ON-LINE MONITORING OF ACETIC ACID CCONCENTRATION IN A DISTILLATION PROCESS USING NEAR-INFRARED ACOUSTO-OPTIC TUNABLE FILTER SPECTROSCOPY

摘要

Near-infrared (NIR) Spectroscopy is a useful analytical technique for on-line process monitoring applications. Because acousto-optic tunable filter (AOTF) technology offers the flexibility and durability of high-speed, no-moving-parts wavelength access, it is extremely well suited for process monitoring applications. The use of NIR AOTF Spectroscopy for on-line process monitoring of acetic acid concentration in a distillation process has been investigated. A pilot plant distillation system producing three fractions of acetic acid was monitored using a commercial NIR AOTF spectrometer in conjunction with a fiber-optically-coupled transmission mode flow cell. The system was set up to measure acetic acid concentration in the range 0 - 26% on a continuous distillation apparatus. The initial trial used a calibration derived with a lab version of the spectrometer using synthetic standards. As these were found to differ from the samples encountered when running on-line, an "on-line" calibration was generated. Accuracy of the analysis using the on-line generated calibration was found to be 0.3% in the range of 10 -22%. The performance of the distillation process could be successfully monitored and could potentially be controlled by the system, with analytical results being used to improve the yield of high-grade acetic acid through control of the heating of the distillation column.