Cotransporter Research Articles

Constructing the positive electrostatic environments by nanosheet in mixed matrix membranes for efficient CO2 separation

Mixed Matrix Membranes (MMMs) have shown advantages in overcoming trade-off effects, but there is still an urgent need to enhance CO2 separation performance in the design of multifunctional fillers. To overcome the trade-off effects in MMMs, a rational design of fillers with selective recognition for CO2 molecules is an effective strategy. A microporous nanosheet Qc-5-Cu was synthesized and incorporated into a Pebax MH 1657 (Pebax) to prepare MMMs for efficiently separating CO2 from CH4. The H atoms of the aromatic rings on the surface of pores in Qc-5-Cu constructed positive electrostatic environments, which significantly improves the CO2/CH4 separation performance of MMMs. On one hand, the constructed positive electrostatic environments in the MMMs attracted the negatively charged O atoms of CO2 molecules through electrostatic attraction, which effectively accelerated CO2 transport. On the other hand, the positive electrostatic environments established a selective barrier for preventing CH4 transport, achieving high CO2/CH4 selectivity in MMMs. Compared to pure Pebax membrane, the Pebax/Qc-5-Cu-0.5 MMM exhibited a remarkable enhancement of 99.52 % in CO2 permeability (934.24 Barrer) and a significant increase of 37.64 % in CO2/CH4 selectivity (25.01). The constructed positive electrostatic environments of nanosheets in MMMs offers a potential prospect for efficient CO2/CH4 separation.

Molecular insights into the synergistic inhibition mechanisms of antifreeze protein and methanol on carbon dioxide hydrate growth

The formation of CO2 hydrates during CO2 transportation and deep-sea injection poses a significant risk of pipeline blockage. Combining kinetic (KHIs) and thermodynamic hydrate inhibitors (THIs) serves as a promising efficient and economical strategy to mitigate this issue, whose performance and microscopic mechanisms yet are still poorly understood. This study employs molecular dynamics simulations to explore the effects of the combination of winter flounder antifreeze protein (wf-AFP) as a KHI and methanol as a THI on CO2 hydrate growth. We find that methanol and wf-AFP exhibit an intriguing synergistic inhibition performance on hydrate growth. In the AFP-only system, AFP serves as a spatial hindrance near the hydrate growth interface. However, in the AFP + methanol system, AFP changes its position due to the attractive force of methanol. Part of the AFP fragment remains on the hydrate interface, while the rest surrounds the CO2 droplet. Methanol, in addition to disrupting the water structure, combines with AFP to act as a double barrier to CO2 dissolution into the aqueous solution, thereby significantly reducing the gas source for hydrate growth. These findings provide molecular-level insights into hydrate inhibition mechanisms and guide the design of efficient inhibitors for safe CO2 transportation and injection.

Molecular insights into CO2 enhanced hydrocarbon recovery and its sequestration in multiscale shale reservoirs

CO2 huff-n-puff (HNP) is an attractive enhanced oil recovery (EOR) technique in shale development due to its low cost, high efficiency, and environmentally friendly feature. Molecular dynamics (MD) simulations have been widely used to investigate the mechanisms of CO2 HNP process. However, the process of CO2 HNP is highly complex, involving the CO2 adsorption and transport in multiscale porous media, while considering the effect of different hydrocarbon compositions of shale oil. In this work, we developed a novel multiscale model (nano + bulk) with the modified Eagle Ford shale oil and water as the reservoir fluid. We investigated the adsorption behaviors and transport dynamics of CO2 in the CO2 HNP process. We quantitatively evaluated the CO2 swelling effect and its miscibility with hydrocarbons. Our results show the preferential adsorption to the graphene wall is pentane < CO2 < octane. CO2 can effectively desorb the light and intermediate hydrocarbons from the graphene wall. In addition, CO2 has good swelling effect and miscibility with the light and intermediate components. Due to the large molecular diameter and the strong interactions with the nanopore wall, the heavy components tend to be trapped in the nanopore after the CO2 HNP process. However, CO2 has similar swelling effect on the light and heavy components, indicating that the heavy components in the bulk pore can be effectively swelled and produced. Different from the unstable diffusion edge in the inorganic nanopores, CO2 has a stable diffusion edge in the organic nanopores. From the adsorption perspective, CO2 has favorable sequestration performance in the inorganic nanopores in shale gas reservoirs. This work provides a comprehensive understanding of the CO2 HNP process and practical implications for CO2 sequestration in shale reservoirs.

A slope scaling heuristic for the multi-period strategic planning of carbon capture and storage

Around the world, efforts are currently underway to implement various decarbonization strategies to meet net-zero emissions objectives. This includes carbon capture and storage (CCS), which involves capturing CO2 at emitter sites, and transporting it to geological reservoirs, where it is to be injected underground for long-term storage. In this work, we focus on the multi-period strategic planning of a CCS value chain involving pipeline CO2 transportation. From an Operations Research standpoint, this problem exhibits the characteristics of combined facility location and network design. To account for multiple scenarios of input parameters (e.g. market and geological variability), this problem has to be solved hundreds or thousands of times. Thus, reaching high-quality solutions quickly is crucial. As commercial solvers struggle to provide high-quality solutions under these time constraints, we propose a slope scaling heuristic based on previous work on single-period CCS planning and network design. This new heuristic approximates the cost of design variables, generates upper bounds via dynamic programming, uses a long-term memory search strategy, and includes a final improvement phase where a restricted model is solved. Computational experiments show that the proposed heuristic generates better solutions than CPLEX for most instances considered, at a fraction of the computational time.

Studying the relationship between CO2 emissions and transport infrastructure development indicators

Subject. The article addresses the problem of increasing the volume of pollutant emissions into the atmosphere, environmental aspects of transport industry development in the Ural, Siberian, and Far Eastern Federal District. Objectives. We focus on the development of a tool to estimate greenhouse gas emissions from transport infrastructure. Methods. The study draws on methods of logical, statistical and econometric analysis. Results. We tested a regression model built on the basis of data reflecting the development of transport infrastructure in the regions of the Ural, Siberian, and Far Eastern Federal District in 2017–2021. The paper found that a particular impact on the volume of carbon dioxide emissions is exerted by the degree of depreciation of fixed assets of transport enterprises. An increase in the cost of fuel also has a negative effect on carbon dioxide emissions. Conclusions. The findings can be used in the reorganization process of transport systems to improve environmental performance in the regions.

Scaling CO2 Electrolyzer Cell Area from Bench to Pilot.

To contribute meaningfully to carbon dioxide (CO2) emissions reduction, CO2 electrolyzer technology will need to scale immensely. Bench-scale electrolyzers are the norm, with active areas <5 cm2. However, cell areas on the order of 100s or 1000s of cm2 will be required for industrial deployment. Here, we study the effects of increasing cell area, scaling over 2 orders of magnitude from a 5 cm2 lab-scale cell to an 800 cm2 pilot plant-scale cell. A direct scaling of the bench-scale cell architecture to the larger area results in a ∼20% drop in ethylene (C2H4) selectivity and an increase in the parasitic hydrogen (H2) evolution reaction (HER). We instrument an 800 cm2 electrolyzer cell to serve as a diagnostic tool and determine that nonuniformities in electrode compression and flow-influenced local CO2 availability are the key drivers of performance loss upon scaling. Machining of an initial 800 cm2 cell results in a standard deviation in MEA compression that is 7-fold that of a similarly produced 5 cm2 cell (0.009 mm). Using these findings, we redesign an 800 cm2 cell for compression tolerance and increased CO2 transport and achieve an H2 FE in the revised 800 cm2 cell similar to that of the 5 cm2 case (16% at 200 mA cm-2). These results demonstrate that by ensuring uniform compression and fluid flow, the CO2 electrolyzer area can be scaled over 100-fold and retain C2H4 selectivity (within 10% of small-scale selectivity).

Preparation of Pebax based ternary mixed matrix membranes for enhancing CO2 transport and separation

As a type of material for membrane separation in carbon capture technology, mixed matrix membranes (MMMs) have the advantages of simple processing and excellent gas separation performance and have great research prospects. However, the affinity between organic matrix and inorganic fillers is usually poor, and microphase separation occurs at the interface. At the same time, as the filler content increases, the filler particles will aggregate, leading to non-selective defects in the homogeneous membrane and reducing the gas separation performance of MMMs. Herein, the strategy of adding a third component was adopted. Small molecule polyethylene glycol dimethyl ether (PEGDME) was introduced into the Pebax/NH2-MIL-101 membrane to prepare a ternary mixed matrix membrane Pebax/PEGDME/NH2-MIL-101. Adding small molecules as the third component optimized the membrane structure by utilizing the interaction between the third component, inorganic fillers, and polymer matrix, effectively improving the physical microenvironment of gas separation. At the same time, NH2-MIL-101 was modified to PEI-MIL-101, further improving the performance of the mixed matrix membrane. The CO2 permeability of the Pebax/PEGDME/NH2-MIL-101 ternary mixed matrix membrane reached 313 Barrer, and the CO2/N2 selectivity reached 47.7. The CO2 permeability coefficient of Pebax/PEGDME/PEI-MIL-101 membrane reached 286 Barrer, and the CO2/N2 selectivity coefficient reached 54.2. This work provides new ideas for optimizing the gas separation performance of mixed matrix membranes.

Preparation and pipeline transport of CO2 as a hydrate slurry – Modelling and techno-economic analysis

CO2 transportation as a hydrate slurry is modelled in Aspen Plus, including the slurry preparation and the pipeline transport. Due to the lack of built-in models for the hydrate formation, mass and energy balances were developed and implemented using a User-block function. NRTL-RK global property method was used, given the accuracy in predicting the CO2 solubility in water under incipient hydrate formation conditions and the dissolution heat of CO2 in water. The conventional process of transporting CO2 in a supercritical state was also modelled to benchmark the hydrate-based technology. The hydrate-based process is safer than the conventional process as it requires lower operating pressures, but the estimated costs are higher due to the need for refrigeration and larger pipeline diameters for transportation. The addition of thermodynamic promoters, that moderate the hydrate formation conditions, the integration of cold streams with other processes, and valuing the water transported with CO2, will enhance the economic attractiveness of the hydrate-based process.

Enhancing CO2 Transport Across the PEG/PPG-Based Crosslinked Rubbery Polymer Membranes with a Sterically Bulky Carbazole-Based ROMP Comonomer.

A series of poly(ethylene glycol)-block-poly(propylene glycol) (PEG/PPG)- and 5,6-di(9H-carbazol-9-yl)isoindoline-1,3-dione (2CZPImide)-based crosslinked rubbery polymer membranes, denoted as PEG/PPG-2CZPImide (x:y), are prepared from the norbornene-functionalized PEG/PPG oligomer (NB-PEG/PPG-NB) and 2-(bicyclo[2.2.1]hept-5-en-2-ylmethyl)-5,6-di(9H-carbazol-9-yl)isoindoline-1,3-dione (2CZPImide-NB) via ring-opening metathesis polymerization (ROMP). The molar ratio (x:y) of the NB-PEG/PPG-NB (x) to 2CZPImide-NB (y) monomers is varied from 10:1 to 6:1. X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and pure gas permeability studies reveal that the comonomer 2CZPImide-NB successfully increases the d-spacing among the crystalline PEG/PPG segments, hence enhancing the diffusivity of gases through the membranes. The synthesized membranes exhibit good CO2 separation performance, with CO2 permeabilities ranging from 311.1 to 418.1 Barrer and CO2/N2 and CO2/CH4 selectivities of 39.4-52.0 and 13.4-16.0, respectively, approaching the 2008 Robeson upper bound. Moreover, PEG/PPG-2CZPImide (6:1), displaying optimal CO2 permeability and CO2/N2 and CO2/CH4 selectivities, shows long-term stability against physical aging and plasticization resistance up to 20 days and 10 atm, respectively.

Early Opportunities for Onshore and Offshore CCUS Deployment in the Chinese Cement Industry

The promotion of deep decarbonization in the cement industry is crucial for mitigating global climate change, a key component of which is carbon capture, utilization, and storage (CCUS) technology. Despite its importance, there is a lack of empirical assessments of early opportunities for CCUS implementation in the cement sector. In this study, a comprehensive onshore and offshore source–sink matching optimization assessment framework for CCUS retrofitting in the cement industry, called the SSM-Cement framework, is proposed. The framework comprises four main modules: the cement plant suitability screening module, the storage site assessment module, the source–sink matching optimization model module, and the economic assessment module. By applying this framework to China, 919 candidates are initially screened from 1132 existing cement plants. Further, 603 CCUS-ready cement plants are identified, and are found to achieve a cumulative emission reduction of 18.5 Gt CO2 from 2030 to 2060 by meeting the CCUS feasibility conditions for constructing both onshore and offshore CO2 transportation routes. The levelized cost of cement (LCOC) is found to range from 30 to 96 (mean 73) USD·(t cement)−1, while the levelized carbon avoidance cost (LCAC) ranges from −5 to 140 (mean 88) USD·(t CO2)−1. The northeastern and northwestern regions of China are considered priority areas for CCUS implementation, with the LCAC concentrated in the range of 35 to 70 USD·(t CO2)−1. In addition to onshore storage of 15.8 Gt CO2 from 2030 to 2060, offshore storage would contribute 2.7 Gt of decarbonization for coastal cement plants, with comparable LCACs around 90 USD·(t CO2)−1.

TROPOMI unravels transboundary transport pathways of atmospheric carbon monoxide in Tibetan Plateau

Numerous studies have reported in situ monitoring and source analysis in the Tibetan Plateau (TP), a region crucial for climate systems. However, a gap remains in understanding the comprehensive distribution of atmospheric pollutants in the TP and their transboundary pollution transport. Here, we analyzed the high-resolution satellite TROPOMI observations from 2018 to 2023 in Tibet and its surrounding areas. Our result reveals that, contrary to the results from in situ surface CO monitoring, Tibet exhibits a distinct seasonality in atmospheric carbon monoxide total column average mixing ratio (XCO), with higher levels in summer and lower levels in winter. This distinctive seasonal pattern may be related to the TP's ‘air pump’ effect and the Asia summer monsoon. Before 2022, the annual growth rate of XCO in Tibet was 1.63 %·year−1; however, it declined by 6.88 % in 2022. Source analysis and satellite observations suggest that CO from South Asia may enter Tibet either by crossing the Himalayas or through the Yarlung Zangbo Grand Canyon. We discovered that spring outbreaks of open biomass burning (OBB) in South and Southeast Asia led to an 11.57–27.98 % increase in XCO over Tibet. Favorable wind pattern and unique topography of the canyon promote the high concentrations CO transport to Tibet. Our greater concern is whether the TP will experience more severe transboundary pollution in the future.

Numerical investigations on the performance of sc-CO2 sequestration in heterogeneous deep saline aquifers under non-isothermal conditions

CO2 sequestration in geological formations is an efficient step towards mitigating climate change by reducing global warming. The CO2 emitted from natural sources and anthropogenic activities is injected into geological formations. The flow and transport of CO2 during sequestration operations require in-depth knowledge of the effects of the type of geological formation. The present work analyses the CO2 migration and storage in a heterogeneous deep saline aquifer with variable porosity and evolving permeability under non-isothermal flow conditions while upscaling the capillary pressure using the Leverett J-function. The developed numerical model is history-matched with CO2 gas saturation profiles reported using analytical and numerical approaches. The novelty of the present work lies in its ability to capture fine-scale heterogeneities in the aquifer, which is modelled through variation in the porosity (ϕ) distribution and the permeability (k). The thermal-hydraulic numerical analysis projected a pronounced effect of the degree of heterogeneity arising from the variation in porosity and permeability on pressure buildup along the top of the formation decreasing from a maximum of about 6.41 MPa at the injection well to about 0.933 MPa at 1200 m and affecting gas characteristics and transmission. The thermal front could only propagate to a maximum extent of about 142 m from the injection well in aquifers, while gas plume lengths migrated to a maximum plume length of about 1010 m. The permeability and porosity of the aquifer are critically observed to vary during the sequestration by a ratio (k/k0) of about 1.07 to 1.01 and a percentage of about 0.791 % – 3.136 % in the low permeable conditions. Maximum effective storage of CO2 by a factor of 0.95 observed in low-permeable heterogeneous aquifers with normally distributed porosity affirms maintenance of optimum gas injection rates below the fracture gradient in these formations to sequester the CO2 economically.

Influences of reformate on the performance of high temperature proton exchange membrane fuel cell and its optimization strategy

Due to the challenges of hydrogen production, storage and transport, hydrocarbon reformate-based high temperature proton exchange membrane fuel cell (HT-PEMFC) has wide application opportunities. However, the inevitable water vapor and CO in reformate significantly determines the fuel cell performance and durability. In this work, a three-dimensional, non-isothermal and multiphase model based on agglomerate sub-model is developed to investigate the effects of reformate components and operating conditions, in which multiphase transport, dissolution, diffusion, adsorption, desorption and reaction of H2 and CO are considered. The results show that the fuel cell performance increases with the rising of water vapor content as CO content higher than 2 % (dry basis, the same below) and water vapor content lower 20 % (wet basis). The alleviation effect of water vapor on CO poisoning is discovered due to reduced CO coverage rather than enhanced CO electrochemical oxidation. An elevated temperature leads to improved performance and the effect of CO poisoning (CO<3%) is weak at 180°C.

Enhancing life cycle assessment methodologies for carbon capture and utilization technologies: A comprehensive guideline for improved decision-making

Carbon Capture Utilization and Storage (CCUS) is an emerging technology that aims to reduce carbon dioxide (CO₂) emissions from industrial processes and power generation. This paper presents a comprehensive Life Cycle Analysis (LCA) of CCUS, evaluating its environmental impacts from cradle to grave. The LCA includes the stages of CO₂ capture, transportation, utilization, and storage. The goal is to provide a holistic understanding of the potential benefits and drawbacks of CCUS, guiding policymakers and industry stakeholders in decision-making processes. Although LCA is a standardized method, there is significant variability in current LCA practices due to differing methodological choices, which limits their effectiveness for decision support. Applying LCA to CCU technologies introduces additional challenges, particularly because CO₂ serves both as an emission and a feedstock. The guidelines aim to enhance the comparability of LCA studies by providing clear methodological directions and predefined assumptions regarding feedstock and utilities. Increased transparency is achieved through detailed interpretation and reporting guidance. By improving comparability, the guidelines support more informed decision-making, enabling more efficient allocation of research funds and time towards the development of technologies for climate change mitigation and negative emissions.

Theoretical and FEA investigation of the mechanical behaviour for offshore LCO2 floating hose

Injecting liquid CO2 (LCO2) into the seabed for storage utilizing an offshore platform to achieve offshore storage of CO2 is one of the effective measures to realize the reduction of CO2 emissions. To solve the difference in motion characteristics between the LCO2 carrier and the receiving platform due to wind and wave currents, floating hoses can be employed as the pipeline in the CO2 transportation. In this study, an LCO2 floating hose based on the structural form of steel wire reinforced thermoplastic composite pipe is proposed. A mechanical model for this hose is developed to analyze the tensile mechanical properties. It is verified that the method is reliable by comparing with the published experimental results of composite hose containing 4 layers of aramid fiber reinforced layers with a maximum error of 11.48%. A comparative analysis was also carried out by finite element analysis (FEA) with a maximum error of 10.67%. On this basis, the damage states of the hose under internal pressure, tension, bending and torsion load were investigated to analyze mechanical properties. The ultimate tensile load capacity, ultimate bending radius and ultimate unit torsion angle are 463 kN, 1.64m and 14°/m, respectively. The components most prone to failure under different loads were clarified. This study can provide technical reference for the design of floating hoses for offshore LCO2 storage and transportation.

Environmental impacts and scale-up efficiency of four carbon capture and storage scenarios

Capture, transportation, and permanent storage of CO2 is considered pivotal in reaching global net-zero emission targets. Conceptualization and deployment of carbon capture and storage (CCS) value chains require substantial resources with current CCS projects trailing behind expectations. To date few studies address the environmental impacts related to introducing CCS into existing value chains, and even fewer focus on the environmental efficiency of scaling-up CCS projects, despite the need for acceleration. Four scenarios were studied, resembling CCS projects at different capture capacities of 0.3, 1.5, 3.5 and 10 million tonnes of CO2 per year (mtpa) deployed within a Northern European region. Using attributional life cycle assessment, we demonstrate that permanent carbon storage today may furnish a 47–91% CO2 net-abatement potential depending on the CO2 source and geographical location of CCS projects. Despite limited operational data, results appear robust with general low uncertainty. Our environmental assessment show that capturing, conditioning and liquefaction account for the largest emission shares of the studied CCS value chains, ranging from 70 to 80%, which is heavily fluctuated by the carbon emission intensity of regional electricity production. Impacts related to permanent storage activities, such as offshore monitoring and well drilling are limited to less than 2% across all scenarios. Moreover, our study suggests that expanding the spatial geographical scope to accumulated 5000 km has a low influence on the efficiency of CCS value chains regardless of capture rate. Freshwater eutrophication shows the highest burden across the assessed environmental impact categories caused by the electricity production for capture processes. Lastly, we identify net-abatement improvement potential for post-combustion CCS projects at capturing capacities between 1.5 and 10 million tonnes per annum ranging from 10 to 20% for transport-related activities, and 60–68% for capturing processes when assuming net-zero energy scenarios.

A Two-Echelon Routing Model for Sustainable Last-Mile Delivery with an Intermediate Facility: A Case Study of Pharmaceutical Distribution in Rome

This paper introduces a two-echelon optimization model for the integrated routing of an electric vehicle (EV) and a traditional internal combustion engine vehicle (ICEV) in an urban environment. The scientific context of this study is sustainable urban logistics. The case study focuses on the distribution of pharmaceuticals in the metropolitan area of Rome. Distributing pharmaceuticals in large cities presents significant challenges, including heavy traffic congestion, the need for strict temperature control, and the maintenance of the integrity and timely delivery of sensitive medications. Furthermore, the complexity of urban logistics and adherence to regulatory requirements introduce additional layers of difficulty. Therefore, the implementation of fast and sustainable distribution mechanisms is crucial in this context. Specifically, the model seeks to minimize both total CO2 emissions and transportation costs while optimizing the use of an EV and an ICEV, all while ensuring that service level requirements are met. Computational results demonstrate the effectiveness of the proposed method in improving the sustainability of pharmaceutical distribution.

In-situ co-growth of ZIF-8-derived bio-carbon spheres with meso-macroporous hierarchy for stable and rapid carbon dioxide capture

Efficient carbon dioxide (CO2) capture from post-combustion flue gases is crucial for industrial applications. Adsorbents with high adsorption capacity, exceptional stability, high selectivity, and low cost are essential to meet these requirements. In this study, we present the synthesis of bio‑carbon spheres derived from zeolitic imidazolate framework-8 (ZIF-8) using a macro-fluidic technique. The bio‑carbon spheres integrate ZIF-8 for structural orientation and chitosan for the directional assembly of ZIF-8, thereby addressing the limitations of low strength in chitosan-derived carbon spheres and the challenge of macroscopic shaping of ZIF-8 particles. Additionally, the incorporation of ZIF-8 and the enhancement of the carbon skeleton increased the meso-macroporosity, improving CO2 transport and adsorption performance. The bio‑carbon spheres demonstrated a 46.9% higher CO2 adsorption capacity (101 kPa, 1.40 mmol·g−1) compared to pure chitosan carbon granules (101 kPa, 0.96 mmol·g−1) and a 17.8% faster mass transport rate compared to ZIF-8 carbon particles. Moreover, the bio‑carbon spheres exhibit a low wear rate in a simulated fluidized bed, good thermal stability, and stable cyclic regeneration performance. This study offers a novel strategy for developing industrially applicable adsorbents with hierarchical pore structures to enhance CO2 capture.

Closed-loop supply chain network of end-of-life wind turbines mathematical model proposal considering environmental, employment, and cost reduction aspects

The worldwide climate issue makes wind energy an attractive renewable energy source. Wind energy reduces carbon emissions, energy prices, creates jobs, improves power access, and ensures energy security. The mass of employed materials in wind turbines indicates a lot of potential raw materials when the whole mass is evaluated. Additionally, a new wind turbine costs $2–$4 million. Remanufacturing or using recycled raw materials from end-of-life wind turbines is practical due to the decreased cost of new wind turbines. To ensure sustainability, CO2 emissions and social advantages like employment must be considered. Given the typical life expectancy of wind turbines at 20–25 years, this issue must be addressed globally in the mid-term. The objective of the conducted study is to provide a multi-objective mathematical framework that encompasses the environmental, social, and economic aspects of wind turbines at the end of their operational lifespan. Hence, this study presents a methodical framework for achieving sustainability in the wind energy sector through the implementation of a closed-loop supply chain. Furthermore, a lexicographic solution approach is offered for each objective of the mathematical model, with the aim of providing decision makers with a comprehensive overview of solutions. The methodology employed in this work involves the utilization of a mixed-integer linear programming (MILP) approach to address the closed-loop supply chain for end-of-life wind turbines. Additionally, a lexicographic solution approach is provided to effectively solve the problem at hand. The novelty of this article lies in its examination of the closed loop supply chain network for end-of-life wind turbines, encompassing the social, environmental, and economic dimensions. This study represents the first of its kind to explore these aspects comprehensively. The proposed mathematical model has three objectives which cover the remanufacturing and recycling and aims to minimize CO2 emissions, unemployment, and transportation cost. In order to evaluate the proposed model, Türkiye is utilized as case with real-life data and Gurobi 9.1.2 is utilized. The locations of wind turbines could not be collected individually, and Euclidian distance was used instead of road distance due to a lack of data. These are the main limitations of the proposed study. The study revealed that the TEC and TCE lexicographic approach has the best recycling and remanufacturing cost-to-manufacturing cost ratio, 52.54 %. The least desired result is 74.50 % from CTE.

Study on the effect of valve openings and multi-stage throttling structures on the pressure and temperature during CO2 pipeline venting processes

The venting operation is an important measure for rapidly eliminating the risk of overpressure in CO2 transportation pipelines. However, the low-temperature phenomenon and vibration generated by the rapid discharge can affect structural reliability. Multi-stage throttle structures have been proven to effectively alleviate vibration phenomena, but their impact on low temperatures remains unclear. In this study, venting tests were conducted on eight groups of single-stage and two-stage throttle structures based on a large-scale pipeline. The results indicate that the nonlinear variation of the valve resistance coefficient when the valve opening changes is the fundamental reason affecting the downstream temperature. Two-stage throttle structures can effectively mitigate the low-temperature conditions in certain spaces within the pipeline. For the remaining low-temperature sections, three-stage throttle structures can provide effective compensation. However, this significantly reduces the pressure drop rate in the main pipeline, contradicting the original purpose of the venting operation. Additionally, considering the temperature of the throttle structure and the pressure within the main pipeline, this study recommends increasing the valve openings for the two-stage throttle structure. The results of this study provide important references for the design of throttle structures and the formulation of on-site venting schemes, with strong prospects for engineering applications.