Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – Including specific material of construction
Reexamination Certificate
1998-09-15
2002-06-11
Johnson, Jerry D. (Department: 1764)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
Including specific material of construction
C422S239000, C422S312000, C095S054000
Reexamination Certificate
active
06403041
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a membrane-type reaction vessel which facilitates oxygen reactions using an oxygen-permeable membrane that allows oxygen, from oxygen-containing gas, to pass therethrough selectively.
BACKGROUND OF THE INVENTION
An oxygen-permeable membrane is a semipermeable membrane which allows oxygen to pass therethrough selectively depending upon the partial pressure of oxygen on opposite sides of the membrane. The membrane typically consists of a solid electrolyte that conducts oxygen ions, and examples of such materials include yttrium-stabilized zirconia (YSZ), calcia-stabilized zirconia, and bismuth oxide.
It is also possible to create an oxygen-permeable membrane with a mixed conductor which conducts both oxygen ions and electrons, instead of a solid electrolyte which conducts ions only. For example, YSZ containing titanium and compounds with a Perovskite structure, such as La—Sr—Co—O, La—Sr—Co—Fe—O and Sr—Co—O, are known.
The use of such oxygen-permeable membranes for oxygen isolation equipment or chemical reaction equipment has become popular recently. For example, U.S. Pat. No. 5,306,411 discloses an electrochemical reactor including a solid membrane made of mixed metal oxides having a Perovskite structure (i.e., a mixed conductor). The solid membrane is used as an electrochemical transportation mechanism for moving oxygen from an oxygen-containing gas to a source gas, to remove oxygen from oxygen-containing compounds, to allow for aromatic compound substitution, and/or to allow for partial oxidation reactions of methane and ethane.
Japanese Patent Application No. JP-A-7-138191 also discloses a membrane reactor which facilitates an oxidative coupling reaction of methane, by using Perovskite-structured oxides such as Sr—Co—Li—O and Sr—Co—Mg—O as membrane compounds.
The reaction vessels described above provide superior selectivity of reaction in comparison to vapor phase reaction vessels, which were commonly used to facilitate such reactions. There are, however, problems that need to be solved so as to allow safe operation of such vessels.
FIGS. 2A and 2B
show one example of a reaction vessel known in the prior art. The reaction vessel
21
includes a vessel wall
22
defining an oxygen-containing gas chamber
28
and a source gas chamber
29
. These two chambers are separated hermetically by an oxygen-permeable membrane
23
. Oxygen-containing gas inlet
24
and outlet
25
allow gas to flow through chamber
28
. Source gas inlet
26
and outlet
27
allow gas to flow through chamber
29
.
There is a concern that, in the case of damage (e.g., cracking) to the oxygen-permeable membrane
23
, a large volume of oxygen-containing gas, which is confined in oxygen-containing gas chamber
28
only by oxygen-permeable membrane
23
, will flow into source gas chamber
29
, or conversely, that a large volume of source gas will flow into oxygen-containing gas chamber
28
. In such cases of large gas volume, there is a danger that the two gases mixed together will react rapidly and result in explosion.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a reaction vessel that is safer to operate and has a lower possibility of explosion even in the event of cracking of or damage to the oxygen-permeable membrane.
In accordance with one embodiment of the present invention, the membrane-type reaction vessel is divided into an oxygen-gas containing chamber and a source gas chamber via an oxygen-permeable membrane which is selectively permeable to oxygen. The vessel is designed so as to allow oxygen from the oxygen-containing gas to pass through the oxygen-permeable membrane to contact and react with source gas in the source gas chamber. The volume ratio between the source gas chamber and the oxygen-containing gas chamber is designed to be outside the range within which the two gases, if combined directly, would result in explosion. Preferably, the volume ratio between the two gas chambers is also designed to be outside the range within which an explosion would result from directly combining the oxygen-containing gas and reaction products resulting from the reaction between oxygen that has already permeated through the oxygen-permeable membrane and the source gas.
In a more preferred embodiment of the present invention, the volume ratio of the oxygen-containing gas chamber with respect to the total volume (V
T
) of the reaction vessel (i.e., the volume (V
O
) of the oxygen-containing gas chamber and the volume (V
S
) of the source gas chamber) should be less than 50%, more preferably less than 30%, and most preferably less than 10%.
In accordance with another preferred embodiment of the present invention, a filler is disposed in the oxygen-containing gas chamber and/or the source gas chamber to adjust the volume of those chambers relative to each other. The filler preferably is one of a metal, ceramic or glass, all of which are inert with respect to the oxygen-containing gas, the source gas and reaction products resulting from reactions between oxygen supplied from the oxygen-containing gas and the source gas.
REFERENCES:
patent: 1685759 (1928-09-01), Walter
patent: 5306411 (1994-04-01), Mazanec et al.
patent: 5573737 (1996-11-01), Balachandran et al.
patent: 5599383 (1997-02-01), Dyer et al.
patent: 5846641 (1998-12-01), Abeles et al.
patent: 5935533 (1999-08-01), Kleefisch et al.
patent: 5972079 (1999-10-01), Foley et al.
patent: 5980840 (1999-11-01), Kleefisch et al.
Takahashi Tomonori
Yoshida Manabu
Burr & Brown
Johnson Jerry D.
NGK Insulators Ltd.
Varcoe Frederick
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