Research On Functional Groups And Moiture Re-absorbing Characteristics Of Lignite Via Thermal Upgrading

Energy consumption in China is growing sharply with the fast development ofeconomy in recent years. However, the reserve of non-renewable energy, especially for thehigh rank coals, is decreasing seriously with the huge consumption every year. At the sametime, the increasing of the exploitation cost of high rank coal resource is also serious.Therefore, people have to focus on the exploitation and utilization of low rank coal, such aslignite, which have a large amount of reservation in China. Lignite thermal upgrading isone of the technologies which are beginning to be widely used fur lignite utilization.Two typical coals from different coalmines, Shengli (SL) in Inner Mongolia andZhaotong (ZT) in Yunnan province，were studied in this article. The surface functionalgroups of different lignite were identified before and after upgrading. The moisturere-absorbing characteristics of upgrading coal was investigated based on the analysis ofoxygen-containing functional group. The results show that the aliphatic structure mainlybreaks down at low temperature range below400℃，while aromatic structure mainly cracksand polycondenses at high temperature range above400℃. The three major typies ofoxygen-containing functional group-OH, C=O and-O-effect the moisture re-absorbingcharacteristics of lignite differently，of which,-OH and C=O have big influence on it.Theatmosphere and temperature are the main factors that affect the distribution of functiongroups and re-absorption characteristics for upgraded coal in the process of upgrading. Theamount of oxygen functional groups decreased with the increasing of temperature, whichcaused the reduction of water re-absorption ratio. Part of the aliphatic structure could beoxidized at low oxygen atmosphere resulting in the increase of oxygen-containing functiongroups as well as re-absorption rate at the same upgrading temperature. With the adding ofethanol, the function groups of–OH decreased remarkably. The water re-absorption rate (>400℃) of upgraded coal obtained from organic atmosphere is obviously lower than theother two atmospheres.This paper studied the surface function groups in upgrading coal and its re-absorbingcharacteristic to reveals the relationship between transportation rules and re-absorbing intwo kind of coal. This will provide guidance for the selection of best conditions forupgrading, improve the efficiency of lignite and reduce the waste of energy.