KR20150027967A - apparatus for recovering carbon dioxide of bio-gas - Google Patents

Abstract

The present invention relates to an apparatus for recovering carbon dioxide of bio-gas, which separates carbon dioxide from bio-gas by using a gas separation membrane unit. Accordingly, the apparatus for recovering carbon dioxide can separate and recover carbon dioxide at a high purity while minimizing the methane loss from bio-gas. The apparatus for recovering carbon dioxide from bio-gas comprises a compressor for compressing purified bio-gas; a buffer tank for storing the compressed bio-gas from the compressor; and a gas separation membrane unit for separating carbon dioxide and methane by passing the bio-gas supplied from the buffer tank through a hollow fiber membrane binder.

Description

[0001] The present invention relates to an apparatus for recovering carbon dioxide from bio-

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biogas carbon dioxide recovery apparatus, and more particularly, to a biogas carbon dioxide recovery apparatus capable of separating and recovering high purity carbon dioxide having a small methane content from biogas.

Recently, interest in biogas has been rising in the renewable energy sector due to the prohibition of marine dumping of organic waste.

Biogas is obtained by introducing organic wastes with high biomass content such as livestock manure, food waste, and wastewater sludge into the fermentation tank and anaerobically digesting them with methanogenic microorganisms.

The biogas thus obtained is purified by removing hydrogen sulfide, siloxane and moisture, and then the carbon dioxide is removed through the solidification process to produce methane gas of high purity and used as a clean fuel.

As a process for separating carbon dioxide from a raw material gas containing methane and carbon dioxide and concentrating methane, absorption and adsorption methods are mainly used.

As an example of the absorption method, Korean Patent Laid-Open No. 10-2012-0013588 discloses a method in which a combustion gas is supplied to an absorber containing an absorbent (e.g., a monoethanolamine aqueous solution) to absorb carbon dioxide into the absorbent through a carbon dioxide absorption reaction to concentrate methane (Wet ammine method).

As an example of the adsorption method, Korean Patent Laid-Open Publication No. 10-2012-0083220 discloses a technique of introducing biogas into an adsorption column filled with an adsorbent and separating carbon dioxide by pressure swing adsorption to concentrate methane .

The conventional technology as described above has a problem that the installation area of the equipment for performing the process is large, the facility operation maintenance cost is high, and the phase change is accompanied by the gas separation, which is inefficient in terms of energy consumption.

In addition, as described above, the conventional technology aims at producing high purity methane having high value, and carbon dioxide is recognized as an impurity. Since carbon dioxide separated from the methane-based biogas separation and solidification system contains a large amount Methane is contained therein and there is no utilization site, so that it is discharged into the atmosphere.

Since the separated carbon dioxide contains a large amount of methane, methane is lost from the viewpoint of methane production.

That is, there has been no technology for recovering high purity carbon dioxide from biogas.

Accordingly, the present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a biogas carbon dioxide recovery device capable of separating and recovering high purity carbon dioxide from biogas using a small- There is a purpose.

According to an aspect of the present invention, there is provided a biosensor comprising: a compressor for compressing purified biogas; a buffer tank for storing biogas compressed by the compressor; and a biogas supplied from the buffer tank through a hollow fiber membrane assembly And a gas separator unit for separating carbon dioxide and methane.

The gas separation membrane module according to claim 1, wherein the gas separation membrane unit comprises a casing having a closed space formed outside thereof and having a carbon dioxide exhaust port formed on a side surface thereof, the hollow fiber membrane assembly incorporated in the casing, a front cover provided on a front end of the casing, And a rear cover provided at a rear end of the front cover and formed with a methane discharge port.

And another gas separation membrane unit having the same structure is further provided behind the gas separation membrane unit.

A methane discharge pipe connected to the methane discharge port of the gas separator unit connected to the gas separator unit is connected to the gas discharge port of the gas separator unit installed in front of the gas supply port of the additional gas separator unit, And a carbon dioxide exhaust pipe connected to the carbon dioxide exhaust port of the installed gas separation membrane unit.

And a compressor is installed in front of and behind the additional gas separation membrane unit.

And a heating unit is installed in the gas separation membrane units.

And a cooling system is installed in the gas separation membrane units.

The gas separation membrane unit located behind the gas separation membrane units is characterized in that the membrane area of the hollow fiber membrane assembly is reduced by 30% to 70% as compared to the gas separation membrane unit located at the front.

As described above, according to the present invention, carbon dioxide can be separated from the biogas by using the selective gas permeation principle of the hollow fiber membrane assembly.

Therefore, it is possible to separate high-purity carbon dioxide which can be practically used from the biogas, and there is no loss of methane at this time, so that the recovery rate of methane can be improved.

Separately produced high-purity carbon dioxide can be used for the growth of crops in vegetable growing houses, for the production of dry ice used as a freezing agent, and for the production of fire extinguishers for fire fighting.

In addition, the carbon dioxide and methane separation equipment using the gas separation membrane unit is simpler in construction and smaller in size than the separation facility using the conventional absorption method and adsorption method, so that the installation area is small and the cost And the energy efficiency is improved because the phase change does not accompany the separation of carbon dioxide and methane.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of an apparatus for recovering a biogas carbon dioxide according to a first embodiment of the present invention; FIG.
2 is a configuration diagram of a gas separation membrane unit which is a constitution of the present invention.
3 is a sectional view taken along the line AA in Fig.
4 and 5 show a second embodiment of the present invention, wherein FIG. 4 shows a configuration in which a compressor is installed in front of a second gas separation membrane unit, FIG. 5 shows a configuration in which a compressor is installed behind a second gas separation membrane unit Fig.
6 and 7 show a third embodiment of the present invention. FIG. 6 shows a configuration in which a compressor is installed in front of a third gas separation membrane unit. FIG. 7 shows a configuration in which a compressor is installed in the rear of the third gas separation membrane unit. Fig.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. The thicknesses of the lines and the sizes of the components shown in the accompanying drawings may be exaggerated for clarity and convenience of explanation.

In addition, the terms described below are defined in consideration of the functions of the present invention, and these may vary depending on the intention of the user, the operator, or the precedent. Therefore, definitions of these terms should be made based on the contents throughout this specification.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram of a carbon dioxide recovery device for a biogas according to a first embodiment of the present invention. As shown in the figure, the first gas separation membrane unit 21 is connected to the biogas supply pipe 11, the first methane discharge pipe 12 is connected to the rear end of the first gas separation membrane unit 21, A first carbon dioxide exhaust pipe (13) is connected to the side surface of the unit (21).

The biogas supply pipe 11 is supplied with purified biogas from which hydrogen sulfide, siloxane gas and other impurities are removed.

The biogas supply pipe 11 is provided with a compressor 31 for compressing and supplying the biogas and a buffer tank 41 for temporarily storing the biogas between the compressor 31 and the first gas separation membrane unit 21, Respectively. By storing the biogas in the buffer tank 41 in this manner, the first gas separation membrane unit 21 can stably supply the biogas without abrupt change in the flow rate.

Another compressor (32) is installed in the first carbon dioxide discharge pipe (13) connected to the side of the first gas separation membrane unit (21).

Valves 51 and 52 for opening and closing the pipeline and controlling the flow rate are provided in the first methane discharge pipe 12 connected to the rear end of the buffer tank 41 of the biogas supply pipe 11 and the rear end of the first gasket separator unit 21 Respectively.

2, the first gasket separating unit 21 includes a casing 21a which is formed in a cylindrical shape and forms a closed space with respect to the outside and has a carbon dioxide discharge port 21aa formed on the side thereof, A front cover 21c formed at the front end of the casing 21a and formed with a gas supply port 21ca and a rear cover 21c formed at the rear end of the casing 21a, And a rear cover 21d provided with a methane discharge port 21da.

A first methane discharge pipe 12 is connected to the methane discharge port 21da and a first carbon dioxide discharge pipe 13 is connected to the carbon dioxide discharge port 21aa, Lt; / RTI >

As shown in FIG. 3, the hollow fiber membrane bundle 21b is formed by joining a large number of hollow fiber membranes having an outer diameter of several hundreds of micrometers (.mu.m) or less, and is easily embedded in the cylindrical casing 21a As shown in FIG.

A space is formed between the both side covers (the front cover 21c and the rear cover 21d) and both side ends of the hollow fiber membrane assembly 21b (the end of the hollow fiber membrane assembly 21b is not in close contact with the cover) Can be smoothly introduced into the hollow fiber membrane at the outer portion of the hollow fiber membrane assembly 21b and the methane passing through the hollow fiber membrane at the outer portion can be smoothly discharged to the methane discharge port 21da.

The hollow fiber membrane constituting the hollow fiber membrane bundle 21b has selective gas permeability. When the biogas passes through the individual hollow fiber membrane, the carbon dioxide is rapidly transmitted in the radial direction of the hollow fiber membrane and the methane is transmitted very slowly. As a result, the carbon dioxide permeates the radial direction of the hollow fiber membrane and is discharged, and methane is discharged in the longitudinal direction of the hollow fiber membrane through the inner hollow fiber membrane. Such movement of the gas is performed in the same manner in the entire hollow fiber membrane assembly 21b.

Accordingly, when the biogas flows into the gas separation membrane unit 21 through the gas supply port 21ca, the carbon dioxide permeates the hollow fiber membrane assembly 21b in the radial direction and is discharged through the carbon dioxide discharge port 21aa, Methane passes through the hollow fiber membrane assembly 21b in the longitudinal direction and is discharged through the methane discharge port 21da. Through the above process, carbon dioxide and methane are separated from the first gas separation membrane unit 21.

In order to increase the purity of the carbon dioxide gas separated and discharged from methane in the first gas separation membrane unit 21, as in the second embodiment shown in FIG. 4, the first gas separation membrane unit 21 is provided at the rear of the first gas separation membrane unit 21 The second gas separation membrane unit 22 may be additionally provided.

The configuration of the second gas separation membrane unit 22 is the same as that of the first gas separation membrane unit 21 described above. However, the membrane area (hollow fiber outer diameter x hollow fiber length x hollow fiber strand count) of the hollow fiber membrane assembly of the second gas separation membrane unit 22 is preferably 30% to 30% of the membrane area of the hollow fiber membrane assembly of the first gas separation membrane unit 21, (The configuration of the third gas separation membrane unit 23 to be described later is also the same as that of the first and second gas separation membrane units 21 and 22. The configuration of the third gas separation membrane unit 23, Is reduced to 30% to 70% of the membrane area of the second gas separation membrane unit 22).

This is because the amount of carbon dioxide separated from the first gas separation membrane unit 21 is 30% to 70% of the amount of the biogas supply, so that the membrane area of the hollow fiber membrane assembly of the second gas separation membrane unit 22 is reduced in proportion to the amount It is economical.

The first carbon dioxide discharge pipe 13 is connected to the gas supply port of the second gas separation membrane unit 22 and the methane discharge port of the second gas separation membrane unit 22 is connected to the second methane discharge pipe 14, The methane discharge pipe (14) is connected to the first methane discharge pipe (12).

A second carbon dioxide discharge pipe (15) is connected to the carbon dioxide discharge port provided on the side surface of the second gas separation membrane unit (22). Therefore, the carbon dioxide gas firstly separated and discharged from the first gas separation membrane unit 21 is supplied to the second gas separation membrane unit 22 through the first carbon dioxide discharge pipe 13, The separation process separates the carbon dioxide and methane.

The carbon dioxide separated from the second gas separation membrane unit 22 is discharged to the second carbon dioxide discharge pipe 15 and the methane is discharged to the second methane discharge pipe 14 and discharged through the first methane discharge pipe 12, Mixed with gas and discharged.

Table 2 below shows the concentration of carbon dioxide and the recovery rate of methane when the two gas separation membrane units 21 and 22 are installed as described above.

As shown in Table 1, the carbon dioxide gas separated and discharged through the second gas separation membrane unit 22 (Stage 2) under the condition that the total stage cut (factor representing the ratio of the carbon dioxide permeation amount to the biogas supply amount) is 0.14, Is 96.0% and has a concentration of 95% or more. In this case, the recovery efficiency of methane was 99.05%, which is very high, more than 99%.

As described above, according to the present invention, it is possible to separate and produce carbon dioxide having a purity of 95% or more from the biogas. Therefore, such high-purity carbon dioxide can be used for the purpose of promoting the growth of crops by supplying the greenhouse for growing crops.

In addition, when the high-purity carbon dioxide is separated as described above, the loss of methane is minimized and, as described above, a high methane recovery rate of 99% or more can be achieved.

On the other hand, in the second embodiment, as shown in Figs. 4 and 5, the compressor 32 can be installed in front of or behind the second gas separation membrane unit 22. Fig.

Since the gas separator unit moves and separates the gas by the partial pressure difference formed by the boundary of the hollow fiber membrane, the supply gas can be pushed when the compressor 32 is placed in front of the gas separator unit as shown in FIG. 4, The separated gas can be drawn out. In both cases, the gas separation using the hollow fiber membrane assembly can be smoothly performed. However, when the compressor 32 is placed on the rear side of the gas separation membrane unit, there is an advantage that the separated carbon dioxide gas can be prevented from flowing backward and the carbon dioxide can be easily discharged from the gas separation membrane unit.

Also in the case of the second embodiment, the valve 53 is provided in the second methane discharge pipe 14.

According to the third embodiment of the present invention, as shown in FIGS. 6 and 7, a third gas separation membrane unit 23 may be additionally installed behind the second gas separation membrane unit 22. That is, the second carbon dioxide discharge pipe 15 is connected to the gas supply port of the third gas separation membrane unit 23, the third methane discharge pipe 16 is connected to the methane discharge port of the third gas separation membrane unit 23, A third methane discharge pipe 16 is connected to the first methane discharge pipe 12 and a third carbon dioxide discharge pipe 17 is connected to the carbon dioxide discharge port of the third gas separation membrane unit 23. [ A valve 54 may be provided in the third methane discharge pipe 16.

 The carbon dioxide concentration and the recovery rate of methane when the three gas separation membrane units 21, 22, and 23 are installed as described above are shown in Table 2 below.

As shown in Table 2, the concentration of the carbon dioxide gas separated and discharged through the third gas separation membrane unit 23 (Stage 3) was 98.7% under the condition that the total stage cut was 0.26, . In this case, the recovery efficiency of methane was 99.45%, which was very high, exceeding 99%.

Also in the case of the third gas separation membrane unit 23, it is preferable to reduce the membrane area of the hollow fiber membrane assembly by 30% to 70% as compared with the second gas separation membrane unit 22. The reason for this is the same as the reason for reducing the membrane area of the second gas separation membrane unit 22 described above with respect to the membrane area of the first gas separation membrane unit 21. [

On the other hand, when the number of the gas separation membrane units is further increased, a larger amount of carbon dioxide can be separated. However, considering that the amount of carbon dioxide originally contained in the biogas is about 30% to 40%, it is not practical to put more than three gas separator units in excess of three, and it is not economically preferable.

On the other hand, although it is not shown in the drawing, it is preferable to install the heating and cooling equipment in each gas separation membrane unit.

Since the gas separation performance of the gas separation membrane unit is affected by the temperature, it is necessary to maintain the temperature of the gas to be separated, that is, the biogas, at a constant level in order to maintain the gas separation performance of the gas separation membrane unit at a constant level. However, since the biogas contains a large amount of methane, it may be dangerous to heat the gas itself, so it is safe to control the temperature of the gas separation membrane unit. Therefore, it is preferable to install the heating and cooling equipment in the gas separation membrane unit as described above.

The gas separation performance of the gas separation membrane unit can be maintained at a constant level by installing the heating device and the cooling device in the gas separation membrane unit, so that the production amount of the high purity carbon dioxide can be easily managed.

On the other hand, even when the third gas separation membrane unit 23 is provided, the compressor 33 can be installed in front of or behind the third gas separation membrane unit 23. [ The effect of each case is the same as in the case of the second gas separation membrane unit 22, and redundant description will be omitted.

The present invention as described above has an effect of significantly reducing the size and installation area of a facility compared to a facility using a conventional adsorption tower or the like because the facility is constructed using the gas separation membrane unit.

Further, since the gas separation membrane unit is formed in a tubular shape, it is possible to easily arrange the facilities and to simplify the layout.

Further, in separating carbon dioxide and methane from the biogas, since the target substance exists only in a gaseous state throughout the apparatus and does not cause a phase change, energy consumption due to the phase change does not occur, thereby improving the energy efficiency of the apparatus.

Also, since the high purity carbon dioxide is separated from the biogas by using the plurality of gas separation membrane units, the amount of methane contained in the carbon dioxide gas is minimized, resulting in a decrease in the methane loss rate, thereby improving the methane recovery rate.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is understandable. Accordingly, the true scope of the present invention should be determined by the following claims.

11: Biogas feed pipe 12: First methane feed pipe
13: First carbon dioxide discharge pipe 14: Second methane discharge pipe
15: second carbon dioxide discharge pipe 16: third methane discharge pipe
17: third carbon dioxide discharge pipe 21: first gas separation unit
22: second gas separator unit 23: third gas separator unit
31, 32, 33: compressor 41: buffer tank

Claims (8)

A compressor for compressing the purified biogas;
A buffer tank for storing biogas compressed by the compressor;
A gas separation membrane unit for passing the biogas supplied from the buffer tank through a hollow fiber membrane assembly to separate carbon dioxide and methane;
Wherein the biogas carbon dioxide recovery device comprises: The method according to claim 1,
The gas separation membrane module according to claim 1, wherein the gas separation membrane unit comprises a casing having a closed space formed outside thereof and having a carbon dioxide exhaust port formed on a side surface thereof, the hollow fiber membrane assembly incorporated in the casing, a front cover provided on a front end of the casing, And a rear cover provided at a rear end of the main cover and formed with a methane discharge port. The method according to claim 1,
And another gas separation membrane unit having the same structure is further installed behind the gas separation membrane unit. The method of claim 3,
A methane discharge pipe connected to the methane discharge port of the gas separator unit connected to the gas separator unit is connected to the gas discharge port of the gas separator unit installed in front of the gas supply port of the additional gas separator unit, And a carbon dioxide discharge pipe is connected to the carbon dioxide discharge port of the installed gas separation membrane unit. The method of claim 3,
And a compressor is installed in front of and behind the additional gas separation membrane unit. The method of claim 3,
And a heating unit is installed in the gas separation membrane units. The method of claim 3,
And a cooling system is installed in the gas separation membrane units. The method of claim 3,
Wherein the gas separation membrane unit located at the rear of the gas separation membrane units has a membrane area of 30% to 70% smaller than that of the gas separation membrane unit located at the front.

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