Carbon dioxide separation recovery device

Abstract

To provide a carbon dioxide separation recovery device which can maximize a carbon dioxide separation recovery amount per unit refrigerant flow rate.SOLUTION: A carbon dioxide separation recovery device 1 includes: a carbon dioxide separation membrane 10 for permeating and separating carbon dioxide from exhaust gas containing the carbon dioxide; a carbon dioxide solidification device 30 for solidifying the carbon dioxide having permeated through the carbon dioxide separation membrane 10 by heat exchange with a coolant; a carbon dioxide supply path 42 for connecting the carbon dioxide separation membrane 10 and the carbon dioxide solidification device 30; and a vacuum pump 20 which is arranged between the carbon dioxide separation membrane 10 and the carbon dioxide solidification device 30 in the carbon dioxide supply path 42, and supplies the exhaust gas having concentrated carbon dioxide having permeated through the carbon dioxide separation membrane 10 to the carbon dioxide solidification device 30.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a carbon dioxide separation and capture device that separates and captures carbon dioxide from combustion exhaust gas, and more particularly to a carbon dioxide separation and capture device that solidifies, separates, and captures carbon dioxide by heat exchange between the combustion exhaust gas and a refrigerant. [Background technology]

[0002] Generally, most of the carbon dioxide released into the atmosphere is contained in exhaust gas from the combustion of fossil fuels. Because carbon dioxide has an impact on global warming, there are studies being conducted on reducing carbon dioxide emissions or utilizing it. However, the concentration of carbon dioxide contained in exhaust gas is low, ranging from a few percent to a dozen percent, and separation of carbon dioxide from exhaust gas is essential for utilizing it.

[0003] Technologies for separating carbon dioxide from gases that contain carbon dioxide have long been used industrially, and well-known methods include those using hot potassium carbonate or amine-based absorption liquids, those using gas separation membranes, and the pressure swing adsorption (PSA) and temperature swing adsorption (TSA) methods that use adsorbents.

[0004] However, these separation technologies have only been used in cases where removing the carbon dioxide would increase the value of the remaining gas or where there are benefits to using the carbon dioxide, such as in enhanced oil recovery (EOR), and both methods consume large amounts of energy to separate the carbon dioxide. If fossil fuels are used to generate this energy, the effect of reducing carbon dioxide emissions will be small, and the amount of energy obtained from each fossil fuel will also decrease, making this economically unacceptable. Therefore, there is a demand for new energy-saving carbon dioxide separation technology that consumes as little energy as possible when separating carbon dioxide as a measure against global warming.

[0005] In this regard, Prior Art Document 1 discloses a technique for solidifying carbon dioxide in exhaust gas by heat exchange between the exhaust gas, from which moisture has been solidified and removed, and LNG, thereby liquefying dry ice. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-317302 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the technology described in Prior Art 1, although water is removed from the exhaust gas before CO2 solidification to slightly reduce the flow rate, the CO2 is solidified by exchanging heat between LNG and low-CO2 concentration exhaust gas (CO2 concentration: several to several tens of mol%) that contains a large amount of components other than CO2 (N2, O2, etc.).

[0008] With this method, the cold energy of the LNG is consumed to cool components other than CO2 (N2, O2, etc.) to the CO2 solidification temperature, so the cold energy of the LNG is not used effectively and it is difficult to increase the overall amount of CO2 captured.

[0009] The present invention has been made to solve the above problems, and has an object to provide a carbon dioxide separation and capture device that can maximize the amount of carbon dioxide separated and captured per unit refrigerant flow rate. [Means for solving the problem]

[0010] (1) The carbon dioxide separation and capture device according to the present invention comprises: a carbon dioxide separation membrane that allows carbon dioxide to permeate and separate from an exhaust gas containing carbon dioxide; a carbon dioxide solidifier that solidifies the carbon dioxide that has permeated the carbon dioxide separation membrane by heat exchange with a refrigerant; a carbon dioxide supply line connecting the carbon dioxide separation membrane and the carbon dioxide solidifier; a vacuum pump that is disposed in the carbon dioxide supply path between the carbon dioxide separation membrane and the carbon dioxide solidifier and that supplies exhaust gas in which carbon dioxide has been concentrated and that has permeated the carbon dioxide separation membrane to the carbon dioxide solidifier.

[0011] (2) The carbon dioxide separation and capture device according to the present invention comprises: a carbon dioxide separation membrane that allows carbon dioxide to permeate and separate the carbon dioxide from an exhaust gas containing carbon dioxide; a carbon dioxide solidifier that solidifies the carbon dioxide that has permeated the carbon dioxide separation membrane by heat exchange with a refrigerant; a carbon dioxide supply line connecting the carbon dioxide separation membrane and the carbon dioxide solidifier; an excess gas exhaust passage for exhausting excess gas that has not been solidified from the carbon dioxide solidifier; and a vacuum pump disposed in the surplus gas exhaust path for sucking in the surplus gas and discharging it to the outside. Effect of the Invention

[0012] According to the present invention, heat exchange can be performed between a low flow rate of exhaust gas containing a high concentration of carbon dioxide separated by a carbon dioxide separation membrane and a refrigerant, thereby maximizing the amount of carbon dioxide separated and recovered per unit refrigerant flow rate. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing a carbon dioxide separation and capture device according to a first embodiment of the present invention. [Diagram 2] FIG. 5 is a schematic diagram showing a carbon dioxide separation and capture device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] [Embodiment 1] First, the structure and function of a carbon dioxide separation and capture device 1 according to this embodiment will be described. As shown in FIG. 1, the carbon dioxide separation and capture device 1 of this embodiment has a carbon dioxide separation membrane 10, a vacuum pump 20, a carbon dioxide solidifier 30, an exhaust gas inlet pipe 41, a carbon dioxide supply pipe 42, a dry ice outlet pipe 43, a first surplus gas outlet pipe 44, a second surplus gas outlet pipe 45, a refrigerant inlet pipe 46, a refrigerant outlet pipe 47, a first dry ice outlet valve 48, and a second dry ice outlet valve 49.

[0016] The carbon dioxide separation membrane 10 is a general-purpose carbon dioxide separation membrane based on zeolite, and uses the differential pressure before and after as a driving force to separate and concentrate carbon dioxide from the exhaust gas supplied via the exhaust gas inlet pipe 41, and discharge it to the carbon dioxide supply pipe 42. The exhaust gas that does not permeate the carbon dioxide separation membrane 10 is discharged from a first surplus gas outlet pipe 44.

[0017] The vacuum pump 20 is disposed in the carbon dioxide supply pipe 42 and is a typical multi-stage Roots type vacuum pump, which sucks in the exhaust gas in which carbon dioxide has been concentrated by the carbon dioxide separation membrane 10 and discharges it toward the carbon dioxide solidifier 30. However, in the present invention, the type of vacuum pump is not limited.

[0018] The carbon dioxide solidifier 30 is a scraping type heat exchanger that solidifies the carbon dioxide in the exhaust gas by heat exchange with LNG as a refrigerant, and scrapes off the dry ice on the surface of the heat transfer tube using a mechanical mechanism and drops it. The dropped dry ice is discharged from the dry ice outlet pipe 43, and the unsolidified nitrogen and oxygen are discharged from the second surplus gas outlet pipe 45.

[0019] The first dry ice outlet valve 48 and the second dry ice outlet valve 49 are ball valves and are installed in series in the dry ice outlet piping.

[0020] Next, the operation of the carbon dioxide separation and capture device 1 according to this embodiment will be described. The carbon dioxide separation membrane 10 concentrates carbon dioxide from the supplied exhaust gas using the pressure difference by the vacuum pump 20 as a driving force. For example, if the carbon dioxide concentration of the exhaust gas is about 5 vol%, it is concentrated to about 50 vol% by passing through the carbon dioxide separation membrane 10. Therefore, the volumetric flow rate of the exhaust gas is reduced to about 1 / 10 by passing through the carbon dioxide separation membrane 10.

[0021] The exhaust gas, which has a low flow rate and a high concentration of carbon dioxide, is supplied to a carbon dioxide solidifier 30 through a vacuum pump 20 .

[0022] In the carbon dioxide solidifier 30, the carbon dioxide in the exhaust gas is solidified by heat exchange between the exhaust gas, which has a carbon dioxide concentration of about 50%, and the LNG. The solidified carbon dioxide is scraped off and discharged to the dry ice outlet pipe 43, and the unsolidified nitrogen and oxygen are discharged from the second surplus gas outlet pipe 45.

[0023] The solid carbon dioxide discharged to the dry ice outlet pipe 43 falls between the first dry ice outlet valve 48 and the second dry ice outlet valve 49 when the first dry ice outlet valve 48 opens. When the first dry ice outlet valve 48 closes and the second dry ice outlet valve 49 opens, the dry ice falls downward from the second dry ice outlet valve 49. In this manner, the first dry ice outlet valve 48 and the second dry ice outlet valve 49 discharge dry ice while maintaining a pressure difference between the carbon dioxide solidifier 30 and below the second dry ice outlet valve 49 .

[0024] According to the carbon dioxide separation and capture device 1 of this embodiment, the carbon dioxide separation membrane 10 converts the exhaust gas into a low flow rate exhaust gas containing a high concentration of carbon dioxide, so it is possible to significantly reduce the amount of cold energy of LNG required in the carbon dioxide solidifier 30. This makes it possible to maximize the amount of carbon dioxide solidified per unit LNG flow rate, thereby maximizing the amount of carbon dioxide separated and captured as a facility.

[0025] Furthermore, in the carbon dioxide solidifier 30, the volume of the exhaust gas is reduced as the entire exhaust gas is cooled to the carbon dioxide solidification temperature, and the carbon dioxide, which accounts for approximately 50% of the volume, is solidified, thereby further reducing the volume and contributing to the generation of negative pressure, thereby reducing the pressure difference of the vacuum pump 20 and reducing the energy consumption of the vacuum pump 20.

[0026] In this embodiment, the carbon dioxide separation membrane 10 has been described as being based on zeolite, but the type of carbon dioxide separation membrane of the present invention is not limited to zeolite, and inorganic membranes based on silica-based amorphous or carbon, and organic membranes such as polymer membranes, facilitated transport membranes, and ionic liquid-impregnated membranes can also be appropriately selected.

[0027] Also, although the carbon dioxide solidifier 30 has been described as a scraping-type heat exchanger, the type of carbon dioxide solidifier of the present invention is not limited to a scraping-type heat exchanger, and may be any type that can selectively solidify carbon dioxide by heat exchange with a refrigerant, such as dropping dry ice with an air blower or knocker, or a type in which carbon dioxide is solidified and then pressurized to liquefy and discharged.

[0028] Moreover, the first dry ice outlet valve 48 and the second dry ice outlet valve 49 are not limited to ball valves, but may be appropriately selected from valves having partitioning capabilities, such as gate valves and butterfly valves.

[0029] In this embodiment, a first dry ice outlet valve 48 and a second dry ice outlet valve 49 are provided at the bottom of the carbon dioxide solidifier 30 to separate it from the downstream, but this is not limited to this form, and any selective transport means such as a screw feeder, screw pump, rotary valve, damper, etc. can be used as long as it separates the carbon dioxide solidifier 30 from the downstream and selectively transports dry ice to the downstream while preventing the flow of gas.

[0030] For example, if the downstream side of the carbon dioxide solidifier 30 is a system for high-pressure liquid carbon dioxide, then a configuration like that of this embodiment, a rotary valve, a screw pump, or the like is adopted to ensure a high pressure difference, and if the downstream side is a system for low-pressure solid carbon dioxide, then a screw feeder, a backflow prevention damper, or the like is adopted. In other words, an appropriate selection is made within the design range according to the system for the downstream side.

[0031] In addition, although the above description uses LNG as a refrigerant, any refrigerant that is in a liquid state at a temperature that can solidify the carbon dioxide in the exhaust gas can be used, and single-component fluids such as nitrogen or hydrogen, or multi-component fluids based on fluorocarbons can also be selected as appropriate.

[0032] [Embodiment 2] A second embodiment of the present invention will be described with reference to Fig. 2. Note that descriptions of configurations, functions, and actions similar to those of the first embodiment will be omitted.

[0033] In the carbon dioxide separation and capture apparatus 101 according to this embodiment, a vacuum pump 20 is disposed in the second surplus gas outlet pipe 45 .

[0034] Next, the operation of the carbon dioxide separation and capture apparatus 101 according to this embodiment will be described. The exhaust gas supplied to the carbon dioxide separation membrane 10 is concentrated with carbon dioxide from the exhaust gas using the pressure difference by the vacuum pump 20 as a driving force.

[0035] The exhaust gas with a high carbon dioxide concentration is supplied to the carbon dioxide solidifier 30, where the carbon dioxide is solidified by heat exchange with the LNG and discharged from the dry ice outlet pipe. The unsolidified nitrogen and oxygen are discharged from the second surplus gas outlet pipe and sucked out by the vacuum pump 20.

[0036] According to the carbon dioxide separation and capture apparatus 101 of this embodiment, the volumetric flow rate of the exhaust gas is reduced by the amount of carbon dioxide solidified in the carbon dioxide solidifier 30, so that the volumetric flow rate of the gas sucked into the vacuum pump 20 can be reduced, and as a result, the power of the vacuum pump can be reduced. [Industrial Applicability]

[0037] INDUSTRIAL APPLICABILITY The present invention can be used as a carbon dioxide separation and capture device that solidifies carbon dioxide by heat exchange between a combustion exhaust gas and a refrigerant, and separates and captures the carbon dioxide. [Explanation of symbols]

[0038] 1, 101 Carbon dioxide separation and capture device 10 Carbon dioxide separation membrane 20 Vacuum Pump 30 Carbon dioxide solidifier 41 Exhaust gas inlet pipe 42 Carbon dioxide supply pipe 43 Dry ice outlet pipe 44 First excess gas outlet pipe 45 Second excess gas outlet pipe 46 Refrigerant inlet pipe 47 Refrigerant outlet piping 48 First Dry Ice Outlet Valve 49 Second Dry Ice Outlet Valve

Claims

1. A carbon dioxide separation membrane that allows carbon dioxide to permeate and separate from an exhaust gas containing carbon dioxide; a carbon dioxide solidifier that solidifies the carbon dioxide that has permeated the carbon dioxide separation membrane by heat exchange with a refrigerant; a carbon dioxide supply line connecting the carbon dioxide separation membrane and the carbon dioxide solidifier; a vacuum pump disposed in the carbon dioxide supply path between the carbon dioxide separation membrane and the carbon dioxide solidifier, for supplying exhaust gas in which carbon dioxide has been concentrated and which has permeated the carbon dioxide separation membrane to the carbon dioxide solidifier.

2. A carbon dioxide separation membrane that allows carbon dioxide to permeate and separate from an exhaust gas containing carbon dioxide; a carbon dioxide solidifier that solidifies the carbon dioxide that has permeated the carbon dioxide separation membrane by heat exchange with a refrigerant; a carbon dioxide supply line connecting the carbon dioxide separation membrane and the carbon dioxide solidifier; an excess gas exhaust passage for exhausting excess gas that has not been solidified from the carbon dioxide solidifier; a vacuum pump disposed in the surplus gas exhaust passage for sucking in the surplus gas and discharging it to the outside.

Images