我国炼焦生产过程排放的颗粒物和挥发有机物的组成特征、排放因子及排放量初步估计

【作者】 何秋生；

【导师】 王新明；

【作者基本信息】 中国科学院研究生院（广州地球化学研究所） ， 环境科学， 2006， 博士

【摘要】 中国是世界主要的焦碳生产和出口国,焦炭产量和出口量分别占世界的40和60%以上。除火力发电外,炼焦作为主要的能源转化形式每年占中国总耗煤量的13%左右。由于炼焦工艺整体落后,焦化生产过程造成大量污染物直接排放,对厂区和周围环境及居民健康构成严重威胁。我国发改委资料显示山西等地由于落后炼焦工艺每年有200亿立方米的焦炉煤气外排,虽然炼焦排放污染物在全国污染物排放总量中所占比例可能较小,但对局部地区环境影响已不可忽视,对炼焦排放的污染物成分谱特征、排放因子和排放量进行深入研究和准确估计对这些受焦化废气影响地区的大气环境控制有较重要的意义。本研究通过焦化厂烟气和焦炉顶空气、厂区及厂外大气采样监测,主要对挥发烃类污染物的组成特征、排放因子和排放量进行了初步探讨,对科学评价炼焦行业对全国和焦碳主产区的环境影响,有较重要的实际价值。主要结论如下: 1 土法炼焦烟气中MAHs高于机械炼焦无组织排放和有组织排放烟气中MAHs浓度,且炼焦烟气MAHs的浓度水平都高于电站燃煤、生物质燃烧、交通尾气等释放源。土法炼焦前期MAHs释放高于后期,而机械炼焦无组织排放与有组织排放烟气中MAHs浓度在装煤和出焦是明显升高。 2 从组成来看,炼焦烟气与汽车尾气、LPG、天然气和油漆等污染源相比,炼焦释放的VOCs具有典型特征,主要是苯含量相对较高。BTEX特征比值显示炼焦作为污染排放源具有不同于其它来源的典型特征。BTEX散点图和相关性分析显示机械炼焦释放的MAHs主要来自焦煤的高温分解,而土法炼焦则除焦煤的不完全燃烧产物外还有其它成因来源。 3 炼焦生产过程中土焦炉烟尘排放为1.21-3.85kg/吨焦,明显高于机焦炉和热回收焦炉（0.14-0.60kg/吨焦）。初步得出的土焦炉SO₂排放因子多在2-3kg/更多还原

【Abstract】 China has the largest coke production and export in the world, and more than 40% global coke output and more than 60% global coke export are from China. Coke production shares about 13% of the total coal consumption in China, only next to coal-fired power plants in China’s coal consumption. Due to backward coking techniques in China, many pollutants directly emit from coking processes, bringing about adverse effects to local environment and human health. Data from National Development and Reform Commission reveal that each year about 20 billion cubic meters coke oven gas directly emit into the atmosphere without being utilized for backward coking techniques in Shanxi province, China. Though emission from coking might share very limited portions in national emission inventories of pollutants, its influence on local or regional environment can not be neglected. Investigation of source profiles, emission factors and emission volumes of pollutants from coke production is of great importance for the control of air pollution in the region influenced by coking exhaust gas. The present study, by analyzing the stack gas, oven-top gas and ambient air inside and near the coking plants in Shanxi province, target on the source profiles, emission factors and total emission volume of pollutants like VOCs, and will obtain preliminary but valuable results for the scientific assessment of coke industry’ influence on national and regional environment. Major conclusions are listed as following:Monocyclic aromatic hydrocarbons （MAHs） in waste gas from beehive coking are much higher than those from byproduct recovery battery coking （BRBC）. Coking gas also has higher MAHs than emission from coal-fired power plant, biomass burning and motor vehicle. Beehive coking has higher MAH emission in the beginning days, and byproduct recovery battery coking has higher MAH emission during charging and coke pushing.VOCs from coking processes show characteristic compositional patterns compared to those from emission sources like vehicle exhaust, liquefied petroleum gas, natural gas and paints. A major distinction is the relatively high benzene levels. Characteristic ratios related to BTEX （benzene, toluene, ethylbenzene and xylenes） can be used to diagnose source contribution from coke production. Scatter plots and correlation analysis of BTEX indicate that MAHs from BRBC might be originated from high-temperature degradation of coking coal, but MAHs from beehive coking might have other origins than incomplete combustion.The emission factors for dust from beehive coking are 1.21-3.85 kg/ ton coke, obviously higher than those from BRBC （0.14-0.60 kg/ton coke）. Preliminary SO₂ emission factors were estimated to be 2-3 kg/ton coke for beehive coking, and1.0-1.69 kg/ton coke for byproduct recovery battery coking, but a few beehive coke oven showed quite high SO2 emission factors. Preliminary estimation found that Dust and SO2 from coking account for about 7.9% and 14.3% of total dust and SO2 emission in Shanxi province.Methane emits mainly via stack gas in coke production, and emission factor was found to be 228.5±56.1g/ton coke, much higher than those of coal and biomass burning in domestic furnace. Although methane emission from byproduct recovery battery coking is estimated to be about 30,000 ton per year and 0.1% of total methane emission in China, it might be second largest source other than coal production in Shanxi province. Meanwhile, about 20 billion cubic meters coke-oven gas is directly discharged per year without being utilized, and related methane emission might be over 1 million tons per year, and should be of great concern.NMHC factors via dust collector and stack gas are 55.83 and 487.16 g/ton coke, and emission factors of ethane, propane, ethyne, propylene, benzene and （m+p）-xylene had emission factors of 14.18, 23.02, 23.96, 11.08, 31.93, 14.00 g/ton coke. Base on the national coke production from byproduct recovery battery coking in 2005, NMHC emission from byproduct recovery battery coking was estimated to be 2.6-5.7x105 ton, less than 1% of national total NMHC emission. In 2005 NMHC emission from coking in Shanxi province was estimated to be 2.4x105 ton, accounting for 5% of the provincial total NMHC emission.更多还原