Gas adsorption device

Abstract

To provide a gas adsorption device which is energy-saving capable of securing a sufficient dehumidification amount even when regeneration temperature is low.SOLUTION: A gas adsorption device of the present invention is configured such that regeneration inlet relative humidity is made lower than processing inlet relative humidity, and regeneration inlet temperature is set to low temperature, so as to cool an adsorption rotor on a regeneration side and remove adsorption heat on a processing side, thereby, dehumidification at the same temperature "isothermal dehumidification" is realized, and a limit value of the dehumidification amount is expanded so as to increase the dehumidification amount compared to that of a normal desiccant.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an energy-saving gas adsorption device in which the amount of adsorption of a target gas can be increased by devising a regeneration method in a temperature swing adsorption rotor. [Background technology]

[0002] Adsorption rotors (collectively referred to as "adsorption rotors") used to adsorb and remove volatile organic compounds (hereinafter referred to as "VOCs") and moisture can adsorb and desorb various gases (hereinafter the gas to be adsorbed is referred to as the "target gas") by changing the type of adsorbent. Other target gases include carbon dioxide, nitrogen, oxygen, and methane.

[0003] Adsorption rotors (VOC concentration rotors) that adsorb and concentrate VOCs include those that use activated carbon or hydrophobic zeolite as adsorbents. VOC concentration devices that use these can concentrate and recover low-concentration, large-volume VOC exhaust gases to high-concentration, low-volume gases, which can significantly reduce the equipment and running costs of the entire treatment facility and achieve efficient VOC treatment.

[0004] Adsorption rotors (dehumidification rotors) used to adsorb and remove water vapor (humidity) include those that use hydrophilic zeolite or silica gel as the adsorbent. Dehumidification devices using these can remove water vapor from the gas to be treated, lowering the dew point and supplying dry gas.

[0005] In this specification, a zone in which the target gas is adsorbed from the gas to be treated is called a "treatment zone", and a zone in which the target gas is desorbed using a regeneration gas is called a "regeneration zone".

[0006] When using an adsorption rotor to adsorb and desorb the target gas using a temperature swing, the process side is generally operated at a low temperature and the regeneration side at a high temperature. In other words, the regeneration inlet temperature is usually higher than the process inlet temperature. For example, in a VOC concentrator, the process inlet temperature is 20 to 30 degrees Celsius (hereinafter, temperatures are referred to as "Celsius"), and the regeneration inlet temperature is around 200 degrees Celsius because it is heated by a heater (such as an electric heater). In a dehumidifier, if the required dew point temperature is low, the process inlet temperature is set to 7 to 15 degrees Celsius by pre-cooling, and the regeneration inlet temperature is heated to 100 to 140 degrees Celsius or higher.

[0007] There are also cases where no active cooling or heating is performed, for example low-temperature regeneration with a regeneration inlet temperature of 50°C or less, or passive operation. For example, in Patent Document 1, the applicant developed an outdoor air conditioner characterized by total heat exchange in the front stage with a total heat exchanger that exchanges heat between return air from the indoor space and outdoor air, latent heat exchange between the return air and supply air in a passive desiccant rotor that does not require a regenerative heat source in the rear stage, and heat exchange in a heat exchanger of a heat pump circuit that exchanges heat between the outdoor air that has been totally heat exchanged and the return air.

[0008] In Patent Document 1, attention is focused on a passive desiccant rotor, which is an adsorption rotor (see paragraphs 0017-0020 and Figures 1-3). In cooling operation in summer, outside air OA (2) that has been subjected to total heat exchange is sent to a heat exchanger 5 that functions as an evaporator. Air (3) that has been cooled to 15°C by the heat exchanger 5 is sent to (the treatment zone of) the passive desiccant rotor 6, where water vapor is adsorbed to become dehumidified air (4), which is then supplied to the indoor space 9. Meanwhile, return air RA (6) at 23°C passes through (the regeneration zone of) the passive desiccant rotor 6, where water vapor is desorbed to become humidified air (8), which is then exhausted outside the device.

[0009] In heating operation in winter, the outside air OA (2) that has been subjected to total heat exchange is sent to the heat exchanger 5 that functions as a condenser. The air (3) that has been heated to 31°C by the heat exchanger 5 is sent to the passive desiccant rotor 6 (the regeneration zone), where water vapor is desorbed to become humidified air (4), which is then supplied to the indoor space 9. Meanwhile, the return air RA (6) at 23°C becomes air (7) at 19.6°C after being humidified by a humidifier 11, and is sent to the passive desiccant rotor 6 (the treatment zone), where water vapor is adsorbed to become dehumidified air (8), which is then exhausted outside the device.

[0010] In this way, the passive desiccant rotor switches between the treatment zone and the regeneration zone in summer and winter. The passive desiccant rotor performs cooling and heating using the evaporator and condenser of the heat pump circuit, but does not perform active cooling or heating. However, even when adsorption and desorption are performed at low temperatures, the regeneration inlet temperature is higher than the treatment inlet temperature.

[0011] The following describes the case where the target gas is water vapor and the adsorption rotor is a dehumidification rotor. Figure 1(A) shows the dehumidification operation in the dehumidifier, and Figure 1(B) shows the psychrometric chart showing the state of the air at that time. By passing the gas to be dehumidified through the treatment zone 2, the water vapor in the gas is adsorbed by the adsorption rotor 1. Meanwhile, in the regeneration zone 3, the water vapor is desorbed by the regeneration gas heated by the heater 4. The adsorption rotor 1 rotates continuously to perform continuous dehumidification. At this time, since no energy is exchanged, the dehumidification is an "adiabatic dehumidification" that transitions on an isoenthalpy line on the psychrometric chart. Note that in an actual dehumidification operation, the dehumidification performance is reduced compared to adiabatic dehumidification due to an increase in enthalpy of the treatment outlet gas due to sensible heat transfer from the regeneration side to the treatment side through the adsorption rotor, adsorption heat larger than the latent heat of vaporization of water, and mass transfer resistance. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] JP 2020-12602 A [Patent Document 2] JP 2023-110694 A [Patent Document 3] Patent No. 6510702 [Non-patent literature]

[0013] [Non-Patent Document 1] Akio Kodama, "Adsorption-type Desiccant Dehumidification and Air Conditioning Process", Journal of the Heat Transfer Society of Japan (Heat Transfer J.HTSJ), January 2006, Vol. 45, No. 190, pp. 39-44 Summary of the Invention [Problem to be solved by the invention]

[0014] Figure 2 shows a psychrometric chart showing the dehumidification limit. When removing water vapor (latent heat) using an adsorption rotor, there is a limit to how much water vapor can be removed. This is called the dehumidification limit, and refers to the relative humidity at the regeneration inlet. In theory, as long as the dehumidification proceeds adiabatically, the intersection P1 of the dehumidification limit (the relative humidity line equal to the regeneration gas (regeneration inlet gas)) and the isenthalpy line of the gas to be dehumidified (treatment inlet gas) is the maximum dehumidification point, i.e., the lower limit of the treatment outlet humidity, and the absolute humidity will not fall below this. In other words, the relative humidity at the treatment outlet will not be lower than the relative humidity at the regeneration inlet. In this way, the air condition (relative humidity) at the regeneration inlet is an important factor in dehumidification performance.

[0015] One way to improve the dehumidification rate of the adsorption rotor is to change the regeneration temperature. By increasing the regeneration inlet temperature, the relative humidity decreases, the dehumidification limit changes to P2, and the dehumidification rate increases. In general, when the required dew point is a low dew point, the dehumidification rate is secured by increasing the regeneration temperature. However, increasing the regeneration temperature increases energy consumption. From the viewpoint of energy saving, when low-temperature regeneration is aimed at, the regeneration temperature is lower than that of high-temperature regeneration, so the relative humidity increases, and the dehumidification rate decreases, resulting in an insufficient dehumidification rate. To improve the dehumidification rate in low-temperature regeneration, methods such as multi-stage rotors, circulation of return air from indoor spaces, pre-cooling the gas to be dehumidified with a precooler, and lowering the absolute humidity of the gas for regeneration can be mentioned. However, all of these methods require additional parts, equipment, energy, etc., which creates problems.

[0016] The present invention has been made to solve the problem of the adiabatic dehumidification limit, and has an object to provide an energy-saving gas adsorption device that can ensure a sufficient amount of adsorption of the target gas even at a low regeneration temperature. [Means for solving the problem]

[0017] The inventors focused on the need for a mechanism for removing the heat of adsorption generated with dehumidification in order to overcome this adiabatic dehumidification limit, and as a result of extensive research, arrived at the present invention. In the gas adsorption device of the present invention, the target gas concentration at the regeneration inlet is made lower than the target gas concentration at the treatment inlet, and the regeneration inlet temperature is made lower than the treatment inlet temperature, thereby cooling the adsorption rotor on the regeneration side and removing the heat of adsorption on the treatment side, thereby suppressing the temperature rise at the treatment outlet and expanding the limit value of the amount of adsorption of the target gas, thereby increasing the amount of adsorption. Effect of the Invention

[0018] According to the present invention, the regeneration inlet temperature is in a lower temperature range than that of normal low-temperature regeneration (e.g., 40 to 80°C), so active heating is not required, resulting in significant energy savings. Compared to various methods for improving the dehumidification capacity in low-temperature regeneration, no additional members or devices are required, and less energy is required.

[0019] Since the temperature rise at the treatment outlet of the present invention is suppressed, the treatment outlet gas leaving the adsorption rotor can be supplied directly to the indoor space, making additional heating or cooling unnecessary. In addition, by introducing the gas in the indoor space as the gas to be treated into the treatment inlet and supplying a gas with a lower concentration than the target gas concentration in the indoor space to the regeneration inlet as a regeneration gas, the target gas is removed on the treatment side and the treatment outlet gas with a reduced concentration is supplied back to the indoor space, making it unnecessary to ventilate the indoor space or reducing the amount of ventilation. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1(A) is a diagram showing the dehumidifying operation in the dehumidifier, and FIG. 1(B) is a psychrometric chart showing the state of the air at that time. [Diagram 2] FIG. 2 is a psychrometric chart showing the dehumidification limits. [Diagram 3] FIG. 3 is a flow diagram showing the configuration of the gas adsorption apparatus of the present invention. [Figure 4] FIG. 4 is a psychrometric chart showing the results of the dehumidification performance test of Example 1. [Diagram 5] FIG. 5 is a psychrometric chart showing the results of trial calculations of dehumidification performance when it is assumed that adiabatic dehumidification occurs in the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] The gas adsorption apparatus of the present invention is equipped with an adsorption rotor, which is divided into at least a treatment zone and a regeneration zone, in which the gas to be treated is passed through the treatment zone to adsorb the target gas, the gas that has passed through the treatment zone is sent to a destination or released to the atmosphere, the regeneration gas is passed through the regeneration zone to desorb the target gas, and the gas that has passed through the regeneration zone is sent to a destination or released to the atmosphere, and the target gas concentration at the regeneration inlet is made lower than the target gas concentration at the treatment inlet, the regeneration inlet temperature is made lower than the treatment inlet temperature, and an adsorption / desorption operation is performed to suppress a temperature rise at the treatment outlet, thereby increasing the amount of adsorption of the target gas.

[0022] The configuration of the gas adsorption device of the present invention will be described below with reference to the flow diagram of Fig. 3. The gas adsorption device of Fig. 3 has the same configuration as the dehumidification device of Fig. 1, but adsorbs a target gas contained in a gas to be treated from an indoor space and desorbs the target gas using outside air as a regeneration gas.

[0023] The adsorption rotor 1 is made by corrugating inorganic fiber paper such as ceramic fiber or glass fiber, resin fiber paper such as PET (polyethylene terephthalate) or PP (polypropylene), metal foil such as aluminum, or resin sheet, and then wrapping or laminating it into a rotor shape. The adsorption rotor 1 supports various adsorbents according to the target gas, such as silica gel, zeolite, polymer adsorption material, activated carbon, and porous solid adsorbent impregnated with an amine absorbent or carbonate absorbent, using inorganic binders such as silica sol or alumina sol, or organic binders such as vinyl acetate or acrylic.

[0024] In the gas adsorption apparatus of the present invention, if the target gas is VOC, hundreds of ppm of VOC are concentrated to thousands of ppm. If the target gas is water vapor, the water vapor concentration of the gas to be treated is several percent, and the water vapor concentration at the regeneration outlet side, which is the concentrated side, is also on the order of several percent. When carbon dioxide is concentrated from exhaust gas, the carbon dioxide of about 10% contained in the gas to be treated is concentrated to several tens of percent, and when carbon dioxide is concentrated and recovered from the atmosphere, the carbon dioxide of about 400 ppm is concentrated to several thousands of ppm. In this way, the type of adsorbent is selected according to the application, and the optimal operating method and device design for the gas adsorption apparatus of the present invention are selected. The target gas is not limited to these gases, and by appropriately changing the adsorbent, it can be applied to other acidic gases, alkaline gases, etc.

[0025] The adsorption rotor 1 is divided into at least a treatment zone 2 and a regeneration zone 3. The adsorption rotor 1 is rotated by a geared motor or the like (not shown), and the target gas is continuously adsorbed and desorbed. On the treatment side, the gas to be treated from the indoor space is passed through an air filter (AF) by a blower 5 and sent to the treatment zone 2 of the adsorption rotor 1, where the target gas is adsorbed. The gas that has passed through the treatment zone 2 is supplied back to the indoor space. On the regeneration side, outside air as the gas to be regenerated is passed through an air filter by a blower 6 and sent to a heater 4 such as a hot water coil or a regeneration heater to be heated. The air that has passed through the heater 4 is sent to the regeneration zone 3 of the adsorption rotor 1, where the target gas is desorbed, and the gas that has passed through the regeneration zone 3 is exhausted outside the device.

[0026] In this embodiment, the gas to be treated from the indoor space is treated by the adsorption rotor 1 and returned to the indoor space, but the gas to be treated is not limited to the gas in the indoor space, and other gases such as outside air may be used. The gas leaving the treatment zone 2 may be sent to a supply destination or released into the atmosphere as necessary. The regeneration gas is not limited to outside air, and other gases may be used. The gas leaving the regeneration zone may be sent to a supply destination.

[0027] In addition, although blower 5 is disposed on the treatment inlet side and blower 6 is disposed on the regeneration outlet side, the present invention is not limited to this. For example, by providing blower 6 on the regeneration inlet side, the heating effect on the regeneration side can be enhanced by raising the temperature with the blower. On the treatment inlet side, the gas to be treated may be cooled using a cooling means such as a cooling coil or a direct expansion coil to increase the relative humidity.

[0028] The gas adsorption device of the present invention is configured as described above, and the key points of the present invention are that (a) the target gas concentration at the regeneration inlet is lower than the target gas concentration at the treatment inlet, (b) the regeneration inlet temperature is lower than the treatment inlet temperature, and (c) the temperature rise at the treatment outlet is suppressed, thereby performing adsorption / desorption operations so that the treatment outlet temperature approaches a temperature isothermal with the treatment inlet temperature, thereby increasing the amount of adsorption of the target gas.

[0029] For example, when the target gas is water vapor, (a) the relative humidity at the regeneration inlet is lower than the relative humidity at the treatment inlet, (b) the regeneration inlet temperature is lower than the treatment inlet temperature, and (c) the adsorption / desorption operation is performed so that the temperature rise of the treatment outlet temperature is suppressed and the temperature approaches the isothermal state with the treatment inlet temperature, thereby causing "isothermal dehumidification" and increasing the amount of dehumidification. The features of this operation will be explained using Example 1. EXAMPLES

[0030] Hereinafter, the gas adsorption device of the present invention will be described assuming that the indoor space is an agricultural greenhouse for growing tomatoes, strawberries, etc. (hereinafter, the term "house" also includes plant factories and horticultural facilities) and that the inside of the greenhouse is to be dehumidified in winter in a cold region at a high latitude such as Hokkaido.

[0031] In Example 1, a dehumidification performance test was carried out under test conditions simulating the indoor and outdoor air conditions in winter in a cold region, using a dehumidification rotor carrying silica gel as the adsorption rotor 1 of the gas adsorption device in Fig. 3. The test results are shown on the left side of Table 1. A psychrometric chart showing the test results is shown in Fig. 4. The rotation speed of the adsorption rotor 1 was set to the optimum rotation speed at which the dehumidification performance was maximized.

[0032] As a comparative example, the right side of Table 1 shows the results of a trial calculation of dehumidification performance when it is assumed that adiabatic dehumidification occurs in the dehumidification rotor. A psychrometric chart showing the results of this trial calculation is shown in Fig. 5. The symbols in Table 1, Fig. 4 and Fig. 5 correspond to the air states at the positions of the numbers in parentheses in Fig. 3. The temperature and humidity conditions at the treatment inlet and regeneration inlet in the dehumidification performance test of Example 1 were adjusted to be as close as possible to the values ​​calculated in the comparative example.

[0033] [Table 1]

[0034] In Example 1, the treatment inlet air (5) had a temperature of 23.6°C and a relative humidity of 59.8%RH, while the regeneration inlet air (2) had a temperature of 9.6°C and a relative humidity of 44.9%RH, and (a) the relative humidity at the regeneration inlet was set lower than the relative humidity at the treatment inlet, and (b) the regeneration inlet temperature was set lower than the treatment inlet temperature. As shown in Table 1, the dehumidification amount on the treatment side in the comparative example assuming that adiabatic dehumidification occurs (the difference between the absolute humidity of the treatment inlet air (5) and the absolute humidity of the treatment outlet air (6)) was 1.0 g / kg (DA), but the test result of Example 1 showed a dehumidification amount of 2.5 g / kg (DA), which greatly exceeded the estimated value (theoretical value).

[0035] The first point of the present invention is that (a) the relative humidity at the regeneration inlet is lower than the relative humidity at the treatment inlet. In the first embodiment, the relative humidity difference between the treatment inlet air (5) and the regeneration inlet air (2) is 44.9%RH, which is the driving force for water vapor adsorption (dehumidification). In other words, dehumidification is performed by "relative humidity swing". In reality, since the temperature often drops below freezing in winter in cold regions, the heater 4 is used to raise the temperature of the outside air (1) at -5°C and a relative humidity of 80%RH to 5°C as in the comparative example, thereby lowering the relative humidity at the regeneration inlet (2) to 38.7%RH, and creating a relative humidity difference with respect to the 80%RH at the treatment inlet (5). In this way, even if the regeneration inlet temperature is low, dehumidification is possible by creating a relative humidity difference.

[0036] The second point of the present invention is that (b) the regeneration inlet temperature is lower than the treatment inlet temperature. Although it depends on the type of target gas, the treatment inlet temperature is often 30°C or lower. For example, in a VOC concentrator, the treatment inlet temperature is 20 to 30°C, and in a dehumidifier, when the required dew point temperature is low, the treatment inlet temperature is 7 to 15°C by pre-cooling. In addition, when the target gas is carbon dioxide, if it is recovered from the atmosphere, the treatment inlet temperature is, for example, 10°C by cooling with a heat pump (see paragraphs 0059 and 0073 of Patent Document 2), and if it is recovered from exhaust gas, it is, for example, 30°C (see paragraphs 0049 and FIG. 5 of Patent Document 3). In the present invention, the regeneration inlet temperature is lower than the treatment inlet temperature. Therefore, the regeneration temperature is lower than 40 to 80°C, which is usually adopted for low-temperature regeneration. In the present invention, as in Example 1 and Comparative Example, even if the regeneration inlet temperature is lower than the treatment inlet temperature, a sufficient amount of dehumidification can be obtained.

[0037] Thus, the second feature of the present invention is the low temperature range that would never normally be used as the regeneration inlet temperature. In addition, the present invention has a reversal phenomenon in which the regeneration inlet temperature is lower than the treatment inlet temperature, which is unthinkable with normal temperature swings, and is an idea for adsorption / desorption operations that even those skilled in the art would not easily come up with. It is possible to dehumidify by increasing the regeneration inlet temperature as with normal temperature swings, but this is not preferred because it increases energy consumption. In order to prevent freezing and condensation in the gas adsorption device, it is preferable that the air leaving the heater 4 (regeneration inlet temperature) be at a temperature at which the regeneration outlet side does not freeze, such as 5°C or higher.

[0038] The heat source of the heater 4 is not particularly limited, but for example, a hot water coil can be used. Because the regeneration inlet temperature is low, the heater 4 does not require active heating, and it is sufficient to use groundwater or circulating water as regeneration heat, which is extremely energy-saving. In addition, geothermal heat, earth heat, and solar heat can also be used. If there is a heat source, even exhaust heat from devices and machines, such as exhaust heat from outdoor units and heat dissipated from control panels, can be used.

[0039] Usually, in temperature swing adsorption using an adsorption rotor, the temperature is low at the treatment inlet side and high at the regeneration inlet side. The regeneration inlet temperature is 40 to 80°C even for low-temperature regeneration, and if it is below 30°C, it is no longer practical and is ignored. The present inventors faced the contradictory situation that the outside temperature in cold regions in winter is extremely low with low humidity, but the temperature inside the greenhouse hardly rises during the day and the humidity rises, as in Example 1, and earnestly investigated an adsorption / desorption operation that dehumidifies the greenhouse without significantly raising the temperature by using outside air as regeneration gas. As a result, the present invention was arrived at by performing an adsorption / desorption operation that combines (a) humidity swing adsorption with regeneration inlet relative humidity < treatment inlet relative humidity, and (b) regeneration in a low-temperature range of regeneration inlet temperature < treatment inlet temperature.

[0040] The inventors also focused on the need for a mechanism for removing the heat of adsorption generated with dehumidification in order to overcome the adiabatic dehumidification limit. The third point of the present invention is (c) suppressing the temperature rise of the treatment outlet temperature and performing a dehumidification operation to approach a temperature that is isothermal with the treatment inlet temperature, that is, to generate "isothermal dehumidification". Compare the psychrometric charts of Figures 4 and 5. In the psychrometric chart of Figure 5, "adiabatic dehumidification" occurs, so the dehumidification amount on the treatment side, that is, the difference between the absolute humidity of the treatment inlet air (5) and the absolute humidity of the treatment outlet air (6) remains at 1.0 g / kg (DA). In addition, the treatment inlet temperature of 20.0°C rises to the treatment outlet temperature of 22.5°C due to the heat of adsorption. On the other hand, in the psychrometric chart of Figure 4, the dehumidification amount on the treatment side is 2.5 g / kg (DA), which is much higher than the estimated value (theoretical value). Focusing on the temperature, the difference in temperature between the treatment inlet and treatment outlet is only slightly increased to 0.2°C. In other words, "isothermal dehumidification" occurred, in which the temperatures of the treatment inlet and treatment outlet were nearly the same.

[0041] "Isothermal dehumidification" means dehumidification in a state where the treatment inlet temperature and the treatment outlet temperature are equal, and in this specification, the range of the treatment outlet temperature of "isothermal dehumidification" is less than the adiabatic dehumidification limit and is equal to or greater than -3°C of the isothermal dehumidification limit. In other words, the upper limit of the treatment outlet temperature is less than the temperature of the intersection (adiabatic dehumidification limit) of the isenthalpy line of the treatment inlet air when adiabatic dehumidification occurs and the relative humidity line (dehumidification limit) equal to the regeneration inlet air, and the lower limit is the treatment inlet temperature (isothermal dehumidification limit temperature) -3°C. This lower limit is set because the treatment outlet temperature may be lower than the treatment inlet temperature due to the introduction of cold air from the regeneration side caused by the rotational shift of the adsorption rotor. In particular, the higher the rotation speed, the greater the effect of this introduction, but if the rotation speed is increased too much, the adsorption performance will deteriorate.

[0042] Normally, the heat of adsorption that adsorbs water vapor on the treatment side causes the temperature at the treatment outlet to rise. However, in the present invention, the temperature on the regeneration side is low, so the rotor rotates from the regeneration zone to the treatment zone while still cold, and the heat of adsorption is removed in the treatment zone due to the heat storage effect of the cold, suppressing the temperature rise. In addition, because the temperature difference in the length direction of the rotor is small, the temperature at the treatment outlet does not rise much, and isothermal dehumidification occurs.

[0043] As shown in Figure 2, this "isothermal dehumidification" makes the treatment inlet temperature and treatment outlet temperature isothermal, so the dehumidification limit P1 (relative humidity at treatment outlet ≧ relative humidity at regeneration inlet) by "adiabatic dehumidification" changes to P3, and the dehumidification amount increases. When comparing the dehumidification amounts obtained by isothermal dehumidification and adiabatic dehumidification, isothermal dehumidification may have a larger dehumidification amount than raising the regeneration inlet temperature, and the effectiveness of isothermal dehumidification becomes more pronounced as the regeneration temperature becomes lower. Normally, dehumidification by the adsorption rotor proceeds in an almost adiabatic state, so the relative humidity of the passing gas further decreases due to the adsorption heat generated during adsorption of water vapor (dehumidification), and the dehumidification amount at the treatment outlet side, i.e., the adsorbent utilization rate, becomes extremely small. Therefore, if the adsorption heat generated during dehumidification can be continuously removed, the decrease in the relative humidity of the passing gas will be mitigated, the adsorbent utilization rate will increase, and dehumidification performance can be improved. In order to achieve isothermal dehumidification, it is essential to devise a way to remove the adsorption heat in the adsorption process (treatment zone).

[0044] As an adsorption rotor aiming at this "isothermal dehumidification", for example, a simultaneous heat exchange type dehumidification rotor is proposed in Non-Patent Document 1 (see pages 43-44). This rotor has a fan-shaped honeycomb adsorbent built between radially arranged aluminum slits, and the heat of adsorption is removed by a cooling fluid passing through the slits. In addition, an improved dehumidification rotor has been proposed in which a special adsorbent having adsorbent properties suitable for isothermal dehumidification is supported on an aluminum honeycomb. However, it is not practical because of its complex structure and the need to devise the properties of the adsorbent, which makes the adsorbent expensive. In addition, these experimental results showed that the dehumidification amount was increased by approaching isothermal dehumidification, but it is still difficult to say that ideal isothermal dehumidification has been achieved.

[0045] Regarding the removal of the heat of adsorption, in the case of another target gas, such as carbon dioxide, Patent Document 3 proposes a method in which water vapor is used in the regeneration zone, the adsorption rotor is rotated to the treatment zone while the water vapor remains in the adsorption rotor, and the heat of adsorption (heat of sorption) is removed by the latent heat of vaporization of the condensed water remaining in the treatment zone (see paragraph 0072). However, this method requires the use of water vapor for regeneration, a water vapor generator, and waterproof / water-resistant equipment and components.

[0046] In the present invention, ideal isothermal dehumidification occurs naturally and simply by simply making (a) the regeneration inlet relative humidity < the treatment inlet relative humidity and (b) the regeneration inlet temperature < the treatment outlet temperature. In other words, there is no need for a complicated structure, special adsorbent, additional equipment, or components as in the above-mentioned document. As mentioned above, in order to increase the amount of dehumidification, it is common for a person skilled in the art to increase the amount of dehumidification by increasing the regeneration inlet temperature to reduce the relative humidity, reducing the absolute humidity of the gas for regeneration, or increasing the relative humidity at the treatment inlet to maximize the amount of dehumidification. However, the present invention is a breakthrough in that (c) isothermal dehumidification occurs based on a simple idea that (b) the regeneration inlet temperature is lower than the treatment inlet temperature, which is not easily conceived by a person skilled in the art.

[0047] The above describes dehumidification using water vapor as the target gas, but it is also possible to create a concentration difference by using other gases such as VOCs and carbon dioxide, not limited to water vapor. In this case, the target gas becomes a "concentration difference swing." For example, if the target gas is carbon dioxide, the treatment side may pass combustion exhaust gas containing, for example, 10% carbon dioxide for adsorption, and the regeneration side may mix water vapor with outside air with a low carbon dioxide concentration of, for example, 400 ppm, and desorb it.

[0048] Adsorption heat is generated by the adsorption of the target gas by the adsorbent supported on the adsorption rotor. If the adsorption rotor is heated by this adsorption heat, the adsorption force and adsorption performance of the adsorption rotor will decrease. Therefore, the present inventors have found that the adsorption heat can be removed at the same time as the target gas is adsorbed, that is, the adsorbent can perform at its maximum function when it is cooled, and have intensively studied an adsorption / desorption operation that achieves this. As conditions for such an adsorption / desorption operation, they have established that (a) the regeneration inlet target gas concentration < the treatment inlet target gas concentration, and (b) the regeneration inlet temperature < the treatment inlet temperature. In the present invention, the regeneration side of the adsorption rotor is cooled by the regeneration gas and remains at a low temperature. As a result, (c) adsorption occurs in which the cold heat of the adsorption rotor and the heating due to the adsorption heat of the adsorbent are equal, that is, so-called isothermal adsorption (in the case of dehumidification, isothermal dehumidification).

[0049] For other target gases, "adiabatic dehumidification" is replaced with "adiabatic adsorption" and "isothermal dehumidification" is replaced with "isothermal adsorption". However, since the temperature rise due to heat of adsorption and the like differs depending on the type of adsorbent and target gas, and the amount of adsorption, in this specification, isothermal adsorption is defined as adsorption in which the temperature range of the treatment outlet is the treatment inlet temperature +5°C or less and the treatment inlet temperature -3°C or more. In the case of water vapor adsorption, the temperature rise when dehumidifying 1g / kg (DA) is 2.5°C or less, so a temperature rise of 5°C corresponds to a dehumidification amount of about 2g / kg (DA), but by suppressing the generation of heat of adsorption, an adsorption operation is performed that is close to isothermal adsorption. In the case of dehumidification, the amount of dehumidification increases compared to isothermal dehumidification when the isothermal dehumidification limit is exceeded and the treatment inlet temperature >> treatment outlet temperature, for example, when the treatment inlet temperature - treatment outlet temperature is -10°C. In summer, it is preferable to have a low temperature and humidity at the treatment outlet, so this is a required condition, but it is not easy and not realistic to lower the temperature and humidity at the regeneration inlet. [Industrial Applicability]

[0050] The gas adsorption device of the present invention is not limited to cold regions, and can be used to dehumidify greenhouses in winter. It is also useful for dehumidifying various indoor spaces other than greenhouses, and is particularly useful when circulating and using air in indoor spaces, since the treatment outlet temperature is almost the same as the treatment inlet temperature. In addition, since the regeneration temperature is lower, various heat utilization is possible, making this a highly energy-saving device. By using another gas such as oxygen or nitrogen as the target gas at the treatment outlet, it can be applied to other uses. [Explanation of symbols]

[0051] 1 Adsorption rotor 2 Treatment Zone 3. Play Zone 4 Heater 5, 6 Blower

Claims

1. A gas adsorption device comprising an adsorption rotor, the adsorption rotor being divided into at least a treatment zone and a regeneration zone, a gas to be treated being passed through the treatment zone to adsorb a target gas, the gas that has passed through the treatment zone being sent to a destination or released to the atmosphere, a gas for regeneration being passed through the regeneration zone to desorb the target gas, and the gas that has passed through the regeneration zone being sent to a destination or released to the atmosphere, and the target gas concentration at the regeneration inlet is lower than the target gas concentration at the treatment inlet.

2. 2. The gas adsorption apparatus according to claim 1, wherein the target gas is water vapor, and the adsorption rotor is a dehumidification rotor.

3. 3. The gas adsorption apparatus of claim 2, wherein the relative humidity at the regeneration inlet is lower than the relative humidity at the treatment inlet.

4. 4. The gas adsorption apparatus according to claim 1, wherein the temperature of the regeneration inlet is lower than the temperature of the treatment inlet.

5. The gas adsorption apparatus according to claim 4, characterized in that an adsorption / desorption operation is performed so that a temperature rise at a treatment outlet is suppressed and the temperature of the treatment outlet approaches a temperature isothermal with the temperature of the treatment inlet, thereby increasing the amount of adsorption of the target gas.

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