A Study on Burning Iron Particles as Carbon-Free Circular Fuels with co-Generation of Value-Added Nanomaterials

从化石燃料到可再生能源的能源转型对于减缓气候变化，从而促进国家健康、繁荣和福利是必要的。然而，可再生能源，主要是太阳能或风能，并不总是在需求高的地点或时间（例如，在高纬度地区，冬季，晚上）可用。因此，一种具有成本竞争力和有效的可再生能源载体必须能够储存可用的能源，并在需要的地方和时间运输能源。这将使长距离储存和/或运输可再生能源成为可能。让大多数人惊讶的是，铁粉是一种很有前途的能量载体。铁燃料循环可以提供丰富的绿色能源和储存方法，以帮助满足世界日益增长的能源需求。亚毫米大小的铁粉可以用现有的工业技术从废金属中制造出来，它可以被运送到现有的或专用的电力设施或工业炉中，在那里它可以像煤粉一样被点燃和燃烧。在燃烧过程中，这些铁颗粒产生与输入铁颗粒大小相似的氧化铁颗粒。燃烧过程中释放的能量（热）可以用来产生蒸汽，然后可以旋转汽轮机并发电。废弃的氧化铁颗粒可以通过使用绿色氢和能源还原为铁，这两种能源都可以从太阳能电池板或风力涡轮机中获得。这项研究正在推进铁粉作为“循环燃料”的科学，并充分表征了产品和任何产生的副产品（如纳米级氧化物颗粒），同时也确定了后一种材料的适当应用，如超级电容器、锂电池阳极、催化剂、环境清洁剂以及医学成像、靶向、药物输送和生物传感材料。这项研究旨在教育研究生和本科生了解可持续能源收集和储存以及燃烧产生的材料的好处和挑战。技术总结铁是一个令人信服的候选无碳循环燃料，由于其丰富，高能量密度，以及强大的储存和传输能量的能力。铁可以在高温（2000 K）下点燃和燃烧，因此，它可以直接替代燃煤锅炉中的煤。通过利用现有的基础设施进行无碳发电，铁燃料可以改变公用事业行业。它产生零排放的二氧化碳（CO2），零排放的二氧化硫（SO2），零排放的未燃烧碳氢化合物（HC）和超低排放的一氧化二氮（NOx）。目前，对铁燃料循环的科学认识尚不完整，并导致产生一些纳米材料副产品，通常被认为是废物流。相反，假设这些铁基纳米材料可以产生高价值的产品。拟议的研究正在对铁颗粒燃烧过程中发生的物理转变以及产生增值铁基纳米材料的条件产生基本的理解。项目的目标是确定process-structure-property关系在两个截然不同的流use-inspired产品:submillimeter-sized氧化物粒子可以回收铁、纳米级粒子和相当大的单分散性和可裁制成衣的属性。通过生成全面的数据集，全面测量铁的燃烧参数，充分表征所产生的纳米颗粒，并完成能量/火用分析，以确定燃料循环中的不可逆性，来评估是否成功。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。

NON-TECHNICAL SUMMARYEnergy transition from fossil fuels to renewables is necessary to mitigate climate change and, thereby, advance the national health, prosperity and welfare. However, renewable energy, mostly solar or wind, is not always available at the location or the time when demand is high (e.g., in high earth latitudes, winter months, evenings). Hence, a cost-competitive and effective renewable energy carrier must be able to store available energy and transport energy to be used where and when it is needed. This would enable storage and/or transportation of renewable energy over long distances. Surprisingly to most people, a promising energy carrier candidate is iron powder. The iron fuel cycle could offer an abundant green energy source and storage methodology to help meet the world’s growing energy needs. Submillimeter sized iron powder can be manufactured from scrap metal with existing industrial techniques, it can be transported to either existing or dedicated electric utility or industrial furnaces, where it can be ignited and burned like pulverized coal. During combustion, these iron particles generate iron oxide particles of sizes similar to the input iron particles. The energy emitted during combustion (heat) can be used to generate steam which, thereafter, can spin a steam turbine and generate electricity. Spent iron oxide particles can be reduced back to iron, using green hydrogen and energy, both of which can be obtained from solar panels or wind turbines. This research is advancing the science of powdered iron as a “circular fuel” and is fully characterizing the products and any generated byproducts (such as nanosized oxide particles) while also identifying appropriate applications for the latter materials, such as in supercapacitors, lithium battery anodes, catalysts, environmental cleanup agents as well as materials for medical imaging, targeting, drug delivery, and biosensing. This research is educating graduate and undergraduate students in the benefits and challenges of sustainable energy harvesting and storage, as well as combustion generated materials. TECHNICAL SUMMARYIron is a compelling candidate for a carbon-free circular fuel due to its abundance, high energy density, and strong ability to store and transport energy. Iron can be ignited and burned at elevated temperatures (2000 K) and, thus, it can be a direct replacement for coal in coal-fired boilers. By leveraging existing infrastructure for carbon-free power generation, iron fuel can be transformative to the utility industry. It generates zero emissions of carbon dioxide (CO2), zero emissions of sulfur dioxide (SO2), zero emissions of unburned hydrocarbons HC) and ultra-low emissions of nitrous oxide (NOx). Currently, the iron fuel cycle has incomplete scientific understanding and results in the generation of some nanomaterial byproducts, typically considered a waste stream. Instead, it is hypothesized that these iron-based nanomaterials can yield high-value products. The proposed research is generating fundamental understanding of the physical transformations that occur during the burning of iron particles and the conditions that produce value-added iron-based nanomaterials. The goal of the project is to determine process-structure-property relationships in two distinct streams of use-inspired products: submillimeter-sized oxide particles that can be recycled back to iron, and nano-sized particles with considerable monodispersity and tailorable properties. Success is being assessed by generating a comprehensive data set on thoroughly-measured iron combustion parameters, fully characterizing the produced nanoparticles and completing an energy/exergy analysis to identify irreversibilities within the fuel cycle.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.