Refrigeration – Cryogenic treatment of gas or gas mixture – Separation of gas mixture
Patent
1996-05-06
1997-11-11
Kilner, Christopher
Refrigeration
Cryogenic treatment of gas or gas mixture
Separation of gas mixture
62902, 62918, 423481, 423488, F25J 308
Patent
active
056851693
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method and apparatus for preparing high purity hydrogen bromide (HBr).
BACKGROUND ART
Hydrogen bromide has been used in etching and others of a semiconductor manufacturing process in place of fluorocarbon gases whose influence on the ozone layer has been questioned and whose utilization is regulated. Hence, there is a demand for developing the technique of preparing high purity hydrogen bromide in a large amount.
An example of a conventional method for preparing high purity hydrogen bromide will be described with reference to FIG. 2. In a cylinder 1, a raw material consisting of hydrogen bromide and impurities is stored. The raw material is evaporated by heating the cylinder 1. The hydrogen bromide gas thus generated is adjusted to a predetermined pressure by means of a pressure regulating valve 2 and introduced into an adsorber 3 filled with molecular sieves. By virtue of the molecular sieves, the impurities other than moisture contained in the gas are removed then the gas is fed to a drier 4 filled with a desiccant to remove the moisture, thereby purifying the hydrogen bromide gas. The hydrogen bromide gas thus purified is introduced into a product cylinder 5. Subsequently the hydrogen bromide gas is cooled by a refrigerant 6 which is a mixture of dry ice and ethyl alcohol, condensed, and stored in the product cylinder 5.
However, in the method for purifying hydrogen bromide mentioned above, the molecular sieves gradually deteriorates with the passage of operation time of the apparatus. So does the purity of the product. To maintain the purity of a product at a predetermined level, molecular sieves must be replaced frequently. Hence, the aforementioned purifying method is not suitable for preparing high purity hydrogen bromide in a large amount.
DISCLOSURE OF INVENTION
The present invention is intended to provide a method and apparatus capable of preparing high purity hydrogen bromide continuously in a large amount.
A method for preparing high purity hydrogen bromide according to the present invention comprises the steps of:
providing a rectifying column composed of
a lower space,
a lower rectifying section,
an intermediate space,
an upper rectifying section, and
an upper space,
supplying a raw material consisting of hydrogen bromide and impurities having boiling points lower than that of hydrogen bromide, into the intermediate space;
allowing a gas phase of the supplied raw material to ascend through the upper rectifying section while the gas phase is brought into contact with a first reflux solution flowing down from the top, leading the gas-phase to the upper space, and storing an uncondensed gas in the upper space;
cooling the uncondensed gas stored in the upper space, thereby condensing part of the uncondensed gas;
allowing the liquid thus condensed to serve as the first reflux solution and to flow down through the upper rectifying section to the intermediate space;
mixing the liquid phase of the supplied raw material with the fist reflux solution in the intermediate spacer thereby making a second reflux solution, and allowing the second reflux solution to flow down through the lower rectifying section to the lower space and then storing a liquid in the lower space;
heating the liquid stored in the lower space to evaporate part of the liquid and allowing the gas generated to contact with the second reflux solution which flows down from the top while ascending through the lower rectifying section; and
discharging the liquid stored in the lower space outside in the form of high-purity hydrogen bromide, simultaneously discharging the uncondensed gas stored in the upper space outside.
A temperature of cooling the uncondensed gas in the upper space is preferred to fall within the range of -30.degree. C. to -50.degree. C. On the other hand, a temperature of heating the solution stored in the lower space is preferred to fall within the range of -15.degree. C. to -20.degree. C.
The apparatus for preparing high purity hydrogen bromide, employed in the
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Nagamura Takashi
Tomita Shinji
Kilner Christopher
Teisan Kabushiki Kaisha
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