煤焦化过程中挥发性卤代烃的生成与排放研究

Recent years, more and more attentions have been paid to volatile halocarbons (VHCS) for its serious environmental effects. But till now, the emission of VHCS like chloromethane, were not fully clear except chlorofluorocarbons. As an important energy source rich in halogens, the coal using processes are the main emission sources of VHCS. Many researchers have focused on the emission of VHCS during the coal combustion and have come up with some relatively mature theories. The coal coking process is an important coal consuming process different from the coal combustion, but there are few studies on the emission of VHCS from the coal coking process which may also be different from the coal coking process. Therefore, in the present study, we propose to investigate the formation, emission factors and influences of VHCS during coking process via the whole stack gas sampling of coking exhaust gas in coke ovens widely used at present and mainly developed future in China, combining with the simulation experiment of tube furnace and experimental furnace model. Based on this, we will conduct coking simulation experiment to fundamentally explore the formation mechanisms of VHCS. The results will provide a direct guide to the rules of the emission of VHCS, and have scientific significance on the VHCS emission control.

挥发性卤代烃由于其极强的环境危害效应受到越来越多的关注。然而，目前除氟氯烃类化合物外，氯甲烷等其它卤代烃的排放还存在极大的不确定性。煤作为重要的能源，由于赋存卤素，其利用过程是挥发性卤代烃的重要排放源。近年来，很多学者开展了煤炭燃烧过程中挥发性卤代烃排放的研究，已经形成了比较成熟的理论。作为重要的耗煤形式，焦化过程与煤燃烧过程不同，其卤素的释放、挥发性卤代烃的生成和排放过程可能不同，这方面报道较少。因此，本研究拟对中国广泛使用的焦炉和重点发展炉型进行生产全过程烟气采样，并结合管式炉和实验焦炉模拟实验，探讨焦化过程中挥发性卤代烃的生成机理、排放因子和影响因素；在此基础上进行焦化模拟实验从根本上探讨煤焦化过程中挥发性卤代烃的生成机理。项目的完成对明确焦化过程中挥发性卤代烃的排放规律和探讨焦化挥发性卤代烃的排放控制有直接的指导意义。

挥发性卤代烃的环境危害受到越来越多的关注。除氟氯烃类化合物外，氯甲烷等其它卤代烃的排放还存在极大的不确定性。由于赋存卤素，煤利用过程是挥发性卤代烃的重要排放源。. 本研究选取山西省焦化炉型和工艺具有代表性的焦炉，正常生产的状况下在对上升管、出焦、装煤和结焦过程废气进行采样分析，并与焦炉顶周围环境空气中的挥发性卤代烃进行对比，探讨煤焦化过程挥发性卤代烃类等化合物成分特征和排放形式。结合焦煤干馏实验，研究挥发性卤代烃排放和理想状况下的挥发性卤代烃生成，并通过实验焦炉进行了验证。同步分析焦炭产区大气中的挥发性卤代烃，探讨焦化排放的挥发性卤代烃在大气中的表征，对环境空气中的挥发性卤代烃的贡献。. 结果表明，煤焦化过程挥发性卤代烃成分以氯甲烷和氯苯为主，其生成可是煤干馏过程分子裂解，自由基结合直接生产，焦化过程是氯甲烷和氯苯的的主要生成过程，占总量的85%。太原市大气TVOCs浓度范围在35.95 ~159.37 ppbv，化学组成以C2-C4为代表的烷烃为主（44.43%），芳烃（18.95%）次之，卤代烃占3.5%。比值分析及PMF结果显示，焦化源对VOCs贡献极大（27.13%），其次为与机动车相关的排放（18.15%）。污染源季节变化显示春季受速西南风影响焦化源更为突出，秋冬季节燃烧源明显增加，冬季受低温供暖影响燃烧源增加更为突出。. 项目的完成对明确焦化过程中挥发性卤代烃的排放规律和焦化污染物排放控制有直接的指导意义。