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Abstract

The observed cyclic operation of a riser near choking was calculated using a computational fluid-dynamic model used previously to predict its flow regimes. An approximate analytical expression for the maximum carrying capacity of Geldart A, B and C particles was developed and compared to data in the literature. In the new theory, an unknown parameter is the pseudosonic velocity of the particles. To estimate this quantity, new granular temperatures were measured and compared to data from the literature for Geldart A, B and C particles. In the riser flow regime (2% to 20% solid volume fraction), the turbulent intensity of the particles is approximately 0.5, in agreement with the theory. The theoretical value involves the ratio of particle viscosity to the granular conductivity.