Fluctuations in the mass flow of solids
in pneumatic conveying lines
P. Hilgraf, J. Bartusch, Claudius Peters Projects GmbH,
Pneumatic conveying systems are often used for supplying downstream reactors with metered mass flows of solids. When a conveying system is being designed it is essential to ensure that the respective target value can be achieved with substantial fluctuations in the mass flow of the solids. The size of these fluctuations is dependent on the chosen operational settings of the conveying system and can lead to problems, possibly even to failure of the reactor being supplied. A description is given of systematic measurements of these mass flow fluctuations that were measured with an impact plate system at the end of the different conveying lines and were accompanied by dimensional analysis that safeguards the scale-up. The conveying gas velocity or Froude number, the loading of the conveying gas with solids and the conveying distance have proved to be the essential factors that influence the size of the fluctuations characterized by the coefficient of variation. A parallel arrangement of several small individual pipes, to which the solids are supplied simultaneously and which are brought together again at the reactor feed point, offers a further option for reducing the fluctuations. The measurements carried out on the conveying lines investigated showed a typical behaviour pattern of the coefficient of variation as a function of the Froude number. At high Froude numbers the coefficient of variation lies on a low plateau, i.e. the measured fluctuations are low, but at small Froude numbers they are many times higher.
Summary CEMENT INTERNATIONAL 06/2019 pp 24-33
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