Underground » Mining Technology and Production
The objective of this project was to conduct an in-depth scoping study to identify the requirements of future high capacity and sustainable underground coal mining in Australia, with a 15MTPA operation from a single underground longwall system as the target (abbreviated as L15). This production target is more than double the current best, and quadruples the current Australian average. The feasibility of achieving such targets and the associated risks and consequences will be identified for the prevailing range of seam geometries and conditions found in Australia, in particular those anticipated in the next 20 years.
The specific targets are:
- Identify current best practice for High Capacity Underground Coal Mining.
- Identify knowledge and technological gaps for a 15 MTPA underground operation.
- Identify and assess the existing published underground coal resource base available for mining in the next 20 years.
- Identify the consequences of a 15 MTPA production profile and any barriers this may generate through a mining environment/condition based analysis.
- Identify the viability of this production profile for current and future sustainability.
- Identify common and strategic issues that may form the basis of research and development projects and post graduate training.
A high production outcome will not only require high capacity and efficient equipment but, most importantly, will require well designed and implemented management controls and processes to facilitate and engender a high productivity environment, thereby achieving improved system uptime. There will be a heightened demand for greater attention to detail and understanding of the various processes and cooperation at all levels to achieve the productivity goal and coordination of all resources to manage significantly greater process cycle requirements (belt extensions/retractions, longwall relocations, etc.). The best equipment in the world will not achieve improved productivity if “best practice” management systems, management style and process engineering principles are not inculcated as the cultural norm.
Equipment Significant design issues will encompass shearer speed, cutting capacity, power requirements, under body clearance of the shearer, the rate of advance of the hydraulic face supports and the capacity requirements of the hydraulic delivery system. These issues will be amplified when operating in thinner working height environments.
The mining footprint from a 15MTPA operation will be significant regardless of seam thickness. Understandably, the larger the footprint the greater the likelihood of intersecting geological structures. Data available in the public domain is not comprehensive and does not readily yield definitive answers to the number of L15 resources available and their potential intersections with geological structures. Optimistically there could be 19 deposits with the potential to support an L15 operation. The Bowen and Sydney basins have the best potential for such resources.
Geotechnical difficulties and delays occur through a combination of weak immediate roof (including faults), periodic overloading and inadequate powered roof support factors (either operability or maintenance) and are more predominant on the face than the gateroads. Geophysical methods for structure location and characterisation have been successfully employed but there is a lack of skilled practitioners and fault negotiation remains problematic. Powered roof support density, operability and operating speed, will need to be optimised for high tonnage operations to be achieved. Real-time, automated and smart monitoring will aid the successful negotiation of structured ground.
Gateroad development rates will come under severe pressure if high tonnage longwalls are to eventuate. Much of the current face equipment is capable of achieving the rates needed however, the main deficiencies lie in the discontinuous nature of the process. Improvement will require integration of the various sub-processes into a truly continuous process. Significantly, new innovations will be required in the provision of extensible coal haulage and ventilation infrastructure. All must be underpinned by clear understanding of the processes and adherence to sound and effective management practices.
High tonnages will exacerbate the issues of ventilation, gas and dust management. Spontaneous combustion incidents should be positively affected with faster retreat rates, but potentially negated by LTCC or wider faces. One of the key limiting factors - effective gas drainage, will depend on technologies such as Medium Radius Drilling for greater drainage lead time and advances in gas flow stimulation.
Water consumption is directly proportional to production on any specific longwall face, however there is no direct correlation of water use to production across the industry – high producers are not always the highest water consumers. Mine water is considered from both input and output perspectives. Opportunities exist for diligence in water usage and management during coal extraction – through monitoring, treatment and re-cycling. The ability to predict and manage mining induced water inflows and aquifer interference can significantly affect mining safety and economics, as well as the granting of approval and licenses for mining projects. The inflow of water requires modelling and validation of hydrogeological conditions in order to predict and manage mining impact and design.
Longwall equipment is generally acknowledged (supported by international benchmarking) as capable of delivering higher production tonnages that are current industry norms. Name plate output rates could readily achieve the 15MTPA target if equipment utilisation rates were increased. There are limiting factors specific to Australian mines that must be overcome as indicated in preceding discussion. Maintenance management research with the application of downtime analysis utilising artificial neural networks provides a significant opportunity for improvement in equipment availability.
Community Societal interaction aspects of high production mining operations are considered in a general licence to operate category. The impacts are variable and generally related to the proximity of and relations with the community. This is increasingly more important regardless of the mine’s location - driven by regulation and responsible corporate impetus on sustainability. The primary areas of concern include: subsidence, water resources, expansion in required infrastructure and Occupational Health and Safety.
Automation and communication systems are essential components for the successful implementation of many of the nominated categories and projects. Longwall automation provides the potential for enhancing operational characteristics of longwall faces and for removing or limiting personal exposure to hazards. Commercial application of the ACARP Longwall Automation project is currently underway and has not been considered as a research subject within this project, but must nevertheless be supported by all facets of the industry. There appears significant opportunities to integrate real-time monitoring, sensing and automation technologies into roadway developments, cutting profiles while traversing faults, service extensions (e.g. scissorveyors, ventilation) and strata monitoring and control.
Leading edge wireless communication hardware typically does not perform well in underground environments. The need to develop high speed, wireless, hardened (multiply redundant and physically toughened) intrinsically safe communications systems remains a priority. There are technologies emerging to support components of modern communications networks, however, a comprehensive development of mine-wide ad-hoc wireless communication networks linked to comprehensive sensor nets, would provide the industry with the same advantages of Ethernet based, realtime communications systems enjoyed by surface-based industries and urban communities for decades. The significant issues of infrastructure dependence, installation and maintenance, signal propagation and cost effective, practical intrinsically safe power systems for these networks remain unresolved.
There is significant scope for improvement in longwall productivity in Australian coal mines, regardless of seam thickness or mining configuration as demonstrated by the respective research categories and projects. Those project areas ultimately recommended reflect a culmination of researcher and operator collaboration as integral to future achievement. The top five recommended projects are:
- High Capacity Gas Drainage;
- Integrated Roadway Development Infrastructure;
- Real Time Maintenance Management System;
- Engineering Design; and
- Management of Adverse Geotechnical and Geological Conditions.
There are understandably minor differences in the agreed order of preference. In addition, a second group of projects is identified that would reduce the potential critical threats to longwall productivity – water use and recycling; aquifer disturbance; subsidence and Occupational Health and Safety (dust, heat & fatigue).