Surface-response analysis for the optimization of a carbon dioxide absorption process using [hmim][Tf2N]

The [hmim][Tf2N] ionic liquid is considered in this work to develop a model in Aspen Plus® capturing carbon dioxide from shifted flue gas through physical absorption. Ionic liquids are innovative and promising green solvents for the capture of carbon dioxide. As an important aspect of this research, optimization is carried out for the carbon capture system through a central composite design: simulation and statistical analysis are combined together. This leads to important results such as the identification of significant factors and their combinations. Surface plots and mathematical models are developed for capital costs, operating costs and removal of carbon dioxide. These models can be used to find optimal operating conditions maximizing the amount of captured carbon dioxide and minimizing total costs: the percentage of carbon dioxide removal is 93.7%, operating costs are 0.66 million ¿/tonCO2 captured (due to the high costs of ionic liquid), and capital costs are 52.2 ¿/tonCO2 captured

Optimization of CCUS supply chains in the UK: A strategic role for emissions reduction

The UK is the second largest emitter of carbon dioxide in Europe. It aims to take urgent actions to achieve the 2030 target for CO_{2} emissions reduction imposed by EU environmental policies. Three different carbon capture utilization and storage (CCUS) supply chains are developed giving economic indicators for CO_{2} utilization routes not implying carbon dioxide hydrogenation (i.e. with high TRL). The study presents an innovative proposal to reduce CO_{2} impact in the UK, a country rich in coal, which requires reduction of carbon dioxide emissions from flue gases as the easiest and best performing solution. Bunter Sandstone, Scottish offshore and Ormskirk Sandstone are the storage sites considered, while several attractive potential utilization options are considered. Through minimization of total costs, the CCUS supply chain with Bunter Sandstone as storage site results in the most economically profitable solution due to the highest value of net present value (€ 0.554 trillion) and lowest value of pay back period (2.85 years). Only carbon tax is considered. The total cost is € 1.04 billion/year. Across the supply chain, 6.4 Mton/year of carbon dioxide emissions are avoided, to be either stored or used for calcium carbonate production. Future work should consider uncertainty, dynamics of market demand and social aspects

Population balances combined with computational fluid dynamics : a modeling approach for dispersive mixing in a high pressure homogenizer

High pressure homogenization is at the heart of many emulsification processes in the food, personal care and pharmaceutical industry. The droplet size distribution is an important property for product quality and is aimed to be controlled in the process. Therefore a population balance model was built in order to predict the droplet size distribution subject to various hydrodynamic conditions found in a high pressure homogenizer. The hydrodynamics were simulated using Computational Fluid Dynamics and the turbulence was modeled with a RANS k–e model. The high energy zone in the high pressure homogenizer was divided into four compartments. The compartments had to be small enough to secure nearly homogeneous turbulent dissipation rates but large enough to hold a population of droplets. A population balance equation describing breakage and coalescence of oil droplets in turbulent flow was solved for every compartment. One set of parameters was found which could describe the development of the droplet size distribution in the high pressure homogenizer with varying pressure drop. An improvement of 65% was found compared to the same model containing just one compartment. The compartment approach may provide an alternative to direct coupling of CFD and population balances

Two-nucleon knockout contributions to the 12^{12}C(e,e′p)(e,e'p) reaction in the dip and {Δ\Delta}(1232) regions

The contributions from $^{12}$C$(e,e'pn)$ and $^{12}$C$(e,e'pp)$ to the semi-exclusive $^{12}$C$(e,e'p)$ cross section have been calculated in an unfactorized model for two-nucleon emission. We assume direct two-nucleon knockout after virtual photon coupling with the two-body pion-exchange currents in the target nucleus. Results are presented at several kinematical conditions in the dip and $\Delta$(1232) regions. The calculated two-nucleon knockout strength is observed to account for a large fraction of the measured $(e,e'p)$ strength above the two-nucleon emission threshold.Comment: 12 Revtex pages, 4 postscript figures (available upon request), University of Gent preprint SSF94-02-0

Inclusive (e,e′N)(e,e^\prime N), (e,e′NN)(e,e^\prime NN), (e,e′π)(e,e^\prime \pi) ... reactions in nuclei

We study the inclusive $(e,e^\prime N)$, $(e,e^\prime NN)$, $(e,e^\prime \pi)$, $(e,e^\prime \pi N)$ reactions in nuclei using a Monte Carlo simulation method to treat the multichannel problem of the final state. The input consists of reaction probabilities for the different steps evaluated using microscopical many body methods. We obtain a good agreement with experiment in some channels where there is data and make predictions for other channels which are presently under investigation in several electron laboratories. The comparison of the theoretical results with experiment for several kinematical conditions and diverse channels can serve to learn about different physical processes ocurring in the reaction. The potential of this theoretical tool to make prospections for possible experiments, aiming at pinning down certain reaction probabilities, is also emphasized.Comment: 21 pages (LaTeX + figure files

Large effect of irradiance on hydrogen isotope fractionation of alkenones in <i>Emiliania huxleyi</i>

The hydrogen isotopic (dD) composition of long-chain alkenones produced by certain haptophyte algae has been suggested as a potential proxy for reconstructing paleo sea surface salinity. However, environmental parameters other than salinity may also affect the dD of alkenones. We investigated the impact of the level of irradiance on hydrogen isotopic fractionation of alkenones versus growth water by cultivating two strains of the cosmopolitan haptophyte Emiliania huxleyi at different light intensities. The hydrogen isotope fractionation decreased by approximately 40‰ when irradiance was increased from 15 to 200 µmol photons m-2 s-1 above which it was relatively constant. The response is likely a direct effect of photosystem I and II activity as the relationship of the fractionation factor a versus light intensity can be described by an Eilers–Peeters photosynthesis model. This irradiance effect is in agreement with published dD data of alkenones derived from suspended particulate matter collected from different depths in the photic zone of the Gulf of California and the eastern tropical North Pacific. However, haptophyte algae tend to bloom at relatively high light intensities (>500 µmol photons m-2 s-1) occurring at the sea surface, at which hydrogen isotope fractionation is relatively constant and not affected by changes in light intensity. Alkenones accumulating in the sediment are likely mostly derived from these surface water haptophyte blooms, when the largest amount of biomass is produced. Therefore, the observed irradiance effect is unlikely to affect the applicability of the hydrogen isotopic composition of sedimentary long chain alkenones as a proxy for paleosalinit