Published in the December 2009 Coal USA Magazine
Highwall mining actually preceded the start of underground operations at the southern Illinois property, with crews pulling coal from the first hole in August 2005.
The operation uses a Superior Highwall Miner, adapted by the OEM with a Joy 1415 mining head. The unit primarily cuts into the Illinois Herrin #6 seam.
Average hole depth for the highwall is a penetration of 800-850ft, with the latter KHC’s typical maximum coal per its mine plan. It aims to produce from one hole per day, with the miner retracted within 12-14 hours and set up for the next hole.
In operation, the Prairie Eagle highwall averages 2600-3000t per hole and has budgeted 25 tons a month, or 300,000 tons per annum.
Prairie Eagle’s reserves are expected to be depleted within the next 2-3 years, but there are plans to move the miner to a different field for its next phase following that mothballing
After coal is pulled from the seam, which averages 72in under about 100ft of overburden on 6ft pillars, it is loaded by WA 600 FEL into trucks from the machine’s rear discharge.
Because little storage is available near the unit on its current plan, it loads output for hauling to the prep plant within hours of cutting.
The creation of bottlenecks is a problem the company seeks to avoid.
“Bottlenecking and holing into previous mined holes are two situations of major concern as they can lead to reduced production, sterilization of reserve, and worse, sticking and losing the mining head,” management noted.
“KHC takes great effort in understanding the geology as we are mining the holes to make sure the we anticipate uplifts/shear/faulting as holes are advanced [and] similarly, [the company] identifies areas, through operating pressures and operational data, where roof conditions are poor.”
The producer works to skip around the voids as well as limit hole depths and monitor the areas closely so that bottlenecks can be avoided.
“To address holing in, KHC puts great effort into lining the machine up parallel to previous holes on each and every hole mined,” Winter noted.
“This is accomplished through survey of machine placement and through precise measurement of machine movement and placement when setting the machine up for mining.”
The highwall is staffed by four experienced individuals – a miner operator, groundman, beam loader and coal leader, all part of a Holmes Safety Award winning surface operation crew at Prairie Eagle – on each of the highwall’s two shifts.
While work on the active area hasn’t always been smooth sailing, crews and management have worked together to overcome challenges.
“KHC is fortunate to have a hard-working, safe, and smart workforce,” management said.
“This has been a key ingredient in our current as well as ongoing success.
“KHC and its employees work together to make this a great place to work now and certainly well into the future.”
