Minimal Supersymmetric CPN Models

Supersymmetric CPN models based on underlying bosonic Kahler manifolds have not been thought to arise directly from constrained linear ones. A counterexample for N=4 is presented using improved understanding of membranes in superstring theories leading to crucial central terms modifying the algebra of supercharge densities. The example has an immediate extension to all higher N

Avoiding the theorem of Lerche and Shore

Supersymmetric $\sigma$-models obtained by constraining linear supersymmetric field theories are ill defined. Well defined subsectors parametrising Kahler manifolds exist but are not believed to arise directly from constrained linear ones. A counterexample is offered using improved understanding of membranes in superstring theories leading to crucial central terms modifying the algebra of supercharge densitie

Optimal Process Design of Commercial-Scale Amine-Based CO2 Capture Plants

Reactive absorption with an aqueous solution of amines in an absorber/stripper loop is the most mature technology for postcombustion CO2 capture (PCC). However, most of the commercial-scale CO2 capture plant designs that have been reported in the open literature are based on values of CO2 loadings and/or solvent circulation rates without an openly available techno-economic consideration. As a consequence, most of the reported designs may be suboptimal, and some of them appear to be unrealistic from practical and operational viewpoints. In this paper, four monoethanolamine (MEA) based CO2 capture plants have been optimally designed for both gas-fired and coal-fired power plants based on process and economic analyses. We have found that the optimum lean CO2 loading for MEA-based CO2 capture plants that can service commercial-scale power plants, whether natural-gas-fired or coal-fired, is about 0.2 mol/mol for absorber and stripper columns packed with Sulzer Mellapak 250Y structured packing. Also, the optimum liquid/gas ratio for a natural gas combined cycle (NGCC) power plant with a flue gas composition of approximately 4 mol % CO2 is about 0.96, while the optimum liquid/gas ratio for a pulverized-coal-fired (PC) power plant can range from 2.68 to 2.93 for a flue gas having a CO2 composition that ranges from 12.38 to 13.50 mol %

Estimation of the Pitzer Parameters for 1–1, 2–1, 3–1, 4–1, and 2–2 Single Electrolytes at 25 °C

The Pitzer model is one of the most important thermodynamic models to predict the behavior of aqueous electrolyte solutions, especially at high ionic strengths. However, most of the parameters in the Pitzer equations have to be obtained experimentally and this represents an important drawback to this model. Therefore, in order to make the Pitzer equations less dependent on experimental data and more dependent on the properties of the solution, new equations that correlate the Pitzer equations with the properties of the solution have been successfully developed for 1-1, 2-1, 3-1, 4-1 and 2-2 electrolytes. In particular, these equations were developed for two cases: (i) considers the original Pitzer equations and (ii) considers some simplifications to the Pitzer equation (assuming CMX , BMX (2) and 2 = 0). In particular, for case (ii), the second virial coefficients BMX (0) and BMX (1) of the Pitzer equations were re-estimated using published experimental data of the osmotic coefficient obtained from the literature. As a conclusion, both the simplified and the original Pitzer equations presented a very good match with this published experimental data for the osmotic coefficients. Additionally, the second virial coefficients BMX (0) and BMX (1) for both cases were successfully correlated with the ionic radius and the ionic charge, and this is confirmed by the very high coefficients of determination achieved (R2>0.96). However, these new equations are valid only to cases in which no significant ion association occurs, which is also the basic premise of the original Pitzer model

Effect of the CO2 enhancement on the performance of a micro gas turbine with a pilot-scale CO2 capture plant

Gas turbines are a viable and secure option both economically and environmentally for combined heat and power generation. Process modelling of a micro gas turbine for CO2 injection and exhaust gas recirculation (EGR) is performed. Further, this study is extended to assess the effect of the CO2 injection on the pilot-scale CO2 capture plant integrated with a micro gas turbine. In addition, the impact of the EGR on the thermodynamic properties of the fluid at different locations of the micro gas turbine is also evaluated. The micro gas turbine and CO2 injection models are validated against the set of experimental data and the performance analysis of the EGR cycle results in CO2 enhancement to 5.04 mol% and 3.5 mol%, respectively. The increased CO2 concentration in the flue gas, results in the specific reboiler duty decrease by 20.5 % for pilot-scale CO2 capture plant at 90 % CO2 capture rate for 30 wt. % MEA aqueous solution. The process system analysis for the validated models results in a much better comprehension of the impact of the CO2 enhancement on the process behaviour

Dynamic economic and emission dispatch model considering wind power under Energy Market Reform: A case study

With the increasing issues in the environmental and the high requirement for energy, the Energy Market Reform (EMR) was introduced by the UK government. This paper develops a novel Dynamic Economic and Emission Dispatch (DEED) model for a combined conventional and wind power system incorporating the carbon price floor (CPF) and the Emission Performance Standard (EPS) that is supported by the EMR. The proposed model aims to determine the optimal operation strategy for the given system on power dispatch taking into account wind power waste and reserve and also the environmental aspect, especially the CPF of greenhouse gases and the emission limit of the EPS for different decarbonisation scenarios. Case studies for the demand profile in the Sheffield region in the UK with different time intervals is presented. The results indicate that renewable power is superior in both the economics and emissions to a mid to long-term energy strategy in the UK

Techno-economic process design of a commercial-scale amine-based CO2 capture system for natural gas combined cycle power plant with exhaust gas recirculation

Post-combustion CO2 capture systems are gaining more importance as a means of reducing escalating greenhouse gas emissions. Moreover, for natural gas-fired power generation systems, exhaust gas recirculation is a method of enhancing the CO2 concentration in the lean flue gas. The present study reports the design and scale-up of four different cases of an amine-based CO2 capture system at 90% capture rate with 30 wt.% aqueous solution of MEA. The design results are reported for a natural gas-fired combined cycle system with a gross power output of 650 MWe without EGR and with EGR at 20%, 35% and 50% EGR percentage. A combined process and economic analysis is implemented to identify the optimum designs for the different amine-based CO2 capture plants. For an amine-based CO2 capture plant with a natural gas-fired combined cycle without EGR, an optimum liquid to gas ratio of 0.96 is estimated. Incorporating EGR at 20%, 35% and 50%, results in optimum liquid to gas ratios of 1.22, 1.46 and 1.90, respectively. These results suggest that a natural gas-fired power plant with exhaust gas recirculation will result in lower penalties in terms of the energy consumption and costs incurred on the amine-based CO2 capture plant

Techno‐economic assessment on the fuel flexibility of a commercial scale combined cycle gas turbine integrated with a CO2 capture plant

Post‐combustion carbon capture is a valuable technology, capable of being deployed to meet global CO2 emissions targets. The technology is mature and can be retrofitted easily with existing carbon emitting energy generation sources, such as natural gas combined cycles. This study investigates the effect of operating a natural gas combined cycle plant coupled with carbon capture and storage while using varying fuel compositions, with a strong focus on the influence of the CO2 concentration in the fuel. The novelty of this study lies in exploring the technical and economic performance of the integrated system, whilst operating with different fuel compositions. The study reports the design of a natural gas combined cycle gas turbine and CO2 capture plant (with 30 wt% monoethanolamine), which were modelled using the gCCS process modelling application. The fuel compositions analysed were varied, with focus on the CO2 content increasing from 1% to 5%, 7.5% and 10%. The operation of the CO2 capture plant is also investigated with focus on the CO2 capture efficiency, specific reboiler duty and the flooding point. The economic analysis highlights the effect of the varying fuel compositions on the cost of electricity as well as the cost of CO2 avoided. The study revealed that increased CO2 concentrations in the fuel cause a decrease in the efficiency of the natural gas combined cycle gas turbine; however, rising the CO2 concentration and flowrate of the flue gas improves the operation of the capture plant at the risk of an increase in the flooding velocity in the column. The economic analysis shows a slight increase in cost of electricity for fuels with higher CO2 contents; however, the results also show a reduction in the cost of CO2 avoided by larger margins

No Significant Evidence of Cognitive Biases for Emotional Stimuli in Children At-Risk of Developing Anxiety Disorders.

This paper explores whether the increased vulnerability of children of anxious parents to develop anxiety disorders may be partially explained by these children having increased cognitive biases towards threat compared with children of non-anxious parents. Parents completed questionnaires about their child’s anxiety symptoms. Children aged 5–9 (n = 85) participated in two cognitive bias tasks: 1) an emotion recognition task, and 2) an ambiguous situations questionnaire. For the emotion recognition task, there were no significant differences between at-risk children and children of non-anxious parents in their cognitive bias scores for reaction times or for accuracy in identifying angry or happy facial expressions. In addition, there were no significant differences between at-risk children and children of non-anxious parents in the number of threat interpretations made for the ambiguous situations questionnaire. It is possible that these cognitive biases only become present subsequent to the development of an anxiety disorder, or only in older at-risk children

Development of a surrogate and its comprehensive compact chemical kinetic mechanism for the combustion of Alcohol-To-Jet fuel

This study develops a compact high-fidelity chemical kinetic mechanism for a proposed surrogate of Alcohol-To-Jet fuel, capable of modelling ignition delay time, laminar flame speed, and species concentration. A combination of 85% iso-dodecane and 15% iso-cetane by wt% that is a close approximation to the real fuel composition was selected as the ATJ surrogate to investigate the simulation of the three given combustion properties. A relatively good agreement has been observed for ignition delay, laminar flame speed, and mole fraction of some species, between the simulation by the Chemkin-Pro software package and the available experimental data in the literature. The authors suggest that this proposed surrogate with its compact validated mechanism can be used by researchers to study the combustion behaviour of ATJ fuel including the investigation on the complex geometries of combustion system such as Equivalent Reactor Network Analysis which require a compact accurate chemical kinetic mechanism