【作者】 陈清；

【导师】 杨毅； 陈龙；

【作者基本信息】 华东师范大学 ， 环境科学， 2022， 硕士

【摘要】 近年来,我国燃煤电厂产生的燃煤固废(包括煤渣、粉煤灰和脱硫石膏)正逐年增加,核算燃煤电厂固废产物的汞赋存量为评估燃煤电厂固废汞潜在风险提供理论支撑,对政府合理规范处置固体汞废物亦有着重要的现实意义。本研究通过采样测定与文献调查相结合的方法,归纳了124个燃煤电厂汞在不同固废产物和向大气排放的分配比例,将这124个电厂按照空气污染控制设施(air pollution control devices,APCDs)分成了11类,使用Crystal Ball和Bootstrap方法模拟预测不同燃煤副产物汞的分布比例。结果表明,汞在煤渣和石膏中的分布比例符合对数正态分布,而在煤灰中的分布比例符合beta和Weibull分布,经烟囱排放的分布比例符合beta和对数正态分布。综合11类APCDs,煤渣、煤灰、石膏和大气的汞分布比例分别为0.03-0.75%、11.2%-93.8%、5.1-68.6%和3.1-53.9%。基于全国电厂信息、省级原煤汞浓度和不同APCDs下燃煤固废产物汞的分配比例,研究采用物质分布模型编制了高空间分辨率的中国燃煤电厂固废产物汞赋存清单。结果表明,2018年,中国燃煤电厂的煤渣、煤灰和石膏中分别赋存了2.2 t(0.7-16.9 t)、154.4 t(98.5-277.8 t)和56.1 t(35.1-119.9 t)的汞。汞赋存量的空间分布表现出显著的区域异质性,高值热点主要集中在中国东部和华北平原。煤灰和石膏的综合利用驱使汞的二次流动。作为粉煤灰最重要的利用途径,输入到水泥厂的汞有3.6 t释放到大气,而35.0 t的汞被固定在水泥熟料中。粉煤灰用于低端建筑材料的制造、混凝土的制造以及道路矿山填埋驱使20.0 t、15.4 t和4.6 t的汞固定在材料中。42.0 t的汞随着脱硫石膏综合利用而进入到各行业,其中29.7 t的汞进入到水泥厂,10.1 t进入到建筑行业且3.1 t的汞被释放到大气,剩余的汞则进入到农业等其他行业。研究进一步运用物质分布法核算大气汞排放,排放总量为56.8 t(35.2-106.7t),用物质分布模型估算的结果比传统排放因子模型估算的结果要高28.9%,区域上的差异则主要体现在海南、江苏等地。造成差异的主要原因是脱硫石膏在污控设施中长期储存时会将汞再次释放到大气中,排放因子法则低估了脱硫石膏的这一部分再排放。研究基于未来超低排放技术安装率变化的各种假设情景,模拟预测了燃煤电厂固废产物汞赋存量和大气汞排放量的未来变化趋势。情景模拟表明,随着中国燃煤电厂未来超低排放技术安装率的增加,燃煤电厂烟气和石膏中的汞将被更多地转移到煤灰中,这将对固体汞废物的处理提出新挑战。但是,随着未来煤炭消耗量的下降,固废汞赋存量和大气汞排放量将逐渐下降,进而降低燃煤电厂汞的风险。本文的研究结果将有助于政府按照《关于汞的水俣公约》的要求,制定有效处理燃煤电厂固体汞废物的政策和标准。更多还原

【Abstract】 Recently,coal combustion residuals(CCRs,including bottom ash,fly ash,and gypsum)from national coal-fired power plants(CFPPs)in China have increased year by year,the inventory of Hg reserves in CCR from national CFPPs in China could be used to evaluate the potential risk of solid Hg waste and help the government safely dispose of solid Hg waste at a national level.This study integrated both national sampling campaign and literature survey to summarize distribution proportion of Hg in CCR of 124 coal-fired power plants.The124 CFPP units were divided into 11 groups according to their types of boilers and APCDs.We used Crystal Ball method and Bootstrap method to simulate the distribution proportion of the type of CCR.The simulations of Crystal Ball method and Bootstrap method revealed that all the Hg distribution proportions in bottom ash and gypsum among the 11 APCD groups met the lognormal distribution.Hg distribution proportions in fly ash met the beta or Weibull distribution.Hg distribution proportions for stack emissions met the beta or lognormal distribution.The Hg distribution proportions in bottom ash,fly ash,gypsum,and stack gas was 0.03-0.75%,11.2%-93.8%,5.1-68.6%,and 3.1-53.9%,resepectively.We developed highly resolved inventories of Hg distributions in CCR and Hg emissions to air from national CFPPs in China using a mass distribution model.The model combined data from individual power plants,provincial Hg concentrations in coal,distribution proportions of Hg in CCR in various APCD combinations.The results illustrated that 2.2 tons(0.7-16.9 tons),154.4 tons(98.5-277.8 tons),and 56.1 tons(35.1-119.9 tons)of Hg were stored in bottom ash,fly ash,and gypsum from China’s CFPPs in 2018,respectively.Spatial distribution of Hg reserves in CCR illustrated strong regional heterogeneities.High Hg reserves in CCR were concentrated in East China and North China Plain.The utilization or deposition of fly ash and gypsum would cause secondary releases of Hg.As the most important utilization approach of fly ash,cement plants re-emitted 3.6 tons of Hg into the air and left 35.0 tons of Hg in the cement clinker.The utilization approaches of fly ash including the manufacture of lowend building materials,manufacture of concrete,and recycling process in paving/minebackfilling caused 20.0 tons,15.4 tons,and 4.6 tons of Hg immobilized in materials,respectively.42.0 tons of Hg flowed into various industries as gypsum was utilized,29.7 tons of Hg flowed into cement plants.10.1 tons of Hg flowed into construction industry and 3.1 tons of Hg was re-emitted into the air.The remaining Hg entered the other industry,such as agriculture.Atmospheric Hg emissions were estimated to be 56.8 tons(35.2-106.7 tons)using the mass distribution model,which were higher 28.9% than those estimated by an emission factor model.Under two methods,atmospheric mercury emissions in Hainan and Jiangsu were greatly different due to the mercury was re-emitted to atmosphere during the long-term storage of gypsum in APCD,which was underestimated in emission factor method.Additionally,we investigated the future trend in the reserves and gas emissions under various scenarios of future installation rate of the ULE technology.Scenario simulations informed that more Hg in flue gas and gypsum would be transported to fly ash with the increasing installation rate of the ultralow emission technology in future CFPPs,which further inform a new challenge regarding the disposal of solid Hg waste.However,as coal consumption declines,mercury in solid waste and atmosphere will gradually decline,which could reduce the risk of Hg pollution.The results can help the government initiate policies to safely dispose of solid Hg waste and develop treatment criteria from CFPPs,as required in the Minamata Convention on Mercury.更多还原