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  • 1.
    Bao, Ningzhong
    et al.
    Nanjing University of Chemical Technology.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Ji, Xiaoyan
    Feng, Xin
    Nanjing University of Chemical Technology.
    Xie, Jingwei
    Nanjing University of Chemical Technology.
    Thermodynamic modeling and experimental verification for ion-exchange synthesis of K2O·6TiO2 and TiO2 fibers from K2O·4TiO22002In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 193, p. 229-243Article in journal (Refereed)
    Abstract [en]

    A thermodynamic model was established to determine ion-exchange conditions for the synthesis of potassium hexatitanate (K2O·6TiO2) and titanium dioxide (TiO2) from potassium tetratitanate (K2O·4TiO2) fiber. In the proposed model equilibrium species in the solid phase and corresponding ion-exchange equilibrium constants at 298.15 K were determined from the experimental data of Sasaki et al. [Inorg. Chem. 24 (1985) 2265]. In order to verify the proposed model, prediction results were compared with experimental data determined in literature and those measured in this work. The comparison shows a good agreement. Based on this, the proposed model was also used to predict more extensive suitable conditions for the synthesis of K2O·6TiO2 and TiO2.

  • 2.
    Bülow, M.
    et al.
    TU Dortmund, Dortmund, Germany.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Held, C.
    TU Dortmund, Dortmund, Germany.
    Incorporating a concentration-dependent dielectric constant into ePC-SAFT. An application to binary mixtures containing ionic liquids2019In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 492, p. 26-33Article in journal (Refereed)
    Abstract [en]

    Primitive thermodynamic models for electrolyte solutions require the dielectric constant ε. This property strongly depends on the concentration of the electrolytes in the mixture. Neglecting this dependency might be reasonable for modeling solutions at low electrolyte concentrations. However, in solutions containing ionic liquids (ILs) and especially for the calculation of liquid-liquid equilibria (LLE) of systems with ILs, liquid phases often contain high IL concentrations. At such conditions, neglecting the influence of concentration on ε is an oversimplification. In this work, an approach to account for the concentration-dependent dielectric constant within the Debye-Hückel theory was implemented into electrolyte Perturbed-Chain Statistical Associating Fluid Theory (original ePC-SAFT). This new approach was then applied to model LLE of binary mixtures containing water and commonly used hydrophobic ILs. These common ILs are comprised of the IL-cations [C n mim] + , [C n py] + , [C n mpy] + , [C n mpyr] + , [C 4 m 4 py] + and the IL-anions [BF 4 ] - , [NTf 2 ] - , [PF 6 ] - , [TFO] - . The LLE of binary mixtures water + IL were modeled at ambient pressure and different temperatures with the new ePC-SAFT and with the original ePC-SAFT [Ji et al. DOI: 10.1016/j.fluid.2012.05.029] without the concentration-dependent ε. Overall, the new approach within ePC-SAFT shows superior modeling as well as correlation capability compared to original ePC-SAFT, which was concluded by comparing both models with LLE data from literature. 

  • 3.
    Carvalho, Lara
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Furusjö, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL – Swedish Environmental Institute, Stockholm, Sweden.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Öhrman, Olov G. W.
    IVL – Swedish Environmental Institute, Stockholm, Sweden;RISE Energy Technology Center AB, Piteå, Sweden.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria.
    Alkali enhanced biomass gasification with in situ S capture and a novel syngas cleaning: Part 2: Techno-economic analysis2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 165, no Part B, p. 471-482Article in journal (Refereed)
    Abstract [en]

    Previous research has shown that alkali addition has operational advantages in entrained flow biomass gasification and allows for capture of up to 90% of the biomass sulfur in the slag phase. The resultant low-sulfur content syngas can create new possibilities for syngas cleaning processes. The aim was to assess the techno-economic performance of biofuel production via gasification of alkali impregnated biomass using a novel gas cleaning systemcomprised of (i) entrained flow catalytic gasification with in situ sulfur removal, (ii) further sulfur removal using a zinc bed, (iii) tar removal using a carbon filter, and (iv) CO2 reductionwith zeolite membranes, in comparison to the expensive acid gas removal system (Rectisol technology). The results show that alkali impregnation increases methanol productionallowing for selling prices similar to biofuel production from non-impregnated biomass. It was concluded that the methanol production using the novel cleaning system is comparable to the Rectisol technology in terms of energy efficiency, while showing an economic advantagederived from a methanol selling price reduction of 2–6 €/MWh. The results showed a high level of robustness to changes related to prices and operation. Methanol selling prices could be further reduced by choosing low sulfur content feedstocks.

  • 4.
    Chen, Jingjing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Wang, Changsong
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Mechanism Study of Heat Transfer Enhancement Using Twisted Hexagonal Tube with Slurry from Biogas Plant2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 880-885Article in journal (Refereed)
    Abstract [en]

    Waste-heat recovery from discharged slurries is important to improve the biogas production efficiency but still remains challenge duo to the special properties of slurries in anaerobic digestion process. In this work, numerical study was carried out to investigate the flow field, and heat transfer performance of slurry from biogas plant in the twisted hexagonal and other twisted tubes was simulated with computer fluid dynamic (CFD) for the first time. The numerical method was validated with experimental data from the literature. The heat transfer performance and flow resistance of twisted hexagon tube were calculated and compared with other types of twisted tubes. The enhancement factor of the twisted hexagonal tube reached to 2 and kept optimum at turbulence flow region compared to the twisted tubes with square and elliptical cross section. Meanwhile, the mechanism of heat transfer enhancement with different twisted tubes was further studied, and the optimal field synergy and minimum local circulation flow near the wall are the main reasons for the high performance and low flow resistance of the twisted hexagonal tube.

  • 5.
    Chen, Jingjing
    et al.
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing.
    Ma, Chunyan
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing.
    Ji, Xiaoyan
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Wang, Changsong
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Mechanism Study of Waste Heat Recovery from Slurry by Surface Scraped Heat Exchanger2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 105, p. 1109-1115Article in journal (Refereed)
    Abstract [en]

    Waste-heat recovery from discharged slurries can improve the net raw biogas production in bio-methane process in order to meet the demand of a new generation of anaerobic digestion. In order to achieve a high efficient waste-heat recovery, in this work, a mathematical model of waste-heat recovery process with surface scraped heat exchanger (SSHE) was proposed with the consideration of the shear rate and temperature-dependent rheological behaviour. The convective heat transfer performance of SSHE was calculated numerically where slurry was considered. The contribution of waste heat recovery from the slurry to biogas production by SSHE and general shell-and-tube heat exchanger (STHE) were firstly calculated quantitatively, and the increase of net raw biogas production could be over 13.5% by SSHE with need of heat exchange area less than a quarter of STHE's, which showed a great potential to increase the net raw biogas production in bio-methane process with low equipment investments and more compactible structure.

  • 6.
    Chen, Jingjing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University.
    Wu, Jiajun
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Wang, Changsong
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing .
    Mechanism of waste-heat recovery from slurry by scraped-surface heat exchanger2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 207, p. 146-155Article in journal (Refereed)
    Abstract [en]

    Waste-heat recovery from discharged slurries can improve the net raw biogas production in the bio-methane process in order to meet the demand for a next-generation of anaerobic digestion. In this study, a numerical model of a scraped-surface heat exchanger was proposed with the consideration of the complete and precise rheological behaviour of the slurry of animal manure for the first time for achieving highly efficient waste-heat recovery. The rheological model results were verified with new experimental data measured in this work. Subsequently, the convective heat-transfer coefficient of the scraped-surface heat exchanger was calculated numerically with the proposed numerical model, and the performance was determined. Then, the contributions of waste-heat recovery from the slurry to the biogas production using a general shell-and-tube heat exchanger and the scraped-surface heat exchanger were calculated quantitatively and compared. For the case of scraped-surface heat exchanger, the increase of net raw biogas production can be up to 8.53%, which indicates that there is a great potential to increase the net raw biogas production in the bio-methane process using a scraped-surface heat exchanger with low-cost equipment and a compactible structure.

  • 7.
    Chen, Yifeng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Novel Solvent for CO2 Capture2019In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 158, p. 5124-5129Article in journal (Refereed)
    Abstract [en]

    To develop novel solvent for CO2 capture, CO2 absorption performance using the aqueous of polyethylene glycol 200 (PEG200) and choline-2-pyrrolidinecarboxylic acid ([Cho][Pro]) was studied and evaluated systematically in this work, in which the critical properties of PEG200 were estimated with group contribution method, and other thermo-physical properties were determined experimentally or taken from literatures directly and then correlated with empirical equations. The CO2 solubility in PEG200 was measured and represented with the Henry’s law and Poynting correction, while the measured CO2 solubility in PEG200/H2O was correlated with RK-NRTL model. [Cho][Pro] was used as the chemical ingredient to enhance the absorption capacity and rate of CO2 in [Cho][Pro]/PEG200/H2O, and the corresponding properties and CO2 solubility were studied. The kinetic parameters, such as enhancement factor (E), reaction rate constant (k), and activation energy (Ea) of CO2 in [Cho][Pro]/PEG200/H2O were estimated from the new experimental data measured in this work and compared with the commercialized aqueous MEA solution. The process simulation and pilot-testing based on [Cho][Pro]/PEG200/H2O will be performed in the future.

  • 8.
    Chen, Yifeng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Thermodynamic study on aqueous polyethylene glycol 200 solution and performance assessment for CO2 separation2020In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 504, article id 112336Article in journal (Refereed)
    Abstract [en]

    To develop polyethylene glycol 200 (PEG200) and aqueous PEG200 solutions (PEG200/H2O) as solvents for CO2 separation, in this study, the available thermo-physical properties of PEG200 and PEG200/H2O measured experimentally were surveyed, evaluated, and correlated with empirical equations. The solubility of CO2 in PEG200 was also surveyed, evaluated and described with the Henry's law with the Poynting correction, while the solubilities of CH4 and N2 in PEG200 were determined experimentally and then described with the Henry's law. The CO2, CH4 and N2 solubilities in PEG200/H2O were measured and described with the Redlich–Kwong Nonrandom-Two-Liquid (RK-NRTL) model. In addition, the performances of PEG200, PEG200/H2O and other commercialized physical solvents for CO2 separation were discussed based on the properties, and the biogas upgrading was chosen as the example to quantitatively evaluate the performances of PEG200 and PEG200/H2O with process simulation and compared with the high pressure water scrubbing (HPWS). It shows that the total energy usage and the amount of recirculated solvent for biogas upgrading can decrease by 9.1% and 26.5%, respectively, when H2O is replaced by PEG200 completely.

  • 9.
    Chen, Yifeng
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sun, Yunhao
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Yang, Zhuhong
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    CO2 separation using a hybrid choline-2-pyrrolidine-carboxylic acid/polyethylene glycol/water absorbent2020In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 257, article id 113962Article in journal (Refereed)
    Abstract [en]

    Developing novel hybrid absorbents is essential for CO2 separation. In this study, the density and viscosity of a hybrid absorbent (choline-2-pyrrolidine-carboxylic acid/polyethylene glycol/water ([Cho][Pro]/PEG200/H2O)) were measured experimentally, and its CO2 solubility was also determined. The excess mole volume and excess Gibbs energy of activation of the hybrid absorbent were further estimated to understand the molecular structure and interactions between [Cho][Pro]/PEG200 and H2O. The CO2 solubilities in [Cho][Pro]/PEG200 and [Cho][Pro]/H2O were analyzed and described using the Redlich–Kwong non-random-two-liquid (RK-NRTL) model. Furthermore, the CO2 solubility in the hybrid absorbent was predicted using the RK-NRTL model and was compared with the new experimental results for verification. The effect of H2O on the CO2 absorption performance was further analyzed. The performance and cost of the hybrid absorbent were compared with those of other commercialized CO2 absorbents. In addition, the recyclability of the hybrid absorbent for CO2 separation was studied. The results of this study indicated that the hybrid absorbent could be promising for CO2 separation.

  • 10.
    Chen, Yifeng
    et al.
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Zhang, Yingying
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Yuan, Shengjuan
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Liu, Chang
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Yang, Zhuhong
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University.
    Thermodynamic Study for Gas Absorption in Choline-2-pyrrolidine-carboxylic Acid + Polyethylene Glycol2016In: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 61, no 10, p. 3428-3437Article in journal (Refereed)
    Abstract [en]

    The solubility of pure CO2, CH4, and N2 in the mixture of choline-2-pyrrolidine carboxylic acid ([Cho][Pro]) and polyethylene glycol (PEG200) (mass ratio = 1:2) was measured experimentally at temperatures from 308.15 to 338.15 K and pressures up to 28 bar, in which [Cho][Pro] is an ionic liquid and PEG200 is a cosolvent with the purpose to decrease the viscosity. It was found that [Cho][Pro]/PEG200 showed a good selectivity for CO2/CH4 and CO2/N2 separation. The measured experimental data points from this work and others were further used to estimate the thermodynamic properties including the Henry's law constants for the gases in [Cho][Pro]/PEG200, the equilibrium constant for the reaction between CO2 and [Cho][Pro], the CO2 absorption enthalpy in [Cho][Pro]/PEG200, and so forth. The consistent results of the CO2 absorption enthalpy at infinite dilution prove the reliability of the thermodynamic properties obtained in this work. The thermodynamic properties of [Cho][Pro]/PEG200 were further compared with other three typical absorbents, and the absorption enthalpy is nearly half of that for 30 wt % MEA aqueous solution. At the same time, the theoretical amount of absorbents needed for [Cho][Pro]/PEG200 is much lower than that of H2O scrubbing. This shows that [Cho][Pro]/PEG200 is a promising absorbent

  • 11.
    Dong, Yihui
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. State Key Laboratory of Materials-Oriented and Chemical Engineering and Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Laaksonen, Aatto
    State Key Laboratory of Materials-Oriented and Chemical Engineering and Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, China. Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden. Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden. Centre of Advanced Research in Bionanoconjugates and Biopolymers, Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, Iasi, Romania.
    Cao, Wei
    State Key Laboratory of Tribology, Tsinghua University, Beijing, China.
    An, Rong
    Herbert Gleiter Institute of Nanoscience, Nanjing University of Science & Technology, Nanjing, China.
    Lu, Linghong
    State Key Laboratory of Materials-Oriented and Chemical Engineering and Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering and Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University, Nanjing, China.
    Determination of the small amount of proteins interacting with TiO2 nanotubes by AFM-measurement2019In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 192, p. 368-376Article in journal (Refereed)
    Abstract [en]

    Detecting the small amounts of proteins interacting effectively with the solid film electrodes surface still remains a challenge. To address this, in this work, a new approach was proposed by the combination of the adhesion forces and the molecular interaction measured with AFM. Cytochrome c (Cyt C) interacting effectively with TiO2 nanotube arrays (TNAs) was chosen as a probe. The amounts of Cyt C molecules interacting effectively on TNAs surface (CTNA) range from 5.5×10-12 to 7.0×10-12 mol/cm2 (68.2-86.8 ng/cm2) and they are comparable with the values obtained by the electrochemistry method in the literature, in evidence of the accuracy of this AFM-based approach. The reliability of the proposed approach was further verified by conducting Surface Enhanced Raman Scattering (SERS) measurements and estimating the enhancement factor (EF). This interaction-based AFM approach can be used to accurately obtain the small amounts of adsorbed substances on the solid film electrodes surface in the applications such as biosensors, biocatalysis, and drug delivery, etc.

  • 12.
    Dong, Yihui
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. State Key Laboratory of Materials-Oriented and Chemical Engineering Nanjing Tech University.
    Laaksonen, Aatto
    Department of Materials and Environmental Chemistry Arrhenius Laboratory Stockholm University. Centre of Advanced Research in Bionanoconjugates and Biopolymers Petru Poni Institute of Macromolecular Chemistry Aleea Grigore Ghica-Voda, Iasi, Romania. State Key Laboratory of Materials-Oriented and Chemical Engineering Nanjing Tech University, China.
    Cao, Wei
    State Key Laboratory of Tribology Tsinghua University, Beijing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering Nanjing Tech University Nanjing, China.
    AFM Study of pH-Dependent Adhesion of Single Protein to TiO2 Surface2019In: Advanced Materials Interfaces, ISSN 2196-7350, Vol. 6, no 14, article id 1900411Article in journal (Refereed)
    Abstract [en]

    The effect of pH-induced electrostatic conditions on the molecular interaction force of a single lysozyme molecule with TiO2 is investigated using atomic force microscopy (AFM). The force between the charged or neutral lysozyme molecule and the TiO2 surface is measured at different pH from 3.6 to 10.8. It is found to be directly proportional to the contact area, given by an effective diameter of the lysozyme molecule, and is further qualitatively verified by the AFM-measured friction coefficients. The results of the Derjaguin–Landau–Verwey–Overbeek theory show that the pH can change the surface charge densities of both lysozyme and TiO2, but the molecular interaction force at different pH is only dependent on the pH-induced effective diameter of lysozyme. The molecular interaction forces, quantified at the nanoscale, can be directly used to design high-performance liquid chromatography measurements at macroscale by tuning the retention time of a protein under varied pH conditions. They can also be applied to develop a model for predicting and controlling the chromatographic separations of proteins.

  • 13.
    Fan, Tengteng
    et al.
    College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Xie, Wenlong
    College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Liu, Cheng
    College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Feng, Xie
    College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    College of Chemistry and Chemical Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    CO2/N2 separation using supported ionic liquid membranes with green and cost-effective [Choline][Pro]/PEG200 mixtures2016In: Chinese Journal of Chemical Engineering, ISSN 1004-9541, E-ISSN 2210-321X, Vol. 24, no 11, p. 1513-1521Article in journal (Refereed)
    Abstract [en]

    The high price and toxicity of ionic liquids (ILs) have limited the design and application of supported ionic liquid membranes (SILMs) for CO2 separation in both academic and industrial fields. In this work, [Choline][Pro]/polyethylene glycol 200 (PEG200) mixtures were selected to prepare novel SILMs because of their green and cost-effective characterization, and the CO2/N2 separation with the prepared SILMs was investigated experimentally at temperatures from 308.15 to 343.15 K. The temperature effect on the permeability, solubility and diffusivity of CO2 was modeled with the Arrhenius equation. A competitive performance of the prepared SILMs was observed with high CO2 permeability ranged in 343.3-1798.6 barrer and high CO2/N2 selectivity from 7.9 to 34.8. It was also found that the CO2 permeability increased 3 times by decreasing the viscosity of liquids from 370 to 38 mPa·s. In addition, the inherent mechanism behind the significant permeability enhancement was revealed based on the diffusion-reaction theory, i.e. with the addition of PEG200, the overall resistance was substantially decreased and the SILMs process was switched from diffusion-control to reaction-control. 

  • 14.
    Furusjö, Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. IVL Swedish Environmental Research Institute, Climate & Sustainable Cities.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Carvalho, Lara
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wetterlund, Elisabeth
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Alkali enhanced biomass gasification with in situ S capture and novel syngas cleaning: Part 1: Gasifier performance2018In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 157, p. 96-105Article in journal (Refereed)
    Abstract [en]

    Previous research shows that alkali addition in entrained flow biomass gasification can increase char conversion and decrease tar and soot formation through catalysis. This paper investigates two other potential benefits of alkali addition: increased slag flowability and in situ sulfur capture.

    Thermodynamic equilibrium calculations show that addition of 2–8% alkali catalyst to biomass completely changes the chemical domain of the gasifier slag phase to an alkali carbonate melt with low viscosity. This can increase feedstock flexibility and improve the operability of an entrained flow biomass gasification process. The alkali carbonate melt also leads to up to 90% sulfur capture through the formation of alkali sulfides. The resulting reduced syngas sulfur content can potentially simplify gas cleaning required for catalytic biofuel production.

    Alkali catalyst recovery and recycling is a precondition for the economic feasibility of the proposed process and is effected through a wet quench. It is shown that the addition of Zn for sulfur precipitation in the alkali recovery loop enables the separation of S, Ca and Mg from the recycle. For high Si and Cl biomass feedstocks, an alternative separation technology for these elements may be required to avoid build-up.

  • 15.
    Gao, Qingwei
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Zhu, Yudan
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Zhu, Wei
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Lu, Linghong
    College of Chemical Engineering, State Key Laboratory of Materials-oriented Chemical Engineering, Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University.
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Effect of water concentration on the microstructures of choline chloride/urea (1:2) /water mixture2018In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 470, p. 134-139Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics was utilized to investigate the properties of ChCl/urea (1:2)/water mixtures from pure ChCl/urea to infinitely dilute solution. To further study the mechanism at molecular scale, the local microstructure variation in the mixtures with the increase of water content was analyzed in detail. Simulation results showed that neither choline cations nor chloride anions are saturated by the coordinated water molecules, even when the water molar fraction reaches 0.9. The hydration number proportions for different ions indicated that the hydration strength of chloride anion is stronger than that of choline cation, which may play greater effects on the properties of mixtures. This result is further confirmed by the analysis of interaction energy between cation (anion) and water molecules. Moreover, the ion pairing between choline cations and chloride anions is a dominant factor to affect the solution properties at lower water content, whereas the hydration turns to be the dominant factor with increasing water content. The competition between ion pairing and ionic hydration could be the intrinsic mechanism resulting in non-ideal properties.

  • 16.
    Han, Jiuli
    et al.
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China. School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China.
    Bai, Lu
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
    Yang, Bingbing
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China. School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China.
    Bai, Yinge
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
    Luo, Shuangjiang
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
    Zeng, Shaojuan
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
    Gao, Hongshuai
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China.
    Nie, Yi
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China. Zhengzhou Institute of Emerging Industrial Technology, Zhengzhou, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Zhang, Suojiang
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China. School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China.
    Zhang, Xiangping
    Beijing Key Laboratory of Ionic Liquids Clean Process, State Key Laboratory of Multiphase Complex Systems, CAS Key Laboratory of Green Process and Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, China. School of Chemical Engineering, University of Chinese Academy of Sciences, Beijing, China.
    Highly Selective Oxygen/Nitrogen Separation Membrane Engineered Using a Porphyrin-Based Oxygen Carrier2019In: Membranes, ISSN 2077-0375, E-ISSN 2077-0375, Vol. 9, no 9, article id 115Article in journal (Refereed)
    Abstract [en]

    Air separation is very important from the viewpoint of the economic and environmental advantages. In this work, defect-free facilitated transport membranes based on poly(amide-12-b-ethylene oxide) (Pebax-2533) and tetra(p-methoxylphenyl)porphyrin cobalt chloride (T(p-OCH3)PPCoCl) were fabricated in systematically varied compositions for O2/N2 separation. T(p-OCH3)PPCoCl was introduced as carriers that selectively and reversibly interacted with O2 and facilitated O2 transport in the membrane. The T(p-OCH3)PPCoCl had good compatibility with the Pebax-2533 via the hydrogen bond interaction and formed a uniform and thin selective layer on the substrate. The O2 separation performance of the thin film composite (TFC) membranes was improved by adding a small amount of the T(p-OCH3)PPCoCl and decreasing the feed pressure. At the pressure of 0.035 MPa, the O2 permeability and O2/N2 selectivity of the 0.6 wt % T(p-OCH3)PPCoCl/Pebax-2533 was more than 3.5 times that of the Pebax-2533 TFC membrane, which reached the 2008 Robeson upper bound. It provides a candidate membrane material for O2/N2 efficient separation in moderate conditions

  • 17.
    Han, Ruiping
    et al.
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Hagos, Kiros
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Zhang, Shaopeng
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Chen, Jingjing
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Yang, Zhuhong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology, College of Chemistry and Chemical Engineering, Nanjing University of Technology.
    Wang, Changsong
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Review on Heat-Utilization Processes and Heat-Exchange Equipment in Biogas Engineering2016In: Journal of Renewable and Sustainable Energy, ISSN 1941-7012, E-ISSN 1941-7012, Vol. 8, no 3, article id 32701Article in journal (Refereed)
    Abstract [en]

    With the increasing demand for environmental protection and renewable energy, bioenergy technology has been attracting considerable attention. Anaerobic digestion (AD) is the process to convert the low-grade biomass into bioenergy, in which both heat-recovery and -recycling should be treated carefully in order to improve the process efficiency. In this work, the heat-recovery and its utilization processes were reviewed, and different types of heat exchangers as well as their advantages in biogas engineering were surveyed. It shows that the recovery and utilization of the waste heat from biogas plants with an internal system, such as slurry effluent unit, the combined heat and power unit, the sanitation unit, and the internal recycle unit, are important for improving the AD efficiency of biogas production. For example, the recovery and recycling of waste heat from the effluent can result in a 2-3 °C temperature increase for the inlet manure slurry. For thermophilic AD, the heat recovery from effluent can save about 50% of the total heat requirement. The external heating process is more suitable for large- and medium-scale biogas plants, and the heat transfer coefficient of external heating (850-1000 W/m2 K-1) is almost two-times higher than that of the internal heating (300-400 W/m2 K-1). To utilize the waste heat in biogas plants, heat exchangers have been designed for biogas slurry. However, further improvement on the heat exchangers with anti-blockage, anti-fouling, high efficiency, and low investment is still needed. Moreover, the heat exchanger suitable for a low-temperature-difference system is specially needed in China, but the development is still in its infancy. Therefore, to tailor to the Chinese national conditions, special external heating processes should be designed and reoriented to the diversity of biomass, the climatic environmental conditions, and the renewable Chinese policies

  • 18.
    He, Hanbing
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Boström, Dan
    Umeå universitet, Energy Technology and Thermal Process Chemistry, Umeå University, Umeå university.
    Backman, Rainer
    Umeå university, Åbo Akademi, Energy Technology and Thermal Process Chemistry, Umeå University.
    Öhman, Marcus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Mechanism of Quartz Bed Particle Layer Formation in Fluidized Bed Combustion of Wood-Derived Fuels2016In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 30, no 3, p. 2227-2232Article in journal (Refereed)
    Abstract [en]

    Agglomeration is among one of the major problems in the operation of fluidized bed boilers. The formation of bed particle layers is thought to play an important role on the occurrence of agglomeration in wood-fired fluidized (quartz) beds. In spite of frequent experimental reports on the quartz bed particle layer characteristics, the underlying bed layer formation process has not yet been presented. By combining our previously experimental results on layer characteristics for samples with durations from 4 h to 23 days, with phase diagrams, thermochemical equilibrium calculations, and a diffusion model, a mechanism of quartz bed particle layer formation was proposed. For younger bed particles (

  • 19.
    He, Ming
    et al.
    Nanjing University of Technology.
    Feng, Xin
    Nanjing University of Technology.
    Lu, Xiaohua
    Nanjing University of Technology.
    Ji, Xiaoyan
    Liu, Chang
    Nanjing University of Technology.
    Bao, Ningzhong
    Nanjing University of Technology.
    Xie, Jingwei
    Nanjing University of Technology.
    A controllable approach for the synthesis of titanate derivatives of potassium tetratitanate fiber2004In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 39, p. 3745-3750Article in journal (Refereed)
    Abstract [en]

    Three types titanate derivatives, K2Ti6O13 fiber, K2Ti8O17 fiber and anatase TiO2 fiber, were synthesized by ion-exchange reaction from potassium tetratitanate fiber (K2Ti4O9) based on the hydrate conditions predicted by a thermodynamic model. These products were formed by a heat treatment of the corresponding hydrate intermediates K1.33H0.67Ti4O9·H2O, KHTi4O9·0.5H2O and H2Ti4O9·1.2H2O which were quantitatively obtained by controlling the pH value and the equilibrium concentration of potassium ion. The mole ratio of Ti/K in solid phase (R) of the target products was taken as the controlling aim in the hydrate process. The temperature for heat treatment of hydrate intermediates was determined by thermogravimetry (TG) and differential scanning calorimetry (DSC). All products retained fibrous morphology similar to that of K2Ti4O9 used as the starting material.

  • 20.
    Huangfu, Changan
    et al.
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Dong, Yihui
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wu, Na
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Mechanistic Study of Protein Adsorption on Mesoporous TiOin Aqueous Buffer Solutions2019In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 35, no 34, p. 11037-11047Article in journal (Refereed)
    Abstract [en]

    Protein adsorption is of fundamental importance for bioseparation engineering applications. In this work, a series of mesoporous TiO2 with various geometric structures and different aqueous buffer solutions were prepared as platforms to investigate the effects of the surface geometry and ionic strength on the protein adsorptive behavior. The surface geometry of the TiO2 was found to play a dominant role in the protein adsorption capacity when the ionic strength of buffer solutions is very low. With the increase in ionic strength, the effect of the geometric structure on the protein adsorption capacity reduced greatly. The change of ionic strength has the highest significant effect on the mesoporous TiO2 with large pore size compared with that with small pore size. The interaction between the protein and TiO2 measured with atomic force microscopy further demonstrated that the adhesion force induced by the surface geometry reduced with the increase in the ionic strength. These findings were used to guide the detection of the retention behavior of protein by high-performance liquid chromatography, providing a step forward toward understanding the protein adsorption for predicting and controlling the chromatographic separation of proteins.

  • 21. Ji, Xiaoyan
    et al.
    Adidharma, Hertanto
    University of Wyoming.
    Ion-based SAFT2 to represent aqueous multiple-salt solutions at ambient and elevated temperatures and pressures2008In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 63, no 1, p. 131-140Article in journal (Refereed)
    Abstract [en]

    Ion-based SAFT2 is extended to the properties of aqueous multiple-salt solutions at ambient and elevated temperatures and pressures. The short-range interactions between two different cations are allowed to obtain better representations of the solution properties. The adjustable parameter used in the mixing rule for the segment energy is fitted to the experimental osmotic coefficients of two-salt solutions containing one common anion at various temperatures and low pressures. The predictions of the osmotic coefficients, densities, and activity coefficients of multiple-salt solutions including brine/seawater are found to agree with experimental data.

  • 22. Ji, Xiaoyan
    et al.
    Adidharma, Hertanto
    University of Wyoming.
    Ion-based SAFT2 to represent aqueous single- and multiple-salt solutions at 298.15 K2006In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 45, p. 7719-7728Article in journal (Refereed)
    Abstract [en]

    SAFT2 with individual-ion parameters, referred to as ion-based SAFT2, is used to represent the properties of aqueous electrolyte solutions. A new set of parameters for 5 cations (Li+, Na+, K+, Ca2+, and Mg2+) and 6 anions (Cl-, Br-, I-, NO3-, SO42-,and HCO3-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 24 aqueous single-salt solutions at 298.15 K. The ion parameters are universal and transferable to different salts containing the same ion. Because of the peculiar segment energy of K+, a mixing rule with a binary interaction parameter for the segment energy describing the shortrange interactions between K+ and other cations is needed. The binary interaction parameter is derived from the osmotic coefficients of chloride solutions. The predictions of the osmotic coefficients, vapor pressures, and liquid densities of single- and multiple-salt solutions including seawater (brine) are found to agree with experimental data.

  • 23. Ji, Xiaoyan
    et al.
    Adidharma, Hertanto
    University of Wyoming.
    Ion-based statistical associating fluid theory (SAFT2) to represent aqueous single-salt solutions at temperatures and pressures up to 473.15 K and 1000 bar2007In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 46, no 13, p. 4667-4677Article in journal (Refereed)
    Abstract [en]

    Ion-based SAFT2 is used to represent the properties of aqueous single-salt solutions in the temperature, pressure, and concentration ranges of 298.15-473.15 K, 1.013-1000 bar, and 0-6 mol/kgH2O in ionic strength, respectively. The short-range interaction between cation and anion is needed to capture the effect of pressure on the properties of electrolyte solutions. A new set of parameters at 298.15 K for five cations (Li+, Na+, K+, Ca2+, Mg2+) and seven anions (Cl-, Br-, I-, NO3-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 26 aqueous single-salt solutions. An additional set of ion-specific coefficients used in the temperature-dependent parameter expressions for five cations (Li+, Na+, K+, Ca2+, Mg2+) and five anions (Cl-, Br-, HCO3-, SO42-, CO32-) is obtained from the fitting of the experimental mean ionic activity coefficients and liquid densities of 15 aqueous single-salt solutions at low pressures and temperatures up to 473.15 K. The activity coefficients, osmotic coefficients, water activities, densities, and vapor pressures of single-salt solutions at elevated temperatures and pressures are predicted without any adjustment.

  • 24.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Adidharma, Hertanto
    Soft Materials Laboratory, Department of Chemical and Petroleum Engineering, University of Wyoming.
    Prediction of molar volume and partial molar volume for CO2/ionic liquid systems with heterosegmented statistical associating fluid theory2012In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 315, p. 53-63Article in journal (Refereed)
    Abstract [en]

    To design ionic liquids (ILs) as effective liquid absorbents for CO2 separation from flue or synthesis gases, it is necessary to know the properties and phase equilibria of the CO2-IL systems. The molar volumes of CO2/IL mixtures are predicted with the heterosegmented statistical associating fluid theory equation of state. The comparison with the available experimental data shows that the model can be used to predict reliably the molar volumes of CO2/IL mixtures from 293 to 413 K and pressures up to 160 bar. In addition, the partial molar volume of CO2 in CO2/IL mixtures and the partial molar volume of CO2 at infinite dilution in an IL are also predicted.

  • 25.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Adidharma, Hertanto
    Soft Materials Laboratory, Department of Chemical and Petroleum Engineering, University of Wyoming.
    Thermodynamic modeling of CO2 solubility in ionic liquid with heterosegmented statistical associating fluid theory2010In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 293, no 2, p. 141-150Article in journal (Refereed)
    Abstract [en]

    Heterosegmented statistical associating fluid theory is used to represent the CO2 solubility in ionic liquids. As in our previous work, ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modeled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modeled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate. Carbon dioxide is modeled as a molecule with three association sites, two sites of type O and one site of type C, where sites of the same type do not associate with each other. The parameters of CO2 are obtained from the fitting of the density and the saturation vapor pressure of CO2. For the CO2-ionic liquid systems, cross association between site of type C in CO2 and another association site in anion is allowed to occur to account for the Lewis acid-base interaction. The parameters for cross association interactions and the binary interaction parameters used to adjust the dispersive interactions between unlike segments are obtained from the fitting of the available CO2 solubility in ionic liquids. The model is found to well represent the CO2 solubility in the imidazolium ionic liquids from 283 to 415 K and up to 200 bar.

  • 26.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Adidharma, Hertanto
    University of Wyoming.
    Thermodynamic modeling of ionic liquid density with heterosegmented statistical associating fluid theory2009In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 64, no 9, p. 1985-1992Article in journal (Refereed)
    Abstract [en]

    Heterosegmented statistical associating fluid theory is used to represent the density of ionic liquid. Ionic liquid molecule is divided into several groups representing the alkyls, cation head, and anion. The cation of ionic liquid is modelled as a chain molecule that consists of one spherical segment representing the cation head and groups of segments of different types representing different substituents (alkyls). The anion of ionic liquid is modelled as a spherical segment of different type. To account for the electrostatic/polar interaction between the cation and anion, the spherical segments representing cation head and anion each have one association site, which can only cross associate to each other. The parameters for alkyls are obtained from those of the corresponding n-alkanes and the parameters of groups representing cation head and anion, including the two association parameters, are fitted to a group of experimental ionic liquid data. The performance of the model is examined by describing the densities of three important series of imidazolium-based ionic liquids, i.e., [Cnmim][Tf2N], [Cnmim][BF4], and [Cnmim][PF6]. The model is found to well represent the densities of these ionic liquids from 293.15 to 415 K and up to 650 bar, and well capture the effects of temperature, pressure, and alkyl types on density.

  • 27. Ji, Xiaoyan
    et al.
    Chen, Dongliang
    Nanjing University of Chemical Technology.
    Wei, Tao
    Nanjing University of Chemical Technology.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Determination of dissolution kinetics of K2SO4 crystal with ion selective electrode2001In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 56, p. 7017-7024Article in journal (Refereed)
    Abstract [en]

    The dissolution kinetics of potassium sulfate crystals was studied and the effects of hydrodynamic situation and temperature on the dissolution were investigated. The dissolution was determined by measuring the change of electromotive force (E) with the potassium ion selective electrode. From the values of E, the concentration of K+ was calculated combined with an activity coefficient model. The results are accurate and rapid, the maximum deviation is less than 2%. Theory, developed for constant bulk concentration in a rotating disk system, was modified in order to analyze the general grain dissolution process. Normal distribution was introduced in calculating the area of crystals in order to obtain reliable dissolution rate. Using the modified theory diffusion rate constant, equilibrium exchange rate constant and thickness of diffusion layer were obtained. It is found that the diffusion rate constants increase while the thickness of diffusion layer decreases with the increase of temperature and stirring speed; the equilibrium exchange rate is dependent on bulk concentration.

  • 28.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Feng, Xin
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Lu, Xiaohua
    State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing University of Technology.
    Thermodynamic analysis on theoretical approach of energy consumption for2009Conference paper (Other academic)
  • 29. Ji, Xiaoyan
    et al.
    Feng, Xin
    Nanjing University of Chemical Technology.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    A generalized method for the solid-liquid equilibrium stage and its application in process simulation2002In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 41, p. 2040-2046Article in journal (Refereed)
    Abstract [en]

    For the important need of simulations of the crystallization process in aqueous electrolyte solutions, a generalized method is proposed in this paper for predicting the solid-liquid equilibrium stage by identifying the number of phases and their identities automatically. The proposed method is also used to generate phase diagrams and crystallization paths and to provide an example of the software that can be used to design, simulate, and optimize the related process. Several cases are studied to demonstrate the capability of the proposed method for systems with hydrate, multi-ion, and complex salts.

  • 30.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling the density of ionic liquids with ePC-SAFT2016In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 410, p. 9-22Article in journal (Refereed)
    Abstract [en]

    ePC-SAFT was used to model the densities of ionic liquids (ILs) up to high pressures and temperatures. The ILs under consideration contained one of the IL-cations [Cnmim]+, [Cnpy]+, [Cnmpy]+, [Cnmpyr]+ or [THTDP]+, and one of the IL-anions [Tf2N]−, [PF6]−, [BF4]−, [tfo]−, [DCA]−, [SCN]−, [C1SO4]−, [C2SO4]−, [eFAP]−, Cl−, [Ac]− or Br−, respectively. Within the ePC-SAFT framework, IL-ion specific parameters were applied that are valid independent of the IL they are part of. Each IL-ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. The ePC-SAFT parameters for [Cnmim]+ (n = 2, 4, 6 and 8), [Tf2N]−, [PF6]−, and [BF4]- were taken from our previous work (Fluid Phase Equilibria 2012 (335) 64–73). Based on these parameters, all parameters of the other IL-ions were fitted to experimental density of pure ILs up to high pressures in a broad temperature range. Being provided with ion-specific and linearly molecular-weight-dependent parameters, ePC-SAFT allows reliably representing/predicting pure-IL and mixed-IL density up to high pressures

  • 31.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Sadowski, Gabriele
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling imidazolium-based ionic liquids with ePC-SAFT: Part II. Application to H2S and synthesis-gas components2014In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 363, p. 59-65Article in journal (Refereed)
    Abstract [en]

    ePC-SAFT was used to model the gas solubility in ionic liquids (ILs). The gases under consideration were CO, H2, H2S and O2, and the imidazolium-based ILs studied were [Cnmim][Tf2N], [Cnmim][PF6] and [Cnmim][BF4] (n = 2, 4, 6 and 8). For the ePC-SAFT modeling, each IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as a non-spherical species exerting repulsive, dispersive and Coulomb forces. CO, H2 and O2 were modeled as non-spherical molecules exerting repulsive and dispersive forces, and H2S was modeled as a non-spherical, associating molecule. ePC-SAFT reasonably predicts the gas solubility in the considered gas/IL mixtures. In order to describe the experimental gas solubilities quantitatively in a broad temperature and pressure range, one ion-specific binary interaction parameter between the IL-anion and the gas was applied, which was allowed to depend linearly on temperature.

  • 32.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Held, Christoph
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Sadowski, Gabriele
    Department for Biochemical and Chemical Engineering, TU Dortmund.
    Modeling imidazolium-based ionic liquids with ePC-SAFT2012In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 335, p. 64-73Article in journal (Refereed)
    Abstract [en]

    ePC-SAFT was used to investigate the density of and gas solubilities in imidazolium-based ionic liquids (ILs) applying different modeling strategies. The ion-based strategy including a Debye-Hückel Helmholtz-energy term to represent the ionic interactions describes the experimental data best. For this strategy, the IL was considered to be completely dissociated into a cation and an anion. Each ion was modeled as non-spherical species exerting repulsive, dispersive, and Coulomb forces. A set of ePC-SAFT parameters for seven ions was obtained by fitting to reliable density data of pure ILs up to 1000 bar with a fitting error of 0.14% on average. The model can be used to quantitatively extrapolate the density of pure ILs at temperatures from 283 to 473 K and pressures up to 3000 bar. Moreover, this strategy allows predicting CO2 solubilities in ILs between 293 and 450 K and up to 950 bar. Applying the same set of IL parameters, the much lower solubility of CH4 compared to CO2 can also be predicted with ePC-SAFT.

  • 33.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Ji, Yuanhui
    Chongwei, Xiao
    Thermodynamic and dynamic investigation for CO2 storage in deep saline aquifers2011In: Proceedings of the World Renewable Energy Congress 2011 (WREC 2011): 9-13 May, Linköping, Linköping: Linköping University Electronic Press, 2011Conference paper (Refereed)
    Abstract [en]

    Thermodynamic and dynamic investigations are needed to study the sequestration capacity, CO2 leakage, and environmental impacts. The results of the phase equilibrium and densities for CO2-sequestration related subsystems obtained from the proposed thermodynamic model on the basis of statistical associating fluid theory equation of state were summarized. Based on the equilibrium thermodynamics, preliminary kinetics results were also illustrated with chemical potential gradient as the driving force. The proposed thermodynamic model is promising to represent phase equilibrium and thermodynamic properties for CO2-sequestration related systems, i.e. CO2-(H2S)-H2O-ions (such as Na+, K+, Ca2+, Mg2+, Cl-, CO32-), and the implementation of thermodynamic model into kinetics model to adjust the non-ideality of species is vital because of the high pressure for the investigation of the sequestration process.

  • 34.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Jonsson, Maria
    Kungliga tekniska högskolan, KTH.
    Yan, Jinyue
    Implementation of a real thermodynamic property model in IPSE pro2004Conference paper (Other academic)
  • 35. Ji, Xiaoyan
    et al.
    Lu, X.
    Nanjing University of Chemical Technology.
    Yan, Jinyue
    Kungliga tekniska högskolan, KTH.
    Saturated humidity, entropy, and enthalpy for the nitrogen-water system at elevated temperatures and pressures2003In: International journal of thermophysics, ISSN 0195-928X, E-ISSN 1572-9567, Vol. 24, p. 1681-1696Article in journal (Refereed)
    Abstract [en]

    A model is used to calculate saturated thermophysical properties (humidity, entropy, and enthalpy) of a nitrogen-water mixture at elevated temperatures and pressures. In the model, a modified Redlich-Kwong equation of state is used to calculate fugacity coefficients for the vapor phase, and the liquid phase follows Henry's law. The model has been investigated by comparing the calculated results with the available experimental data. The comparison shows that the model can be used to calculate saturated thermodynamic properties for the nitrogen-water mixture reliably up to 523.15 K and 300 bar.

  • 36. Ji, Xiaoyan
    et al.
    Lu, X.
    Nanjing University of Chemical Technology.
    Yan, Jinyue
    Kungliga tekniska högskolan, KTH.
    Survey of experimental data and assessment of calculation methods of properties for the air-water mixture2003In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 23, p. 2213-2228Article in journal (Refereed)
    Abstract [en]

    Thermodynamic properties of the air-water mixture at elevated temperatures and pressures are of importance in the design and simulation of the advanced gas turbine systems with water addition. In this paper, comprehensive available experimental data and calculation methods for the air-water mixture were reviewed. It is found that the available experimental data are limited, and the determined temperature is within 75 °C. New experimental data are needed to supply in order to verify the model further. Three kinds of models (ideal model, ideal mixing model and real model) were used to calculate saturated vapor composition and enthalpy for the air-water mixture, and the calculated results of these models were compared with experimental data and each other. The comparison shows that for the calculation of saturated vapor composition, the reliable range of the ideal model and ideal mixing model is up to 10 bar. The real model is reliable over a wide temperature and pressure range, and the model proposed by Hyland and Wexler is the best one of today. However, the reliability of the Hyland and Wexler model approved by experimental data is only up to 75 °C and 50 bar, and it is necessary to propose a new predictive model based on the available experimental data to be used up to elevated temperatures and pressures. In the calculation of enthalpy, compared to the ideal model, the calculated results of the ideal mixing model are closer to those of real model.

  • 37.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    Nanjing University of Technology.
    Modeling mass transfer of CO2 in brine at high pressures by chemical potential gradient2010Conference paper (Other academic)
    Abstract [en]

    To investigate the long-term CO2 behaviors in geological formations and quantification of possible CO2 leaks needs to focus on the potential mobility of CO2 dissolved in formation brines over a wide range of spatial and temporal scales and requires information of the CO2 concentration and density distribution in the geological media. In this paper, the mass transfer of CO2 in reservoir brines at high pressures is investigated by chemical potential gradient modeling based on nonequilibrium thermodynamics instead of concentration gradient modeling and the experimental kinetics data reported by Yang and Gu. In this model, the Statistical Associating Fluid Theory equation of state (SAFT1-RPM) is used to calculate the fugacity and densities of the aqueous CO2 in the investigated systems and the effects of temperature, initial CO2 pressure and volume on the boundary conditions are considered. The calculation results with this model and modified Fick’s second law are compared, the effects of temperature, pressure, the initial CO2 pressure and initial CO2 volume are analyzed and the density distribution of the CO2-dissolved brines are predicted. This study shows considerable differences between the results by the chemical potential gradient modeling and that by the concentration gradient modeling, which shows the importance of considering the non-ideality correction. The results also show the temperature and initial CO2 pressure and initial CO2 volume have great effects on the concentration distribution with distance and greater effects of temperature on the densities of the CO2-dissolved brine than that of initial CO2 pressure and initial CO2 volume.

  • 38. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Li, Shaowu
    Nanjing University of Chemical Technology.
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Determination of the activity coefficients of NaCl in the system NaCl-NH4Cl-H2O2001In: Journal of Solution Chemistry, ISSN 0095-9782, E-ISSN 1572-8927, Vol. 30, p. 463-473Article in journal (Refereed)
    Abstract [en]

    Using ion-selective electrode(s) (ISE) the activity coefficients of NaCl in the system NaCl-NH4Cl-H2O at 10, 25, and 40°C were measured by a computer-controlled automatic titration system. The ionic strength fractions of NH4Cl were 0.2, 0.4, 0.6, and 0.8, respectively. It was found that the influence of the NH4+ cation on the Na glass ISE was small enough to be neglected up to 3.0 mol-kg-1. The Pitzer equation was adopted to calculate the activity coefficients of NaCl in this system and compared with the experimental data. Comparison of results indicates that the Pitzer parameters correlated from solubility data are suitable for calculating the activity coefficients for this system within the saturated solutions.

  • 39. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Li, Shaowu
    Nanjing University of Chemical Technology.
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Lu, Benjamin C.-Y.
    University of Ottawa.
    Activity coefficients of HCl in the HCl + NH4Cl + H2O systems at 298.15 and 313.15 K2000In: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 45, no 1, p. 29-33Article in journal (Refereed)
    Abstract [en]

    Using the ion-selective electrode method with a concentrated electrolyte solution added continuously, the mean activity coefficients of HCl in the HCl + NH4Cl + H2O system were experimentally measured at 298.15 and 313.15 K and at five molality fractions of NH4Cl (y2 = mNH4Cl/(mHCl + mNH4Cl) from 0.1 to 0.9. The measurements were made by an electrochemical cell using a H glass ion-selective electrode and a chloride solid-state ion-selective electrode. It was found that the influence of NH4+ on the H glass ion-selective electrode could be neglected up to 1.3 molkg-1, and this pair of ion-selective electrodes was suitable for determining the activity coefficients of HCl in the system. A new set of Pitzer mixing parameters, correlated from the experimental results, was used to calculate the activity coefficients for HCl in the system from 293.15 to 313.15 K up to 3.0 molkg-1.

  • 40. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Lin, Weilu
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Lu, Benjamin C. -Y.
    University of Ottawa.
    Mean activity coefficients in the NaCl-NH4HCO3-H2O system at 293.15-308.15 K2001In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 178, p. 259-270Article in journal (Refereed)
  • 41. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Lin, Weilu
    Nanjing University of Chemical Technology.
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Lu, Benjamin C. -Y.
    University of Ottawa.
    Mean activity coefficients of NaCl in (sodium chloride + sodium bicarbonate + water) fromT = (293.15 to 308.15) K2001In: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 33, p. 1107-1119Article in journal (Refereed)
    Abstract [en]

    The mean activity coefficients of NaCl in (sodium chloride + sodium bicarbonate + water) were determined experimentally in the temperature range 293.15 K to 308.15 K at four NaHCO3 molality fractions (0.1, 0.3, 0.5, and 0.7). The measurements were made with an electrochemical cell, using a Na+ glass ion-selective electrode and a Cl- solid-state ion-selective electrode. The experimental values reported by Butler and Huston are found to be higher than those calculated from the Pitzer equation using the existing parameters while the experimental results of this work are close to the calculated values, up to an NaHCO3 molality fraction of 0.5. At the NaHCO3 molality fraction of 0.7, the experimental data are much lower than the calculated values, implying that the interference of HCO3- on the Na+ glass ion-selective electrode can only be neglected up to a molality fraction of NaHCO3 of 0.5, an observation which is consistent with that of Butler and Huston.

  • 42.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Yan, Jinyue
    Phase equilibria for the oxygen-water system up to elevated temperatures and pressures2004In: Fluid Phase Equilibria, ISSN 0378-3812, E-ISSN 1879-0224, Vol. 222-223, p. 39-47Article in journal (Refereed)
    Abstract [en]

    A new thermodynamic model was presented to calculate the phase equilibria for the oxygen-water system. The modified Redlich-Kwong equation of state with a new correlated cross-interaction parameter was used to calculate fugacity coefficients for the vapor phase. The dissolved oxygen followed Henry's law. A new expression was correlated from the experimental data to calculate Henry's constant of oxygen. The calculated results of equilibrium composition were compared with the available experimental data and those calculated by other models with different parameters. The comparison revealed that the new model is suitable for calculating both liquid and vapor compositions while the empirical method is only suitable for estimating the liquid composition. Furthermore, compared to the model proposed by Rebenovich and Beketov, the calculated results of the vapor composition with the new model are better.

  • 43. Ji, Xiaoyan
    et al.
    Lu, Xiaohua
    Nanjing University of Chemical Technology.
    Zhang, Luzheng
    Nanjing University of Chemical Technology.
    Bao, Ningzhong
    Nanjing University of Chemical Technology.
    Wang, Yanru
    Nanjing University of Chemical Technology.
    Shi, Jun
    Nanjing University of Chemical Technology.
    Lu, Benjamin C. -Y.
    University of Ottawa.
    A further study of solid-liquid equilibrium for the NaCl-NH4Cl-H2O system2000In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 55, p. 4993-5001Article in journal (Refereed)
  • 44.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Wang, Chuan
    Center for Process Integration in Steelmaking, Swerea MEFOS, Luleå.
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Process simulation and energy optimization for the pulp and paper mill2010In: PRES 2010: 13th Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction, 28 August - 1 September 2010, Prague, Czech Republic / [ed] J.J. Klemeš; H.L. Lam; P.S. Varbanov, 2010, p. 283-288Conference paper (Refereed)
  • 45.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wang, Chuan
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation and energy optimization in a pulp and paper mill: Evaporation plant and digester2011In: Third International Conference on Applied Energy: 16-18 May 2011 - Perugia, Italy, 2011, p. 109-122Conference paper (Refereed)
    Abstract [en]

    A mathematical process integration model of a pulp and paper mill in the Northern Sweden has been developed. The main modelling focus has been put on the two main steam consumers (the evaporation plant and the digester), for which detailed material and energy balances have been established. Operational data have been used to validate the simulation results. By implementing these submodels into the complete plant model, the influence of different operation parameters on the overall plant performance has been investigated. Furthermore, introductory studies with the main objective to minimize the plant energy cost have been carried out. The correlation and differences between economic and energy have been discussed

  • 46.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wang, Chuan
    Dahl, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation and energy optimization of a pulp and paper mill: evaporation plant and digester2012In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 97, no Spec. Issue, p. 30-37Article in journal (Refereed)
    Abstract [en]

    A detailed mathematical process integration model of a pulp and paper mill in the Northern Sweden has been developed. The main objective of this work has been set to describe the practical development of the model with particular emphasis on the development of the digester and evaporation plant sub-models. Actual plant measurements have been used to validate the model. By implementing the sub-models into the complete plant model, the influence of different operation parameters on the overall plant performance has been investigated. Furthermore, introductory studies with the main objective to minimize the plant energy cost have been carried out.

  • 47.
    Ji, Xiaoyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Lundgren, Joakim
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Wang, Chuan
    Grip, Carl-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Simulation and optimization of steam generation in a pulp and paper mill2011In: Proceedings of the World Renewable Energy Congress 2011 (WREC 2011): 9-13 May, Linköping, Linköping University Electronic Press, 2011Conference paper (Refereed)
    Abstract [en]

    A mathematical process integration model for the steam generation part (recovery boiler, bark boiler, and turbine) was developed based on a pulp and paper mill in the Northern Sweden. The material and energy balances were calculated theoretically and then the operation data from a pulp and paper mill in the Northern Sweden were used to validate the simulation results. By implementing it into the whole plant, the effect of the operation conditions on the whole plant performance were investigated. The introductory studies were carried out with an objective function to minimize the energy cost. The influence of different parameters was rigorously studied. The correlation between economic and energy optima was discussed.

  • 48. Ji, Xiaoyan
    et al.
    Tan, Sugata P.
    University of Wyoming.
    Adidharma, Hertanto
    University of Wyoming.
    Radosz, Maciej
    University of Wyoming.
    SAFT1-RPM approximation extended to phase equilibria and densities of CO2-H2O and CO2-H2O-NaCl systems2005In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 44, p. 8419-8427Article in journal (Refereed)
    Abstract [en]

    In SAFT1-RPM approximations of CO2-H2O and CO2-H2O-NaCl systems, relevant to oil recovery and CO2 sequestration, CO2 is modeled as a molecule with three association sites, two sites of type O and one site of type C. H2O is modeled as a molecule with four association sites, two sites of type O and two sites of type H. The salt is modeled as a molecule composed of two charged, but nonassociating, spherical segments, of which one represents the cation and one represents the anion. For the CO2-H2O system, only one type of cross-association is assigned, i.e., between the site of type O in CO2 and the site of type H in H2O. Using temperature-dependent parameters, SAFT1-RPM is found to represent the density and equilibrium data for the CO2-H2O system, including the minimum H2O concentration in the CO2-rich phase in the y-P diagram. For the CO2-H2O-NaCl system, an additional binary interaction constant is used, the same for both CO2-Na+ and CO2-Cl- pairs, which is needed to correct the short-range interactions. SAFT1-RPM is also found to represent the equilibrium and density data for the CO2-H2O-NaCl system.

  • 49. Ji, Xiaoyan
    et al.
    Tan, Sugata P.
    University of Wyoming.
    Adidharma, Hertanto
    University of Wyoming.
    Radosz, Maciej
    University of Wyoming.
    Statistical associating fluid theory coupled with restricted primitive model to represent aqueous strong electrolytes: multiple-salt solutions2005In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 44, p. 7584-7590Article in journal (Refereed)
    Abstract [en]

    Statistical associating fluid theory coupled with the restricted primitive model (SAFT1-RPM), previously proposed for representing single-salt solutions in water, is extended to multiple-salt solutions using a mixing rule for the hydrated diameter. A binary adjustable parameter in this mixing rule, for a pair of salts, is obtained from experimental osmotic coefficients of the corresponding ternary system. The ternary systems considered contain water and all pairs of NaCl, KCl, NaBr, and KBr. LiCl + NaCl and LiCl + KCl pairs are also correlated. The adjustable parameters are used to predict the density of the ternary systems with or without common ions, the solubility of two ternary systems, and the osmotic coefficient of a quaternary NaCl-KCl-LiCl-H2O solution.

  • 50. Ji, Xiaoyan
    et al.
    Tan, Sugata P.
    University of Wyoming.
    Adidharma, Hertanto
    University of Wyoming.
    Radosz, Maciej
    University of Wyoming.
    Statistical associating fluid theory coupled with restrictive primitive model extended to bivalent ions: SAFT2: 2. Brine/seawater properties predicted2006In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 110, p. 16700-16706Article in journal (Refereed)
    Abstract [en]

    Statistical associating fluid theory coupled with restricted primitive model (SAFT2) represents the properties of aqueous multiple-salt solutions, such as brine/seawater. The osmotic coefficients, densities, and vapor pressures are predicted without any additional parameters using the salt hydrated diameters obtained for single-salt solutions. For a given ion composition of brine, the predicted vapor pressure, osmotic coefficient, activity of water, and density are found to agree with the experimental data.

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