System and method for cleaning in-process sensors

1. A cleaning system for an in-process sensor comprising:

(a) a reaction vessel having an interior region and having a process fluid located therein;

(b) a sensor having a surface, wherein the surface of the sensor is positioned on the interior region of the reaction vessel such that the surface of the sensor is capable of contacting the process fluid and having a build up of the contaminants thereon, and wherein the region of the reaction vessel surrounding the sensor is coated with hard-facing material; and

(c) a scouring jet having an inlet in contact with the process fluid and through which the process fluid enters the jet and an outlet from which the process fluid is emitted, the outlet of the scouring jet being positioned so that the process fluid is emitted in a direction toward the surface of the sensor to impinge on the surface of the sensor whereby the impinging process fluid has a scouring action capable of removing one or more of the contaminants from the surface of the sensor; and wherein the process fluid emitted from the scouring jet does not contain a cleaning fluid.

2. The cleaning system of claim 1 wherein the reaction vessel is a closed reaction vessel selected from the group consisting of a tank and a pipe.

3. The cleaning system of claim 1 further comprising one or more valves located between the inlet to the scouring jet and the outlet of the scouring jet.

4. The cleaning system of claim 1 wherein the sensor is an Infrared, Raman or Near Infrared spectroscopic instrument.

5. The cleaning system of claim 4 wherein the instrument has a probe.

6. The cleaning system of claim 5 wherein the probe has a window in contact with the process fluid.

7. The cleaning system of claim 4 wherein the sensor is an Infrared spectroscopic instrument.

8. The cleaning system of claim 1 wherein the sensor surface is positioned in the reaction vessel by way of a port, valve or flange.

9. A cleaning system for an in-process sensor for use in a process for making titanium dioxide by either the chloride or sulfate processes comprising:

(a) a reaction vessel having an interior region and having a process fluid located therein, wherein the process fluid is from either the chloride or sulfate processes;

(b) a sensor having a surface, wherein the surface of the sensor is positioned on the interior region of the reaction vessel such that the surface of the sensor is capable of contacting the process fluid and having a build up of the contaminants thereon, and wherein the region of the reaction vessel surrounding the sensor is coated with hard-facing material; and

(c) a scouring jet having an inlet in contact with the process fluid and through which the process fluid enters the jet and an outlet from which the process fluid is emitted, the outlet of the scouring jet being positioned so that the process fluid is emitted in a direction toward the surface of the sensor to impinge on the surface of the sensor whereby the impinging process fluid has a scouring action capable of removing one or more of the contaminants from the surface of the sensor; and wherein the process fluid emitted from the scouring jet does not contain a cleaning fluid.

10. The cleaning system of claim 9 further comprising one or more valves located between the inlet to the scouring jet and the outlet of the scouring jet.

11. The cleaning system of claim 9 wherein the sensor is an Infrared, Raman or Near Infrared spectroscopic instrument.

12. The cleaning system of claim 11 wherein the instrument has a probe.

13. The cleaning system of claim 12 wherein the probe has a window in contact with the process fluid.

14. The cleaning system of claim 9 wherein the sensor is an Infrared spectroscopic instrument.