JP4430351B2 - Fluorine compound gas separation and purification equipment - Google Patents

Description

  The present invention relates to an apparatus for separating and purifying a fluorine compound gas such as perfluorocarbon.

In the semiconductor manufacturing industry, perfluorocarbons such as CF ₄ , C ₂ F ₆ , and SF ₆ are used as an etching gas for a dry etching apparatus and a chamber cleaning gas for a CVD apparatus. Since these perfluorocarbons are very stable compounds and have a great influence on global warming, there is a concern about adverse environmental effects when released into the atmosphere. Therefore, these perfluorocarbons contained in the exhaust gas discharged from the semiconductor manufacturing process are preferably recovered or decomposed and released to the atmosphere.

However, perfluorocarbons, when decomposed by heating the combustion or plasma treatment or the like, to produce the harmful substances such as HF and SO _X, to atmospheric discharge must detoxify it, abatement at low cost It is also difficult. In addition, the perfluorocarbon actually consumed in the semiconductor manufacturing process etc. is about 30 to 50% of the total, so if exhaust gas containing a large amount of the remaining perfluorocarbon is decomposed, the gas that can still be used is decomposed. Energy efficiency and resource efficiency are extremely poor. Therefore, there is a high expectation for developing a method for efficiently recovering such an exhaust gas containing a large amount of perfluorocarbon instead of decomposing it.

  Here, regarding the method for recovering the perfluorocarbon as described above, there are the following as prior art documents known to the applicant.

JP-A-3-135410 JP-A-8-240382

  In the method described in Patent Document 1, two adsorption towers are arranged in parallel, and a fluorine compound gas is adsorbed and recovered by a pressure swing method. In the adsorption recovery by such an adsorption tower, the gaseous fluorine compound is adsorbed on the adsorbent, and the fluorine compound gas released in the gaseous state is recovered when the adsorption capacity is lowered. As described above, since the fluorine compound is recovered by adsorption by the adsorbent, there is a problem that the adsorption capacity of the adsorbent is relatively low, maintenance is required for a relatively short period of time, and maintenance costs are required. In addition, an impurity gas such as a carrier gas is likely to be mixed into the desorption gas from which the adsorbed gas is desorbed, and a desorption gas purification device needs to be additionally provided. Furthermore, since the fluorine compound is recovered in a gaseous state, a large-capacity storage tank is required to store the recovered gas. For this reason, in order to store the recovered gas in a liquid state, in many cases, it is necessary to separately install a refrigerator. As described above, the recovery method using the adsorption method has a problem that the cost efficiency required for the equipment is not good.

  On the other hand, the method described in Patent Document 2 separates and recovers a mixed gas containing a plurality of gases having different boiling points by arranging a plurality of rectifying columns in series. As described above, in the recovery by the cryogenic separation using the rectification tower, the fluorine compound is separated and recovered by separating the liquid liquefied by cooling and the residual gas by utilizing the difference in boiling points. For this reason, there is a problem that a very small amount of gas that has not been sufficiently liquefied during the cryogenic separation may be mixed as impurities into the residual gas, resulting in relatively poor recovery efficiency. When multiple rectifying columns are arranged in series and multiple gases with different boiling points are cryogenically separated, if the recovery efficiency of the rectifying column is poor, a high boiling point fluorine compound gas is mixed into the next rectifying column and solidified. This may cause trouble. In addition, if there is a large fluctuation in the amount of exhaust gas supplied to be separated and recovered, the operating conditions of the rectification column may also change, leading to a decrease in recovery efficiency. There was still a problem.

  The present invention has been made in view of such circumstances, complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable high recovery rate, and has high equipment efficiency. The purpose of the present invention is to provide a fluorine compound gas separation and purification device with a long maintenance cycle and high cost performance.

In order to achieve the above object, the first fluorine compound gas separation and purification apparatus of the present invention is an apparatus for separating and purifying a fluorine compound gas from a supply gas containing a plurality of types of fluorine compound gases having different boiling points,
A first rectification column that separates a relatively high boiling high-boiling fluorine compound gas as a liquid at the bottom of the column by cryogenic separation, among the fluorine compound gases contained in the supply gas;
An adsorption tower for adsorbing and separating the remaining high-boiling fluorine compound gas from the top gas derived from the top of the first rectification tower;
A second rectifying column that separates a low-boiling point fluorine compound gas having a lower boiling point than the high-boiling point fluorine compound gas from the gas derived from the adsorption tower as a liquid at the bottom of the column by cryogenic separation ;
A pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the first rectification tower,
The gist is that the liquefied gas supplied as a cold source to the second rectification column is used as the desorption gas of the pretreatment adsorption tower .

The second fluorine compound gas separation and purification apparatus of the present invention is an apparatus for separating and purifying a fluorine compound gas from a supply gas containing a plurality of types of fluorine compound gases having different boiling points,
A rectifying column that separates any predetermined fluorine compound gas as a liquid at the bottom of the column by cryogenic separation of the plurality of types of fluorine gas compounds;
A separation and purification means comprising an adsorption tower that adsorbs and separates the predetermined fluorine compound gas remaining from the top gas derived from the top of the rectification tower,
A plurality of sets of the separation and purification means are provided corresponding to each of the plurality of types of fluorine compound gas ,
In the separation and purification means, in order from the one for separating and purifying the relatively high boiling point fluorine compound gas, the one for separating and purifying the low boiling point fluorine compound gas is arranged in series,
It further comprises a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the rectifying tower that cryogenically separates the highest boiling point fluorine compound gas,
The gist is that the liquefied gas supplied as a cold source to the rectification column for cryogenic separation of the fluorine compound gas having the lowest boiling point is used as the desorption gas of the pretreatment adsorption tower .

That is , the first fluorine compound gas separation and purification apparatus of the present invention first separates the fluorine compound gas as a liquid at the bottom of the column by cryogenic separation in the first rectification column and the second rectification column. The residual high-boiling fluorine compound gas is adsorbed and separated from the top gas derived from the top of the rectification column by an adsorption tower. Thus, since the high-boiling point fluorine compound gas remaining in the cryogenic separation is adsorbed and separated by the adsorption tower, the recovery efficiency of the high-boiling point fluorine compound gas is remarkably improved as compared with the recovery by the cryogenic separation alone. Particularly, the cryogenic separation of the high-boiling fluorine compound gas has a lower separation accuracy than the low-boiling fluorine compound gas, so that the recovery efficiency is drastically increased by the adsorption separation of the residual portion by the adsorption tower. Then, the gas from which the high-boiling point fluorine compound gas has been completely separated and removed is introduced into the second rectifying column, where the low-boiling point compound gas is subjected to cryogenic separation, so that the liquid at the bottom of the second rectifying column is liquid. As a result, the high-boiling point fluorine compound gas is hardly mixed in the low-boiling point fluorine compound gas, and the purity of the recovered low-boiling point fluorine compound gas is greatly improved. Further, since the high-boiling fluorine compound gas remaining by the adsorption tower is completely removed, it is possible to prevent troubles caused by the high-boiling fluorine gas mixed into the second rectifying tower and the piping and solidifying. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the rectification column vary, stable recovery efficiency is realized. Furthermore, since the fluorine compound gas is separated as a liquid at the bottom of the column by cryogenic separation and the fluorine compound gas is recovered in a liquid state, a large-capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it. In addition, because the adsorption tower adsorbs residual fluorine compound gas by cryogenic separation, the desorption cycle can be greatly extended and the life of the adsorbent can be extended compared to the conventional collection using only the adsorption tower, greatly increasing the maintenance cost. You can save. In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.
The liquefaction is further provided with a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the supply gas introduced into the first rectification tower, and is supplied as a cold source to the second rectification tower. Since the gas is used as the desorption gas of the pretreatment adsorption tower, the gas utilization efficiency is excellent. For example, by using liquefied nitrogen gas as a cooling source for the second rectification tower, it does not contain moisture or carbon dioxide, so it can be used as a desorption gas without pretreatment. large. In addition, by using liquefied nitrogen as a cooling source for the second rectification column, the fluorine compound gas can be cryogenically separated at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

In the first fluorine compound gas separation and purification apparatus, when a desorption gas desorbed from the high boiling point fluorine compound gas adsorbed on the adsorption tower is supplied to the first rectification tower. Even if an impure gas such as a carrier gas is mixed in the desorption gas, the high-boiling fluorine compound gas separated by adsorption is supplied again to the first rectification column and is subjected to cryogenic separation. Eliminates the need for a new location. In addition, since the fluorine compound gas is always recovered in liquid form from the bottom of the first rectification column, there is no need to provide duplicate product gas recovery lines, no large capacity tank for storing recovered gas, There is no need to install a refrigerator.

In the first fluorine compound gas separation and purification apparatus, the supply gas contains a carrier gas used in the fluorine compound gas utilization facility, and serves as a cold source for the second rectification tower. When the carrier gas to be used is liquefied and supplied, the gas used in the fluorine compound gas utilization equipment and the gas other than the fluorine compound gas do not enter the system of the apparatus, so the atmosphere in the system It becomes easy to maintain. In this case, when the gas used in the fluorine compound gas utilization facility is nitrogen gas, the liquefied nitrogen serves as a cooling source for the second rectification column, and the low boiling point fluorine compound gas is deepened at a sufficiently low temperature. Cold separation is possible, and sufficient recovery efficiency can be secured.

In the second fluorine compound gas separation and purification apparatus of the present invention, the fluorine compound gas is first separated as a liquid at the bottom of the column by cryogenic separation in the rectification column, and is derived from the top of the rectification column. The remaining fluorine compound gas is adsorbed and separated from the top gas by an adsorption tower. Thus, since the fluorine compound gas remaining in the cryogenic separation is adsorbed and separated by the adsorption tower, the recovery efficiency of the fluorine compound gas is remarkably improved as compared with the recovery by only the cryogenic separation. Particularly, the cryogenic separation of the high-boiling fluorine compound gas has a lower separation accuracy than the low-boiling fluorine compound gas, so that the recovery efficiency is drastically increased by the adsorption separation of the residual portion by the adsorption tower. Then, the gas from which the high-boiling fluorine compound gas has been completely separated and removed is introduced into the next rectification column, where the low-boiling compound gas is subjected to cryogenic separation, so that the liquid at the bottom of the next rectification column As a result, the high-boiling point fluorine compound gas is hardly mixed in the low-boiling point fluorine compound gas, and the purity of the recovered low-boiling point fluorine compound gas is greatly improved. Further, since the high-boiling fluorine compound gas remaining by the adsorption tower is completely removed, it is possible to prevent the occurrence of troubles due to the high-boiling fluorine gas mixed into the next rectification tower or piping and solidifying. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the rectification column vary, stable recovery efficiency is realized. Furthermore, since the fluorine compound gas is separated as a liquid at the bottom of the column by cryogenic separation and the fluorine compound gas is recovered in a liquid state, a large-capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it. In addition, because the adsorption tower adsorbs residual fluorine compound gas by cryogenic separation, the desorption cycle can be greatly extended and the life of the adsorbent can be extended compared to the conventional collection using only the adsorption tower, greatly increasing the maintenance cost. You can save. In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.
In addition, since the separation and purification means are arranged in series in order to separate and purify the low-boiling fluorine compound gas in order from the separation and purification of the relatively high-boiling fluorine compound gas, the high-boiling fluorine compound The low boiling point fluorine compound gas can be efficiently separated and recovered from the gas. Further, in the cryogenic separation in each rectifying column, the fluorine compound gas remaining without being subjected to the cryogenic separation in the previous rectifying column is adsorbed and separated in the adsorption tower. The fluorine compound gas is hardly mixed, and the purity of each recovered fluorine compound gas is greatly improved.
Furthermore, the apparatus further comprises a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the rectification tower that performs cryogenic separation of the fluorine compound gas having the highest boiling point. Since the liquefied gas supplied as a cold source to the rectifying column for cryogenic separation of the fluorine compound gas is used as the desorption gas of the pretreatment adsorption tower, the gas utilization efficiency is excellent. For example, by using liquefied nitrogen gas as the cold source, since it originally does not contain moisture, carbon dioxide, etc., it can be used as a desorption gas without pretreatment, and there is a great facility merit. In addition, by using liquefied nitrogen as a cold source for a rectification tower that deeply separates the fluorine compound gas having the lowest boiling point, the fluorine compound gas can be deeply cooled at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

In the second apparatus for separating and purifying fluorine compound gas, when the desorption gas obtained by desorbing the fluorine compound gas adsorbed on the adsorption tower is supplied to the immediately preceding rectification tower, the desorption is performed. Even if an impurity gas such as carrier gas is mixed in the gas, the high-boiling fluorine compound gas separated by adsorption is supplied again to the rectifying tower immediately before it is cryogenically separated, so a desorption gas purification device is additionally provided. There is no need. In addition, since the fluorine compound gas is always recovered in liquid form from the bottom of the rectifying column immediately before, it is not necessary to provide duplicate product gas recovery lines, and no large capacity tank for storing recovered gas is required. There is no need to install a refrigerator.

In the second fluorine compound gas separation and purification apparatus, the supply gas contains a carrier gas used in a fluorine compound gas utilization facility, and the fluorine compound gas having the lowest boiling point among the rectification columns of the separation and purification means. If the carrier gas used in the fluorine compound gas utilization facility is liquefied and supplied to the rectification column that performs cryogenic separation , the fluorine compound gas is used in the system. Since gases other than the gas used for the facility and the fluorine compound gas do not enter, maintenance and management of the system atmosphere is facilitated. Further, in this case, when nitrogen gas is used, the liquefied nitrogen serves as a cold source for a rectifying column that deeply separates the fluorine compound gas having the lowest boiling point, and is sufficient. The low boiling point fluorine compound gas can be cryogenic separated at a low temperature, and sufficient recovery efficiency can be secured.

  Next, the best mode for carrying out the fluorine compound gas separation and purification apparatus of the present invention will be described.

  FIG. 1 is a diagram showing an apparatus for separating and purifying a fluorine compound gas according to an embodiment of the present invention.

This apparatus includes SF ₆ (boiling point: −30 to 40 ° C.) which is a fluorine compound gas having a relatively high boiling point, CF ₄ (boiling point: −150 to 160 ° C.) which is a fluorine compound gas having a relatively low boiling point, and N A mixed gas containing ₂ is used as a supply gas, and SF ₆ and CF ₄ are separated and purified from this mixed gas.

This apparatus includes a first rectifying column 1 that separates SF ₆ having a relatively high boiling point from a fluorine compound gas contained in the supply gas as a liquid at the bottom of the column by cryogenic separation, and the first rectifying column 1. From the adsorption towers 3a and 3b for adsorbing and separating the remaining SF ₆ from the top gas derived from the top of the column, and from the gas derived from the adsorption towers 3a and 3b, CF ₄ having a boiling point lower than that of the SF ₆ is deepened. And a second rectifying column 2 that separates as a liquid at the bottom of the column by cold separation.

  In the figure, reference numeral 4 denotes a buffer tank, which temporarily holds a supply gas introduced therein and buffers pressure fluctuations of the supply gas discharged from a semiconductor manufacturing apparatus or the like. Reference numeral 5 denotes a compressor which raises the supply gas derived from the buffer tank 4 to a predetermined pressure. Reference numeral 6 denotes a cooler that cools the supply gas that has been pressurized by the compressor 5 and raised in temperature to near room temperature.

7a and 7b are pretreatment towers that adsorb and remove H ₂ O and CO ₂ which are components to be solidified in the subsequent cryogenic separation from the supply gas cooled to near room temperature. In the pretreatment towers 7a and 7b, as an adsorbent, for example, synthetic zeolite or the like excellent in CO ₂ adsorption ability can be used, but the present invention is not limited to this.

  In this example, the pretreatment towers 7a and 7b are composed of a set of two towers, one of which is supplying a desorption gas of high temperature while the other is receiving a supply gas at normal temperature and adsorbing moisture and the like. It is a thermal swing type adsorption tower in which desorption of adsorbed moisture and the like is performed. In the figure, reference numeral 9 denotes a supply gas passage for supplying the supply gas to the pretreatment towers 7a and 7b, and reference numerals 10a and 10b denote desorption gas passages for supplying the desorption gas to the pretreatment towers 7a and 7b. The supply gas passage 9 and the desorption gas passages 10a and 10b are provided with valves (not shown) that are controlled to be opened and closed alternately in the two pretreatment towers 7a and 7b.

  The desorption gas path 10a introduces desorption gas into the pretreatment towers 7a and 7b, and is connected to the tower top gas discharge path 13 connected to the tower top of the second rectification tower 2 so that the second rectification tower The nitrogen gas derived from the top of the second column is heated by the regenerative heater 11 and introduced as a desorption gas. The tower top gas discharge passage 13 is provided with a bypass passage 14 that bypasses the regenerative heater 11, and nitrogen gas that is not heated is introduced through the bypass passage 14 when the tower is cooled after desorption. It is like that. The desorption gas path 10b is connected to a discharge path 12 through which the desorption gas introduced from the desorption gas path 10a and circulated in the tower is discharged.

Reference numeral 8 denotes a first heat exchanger, which is cooled when the feed gas from which H ₂ O and CO ₂ have been adsorbed and removed by the pretreatment towers 7 a and 7 b is introduced into the first fractionator 1. By this first heat exchanger 8, the supply gas is cooled to around −30 to 40 ° C., which is the boiling point of SF ₆ .

The first rectifying column 1 includes a condenser 15 provided near the top of the column, a rectifying unit 16 in the middle of the column, and a heater 17 at the bottom of the column. The condenser 15 cools the supply gas at the top of the tower to −30 to 40 ° C., which is not higher than the boiling point of SF ₆ , by the cold source of the refrigerator unit 18, and liquefies the high boiling SF ₆ in the supply gas. When the liquid SF ₆ liquefied by the condenser 15 flows down in the tower, the rectifying unit 16 makes gas-liquid contact with the supply gas to liquefy the gaseous SF ₆ and perform deep cooling separation. Let The heater 17 heats and vaporizes the low boiling point component that flows down the tower and mixes into the bottom of the tower, thereby improving the purity of the high boiling point component at the bottom of the tower.

Connected to the bottom of the first rectifying column 1 is a recovery path 19 for recovering the liquid SF ₆ that has been deeply cooled and collected at the bottom of the column as a product SF ₆ . On the other hand, a lead-out path 20 through which the supply gas remaining after the SF ₆ is cryogenically separated is led to the top of the first rectifying column 1. The lead-out path 20 exchanges heat with the supply gas introduced into the first fractionator 1 via the first heat exchanger 8. Further, the downstream end of the lead-out path 20 is connected to the adsorption towers 3a and 3b.

The adsorption towers 3a and 3b adsorb and remove SF ₆ remaining without being completely separated by the cryogenic separation by the first rectification tower 1 from the supply gas derived from the top of the first rectification tower 1. . In the adsorption towers 3a and 3b, as the adsorbent, for example, an adsorbent such as molecular sieve or activated carbon excellent in the adsorption ability of SF ₆ can be suitably used. It is possible to use an adsorbent.

  In this example, the adsorption towers 3a and 3b are composed of a set of two towers. While one of the adsorption towers 3a and 3b is adsorbed by circulating a high-pressure supply gas, the other is maintained by the vacuum pump 21 from the normal pressure to the reduced pressure state. This is a pressure swing type adsorption tower in which desorption of adsorbed material is performed. In the figure, reference numeral 22 denotes a supply gas passage for supplying the supply gas to the adsorption towers 3a and 3b, and reference numeral 23 denotes a desorption gas passage which is connected to the vacuum pump 21 and discharges the desorption gas. The supply gas passage 22 and the desorption gas passage 23 are provided with valves (not shown) that are controlled to be opened and closed alternately in the two adsorption towers 3a and 3b.

A recovery path 24 provided with a vacuum pump 21 is connected to the desorption gas path 23. The downstream end of the recovery path 24 is connected to the buffer tank 4, and the desorption gas from which the SF ₆ adsorbed by the adsorption towers 3a and 3b is desorbed is supplied again to the first rectification tower 1. ing.

By doing so, even if an impurity gas such as a carrier gas is mixed in the desorption gas, the adsorbed and separated SF ₆ is supplied again to the first rectifying column 1 and is subjected to cryogenic separation. There is no need to install a separate purification device. Further, since SF ₆ is always recovered in liquid form from the bottom of the first rectifying column 1, there is no need to provide duplicate product gas recovery lines, and no large capacity tank for storing recovered gas is required. There is no need to install a refrigerator.

  The recovery path 24 is provided with a bypass path 25 that bypasses the vacuum pump 21.

Reference numeral 26 denotes a second heat exchanger, which is cooled when the supply gas from which SF ₆ has been adsorbed and removed by the adsorption towers 3 a and 3 b is introduced into the second rectification tower 2. By this second heat exchanger 26, the supply gas is cooled to around −150 to 160 ° C., which is the boiling point of CF ₄ .

The second rectifying tower 2 includes a condenser 27 provided near the top of the tower, a rectifying section 28 in the middle of the tower, and a heater 29 at the bottom of the tower. The condenser 27 is connected to a supply path 30 of liquid nitrogen which is a liquefied carrier gas, and the supply gas at the top of the tower is cooled to −150 to 160 ° C. which is lower than the boiling point of CF ₄ by the cold source of liquid nitrogen. Then, CF ₄ having a low boiling point in the supply gas is liquefied. When the liquid CF ₄ liquefied by the condenser 27 flows down in the tower, the rectifying unit 28 is in gas-liquid contact with the supply gas to liquefy the gaseous CF ₄ and perform cryogenic separation. Let The heater 29 heats and vaporizes the low boiling point component that flows down in the tower and enters the bottom of the tower, thereby improving the purity of the high boiling point component at the bottom of the tower.

Connected to the bottom of the second rectifying column 2 is a recovery path 71 for recovering the liquid CF ₄ that has been cryogenically separated and collected at the bottom of the column as a product CF ₄ . On the other hand, a top gas discharge passage 13 is connected to the top of the second rectifying column 2 through which nitrogen gas obtained by evaporating nitrogen gas, which is a carrier gas remaining after cryogenic separation of CF ₄ , is derived. ing.

  The tower top gas discharge passage 13 exchanges heat with the supply gas introduced into the second fractionator 2 via the second heat exchanger 26. On the other hand, the liquid nitrogen introduced into the condenser 27 is vaporized by being deprived of cold by condensation, and is discharged from the discharge passage 70. This discharge path 70 is subjected to heat exchange with the supply gas introduced into the second fractionator 2 through the second heat exchanger 26. Further, the downstream end of the discharge passage 70 is connected to a tower top gas discharge passage 13 through which the carrier gas is discharged from the top of the second rectifying tower 2, and these nitrogen gases merge here. The downstream end of the tower top gas discharge passage 13 is connected to the desorption gas passage 10a of the pretreatment towers 7a and 7b as described above.

As described above, liquid nitrogen, which is a carrier gas liquefied as a cold source, is supplied to the second rectifying column 2, so that a gas other than the carrier gas and the fluorine compound gas is present in the system of the apparatus. Since it does not invade, it becomes easier to maintain and manage the atmosphere in the system. The carrier gas that is the top gas of the second fractionator 2 and the liquefied nitrogen supplied as a cold source to the condenser 27 can be used as the desorption gas of the pretreatment towers 7a and 7b. Excellent. Since this nitrogen gas originally does not contain moisture, carbon dioxide and the like, it can be used as a desorption gas without pretreatment, and has a great merit in terms of equipment. In addition, by using liquefied nitrogen as a cold source for the second rectification column 2, CF ₄ can be subjected to deep cold separation at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

As described above, according to the apparatus for separating and purifying the fluorine compound gas, for adsorbing separating SF ₆ remaining in the cryogenic separation adsorption tower 3a, at 3b, the recovery of SF ₆ as compared with the recovery by only the cryogenic separation Efficiency is greatly improved. Particularly, since the cryogenic separation of SF ₆ has a lower separation accuracy than CF ₄ or the like having a lower boiling point, the recovery efficiency is remarkably increased by the adsorption separation of the residual components by the adsorption towers 3a and 3b. Then, the gas from which SF ₆ has been completely separated and removed is introduced into the second rectification column 2, where CF _{4 is} subjected to cryogenic separation, so that it is separated as a liquid at the bottom of the second rectification column 2. that CF ₄ SF ₆ in a high boiling point almost no be mixed in, the purity of the CF ₄ being recovered is significantly improved.

In addition, since the SF ₆ remaining by the adsorption towers 3a and 3b is completely removed, it is possible to prevent troubles caused by the SF ₆ being mixed into the second rectifying tower 2 and the piping and solidifying. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the first and second rectification columns 1 and 2 vary, stable recovery efficiency is realized. Furthermore, since SF ₆ and CF ₄ are both separated as a liquid at the bottom of the column by cryogenic separation and recovered in liquid form, a large capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it. Further, since the adsorption towers 3a and 3b adsorb the residual SF ₆ by the cryogenic separation, the desorption cycle can be greatly extended and the life of the adsorbent can be extended as compared with the recovery by the conventional adsorption towers 3a and 3b alone. Maintenance costs can be greatly reduced.

  In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.

  FIG. 2 is a diagram showing an apparatus for separating and purifying fluorine compound gas according to a second embodiment of the present invention.

  This apparatus uses a mixed gas containing three types of fluorine compound gases and carrier gases having different boiling points as a supply gas, and separates and purifies each fluorine compound gas from this mixed gas.

The supply gas in this example is SF ₆ having the highest boiling point (boiling point: −30 to 40 ° C.), C ₂ F ₆ having the next highest boiling point (boiling point: −80 to 90 ° C.), and the lowest as the fluorine compound gas. It contains CF _{4 having a} boiling point (boiling point: −150 to 160 ° C.) and N ₂ as a carrier gas.

  The separation and purification apparatus includes a rectifying column (denoted by reference numerals 34, 35, and 36 in the drawing) that separates a predetermined fluorine compound gas from the three types of fluorine gas compounds as a liquid at the bottom of the column by cryogenic separation, Separation and purification including adsorption towers (denoted by reference numerals 37a, 37b, 38a, 38b, 39a, and 39b) that adsorb and separate the predetermined fluorine compound gas remaining from the top gas respectively derived from the top of the rectification tower Means are configured (reference numerals 31, 32, 33 shown in the figure). Three sets of the separation and purification means are provided corresponding to each of the three types of fluorine compound gases.

  The first separation and purification means 31 includes a first rectification column 34 and first adsorption towers 37a and 37b, and the second separation and purification means 32 includes a second rectification column 35 and second adsorption towers 38a and 38b. The third separation and purification means 33 includes a third rectifying column 36 and third adsorption columns 39a and 39b. In the first to third separation / purification means 31, 32, 33, in order from the one that separates and purifies a relatively high boiling point fluorine compound gas, the one that separates and purifies the low boiling point fluorine compound gas is arranged in series. Yes.

The SF ₆ is separated and purified by the first separation and purification means 31, the C ₂ F _{6 is} separated and purified by the second separation and purification means 32, and the CF _{4 is} separated and purified by the third separation and purification means 33, and separated in this order. A purification process is performed.

  By doing in this way, the low boiling point fluorine compound gas can be efficiently separated and recovered sequentially from the high boiling point fluorine compound gas. Further, in the cryogenic separation in each separation and purification means 31, 32, 33, the fluorine compound gas remaining without being subjected to the cryogenic separation in the previous rectification tower is adsorbed and separated in the adsorption tower. The fluorine compound gas on the higher boiling point side is hardly mixed, and the purity of each recovered fluorine compound gas is greatly improved.

  In the figure, reference numeral 40a denotes a buffer tank, which temporarily holds a supply gas introduced therein and buffers pressure fluctuations of the supply gas discharged from a semiconductor manufacturing apparatus or the like. Reference numeral 5 denotes a compressor that raises the supply gas derived from the buffer tank 40a to a predetermined pressure. Reference numeral 6 denotes a cooler that cools the supply gas that has been pressurized by the compressor 5 and raised in temperature to near room temperature.

7a and 7b are pretreatment towers that adsorb and remove H ₂ O and CO ₂ which are components to be solidified in the subsequent cryogenic separation from the supply gas cooled to near room temperature. In the pretreatment towers 7a and 7b, as an adsorbent, for example, synthetic zeolite or the like excellent in CO ₂ adsorption ability can be used, but the present invention is not limited to this.

  In this example, the pretreatment towers 7a and 7b are composed of a set of two towers, one of which is supplying a desorption gas of high temperature while the other is receiving a supply gas at normal temperature and adsorbing moisture and the like. It is a thermal swing type adsorption tower in which desorption of adsorbed moisture and the like is performed. In the figure, reference numeral 9 denotes a supply gas passage for supplying the supply gas to the pretreatment towers 7a and 7b, and reference numerals 10a and 10b denote desorption gas passages for supplying the desorption gas to the pretreatment towers 7a and 7b. The supply gas passage 9 and the desorption gas passages 10a and 10b are provided with valves (not shown) that are controlled to be opened and closed alternately in the two pretreatment towers 7a and 7b.

  The desorption gas path 10a is for introducing the desorption gas into the pretreatment towers 7a and 7b, and the process gas discharge path 69 connected to the tops of the third adsorption towers 39a and 39b is connected to the nitrogen gas derived therefrom. Is heated by the regenerative heater 11 and introduced as a desorption gas. The processing gas discharge passage 69 is provided with a bypass passage 14 that bypasses the regenerative heater 11, and when the inside of the tower is cooled after desorption, unheated nitrogen gas is introduced through the bypass passage 14. It has become. The desorption gas path 10b is connected to a discharge path 12 through which the desorption gas introduced from the desorption gas path 10a and circulated in the tower is discharged.

Reference numeral 40b denotes a buffer tank, which temporarily holds the supply gas from which H ₂ O and CO ₂ have been adsorbed and removed by the pretreatment towers 7a and 7b before introducing the first rectification tower 34 into the first rectification tower. The pressure fluctuation of the supply gas introduced into the column 34 is buffered.

  As described above, the pretreatment towers 7a and 7b for pretreating the supply gas introduced into the first rectifying column 34 are provided, and the buffer tank 40a is provided before introduction into the pretreatment towers 7a and 7b. A buffer tank 40b is provided before the supply gas derived from the columns 7a and 7b is introduced into the first rectification column 34. Since the supply gas introduced into the pretreatment towers 7a and 7b is buffered by the buffer tank 40a, the pressure of the supply gas introduced into the pretreatment towers 7a and 7b is made uniform, and the adsorption capacity is stabilized. Further, since the supply gas derived from the pretreatment towers 7a and 7b and introduced into the first rectification tower 34 is buffered by the buffer tank 40b, the pressure of the supply gas introduced into the first rectification tower 34 is stable. In addition, the cryogenic separation by the first rectifying column 34 is stably performed. This is particularly effective because the gas pressure derived from the pretreatment towers 7a and 7b is likely to fluctuate due to thermal swing valve operation. Furthermore, since a plurality of buffer tanks 40a and 40b are dispersed and arranged in this manner, the pressure can be maintained in each of the buffer tanks 40a and 40b, so that the power of the compressor 5 can be saved and the running cost and equipment cost can be reduced. It becomes possible.

Reference numeral 8 denotes a first heat exchanger, which is cooled when the feed gas from which H ₂ O and CO ₂ have been adsorbed and removed by the pretreatment towers 7 a and 7 b is introduced into the first rectification tower 34. By this first heat exchanger 8, the supply gas is cooled to around −30 to 40 ° C., which is the boiling point of SF ₆ .

The first rectifying column 34 includes a condenser 41 provided near the top of the column, a rectifying unit 42 in the middle of the column, and a heater 43 at the bottom of the column. The condenser 41 cools the supply gas at the top of the tower to −30 to 40 ° C., which is not higher than the boiling point of SF ₆ , by the cold source of the refrigerator unit 18, and liquefies the high boiling SF ₆ in the supply gas. When the liquid SF ₆ liquefied by the condenser 41 flows down in the tower, the rectifying section 42 is in gas-liquid contact with the supply gas to liquefy the gaseous SF ₆ and perform deep cooling separation. Let The heater 43 heats and vaporizes the low boiling point component that flows down the column and mixes into the bottom of the column, thereby improving the purity of the high boiling point component at the bottom of the column.

Connected to the bottom of the first rectifying column 34 is a recovery path 19 for recovering the liquid SF ₆ that has been cryogenically separated and collected at the bottom of the column as a product SF ₆ . On the other hand, a lead-out path 20 through which the supply gas remaining after the SF ₆ is cryogenically separated is led to the top of the first fractionator 34. The lead-out path 20 exchanges heat with the supply gas introduced into the first rectification column 34 through the first heat exchanger 8. The downstream end of the lead-out path 20 is connected to the first adsorption towers 37a and 37b via the buffer tank 44a.

  Here, since the supply gas introduced into the first adsorption towers 37a and 37b is buffered by the buffer tank 44a, the pressure of the supply gas introduced into the first adsorption towers 37a and 37b becomes uniform, and the adsorption capacity is stabilized.

The first adsorption towers 37a and 37b adsorb SF ₆ remaining without being completely separated by the cryogenic separation by the first rectification tower 34 from the supply gas derived from the top of the first rectification tower 34. Remove. In the first adsorption towers 37a and 37b, as the adsorbent, for example, an adsorbent such as a molecular sieve or activated carbon excellent in the adsorption ability of SF ₆ can be suitably used, but the adsorbent is not limited thereto. Various adsorbents can be used.

  In this example, the first adsorption towers 37a and 37b are composed of a pair of two towers, and one of the first adsorption towers 37a and 37b is adsorbed by circulating a high-pressure supply gas, and the other is reduced from normal pressure to a reduced pressure state by the vacuum pump 21. It is a pressure swing type adsorption tower in which adsorbed substances are desorbed while being maintained. In the figure, reference numeral 22 denotes a supply gas passage for supplying the supply gas to the first adsorption towers 37a and 37b, and reference numeral 23 denotes a desorption gas passage which is connected to the vacuum pump 21 and discharges the desorption gas. The supply gas passage 22 and the desorption gas passage 23 are provided with valves (not shown) that are controlled to be opened and closed alternately in the two adsorption towers 37a and 37b.

A recovery path 24 provided with a vacuum pump 21 is connected to the desorption gas path 23. A downstream end of the recovery path 24 is connected to a buffer tank 40a, and a desorption gas desorbed from the SF ₆ adsorbed by the first adsorption towers 37a and 37b is disposed in front of the pretreatment towers 7a and 7b. It is introduced into 40a and supplied again to the first rectification column 34. The recovery path 24 is provided with a branch path 45, and the downstream end of the branch path 45 passes through the compressor 46 after the pretreatment towers 7 a and 7 b, that is, before the first rectification tower 34. Is introduced into the buffer tank 40b, and is supplied again to the first rectification column 34 (A-A in the figure is connected).

By doing so, even if an impurity gas such as a carrier gas is mixed in the desorption gas, the adsorbed and separated SF ₆ is supplied again to the first rectification column 34 and is subjected to cryogenic separation. There is no need to install a separate purification device. In addition, since SF ₆ is always recovered in liquid form from the bottom of the first rectifying column 34, it is not necessary to provide duplicate product gas recovery lines, and a large capacity tank for storing recovered gas is not required. There is no need to install a refrigerator.

  Further, since the desorption gas of the first adsorption towers 37a and 37b is dispersed and returned to the plurality of buffer tanks 40a and 40b, the pressure fluctuation of the supply gas introduced into the first rectification tower 34 is made slower. This is effective for more stable operation of the first rectifying column 34. Furthermore, since the supply gas derived from the first adsorption towers 37a and 37b and introduced into the second rectification tower 35 is buffered by the buffer tank 44b, the pressure of the supply gas introduced into the second rectification tower 35 is reduced. Stable and deep cold separation by the second rectification column 35 is performed stably. This is particularly effective because the gas pressure derived from the first adsorption towers 37a and 37b is likely to fluctuate due to the swing-type valve operation. Further, by arranging a plurality of buffer tanks 44a and 44b in such a distributed manner, the pressure can be maintained in each of the buffer tanks 44a and 44b, so that the power of the compressor 5 and the like can be saved, and running costs and equipment costs can be reduced. It becomes possible to suppress.

  The recovery path 24 is provided with a bypass path 25 that bypasses the vacuum pump 21.

Reference numeral 26 denotes a second heat exchanger, which is cooled when the supply gas from which SF ₆ has been adsorbed and removed by the first adsorption towers 37 a and 37 b is introduced into the second rectification tower 35. By this second heat exchanger 26, the supply gas is cooled to around −80 to 90 ° C., which is the boiling point of C ₂ F ₆ .

The second rectifying column 35 includes a condenser 47 provided near the top of the column, a rectifying unit 48 in the middle of the column, and a heater 49 at the bottom of the column. The condenser 47, refrigerator unit by cooling source 50 to cool the feed gas column top to -80～90 ° C. is below the boiling point C ₂ F _6, C ₂ of the low boiling point in the second in the feed gas to liquefy the F _6. The rectifying section 48 is cooled deeply by bringing the liquid C ₂ F ₆ liquefied by the condenser 47 into gas-liquid contact with the supply gas when it flows down in the tower to liquefy the gaseous C ₂ F _6. Separate and let flow down. The heater 49 heats the liquid C ₂ F ₆ flowing down in the tower and accumulating at the bottom of the tower to prevent solidification due to overcooling.

Connected to the bottom of the second rectifying column 35 is a recovery path 51 for recovering the liquid C ₂ F ₆ that has been cryogenically separated and accumulated at the bottom of the column as a product C ₂ F ₆ . On the other hand, a top gas discharge passage 52 through which the top gas from which C ₂ F ₆ is cryogenically separated is led out is connected to the top of the second fractionator 35.

  The tower top gas discharge passage 52 performs heat exchange with the supply gas introduced into the second fractionator 35 through the second heat exchanger 26. The downstream end of the tower top gas discharge path 52 is connected to the second adsorption towers 38a and 38b via the buffer tank 53a.

  Here, since the supply gas introduced into the second adsorption towers 38a and 38b is buffered by the buffer tank 53a, the pressure of the supply gas introduced into the second adsorption towers 38a and 38b becomes uniform, and the adsorption capacity is stabilized.

The second adsorption towers 38a and 38b are C ₂ F ₆ remaining without being completely separated from the supply gas derived from the top of the second rectification tower 35 by the cryogenic separation by the second rectification tower 35. Is removed by adsorption. In the second adsorption towers 38a and 38b, as the adsorbent, for example, an adsorbent such as molecular sieve or activated carbon having excellent C ₂ F ₆ adsorption ability can be preferably used, but the adsorbent is not limited thereto. It is possible to use various adsorbents.

  In this example, the second adsorption towers 38a and 38b are composed of a pair of two towers, and one of the two adsorption towers 38a and 38b is adsorbed by circulating a high-pressure supply gas, while the other is reduced from normal pressure to a reduced pressure state by the vacuum pump 21. It is a pressure swing type adsorption tower in which adsorbed substances are desorbed while being maintained. In the figure, reference numeral 54 denotes a supply gas passage for supplying the supply gas to each of the second adsorption towers 38a and 38b, and reference numeral 55 denotes a desorption gas passage that is connected to the vacuum pump 21 and discharges the desorption gas. The supply gas passage 54 and the desorption gas passage 55 are provided with valves (not shown) that are controlled to open and close so as to alternately perform adsorption and desorption in the two adsorption towers 38a and 38b.

A recovery path 56 provided with the vacuum pump 21 is connected to the desorption gas path 55. The downstream end of the recovery path 56 is connected to the buffer tank 44a via the compressor 57, and the desorption gas desorbed from the C ₂ F ₆ adsorbed by the second adsorption towers 38a and 38b is used as the first adsorption tower. It is introduced into a buffer tank 44a arranged in front of 37a, 37b and supplied again to the second rectifying column 35. The recovery path 56 is provided with a branch path 58, and a buffer tank 44b disposed at the downstream end of the branch path 58 after the first adsorption towers 37a and 37b, that is, before the second rectification tower 35. And is supplied again to the second rectification column 35 (BB shown in the figure is connected).

By doing so, even if an impurity gas such as a carrier gas is mixed in the desorption gas, the adsorbed and separated C ₂ F ₆ is supplied again to the second rectification column 35 and is subjected to cryogenic separation. There is no need for a separate gas purification device. Further, since C ₂ F ₆ is always recovered in liquid form from the bottom of the second rectification column 35, there is no need to provide duplicate product gas recovery lines, and a large capacity tank for storing recovered gas is required. There is no need to install a refrigerator.

  Further, since the desorption gas of the second adsorption towers 38a and 38b is dispersed and returned to the plurality of buffer tanks 44a and 44b, the pressure fluctuation of the supply gas introduced into the second rectification tower 35 is made slower. This is effective for more stable operation of the second rectification column 35. Furthermore, since the supply gas led out from the second adsorption towers 38a and 38b and introduced into the third rectification tower 36 is buffered by the buffer tank 53b, the pressure of the supply gas introduced into the third rectification tower 36 is reduced. Stable and deep cold separation by the third rectification column 36 is performed stably. This is particularly effective because the gas pressure derived from the second adsorption towers 38a and 38b is likely to fluctuate due to the swing type valve operation. In addition, by arranging a plurality of buffer tanks 53a and 53b in such a manner that the pressure can be maintained in each of the buffer tanks 53a and 53b, the power of the compressor 5 can be saved, and running costs and equipment costs can be reduced. It becomes possible.

  The recovery path 56 is provided with a bypass path 25 that bypasses the vacuum pump 21.

A third heat exchanger 59 is cooled when the supply gas from which C ₂ F ₆ has been adsorbed and removed by the second adsorption towers 38 a and 38 _b is introduced into the third rectification tower 36. By this third heat exchanger 59, the supply gas is cooled to around −150 to 160 ° C., which is the boiling point of CF ₄ .

The third rectifying tower 36 includes a condenser 60 provided near the top of the tower, a rectifying part 61 in the middle of the tower, and a heater 62 in the bottom of the tower. The condenser 60 is connected to a supply path 30 for liquid nitrogen which is a liquefied carrier gas, and the supply gas at the top of the tower is cooled to −150 to 160 ° C. which is lower than the boiling point of CF ₄ by the cold source of liquid nitrogen. Then, CF ₄ having the lowest boiling point in the supply gas is liquefied. When the liquid CF ₄ liquefied by the condenser 60 flows down in the tower, the rectifying unit 61 is in gas-liquid contact with the supply gas to liquefy the gaseous CF ₄ and cool it down. Let The heater 62 heats and vaporizes the low boiling point component that flows down the tower and mixes into the bottom of the column, thereby improving the purity of the high boiling point component at the bottom of the column.

Connected to the bottom of the third rectifying column 36 is a recovery path 71 for recovering the liquid CF ₄ that has been cryogenically separated and collected at the bottom of the column as a product CF ₄ . On the other hand, the top of the third rectifying column 36 is connected to a column top gas discharge path 63 from which nitrogen gas obtained by evaporating nitrogen gas, which is a carrier gas remaining after the cryogenic separation of CF ₄ , is led out. Yes.

  The tower top gas discharge path 63 exchanges heat with the supply gas introduced into the third rectifying tower 36 through the third heat exchanger 59. The downstream end of the tower top gas discharge path 63 is connected to the third adsorption towers 39a and 39b.

The third adsorption towers 39a and 39b adsorb CF ₄ remaining from the supply gas derived from the top of the third rectification tower 36 without being completely separated by the cryogenic separation by the third rectification tower 36. Remove. In the third adsorption towers 39a and 39b, as the adsorbent, for example, an adsorbent such as molecular sieve or activated carbon excellent in the adsorption ability of CF ₄ can be preferably used, but the adsorbent is not limited thereto. Various adsorbents can be used.

  In this example, the third adsorption towers 39a and 39b are composed of a set of two towers, and one of the third adsorption towers 39a and 39b is adsorbed by circulating a high-pressure supply gas, while the other is reduced from normal pressure to a reduced pressure state by the vacuum pump 21. It is a pressure swing type adsorption tower in which adsorbed substances are desorbed while being maintained. In the figure, reference numeral 64 denotes a supply gas passage for supplying the supply gas to each of the second adsorption towers 38a and 38b, and 65 denotes a desorption gas passage that is connected to the vacuum pump 21 and discharges the desorption gas. The supply gas passage 64 and the desorption gas passage 65 are provided with valves (not shown) that are controlled to be opened and closed so as to alternately perform adsorption and desorption in the two adsorption towers 39a and 39b.

A recovery path 67 provided with the vacuum pump 21 is connected to the desorption gas path 65. The downstream end of the recovery path 67 is connected to the buffer tank 53a via the compressor 66, and the desorption gas desorbed from the CF ₄ adsorbed by the third adsorption towers 39a and 39b is converted into the second adsorption tower 38a, It is introduced into a buffer tank 53a arranged in front of 38b and supplied again to the third fractionator 36. The recovery path 67 is provided with a branch path 68, and the downstream end of the branch path 68 is disposed after the second adsorption towers 38a and 38b, that is, before the third rectification tower 36. And is supplied again to the third rectification column 36 (CC shown in the figure is connected).

On the other hand, nitrogen gas, which is a carrier gas remaining after CF ₄ is adsorbed by the third adsorption towers 39 a and 39 b, is exhausted through the processing gas exhaust path 69. On the other hand, the liquid nitrogen introduced into the condenser 60 is vaporized by being deprived of cold by condensation, and is discharged from the discharge passage 70. This discharge path 70 is exchanged for heat with the supply gas introduced into the third fractionator 36 through the third heat exchanger 59. The downstream end of the discharge path 70 is connected to a processing gas discharge path 69 from which the carrier gas is discharged from the third adsorption towers 39a and 39b, and these nitrogen gases merge here. Further, the downstream end of the processing gas discharge passage 69 is connected to the preprocessing towers 7a and 7b via the heater 11 as described above.

In this way, liquid nitrogen, which is a carrier gas liquefied as a cold source, is supplied to the third rectifying column 36, so that a gas other than the carrier gas and the fluorine compound gas is introduced into the system of the apparatus. Since it does not invade, it becomes easier to maintain and manage the atmosphere in the system. The carrier gas that is the top gas of the third rectifying column 36 and the liquefied nitrogen supplied as a cold source to the condenser 60 can be used as the desorption gas for the pretreatment towers 7a and 7b. Excellent. Since this nitrogen gas originally does not contain moisture, carbon dioxide and the like, it can be used as a desorption gas without pretreatment, and has a great merit in terms of equipment. Further, by using liquefied nitrogen as a cooling source for the third rectifying column 36, CF ₄ can be subjected to cryogenic separation at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

  As described above, according to the above-described fluorine compound gas separation and purification apparatus, the fluorine compound gas remaining in the cryogenic separation is adsorbed and separated by the adsorption tower. Therefore, the fluorine compound gas recovery efficiency is higher than the recovery by only the cryogenic separation. Is significantly improved. In particular, since the cryogenic separation of the high-boiling fluorine compound gas has a lower separation accuracy than the low-boiling fluorine compound gas, the recovery efficiency is drastically increased by the adsorption separation of the residual portion by the adsorption tower. Then, the gas from which the high-boiling fluorine compound gas has been completely separated and removed is introduced into the next rectification column, where the low-boiling compound gas is subjected to cryogenic separation, so that the liquid at the bottom of the next rectification column As a result, the high-boiling point fluorine compound gas is hardly mixed in the low-boiling point fluorine compound gas, and the purity of the relatively low-boiling point fluorine compound gas recovered is greatly improved.

  Further, in each separation and purification means 31, 32, 33, in order to completely remove the high-boiling fluorine compound gas remaining in the adsorption tower, the high-boiling fluorine gas is mixed into the next rectification tower or pipe and solidified. Can prevent troubles. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the rectification column vary, stable recovery efficiency is realized. Furthermore, since the fluorine compound gas is separated as a liquid at the bottom of the column by cryogenic separation and the fluorine compound gas is recovered in a liquid state, a large-capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it.

  In addition, each adsorption tower adsorbs residual fluorine compound gas by cryogenic separation, so the desorption cycle is greatly extended and the life of the adsorbent can be extended compared to the conventional collection using only the adsorption tower, greatly increasing maintenance costs. Can save you money. In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.

In the first embodiment shown in FIG. 1, the second rectifying column 2 is not completely separated and removed in the downstream side of the second rectifying column 2 for cryogenic separation of CF ₄ . A second adsorption tower for adsorbing and separating CF ₄ may be provided. By doing so, “the rectification column that cryogenically separates one of the two types of fluorine compound gas, and the above-mentioned fluorine compound gas remaining from the top gas derived from the top of the rectification column. The separation and purification means configured to include an adsorption tower that performs adsorption separation is provided with two sets corresponding to each of the two types of fluorine compound gases.

  In the second embodiment shown in FIG. 2, the relationship between the first rectifying column 34, the first adsorption towers 37a and 37b, and the second rectifying column 35, and the second rectifying column 35 and the second adsorption column. The relationship between the towers 38a and 38b and the third rectifying tower 36 is the "first rectifying tower for separating a relatively high boiling high-boiling fluorine compound gas as a liquid at the bottom of the tower by deep cooling, An adsorption tower that adsorbs and separates the high-boiling fluorine compound gas remaining from the top gas derived from the top of the first rectifying column, and a gas that is lower than the high-boiling fluorine compound gas from the gas derived from the adsorption tower. Satisfies the relationship of “second rectification column that separates low-boiling fluorine compound gas having a boiling point as a liquid at the bottom of the column by cryogenic separation”.

  Further, in each of the above embodiments, the pretreatment tower and each adsorption tower are not limited to those illustrated, but do not limit the operation method such as a thermal swing method, a pressure swing method, and any pretreatment. Any operation method may be adopted in the tower and the adsorption tower.

The first embodiment shown in FIG. 1 illustrates what purifying separating the two fluorine compound gas of SF ₆ and CF _4, in the second embodiment of FIG. 2, SF _6, Examples of purifying and separating three types of fluorine compound gases, C ₂ F ₆ and CF ₄ , are not limited to these, but may be used to separate and purify a plurality of types of fluorine compound gases having different boiling points. For example, a combination of various gases can be applied, and the types of gas are not limited to two or three, and an apparatus for separating and purifying four or more types can also be used.

  In addition, the fluorine compound gas separation and purification apparatus of each of the above embodiments is used to treat exhaust gas from fluorine compound gas utilization facilities including semiconductor manufacturing apparatuses including liquid crystal manufacturing apparatuses and organic EL manufacturing apparatuses, for example. Preferably used.

In this case, the carrier gas corresponds to (1) nitrogen gas for vacuum pump purge or exhaust gas dilution, which is gas used in the semiconductor manufacturing process, and (2) decomposition byproduct gas (COF ₂ ) of fluorine compound gas. , CF _X , SF _X, etc.), (3) gas generated by etching or cleaning action of fluorine compound gas (SiF _4, etc.), and (4) other etching gases (Cl ₂ , BCl ₃ , HBr, etc.).

  With the fluorine compound gas separation and purification apparatus, the semiconductor manufacturing apparatus exhaust gas may be once processed by another PFC recovery apparatus and then processed as a concentrated PFC-containing exhaust gas. It is also possible to treat the exhaust gas directly. In the case of direct treatment, most of the carrier gas is the nitrogen gas of (1) above, but a pretreatment device such as an adsorption tower that removes corrosive gases such as (2), (3), and (4) is required. It becomes.

As described above, the first fluorine compound gas separation and purification apparatus of the present invention performs adsorption separation of the high-boiling fluorine compound gas remaining in the cryogenic separation in the adsorption tower, so that it is higher than the recovery by only the cryogenic separation. The recovery efficiency of the boiling point fluorine compound gas is greatly improved. Particularly, the cryogenic separation of the high-boiling fluorine compound gas has a lower separation accuracy than the low-boiling fluorine compound gas, so that the recovery efficiency is drastically increased by the adsorption separation of the residual portion by the adsorption tower. Then, the gas from which the high-boiling point fluorine compound gas has been completely separated and removed is introduced into the second rectifying column, where the low-boiling point compound gas is subjected to cryogenic separation, so that the liquid at the bottom of the second rectifying column is liquid. As a result, the high-boiling point fluorine compound gas is hardly mixed in the low-boiling point fluorine compound gas, and the purity of the recovered low-boiling point fluorine compound gas is greatly improved. Further, since the high-boiling fluorine compound gas remaining by the adsorption tower is completely removed, it is possible to prevent troubles caused by the high-boiling fluorine gas mixed into the second rectifying tower and the piping and solidifying. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the rectification column vary, stable recovery efficiency is realized. Furthermore, since the fluorine compound gas is separated as a liquid at the bottom of the column by cryogenic separation and the fluorine compound gas is recovered in a liquid state, a large-capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it. In addition, because the adsorption tower adsorbs residual fluorine compound gas by cryogenic separation, the desorption cycle can be greatly extended and the life of the adsorbent can be extended compared to the conventional collection using only the adsorption tower, greatly increasing the maintenance cost. You can save. In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.
The liquefaction is further provided with a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the supply gas introduced into the first rectification tower, and is supplied as a cold source to the second rectification tower. Since the gas is used as the desorption gas of the pretreatment adsorption tower, the gas utilization efficiency is excellent. For example, by using liquefied nitrogen gas as a cooling source for the second rectification tower, it does not contain moisture or carbon dioxide, so it can be used as a desorption gas without pretreatment. large. In addition, by using liquefied nitrogen as a cooling source for the second rectification column, the fluorine compound gas can be cryogenically separated at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

Further, the second fluorine compound gas separation and purification apparatus of the present invention performs adsorption separation of the fluorine compound gas remaining in the cryogenic separation with an adsorption tower, so that the fluorine compound gas recovery efficiency is higher than the recovery by only the cryogenic separation. Is significantly improved. Particularly, the cryogenic separation of the high-boiling fluorine compound gas has a lower separation accuracy than the low-boiling fluorine compound gas, so that the recovery efficiency is drastically increased by the adsorption separation of the residual portion by the adsorption tower. Then, the gas from which the high-boiling fluorine compound gas has been completely separated and removed is introduced into the next rectification column, where the low-boiling compound gas is subjected to cryogenic separation, so that the liquid at the bottom of the next rectification column As a result, the high-boiling point fluorine compound gas is hardly mixed in the low-boiling point fluorine compound gas, and the purity of the recovered low-boiling point fluorine compound gas is greatly improved. Further, since the high-boiling fluorine compound gas remaining by the adsorption tower is completely removed, it is possible to prevent the occurrence of troubles due to the high-boiling fluorine gas mixed into the next rectification tower or piping and solidifying. In addition, even if the supply amount of the supply gas to be separated and recovered varies greatly and the operating conditions of the rectification column vary, stable recovery efficiency is realized. Furthermore, since the fluorine compound gas is separated as a liquid at the bottom of the column by cryogenic separation and the fluorine compound gas is recovered in a liquid state, a large-capacity storage tank is not required to store the recovered gas, and a refrigerator is installed. There is no need to add it. In addition, because the adsorption tower adsorbs residual fluorine compound gas by cryogenic separation, the desorption cycle can be greatly extended and the life of the adsorbent can be extended compared to the conventional collection using only the adsorption tower, greatly increasing the maintenance cost. You can save. In this way, the separation and purification apparatus complements the disadvantages of the recovery method by adsorption separation and the recovery method by cryogenic separation, can be operated at a stable and high recovery rate, and has high equipment efficiency and a long maintenance cycle. Cost performance is high.
In addition, since the separation and purification means are arranged in series in order to separate and purify the low-boiling fluorine compound gas in order from the separation and purification of the relatively high-boiling fluorine compound gas, the high-boiling fluorine compound The low boiling point fluorine compound gas can be efficiently separated and recovered from the gas. Further, in the cryogenic separation in each rectifying column, the fluorine compound gas remaining without being subjected to the cryogenic separation in the previous rectifying column is adsorbed and separated in the adsorption tower. The fluorine compound gas is hardly mixed, and the purity of each recovered fluorine compound gas is greatly improved.
Furthermore, the apparatus further comprises a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the rectification tower that performs cryogenic separation of the fluorine compound gas having the highest boiling point. Since the liquefied gas supplied as a cold source to the rectifying column for cryogenic separation of the fluorine compound gas is used as the desorption gas of the pretreatment adsorption tower, the gas utilization efficiency is excellent. For example, by using liquefied nitrogen gas as the cold source, since it originally does not contain moisture, carbon dioxide, etc., it can be used as a desorption gas without pretreatment, and there is a great facility merit. In addition, by using liquefied nitrogen as a cold source for a rectification tower that deeply separates the fluorine compound gas having the lowest boiling point, the fluorine compound gas can be deeply cooled at a sufficiently low temperature, and sufficient recovery efficiency can be ensured.

It is a block diagram which shows one Embodiment of the separation / purification apparatus of the fluorine compound gas of this invention. It is a block diagram which shows 2nd Embodiment of the separation / purification apparatus of the fluorine compound gas of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st rectification tower 2 2nd rectification tower 3a Adsorption tower 3b Adsorption tower 4 Buffer tank 5 Compressor 6 Cooler 7a Pretreatment tower 7b Pretreatment tower 8 First heat exchanger 9 Supply gas path 10a Desorption gas path 10b Desorption gas path 11 Regenerative heater 12 Release path 13 Tower gas discharge path 14 Bypass path 15 Condenser 16 Rectifier 17 Heater 18 Refrigerator unit 19 Recovery path 20 Derivation path 21 Vacuum pump 22 Supply gas path 23 Desorption gas path 24 Recovery Road
25 Bypass path 26 Second heat exchanger 27 Condenser 28 Rectifier 29 Heater 30 Supply path 31 First separation and purification means 32 Second separation and purification means 33 Third separation and purification means 34 First rectification column 35 Second rectification column Tower 36 third rectification tower 37a first adsorption tower 37b first adsorption tower 38a second adsorption tower 38b second adsorption tower 39a third adsorption tower 39b third adsorption tower 40a buffer tank
40b Buffer tank 41 Condenser 42 Rectifier 43 Heater 44a Buffer tank
44b Buffer tank
45 Branch 46 Compressor
47 Condenser 48 Rectifier 49 Heater 50 Refrigerator unit 51 Recovery path 52 Tower gas discharge path 53a Buffer tank
53b Buffer tank 54 Supply gas path 55 Desorption gas path 56 Recovery path
57 Compressor 58 Branch path 59 Third heat exchanger 60 Condenser 61 Rectifier 62 Heater 63 Tower gas discharge path 64 Supply gas path 65 Desorption gas path 66 Compressor 67 Recovery path 68 Branch path 69 Process gas discharge path 70 Discharge path 71 Collection path

Claims (6)

An apparatus for separating and purifying a fluorine compound gas from a supply gas containing a plurality of types of fluorine compound gases having different boiling points,
A first rectification column that separates a relatively high boiling high-boiling fluorine compound gas as a liquid at the bottom of the column by cryogenic separation, among the fluorine compound gases contained in the supply gas;
An adsorption tower for adsorbing and separating the remaining high-boiling fluorine compound gas from the top gas derived from the top of the first rectification tower;
A second rectifying column that separates a low-boiling point fluorine compound gas having a lower boiling point than the high-boiling point fluorine compound gas from the gas derived from the adsorption tower as a liquid at the bottom of the column by cryogenic separation ;
A pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the first rectification tower,
An apparatus for separating and purifying a fluorine compound gas, wherein a liquefied gas supplied as a cold source to the second fractionator is used as a desorption gas for the pretreatment adsorption tower . Apparatus for separating and purifying a fluorine compound gas of claim 1 wherein the desorption gas desorbed high-boiling fluorine compound gas adsorbed on the adsorption tower so as to supply to said first rectification column. The supply gas includes a carrier gas used in the fluorine compound gas utilization facility, and liquefies and supplies the carrier gas used in the fluorine compound gas utilization facility as a cold source to the second rectification tower. The separation and purification device according to claim 1 or 2 . An apparatus for separating and purifying a fluorine compound gas from a supply gas containing a plurality of types of fluorine compound gases having different boiling points,
A rectifying column that separates any predetermined fluorine compound gas as a liquid at the bottom of the column by cryogenic separation of the plurality of types of fluorine gas compounds;
A separation and purification means comprising an adsorption tower that adsorbs and separates the predetermined fluorine compound gas remaining from the top gas derived from the top of the rectification tower,
A plurality of sets of the separation and purification means are provided corresponding to each of the plurality of types of fluorine compound gas ,
In the separation and purification means, in order from the one for separating and purifying the relatively high boiling point fluorine compound gas, the one for separating and purifying the low boiling point fluorine compound gas is arranged in series,
It further comprises a pretreatment adsorption tower that adsorbs and removes components that solidify in the subsequent cryogenic separation from the feed gas introduced into the rectifying tower that cryogenically separates the highest boiling point fluorine compound gas,
A fluorinated compound gas characterized in that a liquefied gas supplied as a cold source to a rectifying column for cryogenic separation of a fluorine compound gas having the lowest boiling point is used as a desorption gas for the pretreatment adsorption tower. Separation and purification equipment. The apparatus for separating and purifying a fluorine compound gas according to claim 4 , wherein a desorption gas obtained by desorbing the fluorine compound gas adsorbed on the adsorption tower is supplied to a rectification tower immediately before the gas. The supply gas contains a carrier gas used in a fluorine compound gas utilization facility, and a refrigeration source for the rectification column for cryogenic separation of the lowest boiling point fluorine compound gas among the rectification columns of each of the separation and purification means The separation and purification apparatus according to claim 4 or 5, wherein the carrier gas used in the fluorine compound gas utilization facility is liquefied and supplied.

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