JP2004351322A - Production method for high purity gas by pressure change adsorption apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a high purity gas by using a pressure change adsorption apparatus capable of producing a specified gaseous component such as carbon monoxide with high purity at a high production yield. <P>SOLUTION: In the high purity gas production method using the pressure change adsorption apparatus for producing the specified gaseous component in raw material gas involves a purging step to be carried out before a vacuum desorption step by using a gas obtained after the purging and the produced high purity gas as the purging gas and the apparatus is operated under the condition that the ratio of both the gases is controlled so as to be (supply amount of the gas obtained after purging)>(supply amount of the produced high purity gas) in the initial period, the ratio is continuously changed so as to finally supply only the produced high purity gas. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４４】
前記の結果から、９９ｖｏｌ％以上の高純度ガスを製造するにあたり、実施例１においては、従来の方法と比較して、製品ガス使用量が少なく、製品ガス回収量が多くなり、従って、効率的な高純度ガスの製造を行うことができることが明確になった。
【００４５】
【発明の効果】
本発明は、ＰＳＡ装置におけるパージ工程での製品ガスである高純度特定成分ガス供給量を削減することができ、一酸化炭素などの特定成分ガスを高純度に維持しながら、製品ガスの回収率向上を図ることができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態の系統図
【図２】本発明の一実施の形態の４塔式ＣＯ−ＰＳＡ装置の吸着塔における工程説明図
【図３】パージ後ガス中の一酸化炭素濃度の時間推移を示すグラフ
【符号の説明】
１：Ａ吸着塔
２：Ｂ吸着塔
３：Ｃ吸着塔
４：Ｄ吸着塔
５：製品ガスホルダ
６：パージ後ガスホルダ
７：低圧ガス回収ホルダ
８：圧縮機
９：真空ポンプ
１０：ブロワ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a high-purity gas for separating and recovering a high-purity specific component gas from a source gas containing the specific component gas by using a pressure fluctuation adsorption device.
[0002]
[Prior art]
As conventional high-purity gas production methods, a cryogenic separation method, a membrane separation method, a pressure swing adsorption method (Pressure Swing Adsorption: hereinafter, referred to as a PSA method) and the like are known.
[0003]
The cryogenic separation method is an apparatus for producing a specific component gas such as high-purity oxygen and high-purity nitrogen by cooling and liquefying the raw material gas by adiabatic expansion, separating the raw material gas using a difference in boiling points such as nitrogen and oxygen, and so on. Although it is suitable for producing a large-capacity high-purity gas, there are problems such as an increase in power costs such as electric power and an increase in the installation area of the equipment.
[0004]
Further, the membrane separation method is an apparatus for producing a high-purity specific component gas by separating using a polymer organic membrane that selectively permeates a specific component gas. Although suitable, an industrial large-capacity apparatus requires a large amount of expensive membrane separation modules, and thus has a problem of increasing equipment costs.
[0005]
The PSA method can be used to produce high-purity gas such as oxygen or nitrogen from a small volume to a large volume. In addition, the cost of equipment and power is low, and the operation is easy. ing.
[0006]
When a large-volume specific component gas is produced in a pressure fluctuation adsorption apparatus (hereinafter referred to as a PSA apparatus) used in the PSA method, a PSA apparatus mainly composed of four or more adsorption towers is used. In the case of producing a very small volume of a specific component gas, a PSA apparatus comprising one, two or three adsorption towers is also used. In the PSA apparatus, at least a step of selectively adsorbing the specific component gas to the adsorbent by applying pressure and a step of desorbing the adsorbed specific component gas by reducing the pressure are cyclically repeated between the plurality of adsorption towers. Thus, the apparatus continuously produces high-purity product gas of a specific component gas.
[0007]
In addition, conventionally, gas produced as a by-product at steelworks and petrochemical plants, and reformed gas or partially oxidized gas obtained by reforming petroleum and natural gas contain a large amount of carbon monoxide. A method for producing high-purity carbon monoxide by a PSA method using a gas as a source gas is disclosed. (See, for example, Patent Documents 1 and 2)
[0008]
In addition, an oxygen-containing gas such as air is supplied to an adsorption tower filled with a molecular sieve activated carbon adsorbent that mainly adsorbs oxygen selectively, and oxygen is selectively adsorbed by the adsorbent, and nitrogen that is difficult to adsorb is adsorbed by the adsorption tower. There is also known an apparatus that recovers high-purity oxygen by recovering the high-purity oxygen by recovering the high-purity nitrogen by recovering the oxygen adsorbed by the adsorbent through a regeneration step such as a decompression step. See Patent Document 3.).
[0009]
[Patent Document 1]
Japanese Patent Publication No. 3-65207 [Patent Document 2]
JP-A-11-137942 [Patent Document 3]
JP 2001-269532 A
[Problems to be solved by the invention]
In the method for separating and recovering carbon monoxide disclosed in Japanese Patent Publication No. 3-65207, manufactured high-purity carbon monoxide is used for purging a carbon monoxide adsorption tower. In the method disclosed in Japanese Patent No. 269532 for producing oxygen and nitrogen by separating air, the produced high-purity nitrogen is used for purging a nitrogen adsorption tower. In any of the above methods, only the high-purity specific component gas, which is a product, is used as the purge gas for the specific component gas adsorption tower, so that there is a problem that the recovery rate of the product gas is reduced.
[0011]
In the method for separating and recovering carbon monoxide disclosed in JP-A-11-137942, the carbon monoxide adsorption tower is purged by purging with a high-purity carbon monoxide produced after purging with a gas after purging. This is an effective method because the recovery rate of high-purity carbon monoxide can be increased by a two-stage purging method that performs high-purity carbon monoxide. There is a demand for a method capable of producing carbon oxide at a high recovery rate. In the two-stage purging method, it is necessary to maintain a high concentration of carbon monoxide in the gas after purging. There is a problem that is increased more than necessary.
[0012]
The present invention has been made in view of the above-mentioned problems in the various conventional methods, and has a pressure fluctuation adsorption capable of improving the recovery rate of a product gas while maintaining a high purity of a specific component gas such as carbon monoxide as a product gas. The purpose of the present invention is to provide a method for producing a high-purity gas using an apparatus.
[0013]
[Means for Solving the Problems]
The gist of the present invention for achieving the above object is that, in the invention described in claim 1, at least the addition of an adsorbent column filled with an adsorbent for selectively adsorbing a specific component gas in a source gas is performed. In a pressure fluctuation adsorption apparatus that repeats the pressure adsorption step and the vacuum desorption step to produce a product high-purity gas of a specific component gas, a purge step is provided before the vacuum desorption step, and the purged gas and the product Using a purity gas, the purge process is initially operated with the gas supply after purge> supply of product high-purity gas, continuously changing the ratio, and finally supplying only product high-purity gas. A method for producing a high-purity gas using a pressure fluctuation adsorption apparatus.
[0014]
By operating with the configuration of claim 1, the supply amount of the high-purity gas, which is the product gas in the purge step, can be reduced, and the specific component gas such as carbon monoxide is maintained at a high purity while the product recovery rate is maintained. Can be improved.
[0015]
In the invention according to claim 2, at least the pressure adsorption step and the vacuum desorption step are repeated using an adsorption tower filled with an adsorbent for selectively adsorbing the specific component gas in the raw material gas, and the specific component gas is removed. In a pressure fluctuation adsorption apparatus for producing a high-purity gas of a gas, a purge step is provided at a stage preceding the decompression / desorption step, and a purge gas and a product high-purity gas are used as purge gases in the purge step. This is a method for producing a high-purity gas using a pressure fluctuation adsorption apparatus, which is operated by continuously changing the supply ratio of the product high-purity gas from 100: 0 to 0: 100.
[0016]
By operating with the configuration of claim 2, it is possible to reduce the supply amount of the high-purity gas, which is the product gas in the purge step, and to maintain the high purity of the specific component gas such as carbon monoxide while maintaining the product recovery rate. Can be improved.
[0017]
In the third aspect of the present invention, in the method for producing a high-purity gas by the pressure fluctuation adsorption apparatus according to the first or second aspect, the ratio between the supply amount of the purged gas and the supply amount of the product high-purity gas is adjusted. And a method for producing a high-purity gas by a pressure-fluctuation adsorption device based on the concentration of a specific component gas in a gas after purging derived from an adsorption tower.
[0018]
By operating with the configuration of claim 3, the supply amount of the product gas in the purge step can be reduced, and each gas can be supplied at the optimum supply amount, so that the amount of the carbon monoxide or the like can be increased. The product recovery rate can be improved while maintaining the specific component gas at a high purity.
[0019]
According to a fourth aspect of the present invention, in the method for producing a high-purity gas by the pressure fluctuation adsorption apparatus according to the first, second, or third aspect, the specific component gas is carbon monoxide. This is a method for producing high-purity gas.
[0020]
In the configuration of the fourth aspect, the effect of the invention can be further exerted by applying the method for producing a high-purity gas according to the first, second, or third aspect to the production of high-purity carbon monoxide. Can be.
[0021]
As the adsorbent for selectively adsorbing carbon monoxide as the specific component gas, activated carbon, zeolite, a porous carrier such as a cross-linked polystyrene resin, a cuprous halide, cupric halide, and other copper Although an adsorbent carrying ions or aluminum halide can be used, it is preferable to use an adsorbent carrying activated cuprous halide on activated carbon. In addition, molecular sieve activated carbon is mainly used as an adsorbent for selectively adsorbing oxygen, and a zeolite-based adsorbent or the like is mainly used as an adsorbent for selectively adsorbing nitrogen.
[0022]
In addition, the number of adsorption towers used in the method of the present invention is not particularly limited. However, if the number of adsorption towers is two or more, it is preferable to be able to cyclically operate by automatic control. It is more preferable to install the above adsorption tower because automatic control becomes easy.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is an explanatory view of a process in an adsorption tower of a four-column CO-PSA apparatus of an embodiment of the present invention, and FIG. It is a graph which shows a time transition of carbon concentration.
[0024]
The embodiment shown in FIG. 1 is a PSA apparatus for producing high-purity carbon monoxide (hereinafter referred to as a product gas), in which four adsorption towers are installed, but the number of towers is appropriately arranged. It is of course possible, and the present invention is of course not limited to this. 1 is an A adsorption tower, 2 is a B adsorption tower, 3 is a C adsorption tower, and 4 is a D adsorption tower, each of which is filled with an adsorbent for selectively adsorbing carbon monoxide as a specific component gas in the raw material gas. ing.
[0025]
In addition, as an adsorbent for selectively adsorbing carbon monoxide, activated carbon, zeolite, a porous carrier such as a crosslinked polystyrene resin, cuprous halide or cupric halide, and other copper ions or aluminum halide. A supported adsorbent or the like can be used, but it is preferable to use an adsorbent in which activated cuprous halide is supported on activated carbon.
[0026]
5 is a product gas holder for storing the manufactured product gas, 6 is a gas holder after purging for circulating the gas after purging as a purge gas, 7 is a low pressure gas for storing low pressure carbon monoxide discharged in the initial desorption step. A recovery holder 8 is a compressor for increasing the pressure of the low-pressure gas to circulate the low-pressure carbon monoxide stored in the low-pressure gas recovery holder to the source gas.
[0027]
Reference numeral 9 denotes a vacuum pump which decompresses each adsorption tower to desorb carbon monoxide from the adsorbent, collects the product gas, and supplies the product gas to the product gas holder 5, and 10 purges each adsorption tower with a purge gas. The blower is a blower that sucks a gas after purging and supplies the gas to the gas holder 6 after purging.
[0028]
Each of the above-mentioned A adsorption tower 1, B adsorption tower 2, C adsorption tower 3, and D adsorption tower 4 is cyclically and repeatedly operated by the automatic control means in the same series of steps. A description will be given based on the process explanatory diagram of FIG.
[0029]
Source gas adsorption step (adsorption I step): STEPs 11, 12, and 13
In this step, the raw material gas is supplied to the A adsorption tower 1, and the carbon monoxide is adsorbed at the outlet of the A adsorption tower 1 until the adsorbent breaks through and the carbon monoxide flows out.
[0030]
In the above, the reason why the adsorbent breaks through at the outlet of the A adsorption tower 1 and carbon monoxide is adsorbed to just before the carbon monoxide flows out is necessary in the product gas recovery step to increase the purity as much as possible. If the adsorption step is terminated before the above-mentioned state, the residual amount of adsorption of gas components other than the coexisting carbon monoxide increases, and is desorbed and mixed in the product carbon monoxide in the recovery step. , Causing a reduction in the purity of the product gas.
[0031]
Further, in the adsorption I step, by operating the A adsorption tower 1 in a pressurized state, the equilibrium adsorption amount of carbon monoxide can be increased, and therefore, the effective adsorption amount of the adsorbent is increased, The required amount of adsorbent can be reduced. Incidentally, the adsorption pressure in the above step is 0.098 to 0.98 MPa, preferably 0.49 to 0.88 MPa. If the pressure is 0.098 MPa or less, the increase in the equilibrium adsorption amount of carbon monoxide is too small. If the pressure is 0.98 MPa or more, the pressure is too high, and the facility cost and the power cost increase.
[0032]
Equalizing process: STEP21
This is a step in which the A adsorption tower 1 after the completion of the adsorption step and the adsorption tower after the desorption step described later, for example, the B adsorption tower 2, are communicated to substantially equalize the pressure. In this step, the pressure in the B adsorption tower 2 after the completion of the desorption step is increased and the pressure can be easily recovered in each subsequent step.
[0033]
As described above, the pressure in the A adsorption tower 1 in the adsorption step is 0.098 to 0.98 MPa, and the pressure in the B adsorption tower 2 in the desorption step is 100 to 20 torr because the pressure is reduced to vacuum. By connecting them, the pressure in both adsorption towers can be almost equalized to about 0.098 to 0.39 MPa. In this step, it is not always essential that the pressures of both the A adsorption tower and the B adsorption tower be completely equalized, for example, when the adsorption tower after desorption is raised to about atmospheric pressure. The pressure equalizing step may be terminated at the step S <b> 1 to shift to the next pressure reducing step.
[0034]
Decompression step: STEP22
This is a step of reducing the pressure of the A adsorption tower after the pressure is substantially equalized in the pressure equalization step, and is a step of adjusting the pressure in the A adsorption tower 1 to a pressure suitable for a purging step: STEP23 described later. The carbon monoxide contained in the gas generated when the pressure of the A adsorption tower 1 is reduced is supplied to the low-pressure gas recovery holder 7, temporarily stored, and then circulated to the source gas. Further, the pressure in the adsorption tower in the above step is reduced to about 0.019 to 0.196 MPa.
[0035]
Purge step: STEP23
After the pressure is reduced in the pressure reducing step, the purged gas and the product gas stored in the gas holder 6 are introduced as purge gas into the A adsorption tower 1 on which carbon monoxide is adsorbed from the raw material gas in the adsorption step, and the gas is introduced into the adsorption tower. This is a process for purifying gas components other than carbon monoxide such as carbon dioxide present in the voids and the piping of the device and increasing the purity of carbon monoxide to be recovered in the recovery process. The operation is performed with the gas supply amount after the purge> the product gas supply amount, continuously changing the ratio to operate as the gas supply amount after the purge <the product gas supply amount, and finally, supplying only the product high-purity gas. Preferably, the operation is performed while the supply ratio of the purged gas: product gas is continuously changed from 100: 0 to 0: 100. The purged gas discharged from the A adsorption tower 1 in the purging step is supplied to and stored in the post-purging gas holder 6, and the excessive post-purging gas passes through the low-pressure gas recovery holder 7 together with the raw material gas. And the contained carbon monoxide is recovered.
[0036]
Desorption step (carbon monoxide separation and recovery step): STEP31, 32, 33
The desorption step is a step of depressurizing the inside of the A adsorption tower 1 and desorbing the carbon monoxide adsorbed by the adsorbent by decompression and recovering it as a product gas. This is a step of reducing the partial pressure of carbon monoxide for desorption. In addition, since the pressure in the A adsorption tower 1 is reduced to a vacuum, it is 100 to 20 torr, preferably 50 torr or less.
[0037]
The high-purity carbon monoxide recovered in the carbon monoxide separation and recovery step is stored in the product gas holder 5 and supplied as high-purity carbon monoxide of the product for use as a chemical raw material. Circulated.
[0038]
Equalizing process: STEP41
This is a step in which the A adsorption tower 1 after the desorption step and the adsorption tower after the adsorption step, for example, the B adsorption tower 2, are communicated to make the pressure substantially uniform, and the pressure in the A adsorption tower 1 is increased. At the same time, the pressure in the B adsorption tower 2 after the end of the adsorption step is reduced to facilitate the recovery of the pressure in each subsequent step.
[0039]
Step-up step: STEP42, 43
This is a step of increasing the pressure in the A adsorption tower 1 that has been equalized and another adsorption tower discharged from the adsorption step, for example, an outlet gas from the D adsorption tower 4. This is a step for preparing for the subsequent source gas adsorption step. Therefore, the pressure in the A adsorption tower 1 is increased to 1 to 10 kg / cm2G.
[0040]
By repeating the above-described series of steps in a similar cycle with a constant time difference for all the adsorption towers, the operation can be continuously and efficiently performed, and high-purity carbon monoxide can be recovered with high efficiency. The switching of each step of the adsorption tower is performed by controlling the opening and closing of an on-off valve provided in a piping line connected to each adsorption tower by automatic control means (not shown) generally used in many apparatuses. Is
[0041]
【Example】
Hereinafter, the purging step of the present invention is operated by initially operating the gas supply amount after purging> the product high-purity gas supply amount, continuously changing the ratio, and finally supplying only the product high-purity gas. Example 1 and the method of operating the conventional purging process described in Japanese Patent Publication No. 3-65207 by supplying only high-purity gas (Comparative Example 1) and Japanese Unexamined Patent Application Publication No. 11-137942. Product gas usage and product gas recovery when the conventional purge process is operated by supplying only gas after purging and operating by supplying only high-purity product gas and performing a two-stage purge method (Comparative Example 2). 3 shows a comparison of the amounts.
[0042]
The used raw material gas is a gas obtained by reforming natural gas, and its composition is hydrogen: 35%, carbon monoxide: 35%, methane: 0.8%, carbon dioxide: 29. 2%. The adsorbent used was activated carbon loaded with cuprous chloride having a particle size of 0.5 to 2.4 mm. The operating conditions were as follows: raw material gas amount: 4 Nm3 / H, adsorption pressure: 6 kg / cm2 G, desorption pressure: 30 torr, and raw gas temperature: 50 ° C. The results are shown in Table 1 and FIG.
Table 1 shows the amount of product gas used and the amount of product gas recovered, and the graph of FIG. 3 shows the time course of the concentration of carbon monoxide in the gas after purging.
[0043]
[Table 1]

[0044]
From the above results, in producing a high-purity gas of 99 vol% or more, in Example 1, the amount of product gas used is small and the amount of product gas recovered is large compared to the conventional method, and therefore, the efficiency is high. It became clear that high-purity gas could be produced.
[0045]
【The invention's effect】
The present invention can reduce the supply amount of a high purity specific component gas, which is a product gas, in a purging process in a PSA apparatus, and maintain a high purity of a specific component gas such as carbon monoxide while maintaining the product gas recovery rate. Improvement can be achieved.
[Brief description of the drawings]
FIG. 1 is a system diagram of an embodiment of the present invention. FIG. 2 is an explanatory view of a process in an adsorption tower of a four-column CO-PSA apparatus according to an embodiment of the present invention. FIG. Graph showing the time course of carbon oxide concentration [Explanation of symbols]
1: A adsorption tower 2: B adsorption tower 3: C adsorption tower 4: D adsorption tower 5: Product gas holder 6: Purged gas holder 7: Low pressure gas recovery holder 8: Compressor 9: Vacuum pump 10: Blower

Claims (4)

Pressure fluctuation adsorption in which at least the pressure adsorption step and the vacuum desorption step are repeated using an adsorption tower filled with an adsorbent that selectively adsorbs the specific component gas in the source gas to produce a high purity gas of the specific component gas In the apparatus, a purge step is provided before the vacuum desorption step, and a purge gas and a product high-purity gas are used as the purge gas in the purge step. The method for producing a high-purity gas using a pressure fluctuation adsorption apparatus, wherein the method is operated by continuously changing the ratio and finally supplying only the high-purity gas product. Pressure fluctuation adsorption in which at least the pressure adsorption step and the vacuum desorption step are repeated using an adsorption tower filled with an adsorbent that selectively adsorbs the specific component gas in the source gas to produce a high purity gas of the specific component gas In the apparatus, a purge step is provided before the vacuum desorption step, and a purge gas and a product high-purity gas are used as purge gases in the purge step. A method for producing a high-purity gas using a pressure fluctuation adsorption apparatus, wherein the method is operated while continuously changing the ratio from 0 to 0: 100. The pressure according to claim 1 or 2, wherein the ratio between the supply amount of the post-purged gas and the supply amount of the product high-purity gas is adjusted based on a concentration of a specific component gas in the purged gas derived from the adsorption tower. A method for producing high-purity gas using a variable adsorption device. 4. The method for producing a high-purity gas by the pressure fluctuation adsorption device according to claim 1, wherein the specific component gas is carbon monoxide.

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