Non-premixed ammonia combustion in tailored ceramic porous inert media

该项目的重点是无碳化学能载体氨和氨/氢混合物的热化学能转换过程。氨被认为是未来的能源和氢气载体之一，特别是在长途运输方面，因为它的热性质与丙烷相似，而且在现有的运输网络下，它很容易液化储存和运输。然而，氨的燃烧带来了相当大的挑战。三大挑战是，与碳氢化合物相比，其燃烧速度较低，导致火焰稳定性差，氮氧化物生成水平极高，即使在痕量水平上也具有高毒性。解决这些挑战的传统方法是添加高活性燃料，如氢气或甲烷，以解决火焰稳定性问题，在分阶段燃料丰富/贫化过程中进行转化，以解决高NOx形成问题，以及后处理，以避免未燃烧的氨排放。我们建议通过一种新的概念来解决所有的挑战，即在多孔惰性介质(PIM)中非预混燃烧氨气。由于固相中的热再循环，注射成型燃烧比非注射成型燃烧速度提高一个数量级以上。热再循环与固相的热惯性相结合，解决了火焰稳定性问题。非预混方法导致初始富燃料或纯燃料气流高温分解氨而没有明显的NOx生成，而通过PIM的流动的良好混合和温度均化效应导致燃烧后区域内剩余氨的完全燃尽。为了实现这一概念，需要量身定做的耐高温材料，无论是在几何形状上还是在热性能的空间分布上。需要用复合陶瓷材料进行PIM结构的添加制造(ADM)，以通过定制导热、辐射性能、色散和流场等特性来控制工艺。氨和氨/氢混合物非预混PIM燃烧器的基础研究和设计需要一个强大的跨学科研究团队，这些领域包括PIM燃烧的高保真实验(EXP，KIT)、详细的孔分辨数值模拟(SIM，KIT)以及热震和耐腐蚀功能部件的添加制造方法(ADM，TU BAF)。

The project focuses on the thermochemical energy conversion process of the carbon-free chemical energy carrier ammonia and of ammonia/hydrogen mixtures. Ammonia is considered as one of the future energy and hydrogen carriers, especially in terms of long-distance transport since its thermal properties are similar to those of propane and it can easily be liquefied for storage and transport with an established transportation network. However, the combustion of ammonia poses considerable challenges. The three major challenges are its low burning velocity compared to hydrocarbons resulting in poor flame stability, extremely high levels of nitrogen oxide formation and high toxicity even at trace levels. Conventional approaches to address these challenges are the addition of highly reactive fuels like hydrogen or methane to address the issue of flame stability, conversion in staged fuel rich/lean processes to address the high NOx formation and post treatment for avoiding unburnt ammonia emissions. We propose to address all challenges at once by a novel concept for non-premixed combustion of ammonia in Porous Inert Media (PIM). Combustion in PIM can increase burning velocities by more than one order of magnitude compared with non-PIM combustion due to heat recirculation through the solid phase. Heat recirculation combined with the thermal inertia of the solid phase resolves the issue of flame stability. The non-premixed approach results in high temperatures of the initial fuel rich or pure fuel streams decomposing ammonia without significant NOx formation, while the good mixing and temperature homogenization effects by the flow through the PIM lead to a complete burnout of remaining ammonia in a post-combustion zone. In order to realize such concept, tailored high temperature-resistant materials are required, both in terms of geometry as well as spatial distribution of thermal properties. Additive manufacturing (ADM) of PIM structures from composite ceramic materials is needed to control the process through customized properties regarding heat conduction, radiation properties, dispersion and the flow field. The fundamental research and design of the non-premixed PIM burner for ammonia and ammonia/hydrogen-mixtures requires a strong interdisciplinary research team in the fields of high-fidelity experiments for combustion in PIM (EXP, KIT), detailed pore-resolved numerical simulations (SIM, KIT) and additive manufacturing methods for thermal shock and corrosion-resistant functional components (ADM, TU BAF).