Mercury pollution from stationary combustion of fossil and biomass fuels

化石燃料和生物质燃料固定燃烧产生的汞污染

• 批准号: 2114228
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2114228
• 关键词: Mercury; pollution; stationary; combustion; fossil

Mercury pollution from stationary combustion of fossil and biomass fuels is a significant contributor to global Hg emissions, accounting for 24% of global Hg emissions as reported by the Global Mercury Assessment 2018, with no decrease in the sector's emissions since the last report in 2013. While most primary sources of Hg pollution through industrial uses are currently being phased out due to the international ban on Hg through the Minamata Convention on Mercury, the unintentional Hg emissions from energy generation have only started to be regulated for stationary coal power stations in recent years with the introduction of the US Mercury and Air Toxics Standards (MATS) in 2016 and in the EU by the implementing decision by the European Commission on the Best Available Technique decision for large combustion plants in 2017 and is still not regulated with emissions limits in many parts of the world. While common control strategies for other pollutants such as NOx and S may deliver a co-benefit with regards to reducing Hg emissions in stationary solid fuel plants, this effect is often not systematically studied and may vary on the specific operating conditions of the power plants. The demand for cheap and efficient sorbents to inhibit and/or lower Hg emissions will foreseeably rise as stricter Hg regulation moves from large-scale to smaller scale combustion units, and economies that are reliant on combustion for energy generation, such as Poland, China, India and Brazil, are seeking to combat their Hg emissions. Mercury is highly redox-active, with different species exhibiting very different redox behaviours and toxicity in the environment. Elemental Hg0, the single most important Hg species produced during combustion, is volatile and has a residence time of up to 1 year in the atmosphere, enabling it to redeposit on a global scale, contaminating ecosystems far removed from the point source of pollution. Gaseous Hg(II) species on the other hand exhibit a much higher propensity to interact with other particulates in the flue gas and traditional air pollution control units such as selective catalytic reduction units for NOx reduction commonly found in power plants. The fuel and additive chemistry significantly alter the reactions which determine the chemistry of flue gas Hg. While this is well established for coal-fired power stations, less is known about how components in biomass flue gas influence Hg speciation and subsequent emissions. To abate Hg from combustion, it is necessary to control its redox transformations within a gas stream. This PhD project will seek to apply insights from geochemical cycling of Hg, and adapt it to a power plant environment by engineering a biomaterial which is able to stabilise and trap Hg in its oxidised form within a flue gas stream. Biochar has frequently been discussed as a promising low-cost medium for Hg removal. However, especially in the available applied studies, a mechanistic understanding of the reaction by which the doped char captures and oxidises Hg is often lacking, hindering further optimisation of such materials. Hence, a detailed mechanistic understanding of the interactions of Hg with biochar engineered with Mn oxides will be developed as 1) an advanced sorbent for Hg capture and 2) catalyst for redox transformations of Hg so as to capture and store Hg in an amenable chemical form.

化石燃料和生物质燃料的固定燃烧产生的汞污染是全球汞排放的重要贡献者，根据2018年全球汞评估报告，占全球汞排放量的24%，自2013年上一份报告以来，该行业的排放量没有减少。虽然由于《汞问题水俣公约》对汞的国际禁令，大多数主要的工业用途汞污染源目前正在逐步淘汰，近年来，随着美国《汞和空气有毒物质标准》（MATS）的出台，固定燃煤发电站的无意汞排放才开始受到监管在2016年，欧盟委员会在2017年对大型燃烧厂的最佳可用技术决定进行了实施决定，并且在世界许多地方仍然没有对排放限制进行监管。虽然针对氮氧化物和硫等其他污染物的共同控制策略可能会在减少固定式固体燃料发电厂的汞排放方面产生共同效益，但这种影响往往没有得到系统的研究，而且可能因发电厂的具体运行条件而异。随着更严格的汞法规从大规模燃烧装置转向小规模燃烧装置，以及波兰、中国、印度和巴西等依赖燃烧发电的经济体正在努力减少汞排放，对抑制和/或降低汞排放的廉价高效吸附剂的需求将不可避免地上升。汞具有高度的氧化还原活性，不同的物种在环境中表现出非常不同的氧化还原行为和毒性。元素汞0是燃烧过程中产生的最重要的一种汞，具有挥发性，在大气中的停留时间长达1年，使其能够在全球范围内重新沉积，污染远离污染点源的生态系统。另一方面，气态汞（二价汞）更容易与烟道气和传统空气污染控制装置（如发电厂中常见的用于减少氮氧化物的选择性催化还原装置）中的其他颗粒物发生相互作用。燃料和添加剂的化学性质显著改变了决定烟气汞化学性质的反应。虽然这一点在燃煤发电站已经得到了很好的证实，但人们对生物质烟气中的成分如何影响汞的形态和随后的排放却知之甚少。为了减少汞的燃烧，有必要控制其在气流中的氧化还原转化。该博士项目将寻求应用汞的地球化学循环的见解，并通过设计一种能够稳定和捕获烟气流中氧化形式的汞的生物材料，使其适应发电厂环境。生物炭经常被认为是一种有前途的低成本除汞介质。然而，特别是在现有的应用研究中，对掺杂炭捕获和氧化汞的反应的机械理解往往缺乏，阻碍了此类材料的进一步优化。因此，详细的机理的理解，汞与生物炭的相互作用与锰氧化物工程将开发1）先进的吸附剂汞捕获和2）催化剂的氧化还原转化的汞，以捕获和储存汞在一个顺从的化学形式。