuum pump 23a to discharge the desorbed oxygen gas into the atmosphere. . Atmospheric pressure regeneration is performed on the discharged and decompressed adsorption / desorption tower 18 via the silencer 23b, and the one cycle is completed. In this way, the continuous operation of one-cycle nitrogen generation by the two-column switching method is completed. Next, the process shifts to the second cycle, in which nitrogen gas is generated by adsorption of oxygen gas in the adsorption / desorption tower 18, and desorption / discharge operation of oxygen gas in the adsorption / desorption tower 19 is started. In the oxygen gas discharging process, the oxygen gas can be effectively used as the oxygen-added combustion gas of the diesel engine.

Next, the product gas tower 20 of the gas outlet 17
Is supplied through a check valve 21 and a nitrogen gas stopper 21c.
0 and the air pressure adjusting device 10b and the inside air exhaust unit 10
According to a, the replacement of the air in the refrigerator of the CA refrigerator 10 with nitrogen under an appropriate pressure is completed.

Referring to FIG. 3, a description will be given of the operation of the atmosphere gas optimum composition control means after the inside air is replaced with nitrogen gas. First, the inside air exhaust unit 10 of the CA refrigerator 10
a valve 10d is closed, and the switching unit 2 of the gas outlet unit 17 is closed.
2, the switching valve 21a and the nitrogen gas stop valve 21c are closed, and the compressed air valve 12 of the gas air pressure source unit 12 is closed.
Let c be closed. Therefore, the in-compartment air valve 13b of the in-compartment air supply unit 13 is opened to supply the in-compartment air to a stage preceding the drain separator 12d of the air pressure source unit 12 through the blower 13a, and to perform dehumidification through the drain separator 12d. The air in the dehumidifying chamber is obtained, and the air is supplied to the cooling unit 14 to obtain the air in the low-temperature dehumidifying chamber via the blind cooler 14a.
Supply to

Next, the switching valves 18b, 19a,
19c is closed, and the air in the low temperature dehumidifying chamber for circulation is supplied to the adsorption / desorption tower 18 via the switching valve 18a in the open state, and the adsorption / desorption tower 18 selectively adsorbs carbon dioxide gas and ethylene gas. Atmosphere gas control is performed. The atmosphere gas-controlled interior air is supplied to switching valves 18c and 19
It is returned to the CA refrigerator 10 via d and 21b and circulates. Next, the switching valves 18a, 19b, and 18c are closed, 18b, 19a, and 19c are opened, and the air in the low-temperature dehumidifying chamber for circulation is supplied to the adsorption / desorption tower 19 via the switching valve 19a that has been opened. , The adsorption / desorption tower 19
To selectively adsorb carbon dioxide gas and ethylene gas to control the atmosphere gas. The air in the refrigerator controlled by the atmospheric gas is returned to the CA refrigerator 10 via the switching valve valves 19c, 19d, and 21b and circulated. On the other hand, the switching valve 18b is opened, and the adsorption / desorption tower 18 in which the carbon dioxide gas and the ethylene gas are adsorbed first is connected to the suction / discharge unit 23, and the desorbed carbon dioxide gas and the ethylene gas are desorbed and decompressed via the vacuum pump 23a. Is released into the atmosphere. Atmospheric pressure regeneration is performed on the discharged and decompressed adsorption / desorption tower 18 via the silencer 23b, and the one cycle is completed. In this manner, continuous removal of carbon dioxide gas and ethylene gas in one cycle can be achieved by a two-column switching system. Next, the process shifts to the second cycle, in which the adsorption and desorption tower 18 adsorbs carbon dioxide gas and ethylene gas, and the adsorption and desorption tower 19 desorbs and discharges carbon dioxide gas and ethylene gas.

The control of the optimal composition of the atmosphere gas by the above-mentioned circulating VSA apparatus for removing carbon dioxide and ethylene gas is performed by continuously circulating the gas through an in-compartment gas composition analyzer provided in the CA refrigerator 10 until an appropriate value is obtained. / OFF operation. In addition, since the oxygen gas of the inside air decreases as time passes, a small amount of oxygen gas is appropriately supplied from outside air.

[0039]

According to the above construction, 1. The nitrogen purging means of the present invention uses a one-through type two-column switching type PSA apparatus for nitrogen generation, and is operated at low temperature (0 to 13 ° C.) and under high pressure ( (7 atm or less), the oxygen gas adsorption capacity per unit mass of adsorbent is large, a large amount of nitrogen can be continuously secured, and the adsorption tower is compact and highly efficient. Can be. 2. In addition, the MSC that operates under low temperature and low pressure and has a molecular sieve function and can be selectively adsorbed by the atmosphere gas optimum composition control means
(Molecular sieves carbon) Since it is composed of a circulating VSA device for removing carbon dioxide and ethylene gas by switching and using a two-column adsorption tower filled with an adsorbent, selective adsorption of carbon dioxide gas and ethylene gas can be performed, and adsorption and separation can be performed. Easy. 3. In addition, MSC adsorbents have the following functions: a) an adsorption / separation function for sieving multicomponent gases based on the difference in adsorption speed, so that when separating multiple components, conventionally, each separate adsorbent is used for each removal adsorbent. Although a removal device is required, a single removal device using a single adsorbent can be used for removal. b. Since the pores are formed in a slit shape, separation with high fractionation accuracy can be performed. 4. In addition, since a one-through type PSA device for nitrogen generation and a circulating VSA device for removing carbon dioxide and ethylene gas are provided side by side, a two-column adsorption / desorption tower, a cooling unit, and a suction / discharge unit can be used. The cost can be reduced. 5. In addition, since the high pressure dehumidified air supplied to the adsorption / desorption tower and the brine cooler for cooling the air in the circulating dehumidification chamber are also used as the brine / chiller water for the cooler of the CA refrigerator, the load of the refrigerator is made uniform and the refrigeration is performed. The efficiency of machine operation can be improved. 6. In addition, since a blind cooler for cooling air is provided at the entrance of the adsorption / desorption tower, a dryer for removing moisture from the entrance air required for the conventional apparatus can be omitted. 7. In addition, oxygen gas obtained as a by-product during the generation of nitrogen can be effectively used as oxygen-added combustion gas for diesel engines.

[Brief description of the drawings]

FIG. 1 is a process flowchart showing a schematic configuration of an adsorption / separation system for low-temperature CA of the present invention.

FIG. 2 is a flowchart showing a situation in which a nitrogen replacement unit is operated in the flowchart of FIG. 1;

FIG. 3 is a flowchart showing a state in which an atmosphere gas optimum composition control unit is operated in the flowchart of FIG. 1;

FIG. 4 is an isothermal adsorption diagram of an MSC adsorbent showing the selectivity of water for polar molecules and nitrogen for non-polar molecules.

FIG. 5. MSC showing selectivity for ethane and ethylene
It is an isothermal adsorption diagram of an adsorbent.

FIG. 6 is a diagram showing a gas phase separation for a binary system of n-hexane and isooctane in nitrogen gas, (A) using activated carbon, (B) using MSC, and (C) using MSZ-5A. The results are shown below.

FIG. 7 is a schematic diagram of the pore shapes of adsorbents MSC and MSZ-5A.

FIG. 8 is a diagram showing a utilization area occupied by various industrial adsorbents from the viewpoint of selective adsorption.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 CA refrigerator 10a In-compartment air exhaust part 10b In-compartment air pressure control device 10c In-compartment gas composition analyzer 11 Refrigerator 11a Refrigerator 11b Cooler 12 Air pressure source part 12a Compressor 12b Aftercooler 12d Drain separator 13 In-compartment air supply part 13a Blower Reference Signs List 14 cooling unit 14a brine cooler 15 PSA adsorption / desorption unit 16 VSA adsorption / desorption unit 17 gas outlet 18, 19 adsorption / desorption tower 20 product gas tower 21 check valve 21a, 21b switching valve 21c nitrogen gas stop valve 22 switching unit 23 suction / discharge Part 23a vacuum pump 23b silencer

Claims (6)

[Claims] 1. An adsorption / separation system for CA, wherein a nitrogen replacement means for forming the system is alternately used as a two-column adsorption / desorption column filled with MSC (Molecular Sieves Carbon) adsorbent. One-through type nitrogen generator operating at low temperature and high pressure that enables continuous production of nitrogen
Composed of SA (Pressure Swing Adsorption) device,
An adsorption / separation system for low-temperature CA. 2. An adsorption / separation system for CA, wherein an atmosphere gas optimum composition control means for forming the system is MS.
Low-temperature, low-pressure system that enables continuous removal of carbon dioxide gas and ethylene gas from the circulating atmosphere gas by alternately using a two-column adsorption / desorption tower filled with C (molecular sieves carbon) adsorbent CO2 working below,
Vacuum Swing Adso (Vacuume Swing Adso)
rption) An adsorption / separation system for low-temperature CA, comprising an apparatus. 3. An adsorption / separation system for CA, comprising:
The one-through type PSA device for nitrogen generation according to claim 1, wherein the refrigerator is refrigerated, and the air in the refrigerator is replaced with nitrogen gas at a time. 3. An adsorption / separation system for low-temperature CA, wherein the circulation type VSA device for removing carbon dioxide and ethylene gas according to claim 2 for controlling the concentration of gas is used as a main component. 4. The PSA device includes a high-pressure low-temperature air supply unit for supplying compressed air via a dehumidification cooling unit, a PSA two-column type adsorption / desorption unit capable of continuous switching, a desorption suction / discharge unit, The low-temperature CA adsorption / separation system according to claim 3, wherein the system includes a nitrogen gas outlet with a check valve. 5. The VSA device includes an in-compartment air supply section for circulating the in-compartment air through a dehumidifying cooling section, a VSA two-tower adsorption / desorption section capable of continuous switching, and a desorption / extraction section. The adsorption / separation system for low-temperature CA according to claim 3, wherein the system comprises: 6. The adsorption / separation system for low-temperature CA according to claim 3, wherein the dehumidifying cooling section is configured to use and use the brine / chiller water for the refrigerator.