温和条件下的低阶煤多级分离提质及其动力学研究

Low-rank coal dewatering, upgrading and multi-stage fractionation for poly-generationare are being more and more importantin in coal conversion in China. The conventional dewatering and upgrading methods of low-rank coal are high energy-consuming, and the multi-stage fractionation methods for poly-generation generally based on the technologies used for high-rank coal, such as pyrolysis and gasification.We are proposing a new dewatering, upgrading and multi-stage fractionation method targeted for low-rank coal, basing on the solvent extraction method developed by Prof. Miura. By this proposed method, the low-rank coal can be not only dewatered and upgraded,but also separated into several fractions by thermal extraction using recycled light fractions as solvent at rather mild conditions (< 350℃, < 4MPa). The total conversion is expected to be over 70%. The main fractions would be free from ash and moisture, have rather low oxygen and sulfur content and rather high heating value. Also, the fractions have different chemical and physical properties to each other, and can be used for different purposes. This research will start from designing a two-stage fix bed reactor targeted for low-rank coal upgrading and fractionation. The low-rank coal will be upgraded and separated into several fractions by non-isothermal extraction using recycled light fractions as solvent, and the treatment conditions will be investigated. Then, the kinetic model of this process will be developed and the mechanism of it will be studied. Our preliminary experiments showed a high possibility of this proposed method. A new upgrading and multi-stage fractionation method targeted for low-rank coal is expected to be developed.

低阶煤的脱水提质及多联产是我国煤炭加工转化的重点任务之一。目前低阶煤的脱水提质方法普遍耗能较高，分级转化多联产也主要以传统的高阶煤转化技术为基础，如热解和气化等，缺少有针对性的低阶煤分级转化方法。本项目在京都大学Miura教授提出的煤热溶剂萃取法的基础上，提出一种以低阶煤萃取物为萃取溶剂、萃取和提质分段进行的低阶煤多级分离提质方法。此方法无需添加溶剂、催化剂及氢气且条件温和（< 350℃、< 4Mpa），总转化率预计在70%以上。主要产物不仅无水无灰、低氧低硫、发热量高，而且被分成性质不同的若干组分，为实现低阶煤的多联产提供基础。本研究从设计一种针对低阶煤多级分离提质的两段式固定床反应装置开始，循环利用萃取物为溶剂把低阶煤分成若干组分并同时对其脱氧提质，考察此过程中各操作参数对产物收率及性质的影响规律，建立动力学模型，并对其做较深入的机理研究。我们的前期工作已经表明此方法可行性很高。

低阶煤的脱水提质及多联产是我国煤炭加工转化的重点任务之一，也是十三五的重要发展方向。目前低阶煤的脱水提质方法普遍存在耗能较高的问题，分级转化多联产也主要以传统的高阶煤转化技术为基础，如热解和气化等，缺少有针对性的低阶煤分级转化方法。本项目在京都大学 Miura 教授提出的煤热溶剂萃取法的基础上，提出一种以低阶煤萃取物为萃取溶剂、实现低阶煤的提质-多级分离的方法。此方法无需添加溶剂、催化剂及氢气且条件温和（ < 350℃、 < 4Mpa）。本项目主要从四个方面对本方法进行了较深入研究：1）低阶煤和生物质的热溶处理基本条件考察；2）热溶处理机理及动力学研究；3）溶剂循环的可行性及对产物性质的影响规律研究；4）热溶处理产物的利用，及煤的水热提质研究。研究发现，温度对低阶煤和生物质热溶提质效果影响较大，压力影响较小，水分对其产物收率有促进作用，发现热溶处理过程中煤或生物质发生了明显的脱氧反应，主要脱氧产物为CO2和水，萃取物氧含量低至8%左右，碳含量高达85%。通过前期研究，建立了煤或生物质热溶提质反应机理及动力学模型，计算发现不同处理温度下其主要转化途径不同。通过溶剂循环实验发现，低分子量萃取物可以作为溶剂循环使用，并且能促进其高分子量萃取物的收率及脱氧效果。另外，发现提质煤的燃烧特性优于原煤，其也可以作为更好的活性炭制备原料使用。本项目的研究不仅推动了低阶煤热溶萃取技术的实际应用进程，也为低阶煤的分质分级转化利用提供了一个新思路。