Laser Backscattering

Laser Backscattering Provides In-situ Measurement of Bulk Flows

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In-Situ Laser Backscattering

To measure the particle flow, the Labasys instruments use laser backscattering. The particles are illuminated by laser light guided with optical fibres. A photometer converts the backscattered light into electronic signals. From there, the velocities are determined using cross correlation methods. The analysis software Labasoft Control evaluates about 20 single velocities every four seconds, from which stable mean values are derived.

The chart to the right shows typical plant start-up data of a Spherizone process, measured in the downer. The red points show the target quantity velocity. The blue and the green markers below show the raw signals of channel 1 and channel 2 of the measuring instrument. These values correspond to the polymer concentration in the downer, allowing for a close observation of the start-up phase: when the plant is started at ca. 13:30 h, the filling level rises and the polymer particles start to circulate. The velocities of the particles falling onto the packed bed at the bottom of the downer fluctuate strongly and rise as their density rises, as indicated by the concentration signals.

Slowly the filling level moves upwards and at about 14:50 h the packed bed reaches the height of the instrument. From this moment on the velocity of the bulk flow (which is much lower and more regular) is measured instead of the falling particles: the process reaches stationary conditions and only minor variations of the bulk velocity can be observed. The instruments also yield valuable concentration data — at least in qualitative form — which give direct insight into the inner life of the reactor.

Reliable and Long-lasting Operation Around the World

By now instruments are in operation in LyondellBasell’s semi industrial Spherizone plants in Ferrara and Frankfurt and in commercial plants in Thailand, Korea and Saudi Arabia. A reliable and long-lasting operation without costly product interruptions can be assured, as the with Swiss precision engineered, manufactured and tested instrument proved its value well in practice. Or as a supervisor of manufacturing platforms of LyondellBasell said: “We are happy with our three Labasys Control Ex Bulk Flow instruments. In the more than two years they were in operation at our plants now, they run perfectly well and delivered important in-situ information to control our processes efficiently.”

These devices are also well suited to monitor velocities and concentrations in other solids processes — be it in the high concentration ’bulk flow’ or in a more dilute flow range, be it in a R&D or an industrial production environment.

* Dr. Meili is the founder and CEO of MSE Meili AG, Schaffhausen/Switzerland.