褐煤水热提质改善水煤浆的成浆性、流变性和稳定性的实验研究

采用水热法对小龙潭褐煤进行提质处理,从煤质特性、含氧基团、表面亲水性和粒度分布等因素,探究了水热提质对褐煤水煤浆成浆浓度、流变特性以及稳定性的影响。结果表明,水热提质脱除了褐煤中的水分,氧含量降低,煤阶升高。水热提质脱除了褐煤中含氧基团,煤水表面接触角增大,褐煤表面亲水性得到改善。小龙潭褐煤颗粒粒度呈现双峰分布,水热提质后褐煤颗粒粒径减小且趋于规则。水热提质改善了水煤浆的成浆性能,成浆浓度由提质前的44.09%,最高可提升到61.94%。在相近的表观黏度下,水热提质后水煤浆的稠度系数K减小,流变指数n增大,水热提质在降低浆体黏度的同时,仍保持假塑性流体特征。水热提质降低水煤浆的析水率,延缓了浆体出现硬沉淀的时间,改善浆体的稳定性。水热提质从理化特性对褐煤进行深度改性,从而获得高浓度,假塑性以及稳定性良好的符合工业应用的水煤浆。

Hydrothermal dewatering of lignite to improve the slurry-ability,rheology, and stability of coal-water slurry

Xiaolongtan lignite was upgraded by hydrothermal dewatering (HTD). The main factors affecting slurry-ability of the lignite including coal property, oxygen functional groups, surface hydrophilicity, and particle size distribution were analyzed. The effect of HTD on solid concentration, rheology, and stability of the upgraded coal was also investigated. The results show that a substantial amount of moisture was removed, oxygen content decreased, and the coal rank was enhanced by HTD upgrading. The contact angle between coal and water increased after removal of oxygen functional groups by HTD, thereby improving surface property of the upgraded lignite. A typical bimodal distribution of the lignite particle size was observed. The mean particle diameter of lignite decreased and the lignite particles became more regular after HTD. HTD upgrading significantly improved slurry-ability of the lignite. The solid concentration of raw coal was 44.09%, while that of the upgraded coal after HTD increased to 61.94%. The consistency coefficient K decreased, while the rheological index n increased for the CWS prepared from the upgraded coals. HTD upgrading decreased the apparent viscosity, and maintained the shear-thinning behavior of pseudo-plastic fluid. Moreover, as the water separation ratio decreased and formation of hard sedimentation was delayed, stability of the CWS was enhanced after HTD upgrading. Overall, the physico-chemical properties of Xiaolongtan lignite were significantly modified after HTD, thus a high-quality slurry fuel with high solid concentration, superior pseudo-plastic behavior, and good stability could be achieved.