Assisted Fluidization of Nanoparticles through Gas-Phase Pulsation
An experimental study of pulsed fluidization of nanoparticles is presented. The particles used were Degussa Aerosil R974 powder with primary particle size of 12 nm. The fluidization vessel was constructed from a glass tube, 50 mm id and 900 mm in height. High-purity nitrogen was used as fluidizing gas. The nitrogen gas was supplied in two streams, one with a constant flow while the other of a pulsating (oscillating) nature. The pulsating stream was generated by using a solenoid valve and controlled by VisiDAQ software.
We present measurements of bed pressure drop and bed expansion, together with visual observations. As gas velocity was increased, three types of bed behaviour were observed: plug formation and breaking, channeling and uniform fluidization. The technique of gas-phase pulsation was shown to be effective in overcoming plug formation and channeling. It was found that a lower superficial gas velocity was required to achieve uniform fluidization with a pulsed flow than a constant flow of fluidizing gas. The effects of pulsation amplitude and frequency were investigated, enabling optimum operating conditions of pulsed fluidization to be obtained.