JP7481859B2 - Gas Separation and Recovery Equipment - Google Patents

Description

The present invention relates to a gas separation and recovery device that uses an adsorption honeycomb rotor carrying an adsorbent that selectively adsorbs the target gas to separate and recover the target gas from a gas to be treated that is composed of various gas components, and that adsorbs and desorbs the target gas by temperature difference, and that has a simple configuration and is capable of separating and recovering the target gas at a predetermined concentration.

Conventionally, adsorption methods using adsorbents such as zeolite and activated carbon have attracted attention as a method for separating and recovering a target gas from a gas to be treated, which is composed of various gas components. Adsorption methods include the pressure swing adsorption (PSA) method, which uses a pressure difference to perform adsorption and desorption, and the thermal swing adsorption (TSA) method, which uses a temperature difference to perform adsorption and desorption.

For example, when the target gas is carbon dioxide, the PSA method involves treating the gas with a dehumidifying PSA filled with silica gel or zeolite to approximately -20°C DP (Dew Point), and then introducing the gas into a PSA for carbon dioxide separation and capture to capture the carbon dioxide (Non-Patent Document 1). However, a pressure vessel is required to utilize the pressure difference, and peripheral equipment such as solenoid valves, compressors, and vacuum pumps are also required, making it difficult to increase the size and consuming a lot of power.

On the other hand, the TSA method adsorbs carbon dioxide at temperatures below 50 degrees Celsius (hereafter all temperatures are in degrees Celsius), and then heats it to a temperature of around 100-300 degrees Celsius to desorb and recover the carbon dioxide. The TSA method does not require vacuum pumps, which are necessary for the PSA method, so there is the potential for relatively small size and low cost.

Among the TSA methods, the method using a rotating adsorption honeycomb rotor has a large surface area, low pressure loss, and is lightweight yet strong, making it easy to scale up. In recent years, this method has been adopted and spread in large-scale gas treatment equipment, such as desiccant rotor dehumidifiers and rotor-type VOC (volatile organic compounds, hereafter referred to as VOC) concentrators.

When the target gas is carbon dioxide, Patent Documents 1 and 2 show a carbon dioxide concentration and capture device using an adsorption honeycomb rotor. The device disclosed in Patent Document 1 is configured in such a way that, along the direction of rotation of the rotor, there is an adsorption zone, a preheating zone, a low-concentration gas purge zone, a desorption zone using heated gas circulation, a high-concentration gas purge zone, a precooling zone, a cooling zone, and then back to the adsorption zone, thereby simultaneously increasing the carbon dioxide capture rate and capture concentration, and realizing a highly energy-efficient carbon dioxide separation and capture device that can efficiently concentrate carbon dioxide with little energy consumption.

The system disclosed in Patent Document 2 uses a carbon dioxide separation and capture rotor that is divided into four zones in the direction of rotation: an adsorption zone, a purge zone, a regeneration zone, and a cooling zone. By providing a dehumidification rotor in front of the carbon dioxide separation and capture rotor, it is possible to obtain a carbon dioxide-enriched gas that has been dehumidified from the exhaust gas, and it is less susceptible to the effects of water-soluble gases ( _NOx , _SOx , etc.) in the exhaust gas, resulting in high energy efficiency.

However, the systems described in Patent Documents 1 and 2 are divided into multiple zones, resulting in a complex configuration with many pipes and peripheral equipment, high initial costs, and difficulty in miniaturization. Furthermore, when using an adsorption honeycomb rotor carrying a zeolite-based adsorbent, the zeolite preferentially adsorbs water vapor over carbon dioxide, reducing the carbon dioxide capacity, and so it is necessary to dehumidify the dew point temperature to about -20 to -60°C DP through pre-treatment using a honeycomb rotor dehumidifier for pre-dehumidification before introduction.

On the other hand, as in Patent Document 3, a device using an adsorption honeycomb rotor holding an amine-based absorbent regenerates carbon dioxide by the enthalpy difference between the treatment inlet and the regeneration inlet. The regeneration temperature is low at 50°C or less, which is energy-efficient, and since it is desirable to increase the enthalpy of the regeneration air, a dehumidifier is not required in the upstream stage, but a humidity adjustment means is required to humidify the regeneration inlet side and increase the relative humidity.

When the target gas is water vapor or VOC, there are desiccant dehumidifiers and VOC concentrators, respectively, and examples such as those in Patent Documents 4 and 5 are known. The adsorption honeycomb rotors used in these are usually divided into an adsorption zone, a regeneration zone, and a purge zone in the direction of rotation of the rotor, and the gas to be treated is passed through the adsorption zone and the purge zone, the gas that has passed through the adsorption zone is supplied to the destination or exhausted, the gas that has passed through the purge zone is heated and passed through the regeneration zone, and the gas that has passed through the regeneration zone is supplied to the destination or exhausted. As in Patent Document 4, a method of returning part of the gas that has passed through the regeneration zone to the regeneration inlet side to increase the concentration ratio is commonly used.

Patent No. 6498483 Patent Application No. 2018-175486 Patent Publication No. 5877922 JP 2006-187698 A JP 2011-104542 A

"Development of a PSA system for carbon dioxide capture from blast furnace gas: Effects of operating conditions on CO2 separation", Chemical Engineering Journal, Vol. 39, No. 5, 2013, pp. 439-444

As described above, in order to reduce running costs in gas removal/concentration/recovery systems using adsorption honeycomb rotors, systems have been proposed that divide the system into multiple zones other than the treatment zone and regeneration zone as in Patent Documents 1 and 2, and systems that increase the relative humidity at the regeneration inlet as in Patent Document 3, but further cost reductions are required.

In view of this situation, the present invention aims to provide a gas separation and recovery device that is characterized by adsorption and desorption due to temperature difference using an adsorption honeycomb rotor carrying an adsorbent that selectively adsorbs the target gas, in order to separate and recover a target gas from a gas to be treated that is composed of various gas components, unlike the configuration of conventional adsorption honeycomb rotors described in Patent Documents 4 and 5 and with a simpler device configuration than those described in Patent Documents 1 and 2.

The present invention is characterized in that it has an adsorption honeycomb rotor, which is divided into a treatment zone, a pre-purge zone, and a regeneration zone in the direction of rotation, the gas to be treated is ventilated through the treatment zone, the target gas is adsorbed to the honeycomb and removed, the gas that has passed through the regeneration zone of the adsorption honeycomb rotor is branched into two routes, one part is sent to the pre-purge zone, the gas that has passed through the pre-purge zone is exhausted outside the device, and the remaining part is returned to the regeneration zone of the adsorption honeycomb rotor for regeneration circulation to concentrate and recover the target gas. At this time, the temperature of the regeneration outlet is relatively high, and by circulating only the gas desorbed from the adsorption honeycomb rotor without mixing it with outside air, the heating energy for temperature increase can be reduced. In addition, if an adsorption honeycomb rotor carrying a low-temperature regenerative adsorbent is used, the regeneration gas can be heated only by raising the temperature with the regeneration blower, eliminating the need for heating means such as a regeneration heater, which saves energy.

The gas separation and recovery device of the present invention is configured as described above, and even with a simple device configuration, it is possible to separate the target gas from the target gas to be treated, which is composed of various gas components, and concentrate and recover it at a predetermined concentration.

In addition, when using an adsorption honeycomb rotor carrying a low-temperature regenerative adsorbent, the heating means for heating the regeneration gas can be increased by using the regeneration blower, eliminating the need for a heating means such as a regeneration heater, thereby reducing regeneration energy and running costs.

FIG. 1 is a flow diagram of a gas separation and recovery apparatus according to a first embodiment of the present invention. FIG. 2 is a flow diagram of a gas separation and recovery apparatus according to a second embodiment of the present invention. FIG. 3 shows the results of a carbon dioxide separation and recovery test in the gas separation and recovery apparatus according to the present invention, in which a rotor carrying an amine-carrying solid adsorbent is used as the adsorption honeycomb rotor.

The adsorption honeycomb rotor of the present invention 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 non-flammable sheet such as resin sheet, and wrapping or laminating it into a rotor shape. It is a rotor that supports various adsorbents according to the target gas, such as silica gel, zeolite, polymer adsorption material, activated carbon, porous solid adsorbent with amine absorbent or carbonate absorbent, using inorganic binders such as silica sol or alumina sol, or organic binders such as vinyl acetate or acrylic. If necessary, the adsorption honeycomb rotor may support an adsorbent that can be regenerated at low temperature. In the present invention, "low temperature regeneration" means regeneration with a regeneration gas at a temperature of 50°C or less.

In the gas separation and recovery device 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 concentration of the gas to be treated, which is around 10%, is reduced to several tens of percent after concentration, and when carbon dioxide is concentrated and recovered from the atmosphere, carbon dioxide of around 500 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 of the gas separation and recovery device of the present invention are selected. The target gas is not limited to these, and by appropriately changing the adsorbent, it can be applied to other acidic gases, alkaline gases, etc.

Figure 1 shows Example 1 of the present invention. The adsorption honeycomb rotor 1 is divided into a treatment zone 2, a pre-purge zone 3, and a regeneration zone 4 in the direction of rotation of the rotor, and rotates in the direction of the arrow by a geared motor or the like (not shown), continuously separating and removing the target gas from the gas to be treated, and concentrating and recovering it. As mentioned above, the adsorption honeycomb rotor 1 carries various adsorbents according to the target gas.

The gas to be treated (raw gas) passes through a pretreatment device (not shown) such as an air filter or a denitrification device, is cooled and dehumidified through cooling means 5 such as a cold water coil or a direct expansion coil, and is sent to treatment zone 2. In treatment zone 2, the target gas is adsorbed onto a honeycomb, separated and removed, and is supplied to the destination or exhausted by a treatment blower 7 such as a vortex blower. The gas flow rate of the gas passing through treatment zone 2 can be adjusted by an air flow adjustment device 6 such as a damper.

In the regeneration zone 4, the concentrated target gas is circulated through the regeneration circuit by the regeneration blower 10. The regeneration gas is heated by a heating means 8 such as a steam coil or heater and introduced into the regeneration zone 4, where the target gas adsorbed on the honeycomb is desorbed. The desorbed and concentrated target gas leaving the regeneration zone 4 is circulated through the regeneration circuit, where it is further concentrated. In the regeneration zone 4, only the gas desorbed from the adsorption honeycomb rotor 1 circulates, and since there is no mixing of outside air, the concentration of the target gas is likely to increase. The gas in the regeneration circuit is increased by the desorbed target gas, and the increased volume is recovered or supplied to the supply destination through the air flow regulator 9, or exhausted. In addition, a portion of the regeneration circulation gas is sent to the pre-purge zone 3 and exhausted outside the device as exhaust EA. The flow rate of the exhausted gas can be adjusted by the air flow regulator 11 at the pre-purge outlet. The pre-purge zone 3 has the effect of preventing low-concentration target gas in the honeycomb voids from flowing from the treatment zone 2 into the regeneration circuit due to the rotation of the adsorption honeycomb rotor 1, and also has the effect of preheating the adsorption honeycomb rotor 1.

The air flow rate regulator 9 may be closed to allow regeneration and circulation until the target gas reaches a predetermined recovery concentration or higher, at which point the air flow rate regulator 9 may be opened to recover the concentrated target gas, supply it to a destination, or exhaust it.

In addition, a part of the gas that has passed through the processing zone 2 may be branched off and returned to the processing zone. The cooling means 5 and heating means 8 may be a heat pump evaporator and condenser, respectively. The air volume adjustment devices 6, 9, and 11 are not limited to those shown in FIG. 1, and may be provided as appropriate or added. The processing blower 7 and regeneration blower 10 may be provided in appropriate locations as necessary, and may be added. Furthermore, the recovery location of the concentrated target gas is not limited to that shown in FIG. 1, and may be recovered immediately at the regeneration zone outlet or from the regeneration zone inlet. The pre-purge outlet gas is usually exhausted, but may be recovered to increase the recovery rate or introduced back into the regeneration circuit.

In the regeneration zone 4, only the gas desorbed from the adsorption honeycomb rotor 1 circulates, and since there is no outside air mixed in, there is no drop in gas temperature due to outside air mixing in, and it is possible to further reduce heating energy.

Figure 2 shows Example 2 of the present invention. The gas flow in Figure 2 is basically the same as in Figure 1, but it is characterized by the absence of heating means 8 and a heaterless configuration. In other words, the adsorption honeycomb rotor 1 heats the regeneration gas only by raising the temperature with the regeneration blower 10, so energy for heating is not required, leading to energy savings and reduced running costs.

The adsorption honeycomb rotor 1 is supported with a low-temperature regenerative adsorbent that desorbs the target gas at a low temperature of 50°C or less. For example, if the target gas is carbon dioxide, an amine-supported solid adsorbent can be used.

As described in Patent Documents 4 and 5, devices using adsorption honeycomb rotors are usually provided with a regeneration blower on the regeneration outlet side. One reason for this is that a regeneration heater or the like is provided as a heating means on the regeneration inlet side, but also because, in applications where the treatment zone outlet gas is to be supplied to a supply destination, the regeneration inlet and regeneration outlet are under negative pressure relative to the treatment inlet and treatment outlet, reducing the amount of leakage of the target gas desorbed from the regeneration side to the treatment side, improving the efficiency of target gas removal on the treatment outlet side.

On the other hand, the regeneration blower 10 in the second embodiment of the present invention is placed on the regeneration inlet side, that is, just before the inlet of the regeneration zone 4. In the case of applications in which the regeneration outlet gas is recovered or supplied to a destination, the processing inlet and processing outlet are under negative pressure relative to the regeneration inlet and regeneration outlet, and the amount of gas leaking from the processing side, which has a low target gas concentration, to the regeneration side is reduced, improving the concentration performance. However, even if the pressure is controlled in this way, there is a possibility that the concentration performance will decrease due to carry-over from the processing side. Therefore, a pre-purge zone 3 is provided between the processing zone 2 and the regeneration zone 4 along the rotor rotation direction to reduce leakage between the processing side and the regeneration side.

The temperature rise caused by the blower varies depending on the type of blower. For centrifugal blowers such as plug fans and turbo fans, the temperature rise is about 3°C, but for blowers that can generate high static pressure (for example, vortex blowers such as vortex blowers), the temperature rise is 10°C or more. In the regeneration zone 4, only the gas desorbed from the adsorption honeycomb rotor 1 circulates, and there is no mixing of outside air, so there is no drop in gas temperature due to mixing of outside air, and heating energy can be further reduced. In the invention in Example 2, by configuring it as a heaterless system that does not require heating means, a regeneration heater or heat exchanger is not required and the device can be made smaller, which leads to reduced initial costs and a compact design of the device size.

When the target gas is carbon dioxide, if a rotor carrying an amine-supported solid adsorbent is used for the adsorption honeycomb rotor 1, the carbon dioxide adsorption performance is not significantly reduced by the presence of water vapor, so carbon dioxide can be adsorbed and concentrated even without a dehumidifier in the upstream stage. In addition, regeneration at low temperatures reduces performance degradation due to heat, which has the effect of extending the life of the adsorption honeycomb rotor. Furthermore, it is possible to suppress the generation of odors from the adsorption honeycomb rotor, such as amine odors, due to the decomposition of amines. At the same time, moisture is adsorbed and desorbed, so moisture is concentrated on the desorption side, and the humidity of the circulating gas increases even without a humidity adjustment means as in Patent Document 3, so the enthalpy on the regeneration inlet side can be increased. This results in an equipment configuration that is easy to increase the concentration of concentrated carbon dioxide.

A portion of the gas that has passed through the treatment zone 2 may be branched off and returned to the treatment zone. The air flow rate regulators 6, 9, and 11 are not limited to those shown in FIG. 2, and may be provided as appropriate, or additional units may be installed. The treatment blower 7 and regeneration blower 10 may be provided in appropriate locations as necessary, and additional units may be installed. Furthermore, the location where the concentrated target gas is recovered is not limited to that shown in FIG. 2, and it may be recovered immediately at the regeneration zone outlet or from the regeneration zone inlet. The pre-purge outlet gas is usually exhausted, but it may be recovered to increase the recovery rate, or it may be introduced back into the regeneration circuit.

Figure 3 shows the results of a carbon dioxide separation and recovery test when a rotor carrying an amine-supported solid adsorbent was used as the adsorption honeycomb rotor in the gas separation and recovery device of the present invention. The temperature at the treatment inlet was set to 12°C, the carbon dioxide concentration to 10%, and the regeneration inlet temperature to 45°C. By changing the recovery flow rate with the air flow rate adjustment device 9, the recovered carbon dioxide concentration was changed to 20-30%.

The carbon dioxide separation and capture energy calculated from the test results was 1.5 GJ/t-CO _2. In comparison with other conventional methods for carbon dioxide separation and capture, the amine liquid absorption method requires 2 to 3 GJ/t-CO ₂ , and the carbon dioxide separation and capture apparatus according to Patent Document 2 requires 4 GJ/t-CO ₂ , so the method using the gas separation and capture apparatus of the present invention is energy-efficient and has the potential to reduce running costs.

Note that Figure 3 is an example of a test result, and the gas separation and recovery device of the present invention can arbitrarily change the target gas recovery concentration and recovery rate depending on various conditions such as the type and amount of adsorbent in the adsorption honeycomb rotor, the target gas concentration in the gas to be treated, the regeneration temperature, and the recovery flow rate.

The gas separation and recovery device of the present invention can separate and remove the target gas from the gas to be treated and concentrate and recover it at a specified concentration with a simpler device configuration than conventional devices, which allows the device to be made more compact and reduces initial costs. In addition, since only the desorbed gas circulates in the regeneration circuit, there is no mixing of outside air and no temperature drop due to mixing of outside air, there is a possibility that running costs can be reduced. Furthermore, if an adsorption honeycomb rotor carrying an adsorbent that can be regenerated at low temperatures is used, the regeneration gas can be heated only by raising the temperature with the regeneration blower, eliminating the need for heating means such as a regeneration heater, resulting in energy savings.

REFERENCE SIGNS LIST 1 Adsorption honeycomb rotor 2 Treatment zone 3 Pre-purge zone 4 Regeneration zone 5 Cooling means 6, 9, 11 Air flow regulator 7 Treatment blower 8 Heating means 10 Regeneration blower

Claims (6)

A gas separation and recovery apparatus having an adsorption honeycomb rotor, the adsorption honeycomb rotor being divided in the direction of rotation into a treatment zone, a pre-purge zone, and a regeneration zone, a gas to be treated is passed through the treatment zone, and a target gas is adsorbed into the honeycomb and removed, the gas that has passed through the regeneration zone of the adsorption honeycomb rotor is branched into two routes, a portion of which is sent to the pre-purge zone, the gas that has passed through the pre-purge zone is exhausted to the outside of the apparatus, and the remaining portion is returned to the regeneration zone of the adsorption honeycomb rotor for regeneration and circulation , and the increased volume of the desorbed target gas is recovered. The gas separation and recovery device described in claim 1, characterized in that the adsorption honeycomb rotor supports an adsorbent material that can be regenerated at low temperatures at temperatures below 50°C , a regeneration blower is provided in front of the regeneration zone of the adsorption honeycomb rotor, and the regeneration gas is heated by utilizing the temperature increase caused by the regeneration blower. The gas separation and recovery device according to any one of claims 1 and 2, characterized in that a regeneration heater is further provided in front of the regeneration zone of the adsorption honeycomb rotor as a means for heating the regeneration gas. A gas separation and recovery device according to any one of claims 1 to 3, characterized in that a cooling means is provided before the treatment zone of the adsorption honeycomb rotor. 5. The gas separation and recovery apparatus according to claim 4, wherein said cooling means comprises either a cold water coil or a direct expansion coil, or both. The gas separation and recovery apparatus according to claim 4, characterized in that a regeneration heater is further provided in front of the regeneration zone of the honeycomb rotor as a heating means for the regeneration gas, a heat pump evaporator is used as the cooling means, and a heat pump condenser is used as the regeneration heater.

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