Coalification and coal alteration under mild thermal conditions  

作　　者：Pavel Straka Ivana Sykorova 

机构地区：[1]Institute of Rock Structure and Mechanics, v.v.i, The Czech Academy of Sciences, V Holegovickach 41, 18209 Prague 8,Czech Republic

出　　处：《International Journal of Coal Science & Technology》2018年第3期358-373,共16页国际煤炭科学技术学报（英文）

摘　　要：Coalification temperatures are often considered to be approximately 100-170 ℃ for bituminous coal and 170-275 ℃ for anthracite. However, our micropetrographic observations, solid state ^27Al magic-angle spinning nuclear magnetic resonance measurements, interpretation of δ^13C values for whewellite in pelosiderite concretions from Carboniferous sediments, and assessment of whewellite thermal stability show that coalification temperatures can be significantly lower. Also the temperatures of coal alteration may be substantially lower than is stated. Ordinarily, high- temperature alteration is reported, but microthermometric measurements of fluids temperatures and micropetrographic observations show that the coal alteration can take place at low temperatures. For this reason, coals from the Kladno- Rakovnik Basin, part of Late Paleozoic continental basins of the Czech Republic, were analyzed. Regarding coalification, micropetrographic characterizations of unaltered coals, the presence of thermally unstable Al complexes in the coal organic mass documented using ^27Al MAS NMR method, and proven occurrence of whewellite in pelosiderite concretions suggest a lower coalification temperature, max. -70 ℃. Regarding coal alteration, micropetrographic observations revealed （a） the weaker intensity of fluorescence of liptinite, （b） mylonitic structures and microbreccia with carbonate fluid penetration, and （c） high oxygen content in coals （37-38 wt.%）. These phenomena are typical for thermal and oxidative alteration of coal. As the temperature of carbonate fluids inferred from fluid inclusion analysis was evaluated as -100-113 ℃, the temperature of coal alteration was suggested as -113℃; the alteration was caused by hot hydrothermal fluids.

关 键 词：COALIFICATION Thermal and oxidative alteration Kladno-Rakovn Basin - Al complexes ^27Al MAS NMR Fluid inclusions Δ^13C Whewellite 

分 类 号：TQ436.3[化学工程] TF538.63[冶金工程—钢铁冶金]