CN101070144B - Method for removing carbon tetrafluoride foreign matter in nitrogen trifluoride gas - Google Patents
Method for removing carbon tetrafluoride foreign matter in nitrogen trifluoride gas Download PDFInfo
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- CN101070144B CN101070144B CN2007100621562A CN200710062156A CN101070144B CN 101070144 B CN101070144 B CN 101070144B CN 2007100621562 A CN2007100621562 A CN 2007100621562A CN 200710062156 A CN200710062156 A CN 200710062156A CN 101070144 B CN101070144 B CN 101070144B
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Abstract
The invention relates to a method to remove the carbon tetrafluoride in trifluorinated carbon. The invention uses azeotropic rectify to purify the NF3. it inlets the original gas and the entrainer into the rectify tower and go on the gas-liquid contacting continuously, the impurity forms the azeotropic thing with the much different gas steam point which is evaporated from the tower top and go into the second rectify tower to receive the entrainer; the entrainer and the NF3 are collected from the tower bottom and go into the third rectify tower; by using the boil difference if the NF3 and the entrainer, the high purify NF3 is get from the tower top, the entrainer is received from the tower bottom. The invention callbacks the entrainer by setting two towers and save the entrainer. The invention has decreased the CF4 content to 20ppm and decreased the condenser using mass. Also the device is simple and it costs low, has high efficiency.
Description
Technical field
The present invention relates to a kind of employing azeotropic distillation purifying NF
3The method of gas, it is applicable to industrial NF
3The purifying of gas is especially at the CF that wherein contains
4Impurity.
Background technology
NF
3Being a kind of novel electron gas that has just grown up in recent years, is plasma etching and purge gas good in the information industry.NF
3When gas is used for dry etching, can improve the automatization level in the wafer manufacturing, reduce labor intensity, increase safety coefficient; Have high etch rates, highly selective, the residual little advantage of pollutent.To semiconductor materials such as silicon, especially live width is less than the super large-scale integration material of 100nm, NF
3Than other gas more outstanding etching speed and selectivity are arranged; It is during as a kind of purge of gas agent, and cleaning speed is fast, efficient is high, cleaning is thorough and leave no trace, so market application foreground is wide.Its demand constantly increases, but market is high to the purity requirement of this gas, generally must not be lower than 99.99%, and CF4 foreign matter content wherein must not be higher than 40ppm, the boiling point of this impurity and NF3 only differs 1 ℃, and this is equipped with high purity N F3 gas just for the conventional rectification legal system and brings difficulty.
The main impure gas of industrial NF3 crude product gas is: hydrogen fluoride, fluorine gas, carbonic acid gas, tetrafluoro-methane, nitrous oxide, dinitrogen difluoride etc.Except that CF4, other each impurity adopt the method for absorption, cracking, rectifying all can obtain removing, and the boiling point of CF4 is-128 ℃, only differs 1 ℃ with NF3, specific nature such as table 1.
Table 1CF4 and the contrast of NF3 gas property
| The gas title | Boiling point (℃) | Critical temperature (℃) | Emergent pressure (MPa) | Density g/cm3 (130 ℃) | Moment of dipole (dybe) |
| NF3? | -129.02? | -39.26? | 4.530? | 1.561? | 0.234? |
| CF4? | -128.02? | -45.61? | 3.739? | 1.616? | 0? |
As can be seen from the above table: the boiling point of the two is close, and critical properties are more or less the same, and density and moment of dipole are also very close.So be difficult to the separation requirement that reaches higher.Therefore must adopt effective purification process just can obtain highly purified NF3 product gas.
The method of purifying NF3 gas is a lot, utilizes the difference of impurities physico-chemical property in the product gas, some acid gas impurities, the method that can directly adopt alkali lye to absorb; As for CF4 gaseous impurities wherein, the method that has report to adopt adsorbents adsorb such as activated alumina, molecular sieve, silica gel, gac to remove, but will often change sorbent material in the practical application, and NF3 can lose also in absorption CF4, causes the reduction of yield.If adopt the isolating method of gas-solid chromatograph, though can obtain 99.99% grade NF3 product gas, exist that efficient is low, rare gas element consumption height, be difficult to the shortcoming of industrializing implementation.If adopt conventional cryogenic rectification method, need to consume a large amount of condensing agents, could incite somebody to action CF wherein
4Content drops to more than the 100ppm from 500ppm, and the expense of rectifying tower is also very high.
Summary of the invention
In order to overcome the shortcoming of prior art, the invention provides a kind of high efficiency, low cost and remove NF
3Middle CF
4The method of foreign gas.This method can effectively be removed boiling point and NF
3Unusual approaching impurity composition CF
4, the consumption of condensing agent simultaneously obviously is less than the conventional rectification method, obtains CF
4The product gas of content below 20ppm.This method has remedied the deficiency of conventional rectification method, can be met the high-purity N F of the semi-conductor industry of high degree of accuracy requirement
3Product gas.
The present invention includes the following step: make to contain CF
4The unstripped gas of impurity enters the I rectifying tower by valve, entrainer HCI enters the I rectifying tower through valve, and I rectifying Tata still temperature is-73 ℃～-120 ℃, and the top temperature is-80 ℃～-120 ℃, if the too high then entrainer of tower still temperature HCI easily steams from cat head, have little time and CF
4Form azeotrope, then can't form gas-liquid two-phase in the tower if tower still temperature is crossed to hang down, tower still pressure is 0.1MPa～1.6MPa, and entrainer HCI and unstripped gas are carried out gas-to-liquid contact, entrainer HCI and CF in tower
4Form minimum azeotropic mixture from the extraction of I rectifying tower top, divide two portions: through valve return, a part of gas enters the II rectifying tower through valve to a part of gas from the condenser of I rectifying tower top; The pressure of II rectifying tower is 0.16MPa～1.5MPa, and column bottom temperature is-75 ℃～-130 ℃, and the top temperature is-85 ℃～-130 ℃, obtains a small amount of CF by the cat head of II rectifying tower
4, entrainer HCI then is recycled to the I rectifying tower through valve by pipeline and utilizes at the bottom of the tower of II rectifying tower; The tower bottom entrainer HCI and the NF of I rectifying tower
3Mixture enter the III rectifying tower by the road, the pressure of III rectifying tower is 0.17MPa～1.4MPa, column bottom temperature is-78 ℃～-130 ℃, the top temperature be-88 ℃～-130 ℃, cat head obtains CF
4The product gas that foreign matter content 20ppm is following, the entrainer HCI at the bottom of the tower is recycled to the I rectifying tower by the road by valve and utilizes.
In the described unstripped gas, NF
3Molar content is more than 90%, preferably between 95%～99%; CF
4Content be less than 8%, preferably below 5%; The ratio of entrainer HCI and unstripped gas is 1: 5～100.
The diameter of described I number, II number and III rectifying tower is 20mm～100mm, highly is 2m～10m, and the rectifying column of nickel, stainless steel, Monel or above-mentioned any above filler is equipped with in inside, and the specific surface area of filler is 80m
2/ m
3～500m
2/ m
3, form of bio-carrier is regular or diffusing heap.
The removal of highly effective and safe of the present invention impurity CF
4, it is complete that entrainer is recycled measure simultaneously, greatly reduced cost.
Description of drawings
The present invention is further described below in conjunction with drawings and Examples.
Fig. 1 is a process flow sheet of the present invention;
Fig. 2 is the insufficient triangular phase diagram of entrainer of the present invention;
Fig. 3 is the excessive triangular phase diagram of entrainer of the present invention.
Embodiment
Set forth content of the present invention in more detail below by specific embodiment, except that the mentioned embodiment of the present invention, multiple implementation can also be arranged, not limited to by the embodiment among the present invention.
At a diameter is 50mm, highly is the inner nickel Pall ring filler of filling of rectifying column of 5m.The specific surface area of filler is 364m2/m3, and form of bio-carrier is the heap that looses.
Unstripped gas NF3 total amount is 300kg among the present invention, and wherein CF4 content is 500ppm, and this unstripped gas is added in the I rectifying tower 1 by valve 17, adds entrainer hydrogenchloride (HCl) by valve 7 simultaneously under this feed entrance point, and add-on is 15kg.The operating pressure of control rectifying tower between 0.1MPa～1.6MPa, preferred 0.2MPa.In this pressure range, can form the minimum azeotropic mixture of foreign gas and entrainer preferably, too lowly or too high all cause azeotrope not form, can't reach the effect that azeotropic distillation is removed foreign gas.Tower still temperature is-100 ℃, and the top temperature is-120 ℃, and control of reflux ratio is 1000, and the too little interior gas-liquid of tower that then can not make fully contacts, and reflux ratio too greatly then consumes energy greatly, increases cost.Cat head gas phase produced quantity is 4.25 * 10-4m3/h.The cat head azeotrope passes back into I rectifying tower 1 through condenser 4 parts by valve 11, and a part enters II rectifying tower 2 through valve 12.Control II rectifying tower 2 tower still pressure are 0.16MPa, column bottom temperature-105 ℃, the top temperature is-125 ℃, passes back into II rectifying tower 2 through condenser 5 parts by valve 13 by cat head, a part obtains a spot of CF4 through valve 14, and entrainer is recycled to rectifying tower 1 at the bottom of by tower and utilizes.The tower bottom entrainer of described I rectifying tower 1 and the mixture of NF3 enter III rectifying tower 3 by the road.The tower still of control III rectifying tower 3 is pressed and is 0.17MPa, column bottom temperature is-90 ℃, the top temperature is-110 ℃, pass back into III rectifying tower 3 through condenser 6 parts by valve 15 by cat head, a part obtains the product gas of foreign matter content below 20ppm through valve 16, and the entrainer that obtains at the bottom of the tower is recycled to rectifying tower 1 and utilizes.
With gas chromatograph the NF3 gas before and after the azeotropic distillation is carried out proximate analysis, by analyzing as can be known: the CF4 gas among the NF3 has been removed substantially fully, and the loss amount of NF3 gas is about 3%.Its detailed results is seen NF3 gaseous fraction analytical table.
In the comparative example, identical among unstripped gas composition and the embodiment 1, adopt single tower flow process, and rectifying tower 1 is identical in this rectifying tower and the last example, the operating pressure of controlling this tower is 0.3MPa, and the still temperature is-96 ℃ ,-116 ℃ of top temperature, reflux ratio is 1000, and the cat head extraction is 4.25 * 10-4m3/h.
Adopt gas chromatograph that the NF3 gas before and after the rectifying is carried out proximate analysis, as can be known: the CF4 content among the NF3 reaches 100ppm, and foreign matter content is still very high.Detailed results sees Table 2.
Table 2NF3 gaseous fraction analytical table
| ? | Embodiment | The comparative example who does not add entrainer |
| Inlet amount (m 3/h)? | 3.0? | 3.0? |
| CF in the unstripped gas 4Content (ppm) | 500? | 500? |
Wherein embodiment adds the product gas that obtains behind the entrainer to form, and does not add entrainer among the comparative example.Through more as can be known: add entrainer and can significantly reduce the CF4 foreign matter content, improve NF3 product purity grade, reduce the loss amount of NF3 in the treating processes.
According to the rule of rectifying, when the three-component system of any composition carried out rectifying, first cut always obtained the two-pack azeotrope.But the rectifying behavior of forming different mixtures is different.Shown in Fig. 2,3, A and C are pure component, when original solution consists of the F point, add after the entrainer S, the composition of system will S point direction along the FS alignment and move, and when the amount that adds entrainer was suitable, total composition of system moved to the M point, extraction does not contain entrainer at the bottom of the tower, simultaneously separated azeotropic component A fully and entrainer formation azeotrope steam by cat head.Therefore, tower bottoms almost is pure component C, and the composition of distillate no better than or approach azeotrope and form.If the entrainer quantity not sufficient that adds can not steam with the form of azeotrope component fully from cat head, then in the still liquid a certain amount of component A is arranged also, as shown in Figure 2.When if the entrainer that adds is excessive, then contain the entrainer of some amount in the bottom product, as shown in Figure 3.Obviously both of these case all is unfavorable.Therefore in this technology, when selecting HCL as entrainer, the ratio of control entrainer and unstripped gas is between 1: 5～10.
Claims (4)
1. method of removing carbon tetrafluoride foreign matter in the gas of nitrogen trifluoride is characterized in that comprising the following steps: to make containing CF
4The unstripped gas of impurity enters the I rectifying tower by valve (17), entrainer HCl enters I rectifying tower (1) through another valve (7), I rectifying tower (1) tower still temperature is-73 ℃～-120 ℃, the top temperature is-80 ℃～-120 ℃, tower still pressure is 0.1MPa～1.6MPa, entrainer HCl and unstripped gas are carried out gas-to-liquid contact in I rectifying tower (1), entrainer HCL and CF
4Form minimum azeotropic mixture from I rectifying tower (1) top extraction, divide two portions: through valve return, a part of gas enters II rectifying tower (2) through valve to a part of gas from the condenser (4) on I rectifying tower (1) top; The pressure of II rectifying tower (2) is 0.16MPa～1.5MPa, and column bottom temperature is-75 ℃～-130 ℃, and the top temperature is-85 ℃～-130 ℃, obtains a small amount of CF by the cat head of II rectifying tower (2)
4, entrainer HCl is recycled to I rectifying tower (1) through valve by pipeline and utilizes at the bottom of the tower of II rectifying tower (2); The tower bottom entrainer HCl and the NF of I rectifying tower (1)
3Mixture enter III rectifying tower (3) by the road, the pressure of III rectifying tower (3) is 0.17MPa～1.4MPa, column bottom temperature is-78 ℃～-130 ℃, the top temperature be-88 ℃～-130 ℃, cat head obtains CF
4The product gas that foreign matter content 20ppm is following, the entrainer HCl at the bottom of the tower is recycled to I rectifying tower (1) by the road by valve and utilizes.
2. method according to claim 1 is characterized in that: in the described unstripped gas, and NF
3Molar content is more than 90%; CF
4Content be less than 8%; The ratio of entrainer HCl and unstripped gas is 1: 5～100.
3. method according to claim 1 is characterized in that: in the described unstripped gas, and NF
3Molar content is between 95%～99%; CF
4Content below 5%.
4. method according to claim 1, it is characterized in that: the diameter of described I number, II number and III rectifying tower (1,2,3) is 20mm～100mm, highly be 2m～10m, the rectifying column of nickel, stainless steel, Monel or above-mentioned any above filler is equipped with in inside, and the specific surface area of filler is 80m
2/ m
3～500m
2/ m
3, form of bio-carrier is regular or diffusing heap.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007100621562A CN101070144B (en) | 2007-06-13 | 2007-06-13 | Method for removing carbon tetrafluoride foreign matter in nitrogen trifluoride gas |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007100621562A CN101070144B (en) | 2007-06-13 | 2007-06-13 | Method for removing carbon tetrafluoride foreign matter in nitrogen trifluoride gas |
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|---|---|
| CN101070144A CN101070144A (en) | 2007-11-14 |
| CN101070144B true CN101070144B (en) | 2010-12-08 |
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| US8404024B2 (en) * | 2010-04-15 | 2013-03-26 | Air Products And Chemicals, Inc. | Recovery of NF3 from adsorption operation |
| CN101920944A (en) * | 2010-08-30 | 2010-12-22 | 天津市泰源工业气体有限公司 | Technique for preparing high-purity nitrogen trifluoride by extracting, rectifying and separating nitrogen trifluoride and carbon tetrafluoride |
| CN109682770B (en) * | 2018-12-29 | 2024-04-09 | 中国船舶重工集团公司第七一八研究所 | Multicomponent freon gas infrared detection device |
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Effective date of registration: 20190718 Address after: 057550 No. 1 Weiwu Road, Chemical Industry Agglomeration Area, Feixiang County, Handan City, Hebei Province Patentee after: CSIC (Handan) Perry Special Gas Co. Ltd Address before: 056002 No. 17, Exhibition Road, Handan, Hebei Patentee before: No.718 Inst., China Shipping Heavy Industry Group Co. |
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Address after: 057550 No. five Weir Road, chemical industry gathering area, Feixiang District, Handan, Hebei, 1 Patentee after: China shipbuilding (Handan) Perry Special Gas Co.,Ltd. Address before: No.1 Weiwu Road, chemical industry gathering area, Feixiang County, Handan City, Hebei Province Patentee before: PERIC SPECIAL GASES Co.,Ltd. |
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