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Development of an Apparatus for On-Line Analysis of Unburned Carbon in Fly Ash Using Laser-Induced Breakdown Spectroscopy (LIBS)

Volume 65, Number 7 (July 2011) Page 790-796

LEI ZHANG,* WEIGUANG MA, LEI DONG, XIAOJUAN YAN, ZHIYU HU, ZHIXIN LI, YONGZHI ZHANG, LE WANG, WANGBAO YIN,* and SUOTANG JIA


The level of unburned carbon in fly ash is an important criteria for evaluating the combustion efficiencies of boilers, as well as the commercial value of the produced fly ash. In this work, an automated prototype laser-induced breakdown spectroscopy (LIBS) apparatus comprising an isokinetic sampler, a sample preparation module, and a LIBS module has been developed for possible application to power plants for on-line analysis of unburned carbon in fly ash without being affected by the type of coal burned. Emphasis is placed on the structure and operation of the LIBS apparatus, the optimum suction capacity selection, the analytical methods for estimation of the exact C line intensity, and the proper calibration model established for minimizing the matrix effects, which enable the minimization of matrix effects and obtaining more accurate compositional measurements. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The measurement accuracy presented here for unburned carbon analysis is estimated to be 0.26%, while the average relative error is 3.81%.

Index Headings: Laser-induced breakdown spectroscopy; LIBS; Unburned carbon; Fly ash; Isokinetic sampler; Suction capacity; Matrix effects; Multivariate regression calibration model.