Dynamic Modelling and Control of Sorption-Enhanced Green Ammonia Synthesis Integrated with PEM Electrolysis
Author
Taranets, Elizaveta
Term
4. term
Education
Publication year
2025
Submitted on
2025-05-27
Pages
65
Abstract
Efterhånden som andelen af vedvarende energi vokser, er det fortsat en udfordring at lagre og transportere den svingende elproduktion. Power-to-X (PtX) giver en løsning ved at omdanne grøn elektricitet til værdifulde produkter, som kan lagres over tid. Ammoniak (NH3) er en kulstoffri bærer af brint og et centralt produkt i Power-to-Ammonia (PtA). Grøn ammoniaksynthese er et bæredygtigt alternativ til den CO2-intensive Haber-Bosch-proces. Men konventionelle reaktorer, der arbejder ved høje temperaturer og tryk, er dårligt egnede til dynamiske driftsforhold. Dette speciale undersøger derfor en ny sorptionsforstærket ammoniakreaktor, der er designet til fleksibel drift under mildere betingelser, hvor den dannede ammoniak løbende optages for at fremme reaktionen. Der blev udviklet en detaljeret CFD-model (Computational Fluid Dynamics) af den absorptionsintegrerede NH3-reaktor. På baggrund af CFD-data blev der derefter skabt en stationær Functional Mock-up Unit (FMU) med en response surface-metode, som en forenklet erstatningsmodel, der kan integreres med andre PtA-komponenter i MATLAB/Simulink. Den integrerede model blev brugt til at undersøge driftsmuligheder og reaktorstyring ved svingende H2-tilførsel. Blandt de testede scenarier gav drift med to reaktorer i parallel under spidsproduktion af H2 den højeste effektive NH3-produktion (33,1 kg/dag) og det laveste specifikke energiforbrug (17 kWh/kg). Resultaterne viser, at integration af fleksible, absorptionsforstærkede NH3-reaktorer med intermittent vedvarende energi er teknisk mulig, mens den økonomiske analyse peger på, at høje anlægsomkostninger til reaktorer og elektrolysatorer i dag begrænser den økonomiske konkurrenceevne.
As renewable energy grows, storing and transporting its variable output remains difficult. Power-to-X (PtX) offers a path by converting renewable electricity into storable products. Ammonia (NH3) is a carbon-free hydrogen carrier and a key product in Power-to-Ammonia (PtA) systems. Green NH3 synthesis aims to replace the CO2-intensive Haber-Bosch process. However, conventional reactors that run at high temperature and pressure are not well suited to dynamic operation. This thesis investigates a novel sorption-enhanced ammonia reactor designed for flexible operation under milder conditions, where newly formed ammonia is continually absorbed to drive the reaction. A detailed Computational Fluid Dynamics (CFD) model of the absorption-integrated NH3 synthesis reactor was developed. Based on the CFD results, a steady-state Functional Mock-up Unit (FMU) using a response surface method was then created as a simplified surrogate, enabling integration with other PtA plant components in MATLAB/Simulink. The integrated model was used to assess operating feasibility and reactor control strategies under fluctuating hydrogen (H2) supply. Among the scenarios tested, operating two reactors in parallel during peak H2 production achieved the highest effective NH3 output (33.1 kg/day) and the lowest specific energy use (17 kWh/kg). Overall, the results indicate that coupling flexible, absorption-enhanced NH3 reactors with intermittent renewable power is technically feasible, while the economic analysis shows that high capital costs for reactors and electrolyzers currently limit competitiveness.
[This summary has been rewritten with the help of AI based on the project's original abstract]
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