U.S. patent application number 13/927848 was filed with the patent office on 2014-03-27 for carbon dioxide recovering apparatus and method for operating the same.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. The applicant listed for this patent is Kabushiki Kaisha Toshiba. Invention is credited to Hideo Kitamura, Toshihisa Kiyokuni, Satoshi SAITO, Mitsuru Udatsu.
Application Number | 20140086811 13/927848 |
Document ID | / |
Family ID | 48670423 |
Filed Date | 2014-03-27 |
United States Patent
Application |
20140086811 |
Kind Code |
A1 |
SAITO; Satoshi ; et
al. |
March 27, 2014 |
CARBON DIOXIDE RECOVERING APPARATUS AND METHOD FOR OPERATING THE
SAME
Abstract
According to one embodiment, a carbon dioxide recovering
apparatus includes a flow distributor dividing the first rich
solution discharged from an absorbing tower into a second rich
solution and a third rich solution, a reheat exchanger heating the
second rich solution with a lean solution discharged from a
releasing tower as a heat source, a heating unit heating the third
rich solution with a carbon dioxide containing steam to be released
from the releasing tower as a heat source, a gas-liquid separator
separating the carbon dioxide containing steam used to heat the
third rich solution into carbon dioxide and condensate water, a
measuring unit measuring an amount of the condensate water in the
gas-liquid separator, and a controller. The controller controls a
flow dividing ratio in the flow distributor based on a change in
the amount of the condensate water measured by the measuring
unit.
Inventors: |
SAITO; Satoshi; (Kanagawa,
JP) ; Kitamura; Hideo; (Tokyo, JP) ; Udatsu;
Mitsuru; (Kanagawa, JP) ; Kiyokuni; Toshihisa;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Toshiba |
Tokyo |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Toshiba
Tokyo
JP
|
Family ID: |
48670423 |
Appl. No.: |
13/927848 |
Filed: |
June 26, 2013 |
Current U.S.
Class: |
423/220 ;
422/111 |
Current CPC
Class: |
B01D 53/62 20130101;
B01D 2258/0283 20130101; B01D 53/1412 20130101; Y02C 10/04
20130101; B01D 2252/204 20130101; B01D 2259/65 20130101; Y02C 10/06
20130101; B01D 53/1425 20130101; B01D 2252/20478 20130101; B01D
53/1475 20130101; Y02C 20/40 20200801 |
Class at
Publication: |
423/220 ;
422/111 |
International
Class: |
B01D 53/62 20060101
B01D053/62 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2012 |
JP |
2012-141781 |
Claims
1. A carbon dioxide recovering apparatus comprising: an absorbing
tower bringing the flue gas containing carbon dioxide into contact
with an absorbing solution that absorbs carbon dioxide and
generating and discharging a first rich solution that has absorbed
carbon dioxide; a flow distributor dividing the first rich solution
into a second rich solution and a third rich solution; a releasing
tower heating the second rich solution and the third rich solution,
causing carbon dioxide containing steam to be released to generate
a lean solution, discharging the lean solution, and returning the
lean solution to the absorbing tower; a reheat exchanger heating
the second rich solution with the lean solution discharged from the
releasing tower as a heat source; a heating unit heating the third
rich solution before becoming the lean solution with the carbon
dioxide containing steam to be released from the releasing tower as
a heat source; a gas-liquid separator separating the carbon dioxide
containing steam used to heat the third rich solution into carbon
dioxide and condensate water; a measuring unit measuring an amount
of the condensate water in the gas-liquid separator; and a
controller controlling a flow dividing ratio in the flow
distributor based on a change in the amount of the condensate water
measured by the measuring unit.
2. The carbon dioxide recovering apparatus according to claim 1,
wherein the controller raises a flow rate of the third rich
solution from a predetermined value until the amount of the
condensate water measured in the measuring unit becomes
constant.
3. The carbon dioxide recovering apparatus according to claim 2,
further comprising a reboiler heating a stored solution in the
releasing tower, wherein the controller controls a heat input
amount in the reboiler after determination of the flow rate of the
third rich solution so that a carbon dioxide recovering ratio in
the absorbing tower may be a predetermined value.
4. The carbon dioxide recovering apparatus according to claim 3,
wherein the heating unit is a filling layer provided in the
releasing tower, and wherein the filling layer is provided at a
higher position than a part of the releasing tower to which the
second rich solution is supplied.
5. The carbon dioxide recovering apparatus according to claim 3,
further comprising a joining unit joining the second rich solution
heated in the reheat exchanger and the third rich solution heated
in the heating unit and supplying them to the releasing tower.
6. The carbon dioxide recovering apparatus according to claim 2,
wherein the heating unit is a filling layer provided in the
releasing tower, and wherein the filling layer is provided at a
higher position than a part of the releasing tower to which the
second rich solution is supplied.
7. The carbon dioxide recovering apparatus according to claim 2,
further comprising a joining unit joining the second rich solution
heated in the reheat exchanger and the third rich solution heated
in the heating unit and supplying them to the releasing tower.
8. The carbon dioxide recovering apparatus according to claim 1,
wherein the heating unit is a filling layer provided in the
releasing tower, and wherein the filling layer is provided at a
higher position than a part of the releasing tower to which the
second rich solution is supplied.
9. The carbon dioxide recovering apparatus according to claim 1,
further comprising a joining unit joining the second rich solution
heated in the reheat exchanger and the third rich solution heated
in the heating unit and supplying them to the releasing tower.
10. A method for operating a carbon dioxide recovering apparatus,
comprising: introducing the flue gas containing carbon dioxide into
an absorbing tower, bringing the flue gas containing carbon dioxide
into contact with an absorbing solution that absorbs carbon
dioxide, and generating and discharging a first rich solution that
has absorbed carbon dioxide; dividing the first rich solution into
a second rich solution and a third rich solution; heating the
second rich solution with use of a lean solution; heating the third
rich solution with use of carbon dioxide containing steam; in a
releasing tower, releasing and separating steam containing carbon
dioxide from the heated second rich solution and third rich
solution to generate the carbon dioxide containing steam and the
lean solution; with use of a gas-liquid separator, separating the
carbon dioxide containing steam used to heat the third rich
solution into carbon dioxide and condensate water; measuring an
amount of condensate water in the gas-liquid separator; and
controlling a flow dividing ratio between the second rich solution
and the third rich solution based on a change in the amount of the
condensate water.
11. The method for operating a carbon dioxide recovering apparatus
according to claim 10, wherein a flow rate of the third rich
solution is raised from a predetermined value, and the flow rate of
the third solution is set to a flow rate when the amount of the
condensate water becomes constant.
12. The method for operating a carbon dioxide recovering apparatus
according to claim 11, wherein a heat input amount in a reboiler
connected to the releasing tower is controlled after determination
of the flow rate of the third rich solution so that a carbon
dioxide recovering ratio in the absorbing tower becomes a
predetermined value.
13. The method for operating a carbon dioxide recovering apparatus
according to claim 10, wherein a flow rate of the third rich
solution is lowered from a predetermined value, and the flow rate
of the third rich solution is set to a flow rate when the amount of
the condensate water does not fall in a certain range any more.
14. The method for operating a carbon dioxide recovering apparatus
according to claim 13, wherein a heat input amount in a reboiler
connected to the releasing tower is controlled after determination
of the flow rate of the third rich solution so that a carbon
dioxide recovering ratio in the absorbing tower becomes a
predetermined value.
Description
FIELD
[0001] Embodiments described herein relate generally to a carbon
dioxide recovering apparatus and a method for operating a carbon
dioxide recovering apparatus.
BACKGROUND
[0002] Recently, in terms of recovery of carbon dioxide, a carbon
dioxide recovery and storage technique attracts attention as an
effective measure against a globally-concerning global warming
problem. Especially, for exhaust gas from a thermal power plant and
the like, a method for recovering carbon dioxide by an alkaline
aqueous solution is considered.
[0003] As such a carbon dioxide recovering apparatus is known one
including an absorbing tower causing carbon dioxide contained in
the flue gas to be absorbed in an absorbing solution to generate a
rich solution, a releasing tower heating the rich solution
discharged from the absorbing tower to release and separate carbon
dioxide as well as steam and returning a generated lean solution to
the absorbing tower, a first heat exchanger allowing the lean
solution supplied from the releasing tower to the absorbing tower
to pass therethrough, a second heat exchanger allowing carbon
dioxide containing steam separated in the releasing tower to pass
therethrough, and a flow distributor dividing and supplying the
rich solution discharged from the absorbing tower to the first heat
exchanger and the second heat exchanger and adapted to cause the
rich solution introduced into the first heat exchanger and the
second heat exchanger to heat-exchange with the lean solution and
the carbon dioxide containing steam, respectively, and to
thereafter be supplied to the releasing tower.
[0004] In the aforementioned conventional carbon dioxide recovering
apparatus, in a case where a divided flow rate to the second heat
exchanger is lower than an optimum value, heat exchange with the
carbon dioxide containing steam is not performed sufficiently. On
the other hand, in a case where the divided flow rate to the second
heat exchanger is higher than the optimum value, heat exchange with
the carbon dioxide containing steam is performed sufficiently, but
a temperature of the rich solution heated in the releasing tower is
lowered, and a releasing performance of carbon dioxide is degraded.
This case causes a problem in which the lean solution from which
carbon dioxide is not released sufficiently is sent to the
absorbing tower, and in which carbon dioxide in the exhaust gas
cannot be absorbed sufficiently in the absorbing tower. An increase
in energy to be provided to a reboiler to avoid this situation
results in an increase in energy required for recovery of carbon
dioxide.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic configuration of a carbon dioxide
recovering apparatus according to a first embodiment;
[0006] FIG. 2 is a graph illustrating an example of relationship
between a divided flow rate of a rich solution and carbon dioxide
recovering energy;
[0007] FIG. 3 is a graph illustrating an example of relationship
between the divided flow rate of the rich solution and an amount of
condensate water per unit time in a gas-liquid separator;
[0008] FIG. 4 is a schematic configuration of a carbon dioxide
recovering apparatus according to a second embodiment;
[0009] FIG. 5 is a graph illustrating relationship between the
divided flow rate of the rich solution and the carbon dioxide
recovering energy in Example 1; and
[0010] FIG. 6 is a graph illustrating relationship between the
divided flow rate of the rich solution and the amount of the
condensate water per unit time in the gas-liquid separator in
Example 1.
DETAILED DESCRIPTION
[0011] According to one embodiment, a carbon dioxide recovering
apparatus includes a flow distributor dividing the first rich
solution discharged from an absorbing tower into a second rich
solution and a third rich solution, a reheat exchanger heating the
second rich solution with a lean solution discharged from a
releasing tower as a heat source, a heating unit heating the third
rich solution with a carbon dioxide containing steam to be released
from the releasing tower as a heat source, a gas-liquid separator
separating the carbon dioxide containing steam used to heat the
third rich solution into carbon dioxide and condensate water, a
measuring unit measuring an amount of the condensate water in the
gas-liquid separator, and a controller. The controller controls a
flow dividing ratio in the flow distributor based on a change in
the amount of the condensate water measured in the measuring
unit.
[0012] Embodiments will now be explained with reference to the
accompanying drawings.
First Embodiment
[0013] FIG. 1 illustrates a schematic configuration of a carbon
dioxide recovering apparatus according to a first embodiment. This
carbon dioxide recovering apparatus includes an absorbing tower
101, a reheat exchanger 103, a gas-liquid separator 132, coolers
105 and 106, a releasing tower 102A, a reboiler 108, pumps 201,
202, and 203, and a flow distributor 107.
[0014] The flue gas containing carbon dioxide 111 introduced into
the absorbing tower 101 contacts an absorbing solution that absorbs
carbon dioxide, and carbon dioxide is removed. The absorbing
solution absorbs carbon dioxide from the flue gas containing carbon
dioxide 111 to generate a rich solution 301.
[0015] For example, the absorbing tower 101 is a countercurrent
gas-liquid contacting unit that brings the flue gas containing
carbon dioxide 111 supplied from a lower portion into gas-liquid
contact with a lean solution 319 flowing down from an upper
portion.
[0016] The flue gas containing carbon dioxide 111 to be introduced
into the absorbing tower 101 is not particularly limited and is
combustion exhaust gas or process exhaust gas, for example. The
flue gas containing carbon dioxide 111 may be introduced after a
cooling treatment as needed.
[0017] Also, the absorbing solution is not particularly limited as
long as it is an alkaline solution and can be an amine aqueous
solution such as monoethanolamine (MEA) and diethanolamine (DEA),
for example. Decarbonated gas 112 from which carbon dioxide has
been removed in the absorbing tower 101 is discharged from an upper
portion of the absorbing tower 101.
[0018] The rich solution 301 discharged from the absorbing tower
101 is given via the pump 201 to the flow distributor 107 and is
divided into rich solutions 302 and 303. The rich solution 302
heat-exchanges with an after-mentioned lean solution 316 in the
reheat exchanger 103 and is thus heated, and a heated rich solution
320 is supplied via the pump 202 to the releasing tower 102A. Also,
the rich solution 303 is provided to a position of the releasing
tower 102A located further on an upper side than a position to
which the rich solution 320 is provided, specifically to an
after-mentioned heat exchange layer 102b, as illustrated in FIG.
1.
[0019] The releasing tower 102A has a heat exchange layer 102a and
the heat exchange layer 102b provided on an upper stage of the heat
exchange layer 102a. The rich solution 303 is supplied to the heat
exchange layer 102b on the upper stage, passes through the heat
exchange layer 102b, and moves downward. The rich solution 320 is
supplied between the heat exchange layer 102a and the heat exchange
layer 102b, passes through the filling layer 102a on the lower
stage, and moves downward. Carbon dioxide containing steam passes
through the filling layers 102a and 102b upward for heat exchange.
The rich solutions 303 and 320 are heated to cause most carbon
dioxide as well as steam to be released, separated, and discharged
from an upper portion of the releasing tower 102A as carbon dioxide
containing steam 310, and a high-temperature lean solution 316 from
which most carbon dioxide has been removed is discharged from a
lower portion of the releasing tower 102A.
[0020] The releasing tower 102A is a countercurrent gas-liquid
contacting unit, for example. The reboiler 108 heats a stored
solution in the releasing tower 102A with use of high-temperature
steam 140 as an externally-supplied heat. By doing so, the carbon
dioxide containing steam moves upward in the releasing tower
102A.
[0021] The carbon dioxide containing steam 310 discharged from the
releasing tower 102A is supplied to the cooler 105, is cooled by a
refrigerant 142 such as cold water to be supplied externally, and
is discharged to the gas-liquid separator 132.
[0022] The carbon dioxide containing steam 310 cooled in the cooler
105 is separated into carbon dioxide 315 and condensate water 314
in the gas-liquid separator 132, and the carbon dioxide 315 is
discharged and recovered. The gas-liquid separator 132 is provided
with a water gauge 401 for measurement of water level changes of
the condensate water 314. In other words, an amount of the
condensate water in the gas-liquid separator 132 (an amount of the
condensate water to be generated per unit time) is measured. The
condensate water 314 can be supplied to the releasing tower
102A.
[0023] The lean solution 316 discharged from the releasing tower
102A heat-exchanges with the rich solution 302 in the reheat
exchanger 103. A lean solution 318 after heat exchange in the
reheat exchanger 103 is supplied to the cooler 106 and is cooled by
a refrigerant 143 such as cold water to be supplied externally. A
lean solution 319 cooled in the cooler 106 is supplied to the
absorbing tower 101, absorbs carbon dioxide from the flue gas
containing carbon dioxide 111, and becomes the rich solution 301.
In this manner, in the carbon dioxide recovering apparatus, the
absorbing solution circulates between the absorbing tower 101 and
the releasing tower 102A, and carbon dioxide is recovered.
[0024] The carbon dioxide recovering apparatus also includes a
controller 402 that obtains a measurement result of the water gauge
401 and controls divided flow rates (flow dividing ratio) of the
rich solutions 302 and 303 in the flow distributor 107 and a heat
input amount in the reboiler 108.
[0025] An example of relationship between the divided flow rate of
the rich solution 303 and carbon dioxide recovering energy in such
a carbon dioxide recovering apparatus is illustrated in FIG. 2. As
illustrated in FIG. 2, when the divided flow rate of the rich
solution 303 is raised from zero gradually, the carbon dioxide
recovering energy is lowered gradually. This suggests that heat
recovery of the rich solution 303 from the carbon dioxide
containing steam at the upper portion of the releasing tower 102A
is carried out effectively. When the divided flow rate is between
predetermined values .alpha. and .beta., the carbon dioxide
recovering energy keeps a low value. When the divided flow rate
exceeds the predetermined value .beta., the carbon dioxide
recovering energy is significantly raised along with the raise of
the divided flow rate of the rich solution 303. This suggests that,
by supplying the rich solution 303 to the releasing tower 102A
excessively, a temperature in the releasing tower 102A is lowered,
which prevents release of carbon dioxide. Accordingly, it is
preferable to set the divided flow rate of the rich solution 303 in
a range of .alpha. to .beta..
[0026] FIG. 3 illustrates an example of relationship between the
divided flow rate of the rich solution 303 and the amount of the
condensate water per unit time in the gas-liquid separator 132. As
illustrated in FIG. 3, when the divided flow rate of the rich
solution 303 is raised from zero, the amount of the condensate
water per unit time is decreased along with the raise of the
divided flow rate. The reason for this is that heat recovery of the
rich solution 303 from the carbon dioxide containing steam at the
upper portion of the releasing tower 102A is carried out
effectively, which causes a decrease in a steam amount to be
carried to the gas-liquid separator 132. It is apparent from FIG. 3
that the amount of the condensate water becomes almost constant
when the divided flow rate of the rich solution 303 exceeds the
predetermined value .alpha..
[0027] Accordingly, from FIGS. 2 and 3, a divided flow rate when
the amount of the condensate water becomes almost constant, that
is, when a water level change of the condensate water 314 in the
gas-liquid separator 132 to be measured by the water gauge 401
becomes almost constant, after a gradual raise of the divided flow
rate of the rich solution 303 from zero, is an optimum divided flow
rate in which the carbon dioxide recovering energy is
restricted.
[0028] In this manner, by determining the divided flow rate of the
rich solution 303 while monitoring the water level change of the
condensate water 314 in the gas-liquid separator 132, the divided
flow rate of the rich solution 303 can be optimum, heat recovery of
the rich solutions 302 and 303 from the lean solution 316 and the
carbon dioxide containing steam can be performed effectively, and
the carbon dioxide recovering energy can be restricted.
Second Embodiment
[0029] FIG. 4 illustrates a schematic configuration of a carbon
dioxide recovering apparatus according to a second embodiment. The
carbon dioxide recovering apparatus according to the present
embodiment differs from the first embodiment illustrated in FIG. 1
in that a carbon dioxide generator 104 and a joining unit 109 are
provided, and in that heat exchange between the rich solution 303
and the carbon dioxide containing steam 310 is performed in the
carbon dioxide generator 104.
[0030] The rich solution 301 discharged from the absorbing tower
101 is divided into the rich solutions 302 and 303 by the flow
distributor 107. The rich solution 302 heat-exchanges with the lean
solution 316 in the reheat exchanger 103 and is heated. On the
other hand, the rich solution 303 heat-exchanges with the carbon
dioxide containing steam 310 in the carbon dioxide generator (heat
exchanger) 104 and is heated. Carbon dioxide containing steam 311
that has passed through the carbon dioxide generator 104 is
supplied to the cooler 105.
[0031] The rich solution 320 heated in the reheat exchanger 103 and
a rich solution 306 heated in the carbon dioxide generator 104 are
joined in the joining unit 109 and are supplied to a releasing
tower 102B.
[0032] The rich solution supplied to the releasing tower 102B
passes through the filling layer 102a and moves downward. Carbon
dioxide containing steam passes through the filling layer 102a
upward for heat exchange with the rich solution. The rich solution
is heated to cause most carbon dioxide as well as steam to be
released, separated, and discharged from an upper portion of the
releasing tower 102B as the carbon dioxide containing steam 310,
and the high-temperature lean solution 316 from which most carbon
dioxide has been removed is discharged from a lower portion of the
releasing tower 102B.
[0033] In the carbon dioxide recovering apparatus configured in
this manner as well as in the aforementioned first embodiment, an
optimum divided flow rate of the rich solution 303 can be
determined easily while a water level change of the condensate
water 314 in the gas-liquid separator 132 can be monitored.
Accordingly, heat recovery of the rich solutions 302 and 303 from
the lean solution 316 and the carbon dioxide containing steam can
be performed effectively, and carbon dioxide recovering energy can
be restricted.
[0034] In the above first and second embodiments, a method of
raising the divided flow rate of the rich solution 303 gradually
from zero until the amount of the condensate water becomes almost
constant has been described. However, an initial value of the
divided flow rate of the rich solution 303 may be set to a certain
large value, and an optimum divided flow rate may be obtained by
decreasing the divided flow rate of the rich solution 303 gradually
while confirming that the amount of the condensate water is not
increased excessively (that the amount of the condensate water is
almost constant). Specifically, the divided flow rate of the rich
solution 303 is lowered gradually until the amount of the
condensate water does not fall in a certain range any more.
[0035] Also, after determination of the optimum divided flow rate
of the rich solution 303, to achieve a desired carbon dioxide
recovering ratio, the heat input amount in the reboiler 108 may be
controlled while confirming that the amount of the condensate water
is not increased excessively (that the amount of the condensate
water is almost constant).
[0036] For measurement of the amount of the condensate water per
unit time in the gas-liquid separator 132, a mass meter may be used
instead of the water gauge 401, or a flowmeter may be used to
measure a flow rate of the condensate water 314 to be returned from
the gas-liquid separator 132 to the releasing tower 102A or 102B,
and the amount of the condensate water may be derived from the
measured flow rate.
EXAMPLES
Example 1
[0037] In the carbon dioxide recovering apparatus illustrated in
FIG. 1, the flue gas containing carbon dioxide 111 with 12% carbon
dioxide with a flow rate of 100 Nm.sup.3/h was supplied to the
absorbing tower 101 and was brought into countercurrent contact
with an amine absorbing solution in the absorbing tower 101 to
prepare the rich solution 301. First, the divided flow rate of the
rich solution 303 was set to zero, and an entire amount of the rich
solution 301 was set as the rich solution 302. At this time, a
carbon dioxide recovering ratio at an exit of the absorbing tower
101 was 80%. When the heat input amount in the reboiler 108 (an
amount of steam to be supplied) was increased to raise the carbon
dioxide recovering ratio to 95%, the recovering energy became 4.0
GJ/t-CO.sub.2. At this time, the amount of the condensate water in
the gas-liquid separator 132 was 200 L per unit time.
[0038] Subsequently, while monitoring that a measurement result of
the water gauge 401 provided in the gas-liquid separator 132 was
being decreased, the flow distributor 107 was controlled by the
controller 402 to raise the divided flow rate of the rich solution
303. FIG. 5 illustrates relationship between the divided flow rate
of the rich solution 303 and carbon dioxide recovering energy.
Also, FIG. 6 illustrates relationship between the divided flow rate
of the rich solution 303 and the amount of the condensate water per
unit time in the gas-liquid separator 132.
[0039] As is apparent from FIG. 6, when the flow rate of the rich
solution 303 exceeded 5% of the rich solution 301, the amount of
the condensate water in the gas-liquid separator 132 was decreased
to approximately 20 L per unit time and became almost constant. It
was confirmed that, when the flow rate of the rich solution 303 was
5% of the rich solution 301, the carbon dioxide recovering ratio at
the exit of the absorbing tower 101 was 90%, the carbon dioxide
recovering energy was 3.1 GJ/t-CO.sub.2, and the carbon dioxide
recovering energy was able to be lowered further by 0.9
GJ/t-CO.sub.2 than in a case of setting the entire amount of the
rich solution 301 as the rich solution 302. It was confirmed that,
by raising the divided flow rate of the rich solution 303 gradually
from a predetermined value (zero, for example) until the amount of
the condensate water became almost constant, the optimum divided
flow rate was able to be obtained, heat recovery of the rich
solutions from the lean solution and the carbon dioxide containing
steam was able to be performed effectively, and carbon dioxide
recovering energy was able to be restricted.
Example 2
[0040] In the carbon dioxide recovering apparatus illustrated in
FIG. 1, the flue gas containing carbon dioxide 111 with 12% carbon
dioxide with a flow rate of 100 Nm.sup.3/h was supplied to the
absorbing tower 101 and was brought into countercurrent contact
with an amine absorbing solution in the absorbing tower 101 to
prepare the rich solution 301. First, the divided flow rate of the
rich solution 303 was set to 30% of the rich solution 301, and the
divided flow rate of the rich solution 302 was set to 70% of the
rich solution 301. At this time, the carbon dioxide recovering
ratio at the exit of the absorbing tower 101 was 70%, and the
amount of the condensate water in the gas-liquid separator 132 was
10 L per unit time. Also, the carbon dioxide recovering energy
became 3.8 GJ/t-CO.sub.2.
[0041] Subsequently, when the flow distributor 107 was controlled
by the controller 402 to lower the divided flow rate of the rich
solution 303 to approximately 10% of the rich solution 301 while
monitoring that a measurement result of the water gauge 401
provided in the gas-liquid separator 132 was not increased
excessively (that the measurement result was almost constant), the
carbon dioxide recovering ratio in the absorbing tower 101 was
raised, and a 90% carbon dioxide recovering ratio was able to be
achieved. The amount of the condensate water in the gas-liquid
separator 132 at this time was 15 L per unit time and was almost
constant. At this time, the carbon dioxide recovering energy was
3.0 GJ/t-CO.sub.2, and it was confirmed that the carbon dioxide
recovering energy was able to be lowered further by 0.8
GJ/t-CO.sub.2 than in a case of setting the divided flow rate of
the rich solution 303 to 30% of the rich solution 301.
Example 3
[0042] In the carbon dioxide recovering apparatus illustrated in
FIG. 1, the flue gas containing carbon dioxide 111 with 12% carbon
dioxide with a flow rate of 100 Nm.sup.3/h was supplied to the
absorbing tower 101 and was brought into countercurrent contact
with an amine absorbing solution in the absorbing tower 101 to
prepare the rich solution 301. First, the divided flow rate of the
rich solution 303 was set to 30% of the rich solution 301, and the
divided flow rate of the rich solution 302 was set to 70% of the
rich solution 301. Example 3 differs from Example 2 only in that
the heat input amount in the reboiler is approximately 5% smaller
than that in Example 2. At this time, the carbon dioxide recovering
ratio at the exit of the absorbing tower 101 was 65%, and the
amount of the condensate water in the gas-liquid separator 132 was
15 L per unit time. Also, the carbon dioxide recovering energy
became 3.9 GJ/t-CO.sub.2.
[0043] Subsequently, when the flow distributor 107 was controlled
by the controller 402 to lower the divided flow rate of the rich
solution 303 to approximately 10% of the rich solution 301 while
monitoring that a measurement result of the water gauge 401
provided in the gas-liquid separator 132 was not increased
excessively (that the measurement result was almost constant), the
carbon dioxide recovering ratio in the absorbing tower 101 was
raised, and a 85% carbon dioxide recovering ratio was able to be
achieved.
[0044] In addition, when the heat input amount in the reboiler 108
was increased, the carbon dioxide recovering ratio was raised to
90%. At this time, the carbon dioxide recovering energy was 3.0
GJ/t-CO.sub.2, and it was confirmed that the carbon dioxide
recovering energy was able to be lowered by 0.9 GJ/t-CO.sub.2.
Example 4
[0045] In the carbon dioxide recovering apparatus illustrated in
FIG. 4, the flue gas containing carbon dioxide 111 with 12% carbon
dioxide with a flow rate of 100 Nm.sup.3/h was supplied to the
absorbing tower 101 and was brought into countercurrent contact
with an amine absorbing solution in the absorbing tower 101 to
prepare the rich solution 301.
[0046] First, the divided flow rate of the rich solution 303 was
set to zero, and an entire amount of the rich solution 301 was set
as the rich solution 302. At this time, a carbon dioxide recovering
ratio at an exit of the absorbing tower 101 was 80%. When the heat
input amount in the reboiler 108 (an amount of steam to be
supplied) was increased to raise the carbon dioxide recovering
ratio to 95%, the recovering energy became 4.0 GJ/t-CO.sub.2. At
this time, the amount of the condensate water in the gas-liquid
separator 132 was 200 L per unit time.
[0047] Subsequently, while monitoring that a measurement result of
the water gauge 401 provided in the gas-liquid separator 132 was
being decreased, the flow distributor 107 was controlled by the
controller 402 to raise the divided flow rate of the rich solution
303. When the flow rate of the rich solution 303 exceeded 5% of the
rich solution 301, the amount of the condensate water in the
gas-liquid separator 132 was decreased to approximately 20 L per
unit time and became almost constant. It was confirmed that, when
the flow rate of the rich solution 303 was 5% of the rich solution
301, the carbon dioxide recovering ratio at the exit of the
absorbing tower 101 was 90%, the carbon dioxide recovering energy
was 3.1 GJ/t-CO.sub.2, and the carbon dioxide recovering energy was
able to be lowered further by 0.9 GJ/t-CO.sub.2 than in a case of
setting the entire amount of the rich solution 301 as the rich
solution 302. It was confirmed that, by raising the divided flow
rate of the rich solution 303 gradually from zero until the amount
of the condensate water became almost constant, the optimum divided
flow rate was able to be obtained, heat recovery of the rich
solutions from the lean solution and the carbon dioxide containing
steam was able to be performed effectively, and carbon dioxide
recovering energy was able to be restricted.
[0048] In at least one of the embodiments described above, heat
recovery of the rich solutions from the lean solution and the
carbon dioxide containing steam can be performed effectively, and
carbon dioxide recovering energy can be restricted.
[0049] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
methods and systems described herein may be embodied in a variety
of other forms; furthermore, various omissions, substitutions and
changes in the form of the methods and systems described herein may
be made without departing from the spirit of the inventions. The
accompanying claims and their equivalents are intended to cover
such forms or modifications as would fall within the scope and
spirit of the inventions.
* * * * *