A system approach to selective catalyst reduction DeNOx monolithic reactor modelling using bond graphs

Abstract

Stricter NOx emission limits for marine diesel engines have resulted in a market demand for engine external NOx reduction solutions. This demand has led to the development of ammonia-based selective catalytic reduction DeNOx systems for marine applications. For selective catalytic reduction systems in general, mathematical modelling and numerical simulation have been essential for increasing knowledge, improving the design and developing control algorithms. This has resulted in higher NOx reduction performance, reducing NH3 slip and improving transient and start-up performance. Due to the increasing complexity of diesel-engine-based power systems, it is often argued that system development requires a simulation-based design approach to reduce development cost and increase development speed. For this to be cost-effective, reusable and interchangeable models of appropriate complexity need to be available. In this article, a system approach is applied to modelling of selective catalytic reduction DeNOx monolithic reactors. Three models with different levels of fidelity are developed using the bond graph method. The three models are compared by simulating dynamic conditions to uncover differences between the models. In addition, accuracy is investigated by comparing the simulation results with measurement data. The contribution in this article can be summarized to be an exploration of monolith selective catalytic reduction DeNOx modelling in a system simulation framework, and investigation of the effect of selective catalytic reduction model fidelity on a coupled system performance prediction.