The use of Positron Emission Particle Tracking (PEPT) to determine the grinding mechanisms within a vertically stirred media mill

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Skuse, Thomas Richard (2016). The use of Positron Emission Particle Tracking (PEPT) to determine the grinding mechanisms within a vertically stirred media mill. University of Birmingham. Ph.D.

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Abstract

A Positron Emission Particle Tracking (PEPT) based technique was developed and used to study laboratory grinding of calcium carbonate in a vertically stirred media mill. The PEPT data along with particle fracture data obtained by micromanipulation were used to understand the grinding mechanisms.

The PEPT methodology allowed measurements of grinding media occupancy, velocity, force, stress and media–media collisions at different positions within the mill. The stresses exerted by the media were compared with calcium carbonate strength measurements made using the micromanipulator to determine the percentage of the grinding media with sufficient stress to overcome the strength of the calcium carbonate particle. The collision frequency and total number of collisions were estimated using a modified Arrhenius equation approach by measuring the mean relative velocity of the grinding media (estimated to be the standard deviation of velocity measurements made in a block volume) and the number of media particles in a unit volume.

This approach was used to characterise the behaviour of a benchmark grinding experiment performed under standard conditions and to understand the effect different operating conditions had on the number of collisions and stress exerted at these collisions. A number of suggestions for improved mill performance are given.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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