低阶煤热溶萃取提质-多级分离过程中循环溶剂与煤的交互作用机理研究

The utilization of low-rank coals in China has been paid more and more attention, especially its multi-stage conversion and utilization being considered a promising method. However, the high water and high oxygen content, low calorific value of the low-rank coals lead to its quite low thermal conversion efficiency. Recently, the proposed degradative solvent extraction method by the domestic and foreign scholars is an effective approach to achieve the dehydration, deoxygenation, and multi-stage separation of low-rank coals, and the obtained coal extracts have many applications. However, the complicated process, high cost and energy consumption of the separation between the solvent and the extracts has long been the bottlenecks of this technology. Therefore, the effective separation of the extract and the solvent, and the solvent’s recycling are the keys to the development of this degradative solvent extraction method. To solve the existing problems, the applicant team put forward the solution named "low-molecular-weight extract as part of the recycling solvent", and the feasibility of this solution has been preliminarily verified. Based on previous studies, this project will in-depth investigate the influence of the key physical parameters on degradative solvent extraction of low-rank coals, the evolution of the low-molecular-weight extract's physical and chemical properties during the cycling process, the influence of the physical and chemical properties of the solvent, and the mechanism of interaction between low-molecular-weight extract and the solvent. It is hoped that this project will further improve the feasibility of degradative solvent extraction of low-rank coals and provide a new method for multi-stage conversion and utilization of low-rank coals in China.

我国低阶煤的利用越来越受到重视，特别是其分质利用（多联产）被认为是很有前景的利用途径。但是由于其高水高氧含量、低热值等缺点导致其热转化利用效率低。近年国内外学者提出的低阶煤热溶萃取技术是对其脱水脱氧提质、多级分离的有效途径之一，所得的多种产物可在多个领域得到广泛应用。但是此技术发展的瓶颈在于萃取物与溶剂的分离过程复杂、能耗大、成本高。所以，实现萃取物与溶剂的有效分离及其循环利用是低阶煤热溶萃取技术发展的关键。基于此，申请人团队提出了“低分子量萃取物作为部分溶剂循环利用”的解决方案，并已经对此方案的可行性做了初步验证。本项目在前期研究的基础上，对低阶煤关键物性参数对其热溶萃取的影响机理，循环过程中低分子量萃取物自身物化特性的演变机制、对溶剂物化特性的影响规律、及其与煤的相互作用机理进行深入研究。希望通过本研究进一步提高低阶煤热溶萃取技术的可行性，为我国低阶煤分质分级转化利用提供一个新思路。

低阶煤的分质利用是很有前景的利用途径。但是由于其高水高氧含量、低热值等缺点导致其热转化利用效率低。低阶煤热溶萃取技术是对其脱水脱氧提质、多级分离的有效途径之一。但是此技术发展的瓶颈在于萃取物与溶剂的分离过程复杂、能耗大、成本高。所以，实现萃取物与溶剂的有效分离及其循环利用是低阶煤热溶萃取技术发展的关键。基于此，申请人团队提出了“低分子量萃取物作为部分溶剂循环利用”的解决方案。. 本项目在前期研究的基础上，对低阶煤关键物性参数对其热溶萃取的影响机理，循环过程中低分子量萃取物自身物化特性的演变机制、对溶剂物化特性的影响规律、及其与煤的相互作用机理进行深入研究。希望通过本研究进一步提高低阶煤热溶萃取技术的可行性，为我国低阶煤分质分级转化利用提供一个新思路。. 结果表明，煤种能影响产物的收率，但对目标萃取产物SL和DP的元素组成和化学结构无明显影响；溶煤比降低至6之前，对目标产物的收率和特性无明显影响，但进一步增大煤的比例会影响分散效果，降低目标产物收率；增大原煤中的水分能提高热溶萃取过程的萃取能力，且几乎不影响目标产物SL和DP的品质。因此，热溶萃取过程不需要进行干燥处理，从而降低成本。洗油中60%左右为甲基萘，其作为溶剂获取的产物特性与一甲基萘作为溶剂时的产物特性高度相似。并且，由于洗油中存在极性较强的有机物，因此能进一步提高萃取率，是一种理想的替代品。此外，将溶剂循环使用后，产物特性无明显改变，收率上SL会向高值的DP发生转变，但两者之和几乎无明显变化，符合项目预期。. 解决溶剂回收困难、能耗高的问题是低阶煤热溶萃取技术发展的关键。本项目针对上述问题，提出“低分子量萃取物作为部分溶剂循环利用”的优化方案。对优化方案的核心科学问题“循环过程中低分子量萃取物与煤的相互作用机理”进行深入研究。本研究可以进一步推动低阶煤热溶萃取技术的实际应用，为我国低阶煤分质分级转化利用提供一个新思路。