ABSTRACT

Lignite with high moisture content needs to be dried. The variations of internal and external water of Mindong lignite during microwave drying were studied. The effects of coal particle size (<0.2 mm, 1–4 mm, 8–12 mm) and target moisture content (20%, 15%, 10%) on the moisture re-absorption characteristics of dried samples were analyzed. It was found that microwave heating quickly removes the moisture of lignite, showing an exceptionally positive effect on the removal of internal water. During the drying process, the pore volume of lignite first decreases and then increases, while the content of oxygen-containing functional groups such as hydroxyl and carboxyl group on the surface of lignite decreases. When dried lignite is under a normal atmosphere, lower moisture content and smaller particle size lead to more water to be reabsorbed; The external water contents of coal samples (8–12 mm) with target moisture content of 20%, 15% and 10% are 5.45%, 5.44% and 5.21%, respectively, which shows the similar external water content. The experimental results are conducive to exploring the moisture migration path during drying and re-absorption of dried lignite. Considering the balance of drying and re-absorption, microwave drying of lignite should have optimum target moisture contents and material particle sizes, depending on the specific conditions and requirements. The research provides theoretical guidance for the industrial application of lignite drying.

摘要

水分含量高的褐煤需要干燥。研究了闽东褐煤微波干燥过程中内部和外部水的变化。分析了煤颗粒尺寸（<0.2 mm，1-4 mm，8-12 mm）和目标水分含量（20％，15％，10％）对干燥样品的水分再吸收特性的影响。已经发现，微波加热快速去除褐煤的水分，对去除内部水表现出异常积极的作用。在干燥过程中，褐煤的孔体积先减小然后增大，而褐煤表面上的含氧官能团如羟基和羧基的含量减少。当干燥的褐煤在正常气氛下时，较低的水分含量和较小的粒度会导致更多的水被吸收。目标水分含量为20％，15％和10％的煤样品（8–12 mm）的外部含水量分别为5.45％，5.44％和5.21％，显示出相似的外部含水量。实验结果有助于探索干燥褐煤在干燥和再吸收过程中的水分迁移路径。考虑到干燥和再吸收的平衡，褐煤的微波干燥应具有最佳的目标水分含量和物料颗粒尺寸，具体取决于特定条件和要求。该研究为褐煤干燥的工业应用提供了理论指导。实验结果有助于探索干燥褐煤干燥和再吸收过程中的水分迁移路径。考虑到干燥和再吸收的平衡，褐煤的微波干燥应具有最佳的目标水分含量和材料颗粒尺寸，具体取决于特定条件和要求。该研究为褐煤干燥的工业应用提供了理论指导。实验结果有助于探索干燥褐煤干燥和再吸收过程中的水分迁移路径。考虑到干燥和再吸收的平衡，褐煤的微波干燥应具有最佳的目标水分含量和物料颗粒尺寸，具体取决于特定条件和要求。该研究为褐煤干燥的工业应用提供了理论指导。