Particle separation in cyclones of circulating fluidized bed systems

Abstract

Circulating fluidized bed (CFB) plants are widely used in energy, petrochemicals, aluminum production (alumina firing), and other industrial sectors. The CFB technology is characterized by relatively high reactor velocity that exceed the transport velocity of medium-sized particles, and the presence of separators (mainly of the cyclone type) with a system for returning trapped particles to the reactor. This ensures a long residence time of the particles in the reaction zone, a high circulation rate, and a stable and relatively low temperature in the reactor. In fact, it is the cyclone capture efficiency that directly determines the multiplicity of circulation and the flow rate of circulating particles and their size characteristics. The report discusses the current state of development and methods for cyclones calculating. Data from our and foreign studies are reviewed and the dependence of the correction on the mass concentration of particles is proposed. A brief description of the test rigs and the results of our own studies of particle separation in cyclones are given. Experimental data on the effect of dust on the capture efficiency are presented in the form of a dependence of the relative entrainment of particles (1-efficiency) on the mass concentration of particles at the entrance to the cyclone. Entrainment is noticeably reduced when the concentration increases, as small particles are attracted by larger ones to the wall of the cyclone.