JPH1015334A - Refining of carbon dioxide gas and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a carbon dioxide gas refining device and reduce running cost for refining. SOLUTION: A feedstock gas containing a water insoluble impure gas and carbon dioxide gas are continuously transferred to a pressure suction tower 2. Water is stored in the pressure absorbing tower 2, and the carbon dioxide gas with high solubility in water is dissolved in an absorbing liquid under pressure. On the other hand, the impure gas which is hardly dissolved in water ascends through the absorbing liquid and is accumulated in the inner upper space A of the pressure absorbing tower 2 to be exhausted from an exhaust pipe 16. The absorbing liquid in which the carbon dioxide gas is selectively dissolved from the lower part of the pressure absorbing tower 2, is exhausted into a carbon dioxide gas diffusion tower 3. In the tower 3, the carbon dioxide gas is diffused and is recovered as a high-purity refined carbon dioxide gas through piping for refining 10, as an atmospheric pressure state is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for purifying carbon dioxide gas for easily purifying carbon dioxide having high purity.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional carbon dioxide gas purifying apparatus 30. The flow rate of the source gas including the impurity gas and the carbon dioxide gas is controlled by a source gas flow control valve 31 from a supply source (not shown), and is introduced into a lower portion of the absorption tower 32. A supply pipe 32a is provided at an upper portion of the absorption tower 32, and an absorption liquid flow control valve 33 is provided.
Thus, a constant flow rate of the absorbing liquid is supplied into the absorption tower 32.
A monoethanolamine aqueous solution is used as the absorbing solution. In the source gas introduced into the absorption tower 32, only carbon dioxide gas is absorbed by the absorption liquid, and other impurity gases are hardly absorbed by the absorption liquid, and are discharged as exhaust gas from the exhaust port 32b at the upper part of the absorption tower 32. .

The absorbing solution that has absorbed the carbon dioxide gas is stored in a carbon dioxide absorbing liquid tank 35 through a pipe 34. Next, the absorbing liquid is discharged from the absorbing liquid tank 35 by the feed pump 36, adjusted to a constant flow rate by the feed liquid flow control valve 37, and sent to the evaporation tower 38. In the distillation column 38, the absorbing solution having absorbed the carbon dioxide gas is indirectly heated by the steam of the reboiler 39. Then, the carbon dioxide gas and the absorption liquid vapor distill from the top 38a of the distillation column 38 into the cooler 40, where only the absorption liquid vapor is cooled and condensed, and the absorption liquid is returned to the top 38a from the reflux line 41 and purified. Only the carbon dioxide gas collected is recovered from the conduit 40a. On the other hand, the distillation column 38
The absorption liquid from which the absorbed carbon dioxide gas has been removed from the bottom 38b is sent by an absorption circulation pump 44 and cooled by a cooler 43.
After being adjusted to a constant flow rate by the above-mentioned absorption liquid flow control valve 33, it is again introduced as an absorption liquid for absorbing carbon dioxide from a supply pipe 32a arranged above the absorption tower 32.

[0004]

The operation of the above-mentioned carbon dioxide gas purifying apparatus is very complicated because a distillation column or the like is used to release carbon dioxide from the absorbing solution having absorbed carbon dioxide gas. In addition, it requires a heat source to heat the distillation column, running costs are high, it is necessary to use a special absorbing solution to absorb carbon dioxide gas, and it is necessary to consider measures to deal with deterioration of the absorbing solution. is there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method for purifying carbon dioxide and a device capable of simplifying a driving operation, simplifying a device, and reducing running costs. And

[0006]

The above object is achieved by the present invention.
According to the invention, carbon dioxide gas containing an impurity gas having low solubility in water is passed through pressurized water, the carbon dioxide gas is dissolved in the water, and the impurity gas and the carbon dioxide gas are separated. Achieved by the method. Claim 2
According to the invention of the present invention, the pressure of pressurized water in which carbon dioxide gas is selectively dissolved is reduced, and the equilibrium solubility of carbon dioxide gas in water is reduced, whereby carbon dioxide dissolved in water is vaporized and collected. Achieved by gas purification methods. Also,
According to the third aspect of the present invention, a carbon dioxide gas containing an impure gas having a low solubility in water is passed through pressurized water to dissolve the carbon dioxide gas in the water and pressurized absorption for separating the impure gas and the carbon dioxide gas. Tower, a pressure control valve for exhausting the impure gas in the pressurized absorption tower, and decompressing the pressurized water in which the carbon dioxide gas is dissolved, thereby lowering the equilibrium solubility of the carbon dioxide gas in water,
This is achieved by a carbon dioxide purifying apparatus including a gas stripper for vaporizing and recovering carbon dioxide dissolved in water and an absorbent circulating pump for circulating water in the gas stripper to a pressurized absorption tower.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given, with reference to the drawings, of a method for purifying carbon dioxide and an apparatus therefor according to an embodiment of the present invention.

FIG. 1 shows a carbon dioxide gas purifying apparatus 1 according to the present invention.
Is shown. The carbon dioxide purification device 1 mainly includes a pressurized absorption tower 2
And a carbon dioxide stripping tower 3. Pressurized absorption tower 2
, Water 4 is stored in a pressurized state inside. A source gas injection nozzle 5 is provided below the pressurized absorption tower 2,
The nozzle 5 is connected via a line 6 to a pressure pump (not shown) and a supply source of a source gas pumped by the pump. The blowing nozzle 5 has a large number of blowing ports 5a, and the flow rate is controlled by a source gas flow control valve 7. The outlet 5a is disposed deep below the water surface so that the source gas and the water come into wide contact when the blowing nozzle 5 discharges the source gas into water.

A pipe 8 is provided at the bottom 2 a of the pressurized absorption tower 2, and the pipe 8 is connected to the above-mentioned carbon dioxide stripping tower 3 via an absorption liquid extraction flow control valve 9. The upper part of the carbon dioxide stripping tower 3 is connected to a purification pipe 10 from which carbon dioxide is exhausted, and the lower part is connected to a pipe 11 for draining the absorbent. An absorption liquid circulation pump 12 for circulating the absorption liquid to the pressurized absorption tower 2, and an absorption liquid flow control valve 13 for flowing a constant flow of the absorption liquid to the pressure absorption tower 2 are provided in the pipe 11.
Is connected. As the pump 12, a high-pressure pump is used.

The end of the pipe 11 extends to the upper part of the pressurized absorption tower 2, and an absorption liquid spray nozzle 14 is connected to the end. Further, in the pressurized absorption tower 2, below the absorption liquid spray nozzle 14, a liquid level gauge 15 for detecting the water level of the absorption liquid is provided. The liquid level gauge 15 outputs the value of the water level position of the absorbing liquid to the absorbing liquid flow control valve 13,
The control valve 13 adjusts the absorption liquid to a predetermined flow rate based on the magnitude of the input value. An exhaust pipe 16 for discharging impure gas is connected to the upper part of the pressurized storage tower 2, and a pressure control valve 17 and a pressure gauge 18 for detecting the internal pressure of the pressurized absorption tower 2 are provided in the exhaust pipe 16. Have been. The pressure control valve 17 is a pressure gauge 1
The pressure value is input from 8 and the exhaust gas amount is controlled so that the inside of the pressurized storage tower 2 has a predetermined internal pressure.

The configuration of the carbon dioxide gas purifying apparatus 1 according to the embodiment of the present invention has been described above. Next, the operation thereof will be described. Impurity gas having a low solubility in water, for example, nitrogen gas, a source gas containing oxygen gas or air and carbon dioxide gas is pressurized by a compressor or the like not shown,
The gas is adjusted to a constant flow rate by the source gas flow control valve 7 and is continuously transferred to the pressurized absorption tower 2. In the pressurized absorption tower 2, the source gas is ejected from the outlet 5 a of the injection nozzle 5. In the pressurized absorption tower 2, water 4, which is an absorbing solution of carbon dioxide gas, is contained.
Is stored, and carbon dioxide gas having high solubility in water is dissolved in the absorbing solution. For example, an impurity gas that is hardly soluble in water is only slightly dissolved and almost rises in the absorbing solution. Collect in space A. Table 1 shows the solubility of each gas in water. It can be seen that carbon dioxide (CO ₂ ) has a higher solubility in water than oxygen and nitrogen and is easily soluble in water.

[0012]

[Table 1]

On the other hand, the internal pressure of the upper space A gradually increases as the source gas is continuously fed into the pressurized absorption tower 2. An impure gas exhaust pipe 16 is connected to the pressurized absorption tower 2, and a pressure control valve 17 provided therein receives a pressure value of a pressure gauge 18 so that the pressure in the upper space A is constant.
In this embodiment, when the pressure reaches 5 atm, impurity gases such as oxygen and nitrogen are exhausted by an amount exceeding 5 atm. Thus, the pressure in the pressure absorption tower 2 is maintained at 5 atm. When the upper space A of the pressurized absorption tower 2 is at normal pressure when the carbon dioxide gas refining device 1 is started, the water 4 is supplied to the pressurized absorption tower 2 using the absorbent circulation pump 12. It is also possible to pressurize the water 4 by increasing the water level by supplying it to the inside and reducing the volume of the upper space A. From the lower part of the pressurized absorption tower 2, an absorption liquid in which carbon dioxide gas is selectively dissolved flows through a pipe 8, and continuously flows out in a constant amount by an absorption liquid extraction flow control valve 9. It is discharged to 3. In the carbon dioxide stripping tower 3, the absorbing solution is maintained at normal pressure.

FIG. 2 shows the solubility of each gas in water with respect to a pressure change at a temperature of 10 ° C. From this figure, it can be seen that the solubility of carbon dioxide in water is proportional to the pressure (Henry's law). As described above, the equilibrium solubility of carbon dioxide in water decreases in proportion to the pressure.
Carbon dioxide gas having an equilibrium solubility or higher is released in the carbon dioxide release tower 3. Since almost only carbon dioxide gas is dissolved in the absorbing solution, it is recovered from the purification pipe 10 as high-purity purified carbon dioxide gas.

The absorbing solution from which the carbon dioxide gas has been diffused is pressure-fed in the pipeline 11 by the absorbing solution circulating pump 12 and is ejected from the absorbing solution spray nozzle 14 connected to the end of the pipeline 11, and the compressed fluid is absorbed by the pressurized absorption tower. It is returned in 2. The flow rate of the flow control valve 13 is controlled by the liquid level gauge 15 and the absorption liquid flow control valve 13 installed in the pressure absorption tower 2 so that the height of the absorption liquid level in the pressure absorption tower 2 becomes constant. . Table 2 shows an example of purification of carbon dioxide purified by the carbon dioxide purification apparatus 1 according to the present embodiment. As shown in the table, 95% purity containing 5% air
Of carbon dioxide was improved to 99.7% purity.

[0016]

[Table 2]

As shown in FIG. 2, the solubility of the gas is proportional to the pressure. As the pressure in the pressurized absorption tower 2 increases, the amount of carbon dioxide that can be treated per unit amount of the absorption liquid increases. In addition, the pressure absorption tower 2 can be downsized. In the purification example shown in Table 2, 5 atm was used as the pressurizing pressure, but may be higher. However, if the pressure is increased, the pressure resistance of the pressurized absorption tower must be strengthened, and the pressure of the absorbing liquid circulation pump 12 needs to be increased, which increases the cost. However, it is desirable in terms of cost. At higher cost, higher pressures can be used.

A carbon dioxide gas purifying apparatus 1 according to the present embodiment.
Has the following effects as compared with a conventional carbon dioxide gas purification apparatus. In the conventional carbon dioxide purifying apparatus 30 shown in FIG. 3, the absorption liquid that has absorbed carbon dioxide with monoethanolamine in the absorption tower 32 separates the carbon dioxide gas and monoethanolamine by distillation using steam heating in the distillation tower 38. There is a need. The operation in the absorption tower 32 only requires spraying the absorption liquid at a constant flow rate from the top, but in the distillation tower 38, the amount of steam for heating the bottom liquid in the lower part of the distillation tower is adjusted and the purified carbon dioxide gas extracted from the upper part of the distillation tower It is necessary to delicately adjust the extraction amount of the water according to the change in the concentration of carbon dioxide in the absorbing solution fed to the distillation column. Therefore, the operation and control of the carbon dioxide gas purification device 30 become very complicated.

[0019] Carbon dioxide purifier 1 in the present embodiment
Then, at the same time as circulating the absorbing solution so that the liquid level of the absorbing solution in the pressurized absorbing tower 2 is constant, the gas is also controlled such that the pressure of the impurity gas other than carbon dioxide gas in the upper part of the pressurizing absorbing tower 2 is constant. You only need to make adjustments to discharge. Therefore, the driving operation is easier than that of a conventional carbon dioxide gas purification device.

The continuous operation equipment, heating material, cooler and the like required to operate the conventional carbon dioxide gas purification apparatus 30 include an absorption liquid feed pump 36 and an absorption liquid circulation pump 4.
4. Monoethanolamine, steam for heating the distillation tower, canister liquid for the distillation tower, and cooling water for cooling purified carbon dioxide gas. In the carbon dioxide gas purifying apparatus 1 according to the present embodiment, only the absorbent circulation pump 12 for pressurized circulation and water are used, and no heating material or cooling material is required. Therefore, the running cost for operating the carbon dioxide purification device 1 is less than half that of the conventional product. Furthermore, the carbon dioxide purification device 1 is, as in the prior art,
Since the distillation column 38 and the cooler 43 shown in FIG. 3 are not required, the installation space can be reduced to less than half and the size can be reduced.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention. For example, in the above embodiment, the absorption liquid is
The pressure was increased by the atmospheric pressure, and the pressure was set to the normal pressure in the gas stripping tower 3. However, the pressure difference may be any pressure difference as long as there is a pressure difference. It does not need to be performed and need not be performed at a constant pressure. Further, a combustion exhaust gas can be used as a source gas used in the above embodiment. However, since the concentration of carbon dioxide in the combustion exhaust gas is about 15%, to obtain carbon dioxide of high purity,
At the end of the carbon dioxide purification pipe 10 of the carbon dioxide purification device 1,
By arranging similar carbon dioxide purifiers 1 in series and using them in multiple stages, it is possible to purify high-purity carbon dioxide.

[0022]

As described above, according to the first aspect of the present invention, a purified gas containing an impure gas having a low solubility in water is dissolved in water by passing carbon dioxide gas which has been passed through pressurized water. Therefore, the impurity gas and the carbon dioxide gas can be separated.
Further, according to the second aspect of the present invention, since the pressurized water in which carbon dioxide is selectively dissolved is depressurized, the carbon dioxide dissolved in water can be vaporized and collected. According to the third aspect of the present invention, it is possible to reduce the installation space of the carbon dioxide gas purification apparatus, reduce the running cost, and simplify the operation and control of the apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a carbon dioxide gas purifying apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the solubility of carbon dioxide gas, oxygen gas, and nitrogen gas in water with respect to changes in atmospheric pressure.

FIG. 3 is a schematic view of a conventional carbon dioxide gas purifying apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide purification apparatus 2 Pressure absorption tower 3 Carbon dioxide release tower 4 Water 5 Source gas injection nozzle 7, 13 Flow control valve 8, 11 Pipe line 10 Purification pipe 12 Absorbent circulation pump 17 Pressure control valve 18 Pressure gauge

Claims (3)

[Claims] 1. A method of purifying carbon dioxide gas, comprising the steps of: passing a carbon dioxide gas containing an impure gas having a low solubility in water into pressurized water, dissolving the carbon dioxide gas in the water and separating the carbon dioxide gas from the impurity gas. . 2. Carbon dioxide gas characterized by reducing the pressure of pressurized water in which carbon dioxide gas is selectively dissolved and reducing the equilibrium solubility of the carbon dioxide gas in water, thereby vaporizing and collecting the carbon dioxide gas dissolved in water. Purification method. 3. A carbon dioxide gas containing an impurity gas having a low solubility in water is passed through pressurized water to dissolve the carbon dioxide gas in the water.
A pressurized absorption tower for separating the impure gas and the carbon dioxide gas, a pressure control valve for exhausting the impure gas in the pressurized absorption tower, and a pressurized water in which the carbon dioxide gas is dissolved; A gas stripping tower for evaporating and recovering carbon dioxide dissolved in water by lowering the equilibrium solubility in water, and an absorption liquid circulation pump for circulating water in the gas stripping tower to the pressurized absorption tower were provided. Carbon dioxide purification equipment.