龙岩煤不同宏观煤岩组分的热破碎性质研究

Thermal fragmentation of Longyan anthracite with different lithotypes

用筛分和浮选法对龙岩煤进行分选,得到不同粒径、不同宏观煤岩的龙岩煤颗粒。在热天平上进行热解破碎研究,并在自制的小型流化床上进行燃烧破碎试验。结果表明,亮煤与灰煤均发生一次破碎,破碎后生成许多细小颗粒,其中粒径0.8mm以下的细颗粒占多数;暗煤则不发生一次破碎。随着升温速率和颗粒粒径的增大,一次破碎变得较为剧烈;颗粒性质、颗粒粒径、炉床温度和燃烧时间等因素对龙岩煤在流化床燃烧中的破碎均有重要影响。亮煤与灰煤因结构致密,颗粒中大孔隙少,显微硬度大,灰分少等原因使得它们在燃烧中发生严重破碎;而暗煤颗粒则因相反的原因不发生破碎或仅发生轻微破碎。粒径越大,炉床温度越高,燃烧时间越长,破碎越剧烈;亮煤与灰煤在燃烧中均发生了二次破碎,其中亮煤的二次破碎更剧烈;燃烧后期,亮煤的颗粒破碎比灰煤更快;由于破碎,入炉煤颗粒平均粒径在燃烧早期迅速减小,而后随着燃烧的进行而逐步趋于一个稳定值;亮煤在流化床燃烧中服从等密度燃烧模式,暗煤服从等直径燃烧模式,而灰煤则服从混合燃烧模式。

Three different lithotypes of Longyan （LY） anthracite with different particle size were separated by means of flotation technique. Experiments of the particle fragmentation during pyrolysis and combustion were conducted in a TGA system and a pilot scale fluidized bed furnace, respectively. It is shown that for clarain and culm many new fine particles are generated during pyrolysis, most of which has a size smaller than 0.8 mm. The primary fragmentation reaction of clarain and clum becomes severely with the increase of heating rate and the sample particle size. For durain particle, no obvious fragmentation is found under the same experimental condition. Factors, such as particle properties, particle size, furnace＇s bed temperature and combustion time, have an important effect on the fragmentation of LY anthracite during its combustion in fluidized bed. Clarain and culm occur tremendous fragmentation in fluidized bed due to their compact structure, few large pores in inner particle, high microscope-hardness （ H m,v） and low ash content. The fragmentation of clarain and culm tends to be severely with the increase of particle size, bed temperature and combustion time. Durain doesn＇t have obvious fragmentation during combustion in fluidized bed. Both clarain and culm undergo the secondary fragmentation during combustion, but the secondary fragmentation of clarain is severely in the late stage of combustion. The particle size of clarain declines more rapidly than that of culm. In the early stage of combustion, the mean particle size of clarain decreases promptly as a result of primary fragmentation, but with the time going it fails to a stable size. The combustion model of clarain in fluidized bed is equidensity shrinking core model, while that of durain is equidiameter one, and that of culm is a mixed model.