CO2 aided H2 recovery from water splitting processes

Solar energy can be utilized to produce H₂ via photocatalytic water splitting. One major drawback of the one-step approach is the co-production of H₂ and O₂ in the same reactor environment creating a potentially hazardous scenario. This obstacle can be avoided by utilizing CO₂ as a flammability suppressant which is proven to be more effective than N₂. In this case study, several membrane cascade designs were implemented to recover the H₂ while maintaining compositions outside the flammability range. The optimizations are based on the use of commercially available composite polymer membranes from Membrane Technology and Research, Inc. (MTR) in the spiral wound architecture. Both the H₂-selective membrane (Proteus?) and CO₂-selective membrane (Polaris?) were explored in three layouts. The process optimization is solved by nonlinear programming. The aim of the study was to minimize the present value of all outgoing cash flow (no income) for the separation process and achieving 99% product (H₂) purity. Optimization results showed that utilizing three membrane units of Proteus? material with one recycle stream is the optimum layout over a wide range of recovery values. Incorporating the CO₂-selective membrane (Polaris?) leads to more expensive process due to higher recycle flow rates to compensate for the low selectivity of this material. Overall, the best economic results for this process were obtained at 85% recovery rate with 99% product purity at a cost of 6.40 $/kg. Comparing to our previous study using a N₂ diluent, higher purity product with lower specific cost can be achieved with CO₂ diluent system but with slight decrease in recovery rate. As a final element to this study, comparative simulations were executed to demonstrate the potentially added value of using hollow fiber membranes versus spiral wound for this separation process.     

Calculated Relative Stabilities of C84

C₈₄ is treated as a system composed of 24 local minima whose energies, geometries, and vibrational frequencies are obtained from MNDO calculations. The predicted global minimum of D_2d symmetry remains the most abundant species in the equilibrium isomeric mixture only till 276 K, being replaced by a D₂ species beyond that point. However, a C ₁ structure is prevalent in the high temperature limit. The calculated composition around a temperature of 1000 K is consistent with very recent NMR observations.     

Introduction: Perspectives on Cold War Science in Small European States

With this introduction we aim to illuminate Western Europe's place on the map of Cold War science and, specifically, to draw attention to the differences in and the diversity of Western European Cold War science in comparison to the United States. By discussing narratives of Cold War science in small states and asking how they fit into the European condition, we suggest that the fact of being a small state affects the conditions for and the scope of Cold War science. As a whole, this special issue also emphasizes the importance of the spatial dimension; that is, the significant dependence of Cold War science on geographical relations and geopolitical interests.     

Ökonomische Bewertung und Optimierung des Automatisierungsgrades von Versicherungsprozessen

In the context of value and customer orientation there are various requirements concerning the process – especially in insurance companies: processes are meant to be standardized, automated, and flexible. It is in question whether a fast and cheap automated processing is preferred to manual handling. For which claims and which process steps is it of economic value to have the flexibility and the competence and ability to solve problems of human operators at your disposal? Various combinations, representing different degrees of automation, are possible. The different degrees of automation for the processing of an insurance claims are compared and resulting cash flows are determined. It is essential to include all consequences that can be attributed to a single process and to consider customer reactions and restrictions to the capacity of processing. Instead of using heuristic rules to decide on automation in practice, here the decision is flexible and depends on the given situation. Viewing an aggregated number of insurance claims it is possible to deduce information about the performance of the process. The model is exemplarily illustrated with help of a part of the process for handling own damage glass claims.