黏结性富油煤受热产生的软化、熔融现象可能导致井筒堵塞和地层扰动,这是原位热解需考虑的重要因素。在300~700℃下对黏结性富油煤热解,考察油气析出规律和组成性质,分析半焦的物性演变特征及其对原位热解的指示意义。结果表明,焦油产率在500℃取得最大值7.75%,此时<300℃轻质组分含量最高(32.2%),且焦油成分在400~500℃变化显著,酚类和芳烃含量分别呈现增大和降低趋势。煤样的软化温度和固化温度分别为389和455℃,使半焦的宏观孔率度在≥400℃时由不足10%增至约50%,而微观孔隙结构仅在600~700℃高温脱气阶段更发达;半焦导热系数随温度先减小后增大,并在400℃达到最小值0.06W/(m·℃)。黏结性富油煤原位热解面临通道堵塞、挥发分析出受阻和煤层导热速率偏慢等潜在问题,可尝试采用具有破黏效应的压裂支撑剂或近临界水原位转化技术加以解决。

The softening and melting of cohesive tar-rich coal caused by heating may lead to wellbore blockage and formation disturbance,which is an important factor to be considered for in-situ pyrolysis. In this paper, the pyrolysis of cohesive tar-rich coal at 300-700 ℃was conducted to investigate the oil and gas precipitation rules and their composition properties, and the evolution characteristics of physical properties of semi-coke and its indicative significance for in-situ pyrolysis were analyzed. The results shows that the tar yield reachesthe maximum value of 7.75% at 500 ℃ , and the content of light components (boiling point lower than 300 ℃ ) of the derived tar is thehighest (32.2%). The tar components chang significantly at 400-500 ℃ , and the content of phenols increases while that of aromatics decreases. The softening temperature and curing temperature of the coal sample are 389 and 455 ℃ respectively. Consequently, the macroporosity of semi-coke increases from less than 10% to about 50% at ≥400 ℃ , while the micro-pore structure is more developed only atthe high temperature stage of 600-700 ℃ . The thermal conductivity of semi-coke decreases first and then increases with temperature, andreaches a minimum value of 0.06 W/ (m·℃ ) at 400 ℃ . In-situ pyrolysis of cohesive tar-rich coal may be confronted with potentialproblems such as channel blockage, volatile precipitation obstruction and slow thermal conductivity of coal seam. These problems are expected to be solved by using fracturing proppant with viscosity breaking effect or applying near critical water in-situ conversion technology.

0 引言

1 试验

   1.1 试验原料

   1.2 热解试验

   1.3 热解产物表征

2 结果与讨论

   2.1 富油煤的黏结性

   2.2 热解产物产率

   2.3 油气产物的组成性质

   2.4 富油煤热解物性演变特征

   2.5 黏结性富油煤原位热解的难点和对策

3 结论