1,720,959 research outputs found
The use of exergy in life cycle analyses: Literature review
No full textIn this study, the literature linking exergy to three parts of life cycle analyses of technical processes is reviewed, namely the use of exergy with respect to the extraction of resources, the use of exergy in the analysis of production processes and the use of exergy with respect to emissions to the environment. Exergy is a measure of the quality of material and energy streams. In other words, it is measure for the amount of work can you perform with a certain material or energy stream. Its concepts are based on the first and the second law of thermodynamics. Various authors use exergy to measure the depletion of both material and energetic resources in a certain process, a complete process chain or even a complete country. It is important to use clearly defined system boundaries and it is preferable to use system boundaries similar to those used in the relatively well established methodology of Life Cycle Assessment (LCA). In the future, the depletion of natural resources, measured with the help exergy, can become an important instrument to analyse and compare various processes and process chains. Exergy is already used quite intensively to analyse technical processes, especially in the field of power generation, because second law concepts are important there. Exergy analysis can be used to determine major exergy losses in a certain process and is useful tool in process development and improvement. The exergy of emissions can only qualitative be linked with the damage of these emissions. No direct conclusions can be drawn about the environmental harm of emissions and their exergetic content. It is possible however to incorporate exergetic inputs needed to avoid emissions or to bring emissions back to environmental acceptable levels into life cycle analyses.Applied Science
From Small Scale to Large Scale: in the World of CO2 Reduction
No full textThe development of carbon dioxide sequestration and conversion technologies can help set up additional loops in the naturally occurring carbon cycle. It presents the unique opportunity to transition from a fossil fuel based industry to a CO2 based industry. Life cycle analysis of CO2 conversion processes which take into account the entire chemical conversion process have shown the advantages of using CO2 as a source of chemicals. Coupling these technologies with renewable sources of energy such as solar and wind, will reduce the global warming impact (GWI), by reducing the total carbon content in the atmosphere and thus mitigating the climate disasters. These technologies can help ensure peoples lives are secured and that vulnerable cultures which aremore dependent on nature are not washed away. It would help protect the lives of creatures who have no means of protection against the anthropological climate change....ChemE/Materials for Energy Conversion and Storag
Pathways to Industrial-Scale Fuel Out of Thin Air from CO<sub>2</sub> Electrolysis
No full textUsing renewable energy as an input, Power-to-X technologies have the potential to replace fossil fuels and chemicals with dense-energy carriers that are instead derived out of thin air. In this work, we put into context what the industrial-scale production of chemicals from ambient CO2 using CO2 electrolysis means in terms of future required operating conditions and the device and catalyst scales that will be needed for the technology to assume its role in our global energy system.Accepted Author ManuscriptChemE/Materials for Energy Conversion and StorageChemE/Transport Phenomen
CO<sub>2</sub> Capture and Reduction: Placing the process in an industrial framework
No full textCapturing and utilizing the emissions of CO2 has become a method to reduce the occurring emissions from industrial flue gases. One of the methodologies to capture and use the CO2 is through the CO2 capture and reduction (CCR) process. This process uses a bi-functional catalyst to capture CO2 from diluted gas streams and subsequently reduce it to CO in the presence of H2. The obtained product (syngas) can be further used as feedstock in for example the Fischer-Tropsch process. To implement a novel technology in industry, thetechnology itself should be economical feasible.To determine the feasibility of the process a technoeconomical analysis is executed. The analysis uses process parameters obtained by evaluating the catalytic activity of the bifunctional catalysts. Two catalyticsystems have been evaluated: Cu-K/𝛾-Al2O3 and FeCrCuK/PMG20. Effect on the synthesis conditions of Cu-K/𝛾-Al2O3 were also investigated. Cu-K/𝛾-Al2O3without additional drying steps during the synthesis shows a higher CO2 capacity and a faster CO production rate compared to the other catalysts. Furthermore, toestimate the H2 requirement in an industrialized process the consumption of H2 during the process has been quantified.To ensure a continuous process operation, a two reactor process has been proposed in the techno-economical analysis. The sizing and subsequent cost of the process equipment has been determined by utilizing the obtained process parameters. Besides the capital costs, the operating costs were also estimated to determine the profitability of the process. After the monetary benefit of selling the syngas was determined, it could be stated that the process is profitable under certain conditions. The process is profitable if the used H2 source has a buying price below 2.4 to ensure a profitable process.Applied Science
Converting the LNG-Peakshaver to be fit for processing LH2: An LH2 import terminal
No full textTo reach the goals of the European Green Deal (CO2 emission reduction of 55% by 2030 and climate neutral by 2050), North-Western Europe has to import sustainable energy as locally produced renewable energy will not be sufficient to meet the total demand. This will be realised by importing green hydrogen from areas with a surplus of renewable energy. If those areas are in another continent, the hydrogen is expected to be imported by vessel and received and stored in a hydrogen import terminal. Since Gasunie has an LNG plant in the Port of Rotterdam that becomes available within a few years, they want to investigate the possibilities to retrofit this plant into a hydrogen import terminal.This research has investigated if the current LNG-Peakshaver can be retrofitted to an LH2 import terminal. This import terminal will receive, store and process LH2 to be delivered to the hydrogen Backbone (future hydrogen grid in the Netherlands owned by Gasunie). The imported LH2 will be received from maritime vessels at conditions just above ambient pressure and below its boiling point (-253˚C). It will be stored in the retrofitted LNG storage tanks, and depending on the hydrogen demands of the grid, LH2 will be processed (regasified) to the requirements of the grid (5˚C and 50 bar). This send-out process is very similar to LNG and requires pumps, BOG compressors and evaporators as process equipment.The differences in physical and chemical properties have been analysed to determine if retrofitting LNG process equipment into LH2 application is feasible. The three main property differences that most affect the processes at the terminal are 1. the lower temperature (-253˚C instead of -162˚C), 2. the lower density and 3. the lower latent heat of vaporization of LH2 as compared to LNG. In view of these differences, it has been established that the reuse of the current LNG equipment is not possible. Even the pipes cannot be reused, as the LH2 pipes must be vacuum insulated to prevent liquid oxygen formation at the outside of these pipes.Enhanced research has been carried out into the required process equipment. For the LH2 pumps, cavitation and the low pressure-head of the centrifugal pump are a problem. To overcome these, a special inducer is used, and three HP pumps in series to reach the desired pressure of 50 bar. Regarding the hydrogen BOG compressors, a vertical labyrinth (reciprocating) type is considered. However, manufacturers cannot yet design compressors that operate at temperatures as low as -250˚C. For the evaporator, a Super-ORV design with seawater as the heat source is considered the best option to evaporate the LH2. This design is an enhanced ORV that improves the heat transfer, which is desirable considering the lower temperatures of LH2. Retrofitting the LNG tank is essential since it is the most expensive part of the plant. The current inner tank material and insulation are not capable of handling LH2. Therefore, two solutions have been explored to retrofit the storage tank. The more expensive solution -resulting in a lower BOR- is implementing a new vacuum insulated storage tank inside the existing concrete construction. The other option is to attach membrane insulation panels at the inside of the current storage tank.Simulations have been performed to analyse the desired terminal configuration with regard to energy efficiency. The differences in configuration depend on the tank's insulation method, BOG processing, and cold exergy utilization. From these results, it is concluded that a compressor that can handle temperatures as low as -250˚C is essential for an LH2 terminal as it dramatically improves energy efficiency. Considering the terminal configuration, it is concluded that a membrane insulated tank combined with a recondenser to process the BOG flow is the desired solution if the terminal has baseload send-out. However, when a low minimum flow is required, a vacuum insulated tank in combination with “cold” BOG compressors is the best solution. Both configurations have an energy efficiency loss for baseload send-out of 0,13% of the HHV. To determine the feasibility of the terminal configuration, a further cost-efficiency evaluation is essential, next to this energy efficiency analysis.The overall conclusion is that for the storage tank, the most expensive part of the plant, potential solutions to retrofit it exists. Especially the membrane insulation method is very promising and deserves more in-depth research. However, reusing the LNG process equipment is not possible. The equipment for the LH2 process is not yet commercially available except for the LH2 pumps. Further research is recommended because an LH2 import terminal has many advantages over other hydrogen import terminals, namely a relatively simple and flexible send-out process that requires little energy input.Mechanical Engineerin
Solid oxide fuel cell (SOFC) integrated power plants: System and kinetic studies
No full textIncreased climate change over past decades has resulted in an increase in the average temperature (also called global warming) of Earth’s climate system. At the recent Paris climate conference (COP21) in 2015, 195 countries in the world have agreed upon a stringent plan to limit global warming below 2oC. This demands a significant reduction in the industrial emission of greenhouse gases, predominantly carbon dioxide (CO2). Existing fossil fuel (coal, natural gas) fired power plants account for the majority share in global carbon dioxide (CO2) and other harmful (SOx , NOx) emissions. Therefore clean, efficient and flexible power plant concepts need to be developed towards upgrading existing power plants and to meet the strict CO2 emission targets. Combined cycle power plants like the integrated gasification combined cycle, IGCC (coal based) and integrated reforming combined cycle, IRCC (natural gas based) can be utilized to produce electricity using fossil fuels at relatively high efficiencies compared to conventional single cycle plants.Possible approaches to make IGCC/IRCC power plants cleaner, efficient and more flexible include biomass utilization (renewable energy source), application of CO2 capture technologies, retrofitting with highly efficient fuel conversion technologies like solid oxide fuel cells (SOFCs) and energy/fuel storage. This dissertation primarily aims to provide design concepts and thermodynamic system analysis for large scale IGCC and IRCC power plants with a focus on achieving high electrical efficiencies, low CO2 emissions and high operational flexibility. SOFCs have been explored as an efficiency augmenting technology and metal hydride based hydrogen storage as a flexibility option. Furthermore, future development of safe and optimally operating hydrocarbon (like natural gas (methane)) fuelled SOFC units on the basis of system and numerical models, requires reliable experimental data and understanding in the underlying reaction kinetics. Thereupon, an extended experimental study has been carried out in this work on methane steam reforming (MSR) kinetics in single operating SOFCs.Energy Technolog
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Assessing Silver Palladium Alloys for Electrochemical CO<sub>2</sub> Reduction in Membrane Electrode Assemblies
No full textThe field of electrochemical CO2 reduction has been transitioning to industrially relevant scales by changing the architecture of the electrochemical cells and moving away from the traditional aqueous H-cells to membrane electrode assemblies (MEA). The reaction environments in MEAs vary drastically from that of aqueous H-cells, which could result in significantly different catalytic activity. In this paper, we test AgPd alloys, one of the most promising CO producing catalysts reported, at industrially relevant scales (50 to 200 mA/cm2) in a MEA configuration. We report that, with increasing Pd composition in the electrode, the CO selectivity reduces from 99 % for pure Ag to 73 % for pure Pd at 50 mA/cm2. The MEA configuration helps attain a high CO partial current density of 123 mA/cm2. We find that catalytic activity reported in aqueous H-Cells does not translate at higher current densities and that cell architecture must play an important role in benchmarking catalytic activity.ChemE/Materials for Energy Conversion and Storag
- …
