| 1. |
- Liu, Zhenzhong, et al.
(författare)
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Geochemical and S isotopic studies of pollutant evolution in groundwater after acid in situ leaching in a uranium mine area in Xinjiang
- 2023
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Ingår i: Nuclear engineering and technology. - : Elsevier BV. - 1738-5733 .- 2234-358X. ; 55:4, s. 1476-1484
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Tidskriftsartikel (refereegranskat)abstract
- Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that delta S-34 increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%-48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.
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| 2. |
- Liu, Zhenzhong, et al.
(författare)
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Study of natural attenuation after acid in situ leaching of uranium mines using isotope fractionation and geochemical data
- 2023
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 865, s. 161033-
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Tidskriftsartikel (refereegranskat)abstract
- Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tail-ings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentra-tion of contaminants at post-mining sites and in the surroundings soon after the mining ceases. As a potential AISL remediation strategy, natural attenuation has not been studied in detail. To address this problem, groundwater collected from 26 wells located within, adjacent, upgradient, and downgradient of a post-mining site were chosen to analyze the fate of U(VI), SO42-, delta 34S, and delta 238U, to reveal the main mechanisms governing the migration and atten-uation of the dominant contaminants and the spatio-temporal evolutions of contaminants in the confined aquifer of the post-mining site. The delta 238U values vary from -0.07 %o to 0.09 %o in the post-mining site and from -1.43 %o to 0.03 %o around the post-mining site. The delta 34S values were found to vary from 3.3 %o to 6.2 %o in the post-mining site and from 6.0 %o to 11.0 %o around the post-mining site. Detailed analysis suggests that there are large differences between the range of isotopic composition variation and the range of pollutants concentration distribution, and the es-timated Rayleigh isotope fractionation factor is 0.9994-0.9997 for uranium and 1.0032-1.0061 for sulfur. The isotope ratio of uranium and sulfur can be used to deduce the migration history of the contaminants and the irreversibility of the natural attenuation process in the anoxic confined aquifer. Combining the isotopic fractionation data for U and S with the concentrations of uranium and sulfate improved the accuracy of understanding of reducing conditions along the flow path. The study also indicated that as long as the geological conditions are favorable for redox reactions, natural attenuation could be used as a cost-effective remediation scheme.
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| 3. |
- Arjmand, Mehdi, et al.
(författare)
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Energy Saving in Crude Oil Atmospheric Distillation Columns by Modifying the Vapor Feed Inlet Tray
- 2011
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Ingår i: Chemical Engineering & Technology. - : Wiley. - 0930-7516 .- 1521-4125. ; 34:8, s. 1359-1367
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of a typical crude oil atmospheric distillation unit and reduction of energy conservation were carried out through modifying the implementation and change in the flash zone of the tower. A conventional procedure in such units involves the combination of liquid and vapor product of the prefractionation train surge drum upon introduction to the tower. However, it is theoretically illustrated and represented by simulation means that introducing the vapor feed into the upper stages of the distillation column separately can lead to an energy saving of 12.6% in the condenser duty, an increased liquid-to-gas flow (L/G) at certain points of the column, and hence to a reduction in diameter and investment costs of new tower designs of approximately US$ 0.7 million a(-1). The proposal can be put into practice without the need of additional equipments or additional cost of difficult rerouting the streams. An industrial case study of a steadystate crude oil distillation unit is given by simulation provision of AspenHysys (TM).
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| 4. |
- Arjmand, Mehdi, et al.
(författare)
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Exergetic efficiency of high-temperature-lift chemical heat pump (CHP) based on CaO/CO2 and CaO/H2O working pairs
- 2013
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Ingår i: International Journal of Energy Research. - : Wiley-Blackwell. - 0363-907X .- 1099-114X. ; 37:9, s. 1122-1131
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Tidskriftsartikel (refereegranskat)abstract
- The use of reversible chemical reactions in recuperation of heat has gained significant interest due to higher magnitude of reaction heat compared to that of the latent or sensible heat. To implement chemical reactions for upgrading heat, a chemical heat pump (CHP) may be used. A CHP uses a reversible chemical reaction where the forward and the reverse reactions take place at two different temperatures, thus allowing heat to be upgraded or degraded depending on the mode of operation. In this work, an exergetic efficiency model for a CHP operating in the temperature-level amplification mode has been developed. The first law and the exergetic efficiencies are compared for two working pairs, namely, CaO/CO2 and CaO/H2O for high-temperature high-lift CHPs. The exergetic efficiency increases for both working pairs with increase in task, TH, decrease in heat source, TM, and increase in condenser, TL, temperatures. It is also observed that the difference in reaction enthalpies and specific heats of the involving reactants affects the extent of increase or decrease in the exergetic efficiency of the CHP operating for temperature-level amplification.
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| 5. |
- Arjmand, Mehdi, et al.
(författare)
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Optimization for energy conservation of crude oil atmospheric distillation columns by modifying vapour feed inlet tray from pre-fractionation train
- 2010
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Ingår i: 2010 AIChE Annual Meeting. - 9780816910656
-
Konferensbidrag (refereegranskat)abstract
- Optimization of a typical crude oil atmospheric distillation unit and reduction of energy conservation were carried out through modifying the implementation and change in the flash zone of the tower. Conventional procedure in such units involves combination of liquid and vapour product of the pre-fractionation train surge drum upon insertion to the tower. However it is theoretically illustrated and represented by simulation means that introducing the vapour feed into the upper stages of the distillation column separately can lead to an energy saving of 12.6% in the condenser duty, increased liquid to gas flow (L/G) at certain points of the column and hence a reduction in diameter and investment costs of new tower designs of approximately 0.7 × 10 6 $/y. The proposal can be put into practice without the need of additional equipments or additional cost of difficult re-routing the streams. An industrial case study of a steady-state crude oil distillation unit is given by simulation provision of AspenHysys™.
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| 6. |
- Bian, Wenjie, et al.
(författare)
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Diffusion behavior of Se(IV) and Re(VII) in biotite: effects of dry density and ionic strength
- 2023
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Nature. - 0236-5731 .- 1588-2780. ; 332:11, s. 4413-4425
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Tidskriftsartikel (refereegranskat)abstract
- Biotite is an important adsorption carrier in the constituent minerals of Beishan granite. In this work, the effects of compaction density and ionic strength on the diffusion behavior of Se(IV) and Re(VII) in biotite were studied by capillary in-diffusion method and diffusion cell through-diffusion method. When the compaction density decreases or the ionic strength increases, the apparent diffusion coefficient increases, and its values range between 10–11 and 10–9 m2/s. The relationship between De and εacc, ionic strength and εacc was fitted using Archie's law and compared with the parameters of other researchers.
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| 7. |
- Bian, Xiaolei, et al.
(författare)
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A model for state-of-health estimation of lithium ion batteries based on charging profiles
- 2019
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Ingår i: Energy. - : Elsevier Ltd. - 0360-5442 .- 1873-6785. ; 177, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- Using an equivalent circuit model to characterize the constant-current part of a charging/discharging profile, a model is developed to estimate the state-of-health of lithium ion batteries. The model is an incremental capacity analysis-based model, which applies a capacity model to define the dependence of the state of charge on the open circuit voltage as the battery ages. It can be learning-free, with the parameters subject to certain constraints, and is able to give efficient and reliable estimates of the state-of-health for various lithium ion batteries at any aging status. When applied to a fresh LiFePO 4 cell, the state-of-health estimated by this model (learning-unrequired or learning-required)shows a close correspondence to the available measured data, with an absolute difference of 0.31% or 0.12% at most, even for significant temperature fluctuation. In addition, NASA battery datasets are employed to demonstrate the versatility and applicability of the model to different chemistries and cell designs.
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| 8. |
- Bian, Xiaolei, et al.
(författare)
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A Novel Model-based Voltage Construction Method for Robust State-of-health Estimation of Lithium-ion Batteries
- 2021
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Ingår i: IEEE Transactions on Industrial Electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0278-0046 .- 1557-9948. ; 68:12, s. 12173-12184
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Tidskriftsartikel (refereegranskat)abstract
- Accurate estimation of the state-of-health (SOH) is vital to the life management of lithium-ion batteries (LIBs). This paper proposes a fusion-type SOH estimation method by combining the model-based feature extraction and data-based state estimate. Particularly, a novel model-based voltage construction method is proposed to eliminate the unfavorable numerical condition and reshape the disturbance-free incremental capacity (IC) curves. Leveraging the modified IC curves, a set of informative features-of-interest are extracted and evaluated, while eventually several cautiously-selected ones are used to estimate the SOH of LIB accurately. Furthermore, the impact of model order on the estimation performance is scrutinized, to give insights into the parameterization in practical applications. Long-term cycling tests on different types of LIB cells are used for evaluation. The proposed method is validated with a good robustness to the cell inconsistency, temperature uncertainty, noise corruption, and a satisfied generality to different battery chemistries.
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| 9. |
- Bian, Xiaolei, et al.
(författare)
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A two-step parameter optimization method for low-order model-based state of charge estimation
- 2020
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Ingår i: IEEE Transactions on Transportation Electrification. - : Institute of Electrical and Electronics Engineers Inc.. - 2332-7782. ; , s. 1-1
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Tidskriftsartikel (refereegranskat)abstract
- The state of charge (SOC) estimation is an enabling technique for the efficient management and control of lithium-ion batteries (LIBs). This paper proposes a novel method for online SOC estimation which manifest itself with both high accuracy and low complexity. Particularly, the particle swarm optimization (PSO) algorithm is exploited to optimize the model parameters to ensure a high modeling accuracy. Following this endeavor, the PSO algorithm is used to tune the error covariances of extended Kalman filter (EKF) leveraging the early-stage segmental data of LIB utilization. Within this PSO-based tuning framework, the searching boundary is derived by scrutinizing the error transition property of system. Experiments are performed to validate the proposed two-step PSO-optimized SOC estimation method. Results show that even by using a simple first-order model, the proposed method can give rise to a high SOC accuracy which is comparative to those using complex high-order models. The proposed method is validated to excavate fully the potential of model-based estimators so that the computationally expensive model upgrade can be avoided. IEEE
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| 10. |
- Bian, Xiaolei, et al.
(författare)
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An open circuit voltage-based model for state-of-health estimation of lithium-ion batteries : Model development and validation
- 2020
-
Ingår i: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 448
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Tidskriftsartikel (refereegranskat)abstract
- An open circuit voltage-based model for state-of-health estimation of lithium-ion batteries is proposed and validated in this work. It describes the open circuit voltage as a function of the state-of-charge by a polynomial of high degree, with a lumped thermal model to account for the effect of temperature. When applied for practical use, the model requires a prior learning from the initial charging or discharging data for the sake of parameter identification, using e.g. a nonlinear least squares method, but it is undemanding to implement. The study shows that the model is able to estimate the state-of-health of a LiFePO4 cell cycled under conditions where the temperature has fluctuated significantly with a relative error less than 0.45% at most. A short part of a constant current profile is enough for state-of-health estimation, and the effect of size and location of voltage window on the model's accuracy is also studied. In particular, the reason of accuracy change with different voltage windows is explained by incremental capacity analysis. Additionally, the versatility and flexibility of the model to different chemistries and cell designs are demonstrated.
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| 11. |
- Bian, Xiaolei, 1990-
(författare)
-
State Estimation of Lithium-ion Batteries
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To guarantee the safety operation, the key states of lithium-ion battery, e.g., the state of charge and the state of health, must be estimated and monitored accurately. This thesis is mainly to develop models and algorithms to accurately and robustly estimate the key battery states, based on the available measurements i.e., current and voltage. All the work is based on four published papers and can be divided into three parts.The first part of this work presents a two-step parameter optimization method for online state of charge estimation of lithium-ion battery. The particle swarm optimization is exploited for model parametrization and extended Kalman filter tuning. Within this particle swarm optimization-based framework, the searching boundary is derived by scrutinizing the error transition property of the test system, which can narrow the searching region and increase the computational efficiency. In general, the proposed method can well exploit the potential of model-based estimators, leading to a robust model compatibility and optimized performance.In the second part of this thesis, two novel models are developed to estimate the state of health of lithium-ion battery. The first one is an open circuit voltage-based model, which describes the open circuit voltage as a function of the state of charge by a polynomial, with a lumped thermal model to account for the effect of temperature. It requires a prior learning from the initial constant-current profile. The second model is an incremental capacity analysis-based model, which defines the dependence of the state of charge on the open circuit voltage using a capacity model. It can be learning-free, with the parameters subject to certain constraints. Both models use an equivalent circuit model to characterize the constant-current profiles and a nonlinear least squares method to identify the involving parameters. These two models are validated by aging experiments, and the results show that both can give accurate state-of-health estimation.The third part of the thesis introduces a fusion-type state-of-health estimator by combining the model-based profile reconstruction and the incremental capacity analysis-based state estimation. The above-mentioned open circuit voltage-based model is employed here to mitigate the noise-induced unfavorable numerical conditions and to modify the incremental capacity curves. Leveraging the modified incremental capacity curves, a set of feature-of-interests are extracted and evaluated, and several cautiously selected ones are used to estimate the state of health of lithium-ion battery. Long-term cycling tests on different lithium-ion batteries are used for validation. This fusion-type method has comparable accuracy and better robustness, compared with the model-based methods. Moreover, the proposed estimator has a good generality to different batteries and also promises an excellent robustness against cell inconsistency, noise corruption, temperature variety, and profile partialness.
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| 12. |
- Bian, Xiaolei, et al.
(författare)
-
State-of-Health Estimation of Lithium-Ion Batteries by Fusing an Open Circuit Voltage Model and Incremental Capacity Analysis
- 2022
-
Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 37:2, s. 2226-2236
-
Tidskriftsartikel (refereegranskat)abstract
- The state of health (SOH) is a vital parameter enabling the reliability and life diagnostic of lithium-ion batteries. A novel fusion-based SOH estimator is proposed in this study, which combines an open circuit voltage (OCV) model and the incremental capacity analysis. Specifically, a novel OCV model is developed to extract the OCV curve and the associated features-of-interest (FOIs) from the measured terminal voltage during constant-current charge. With the determined OCV model, the disturbance-free incremental capacity (IC) curves can be derived, which enables the extraction of a set of IC morphological FOIs. The extracted model FOI and IC morphological FOIs are further fused for SOH estimation through an artificial neural network. Long-term degradation data obtained from different battery chemistries are used for validation. Results suggest that the proposed fusion-based method manifests itself with high estimation accuracy and high robustness.
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| 13. |
- Galanopoulos, Christos, et al.
(författare)
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Impacts of acidic gas components on combustion of contaminated biomass fuels
- 2018
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Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 111, s. 263-277
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Tidskriftsartikel (refereegranskat)abstract
- The formation of high concentrations of acid gases; in combustion with large variations in fuel qualities, represents a major challenge for energy production from contaminated biomass fuels. This paper provides a comprehensive evaluation of the effects of acid gas formation and retention in the combustion of recycled wood fuels. A model has been developed based on the chemical reactions involved and empirical correlations from plant monitoring and testing. The model has been used to study the behaviour of acidic gas components in critical stages of a bubbling fluidised bed boiler process. Results indicate that the variation in type of fuel contamination is the most important issue to deal with in the combustion of recycled wood fuels. Peaks in the flue gas chlorine concentrations cannot be suppressed easily by conventional flue gas cleaning measures. Upon applying ammonium sulphate dosing for the protection of chlorine induced corrosions, it is sometimes difficult to maintain the required S/Cl ratio when large variations of fuel chlorine occur. Moreover, a high level of chlorine in the fuel can also indirectly affect the emission control of sulphur dioxide because it would require an increased level of ammonium sulphate decomposition, which results in a high level of SO2 in flue gas. The study also shows a beneficial effect of the recirculation of quench water from the flue gas condenser to the boiler. It offers opportunities for the optimisation of flue gas cleaning and flue gas condensation, for improving the efficiencies of water and wastewater treatment, as well as for emission reduction with a sustainable way.
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| 14. |
- He, J., et al.
(författare)
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Comparative study of curve determination methods for incremental capacity analysis and state of health estimation of lithium-ion battery
- 2020
-
Ingår i: Journal of Energy Storage. - : Elsevier. - 2352-152X .- 2352-1538. ; 29
-
Tidskriftsartikel (refereegranskat)abstract
- Incremental capacity analysis (ICA) is a favorable candidate for state of health (SOH) estimation of lithium-ion battery (LIB). Although abundant works have been carried out on the ICA-based methods, a comprehensive comparison of them to clarify the application boundary is still lacking. Moreover, more efficient method for extracting more informative features of interest (FOIs) for SOH estimation is less explored. Motivated by this, this paper performs a comparative study over the filtering-based and the voltage-capacity (VC) model-based ICA methods with respect to the IC fitting accuracy, robustness to aging and the computing cost. In this framework, a set of novel FOIs different from traditional ones are captured along with the parameterization of VC models. Comparative results reveal the optimality of revised Lorentzian VC model with three peaks (RL-VC-3) for both LiFePO4 (LFP) and LiNi1/3Co1/3Mn1/3O2 (NCM) battery. The mean relative errors of capacity modeling are 0.34% and 0.15%, respectively. The newly captured FOIs have been further validated with high linearities with the reference capacity, offering deep insights into more straightforward SOH estimation for LIB. Illustrative case studies suggest that particular FOIs can offer accurate SOH estimation with absolute error of 0.079% and 0.661% respectively for the LFP and NCM battery.
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| 15. |
- Larsson, Magnus, et al.
(författare)
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Characterisation of stormwater in biomass-fired combined heat and power plants : Impact of biomass fuel storage
- 2016
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 170, s. 116-129
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Tidskriftsartikel (refereegranskat)abstract
- Characteristics of stormwater in industrial areas are evaluated, specifically based on a biomass-fired combined heat and power (CHP) plant with on-site biomass fuel storage. An evaluation method is developed to combine general methodology applied for stormwater characterisation with the on-site features of the biomass-fired CHP plant. Investigations were carried out through on-site monitoring and laboratory experiments with the defined methodology. Recycled wood chips as biomass fuel currently used in Swedish biomass-fired CHP plants have been used as an example for this study. The impacts of outdoor biomass fuel storage have been analysed for both runoff water quantity and quality. The results indicate that the properties of stored biomass fuels will significantly affect the runoff quantity by its water absorption capability. The overall runoff quality is highly depended on precipitation intensity and the runoff volume from the biomass storage piles, which is influenced by the water retention capacity and leaching ability of biomass fuels. The practical data and information presented in this paper can be used to understand the principal issues and the most important factors for internal control of contamination sources in order to achieve sustainable Energy-Water systems for bioenergy conversion in biomass-fired CHP plants.
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| 16. |
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| 17. |
- Li, Xiaodong, et al.
(författare)
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A modification of the electromigration device and modelling methods for diffusion and sorption studies of radionuclides in intact crystalline rocks.
- 2020
-
Ingår i: Journal of Contaminant Hydrology. - : Elsevier BV. - 0169-7722 .- 1873-6009. ; 231, s. 103585-
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Tidskriftsartikel (refereegranskat)abstract
- To determine the diffusion and sorption propertiesof radionuclides in intact crystalline rocks, a newelectromigration devicewas built and tested by running with I-and Se(IV) ions. By introducing a potentiostatto impose a constant voltageover the studied rock sample, the electromigration device cangive more stable and accurateexperimental resultsthan those from the traditional electromigration devices.In addition, the variation in the pHofthe background electrolytes wasminimised by adding a small amount of NaHCO3as buffers.To interpret the experimental results with moreconfidence, anadvection-dispersion model was also developed in thisstudy, which accounts for the most important mechanisms governing ionic transport in the electromigration experiments.Data analysis of the breakthrough curves by the advection-dispersion model, instead of the traditional ideal plug-flowmodel,suggest that the effective diffusivitiesof I-and Se(IV)are (1.15±0.06) ×10-13m2/s and (3.50±0.86) ×10-14m2/s, respectively. The results also show thatI-is more mobile than Se(IV) ions when migrating through the sameintact rock sampleand that theirsorption properties are almost identical.
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| 18. |
- Li, Xiaodong, et al.
(författare)
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Diffusion and Sorption Studies of Cs, Sr and Co in Intact Crystalline Rock
- 2022
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Ingår i: Minerals. - : MDPI AG. - 2075-163X. ; 12:2
-
Tidskriftsartikel (refereegranskat)abstract
- Three cationic tracers, Sr2+, Co2+ and Cs+ were tested with a modified electromigration device by applying 2V, 3V and 4V voltage gradients over an intact Grimsel granodiorite rock sample. An ideal plug-flow model and an advection-dispersion model were applied to analyze the breakthrough curves. Matrix characterization by C-14-PMMA autoradiography and scanning electron microscopy showed that in the centimeter scale of Grimsel granodiorite rock, the interconnected matrix porosity forms a well-connected network for diffusion. Micrometer-scale fissures are transecting biotite and chlorite minerals, indicating sorption of the studied cations. The ideal plug-flow model indicated that the effective diffusion coefficients (D-e values) for Sr2+, Co2+ and Cs+ tracer ions within the Grimsel granodiorite rock were 3.20 x 10(-13) m(2)/s, 1.23 x 10(-13) m(2)/s and 2.25 x 10(-12) m(2)/s, respectively. D-e values were also derived from the advection-dispersion model, from which 2.86 x 10(-13) m(2)/s, 1.35 x 10(-13) m(2)/s and 2.26 x 10(-12) m(2)/s were calculated. The diffusion speed for the tracers was in the sequence of Cs+ > Sr2+ > Co2+ that is in the same sequence as their diffusion in diluted water. The distribution coefficients (K-d values) calculated from the models covered the range of two magnitudes (from 10(-7) m(3)/kg to 10(-5) m(3)/kg). The result indicated that the sorption process of the studied elements did not reach equilibrium during the electromigration process, mainly due to the too much acceleration of the migration speed by the voltage gradients applied over the rock sample.
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| 19. |
- Li, Xiaodong, et al.
(författare)
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Multi-site surface complexation modelling of Se(IV) sorption on biotite
- 2020
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Ingår i: Chemical Geology. - : ELSEVIER. - 0009-2541 .- 1872-6836. ; 533
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Tidskriftsartikel (refereegranskat)abstract
- A surface complexation model of Se(IV) sorption on biotite with one type of strong sorption sites and two types of weak sorption sites were developed based on experimental data obtained from titration, sorption edge and sorption isotherm experiments. Titration data was collected using a batch-wise manner together with back-titration to calibrate the effect of mineral dissolution in 0.01 M KClO4 background electrolytes from pH 3 to 11 in an inert atmosphere glovebox. Further calibrations of the titration curve include proton exchange and cation exchange in which the calculations of cation occupancies on biotite surfaces were taken into account. The sorption edge measurements were determined by measuring the sorption of 10(-9) M total Se with a radioactive Se-75 tracer on converted biotite in 0.01 M KClO4 solution from pH 3 to 11. Se sorption was observed to be strongly dependent on pH. Surface complexation modelling was performed by deriving a set of optimized parameters that can fit titration, sorption edge and sorption isotherm (at pH similar to 7.7) experimental data. A CASTEP code implemented into Materials Studio was used to calculate the site densities and site types on the biotite surfaces. Weak sorption sites with site densities of 3.2 sites/nm(2) and 1.4 sites/nm(2) were derived from the codes and used in the sorption model. A computer code that coupled PHREEQC with Python was developed for the fitting and optimizing processes. The model was validated by sorption data at pH similar to 9.5. The results show that the model can provide quantitative predicts of Se(IV) sorption in groundwater conditions of a deep geological repository and help improve the performance assessments by giving more convincing estimates of the release of radionuclides towards aquifers and biosphere.
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| 20. |
- Li, Yongmei, et al.
(författare)
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Update to the Newly Developed Expression for the Stability Ratio of Colloidal Dispersions
- 2023
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 39:15, s. 5284-5293
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Tidskriftsartikel (refereegranskat)abstract
- The colloidal stability, one of the basic and important properties of a colloidal dispersion, is commonly evaluated in terms of the stability ratio. In this study, a recently developed expression for the stability ratio is updated, by reformulating the fraction of successful collisions leading to secondary minimum coagulation. The updated formula reinterprets the statistical meaning of the fraction of successful collisions leading to primary or secondary minimum coagulation, ensuring that the total fraction of successful collisions is always less than or equals to 1. It was shown to be superior to the available expressions in accounting for the contribution of the primary and secondary minimum coagulations on the stability ratio. It can well interpret the stability of colloidal dispersions of spherical particles; moreover, it is of great potential to be applied to colloidal dispersions of plate-like particles. In addition, this formula is found to be consistent with the concept of the critical coagulation concentration and well interpret the effects of particle size, counterion valence, surface potential, and Hamaker constant on the colloidal stability.
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| 21. |
- Liu, Longcheng, et al.
(författare)
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A coupled model for oxidative dissolution of spent fuel and transport of radionuclides from an initially defective canister
- 2001
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Ingår i: Nuclear Technology. - 0029-5450 .- 1943-7471. ; 135, s. 273-285
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Tidskriftsartikel (refereegranskat)abstract
- An earlier model for oxidative dissolution of spent fuel was developed by including the release behavior of actinides from the fuel surface and the barrier effect of Zircaloy claddings. The aim here is to explore the possibility and consequences of precipitation in the water film around the fuel pellets due to solubility, and transport limitations of nuclides. The model has been applied in the performance assessment of a damaged canister under natural repository conditions, by coupling to a redox-front-based model for transport of nuclides. The simulation results identify? that the time of penetration of the canister, the size of the damage, and the initial free volume of the fuel rods are important factors that dominate the dissolution behavior of the fuel matrix and thus the transport behavior of actinides in the nearfield of a repository.
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| 22. |
- Liu, Longcheng, et al.
(författare)
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A Dynamic Force Balance Model for Colloidal Expansion and Its DLVO-Based Application
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:2, s. 679-687
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Tidskriftsartikel (refereegranskat)abstract
- A force balance model that describes the dynamic expansion of colloidal bentonite gels/sols is presented. The colloidal particles are assumed to consist of one or several thin sheets with the other dimensions much larger than their thickness. The forces considered include van der Waals force, diffuse double layer force, thermal force giving rise to Brownian motion, gravity, as well as friction force. The model results in an expression resembling the instationary diffusion equation but with an immensely variable diffusivity. This diffusivity is strongly influenced by the concentration of counterions as well as by the particle concentration in the colloid gel/sol. The properties of the model are explored and discussed, exemplified by the upward expansion of an originally highly compacted bentonite tablet in a test tube. Examples are presented for a number of cases with ionic concentrations varying between very dilute waters up to several molar of counterions. The volume fraction of particles ranges from 40% to very dilute sols.
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| 23. |
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| 24. |
- Liu, Longcheng
(författare)
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A model for the viscosity of dilute smectite gels
- 2011
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Ingår i: Physics and Chemistry of the Earth. - : Elsevier. - 1474-7065 .- 1873-5193. ; 36:17-18, s. 1792-1798
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Tidskriftsartikel (refereegranskat)abstract
- A simple yet accurate model describing the viscosity of dilute suspensions of sodium montmorillonite in dilute homoionic solutions is presented. Taking the clay particle and the surrounding clouds of ions as a whole as an uncharged but soft, coin-like particle, the Huggins’ equation for a suspension of uncharged particles is extended in the model to account for not only the primary and the secondary electroviscous effects, but also the multi-particle interaction. The agreements between the predicted and measured results are excellent. The Huggins’ coefficient obtained compares favorably with available data, while the intrinsic viscosity reduces to the Simha’s equation in the large limit of ionic strength, suggesting that the model is robust.
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| 25. |
- Liu, Longcheng, et al.
(författare)
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A new analytical solution of contaminant transport along a single fracture connected with porous matrix and its time domain random walk algorithm
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 610, s. 127828-
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a new solution is developed for the problem of contaminant transport in a single fracture-matrix system, where the first-order reaction rate constants are different in both fracture and matrix. It takes a form of convolution with three functions as a basis to consider different transport mechanisms separately. The statistical nature of the three functions, as well as the interpretation of the solution as a marginal probability distribution in the case of no first-order reactions, allows us to develop a simple Time Domain Random Walk (TDRW) algorithm to calculate the breakthrough curves at a given point of observation downstream the fracture. Compared with the existing versions of the TDRW algorithm, it is superior not only in the physical reasoning and statistical interpretations but also in its numerical implementations. In addition, the developed algorithm can not only be used to estimate the distribution profile of the contaminant concentration along the fracture but also the concentration within the matrix, since the analytical solution to contaminant concentration in the matrix also takes a convolution form of three functions. Also, the distribution profile of contaminant concentration within the matrix can readily be determined by the use of our TDRW algorithm. To validate the developed algorithm, three benchmark cases are considered for either nuclide or colloid transport through a fractured rock. The results show that TDRW algorithm is superior to the Gaussian quadrature solution, but similar to inverse Laplace transform solution, in computational expense when nearly identical results are obtained. However, the Monte Carlo nature of the TDRW algorithm implies that the accuracy of the computational result is related to the number of particles applied in the simulation, which might make the obtained results fluctuated.
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