Refrigeration – Processes – Circulating external gas
Patent
1994-11-16
1996-03-19
Capossela, Ronald C.
Refrigeration
Processes
Circulating external gas
62 24, F25J 300
Patent
active
054995060
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a ultra-high purity monosilane producing process and a unit therefor, and especially to a process for producing ultra-high purity monosilane gas or liquid monosilane which is free from hydrogen having a lower boiling point than that of monosilane and from chlorides or the like haying higher boiling points than that of monosilane by liquefying and rectifying a monosilane feed gas, and a unit therefor.
In general, monosilane gas or the like is indispensable for the manufacture of super LBl, solar cells and photosensitive substances.
A process for producing such monosilane gas is described in Japanese Patent Publication No. 3,806/1989.
For such monosilane gas, monosilane gas haying a high purity, for example of 99.9999% or more is preferable. At present, however, processes and units capable of continuously obtaining such ultra-high purity monosilane gas as mentioned above have not yet been developed.
The present invention is intended to achieve the aforementioned purpose.
The ultra-high purity monosilane producing process according to the present invention is characterized by comprising: column; rectification of the feed gas by the rectification column, by refrigeration in the upper portion of the rectification column, thereby providing a reflux liquid; and components other than monosilane are separated from the feed gas, thereby obtaining ultra-high purity monosilane gas or liquefied monosilane.
Preferably, the process further comprises: rectification column which is sectioned into an upper stage, a middle stage and a lower stage by means of respective reboiler-condensers disposed in each of its lower potion and intermediate potion so that the feed gas is cooled down and condensed by cold in the lower portion reboiler-condenser, thereby separating and removing higher boiling point components from the feed gas; the pressure-reduced component to the middle stage of the duplex rectification column so that the pressure-reduced component is cooled down and condensed by cold in the intermediate portion reboiler-condenser, thereby providing a reflux liquid; and the middle stage; and introducing the pressure-reduced gas component to the upper stage of the duplex rectification column so that the pressure-reduced gas component is cooled down and condensed by cold in a condenser disposed in the top portion of the upper stage, thereby separating monosilane gas as a reflux liquid from the lower boiling point gas component.
The ultra-high purity monosilane producing unit according to the present invention is characterized by comprising: through rectification of said feed gas, to provide a reflux liquid.
Preferably, the unit further comprises: middle stage and a lower stage by means of a reboiler-condenser disposed in each of a lower portion and an intermediate portion of said column; disposed in each of the upper stage and middle stage; the lower stage between the upper side and lower side rectifying portions in the middle stage by way of the lower portion reboiler-condenser; the upper side and lower side rectifying portions in the upper stage by way of the intermediate portion reboiler-condenser; comprising: means for supplying refrigeration to the cooling condenser, obtained from the lower portion of the upper stage.
One embodiment of the present invention will be described referring to the FIGURE, which is an illustrative view of a unit for use with a process according to the invention.
In the present invention, a monosilane feed gas is used as feed fluid.
The composition of a monosilane feed gas used in one embodiment of the present invention and the boiling points of its component gases are as shown in Table 1.
TABLE 1 ______________________________________
Composition of Boiling point (.degree.C. at
monosilane feed gas
% 1 atm)
______________________________________
Hydrogen (H.sub.2)
16.0 -252.9
Monosilane (SiH.sub.4)
69.2 -111.5
Monochlorosilane (SiH.sub.3 Cl)
4.1 -30.4
Dichlorosilane (SiH.sub.2 Cl.sub.2)
9.9 8.2
Trichlorosilane (SiHCl.sub.3)
0.8 31.8
REFERENCES:
patent: 4755201 (1988-07-01), Eschwey et al.
Nagamura Takashi
Tomita Shinji
Capossela Ronald C.
L'Air Liquide Societe Anonyme pour l'Etude et, l'Exploitation de
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