Determination of total sulfur content in coal by using energydispersive X-ray fluorescence spectrometry

Eschka method,Coulometric Titration method,High Temperature Combustion method and Infrared Spectroscopy method have been used to determine the total sulfur content in coal by Chinese national standards,which have several shortcomings,such as more chemical reagents consumption and complicated operating procedure. Based upon Energy Dispersive X-Ray Fluorescence ( EDXRF) spectrometer, a rapid, reliable and non-destructive method has been developed for determining the total sulfur content in coal. As a relative analysis method,EDXRF obtains the total sulfur content in any coal by comparing the spectra with those of known samples. The preparation procedure of samples was explored,and the measuring conditions were selected for determining the sulfur content in coal. A reasonable calibration curve was suggested after sample data collection,spectral pretreatment and matrix correction. Experimental results show that smooth and unbreakable tablets are obtained by employing powder tableting with boric acid as adhesive at 12 MPa for 40 seconds. 13 kV and 800 μA are reasonable voltage and current,respectively. A vacuum device adopted in this study can reduce the scattering caused by light matrix as well as the absorption of sulfur’s characteristic X fluorescence line by air. The matrix effect can be corrected by using the empirical coefficient method together with small particle size. The resolution of selected spectra is enhanced and the accuracy of measured data is improved when smooth method is used for pretreatment procedure. The method suggested in this study could shorten the measuring time to 60 seconds and R2 is 0. 996 3 for the correction curve. EDXRF data from 10 random samples are consistent with Coulomb Method except two of them. The relative standard deviation (RSD) of the reproducibility and repeatability tests are respectively 3. 21% and 1. 57% for ultra-low sulfur coal samples,whilst 0. 56% and 0. 47% for lowmedium sulfur coal ones,0. 26% and 0. 22% for medium-high sulfur samples.