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Ammonia is exclusively synthesized by the Haber-Bosch process starting from precious carbon resources such as coal or CH4. With H2O, H2 is produced and with N2, NH3 can be synthesized at high pressures and temperatures. Regrettably, the carbon is not incorporated into NH3 but emitted as CO2. Valuable carbon sources are consumed which could be used otherwise when carbon sources become scarce. We suggest an alternative process concept using an electrochemical membrane reactor (ecMR). A complete synthesis process with N2 production and downstream product separation is presented and evaluated in a multi-scale model to quantify its energy consumption. A new micro-scale ecMR model integrates mass, species, heat and energy balances with electrochemical conversions allowing further integration into a macro-scale process flow sheet. For the anodic oxidation reaction H2O was chosen as a ubiquitous H2 source. Nitrogen was obtained by air separation which combines with protons from H2O to give NH3 using a hypothetical catalyst recently suggested from DFT calculations. The energy demand of the whole electrochemical process is up to 20% lower than the Haber-Bosch process using coal as a H2 source. In the case of natural gas, the ecMR process is not competitive under today's energy and resource conditions. In future however, the electrochemical NH3 synthesis might be the technology-of-choice when coal is easily accessible over natural gas or limited carbon sources have to be used otherwise but for the synthesis of the carbon free product NH3.

Conventional models for simulating gas-separation processes often neglect nonideal effects such as concentration polarization, the Joule-Thomson Effect, pressure losses, and real gas behavior. This study presents a comprehensive model which accounts for such nonideal effects and can be applied in commercial process simulations. A model of a hollow-fiber gas permeation module was programmed in Aspen Custom Modeler. In general, pure gas measurements at a single feed pressure were sufficient to predict the mixed gas behavior of the module. The influence of nonideal effects on the module efficiency was investigated in two case studies addressing the separation of CO2/propane and CO2/methane gas mixtures. For the first case, the curves of CO2 concentration versus module length were congruent for both ideal and realistic scenarios. The divergence of the curves in the second case was attributed to the influence of cummulating nonideal effects. The simulations are in agreement with the new data obtained for these gas mixtures measured at a commercial polyimide membrane module. The model predicts the experimental gas permeation data, in particular, when nonideal effects are pronounced. Ultimately, this model can easily be used in process simulation and enables optimization of large-scale gas separation systems.