Process for the gaseous phase production of metal oxide particles

Claim 2

In a process for the production of finely-divided metal oxides which comprises oxidizing the corresponding metal halide with an oxidizing gas by introducing into one end of a reaction zone a hot stream of primary gas selected from an inert gas, the oxidizing gas or the metal halide, introducing a secondary gas selected from the oxidizing gas, the metal halide or mixtures thereof into the primary gas stream through an injection device surrounding at least part of the reaction zone, said injection device comprising a wall having a plurality of separate apertures therethrough, each aperture having an inlet end and an outlet end and each aperture connecting the reaction zone to a secondary gas jacket, said wall dividing said reaction zone from said jacket, the inlet end of said aperture being at the interface of said wall and said reaction zone, the secondary gas being supplied to the reaction zone through said jacket in such a manner that it cools the wall of the injection device and is thereby preheated before it passes through the apertures into the primary gas stream, the improvement comprising forming said apertures with at least two segments of different cross-sectional areas along their length, the segment of smaller cross-sectional area being at the inlet end of the apertures for the secondary gas, and the segment of larger cross-sectional area being at the outlet end of said apertures, said segment of larger cross-sectional area being of sufficient cross-section and extending for a sufficient length of said apertures to preclude substantial accretion of metal oxide around the edge of the aperture.

Claim 3

A process as claimed in claim 1 wherein the length of that segment of the aperture which is of larger cross-section is at least 1.5 times the diameter of said segment of larger cross-section.

Claim 4

A process as claimed in claim 2 wherein the apertures have a smaller cross-sectional area with a diameter in the range 0.01 inches to 0.20 inches.

Claim 5

A process as claimed in claim 2 wherein the apertures are circular orifices having a smaller diameter in the range 0.01 inches to 0.20 inches and a larger diameter in the range 0.05 inches to 0.50 inches.

Claim 6

A process as claimed in claim 2 wherein said smaller cross-sectional area portion of said apertures is of sufficient diameter to provide a pressure drop across that part of the aperture of from 0.1 to 10 p.s.i., said smaller cross-sectional area portion extending from 10% to 50% of the length of the aperture.

Claim 7

A process as claimed in claim 1 wherein the apertures have a smaller cross-sectional area with a diameter in the range 0.01 inches to 0.20 inches.

Claim 8

A process as claimed in claim 6 wherein the diameter of said smaller cross-sectional areas of said apertures is in the range 0.02 inches to 0.10 inches.

Claim 9

A process as claimed in claim 1 wherein the pressure drop across the smaller cross-sectional area of the aperture is from 0.1 to 10 p.s.i.g.

Claim 10

A process as claimed in claim 8 wherein said pressure drop is in the range 0.5 to 5 p.s.i.g.

Claim 11

A process as claimed in claim 1 wherein the smaller cross-sectional area segment of the aperture extends for from 10% to 50% of the length of the aperture.

Claim 12

A process as claimed in claim 1 wherein the diameter of the aperture increases to one in the range 0.05 inches to 0.50 inches.

Claim 13

A process as claimed in claim 1 wherein the diameter of the aperture increases to one in the range 0.10 inches to 0.30 inches.

Claim 14

A process as claimed in claim 1 wherein the cross-sectional area between the inlet and outlet ends of each aperture continually increases from the smaller cross-sectional area of the inlet end of the aperture.

Claim 15

A process as claimed in claim 1 wherein the wall of the injection device is made of aluminum, nickel, alloys thereof or of stainless steel.

Claim 16

A process as claimed in claim 1 wherein the primary gas is oxygen and oxygen and metal halide comprise the secondary gas or gases.

Claim 17

A process as claimed in claim 1 wherein the primary gas is heated by passage through an electric arc.

Claim 18

In a process for the production of finely-divided metal oxides which comprises oxidizing the corresponding metal halide with an oxidizing gas by introducing into one end of a reaction zone a hot stream of primary gas selected from an inert gas, the oxidizing gas or the metal halide, introducing a secondary gas selected from the oxidizing gas, the metal halide or mixtures thereof into the primary gas stream through an injection device surrounding at least part of the reaction zone, said injection device comprising a wall having a plurality of separate apertures therethrough, each aperture having an inlet end and an outlet end and each aperture connecting the reaction zone to a secondary gas jacket, said wall dividing said reaction zone from said jacket, the inlet end of said aperture being at the interface of said wall and said reaction zone, the secondary gas being supplied to the reaction zone through said jacket in such a manner that it cools the wall of the injection device and is thereby preheated before it passes through the apertures into the primary gas stream, the improvement comprising forming said apertures with at least two segments of different cross-sectional areas along their length, the segment of smaller cross-sectional area being at the inlet end of the apertures for the secondary gas, and the segment of larger cross-sectional area being at the outlet end of said apertures, said segment of larger cross-sectional area being of sufficient cross-section and extending for a sufficient length of said apertures to preclude substantial accretion of metal oxide around the edge of the aperture, the length of said segment of larger cross-section being at least three times the diameter of said segment of larger cross-section.

Claim 19

In a process for the production of finely-divided metal oxides which comprises oxidizing the corresponding metal halide with an oxidizing gas by introducing into one end of a reaction zone a hot stream of primary gas selected from an inert gas, the oxidizing gas or the metal halide, introducing a secondary gas selected from the oxidizing gas, the metal halide or mixtures thereof into the primary gas stream through an injection device surrounding at least part of the reaction zone, said injection device comprising a wall having a plurality of separate apertures therethrough, each aperture having an inlet end and an outlet end and each aperture connecting the reaction zone to a secondary gas jacket, said wall dividing said reaction zone from said jacket, the inlet end of said aperture being at the interface of said wall and said reaction zone, the secondary gas being supplied to the reaction zone through said jacket in such a manner that it cools the wall of the injection device and is thereby preheated before it passes through the apertures into the primary gas stream, the improvement comprising forming said apertures with at least two segments of different cross-sectional areas along their length, the segment of smaller cross-sectional area being at the inlet end of the apertures for the secondary gas, and the segment of larger cross-sectional area being at the outlet end of said apertures, said segment of larger cross-sectional area being of sufficient cross-section and extending for a sufficient length of said apertures to preclude substantial accretion of metal oxide around the edge of the aperture, the length of said segment of larger cross-section being at least three times the diameter of said segment of larger cross-section.