Determination Of Sulfur Content In Coal By X-ray Fluorescence Spectrometry

Coal is an important fuel for power generation in the world and the major source of primary energy in China.Sulfur is one of principal elements,which has a grate influence on its quality and clean utilization.However,some key issues,such as complication,long time and delaying result,should be improved for the existed methods.The aim of this thesis is to explore a novel method based on energy dispersive X-ray fluorescence spectrum(EDXRF)to determine total sulfur content in coals.A detailed test process of EDXRF was carefully examined.The effect of operational parameters on the propagation and detection of sulfur fluorescence was conducted,which mainly included voltage and current of the X-ray tube,light path atmosphere,and measuring time.The obtained results showed that the measuring time could be shortened to 60 s.Based on the chemical constitution of coals,powder tableting with boric acid was selected as the sample preparation method to deal with the difficulty in total sulfur content determination.Then,both linear regression analysis and partial least-square method(PLS)were used to establish the calibration curve after the collected spectra were pre-processed.YQ samples with large matrix differences were firstly examined.Compared to unary linear regression(ULR),multiple linear regression analysis(MLR)or PLS could significantly increase the accuracy of the analysis result.The R2 of the calibration curve increased from 0.4773 to 0.8866 by MLR method considering on the effect of proximate analysis data and fluorescence intensities of Fe,Ca,Cl and other elements on the S element in coal.Furthermore,the R2 of the calibration set and the validation set are both greater than 0.949 by PLS with the full spectra,which showed the predicted total sulfur contents in the major samples were within the range of ±0.35%by checked with the corresponding Coulomb titration method.Focusing on the blended coals with stable source in the coal-fired power plants of China,SC samples and blended ones with small matrix difference were tested by compared with the Coulomb titration method.The results showed that ULR or PLS had consistent analysis data within the error of±0.10%,whilst ULR with a good linearity for mixed coal samples,which identifed EDXRF method suggested in this thesis could be used for the determination of total sulfur content in coals with similar matrix.