JPS5969415A - Manufacture of liquefied gaseous carbon dioxide - Google Patents

Abstract

PURPOSE:To manufacture liquefied gaseous CO2 of high purity from exhaust gas contg. gaseous CO2 after combustion by passing the exhaust gas through a selective permeable membrane, compressing the resulting gaseous CO2 of high concn., and liquefying it by cooling. CONSTITUTION:Part of exhaust gas contg. much gaseous CO2 after combustion is sucked with a blower 4, cooled to ordinary temp. with a cooler 5, and passed through a CO2 enricher 6. The enricher 6 is provided with a selective permeable membrane 7 for CO2 such as a polymer membrane of porous ''Vycor'' glass or the like so as to pass selectively gaseous CO2 in exhaust gas. The resulting CO2 enriched gas is compressed with a compressor 9, fed to a cooler 10, and cooled to about 10 deg.C with a refrigerant such as LNG. Water (b) produced by condensation is removed. The gas is then introduced into a dryer 11 packed with silica gel or the like to remove thoroughly the residual water. It is liquefied by intense cooling with a cooler 12 and rectified in a rectifying tower 13 to obtain liquefied gaseous CO2 (c) of high purity.

Description

[Detailed Description of the Invention] In particular, a highly concentrated carbon dioxide-containing gas is separated and collected by passing the carbon dioxide-containing exhaust gas through a selective permeation membrane, and the collected carbon dioxide is used to generate liquefied carbonic acid. The present invention relates to a method for producing liquefied carbonic acid.

Generally, to produce liquefied carbon dioxide (liquefied carbon dioxide) on an industrial scale, carbon dioxide released by igniting limestone or carbon dioxide obtained during the decomposition process of chemical substances is sent to an absorption tower, for example. Carbon dioxide is absorbed into a carbonate solution to form bicarbonate, which is then heated to collect nearly pure carbon dioxide, which is then cooled and condensed.
ing.

By the way, in this type of production method, the carbon dioxide initially obtained contains various impurities, so in order to purify the carbon dioxide obtained, the carbon dioxide obtained in the gas phase, liquid phase, and gas phase are Not only is this extremely troublesome, but also large-scale equipment had to be installed to carry out this series of operations.

On the other hand, as the consumption of fossil energy increases with the development of industry, the amount of carbon dioxide contained in exhaust gas and emitted as ``!.f'' is on the rise worldwide. As a result, there is a tendency for abnormal weather to occur due to the so-called greenhouse effect.Therefore, efforts are being made to reduce the total amount of carbon dioxide emitted from facilities with large-scale combustion equipment such as thermal power plants. It has reached the point where it is desired.

The present invention was devised in order to effectively solve the above-mentioned problems, and its purpose is to convert carbon dioxide-containing exhaust gas into a selectively permeable membrane. By passing it through, gas containing high concentration carbon dioxide is separated and collected,
By generating liquefied carbon dioxide from the captured carbon dioxide, not only can carbon dioxide be easily captured without undergoing a phase change, but also the amount of carbon dioxide released into the atmosphere can be reduced. The purpose of the present invention is to provide a method for producing liquefied carbonic acid from exhaust gas.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic system diagram showing an apparatus for producing liquefied carbonic acid for carrying out the method according to the present invention. In the figure, 1 is a flue for transferring the purified exhaust gas discharged from combustion equipment (not shown) such as a boiler to the chimney 2. From this flue 1, a carbon dioxide processing passage 3 branches off. Exhaust gas can be sucked into the passage 3 by a blower 4 provided in the middle of the passage.

Since the temperature of the introduced exhaust gas is high, around 100 to 120 degrees Celsius, there is a cooler 5 in the passage 3.
Additionally, the exhaust gas can be lowered to room temperature. A carbon dioxide enricher 6, which is a feature of the present invention, is provided on the downstream side, and this enricher 6 has a selective permeation membrane 7 that preferentially permeates carbon dioxide. . Specifically, this permeable membrane 7 is made of a polymer membrane such as porous Vycor glass, and carbon dioxide molecules 8 are passed through a large number of pores 7a formed therein as shown in FIG.
can be transmitted preferentially. Note that the permeable membrane 7 is not limited to a porous permeable membrane, and a non-porous permeable membrane or a biopolymer membrane may be used.

In the illustrated example, only one enricher 6 is provided, but in order to improve the concentration of carbon dioxide, it is desirable to provide a plurality of enrichers 6 in multiple stages.

A compressor 9 is provided downstream of the enricher 6.
The carbon dioxide separated and collected in the enricher 6 can be compressed. Further, on the downstream side of the compressor 9, a cooler 1o is provided to cool the carbon dioxide which has reached a high temperature during compression, and is capable of cooling the carbon dioxide to about 10°C. Further, on the downstream side of this cooler 10, a dryer 11 filled with a desiccant such as an alcoholic cage or a molecular sieve is provided.
The moisture contained in the compressed carbon dioxide can be reliably removed. This is to prevent ice from forming when carbon dioxide is liquefied.

A carbon dioxide liquefaction cooler 12 is provided downstream of this 1-layer 11, so that carbon dioxide introduced into the cooler can be cooled and liquefied. The refrigerant used here is liquefied carbon dioxide, or this facility uses LNG.
(Liquefied natural gas) L if installed in parallel with a storage facility
It is better to use NG or the like to utilize the cold energy they have.

Furthermore, if high-purity carbon dioxide is required, a rectification column 13 is installed downstream of this liquefaction cooler 12, and the above-mentioned cooler 1
Impurities are removed from the crude carbonic acid obtained in step 2, and the fL is rectified, and the impurity gas is discharged to the flue 1 to finally obtain highly pure liquefied carbonic acid.

The method according to the present invention will be explained based on the liquefied carbonic acid production apparatus configured as described above.

First, exhaust gas discharged from combustion equipment such as a boiler flows through a flue 1 toward a chimney 2 after undergoing various treatments such as desulfurization. A part of this exhaust gas is transferred to the blower 4 through the p flue 1.
The carbon dioxide is suctioned into the carbon dioxide processing passage 3 from the carbon dioxide treatment passage 3. Since the temperature of the introduced exhaust gas is as high as approximately 100 to 120°C, it is first cooled to room temperature by a cooler 5 using cooling water as a refrigerant, and then transferred to a carbon dioxide enricher 6. . Incidentally, at this time, the moisture a condensed during cooling is removed. The exhaust gas introduced into the enricher 6 is passed through a selectively permeable membrane 7 provided therein. As shown in FIG. 2, carbon dioxide molecules 8 preferentially pass through the permeable membrane 7, and thus there is no enrichment of carbon dioxide.

Normal air contains only about 0.03% (by volume) of carbon dioxide, but combustion exhaust gas contains about 5-10%.
Because it is contained in a large amount (volume ratio) and its partial pressure is also large,
Compared to simply recovering carbon dioxide from the air, the present invention allows a much larger amount of carbon dioxide to be recovered.

In addition, in the conventional example, in order to separate only carbon dioxide from impurity gas, it was necessary to absorb it into an absorption liquid and change the phase from gas to liquid, but with the present invention, Carbon dioxide can be enriched through the membrane without any phase change.

In particular, if a plurality of enrichers 6 are installed in multiple stages, the concentration of carbon dioxide can be further improved.

Impurity gases such as nitrogen gas and oxygen gas and some carbon dioxide gas blocked by the permeable membrane 7 are returned to the flue 1 as they are and are exhausted.

The carbon dioxide collected in the enricher 6 is then transferred to the compressor 9.
After being compressed, it is introduced into a cooler 10, where it is cooled to about 10° C. using a refrigerant such as LNG, and the condensed and precipitated moisture is removed. The cooled carbon dioxide is then introduced into the dryer 11, where it is filled with a desiccant agent such as silica gel or Molecuy-Kohler Sieg to ensure dryness. The moisture will be removed. .

The dried carbon dioxide is further transferred to a carbon dioxide liquefaction cooler 12.
There, it is cooled and liquefied by a refrigerant such as LNG or liquefied carbon dioxide.

The crude carbonic acid liquefied here is further introduced into a rectification column 13 where it is rectified, and impurities are removed to finally obtain highly pure liquefied carbonic acid C.

Further, the separated impurity gas d is returned to the flue 1 and exhausted from the chimney 2.

In this way, we decided to use a selective permeable membrane to separate and collect carbon dioxide from a gas that contains a large amount of carbon dioxide. It is possible to collect carbon dioxide in the gaseous state without causing any change, and there is no need to use equipment such as large-scale absorption towers.

Furthermore, since carbon dioxide is recovered from exhaust gas, the amount of carbon dioxide emitted into the atmosphere can be reduced.

In summary, the present invention can exhibit the following excellent effects.

(1) When collecting carbon dioxide, a selectively permeable membrane is used, so that carbon dioxide can be enriched to the gaseous state without causing a phase change.

(2) Therefore, not only is it possible to eliminate the need for complicated equipment such as conventional absorption towers and reduce equipment costs, but also it is possible to change the phase from the gas phase to the liquid phase or from the liquid phase to the gas phase. This eliminates the need for the energy required to close the system, promoting energy savings.

(3) Since the amount of carbon dioxide released into the atmosphere can be suppressed, the occurrence of pollution caused by carbon dioxide can be prevented.

(4) Since the structure is simple, it can be easily adopted in existing equipment.

[Brief explanation of drawings]

FIG. 1 is a schematic system diagram showing an apparatus for producing liquefied carbonic acid for carrying out the method according to the present invention, and FIG. 2 is an explanatory diagram for explaining the action of a carbon dioxide selectively permeable membrane. In the figure, 6 is a carbon dioxide enricher, 7 is a selective permeable membrane, and 9 is a carbon dioxide enricher.
is a compressor, 12 is a carbon dioxide liquefaction cooler, and C is liquefied carbonic acid. Patent applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Agent Patent attorney: Nobuo Kinutani

Claims (1)

[Claims] Exhaust gas containing a large amount of carbon dioxide emitted from combustion equipment such as boilers is passed through a selective permeable membrane to separate and collect the gas containing high concentration carbon dioxide. A method for producing liquefied carbonic acid from exhaust gas, characterized in that after compressing the gas, liquefied carbonic acid is produced by resisting cooling.