PDF Publication Title:
Text from PDF Page: 112
326 Y. Xie et al. / Applied Energy 136 (2014) 325–335 because of its advantages, such as non-volatility, functionality, high CO2 solubility and lower energy requirements for regenera- tion [9–12]. In order to develop IL technology for CO2 separation, a signifi- cant amount of research work has been carried out. The thermo- physical properties of ILs (density, viscosity and surface tension) as well as the effects of cation and anion of ILs on CO2 solubility and their properties have been extensively studied. With respect to energy consumption and process simulation for a CO2 separa- tion process using ILs as liquid absorbent, Shiflett et al. [13,14] evaluated the performance of [bmim][Ac] and compared with the MEA technology. It was found that the energy consumption of [bmim][Ac]-based technology was reduced by 16% compared to the MEA-based technology. Basha et al. [15,16] developed a con- ceptual process for CO2 capture from the fuel gas streams produced in a 400 MWe IGCC power plant, in which [hmim][Tf2N] and two TEGO ILs were used as liquid absorbents. Their results showed that the studied ILs can be used as a physical solvent for CO2 capture. Huang et al. [17] compared the IL-MEA and MEA processes and found that the IL-MEA process saves 15% regeneration heat duty compared to the MEA process. However, the research work on energy consumption is rare and with the focus only on several spe- cific ILs. Meanwhile, in order to analyze the energy consumption for a CO2 separation process, enthalpy is one of the most important properties [18–20]. Due to the low heat release for the absorption of CO2 in ILs, it is difficult to measure the CO2 absorption enthalpy. Therefore, it is desirable to estimate the CO2 absorption enthalpy with a proper thermodynamic model based on CO2 solubility data which has been measured extensively. Meanwhile, although a lot of ILs have been developed and proposed as potential liquid absor- bents for CO2 separation, to the best of our knowledge, the energy consumption of a CO2 separation process using different ILs has not yet been carried out well, which makes it difficult for users to choose a proper IL for a specific application. The goal of this work is to perform energy consumption analysis for a CO2 separation process with ILs as liquid absorbents. To achieve this goal, in this work, the imidazolium-based ILs were studied because sufficient experimental data is available for such ILs. In order to get reliable results, the experimental CO2 solubili- ties in imidazolium-based ILs were firstly surveyed and evaluated with non-random two liquids (NRTL)-Redlich–Kwong (RK) model. Based on the reliable experimental data, the model of NRTL-RK was used to represent the gas solubility, and the enthalpy of CO2 absorption was then predicted by NRTL-RK model. The effects of anion and chain length in cation on the CO2 absorption enthalpy were studied. Furthermore, the energy consumption for a CO2 sep- aration process using imidazolium-based ILs as liquid absorbents was analyzed and compared for both pressure swing and temper- ature swing options for solvent regeneration, and suggestions were provided for choosing a proper IL for a CO2 separation process from the energy point of view. 2. Theory 2.1. Thermodynamic modeling The vapor-liquid equilibrium representing the CO2 solubility in ILs can be expressed as: PyCO2 umCO2 1⁄4 HCO2 xCO2 cCO2 ð1aÞ where P is the system pressure, yCO2 is the mole fraction of CO2 in the vapor phase, um is the fugacity coefficient of CO2 in the vapor CO2 phase, HCO2 is the Henry’s constant, xCO2 is the CO2 mole fraction in the liquid phase, and cCO2 is the activity coefficient of CO2 in the liquid phase at the infinite dilution reference state. Due to the negligible vapor pressure of ILs, in this work, it was assumed that only CO2 exists in the vapor phase (yCO2 1⁄4 1), i.e.: PumCO2 1⁄4 HCO2 xCO2 cCO2 ð1bÞ In this work, Redlich–Kwong (RK) equation of state [21] was used to calculate the fugacity of pure CO2 in the vapor phase, in which the critical temperature and pressure of CO2 were taken from NIST webbook with the values of 304.2 K and 7.38 MPa [22], respectively. Following RK equation of state, the expression of the fugacity coefficient of CO2 was calculated as: lnu1⁄4Z1lnðZBPÞðA2=BÞlnð1þBP=ZÞ ð2Þ 8> P 1⁄4 RT=ðV bÞa=T1=2VðV þbÞ > A2 1⁄4 a=R2T2:5 1⁄4 0:4278T2:5=P T2:5 >< cc B 1⁄4 b=RT 1⁄4 0:0867Tc=PcT > Z 1⁄4 1=ð1 hÞ ðA2=BÞh=ð1 þ hÞ > Z 1⁄4 PV=RT : h 1⁄4 BP=Z 1⁄4 b=V ð3Þ The Henry’s constant of CO2 was calculated from the following equations: V1CO2 P HCO2 ðT; PÞ 1⁄4 HCO2 ðTÞ exp RT ð4Þ lnHCO2ðTÞ1⁄4c1 þc2=T ð5Þ where T is the temperature, HCO2 ðT; PÞ is the Henry’s constant of CO2 at system temperature and pressure, HCO2 ðTÞ is the Henry’s constant of CO2 at zero pressure, and V1CO2 is the infinite dilution partial vol- ume of CO2 in ILs. The non-random two liquids (NRTL) model [23] was used to represent the activity coefficient of CO2 in the liquid phase that can be calculated by the following equations: G21 s12G12 þ 2 ð6Þ 2 lnc11⁄4x2 s21 "2 # x1 þ x2G21 ðx2 þ x1G12Þ G12 1⁄4 expðas12 Þ and G21 1⁄4 expðas21 Þ where a was assumed to be 0.2 in this work, G12, G21, s12 and s21 are binary interaction parameters. s12 and s21 are temperature-dependent, i.e.: (s12 1⁄4sð0Þ þsð1Þ=T 12 12 ð7Þ s21 1⁄4sð0Þ þsð1Þ=T 21 21 In this work, the temperature-dependent V1CO2 was expressed as Eq. (8). V1CO2 was obtained from the fitting of the CO2 solubility in ILs by setting the binary interaction parameters of s12 and s21 to be zero. With the fitted V1CO2 , the binary interaction parameters of s12 and s21 were further obtained from the fitting of the CO2 solu- bility in ILs. V1CO2 1⁄4c3þc4T ð8Þ The enthalpy for absorbing 1mol of CO2 (CO2 absorption enthalpy per mol CO2) can be calculated from the following equa- tions [20]: DHabs 1⁄4 Hdis þ ð1 þ mÞHex ð9Þ Hdis 1⁄4 RT2 @ ln HCO2 ðT; PÞ ð10Þ @T X ex 2 @lnci H1⁄4RTxi@T ð11ÞPDF Image | CO2 Separation with Ionic Liquids
PDF Search Title:
CO2 Separation with Ionic LiquidsOriginal File Name Searched:
co2-separation-ionic-liquids.pdfDIY PDF Search: Google It | Yahoo | Bing
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
IT XR Project Redstone NFT Available for Sale: NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Be part of the future with this NFT. Can be bought and sold but only one design NFT exists. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Turbine IT XR Project Redstone Design: NFT for sale... NFT for high tech turbine design with one part 3D printed counter-rotating energy turbine. Includes all rights to this turbine design, including license for Fluid Handling Block I and II for the turbine assembly and housing. The NFT includes the blueprints (cad/cam), revenue streams, and all future development of the IT XR Project Redstone... More Info
Infinity Turbine ROT Radial Outflow Turbine 24 Design and Worldwide Rights: NFT for sale... NFT for the ROT 24 energy turbine. Be part of the future with this NFT. This design can be bought and sold but only one design NFT exists. You may manufacture the unit, or get the revenues from its sale from Infinity Turbine. Royalties go to the developer (Infinity) to keep enhancing design and applications... More Info
Infinity Supercritical CO2 10 Liter Extractor Design and Worldwide Rights: The Infinity Supercritical 10L CO2 extractor is for botanical oil extraction, which is rich in terpenes and can produce shelf ready full spectrum oil. With over 5 years of development, this industry leader mature extractor machine has been sold since 2015 and is part of many profitable businesses. The process can also be used for electrowinning, e-waste recycling, and lithium battery recycling, gold mining electronic wastes, precious metals. CO2 can also be used in a reverse fuel cell with nafion to make a gas-to-liquids fuel, such as methanol, ethanol and butanol or ethylene. Supercritical CO2 has also been used for treating nafion to make it more effective catalyst. This NFT is for the purchase of worldwide rights which includes the design. More Info
NFT (Non Fungible Token): Buy our tech, design, development or system NFT and become part of our tech NFT network... More Info
Infinity Turbine Products: Special for this month, any plans are $10,000 for complete Cad/Cam blueprints. License is for one build. Try before you buy a production license. May pay by Bitcoin or other Crypto. Products Page... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)