Nitrogenated Hydrocarbon Cross-Product Formation during Combustion of Ammonia Co-Fired with Regular Hydrocarbons

可以说，当今社会面临的最大挑战是在满足能源需求的同时减少使地球变暖的排放。因此，氨作为燃烧时不会直接排放二氧化碳的无碳燃料而备受关注。它可以在国内使用清洁电力从空气和水中生产，而且比氢更容易液化。由于氨的燃烧特性很差，在许多应用中，它将与碳氢化合物燃料（如天然气）共燃。这为基础燃烧化学的一个新领域打开了大门：氮化交叉产物的形成，将燃料中碳氢化合物部分的碳原子与氨中的氮原子结合起来。我们有初步的数据证实了这种交叉产物的形成，并表明它们通过将碳隔离在一种不能生长成烟灰的形式中，从而在化学上抑制了燃料中碳氢化合物部分的烟灰颗粒的形成。拟议项目的目标是系统地探索氨与传统燃料燃烧时交叉产物的形成，确定它们与烟灰形成的关系，并确定产生它们的化学机制。该项目将使用火焰采样和在线光电离质谱法生成第一个痕量碳氢化合物浓度分布数据库，该数据库采用敏感的宽带诊断方法，在以氨+甲烷、乙烯和其他碳氢化合物为燃料的火焰中测量。它将测量同一火焰中煤烟的体积分数，并测试交叉产物形成化学抑制共燃碳氢化合物形成煤烟的假设。它将表征从火焰中热反射取样的烟尘颗粒的形态、纳米结构和原子组成，以进一步确定交叉产物和烟尘之间的关系。测量将使用一种新的实验设计，通过比较氨+碳氢化合物火焰和相应的氮+碳氢化合物火焰，来区分氨的化学效应和它的物理效应。火焰将在温度，主要物种和边界条件方面进行彻底的表征，以便可以通过计算模拟来测试和改进交叉产物的详细动力学机制。温度测量将进一步发展一种新型x射线荧光诊断技术，该技术具有独特的能力，可以测量烟尘火焰所有区域的热边界条件和现场温度，而颗粒的干扰可以忽略不计。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。

Arguably the greatest challenge confronting our society today is to satisfy our energy needs while reducing emissions that warm the planet. In this regard, ammonia is gaining attention as a carbon-free fuel that can be burned with no direct carbon dioxide emissions. It can be produced domestically from air and water using clean electricity and is much more easily liquified than hydrogen. Since ammonia has poor burning characteristics, in many applications it will be co-fired with hydrocarbon fuels such as natural gas. This opens the door to a novel area of fundamental combustion chemistry: the formation of nitrogenated cross-products that combine carbon atoms from the hydrocarbon portion of the fuel with nitrogen atoms from the ammonia. We have preliminary data that verifies the formation of such cross-products and suggests that they chemically suppress formation of soot particles from the hydrocarbon portion of the fuel by sequestering carbon in a form that cannot grow to soot. The objective of the proposed project is to systematically explore the formation of cross-products when ammonia is burned with conventional fuels, determine their relationship to soot formation, and identify the chemical mechanisms that produce them.This project will use flame sampling and online photoionization mass spectrometry to generate the first database of trace hydrocarbon concentration profiles measured with a sensitive, broadband diagnostic in flames fueled with ammonia + methane, ethylene, and other hydrocarbons. It will measure soot volume fractions in the same flames and test the hypothesis that cross-product formation chemically suppresses soot formation from the co-fired hydrocarbons. It will characterize the morphology, nanostructure, and atomic composition of soot particles sampled thermophoretically from the flames to further determine the relationship between cross-products and soot. The measurements will use a novel experimental design to distinguish the chemical effects of ammonia from its physical effects by comparing the ammonia + hydrocarbon flames with a corresponding set of nitrogen + hydrocarbon flames. The flames will be thoroughly characterized with respect to temperature, major species, and boundary conditions so that they can be computationally simulated to test and improve detailed kinetic mechanisms for cross-products. The temperature measurements will further the development of a novel X-ray fluorescence diagnostic that is uniquely capable of measuring thermal boundary conditions and in-situ temperatures in all regions of sooting flames with negligible interferences from particles.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.