Two dimensional 1H magnetic resonance relaxometry-based analyses of Argonne premium coals. (15th October 2021) - Guo, Jiangfeng
Highlights: T 1 - T 2 * and T 1ρ - T 2 * relaxometry are used for 1 H identification of coal rank. High rank coals contain an abundance of crystallite structure based on Sinc Gaussian 1 H FID. Insight into the change of coal during low temperature oxidation using 2D 1 H MR relaxometry. T 1 - T 2 * technique provides 1 H content evaluation of coal. Abstract: 1 H magnetic resonance (MR) is a useful technique for determining molecular structure of coals. Most previous MR studies were based on one-dimensional 1 H magnetic resonance relaxometry. Two-dimensional (2D) 1 H magnetic resonance relaxation correlation methods, T 1 – T 2 * and T 1ρ – T 2 *, were used to evaluate Argonne premium coals, including Beulah-Zap (BZ), Wyodak-Anderson (WA), Pittsburgh #8 (PIT), Upper Freeport (UF), and Pochontas #3 (POC) coals as received. Samples were also measured after oxidization at low temperature (110 and 210 °C). From the 2D relaxation correlations, various hydrogen-containing components were distinguished and characterized. The change of hydrogen during low temperature oxidation was analyzed, and the hydrogen content estimated. The technique captured significant differences between low rank coals (BZ and WA) and high rank coals (PIT, UF, and POC). The order of T 1 / T 2 * ratios is aliphatic hydrogen > aromatic hydrogen > hydrogen- and oxygen-containing functional groups > moisture in BZ and WA coals. The PIT, UF, and POC coals mainly contain aromatic hydrogens. The T 1 – T 2 * and T 1ρ – T 2 * spectra of BZ and WA coals change significantly during low temperature oxidation. Our new MR method provides new insight into coal behaviour.