干燥温度对褐煤干燥后复吸特性的影响

Effects of drying temperature on reabsorption characteristics of dried lignite

采用自制卧式干燥实验台,制得不同干燥温度下的褐煤煤样,采用核磁共振法测定干燥试样的有效含水孔隙,采用傅里叶红外法测定试样的表面含氧官能团,使用自制复吸实验装置测定不同干燥程度褐煤煤样的平衡含水率。实验结果表明,对于低温干燥褐煤（干燥温度为140～230℃,干燥时间为10 min）,干燥温度对褐煤的有效含水孔隙体积影响较小,对主要含氧官能团影响较大,煤中主要含氧官能团表现为随干燥温度升高先减少后增加。对于高温干燥褐煤（干燥温度为600～800℃,干燥时间为30 s）,干燥温度对褐煤的有效含水孔隙体积和含氧官能团均有较大影响,表现为随干燥温度升高有效含水孔隙体积减少,含氧官能团增多。不同干燥条件下,干燥褐煤的复吸特性影响因素不同,低温干燥条件下,干燥温度通过改变褐煤含氧官能团数量来影响干燥褐煤复吸特性,而有效含水孔隙结构是高温干燥褐煤平衡含水量的主导因素。

Lignite samples dried under different temperatures were prepared using a horizontal fixed-bed dryer. The oxygen-containing functional groups on the surface of the dried lignite samples were analyzed using Fourier-transform infrared（ FTIR） analyzer and the effective water-filled porosities of the samples were analyzed by nuclear magnetic resonance（ NMR） spectrometer. The equilibrium moisture content of the samples was measured by a self-made reabsorption device. The experimental results from the lignite samples dried at low temperature show that the drying temperature has little effect on the effective water-filled porosities and the amount of the main oxygen-containing functional groups firstly decreases and then increases with the drying temperature increase. The reabsorption characteristics of lignite dried at low temperature was influenced by the amount of oxygen-containing functional groups. In the case of the lignite samples dried at high-temperature drying group,with the increase of drying temperature,the amount of the effective water-filled porosities of the samples decreases and the amount of oxygen-containing functional groups increases and the equilibrium moisture content decreases. The effective water-filled porosity is a main factor for the lignite dried at high temperature.