Development and commercial evaluation of laser-induced breakdown spectroscopy chemical analysis technology in the coal power generation industry

An instrumentation variation on laser-induced breakdown spectroscopy (LIBS) has been developed and applied in the operations of power generating companies utilizing low-ash lignite as the fuel source. The instrument design allows simultaneous determination of all detectable elements using a multiple spectrograph and a synchronized, multiple charge-coupled device (CCD) spectral acquisition system. The application of internal ratio analysis has enabled the development or a stable system that can be operated routinely for over a month without recalibration. Detection limits vary depending on the element but are typically on the order of 0.01%, by weight for heterogeneous materials such as the moist lignite used in these power stations. Independent testing of the instrument has shown good correlation between the routine LIBS analysis and the analysis of the coal via acid extraction techniques for key ash-forming elements. Testing over a one month period shows excellent correlation between the two methods for elements such as Al (R = 0.96) and Na (R = 0.92). The principle limitation is not the accuracy of the LIBS method but rather the inherent errors in sampling heterogeneous materials such as lignite. Because the LIBS analysis takes less than 30 seconds it has clear advantages over traditional methods used in elemental analysis for these materials.