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Mining Contract: Sensors for Automated Control of Coal Dust (SACCD)

Contract #200-2013-57155
Start Date9/17/2013
Research Concept

This contract proposes the development of wireless sensor technology using functional prototypes to continuously monitor underground coal mine surfaces to determine the ratio of rock dust to coal dust. Through in-situ, near real-time monitoring sensors and wireless communication, the rock dust coverage could be automated, thus greatly reducing response time for rock dusting and the chance of an explosion in an underground coal mine.

Topic Area

Contract Status & Impact

This contract is ongoing.

Underground coal mining operations produce finely divided coal dust (float dust) which can propagate an explosion. Limestone powder, known as rock dust, is widely used to inert coal dust to reduce explosion likelihood and to achieve compliance with mine safety regulations. To assist mine operators in monitoring the ratio of rock dust to coal dust on underground coal mine surfaces, OMSHR has developed the Float Dust Deposition Meter (FDDM) and the Coal Dust Explosibility Meter (CDEM). Building on these advances, improved methods that will address the problem of monitoring adequate rock dust coverage are now possible.

Under this contract, the University of California is developing small and inexpensive wireless sensors that can be deployed throughout the underground coal mine to monitor the coal and rock dust conditions. These devices would form an integrated wireless network that automatically measures the ratio of rock dust to coal dust and indicates when the ratio is below the explosibility threshold—i.e., when insufficient rock dust is present. The proposed approach will result in small sensors that would require little manual labor once placed in the mine, be capable of continuously monitoring large areas in multiple locations, produce real-time data that can be used to automate rock dusting equipment, and trigger alarm conditions when necessary.

To date, the contractor has developed a sensor test fixture with the following basic components: (a) a deposition plate with a mass sensing resonator, including in-situ humidity and temperature sensors; (b) a light-emitting diode (LED); (c) light-sensing detectors; and (d) housing for the low-power radio and supporting electronics. The probing LED directs an incident light beam onto the surface of the deposition plate and the reflected light is measured by a light-sensing detector at the same wavelength. The ratio of reflected light to incident light provides an estimate of the incombustible fraction of material deposited relative to calibration points. A reference beam allows for automatic compensation due to deposition of particles on the emitter or detector cover plates. Because the surface coatings are expected to be thick in underground mines, the collection surface will be periodically cleaned by a high-amplitude frequency pulse applied to “shake” a majority of the accumulated dust off the mass sensing and optical reflective surfaces.

Development continues on the design and testing of the wireless network as well as the investigation of candidate hardware for wireless communication. If this sensor development is successful and the results are proven to be effective in follow-up testing, there is good potential for a commercial product.