Combustion characteristics of pulverized torrefied biomass for use in co-firing boilers

为了满足快速增长的全球人口对能源的需求，并尽量减少对环境的负面影响，需要替代能源。美国拥有大量的可再生生物质生产能力，其利用可以减少碳排放总量。大多数替代能源（风能、太阳能、潮汐能）由于其间歇性而无法提供基本负荷电力，用生物质能部分替代煤炭可能是一种可行的选择。然而，生物质是湿润的、可生物降解的和纤维状的。因此，运输、储存和研磨用于锅炉是昂贵的。这项研究将解决碳化生物质的燃烧问题，这些生物质已经经过了烘烤过程（类似于咖啡烘焙），以去除水分、氯和硫。然而，随着粉碎成本的急剧增加，目标粉碎粒度的降低，本工作旨在确定在现有锅炉中有效燃烧的适当的最大碳化生物质粒度范围。要使碳化生物质成为一种标准化产品，在几乎未经改造的燃煤电厂中燃烧，就需要这些知识。在这项研究的过程中，学生将接受能源领域的教育，并将在收集生物能源的主题上推进若干国际合作，以帮助实现可持续发展的环境。本研究将产生新的知识，有关有效燃烧碳化生物质在公用事业锅炉。本研究将确定评估各种碳化生物质材料（包括几种典型的木质和草本生物质类型）与煤粉共烧的适当尺寸的方法，同时在现有锅炉中保持高燃烧效率和高辐射通量。与颗粒燃尽时间、挥发物火焰和残余炭的温度、火焰内烟尘体积分数、颗粒间相互作用、碳燃尽有关的数据需要用于预测锅炉中的反应速率、热通量以及结渣和结垢趋势。提出的基础研究将通过高温法和电影摄影法监测单个颗粒的整个燃烧历史，在颗粒水平上评估粉碎碳化生物质的这些燃烧参数。这些数据将与以前在本实验室收集的所有等级煤颗粒的类似数据进行比较。随后，燃烧效率和粒子间的相互作用将通过纯燃料和混合燃料的燃烧流进行评估，并监测排放。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

To satisfy energy needs of the fast-growing global population and minimize the negative impact on the environment, alternative energy sources are needed. The U.S. has a large capacity for renewable biomass production, the utilization of which can reduce the total carbon emissions. Partial substitution of coal with biomass can be a viable option for generating the baseload power that most alternative sources (wind, solar, tidal) cannot supply due to their intermittent nature. However, biomass is moist, biodegradable and fibrous. Thus, it is costly to transport, store and grind for use in the boilers. This research will address the combustion of torrefied biomass, which has been subjected to the process of torrefaction (akin to coffee roasting) to remove moisture, chlorine and sulfur. However, as grinding costs drastically increase with decreasing targeted grind size, this work aims to identify appropriate maximum torrefied biomass particle size ranges for effective combustion in existing boilers. Such knowledge is needed for torrefied biomass to become a standardized product for burning in virtually unmodified coal-fired plants. During the course of this research, students will be educated in the energy field and several international collaborations will be advanced on the subject of harvesting bioenergy to help achieve a sustainable environment.This research will generate new knowledge pertinent to effective combustion of torrefied biomass in utility boilers. This investigation will identify methods for assessing the proper size of various kinds of torrefied biomass materials (including several typical woody and herbaceous biomass types) for co-firing with pulverized coal, while maintaining high combustion efficiencies and high radiative fluxes in existing boilers. Data pertinent to particle burnout times, temperatures of both volatile matter flames and residual chars, in-flame soot volume fractions, particle-to-particle interactions, carbon burnout are needed to predict reaction rates, heat fluxes, and slagging and fouling deposition tendencies in boilers. The proposed fundamental research will assess these combustion parameters of pulverized torrefied biomass at the particle level, by monitoring entire combustion histories of single particles pyrometrically and cinematographically. These will be compared to analogous data for coal particles of all ranks, previously collected in this laboratory. Subsequently, combustion effectiveness and particle-to-particle interactions will be assessed by burning streams of neat and blended fuels and emissions will be monitored.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.