Quantitative Study Of Fe,Ca,Al In Coal Using Laser-Induced Breakdown Spectroscopy

Coal quality analysis is concerned by power plants all the time. The mineral elements content in coal (eg. alkali metal, Fe, etc.) is an important parameter affecting deposition,slagging and contamination of heating surfaces. The element composition of coal could be used to calculate combustion heat, principal combustion temperature, the constituents of combustion product and thermal equilibrium,and it is one of the most necessary data for thermal calculation and combustion adjustment of boiler.The available mineral elements contents using traditional methods should transfer coal to ash, which is troublesome and time-consuming. A brief introduction and comment of typical fast element analysis technologies were given, and a new method——laser-Induced Breakdown Spectroscopy(LIBS)——was proposed for fast analysis of coal. Firstly, the principle and characteristics of LIBS was introduced, meanwhile, the generation and influence of continuum background occurred in laser plasma was analyzed, and then the quantitative calibration model was presented.The LIBS experimental set-up was described in details. Theoretically, two physics parameters, i.e. plasma temperature T and electron density N e, which affected spectra intensity significantly in theory, were expatiated and validated by experiments of choosing coal samples. The values of plasma temperature T and electron density N e were obtained through the gained coal spectra.Six representative coal samples were selected for quantitative analysis, which was analyzed by traditional method prior to experiments. Spectra were obtained and qualitatively analyzed first, the results then compared with the published literatures, which give reasonable qualitative results. In order to get further quantitative analysis, the calibration curves of Al,Ca,Fe were constructed by spectra and chemical analysis results At the same time, a method of how to determine the upper limit of linear calibration range was proposed. A test coal sample of unknown composition was analyzed utilizing calibration curves, subsequently; the results were compared with traditional method, which showed closely consistent between LIBS and traditional method, therefore, it validated that LIBS is capable of coal analysis.Finally, a summarization was given and the suggestion and prospect were proposed for the fast analysis of coal.