Mining Contract: Continuous Float Dust Monitor
This research proposes the design, fabrication, and testing of a continuous float dust monitor (CFDM) in both the laboratory and in a test coal mine setting, with the goal of optimizing the design to provide the necessary sensitivity, dynamic range, and battery lifetime. This instrument will measure the concentration of in-mine, airborne float coal dust in real time. This measurement is intended to be used as an input to an automated rock duster whereby the rock duster will vary the amount of inerting dust with respect to the concentration of explosive coal dust.
Contract Status & Impact
This contract is ongoing.
The airborne presence and surface accumulation of float coal dust in underground coal mines poses a serious safety hazard to miners. Unless inerted properly, float coal dust can be re-entrained and aerosolized into the airstream by the pressure wave of a methane explosion. To control float coal dust, mines apply inerting rock dust to achieve mixtures of at least 80% inerting material and 20% coal dust. Compliance with 30 CFR 75.403 requires that samples be taken from the mine roof and rib and sent off for analysis, which results in the percentage of incombustible material. After receiving these results, a mine will then know whether more or less rock dust is required.
A necessary input to an automated, programmable rock duster capable of distributing rock dust concentrations “on demand” is the concentration of float coal dust in real time; however, no sensor technology for this purpose currently exists. While instruments are available to measure coal dust in real time, these units are not intended to be used under the same conditions as a float dust monitor. Specifically, a float dust monitor must be able to measure both very low and very high (0–1,000 milligrams per cubic meter) concentrations of float dust. Because float coal dust has a larger size range than respirable mine dust (sub-75 microns compared to sub-10 microns), a sensor must be able to avoid dust losses within a unit’s internal components. It must also be robust against excessive dust loading associated with float coal and rock dust that will inevitably occur in a permanent sensor installation.
Under this contract, Akita Innovations is designing, fabricating, and testing a continuous float dust monitor in both the laboratory and in a test coal mine setting with the goal of optimizing the design to provide the necessary sensitivity, dynamic range, battery lifetime, and real-time responsiveness. After investigating more than five different measurement techniques, Akita has chosen to pursue a light transmission/extinction method using a multi-pass optical absorbance cell. A benchtop working prototype has been built and tested which exhibits excellent sensitivity and linearity when exposed to glass slides with various representative concentrations of float coal dust. Currently, a second more mobile prototype is under construction and scheduled to be tested at OMSHR’s simulated longwall section at the Bruceton Research Laboratory in Pittsburgh, PA.