Titanium bearing material flow control in the manufacture of titanium tetrachloride using a combination of feedback and feed forward responses

1. A process for controlling chlorination reactions in manufacturing titanium tetrachloride in a fluidized bed reactor, optionally followed by processing to form a titanium product comprising a minor amount of silica, the process comprising:

(a) feeding carbonaceous material, titanium bearing material comprising an amount of silica, and chlorine to the fluidized bed reactor to form a gaseous stream, and condensing the gaseous stream to form titanium tetrachloride, a non-condensed gas stream and a condensable product stream, wherein at least one of the titanium tetrachloride and the non-condensed gas stream comprise silicon tetrachloride;

(b) analyzing the non-condensed gas stream, the titanium tetrachloride or both, to determine the analyzed concentration of silicon tetrachloride;

(c) identifying a set point concentration of silicon tetrachloride based on the desired amount of silica in the titanium product;

(d) calculating the difference between the analyzed concentration of silicon tetrachloride and the set point concentration of silicon tetrachloride;

(e) measuring the titanium tetrachloride flow to a processing reactor that releases chlorine;

(f) measuring the flow of fresh chlorine added to the fluidized bed;

(g) measuring the flow of the titanium bearing material added to the fluidized bed reactor and establishing a historic average flow of the titanium bearing material added to the fluidized bed reactor;

(h) calculating the chlorine released from the titanium tetrachloride that is processed using the titanium tetrachloride flow data from step (e);

(i) calculating the total chlorine flow to the fluidized bed reactor by adding the chlorine flow in step (f) to the chlorine flow calculated in step (h) and establishing a historic average chlorine flow;

(j) calculating a unit titanium bearing material consumption per unit chlorine;

(k) calculating an estimated current consumption rate of titanium bearing material based on the total chlorine flow from step (i) times the unit titanium bearing material consumption per unit chlorine from step (j); and

(l) generating a signal based on difference generated in step (d) that provides a feedback response and combining this to the estimated current consumption rate of titanium bearing material from step (k) to provide a feed forward response to control the flow of the titanium bearing material into the fluidized bed reactor.

2. The process of claim 1 wherein the analyzed concentration of silicon tetrachloride is greater than the set point concentration of silicon tetrachloride.

3. The process of claim 1 wherein the analyzed concentration of silicon tetrachloride is less than the set point concentration of silicon tetrachloride.

4. The process of claim 2 wherein the analyzed concentration of silicon tetrachloride is greater than the set point concentration of silicon tetrachloride and the feedback response comprises increasing the amount of titanium bearing material being introduced into the fluidized bed reactor.

5. The process of claim 3 wherein the analyzed concentration of silicon tetrachloride is less than the set point concentration of silicon tetrachloride and the feedback response comprises decreasing the amount of titanium bearing material being introduced into the fluidized bed reactor.

6. The process of claim 1 wherein the analyzed concentration of silicon tetrachloride is determined by analyzing the non-condensed gas stream.

7. The process of claim 1 wherein the analyzed concentration of silicon tetrachloride is determined by analyzing the titanium tetrachloride.

8. The process of claim 1 wherein analyzing the non-condensed gas stream is achieved by spectroscopy, spectrometry or chromatography.

9. The process of claim 8 wherein analyzing the non-condensed gas stream is

by infrared spectroscopy.

10. The process of claim 1 wherein the silicon tetrachloride is present in the non-condensed gas stream in the amount of about 0 to about 0.3 mole %, based on the total weight of the analyzed stream.

11. The process of claim 10 wherein the silicon tetrachloride is present in the non-condensed gas stream in the amount of about 0.01 to about 0.1 mole %, based on the total weight of the analyzed stream.

12. The process of claim 11 wherein the silicon tetrachloride is present in the non-condensed gas stream in the amount of about 0.01 to about 0.05 mole %, based on the total weight of the analyzed stream.

13. The process of claim 1 wherein the set point of silicon tetrachloride is about 0.01 to about 0.25 mole %.

14. The process of claim 1 wherein the signal is electrical, pneumatic, digital or manual.

15. The process of claim 1 wherein the feedback response is provided by a feedback controller selected from the group consisting of a proportional, a proportional integral action controller, a proportional integral derivative action controller; or suitable computer software or algorithm that provides a feedback response to a control device.

16. The process of claim 1 wherein the processing reactor is an oxidation reactor and the titanium tetrachloride is oxidized to a titanium product comprising titanium dioxide.

17. The process of claim 1 wherein the feed forward response is provided by a feed forward controller selected from the group consisting of a proportional action controller, a proportional integral action controller, a proportional integral derivative action controller; or suitable computer software or algorithm that provides a feed forward response to a control device.