Reactor for the generation of water

Details Reactor for the generation of water Reactor for the generation of water

1998-09-25

2001-01-30

Beck, Shrive (Department: 1764)

Chemical apparatus and process disinfecting, deodorizing, preser

Chemical reactor

Including heat exchanger for reaction chamber or reactants...

C422S186220, C422S198000, C422S211000, C422S236000

Reexamination Certificate

active

06180067

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an improvement of a reactor for generation of moisture (i.e., water) intended chiefly for use in semi-conductor manufacturing facilities.
BACKGROUND OF THE INVENTION
In the silicon oxide film coating step by moisture oxidation process in the semi-conductor production, for example, super high-purity water vapor is required at the rate of some 1,000 cubic centimeters/minute (sccm).
Earlier, the inventors developed a reactor for generation of water which was suitable for such a purpose, the construction of which is shown in FIG.
13
. It should be understood that this reactor will be referred to as prior art reactor throughout the present specification.
As shown in
FIG. 13
, the prior art reactor includes a reactor shell
21
comprising bottomed cylindrical first and second reactor structural components
22
and
23
put together, the first reactor structural component
22
provided with a gas feed passage
24
a
on the outside surface thereof and an inlet reflector unit
29
a
on the inside surface thereof, and the second reactor structural component
23
provided with a (water vapor) outlet passage
25
a
on the outside surface thereof and an outlet reflector unit
29
b
on the inside surface thereof, with a diffusion filter
30
provided on the borderline between the two reactor structural components
22
and
23
and with a platinum coated catalyst layer provided over the inside surface of the second reactor structural component
23
.
In the prior art reactor, a starting material gas comprising a mixture of hydrogen and oxygen is led into the reactor shell through the gas feed passage
24
a
is diffused by a gas diffusion means comprising the inlet reflector
29
a
, the diffusion filter
30
and the outlet reflector
29
b
and brought into contact with the platinum coated catalyst layer
32
. Coming in contact with the platinum coated catalyst layer
32
, oxygen and hydrogen are enhanced in reactivity by the catalytic action of platinum and turned into what is called the radicalized state. The radicalized hydrogen and oxygen instantaneously react at a temperature much lower than the ignition temperature of the hydrogen-mixed gas under formation of water without undergoing combustion at a high temperature.
FIG. 14
shows the change with time in moisture-producing reactivity found in an experiment with the prior art reactor operated under the following conditions: moisture production, 1,000 sccm; and reactor temperature (temperature inside the reactor shell
21
), about 400° C. The volume of the space provided with the platinum coated catalyst layer
32
(volume inside the second reactor structural component) was about 490 cc. As is evident from
FIG. 14
, the prior art reactor can produce water vapor at a moisture-producing reactivity efficiency of some 98.5 to 99.9 percent not only where the mixing ratio of the starting material gas between oxygen and hydrogen is optimized (with no excess of either of the two material constituent gases) but also where the mixed gas contains more oxygen or hydrogen than the other.
Thus, the prior art reactor can produce more than 1,000 sccm of water vapor (high-purity water vapor or mixture of high-purity water vapor and oxygen) with a high degree of reactivity and responsiveness and is suitable for use in the semi-conductor manufacturing technological field. The reactor also allows size reduction of the moisture-producing facilities.
However, it has been found that the prior art reactor still leaves something to be improved. That is, the prior art can not raise the moisture-producing reactivity efficiency over 99.0 percent when the temperature of the reactor shell
21
is less than some 400° C. with the moisture production not lower than 1,000 scm. And it is feared that some one percent of unreacted oxygen or hydrogen will be mixed in the moisture produced. That makes it difficult for the reactor to reliably turn out pure water without hydrogen or oxygen mixed or a mixture of pure water and oxygen without hydrogen mixed.
Meanwhile, there are two probable causes of unreacted hydrogen or oxygen reaching the water vapor outlet passage
25
a
in the prior art reactor: (a) Oxygen or hydrogen flows direct into the water vapor outlet passage
25
a
without coming in contact with the platinum coated catalyst layer
32
. (b) Hydrogen or oxygen is radicalized but proceeds unreacted with oxygen or hydrogen straight to the water vapor outlet passage
25
a
where the radicalized hydrogen or oxygen is unradicalized back to the original state. Of the two probable causes, it was thought that the first one was overwhelmingly greater according to various experiments conducted by the inventors and their experiences. So, the inventors carried out a moisture-producing experiment to study the moisture-generating reactivity efficiency using the prior art reactor with the outlet reflector unit
29
b
removed. As shown in
FIG. 15
, the moisture-producing reactivity efficiency stood at about 91 percent when the temperature of the reactor shell
21
was 400° C. with the moisture production at 500 sccm with the mixed material gas with an optimized mixing ratio. While the test results were not obtained under exactly the same conditions for those shown in
FIG. 14
because the moisture production was different, it is noted that the moisture-producing reactivity efficiency is some 7 percent lower than that shown in FIG.
14
. This difference indicates that, without the reflector unit
29
b
on the outlet side, a substantial amount of oxygen or hydrogen arrives unradicalized at the moisture gas outlet passage
25
a
and that an improvement of the reflector unit
29
b
on the outlet reflector unit
29
b
could increase the moisture-producing reactivity efficiency. Also, as
FIG. 15
suggests, if the reflector unit
29
b
is absent on the outlet side, the moisture-producing reactivity efficiency goes down as the percentage of hydrogen in the material gas increases. When the temperature of the reactor shell is 400° C. with the moisture production at 500 sccm, for example, the moisture-producing reactivity efficiency is some 86 percent with the starting material gas with the hydrogen content being 100 percent larger than the balanced level and some 97 percent with the material gas with the oxygen content being 100 percent larger. The difference in efficiency between the two mixing ratios is some 11 percent.
That is, it is surmised that oxygen diffuses with relative ease and tends not to move in a straight line, while hydrogen is rather difficult to diffuse and tends to flow linearly inside the reactor shell
21
of the construction as shown in FIG.
13
. With hydrogen-rich starting material gas, therefore, it is considered that the tendency for hydrogen to flow linearly is so strong that oxygen is swept along with the hydrogen and reaches the water vapor outlet passage
25
a
unradicalized to a great extent.
Based on that theory, the inventors concluded that if the outlet reflector unit
29
b
in the reactor shell
21
was so improved as to enhance the diffusion of especially hydrogen, still a higher yield than the moisture producing reactivity efficiency or reaction rate of some 98 to 99 percent shown in
FIG. 14
could be achieved not only with oxygen-rich starting material gas but also with hydrogen-rich starting material gas.
The present invention was built on that theory.
SUMMARY OF THE INVENTION
It is an object of the present to provide a reactor for generation of moisture which can further raise the reaction rate of hydrogen and oxygen in the reaction shell of the same construction as that of the prior art reactor without causing the temperature to rise in the reactor shell that can achieve a reaction rate of more than 99 percent under the conditions that the temperature of the reactor shell is less than some 400° C. with the moisture production at more than 1,000 sccm.
The object of the present invention is attained by providing either of the following two types of reactor for generation of moisture. The first t

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