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Mechanics of elastic contact with an interface between adjacent materials
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Deformation mechanisms of hierarchically structured 2D single-crystal materials revealed by real-time high-resolution in-situ nanomechanical testing
Get PDFHierarchically structured materials such as two-dimensional (2D) single-crystal transition metal dichalcogenides (TMDs) are being increasingly explored for their electronic and piezoelectric properties for applications in devices and sensors. These materials exhibit complex deformation mechanisms that can only be revealed by real-time, nanomechanical investigations. This study investigated the plastic delamination response of 2D, single-crystal TMDs with varying lattice parameters by an integrated in-situ nano scratch, visualization, and analytical modeling approach. Nanowear at systematically progressing depths from 15 – 45 nm delaminates 50 – 80 layers with an increasing lateral force of resistance from 3.5 – 8.0 mN, thereby consuming 80 – 154 nJ of energy. Based on in-situ visualizations, the evolution of lateral force over delamination distance is modeled on linear debonding and sinusoidal pile-up forces. These novel insights on the multi-scale, hierarchical mechanical and tribological responses and failure mechanisms constitute a significant advancement in the understanding of the processing-property correlations in these architecture materials
Micro-mechanical approach of the intergranular stress corrosion cracking of austenitic stainless steels in PWR environment
Get PDFAustenitic stainless steels are used in the nuclear industry to make the internals parts of Pressurized Water Reactors (PWR) such as baffle and former plates. Numerous Baffle-to-Former Bolts (BFB) intergranular failures have been reported as a result of Irradiation Assisted Stress Corrosion Cracking (IASCC) phenomenon. In order to predict the cracking of the grain boundary through a micro-mechanical approach, it is necessary to determine the intragranular mechanical behavior of the steel and the grain boundary strength.
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Challenges and Limitations of Processing Carbonatite Rare Earths Deposits in Brazil
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Economic and environmental assessment of lithium-ion battery recycling processes for electric vehicles
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Advanced Thermochemical Conversion of Various Waste Feedstocks with CCS for Clean Hydrogen Production - a Life Cycle Assessment
Get PDFThis research work focuses on a complex product system that c) utilises different waste feedstock, thereby diverting its fate from landfill or incineration b) produces hydrogen as the main product (for heating and transport applications) c) captures and permanently sequesters carbon dioxide, a by-product. The multi-functionality of such a system lends itself to complexities arising from the choice of system boundaries, functional unit, and assumptions in order to integrate mature, commercial scale elements of the process with other sections at a lower technology readiness level. This research focuses on novel waste technology and their integration into connected systems, specifically transport of waste from source and its pre-treatment, hydrogen for heating and captured carbon dioxide for permanent sequestration.
Recently, hydrogen from low-carbon routes has garnered attention as a high-density energy vector with low greenhouse-gas production emissions and no emissions at its point of use. The UK Hydrogen strategy sets forth a target of 5GW of low carbon hydrogen production capacity by 2030 [1]. A proposed low-carbon route to produce hydrogen is the gasification of waste feedstock coupled with pre-combustion capture and long-term geological storage of carbon dioxide. This research also analyses the effect of waste feedstock composition on the environmental impact of the process. The three feedstock analysed are waste wood, municipal solid waste (MSW) and mixed plastic waste (MPW).
The facility is designed and modelled to convert approximately 110,000 tonnes per annum of chosen waste to approximately 50 MWh of grid-quality hydrogen. Carbon dioxide is captured using a Benfield CO2 stripper technology. Following the guidelines of the ISO 14040 and ISO 14044 standards the LCA methodology was applied. The goal of this study was to investigate the environmental and carbon performance of converting waste wood, MSW and MPW to hydrogen, while also capturing CO2 process emissions. The comprehensive LCA also includes the integration into connected systems, namely the transport of waste, pipeline transport and sequestration of CO2. All impact categories were considered according to the EF 3.0 method.
A hotspot analysis of the process reveals largest climate change burdens during the gasification (syngas generation) and the carbon capture stages due to high thermal and electricity consumption. Although pre-treatment of waste is overall a minimal climate change contributor of the process, variations in feedstock composition and flowrates result in large relative differences as MPW benefits from a high calorific content and requires significantly lower feedstock for equivalent hydrogen production. The sequestration of biogenic CO2 from the natural carbon cycle uniquely results in negative carbon dioxide emissions. Thus, distinguishing between sequestration of biogenic and fossil carbon is the most significant differentiator in how these technologies fare environmentally. Using waste wood and MSW feedstock result in negative emission processes, while MPW does not advantage from biogenic carbon sequestration. Despite this, results when considering counterfactual scenarios, namely incineration and landfill, reveal the avoided burdens of MPW treatment. Nonetheless, gasification technology applied to the treatment of waste to produce hydrogen with CCS is proposed as a suitable technology for treatment of varied waste feedstock.
[1] Business, Energy & Industrial Strategy. 2021. UK Hydrogen Strategy. ISBN 978-1-5286-2670-
Forestry Waste in British Columbia - overcoming bad habits and perverse life cycle accounting
Get PDFThe western Canadian province of British Columbia (BC) is renowned for its extensive forests and forestry sector. For a number of historical reasons, practices for “harvesting” trees are BC is wasteful, with large quantities of material left to be destroyed by open-air “slash burning” to avoid providing potential fuel for wildfires. This unused waste is analogous to agricultural waste, or process waste from industrial production. It potentially represents a significant energy resource, equivalent to about 20% of the fossil fuels used in BC. This contribution will cover: - why a potential resource is currently discarded; - how combining LCA with economic analysis identifies the Pareto-optimal uses for the waste, both domestically and as an internationally traded commodity; - why the supply chain means that Canadian wood pellets sold into European markets have a different life cycle environmental profile compared to pellets from other sources; - how current international agreements on accounting for life cycle emissions of greenhouse gases give perverse signals that discourage production of wood pellets in BC. Although the case study is specific to BC, it illustrates a number of general principles in and barriers to “valorisation” of materials currently regarded as waste
Life cycle assessment of multi-loop recycling: Opportunities and Challenges
Get PDFToday, circular economy plays a prominent role in optimization of natural resource consumption, while also minimizing waste generation throughout the life cycle of a product. Both in relation to climate targets, the UN Sustainability Development Goals, as well as simply meeting recycling targets at national level. Keeping products, materials and resources in subsequent production cycles, for as long as possible, is one of the fundamental concepts of circular economy, and consistent strategies for how to improve resource utilization throughout the life cycle(s) of products are needed. Regarding the end-of-life waste stage of the product cycle, this can be achieved by reusing, repairing and recycling waste materials. However, within waste management most focus has been simply on recycling with little reflection of the material loops in a longer time perspective. Therefore, to avoid implementation of circular economy initiatives that may lead to net environmental impacts rather than benefits, comprehensive and systemic assessments are needed also involving subsequent recycling loops. While life cycle assessment (LCA) of repairing, reuse, recycling, and utilization options have been provided in literature, little attention has been placed on cascading and multiple recycling loops, although this is one of the primary intentions behind circular economy.
This study provides preliminary results evaluating LCA approaches from the perspective of multi-loop and cascading recycling with the aim of identifying opportunities, limitations and challenges based on current literature. Recommendations are provided based on evaluation of simple cases
Economic and environmental assessment of lithium‐ion battery recycling processes for electric vehicles
Get PDFLithium ion batteries (LIBs) are the best practice for e-mobility applications due to their power and energy densities. The capacity of automotive batteries decreases with usage and time and the life of lithium ion batteries is recently estimated longer, until about ten years. Even considering the following “second life” applications, in which batteries are reused for static energy storage systems (ESS), an End of Life (EoL) must be considered to recover the high value material (such as copper, cobalt, aluminum, iron, nickel and seldom lithium and manganese) still available inside. Different recycling main routes can be used to recover the valuable materials: the pyrometallurgical process, the hydrometallurgical process and the direct recycling method. At this moment it is not clear which batteries recycling route should exhibit a lower impact on climate change, because the single steps of the recycling processes are described inaccurately, probably because many technical information are confidential. From a general point of view, the pyrometallurgical route uses high temperature to reduce metal oxide components to a metallic alloy made of copper, cobalt, iron and nickel. Being the pyrometallurgical process used for other types of batteries, it is already well commercially established. The hydrometallurgical route uses aqueous solutions to leach material from cathode. The most used leaching combination is H2SO4/H2O2. The hydrometallurgical process is still under development and not yet commercial diffuse. The direct recycling route ensure the removal of cathode or anode material for repurposing in lithium ion batteries manufacturing processes. Despite being one of the possible recycling routes for the lithium ion batteries there are few information available. In fact, among the three-recycling route the direct recycling one is the least developed technology.
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Environmental and economic analysis to evaluate the valorization process of metallurgical waste and by‐products
Get PDFEnergy and resource efficiency are today key elements for the European industry. More specifically, the metallurgical industry is energy and resource-intensive, mostly located in big centralized plants, and it is today responsable for a large number of carbon emissions. While a big plant allows for stability in productivity, it also makes the process less adaptable towards innovative units/systems developed for more efficient use of energy and resources. Therefore, the future decarbonization targets might not be met without the development of new flexible and innovative technologies and strategies. In this context, the goal of the H2020 project CIRMET (innovative and efficient solution, based on modular, versatile, and smart process units for energy and resource flexibility in highly energy-intensive processes) is to develop and validate an innovative and flexible circular solution for energy and resource efficiency in a metallurgical plant, that can also be replicable to other sectors of the process industry. The proposed circular model, represented in Figure 1, is composed of three units: (1) a metallurgical furnace for the recovery of valuable metals from industrial metallurgical residues and by-products, (2) a unit for heat recovery from the furnace’s exhaust gases, and (3) a digital platform for the optimization of the whole process. The substitution of metallurgical coke (based on fossil carbon) with biobased material (Biochar) is also investigated, aiming at future carbon neutral emissions for energy intensive industries.
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