Temperature Measurements and Submicron Ash Formation in Oxy-Coal Combustion

氧煤燃烧是一种很有前途的清洁煤炭技术，可以减少全球变暖。尽管探索可再生能源很重要，但在任何可想象的未来能源情景中，煤炭可能仍是一个重要的来源。为了减缓全球变暖，应该通过提高发电、输电、配电和使用效率，以及通过二氧化碳的捕获和封存来限制二氧化碳的排放。废气中氮稀释的二氧化碳浓度低，这是传统吹吹煤粉燃烧捕获二氧化碳成本高的主要原因。在纯氧中燃烧煤炭或在与回收烟气混合的氧气中燃烧煤炭可产生富含二氧化碳的排出物，从而降低直接压缩和储存烟气的成本。为了使全氧煤燃烧技术的发展充分发挥其潜力，本研究为在相关条件下使用单煤颗粒的过程提供了基本的理解。煤在O2/CO2气氛中而不是O2/N2气氛中的燃烧动力学很重要，因为CO2可以(1)与煤发生反应，不像N2；(2)通过其相对于氮的传输性质和热容量的差异影响温度；(3)通过MO + CO = M + CO2可逆反应抑制灰分难熔氧化物的汽化，其中M可能是Fe、Mg或SiO。这项工作将多年来在传统煤/空气燃烧研究中开发的所有实验和分析工具应用于全氧煤燃烧领域，并解决了重要的基本问题：煤颗粒在全氧煤燃烧中燃烧得更热更快，污染物排放是增加还是减少？用多色光学热法观察了单个煤颗粒的燃尽历史，并推导了燃烧温度和反应速率。由于煤颗粒的最高温度可以超过最高气体温度数百度，因此颗粒温度的知识对于评估整体炉效率、炉膛出口气体温度以及锅炉中灰的段塞和结垢趋势非常重要。此外，在这项工作中，燃烧产生的颗粒和其他污染物在氧煤燃烧的排出气体中进行监测，并在性质上与传统燃烧过程中产生的颗粒进行比较。由于处理含氧煤电厂污染物排放的策略仍处于形成阶段，这些数据将特别有价值。

CBET-0755431LevendisOxy-coal combustion is a promising clean-coal technology that may reduce global warming. Coal is likely to remain a vital source in any conceivable future energy scenario despite the importance of exploring renewable sources of energy. To mitigate global warming, CO2 emissions should be constrained by improving efficiency of power generation, transmission, distribution, and use, as well as through CO2 capture and sequestration. The low, nitrogen-diluted CO2 concentration in the exhaust gas is a major driving force for high costs of capturing CO2 from conventional air-blown pulverized-coal combustion. Burning coal in pure oxygen or in oxygen blended with recycled flue gases can produce a CO2-rich effluent, thereby lowering the costs of the direct compression and storage of the flue gas. For technology development in oxy-coal combustion to reach its full potential, this study provides a fundamental understanding of the process using single coal particles, under pertinent conditions. Combustion kinetics of coal in an O2/CO2 atmosphere rather than O2/N2 is important because CO2 can (1) react with coal, unlike N2, (2) influence temperature through the differences in its transport properties and heat capacity relative to nitrogen, and (3) inhibit vaporization of refractory oxides of ash through the reversible reaction MO + CO = M + CO2, where M might be Fe, Mg, or SiO. This work applies all of the experimental and analytical tools developed over years of study in conventional coal/air combustion to the domain of oxy-coal combustion, and addresses important fundamental questions: Do coal particles burn hotter and faster in oxy-coal combustion Are pollutant emissions enhanced or reduced. Burnout histories of individual coal particles are observed, with multi-color optical pyrometry, and combustion temperatures and reaction rates are deduced. Because maximum coal-particle temperatures can exceed maximum gas temperatures by as much as several hundred degrees, knowledge of particle temperatures is important for evaluation of overall furnace efficiencies, furnace exit gas temperatures, as well as slugging and fouling tendencies of ash in a boiler. Furthermore, in this work, combustion-generated particulates and other pollutants are monitored in the effluent gases of oxy-coal combustion and are compared in character to those from the conventional combustion process. Because the strategies for handling pollutant emissions from oxy-coal plants are still in their formative stages, these data will be especially valuable.