In-Line Raman Spectroscopy for Process Optimization

Feb. 16, 2022
With their ability to provide highly accurate material analysis in real-time, Raman spectrometers are moving outside the lab to help end users improve product quality, speed cycle times, and increase yields.

During a recent Endress+Hauser digital press event, the company focused on its advanced process measurement and analysis technologies with an emphasis on its Raman spectrometers.

Raman spectroscopy is a process that allows the chemical composition of material samples to be determined by exposing them to electromagnetic radiation. After exposure, test samples emit material-specific radiation that allow their properties to be ascertained. By plotting the changes in the wavelength of the reflected light, Raman spectroscopy allows end users to obtain a molecular footprint that can be used to identify, quantify, and monitor various substances.

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According to Andreas Meyer, business development manager for liquid analysis at Endress+Hauser, when using conventional field instruments for measurement and analysis, parameters such as level, flow, pressure, and temperature are recorded individually and fed into regression models that make determinations about a sample’s quality. However, this must be done using many different sensors and requires new models to be programmed for each specific application. By contrast, Raman spectroscopy can measure multiple variables at once with high accuracy, allowing results to be delivered in real-time for continuous, on-the-fly optimization. Because of this, it can help process manufacturers improve product quality, speed cycle times, increase yields, and comply with regulatory standards more effectively, Meyer said.

For industrial applications, the issue with Raman spectroscopy is that is largely limited to laboratory use and has yet to be applied to in-line applications. When set up for use in a lab rather than integrated directly into a process control system, there are several disadvantages. For one, samples taken from a plant floor can change while being drawn or during transport. Moreover, because of the delay in obtaining a test result, operators cannot engage in timely corrective measures while the process is still running. This means that if an issue is detected, an entire batch of product may have to be thrown out.

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“Making the decisive step in the direction of compact field instruments calls for newer or different technologies for the spectrometer components. The elimination of fiber optics and the integration of the measurement probes in an in-line spectrometer promises an even more streamlined solution,” Meyer said. “The use of cost-effective standard components from conventional field instruments, such as field enclosures, embedded computers, displays or compact transmitters, offers further savings potential. By exploiting every possibility, manufacturers can deploy process spectrometers as compact field instruments that are much simpler to use and, above all, can be operated at a lower cost.”

As an example, Meyer mentioned the Rxn5 Raman process analyzer from Endress+Hauser. The Rxn5 is a Raman spectrometer that fulfills all explosion protection requirements and features solid state cooling as well as an embedded computer. Models for calculating quality are pre-coded for many applications and can be created for others as needed. 

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