JP2009214089A - Carbon dioxide recovery apparatus and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carbon dioxide recovery apparatus saving energy by reduction of cooling heat loss. <P>SOLUTION: The carbon dioxide recovery apparatus is provided with: an absorbing tower 101 absorbing carbon dioxide-containing gas into an absorbing liquid to form a rich liquid 120; a releasing tower 102 releasing and separating carbon dioxide and steam by heating the rich liquid 120 discharged from the absorbing tower 101 and returning formed lean liquid 123 to the absorbing tower 101; and a splitting device 107 splitting the rich liquid 120 discharged from the absorbing tower 101 into a first heat exchanger 103 and a second heat exchanger 104. The rich liquid 120 led to the first heat exchanger 103 and second heat exchanger 104 is heat-exchanged with the lean liquid 123 and steam 131 containing carbon dioxide, respectively, and supplied to the releasing tower 102. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carbon dioxide recovery apparatus and method.

  In recent years, CO2 capture and storage technology has attracted attention as an effective measure against the global warming problem of concern on a global scale. In particular, combustion exhaust gas and process exhaust gas generated from large-scale CO2 sources such as thermal power plants and steelworks A method for recovering CO2 with an aqueous solution has been studied.

As a conventional CO2 recovery device, for example, a configuration disclosed in Patent Document 1 is known. As shown in FIG. 4, the carbon dioxide recovery device 50 includes a cooling tower 51 that cools combustion exhaust gas, an absorption tower 52 that absorbs carbon dioxide in the cooled combustion exhaust gas, and a carbon dioxide absorption solution. A regeneration tower 53 is provided that is heated to separate it into carbon dioxide and a regenerated absorbent. The regenerated absorbing liquid discharged from the regenerating tower 53 is heat-exchanged with the carbon dioxide absorbing solution supplied from the absorbing tower 52 in the heat exchanger 54, and then supplied to the absorbing tower 52 through the first cooler 55. . Further, the vapor containing carbon dioxide discharged from the regeneration tower 53 is condensed by the second cooler 56 and separated into carbon dioxide and condensate by the gas-liquid separator 57, and then the condensate is regenerated. Returned to
JP 2003-225537 A

  Patent Document 1 describes that hot water return water for cooling is used for heating or the like because a large amount of exhaust heat is generated in the first cooler 55 and the second cooler 56. However, from the viewpoint of energy saving, it is preferable that the amount of heat supplied from the outside be reduced as much as possible by suppressing the amount of heat lost in cooling by the first cooler 55 and the second cooler 56.

  Therefore, an object of the present invention is to provide a carbon dioxide recovery apparatus and method that can save energy by reducing the heat of cooling loss.

  The object of the present invention is to absorb a carbon dioxide-containing gas into an absorption liquid to produce a rich liquid, and to separate and separate carbon dioxide with steam by heating the rich liquid discharged from the absorption tower. A stripping tower for returning the produced lean liquid to the absorption tower, a first heat exchanger through which the lean liquid supplied from the stripping tower to the absorption tower passes, and carbon dioxide separated by the stripping tower A second heat exchanger through which the contained steam passes, and a diversion device for diverting the rich liquid discharged from the absorption tower to the first heat exchanger and the second heat exchanger, The rich liquid introduced into the heat exchanger and the second heat exchanger is configured to be supplied to the stripping tower after heat exchange with the lean liquid and the carbon dioxide-containing steam, respectively. Achieved by carbon dioxide capture device That.

  Further, the object of the present invention is to absorb the carbon dioxide-containing gas in the absorption tower in the absorption liquid to generate a rich liquid, and to heat the rich liquid discharged from the absorption tower in the diffusion tower. And a regeneration step for returning the generated lean liquid to the absorption tower by dispersing the carbon together with the vapor, and the regeneration step converts the lean liquid supplied from the diffusion tower to the absorption tower with a first heat. Including a step of passing through an exchanger and a step of passing the carbon dioxide-containing vapor separated in the stripping tower through a second heat exchanger, the rich liquid discharged from the absorption tower being diverted to the first This is achieved by a carbon dioxide recovery method characterized in that it is introduced into the heat exchanger and the second heat exchanger, heat exchanged with the lean liquid and the carbon dioxide-containing steam, respectively, and then supplied to the stripping tower.

  According to the present invention, it is possible to provide a carbon dioxide recovery apparatus and method capable of saving energy by reducing cooling loss.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a carbon dioxide recovery device according to an embodiment of the present invention.

  As shown in FIG. 1, the carbon dioxide recovery device 1 is configured to bring the introduced carbon dioxide-containing gas into contact with an absorption liquid that absorbs carbon dioxide to generate a rich liquid 120 that absorbs carbon dioxide, A diffusion tower 102 that heats the rich liquid 120 discharged from the absorption tower 101 to dissipate and separate carbon dioxide together with the vapor and returns the lean liquid 123 from which most of the carbon dioxide has been removed to the absorption tower 101. ing.

  The absorption tower 101 is composed of, for example, a countercurrent gas-liquid contact device, and is configured to bring the carbon dioxide-containing gas supplied from the lower part into gas-liquid contact with the lean liquid 123 flowing down from the upper part. Although the carbon dioxide containing gas supplied to the absorption tower 101 is not specifically limited, combustion exhaust gas, process exhaust gas, etc. can be illustrated and may be introduce | transduced after cooling processing as needed. Moreover, a conventionally well-known thing can be utilized for absorption liquid, For example, amine-type aqueous solution, such as a monoethanolamine (MEA) and a diethanolamine (DEA), can be illustrated. The de-CO 2 gas from which carbon dioxide has been removed by the absorption tower 101 is discharged from the upper part of the absorption tower 101.

  The stripping tower 102 is, for example, a countercurrent gas-liquid contact device, and the stored liquid is heated by exchanging heat with the high-temperature steam 140 that is externally supplied heat in the reboiler 108. The carbon dioxide containing vapor diffused inside the stripping tower 102 is discharged from the upper part of the stripping tower 102.

  In addition, the carbon dioxide recovery apparatus 1 of the present embodiment includes the first heat exchanger 103 through which the lean liquid 123 supplied from the stripping tower 102 to the absorption tower 101 passes, and the carbon dioxide-containing steam separated by the stripping tower 102. And a second heat exchanger 104 through which 131 passes, and a flow dividing device 107 for diverting the rich liquid 120 discharged from the absorption tower 101 to the first heat exchanger 103 and the second heat exchanger 104. Yes. The rich liquid 120 supplied to the first heat exchanger 103 and the second heat exchanger 104 is heated by heat exchange with the lean liquid 123 and the carbon dioxide-containing steam 131, respectively, and then supplied to the diffusion tower 102. The

  In the flow path of the lean liquid 123 supplied from the stripping tower 102 to the absorption tower 101, a first cooler 106 is provided between the first heat exchanger 103 and the absorption tower 101, and is supplied from the outside. The lean solution 123 is cooled by the refrigerant 143 such as cold water. The second heat exchanger 104 is connected to the second cooler 105 and the gas-liquid separator 132, and the carbon dioxide-containing steam that has passed through the second heat exchanger 104 is second cooled. In the vessel 105, the vapor is condensed by being cooled by a refrigerant 142 such as cold water supplied from the outside, and is separated into condensed water 133 and carbon dioxide 134 in the gas-liquid separator 132. The separated condensed water 133 is returned to the stripping tower 102, while the carbon dioxide 134 is recovered.

  The diversion device 107 diverts the rich liquid 120 to the first heat exchanger 103 and the second heat exchanger 104 through the pipes 121 and 122 so that a desired flow rate ratio is obtained. Specifically, the ratio (diversion ratio) of the flow rate of the rich liquid 120 supplied from the flow dividing device 107 to the second heat exchanger 104 to the flow rate of the rich liquid 120 introduced from the absorption tower 101 to the flow dividing device 107 is expressed as α. The value of α is preferably 0.05 or more and 0.5 or less, and more preferably 0.05 or more and 0.15 or less.

  The value of the diversion ratio α may be set in advance in consideration of the use conditions, or may be configured so that the user can appropriately change it by adjusting the valve opening degree or the baffle plate. As the flow rate for setting the value of α, the volume flow rate is used in the present embodiment, but it may be a mass flow rate.

  According to the carbon dioxide recovery apparatus 1 having the above configuration, an absorption step of generating the rich liquid 120 by absorbing the carbon dioxide-containing gas in the absorption liquid is performed in the absorption tower 101. The rich liquid 120 discharged from the absorption tower 101 is circulated and supplied to the reboiler 108 and heated in the diffusion tower 102, and carbon dioxide and vapor are released. The carbon dioxide-containing vapor is discharged from the upper part of the diffusion tower 102, while the lean liquid 123 is returned to the absorption tower 101. In this way, a regeneration process is performed in which the rich liquid 120 that has absorbed carbon dioxide is made into the lean liquid 123 and can be reused.

  In the regeneration step, the lean liquid 123 discharged from the diffusion tower 102 passes through the first heat exchanger 103 and the first cooling tower 106 and is supplied to the absorption tower 101 and is separated by the diffusion tower 102. The vapor 131 containing carbon dioxide passes through the second heat exchanger 104 and the second cooling tower 105 and is supplied to the gas-liquid separator 132.

  The rich liquid 120 discharged from the absorption tower 101 is diverted by the diversion device 107 and introduced into the first heat exchanger 103 and the second heat exchanger 104, and the lean liquid 123 and the carbon dioxide-containing steam 131 are respectively obtained. After heat exchange, it is supplied to the diffusion tower 102. Thereby, the temperature of the rich liquid 120 introduced into the stripping tower 102 can be sufficiently increased by using both the first heat exchanger 103 and the second heat exchanger 104, and carbon dioxide is removed from the stripping tower 102. The heat energy for transpiration can be reduced.

  On the other hand, since the temperatures of the lean liquid 123 and the carbon dioxide-containing steam 131 introduced into the first cooler 106 and the second cooler 105 can be lowered, the first cooler 106 and the second cooler The cooling load in 105 can be reduced and the cooling loss can be suppressed. The condensed water 133 separated by the gas-liquid separator 132 is configured to be returned to the stripping tower 102 in this embodiment, but can also be returned to the absorption tower 101 or used for other purposes. May be.

  FIG. 2 is a graph showing the measurement result of the externally supplied heat with respect to the diversion ratio α in the carbon dioxide recovery apparatus 1 shown in the present embodiment. As the absorbing solution, a 30 wt% aqueous solution of monoethanolamine (MEA) was used, and CO2 recovery was performed for a gas containing CO2 equivalent to the blast furnace gas (20% -CO2) of the steelworks.

  In FIG. 2, the CO2 dissipated heat (141) is a physical quantity determined by the type of the absorbing liquid, and is substantially constant regardless of the magnitude of the diversion ratio α. On the other hand, both the cooling loss heat (143) generated in the first cooler 106 and the cooling loss heat (142) generated in the second cooler 105 change depending on the magnitude of the flow dividing ratio α. The carbon dioxide recovery device 1 of the present embodiment is configured so that the externally supplied heat (140), which is the sum of the CO2 diffused heat (141), the cooling loss heat (142), and the cooling loss heat (143), becomes small. Thus, the rich liquid 120 can be diverted, so that energy saving can be achieved.

  More specifically, by setting the diversion ratio α to 0.05 or more, as shown by the solid line in FIG. 2, the effect of reducing the externally supplied heat (140) can be confirmed, and when α is further increased. As a result, the temperature of the carbon dioxide-containing steam 131 introduced into the second cooler 105 is reduced, so that the cooling loss heat (142) is reduced and the externally supplied heat (140) is reduced. However, in the region where α is larger than 0.5, the temperature of the lean liquid 123 introduced into the first cooler 106 becomes high, so that the heat of cooling loss (143) increases rapidly, and the external temperature necessary for CO2 recovery is increased. Supply heat (140) increases. Therefore, in order to suppress externally supplied heat (140), the value of α is preferably set to 0.05 or more and 0.5 or less.

  The externally supplied heat (140) indicated by a solid line in FIG. 2 is obtained when an ideal heat exchanger (apparatus A) having a very large heat transfer area is used as the first heat exchanger 103 shown in FIG. As a result, the thermal efficiency is about 0.7, and the heat of cooling loss (143) in the first cooler 106 is most reduced by making maximum use of the heat of the high-temperature lean liquid 123. Here, the thermal efficiency is a value obtained by dividing the actual exchange heat quantity between the rich liquid 120 and the lean liquid 123 by the heat quantity corresponding to the maximum temperature difference between the lean liquid 123 and the rich liquid 120.

  On the other hand, when the first heat exchanger 103 having lower thermal efficiency (apparatus B and apparatus C) is used, the preferable range of α is narrowed as indicated by a two-dot chain line and a broken line in FIG. It was a trend. The apparatus C uses a heat exchanger having a specification as selected in the design of a conventional carbon dioxide recovery apparatus as it is, and has a lower thermal efficiency than the apparatus B. In this case, a preferable range of α is , 0.05 to 0.15 or less.

  Thus, as long as the diversion ratio α is used under the optimum conditions, it is effective to set it in the range of 0.05 or more and 0.5 or less. Change. Further, in consideration of the possibility that the thermal efficiency may decrease with time due to adhesion of scales, in order to obtain a good reduction effect of the externally supplied heat regardless of the thermal efficiency value, the shunt ratio α is set to 0.05. More preferably, it is set to 0.15 or less.

  As mentioned above, although one Embodiment of this invention was explained in full detail, the specific aspect of this invention is not limited to the said embodiment. For example, in the present embodiment, the second heat exchanger 104 is disposed outside the stripping tower 102. However, the second heat exchanger 104 is disposed inside the stripping tower 102, and the carbon dioxide-containing steam is disposed. You may comprise so that heat exchange with 131 and the rich liquid 120 may be performed inside the diffusion tower 102. FIG.

  Further, the flow dividing device 107 in the present embodiment branches the flow path of the rich liquid 120 outside the absorption tower 101, and passes through the pipes 121 and 122 to the first heat exchanger 103 and the second heat exchanger 104. Although it supplies, it will not be limited to the thing of this embodiment if it is the structure which can supply to both the 1st heat exchanger 103 and the 2nd heat exchanger 104 with a desired flow rate ratio. For example, as shown in FIG. 3, two pipes 121 and 122 are connected to the absorption tower 101, and pumps and valves (both not shown) are interposed in the pipes 121 and 122, respectively. Since the flow rate ratio of the rich liquid flowing through the pipes 121 and 122 can be adjusted by controlling the drive voltage and the valve opening, the pipes 121 and 122 having these pumps and valves can function as a flow dividing device. You can also. In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals.

  EXAMPLES Next, an Example is given and this invention is demonstrated still in detail. However, the present invention is not limited to the following examples.

  In the carbon dioxide recovery apparatus 1 shown in FIG. 1, a 30% by weight aqueous solution of monoethanolamine (MEA) is used as an absorbent, and a gas containing 20% CO2 equivalent to blast furnace gas at a steel works (20% -CO2), CO2 capture was carried out. As the first heat exchanger 103, an apparatus A that can achieve a thermal efficiency of 0.7 (see FIG. 2) was used, and the diversion ratio α of the diversion apparatus 107 was set to 0.3 (Example 1). Further, CO2 recovery was carried out under the same conditions as in Example 1 except that no rich liquid was allowed to flow through the second heat exchanger 104 (that is, α = 0) (conventional method 1). The results are shown in Table 1.

表１から明らかなように、実施例１においては外部供給熱（１４０）が、３．５３ＭＪ／ｋｇ−ＣＯ２となり、従来法１の外部供給熱（１４０）である３．９６ＭＪ／ｋｇ−ＣＯ２に対して１１％のエネルギー低減効果を示した。

As is apparent from Table 1, in Example 1, the externally supplied heat (140) is 3.53 MJ / kg-CO2, which is 3.96 MJ / kg-CO2, which is the externally supplied heat (140) of the conventional method 1. On the other hand, an energy reduction effect of 11% was shown.

It is a schematic structure figure of a carbon dioxide recovery device concerning one embodiment of the present invention. It is a graph which shows the change of the external supply heat with respect to the flow dividing ratio of a flow dividing apparatus. It is a schematic block diagram of the carbon dioxide recovery apparatus which concerns on other embodiment of this invention. It is a schematic block diagram of the conventional carbon dioxide recovery apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carbon dioxide recovery apparatus 101 Absorption tower 102 Dissipation tower 103 1st heat exchanger 104 2nd heat exchanger 105 2nd cooler 106 1st cooler 107 Shunt apparatus 120 Rich liquid 123 Lean liquid 131 Carbon dioxide containing Steam 140 External supply heat 141 CO2 dissipated heat 142 Cooling loss heat 143 in the second cooler 143 Cooling loss heat in the first cooler

Claims (4)

An absorption tower that absorbs the carbon dioxide-containing gas into the absorption liquid and generates a rich liquid;
A diffusion tower that dissipates and separates carbon dioxide with steam by heating the rich liquid discharged from the absorption tower, and returns the produced lean liquid to the absorption tower;
A first heat exchanger through which a lean liquid supplied from the stripping tower to the absorption tower passes;
A second heat exchanger through which the carbon dioxide-containing vapor separated in the diffusion tower passes;
A diversion device for diverting the rich liquid discharged from the absorption tower to the first heat exchanger and the second heat exchanger,
The rich liquid introduced into the first heat exchanger and the second heat exchanger is configured to be supplied to the stripping tower after exchanging heat with the lean liquid and the carbon dioxide-containing steam, respectively. Carbon dioxide recovery device characterized by A first cooler that cools the lean liquid that has passed through the first heat exchanger;
The carbon dioxide recovery apparatus according to claim 1, further comprising a second cooler that cools the carbon dioxide-containing steam that has passed through the second heat exchanger. In the diversion device, a ratio α of a flow rate of the rich liquid supplied to the second heat exchanger to a flow rate of the rich liquid introduced from the absorption tower is set in a range of 0.05 to 0.5. The carbon dioxide recovery device according to claim 1 or 2. An absorption step of absorbing the carbon dioxide-containing gas into the absorption liquid in the absorption tower to generate a rich liquid;
The rich liquid discharged from the absorption tower is heated in the diffusion tower to dissipate and separate carbon dioxide together with the vapor, and the regeneration step returns the produced lean liquid to the absorption tower.
The regeneration step includes
Passing the lean liquid supplied from the stripping tower to the absorption tower through a first heat exchanger;
Passing the carbon dioxide-containing vapor separated in the stripping tower through a second heat exchanger,
The rich liquid discharged from the absorption tower is divided and introduced into the first heat exchanger and the second heat exchanger, and after heat exchange with the lean liquid and the carbon dioxide-containing steam, is supplied to the diffusion tower. The carbon dioxide recovery method characterized by performing.

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