Analysis on numerical simulations of CO2 absorption process of carbon solidification system

Carbon dioxide (CO2) emission control has been a popular topic since global warming affects our living conditions on the planet. Carbon Capture and Storage (CCS) is a feasible solution for mitigating the global warming effect by capturing the CO2 from power stations and industrial processes and storing them underground. There are great many of active CCS projects onshore. International Maritime Organization (IMO) has adopted guidelines for CO2 emission control by improving ship energy efficiency. The project is aiming to apply CCS on ships by capturing the CO2 emission from the engine exhaust gases and solidifying them for easy storage. It will enable ships to comply with various regional and international CO2 emission regulations and also maintain the efficiency of waterborne transportation. The simulation of carbon absorption develops and investigates the multiphase reaction model in CFD software, focusing on bubble column effect with chemical reaction. This paper presents the analysis of the numerical simulation of the CO2 absorption process. Simulation results illustrate the pressure distribution of solution and gas path and velocity in solution. This numerical simulation results also indicates the impact of environment temperature on chemical reaction rate. A comparison between experiment and simulation results is presented to figure out the impact of initial NaOH solution concentration on gas absorption process. An optimized NaOH solution concentration is figured out and will be used for further practical design of absorption system for ships

A case ship study on practical design and installation of carbon absorption and solidification system

Onboard carbon capture and storage is an excellent solution to reduce the greenhouse gas emissions from shipping. This paper focuses on a case ship study on design and installation of a practical carbon absorption and solidification system which was proposed in authors’ previous work (Peilin and Haibin, 2014). The design process is based on authors’ previous work of simulation on lab-scale experiment. The specifications of the selected ship will be presented and utilized for its modelling. The processes of simulation illustrate modifications of simulation model, design of physical model, application of orthogonal design method, introduction of equipment and software and analysis of results. This paper also presents tank design, positioning and CAD drawing of the system on board after all processes and systems are derived. This paper demonstrates general processes of carbon absorption and solidification system design for a case ship so that design of the system for a new ship could follow the same procedures

Reviews on current carbon reduction technologies and experimental and numerical analysis on financial feasibility and practical application of a carbon absorption method

Global warming has become a popular topic and IMO’s regulations have come in forces to reduce carbon emission from international shipping by improving the energy efficiency with EEDI and EEOI. Carbon capture and storage is an alternative method utilizing different technologies to capture the CO2 from emission sources and storage/utilize them to reduce the carbon emission from exhaust gas or the content of CO2 in atmosphere. This paper reviews current carbon capture method and introduces a chemical absorption technology for carbon reduction on ships, which is a feasible method and applied by onshore industry. Experimental analysis indicates the average absorption rate for carbon dioxide feed in can reach 68%. A financial analysis is presented to evaluate a case ship in comparison with liquefaction method which indicates the absorption method is cost effective and earns profit after selling the final product from the chemical processes at the destination of a voyage. This paper also presents the design, analysis and validation of the numerical simulation model and a case ship study of practical absorption system installation is conducted based on the validated model

CFD simulations of absorption reaction in carbon solidification processes

Carbon capture and storage (CCS) is a promising task solution for reduction of CO2 emission from ships. To meet the IMO proposed target of 20% CO2 reduction from shipping by 2020, proposal of solidifying CO2 separated from engine exhaust had been made and tested by the authors. Laboratory experiment [1] on CO2 absorption has illustrated the feasibility of solidifying carbon onboard ships. To further verify the accuracy of results from CO2 absorption experiment, simulation with computational fluid dynamics (CFD) of the CO2 absorption and solidification processes is carried out, including system modelling and meshing, reactions simulating and post-CFD treatments. Eulerian multiphase model and species transport model are applied for the simulation. These models will present the interaction between gas phase (CO2) and chemical solution in both physical phase interactions and chemical reactions between the species. The mass fractions of Na2CO3 in solution are monitored during the absorption process. Conclusions has been reached that the simulation results have a good agreement with the experiment results

Life cycle assessment as an evaluation tool for carbon reduction techniques in marine industry

Global warming has been drawing researchers' attention for decades and in marine industry many different strategy and technologies are introduced to mitigate the global warming effect. As a main contributor to global warming, carbon dioxide has been targeted as a significant emission to reduce from marine activities and there are many carbon emission reduction technologies introduced to shipping. However, the results of the reduction are varied and an evaluation tool to investigate their performances in a long term are necessary. Life cycle assessment is an evaluation method considering a product or system's life span, from cradle to grave, covering all the activities which generate carbon emissions. While applying new carbon reduction technologies, the emissions from different activities are estimated and determined through life cycle assessment. Considering the related costs, a life cycle economic assessment can illustrate the overall savings with the application of carbon emission reduction technologies. Currently the assessments have been conducted to evaluate the applying of hybrid propulsion system, selection of engine configuration, utilization of solar panel array, adoption of carbon capture system, determination of maintenance strategy and so on. The results have indicated the performances of these carbon reduction methods from the perspectives of environment and economy which indicates that life cycle assessment is a feasible and comprehensive evaluation tool for the performance evaluations on carbon reduction techniques

A life cycle assessment on carbon capture and solidification method on ship

Greenhouse gas reduction has become a severe topic in the shipping industry and researchers are striving to investigate different GHG reduction technologies to determine their feasibility especially on the environment impact. However, there is no specific evaluation process currently available so this paper presents a Life Cycle Assessment for a carbon emission reduction method to introduce Life Cycle Assessment as a systematic evaluation approach which can guide policy makers to evaluate the performances and help ship owners to select suitable reduction technologies. The carbon reduction method proposed by authors was proved to be cost effective in previous works and this paper applies life cycle analysis focusing on all stages of ship life to investigate, determine and compare the feasibility of this method. The environmental impacts are considered to be the most significant standard for the assessment. From the results of the assessment, the proposed reduction method meets the carbon reduction target and can lead to a lower global warming potential while leveling up the carbon reduction target. This paper also indicates, to achieve carbon reduction target set up by regulations, a marginal target will be necessary due to the energy requirement and efficiency of the method/system as well as the consideration of activities in different life stages. It is also recommended that the evaluation of carbon reduction method could apply Life Cycle Assessment so that policy makers and ship owners are provided with comparable results for reasonable decision makings

Graphene-based spintronic components

A major challenge of spintronics is in generating, controlling and detecting spin-polarized current. Manipulation of spin-polarized current, in particular, is difficult. We demonstrate here, based on calculated transport properties of graphene nanoribbons, that nearly +-100% spin-polarized current can be generated in zigzag graphene nanoribbons (ZGNRs) and tuned by a source-drain voltage in the bipolar spin diode, in addition to magnetic configurations of the electrodes. This unusual transport property is attributed to the intrinsic transmission selection rule of the spin subbands near the Fermi level in ZGNRs. The simultaneous control of spin current by the bias voltage and the magnetic configurations of the electrodes provides an opportunity to implement a whole range of spintronics devices. We propose theoretical designs for a complete set of basic spintronic devices, including bipolar spin diode, transistor and logic gates, based on ZGNRs.Comment: 14 pages, 4 figure

Experimental and numerical analysis on impacts of significant factors on carbon dioxide absorption efficiency in the carbon solidification process

Onboard carbon capture and storage is an excellent solution to reduce the greenhouse gas emissions from shipping. This paper focuses on the absorption process and CO2 gas flow rate, the geometry of absorption tank and the concentration of absorption solution are key factors affecting the absorption efficiency. This paper will illustrate the experimental results of the impacts of these factors on the CO2 absorption efficiency. Meanwhile, results from CFD simulations of effects of the key factors on CO2 absorption rates will be presented in this paper. Pressure distributions, solution concentration and velocity of CO2 gas and solution are derived from the simulations. The results of the simulations provide fundamentals and insight understanding of the design of a proto-type demonstration system onboard a case ship. In addition to the key factors, the effect of atmosphere temperature was simulated and analyzed. Comparisons between the experiment and simulation have been conducted and the results have shown a good agreement. Optimized values of the factors are obtained from the comparisons and analyses. The numerical simulations of temperature effects on CO2 absorption rate and optimized temperature for the absorption process are also presented in the paper

The optimization of ejector geometry for mixing NaOH powders with water in on-board carbon solidification system

Owing to increasing requirement of greenhouse gas emissions reductions, researchers all over the world has been investigating and developing technology applying to all different sectors. According to the report from International Maritime Organization (IMO), the international shipping has contributed 2.2% of global carbon emissions in 2012. To mitigate this situation, organizations, researchers and engineers are striving to reduce the emissions by increasing the energy efficiency or applying emission reduction regulations and techniques. Authors has investigated a chemical absorption method to absorb and solidify the carbon content in the exhaust gases from ships. In the chemical absorption method, to absorb the carbon dioxide from exhaust gases, sodium hydroxide (NaOH) solution is applied as absorbent. However, the storage of NaOH solution may cause stability and corrosion problems on ships. To eliminate these problem, this paper introduce the ejector technology to mix NaOH powders with water to supply and replenish absorbent to the system which will reduce the storage of NaOH solution and instead only NaOH powders should be stored on board. This paper also investigates the impact of swapping fluid inlets to determine a preferred design. With the application of design of experiment and computing fluid dynamic, the optimization of the preferred design is also carried out in order to determine an optimal design of the ejector geometry