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Measurement and correlation of supercritical CO2 and ionic liquid systems for design of advanced unit operations
Hiroshi MACHIDA, Ryosuke TAGUCHI, Yoshiyuki SATO, Louw J. FLOURUSSE, Cor J. PETERS, Richard L. SMITH
Front Chem Eng Chin. 2009, 3 (1): 12-19.
https://doi.org/10.1007/s11705-009-0151-3
Ionicliquids combined with supercritical fluid technology hold great promise as working solvents for developing compact processes. Ionic liquids, which are organic molten salts, typically have extremely low volatility and high functionality, but possess high viscosities, surface tensions and low diffusion coefficients, which can limit their applicability. CO2, on the other hand, especially in its supercritical state, is a green solvent that can be used advantageously when combined with the ionic liquid to provide viscosity and surface tension reduction and to promote mass transfer. The solubility of CO2 in the ionic liquid is key to estimating the important physical properties that include partition coefficients, viscosities, densities, interfacial tensions, thermal conductivities and heat capacities needed in contactor design. In this work, we examine a subset of available high pressure pure component ionic liquid PVT data and high pressure CO2 - ionic liquid solubility data and report new correlations for CO2-ionic liquid systems with equations of state that have some industrial applications including: (1) general, (2) fuel desulfurization, (3) CO2 capture, and (4) chiral separation. New measurements of solubility data for the CO2 and 1-butyl-3-methylimidazolium octyl sulfate, [bmim][OcSO4] system are reported and correlated. In the correlation of the CO2 ionic liquid phase behavior, the Peng-Robinson and the Sanchez-Lacombe equations of state were considered and are compared. It is shown that excellent correlation of CO2 solubility can be obtained with either equation and they share some common characteristics regarding interaction parameters. In the Sanchez-Lacombe equation, parameters that are derived from the supercritical region were found to be important for obtaining good correlation of the CO2-ionic liquid solubility data.
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A multi-scale model for CO2 sequestration enhanced coalbed methane recovery
G. X. WANG, X. R. WEI, V. RUDOLPH, C. T. WEI, Y. QIN
Front Chem Eng Chin. 2009, 3 (1): 20-25.
https://doi.org/10.1007/s11705-009-0138-0
This paper presents a multi-scale model to simulate the multicomponent gas diffusion and flow in bulk coals for CO2 sequestration enhanced coalbed methane recovery. The model is developed based on a bi-dispersed structure model by assuming that coal consists of microporous micro-particles, meso/macro-pores and open microfractures. The bi-disperse diffusion theory and the Maxwell-Stefan approach were incorporated in the model, providing an improved simulation of the CH4—CO2/CH4—N2 counter diffusion dynamics. In the model, the counter diffusion process is numerically coupled with the flow of the mixture gases occurring within macro-pores or fractures in coal so as to account for the interaction between diffusion and flow in gas transport through coals. The model was validated by both experimental data from literature and our CO2 flush tests, and shows an excellent agreement with the experiments. The results reveal that the gas diffusivities, in particular the micro-pore diffusivities are strongly concentration-dependent.
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Adsorption of 1,3-propanediol from synthetic mixture using polymeric resin as adsorbents
W. LUERRUK, A. SHOTIPRUK, V. TANTAYAKOM, P. PRASITCHOKE, C. MUANGNAPOH
Front Chem Eng Chin. 2009, 3 (1): 52-57.
https://doi.org/10.1007/s11705-009-0087-7
The aim of this work was to separate 1,3-PDO from a synthetic mixture using polymeric resins, Amberlite XAD-7 and XAD-16 resins. The equilibrium adsorption of 1,3-PDO onto two polymeric resins were investigated in binary and tertiary systems. Experimental results of binary component adsorption equilibrium indicated that the adsorption capacity (q) of 1,3-PDO at 160 g/L onto XAD-7 and XAD-16 was 835.96 and 584.61 mg 1,3-PDO/g dry resin, respectively. The adsorption isotherms were closely predicted by the Langmuir-Freundlich model among the two isotherm model tested. The value of n of 1,3-PDO adsorbed on XAD-7 are much higher than those on XAD-16. This result suggested that XAD-7 resin has a higher affinity for the 1,3-PDO adsorption than XAD-16 resin. Moreover, the value of adsorption capacity of 1,3-PDO in the binary and tertiary component were compared at the same conditions. In the tertiary system, although the selectivity of 1,3-PDO from XAD-7 was approximately six times higher than XAD-16, the adsorption capacity of 1,3-PDO at 160 g/L onto XAD-16 was higher than XAD-7. Interestingly, the reusability of XAD-7 and XAD-16 resins in the three cycle times shows a slight loss of adsorption capacity. Furthermore, the investigation about desorption by an ethanol/water mixture at 50% (V/V) indicated that the desorption yield of 1,3-PDO from XAD-7 was lower than XAD-16 resin for both the binary and tertiary component. This was due to the more favorable adsorption characteristics of XAD-7 resin than XAD-16 resin.
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Characterization of micro-mixing in a novel impinging streams reactor
Hui HU, Zhiming CHEN, Zhen JIAO
Front Chem Eng Chin. 2009, 3 (1): 58-64.
https://doi.org/10.1007/s11705-009-0106-8
This paper presents an experimental investigation of a novel impinging stream reactor (ISR) with the aim of high mixing intensity. The integral mixing quality in the reactor was measured with the iodide-iodate reaction and showed excellent mixing performance. The impact of the operating parameters, such as fluxes, circulation and inter-nozzle distances, was investigated in terms of segregation index. The results showed that the increase of flux, the decrease of inter-nozzle distance and a suitable circulation can improve the micro-mixing efficiency. Based on turbulence theory, it was estimated that the characteristic micro-mixing time was 0.002—0.02 s, which was much shorter than that in the stirred tank reactor. The micro-mixing time was related to the segregation index, which was in good agreement with those in the literature.
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Preparation of lithium ion-sieve and utilizing in recovery of lithium from seawater
Lu WANG, Changgong MENG, Wei MA
Front Chem Eng Chin. 2009, 3 (1): 65-67.
https://doi.org/10.1007/s11705-009-0105-9
Lithium is one of the most important light metals, which is widely used as raw materials for large-capacity rechargeable batteries, light aircraft alloys and nuclear fusion fuel. Seawater, which contains 250 billion tons of lithium in total, has thus recently been noticed as a possible resource of lithium. While, since the average concentration of lithium in seawater is quite low (0.17 mg·L-1), enriching it to an adequate high density becomes the primary step for industrial applications. The adsorption method is the most prospective technology for increasing the concentration of lithium in liquid. Among the adsorbents for lithium, the ion-sieve is a kind of special absorbent which has high selectivity for Li+, especially the spinel manganese oxides (SMO), which among the series of ion-sieves, has become the most promising adsorption material for lithium. In this study, the SMO ion-sieve was prepared by a coprecipitation method. The preparation conditions were discussed and the sample characters were analyzed. Recovery of Li+ from seawater were studied in batch experiments using prepared ion-sieve, and the effect of solution pH and the uptake rates were also investigated in different Li+ solutions.
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Effects of baffles on separation of aqueous ethanol solution with hollow fibers
Zhihong YANG, Guoliang ZHANG, Lan LIN, Danping REN, Qin MENG, Hongzi ZHANG
Front Chem Eng Chin. 2009, 3 (1): 68-72.
https://doi.org/10.1007/s11705-009-0130-8
The effects of baffles on the operation and mass-transfer characteristics in novel hollow fiber membrane contactor used in distillation were investigated. Hollow fiber membranes, coated with a 7 μm polydimethyl-siloxane, were operated as structural packing in the separation of ethanol-water solutions. The parallel flow mode was chosen for separation due to the stronger driving force of the concentration difference, in which liquid flows through the lumens of the fibers and vapor flows countercurrent-wise outside the fibers. Two baffles were installed on the shell side of the membrane contactors to enhance separation, which had a round shape with a semi-lunar hole. The results show that both baffled and unbaffled membrane contactors gave better, more productive separations than traditional packing in distillation, such as the excellent Sulzer Gauze BX structured packing. The baffled membrane contactors performed better than unbaffled ones, especially at high vapor velocities. The minimal HTU of membrane contactor with baffles could reach as low as 4.5 cm, and almost all the contactors could work well above the limit where flooding normally occurs in conventional cases. Theoretical analysis predicted that baffles helped membrane module to obtain a higher mass-transfer coefficient and a smaller mass-transfer resistance. Finally, theoretical mass-transfer coefficient and experimental value were compared as well as the contribution of each individual mass-transfer coefficients among liquid, gas and membrane.
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Primary nucleation of lithium carbonate
Yuzhu SUN, Xingfu SONG, Jin WANG, Yan LUO, Jianguo YU
Front Chem Eng Chin. 2009, 3 (1): 73-77.
https://doi.org/10.1007/s11705-009-0091-y
A set of laser apparatus was used to explore the induction period and the primary nucleation of lithium carbonate. Results show that the induction period increases with the decrease of supersaturation, temperature and stirring speed. Through the classical theory of primary nucleation, many important properties involved in primary nucleation under different conditions were obtained quantitatively, including the interfacial tension between solid and liquid, contact angle, critical nucleus size, critical nuleation free energy etc.
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A study of spray granulation in vibrated fluidized bed with internal heating tubes
Xiaoheng PAN, Shichao YE, Zeguang ZHANG, Li ZHANG, Xuejun ZHU
Front Chem Eng Chin. 2009, 3 (1): 78-82.
https://doi.org/10.1007/s11705-009-0084-x
The granulation process in a vibrated fluidized bed with immersed horizontal heating tubes was studied in this paper, with small monoammonium phosphate particles as the initial particles and monoammonium phosphate solution sprayed on them. The concrete influences on the granulating performance of the immersed horizontal heating power, fluidizing gas velocity, vibration frequency and amplitude had been analyzed theoretically. The results show that appropriate vibration intensity is a preferred condition for the growth of partials, but the fine dust will become much more along with prolonged vibration. Increasing the heating power is beneficial to raise the growth rate. Particles will grow faster if the fluidizing gas velocity is higher, but this will cause more fine dust. The optimized condition of A=0.002 m, f=6.67 Hz, u=1.4 m/s was given after the analysis of the experimental results. In the end, a semiempirical formula was derived from the experiment data, and the calculation results show good agreement with the experimental data.
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Additives effects on crystallization and morphology in a novel caustic aluminate solution decomposition process
Ying ZHANG, Shili ZHENG, Yifei ZHANG, Hongbin XU, Yi ZHANG
Front Chem Eng Chin. 2009, 3 (1): 88-92.
https://doi.org/10.1007/s11705-009-0133-5
A novel process of caustic aluminate solution decomposition by alcohol medium was developed by the Institute of Process Engineering, Chinese Academy of Sciences in order to solve the problem of low decomposition ratio in the traditional Bayer seeded hydrolysis process. In this research, effects of additives on the crystallization ratio, secondary particle size and morphology of aluminum hydroxide in the new process were studied to obtain high-quality products. On the basis of primary selection of additives, an orthogonal design L9(34) was used as a chemometric method to investigate the effects of additives. The studied parameters include the reaction style, quantity of additives, caustic soda concentration, as well as the combination manner. The crystallization ratios of sodium aluminate solution and crystal size of aluminum hydroxide, determined by ICP-OES, SEM and MLPSA (Malvern Laser Particle Size Analyzer), were used to evaluate the effects of the additives. The results showed that different combination manners could promote agglomeration or dispersion. An additive composed by Tween 80 and PEG 200 could promote agglomeration, while a spot of PEG species had a relatively strong dispersion effect. However, the additives had little effects on the crystallization ratios. According to the Raman spectra result, the added alcohol medium might serve as a kind of solvent.
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Removal of dissolved oxygen from water using a Pd-resin based catalytic reactor
Wenxin SHI, Chongwei CUI, Liye ZHAO, Shuili YU, Xia YUN
Front Chem Eng Chin. 2009, 3 (1): 107-111.
https://doi.org/10.1007/s11705-009-0154-0
The removal of dissolved oxygen (DO) from water was studied experimentally in a Pd-resin base catalyst reactor using purified hydrogen gas as a reducing agent. The effects of various operating conditions, such as hydrogen and water flow rates, height of the catalytic resin bed, temperature, pH value and run time, on the removal of DO, had been studied extensively. The results shows that DO could be removed by the reactor from ppm to ppb levels at ambient temperature. Increases of temperature, H2 gas rate and the height of the catalytic resin were helpful to improve the DO removal rate. The change of pH value from 4 to 12 resulted in no effect on DO removal. Reaction time was the key factor to control the DO removal efficiency. Only when the reaction time was longer than 2.3 minutes under the experimental conditions, could a very low DO level be achieved.
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