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Purification of inert gases to remove trace impurities

a technology of inert gas and impurity removal, which is applied in the direction of cold treatment separation, liquefaction, lighting and heating apparatus, etc., can solve the problems of inability to remove impurities below the level of part per million (ppm) and current systems that do not address methane slippag

Inactive Publication Date: 2014-06-19
LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a method for purifying inert gases, specifically argon, using cryogenic distillation separation. The method includes pretreating an argon waste stream to remove impurities, cooling the waste stream with a cryogenic heat exchanger, and separating the cooled waste stream in a cryogenic distillation column. The purified argon stream is then combined with a cooled bottoms argon product stream and an argon lift stream, and the combined stream is vaporized in an overhead condenser to create a purified vapor phase argon stream. The purified stream is then used to cool the pre-treated argon waste stream. The gas waste stream is removed from the column. The method can also include feeding the gas waste stream to a cryogenic heat exchanger to cool the pre-treated argon waste stream, and using a sorbent bed system to further remove impurities from the bottoms argon product stream. The technical effect of the invention is to provide a simple and efficient method for purifying argon gas to high purity levels.

Problems solved by technology

Purity of the argon stream is critical because it affects the both the purity and the quality of the silicon ingot grown in the Czochralski Process.
However, current systems do not address methane slippage and are incapable of removing impurities below part per million (ppm) levels.

Method used

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  • Purification of inert gases to remove trace impurities
  • Purification of inert gases to remove trace impurities
  • Purification of inert gases to remove trace impurities

Examples

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example 1

[0033]The present invention is further demonstrated by the following illustrative embodiment, which does not limit the claims of the present invention.

[0034]Table 1 provides data for a representative process, utilizing the embodiment illustrated in FIG. 1. The manufacturing process pre-treated argon gas waste stream is provided from a monocrystalline silicon production process. A molar gas flowrate of 500 m3 / h was chosen for simulation purposes. The process conditions of pre-treated argon waste stream 2 are based on the outlet of a pre-treatment process, which typically takes place at an ambient temperature, but with a compressed gas stream, thus for simulation purposes an inlet temperature of 20° C. and 147 psig were chosen. Finally, the composition of pre-treated argon waste stream 2 assumes some CH4 leakage and impurities of CO and O2 on the part per million scale.

TABLE 1Representative DataStream Name21232225224142616Vapor Fraction11000.03031111Temperature (C.)20−153.6−156.9−159−...

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Abstract

A method for purifying an argon stream is provided. The method includes pretreating an argon waste stream to remove impurities to provide a pre-treated argon waste stream having argon, nitrogen, and hydrogen; cooling the argon waste stream to create a cold feed stream; and condensing the cold feed stream to create a liquid feed stream. The liquid feed stream is fed to the cryogenic distillation column to create a bottoms argon product stream and a gas waste stream. The bottoms argon product stream travels to an expansion device to provide a cooled bottoms argon product stream, which can optionally be combined with an argon lift stream downstream of the expansion device. The combined argon lift stream and cooled bottoms argon product stream are fed to the overhead condenser and vaporized to create a purified vapor phase argon stream.

Description

TECHNICAL FIELD OF INVENTION[0001]The present invention relates to a method for the purification of inert gases. More specifically, the present disclosure relates to a method for the onsite removal of trace impurities, such as nitrogen and methane, from an argon stream using cryogenic distillation separation.BACKGROUND OF THE INVENTION[0002]The use of argon as an inert gas is important to a number of industries including the production of monocrystalline and polycrystalline silicon, steel making (e.g., using the hot isotatic pressing (HIP) process to make steel, aluminum and nonmetallic castings from powders), heat treating, and semiconductor, wafer, and electronics manufacturing. Given the rising costs of argon gas, onsite purification of waste argon streams to recycle back to the manufacturing process is increasingly common.[0003]One manufacturing process suitable for argon purification and recycle is the production of monocrystalline silicon using the Czochralski Process. High pu...

Claims

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Application Information

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IPC IPC(8): F25J3/02
CPCF25J3/0204F25J3/08F25J2200/02F25J2200/04F25J2200/40F25J2200/50F25J2200/72F25J2205/40F25J2205/60F25J2210/58F25J2220/04F25J2235/06F25J2235/58F25J2270/58F25J2270/904C01B23/0094C01B2210/0004C01B2210/0009C01B2210/0015C01B2210/0034C01B2210/0045C01B2210/0046C01B2210/005C01B2210/0051C01B2210/0053C01B2210/0062C01B2210/007F25J2215/58F25J3/0285
Inventor HA, BAOGARY, DANIELSHANBHAG, PURUSHOTTAM V.
Owner LAIR LIQUIDE SA POUR LETUDE & LEXPLOITATION DES PROCEDES GEORGES CLAUDE