Application of Avery
| Decision Date | 26 June 1975 |
| Docket Number | Patent Appeal No. 74-625. |
| Parties | Application of Julian Miles AVERY. |
| Court | U.S. Court of Customs and Patent Appeals (CCPA) |
Douglas E. Whitney, William H. Sudell, Jr., Wilmington, Del. (Morris, Nichols, Arsht & Tunnell, Wilmington, Del.) attorneys of record, for appellant.
Joseph F. Nakamura, Washington, D. C., for the Commissioner of Patents, Gerald H. Bjorge, Washington, D. C., of counsel.
This is an appeal from the decision of the Patent and Trademark Office Board of Appeals affirming the examiner's rejection of claims 1-23, all of the claims in application serial No. 26,118, filed April 6, 1970, for the "Metallothermic Production of Magnesium in the Presence of a Substantially Static Atmosphere of Inert Gas." We affirm.
The subject matter of the claims is a method of controlling the level of impurities in magnesium produced by the reduction of magnesium oxide:
2 MgO + Si > 2 Mg ( ? ) + SiO2
Magnesium oxide and a metallic reducing agent such as silicon react in the presence of a molten slag bath, and magnesium vapor is evolved. The magnesium vapor is evolved in a reaction zone and moves predominately by diffusion through a substantially static atmosphere of inert gas to a condensation zone.
By a "substantially static" atmosphere of an inert gas and the passage of magnesium vapor "predominately by diffusion" it is meant that the movement of the magnesium vapor is faster than the movement, if any, of the inert gas from the reaction zone to the condensation zone. That is, the magnesium vapor passes through the inert gas, rather than the other way around.
In view of the reaction set forth above, a low concentration of magnesium vapor in the reaction zone might be thought to be desirable to increase the driving force of the reaction. Indeed, prior processes transfer magnesium vapor from a reaction zone to a condensation zone essentially by vacuum distillation. However, appellant has found that the magnesium vapor pressure in the reaction zone can be increased without substantially decreasing the reduction reaction. In appellant's method, the magnesium vapor pressure immediately above the slag in the reaction zone is at least about 0.05 atmospheres, and preferably as high as possible, up to about 1.5 atmospheres. The total pressure of the system, including the vapor pressure of both magnesium vapor and inert gas, is at least 0.1 atmospheres and preferably about 0.25 to 1.5 atmospheres.
Reducing magnesium oxide ores under these conditions has been found to significantly increase the purity of the magnesium product obtained. Prior vacuum distillation processes, for example, are accompanied by substantial agitation of the molten slag bath in the reaction zone. As a result of this agitation and the high vacuum conditions above the molten slag bath, small particles of contaminants are carried from the bath to the condensation zone, with a consequent contamination of the magnesium product. The relatively high pressures used in the present invention inhibit the movement of these small particles of contaminants, resulting in a purer magnesium product.
The patents relied upon by the board are:
Parry 2,497,096 Feb. 14, 1950
Bretschneider et al. 3,017,263 Jan. 16, 1962
Peplinski 3,312,456 Apr. 4, 1967
Magee et al. 3,441,402 Apr. 29, 1969
(filed Dec. 15, 1965)
Avery 3,658,509 Apr. 25, 1972
(filed Feb. 3, 1969)
Parry discloses a process for continuously carrying out a reaction between solid material and a gas or vapor which uses external heating efficiently. A counter-current heat exchanger is described in which reactants fall downwardly through an externally heated, vertically arranged, elongated annular reaction zone. Gaseous products removed from the reaction zone are passed upwardly in indirect heat exchange relation to the falling reactants. The process is applied to the reduction of magnesium ores in high vacuum. Optionally in the reduction of magnesium ores in high vacuum, the reaction zone may be filled with a suitable inert gas, for example, hydrogen, helium or argon. The partial pressure of magnesium vapor in the reaction zone may be lowered to take account of the partial pressure of the inert gas so as to approximate the usual high vacuum conditions.
Magee et al. disclose a process for the continuous production of magnesium metal. A mixture of magnesium ores is heated with a reducing agent in an electric arc furnace. The furnace is operated at one atmosphere pressure. Magnesium vapor is withdrawn from the furnace and condensed to obtain liquid magnesium. Operation of the furnace at atmospheric pressure is said to be desirable for the continuous production of magnesium because feeding and discharging operations are simplified and stress on materials of construction is minimized.
Bretschneider et al. and Peplinski both disclose purified magnesium metal. Bretschneider et al. for example disclose magnesium metal having the following composition: 99.93% magnesium, 0.02% silicon, 0.03% manganese, 0.01% calcium and 0.001% iron (calculated in percent by weight).
Avery, which issued to appellant on an application of which the instant application is a continuation-in-part, discloses a method of producing magnesium by the reduction of magnesium oxide by means of a metallic reducing agent, in the presence of a molten oxidic slag, wherein the system contains an inert gas. Claims 1, 2, and 4 through 7 of Avery read as follows:
The examiner rejected claims 1 through 23 on the ground of double patenting over claims 1, 2, and 4 through 7 of the Avery patent. It appears the examiner intended an obviousness-type double patenting rejection. The board first considered whether the claims herein were for the same invention that is claimed in the Avery patent. The board did not enter a new ground of rejection under 35 U.S.C. § 101; see In re Boylan, 392 F.2d 1017, 55 CCPA 1041 (1968). The board then stated:
We are therefore in complete agreement with the rejection grounded on...
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