CFD modelling and optimization of ammonia synthesis-absorption integrated reactor under mild conditions
Author
Olsen, Line Flansmose
Term
4. term
Education
Publication year
2025
Submitted on
2025-10-02
Pages
28
Abstract
Dette speciale undersøger integreret, absorptionsforstærket ammoniaksynthese—hvor dannet ammoniak bindes undervejs for at skubbe reaktionen fremad—ved hjælp af Computational Fluid Dynamics (CFD), dvs. computersimuleringer af strømnings- og kemiske reaktionsforhold, kombineret med to kinetiske modeller, der beskriver reaktions- og absorptionshastigheder. Arbejdet fokuserer på at modellere, validere og optimere en enkelt‑kammer‑reaktor som et potentielt mere bæredygtigt alternativ til den konventionelle Haber–Bosch‑proces. Modellen er valideret mod forsøgsdata fra litteraturen, og der er udført et netuafhængighedsstudie for at kontrollere, at CFD‑resultaterne ikke afhænger af netopløsningen. Et parametervariationsstudie viser, at flere lag af katalysator og absorbent kan opnå hydrogenkonverteringer på niveau med et enkelt gennemløb i Haber–Bosch, men ved lavere driftsbetingelser. En flerobjektiv optimering baseret på et centralt kompositdesign (en statistisk forsøgsplan) fremhæver den afgørende betydning af gas hourly space velocity (GHSV, gasgennemstrømning pr. katalysatorvolumen) og reaktorens geometri for balancen mellem konverteringseffektivitet og absorptionskapacitet. Samlet set peger resultaterne på, at CFD‑baseret modellering er et nyttigt værktøj til at undersøge ammoniakproduktion under vilkår, der er forenelige med vedvarende energi, samtidig med at de understreger behovet for yderligere eksperimentel validering og økonomiske vurderinger.
This thesis investigates integrated, absorption‑enhanced ammonia synthesis—where newly formed ammonia is captured to drive the reaction forward—using Computational Fluid Dynamics (CFD), that is, computer simulations of fluid flow and chemical reactions, combined with two kinetic models that describe reaction and absorption rates. The work focuses on modeling, validating, and optimizing a single‑vessel reactor as a potentially more sustainable alternative to the conventional Haber–Bosch process. The model is validated against experimental data from the literature, and a grid‑independence study is used to check that the CFD results do not depend on mesh resolution. A parametric study shows that multiple layers of catalyst and absorbent can achieve hydrogen conversions comparable to a single pass in Haber–Bosch, but at lower operating conditions. Multi‑objective optimization based on a central composite design (a statistical design of experiments) highlights the critical influence of gas hourly space velocity (GHSV, gas flow per catalyst volume) and reactor geometry in balancing conversion efficiency and absorption capacity. Overall, the findings indicate that CFD‑based modeling is a useful tool for exploring ammonia production under conditions compatible with renewable energy, while underscoring the need for further experimental validation and economic assessment.
[This summary has been rewritten with the help of AI based on the project's original abstract]
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