Top of Coal Detection in a Rotary Air Blast Drill Rig

Accurately detecting the approaching top of a coal seam prior to blasting is fundamental to efficient coal recovery.  Previous investigations by member mining companies reported a 66% reduction in coal dilution through disciplined and detailed overburden drilling and blasting practices.

With support from the Australian Coal Association Research Program (ACARP), Mining3 has developed a novel concept for detecting Top of Coal (TOC) whilst drilling in Rotary air blast over-burden blast-hole drill rig.

The method of detecting TOC while drilling brings significant benefits to surface mining operations, including the:

· Reliable indication of the approach to TOC enabling drilling to be stopped before touching coal or at a minimum standoff distance;

· Increased production by reducing damage to coal from blasting;

· Providing strata recognition and mapping during routine blast hole drilling.

The project was guided by a steering committee, including appointed industry monitors Kirk Henderson (Peabody Coal), Vishwa Bhushan (RTCA) Steve Simmons (AAMC) and Andrew Denman (BHP). The enthusiastic and generous contribution of both Hughes Drilling and Jellinbah East mine in north Queensland which provided assistance, support, equipment and a site for a field trial is acknowledged and greatly appreciated.

The aim of the TOC detection project is to demonstrate a prototype Measurement While Drilling system that can detect approaching TOC while performing routine drilling of blast holes in a Rotary air blast drill rig. Benefits of the system are:

· Increased production by reducing damage and dilution to coal from blasting;

· Increased knowledge of overburden strata to inform better blast design;

· Improved productivity, time savings and expense of drilling and/or logging holes just to map the top of coal if the same or better information is produced during production drilling;

· Provide information that will assist with drill automation; and

· Enable other coal dilution technologies such as blast-hole slotting.

The ability to detect approaching Top of Coal would revolutionize blast hole drilling, leading to a significant reduction in coal loss and dilution.

Related previous ACARP project reports, also available from the ACARP website, are C19023 and C21005.