Exergetic analysis of reactive systems for polygeneration

这个子项目设计了使用燃料丰富的均质压燃发动机进行功、热和有用化学品多联产的工艺概念，并对其进行热力学和经济性评估。同以往一样，有关有用化学品的重点将放在合成气和乙炔和乙烯等价值较高的碳氢化合物上。由于甲烷/空气混合物的缓慢自燃，添加剂和通过废气再循环或恢复的方式对新鲜气体进行预热起着重要的作用。在前一个项目期间，反应性添加剂如正庚烷和二甲醚的积极作用得到了展示。这主要是由于降低了均质压燃发动机甲烷点火所需的进口温度。然而，很大一部分能量和碳是由添加剂引入的。因此，替代添加剂，如臭氧，是有趣的，它们在低得多的浓度下起作用。现在将在拟议的项目期内对这些问题进行调查。在初步研究中，示例性地表明，即使在富油范围内，极少量的臭氧也可以在较低的温度下点火。因此，现在的目标是通过模拟来量化甲烷和乙醇混合物与臭氧在富油范围内的发动机动力学和热力学。一方面，有必要揭示在压缩-膨胀循环中，对于燃料丰富的范围，臭氧数量、活性中间体和最终产物之间的相关性。另一方面，目的是为发动机多联产找到现实的参数范围，也是关于压力升高率和燃烧阶段。最后，发动机过程的质量，也与实验子项目合作，将通过火用概念进行评估，以减少不可逆性。由于发动机过程只能被视为一个子系统，有关其热力学质量的结论很重要，但也必须与上下游工艺步骤一起考虑，包括热力学和经济方面的考虑。是否使用发动机多联产，最终取决于能源和化学产品的总成本以及与竞争对手的转换方法相比的价值。对(火用)销毁成本和投资成本的经济考量提供了关于改进可能性的重要信息。到目前为止，已经确定基于发动机的多联产过程作为一个整体系统在热力学和经济上也是有利的，但也发现了弱点。该项目的目的是开发包括材料分离和能量集成在内的工艺概念，以便在添加臭氧的情况下具有良好的马达条件，并将它们与替代概念进行比较。

This subproject designs process concepts for the use of fuel-rich HCCI engines for the polygeneration of work, heat, and useful chemicals and evaluates them thermodynamically and exergoeconomically. As before, the focus with regard to useful chemicals will be on synthesis gas and higher-value hydrocarbons such as ethyne and ethene. Due to the slow auto-ignition of methane/air mixtures, additives and preheating of the fresh gas by means of exhaust gas recirculation or recuperation plays an important role. In the preceding project period, the positive effects of reactive additives such as n-heptane and dimethyl ether were demonstrated. These are mainly due to the reduction of the inlet temperature required for methane ignition in HCCI engines. However, a substantial part of the energy and carbon is introduced by the additive. Therefore, alternative additives, such as ozone, are interesting, that are active at much lower concentration. These will now be investigated in the proposed project period. In preliminary studies it was exemplarily shown that very small amounts of ozone enable ignition at reduced temperature even in the fuel-rich range.Therefore, it is now aimed to quantify the engine kinetics and thermodynamics of methane and ethanol mixtures with ozone in the fuel-rich range by means of simulations. On the one hand, it is necessary to uncover correlations between ozone quantity, reactive intermediates and end products for the fuel-rich range in compression-expansion cycles. On the other hand, the aim is to find realistic parameter ranges for engine polygeneration also with regard to pressure rise rates and combustion phasing. Finally, the quality of the engine process, also in cooperation with the experimental subprojects, is to be evaluated by means of the exergy concept, in order to reduce irreversibilities.Since the engine process can only be regarded as a subsystem, conclusions about its thermodynamic quality are important, but must also be considered together with upstream and downstream process steps, both applying thermodynamic and economic considerations. Whether engine polygeneration will be used, depends ultimately on the total costs and the value of the energy and chemical products compared to competing conversion methods. The exergo-economic consideration of the costs of exergy destruction and the investment costs provides important information about possibilities for improvement. So far, it has been established that the engine-based polygeneration process is also thermodynamically and economically advantageous as an overall system, but weak points have also been uncovered. The aim of this project is to develop process concepts including material separation and energy integration for promising motor conditions with ozone addition and to evaluate them in comparison to alternative concepts.