Gas separation: processes – Solid sorption – Moving sorbent
Reexamination Certificate
2001-01-19
2002-12-31
Smith, Duane S. (Department: 1724)
Gas separation: processes
Solid sorption
Moving sorbent
C095S139000, C096S125000
Reexamination Certificate
active
06500236
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-015892, filed Jan. 25, 2000 the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for continuously adsorbing and removing CO
2
from waste gas discharged from a boiler of a thermal power plant or from a combustion furnace of an incinerator.
In order to prevent global warming, it is required to regulate release of CO
2
(carbon dioxide) gas, which is a greenhouse effect gas, into the atmosphere. One of methods of suppressing the release of the carbon dioxide gas into the atmosphere is to decarbonate waste gas from a thermal power plant or the like by physical adsorption before the waste gas is released into the atmosphere.
An apparatus for physically adsorbing carbon dioxide gas contained in waste gas having four adsorption towers loaded with an adsorbent, which are operated in parallel, is known to the art. In this case, a granular adsorbent or an adsorbent of honeycomb structure is loaded in each adsorption tower. In the apparatus, supply of waste gas at a low pressure and low temperature, carbon dioxide adsorption under pressure, carbon dioxide desorption by heating, and recovery of desorbed carbon dioxide under a reduced pressure are successively repeated in these four adsorption towers so as to carry out the carbon dioxide adsorption and the regeneration of the adsorbent continuously. However, the conventional apparatus is defective in that the apparatus includes four adsorption towers and, thus, requires a large site.
Japanese Patent Disclosure (Kokai) No. 6-91128 discloses another apparatus for physically adsorbing and removing carbon dioxide contained in waste gas. In this apparatus, waste gas of a low temperature and a high pressure and a regenerating gas of a high temperature and a low pressure are allowed to flow counter-currently through a drum rotor loaded with a granular adsorbent. The drum is rotated while allowing these gases to flow through it so as to carry out continuously adsorption of carbon dioxide gas contained in the waste gas and desorption of carbon dioxide gas adsorbed by the adsorbent.
However, in this apparatus, the waste gas itself having a low temperature and a high pressure is used for cooling the adsorbent. Therefore, carbon dioxide gas within the waste gas is unlikely to be adsorbed until the adsorbent heated by the regenerating gas of a high temperature is cooled sufficiently, leading to the defect that the recovery rate of carbon dioxide gas is low. Also, since the flow rate of the waste gas is markedly lowered in the case of using a granular adsorbent, it is necessary to introduce the entire amount of the waste gas from a flue into the apparatus for processing the waste gas. In addition, in order to prevent the granular adsorbent from being moved and distributed unevenly in accordance with rotation of the drum, it is necessary to arrange a plurality of partitioned chambers within the drum, leading to a complex construction of the apparatus.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a decarbonating apparatus simple in construction, not requiring a large space, and capable of continuously recovering carbon dioxide gas from waste gas with a high recovery efficiency.
According to the present invention, there is provided a method for decarbonating waste gas, comprising steps of: rotating a drum rotor loaded with a CO
2
adsorbent having a honeycomb structure; allowing the waste gas to flow through a region of the drum rotor so as to permit CO
2
contained in the waste gas to be adsorbed by the CO
2
adsorbent; supplying a heated gas to a region of the drum rotor so as to desorb CO
2
from the CO
2
adsorbent; and supplying a cooled gas to a region of the drum rotor so as to regenerate the CO
2
adsorbent, wherein these steps are performed simultaneously so as to permit the CO
2
adsorbent within the rotating drum rotor to be subjected successively to the CO
2
adsorption step, the CO
2
desorption step and the regeneration step.
According to the present invention, there is provided a decarbonating apparatus, comprising: a drum rotor loaded with a CO
2
adsorbent having a honeycomb structure, the CO
2
adsorbent being arranged so as to adsorb CO
2
contained in waste gas that is allowed to flow through a region thereof; a heated gas supply pipe for supplying a heated gas to a region of the drum rotor so as to permit adsorbed CO
2
to be desorbed from the CO
2
adsorbent; a cooling gas supply pipe for supplying a cooling gas to a region of the drum rotor so as to regenerate the CO
2
adsorbent; a heated gas recovery pipe for recovering the heated gas that has flowed through the CO
2
adsorbent; and a cooling gas recovery pipe for recovering the cooling gas that has flowed through the CO
2
adsorbent, wherein the drum rotor is configured to rotate with successively passing through the adsorption region for adsorbing CO
2
contained in the waste gas, the desorption region to which the heated gas is supplied, and the regeneration region to which the cooling gas is supplied.
In the present invention, it is desirable to provide a purge region, for purging the CO
2
desorbed from the CO
2
adsorbent, between the desorption region and the regeneration region. It should be noted that the CO
2
desorbed from the CO
2
adsorbent by the heating gas can be removed to some extent accompanying with the heating gas. However, it is more desirable to employ purging with a purge gas for achieving removal of the desorbed CO
2
without fail.
Namely, according to another aspect of the present invention, there is provided a method for decarbonating waste gas, comprising steps of: rotating a drum rotor loaded with a CO
2
adsorbent having a honeycomb structure; allowing the waste gas to flow through a region of the drum rotor so as to permit CO
2
contained in the waste gas to be adsorbed by the CO
2
adsorbent; supplying a heated gas to a region of the drum rotor so as to desorb CO
2
from the CO
2
adsorbent; supplying a purge gas to a region of the drum rotor so as to purge CO
2
desorbed from the CO
2
adsorbent; and
supplying a cooling gas to a region of the drum rotor so as to regenerate the CO
2
adsorbent, wherein these steps are performed simultaneously so as to permit the CO
2
adsorbent within the rotating drum rotor to be subjected successively to the CO
2
adsorption step, the CO
2
desorption step, the CO
2
purging step and the regeneration step.
A decarbonating apparatus for carrying out the method described above comprises: a drum rotor loaded with a CO
2
adsorbent having a honeycomb structure, the CO
2
adsorbent being arranged so as to adsorb CO
2
contained in waste gas that is allowed to flow through a region thereof; a heated gas supply pipe for supplying a heated gas to a region of the drum rotor so as to permit adsorbed CO
2
to be desorbed from the CO
2
adsorbent; a purge gas supply pipe for supplying a purge gas to a region of the drum rotor so as to purge CO
2
desorbed from the CO
2
adsorbent; a cooling gas supply pipe for supplying a cooling gas to a region of the drum rotor so as to regenerate the CO
2
adsorbent; a heated gas recovery pipe for recovering the heated gas that has flowed through the CO
2
adsorbent; a purge gas/CO
2
recovery pipe for recovering the purge gas that has flowed through the CO
2
adsorbent and CO
2
purged from the CO
2
adsorbent; and a cooling gas recovery pipe for recovering the cooling gas that has flowed through the CO
2
adsorbent, wherein the drum rotor is configured to rotate with successively passing through the adsorption region for adsorbing CO
2
contained in the waste gas, the desorption region to which the heated gas is supplied, the purging region to which the purge gas is supplied, and the regeneration region to which the cooling gas is supplied.
In the present invention, it is desirable to provide a dehumi
Imada Jun
Ishibasi Mitio
Ootake Kuninobu
Suzuki Minoru
Takagi Hiroyuki
Smith Duane S.
The Tokyo Electric Power Company Incorporated
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