Cold flow model of a PFBC cyclone

Cyclone separators used in Pressurized Fluidized Bed Combustion (PFBC) possess unique design and operational features: high gas velocities and solid loads, wide range of particle sizes and a pneumatic extraction of collected solids. As a consequence, their performance is noticeably different from that normally expected when using this kind of equipment in more conventional applications. At the same time, little information has been published devoted to PFBC cyclones, and there is a general lack of data on their collection efficiency and pressure drop. In order to study these aspects, a scaled-down model has been designed and built, intended to operate at room temperatures and moderate absolute pressures. In this paper, the corresponding simplified set of dimensionless scaling parameters is developed, starting from the classical knowledge of standard cyclones and introducing adequate assumptions to account for unexplored factors, in particular, the pneumatic extraction. The validity of the proposed scaling laws is then examined by means of a comparison between experimental measurements at the model scale and actual performance data from a full-size PFBC power plant. A satisfactory agreement is found in the dimensionless criteria, therefore leading to the conclusion that a reasonable flow similarity has been achieved in the cold flow model apparatus. (C) 2001 Elsevier Science B.V. All rights reserved.