ChemEngineering

The time-dependent electrochemical behavior of a nominal Ni20Cr alloy exposed to molten Solar Salt (60 wt.% NaNO₃–40 wt.% KNO₃) was investigated at 300, 400, and 500 °C for isothermal exposure times of up to 100 h. Open-circuit potential (OCP), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were used to monitor the evolution of the alloy/molten-salt interface. OCP measurements revealed time-dependent potential changes during exposure. Because a Pt pseudo-reference electrode was used without independent calibration against a thermodynamic reference or internal redox couple, the OCP data were interpreted primarily in terms of their temporal evolution within each isothermal experiment rather than through direct comparison of absolute potential values between temperatures. LPR measurements showed a strong temperature dependence of the polarization resistance, with a pronounced decrease at 500 °C. The impedance response was consistent with two interfacial contributions, represented using a two-time-constant equivalent circuit and tentatively associated with the surface corrosion-product layer and the underlying alloy/corrosion-product interface. At 500 °C, both resistance contributions were markedly lower than those measured at 300 and 400 °C, consistent with a substantial loss of interfacial barrier effectiveness. The persistence of a surface-related impedance response at 500 °C was therefore not considered evidence of a highly protective layer. Rather, the electrochemical results suggest that a surface-related interfacial contribution remained distinguishable at 500 °C, although its associated resistance was substantially lower than at 300 and 400 °C. These assignments represent electrochemically based interpretations and should not be regarded as unique identification of the underlying microscopic processes. Overall, the results demonstrate that temperature strongly influences the electrochemical behavior of Ni20Cr in molten nitrate salts and that the electrochemical resistance to corrosion-related processes decreases markedly at 500 °C. The 100 h electrochemical exposures investigated here characterize short-term interfacial behavior and do not establish the long-term structural suitability of Ni20Cr for concentrated solar power service.

This study develops a physics-informed surrogate for predicting three-dimensional gas–liquid hydrodynamics in an aerated double-impeller stirred tank. Reference fields were generated using steady-state computational fluid dynamics (CFD) simulations in ANSYS Fluent at impeller speeds of 200–500 rpm. Three models with identical network architectures were examined: a supervised neural network (NN) trained on CFD data, a boundary-informed neural network (BINN) incorporating boundary constraints, and a physics-informed neural network (PINN) incorporating boundary and reduced physics constraints. At 400 and 500 rpm, the PINN outperformed the NN and BINN, achieving normalized liquid- and gas velocity errors below 10% and pressure errors of approximately 3–4%. The NN and BINN showed greater attenuation of impeller-induced gradients in high-shear regions. At the unseen intermediate speeds of 350 and 450 rpm, the PINN reproduced the principal CFD flow structures. Normalized gas velocity errors were approximately 11–14%, while normalized pressure errors ranged from 4.48% to 9.22%, depending on the operating speed and error metric. Each CFD simulation required approximately 100–140 h, whereas PINN inference at 200,000 spatial locations required approximately 2–3 h per operating condition. The initial cost of generating the CFD training data must be considered when assessing the benefit of repeated surrogate evaluations.

An important process of chemical engineering is the removal of moisture from natural gas and process gases by fixed-bed adsorption. Experiments were conducted to design (ad)sorption columns, predict breakthrough behavior, and determine the velocity of the (ad)sorption front. The data obtained from these adsorption experiments served as input parameters for modeling by the linear driving force approach. In this study, the supported ionic liquid (SILP) 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MeSO₃]), coated on porous silica, was used as drying agent in fixed-bed adsorption. A novel method for the operando monitoring of (ad)sorption fronts in fixed-bed adsorbers is the radio-frequency-based cavity perturbation method. Here, the adsorber forms a cavity resonator. A model based on S-shaped advancing sorption profiles that is represented by a cumulative Gaussian distribution (CDF) is applied. Furthermore, it is shown that the modeled (ad)sorption fronts lead to resonance parameters measured via the microwave-based cavity perturbation method with high precision. It is demonstrated that the breakthrough curves in SILPs can be accurately reproduced both by the new radio-frequency-based method and by a classical chemical engineering tool such as the linear driving force model.