Impact of High Concentrations of SO2 and SO3 in Carbon Capture Applications and its Mitigation

富氧燃烧是碳捕集的关键技术之一。近年来，燃用循环烟道气的氧煤燃烧被发电行业视为可能的选择之一，对二氧化碳减排战略具有潜在的贡献。通过在现有锅炉上实施碳捕获技术可以减少二氧化碳排放，但实施二氧化碳捕获的技术困难是巨大的。氧燃料技术的全面应用仍在开发中，但SO3的生产被认为是氧燃料和胺洗涤技术的问题。喷吹脱硫剂比湿法烟气脱硫更有效。因此，脱硫剂喷射可与FGD串联使用，用于富氧燃料燃烧(以减少高浓度的SO3--一种腐蚀诱导物质)和燃烧后捕集。此外，汞与其他烟气组分之间的相互作用极其复杂，煤的化学和矿物组成、燃烧条件、植物配置、其他烟气组分以及烟气从燃烧带到烟囱的时间/温度历史等多种因素都会影响烟气中汞的形态。燃烧后烟气中汞的转化被认为是一个既涉及均相反应又涉及多相反应的动力学限制过程。烟气中汞的形态分配取决于煤的类型，而汞的捕集会受到SO2和SO3浓度的影响。因此，本项目将通过实验和理论研究相结合的方式，解决高浓度SO2和SO3对氧气燃料系统性能的主要问题，包括汞捕获的抑制和整个生命周期的成本。该项目的总体目标如下：将首次在中试规模上评估脱硫剂在降低SO3方面的效率，此前的研究仅集中在与富氧燃烧和燃烧后捕获相关的条件下(空气燃烧条件)。这项工作将由我们的工业合作伙伴进行。利兹研究小组将开发和验证工程计算代码，以提供对氧燃料燃烧用于发电的潜在应用的详细工程评估，并开发工程能力和工具，以帮助未来氧燃料工厂的设计。在此项目中开发和验证的新物理模型将被集成到商业CFD代码中，以预测氧燃料燃烧器的性能行为和干法脱硫剂性能。该代码将为工程师提供一个有用的工具，以评估和优化碳捕获应用中的SO3去除。此外，利兹研究小组要解决的这个项目的另一个目标是了解气相和固相成分在汞氧化反应化学中的重要性，并将调查氯、氮氧化物、二氧化硫和火山灰颗粒对汞氧化的影响。利用建立的汞氧化反应机理，通过预期的Cl2和SO2之间的相互作用，研究烟气中高水平的SO2对氯促进的汞转化的影响。

Oxy-Fuel Combustion is one of the key technologies considered for carbon capture. In recent years oxy-coal combustion with recycled flue gas has been strongly considered by the power generation industry as one of the possible options with a potential contribution to carbon dioxide mitigation strategies. CO2 emissions can be cut by the implementation of carbon capture technologies to existing boilers but the technical difficulties in implementing CO2 capture are formidable. The full-scale application of oxy-fuel technology is still under development but the production of SO3 is considered to be problematic for oxy-fuel and amine scrubbing technologies. Sorbent injection is more efficient for reducing SO3 than wet-FGD. Sorbent injection can therefore be used to advantage in series with FGD for both oxy-fuel combustion (to reduce the otherwise high concentration of SO3 - a corrosion inducing species) and for post combustion capture. In addition, interactions between mercury and other flue gas constituents are extremely complicated, and a variety of factors, including coals' chemical and mineralogical composition, combustion condition, plant configuration, other flue gas constituents, and time/temperature history of flue gas from combustion zone to stack, can affect mercury speciation in flue gas. It is believed that the transformations of mercury in post-combustion flue gas are kinetic limiting processes that involve both homogeneous gas-phase and heterogeneous reactions. The partitioning of mercury species in flue gas will depend on coal type, and mercury capture can be influenced by SO2 and SO3 concentration. Therefore the major issues concerning high concentrations of SO2 and SO3 on the performance of oxy-fuel systems including inhibition of mercury capture and whole life costs will be addressed in the project by combination of experimental and theoretical studies. The overarching goals of this project are as follows: The efficiency of sorbents in reducing SO3 will be assessed for the first time at pilot scale, previous studies having only concentrated on SO2, at conditions pertinent to oxy-fuel firing and post-combustion capture, (air firing conditions). This work will be carried out by our industrial partner. The Leeds research team will develop and validate an engineering computational code to provide a detailed engineering assessment of the potential application of oxy-fuel firing for electricity generation, and to develop an engineering capability and tool to assist with the design of oxy-fuel plants in the future.New physical models developed and validated in this project will be integrated into a commercial CFD code to predict the performance behaviour of oxy-fuel combustors and dry sorbent performance. The code will provide a useful tool for engineers to assess and optimise the SO3 removal for carbon capture application. In addition another objective of this project to be addressed by the Leeds research group is to understand the importance of gas- and solid-phase constituents in mercury oxidation reaction chemistry, and the effects of chlorine, nitrogen oxide, sulphur dioxide and ash particles on mercury oxidation will be investigated. Using the developed mercury oxidation reaction mechanism, the impact of high levels of SO2 in flue gas through anticipated interactions between Cl2 and SO2 on chlorine-promoted mercury transformation will be investigated.