煤炭是保障我国能源安全的压舱石和稳定器。随着优质煤炭资源的消耗,低品质煤的利用逐渐占据主导地位。高含水低品质煤储量大,水分含量高,降低了其后续利用效率。煤炭干燥可有效降低煤炭水分,提高煤炭质量,促进高含水低品质煤的清洁高效利用。将煤中水分按照赋存的位置和性质进行总结分类;综述了煤中孔隙结构和含氧官能团的分类及干燥过程对煤炭物理化学结构的影响,进而分析了煤物理化学结构对水分脱除和复吸的影响。结果表明,小孔隙中的水分和以氢键形式结合的水分较难脱除,干燥后孔隙体积和含氧官能团的减少可有效抑制水分复吸,煤炭的着火温度受煤种和水分的影响,应合理控制干燥温度上限防止煤炭在干燥时过热燃烧。综述了目前蒸发干燥脱水技术的应用现状,包括滚筒干燥、低温蒸汽干燥、流化床干燥、振动混流干燥、微波干燥等干燥方式,对不同干燥方式进行对比评价,并对未来干燥脱水技术的研究方向进行探讨,其中热烟气干燥设备结构简单、处理量大,但干燥过程需严格控制含氧量,安全性相对较低,微波干燥具有选择性加热的优势,干燥速率快,但干燥后期可能出现热失控,目前主要处于实验室/中试研究阶段;用蒸汽作为干燥介质的干燥技术安全性较高且无废水废气排出,具有能耗低、安全性高特点,可进一步研究蒸汽温压瞬态脱水技术,解决宽粒级煤炭的安全高效脱水提质。

Coal is the ballast and stabilizer for ensuring China′s energy security. With the depletion of high-quality coal resources, the utilization of low-quality coal has gradually taken the lead. Low-rank coal reserves are large and have high moisture content, which reducesits subsequent utilization efficiency. Coal drying can effectively reduce coal moisture, improve coal quality, and promote the clean and efficient utilization of high water content low quality coal. The moisture in coal was summarized and classified according to the location andnature of the storage. The classification of the pore structure and oxygen-containing functional groups in coal and the influence of the drying process on the physicochemical structure of coal were reviewed, and the influence of the physicochemical structure of coal on the removal and reabsorption of moisture was then analyzed. The results show that the moisture in small pores and the moisture bonded in theform of hydrogen bonding are more difficult to remove, and the reduction of pore volume and oxygen-containing functional groups after drying can effectively inhibit the moisture reabsorption, and the ignition point of coal is affected by the type of coal and the moisture content,and the upper limit of the drying temperature should be reasonably controlled to prevent overheating and combustion of the coal during drying. The current application status of evaporation drying and dehydration technology was summarized, including drum drying, low-temperature steam drying, fluidized bed drying, vibration mixed-flow drying, microwave drying and other drying methods, and different drying methods were compared and evaluated, and the research direction of future drying technology was explored. The structure of the hotflue gas drying equipment is simple, the processing capacity is large, but the drying process needs to strictly control the oxygen content,and the safety is relatively low. Microwave drying has the advantages of selective heating and fast drying rate, but it may have thermal runaway in the late stage of drying, and it is mainly in the laboratory/ pilot research stage at present. The drying technology using steam as theheat medium has high safety and no waste water and exhaust gas discharge, with low energy consumption and high safety features, and canbe further researched on steam transient drying technology, to solve the safety and high efficiency dewatering and quality improvementof coal with wide grain size.

0 引言

1 高含水低品质煤含水机理

   1.1 高含水煤水分赋存

   1.2 高含水煤物理化学结构特性

   1.3 物理化学结构对水分赋存的影响

2 煤炭干燥技术

   2.1 煤炭干燥机理

   2.2 典型干燥技术

3 结语及展望