Abstract
The hydrodynamics behavior of gas - solid fluidized beds is complex and it should be analyzed and understood due to its importance in the design and operating of the units. The effect of column inside diameter and static bed height on the minimum fluidization velocity, minimum bubbling velocity, fluidization index, minimum slugging velocity and slug index have been studied experimentally and theoretically for three cylindrical columns of 0.0762, 0.15 and 0.18 m inside diameters and 0.05, 0.07 and 0.09 m static bed heights .The experimental results showed that the minimum fluidization and bubbling velocities had a direct relation with column diameter and static bed height .The minimum slugging velocity had an inverse relation with static bed height and a direct one with column diameter .There was no agreement between the experimental and calculated values of Umb for Di=0.0762m ,this was a result to the assumption used in the correlation development. The fluidization index values were around 1 in all cases and that proved that the material is of Geldart type B. There was not a significant dependence of fluidization index and slug index on static bed height and column diameter. 
Highlights
1.INTRODUCTION The application of gas- solid fluidized beds technique in chemical processes is widely used such as gas cleaning, blending of solids, heat sensitive materials drying, crude oil thermal cracking, gasification and combustion of waste material or coal, coating and granulation )Gajbliye, et al, 2013 ), mentioned that more applications of fluidization technique can be seen in circulation of solid particles, pneumatic transportation, chemical synthesis and chemical regeneration. (Sulaymon, et al, 2013), used fluidized bed for heavy metals removal by algal biomass. (Ebrahim, 2016), worked on using fluidized beds in Fluoride ions removal from waste water using blue and green algae biomass
The flow shifts from slug in to turbulent with further rise in gas velocity, the turbulent flow marked with the bubbles and slug absence in the bed and that followed by particles movement and transportation .(Jaiswal, et al, 2018) and (Agu, et al, 2017) mentioned that the transition from a type of flow to another depends on many factors i.e. static bed height, fluidizing gas flow rate, column diameter, particle density, particle size and others
The main objective of this work was to study the effect of column inside diameter and static bed height on the minimum fluidization velocity, minimum bubbling velocity, fluidization index, minimum slugging velocity, bubbling bed index and slug index and the experimental results were compared with the theoretical values by using the correlation equations
Summary
The application of gas- solid fluidized beds technique in chemical processes is widely used such as gas cleaning, blending of solids, heat sensitive materials drying, crude oil thermal cracking, gasification and combustion of waste material or coal, coating and granulation )Gajbliye, et al, 2013 ), mentioned that more applications of fluidization technique can be seen in circulation of solid particles, pneumatic transportation, chemical synthesis and chemical regeneration. (Sulaymon, et al, 2013), used fluidized bed for heavy metals removal by algal biomass. (Ebrahim, 2016) , worked on using fluidized beds in Fluoride ions removal from waste water using blue and green algae biomass. Further increase in gas superficial velocity causes the bubbles size and rise velocity to increase, they collapse and grow in size until they reached (0.3-0.6) of column diameter and the bed starts to slug, the gas velocity at this point is called minimum slugging velocity. The flow shifts from slug in to turbulent with further rise in gas velocity, the turbulent flow marked with the bubbles and slug absence in the bed and that followed by particles movement and transportation .(Jaiswal, et al, 2018) and (Agu, et al, 2017) mentioned that the transition from a type of flow to another depends on many factors i.e. static bed height, fluidizing gas flow rate, column diameter, particle density, particle size and others
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