Abstract

The hydrophilic surface and developed pore structure restricted the application of abundant low rank coals (LRC) for the preparation of coal water slurry (CWS) with high concentration. In this work, emulsified asphalt was applied as an effective and low cost modifier to modify coal surface and improve the slurry making performance of LRC. The successful modification was verified by various technologies, such as chemical titration, X-ray photoelectron spectroscopy (XPS) and Zeta potential measurements. The results revealed that the oxygen containing groups located at LRC surface were covered by emulsified asphalt, which further caused the decrease of Zeta potential. The influence of modification on wettability of coal was also evaluated by contact angle and moisture re-adsorption. It showed that the hydrophobicity of LRC significantly increased, which is accompanied with the reduction of inherent moisture. Besides, the results of nitrogen adsorption and scanning electron microscope (SEM) verified that the hydrophobic layer formed by emulsified asphalt blocked the pores of LRC. The modified LRC also exhibited better adsorption ability to the widely used anionic dispersant naphthalene sulfonate formaldehyde condensate (NSF) than that of raw coal (RC) and microwave dehydration coal (MDC). Anyhow, modified LRC possessed the characteristics as high rank coal. Afterwards, modified coal was applied to prepare CWS. The results showed that CWS prepared by modified LRC exhibited superior slurry making performance as compared to RC and MDC. The surface modification reduced the inherent moisture and promoted the adsorption of dispersant, which increased the free water amount and enhanced electrostatic repulsion and steric hindrance among coal particles. Accordingly, the maximum concentration for CWS increased, and the static stability enhanced.

摘要

亲水表面和发达的孔隙结构限制了丰富的低阶煤（LRC）在制备高浓度水煤浆（CWS）中的应用。在这项工作中，乳化沥青被用作一种有效且低成本的改性剂来改性煤表面并改善 LRC 的制浆性能。通过化学滴定、X 射线光电子能谱 (XPS) 和 Zeta 电位测量等多种技术验证了成功的修饰。结果表明，位于LRC表面的含氧基团被乳化沥青覆盖，进一步导致Zeta电位降低。改性对煤润湿性的影响也通过接触角和水分再吸附来评估。这表明 LRC 的疏水性显着增加，这伴随着固有水分的减少。此外，氮气吸附和扫描电子显微镜（SEM）的结果证实，乳化沥青形成的疏水层堵塞了LRC的孔隙。改性后的 LRC 对广泛使用的阴离子分散剂萘磺酸盐甲醛缩合物 (NSF) 也表现出比原煤 (RC) 和微波脱水煤 (MDC) 更好的吸附能力。总之，改性LRC具有高阶煤的特性。随后，改质煤被用于制备水煤浆。结果表明，与 RC 和 MDC 相比，由改性 LRC 制备的 CWS 表现出更优异的制浆性能。表面改性降低了固有水分，促进了分散剂的吸附，增加了游离水量，增强了煤颗粒间的静电斥力和空间位阻。因此，CWS 的最大浓度增加，静态稳定性增强。