KR20170126372A - Separation membrane system for recovering the carbon dioxide in the combustion gas - Google Patents

Abstract

The present invention relates to a separation membrane system for recovering carbon dioxide in combustion gas, comprising: a first stage gas separation unit; a second stage gas separation unit; and a third stage gas separation unit. According to the present invention, carbon dioxide can be separated from combustion gas and condensed at high efficiency by the separation membrane system.

Description

[0001] The present invention relates to a separation membrane system for recovering carbon dioxide in a combustion gas,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation membrane system for separating and concentrating carbon dioxide in a combustion gas generated when a fossil fuel and a waste are burned in a power plant, a steel mill, an incinerator or the like using a gas separation membrane.

As the industry develops, the use of fossil fuels increases rapidly, and global warming and resource depletion problems arise, threatening sustainable growth. Therefore, for sustainable growth, carbon capture and sequestration (CCS) is required to capture and store carbon dioxide, a greenhouse gas.

Carbon dioxide is the most representative greenhouse gas, accounting for about 77% of global greenhouse gas emissions. Typical sources include coal-fired power plants, steel mills, and oil refineries. The emissions of these sources account for 45% of total CO2 emissions.

Combustion gases from thermal power plants contain about 12-17% carbon dioxide, 76-78% nitrogen, 4-5% oxygen, and other trace amounts of moisture and SOx and NOx compounds. In particular, carbon dioxide has been identified as a major cause of global warming, and measures to reduce and reuse its emissions have emerged as a global concern. Some developed countries are trying to freeze carbon dioxide emissions at a certain point in time and insist on the introduction of carbon taxes in this regard. Therefore, recovery of carbon dioxide from burning gas of thermal power plant, which is one of the largest sources of carbon dioxide, is an urgent problem to be solved urgently.

In addition to thermal power plants, carbon dioxide emission plants are steel mills, cement plants, petrochemical plants, fermentation plants, etc. Exhaust gases emitted by most factories except coal-fired power plants have a concentration of carbon dioxide of 25% While the thermal power plant is known to have low economic efficiency when it is commercialized because it is difficult to separate it because the concentration of carbon dioxide is low.

Commercial techniques for separating / purifying carbon dioxide in combustion gases include pressure swing adsorption, water scrubbing, methanol scrubbing, polyethylene glycol scrubbing, and membrane separation. The absorption process is mainly applied by water scrubbing process, which depends on the type of absorption liquid, gas-liquid contact area, gas and water temperature. In addition, the purified methane gas is saturated with water, requiring a post-treatment process for removing moisture.

The adsorption process is a technique for selectively separating specific components of the mixed gas by utilizing the difference in the adsorption equilibrium amount caused by the pressure cycling between the adsorbent and the mixed gas, and mainly adsorbs carbon dioxide at high pressure and desorbs adsorbed components at low pressure. Since the adsorption process is in abnormal condition, it is difficult to predict and design various operating parameters during the operation stage and it is necessary to pretreat water according to the adsorbent.

Compared with the understanding, the separation membrane process is energy-saving because it does not require the energy required for the phase change and can be operated only by the minimum driving force required for the membrane process, and there is no phase change. In addition, there is no evaporator or condenser, and most of them are composed of pump, piping, membrane, and control part.

In the case of a polymer membrane, there is a method in which a gas molecule passes through a minute gap existing between the side chain of a polymer and a side wall of the polymer due to a difference in speed of movement within the membrane after absorption or dissolution. Hydrogen and helium are permeated by the gap between polymer side chains as in the latter case, and water vapor and CO ₂ are absorbed or dissolved and transmitted through the inside of the membrane.

The initial gas separation process started for hydrogen separation (H ₂ / CO, H ₂ / CH ₄ ) and recovery, but now it is used in various fields such as nitrogen generation, oxygen enriched air production, hydrogen and volatile organic vapor recovery, .

In the case of separating carbon dioxide from flue gas by separation of the membrane by conventional techniques, there is a problem in that the recovery rate is low and an additional re-recovery process is required. Also, energy consumed by the system is also excessively high, .

Korean Registered Patent No. 10-1327337 (April 11, 2013) Korean Patent No. 10-1275685 (Jun. 11, 2013) Korean Patent Publication No. 10-1997-7006886 (December 1, 1997) Korean Patent No. 10-0324709 (Feb. 2, 2002)

In order to solve the problems of the related art as described above, it is an object of the present invention to provide a separation membrane system for recovering carbon dioxide contained in a combustion gas, which comprises separating carbon dioxide into a high concentration through a configuration of a multi- To provide a membrane system.

However, the objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a separation membrane system for recovering carbon dioxide in a combustion gas, comprising a first stage gas separation unit, a second stage gas separation unit and a third stage gas separation unit, wherein the first to third gas separation units comprise carbon dioxide, oxygen, A first-stage to third-stage compressor for introducing the mixed gas containing the mixed gas into the first and second stages, And a first to third separation membrane including a permeable portion through which the pressurized mixed gas flows and a component permeated through the permeable membrane of the introduced mixed gas is concentrated, and an exclusion portion through which the component that does not permeate the permeable membrane is concentrated, And a carbon dioxide concentrated gas flowing out of the permeate portion of the separation membrane is introduced into the compressor included in the gas separation portion at the next stage.

The separation membrane system according to the present invention includes a multi-stage gas separation unit for separating carbon dioxide at a high concentration from a mixed gas containing carbon dioxide, oxygen, and nitrogen, thereby separating and concentrating carbon dioxide at high efficiency from the combustion gas.

In addition, the separation membrane system according to the present invention includes a compressor and a separation membrane in the gas separation unit at each stage, separates the mixed gas from the separation membrane by the supply pressure through the compressor, and further, by the suction pressure generated by the compressor, The separation efficiency of the separation membrane included in the separation section can be increased.

In the separation membrane system according to the present invention, the pressure supplied to the separation membrane is kept constant by the compressor included in the gas separation section at each stage, and the carbon dioxide separation efficiency is increased by the suction pressure generated in the separation membrane. It is possible to provide a mixed gas in which carbon dioxide is concentrated even if a separating membrane having a small area is used as it goes to the rear end.

In addition, it can provide the effect of reducing greenhouse gas by removing carbon dioxide from combustion gas generated from thermal power plant, etc. and supply separated and concentrated carbon dioxide as raw materials for various industrial fields such as calcium carbonate synthesis, dry ice production, polymer production and formic acid production Thereby providing an effect that contributes to creation of added value.

FIG. 1 schematically shows the structure and flow of a separation membrane system for recovering carbon dioxide in a combustion gas according to an embodiment of the present invention. Referring to FIG.
FIG. 2 shows a configuration and a flow of a separation membrane system for recovering carbon dioxide in a combustion gas according to an embodiment of the present invention.

Before describing the present invention in detail, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention, which is defined solely by the appended claims. shall. All technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art unless otherwise stated.

Throughout this specification and claims, the word "comprise", "comprises", "comprising" means including a stated article, step or group of articles, and steps, , Step, or group of objects, or a group of steps.

On the contrary, the various embodiments of the present invention can be combined with any other embodiments as long as there is no clear counterpoint. Any feature that is specifically or advantageously indicated as being advantageous may be combined with any other feature or feature that is indicated as being preferred or advantageous. Hereinafter, embodiments of the present invention and effects thereof will be described with reference to the accompanying drawings.

In the case of a thermal power plant, the composition of the combustion gas discharged through the stack is 10 to 15% of carbon dioxide, 70 to 73% of nitrogen, 4 to 9% of oxygen, 9 to 11% of moisture, About 80 ppm or less of nitrogen oxide, and about 5 mg / Sm ³ of dust.

The present invention provides a separation membrane system capable of recovering carbon dioxide from a combustion gas having the above composition with high efficiency. The separation membrane system according to an embodiment of the present invention includes a pretreatment device for removing impurities except for carbon dioxide, nitrogen and oxygen from a combustion gas, and a gas separation device including a multistage gas separation part.

Mechanisms for separating gases using membranes can be explained by the dissolution-diffusion model. The gas permeation phenomenon in the polymer membrane is divided into two stages: (i) diffusion from the upper part (partial pressure relatively high at the boundary of the membrane) to the interface, (ii) relative adsorption of gas molecules to the polymer membrane, (iii) diffusion of gas into the polymer membrane, Desorption of gas at the permeate portion (relatively low partial pressure), and diffusion at the lower boundary surface to the outside.

The gas permeation rate in the membrane is determined by factors such as the kinetic diameter, the intimacy of the membrane as the membrane material, the permeability of the permeable gas, and the temperature of the gas. At this time, the membrane permeation rate of components constituting the pretreatment combustion gas in which impurities are removed, that is, the gas containing carbon dioxide, oxygen and nitrogen (hereinafter referred to as "mixed gas"), It is fast in order. Therefore, whenever the mixed gas passes through the multi-stage separation membrane including the permeate and the retentate, carbon dioxide having a relatively high permeation rate is concentrated at the permeate portion and nitrogen having a relatively low permeation rate is concentrated at the rejection portion So that a high concentration of carbon dioxide can be recovered from the final transmission portion.

1, a separation membrane system according to an embodiment of the present invention includes a pretreatment unit 10 for removing impurities except for carbon dioxide, oxygen, and nitrogen in a combustion gas, and a pretreatment unit 10 for removing carbon dioxide from a mixed gas containing carbon dioxide, Stage gas separation unit 20, a two-stage gas separation unit 30, and a three-stage gas separation unit 40, which are separated at high concentration.

As shown in FIG. 2, the first stage gas separator 20, the second stage gas separator 30 and the third stage gas separator 40 are respectively connected to compressors 21, 31 and 41 and separation membranes 23, 33 and 43 ). The first stage gas separator 20 includes a first stage compressor 21 and a first stage separator 23 and the second stage gas separator 30 includes a second stage compressor 31 and a second stage separator 33 Stage gas separator 40 includes a three-stage compressor 41 and a three-stage separator 43. The three-

Each of the separation membranes 23, 33, and 43 includes an elimination portion having a relatively high concentration of relatively high concentration of carbon dioxide and a relatively high concentration of nitrogen with a low permeation rate.

More specifically, in the separation membrane system according to an embodiment of the present invention, after the impurities are removed in the pretreatment unit 10, the mixed gas pressurized by the first stage compressor 21 is supplied to the inlet of the first separation membrane 23, The mixed gas in which the carbon dioxide is first concentrated in the permeate portion of the second step 23 is pressurized by the second stage compressor 31 and is supplied to the inlet of the second step separator 33. The mixed gas in which the carbon dioxide is secondarily condensed at the transmitting portion of the two-stage separating membrane 33 is pressurized by the three-stage compressor 41 and supplied to the inlet of the three-stage separating membrane 43, Concentration of carbon dioxide can be produced.

The combustion gas generated from a stack of a power plant, a steel mill, and an incinerator forms a negative pressure with a blower and is sent to the pretreatment unit 10. The pretreatment unit 10 includes a filter 11, a dryer 12 and an adsorption tower 13 to remove trace amounts of impurities such as acid gas, particulate matter, and moisture in the combustion gas.

The filter 11 is for removing particulate matter in the combustion gas and impurities and moisture are removed by an inertial impact action by an element having a filtration degree of 3 micron in the separator of the filter 11. The sintered metal element is formed by filling fine metal particles into a mold and heating them with an electric furnace so that only the contact portions between the particles are in close contact with each other to form a filtration layer having many fine holes , The filtering action of the combustion gas that flows in a straight line without flowing does not occur on the element surface but also on the inside, thereby removing moisture and particulate matter.

The dryer 12 is a device for forcibly cooling the combustion gas by a low-temperature refrigerant gas to condense and discharge moisture contained in the gas. The dew point of the combustion gas supplied to the dryer 12 varies depending on the magnitude of the load. The lower the temperature, the lower the flow rate, and the lower the ambient air temperature, the smaller the load, and the dew point becomes lower, the higher the pressure of the combustion gas, the lower the temperature. In the opposite case, however, the load is large and the dew point is high. When the temperature is the same, the water vapor contained in the gas per unit mass is decreased as the pressure is higher. When the pressure is the same, the lower the temperature is, the less. Further, when the ambient air temperature is low, the heat radiation effect from the condenser for liquefying the refrigerant gas used for cooling the combustion gas becomes high, and the same effect as that for reducing the load is obtained.

Depending on the composition of the incoming combustion gas, the adsorption tower 13 can be arranged in parallel so that the individual adsorption towers can be operated independently when the water content is low, and the multiple adsorption towers can be operated in parallel when the amount of water is large. The adsorption tower 13 is filled with an adsorbent in the lower gas supply line and the upper gas discharge line. The gas supplied to the lower part of the adsorption tower 13 is removed by the adsorbent filled in the adsorption tower 13, And the gas is discharged to the upper part.

The mixed gas from which impurities have been removed by the pretreatment unit 10 is sent to the first stage gas separation unit 20. The gas separator is composed of a compressor and a separator. The compressor is a device that provides a driving force for smooth separation of carbon dioxide, nitrogen, and oxygen in the mixed gas. The separator is a device for passing It is a device that separates by using speed difference.

The compressor has a structure in which a screw rotor having a screw structure of six compartments having a large twist at the center in the screw top and two gate rotors having eleven teeth each are engaged with the shaft. When the screw rotor in the center is rotated, The outer gas is sucked into the space of the groove and a single compression chamber is formed by the cylinder and the gate rotor. The teeth of the gate rotor move according to the rotation of the screw rotor, and the volume of the gap is reduced in the space of the opened groove. The compressed gas is discharged from the discharge port provided outside the pipe when the pressure is increased and the rotation further proceeds to increase the internal pressure to a predetermined pressure.

The gas pressurized by the compressor passes through the separation membrane, and the separation membrane includes a permeate having a relatively high concentration of the gas component having a high permeation rate and a retentate having a relatively high concentration of the gas component having a low permeation rate. As a by-product gas, the gas passing through the separation membrane maintains a pressure similar to the supply pressure, and the gas passing through the permeation section is decompressed as carbon dioxide is separated and concentrated, And flows into the gas separation section at the next stage at a low pressure.

The compressor provides a supply pressure to pressurize the condensed gas flowing out of the separator permeable portion of the gas separation portion at the front end to a pressure of 2 to 10 times the outlet pressure of the concentrated mixed gas to flow into the separator of the gas separation portion at the downstream. The mixed gas introduced into the separation membrane is decompressed while passing through the separation membrane. The mixture gas is introduced into the separation membrane at the downstream end after being pressurized by the compressor of the downstream gas separation unit by the supply pressure.

For example, the combustion gas is pressurized by the compressor at a supply pressure of 2 to 10 Bar · G and flows into the separation membrane at the downstream, and the mixed gas, which is concentrated through the permeation portion of the separation membrane, do. The decompressed mixed gas is again pressurized by the compressor included in the gas separation unit at the downstream stage at a supply pressure of 2 to 10 Bar G to be introduced into the downstream separation membrane.

More specifically, the mixed gas from which the impurities have been removed from the preprocessing unit 10 flows into the first stage compressor 21, and the mixed gas pressurized by the first stage compressor 21 flows into the inlet of the first stage separator 23 , The carbon dioxide in the mixed gas passes through the separator at a relatively high speed, is first concentrated in the permeate portion of the first separation membrane 23, and then flows into the second compressor 31. Nitrogen in the mixed gas can pass through the exclusion portion of the first separation membrane 23 or be transported to the chimney through the separation membrane system again without passing through the separation membrane due to the relatively slow velocity.

The separation membrane may be a separation membrane having a ground structure of an inner hollow portion, a micro pore of an intermediate layer, and a non-porous structure on the surface.

The mixed gas obtained through the first-stage separation membrane (23) in which the carbon dioxide is first concentrated contains carbon dioxide having a concentration of 35% or more.

The two-stage compressor 31 pressurizes the first concentrated gas mixture into the two-stage separator 33. At this time, the pressure of the two-stage compressor 31 causes the pressure of the carbon dioxide The separation efficiency is increased.

The first concentrated gas mixture having passed through the permeate portion of the first separation membrane 23 flows into the second stage compressor 31 at a pressure lower than the supply pressure to the first separation membrane 23, Is pressurized by the compressor (31) and flows into the inlet of the two-stage separation membrane (33).

Among the primarily concentrated mixed gas flowing into the inlet of the two-stage separation membrane 33, carbon dioxide passes through the separation membrane at a relatively high speed, is secondarily concentrated in the permeate portion of the two-stage separation membrane 33 and flows into the three- . Nitrogen in the first concentrated gas mixture can pass through the exclusion portion of the two-stage separation membrane 33 or be transported to the chimney and pass through the separation membrane system again because most of the nitrogen is not passed through the separation membrane due to the relatively slow velocity.

The mixed gas obtained through the two-stage separation membrane 33 with the carbon dioxide being secondarily concentrated contains carbon dioxide having a concentration of 70% or more.

The three-stage compressor 41 pressurizes the second-concentrated gas mixture into the three-stage separator 43. At this time, due to the suction pressure of the three-stage compressor 41, the carbon dioxide The separation efficiency is increased.

The secondarily concentrated mixed gas that has passed through the transmission portion of the two-stage separation membrane (33) flows into the three-stage compressor (41) at a pressure lower than the supply pressure to the two-stage separation membrane (33) And is pressurized by the compressor 41 to be introduced into the inlet of the three-stage separation membrane 43.

Among the second concentrated mixture gas flowing into the inlet of the three-stage separation membrane 43, carbon dioxide passes through the separation membrane at a relatively high speed and is thirdly concentrated in the permeate portion of the three-stage separation membrane 43 to generate more than 95% of carbon dioxide. Nitrogen in the second concentrated gas mixture can pass through the exclusion portion of the three-stage separation membrane 43 or be transported to the chimney and pass through the separation membrane system again because most of the nitrogen is not passed through the separation membrane at a relatively slow rate.

The separation efficiency of the carbon dioxide can be increased while reducing the membrane area by decreasing the membrane area as the mixed gas is separated and condensed as it goes through the first to third stages. More specifically, the area of the two-stage separation membrane (33) of the two-stage gas separation unit (30) is in the range of 10 to 50 times the area of the first separation membrane (23) %, And the area of the three-stage separation membrane 43 of the three-stage gas separation section 40 is 20 to 60% of the area of the two-stage separation membrane 23.

The pressure supplied to the separation membrane by the compressor included in the gas separation section at each stage is kept constant and the carbon dioxide separation efficiency is increased by the suction pressure generated in the front separation membrane. Therefore, even if the separation membrane It is possible to provide a mixed gas in which carbon dioxide is more concentrated.

The separation membrane is made of a separation membrane made of at least one selected from the group consisting of polysulfone, polyimide, and polyisophthalon.

The separation membrane system according to an embodiment of the present invention includes a control unit for controlling the flow rate of the exclusion part of the separation membrane included in the first stage gas separation unit 20, the second stage gas separation unit 30, and the third stage gas separation unit 40, (50).

The control unit 50 controls the flow rate of the exclusion portion of each of the first-stage separation membrane 23, the second-stage separation membrane 33, and the third-stage separation membrane 43 at a constant pressure to flow out to the permeation portion with respect to the flow rate of the mixed gas flowing into the separation membrane And the ratio of the flow rate of the mixed gas (stage-cut) is controlled.

More specifically, the control unit controls the ratio of the permeate flow rate to the flow rate of the mixed gas flowing into the first-stage separation membrane 23 to be in the range of 0.2 to 0.6, and controls the flow rate of the mixed gas flowing into the two- The ratio of the permeate flow rate is controlled to be in the range of 0.2 to 0.6, and the ratio of the permeate flow rate to the flow rate of the mixed gas flowing into the three-stage separation membrane 43 is controlled within the range of 0.4 to 0.7.

As the ratio of the flow rate of the permeate to the flow rate of the mixed gas flowing into the separation membrane at each stage becomes smaller within the above range, the concentration of carbon dioxide in the permeate permeate portion becomes higher. Further, when the respective membranes are controlled to exceed the above-mentioned ratio, the concentration of recovered carbon dioxide is lowered.

Example

A first simulated gas of the combustion gas was produced to evaluate the membrane performance of the membrane system 100a according to an embodiment of the present invention. The composition of the first simulated gas was 10 to 15% of carbon dioxide, 70 to 73% of nitrogen, and 4 to 9% of oxygen.

The first simulated gas was introduced into the first separation membrane at a pressure of 7 Bar ∘ G through a regulator and separated into an exclusion section and a permeation section of the first separation membrane. Table 1 shows the concentrations of carbon dioxide, oxygen and nitrogen in the exclusion portion and the permeation portion of the first-stage separation membrane obtained by controlling the stage-cut.

No. 1 ^st membrane
in-flow rate (LPM) 1 ^st Permeate
out-flow rate (LPM) 1 ^st Retentate Conc. (%) 1 ^st Permeate Conc. (%) CO ₂ O ₂ N ₂ CO ₂ O ₂ N ₂ 1-1 101 13.0 7.03 6.21 86.75 46.70 11.24 42.06 1-2 73 13.0 4.85 5.91 89.25 45.80 11.26 42.94 1-3 63 13.0 3.91 5.67 90.42 43.80 11.42 44.78 1-4 53 13.0 2.86 5.31 91.83 40.70 11.62 47.68 1-5 43 13.0 1.24 4.76 94.00 37.30 11.70 51.00

The first simulated gas was prepared from the gas composition (No. 1-1) passed through the permeate of the first separator membrane and the second simulated gas was introduced into the second separator membrane at a pressure of 7 Bar · G, And separated into permeable parts. Table 2 shows the concentration of carbon dioxide, oxygen and nitrogen in the exclusion portion and the permeation portion of the two-stage separation membrane obtained by controlling the stage-cut.

No. 2 ^nd Membrane
in-flow rate (LPM) 2 ^nd permeate
out-flow rate (LPM) 2 ^nd Retentate Conc. (%) 2 ^nd Permeate Conc. (%) CO ₂ O ₂ N ₂ CO ₂ O ₂ N ₂ 2-1 115 5.8 23.14 11.04 65.82 86.30 6.03 7.67 2-2 89 6.6 17.54 11.36 71.10 85.30 6.35 8.35 2-3 79 6.9 14.29 11.45 74.27 83.30 6.77 9.93 2-4 68 7.0 11.07 11.28 77.64 8040 7.51 12.09 2-5 56 7.0 6.88 11.14 81.98 77.47 8.10 14.50 2-6 44 7.0 2.32 10.32 87.36 70.70 9.24 20.06

The second simulated gas was prepared from the gas composition (No. 2-1) passed through the permeate portion of the two-stage separator membrane and the third simulated gas was introduced into the third-stage separator at a pressure of 7 Bar · G, And the permeable part. Table 3 shows the concentrations of carbon dioxide, oxygen and nitrogen in the exclusion portion and the permeation portion of the three-stage separation membrane obtained by controlling the stage-cut.

No. 3 ^rd Membrane
in-flow rate (LPM) 3 ^rd Permeate
out-flow rate (LPM) 3 ^rd Retentate Conc. (%) 3 ^rd Permeate Conc. (%) CO ₂ O ₂ N ₂ CO ₂ O ₂ N ₂ 3-1 113 5.9 49.84 12.58 37.58 95.64 4.36 0.00 3-2 98 6.8 44.37 13.31 42.33 95.31 4.69 0.00 3-3 88 7.1 39.16 13.82 47.02 94.85 5.15 0.00 3-4 76 7.0 32.74 14.30 52.96 94.26 5.74 0.00

As shown in Tables 1 to 3, it can be seen that as the stage-cut becomes smaller, the concentration of carbon dioxide in the permeate increases, and in the case of the first stage membrane, the concentration of carbon dioxide becomes higher than 35% 70% or more, and 95% or more in the case of the three-stage separation membrane, thereby producing concentrated carbon dioxide at a high concentration.

The features, structures, effects, and the like illustrated in the above-described embodiments can be combined and modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

100: Membrane system
10:
11: Filter
12: Dryer
13: Adsorption tower
20: First stage gas separation unit
21: 1 stage compressor
23: 1 short separation membrane
30: Second stage gas separation unit
31: Two-stage compressor
33: two-stage separation membrane
40: Third stage gas separation unit
41: Three-stage compressor
43: triple separation membrane
50:

Claims (7)

A separation membrane system for recovering carbon dioxide in a combustion gas, including a first stage gas separation section, a second stage gas separation section, and a third stage gas separation section,
Stage gas separation unit,
A first-stage to third-stage compressor into which a mixed gas containing carbon dioxide, oxygen and nitrogen is introduced and which flows out by pressurizing the introduced mixed gas at a supply pressure; And
A first through third separation membranes including a permeate portion into which the pressurized mixed gas is introduced and a component permeated through the separation membrane of the introduced mixed gas are concentrated and an exclusion portion through which components that can not permeate the separation membrane are concentrated,
Wherein a mixed gas of carbon dioxide concentrated from the permeate portion of the separation membrane flows into a compressor included in a gas separation unit of the next stage.
The method according to claim 1,
The membrane area of the two-stage separation membrane is 10 to 50% of the area of the first separation membrane,
Wherein the membrane area of the three-stage separation membrane is 20 to 60% of the area of the two-stage separation membrane.
The method according to claim 1,
The separation membrane system further includes a controller for controlling the flow rate of the mixed gas flowing out to the permeate portion with respect to the flow rate of the mixed gas flowing into the separation membrane by controlling the flow rate of the exclusion portion of each of the first to third separation membranes,
Wherein the control unit controls the ratio of the flow rate of the permeate to the flow rate of the mixed gas flowing into the first stage separation membrane to be in the range of 0.2 to 0.6 and the ratio of the flow rate of the permeate to the flow rate of the mixed gas flowing into the two- 0.6, and the ratio of the permeate flow rate to the flow rate of the mixed gas flowing into the three-stage separation membrane is controlled within the range of 0.4 to 0.7.
The method according to claim 1,
Wherein the first-stage to third-stage compressors pressurize the introduced mixed gas at a supply pressure of 2 to 10 Bar-G to flow out.
The method according to claim 1,
Wherein the first to third separation membranes are formed of at least one selected from the group consisting of polysulfone, polyimide, and polyisophthalon.
The method according to claim 1,
And a pretreatment unit for introducing a combustion gas containing carbon dioxide, oxygen, nitrogen and impurities into the first stage compressor, and removing impurities from the combustion gas to discharge a mixed gas containing carbon dioxide, oxygen and nitrogen into the first stage compressor system.
The method according to claim 6,
Wherein the pretreatment unit comprises a filter, a dryer, and an adsorption column for removing impurities including particulate matter and moisture in the combustion gas.

Images