422 research outputs found
Analysis and optimization of carbon supply chains integrated to a power to gas process in Italy
No full textThe mathematical model for carbon capture, utilization and storage supply chains is developed for Italian regions. This model is used to design supply chains minimizing total costs and reducing significantly carbon dioxide emissions. Carbon dioxide can be stored or utilized to produce methane through a power to gas system, where hydrogen is obtained by the electrolysis of water using renewable power while methane is fed to the gas grid. The Mixed Integer Linear Program model is applied to design carbon systems developed for ten regions with major carbon dioxide emissions, while different saline aquifers are proposed as storage sites. Results show that the Adriatic sea is the most appropriate offshore storage site in the supply chain. This leads to a lower net methane production cost and to the lowest level of economic incentives as compared to other cases. The total costs of this supply chain are 7.34·104 million €/year (953 €/tonCO2 captured), and 16.1 Mton/year of methane are produced. The supply chain does not result economically favorable without substantial financial incentives (80 €/tonCO2 for carbon tax and 260 €/MWh economic incentive for methane production). Comparing supply chains that include simultaneous utilization and storage of carbon dioxide with a carbon capture and utilization supply chain (without storage) shows that the latter is economically less favorable. In addition to mitigation of carbon environmental impact for the whole Country, the large scale supply chain proposed here meets 35% of Italy’s methane demand as a whole, a significant contribution to a global economic perspective, widely discussed nowadays, which should include self-sustainment elements at regional level
A decision support platform for a bio-based supply chain: Application to the region of Lower Saxony and Bremen (Germany)
No full textIn this work, a biomass supply chain model, for the region of Lower Saxony and Bremen in northern Germany, has been developed. Because of Germany's high demand for biofuels, the production and distribution of levulinic acid and bioethanol by wheat straw is studied. An illustrative bio-based supply chain model is developed and implemented in the Advanced Interactive Multidimensional Modeling (AIMMS) software. Then, this model is used to study the logistics, network optimization, transportation and inventory management, and the resulting environmental and economic impacts. In the end, a sensitivity analysis is conducted to evaluate the influence of key model parameters on these impacts. The results showed that a wheat straw supply chain network is profitable in the area of Bremen and Lower Saxony even though the bioproducts demand is not fully covered and that the transportation costs did not have a strong impact on the supply chain network
Carbon Dioxide to Methanol: A Green Alternative to Fueling the Future
No full textCarbon dioxide is a greenhouse gas causing the current climate change and global warming so that its capture and conversion into several chemical compounds and fuels is important. Methanol is a main product from carbon dioxide reduction that can be used as fuel and as raw material for other important chemicals. This work presents a critical description of different routes for methanol production from carbon dioxide. Methanol can be obtained from carbon dioxide through a direct route such as carbon dioxide hydrogenation, carbon dioxide electrochemical conversion, carbon dioxide photochemical conversion, carbon dioxide photoelectrochemical reduction and carbon dioxide bioconversion. On the other hand, methanol can also be obtained from carbon dioxide through an indirect route through syngas produced via either methane dry reforming or carbon dioxide-water co-electrolysis in a solid oxide electrolytic cell. Among these solutions, carbon dioxide hydrogenation is the most mature technology at the industrial level although it has high costs while other routes are mostly at a lab scale. Carbon dioxide electrochemical reduction is currently the most interesting technology for methanol production due to its simplicity and environmental friendliness
Capturing CO2 from the atmosphere: Design and analysis of a large-scale DAC facility
No full textDirect air carbon capture (DAC) technologies can substantially lower the CO2 concentrations in the atmosphere by enabling negative emissions. This study shows in detail the design of the DAC plant at industrial scale and provides insights on its performance in terms of process economic and CO2 emissions count. The proposed DAC plant is optimized to capture CO2 directly from the atmospheric air, employing a sensitivity analysis to find the influence of operation and design parameters on the total cost. Absorption using sodium hydroxide as chemisorbent is utilized with a capture rate of 0.7. Industrially mature common process units are considered to achieve a design that is relevant in the near future. An initial base case design indicates a carbon cost of 244 /ton-CO2, with two additional heat exchangers added to the network. Furthermore, renewable scenario is considered where a parallel electrolysis stage feeds the process hydrogen fuel and oxygen required for combustion in the calciner. This scenario indicates that higher operating costs are incurred due to the expensive green fuel. Finally, a profitability analysis is performed to establish the feasibility for further processing to methanol in a Power-to-X facility. The estimations indicate that the hydrogen price has to go down by 46.3% in order to break-even
Design of a wheat straw supply chain network in Lower Saxony, Germany through optimization
No full textIn this work, a biomass supply chain model for the region of Lower Saxony in northern Germany has been developed. Because of Germany's high demand for biofuels, the production and distribution of levulinic acid and bioethanol is studied by using the Advanced Interactive Multidimensional Modeling (AIMMS) software. The economic benefits that this supply chain provides show to what extent Lower Saxony can become fossil fuel independent. These results are used to answer the following question: has biomass the potential to successfully take up the torch from fossil fuels?a
An integrated methodology for the economic and environmental assessment of a biorefinery supply chain
No full textA supply chain network MILP model, developed by means of AIMMS software, and a pro-cess plant simulation model, developed by means of Aspen Plus, are combined for theoptimization of a biorefinery network. Optimization of the supply chain network is initiallyaddressed using literature process and economic data. The results are used as input in theAspen Plus model where the technical and economic performance of the biorefineries iscalculated rigorously. The two computational tools are iteratively executed until convergence on number, locations and size of the biorefineries and on process yield to productsand total costs is achieved. The final results are used to perform the Economic Value and Environmental Impact (EVEI) analysis of the overall biorefinery network. The methodologyis applied to a case study concerning the deployment of cereal straw in Germany to pro-duce ethanol, ethyl levulinate and electricity. Optimization results reveal that the wheatstraw supply network with four biorefineries is economically feasible and determines anenvironmental margin in terms of equivalent emissions savings of about 4 Mt of CO2peryear
The Joys of Collecting
No full textFollowed by a tour of the Edwin Brown Collection of Lewis, MacDonald, Barfield, Sayers, and Williams first editions and manuscripts at Taylor University\u27s Zondervan Library
Optimization under uncertainty of melatonin dosing for critically ill patients
No full textComputer-aided modelling and simulation are effective tools to provide guidance in the design of clinical experiments and treatments. Simulations with physiologically-based pharmacokinetic (PBPK) models combine the drug material balances within the body to its real physiological and anatomical features and can be used to optimize drugs dosing and administration timing. We focus on melatonin administration to critically ill patients, a challenging population because of their high inter-individual variability in the pharmacokinetics (due to their heterogeneous and severe conditions). We show how the optimization problem can be suitably formulated to tackle this uncertainty, and compare the results obtained for critically ill patients and healthy individuals. The approach can be easily transferred to any other drug routinely administered in intensive care units whenever a desired pharmacokinetic profile is available
Optimal dose administration of renally excreted drugs
No full textThe paper presents and discusses a basic pharmacokinetic model for vancomycin, an antibiotic that is principally excreted by kidneys. The model accounts for the degree of renal function by employing the CKD-EPI equation. Only one parameter of the model is identified by a nonlinear regression of experimental data, while the other parameters are evaluated a priori via correlations from the scientific literature. We simulate the pharmacokinetic time-curves of vancomycin by accounting for different values of the glomerular filtration rate and show the strong influence of the degree of renal function on the drug pharmacokinetics. In addition, the model can be used to determine the optimal dose for patients featuring varying degrees of renal function. Results underline the importance of individualized treatment
An optimization model for a biorefinery system based on process design and logistics
No full textDesign of biorefineries has been often addressed by process flowsheet optimization tools without adequately considering the relevant supply chain network. In this work, an integrated optimization algorithm including the biorefinery process flowsheet structure and biobased supply chain network was developed. A superstructure of different process pathways for a biorefinery co-producing ethanol, ethyl levulinate and electricity is built on the base of up-to-date technologies. The bio-based supply chain model was implemented to address the transportation, the inventory management and the size of the biorefinery. Mixed Integer Linear Programming (MILP) was used as a modeling approach. The efficiency of the algorithm was demonstrated by applying it to a case study consisting of a wheat straw supply chain network for bioproducts demand in Germany. The algorithm reached convergence after three iterations providing a final optimal number of biorefineries distributed in different regions of the country corresponding to a maximum Net Present Value
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