KR100324709B1 - Pressure Swing Adsorption System for Highly Concentrated Carbon Dioxide Recovery from Power Plant Flue Gas and Recovery Method Using thereof - Google Patents

Abstract

The present invention relates to a pressure swing adsorption device (PSA) for recovering high purity carbon dioxide from a combustion power plant combustion gas and a method for recovering high purity carbon dioxide (CO ₂ ) using the same. In the present invention, a process for recovering carbon dioxide from the combustion gas of a thermal power plant using activated carbon as an adsorbent was developed, and a pressure swing adsorption system was implemented as an adsorption tower, a vacuum pump, a branch pipe, a pressure control valve, a flow control valve, and a product storage tank. By using this apparatus, high-purity carbon dioxide can be recovered by performing a circulation operation of cocurrent depressurization, pressure equalization, washing with a product, and vacuum desorption.

Description

Pressure swing adsorption system and CO2 recovery method for recovering high purity carbon dioxide from thermal power plant combustion gas {Pressure Swing Adsorption System for Highly Concentrated Carbon Dioxide Recovery from Power Plant Flue Gas and Recovery Method Using

The present invention relates to a pressure swing adsorption device (PSA) for recovering high purity carbon dioxide from a combustion power plant combustion gas and a method for recovering high purity carbon dioxide (CO ₂ ) using the same.

Combustion gases from coal-fired power plants contain about 12-17% carbon dioxide, 76-78% nitrogen, 4-5% oxygen and other traces of moisture, SOx and NOx compounds. In particular, since carbon dioxide is regarded as a major cause of global warming, the reduction of its emission and reuse is emerging as a global concern. Some developed countries are trying to freeze carbon dioxide emissions based on their emissions at some point, and insist on introducing carbon taxes. Therefore, the recovery of carbon dioxide from the combustion power of the thermal power plant, one of the largest emission sources of carbon dioxide is an important problem to be solved urgently.

Plants that emit carbon dioxide include steel plants, cement plants, petrochemical plants, and fermentation plants, and most of the plants except for thermal power plants emit 25% or more of carbon dioxide. On the other hand, thermal power plants are known to have low economical efficiency when commercialized due to the low concentration of carbon dioxide.

Conventionally, the separation of the mixed gas mainly uses absorption, membrane separation, and adsorption processes. Among them, the pressure swing adsorption process using the adsorption principle is small and medium-sized, which requires less investment and energy costs. Has been repeated. The characteristic of pressure swing adsorption process is that the adsorption and desorption are repeated while changing the pressure by separating the gas mixture by using the property that the adsorption agent adsorbing a specific substance is higher than the adsorption amount at low pressure. It is about 30 years since it was established as a process for adsorption.

Since the first development by Finlayson et al. (UK Patent No. 365,092) in the 1930s, research has continued, and in the 1950s it was introduced that carbon dioxide, hydrocarbons and water can be separated from air, and zeolites in the late 1950s. Adsorption separation technology has developed significantly. Until now, the pressure swing adsorption process has been mainly applied to the separation of weakly adsorbable components such as gas drying, air separation, and hydrogen purification, but recently, process development research aimed at separating strong components such as methane, carbon dioxide, and sulfur dioxide. It is actively underway.

In this case, the recovery of the product, which is a strong adsorption component, is carried out in a desorption step, particularly in a vacuum step, and a vacuum desorption step is necessary because the pressure swing adsorption process recovers carbon dioxide having strong adsorption capacity from the combustion gas. The first process to obtain the product by vacuum desorption was developed by Guerin de Montgareuil, France, and the like (French Patent No. 1,233,261) and is still widely used as a method of separating components having high adsorption capacity.

As a conventional technique, a method of separating carbon dioxide using a pressure swing adsorption process is mainly a method of separating methane and carbon dioxide from natural gas (US Patent Nos. 5,411,721, 4,857,083), and a method of separating hydrogen and carbon dioxide (US Patent No. 4,791,858, 4,913,709), a method for separating carbon dioxide from ammonia synthesis gas (US Pat. No. 4,813,980), a method for removing water and carbon dioxide from air (US Pat. No. 4,249,915), or hydrogen discharged from a gasification process of coal. , And methods for separating mixed gases such as methane and carbon dioxide (US Pat. Nos. 4,406,674, 4,404,004, 4,914,218, 4,814,456, 4,696,680, 5,582,029, and British Patent 2,155,805).

In addition, U.S. Patent No. 4,988,490 discloses a method of obtaining high purity nitrogen as a product of a mixture of carbon dioxide and nitrogen as a main component, and German Patent No. 3,345,379 (1983/12/15) uses a four- tower pressure swing adsorption system. The process of separating carbon dioxide from mixed gas was presented, but they used four adsorption towers to separate carbon dioxide and carbon molecules as adsorbent. Carbon molecules or zeolites are considerably more expensive than activated carbon and have higher heat treatment temperature at the beginning of the operation. There is a disadvantage in that the cost of equipment is large.

The present invention is based on the existing four steps of pressure, adsorption, decompression, vacuum desorption using activated carbon as an adsorbent to recover carbon dioxide, which has a strong adsorption capacity, the effect of the direction of the decompression step, the amount of carbon dioxide lost in the decompression step In order to reduce the pressure, the pressure equalization step and the adsorption step are carried out through a combination of steps to improve the performance, taking into account the effects of the pressure equalization step and the cleaning step using the high-purity product recovered in the vacuum step to increase the purity. It provides an optimum process and pressure swing adsorption device to recover the carbon dioxide in the vacuum step through.

The present invention is to recover the carbon dioxide in the combustion gas of the thermal power plant, it is configured to be operated by a pressure swing adsorption device consisting of three adsorption tower and one vacuum pump to obtain high purity carbon dioxide.

The present invention comprises a pressurizing step of pressurizing the adsorption tower to a working pressure with a raw material gas introduced; An adsorption step of adsorbing carbon dioxide in the raw material gas by activated carbon in an adsorption column maintained at a constant pressure; A cocurrent decompression step of lowering the pressure from the working pressure to the normal pressure inside the adsorption tower; A cocurrent pressure reducing pressure equalizing step of connecting the adsorption tower of adsorption completed with the adsorption tower of desorption until equilibrium is achieved; A constant pressure pressurizing pressure equalizing step of connecting the adsorption tower in the desorption state to the adsorption tower in the adsorption state; After the pressure equalization step is completed, the cocurrent pressurization step by the product for pressurizing the inside of the adsorption tower to the atmospheric pressure using the product mostly carbon dioxide; A washing step using a product such that only carbon dioxide is present in the adsorption tower; After the cleaning is completed, the carbon dioxide is desorbed and recovered by using a vacuum pump in the adsorption tower, and is characterized in that the carbon dioxide in the exhaust gas of the thermal power plant is recovered.

1 is a block diagram of an apparatus of the present invention

2 is a process diagram for operating the device of the present invention;

Figure 3 is a diagram showing the pressure change according to the circulation operation of the apparatus of the present invention

Figure 4 is a chart comparing the efficiency according to the method of the present invention and the conventional method

<Description of Symbols for Major Parts of Drawings>

1, 2, 3: adsorption tower 4: vacuum pump

5, 6, 7, 8, 9, 10: branch pipes 11 to 16: automatic opening and closing valves

21 to 26: automatic open / close valve 31 to 36: automatic open / close valve

41: pressure regulating valve 42, 43: flow regulating valve

51: product storage tank 110: pressurization step

120: adsorption step 130: cocurrent decompression step

140: cocurrent decompression type pressure equalization step 150: cocurrent decompression step by product

160: washing step using the product 170: vacuum desorption step

180: countercurrent pressure type pressure equalization step 200: product flow stop step

In order to compose the pressure fluctuation adsorption process, the first consideration should be to understand the isothermal adsorption characteristics of each pure gas and to configure the process in the necessary steps. According to the equilibrium adsorption isotherm at each temperature for activated carbon of nitrogen and carbon dioxide, the amount of nitrogen adsorption is relatively small but negligible compared to carbon dioxide, which affects the purity, which makes it difficult to recover carbon dioxide using activated carbon. Act as a factor. In particular, in the case of the combustion gas of the thermal power plant, which is the object of the present invention, since nitrogen occupies most of the raw material gas, the amount of adsorbed carbon in the activated carbon is relatively high, so that a large amount of nitrogen is present in the adsorption column after the adsorption is completed. It is to lower the purity, and in order to recover high-purity carbon dioxide, it is important to prioritize the desorption of nitrogen. Therefore, as the concentration of carbon dioxide in the adsorption tower is increased immediately before the desorption step in the process configuration, high purity carbon dioxide can be obtained, which is greatly affected by the performance of the decompression step. In the present invention, in order to examine these effects, the processes are configured according to a combination of various steps in which the decompression direction and the depressurization step are modified. In addition, the purity of the carbon dioxide recovery was improved by introducing a washing step as a method for substituting nitrogen in the column with carbon dioxide.

In the present invention, the purity, recovery and reflux ratio were used as three criteria to show the performance of the process. Recovery is defined as the amount of the desired component included in the product stream divided by the amount of the same component in the feed mixture. However, when the washing step is introduced, it is calculated by excluding the amount of the desired component to be refluxed. Here, the reflux ratio is defined as a value obtained by dividing the amount of the target component used in the washing step by the amount of the recovered target component. Purity was also defined as the average concentration of feed components present in the recovered stream.

The direction of the gas flow of the present invention is the direction from the bottom of the tower to the top where the co-current is the flow direction of the raw material gas, and the countercurrent is the direction from the top to the bottom of the tower. Each process is the first step: pressurization step 110, the second step: adsorption step 120, the third step: cocurrent decompression step 130, the fourth step: cocurrent decompression type pressure equalization step 140, Step 5: cocurrent pressurization step 150 with the product, step 6: washing step 160 using the product, step 7: vacuum desorption step 170, step 8: countercurrent pressure type pressure equalization step 180 It is divided into eight steps, and will be described in detail below.

In the pressurization step 110 of the first step, the adsorption towers 1, 2, and 3 are pressurized to the working pressure with the raw material gas introduced. The raw material gas is a combustion power plant with combustion power of nitrogen, carbon dioxide, oxygen and moisture, and trace amounts. Includes SOx and NOx. The working pressure may be any pressure of 1 atm or more, and in the present invention, a pressure of 1.5 atm or less is most suitable in view of the reduction of operating cost required for pressurization, and the pressurization time is determined by the flow rate of the gas to be introduced. The more, the shorter the pressurization time.

In the adsorption step 120 of the second step, the raw material gas is continuously introduced from the downward direction upwards to the adsorption towers 1, 2 and 3 in which the constant pressure is maintained in the pressurization step 110. In the present invention, it is important to sufficiently maintain the adsorption time because it is important to reduce the amount of carbon dioxide emitted from the combustion power plant combustion gas to the atmosphere and to increase the purity of the carbon dioxide. This is because the higher the carbon dioxide concentration in the adsorption tower (1) (2) (3), the higher the purity of the product can be adjusted to the desired value by controlling this time.

In the co-current decompression step 130 of the third step, the pressure inside the adsorption tower 1, 2, 3 is lowered from the working pressure to the normal pressure, and the pressure is reduced above the adsorption tower 1, 2, 3. . The direction of decompression affects the performance of the process, and the effect of the decompression direction on the decompression stage showed the best results in terms of the performance of the process. When depressurizing to the bottom of the column, although the desorption rate of nitrogen is superior, the purity and recovery rate decrease because the carbon dioxide that is present in the lower part of the tower flows out of the tower as the desorption proceeds due to the rapid pressure drop. On the other hand, if the top and bottom of the tower are divided into half and discharged to the top, and the discharge to the bottom, the average value of the performance is shown. Therefore, when the process is configured by including a depressurization step, it is best to proceed with decompression toward the top. In the present invention, co-current decompression was performed immediately after the adsorption step 120, thereby improving the performance of the process.

In the co-current pressure reduction step 140 of the fourth step, the adsorption tower that has been adsorbed is connected to the adsorption tower that has been desorbed and left until equilibrium is achieved. The connection direction is the adsorption tower after the adsorption is connected in the co-current direction, the adsorption tower after the desorption is connected in the countercurrent direction, which is connected to the upper portion of the adsorption tower. This pressure equalization step has the primary effect of reducing the operating cost by reducing the load on the compressor or vacuum pump, and is another way of maximizing the effect of decompression. That is, the third step of depressurizing to atmospheric pressure is not possible to depressurize below atmospheric pressure, and the pressure equalization step 140 is halfway between vacuum and atmospheric pressure because it is directly connected to the vacuum pump 4 and the depressurization proceeds directly to the desorption step. The pressure is reduced once more to the pressure. Therefore, in the present invention, as described above, the method of decompression greatly affects the overall performance of the process, so that the cocurrent pressure reducing pressure equalizing step 140 is added between the adsorption step 120 and the washing step 160 to perform the performance. The improvement was aimed at. This decompression method primarily contributes to lowering the concentration of nitrogen in the adsorption column and affects purity by redistributing the components present in the column as well as redistributing components. In the pressure equalization step, the carbon dioxide discharged from the decompression step is released. In addition to the increase in recovery rate due to the effect of preventing the maximum, the pressure difference of the reduced pressure is increased by connecting with the tower of the vacuum to increase the amount of desorption obtained by the combined action will lead to an improvement in performance. Among the connection methods, the best performance is achieved in the case of the process of pressure equalization and pressure equalization at the top of the tower. This means that increasing the nitrogen concentration at the top of the tower by pressurizing with a large amount of nitrogen in the direction of the top of the tower where a large amount of nitrogen is present helps to improve performance. On the other hand, if the pressure is reduced in the bottom direction of the tower is greatly influenced according to the direction of the press, the case of pressing in the direction of the tower bottom was superior to the case of pressing in the direction of the tower top. This means that when pressurized toward the bottom of the tower, a large amount of carbon dioxide is present in the lower part of the column, thereby assisting the adsorption of carbon dioxide when the feed is introduced. This will leak out of the tower and cause performance degradation. As a result, the introduction of a pressure equalization step does not always increase the recovery rate or purity, and when the pressure equalization step is introduced, work must be taken into account in the tower. In the present invention, the optimum performance was obtained by simultaneously using the pressure equalization step of connecting the tops of the two towers together with the cocurrent pressure reduction.

From the effects of decompression and pressure equalization, where is the best stopping of the pressure equalization step ?, the effect of the final equilibrium pressure of the pressure equalization step is that the lower the final pressure, that is, the sufficient time pressure equalization is performed. The better performance is shown in the present invention, the working pressure is 1.5 atm and the desorption pressure is 0.1 atm. This means that the desorption of nitrogen is superior to that of carbon dioxide, and even though the pressure equalization step proceeds, there is almost no loss of carbon dioxide in the depressurization step. That is, in the pressure reduction step, almost all nitrogen is desorbed and purity can be improved by reducing the loss of carbon dioxide in the process of decompression from normal pressure to equalization pressure. In addition, even if the pressure is sufficiently reduced in the decompression equalization step, the amount of carbon dioxide that is lost is considerably small, which means that removing as much nitrogen as possible through decompression helps to improve performance. Therefore, it is a pressure equalization condition in the present invention that the pressure equalization process is sufficiently performed until the pressure between the towers is the same.

The co-pressurization step 150 by the product of the fifth step is a step of pressurizing the inside of the adsorption tower 1, 2, 3 immediately after the pressure equalization step 140 to atmospheric pressure using most of the carbon dioxide. This method was used to replace nitrogen, which still occupies a large amount in the adsorption tower (1) (2) (3), with carbon dioxide. This process was carried out in the adsorption tower (1) immediately before the product cleaning step (160). Since the pressure in the (2) (3) is lower than the normal pressure, it serves to raise it to the normal pressure. In this step, a considerable amount of carbon dioxide is resorbed in the adsorption tower (1) (2) (3).

The washing step 160 using the product of the sixth step is a substantial process of changing the presence of only carbon dioxide in the adsorption tower (1) (2) (3). This step is the most important step to improve the purity of the product and is the most important step to improve the purity of the product during the whole process. Purity is greatly improved by introducing the washing step 160, which increases the concentration of carbon dioxide in the tower by substituting the carbon dioxide remaining in the tower with carbon dioxide after the decompression 130 and the pressure equalization step 140 in the washing step 160. Because it plays a role. Therefore, the cleaning step 160 may be said to play the most important role in improving the purity of the pressure equalization process for carbon dioxide recovery. Another important point is that the performance of a process with a pressure equalization step just prior to cleaning is superior to that of a process that does not. This can be said to be the effect of pressure equalization mentioned above because the nitrogen in the tower is removed as much as possible before the carbon dioxide cleaning. Along with this, the pressure equalization increases the pressure difference between the product storage tank 51 and the column, which promotes the resorption of carbon dioxide due to the large difference in the relative adsorption amount of nitrogen and carbon dioxide at low pressure. That is, the introduction of a pressure equalization step together with the cleaning step 160 is essential to obtain optimal performance.

In addition, the reflux ratio also has a significant effect on the performance of the process. The recovery rate decreases according to the reflux ratio in the washing step 160, but since the reduction is small compared to the purity, the introduction of the washing step 160 improves the overall performance of the process. It can be seen. Therefore, it is important to properly control the reflux ratio as an operating variable to achieve the desired performance under certain operating conditions. In the present invention, in order to use the high purity carbon dioxide obtained in the vacuum desorption step 170 in the co-current pressure step 150 by the product of the fifth step, the carbon dioxide obtained initially is sent and cleaned until the tower is cleaned at atmospheric pressure. From the moment the tower was at atmospheric pressure, carbon dioxide was obtained as a product. The reflux ratio at this time is about 0.4.

The vacuum desorption step 170 of the seventh step is to recover carbon dioxide, which is actually a product of the process, by desorbing and recovering carbon dioxide using the vacuum pump 4 in the cleaned adsorption tower (1) (2) (3). Step. The reflux ratio is also important at this stage and the performance of the process depends on the reflux ratio. As can be seen from the adsorption isotherm of pure gas, the lower the desorption pressure, the greater the difference in the relative adsorption amount, and the better the performance.However, lowering the desorption pressure unconditionally leads to an increase in the operating cost, so It is important to decide. In the present invention, it is most appropriate when the desorption pressure is 0.05 to 0.1 atmosphere.

The countercurrent pressure type pressure equalization step 180 of the eighth step is a step connected to the cocurrent pressure reduction type pressure equalization step 140 of the fourth step, in which the adsorption tower in the desorption state is connected to the adsorption tower in the adsorption state. .

In the above eight steps, the same operation is continuously performed for each adsorption tower, and using this process, carbon dioxide having a purity of 99.8% can be obtained as a product.

Hereinafter, the present invention will be described in more detail with reference to Examples and accompanying drawings. However, these are intended to describe the present invention in more detail, these examples do not limit the technical scope of the present invention.

<Example 1>

Fill the adsorption tower (1) (2) (3) with activated carbon with surface area (1300m ² / g) and pore volume (0.6cm ³ / g) with pore volume and pore volume larger than zeolite with adsorbent. It was adjusted to be 10 liters per minute as a reference. The adsorption pressure was set at 1.5 atm, the desorption pressure was maintained at 0.1 atm, and the equilibrium pressure at the pressure equalization step was maintained at 0.55 atm. As a raw material gas, a mixture of 17% carbon dioxide, 79% nitrogen and 4% oxygen was used. The specifications of the adsorption device and the adsorbent used are shown in Table 1 below.

Table 1. Specifications of adsorber and adsorption tower

Adsorbent Amount (g) 564 Sorbent mesh 8 to 12 Adsorbent Surface Area (m ² / g) 1300 Adsorption tower packing density (g / cm ³ ) 0.47 Adsorption tower height (cm) 90 Adsorption tower diameter (cm) 4.12

As shown in Fig. 1, the apparatus of the present invention is a suction tower (1) (2) (3) and vacuum pump (4), branch pipe (5) (6) (7) (8) (9) (10), automatic opening and closing The valves 11-16, 21-26, 31-36, the flow regulating valves 42 and 43, and the pressure regulating valve 41 are comprised. First, the raw material gas mainly composed of nitrogen passes through the flow regulating valve 42, and the flow rate is regulated uniformly so that the respective adsorption towers 1, 2 are provided through branch pipes 5 and automatic opening and closing valves 11, 21, 31. It is introduced into (3) and passed through the adsorption tower (1) (2) (3) and is discharged to the outside through the branch pipe (9) via the automatic opening and closing valves (15, 25, 35). At this time, the end of the branch pipe (9) is attached with a pressure control valve 41 for controlling and maintaining the operating pressure of the whole process. Once the adsorption of the raw material gas is completed by the adsorbent, the pressure in the adsorption tower is reduced to atmospheric pressure. Is emitted and little carbon dioxide is lost in this process. The adsorption tower depressurized to the atmospheric pressure is connected to the adsorption tower and the desorption tower to each other to further lower the pressure. In this case, the upper portions of the adsorption towers are connected to the branch pipes 10 by the automatic opening and closing valves 16, 26, 36. . In this state, washing is performed using a part of carbon dioxide, which is a product, and the direction is co-current, and the respective adsorption towers 1, 2, (2) using the automatic opening / closing valves 12, 22, 32 and branch pipes 6 are used. Gas is supplied to the bottom of 3). To this end, the flow control valve 43 is installed at the end of the branch pipe 6. In the desorption step of finally obtaining the product, carbon dioxide, which is a product, is obtained through the automatic opening / closing valves 13, 23, 33 using the vacuum pump 4 connected to the branch pipe 7. In addition, the product storage tank 51 is positioned for the reflux of the carbon dioxide generated by connecting to the vacuum pump (4).

Fig. 2 shows the procedure for operating the apparatus of the present invention and shows the conditions for the three adsorption towers 1, 2, 3 to be operated periodically in the same order. That is, while one adsorption tower performs pressure 110, adsorption 120, and cocurrent decompression 130, the other two towers undergo vacuum desorption 170 and a washing step 160 using the product. While the pressure equalization step 180 is performed between the two towers, the other tower has a stop step 200 for a short time because the product flow of the desorption step stops for a while. In order to periodically operate this process, each of the automatic opening and closing valves 11 to 16 (21 to 26) and 31 to 36 is operated in the form shown in Table 2 below.

Table 2. Operation of automatic shut off valve

step One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 valve Valve condition Adsorption tower 1 11 ○ ○ ○ 12 ○ ○ ○ ○ 13 ○ ○ ○ ○ 14 ○ ○ ○ ○ 15 ○ 16 ○ ○ Adsorption tower 2 21 ○ ○ ○ 22 ○ ○ ○ ○ 23 ○ ○ ○ ○ 24 ○ ○ ○ ○ 25 ○ 26 ○ ○ Adsorption tower 3 31 ○ ○ ○ 32 ○ ○ ○ ○ 33 ○ ○ ○ ○ 34 ○ ○ ○ ○ 35 ○ 36 ○ ○

○: valve open

3 is a view showing a pressure change during one cycle in the process of operation in the order of Figure 2 and Table 2. That is, the adsorption proceeds at a pressure higher than the normal pressure (1.5 atm in the present invention) and reaches the intermediate pressure (0.55 atm) through two depressurization processes, and then pressurization and washing are performed simultaneously using a part of the product.

The working time of each step is repeated from step 1 to step 5 periodically. The first step, which is the co-pressurization step 150 by the product, is defined as the time taken for the adsorption tower to naturally rise to 1 atm. Pressing step 110 was also determined as the time to reach the adsorption pressure of the pressure in the adsorption tower by the raw material gas. Pressure reduction type pressure equalization step 140 and the cocurrent pressure step 150 by the product were also determined as the time to reach the desired pressure. However, only the adsorption step 120 used 350 seconds as the time to be adjusted to improve the performance. This is a side advantage of the present invention, since it is most determined naturally according to the operating conditions in determining the working time, it is very easy to determine the working conditions.

4 is a diagram comparing the results of the operation method and the other general method presented in the present invention. In the figure, the purity is indicated by the bar graph indicated by the diagonal line and the recovery rate is indicated by the white bar graph. As can be seen in Figure 4 using the method proposed in the present invention can obtain a superior purity than other methods.

By circulating the apparatus of the present invention in the order of Table 2, it was possible to obtain carbon dioxide as a product with a purity of 99.8%, with a recovery of 51% based on the introduced carbon dioxide.

<Example 2>

As a raw material gas, 13% of carbon dioxide, 82% of nitrogen, and 5% of oxygen, which are similar to those of a combustion power plant of a coal fired power plant, were mixed. Three adsorption towers (1), (2) and (3) were filled with activated carbon with an adsorbent and the raw material gas was adjusted to 10 liters per minute based on the total flow rate. The adsorption time (step 3) was set at 470 seconds, the adsorption pressure was set to 1.5 atm, the desorption pressure was maintained at 0.1 atm, and the equilibrium pressure at the pressure equalization step was maintained at 0.55 atm. By circulating the apparatus of the present invention in the same manner as in Example 1, it was possible to obtain carbon dioxide as a product with a purity of 99.7%, with a recovery of 40% based on the introduced carbon dioxide.

The present invention is characterized by combining the co-current decompression, top column-type pressure equalization, cleaning with the product in the vacuum process, it is possible to obtain the desired purity of the product with only one vacuum pump and three adsorption tower, so the equipment cost is low and vacuum pump It is economical because it can operate with only one power cost.

In addition, in the present invention, four or more adsorption towers are used in a pressure swing adsorption apparatus for recovering a strong adsorbate, whereas in the present invention, only three adsorption towers are used to obtain a pressure equalization step and a product connecting two towers to obtain high purity carbon dioxide. The cleaning steps used together or the pressure equalization and product wash steps can be used separately to improve the purity of the product.

Claims (12)

delete A plant for recovering carbon dioxide in combustion gas of a coal-fired power plant, which is operated by a pressure swing adsorption system composed of three adsorption towers (1) (2) (3) and one vacuum pump (4). In the pressure swing adsorption system for recovering carbon dioxide in the gas, a branch pipe (5) for branching the raw material gas controlled by the flow control valve (42) to the adsorption tower (1), (2), and (3), respectively; And automatic shutoff valves 11, 21 and 31 for controlling the flow of the raw material gas supplied by the branch pipe 5, and the automatic shutoff valves 11, 21 and 31. Adsorption tower (1), (2), (3) for adsorbing carbon dioxide in the raw material gas introduced through the automatic opening and closing valve (15), (25) through the adsorption tower (1), (2), (3) ), (35) and the branch pipe (9), the suction and working pressure control unit for discharge by pressure control through the pressure control valve 41; A nitrogen gas discharge unit comprising automatic opening / closing valves 14, 24, and 34 which branch and line reduce and reduce the nitrogen discharged from the adsorption towers 1, 2, and 3; A pressure equalization unit configured by commonly connecting the automatic opening and closing valves 16, 26, and 36 connected to the adsorption towers 1, 2, and 3 to the branch pipe 10; A branch pipe 6 is connected to the automatic opening / closing valves 12, 22, and 32 connected to the adsorption towers 1, 2, and 3, respectively, and a flow rate is provided at the end of the branch pipe 6. A product cleaning unit connecting the control valve 43 and the product storage tank 51 to each other; The automatic opening / closing valves 13, 23, and 33 connected to the adsorption towers 1, 2, and 3 are connected to branch pipes 7, respectively, and the branch pipes 7 and the product storage tanks. A pressure swing adsorption system for recovering carbon dioxide in a flue gas of a thermal power plant, characterized by comprising a carbon dioxide recovery unit formed by installing a vacuum pump (4) between the (51). 2. The coal fired power plant according to claim 1, wherein the adsorption tower (1) (2) (3) is filled with activated carbon having a surface area (1300 m2 / g) and a pore volume (0.6 cm3 / g) larger than zeolite as an adsorbent. Pressure swing adsorption system for recovering carbon dioxide in the gas. The pressure swing adsorption system for recovering carbon dioxide in the exhaust power of a thermal power plant according to claim 2, wherein a part of the carbon dioxide in the product storage tank (51) is washed at a rate of 0.1 to 0.7 based on the total carbon dioxide generated. . A pressurizing step 110 for pressurizing the adsorption tower to a working pressure with the raw material gas introduced therein; An adsorption step 120 for adsorbing carbon dioxide in the raw material gas by activated carbon in the adsorption column maintained at a constant pressure; A washing step 160 using a product such that only carbon dioxide is present in the adsorption column; In the method for recovering the carbon dioxide in the combustion power plant combustion gas comprising a vacuum desorption step 170 of desorbing, recovering carbon dioxide using a vacuum pump in the adsorption tower after the cleaning, between the adsorption step 120 and the washing step 160 The cocurrent depressurization step 130 for lowering the pressure from the working pressure to the atmospheric pressure and the cocurrent decompression type pressure equalization step 140 are sequentially added to connect the adsorption tower, which is completed with adsorption, to the equilibrium, and to stand until equilibrium is achieved. In the vacuum desorption step 170, the adsorption tower in the desorption state is added to the countercurrent pressure equalization step 180 to connect with the adsorption tower in the adsorption state, and after completion of the decompression type pressure equalization step 140, It is characterized by sequentially adding the co-current pressure step 150 by the product pressurized to atmospheric pressure using a product containing mostly carbon dioxide. A method for recovering carbon dioxide in a thermal power plant exhaust gas using pressure swing adsorption apparatus. The pressure swing adsorption apparatus according to claim 5, wherein the pressure during vacuum desorption of the vacuum desorption step 170 is 0.05 to 0.1 atm, and the equilibrium pressure in the pressure equalization step 140 is 0.5 to 0.55 atm. A method for recovering carbon dioxide from exhaust power of thermal power plants. The method according to claim 5, wherein one of the two towers performs vacuum desorption and product cleaning while one of the adsorption towers is pressurized, adsorbed, and cocurrent decompression, and the other one is subjected to a pressure equalization process between the two adsorption towers. The tower is a method of recovering carbon dioxide in the exhaust power of the thermal power plant using pressure swing adsorption, characterized in that the flow of the product is operated to stop the operation for a while. 6. The method of claim 5, wherein the pressure reduction and pressure equalization and the cleaning step using the product are performed together in a circulation cycle to improve the purity of the carbon dioxide. . [Claim 6] The method of claim 5, wherein in the cocurrent depressurization step (130), the pressure reduction adsorption apparatus is used to recover carbon dioxide in the flue gas of a thermal power plant using a pressure swing adsorption device. 6. The pressure equalization step of claim 5, wherein the adsorption tower in which the adsorption is completed in the pressure equalization step 140 is in the cocurrent direction, and the adsorption tower in which the desorption is completed is in the countercurrent direction, thereby connecting the opposite ends in which the raw material gas is introduced to perform pressure equalization. A method of recovering carbon dioxide in a flue gas of a thermal power plant using a pressure swing adsorption device. The carbon dioxide in the thermal power plant exhaust gas using the pressure swing adsorption apparatus according to claim 5, wherein in the washing step (160) using the product, the washing gas flow is made at the same direction as the flow direction of the raw material gas at normal pressure. How to recover. The method of claim 5, wherein the adsorption pressure of the pressure swing adsorption process is performed at 1.5 to 2 atmospheres.