二次炭化温度对热压型煤力学性质及微观结构影响的试验研究

Experimental study of the effect of secondary carbonization temperature on mechanical properties and microstructure of hot-pressed coal briquette specimens

为了使型煤试件与原煤的性质更加接近,提高相关物理模拟试验研究与工程实际的吻合度,通过改变温度条件制备二次炭化热压型煤,对其单轴压缩力学特性、渗流特性及微观结构进行了测试分析,考察温度对二次炭化热压型煤力学性质及微观结构特性的影响。结果表明:(1)随着炭化温度升高,二次炭化热压型煤试件的单轴抗压强度表现出先升高后降低的趋势,在300℃炭化温度条件下其单轴抗压强度与原煤较为接近;(2)在三轴压缩条件下,二次炭化热压型煤试件的渗透率随轴压增大呈现先减小后增大的演化规律,其初始渗透率和最小渗透率均随着炭化温度升高而增大;(3)二次炭化热压型煤与原煤在FT-IR有机官能团测试中的特征峰位置基本保持一致,但所对应的特征峰强度有所差异,且在300℃和450℃炭化温度条件下二次炭化热压型煤红外谱图的官能团响应与原煤最为接近;(4)二次炭化热压型煤相较于原煤,其孔径分布更为均匀,微孔占比少,比表面积小,且随着炭化温度升高,二次炭化热压型煤的平均孔径和比表面积呈现先降后增的趋势,并在300℃炭化温度条件下其孔径和比表面积相对最小。研究成果可为二次炭化热压型煤成型条件优化及二次炭化型煤力学特性研究提供参考。

In order to make the properties of the coal briquette specimens(CBS)been closer to that of the raw coal specimens(RCS),and to improve the consistency between the relevant physical simulation test and the actual engineering,uniaxial compression mechanical properties,seepage characteristics and microstructure of the secondary carbonized hot-pressed CBS are tested and analyzed by changing the temperature conditions,and effects of temperature on the mechanical properties and microstructure of the briquette are also investigated.The results show that:(1)With the increase of carbonization temperature,an increase followed by a decrease is observed in the uniaxial compressive strength of secondary carbonized hot-pressed CBS.When the carbonization temperature is 300℃,its uniaxial compressive strength is close to that of RCS.(2)Under triaxial compression,the permeability of the hot-pressed CBS firstly decreases and then increases with the increase of axial compression,and the initial permeability shows an increasing trend with the increase of carbonization temperature.(3)The characteristic peak positions of the secondary carbonized hot-pressed CBS and RCS in the FT-IR organic functional group test are basically consistent.However,the corresponding characteristic peak strength is different,and the functional group response of the infrared spectrum of the secondary carbonized hot-pressed CBS at 300℃and 450℃is the closest to that of the RCS.(4)Compared with the RCS,the secondary carbonized hot-pressed CBS has a more uniform pore size distribution with a small proportion of micropore and small specific surface area.Moreover,as the carbonization temperature increases,the average pore size and specific surface area of the secondary hot-pressed CBS firstly decrease and then increase.Additionally,the pore size and specific surface area are relatively the smallest when the carbonization temperature is 300℃.The research results can provide references for the optimization of forming conditions of secondary carbonized hot-pressed CBS and the study of mechanical properties of secondary carbonized briquette.