IN-SITU MEASUREMENT OF SUBMICRON PARTICLES DURING SYNTHESIS FROM GASEOUS PRECURSORS

AEROSOL PROCESSING IS A POPULAR METHOD TO PRODUCE SUBMICRON PARTICLES FOR TECHNOLOGIES LIKE PIGMENTS AND SINTERABLE CERAMICS. ALTHOUGH THE PARTICLE SIZE DISTRIBUTION (PSD) OFTEN CONTROLS THE QUALITY OF THE FINAL PRODUCT, THIS PARAMETER CANNOT CURRENTLY BE MEASURED ON-LINE BECAUSE OF THE DENSE PARTICLE STREAMS. IN ADDITION, THE NUMBER DENSITYAND TEMPERATURE OF THE PARTICLES IN THE REACTOR ARE ALSO UNKNOWN. CONSEQUENTLY, EFFECTIVE PROCESS MONITORING AND CONTROL IS NOT READILY AVAILABLE. ADVANCED FUEL RESEARCH, INC. (AFR) HAS DEVELOPED A NOVEL FOURIER TRANSFORM INFRARED (FT-IR) EMISSION/TRANSMISSION (E/T) TECHNIQUE THAT CAN OVERCOME THE ABOVE PROBLEMS. THE TECHNIQUE USES THE WAVELENGTH DEPENDENCE OF IR LIGHT SCATTERING TO SIZE PARTICLES. AS A RESULT, IT CAN OPERATE IN DENSE AEROSOL STREAMS BECAUSE PARTICLES < 10 MUM DO NOT SCATTER IR AS EFFICIENTLY AS VISIBLE LIGHT. E/T FT-IR CAN ALSO SIMULTANEOUSLY MEASURE PARTICLE NUMBER DENSITY AND PARTICLE TEMPERATURE AS WELL AS GAS CONCENTRATIONS AND TEMPERATURE. APPLYING THE ABOVE METHOD TO YIELD A PSD REQUIRES DEVELOPINGNEW WAYS TO DECONVOLUTE THE FT-IR SPECTRA, HOWEVER. FORTUNATELY, RESEARCHERS AT THE UNIVERSITY OF MAINE CAN MODIFY AN ULTRASONIC DECONVOLUTION METHODOLOGY TO FIT THE PROPOSED FT-IR APPLICATION. BY COMBINING E/T FT-IR AND A DECONVOLUTION ALGORITHM, A SINGLE FT-IR SPECTROMETER SHOULD BE ABLE TO MONITOR PARTICLE SIZE DISTRIBUTIONS AND TEMPERATURES IN A PROCESS STREAM AND ISSUE PROCESS CONTROL COMMANDS. THIS PROPOSAL IS A COMBINED RESEARCH EFFORT BY AFR AND THE UNIVERSITY OF MAINE TO DEVELOP A SENSOR FOR PARTICLE ANALYSIS OF HIGH-TEMPERATURE GAS REACTION MIXTURES. THE SENSOR WILL BE ON-LINE AND IN-SITU AND WILL DECONCOLUTE THE FT-IR SPECTRA TO YIELD THE PARTICLE SIZE DISTRIBUTION. THE PHASE I RESEARCH WILL DEMONSTRATE THE TECHNOLOGY BY DECONVOLUTING THE MEASURED IR SPECTRA OF KNOWN TIO2 PARTICLES TO YIELD AN ACCURATE PSD. A SIMPLE LABORATORY SCALE FLAME WILL SHOW THAT IN-SITU MEASUREMENTS ARE FEASIBLE. PHASE II RESEARCH WILL INCLUDE EXTENSIVE RESEARCHON A TIO2FLAME IN AN INDUSTRIAL LABORATORY. THE FINAL STEP OF PHASE II WILL BE A FIELD TEST ON A COMMERCIAL TIO2 REACTOR.