Use of a Directional Spray System Design to Control Respirable Dust and Face Gas Concentrations Around a Continuous Mining Machine

Abstract

A laboratory study assessed the impacts of water spray pressure, face ventilation quantity, and line brattice setback distance on respirable dust and SF6 tracer gas concentrations around a continuous mining machine using a sprayfan or directional spray system. Dust levels were measured at locations representing the mining machine operator and the standard and off-standard shuttle car operators, and in the return airway. The results showed that changes in all three independent variables significantly affected log-transformed dust levels at the three operator sampling locations. Changes in setback distance impacted return airway dust levels. Laboratory testing also identified numerous variable interactions affecting dust levels. Tracer gas levels were measured on the left and right sides of the cutting drum and in the return. Untransformed gas levels around the cutting drum were significantly affected by changes in water pressure, face ventilation quantity, and setback distance. Only a few interactions were identified that significantly affected these concentrations. Gas levels in the return airway were grouped by face ventilation quantity. Return gas levels measured at the low curtain quantity were generally unaffected by changes in water pressure or curtain setback distance. At the high curtain quantity, return airway gas levels were affected by curtain setback distance. A field study was conducted to assess the impact of these parameters in an actual mining operation. These data showed that respirable dust levels may have been impacted by a change in water pressure and, to a lesser extent, by an increase in curtain setback distance. A series of tracer gas pulse tests were also conducted during this study. The results showed that effectiveness of the face ventilation was impacted by changes in curtain flow quantity and setback distance. Laboratory testing supported similar conclusions.

Determining the Spatial Variability of Personal Sampler Inlet Locations

“…The first method used NIOSH's PRL full-scale continuous miner gallery (7) and three prototype PDMs, (8) which were mounted onto a modified backpack frame, and the inlets were then positioned at the miner's cap lamp, nose, and lapel. The test gallery was filled with coal dust at typical mine levels, and airflows were generated to simulate a continuous miner section.…”

Best practices for dust control in coal mining, second edition.

“…However, from a dust control perspective, turbulence created by high-pressure sprays can result in dust rollback toward the CM operator. NIOSH laboratory testing evaluated the spray fan system while simulating a deep cut face at two operating pressures (70 and 190 psi), two face airflow quantities, and two curtain setback distances [Goodman and Pollock 2004]. Results showed higher CM operator dust levels at the higher operating pressure for all test conditions.…”

Design of a water curtain to reduce accumulations of float coal dust in longwall returns

“…However, for FCD controls to be effective, they must remove dust from the airstream. There have been extensive studies focused on understanding the effects of specific factors, such as operating pressure, orientation, ventilating airflow, droplet size, and spray nozzle type, on the knockdown performance of sprays in the presence of respirable dust [ 7 – 13 ]. While these factors have been shown to directly control droplet size, droplet frequency, and velocity, which affect the collision efficiency of the system, these findings needed to be verified with respect to FCD particles.…”