无烟煤中碘燃烧释放和转化行为研究

采用逐级化学提取法研究无烟煤及其不同温度燃烧产物中碘的各种赋存状态;以小型管式炉模拟煤燃烧装置,考察了加热温度、加热时间、O_2流量以及通入水蒸气对无烟煤中不同形态碘燃烧释放影响及其机理。结果表明,无烟煤中碘主要以有机结合态、铁锰氧化物结合态和水溶态形式存在。加热温度对碘释放和转化有明显影响,碘释放率随温度升高而增加,500-900℃是碘释放的主要阶段。其中,700℃以前,水溶态、离子交换态和有机结合态碘大部分释放,小部分转化为碳酸盐结合态、铁锰氧化物结合态和残留态碘;铁锰氧化物结合态碘主要在700-900℃释放,部分残留态碘在1 100℃前也可释放。无烟煤中碘释放率随燃烧时间延长和O_2流量增大而增大,水蒸气的参与能明显促进碘的释放。在1 100℃、通入水蒸气、O_2流量120 m L/min、燃烧20 min时,93.8%-95.9%碘主要以HI和I_2释放。

Study on release and transformation of iodine from anthracite during combustion

Modes of iodine occurrence in 4 Chinese anthracites and the combustion residues obtained at each temperature were extracted with sequential chemical extraction. The coal combustion was simulated with a tube furnace, the effects and mechanisms of heating temperature, heating time, O₂ flow rate and water vapor on iodine release and transformation behavior during anthracite combustion were investigated. The results showed iodine in anthracites can present typically in three main modes of occurrence:organic matter-bound, Fe-Mn oxide-bound and water-soluble form. Temperature had a pronounced effect on iodine release and transformation. Iodine release increased with the increase of temperature, and 500-900℃ was a main stage for iodine release. Before 700℃, some forms of iodine which include water-soluble, ion-exchangeable and organic matter-bound iodine can be almost emitted completely and partly transformed into the carbonate-bound, Fe-Mn oxide-bound and residue-bound iodine. The Fe-Mn oxide-bound iodine may be mainly emitted in 700-900℃, and the residue-bound iodine was emitted partly before 1 100℃.Moreover, the iodine release from anthracite increased with the increase of heating time and O₂ flow rate, and water vapor can obviously promote the iodine release. 93.8%-95.9% of iodine may be emitted in the form of HI and I₂ at the given experimental condition of 1 100℃, water vapor access, O₂ flow rate of 120 mL/min and combustion time of 20 min.