褐煤煤层自燃火灾发展进程中孔隙结构演化特征

为深入研究煤层自燃火灾发展进程中热解干馏区煤孔隙结构的演化对自燃火灾发展和蔓延的影响，以褐煤为研究对象，应用压汞法分别对300～600 ℃常规热解和600 ℃高温蒸气热解条件下热解固体产物的孔隙结构参数进行了测定和分析，计算不同热解温度下的孔隙分形维数，比较了两种不同的热解方式下固体产物的孔隙特性。研究结果表明：① 常规热解过程中，褐煤的总孔隙体积和孔隙率的变化严格受热解温度的控制，而且孔隙结构始终是向着有利于改善煤体渗透性能的方向发展的，进而促进自燃火灾的发展；② 常规热解条件下，随着热解温度的升高，褐煤孔隙比表面积明显下降，对热解气体的吸附性能降低，使这些气体更容易沿着孔裂隙通道离开热解干馏区而到达自燃火源位置；③ 对于水分含量比较高的褐煤，煤体温度的升高使煤中水分蒸发而形成高温蒸气热解的条件，与常规热解相比，煤体孔隙率更大，渗透性能更强；④ 经过高温蒸气热解后，褐煤孔隙拓扑结构较常规热解变得更加均匀化，孔隙表面也更加光滑，更有利于热解气体的流动。

STUDY ON EVOLUTION CHARACTICS OF PORE STRUCTURE DURING LIGNITE SEAM SPONTANEOUS COMBUSTION DEVELOPING

In order to deep study the effect of evolution charactics of coal pore structure in pyrogenic distillation region on spontaneous combustion developing and spreading during coal seam spontaneous combustion developing,took lignite as the study object,a mercury intrusion method was applied to measure and analyze the inernal physical parameters of solid pyrolysis products generated at different temperature levels under the conditions in the vacuum system from 300 to 600 ℃,at 600  ℃ in the high temperature steam,computed the pore fractal dimension according to the data of mercury intrusion method experiment at different pyrolysis temperature,and compared,in detail,pore property of solid products in different pyrolysis way.The results indicate that:① Under the condition of the conventional pyrolysis,the change of total pore volume and porosity is controlled by pyrolysis process,pore structure is always developed to the direction for improving permeability performance,and then promoting spontaneous combustion development;② Under the condition of the conventional pyrolysis,with pyrolysis temperature increases,pore specific surface area of lignite is obviously decreased,and adsorption performance to pyrolysis gas is depressed,so these gas more easily depart from pyrogenic distillation region and reach spontaneous combustion center position down the channel of pore and fracture;③ To lignite,because its humidity is great,moisture evaporation of coal form the pyrolysis condition of the high temperature steam with temperature,compared with conventional pyrolysis,its porosity is bigger and permeability performance is better;④ After the high temperature steam pyrolysis,compared with conventional pyrolysis,pore topological structure is more uniform and pore surface is more glossy,pyrolysis gas flow is easier.