Multi-Objective Optimization of Braun-Type Exothermic Reactor for Ammonia Synthesis

The exothermic reactor for ammonia synthesis is a primary device determining the performance of the energy storage system. The Braun-type ammonia synthesis reactor is used as the exothermic reactor to improve the heat release rate. Due to the entirely different usage scenarios and design objectives, its parameters need to be redesigned and optimized. Based on finite-time thermodynamics, a one-dimensional model is established to analyze the effects of inlet gas molar flow rate, hydrogen–nitrogen ratio, reactor length and inlet temperature on the total entropy generation rate and the total exothermic rate of the reactor. It’s found that the total exothermic rate mainly depends on the inlet molar flow rate. Furthermore, considering the minimum total entropy generation rate and maximum total exothermic rate, the NSGA-II algorithm is applied to optimize seven reactor parameters including the inlet molar flow rate, lengths and temperatures of the three reactors. Lastly, the optimized reactor is obtained from the Pareto front using three fuzzy decision methods and deviation index. Compared with the reference reactor, the total exothermic rate of the optimized reactor is improved by 12.6% while the total entropy generation rate is reduced by 3.4%. The results in this paper can provide some guidance for the optimal design and application of exothermic reactors in practical engineering.

Solar Thermochemical Conversion of Carbon Dioxide into Fuel via MnFe2O4 based Two-Step Redox Cycle

Thermodynamic efficiency analysis of [[EQUATION]] based CO 2 splitting (CDS) cycle is reported. HSC Chemistry software is used for performing the calculations allied with the model developed. By maintaining the reduction nonstoichiometry equal to 0.1, variations in the thermal energy required to drive the cycle ( [[EQUATION]] ) and solar-to-fuel energy conversion efficiency ( [[EQUATION]] ) as a function of the ratio of the molar flow rate of inert sweep gas ( [[EQUATION]] ) to the molar flow rate [[EQUATION]] ( [[EQUATION]] ), i.e., [[EQUATION]] , reduction temperature ( [[EQUATION]] ), and gas-to-gas heat recovery effectiveness ( [[EQUATION]] ) are studied. The rise in [[EQUATION]] is responsible for the decrease in [[EQUATION]] . At [[EQUATION]] = 0.7, [[EQUATION]] increases from 176.0 kW to 271.7 kW when [[EQUATION]] escalates from 10 to 100. Conversely, [[EQUATION]] reduces from 14.9% to 9.9% due to the similar increment in [[EQUATION]] . The difference between [[EQUATION]] at [[EQUATION]] = 10 and 100 decreases from 363.3 kW to 19.2 kW as [[EQUATION]] rises from 0.0 to 0.9. As [[EQUATION]] and subsequently [[EQUATION]] reduces as a function of [[EQUATION]] , [[EQUATION]] increases noticeably. At [[EQUATION]] equal to 0.9 and [[EQUATION]] equal to 10 as well as 20, the maximum [[EQUATION]] equal to 17.5% is realized.

Solar Energy Storage via Thermochemical Metal Oxide/Metal Sulfate Water Splitting Cycle

ABSTRACTThis paper reports the effect of Ar molar flow-rate on thermodynamic efficiency analysis of zinc oxide-zinc sulfate (ZnS-ZnO) water splitting cycle useful for solar H2 production. The thermodynamic efficiency analysis is conducted using the HSC Chemistry 7.1 software and its thermodynamic database. Influence of Ar molar flow-rate on total solar energy input essential for the continuous operation of the cycle is explored. Furthermore, the solar-to-fuel energy conversion efficiency for the ZnS-ZnO water splitting cycle is determined.

Degradation Kinetics of Fe-EDTA in Hydrogen Sulfide Removal Process

Available data on the degradation of Fe-EDTA liquid redox H2S removal processes are reviewed, and the effect of H2S molar flow rate, the initial concentration of Fe(III)EDTA, and the presence of sodium citrate in Fe-EDTA solution were investigated in this study. The semibatch with continuous flow of H2S containing biogas was used under a wide range of experimental conditions; , H2S molar flow rate, (1.08 × 10−3–3.40 × 10−3 mol/h), the initial concentration of Fe(III)EDTA, (2.17–8.16 mol/m3), and the concentration of sodium citrate, (0–300 mol/m3). The result showed that sodium citrate acted as stabilizer with a good ability to reduce the degradation rate. The degradation rate of Fe-EDTA was found to follow pseudo first-order kinetics. Empirical correlations expressed the degradation rate constant as a function of significant H2S molar flow rate, and the initial Fe(III)EDTA and sodium citrate concentration were successfully developed for the prediction of Fe-EDTA degradation rate. Moreover, the precipitated solid, called sulfur cake, was recovered, and its composition was investigated. The result revealed that the sulfur cake contained more than 98% sulfur element and almost balances with iron, and no significant EDTA was degraded into the solid form.

Alternative Group V Precursors for the Growth of Al-Based III-V Epitaxial Layers by OMVPE

ABSTRACTTertiarybutylarsine (TBAs), tris-dimethylaminoarsenic (DMAA), and tertiarybutylphosphine (TBP) were investigated as alternatives to arsine and phosphine for the growth of AlGaAs, AlInAs, and AlInP by organometallic vapor phase epitaxy. The use of TBAs led to a significant reduction in carbon and oxygen incorporation compared to ASH3 for AlGaAs. Increasing the TBAs molar flow rate reduced the oxygen (and carbon) concentration. Lower oxygen concentration was observed in AllnP grown with TBP compared to PH3. Increasing the PH3 molar flow rate decreased the oxygen incorporation in AllnP. The morphology of AllnP improved considerably as the growth temperature was increased from 650°C to 750°C, similar to the case of PH3. AlInAs and AlGaAs layers grown with DMAA exhibited rough morphology, presumably due to oxygen-containing impurities in the DMAA source.