低温热提质褐煤的复吸水特性研究

Study on Moisture Re-Adsorption and Combustion Characteristics of a Lignite After Mild Thermal Upgrading

选取云南昭通褐煤,经NaBH4和盐酸预处理后在200~500℃下热解体质,采用FTIR分析了提质过程中煤表面含氧官能团OH和C=O相对含量的变化,采用N2吸附法分析了提质煤的孔隙结构,在恒温恒湿箱中研究了提质煤的复吸水特性。实验旨在研究提质煤的复吸水机制并探索降低复吸水率的方法。结果表明,提质煤的复吸水率随热解温度的升高而降低;HCl处理降低了OH氢键和C=O的相对含量,明显降低了提质煤的复吸水率,NaBH4处理抑制了褐煤的热解且只能还原部分COOH中的C=O,对降低复吸水率的效果不明显。

A lignite from Zhaotong coal field in Yunan province was thermally upgraded from 200℃to 500℃ after pretreatment by hydrochloric acid or sodium borohydride.The changes in chemical structures of the upgraded lignite,such as hydroxyl groups and carbonyl groups,were investigated using Fourier transform infrared spectroscopy（FTIR）.The changes in pore structures of the upgraded lignite were analyzed by N2 adsorption isotherm.The moisture re-adsorption characteristics of the upgraded lignite were studied by using a constant temperature/humidity chamber.This work is aimed at studying the moisture readsorption mechanism of upgraded lignite and finding out ways to reduce the moisture readsorption ratio.The results indicated that the moisture readsorption ratio of the upgraded lignite decreased with the upgrading temperature.Hydroxyl and carbonyl groups in the upgraded lignite by hydrochloric acid pretreatment was significantly reduced,thus lowered the moisture readsorption ratio.The sodium borohydride pretreatment process inhibited the thermal upgrading and only a little proportion carbonyl in the lignite was reduced,therefore it showed little effect on reducing the moisture readsorption ratio.