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EPSRC Reference: EP/C547195/1
Title: The Use of Ultra-Fast Magnetic Resonance Imaging to Investigate Solids Mixing and Voidages in Bubbling and Turbulent Gas-Fluidised Beds
Principal Investigator: Dennis, Professor J
Other Investigators:
Gladden, Professor L Sederman, Professor AJ Hayhurst, Professor A
Davidson, Professor J Mantle, Dr MD
Researcher Co-Investigators:
Project Partners:
Department: Chemical Engineering and Biotechnology
Organisation: University of Cambridge
Scheme: Standard Research (Pre-FEC)
Starts: 04 November 2005 Ends: 03 November 2008 Value (£): 269,018
EPSRC Research Topic Classifications:
Image & Vision Computing Multiphase Flow
Particle Technology Reactor Engineering
EPSRC Industrial Sector Classifications:
Chemicals Environment
Related Grants:
Panel History:  
Summary on Grant Application Form
The ability to predict and model fluidised bed phenomena using Distinct Element modelling approaches has made a major impact on the understanding of fluidisation. However, there is a pressing need to validate the results obtained from these models by direct experimental observation. The work proposed here will lay the foundations for undertaking validation using MRI and therefore improve the ability to design fluidised systems.Recent feasibility experiments at Cambridge have shown that ultra-fast Magnetic Resonance Imaging (MRI) can give detailed information about the rate of dispersion, in real time, of a batch of tracer solids when added to a bubbling bed. Other work has shown, amongst other things, that jetting phenomena at the distributor can be imaged and that the voidage in both bubbling and turbulent beds could, in principle, be determined as a function of time and spatial position. These experiments have opened up the possibility of studying a number of problems of great industrial and theoretical interest, to provide quantitative information which is either complementary to existing imaging techniques (such as Positron Emission Particle Tracking PEPT) or, in many cases, provides a unique insight. Of particular importance is the possibility of observing and quantifying phenomena in 3-D systems to provide information for the validation of the current generation of models based on discrete elements. This proposal is therefore concerned with the use of current MRI techniques, and theextension of these to increase temporal and, or, spatial resolution to investigate particular problems of dispersion and segregation in bubbling and slugging fluidised beds, namely:a) the axial displacement of solids and thus factors affecting the rate of axial mixing and segregation of solids, b) the impact of the distributor design on the behaviour of the bed,c) the variation in voidage in the dense phase with the velocity of the fluidising gas, andd) the motion of individual particles, larger than, and with a different density to, the principal bed solids.The ability to predict and control these phenomena plays a critical role in the maintenance of product quality and productivity in many industrial applications of fluidised beds.Important outcomes will be the development of a portfolio of MRI and data analysis protocols, which will identify (i) limits of spatial and temporal resolution in 1-D and 2-D, (ii) evaluate information obtained from the time-averaged results (-0.1 mm resolution recorded over timescales of minutes) and comparison with results acquired from a single-shot acquisition at lower spatial resolution (typically 0.2 - 0.6 mm resolution over timescales of a few ms), (iii) the extent to which the results can be quantified, taking into account relaxation time and velocity contrast effects, and (iv) the extent to which direct velocity imaging of the solid and gas phases can be achieved. If these objectives can be achieved, an important future possibility, but outside the present scope, will be to compare PEPT and MRI predictions of solids movement to check their agreement.
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Organisation Website: http://www.cam.ac.uk