Chemical and structural changes in XiMeng lignite and its carbon migration during hydrothermal dewatering

Changes in the physicochemical characteristics and spontaneous combustion propensity of Ximeng lignite after hydrothermal dewatering

“…As upgrading temperature increased, these groups gradually decreased from 16.52 % to 15.33 %. This trend was consistent with the results reported in previous literatures, which revealed that phenols, alcohols, and ethers in coal thermally decomposed during HTD . C=O and O‐C=O were attributed to carbonyl and carboxyl groups, respectively.…”

“…With increasing upgrading temperature, C=O monotonously decreased from 3.91 % to 2.01 %, and O‐C=O decreased from 5.41 % to 3.72 %. CO and CO 2 were detected in the gaseous products of HTD, and they were respectively identified as the decomposition products of carbonyl and carboxyl groups . C‐C and C‐H represented aliphatic and aromatic carbons in lignite.…”

“…They thought this was caused by the removal of oxygen‐containing functional groups on the coal surface, such as hydroxyl and carboxyl. Other studies on HTD mainly involve the following aspects: the effect of HTD on the combustion, slurrying, gasification, and liquefaction characteristics of coal, the dewatering and upgrading mechanism of HTD for low‐rank coal, the properties of gas‐ and liquid‐phase products of HTD, and disposal methods for wastewater generated during HTD …”

Influence of the hydrothermal dewatering on the combustion characteristics of Chinese low-rank coals

“…For example, f a was improved from 0.261 (ZT) to 0.525 (ZT-250) and 0.541 (ZT-300), from 0.580 (YM) to 0.637 (YM-250) and 0.638 (YM-300), and from 0.721 (ZD) to 0.724 (ZD-250) and 0.727 (ZD-300). Wu et al [13] investigated the changes in the structural features of Xi Meng brown coal during HTD by solid-state nuclear magnetic resonance spectroscopy, and also found the same results. The aliphatic components decreased whereas aromatic components increased after HTD, indicated coal rank improved.…”

“…Yu et al [12] studied the effect of HTD on the slurryability of brown coals, and found that the maximum solid concentration of coal water slurry increased. Wu et al [13] studied the gas-, solid-, and liquid-phase products obtained after HTD, and analyzed the occurrence of carbon and its migration mechanism during HTD. In recent years, there has been a growing interest of HTD in coal treatment and a number of potential applications of hydrothermal processing have been investigated, such as preparing coal water slurry with the solid and liquid products of HTD [14], improving the space time yield of brown coal liquefaction reactor [15], upgrading and dewatering of raw tropical peat [16], dewatering of sludge [17], generating alternative solid fuel from paper sludge [18], and producing liquid and solid biofuels [19,20].…”