Gas separation: processes – Selective diffusion of gases – Selective diffusion of gases through substantially solid...
Reexamination Certificate
1999-11-09
2001-09-25
Spitzer, Robert H. (Department: 1724)
Gas separation: processes
Selective diffusion of gases
Selective diffusion of gases through substantially solid...
C095S138000, C096S004000, C096S009000, C096S136000
Reexamination Certificate
active
06293997
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a method for delivering at least two working gases, having different limiting O
2
contents, from a common air supply.
Many industrial processes require the use of N
2
/O
2
working atmospheres having different limiting O
2
contents. Such processes are sometimes employed on the same industrial site.
This is the case, for example, in the electronics industry in which the reflow-soldering and wave-soldering processes for assembling electronic components make use of N
2
/O
2
atmospheres typically having limiting O
2
contents of respectively a few % in one case and a few thousand ppm in the second case.
Depending on the limiting O
2
content to be obtained, several means for depleting the air from the supply in O
2
may be used: cryogenic distillation, adsorption of oxygen on a catalytic bed, combination of oxygen with another gas, or selected permeation through a membrane.
In general, in order to deliver N
2
/O
2
working atmospheres of different limiting O
2
contents for the implementation of industrial processes on the same site, either separate delivery means are used, thus multiplying the working-gas delivery devices, or a single atmosphere feed is used for all the processes, thus resulting in superfluous depletion in O
2
for some of the processes. Such solutions are not optimal.
The object of the invention is to remedy the abovementioned problem and, in particular, to provide an economic method for delivering working gases having different limiting O
2
contents from a common air supply.
For this purpose, the subject of the invention is a method for delivering at least two working gases from a common air supply, the limiting O
2
contents, respectively t
1
and t
2
, of which gases are such that t
1
is greater than t
2
, characterized in that:
the air is depleted in O
2
in order to obtain a first gas mixture having an O
2
content less than or equal to t
1
;
a portion of this first gas mixture is used to deliver the first working gas;
another portion of this first gas mixture is depleted in O
2
in order to obtain a second gas mixture having an O
2
content less than or equal to t
2
; and
this second gas mixture is used to deliver the second working gas.
Depending on the particular embodiments, the method may include one or more of the following characteristics:
said first and second gas mixtures are the working gases directly;
at least one oxygen-containing product resulting from one of said depletions in O
2
is recovered for the purpose of using this oxygen-containing product;
the oxygen-containing product is superoxygenated air coming from the first depletion in O
2
;
t
1
is greater than or equal to 0.5% (and preferably between 0.5% and 10%) and t
2
is less than or equal to 1% (and preferably between 100 ppm and 5000 ppm).
The subject of the invention is also a device for delivering at least two working gases, having different limiting O
2
contents, from a common air supply, characterized in that it comprises:
first means of depletion in O
2
;
second means of depletion in O
2
;
means connecting an inlet of the first means of depletion in O
2
to the air supply;
means connecting an inlet of the second means of depletion in O
2
to an outlet of the first means of depletion;
means for producing the first working gas, these being connected to an outlet of the first means of depletion; and
means for producing the second working gas, these being connected to an outlet of the second means of depletion.
Depending on particular embodiments, the device may include one or more of the following characteristics:
the means for producing the working gases are means for tapping off the gas mixtures directly to the outlet of the means of depletion;
means of depletion in O
2
have an outlet for oxygen-containing product, and the device comprises means connecting this outlet to a unit for consuming this oxygen-containing product;
the oxygen-containing product is superoxygenated air coming from the first means of depletion;
the first and/or second means of depletion in O
2
are means of depletion in O
2
by combination of the O
2
with another gas or by adsorption of the O
2
on a catalytic bed or else by selective permeation through a membrane.
Finally, the subject of the invention is a plant for the assembly of electronic components, comprising a chamber for storing electronic components in a controlled atmosphere, the limiting O
2
content of the atmosphere in this chamber being t
1
, and at least one machine for assembling the components in a controlled atmosphere, the limiting O
2
content of the atmosphere in this machine being t
2
<t
1
, the plant being characterized in that it comprises a device for delivering working gases, which feeds said chamber with said first gas mixture and said assembly machine with said second gas mixture.
The invention will be better understood on reading the description which follows, given solely by way of example, and with reference to the appended figures.
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Bonet Claude
Sindzingre Thierry
Verbockhaven Denis
Burns Doane Swecker & Mathis L.L.P.
L'Air liquide, Societe Anonyme pour l'Etude et l'
Spitzer Robert H.
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