The power of light in industrial process management: spectroscopy

April 28th, 2016, Published in Articles: EE Publishers, Articles: EngineerIT


Process analysis technology (PAT) is an essential prerequisite for the management and control of processes which is optimal both technically and economically. Optical spectroscopy is a well-established method for quantifying compositions.

Günter Pinkowski

Günter Pinkowski

It also allows for maximising the performance of a system, for example the so-called “space-time yield.” In addition to the use of “classical” process measuring technology (flow, level, temperature, etc.) PAT tools are increasingly being used to achieve this aim. The requirements for PAT are very different; batch processes require a temporal extension of the measurements across all concentration ranges. The composition of the substance on the probe changes constantly. In continuous processes, however, the same composition or the same concentration often appears in only one point in the production chain and the measurements take place according to the various process steps. The ideal state of always knowing all relevant information or data would mean a great expense, even in a small plant. With well-placed PAT measuring points, on the other hand, a higher level of control technology can be achieved and previously unused potential realised.

An optical spectroscopy system has been developed for applications with milk, wastewater and edible oil and fat. Typical applications include the continuous measurement of protein, fat, lactose and total solids in milk products, chemical oxygen demand (COD) in the wastewater flow of dairies or cheese factories, as well as free fatty acids (FFA), total polar material (TPM), peroxide value (POV), moisture, dirt and other values in edible oil and fat processing.

Fig. 1: Inline analyser for edible oil and fat processing.

Fig. 1: Inline analyser for edible oil and fat processing.

This optical spectroscopy measures the contents of milk products continuously and without contact. In the process, light of varying wavelengths is coupled into the product through an optical window. The system simultaneously determines the values of up to four optical effects (transmission, scattering, fluorescence and refraction) which manifest in different ways depending on the substances in the product, and then uses them to calculate, for example in dairy applications, the amounts of protein, fat, lactose and total solids. The measurement is tailored to the application with up to twelve wavelengths from UV to IR. The measuring cycle lasts only a few seconds. Typical applications for dairies include strategically increasing the protein content in cheesemaking milk/vat milk, standardising the fat content in drinking milk or setting a constant ratio of fat to protein in cheese production.

Unlike bypass devices which are sometimes costly to clean, this instrument measures without contact directly in the pipeline. The system is connected to the process via a standard process connection (nominal sizes DN 40 to DN 150). The measuring section is FDA-compliant and is cleaned using CIP. There is no need for daily recalibration thanks to the long-term stability of the optical measurement, which requires no moving parts. In addition, operating and maintenance costs are lowered as there is no need for chemicals, reagents or cleaning products. Operating the device requires no special knowledge.

Contact John Alexander, Krohne, Tel 011 314-1391,

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