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  • 1.
    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.

  • 2.
    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.

  • 3.
    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.

  • 4.
    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.

  • 5.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Development of low-cost ionic liquids based technology for CO2 separation2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    CO2 separation plays an important role to mitigate the CO2 emissions due to burning of fossil fuels, and it is also of importance in biofuel production (e.g. biogas upgrading and bio-syngas purification and conditioning). The solvent-based absorption is the state-of-art technology for CO2 separation, where various solvents, e.g. amine solutions, Selexol (i.e. dimethyl ethers of polyethylene glycol), and propylene carbonate, have been introduced. However, these solvent-based technologies meet challenges such as high solvent degradation, high corrosion rate to equipment, high construction cost, high energy demand for solvent regeneration and high solvent make-up rate. Therefore, the development of novel solvents to overcome the challenges of the currently available solvents is essential.

    Recently, ionic liquids (ILs) have gained great interest as new potential solvents for CO2 separation, mainly due to their very low vapor pressure and relatively high CO2 solubility. In addition, ILs have lower corrosive characteristic, lower degradation rate and lower energy requirement for solvent regeneration compared with the conventional organic solvents. However, the main challenge of the application of ILs is their higher viscosity than the conventional solvents, which can be solved by adding co-solvents such as water.

    The overall objective of this thesis work was to develop low-cost IL based technologies for CO2 separation. To achieve this objective, the deep eutectic solvent (DES) of choline chloride (ChCl)/Urea with molar ratio 1:2 as a new type of IL was selected as an absorbent and H2O was used as co-solvent for CO2 separation from biogas. The conceptual process was developed and simulated based on Aspen Plus, and the effect of water content on the performance of ChCl/Urea for CO2 separation was evaluated. It was found that the optimal proportion of aqueous ChCl/Urea was around 50 wt% (percentage by weight) of water with the lowest energy usage and environmental effect.

    The performance of aqueous ChCl/Urea was further compared with the commercial organic solvents in this thesis work. The rate-based process simulation was carried out to compare the energy usage and the cost for CO2 separation from biogas. It was found that aqueous ChCl/Urea achieved the lowest cost and energy usage compared with other commercial solvents except propylene carbonate. The performance comparison proved that CO2 solubility, selectivity and viscosity were three important parameters which can be used as criteria in the development of novel physical solvents for CO2 separation.

    ILs with acetate anions normally show high CO2 solubility and selectivity, and the ILs with alkylmorpholinium as cations have low toxicity leading to lower environmental effect. Therefore, in this thesis work, a series of N-alkyl-N-methylmorpholinium-based ILs with acetate as counterpart anion were investigated, and water was added as co-solvent to adjust the viscosity. The CO2 solubility in these aqueous ILs was measured at different temperatures and pressures. It was found that the increase of alkyl chain length in the cation led to an increase of CO2 solubility of the ILs with the same anion. Aqueous N-butyl-N-methylmorpholinium acetate ([Bmmorp][OAc]) had the highest CO2 solubility, and it was selected to further carry out thermodynamic modeling and process simulation. The energy usage and the size of equipment of using aqueous [Bmmorp][OAc], aqueous ChCl/Urea, water, Selexol, and propylene carbonate for CO2 separation from biogas were compared. It was found that this novel IL mixing with water had better performance, that is, with lower energy usage and smaller size of equipment than the other solvents. This result suggests that using this aqueous [Bmmorp][OAc] has the potential to decrease the cost of CO2 separation.

  • 6.
    Ma, Chunyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. College of Chemical Engineering, Nanjing Tech University.
    Guo, Yanhua
    College of Chemical Engineering, Nanjing Tech University.
    Li, Dongxue
    College of Chemical Engineering, Nanjing Tech University.
    Zong, Jianpeng
    College of Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Liu, Chang
    College of Chemical Engineering, Nanjing Tech University.
    Molar enthalpy of mixing and refractive indices of choline chloride-based deep eutectic solvents with water2017In: Journal of Chemical Thermodynamics, ISSN 0021-9614, E-ISSN 1096-3626, Vol. 105, p. 30-36Article in journal (Refereed)
    Abstract [en]

    The molar enthalpies of mixing were measured for binary systems of choline chloride-based deep eutectic solvents (glycerol, ethylene glycol and malonic acid) with water at 298.15 K and 308.15 K, and atmospheric pressure with an isothermal calorimeter. Refractive indices were also measured at 303.15 K and atmospheric pressure. The binary mixtures of {chcl/glycerol (1:2) + water, chcl/ethylene glycol (1:2) + water} showed exothermic behaviour over the entire range of composition, while the binary mixture of {chcl/malonic acid (1:1) + water} showed endothermic behaviour at first and then changed to be exothermic with the increasing content of chcl/malonic acid (1:1). Experimental refractive indices were fitted with the Redlich–Kister equation, and experimental molar enthalpies of mixing were correlated with the Redlich–Kister equation and the non-random two-liquid (NRTL) model. The NRTL model with the fitted parameters was used to predict the vapour pressures of these three mixtures. For mixtures of {chcl/glycerol (1:2) + water} and {chcl/ethylene glycol (1:2) + water}, the predicted vapour pressures agreed well with the experimental reults from the literature. While for mixture of {chcl/malonic acid (1:1)+water}, the predicted vapour pressures showed deviation at the high concentration of chcl/malonic acid (1:1), and this was probably because of the complex molecular interaction between chcl/malonic acid (1:1) and water

  • 7.
    Ma, Chunyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Guo, Yanhua
    College of Chemical Engineering, Nanjing Tech University.
    Li, Dongxue
    College of Chemical Engineering, Nanjing Tech University.
    Zong, Jianpeng
    College of Chemical Engineering, Nanjing Tech University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Liu, Chang
    College of Chemical Engineering, Nanjing Tech University.
    Lu, Xiaohua
    College of Chemical Engineering, Nanjing Tech University.
    Molar Enthalpy of Mixing for Choline Chloride/Urea Deep EutecticSolvent + Water System2016In: Journal of Chemical and Engineering Data, ISSN 0021-9568, E-ISSN 1520-5134, Vol. 61, no 12, p. 4172-4177Article in journal (Refereed)
    Abstract [en]

    The molar enthalpies of mixing for binary systems of choline chloride (chcl)/urea deep eutectic solvents (mole ratios of 1:1.5, 1:2, and 1:2.5) with water were measured at 308.15 and 318.15 K under atmospheric pressure with an isothermal calorimeter. The binary mixture of (chcl/urea (1:2.5) + water) showed endothermic behavior over the entire range of compositions, while the binary mixtures of (chcl/urea (1:1.5) + water) and (chcl/urea (1:2) + water) showed endothermic behavior first and then was changed to be exothermic with increasing content of deep eutectic solvents. The Redlich–Kister (RK) equation and the nonrandom two-liquid (NRTL) model were used to fit experimental molar enthalpies of mixing. The NRTL model with the fitted parameters was further used to predict the vapor pressure for the three systems and was compared with the experimental data from literature. For the binary mixtures of (chcl/urea (1:2) + water), the predicted vapor pressure agreed well with the experimental data only when the temperature was lower than 333.15 K and the mole fraction of chcl/urea (1:2) was lower than 0.1. Otherwise, the deviation increased greatly with an increase of the amount of chcl/urea (1:2). 

  • 8.
    Ma, Chunyan
    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, Nanjing, 210009, China.
    Laaksonen, Aatto
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, 210009, 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.
    Liu, Chang
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China.
    Lu, Xiaohua
    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. State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China.
    The peculiar effect of water on ionic liquids and deep eutectic solvents.2018In: Chemical Society Reviews, ISSN 0306-0012, Vol. 47, no 23, p. 8685-8720Article, review/survey (Refereed)
    Abstract [en]

    Ionic liquids (ILs) and deep eutectic solvents (DESs) have been suggested as eco-friendly alternatives to organic solvents. A trace amount of water is often unavoidable as impurity, and water is also added on purpose to reduce their problematically high viscosity and lower their high price. Understanding the distinct effects of water on the properties of ILs/DESs is highly important. In this review, we collect published experimental and theoretical results for IL/DES-H2O systems at varied water concentrations and analyze them. Results from mechanistic studies, thermodynamic modelling and advanced experiments are collected and critically discussed. Six commonly studied IL/DES-H2O systems were selected to map experimental observations onto microscopic results obtained in mechanistic studies. A great variety of distinct contours of the excess properties can be observed over the entire compositional range, indicating that the properties of IL/DES-H2O systems are highly unpredictable. Mechanistic studies clearly demonstrate that the added H2O rapidly changes the heterogeneous 3D structures of pure ILs/DESs, leading to very different properties and behaviour. There are similarities between aqueous electrolytes and IL/DES solutions but the bulky and asymmetric organic cations in ILs/DESs do not conform to the standard salt dissolution and hydration concepts. Thermodynamic modelling previously assumes ILs/DESs to be either a neutral ion-pair or completely dissociated ions, neglecting specific ion hydration effects. A new conceptual framework is suggested for thermodynamic modelling of IL/DES-H2O binary systems to enable new technologies for their practical applications.

  • 9.
    Ma, Chunyan
    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, Nanjing.
    Liu, Chang
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing.
    Lu, Xiaohua
    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.
    Erratum: Techno-economic analysis and performance comparison of aqueous deep eutectic solvent and other physical absorbents for biogas upgrading2019In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 235, p. 1669-1670Article in journal (Refereed)
    Abstract [en]

    The authors regret to inform that there are errors in the vertical axis of Figs. 4 and 5 as well as corresponding text. The corrected versions are given below. (Figure presented.) Fig. 4b: the left y-axis should read “$·Nm-3 CH4” instead of “k$·Nm-3 CH4”; The corrected version of Fig. 5 is shown below. Abstract: The text at the end of Abstract: ‘For the case with …respectively’ should read: “…with AQ50wt.%DESand PC decrease by…” instead of “…with PC and AQ50wt.%DES decrease by…” Section 3.3.2: The text at the end of paragraph 5: ‘The results of specific TAC of using…than that using water, respectively. ’ should read: “…using AQ50wt.%DES and PC decrease by ….” instead of “…using PC and AQDES decrease by…” “…using AQ50wt.%DES and PC increase up to…” instead of “…using PC and AQ50wt.%DESincrease up to…” The text at the end of paragraph 6: ‘While, using…raw biogas capacity. ’ should read: “…and 25% than water…” instead of “…and 50% than water…” Conclusion: The text at the end of paragraph 2: ‘The results of specific TAC of using PC …than PC should be developed.’ should read: “…using AQ50wt.%DES and PC decrease by…” instead of “…using PC and AQ50wt.%DES decrease by…” “…using AQ50wt.%DES and PC treated with…” instead of “…using PC and AQ50wt.%DES treated with…” The above errors do not reflect any calculations errors and do not compromise the findings of the paper. The authors would like to apologize for any inconvenience caused. 

  • 10.
    Ma, Chunyan
    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.
    Liu, Chang
    College of Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    Key Laboratory of Material and Chemical Engineering, Nanjing Tech University, Nanjing .
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Evaluation and comparison of aqueous ChCl/Urea and other physical absorbents for biogas upgrading process2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 3631-3636Article in journal (Refereed)
    Abstract [en]

     Biogas has been considered as an alternative renewable energy, and CO2 removal from raw biogas (i.e. biogas upgrading) is needed for producing biomethane used as vehicle fuels or injected into the natural gas grid. Biogas upgrading using physical absorbents is a simple and efficient technology with low energy requirements for regeneration. In this work, the conceptual process for biogas upgrading using 4 kinds of physical solvents, i.e. water, dimethyl ether of polyethylene glycol (DEPG), propylene carbonate (PC) and aqueous choline chloride (ChCl) /urea (AQDES) was developed and simulated with Aspen Plus. The energy utilization, the amount of recirculated solvent and the diameters of absorber and desorber were analyzed based on equilibrium approach. After that, the rate-based simulation was established to evaluate the specific cost of the process using different solvents. Based on equilibrium approach the comparison between the solvents in respect to the energy utilization for biogas upgrading using different solvents shows the following order: DEPG > water > AQDES > PC, whereas the amount of recirculated solvent and the diameters of absorber and desorber follow another order: water > DEPG > AQDES > PC. The rate-based results show that the process using PC has the lowest total specific cost, followed by AQDES, water and DEPG.

  • 11.
    Ma, Chunyan
    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, Nanjing.
    Liu, Chang
    State Key Laboratory of Material-Oriented Chemical Engineering, Nanjing Tech University, Nanjing.
    Lu, Xiaohua
    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.
    Techno-economic analysis and performance comparison of aqueous deep eutectic solvent and other physical absorbents for biogas upgrading2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 225, p. 437-447Article in journal (Refereed)
    Abstract [en]

    Biogas has been considered as an alternative renewable energy, and CO2 removal from raw biogas (i.e. biogas upgrading) is needed for producing biomethane to be used as vehicle fuels or injected into the natural gas grid. Biogas upgrading with physical absorbents, such as water and other commercial organic solvents, is simple, efficient and with low energy requirements for regeneration. Recently, deep eutectic solvents (DESs) with nonvolatility, nonflammability and low price have been reported as promising alternatives to replace conventional physical absorbents in many research areas including biogas upgrading. However, the performances of these physical solvents including conventional physical absorbents and DES-based solvents have not been evaluated and compared with each other. In this work, the properties of 4 physical solvents (i.e. water, dimethyl ether of polyethylene glycol (DEPG), propylene carbonate (PC), and aqueous DES (AQDES)) were compared. Furthermore, a conceptual process was developed to upgrade biogas with these solvents and simulated based on Aspen Plus in order to conduct performance comparison. The simulation results of energy utilization, the amount of recirculated solvents and the diameters of absorber and desorber were analyzed and compared based on equilibrium and rate-based approaches, respectively. The simulation results based on the rate-based approach were further used to estimate the costs of biogas upgrading process with a same raw biogas capacity for comparison. Meanwhile, the specific cost of biogas upgrading process with a same size of equipment was also evaluated. The results show that the CO2 solubility, selectivity and viscosity are three more important properties, providing valuable information for developing novel physical solvents for CO2 separation. The simulation results show that the equilibrium and rate-based approaches result in different conclusions, especially when the solvent viscosity is relatively high, and the rate-based approach is preferable. Based on the simulation results from the rate-based approach, the performances of AQDES and PC are similar with a same amount of energy utilization, that is around 11% lower than water, and DEPG is inferior to water. For the case with the same gas capacity, the total annual costs of biogas upgrading process with these solvents show the following order: DEPG > AQ60wt.%DES > water > AQ50wt.%DES ≈ PC. For the case with the same size of equipment, compared to water, the total specific costs of biogas upgrading process with PC and AQ50wt.%DES decrease by about 30% and 45%, respectively, and the treated biogas capacities increase to 1.5 and 2 times, respectively. In general, both PC and AQ50wt.%DES show better performance than the other solvents. Considering that DES is an environmentally benign solvent, and the performance of DES can be greatly improved by further designing, it is more promising

  • 12.
    Ma, Chunyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Sarmad, Shokat
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mikkola, Jyri-Pekka
    Technical Chemistry, Department of Chemistry, Chemical-Biological Centre, Umeå University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Development of Low-Cost Deep Eutectic Solvents for CO2 Capture2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 142, p. 3320-3325Article in journal (Refereed)
    Abstract [en]

    CO2 capture plays an important role to mitigate CO2 emissions. Deep eutectic solvents (DESs) as promising absorbents for CO2 separation have raised lots of attention. As a new class of ionic liquids (ILs), DESs maintain most of the favorite properties of ILs but avoid their economic and environmental problems. However, the viscosity of the synthesized DESs is relatively high, resulting in slow mass transfer rate (or slow sorption kinetics) and then may lead to a large equipment-size. The CO2 solubility in the DESs still needs to be improved. In our work, 35 DESs were prepared and screened in terms of their CO2 solubility and viscosity. Among them, 15 DESs with high CO2 solubility and low viscosity compared to the conventional ILs were chosen as the promising candidates. In addition, the effect of water as a co-solvent for the glycerol-based DES with relatively high viscosity was investigated, and two other DESs that demonstrated relatively high sorption capacity and low viscosity were chosen for functionalization to further improve their CO2 sorption capacity. The results showed that the viscosity decreased drastically from 716 to 20 mPa·s, while the CO2 solubility increased from 0.26 to 0.33 mol/kg DES by the addition of a small amount of water into the glycerol-based DES (BTMA/GLY (1:2)). The further increase of the amount of H2O decreased the CO2 solubility due to the low CO2 solubility in H2O. In addition, after functionalization of TPAC/ EA(1:4), the CO2 solubility increased from 1.4 to 3.2 mol/kg DES, which showed a better performance compared with the common ILs.

  • 13.
    Ma, Chunyan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science. College of Chemical Engineering, Nanjing Tech University, Nanjing.
    Xie, Yujiao
    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.
    Liu, Chang
    College of Chemical Engineering, Nanjing Tech University, Nanjing .
    Lu, Xiaohua
    College of Chemical Engineering, Nanjing Tech University, Nanjing .
    Modeling, simulation and evaluation of biogas upgrading using aqueous choline chloride/urea2017In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 229, no 1, p. 1269-1283Article in journal (Refereed)
    Abstract [en]

    Biogas has been considered as an alternative renewable energy, and raw biogas needs to be upgraded in order to be used as vehicle fuels or injected into the natural gas grid. In this work, the conceptual process for biogas upgrading using aqueous choline chloride (ChCl)/urea (1:2 on a molar basis) was developed, simulated and evaluated based on the commercialized software Aspen Plus. Reliable thermophysical properties and phase equilibria are prerequisite for carrying out process simulation. In order to carry out the process simulation, the thermophysical properties of ChCl/Urea (1:2) and its aqueous solutions as well as the phase equilibria of gas-ChCl/Urea (1:2), ChCl/Urea (1:2)-H2O and gas-ChCl/Urea (1:2)-H2O were surveyed and evaluated. After evaluation, the consistent experimental data of these thermophysical properties were fitted to the models embedded in Aspen Plus. The properties needed but without available experimental results were predicted theoretically. The Non-Random Two-Liquid model and the Redlich-Kwong equation (NRTL-RK) model were used to describe the phase equilibria. The equilibrium approach was used for process simulation. Sensitivity analysis was conducted to determine the reasonable operating parameters. With a set of reasonable operating conditions, the effects of ChCl/Urea (1:2) content on the total energy utilization, the diameters and pressure drops of absorber and desorber as well as the environmental assessment of the process were studied. The simulation results showed that, with the addition of ChCl/Urea (1:2), the total energy utilization decreased by 16% compared to the process with pure water, and the diameters of both absorber and desorber decreased with increasing content of ChCl/Urea (1:2). The process using aqueous ChCl/Urea (1:2) was more environmentally benign than that with pure water. Therefore, aqueous ChCl/Urea (1:2) is a promising solvent for biogas upgrading.

  • 14.
    Xie, Yujiao
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Björkmalm, Johanna
    SP Technical Research Institute of Sweden, Box 857, 501 15 Borås.
    Ma, Chunyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Willquist, Karin
    SP Technical Research Institute of Sweden, Box 857, 501 15 Borås.
    Yngvesson, Johan
    SP Technical Research Institute of Sweden, Box 857, 501 15 Borås.
    Wallberg, Ola
    Department of Chemical Engineering, Lund University.
    Ji, Xiaoyan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Techno-economic evaluation of biogas upgrading using ionic liquids in comparison with industrially used technology in Scandinavian anaerobic digestion plants2018In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 227, p. 742-750Article in journal (Refereed)
    Abstract [en]

    The process of biogas upgrading with ionic liquids, i.e. pure 1-butyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide ([bmim][Tf2N]), aqueous choline chloride/urea (ChCl/Urea), and aqueous 1-allyl-3-methyl imidazole formate ([Amim][HCOO]), was simulated in Aspen Plus and compared with the conventional water scrubbing upgrading technique. The comparisons of the performances on the amount of recirculated solvents and energy usage show the following order: aqueous [Amim][HCOO]<aqueous ChCl/Urea<[bmim][Tf2N]<water. Six different co-digestion plants (anaerobic digestion, AD, plants) were surveyed to acquire data for comparison. The selected plants had different raw biogas production capacities and produced gas with differing methane content. The data confirmed the simulation results that the type of substrate and the configuration of AD process are two factors affecting energy usage, investment cost, as well as operation and maintenance costs for the subsequent biogas upgrading. In addition, the simulation indicated that the energy usage of the ionic liquid-based upgrading was lower than that of the conventional upgrading techniques in Scandinavian AD plants. The estimated cost including investment, operation and maintenance for the ionic liquid technology showed to be lower than that for the water scrubbing upgrading process.

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