A computational fluid dynamics design of a carbon dioxide sorption circulating fluidized bed

A kinetic theory based hydrodynamic model with experimentally determined sorption rates for reaction of CO₂ with K₂CO₃ solid sorbent is used to design a compact circulating fluidized bed sorption‐regeneration system for CO₂ removal from flue gases. Because of high solids fluxes, the sorber does not require internal or external cooling. The output is verified by computing the granular temperatures, particle viscosities, dispersion, and mass transfer coefficients. These properties agree with reported measurement values except the radial dispersion coefficients, which are much higher due to the larger bed diameter. With the solid sorbent prepared according to published information, the CO₂ removal percentage at the riser top is 69.16%. To improve the CO₂ removal, an effort is needed to develop a better sorbent or to simply lower the inlet gas velocity to operate in a denser mode, leading to a larger system. Also, the effect of temperature rise on the removal efficiency is investigated. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

ZL50活性炭吸附脱除二氧化硫的吸附动力学模型(英文)

A semi-empirical adsorption kinetic model was proposed with the time compensation method to describe the chemisorption of SO2 in flue gas by carbon adsorbents for flue gas purification. The change in adsorption capacity and adsorption rate with time at different water vapor concentrations and different SO2 concentrations was studied. The model was in good agreement with experimental data. The surface reaction was probably the rate controlling step in the early stage for SO2 adsorption by ZL50 activated carbon. The parameters m and n in the nth order adsorption kinetic model were related to the magnitude of the time compensation and adsorption driving force, respectively. The change of parameter n with water vapor concentrations and sulfur dioxide concentrations was studied and some physical implications were given. The sum of square errors was less than 1.0 and the average absolute percentage deviations ranged from 0.5 to 3.2. The kinetic model was compared with other models in the literature.     

双螺带桨Metzner常数的模拟计算

Using the multiple reference frames （MRF） impeller method, the three-dimensional non-Newtonian flow field generated by a double helical ribbon （DHR） impeller has been simulated. The velocity field calculated by the numerical simulation was similar to the previous studies and the power constant agreed well with the experimental data. Three computational fluid dynamic （CFD） methods, labeled Ⅰ, Ⅱ and Ⅲ, were used to compute the Metzuer constant k5. The results showed that the calculated value from the slop method （method Ⅰ） was consistent with the experimental data. Method Ⅱ, which took the maximal circumference-average shear rate around the impeller as the effective shear rate to compute ks, also showed good agreement with the experiment. However, both methods suffer from the complexity of calculation procedures. A new method （method Ⅲ） was devised in this paper to use the area-weighted average viscosity around the impeller as the effective viscosity for calculating k5. Method Ⅲ showed both good accuracy and ease of use.     

Efficient acetylene/carbon dioxide separation with excellent dynamic capacity and low regeneration energy by anion-pillared hybrid materials

Adsorptive separation of acetylene/carbon dioxide mixtures by porous materials is an important and challenging task due to their similar sizes and physical properties. Here, remarkable acetylene/carbon dioxide separation featuring a high dynamic breakthrough capacity for acetylene (4.3 mmol·g^–1) as well as an ultralow acetylene regeneration energy (29.5 kJ·mol^–1) was achieved with the novel TiF₆^2–-pillared material ZU-100 (TIFSIX-bpy-Ni). Construction of a pore structure with abundant TiF₆^2– anion sites and pores with appropriate sizes enabled formation of acetylene clusters through hydrogen bonds and intermolecular interactions, which afforded a high acetylene capacity (8.3 mmol·g^–1) and high acetylene/carbon dioxide uptake ratio (1.9) at 298 K and 1 bar. Moreover, the NbO₅^2– anion-pillared material ZU-61 investigated for separation of acetylene/carbon dioxide. In addition, breakthrough experiments were also conducted to further confirm the excellent dynamic acetylene/carbon dioxide separation performance of ZU-100.     

钠石灰动态吸附CO2效能分析

为了深入研究钠石灰动态吸附CO2的规律特性,更好地将钠石灰用于地下工程空气环境保障工程实践,进行了钠石灰动态吸附CO2的测试实验,测得了钠石灰的最大吸附效率,通过控制不同的环境参数来探究环境因素对于钠石灰动态吸附CO2效率和吸附速率的影响,实验选取了温度和相对湿度两个变量因素,设置了4组不同的环境参数。通过实验可得出结论:相对湿度和温度对于钠石灰动态吸附CO2的效率和速率都有影响,并且呈正相关,其中相对湿度的影响要强于温度,在等温不等湿时的最大动态吸附效率差达到6%,最大平均吸附速率差达281 mL/min;钠石灰对CO2的动态吸附稳定,不易出现解吸附,适合用于地下工程中消除CO2。     

二氧化碳的活化及其催化加氢制二甲醚的研究进展

CO₂是一种稳定的物质,其化学惰性限制了CO₂转化技术的发展。本文介绍了化学催化、生物活化、光电活化及等离子体活化等CO₂活化方式,从CO₂催化加氢合成二甲醚的工艺研究、催化剂开发、催化加氢机理和本征动力学研究等方面综述了CO₂催化加氢合成二甲醚的研究进展,认为化学催化法是目前应用最广泛的一种CO₂活化方式。对于一步法催化CO₂加氢合成二甲醚的工艺,其难点是制备高效CO₂活化催化剂。开发高效的CO₂活化及转化催化剂及对CO₂合成二甲醚的反应过程进行机理探究,是推广CO₂转化技术的关键。     

反应共混改性纳米二氧化硅/炭黑填充溶聚丁苯橡胶的结构与性能

采用动态反应共混法制备了含硫的硅烷偶联剂双-[γ-(三乙氧基硅)丙基]-四硫化物(Si-69)和双-[γ-(三乙氧基硅)丙基]-二硫化物(Si-75)改性纳米SiO2/炭黑填充溶聚丁苯橡胶(SSBR)硫化胶,分析了胶料的微观结构,研究了胶料的物理机械性能和动态力学性能等。结果表明,纳米填料在胶料中呈现较理想的分散状态;当纳米SiO2与炭黑填料的总量为70份时,随改性纳米SiO2用量的增加,SSBR硫化胶的邵尔A硬度、扯断伸长率、永久变形、撕裂强度下降,拉伸强度变化不大,300%定伸应力显著提高,生热明显下降,其中Si-75改性纳米SiO2/炭黑填充的SSBR综合性能更优;纳米填料在橡胶基体中的分散性好,胶料的动态生热低。     

Quality of wheat germ oil extracted by liquid and supercritical carbon dioxide

The extraction of wheat germ oil by liquid and supercritical CO₂ is described from the point of view of both operative method and pretreatment of raw material. The best conditions for wheat germ oil extraction are: pressure, 150 bar; temperature, 40°C; and solvent flow rate, 1.5 L/min at standard temperature and pressure. The yields and fatty acid compositions obtained are very similar to those resulting from the conventional extraction process using hexane as solvent (8.0 wt%), although a higher-quality oil is obtained by using CO₂ as solvent (free fatty acids, 12.4%; tocopherol content, 416.7 mg tocopherol/g wheat germ oil). These factors lead to the conclusion that the extraction process using CO₂ could be economically competitive with the conventional process, since it considerably simplifies the oil refinement stages and completely eliminates the solvent distillation stage, which are the most costly processing steps in terms of energy consumption.     

焚硫炉内燃烧过程的CFD研究

介绍了焚硫炉计算流体动力学（CFD）模型及模型建立中涉及的一些关键因素。利用CFD模型可以更好地理解焚硫炉、焚硫炉与周围管道的关系、焚硫炉对不同硫原料系统或流量的处理能力,从而为焚硫炉设计和改造提供依据。NORAM公司几项新焚硫炉设计和旧焚硫炉改造项目表明,合理使用CFD技术并选用合适的磺枪,一台与原设备尺寸相同的焚硫炉可以获得更高的产能。     

Adsorption of hydrogen sulfide,carbon dioxide,methane, and their mixtures on activated carbon

Abstract

H₂S and CO₂ are acid contaminants of natural gas and biogas, which removal have been studied using adsorption data for monocomponent and binary mixtures. However, equilibrium adsorption data for H₂S?+?CO₂ + CH₄ mixture has not been investigated yet. In this work, H₂S and CO₂ partition coefficients (K) and activated carbon (AC) selectivity (S) for H₂S?+?CO₂ + CH₄ mixture separation at high-pressure and different temperatures were determined. To reach this goal, monocomponent isotherms for H₂S, CO₂ and CH₄ on Brazilian babassu coconut hush AC were experimentally determined at different temperatures and pressures. Then, obtained data were correlated by Langmuir and Tóth models, and multicomponent adsorption was predicted using Extended Langmuir, Extended Tóth and Ideal Adsorption Solution Theory (IAST) methods. Results indicate AC captures approximately 26?wt% of H₂S or CO₂. K values for CO₂ and H₂S reached more than 3 and 26, respectively, depending on the predictive model utilized and were higher for diluted mixtures (high CH₄ content in gas phase). S values for CO₂ and H₂S can reach values greater than 25 for Tóth?+?IAST. Furthermore, selectivity toward H₂S is approximately 5.6 times greater than CO₂. The effect of temperature on multicomponent results indicate K and S values decrease as temperature increases. Therefore, results obtained herein show that is possible to separate H₂S and CO₂ from mixture containing CH₄ using this AC as adsorbent and better separation performance was observed for low H₂S and CO₂ concentrations and lower temperatures.     

Solubility of cyproheptadine in supercritical carbon dioxide; experimental and modeling approaches

Solubility of solute in supercritical fluids at different pressures and temperatures is one of the most important parameters necessary for design of any supercritical fluid-based processes. Among different supercritical fluids, carbon dioxide is one of the most widely used solvents due to its useful and green characteristics. In this work, with the assist of supercritical carbon dioxide as the solvent, solubility of cyproheptadine in different temperatures (308–338 K) and pressures (160–400 bar) are measured using static method. The obtained results demonstrated that solubility of cyproheptadine ranged between 3.35 × 10⁻⁵ and 3.09 × 10⁻³ based on mole fraction. A closer examination of measured solubility data show that not only solubility of cyproheptadine increases by increasing pressure but also experiences a cross over pressure about 200 bar. At last, the measured solubility data are correlated using four widely used density based correlations namely Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. The obtained results demonstrated that the best correlative capability was observed for KJ model leads to the average absolute relative deviation percent (AARD %) of 6.3%.     

Experimental investigation and modeling of the solubility of carvedilol in supercritical carbon dioxide

This study was aimed to measure the solubility of carvedilol in the temperature and pressure ranges of 308⿿338 K and 160 bar to 400 bar, respectively. In this direction, a homemade high pressure visual equilibrium cell was used to measure the solubility of carvedilol using a static method coupled with gravimetric technique. The results revealed that the carvedilol solubility was ranged between 1.12 ÿ 10^⿿5 and 5.01 ÿ 10^⿿3 based on the mole fraction (mole of carvedilol/mole of carvedilol + mole of CO₂) in this study as the temperature and pressure was changed. Finally, the results were correlated using four density-based semi-empirical correlations including Chrastil, Mendez⿿Santiago⿿Teja (MST), Bartle et al., and Kumar and Johnston (K-J) models. Results revealed that although the K-J model leads to the lowest average absolute relative deviation percent (AARD %) of 6.27%, but it could not be considered as the most accurate correlation since all the used four correlations introduces AARD % of about 6⿿10% which may be in the same range as the experimental error.     

Molecular-level kinetic modeling of heavy oil fluid catalytic cracking process based on hybrid structural unit and bond-electron matrix

In this presented work, a heavy petroleum fluid catalytic cracking (FCC) process model based on the use of a hybrid structural unit and bond-electron matrix (SU-BEM) framework on a molecular level has been developed. The SU-BEM uses a simplified structural unit to represent the petroleum's molecular structure and chemical conversion, while retaining substantial details regarding atom-connectivity. The chemical reaction information from the FCC unit was characterized in terms of reaction rules, indicating the conversion between structural units. After implementing via iteration the reaction rules on feedstock molecules, a complex molecular reaction network was created, containing all the primary product molecules (~3,800) and the reactions (~7,500). Next, the process mathematical model was built, including the micro-kinetic model and the FCC unit reactor model. For validation purposes, the product yield was selected as a predicted variable. Following a parameter estimation procedure, a good agreement between the calculated and experimental values was observed.     

单,双核络合物催化二氧化碳与环氧乙烷反应研究

报道了１０个含Ｐ配体的单,双核络合物在二氧化碳和环氧乙烷反应中的均相催化活性,分析了活性差异的原因。     

环氧乙烷与CO2合成碳酸乙烯酯动力学研究

环氧乙烷与CO2合成法是一种具有工业应用价值的碳酸乙烯酯生产方法,有必要对其反应机理和动力学加以研究。文中假设CO2与环氧乙烷合成碳酸乙烯酯的反应按照亲核加成反应机理分3步进行,其中催化剂溴化四乙铵作为亲核试剂。在一定温度和一定的压力下,碳酸乙烯酯的合成反应速率正比于催化剂和环氧乙烷浓度。提出了动力学方程,通过实验对假设机理进行了验证,并回归得到动力学方程参数。所得合成碳酸乙烯酯的反应动力学方程对大规模工业化生产具有一定参考价值。     

Biological activities of the rice bran extract and physical characteristics of its entrapment in niosomes by supercritical carbon dioxide fluid

The objectives of this study were to compare the biological activities of the rice bran (Oryza sativa Linn.) extracts prepared by supercritical carbon dioxide fluid (scCO₂) and ethanolic maceration, and the physical properties of niosomes entrapped with the extracts prepared by scCO₂ and chloroform film method. The scCO₂ extract showed higher unsaturated fatty acid and phenolic contents than the maceration extract. All extracts showed no significant difference of biological activities. The characteristics of niosomes entrapped and not entrapped with the extract prepared by scCO₂ and chloroform film method were not different with a unilamellar nano-sized structure and the phase transition temperatures at 80 °C. The gradual decrease trend of the vesicular membrane microviscosity with less membrane rigidity at higher extract concentrations was observed. The scCO₂ technique is advantageous for the preparation of the rice bran extracts and niosomes because of no requirement of organic solvents and having less step.     

Generation of microcellular foams of PVDF and its blends using supercritical carbon dioxide in a continuous process

Use of supercritical carbon dioxide (scCO₂) as a blowing agent to generate microcellular polymer foams (MPFs) has recently received considerable attention due to environmental concerns associated with conventional organic blowing agents. While such foams derived from amorphous thermoplastics have been previously realized, semicrystalline MPFs have not yet been produced in a continuous scCO₂ process. This work describes the foaming of highly crystalline poly(vinylidene fluoride) (PVDF) and its blends with amorphous polymers during extrusion. Foams composed of neat PVDF and immiscible blends of PVDF with polystyrene exhibit poor cell characteristics, whereas miscible blends of PVDF with poly(methyl methacrylate) (PMMA) yield foams possessing vastly improved morphologies. The results reported herein illustrate the effects of blend composition and scCO₂ solubility on PVDF/PMMA melt viscosity, which decreases markedly with increasing PMMA content and scCO₂ concentration. Morphological characterization of microcellular PVDF/PMMA foams reveals that the cell density increases as the PMMA fraction is increased and the foaming temperature is decreased. This study confirms that novel MPFs derived continuously from semicrystalline polymers in the presence of scCO₂ can be achieved through judicious polymer blending.     

Experimental study on the simultaneous adsorption of carbon dioxide and moisture from nitrogen in linde 5 a molecular sieves

Experimental data for the simultaneous adsorption of CO₂ and moisture with variations of some process variables, such as inlet adsorbate concentration, particle Reynolds number, and bed diameter to bed length ratio, have been generated to see their effects on the efficiency of adsorption of CO₂ and moisture. Presence of moisture strongly affects the CO₂ adsorption behaviour leading to roll up of CO₂ concentration breakthrough curves, whereas the presence of CO₂ has an insignificant effect on the moisture adsorption behaviour.     

新型光化学反应器及二氧化碳光解反应研究

研究设计了可产生波长小于200 nm真空紫外光的光化学反应器,首次利用该波段的光在该反应器中进行了CO2光解反应的研究。用氮气为发光介质对其进行光强标定,实验表明主要产生120、149、174 nm波长的光(N原子谱线);实验条件下CO2光解后生成产物CO,结果表明光源电流一定时产生CO的量与光源工作气体的压力有关,在CO2和N2反应物系中,光源内发光介质N2的压力在2 500 Pa左右时CO的产率最大,而在该反应物系中加入甲烷后,CO的产率明显增大。     

Effects of process conditions and electrode material on reaction pathways for carbon dioxide electroreduction with particular reference to formate formation

This paper reviews the most common reaction pathways for CO₂ electroreduction proposed by various workers in recent years. Each pathway involves certain intermediate compounds and certain end products and thus the pathways promoted, within a specific process, can be deduced from which of these have been detected. There are considered to be four principal pathways, each based on one of the following reactions: (1) CO(g) formation via disproportionation, (2) CO₂ ^– radical formation, (3) COOH(ad) formation and (4) the formation of reduced CO _x ^y–(ad) species giving a range of reduced CO₂ end products. This paper places particular emphasis on the formation of HCOOH. The effects of electrocatalyst and process conditions on reaction pathways is also reviewed.