Master of Engineering Science
Chemical and Biochemical Engineering
A three-phase system consisting of free settling and free rising particles were fluidized in tandem with gas bubbles in a liquid batch operation. Hydrodynamic properties were investigated, using one kind of heavy particles (ρH=1050kg/m3) and three different kinds of light particles (ρL=930-880kg/m3. Gas holdups are inferred from measured pressure drop and increased with superficial gas velocity (Ug), axial location, particle loading and decreasing densities of the free rising particles. The volume fraction of free settling particles over total particles were measured and then used to calculate particle holdups of free settling and free rising particles. The axial distribution of the solid holdups transferred from higher in the lower sections and lower in the top sections under low Ug, to axially uniform under moderate Ug, then became lower in the bottom section and higher in the top section under high Ug.
Summary for Lay Audience
To solve the global water recourses shortage, effectively recycling and reusing wastewater has drawn the attention of researchers all around the world. Over the years, we developed a wastewater treatment system with an attached growth process treatment and fluidized bed technology. Attached growth process means microorganisms attached to solid medium consume organic waste in wastewater on their reproduction so that the organic waste is removed from the water. This incorporation increased the wastewater treatment capability by 5-10 times with fluidized bed technology compared to conventional wastewater treatment plot. In this research, we constructed a novel fluidized bed system which would be suitable for wastewater treatment since it has gas, liquid and solid 3 phase involved in the reaction. Gas provided oxygen for the metabolism of microorganisms and serve as the driving force, the liquid could provide buoyancy for the particles and be replaced by actual wastewater in practical application, and solid particles played the role of the carrier of microorganisms. A uniform distribution is generally preferred in a fluidized bed for its uniform temperature distribution and exclusive reaction intensity. While, in a 3-phase fluidized bed, solid particles whose density is higher than liquid and named as free settling particles aggregate at the bottom of the column and solid particle whose density is lower than liquid and named as free rising particles aggregate at the top of the column. To achieve relatively uniform particle axial distribution, we added free settling particle and free rising particle at the same time into the column. Our research project is to study the gas and solid distribution of this system while operated under different conditions. Through analyzing experimental data, it was found out that gas holdups increased with superficial gas velocity (Ug), axial location, particle loading and decreasing densities of the free rising particles. The volume fraction of free settling particles over total particles transferred from higher in the lower sections and lower in the top sections under low Ug, to axially uniform under moderate Ug, then became lower in the bottom section and higher in the top section under high Ug.
Jin, Xueke, "Gas-induced fluidization of free settling and free rising particles in liquid batch operation" (2019). Electronic Thesis and Dissertation Repository. 6330.
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