Two New Advancements in Fluidization Research and Technologies

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Since its first industrial application of fluidization 90 years ago, fluidization has been developing from gas-solid fluidization to liquid-solid and gas-liquid-solid fluidization, and from conventional low-velocity fluidization to high-velocity fluidization. In the three fluidization systems (g-s, l-s and g-l-s), various fluidization regimes have also been identified and many attempts have been made to characterize the fluidization behaviour in each of those regimes and to demarcate the boundaries. The applicant has recently conceived a four quadrant map on a Cartesian coordinate with fluid velocity as abscissa and solids flowrate as ordinate, to place the various fluidization operations on the map and to identify future research need and potential for technological breakthroughs. Quadrant 2 was found empty, where particles would flow upwards and liquid downwards. This can actually be achieved using liquid and lighter-than-liquid particles in an inverse circulating fluidized bed where the particles' buoyancy force is larger than gravity, so that they would "float" to the top of the column in a steady state and therefore in quadrant 2. As a result, the first proposed project is to develop an inverse Liquid-Solid Circulating Fluidized Bed (i-LSCFB) for possible applications such as wastewater treatment. The applicant is one of the pioneers who first studied the (upright) Liquid-Solid Circulating Fluidized Bed (LSCFB) and explored it for applications, mostly in the bio and environmental engineering areas, so has the experience. We will build, commission and test this new design. After getting the particles circulated inside the system, we will use some of our existing instrumentation, such as the optical fibre system, the Electro-Resistant Tomography (ERT), to map the column with particle concentration and particle velocity. With those measurements, we will be able to fully characterize the flow structure of i-LSCFB, so as to pave the road for its applications. The second project is also at the frontier of fluidization: to fully test the high-density circulating fluidized bed (HDCFB) and the circulating turbulent fluidized bed (CTFB), using ozone decomposition as the sample reaction. One trend in gas-solid fluidization is to move towards high gas velocity so that the adverse effect of gas bubbles be avoided. While there are significant benefits of high velocity fluidization, such as much higher contact efficiency and reduced backmixing, there are also some drawbacks such as lower bed density. Responding to this request, the applicant has been devoting his time in developing HDCFB and CTFB, which have been shown to have many advantages over the more traditional low density circulating fluidized bed (LDCFB) and turbulent fluidized bed (TFB). As the second project, we plan to conduct real reaction studies over those two as well as other more traditional operations to demonstrate the superior performance of two high-density operations over the other fluidized bed reactors. For this second project, we have designed and built a multifunctional fluidized bed unit, that can be operated as bubbling, turbulent, CTFB, LDCFB and HDCFB. We shall utilize the ozone decomposition reaction as the sample reaction to study those operations and to quantify their relative performance.