The objective of this study is to investigate the effects of alternative mining and processing methods on final product recovery in coal processing. Coal losses and dilution are two important mining problems facing the coal industry, which has not been previously investigated in detail. Both of them affect the mining recovery and revenue significantly with different magnitude. To determine the magnitude of change in recovery, there is need for development of a single piece of software capable of simulating the entire process from in situ coal to a product loaded on a train.
Therefore, the aim of this thesis is:
• To gain an understanding into the operation of open cut coal mines, with particular attention to estimation of coal losses and dilution resulting from different mining conditions and using different mining equipment
• Investigate the effect of mining and handling methods on coal degradation and fine coal generation
• Investigate the effect of mining methods on ROM coal recovery, (and describe the property of ROM coal based on their original in-situ characteristics)
• Combine the estimate of loss and dilution and the in-situ coal property to estimate ROM property
• Apply washing models on the resulting ROM to predict the resulting yield and product coal properties
• Select the most appropriate existing models and link them into one piece of software to provide the industry with a tool to estimate the recovery of coal from its in-situ condition
• To track relative costs so that the benefit of alternative mining, handling or washing practices can be quantitatively assessed
• To assess the merits of alternative strategies and to maximise saleable product and the net revenue by designing the most effective mining, handling and washing method.
This project provided the industry with software as a tool for economic analysis of current mining and washing practices with ability to investigate effect of alternative strategies on the final saleable product. The program is written in Visual Basic, and its simulation capabilities were validated on site and demonstrated through case study.
Definition of the problem
A previous ACARP project "The Assessment and Control of Coal Damage and Loss" project (Scott and Wedmaier, 1995) demonstrated that very few Australian open cut mines realistically schedule, monitor or report mining recovery. It also demonstrated the feasibility of measuring and understanding the factors that affect mining recovery, loss and dilution.
Problems identified include:
• The confusion of actual and apparent estimates of mining recovery (Scott and Wedmaier, 1995),
• The failure to relate preparation plant yield to the quality of the run-of-mine feed (Scott and Wood, 1996),
• The common application of inappropriate moisture corrections for the estimation of in-situ density from standard air-dried laboratory results (Preston and Sanders, 1992).
Any strategy that increases the overall recovery of coal provides strong economic leverage through increased sales revenue. Unless the consequences of improved pit practices on the overall recovery of saleable coal can be reliably quantified; any resulting increase in cost cannot be justified. This results in a loss of opportunity to significantly increase revenue for little additional expenditure.
• Literature survey on the aspects of mining, handling and washing and critical review of work to date
• Selection of recovery and dilution models
• Selection of degradation and washing models
• Coal mine and preparation plant visits and data collection
• Development of suitable computer framework
• Review and refine models
• Software development and evaluation.