Coal Age

MAY 2017

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22 www.coalage.com May 2017 longwall usa 2017 continued the San Juan mine's successful experience operating an automated longwall face using new technology. Joe Defibaugh, engineer, dust and ventilation, Komatsu Mining Corp., will present Evaluation of Noise Controls for Longwall Cutting Drums. NIOSH has con- ducted research to develop noise controls for longwall mining systems. Previous research determined that the dominant sound-radiating components on a longwall shearer are the two cutting drums. There- fore, NIOSH developed numerical models of these drums to predict their dynamic and acoustic responses. Upon validation, the models were used to explore various noise control options including force iso- lation, increasing structural damping, and increasing the stiffness of the vanes. The most practical solution was to increase the stiffness by adding gussets, and to increase the thickness on the outermost helical vane plates. A set of modified drums were built and tested at a mine in New Mexico. Test results showed noise reduction across the entire frequency spectrum with overall noise reductions of around three decibels. Researchers with the Pittsburgh Re- search Laboratory (PRL) for NIOSH recent- ly constructed a 1:30 scale physical model of a portion of a longwall operation to sim- ulate the airflow characteristics along the face and along or through the gob. In their presentation, Applications of a Scaled Aero- dynamic Model for Simulations of Airflows in a Longwall Mine, they will discuss how the Longwall Instrumented Aerodynamic Model (LIAM), which was built with critical details of the face and face machinery, such as shearer, shields, conveyor belt etc., as well as a portion of the gob and the barrier pillars. LIAM is instrumented with pressure gauges, flow anemometers, temperature probes, a variable speed fan, and a data ac- quisition system to enable investigation of face, entry and gob flows for variable min- ing configurations. LIAM offers the flexibil- ity of carrying out tests for variable mining configurations such as bleeder/bleederless and exhausting/blowing ventilation sys- tems to supplement numerical modeling studies and mine site studies where field measurements may be limited. The LIAM design is described in detail and results are presented from a study of gob-face ex- changes, distribution of air at the critical face-tailgate air split, and airflow patterns in the gob for different caving character- istics. Scaling relationships were derived on the basis of Reynolds and Richardson's number to preserve the physical and dy- namic similitude by optimally scaling tur- bulent dispersion, pressure gradients, flow velocity, permeability, face dimensions, transit times and ventilation airflow. These results are compared to field data and pre- vious numerical modeling studies. The technical conference on Tuesday will conclude with Controlling Dust Concen- tration at a Longwall Face Through Applica- tion of a Flooded-bed Scrubber to a Long- wall Shearer. Sampurna Arya, a researcher with the University of Kentucky, will discuss a full-scale physical model of a Joy 7LS long- wall shearer, modified with an integrated flooded-bed scrubber, which was designed and fabricated at the University of Ken- tucky. The mockup was assembled and test- ed in the longwall dust gallery at the PRL for NIOSH. The test results indicate an average 68% dust reduction at the longwall face. The experimental results of the tests conducted at the PRL, as well as the validation of CFD simulations, will be presented. Mine Development & Planning The technical sessions reopen again Wed- nesday morning, June 14, at 9 a.m. Long- wall miners from CNX Resources (formerly CONSOL Energy) will unveil their plans for the Monster Wall. This presentation will ex- pand on the concepts, factors, restrictions and other considerations in lengthening the longwall face from 1,500 ft to 2,000 ft. Among other items, this presentation will answer why and cover: ventilation, devel- opment, production, equipment, mainte- nance and power requirements Robert Ochsner, chief engineer, Sig- nal Peak Energy, will present Ultra-length Longwall Panels: Critical Factors and Is- sues. Signal Peak Energy is the only under- ground coal mine in Montana and it start- ed longwall mining operations in 2009 and is presently mining its sixth panel. These panels are 1,250 ft wide and typically vary between 18,000 ft and 22,000 ft in length. Each panel typically has between 10 million and 14 million raw tons, and will operate from 12 months to 16 months. This presents several unique challenges, such as: • Ensuring the equipment is rebuilt for a complete panel without significant downtime or major exchanges; • Predictive analysis of wear prior to failures of components such as chain, flights, gearboxes and sprockets; and • Optimum shift and manpower sche- duling to optimize production and maintenance. This presentation will also address roof support asset management for optimizing the life of the reserve, as well as the use of face automation to maximize productivity. Australian longwall miners will present Longwall Top Coal Caving at the Broadmead- ow Mine. Few underground coal seams in the U.S. compare to those in Australia, such as the Goonyella Middle Seam, which is located in the Bowen Basin, Queensland, Australia. It is a source of high-quality metallurgical coal. The seam sub-crops in a north-south direc- tion at a depth of about 60 meters (m) or 200 ft and dips to the east at 5°-8°. Seam thickness varies from 5 m (16 ft) to 12 m (39 ft) with the average seam thickness in the current min- ing area being about 7.6 m (25 ft). The Broadmeadow mine was started using a longwall to extract coal at 4.7 m (15 ft) leaving the top section of the seam to fall into the gob. The adjacent open-cut mine has been mining the full seam sec- tion for more than 30 years. Investigations and evaluations were made into the Top Coal Caving method and its suitability for the operation. Longwall Top Coal Caving (LTCC) was introduced in 2012. The presentation will discuss the management of an LTCC face compared to a conventional longwall face and what was learned from both an operational and maintenance perspective. The authors will share their ideas on controlling dilution on the rear conveyor as well as their suc- cessful use of automation. In 2015, 40 longwall mines provided nearly 60% of the U.S. coal production from underground mining methods. This rep- resents a substantial, yet gradual increase from just under 50% over the last five years. As a result of this increased production share, the percentage of ground fall-relat- ed fatalities in longwall mines has also in- creased when compared to all U.S. under- ground coal mines. Additionally, about 80% of ground fall related fatalities have occurred in areas where the roof was supported. The Wednesday morning session will conclude with an Overview of Current U.S. Longwall Gateroad Support Practices. In an attempt to better understand the sta-

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