(236e) Application of Magnetic Resonance Imaging Techniques to Particulate Systems

Magnetic Resonance Imaging (MRI) has traditionally been used for investigating liquid and sometimes gaseous systems to extract information about position and particularly transport occurring within optically opaque samples. Its application to imaging solids has been limited due to the short relaxation times associated with most solids and therefore the difficulty in implementing MRI techniques. Despite this, a number of studies have been done, typically utilising signal from oils in certain seeds, and there is now increasing interest in this area. This paper will give an overview of the state-of-the-art work being done in the area of MRI of particulate systems and will focus on some of the recent work from our group including the implementation of new techniques that have enabled us to look at a number of particulate systems. Specifically:

i) Gas-fluidised beds

ii) Vibro-fluidised beds

iii) Rotating beds

A number of MRI techniques will be described which have allowed new information to be gained from these applications. Ultra-fast 1-D imaging of solids distribution in gas-fluidised beds is used to extract local instantaneous bubble velocities. Ultra-fast FLASH imaging at a time resolution of 1.3 ms allows velocities of over 10 m/s to be measured, though time averaged 2-D velocity images show typical velocities up to 0.3 m/s for U/Umf=1.3, in agreement with theory for our experimental setup. Vibro-fluidised beds require the development of different MRI techniques to extract quantitative velocity distribution maps which have been oscillation phase resolved. From these, detailed information about the nature of the fluidisation, such as local granular temperature, are extracted. Finally, high resolution images of segregating particles in a rotating kiln will be shown. In the highest resolution images, the individual particles of both types are well resolved and the mechanics of segregation can be probed along with the underlying dispersion processes.