低温热改质煤表面性质变化及其对浆体流变特性的影响

SURFACE PROPERTIES OF THERMALLY UPGRADED LOW-RANK COALS AND THEIR EFFECT ON THE RHEOLOGICAL BEHAVIOR OF COAL WATER SLURRY

考察了几种褐煤热改质过程中表面性质的变化及其对浆体流变特性的影响。研究发现，在２００～３００℃温度范围内，热改质煤表面产生显著的收缩作用，活性含氧官能团尤其是羟基官能团的分解使煤表面疏水化作用显著增强，从而使煤的吸水性大幅度降低。上述煤表面性质的变化是该温度范围内热改质煤成浆性得以大幅度提高的主要原因。相关微分分析进一步表明，煤表面羧基官能团和与之相关的煤的吸水性是制约煤成浆性尤其是低阶煤成浆性的首要因素，而未发现酚羟基官能团能产生重要的影响。对浆体流变特性的研究表明，浆体的屈服假塑性与煤表面活性含氧官能团和矿物质的含量有关，煤表面较高的亲水性有利于浆体屈服假塑性的改善，从而使其对浆体性质的影响具有双重性。

The changes of the surface properties of several low-rank coals during upgrading and their effect on rheological behavior of coal water slurry were characterized in detail. The results indicated that the decomposition of reactive oxygen-bearing functional groups on coal surface and its partly reslutant surface shrinkage of low-rank coal make thermally upgraded low-rank coal surface less hydrophilic and porous in the upgrading temperature range 200～300℃, the moisture-holding capacity of thermally upgraded coal is there-fore greatly decreased. All these changes of coal surface properties account for the great improvement in the slurryability of thermally upgraded low-rank coals. Differential analyses seem that the carboxyl groups on coal surface play a far more important role in determining coal slurryablity than phenolic hydroxyl groups. It is also indicated that the hydrophilic oxygen-bearing groups and mineral matters on coal surface is beneficial to slurry pseudoplastic behavior although they are harmful to coal slurryability.