Collaborative Research: Combustion Behavior of Hydrochars from Wet Biomass

来自日常来源的碳基废物，如垃圾填埋场、农业加工、废水处理等，通常是“湿”废物，这使得它们难以用传统方法转化为生物燃料。这项工作的重点是一种被称为“水热碳化”（HTC）的过程，它将这些已经潮湿的生物材料转化为高级燃料，这比典型的方法更高效，成本更低。由此产生的燃料被称为“碳氢化合物”，这是一种碳浓缩固体，因其“类似煤”的特性而被称为生物煤。与煤炭燃烧相比，碳氢化合物排放的有害空气污染物更少，对二氧化碳的净影响几乎为零。然而，在这些碳氢化合物的形成过程中，表面会形成一种类似焦油的物质，初步研究表明，这种物质可能会显著改变它们的燃烧行为。这项工作的目标有两个：首先，了解焦油状物质的形成途径和化学成分；其次，了解焦油状物质对点火和颗粒燃烧等重要燃烧行为的影响。这项工作将包括不同领域之间的密切合作，通过精心设计的实验，拉近燃料合成和燃烧领域的距离。与技术社区和他们所支持的行业进行大量接触，将支持采用碳氢化合物作为能源生产中煤炭的替代品。使用这种可再生固体燃料发电的能力有助于减缓气候变化，并将美国转变为绿色能源出口国和就业机会创造者。为了填补这些高科技职位，我们需要多样化的劳动力；康奈尔大学（Cornell）和宾夕法尼亚州立大学（Penn State）的终身女教授在培养来自弱势群体的学生方面都有良好的记录。至少有两名研究生和两名本科生将接受这个项目的培训。热液碳化被广泛吹捧，因为它能够将潮湿的生物质流转化为可再生的固体燃料，可以用作能源发电中煤炭的替代品。尽管HTC在废物管理方面具有潜在的好处，但在炭化过程中，固体碳氢化合物表面经常形成反应性无定形二次炭。由于二次炭的反应性截然不同，这种二次炭可能会妨碍这些“生物煤”作为替代燃料用于燃烧。迄今为止，可再生燃料文献仅通过快速氧化的热重分析来表征碳氢化合物，而不是真正的燃烧行为。因此，我们对它们的燃烧行为知之甚少，只能依靠基本的燃料特性来衡量这种可再生固体燃料的潜力。这项工作的目标——同类研究的第一个——是了解生物质基碳氢化合物的基本燃烧行为，这是一种具有独特燃烧特性的固体燃料。这项工作将提高我们对(1)水热碳化机理和(2)具有凝聚焦油相的可再生固体燃料的燃烧行为的基本理解。拟议工作的一个关键的更广泛的影响是严格连接两个（令人惊讶的）完全不同的领域-可再生燃料科学和燃烧科学。pi之间紧密耦合的工作不仅将为这两个社区的联系提供科学基础，而且pi将积极参与彼此的研究社区以弥合差距。pi将与HTC的一家技术开发公司合作，向大型HTC加工设备的设计者和对水力发电感兴趣的潜在客户传播信息。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。

Carbon-based waste from everyday sources, like landfills, agricultural processes, wastewater treatment, and more, are typically “wet” wastes, which makes them difficult to convert to biofuels using traditional methods. This work focuses on a process called “hydrothermal carbonization” (HTC), which converts these already wet bio-materials into high-grade fuels, which is both more efficient and cost effective than typical methods. The resultant fuel is known as “hydrochar,” a carbon-condensed solid often referred to as bio-coal for its “coal-like” properties. Compared to coal combustion, hydrochars emit fewer hazardous air pollutants and have a near net-zero CO2 impact. During the formation of these hydrochars, however, a tar-like substance forms on the surface, which initial research suggests could significantly change their combustion behavior. The goal of this work is two-fold: first, understand the formation pathways and chemical composition of the tar-like substance and second, understand the impact that the tar-like substance has on important combustion behaviors like ignition and particle burn-out. The work will include a close collaboration between different fields, bringing the fields of fuel synthesis and combustion closer through carefully-designed experiments. Significant outreach to both technical communities and the industries they support will support the adoption of hydrochars as a replacement for coal in energy production. The ability to use such renewable solid fuels for energy generation can help mitigate climate change and transform the U.S. into a green energy exporter and job opportunity creator. To fill such high-tech positions, we need a diverse workforce; the PIs – tenure-track female professors at Cornell and Penn State – both have strong track records training students from under-represented groups. At least two graduate and two undergraduate students will be trained on this project.Hydrothermal carbonization is widely touted for its ability to transform moist biomass streams into renewable solid fuels that could be used as replacements for coal in energy generation. Despite the potential benefits of HTC for waste management, a reactive amorphous secondary char often forms on the surface of the solid hydrochar during carbonization. This secondary char may hamper the ability of these “bio-coals” to be used as drop-in fuels for combustion due to the drastically different reactivity of the secondary char. To date, the renewable fuels literature characterizes hydrochars only through thermogravimetric analysis of rapid oxidation, not true combustion behavior. As such, we know little about their combustion behavior, relying only on basic fuel characterizations to gauge this renewable solid fuel’s potential. The goal of the work – the first study of its kind – is to understand the fundamental combustion behavior of biomass-based hydrochars, a solid fuel with unique burning characteristics. The work will improve our fundamental understanding of (1) the mechanisms of hydrothermal carbonization and (2) the combustion behavior of renewable solid fuels with condensed tarry phases. A key broader impact of the proposed work is to rigorously connect two (surprisingly) disparate fields – Renewable Fuel Science and Combustion Science. The closely-coupled work between the PIs will provide not only a scientific foundation for linking these two communities, but the PIs will actively participate in each other’s research communities to bridge the gap. The PIs will work with an HTC technology development firm to disseminate information to the designers of large-scale HTC processing equipment and potential customers interested in firing hydrochars for energy generation.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.