Abstract:
The present invention provides a carbon dioxide recovery apparatus capable of recovering heat energy of carbon-dioxide-containing gas which includes an absorbing tower to generate and discharge a rich liquid absorbing carbon dioxide as carbon-dioxide-containing gas is introduced and contacted to an absorbing liquid to absorb carbon dioxide, carbon dioxide release devices to discharge semi-lean liquids which have steam containing a part of carbon dioxide released by heating the rich liquid discharged from the absorbing tower, and a regeneration tower to generate a lean liquid which has steam containing remaining carbon dioxide released and separated by heating the semi-lean liquids discharged from the carbon dioxide release devices and to return the lean liquid to the absorbing tower.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims benefit of priority under 35 USC 119 from the Japanese Patent Application No. 2010-256969, filed on Nov. 17, 2010, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a carbon dioxide recovery apparatus and a carbon dioxide recovery method. 
     2. Related Art 
     Recently, carbon dioxide recovery-storage technologies have received attention as effective countermeasures against global warming issues on fears of a global mass scale for recovering carbon dioxide. In particular, methods to recover carbon dioxide utilizing aqueous solutions have been studied as targeting thermal power stations and process exhaust gas. 
     Such a carbon dioxide recovery apparatus has been disclosed in Japanese Patent Application Laid-open 2009-214089, for example. The carbon dioxide recovery apparatus includes an absorbing tower which generates a rich liquid by absorbing carbon-dioxide-containing gas into an absorbing liquid, a releasing tower which generates a lean liquid by heating the rich liquid discharged from the absorbing tower to release and separate carbon dioxide along with steam and which returns the lean liquid to the absorbing tower, a first heat exchanger through which the lean liquid to be supplied from the releasing tower to the absorbing tower passes, a second heat exchanger through which carbon-dioxide-containing steam separated at the releasing tower passes, and a splitting device which splits the rich liquid discharged from the absorbing tower to the first and second heat exchangers. Here, the rich liquids introduced to the first and second heat exchangers are supplied to the releasing tower after performing heat exchange respectively with the lean liquid and the carbon-dioxide-containing steam. 
     With the above carbon dioxide recovery apparatus in the related art, heat energy included in the carbon-dioxide-containing steam which is separated at the releasing tower can be recovered at the second heat exchanger utilizing the split rich liquid. However, temperature of the rich liquid passing through the first heat exchanger is apt to be increased owing to decrease of flow quantity thereof. As a result, since temperature difference against the lean liquid being high temperature side fluid becomes small, there arises a problem that heat energy recovery quantity from the lean liquid at the portion is decreased compared to a case without splitting. The tendency becomes more apparent in a case that performance of the first heat exchanger is enhanced as taking measures such as increasing of heat-transfer area to reduce steam consumption of the carbon dioxide recovery apparatus. 
     SUMMARY OF THE INVENTION 
     To address the above issues, the present invention provides a carbon dioxide recovery apparatus and a carbon dioxide recovery method capable of performing effective heat recovery from a lean liquid and carbon-dioxide-containing steam with a rich liquid. 
     According to one aspect of the present invention, there is provided a carbon dioxide recovery apparatus, comprising: an absorbing tower to generate and discharge a rich liquid absorbing carbon dioxide as carbon-dioxide-containing gas is introduced and contacted to an absorbing liquid to absorb carbon dioxide; a carbon dioxide release device to discharge a semi-lean liquid which has steam containing a part of carbon dioxide released by heating the rich liquid discharged from the absorbing tower; and a regeneration tower to generate a lean liquid which has steam containing remaining carbon dioxide released and separated by heating the semi-lean liquid discharged from the carbon dioxide release device and to return the lean liquid to the absorbing tower. 
     Further, according to one aspect of the present invention, there is provided a carbon dioxide recovery method, comprising: generating and discharging a rich liquid which absorbs carbon dioxide as introducing carbon-dioxide-containing gas and contacting the gas to an absorbing liquid to absorb carbon dioxide; discharging a semi-lean liquid which has steam containing a part of carbon dioxide released by heating the rich liquid; and generating a lean liquid which has steam containing remaining carbon dioxide released and separated by heating the semi-lean liquid. 
     According to the carbon dioxide recovery apparatus and the carbon dioxide recovery method of the present invention, it is possible to perform effective heat recovery from the lean liquid and the carbon-dioxide-containing steam with the rich liquid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  1  according to a first embodiment of the present invention; 
         FIG. 2  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  2  according to a second embodiment of the present invention; 
         FIG. 3  is a layout view illustrating a modified example of the carbon dioxide recovery apparatus  2  according to the second embodiment of the present invention; 
         FIG. 4  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  3  according to a third embodiment of the present invention; 
         FIG. 5  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  4  according to a fourth embodiment of the present invention; 
         FIG. 6  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  5  according to a fifth embodiment of the present invention; 
         FIG. 7  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  6  according to a sixth embodiment of the present invention; and 
         FIG. 8  is a layout view illustrating a structure of a carbon dioxide recovery apparatus  7  according to a seventh embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Hereafter, carbon dioxide recovery apparatuses and carbon dioxide recovery methods according to first to seventh embodiments of the present invention will be described with reference to the drawings. 
     (First Embodiment) 
     A carbon dioxide recovery apparatus according to the first embodiment of the present invention will be described with reference to  FIG. 1  which illustrates the structure thereof. 
     The carbon dioxide recovery apparatus  1  according to the first embodiment is provided with an absorbing tower  101 , carbon dioxide release devices  103 ,  104 , a gas-liquid separator  132 , coolers  105 ,  106 , a regeneration tower  102 A and a re-boiler  108  as main structural elements. 
     Further, the carbon dioxide recovery apparatus  1  is provided with pumps  201 ,  202 ,  203 , a splitting device  107  and a merging device  109 . 
     In the absorbing tower  101 , a rich liquid  301  having carbon dioxide absorbed is generated while carbon-dioxide-containing gas  111  is introduced and contacted to an absorbing liquid which absorbs carbon dioxide. 
     The absorbing tower  101 , for example, being constituted with a counter flow type gas-liquid contacting device is structured to perform gas-liquid contacting between the carbon-dioxide-containing gas  111  supplied from a lower part and a lean liquid  319  flowing down from an upper part. 
     Not being particularly limited, the carbon-dioxide-containing gas  111  to be supplied to the absorbing tower  101  may be, for example, combustion exhaust gas, process exhaust gas and the like and may be introduced after receiving a cooling process if required. 
     Further, not being particularly limited, the absorbing liquid may adopt aqueous solution of amine series such as monoethanol-amine (MEA) and diethanol-amine (DEA), for example. Carbon-dioxide-removed gas  112  having carbon dioxide removed is discharged from an upper part of the absorbing tower  101 . 
     The rich liquid  301  discharged from the absorbing tower  101  is supplied to the splitting device  107  via the pump  201  and is split into rich liquids  302 ,  303  at a desired flow ratio. 
     The rich liquids  302 ,  303  are heated respectively at the carbon dioxide release devices  103 ,  104  having a part of carbon dioxide released along with steam and are discharged as being gas-liquid two-phase semi-lean liquids  320 ,  306  having a part of carbon dioxide removed. 
     Here, a lean liquid  316  to be supplied from the regeneration tower  102 A to the absorbing tower  101  passes through the carbon dioxide release device  103  being a first carbon dioxide release device. 
     As described later, carbon-dioxide-containing steam  310  separated at the regeneration tower  102 A passes through the carbon dioxide release device  104  being a second carbon dioxide release device. 
     Accordingly, the rich liquids  302 ,  303  supplied respectively to the carbon dioxide release devices  103 ,  104  are heated owing to heat exchange with the lean liquid  316  and the carbon-dioxide-containing steam  310 , so that a part of carbon dioxide is released along with steam. 
     Carbon-dioxide-containing steam  311  having a part of water vapor condensed at the carbon dioxide release device  104  is discharged and supplied to the cooler  105  and is discharged to the gas-liquid separator  132  after being cooled owing to refrigerant such as cold water to be supplied from the outside, and then, is discharged from the gas-liquid separator  132  as being separated into carbon dioxide  315  and condensed water  314 . 
     The semi-lean liquids  320 ,  306  having a part of carbon dioxide released are merged at the merging device  109  respectively via the pumps  202 ,  203 , and then, are supplied to the regeneration tower  102 A. 
     The regeneration tower  102 A including a loading layer  102   a  heats the semi-lean liquid  309 . Accordingly, the most part of carbon dioxide is separated as being released along with steam and is discharged from an upper part thereof as the carbon-dioxide-containing steam  310 . The lean liquid  316  having the most part of carbon dioxide removed is returned to the absorbing tower  101 . 
     The regeneration tower  102 A is a counter flow type gas-liquid contacting device, for example. Here, heating of a stored liquid is performed at the re-boiler  108  by performing heat-exchange with high temperature steam which is external supply heat. 
     The cooler  106  is provided between the carbon dioxide release device  103  and the absorbing tower  101  on a route through which the lean liquid  316  is supplied from the regeneration tower  102 A to the absorbing tower  101 . A lean liquid  318  is cooled owing to refrigerant such as cold water to be supplied from the outside, and then, is returned to the absorbing tower  101  as a lean liquid  319 . 
     According to the carbon dioxide recovery apparatus  1  of the first embodiment having the above configuration, following operation and effects can be obtained. 
     First, an absorbing process of carbon dioxide, in which the rich liquid  301  is generated as the carbon-dioxide-containing gas  111  is absorbed to the absorbing liquid, is performed at the absorbing tower  101 . 
     The rich liquid  301  discharged from the absorbing tower  101  is split and is supplied to the regeneration tower  102 A as the gas-liquid two-phase semi-lean liquids  320 ,  306  having a part of carbon dioxide released respectively at the carbon dioxide release devices  103 ,  104 . Subsequently, circulation supplying is performed as the carbon-dioxide-containing steam  131  as being heated by the re-boiler  108 , and then, remaining carbon-dioxide-containing steam is released. 
     The carbon-dioxide-containing steam is discharged from the upper part of the regeneration tower  102 A as the carbon-dioxide-containing steam  310  while the lean liquid  316  is returned to the absorbing tower  101 . 
     In this manner, a rejuvenating process for energy reutilization is performed until the rich liquid  301  absorbing carbon dioxide becomes the lean liquid  316 . 
     In the rejuvenating process, the lean liquid  316  discharged from the regeneration tower  102 A is supplied to the absorbing tower  101  as passing through the carbon dioxide release device  103  and the cooler  106 . Meanwhile, the carbon-dioxide-containing steam  310  separated at the regeneration tower  102 A is supplied to the gas-liquid separator  132  as passing through the carbon dioxide release device  104  and the cooler  105 . 
     The rich liquid  301  discharged from the absorbing tower  101  is introduced to the carbon dioxide release devices  103 ,  104  as being split at the splitting device  107 , and then, is supplied to the regeneration tower  102 A after performing heat exchange respectively with the lean liquid  316  and the carbon-dioxide-containing steam  310 . 
     Temperature of the semi-lean liquids  320 ,  306  to be introduced to the regeneration tower  102 A can be sufficiently raised by utilizing the two carbon dioxide release devices  103 ,  104 , while a part of carbon dioxide is released. Here, the releasing of carbon dioxide and water evaporation corresponding thereto are endothermal reactions. Therefore, temperature difference between the rich liquid and the lean liquid in the carbon dioxide release device  103  or temperature difference between the rich liquid and the carbon-dioxide-containing steam in the carbon dioxide release device  104  can be enlarged compared to a case that the rich liquid does not change in phase. Accordingly, heat recovery utilizing the rich liquid from the lean liquid and the carbon-dioxide-containing steam can be performed more effectively. 
     Further, by setting pressure in the carbon dioxide release devices  103 ,  104  to be low, the semi-lean liquids  320 ,  306  can be easily varied into two phases as being liquid and carbon-dioxide-containing steam. Since the degree of being two phases and efficiency of heat recovery can be increased, heat energy for releasing carbon dioxide at the regeneration tower  102 A can be further reduced. 
     As a result, temperature of the lean liquid  318  and the carbon-dioxide-containing steam  311  to be introduced respectively to the coolers  106 ,  105  can be set low. Accordingly, cooling loss can be suppressed by reducing cooling load at the coolers  106 ,  105 . 
     As described above, according to the first embodiment, it becomes possible to efficiently perform heat recovery with the rich liquid from the lean liquid and the carbon-dioxide-containing steam. 
     In the first embodiment, the condensed water  314  separated at the gas-liquid separator  132  is to be returned to the regeneration tower  102 A. However, the condensed water  314  may be returned to the absorbing tower  101  or may be merged with the lean liquid  318  after the carbon dioxide release device  103 . Alternatively, it is also possible to be used for another purpose. 
     Further, the first embodiment includes the pumps  201  to  203 . However, it is not necessarily required to provide all of the pumps. The number thereof can be reduced. 
     In the first embodiment, the splitting device  107  is provided at the outside of the absorbing tower  101  and the flow passage of the rich liquid  301  is connected to the carbon dioxide release devices  103 ,  104  via two pipes after being split by the splitting device  107 . However, not limited to the above, it is possible to adopt a structure to supply to the carbon dioxide release devices  103 ,  104  as being split from the absorbing tower  101 , and the like as long as the structure is capable of supplying to both of the carbon dioxide release devices  103 ,  104  at a desired flow ratio. 
     (Second Embodiment) 
     A carbon dioxide recovery apparatus  2  according to the second embodiment of the present invention will be described with reference to  FIG. 2  which illustrates the structure thereof. 
     Compared to the carbon dioxide recovery apparatus  1  according to the first embodiment, the carbon dioxide recovery apparatus  2  according to the second embodiment differs in including gas-liquid separators  133 ,  134 ,  135  and a merging device  110 , and a pump  204 . 
     The rich liquid  301  discharged from the absorbing tower  101  is supplied to the carbon dioxide release devices  103 ,  104  as the rich liquids  302 ,  303  via the splitting device  107 . The rich liquids  302 ,  303  are heated respectively having a part of carbon dioxide released along with steam and are discharged as being the gas-liquid two-phase semi-lean liquids  320 ,  306  having a part of carbon dioxide removed from the liquid. 
     The lean liquid  316  to be supplied from the regeneration tower  102 A to the absorbing tower  101  passes through the carbon dioxide release device  103 . The carbon-dioxide-containing steam  310  separated at the regeneration tower  102 A passes through the carbon dioxide release device  104  after being merged with carbon-dioxide-containing steam  305 ,  308  at a merging device  110  as described later. 
     Accordingly, the rich liquids  302 ,  303  supplied respectively to the carbon dioxide release devices  103 ,  104  are heated owing to heat exchange with the lean liquid  316  and the carbon-dioxide-containing steam  305 ,  308 ,  310 , so that a part of carbon dioxide is released along with steam. 
     The carbon-dioxide-containing steam  311  having a part of water vapor condensed at the carbon dioxide release device  104  is discharged and supplied to the gas-liquid separator  135 , and then, is discharged as being separated into carbon-dioxide-containing steam  313  and condensed water  312 . The carbon-dioxide-containing steam  313  is supplied to the cooler  105  and is discharged to the gas-liquid separator  132  as being cooled owing to refrigerant such as cold water to be supplied from the outside, and then, is discharged from the gas-liquid separator  132  after being separated into the carbon dioxide  315  and the condensed water  314 . The condensed water  312  discharged from the gas-liquid separator  135  is returned to the regeneration tower  102 A via the pump  204  along with the condensed water  314  discharged from the gas-liquid separator  132 . Here, it is also possible to supply the carbon-dioxide-containing steam  311  directly to the cooler  105  without providing the gas-liquid separator  135 . 
     The semi-lean liquids  320 ,  306  discharged from the carbon dioxide release devices  103 ,  104  are separated into carbon-dioxide-containing steam  305 ,  308  and semi-lean liquids  304 ,  307  respectively by the gas-liquid separators  133 ,  134 . 
     The carbon-dioxide-containing steam  305 ,  308  are supplied to the merging device  110  to be merged with the carbon-dioxide-containing steam  310  which is discharged from the regeneration tower  102 A, and then, is supplied to the carbon dioxide release device  104 . 
     The semi-lean liquids  304 ,  307  having a part of carbon dioxide released are merged at the merging device  109  respectively via the pumps  202 ,  203 , and then, are supplied to the regeneration tower  102 A. 
     The rest of the structure and operation is the same as that of the first embodiment and description thereof will not be repeated. 
     In the second embodiment, likewise for the first embodiment, the semi-lean liquids  320 ,  306  can be easily varied into two phases as being liquid and carbon-dioxide-containing steam by setting the pressure in the carbon dioxide release devices  103 ,  104  to be low. Accordingly, it becomes possible to perform heat recovery more effectively. 
     Further, according to the second embodiment, the regeneration tower  102 A and the gas-liquid separators  133 ,  134  are communicated respectively through a gas single phase. Therefore, in a case that distances between the gas-liquid separator  133  and the carbon dioxide release device  103  and between the gas-liquid separator  134  and the carbon dioxide release device  104  are short, pressure loss in pipes is smaller than that of the first embodiment in which the regeneration tower  102 A and the carbon dioxide release devices  103 ,  104  are communicated respectively through a supply line of the gas-liquid two-phase semi-lean liquid. Accordingly, rich liquid pressure in the carbon dioxide release devices  103 ,  104  can be set low. In addition, since the rich liquid pressure in the carbon dioxide release devices  103 ,  104  can be set low by the amount of elimination or reduction of liquid phase heads in pipes toward the regeneration tower  102 A which are to be noticeable when the carbon dioxide release devices  103 ,  104  are placed at low positions, the degree of being two phases of the semi-lean liquids  320 ,  306  can be increased and heat recovery from the lean liquid and the carbon-dioxide-containing steam utilizing the rich liquids can be performed more effectively. 
     In addition, since the semi-lean liquids  304 ,  307  are supplied to the regeneration tower  102 A after having carbon dioxide separated to some extent owing to the gas-liquid separators  133 ,  134 , it is possible to suppress reabsorption of carbon dioxide at the regeneration tower  102 A. 
     In the second embodiment, it is also possible to adopt a structure in which the semi-lean liquids  320 ,  306  are introduced to the gas-liquid separator  133  after being merged and the carbon-dioxide-containing steam  305  separated thereat and the carbon-dioxide-containing steam  310  discharged from the regeneration tower  102 A are supplied to the carbon dioxide release device  104  after being merged, as illustrated in  FIG. 3 , for example. 
     Further, the second embodiment includes the pumps  201  to  204 . However, not necessarily required to provide the all, it is also possible to reduce the number thereof by placing the regeneration tower  102 A at a low position, and the like. 
     The rest of the structure and operation is the same as that of the first embodiment and description thereof will not be repeated. 
     (Third Embodiment) 
     A carbon dioxide recovery apparatus  4  according to the third embodiment of the present invention will be described with reference to  FIG. 4  which illustrates the structure thereof. 
     Compared to the carbon dioxide recovery apparatus  2  according to the second embodiment, the carbon dioxide recovery apparatus  4  according to the third embodiment differs in including carbon dioxide release devices  121 ,  122 , a cooler  113 , a gas-liquid separator  136  and pumps  205 ,  206 . 
     The rich liquid  301  discharged from the absorbing tower  101  is supplied to the carbon dioxide release device  103  being the first carbon dioxide release device via the splitting device  107  as the rich liquid  302  and is heated having a part of carbon dioxide released along with steam, and then, is discharged as being the gas-liquid two-phase semi-lean liquid  320  having a part of carbon dioxide removed from the liquid. Meanwhile, the rich liquid  303  is supplied sequentially to the carbon dioxide release devices  121 ,  122 ,  104  being the second carbon dioxide release device and is heated thereat respectively having a part of carbon dioxide released along with steam, and then, is discharged as being the gas-liquid two-phase semi-lean liquid  306  having a part of carbon dioxide removed from the liquid. 
     The lean liquid  316  to be supplied from the regeneration tower  102 A to the absorbing tower  101  passes through the carbon dioxide release device  103  and heats the rich liquid  302  owing to heat exchange with the rich liquid  302 . Accordingly, a part of carbon dioxide is released along with steam. 
     The carbon-dioxide-containing steam  308  discharged from the gas-liquid separator  134  passes through the carbon dioxide release device  121 . The carbon-dioxide-containing steam  310  separated at the regeneration tower  102 A passes through the carbon dioxide release device  122 . The carbon-dioxide-containing steam  305  discharged from the gas-liquid separator  133  passes through the carbon dioxide release device  104 . Accordingly, the rich liquid  303  sequentially supplied to the carbon dioxide release devices  121 ,  122 ,  104  is heated owing to heat exchange respectively with the carbon-dioxide-containing steam  308 ,  310 ,  305 , so that a part of carbon dioxide is released along with steam. 
     The carbon-dioxide-containing steam  128 ,  311  having a part of water vapor condensed at the carbon dioxide release devices  121 ,  104  is discharged and supplied to the gas-liquid separator  135  as the carbon-dioxide-containing steam  124  after being supplied to and merged at the merging device  110 , and then, is discharged as being separated into the carbon-dioxide-containing steam  313  and the condensed water  312 . The carbon-dioxide-containing steam  313  is supplied to the cooler  105  and is discharged to the gas-liquid separator  132  as being cooled owing to refrigerant such as cold water to be supplied from the outside, and then, is discharged from the gas-liquid separator  132  after being separated into the carbon dioxide  315  and the condensed water  314 . The condensed water  312  discharged from the gas-liquid separator  135  is returned to the regeneration tower  102 A via the pump  204  along with the condensed water  314  discharged from the gas-liquid separator  132 . Here, it is also possible to supply the carbon-dioxide-containing steam  124  directly to the cooler  105  without providing the gas-liquid separator  135 . 
     Carbon-dioxide-containing steam  127  having a part of water vapor condensed at the carbon dioxide release device  122  is discharged and supplied to the cooler  113  and is discharged to the gas-liquid separator  136  after being cooled owing to refrigerant such as cold water to be supplied from the outside, and then, discharged from the gas-liquid separator  136  as being separated into carbon dioxide  325  and condensed water  324 . The condensed water  324  discharged from the gas-liquid separator  136  is returned to the regeneration tower  102 A via the pump  206 . 
     The semi-lean liquids  320 ,  306  discharged from the carbon dioxide release devices  103 ,  104  are separated into carbon-dioxide-containing steam  305 ,  308  and semi-lean liquids  304 ,  307  respectively by the gas-liquid separators  133 ,  134 . 
     The semi-lean liquids  304 ,  307  having a part of carbon dioxide released are merged at the merging device  109  respectively via the pumps  202 ,  203 , and then, are supplied to the regeneration tower  102 A. 
     Here, supply lines of the carbon-dioxide-containing steam  305 ,  308  and a supply line of the carbon-dioxide-containing steam  310  are not merged. Accordingly, being different from the second embodiment, pressure in the gas-liquid separators  133 ,  134  can be remarkably lowered than pressure in the regeneration tower  102 A owing to adjustment of a pressure adjusting valve (not illustrated) provided to a supply line etc. of the carbon dioxide  315 . Therefore, since each rich liquid pressure in the carbon dioxide release devices  103 ,  121 ,  122 ,  104  can be lowered, the degree of being two phases of the semi-lean liquids  320 ,  306  can be increased and heat recovery from the lean liquid and the carbon-dioxide-containing steam utilizing the rich liquids can be performed more effectively. 
     Here, it is also possible to lower the rich liquid pressure in the carbon dioxide release devices than the pressure in the regeneration tower  102 A with a structure in which the semi-lean liquids  320 ,  306  are introduced to a gas-liquid separator after being merged and carbon-dioxide-containing steam separated thereat and the carbon-dioxide-containing steam  310  discharged from the regeneration tower  102 A, without being merged, sequentially heat the rich liquid  303  with separate carbon dioxide release devices. 
     The rest of the structure and operation is the same as that of the second embodiment and description thereof will not be repeated. 
     (Fourth Embodiment) 
     A carbon dioxide recovery apparatus  5  according to the fourth embodiment of the present invention will be described with reference to  FIG. 5  which illustrates the structure thereof. 
     Compared to the carbon dioxide recovery apparatus  1  according to the first embodiment, the carbon dioxide recovery apparatus  5  according to the fourth embodiment differs in including a lean liquid cooler  123 . 
     At the lean liquid cooler  123  placed before the carbon dioxide release device  104 , the rich liquid  303  supplied after being split cools the lean liquid  318  discharged from the carbon dioxide release device  103  as being heated thereat. It is possible to reduce usage quantity of high temperature steam supplied at the re-boiler  108  by performing heat recovery from the lean liquid to a maximum extent. Further, it is also possible to suppress power usage quantity by reducing cooling load at the cooler  106 . 
     The rest of the structure and operation is the same as that of the first embodiment and description thereof will not be repeated. 
     Naturally, it is also possible to provide the lean liquid cooler  123  to the carbon dioxide recovery apparatus of the second embodiment or the third embodiment. Here, similar effects are obtained. 
     (Fifth Embodiment) 
     A carbon dioxide recovery apparatus  6  according to the fifth embodiment of the present invention will be described with reference to  FIG. 6  which illustrates the structure thereof. 
     In the first to fourth embodiments, the carbon dioxide release device  104  is arranged at the outside of the regeneration tower  102 A. On the contrary, in the fifth embodiment, the carbon dioxide release device  104  is not arranged at the outside of a regeneration tower  102 B. Accordingly, the rich liquid  303  discharged from the splitting device  107  is supplied directly to the regeneration tower  102 B. Since the carbon dioxide release device  104  is not arranged at the outside of the regeneration tower  102 B, the merging device  109  becomes unnecessary. 
     Here, heat exchange of the semi-lean liquid  320  and the rich liquid  303  with the carbon-dioxide-containing steam  131  is performed at the inside of the regeneration tower  102 B. In the first to fourth embodiments, the regeneration tower  102 A is provided simply with the loading layer  102   a . In contrast, the regeneration tower  102 B of the fifth embodiment is provided with a loading layer  102   b  at the upper stage as well as with the loading layer  102   a  at the lower stage. The rich liquid  303  is supplied from above the loading layer  102   b  at the upper stage and is moved downward as passing through the loading layer  102   b . The semi-lean liquid  320  is supplied between the loading layers  102   a ,  102   b  and is moved downward as passing through the loading layer  102   a  at the lower stage. The carbon-dioxide-containing steam  131  passes upwards through the loading layers  102   a ,  102   b , so that heat exchange is performed. That is, instead of the carbon dioxide release device  104 , the loading layer  102   b  having a similar function is arranged in the regeneration tower  102 B as the second carbon dioxide release device. Here, the carbon-dioxide-containing steam contained in the semi-lean liquid  320  also functions as a heating medium for the rich liquid  303  along with the carbon-dioxide-containing steam  131  owing to upward movement thereof after being introduced to the regeneration tower  102 B. 
     In the first to fourth embodiments, the carbon-dioxide-containing steam  310  discharged from the upper part of the regeneration tower  102 B passes through the carbon dioxide release device  104  and the like. In the fifth embodiment, the carbon-dioxide-containing steam  310  is supplied directly to the cooler  105  and cooled, and is supplied to the gas-liquid separator  132 . 
     According to the fifth embodiment, since the carbon dioxide release device  104  and the merging device  109  are not provided, it is possible to reduce manufacturing cost requiring less pipes compared to the first embodiment. Here, the fifth embodiment includes the pumps  201  to  203 . However, it is not necessarily required to provide all of the pumps. The number thereof can be reduced. 
     (Sixth Embodiment) 
     A carbon dioxide recovery apparatus  7  according to the sixth embodiment of the present invention will be described with reference to  FIG. 7  which illustrates the structure thereof. 
     Compared to the carbon dioxide recovery apparatus  6  according to the fifth embodiment, the carbon dioxide recovery apparatus  7  according to the sixth embodiment differs in including the gas-liquid separator  133 . 
     The semi-lean liquid  320  discharged from the carbon dioxide release device  103  is separated into the carbon-dioxide-containing steam  305  and the semi-lean liquid  304  by the gas-liquid separator  133 . 
     The semi-lean liquid  304  is supplied between the loading layers  102   a ,  102   b  by the pump  202  and is moved downward as passing through the loading layer  102   a  at the lower stage. The carbon-dioxide-containing steam  305  is supplied at a position of the same height as the semi-lean liquid  304  or higher to the regeneration tower  102 B and functions as a heating medium for the semi-lean liquid  303  along with the carbon-dioxide-containing steam  131  as being moved upward. 
     Further, according to the sixth embodiment, the regeneration tower  102 B and the gas-liquid separator  133  is communicated through a gas single phase. Therefore, in a case that distance between the gas-liquid separator  133  and the carbon dioxide release device  103  is short, pressure loss in pipes is smaller than that of the fifth embodiment in which the regeneration tower  102 B and the carbon dioxide release device  103  are communicated through a supply line of the gas-liquid two-phase semi-lean liquid. Accordingly, rich liquid pressure in the carbon dioxide release device  103  can be set low. In addition, since the rich liquid pressure in the carbon dioxide release device  103  can be set low by the amount of elimination or reduction of a liquid phase head in pipes toward the regeneration tower  102 B which is to be noticeable when the carbon dioxide release device  103  is placed at a low position, the degree of being two phases of the semi-lean liquid  320  can be increased and heat recovery from the lean liquid and the carbon-dioxide-containing steam utilizing the rich liquid can be performed more effectively. 
     The rest of the structure and operation is the same as that of the fifth embodiment and description thereof will not be repeated. 
     (Seventh Embodiment) 
     A carbon dioxide recovery apparatus  8  according to the seventh embodiment of the present invention will be described with reference to  FIG. 8  which illustrates the structure thereof. 
     Compared to the carbon dioxide recovery apparatus  6  according to the fifth embodiment, the carbon dioxide recovery apparatus  8  according to the seventh embodiment differs in including the lean liquid cooler  123 . 
     At the lean liquid cooler  123  placed before the regeneration tower  102 B, the rich liquid  303  supplied after being split cools the lean liquid  318  discharged from the carbon dioxide release device  103  as being heated thereat. It is possible to reduce usage quantity of high temperature steam supplied at the re-boiler  108  by performing heat recovery from the lean liquid to a maximum extent. Further, it is also possible to suppress power usage quantity by reducing cooling load at the cooler  106 . 
     The rest of the structure and operation is the same as that of the fifth embodiment and description thereof will not be repeated. 
     Naturally, it is also possible to provide the lean liquid cooler  123  to the carbon dioxide recovery apparatus of the sixth embodiment. Here, similar effects are obtained. 
     The above description is performed on examples of the first to seventh embodiments of the present invention and is not intended to limit the present invention. Modification can be performed within the technical scope of the present invention.