Further investigation into regime transition from bubbling to turbulent fluidization

Introduction Over the last fifty years gas-solids fluidized beds have played a very important role in many areas in the process industry, especially in chemical and petroleum industries. The existence of different flow regimes in fluidized beds at different operating conditions has been known for a long time and numerous studies have been carried out to define the flow regimes [1-6]. It is well accepted that with increasing gas velocity, the bed goes through particulate fluidization, bubbling fluidization, turbulent fluidization, fast fluidization and pneumatic transport [7]. According to the experimental evidence available in the literature so far, a common way to classify the flow regimes is to determine the transition velocities by means of different measurement techniques and interpretation methods [6, 8-9]. The transition velocities have been found to be influenced by many factors such as solids properties [10-12], solids inventory [13], column diameter [14], distributor design [15-16], operating temperature and pressure [17-18], the measuring techniques and data analysis methods [19]. Therefore it should be very careful to compare the regimes transition velocities obtained with different flow systems and different data analysis methods.