Effect of Pre-drying on the Combustion Characteristics of Zhundong Lignite

摘要

In this study, the ignition and combustion behaviour of raw and pre-dried single particles of Zhundong lignite were experimentally investigated, with a focus on the effect of pre-drying temperatures. The lignite particles were dried at 20 Kmin"1 to various final temperatures (473, 623 and 773 K) in nitrogen and characterised using proximate, ultimate and Fourier transform infrared spectroscopy (FTIR) analysis. A single particle lignite with a diameter of 2 or 3 mm was suspended on a silicon carbide fibre and burned in air in a horizontal tube furnace operating at 1123 K. The ignition and combustion process of the particle was record using a colour CCD camera at 25 fps. The ignition behaviour and combustion characteristics, including the ignition mechanism, ignition delay time, volatile flame duration and burnout time of the single particles were determined by processing the recorded images. The proximate and ultimate analysis results indicated that the volatile matter and oxygen contents decreased, while the carbon content increased with increasing temperature of drying. This trend was consistent with observations in the FTIR analysis, in which the intensity of oxygen-containing functional groups decreased with increasing the pre-drying temperature. The ignition of raw and dried Zhundong lignite particles followed a joint hetero-homogeneous mechanism under all conditions studied. The ignition delay time, volatile flame extinction time and the total combustion time decreased with increasing pre-drying temperature up to 623K. A further increase in the pre-drying temperature to 773K resulted in prolonged key ignition and combustion characteristic times.