The analysis of coal is demonstrated, with specific emphasis on the measurement of Na₂ O, using a Cartesian geometry energy dispersive X-ray fluorescence (EDXRF) spectrometer employing the Fundamental Parameters (FP) approach.

During the mining, processing, and burning of coal, process monitoring and control are vital to the efficiency and quality of the final product. Whether screening incoming raw materials, monitoring production processes, or QA/QC out-processing, a fast, simple, and accurate method for analyzing samples is important throughout the production cycle. Specific attention is often given to the sodium content (Na₂O). High sodium content can combine with sulfur or aluminum and silicon to form sodium sulfate or sodium alumina-silicate compounds. Such compounds, formed when burning high sodium coals, can lead to fouling of the cyclone or heat exchange surfaces. Cartesian geometry EDXRF spectrometry is demonstrated to meet the challenge of analyzing low sodium coals.

Experimental

Figure 1: Rigaku NEX CG EDXRF spectrometer.

Known (previously assayed) coal samples were ground, using a ball mill, to a homogeneous dry powder of <200 mesh (~75 µm grain size). The powder was then converted into a pellet using a hydraulic press at 20 tons pressure. Measurements were made, under vacuum conditions, using a Rigaku NEX CG Cartesian geometry EDXRF spectrometer (see Figure 1) equipped with polarization and secondary excitation targets. Total analysis time was 1400 s per sample.

Results

Results presented were based on the proprietary Fundamental Parameters (FP) software package developed for the Rigaku NEX CG Spectrometer. The RPF-SQX pellet FP template uses an advanced "scattering FP" program that automatically deconvolutes spectral peaks and models the sample matrix using fundamental X-ray fluorescence (XRF) equations.