PERSPECTIVE

The objective of process control is to improve the yield, capacity, and quality of the product. This requires knowledge of the concentrations of key components in various process streams. However, the frequency and the number of laboratory and on-line measurements of these concentrations have steadily declined because of ongoing attrition of analytical chemists, analyzer specialists, and technicians. As a result, many production units are essentially flying blind.

Advanced control systems need concentration measurements in order to truly optimize the process. Neural networks or estimators can utilize conventional measurements of pressure, temperature, and flow to provide virtual analyzers (intelligent sensors), but these models predict steady-state concentrations and ultimately depend upon a concentration somewhere for building and correcting the models.

Thus, as part of any process control improvement, the need for analyzers should be studied. The following compilation of new developments should be valuable in making this assessment, particularly those techniques that require less sample conditioning and recalibration. This means less on-site support and/or opens up the opportunity to measure new components reliably on line.

Many of these newer analyzers utilize technologies that are sophisticated and require extensive engineering and setup. However, often the analyzer either works or does not work and therefore there is less ongoing attention. Also, the manufacturer is willing to provide a turn-key installation and a free plant trial in which...