JP6728875B2 - Carbon dioxide recovery device and natural gas combustion system - Google Patents

Description

The present invention relates to a carbon dioxide recovery apparatus for separating and concentrating carbon dioxide from a combustion exhaust gas of natural gas and a combustion system for natural gas using the carbon dioxide recovery apparatus, and more particularly, to a pressure using an adsorbent that selectively adsorbs carbon dioxide. The present invention relates to a carbon dioxide recovery device for recovering carbon dioxide according to a swing adsorption method, and a natural gas combustion system for ships and the like using the carbon dioxide recovery device.

LNG is used as fuel for propulsion in a liquefied natural gas (LNG) transport ship. LNG is also used as fuel in boilers and gas turbines of thermal power plants. In recent years, carbon dioxide has been regarded as a problem as the main cause of global warming, and the movement to suppress the emission has become active worldwide. For this reason, various studies have been vigorously carried out in order to enable the recovery and storage of the combustion exhaust gas and the carbon dioxide of the process exhaust gas without being released into the atmosphere. From the standpoints of preventing air pollution and preserving the global environment, carbon dioxide is being separated and collected from exhaust gas from the combustion system using LNG as a fuel.

Conventionally, as a method for recovering carbon dioxide from exhaust gas, concentrated carbon dioxide remaining after removing various impurities (sulfur oxides, nitrogen oxides, chlorine, mercury, etc.) from exhaust gas is subjected to cryogenic separation (liquefaction and precision distillation). The method of refining is effective and is being studied variously for practical use.

Since LNG is a fuel that is very easily vaporized, it is stored in a container that is cooled to an extremely low temperature and adiabatic. However, it is difficult to avoid vaporization of LNG, and in the storage container, LNG is always vaporized and cold gas (natural gas) can be diffused. Therefore, it is considered to effectively use the gas generated in the container in some form. For example, Patent Document 1 below describes a carbon dioxide solidification device that uses cold heat of gas vaporized from LNG in cooling for solidifying carbon dioxide separated from exhaust gas of a marine engine.

JP, 2014-100696, A

In Patent Document 1 described above, when utilizing the cold heat of the vaporized gas for solidifying and separating carbon dioxide, a supplementary device for adjusting the conditions for solidifying is required. For this reason, complication of the device and increase in cost become problems, which is not preferable especially for a ship that requires compactness.

An object of the present invention is to solve the above-mentioned problems, and to effectively and effectively use gas vaporized from LNG in a simple form, while being able to recover carbon dioxide from combustion exhaust gas of natural gas economically and efficiently. To provide a natural gas combustion system using the recovery device.

In order to solve the above problems, the present inventors have conducted extensive studies on carbon dioxide separation and recovery technology, and as a result, applied carbon dioxide separation by a pressure swing adsorption (PSA) method to produce a combustion exhaust gas of natural gas. During the processing, a method of effectively utilizing the cold heat of gas vaporized from LNG was reached, and the present invention was completed.

According to one aspect of the present invention, a carbon dioxide recovery device is a carbon dioxide recovery device for recovering carbon dioxide from an exhaust gas obtained by burning natural gas, and is capable of adsorbing and desorbing carbon dioxide on an adsorbent due to pressure fluctuations. Separation device for separating carbon dioxide from exhaust gas by utilizing, a drying device having a hygroscopic agent for drying the exhaust gas supplied to the separation device, a container for storing liquefied natural gas , liquefied natural gas in the container To a combustion device, and a second flow path provided separately from the first flow path for supplying a cold gas that vaporizes from liquefied natural gas in the container. And a cooling system for cooling the exhaust gas so that the exhaust gas supplied to the drying device has a temperature suitable for drying by using the cold gas in the second flow path .

The cooling system has at least one heat exchanger that exchanges heat between the exhaust gas supplied to the drying device and the cold gas, and the low temperature of the cold gas vaporized from LNG can effectively cool the exhaust gas. It is useful for processing efficiency due to the volume reduction of. The cooling system further includes at least one flow meter for detecting a flow rate of the cold gas supplied to the at least one heat exchanger, and a temperature of the cold gas according to the flow rate detected by the at least one flow meter. By having at least one flow rate adjusting valve controlled so that the flow rate is maintained at a predetermined amount, the cooling adjustment by the cold gas becomes easy. The recovery device further includes a pressurizing device for pressurizing the exhaust gas supplied to the separating device, and a depressurizing device for depressurizing carbon dioxide so as to desorb carbon dioxide from the adsorbent of the separating device, and the at least one heat exchange device. The reactor is configured to include a heat exchanger that exchanges heat between the exhaust gas pressurized by the pressurizing device and the cold gas, so that the cold gas effectively cools the pressurized hot exhaust gas. Used. The recovery device further has a regeneration system that heats the residual gas from which carbon dioxide has been removed from the exhaust gas by the separation device and supplies it to the drying device as a regeneration gas that regenerates the hygroscopic agent of the drying device. The exhaust gas cooled by the gas is effectively dehumidified even by the hygroscopic agent whose temperature is raised by regeneration. Further, the recovery device has a liquefaction device that cools and liquefies the carbon dioxide recovered from the separation device, and the cooling system is configured to supply a part of the cold gas to the liquefaction device. It can also be used to liquefy carbon dioxide.

Further, according to one aspect of the present invention, a natural gas combustion system uses a combustion device that burns natural gas to supply energy and adsorption and desorption of carbon dioxide to an adsorbent due to pressure fluctuations. Separating carbon dioxide from the exhaust gas discharged from the combustion device, a separation device for discharging the residual gas from which carbon dioxide has been removed, and a drying device having a hygroscopic agent for drying the exhaust gas supplied to the separation device, A container for containing liquefied natural gas, a first flow path for supplying the liquefied natural gas in the container to the combustion device, and a first flow path for supplying a cold gas vaporized from the liquefied natural gas in the container A second flow path provided separately from the above flow path, and using the cold gas of the second flow path so that the exhaust gas supplied to the drying device has a temperature suitable for drying. The gist is to have a cooling system for cooling the exhaust gas.

The cooling system is configured to supply the cold gas used for cooling the exhaust gas to the combustion device, whereby natural gas is efficiently consumed. In a combustion system, as appropriate amount of natural gas before Symbol combustion apparatus corresponding to the energy supplied is supplied to the combustion device, from the container in response to said cold gas supplying said cooling system to said combustion device It can be configured to have a regulating system for regulating the amount of natural gas supplied to the combustion device. As a result, the supply of natural gas to the combustion device becomes accurate. Such combustion systems, because it is advantageous in miniaturization easy easy Do construction is useful when applied to marine engines or thermal power.

According to the embodiment of the present invention, when the high-purity carbon dioxide is separated and recovered from the combustion exhaust gas of natural gas by using the pressure swing adsorption method, and the temperature of the exhaust gas is adjusted to the conditions suitable for the separation of carbon dioxide. In addition, since the cold heat of the gas vaporized from LNG can be effectively used, the efficiency of energy utilization is improved, and the process of separating carbon dioxide from the combustion exhaust gas of natural gas can be economically and efficiently performed. A carbon capture device and a natural gas combustion system are provided.

1 is a schematic configuration diagram showing a natural gas combustion system including a carbon dioxide recovery device according to an embodiment of the present invention.

Known methods for recovering carbon dioxide include a pressure swing adsorption (PSA) method, a membrane separation concentration method, and a chemical absorption method utilizing reaction absorption by a basic compound. The pressure swing adsorption method is a method of separating and removing a specific component in a mixed gas by using adsorption and desorption of a specific component with respect to an adsorbent due to pressure fluctuation, and using a substance capable of adsorbing carbon dioxide as the adsorbent. Then, it can be used to recover carbon dioxide from a gas containing carbon dioxide such as combustion exhaust gas. By increasing (pressurizing) the pressure of the gas supplied to the adsorbent to a relatively high pressure (adsorption pressure), carbon dioxide is adsorbed on the adsorbent and the pressure is reduced to a relatively low pressure (desorption pressure) (decompression). ) And the adsorbed carbon dioxide are desorbed and released from the adsorbent. By repeatedly increasing and decreasing the pressure in this manner to adsorb and desorb carbon dioxide in the gas to the adsorbent (desorb the adsorbate), the decarbonized gas and concentrated (or purified) dioxide are removed from the gas. Carbon is obtained. In the PSA method, it is relatively easy to selectively separate carbon dioxide from the exhaust gas containing carbon dioxide and many kinds of impurities to recover high-purity carbon dioxide. Therefore, in this respect, the recovery of carbon dioxide by the PSA method is more chilled separation (liquefaction and precision distillation) after removing various impurities (sulfur oxides, nitrogen oxides, chlorine, mercury, etc.) from the exhaust gas. ) Is superior to the recovery method. Further, there is also an advantage that the burden of maintenance for dealing with corrosion of the instruments and devices for removing the above-mentioned impurities is reduced.

In order to prevent the selective adsorption ability of the adsorbent in the PSA method from being hindered, it is effective to subject the exhaust gas supplied to the adsorbent to a drying treatment in advance. The hygroscopic agent used in the drying process can be regenerated by supplying heated dry gas and can be used repeatedly. Since the hygroscopic agent after regeneration is heated, it is desirable that the exhaust gas supplied to the hygroscopic agent is cooled so that the temperature condition suitable for use in the hygroscopic treatment is obtained. Further, since the adsorbent of the PSA method also generates heat due to the adsorption of carbon dioxide, it is desirable that the exhaust gas supplied to the adsorbent is cooled to a temperature suitable for the adsorption treatment. Therefore, in the present application, the cold heat of the cold gas (natural gas) vaporized in the storage container of liquefied natural gas (LNG) is used for cooling the gas supplied to the hygroscopic agent. Although the internal pressure of the LNG storage container is kept constant, it is difficult to prevent the LNG from vaporizing because the LNG easily vaporizes when the internal pressure fluctuates with the supply to the combustion device. Therefore, it is important to effectively use the cold heat of the vaporized cold gas, and it is desirable to effectively use the cold heat. Cooling of the exhaust gas supplied to the moisture absorption treatment and the adsorption treatment does not have to be at a low temperature required for solidification of carbon dioxide and the like, and can be easily performed using a heat exchanger. Therefore, the device configuration is not complicated. Hereinafter, a carbon dioxide recovery device and a natural gas combustion system having the same according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of a natural gas combustion system including a carbon dioxide recovery device of the present invention. The combustion system includes a combustion device E that burns natural gas to supply energy, a container F that stores LNG (liquefied natural gas), and a carbon dioxide recovery device 1. The recovery device 1 is a combustion device. Carbon dioxide C is recovered from the exhaust gas G generated by the combustion at E. The recovery device 1 includes a separator SP having an adsorbent A for separating carbon dioxide from the exhaust gas G by the PSA method, and a dryer DR having a hygroscopic agent H for drying the exhaust gas G supplied to the separator SP. And a cooling system for cooling the exhaust gas G supplied to the drying device DR using the cold gas vaporized from the LNG in the container F, and the exhaust gas G supplied to the drying device DR is generated by the hygroscopic agent H. It is cooled to a temperature suitable for drying. The recovery device 1 is configured to heat the residual gas G′ from which the carbon dioxide C has been removed from the exhaust gas G by the separation device SP and use it as a regeneration gas for the hygroscopic agent H. Considering that the temperature of the hygroscopic agent H after regeneration is relatively high, it is very convenient to use the cold gas vaporized from LNG to cool the exhaust gas G for efficient drying.

The separation device SP, which is the main part of the recovery device 1, has at least one pair of columns C1 and C2 in which the adsorbent A is stored. A compressor 3 as a pressurizing device for applying a pressure at which the carbon dioxide is adsorbed to the adsorbent A to the exhaust gas G, and a pressure in the columns C1 and C2 is lowered to a pressure at which carbon dioxide can be desorbed from the adsorbent A. And an expander 5 as a pressure reducing device. By operating the compressor 3 and the expander 5, pressure fluctuations can be generated in the columns C1 and C2, and carbon dioxide is separated from the exhaust gas G by using adsorption and desorption of carbon dioxide to the adsorbent A due to the pressure fluctuations. can do. As a result, the carbon dioxide C concentrated to a high concentration and the residual gas G′ from which carbon dioxide has been removed are discharged from the separation device SP. The adsorptive separation of carbon dioxide can also be carried out by a single column, but in this case, the exhaust gas G is intermittently supplied according to the switching of adsorption/desorption, resulting in intermittent treatment. By using the paired columns, the separated carbon dioxide C and the residual gas G′ are continuously discharged from the separator SP.

The drying device DR has a hygroscopic agent H for drying the exhaust gas G supplied to the separation device SP, and the hygroscopic agent H is housed in at least one pair of columns C3 and C4. The exhaust gas G pressurized by the compressor 3 is dehumidified by the moisture absorbent H of the drying device DR and then supplied to the separating device SP. The hygroscopic agent H which has absorbed moisture can be regenerated by heating or supplying a dry gas.

Since the exhaust gas G supplied to the separation device SP is dried, the residual gas G′ after carbon dioxide is removed in the separation device SP contains substantially no water. Therefore, the residual gas G′ can be used as a regeneration gas for regenerating the hygroscopic agent H of the drying device DR, and the residual gas discharged from the separating device SP as a regenerating gas for regenerating the hygroscopic agent H of the drying device DR. A regeneration system for supplying the gas G′ to the drying device DR is configured. The regeneration system includes a flow path L7 for supplying the residual gas G′ discharged from the separation device SP to the drying device DR, and a heater connected to the flow path L7 as a means for heating the residual gas G′ in order to enhance the regeneration efficiency. 19 and.

The cooling system has at least one heat exchanger and exchanges heat between the exhaust gas G supplied from the combustion device E to the drying device DR and the cold gas vaporized in the container F. In the embodiment of FIG. 1, two heat exchangers 11 and 13 are provided, the heat exchanger 11 cools the exhaust gas G before pressurization in a stage before the compressor 3, and the heat exchanger 13 is a compressor. In the latter part of 3, the exhaust gas G after pressurization is cooled. Although the temperature of the exhaust gas G rises due to the compression in the compressor 3, the exhaust gas G suitably cooled by the subsequent heat exchanger 13 is supplied to the drying device DR. The number of heat exchangers that cool the exhaust gas G using the cold gas can be changed as necessary. For example, the heat exchanger 11 may be omitted, and the exhaust gas G may be changed only by the heat exchanger 13 subsequent to the compressor 3, or the exhaust gas G supplied from the drying device DR to the separation device SP may be cooled. It may be modified to add a heat exchanger for.

The recovery device 1 includes a liquefaction device R that liquefies the carbon dioxide C and a compressor 9 that pressurizes the carbon dioxide C supplied from the separation device SP to the liquefaction device R, and the carbon dioxide recovered from the separation device SP. C is liquefied by being supplied to the liquefying apparatus R and being cooled. Carbon dioxide is liquefied by adjusting the pressure to about 0.518 MPa or more and the temperature to about -55°C or less. In this regard, in the embodiment of FIG. 1, the cooling system is further configured to use a portion of the cold gas to enhance the liquefaction efficiency of carbon dioxide in the liquefier R. That is, the heat exchanger 17 for exchanging heat between the carbon dioxide C supplied from the separation device SP to the liquefaction device R and the cold gas vaporized in the container F is provided, and the carbon dioxide C cooled to some extent by the cold gas is generated. It is liquefied in the liquefier R. Further, the cold gas is also used for liquefaction in the liquefying apparatus R and maintenance of low temperature. That is, the liquefying device R has a flow path L14 for circulating carbon dioxide, and the cooling system is configured to supply a part of the cold gas to the heat exchanger 15 provided in the flow path L14 of the liquefying device R. It This heat exchange promotes cooling and liquefaction of carbon dioxide.

As the heat exchangers 11, 13, 15, 17 for cooling by heat exchange with the cold gas, known gas-gas heat exchangers may be used. It may be of any type such as a counter flow type, a parallel flow type and a cross flow type. For example, it is possible to appropriately select from a static heat exchanger, a rotary regeneration heat exchanger, a periodic flow heat storage heat exchanger and the like. is there. By using a heat exchanger having a gas-liquid separation function capable of removing the condensed liquid as the heat exchangers 11, 13, 17, it is possible to separate the condensed water from the exhaust gas G and the carbon dioxide C. The vessels 11 and 13 can reduce the load on the subsequent drying device DR, and the heat exchanger 17 can be prevented from lowering the liquefaction efficiency in the liquefying device R.

The cold gas heated by heat exchange with the exhaust gas G is suitable for use in combustion in the combustion apparatus E. Therefore, the cooling system is configured to supply the cold gas used for cooling the exhaust gas G to the combustion device E. Since a proper amount of natural gas corresponding to the amount of energy required for the combustion device E needs to be supplied to the combustion device E, the cooling system supplies the combustion gas to the combustion device E from the container F to the combustion device. A regulation system is provided for regulating the supply of natural gas supplied to E. The details will be described later.

A specific configuration of the combustion system and the recovery device 1 of FIG. 1 will be described below. The broken line in the figure indicates electrical connection. The combustion device E is a device or facility that supplies thermal energy by combustion, such as an engine, a boiler for power generation, a gas turbine, and the like, and includes a mechanism that converts the thermal energy into motive power, electric power, etc., and outputs the power. The LNG in the container F is supplied to the combustion device E through the flow path La, and the thermal energy generated by the combustion of the natural gas is converted into the required energy. Means for re-vaporizing LNG to raise the temperature of natural gas to room temperature can be appropriately provided on the combustion device E or the flow path La. Although the internal pressure of the container F is maintained constant, LNG is easily vaporized due to negative pressure and pressure fluctuations. Therefore, the pressure increase due to the vaporized gas while the combustion device E is stopped causes the gas to flow from the flow path Lb to the processing unit B. This can be avoided by escaping and properly performing incineration or the like.

The recovery device 1 has a cooler 7 connected to the combustion device E via a flow path L1, and the cooler 7 is connected to the heat exchanger 11 via a flow path L2. The exhaust gas G containing high-temperature carbon dioxide discharged from the combustion apparatus E by the combustion of natural gas is precooled by the cooler 7 through the flow path L1 and supplied to the heat exchanger 11 from the flow path L2. The cooler 7 is a facility for cooling the exhaust gas G to a temperature suitable for the treatment in the subsequent equipment, and the exhaust gas G is cooled to an outlet temperature of about 40° C. or lower, preferably about 30° C. or lower. Is composed of. Since the volume of gas in the flue gas is reduced by cooling the flue gas, the throughput of subsequent equipment can be increased. An indirect contact type cooler is suitable for the cooler 7 in order not to increase the water content of the exhaust gas G. The refrigerant of the cooler 7 may be any of commonly used refrigerants such as water, air, refrigerant of a refrigeration cycle, etc., and when the combustion apparatus E is a ship engine, it is convenient to use seawater as the refrigerant. .. However, the cooler 7 can be omitted, and whether to use the cooler 7 may be determined according to the generation state of the cold gas in the container F. In the heat exchanger 11, the exhaust gas G is cooled by heat exchange with the cold gas vaporized in the container F. The temperature of the cold gas is generally 0° C. or lower, and the exhaust gas G is cooled to about 0 to 10° C. in the heat exchanger 11.

The heat exchanger 11 is connected to the compressor 3 through the flow path L3, and the exhaust gas G is supplied from the cooler 7 to the compressor 3 and compressed, so that the pressure thereof rises. The compressor 3 is operated by a power source such as a motor, and applies a pressure required for adsorption of carbon dioxide to the exhaust gas G in the subsequent separation device SP. Specifically, the exhaust gas G is provided with a pressure such that the carbon dioxide partial pressure of the exhaust gas G supplied to the separation device SP becomes the adsorption pressure (relatively high pressure). Therefore, the pressure applied using the compressor 3 is determined based on the carbon dioxide concentration of the exhaust gas G and the adsorption pressure. Since the adsorption pressure is appropriately set based on the adsorption isotherm of carbon dioxide of the adsorbent A used in the separation device SP, the pressurization pressure of the exhaust gas G depends on the carbon dioxide concentration of the exhaust gas G. The pressure is set so that the carbon dioxide partial pressure becomes the adsorption pressure. Therefore, the pressure of the pressurized exhaust gas G is 100×adsorption pressure/carbon dioxide concentration [%] of the exhaust gas G. The adsorption pressure applied in the separation device SP is preferably a pressure equal to or higher than the threshold value indicated by the adsorption isotherm of the adsorbent, and although it varies depending on the adsorbent used, it is generally set to about 0.3 to 0.6 MPa. You can As the pressurizing device, any pressure applying means capable of generating a flow pressure capable of pressurizing the exhaust gas G so that the carbon dioxide partial pressure becomes an appropriate adsorption pressure can be used. As such means, for example, , A pressure pump, a compressor, a blower and the like. Therefore, the compressor 3 may be replaced with another pressurizing means capable of pressurizing the exhaust gas G so that the partial pressure of carbon dioxide in the exhaust gas G becomes the adsorption pressure. However, in the PSA method, the one having a relatively small applied pressure can be used as compared with the conventional method, so that the compressor and the blower can be preferably used, and the compressor is the most suitable. The pressure applied to the exhaust gas G by the compressor 3 can be maintained in the separation device SP by providing a pressure control valve downstream of the separation device SP, and the pressure of the exhaust gas G can be controlled by controlling the pressure control valve. It can be adjusted. In this embodiment, the residual gas G′ from which carbon dioxide has been removed in the separation device SP is used as the regeneration gas for the drying device DR, and the pressure control valve V10 provided in the flow path L8 for discharging the regeneration gas from the drying device DR is used. The pressurizing pressure can be adjusted by. The pressure of the compressor 3 causes the temperature of the exhaust gas G to rise. For example, when the exhaust gas G having a temperature of 0° C. and a carbon dioxide concentration of 10% (volume ratio) is pressurized to about 1.1 MPa, the carbon dioxide partial pressure becomes about 1 MPa, which is an appropriate adsorption pressure. Is about 200°C. As described above, when the pressurizing pressure of the exhaust gas G in the compressor 3 is appropriately adjusted according to the carbon dioxide concentration, the temperature of the exhaust gas G after the pressure increase generally rises to about 100 to 200°C.

The compressor 3 is connected to the heat exchanger 13 via the flow path L4. In the heat exchanger 15, the pressurized exhaust gas G is cooled to about 20 to 30° C. or lower by heat exchange with the cold gas supplied from the container F through the flow paths Lc and Le.

The heat exchanger 13 is connected to the drying device DR through the flow path L5, and the cooled exhaust gas G is dried by the drying device DR. The drying device DR is a device that removes moisture from the exhaust gas G in order to prevent functional deterioration and damage of the adsorbent A used in the separation device SP. The drying device DR has columns C3 and C4 in which the hygroscopic agent H is housed, the exhaust gas G is dehumidified by bringing the exhaust gas G and the hygroscopic agent H into contact with each other, and the low-humidity exhaust gas G passes through the flow path L6. It is supplied to the separation device SP. The hygroscopic agent H may be appropriately selected and used from commonly used hygroscopic agents such as silica gel, alumina gel, molecular sieve, zeolite and activated carbon. Economically, a hygroscopic agent that can be easily regenerated by heating silica gel or the like is advantageous, and a temperature swing hygroscopic tower can be constructed. By constructing the drying device DR using one or more pairs of hygroscopic columns loaded with the hygroscopic agent H, the exhaust gas G and the high-temperature regenerated gas are alternately supplied to the hygroscopic column to absorb the exhaust gas G and the hygroscopic agent. The reproduction of H can be performed alternately. That is, the drying process and the regeneration of the hygroscopic agent H can be repeatedly performed continuously without stopping the treatment of the exhaust gas G. This is performed by the switching control of the switching valves V1, V2, V3, V4, and the flow is controlled by controlling the switching valves V1, V2 so that the flow paths L5 and L6 communicate with one of the columns C3, C4. The exhaust gas G supplied from the path L5 is dehumidified in one of the columns C3 and C4 and is supplied from the flow path L6 to the separation device SP. At this time, the connection of the switching valves V3, V4 is controlled so that the regeneration gas supplied to the drying device DR flows through the other column and is discharged from the flow path L8. By reversing the connection of the switching valves V1, V2, V3 and V4, the absorption and regeneration of the columns C3 and C4 are switched. The switching valves V1, V2, V3, V4 may be configured to automatically switch according to the water concentration of the exhaust gas G discharged from the flow path L6. For example, a concentration sensor is provided in the flow path L6 and is electrically connected to the switching valves V1, V2, V3, V4, and the switching valves V1, V2, V3, V4 are set based on the increase in the water concentration detected by the concentration sensor. Each column can be switched so that the column communicating with the flow path L5 and the flow path L6 can be changed.

The main part of the separation device SP is composed of columns C1 and C2 containing an adsorbent A for separating carbon dioxide from gas according to the PSA method. Due to the supply of the exhaust gas G, the adsorbent A adsorbs carbon dioxide contained in the exhaust gas G, and the residual gas G′ with reduced carbon dioxide is discharged. That is, the exhaust gas G supplied from the drying device DR to the separating device SP through the flow path L6 is the carbon dioxide C concentrated or purified in the columns C1 and C2 and the decarbonized gas in which carbon dioxide is reduced or removed. It is separated into a certain residual gas G′. The columns C1 and C2 are connected to the expander 5 through the flow path L10, and are also connected to the drying device DR through the flow paths L7 and L9. The residual gas G′ from which carbon dioxide has been removed by the adsorbent A flows out of the column, is discharged from the separation device SP, is heated to about 150 to 200° C. by the heater 19 between the flow paths L7, L9, and is the drying device DR. Supplied to. On the other hand, the carbon dioxide adsorbed on the adsorbent A is desorbed due to the pressure drop when the column communicates with the flow path L10 and the expander 5 by the connection switching by the switching valve, and the concentrated or purified carbon dioxide C is flow path L11. , L12, L13 to the liquefier R. When the expander 5 is connected to cooperate with the compressor 3, the fluid pressure when the pressure of the expander 5 is released is recovered as power and used as a part of the driving force of the compressor 3. Therefore, the energy consumed by the power source of the compressor 3 can be saved.

The adsorbent A contained in the columns C1 and C2 is an adsorbent capable of selectively adsorbing carbon dioxide by the PSA method. Activated carbon and zeolite conventionally known as substances capable of adsorbing carbon dioxide have a desorption pressure of negative pressure, and therefore a vacuum pump is required for desorption of carbon dioxide. On the other hand, in the metal-organic structure which has been studied as an adsorbent in recent years, the adsorption isotherm showing the relationship between the pressure of the adsorbate and the equilibrium adsorption amount shows an S-shaped curve, and a sharp rise near a certain pressure. Since it has a portion, the difference in the equilibrium adsorption amount (=adsorption capacity) can be increased even if the pressure difference between the adsorption pressure and the desorption pressure is small. In the embodiment of FIG. 1, metal-organic frameworks (MOFs) capable of selectively adsorbing carbon dioxide are used as the adsorbent A. Metal-organic structures are porous materials also called porous coordination polymers (PCPs: Porous Coordination Polymers). The metal-organic structure is one in which a skeleton having a perforated structure is formed on the basis of a complex formed by a coordinate bond of a metal ion and an organic ligand, and utilizing the perforated structure, Functions as an adsorbent. Examples of the metal-organic structure include [Cu(4,4′-dihydroxybiphenyl-3-carboxyl) ₂ (4,4′-bipyridyl)] _n , [Cu(PF ₆ ⁻ ) ₂ (1,2-bis) (4-pyridyl)ethane)] _n , [Cu(CF ₃ SO ₃ ^- ) ₂ (1,3-bis(4-pyridyl)propane) ₂ ] _n , {[Cu(PF ₆ ^- )(2,2- Bis(4-pyridyl))PF ₆ ^- } _n , [Cu ₂ (PF ₆ ^- ) ₂ (4,4'-bipyridyl)propane) ₂ ] _n , [Cu ₂ (PF ₆ ^- ) ₂ (pyridine) ₄ ] _N , [M ₂ (2,5-dioxide-1,4-benzenedicarboxylate)] (where M is Mg ²⁺ , Mn ²⁺ , Co ²⁺ , Ni ²⁺ , Fe ^{2 +} Or Zn ²⁺ ), [Cu(4,4′-dioxidebiphenyl-3-carboxylate) ₂ (4,4′-bipyridyl)] _n , [Zn ₄ O(4,4′,4″-( Benzene-1,3,5-triyl-tris(benzene-4,1-diyl)tribenzoate)] _n, etc. Also, a commercially available metal-organic structure that exhibits adsorptivity to carbon dioxide. By using a plurality of pairs of columns, it is possible to carry out a multi-stage adsorption treatment, and in such a case, different types of metal-organic structures are used in each pair. The metal-organic structure may have a property of adsorbing a plurality of kinds of gases, and even in such a structure, the metal-organic structure generally has an adsorbing property. The threshold pressure in the isotherm varies depending on the type of gas, and selective adsorption of carbon dioxide can be suitably performed by setting an appropriate pressure.

In each of the columns C1 and C2, when the exhaust gas G is supplied at a pressure at which the carbon dioxide partial pressure becomes the adsorption pressure (relatively high pressure), the carbon dioxide contained in the exhaust gas G is adsorbed by the adsorbent A and the pressure is desorbed. When the pressure (relative low pressure) is reduced, carbon dioxide is desorbed and released from the adsorbent A. For example, when [Cu(4,4′-dihydroxybiphenyl-3-carboxyl) ₂ (4,4′-bipyridyl)] _n is used as the metal-organic structure, the equilibrium adsorption amount is rapidly increased near 0.25 MPa. As the equilibrium adsorption amount increases rapidly, the adsorption pressure falls within the pressure range on the high pressure side (>0.25 MPa) with the pressure value (threshold) at which the equilibrium adsorption amount increases rapidly, and the adsorption pressure falls on the low pressure side (<0.25 MPa). The desorption pressure can be set individually. With this setting, the difference in the equilibrium adsorption amount (=adsorption capacity) can be increased even if the pressure difference between the adsorption pressure and the desorption pressure is small. Therefore, the load applied to the device due to the pressure fluctuation between the adsorption pressure and the desorption pressure is significantly smaller than in the conventional case, and the load for imparting durability to the device structure can be reduced. Moreover, since the desorption pressure can be set to atmospheric pressure or positive pressure (above atmospheric pressure) instead of negative pressure, the adsorption pressure and desorption pressure can be set and adjusted by the pressure control valve without using a vacuum pump. It is possible. Therefore, the energy consumed by the vacuum pump is reduced, and the limitation of the processing capacity of the recovery device due to the performance of the vacuum pump, which is a problem in the conventional PSA method, is eliminated.

Separation of carbon dioxide from the exhaust gas G in each column is repeated by repeating a series of operations of supplying the exhaust gas G and decreasing the pressure so that adsorption and desorption of carbon dioxide are alternately performed between the two columns C1 and C2. And collection are alternately repeated. This is performed by switching control of the switching valves V5, V6, V7, and by controlling the switching valves V5, V6 so that the flow channels L6 and L9 communicate with one of the columns C1, C2, the flow channel L6 is controlled. In the exhaust gas G supplied from the column C2, carbon dioxide is adsorbed and removed in one of the columns C1 and C2, and the residual gas G'is discharged from the flow path L9. At this time, in the other column, the connection of the switching valve V7 is controlled so as to communicate with the flow path L10 and the expander 5, the pressure in the column is reduced to the desorption pressure, and carbon dioxide is released from the adsorbent A. .. Thereafter, the adsorption and desorption of the columns C1 and C2 are switched by reversing the connection of the switching valves V5, V6 and V7. Therefore, the carbon dioxide C is alternately collected from the pair of columns of the separation device SP through the flow path L10 by using the exhaust gas G continuously supplied from the compressor 3 through the drying device DR. The desorption pressure in the columns C1 and C2 can be adjusted by the pressure control valve V8 of the flow path L10. The residual gas G′ from which carbon dioxide has been removed is recirculated to the drying device DR through the flow paths L9 and L7. If a carbon dioxide concentration sensor is installed on the downstream side of the switching valve V6, the carbon dioxide concentration of the residual gas G′ in the flow path L9 can be detected, and therefore the increase in carbon dioxide concentration due to the lysate of the adsorbent A can be detected. .. Therefore, if the concentration sensor is electrically connected to the switching valves V5, V6, V7 and the switching valves V5, V6, V7 are set to automatically switch based on the detected carbon dioxide concentration, the adsorbent A It is possible to switch the adsorption/desorption at a suitable timing so that the adsorption capacity is utilized to the maximum extent.

The flow path L11 for releasing the carbon dioxide C from the separation device SP is connected to the compressor 9, and the carbon dioxide C is pressurized by the compressor 9 to about 0.5 MPa or more, which is the pressure at which the carbon dioxide C can be liquefied. The compressor 9 is connected to the heat exchanger 17 through the flow path L12, and the pressurized carbon dioxide C is supplied to the heat exchanger 17 through the flow path L12 and is supplied from the container F through the flow paths Lc and Lg. It is cooled to about -30 to -10°C by heat exchange with cold gas. Therefore, the carbon dioxide C is supplied to the liquefying device R from the flow path L13 in a state where it is easily liquefied.

The liquefaction device R can be configured using a pressurizing device for pressurizing the carbon dioxide C and a cooling device, and the concentrated or purified carbon dioxide C supplied from the separation device SP has a boiling line temperature or lower, It is preferably liquefied by cooling to about -20 to -50°C and compressing under pressure to 0.518 MPa or more. In the embodiment of FIG. 1, since the compressor 9 and the heat exchanger 17 are pressurized and cooled to a state where they are easily liquefied, it is easy to realize the simplification and downsizing of the configuration of the liquefying device R. The liquefied carbon dioxide C is preferably prepared in a supercritical state, and the liquefied and purified carbon dioxide C having a purity of about 95 to 99% is generally obtained.

On the other hand, the regeneration system that uses the residual gas G′ discharged from the separation device SP as the regeneration gas is configured by the flow path L7 and the heater 19 that heats the residual gas G′ to a high temperature. The residual gas G′ of about 20 to 40° C. discharged from the separator SP is heated to about 150 to 200° C. As a result, the regeneration gas supplied to the drying device DR becomes a high-temperature dry gas having a dew point of approximately −90 to −60° C. that contains almost no water. By supplying the regeneration gas to the columns C3 and C4, moisture is released from the hygroscopic agent H after use. When a detector for detecting the temperature of the regeneration gas is installed on the downstream side of the heater 19 in the flow path L7 and electrically connected to the heater 19, when the temperature of the regeneration gas detected by the detector is below a predetermined temperature. The heating of the regeneration gas can be controlled depending on the temperature detected by the detector. The heater 19 may be replaced with one that heats by utilizing exhaust heat of other equipment. For example, a heat exchanger that exchanges heat with high-temperature exhaust gas can be used, and in the embodiment of FIG. 1, a heat exchanger is arranged instead of the cooler 7, and in this heat exchanger, the separation device SP The residual gas G′ discharged from the exhaust gas and the exhaust gas G of the combustion device E can be changed so as to exchange heat. Further, such a heat exchanger and the cooler 7 may be used together. The residual gas G'(gas after regeneration) used for regeneration is discharged to the outside from the flow path L8. A pressure control valve V10 and a silencer X are provided on the flow path L8. The pressure applied to the exhaust gas G by the compressor 3 is maintained by the pressure control valve V10 through the separation device SP, the flow path L9 and the flow path L7, and the pressure of the post-regeneration gas discharged from the drying device DR is released. To atmospheric pressure.

The cooling system using the cold gas supplied from the container F includes the flow paths Ld, Le, Lf, Lg that branch from the flow path Lc and are connected to the heat exchangers 11, 13, 15, 17, respectively. It has flow paths Ld′, Le′, Lf′, and Lg′ that reach the flow path Lh from each of the exchangers 11, 13, 15, and 17, and the flow path Lh is connected to the combustion apparatus E. Therefore, the cold gas vaporized in the container F is distributed and supplied to each of the heat exchangers 11, 13, 15, 17 through the flow path Lc and the flow paths Ld, Le, Lf, Lg. The cold gas that has undergone heat exchange merges with each heat exchanger through the flow paths Ld′, Le′, Lf′, and Lg′ in the flow path Lh, and is supplied to the combustion apparatus E. A flow meter and a flow rate adjusting valve are provided to adjust the flow rate of each cold gas distributed and supplied to the heat exchangers 11, 13, 15, and 17. That is, the flow rate of the cold gas supplied to the heat exchanger 11 includes the flow rate meter S3 that detects the flow rate of the cold gas supplied to the heat exchanger 11 on the flow path Ld′, and the flow rate provided on the flow path Ld. It is adjusted by a flow rate adjusting valve V13 electrically connected to the meter S3, and the flow rate adjusting valve V13 is controlled so that the flow rate of the cold gas is maintained at a predetermined amount according to the flow rate detected by the flow meter S3. It Similarly, the flow rate of the cold gas supplied to the heat exchanger 13 is provided in the flow path Le and the flow meter S4 that detects the flow rate of the cold gas supplied to the heat exchanger 13 on the flow path Le'. The flow rate adjusting valve V14 is adjusted by a flow rate adjusting valve V14 electrically connected to the flow meter S4, and the flow rate adjusting valve V14 is controlled so that the flow rate of the cold gas is maintained at a predetermined amount according to the flow rate detected by the flow meter S4. To be done. The flow rate of the cold gas supplied to the heat exchanger 15 is the flow meter S5 for detecting the flow rate of the cold gas supplied to the heat exchanger 15 on the flow path Lf′, and the flow meter S5 provided on the flow path Lf. Is adjusted by a flow rate adjusting valve V15 electrically connected to. The flow rate of the cold gas supplied to the heat exchanger 17 is the flow meter S6 for detecting the flow rate of the cold gas supplied to the heat exchanger 17 on the flow path Lg′, and the flow meter S6 provided in the flow path Lg. Is adjusted by a flow rate adjusting valve V16 electrically connected to. The flow rate of the cold gas supplied to the heat exchangers 11, 13, 15, 17 may be appropriately set according to the cooling conditions in each heat exchanger. Since the heat exchangers 13 and 17 arranged in the latter stage of the compressors 3 and 9 cool the pressurized relatively high temperature gas, the supply flow rate of the cold gas becomes relatively large. Further, the flow rate of the cold gas supplied to the heat exchanger 13 is adjusted so that the temperature of the exhaust gas G becomes an appropriate temperature in the drying device DR and the separating device SP. Similarly, the flow rate of the cold gas supplied to the heat exchanger 15 is adjusted by the flow rate adjusting valve V15 and the flow meter S7 on the flow paths Lf and Lf'.

The embodiment of FIG. 1 is configured such that the cold gas is distributed and supplied in parallel to the heat exchangers 11, 13, 15, 17 but the invention is not limited to this supply mode. For example, from the viewpoint of the cooling temperature, the flow paths Le and Le′ and the flow paths Ld and Ld′ are arranged in series so that the cold gas is supplied to the heat exchanger 11 via the heat exchanger 13, or the cold gas is supplied. The flow paths Lf and Lf′ and the flow paths Lg and Lg′ may be arranged in series so that the water is supplied to the heat exchanger 17 via the heat exchanger 15.

In the combustion system of FIG. 1, since the cold gas used for cooling the exhaust gas G and the like is supplied to the combustion device E, the amount of natural gas directly supplied from the container F to the combustion device E through the flow passage La is equal to the flow passage. It is preferable to adjust in consideration of the amount of cold gas supplied from Lh. Therefore, the combustion system has an adjustment system that adjusts the supply amount of LNG or natural gas supplied from the container F to the combustion device E in accordance with the cold gas supplied to the combustion device E by the cooling system. A proper amount of natural gas corresponding to the energy supplied by E is supplied to the combustion device E. Specifically, a detector S1 that detects the internal pressure is installed in the container F, and a flow meter S2 that detects the flow rate of the cold gas is installed in the flow path Lh that supplies the cold gas to the combustion device E. To be done. Flow rate control valves V11 and V12 are attached to the flow paths La and Lb connected to the combustion device E and the processing unit B, respectively, and the flow rate control valves V11 and V12 are electrically connected to the detector S1 and the flow meter S2. Connected. While the combustion device E is stopped, the flow rate adjustment valve V12 is opened and closed according to the pressure detected by the detector S1 so that the internal pressure of the container F is maintained constant. While the combustion device E is operating, the flow rate adjusting valve V12 is closed, and the flow rate adjusting valve V11 is connected to the natural gas supplied from the container F through the flow path La according to the flow rate of the cold gas detected by the flow meter S2. The total amount of the cold gas supplied from the flow path Lh is controlled so as to correspond to the energy supply amount required for the combustion device E. Therefore, the thermal energy generated by the combustion of the natural gas and the cold gas directly supplied from the container F is converted into motive power, electric power and the like. This adjustment system is very useful when the present invention is applied to a combustion system that requires control capable of accurately adjusting and changing the amount of energy supplied by the combustion device E. Therefore, in a combustion system that outputs propulsive energy such as a ship engine, the adjustment system contributes to accurate drive control, and contributes to efficient operation and stable operation in energy supply equipment such as a thermal power plant.

With regard to the above-described configuration, the number of columns in which the hygroscopic agent H is housed in the drying device DR is appropriately determined depending on the hygroscopic rate, the hygroscopic capacity, the regeneration rate, etc. of the hygroscopic agent H used so that a suitable drying process can be performed. You may change it. Also in the separation device SP, by increasing the number of column pairs so as to increase the number of adsorption/desorption processes according to the separation selectivity of the adsorbent A, the purity of the carbon dioxide recovered can be increased. Can be improved. For example, if a configuration of a pair of columns similar to the columns C1 and C2 is additionally provided in the middle of the flow path L10, the separation performance is improved by the two-stage adsorption separation. In this case, the residual gas separated from carbon dioxide in the second column may be refluxed in the adsorption separation process of the first column.

Alternatively, a concentration sensor as a detector for detecting the concentration of carbon dioxide is provided in the flow channel L10 or the flow channel L11 so that the carbon dioxide C is returned to the flow channel L6 when the concentration of the recovered carbon dioxide C is low. Is also good. Thereby, low concentration carbon dioxide is supplied to the columns C1 and C2 together with the exhaust gas G, and the concentration of carbon dioxide obtained from the pair of columns can be increased.

In the above-mentioned configuration, a processing unit such as a CPU is used to manage the detection information of the detector or the sensor in the processing unit while automatically controlling the switching valve and the flow rate adjusting valve based on the detection information. You may do it. As a result, it becomes possible to perform complicated processing such as operation correction by correction of detection information and response to abnormality.

The method of recovering carbon dioxide carried out in the recovery device 1 has a separation process, a drying process and a cooling process as main processes, and a regenerating process of the hygroscopic agent is carried out to continue the drying process. In the separation treatment, the adsorption and desorption of carbon dioxide with respect to the adsorbent due to pressure fluctuation is used to separate carbon dioxide from the exhaust gas from which natural gas has been burned, and the residual gas from which carbon dioxide has been removed is discharged. In the drying process, the gas supplied to the separation process is dried using a hygroscopic agent. In the cooling process, the cold gas vaporized from the LNG is used to cool the exhaust gas to a temperature suitable for the drying process. In the regeneration treatment, the residual gas discharged from the separation treatment is supplied to the hygroscopic agent used in the drying treatment as a regeneration gas for regenerating the hygroscopic agent. More specifically, the following work is carried out.

The supplied exhaust gas G is subjected to a cooling treatment in the cooler 7 and the heat exchanger 11 in advance, and is cooled to a temperature of about 50° C. or lower, preferably about 40° C. or lower, and then pressurized in the compressor 3. After the treatment, the exhaust gas G is compressed to a pressure at which the carbon dioxide separation treatment is performed (the carbon dioxide partial pressure of the exhaust gas G becomes the adsorption pressure (relatively high pressure)). For this pressurization, a pressure at which the adsorption pressure (carbon dioxide partial pressure) is about 0.2 to 1.0 MPa is generally applied. The temperature of the pressurized exhaust gas G rises to about 120 to 180° C., and the exhaust gas G is cooled by the heat exchanger 13 before being subjected to the drying treatment with the hygroscopic agent and the separation treatment with the adsorbent, and the temperature is about 50° C. or less. , Preferably about 40° C. or lower, more preferably about 30° C. or lower. After that, the exhaust gas G is subjected to a drying process by the drying device DR, and the water content is reduced to about 1 ppm or less.

By adsorbing carbon dioxide by the adsorbent A of the separation device SP to the exhaust gas G that has undergone the drying process, the exhaust gas G is separated into carbon dioxide C and the residual gas G′ (separation process). Since the adsorption reaction in which the metal-organic structure adsorbs carbon dioxide is an exothermic reaction and the desorption reaction is an endothermic reaction, the temperature may vary up to about 20° C. due to repeated adsorption and desorption. Therefore, in order to quickly adsorb carbon dioxide, it is desirable to maintain the temperature during adsorption at a low temperature. The exhaust gas G supplied to the columns C1 and C2 in the separation treatment is cooled in advance in the heat exchanger 15 as described above. However, if the temperature of the exhaust gas G is higher than the temperature suitable for the separation treatment, it is necessary. Then, a cooling device may be appropriately used for cooling before the separation process. The cooling method of the exhaust gas G in this case is not particularly limited as long as it is not humidified, and may be appropriately selected and applied from well-known indirect contact cooling techniques such as water cooling type and air cooling type, and water cooling type using seawater. It can be favorably carried out by cooling or a cooling system utilizing heat exchange with the cold gas from the LNG mentioned above.

In the separation process, for example, when the exhaust gas G having a carbon dioxide concentration of 10%, a temperature of 20° C. and a pressure of 1.1 MPa is supplied to one of the columns C1 and C2, adsorption of carbon dioxide is started at an adsorption pressure of 1 MPa. The gas discharged from this column is discharged as the residual gas G′ through the flow path L9. The carbon dioxide concentration of the residual gas is extremely low until the amount of adsorbed carbon dioxide approaches the adsorption capacity of the adsorbent A. However, when the desorption (adsorption saturation) of the adsorbent A approaches, the adsorption rate decreases and the residual gas G 'Carbon dioxide concentration begins to increase. When the adsorbent A breaks down, the carbon dioxide concentration of the residual gas G′ reaches 100% of the original concentration. In the other column, the carbon dioxide adsorbed by the adsorbent A is released by the decompression pressure reduction. The pressure is regulated to a desorption pressure of about 0.2 MPa by the pressure control valve V8, and the concentration of carbon dioxide discharged from the column to the flow path L10 increases to 90% due to the desorption of carbon dioxide from the adsorbent A, and the concentration is increased. The generated carbon dioxide C is recovered from the flow path L11. Since the temperature of the adsorbent A decreases due to the endothermic reaction during desorption, even if the supplied exhaust gas G is cooled to a constant temperature, the temperature inside the adsorbent A during adsorption becomes higher than that during desorption. For this reason, the rate at which the adsorbent A takes in carbon dioxide during adsorption is faster than the rate at which it is released during desorption, and can be approximately 1.2 times as large. Therefore, the release of carbon dioxide from the adsorbent A on the desorption side is substantially continued until the adsorbent A on the adsorption side reaches the meltdown.

In the separation process, the carbon dioxide concentration of the gas released from the adsorbent by desorption can be increased from the carbon dioxide concentration of the exhaust gas G to reach a purity of 95% (volume ratio) or higher. For example, when the concentration of carbon dioxide in the exhaust gas G is about 60% or more, it is generally possible to recover the carbon dioxide C concentrated or purified to a concentration of 90 to 99%. Instead of recovering the low-concentration carbon dioxide at the initial stage of desorption, the carbon dioxide C may be recovered when the concentration of the desorbed carbon dioxide C exceeds a predetermined concentration. The recovered carbon dioxide is subjected to a liquefaction treatment if necessary.

In this way, the adsorption and desorption of carbon dioxide are alternately repeated in the columns C1 and C2, and the residual gas G′ having a reduced carbon dioxide concentration and the desorbed carbon dioxide C are alternately and repeatedly released from each column. .. The residual gas G'separated and discharged in the separation treatment is used in the regeneration treatment as a regeneration gas of the dehumidifying agent used in the drying treatment. When the flow rate of the residual gas G′ is insufficient in the regeneration process, it is possible to replenish it by using the outside air, and according to the flow rate of the residual gas G′, the supplementary gas is appropriately supplied from the outside and the flow rate of the regenerated gas is increased. It is good to maintain. However, it is necessary that the water content of the supplementary gas is low, and when outside air is used, it is appropriately dehumidified before use.

The regeneration gas is heated to a temperature of about 150 to 200° C. by the heater 19 and becomes a high-temperature dry gas having a dew point of about −90 to −60° C. that contains almost no water. The regeneration gas is used to regenerate the hygroscopic agent H used in the drying process. After the regeneration treatment, the gas containing moisture after regeneration is discharged. The pressure is released to the atmospheric pressure through the pressure control valve V10, and is discharged to the outside through the silencer X.

The composition of flue gas differs depending on the fuel and combustion type, and the flue gas from the combustion of natural gas generally contains about 10% carbon dioxide, about 70% nitrogen and about 20% water vapor (volume ratio). In addition, a small amount of impurities such as sulfur oxide and nitrogen oxide may be contained. When such a combustion gas is treated as the exhaust gas G in the recovery device 1, carbon dioxide concentrated to a high concentration of about 98% or more can be recovered from the separation device SP including the metal-organic structure as an adsorbent. Since the exhaust gas G supplied to the separation device SP has its water vapor removed through the drying device DR, the residual gas G′ discharged from the separation device SP contains almost no water vapor and is used as a regeneration gas in the drying device DR. It is suitable for use.

When the pressure applied in the compressor 3 is increased so that the carbon dioxide partial pressure of the exhaust gas G becomes a suitable adsorption pressure, the partial pressure of other components (nitrogen, etc.) contained in the exhaust gas G also increases. When the adsorption of the other component may proceed, the pressure of the exhaust gas G is set within a range in which the equilibrium adsorption amount of the other component in the partial pressure of the other component is small.

The configurations of the separation device SP and the separation process can be appropriately changed depending on the situation. For example, carbon dioxide released from the desorption side and having a concentration lower than the predetermined concentration may be temporarily collected in a storage container and separately separated. Further, when the metal-organic structure used has a relatively low selective adsorption property to carbon dioxide, as described above, the separation treatment by the paired columns is configured in multiple stages to concentrate or purify carbon dioxide. Can improve the purity. Also, a plurality of pairs of columns may be arranged in parallel to increase the gas processing capacity.

Further, the separation device SP can also make changes relating to fluctuations in the internal temperature of the adsorbent A due to adsorption and desorption. Specifically, a pipe for indirect heat exchange is arranged inside the adsorbent A in the column to circulate the heat medium in the pipe, or a heat storage material is arranged in the adsorbent A for heating by the heat medium. Alternatively, the temperature fluctuation of the adsorbent A can be suppressed by cooling or by absorbing or releasing heat by the heat storage material. Alternatively, instead of arranging the pipe inside the adsorbent A, it is possible to provide a jacket that covers the outer periphery of the adsorption tower, and change the heating medium to flow through the jacket to heat or cool from the outside. The separation device SP configured as described above can cope with a sudden temperature change. For example, when the separation device SP is applied to the purification of carbon dioxide having a relatively high concentration, the adsorbent A of the adsorbent A due to vigorous heat generation during adsorption is used. The temperature rise can be suppressed from the inside.

The combustion exhaust gas of natural gas is a gas that contains a high concentration of nitrogen and has a relatively low carbon dioxide concentration. Therefore, a pretreatment for increasing the carbon dioxide concentration in the exhaust gas by an adsorption treatment using an adsorbent that exhibits selective adsorption to nitrogen, for example, a crystalline hydrous alkaline earth metal aluminosilicate (zeolite). If it is changed so as to be applied, it is advantageous in separating carbon dioxide. In this case, if the adsorbed nitrogen is recovered in the pretreatment, it can be used as a replenishing gas from the outside and used for the regeneration of the hygroscopic agent H.

INDUSTRIAL APPLICABILITY The present invention is capable of efficiently separating and recovering carbon dioxide concentrated or purified to a high concentration from the combustion exhaust gas of natural gas by the PSA method, and is economically advantageous in dioxide without requiring a means for generating a negative pressure such as a vacuum pump. Since carbon capture technology is provided and the cold gas vaporized from LNG is effectively used in carbon dioxide separation and capture, carbon dioxide in comprehensive exhaust gas treatment in combustion facilities such as ship engines, thermal power plants, and boilers The practicality of the technology for treating the contained gas is improved. In addition, it contributes to the construction of energy supply technology in consideration of energy saving and environmental protection, and can promote miniaturization and general-purpose use of devices and equipment for recovering carbon dioxide.

1 Recovery Device 3, 9 Compressor 5 Expander 7 Cooler 11, 13, 15, 17 Heat Exchanger 19 Heater SP Separator DR Dryer E Combustor F Container R Liquefier C1, C2, C3, C4 Column X Silencer A Adsorbent H Hygroscopic agent G Exhaust gas G′ Residual gas C Carbon dioxide V1, V2, V3, V4, V5, V6, V7 Switching valve V8, V10 Pressure control valve V9, V11, V12, V13, V14, V15, V16 Flow rate Adjustment valve S1 Detector S2, S3, S4, S5, S6, S7 Flow meter

Claims (10)

A carbon dioxide recovery device for recovering carbon dioxide from exhaust gas that burns natural gas,
A separation device for separating carbon dioxide from exhaust gas by utilizing adsorption and desorption of carbon dioxide to an adsorbent due to pressure fluctuation,
A drying device having a hygroscopic agent for drying the exhaust gas supplied to the separation device,
A container for containing liquefied natural gas,
A first flow path for supplying liquefied natural gas in the container to a combustion device,
In the container has a second flow path provided separately from the first flow path to supply a cold gas that vaporizes from liquefied natural gas, and using the cold gas in the second flow path , And a cooling system for cooling the exhaust gas so that the exhaust gas supplied to the drying device has a temperature suitable for drying. The carbon dioxide recovery device according to claim 1, wherein the cooling system includes at least one heat exchanger that exchanges heat between the exhaust gas supplied to the drying device and the cold gas. The cooling system further includes at least one flow meter for detecting a flow rate of the cold gas supplied to the at least one heat exchanger, and a temperature of the cold gas according to the flow rate detected by the at least one flow meter. The carbon dioxide recovery device according to claim 2, further comprising at least one flow rate adjusting valve that is controlled so that the flow rate is maintained at a predetermined amount. Furthermore, it has a pressurizing device for pressurizing the exhaust gas supplied to the separation device, and a depressurizing device for depressurizing so that carbon dioxide is desorbed from the adsorbent of the separation device,
The carbon dioxide recovery device according to claim 3, wherein the at least one heat exchanger includes a heat exchanger that exchanges heat between the exhaust gas pressurized by the pressurizing device and the cold gas. Furthermore, any one of claims 1 to 4 further comprising a regeneration system that heats the residual gas from which carbon dioxide has been removed from the exhaust gas by the separation device and supplies it to the drying device as a regeneration gas for regenerating the hygroscopic agent of the drying device. The carbon dioxide recovery device according to claim 1. Furthermore, it has a liquefaction device which cools and liquefies the carbon dioxide recovered from the said separation device, The said cooling system is comprised so that a part of said cold gas may be supplied to the said liquefaction device. 5. The carbon dioxide recovery device according to any one of 5 above. A combustion device that burns natural gas to supply energy,
Utilizing adsorption and desorption of carbon dioxide to the adsorbent due to pressure fluctuation, separating carbon dioxide from the exhaust gas discharged from the combustion device, and a separation device for discharging the residual gas from which carbon dioxide has been removed,
A drying device having a hygroscopic agent for drying the exhaust gas supplied to the separation device,
A container for containing liquefied natural gas,
A first flow path for supplying liquefied natural gas in the container to the combustion device;
In the container has a second flow path provided separately from the first flow path to supply a cold gas that vaporizes from liquefied natural gas, and using the cold gas in the second flow path , And a cooling system for cooling the exhaust gas so that the exhaust gas supplied to the drying device has a temperature suitable for drying. The combustion system for natural gas according to claim 7, wherein the cooling system is configured to supply the cold gas used for cooling the exhaust gas to the combustion device. Furthermore ,
Supply from the container to the combustion device according to the cold gas supplied to the combustion device by the cooling system so that an appropriate amount of natural gas corresponding to the energy supplied by the combustion device is supplied to the combustion device combustion system of natural gas according to claim 8 having adjusting system for adjusting the supply of natural gas to be. The natural gas combustion system according to any one of claims 7 to 9, which is applied to a marine engine or a thermal power generation.