Thermal forming method and device for secondary carbonized briquette coal
XU Jiang,GAN Qingqing,CAI Guoliang,WANG Ruifang,PENG Shoujian
针对煤与瓦斯突出事故研究中物理模拟实验所需型煤材料具有强度低、渗透性高等特性, 自主研制了二次炭化型煤热压成型装置和型煤制作新方法。 该装置主要由电液伺服加载控制系 统、加热炉体及密封系统、真空及气氛保护系统、炉体电控系统、水冷系统和石墨模具、碳钢模具等 6 个部分组成,其最大轴压为 200 kN、最高温度为 1 200 °C 、炉膛温度均匀性为±6 °C 、升温速率为± 0.01~10 °C、炉膛使用真空度≤10 Pa、炉膛工作室尺寸为 φ240 mm×260 mm(直径×高),石墨模具 和碳钢模具均可制备尺寸分别为 φ25 mm×50 mm 和 φ50 mm×100 mm(直径×高)的圆柱体型煤试 件。 该热压成型装置具有如下特点:1 系统采用计算机控制自动加荷载,实现力、位移的闭环控 制;2 炉膛尺寸设计紧凑、炉内温度均匀性好,能实现热压、无压、真空和气氛保护烧结等;3 模具 耐高温、热膨胀系数低,组装、拆卸均方便,可成型多种类、多数量热压型煤。 并利用该装置进行了 不同炭化温度的型煤试件的制作,其中煤粉颗粒配比采用致密堆积理论优化后其粒径为 0.250 ~ 0.425,0.125 ~ 0.150,0.075 ~ 0.083 mm ,占比依次为 91.77‥5.87‥2.35。 基于所开展的单轴压缩荷 载作用下的力学特性试验、三轴压缩荷载作用下的渗流特性试验等,通过对比分析热压型煤的密 度、单轴抗压强度、泊松比、弹性模量、初始渗透率和最小渗透率等,揭示了不同温度下型煤强度增 加与渗透性降低的影响机制。 其中密度变化率呈先增后减再增的趋势;单轴抗压强度和弹性模量 呈现先增后减,泊松比则为先减后增的趋势;初始渗透率及最小渗透率均呈不断增大的趋势,综合 考虑热压型煤的密度、强度和渗透率等,确定了二次炭化型煤制作中最佳炭化温度为 300 °C ,从而 优化了型煤与原煤之间的相似性,提高了煤与瓦斯突出物理模拟实验研究真实还原性。
Based on the low strength and high permeability of briquette coal(BC)used in coal and gas outburst physi⁃ cal simulations for coal mine disasters,a self⁃developed thermal forming method and device for secondary carbonized briquette coal under vacuum conditions was introduced. The thermal forming device is composed of a servo⁃controlled loading system, heating furnace, vacuum and atmosphere protection system, electric control system, water⁃cooling system,graphite molds,and carbon steel molds. The maximum pressure of this device is 200 kN and the highest sintering temperature is 1 200 °C . The vacuum working temperature uniformity,heating rate,and vacuum are ±6 °C ,0.01 ~ 10 °C / min,and ≤ 10 Pa, respectively. The internal dimensions of the furnace body is 240 mm × 260 mm (diameter × height),respectively. Cylindrical BC specimens with sizes of φ25 mm×50 mm and φ50 mm×100 mm(di⁃ ameter×height)can be formed by using graphite and carbon steel molds. The thermal forming device has the follow⁃ ing characteristics:1 The closed⁃loop control of force and displacement is achieved by automatic loading with a com⁃ puter.2 The furnace size design is compact,the temperature is uniform in the furnace,and the furnace can be adjus⁃ ted to achieve hot⁃pressing sintering,non⁃pressing sintering,vacuum sintering,and atmosphere protection sintering. 3 The mold has high⁃temperature resistance,corrosion resistance,good thermal stability,low thermal expansion coeffi⁃ cient,so many kinds of briquette coals can be formed by the device. Using the thermal forming device,several groups of briquette coal specimens with different heating temperatures were made. Based on the packing density theory,the optimal ratio of the 0.250-0.425,0.125-0.150,0.075-0.083 mm particle sizes is 91.77‥5.87‥2.35. Then a series of uniaxial compression tests and triaxial compression seepage tests on these briquette coal specimens were carried out. The density,uniaxial compressive strength,Poisson’ s ratio,elastic modulus,the effect of the initial permeability and minimum permeability were analyzed,and the mechanism of changes in the strength and permeability of these specimens was revealed. The rate of the change of and density of the BC first increases,then decreases,and then in⁃ creases again. The mechanical parameters(strength and elastic modulus)first increase and then decrease,whereas the Poisson’s ratio first decreases and then increases. Both the initial and minimum permeability increase. Considering the density,strength,and permeability of BC,the optimal heating temperature,at which the similarity be⁃ tween the BC and raw coal(RC)is the highest,was determined as 300 °C. It strengthens the bonds between raw coal and briquette coal and helpful for the similar simulation study of coal and gas outburst.
secondary carbonized briquette coal; graphite mold; particle size optimization; uniaxial compression strength;permeability;coal mine gas disaster
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会