煤粉在热分解过程中比表面积和孔隙结构的变化

VARIATION OF SURFACE AREA AND PORE STRUCTURE OF PULVERIZED COAL DURING PYROLYSIS

用氮气等温吸附（７７Ｋ）方法测量了四种不同煤粉在热分解过程中的ＢＥＴ比表面积和孔隙结构。结果表明，不同煤种的比表面积在热分解过程中其变化有着相似的规律。在热分解温度低于５００℃时，煤粉所释放的挥发份主要来自煤粒外表面。当热分解温度高于５００℃后，煤粉释放出的挥发份主要来自煤粒内部深处。在８００℃时，由于煤的塑性，煤粒的部分孔减小和关闭，使其比表面积以及孔隙明显减少。在热分解温度高于８５０℃后，煤粉的比表面积随温度升高而急剧增大。

Nitrogen adsorption isotherm(77K) was used to measure the BET surfacearea,pore surface and pore volume of four pulverized coals from pyrolysis process.Theresluts show that four coals have similar changes in BET surface area with pyrolysis temper-ature. When pyrolysis temperature is below 500℃,the pore surface and volume(pore diam-eter<500nm)of coal particles have no significant change. This means that at lower temper-ature the volatile matter comes out from coal particle surface. When pyrolysis temperature ishigher than 500℃,the volatile matter comes out from deep inner of the particles. Because ofthe plasticity of coal, some of the pores in the particle reduce in their diameter or even closeat 800℃. So the surface area and pore surface reduce a lot. After 850℃ the surface area in-creases sharply with temperature rise.