Gas separation: apparatus – Gas and liquid contact apparatus for gas separation... – Heating or cooling means
Reexamination Certificate
2000-11-28
2002-11-26
Smith, Duane S. (Department: 1724)
Gas separation: apparatus
Gas and liquid contact apparatus for gas separation...
Heating or cooling means
C096S266000
Reexamination Certificate
active
06485547
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-115379, filed Apr. 17, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
This invention relates to an exhaust gas cooling system.
The exhaust gas to be emitted from the combustion in a boiler, etc. incorporated in a power-generating installation such as a thermal power plant for instance contains a large quantity of carbon dioxide. This carbon dioxide is known to bring about a green house effect causing a global warm-up phenomenon, and hence researches for the countermeasure to the generation of carbon dioxide is an urgent problem internationally at present in view of preserving the global environment. Under the circumstances, a method of removing and recovering carbon dioxide from exhaust gas by contacting the exhaust gas with an absorbent such as an aqueous solution of alkanolamine as well as a method of reserving the carbon dioxide thus recovered without allowing carbon dioxide to be released into air atmosphere are intensively studied.
However, since the exhaust gas generated from the combustion in a boiler is high in temperature (for example, about 190° C.), it is impossible to directly contact the exhaust gas with the aforementioned aqueous solution of alkanolamine. Therefore, the absorption and recovery of the exhaust gas is now precooled to about 40° C. before the exhaust gas is introduced into the aqueous solution of alkanolamine.
In the meantime, there is known an apparatus shown in
FIG. 5
as a cooling system for cooling the exhaust gas. Namely, according to this cooling system of exhaust gas, an exhaust gas-processing tower
103
has an exhaust gas inlet port
101
at a lower portion thereof and an exhaust gas outlet pipe
102
at an upper portion thereof. A spray member
104
for spraying cooled water is provided at an upper portion of the interior space of the processing tower
103
. A circulating passageway
105
is provided in such a way that one end thereof is connected with a lower sidewall of the processing tower
103
, while the other end thereof is connected with the spray member
104
. A first pump
106
is provided at a midway of the circulating passageway
105
which is located in the vicinity of an exhaust gas-processing water discharge port of the processing tower
103
. A heat exchanger
107
for cooling the exhaust gas-processing water is provided at a midway of the circulating passageway
105
.
A cooling tower
109
provided at an upper portion thereof with a fan
108
for generating the cooling water by taking advantage of the evaporation heat of water is disposed next to the exhaust gas-processing tower
103
. A spray member
110
for spraying cooled water is provided at an upper portion of the interior space of the cooling tower
109
. A cooling water-circulating passageway
111
is provided in such a way that one end thereof is connected with a lower sidewall of the cooling tower
109
, while the other end thereof is connected via the heat exchanger
107
with the cooling water spray member
110
. The cooling water-circulating passageway
111
is designed to circulate cooling water from a lower sidewall of the cooling tower
109
via the heat exchanger
107
to the cooling water spray member
110
.
A second pump
112
is provided at a midway of the cooling water-circulating passageway
111
which is located in the vicinity of the cooling tower
109
. A make-up passageway
113
is connected with a lower sidewall of the cooling tower
109
so as to supply water from outside the system to the bottom portion of the cooling tower
109
. A blow-down passageway
114
is connected with the bottom of the cooling tower
109
, thereby allowing water to be continuously or periodically discharged from the bottom portion of the cooling tower
109
.
According to this conventional exhaust gas cooling system, an exhaust gas containing water, for example an exhaust gas generated through the combustion of hydrocarbon, is introduced from the inlet port
101
into the exhaust gas-processing tower
103
. The first pump
106
is actuated so as to supply an exhaust gas-processing water from the bottom portion of the exhaust gas-processing tower
103
via the circulating passageway
105
to the heat exchanger
107
. On this occasion, as the second pump
112
is actuated, the cooling water of the bottom of the cooling tower
109
is supplied via the cooling water-circulating passageway
111
to the heat exchanger
107
.
As a result, the exhaust gas-processing water is cooled down, and the resultant cool water is supplied via the circulating passageway
105
to the spray member
104
. The cooled water is then ejected from the spray member
104
into the space inside the exhaust gas-processing tower
103
so as to cool the exhaust gas that has been introduced into the exhaust gas-processing tower
103
. The exhaust gas thus cooled is then transferred via the exhaust gas outlet pipe
102
to the absorption tower for carbon dioxide for example. On the other hand, the cooling water whose temperature has been raised at the heat exchanger
107
through the heat exchange thereof with the exhaust gas-processing water is fed via the cooling water-circulating passageway
111
to the cooling water spray member
110
of the cooling tower
109
.
The cooling water thus warmed is then ejected from the spray member
110
into the space inside the cooling tower
109
and by the actuation of the fan
108
, is cooled due to the evaporation heat to be generated through the evaporation of water accumulated at the bottom of the cooling tower
109
. This cooling water is then accumulated at the bottom portion of the cooling tower
109
. The water inside the cooling tower
109
is consumed through the evaporation thereof. In order to compensate this consumption of water, water (make-up water) is supplied from outside the system to the cooling tower
109
through make-up passageway
113
.
According to the aforementioned exhaust gas cooling system however, when an exhaust gas containing moisture (for example, an exhaust gas to be generated from the combustion of hydrocarbon) is introduced into the exhaust gas-processing tower
103
and then, cooled water is ejected through the spray member
104
disposed at an upper portion of the exhaust gas-processing tower
103
, the water included in the exhaust gas is caused to condense and stored, as a condensate, at the bottom portion of the exhaust gas-processing tower
103
. Since the volume of exhaust gas-processing water is caused to substantially increase due to the generation of this condensed water, part of exhaust gas-processing water is required to be discharged outside the system from the bottom of the exhaust gas-processing tower
103
via a discharge passageway
115
. As a result, the load for processing waste water is caused to increase, thus raising a problem.
Furthermore, since the water circulating through the cooling water-circulating passageway
111
is cooled by taking advantage of the evaporation of water at the water inside the cooling tower
109
, it is required to supply water from outside the system to the cooling tower
109
through make-up passageway
113
. Since this external water contains salts such as calcium, etc., the salts are also caused to concentrate in the circulation process in the cooling water-circulating passageway
111
. As a result, the water containing a concentration of salts is required to be frequently discharged outside the system from the bottom of the cooling tower
109
via the blow-down passageway
114
.
BRIEF SUMMARY OF THE INVENTION
Therefore, an object of this invention is to provide an exhaust gas cooling system wherein a portion of exhaust gas-processing water incorporating therein the condensed water that has been generated through the condensation of moisture included in the exhaust gas at the exhaust gas-processing tower is introduced as a make-up water into a cooling tower, thereby making
Birch & Stewart Kolasch & Birch, LLP
Mitsubishi Heavy Industries Ltd.
Smith Duane S.
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