Apparatus for measuring the concentration of a species at a distance
Corrosion of refractory silica brick and air quality issues due to particulate emissions are two important glass manufacturing issues that have been tied to sodium vapor and its transport throughout the melt tank. Knowledge of the relationship between tank operating conditions and tank atmosphere sodium levels are therefore important considerations in correcting corrosion and air quality issues. However, until recently direct quantitative measurements of sodium levels has been limited to extractive sampling methods followed by laboratory analysis. Excimer laser induced fragmentation (ELIF) fluorescence spectroscopy is a technique that permits the measurement of volatilized NaOH in high temperature environments on a timescale of less than one second. The development of this method and the construction of field-portable instrumentation for glass furnace applications are herein disclosed. The method is shown to be effective in full-scale industrial settings. Characteristics of the method are outlined, including equipment configuration, detection sensitivity, and calibration methodology.
1. An Excimer Laser Induced Fragmentation Fluorescence (ELIF) stand-off probe, comprising:
a high intensity laser, said laser providing a high intensity light beam;
a fused silica or fused glass window through which said light beam passes;
a spectrometer having a light receiving aperture;
a slit mounted over said light receiving aperture;
a light collecting means comprising a mirror mounted on a rotatable stage and at least one focusing lens, said light collecting means disposed adjacent to said light beam, wherein said light collecting means images a predefined region in space along said light beam and gathers light generated by a photo-dissociation reaction between said light beam and any of a population of molecular species occupying said region of space traversed by said light beam, said mirror directing said generated light into said lens, wherein said lens focuses said generated light onto said slit and thence into said spectrometer, wherein said spectrometer disperses said generated light into a light spectrum; and
means for detecting for said light spectrum and providing an electronic output signal proportional to said light spectrum over a wavelength range of between about 400 nm to about 1200 nm.
2. The ELIF stand-off probe of claim 1 , further comprising an insulated housing.
3. The ELIF stand-off probe of claim 2 , wherein the insulated housing comprises an interior cooling means.
4. The ELIF stand-off probe of claim 2 , wherein said insulated housing is maintained at a temperature below 40° C.
5. The ELIF stand-off probe of claim 1 , wherein the rotatable stage is capable of an angular resolution of about 0.08° (±0.04°).
6. The ELIF stand-off probe of claim 5 , wherein the rotatable stage comprises a mechanical or an electrical rotation means.
7. The ELIF stand-off probe of claim 6 , wherein the rotation means comprises a micrometer.
8. The ELIF stand-off probe of claim 6 , wherein the rotation means comprises a closed-loop motorized actuator.
9. The ELIF stand-off probe of claim 8 , wherein the closed-loop motorized actuator comprises a piezoelectric actuator.
10. The ELIF stand-off probe of claim 6 , wherein the rotation means comprises a micrometer and a closed-loop motorized actuator.
11. The ELIF stand-off probe of claim 10 , wherein the rotation means comprises a micrometer and a closed-loop motorized piezoelectric actuator.
12. The ELIF stand-off probe of claim 1 , wherein said means for the detecting comprises a multi-channel light detector.
13. The ELIF stand-off probe of claim 12 , wherein the multi-channel light detector comprises a charge coupled device (“CCD”) array.
14. The ELIF stand-off probe of claim 13 , wherein the CCD array is an intensified multi-channel diode-array.
15. The ELIF stand-off probe of claim 13 , wherein the CCD array is an intensified multi-channel CCD array.