Bubble size reduction in electric-field-enhanced fluidized beds

Fluidized beds are a common form of a chemical reactor, in which a deep layer of solid particles is set in motion by a stream of gas blowing upward. However, the appearance of gas bubbles can significantly limit the selectivity, conversion, and product properties of gas–solid fluidized beds. We present results on the application of low-intensity electric fields in fluidized beds for reducing the bubble size up to 85% while maintaining the free movement of particles so essential to fluidization, at an energy cost as low as 50 W/m33. An analysis is presented of the qualitative response of particles to electric fields, including both drift and diffusion of charges. On this basis, the influence of particle size and particle conductivity on the overall dipole moment, and therefore the interparticle forces, is discussed. Experimental results in a two-dimensional bed show the predicted response to changes in particle size, while variations in optimal frequency response can be explained on the basis of particle conductivity. A maximum reduction in bubble diameter of 25% is achieved with small particles View the MathML source(77μm), while for large particles View the MathML source(700μm) the bubble diameter can be reduced by as much as 85%.