Engineering & Mining Journal

JUN 2013

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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O N L I N E A N A LY S I S tent at a given PRB mine, there can be enough variation, especially in today's highly competitive market, to warrant an online analyzer to monitor and respond to real-time trends. This mine has two adjacent truck dumps from where the coal is transported directly to the four loadout silos by a 60-in. conveyor at rates of 3,000 to 6,000 t/h. A two-stage sweep-arm sampling system is installed on this belt to determine the coal quality entering the silos. Physical samples are taken every three to four hours and subjected to both quick and ASTM analyses. The quick analysis results (sulfur, ash, moisture and Btu/lb) are available approximately three hours later. The ASTM results arrive up to 24 hours after the sample was taken. For the mine to respond to even the quick analysis, it is reacting to data that is on average almost five hours old. The need for online analysis was clear. Not only could a coal analyzer provide prompt coal quality data to pit operations for corrective action, it could also give the control room operator advance warning of impending problems in satisfying the contract specs of an upcoming train. Moreover, not only was the quick lab analysis not really all that quick, it also failed to include an analysis of the Na2O fraction in the ash, itself a criterion for rejecting a train. A New Solution The new online analyzer that this mine decided to test could not only detect the low levels of Na2O that other online analysis technologies cannot, but it could also measure moisture directly, without having to make any assumption of bound moisture levels, as microwave moisture meters must. The analyzer itself operates on a sample stream; hence, the logical location for the unit was in the vicinity of the existing sampling system, where a sample could be routed to the analyzer. (See Figure 2). There are actually two technologies deployed in the Progression Titan CCA: Magnetic Resonance (MR) and Laser Induced Breakdown Spectroscopy (LIBS). MR has always held promise for online moisture measurement; the challenge was designing an analyzer that could incorporate an analysis chamber small enough for MR to operate. The Titan CCA does just that with its 1.2-in. Figure 4: Block diagram of the Titan CCA. diameter analysis chamber. The use of LIBS for online elemental analysis wasn't entirely new, with an Israeli company having done trials in South Africa a few years ago without commercial success. The Titan CCA's LIBS analysis, in contrast, has shown excellent ability to do elemental analysis. Magnetic Resonance operates by the rapid application and removal of Radio Frequency (RF) electrical pulses within a magnetic field. The technology is equivalent to receiving a full body MRI at a hospital—the difference being the analyzer returns spectroscopy data while the hospital MRI returns images. This phenomenon provides precise Figure 5: Titan CCA–PRB installation. (Photo: Amy Donle) hydrogen proton measurements leading to very accurate moisture measurement and hydrogen proton inputs into the calorific value determination. LIBS operates by focusing a laser into a second analysis chamber and analyzing the spectrum of the vaporized material (See Figure 3). Not only can LIBS achieve accuracies comparable to those of other elemental analysis technologies (primarily PGNAA) for sulfur and the six major ash Figure 6a: Titan CCA moisture performance. JUNE 2013 • E&MJ 93

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