To confront this tricky issue ACARP has granted CSIRO researchers $100,000 to investigate air and respirable dust flow patterns around the shearer on longwall faces, using Computational Fluid Dynamics (CFD) modelling techniques. This project forms part of ACARP’s major research initiative to develop innovative dust control techniques for thick seam longwall faces.
Traditionally, much of the work carried out on longwall dust control in the USA and UK has related to thin to medium thick coal seams.
This project, overseen by CSIRO’s Rao Balusu, will focus on numerical simulation of the effects of various mining parameters and dust control options on thick seam longwall faces.
By understanding how and why airflow behaves as it does in thick coal seams, effective dust strategies can be developed and implemented.
“The effects of variations in mining parameters such as face airflow, face height, cut-coal profiles, clearances and cutting direction will be investigated. Respirable dust flow from various sources such as face spalling, cutting face, and MG crusher will be simulated during these studies,” said Balusu.
“The control options to be investigated include a number of management strategies, various shearer clearer designs for thick seams and air-movers/venturis at different locations.”
A detailed analysis of the results of various dust control options and management strategies will be carried out to identify the potential/ effective control options for further investigations and field studies.
The work program consists of a review and summary of dust management on Australian longwall faces, including field visits to a number of longwall faces; brief literature review of previous attempts to model dust; construction of a CFD model for a thick seam longwall face (and a thin seam one for comparison); series of modelling investigations to simulate air and respirable dust flow patterns with various dust control options and management strategies; and a detailed analysis and recommendations for future work.
The initial modelling research project started in June 2003 and will run up to June 2004.
The results of the project investigations would also provide a detailed background on airflow patterns around the shearer for development of effective strategies to reduce frictional ignition risk on the longwall faces.
Much of the project will utilise on CFD modelling, a powerful tool being used in a wide variety of applications, ranging from aerospace, nuclear, automobile and manufacturing industries to environmental engineering.
Applications of CFD techniques in mining engineering are relatively recent, but have been used successfully over the last few years in a number of areas. In South Africa, CFD techniques have been successfully used for development of gas and dust control devices/methods in development headings/roadways. In Australia, UK, France and USA, the CFD simulation techniques proved to be successful in understanding of the effects of various parameters on air and gas flow behaviour in roadways and longwall goafs.
The CFD task initially consists of developing a finite element model representing the physical variables such as longwall dimensions, shearer and AFC details, with provisions for simulation of various dust control strategies in the later stages.
“The extensive modelling of the various dust control designs helps in minimising the expensive field trials required for development of new control techniques/ devices. Without modelling and proper understanding of the 3D airflow patterns on the face, the number of field trials required with new control devices would be huge and expensive,” said Balusu.
“Successful completion of the project results in substantial safety, productivity and financial benefits to a number of existing and new underground coal mines in Australia.”
Follow-up projects to this investigation will include field demonstration studies with innovative dust control techniques at one of the operating longwall faces in thick seams. The successful control techniques will be implemented in other mines in later stages.