Doctor of Philosophy
Department of Civil and Mining Engineering
Srinivasa Rao, Balusu, Design and development of a multi-scrubber dust control system for longwall faces: experimental and modelling studies, Doctor of Philosophy thesis, Department of Civil and Mining Engineering, University of Wollongong, 1993. http://ro.uow.edu.au/theses/1233
The control of respirable dust continues to present a challenge as the longwall mining industry strives for increased productivity and miner safety. Despite extensive research into the development of dust control techniques, it is still difficult to achieve Australian statutory standard of 3.0 mg/m3 at the face without loss of production. is because of the complex nature of longwall mining, its environment and the introduction of high capacity machines. The objective of this thesis' research has to address this problem and advance respirable dust control in longwall mining through the development of a new dust control technique. Major aspect of the research has been to provide a better understanding of the air velocities and respirable dust behaviour, through field studies and mathematical modelling, to assist in the development of new control techniques.
This research has co-ordinated several elements in developing a dust control technique and in understanding respirable dust behaviour. They are: (i) A literature review dust control on longwall faces (ii) Field investigations in longwall faces to develop fundamental data set on respirable dust distribution (iii) A new 'multi-scrubber' to control dust levels along the walkway of the face; the design and development of compact prototype scrubber and field tests of the scrubber system in operating longwall faces, and (iv) Mathematical modelling of a longwall face, using finite element techniques to simulate air flow patterns, dust distribution and to assist in the evaluation of dust control methods; field investigations to validate the modelling results.
EThe first series of field investigations in four longwall faces were conducted to data on respirable dust levels, the spatial and temporal behaviour of dust in the face, and to provide input data for mathematical modelling. The dust concentration data were related to shearer location, face operations and time, and showed that large dust gradients occur, not only around the shearer, but also across the whole cross-section the longwall face. The surveys helped in gaining a better understanding of the respirable dust problem at the longwall face, and along with the literature review, formed the basis of the development of the new dust control technique.
A new 'multi-scrubber' concept was proposed to reduce the longwall face operator's exposure to dust. This system envisages a number of moderate capacity scrubbers, which deliver cleaned air at high velocity, to create a relatively clean air zone walkway in the longwall face. A prototype air-powered venturi scrubber was developed for use in longwall faces which, when tested in the laboratory, yielded average efficiency of 92%. A second series of underground investigations in three longwall faces ascertained that the scrubber system achieved protection efficiencies ranging between 26 and 55%, at 3m from the scrubber, with face air velocities from 4.5 to 2.0 m/s.
As a supplement to the field studies, a three-dimensional finite element longwall model was developed to simulate the airflow patterns and respirable dust behaviour. facilitated the analysis of the effect of the shearer body and cutting direction on longwall airflow characteristics and respirable dust behaviour. The model was also used to predict the effectiveness of the scrubber system and other dust control techniques. A third series of field experiments were conducted to validate the model's predictions under similar operating conditions. A comparative analysis of the airflow patterns, respirable dust distribution and effectiveness of control techniques shows close agreement between the mathematical modelling results and field measured values.