A modular membrane reactor concept for intensified ammonia synthesis
Chemical Engineering Journal, cilt.519, 2025 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 519
- Basım Tarihi: 2025
- Doi Numarası: 10.1016/j.cej.2025.165119
- Dergi Adı: Chemical Engineering Journal
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, Chemical Abstracts Core, Chimica, Compendex, INSPEC
- Anahtar Kelimeler: Ammonia, Haber-Bosch, Membrane, Modeling, Process intensification
- Boğaziçi Üniversitesi Adresli: Evet
Özet
Intensified NH3 synthesis is modeled in a cascade of adiabatic packed-bed reactor (PBR) and NH3-selective membrane-decorated microchannel heat exchanger (HEXM+) units. Each PBR, comprising a Fe-based catalyst, is directed to a HEXM+ that provides simultaneous heat and NH3 transport to the neighboring N2-swept permeate channels through layers of a supported ZnCl2-immobilized molten salt membrane. The HEXM+ exit stream is fed to the succeeding PBR at conditions favoring catalysis away from thermodynamic limitations. This novel operation is simulated by combining a PBR model, benchmarked with literature-based experimental data, and a HEXM+ model benchmarked with a CFD-based counterpart. Membrane stability, pressure drop, and NH3 recovery are imposed as constraints. At inlet conditions of 573 K, 50 bar, H2/N2 = 3 and 2.5 mol s−1 H2 flow, in-situ NH3 separation gives a fourfold increase in N2 conversion from 13.5% of the membraneless case (HEXM–) to 55%. Counter-current partitioning of the PBR effluent and sweep flow in a HEXM+ yields higher NH3 recovery and better temperature regulation than the co-current configuration. Addition of pure N2 feeding to each PBR notably improves temperature regulation, allows ~25% increase in N2 consumption, and maximizes productivity to ~1 × 10−2 molNH3 kgcat−1 s−1 as of PBR5. This peak productivity can be achieved in PBR3 by interconnecting the permeate channel flow of the HEXM+ units, rather than dosing sweep N2 to each HEXM+. The optimal cascade system doubles the productivity achieved in a benchmark microchannel membrane reactor, offering a capacity of ~0.45 t NH3 d−1, which is compatible with small-scale NH3 synthesis.