Resource and energy efficiency are essential in process synthesis of chemical plants as they combine economic with ecological benefits. The two main targets of the process synthesis problem-mass and energy flux optimization-are typically split into two steps: single unit optimization and subsequent energy integration preventing the identification of the globally optimal solution. This article presents a single-step procedure for resource-efficient process synthesis through simultaneous heat and mass flux optimization called FluxMax approach which is demonstrated for the production of hydrogen cyanide (HCN). The impact of simultaneous heat integration on the optimal process structure is demonstrated and two resource-optimal processes for HCN production are identified consisting of a combination of different reactor and recycling strategies reducing total variable cost by 68 %. For convex objective functions, the globally most resource-efficient process is identified highlighting the potential of the FluxMax approach for site planning and retrofitting of existing plants.

No abstract

No abstract

No abstract

No abstract

High-temperature reactors are employed to produce key intermediates within the chemical value chain such as synthesis gas and hydrogen cyanide. The drawback of those reactors is their high energy consumption. In practice, intensive simulations, know-how based on experience as well as heuristics are used to optimize those reactors. Knowledge of the key transport phenomena that govern the reactor behavior, however, enables a systematic reactor design and optimization. Using a simplified but effective rigorous two-dimensional reactor model modeling assumptions are scrutinized and key flow and heat transfer phenomena are identified using the case study of synthesis of hydrogen cyanide (HCN). Following the model validation, it is shown that buoyant forces are significant near the walls whereas turbulent flow is negligible. In contrast to estimates using dimensionless numbers both conduction accounting for 81.9 % and radiation with 18.1 % are significant in providing the energy to the reacting gas mixture 1 inside the synthesis compartments. The results demonstrate the importance of a careful model selection for high-temperature reactors and enable a targeted reactor design optimization.

Steam methane reforming processes represent the economically most competitive processes for the production of synthesis gas and hydrogen despite their high energy costs. Although there is a strong need for highly resource-efficient production, literature on the optimal design of reformers remains scarce due to the inherently high complexity of these processes. This contribution addresses design aspects of reformers for the case study of a side-fired reformer. Based on a two-dimensional furnace representation heat transfer and the optimal tube bundle arrangement for a fixed furnace chamber are investigated using simulation-based parametric study with both a lean radiation-based model and a computational fluid dynamics model that enables the consideration of fuel efficiency. Radiative heat transfer prevails in the reformer on the furnace side and inter-tube distances of at least three diameters are optimal within the investigated design space. The line arrangement of reformer tubes is beneficial in terms of total heat transferred, fuel efficiency as well as the homogeneity of the tube surface temperatures. These findings pave the way for further studies such as three-dimensional design aspects.

No abstract