Year

2019

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials, Mechatronic and Biomedical Engineering

Abstract

Airborne dust control and minimisation is a major consideration and concern in the industries that rely on bulk materials handling and processing. Health concerns due to inhalation, environmental issues arising from dust pollution, the dangers of dust explosions, damage to equipment and loss of product are some of many reasons for the control of fugitive dust. In the pursuit of dust control one of the most commonly applied techniques is the use of water sprays and as such one would think that their widespread application would mean their performance under various conditions would be well known and quantifiable. However, this is not the case – research into the implementation of water sprays is lacking, often focusing on application specific requirements rather than methods to predict their performance across all applications. The lack of research to enable engineers to predict the performance of these systems has resulted in many systems implemented in the bulk materials handling industry suffering from poor design and subsequently poor performance. Compounded by a lack of maintenance on what are commonly thought of as non-critical systems, has resulted in a view among many in the industry that dust suppression by means of water spray is ineffective. However, recent work by Bulk Materials Engineering Australia and the University of Wollongong in collaboration with dust suppression equipment supplier EnviroMist has shown that utilising the correct type of spray with an engineering approach to their implementation can result in very effective and reliable dust suppression systems in bulk materials applications.

This thesis aims to show how the characterisation of dust suppression nozzles in combination with a strong engineering methodology utilising CAE techniques can result in better prediction and ultimately better performance of dust suppression systems being implemented in the bulk materials handling industry. The first stage in achieving this was the characterisation of new high-energy micro-mist nozzles that have shown success in a number of projects (some of which are outlined in this thesis); characterisation included measurement of mist profile, droplet size, mist velocity, and mist penetration in crosswinds, all of which were measured across a range of pressures.

The second stage utilised the data collected in combination with computational fluid dynamics (CFD) to calibrate a spray model for predicting the performance of the sprays under typical industry conditions. Many systems installed in industry suffer from poor performance due to incorrect selection, sizing, and/or operation of the nozzle/s. This also often results in too much water being applied due to oversized nozzles, or mist being blown away by crosswinds due to undersized nozzles. The use of CFD to predict airflows in many applications has become fairly common place and as such implementing a spray model to this issue was a logical step. A validated simulation of the sprays presented in this thesis is shown and the subsequent application of the model to industrial applications is presented.

Two projects are presented in this thesis showing successful implementation of dust suppression systems to industry. Firstly, a dust suppression system was developed for a West Australian iron ore mine utilising computer aided design (CAD), and data collected during the preliminary stages of this thesis. The project consisted of a mist curtain applied over a truck dump pocket that was generating extreme levels of dust during the dumping process; a successful design is presented which was recognised by industry experts via a ‘Dust Control Application or Practice’ award at the annual Bulk Materials Handling Awards in 2015. Secondly, a project was funded by the Australian Coal Association Research Program (ACARP) for the application of dust suppression technology to longwall coal mining. This project showed the application of both the data collected experimentally for the sprays and the use of CFD to simulate the sprays under the conditions expected within the mine. Dust monitoring was conducted for the systems installed, with reductions in measured dust concentration in excess of 80% achieved.

FoR codes (2008)

0907 ENVIRONMENTAL ENGINEERING, 0913 MECHANICAL ENGINEERING

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.