Browsing by Author "Wang, Xin"

Now showing 1 - 12 of 12
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    A New Kinetic Assay Method for Effective Scale Inhibitor Concentration Determination with Low Detection Limit
    (SPE, 2022) Dai, Zhaoyi; Ko, Saebom; Wang, Xin; Dai, Chong; Paudyal, Samridhdi; Zhao, Yue; Li, Wei; Leschied, Cianna; Yao, Xuanzhu; Lu, Yi-Tsung; Kan, Amy; Tomson, Mason
    Scale inhibitors are widely used for mineral scale control in various industries, including oil and gas productions, geothermal energy acquisitions, and heat exchanger scale control to mention a few. In most applications, these scale inhibitors are effective at substoichiometric concentrations (e.g., 1 mg/L or lower), and the optimization of these applications is based on the ability to accurately measure the effective inhibitor concentration at such low concentrations. For example, the continuous treatment injection rate, the squeeze treatment frequency, or the batch treatment schedule need to be optimized to ensure the minimum inhibitor concentration (MIC) is achieved during production. However, the non- or low-phosphorous polymeric scale inhibitor concentration determination is difficult using inductively coupled plasma (ICP)-optic emission spectroscopy/mass spectrometry or ion chromatography, especially at mg/L level concentrations due to their high detection limits. The recently developed hyamine method or high-pressure liquid chromatography (HPLC) method involves intensive labor and high costs. Furthermore, in the complex oilfield operational conditions, the presence of other chemicals (e.g., surfactants, biocides, and corrosion inhibitors), the potential degradation of scale inhibitors and the use of combination scale inhibitors require the measurement of effective scale inhibitor concentration, which cannot be accomplished by the traditional methods. In this study, a new kinetic assay method has been developed to determine the effective scale inhibitor concentration with limits of detection (LODs) less than or around 0.1 mg/L for most cases. This method uses a continuous stirring tank reactor (CSTR) apparatus and is developed based on the linear correlation between the effective inhibition concentration and the measured critical time when laser signal changes. The results show that the inhibitor concentrations of various non- or low-phosphorous polymeric scale inhibitors in synthetic field brine, laboratory solutions, and real oilfield brines can be accurately determined at mg/L level, or lower, with less than 10% error. The method is robust, accurate, and much less time- or labor-consuming than other existing methods especially for non- or low-phosphorous polymeric scale inhibitors.
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    Battery metal recycling by flash Joule heating
    (AAAS, 2023) Chen, Weiyin; Chen, Jinhang; Bets, Ksenia V.; Salvatierra, Rodrigo V.; Wyss, Kevin M.; Gao, Guanhui; Choi, Chi Hun; Deng, Bing; Wang, Xin; Li, John Tianci; Kittrell, Carter; La, Nghi; Eddy, Lucas; Scotland, Phelecia; Cheng, Yi; Xu, Shichen; Li, Bowen; Tomson, Mason B.; Han, Yimo; Yakobson, Boris I.; Tour, James M.; Welch Institute for Advanced Materials; NanoCarbon Center; Applied Physics Program; Smalley-Curl Institute
    The staggering accumulation of end-of-life lithium-ion batteries (LIBs) and the growing scarcity of battery metal sources have triggered an urgent call for an effective recycling strategy. However, it is challenging to reclaim these metals with both high efficiency and low environmental footprint. We use here a pulsed dc flash Joule heating (FJH) strategy that heats the black mass, the combined anode and cathode, to >2100 kelvin within seconds, leading to ~1000-fold increase in subsequent leaching kinetics. There are high recovery yields of all the battery metals, regardless of their chemistries, using even diluted acids like 0.01 M HCl, thereby lessening the secondary waste stream. The ultrafast high temperature achieves thermal decomposition of the passivated solid electrolyte interphase and valence state reduction of the hard-to-dissolve metal compounds while mitigating diffusional loss of volatile metals. Life cycle analysis versus present recycling methods shows that FJH significantly reduces the environmental footprint of spent LIB processing while turning it into an economically attractive process.
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    Discontinuous Galerkin Time Domain Methods for Acoustics and Comparison with Finite Difference Time Domain Methods
    (2010-03) Wang, Xin
    This thesis describes an implementation of the discontinuous Galerkin finite element time domain (DGTD) method on unstructured meshes to solve acoustic wave equations in heterogeneous media. In oil industry people use finite difference time domain (FDTD) methods to simulate seismic surveys, the first step to explore oil and gas in the earth's subsurface, conducted either in land or sea. The results in this thesis indicate that the first order time shift effect resulting from misalignment between numerical meshes and material interfaces in the DGTD method occurs in the same way as interface errors in the finite difference simulation of wave propagation. This thesis describes two approaches: interface-fitting mesh and local mesh refinement, without modifying the DGTD scheme, to decrease this troublesome effect with verifications of 2D examples. The comparison of the DGTD method on the piecewise linear interface- fitting mesh and the staggered FDTD method both applied to a square-circle model and a 2D dome model in this thesis confirms the fact that the DGTD method can achieve a suboptimal second order convergence rate while the error in the staggered FDTD method is dominated by the first order interface error when the curved material interfaces are presented. I conclude that the DGTD method is more efficient than the staggered FDTD method for the two solutions to have roughly the same accuracy when the accuracy requirement becomes more and more strict and the model becomes more and more complex.
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    Discontinuous Galerkin time domain methods for acoustics and comparison with finite difference time domain methods
    (2010) Wang, Xin; Symes, William W.
    This thesis describes an implementation of the discontinuous Galerkin finite element time domain (DGTD) method on unstructured meshes to solve acoustic wave equations in heterogeneous media. In oil industry people use finite difference time domain (FDTD) methods to simulate seismic surveys, the first step to explore oil and gas in the earth's subsurface, conducted either in land or sea. The results in this thesis indicate that the first order time shift effect resulting from misalignment between numerical meshes and material interfaces in the DGTD method occurs in the same way as interface errors in the finite difference simulation of wave propagation. This thesis describes two approaches: interface-fitting mesh and local mesh refinement, without modifying the DGTD scheme, to decrease this troublesome effect with verifications of 2D examples. The comparison of the DGTD method on the piecewise linear interface-fitting mesh and the staggered FDTD method both applied to a square-circle model and a 2D dome model in this thesis confirms the fact that the DGTD method can achieve a suboptimal second order convergence rate while the error in the staggered FDTD method is dominated by the first order interface error when the curved material interfaces are presented. I conclude that the DGTD method is more efficient than the staggered FDTD method for the two solutions to have roughly the same accuracy when the accuracy requirement becomes more and more strict and the model becomes more and more complex.
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    Essays on financial analysis: Capital structure, dynamic dependence and extreme loss modeling
    (2008) Wang, Xin; El-Gamal, Mahmoud A.
    This dissertation contains three essays concerning two broad areas, namely, optimal capital structure and risky assets modeling. In the first paper, we study corporate debt values, capital structure, and the term structure of interest rates in a unified framework. We employ numerical techniques to compute the firm's optimal capital structure and the value of its long-term risky debt with call option embedded and yield spreads when the value of the firm's unleveraged assets and the instantaneous default-free interest rate are risk factors. Debt and leveraged firm value are thus explicitly linked to properties of the firm's unleveraged assets, the term structure of default-free interest rates, taxes, bankruptcy costs, payout rates, and bond covenants. The results clarify the relationship between a firm's capital structure and movements in the term structure and other important aspects of the capital structure decision. In the second chapter, we propose a dynamic copula modeling framework that allows copula association parameters to change with time and macroeconomic variables. We find empirical evidence that nominal interest rate and price index for traded goods differentials between two countries have significant impact on the co-movement of foreign exchange rates. Our Pearson-type goodness-of-fit test has the power to reject constant and time-varying copula modeling approaches at the 95% confidence level. In the third chapter, a new method for solving sample size problem in probabilistic risk assessment has been developed. We propose the use of Bayesian power prior distributions to improve extreme value theory and provide reliable estimates of Value-at-Risk (VaR) and expected shortfall. The Bayesian Monte Carlo Markov chain computational scheme with power prior distributions allows us to properly incorporate historical data and borrow strength and information from related sources to current study.
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    Gypsum scale formation and inhibition kinetics with implications in membrane system
    (Elsevier, 2022) Dai, Zhaoyi; Zhao, Yue; Paudyal, Samridhdi; Wang, Xin; Dai, Chong; Ko, Saebom; Li, Wei; Kan, Amy T.; Tomson, Mason B.
    Water desalination using membrane technology is one of the main technologies to resolve water pollution and scarcity issues. In the membrane treatment process, mineral scale deposition and fouling is a severe challenge that can lead to filtration efficiency decrease, permeate quality compromise, and even membrane damage. Multiple methods have been developed to resolve this problem, such as scale inhibitor addition, product recovery ratio adjustment, periodic membrane surface flushing. The performance of these methods largely depends on the ability to accurately predict the kinetics of mineral scale deposition and fouling with or without inhibitors. Gypsum is one of the most common and troublesome inorganic mineral scales in membrane systems, however, no mechanistic model is available to accurately predict the induction time of gypsum crystallization and inhibition. In this study, a new gypsum crystallization and inhibition model based on the classical nucleation theory and a Langmuir type adsorption isotherm has been developed. Through this model, it is believed that gypsum nucleation may gradually transit from homogeneous to heterogeneous nucleation when the gypsum saturation index (SI) decreases. Such transition is represented by a gradual decrease of surface tension at smaller SI values. This model assumes that the adsorption of inhibitors onto the gypsum nucleus can increase the nucleus superficial surface tension and prolong the induction time. Using the new model, this study accurately predicted the gypsum crystallization induction times with or without nine commonly used scale inhibitors over wide ranges of temperature (25–90 °C), SI (0.04–0.96), and background NaCl concentration (0–6 mol/L). The fitted affinity constants between scale inhibitors and gypsum show a good correlation with those between the same inhibitors and barite, indicating a similar inhibition mechanism via adsorption. Furthermore, by incorporating this model with the two-phase mineral deposition model our group developed previously, this study accurately predicts the gypsum deposition time on the membrane material surfaces reported in the literature. We believe that the model developed in this study can not only accurately predict the gypsum crystallization induction time with or without scale inhibitors, elucidate the gypsum crystallization and inhibition mechanisms, but also optimize the mineral scale control in the membrane filtration system.
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    Non-equilibrium BaxSr1-xSO4 solid solution compositions at elevated Sr2+ concentration, ionic strength, and temperature
    (Elsevier, 2022) Zhao, Yue; Dai, Zhaoyi; Wang, Xin; Dai, Chong; Paudyal, Samridhdi; Ko, Saebom; Li, Wei; Kan, Amy T.; Tomson, Mason
    The BaxSr1-xSO4 solid solution is ubiquitously present in both geological and industrial processes, where they mostly form under non-equilibrium conditions. Compared with those formed under equilibrium conditions, the BaxSr1-xSO4 solid solution formed at non-equilibrium condition has significantly higher Sr incorporation at the same aqueous phase compositions. The solid composition of BaxSr1-xSO4 formed at non-equilibrium condition is critical for the study of chemical palaeoceanography as well as the solid solution nucleation and growth kinetics. However, few studies have been conducted to investigate the composition of the BaxSr1-xSO4 solid solution when it precipitates at non-equilibrium conditions. In this study, the distribution coefficient of Ba2+ and Sr2+ between the BaxSr1-xSO4 solid solution and the aqueous phases (KD,Sr-Barite) at non-equilibrium conditions was studied with barite saturation index (SIbarite) from 0.9 to 1.5, [Sr2+]/[Ba2+] molality ratio from 0.33 to 30, temperature (T) from 50 to 90 °C and ionic strength (IS) from 0.01 M to 3 M as NaCl, with celestite being undersaturated. The composition of the BaxSr1-xSO4 solid solution formed at non-equilibrium conditions can then be calculated from the KD,Sr-Barite values. The results show that the KD,Sr-Barite value decreases with the increase of aqueous Sr2+ concentration at fixed SIbarite and T conditions. The IS effect on the KD,Sr-Barite value is small. Based on the experimental results, a new empirical model is developed to accurately predict the measured compositions of BaxSr1-xSO4 solid solution at non-equilibrium conditions under a wide T and IS conditions as follows (the plot of the predicted log10KD,Sr-Barite versus the measured log10KD,Sr-Barite with : Several theoretical models have also been compared against the experimental data. The birth and spread crystal growth model (B + S model) could accurately predict the solid composition of BaxSr1-xSO4 at higher barite SI and/or higher T conditions (barite SI = 1.5 at 70 °C and barite SI = 1.2–1.5 at 90 °C with [Sr2+]/[Ba2+] = 0.33–10). However, the B + S model predictions show larger deviations at lower SI and/or lower T conditions (barite SI = 0.9 and 1.2 at 50 °C and barite SI = 0.9 at 70 °C with [Sr2+]/[Ba2+] = 0.33–10 in this study). For other theoretical models, such as the CNT model and the BCF model, the predicted solid compositions of BaxSr1-xSO4 are significantly higher than the measured results. This quantitative study of the BaxSr1-xSO4 solid solution compositions could help reconstruct oceanic physical conditions and chemistry. It also establishes a solid foundation to further investigate the kinetics of the BaxSr1-xSO4 solid solution formation during non-equilibrium geological and industrial processes.
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    Observations of CO2 Corrosion-Induced Carbonate Scale Formation and Inhibition on Mild Steel
    (SPE, 2022) Li, Wei; Dai, Zhaoyi; Wang, Xin; Ko, Saebom; Paudyal, Samiridhdi; Yao, Xuanzhu; Leschied, Cianna; Shen, Yu-Yi; Pimentel, Daniel; Kan, Amy T.; Tomson, Mason
    Aqueous CO2-containing environment is ubiquitous in oil and gas production. Carbonate scales (e.g., calcite) tend to form in such an environment. Meanwhile, the CO2 corrosion of mild steel infrastructure may result in corrosion-induced scales including siderite (FeCO3). Previously, siderite was generally treated as a corrosion problem rather than a scale problem. However, the relationship between the corrosion-induced scale and other metal carbonate scales on the steel surface is unclear. For example, how does siderite influence calcite deposition on the mild steel? In this study, the mild steel corrosion and mineral carbonate scaling behaviors were investigated simultaneously in the presence of various cations such as Ca2+ and Mg2+. We observed a two-layer scale structure on the mild steel surface under simulated oilfield conditions. The inner layer is an iron-containing carbonate scale such as ankerite or siderite, while the outer layer is calcite. In addition, calcite deposition at a very low saturation index was observed when the inner layer was present. Furthermore, a common scale inhibitor [diethylenetriaminepentakis(methylenephosphonic acid) or DTPMP] can effectively mitigate calcite, siderite, and ankerite formation on the steel surface, but meanwhile, aggravate the steel corrosion because of the absence of protective scale layers.
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    Prediction Models of Barite Crystallization and Inhibition Kinetics: Applications for Oil and Gas Industry
    (MDPI, 2021) Dai, Chong; Dai, Zhaoyi; Zhao, Yue; Wang, Xin; Paudyal, Samiridhdi; Ko, Saebom; Kan, Amy T.; Tomson, Mason B.
    Barite is one of the most common mineral scales in the oilfield and its formation can sequester toxic strontium (Sr) and radium (Ra). Various scale inhibitors are widely used to inhibit its formation. The inhibition efficiencies of 18 common inhibitors were tested using an improved kinetic turbidity method over broad oil and gas production conditions. A theoretical and a semi-empirical barite crystallization and inhibition model were developed for the 18 most used scale inhibitors. Both models can work under a broad range of production conditions and are carefully reviewed against all available experimental data. These models have shown wide applications in industrial operations, field testing, and laboratory testing. Using the new models and testing method, a novel fast inhibitor performance testing method was proposed and validated. Furthermore, the barite crystallization and inhibition models also work well to predict the inhibition performance of mixed inhibitors. This study not only advanced barite scale inhibition in an efficiency and low-cost way during oil and gas production, but also provided new insights on understanding the fate and transport of toxic Sr and Ra.
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    Printing Highly Controlled Suspended Carbon Nanotube Network on Micro-patterned Superhydrophobic Flexible Surface
    (Macmillan Publishers Limited, 2015) Li, Bo; Wang, Xin; Jung, Hyun Young; Kim, Young Lae; Robinson, Jeremy T.; Zalalutdinov, Maxim; Hong, Sanghyun; Hao, Ji; Ajayan, Pulickel M.; Wan, Kai-Tak; Jung, Yung Joon
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    Solubility, Precipitation Kinetic, and Chemical Control of Iron Sulfide
    (2024-04-18) Wang, Xin; Tomson, Mason B; Chapman, Walter G; Getachew, Bezawit
    The iron sulfides (FeS) constitute a diverse group of solids and dissolved complexes, many of which play critical roles in the natural system, such as marine sedimentation and biochemical processes. It has also become a significant problem in various industrial processes, such as water and wastewater treatment, metal equipment corrosion by hydrogen sulfide, and oil and gas production. Extensive studies have been done in the past century to better understand, predict, and control the sulfide mineral precipitation, of which the importance can never be overstated. In this work, a systematic study of the solubility, precipitation kinetics, and the chemical dispersion control of iron sulfide is conducted to better understand iron sulfide scale prediction and control in industrial processes.
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    Transfer-of-approximation Approaches for Subgrid Modeling
    (2013-07-24) Wang, Xin; Symes, William W.; Warburton, Tim; Riviere, Beatrice M.; Zelt, Colin A.
    I propose two Galerkin methods based on the transfer-of-approximation property for static and dynamic acoustic boundary value problems in seismic applications. For problems with heterogeneous coefficients, the polynomial finite element spaces are no longer optimal unless special meshing techniques are employed. The transfer-of-approximation property provides a general framework to construct the optimal approximation subspace on regular grids. The transfer-of-approximation finite element method is theoretically attractive for that it works for both scalar and vectorial elliptic problems. However the numerical cost is prohibitive. To compute each transfer-of-approximation finite element basis, a problem as hard as the original one has to be solved. Furthermore due to the difficulty of basis localization, the resulting stiffness and mass matrices are dense. The 2D harmonic coordinate finite element method (HCFEM) achieves optimal second-order convergence for static and dynamic acoustic boundary value problems with variable coefficients at the cost of solving two auxiliary elliptic boundary value problems. Unlike the conventional FEM, no special domain partitions, adapted to discontinuity surfaces in coe cients, are required in HCFEM to obtain the optimal convergence rate. The resulting sti ness and mass matrices are constructed in a systematic procedure, and have the same sparsity pattern as those in the standard finite element method. Mass-lumping in HCFEM maintains the optimal order of convergence, due to the smoothness property of acoustic solutions in harmonic coordinates, and overcomes the numerical obstacle of inverting the mass matrix every time update, results in an efficient, explicit time step.