The thermodynamic method for selecting oxygen carriers used for chemical looping air separation

Chemical looping air separation (CLAS) has been suggested as a new and energy saving method for producing oxygen from air. The selection of suitable oxygen carriers is the key issue for CLAS system. This paper shows a comprehensive thermodynamic method for selecting oxygen carriers used for CLAS through studying the properties of 34 different oxygen releasing reactions referring to 18 elements at different temperatures. The research mainly includes analysis of oxygen releasing capacity by calculating the Gibbs free energy change (ΔG) and the equilibrium partial pressure of oxygen of the reduction or oxidation reaction at different temperatures. Oxygen content and transport capacity were calculated. The spontaneous reaction temperatures for oxygen releasing reactions were presented to determine the operating temperatures. Also, the minimum demand of the steam for the reduction reaction was discussed. On the basis of the comprehensive thermodynamic study, the oxide systems of CrO₂/Cr₂O₃, PbO₂/Pb₃O₄, PbO₂/PbO, Pb₃O₄/PbO, MnO₂/Mn₂O₃, and Ag₂O/Ag have been found suitable for the CLAS process in low temperatures (500–800 K). The systems of PdO₂/PdO, PdO₂/Pd, PdO/Pd, MnO₂/MnO, and MnO₂/Mn₃O₄ were suitable for medium temperatures (800–1100 K) CLAS process. And Co₃O₄/CoO, CuO/Cu₂O, Mn₂O₃/Mn₃O₄, and OsO₂/Os systems only worked successfully in high temperatures (1100–1400 K). In addition, the CaO₂/CaO system was not suitable for CLAS because of the reaction with steam. The various binders such as SiO₂, TiO₂, Al₂O₃, Y₂O₃, ZrO₂, and YSZ which have been used for CLC could also be the supports for CLAS oxygen carriers.     

The adaptability of Cu/Zr oxides as oxygen carrier used for chemical looping air separation (CLAS)

Chemical looping air separation (CLAS), based on the chemical looping principle, is a novel and energy-efficient method to separate oxygen from air. The oxygen carriers used capture oxygen from air in an oxidation reactor and release oxygen in a reduction reactor. In this work, the adaptability of Cu/Zr oxygen carrier used for CLAS was investigated through thermodynamic analysis and experimental methods. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to measure the phases and surface morphology of oxygen carriers before and after experiments. The results show that CuO has the capability of releasing oxygen when the temperature is higher than 725 °C in the nitrogen atmosphere, and the minimum oxygen reduction temperatures increase with the increasing of oxygen concentrations. The Cu/Zr oxygen carrier has high oxygen reduction and oxidation rates when temperature is higher than a certain values. For reduction, the value is about 860 °C. For oxidation, the value is about 500 °C. The reactivity of oxygen carrier increases significantly with the temperature increasing. On overall, reactivity of oxygen carrier has little difference under different particle sizes. The oxygen carrier exhibits a stable oxygen reduction and oxidation behavior during reduction–oxidation cycles. XRD patterns show that the main phases in reduced samples are Cu₂O and ZrO₂. The main phases in fresh and oxidized samples are CuO and ZrO₂. SEM images show that the fresh and reacted oxygen carriers are porous. The surface of reacted samples is smoother than fresh samples and no agglomeration has been found.     

基于Aspen Plus软件对制药化工原理精馏实验的模拟与分析

介绍并探讨了Aspen Plus化工流程模拟软件在“制药化工原理精馏实验”操作型问题分析中的应用.实践表明,采用该流程模拟软件辅助解决精馏实验操作问题,可以把精馏过程中复杂计算和繁琐图解过程化为直观、简单、精确、高效的计算,便于学生的理解和掌握, 提高了学生的学习积极性,不仅拓宽学生的视野,使学生加深了对精馏原理的深刻理解,而且有助于培养学生利用流程模拟技术解决工程实际问题和科研问题.     

流程模拟软件Aspen Plus在化工原理课程设计教学中的应用

介绍了化工原理课程设计的特点和重要性,通过实例说明流程模拟软件Aspen Plus在课程设计教学中的应用。应用DSTWU模型进行简捷设计计算、应用灵敏度分析优化工艺流程、应用RadFrac模型进行严格精馏计算、塔板或填料的设计与校核,并与手工计算结果进行对比。实践经验表明,将流程模拟软件同传统课程设计相结合的教学方式拓宽了教师的选题范围,提高了课程设计的质量和效率,强化了学生的工程意识,提高了课程的教学质量。     

基于Aspen Plus的煤层气精馏分离案例教学探讨

为帮助学生掌握“煤矿区煤层气利用技术”基本理论,结合煤层气低温精馏分离科研成果案例,运用Aspen Plus流程模拟软件对煤层气气液相平衡和低温精馏过程进行模拟和案例教学,根据煤层气精馏分离工艺要求,进行精馏塔操作变量计算和灵敏度分析,分析操作变量变化对精馏过程的影响,让学生直观了解塔内各参数的变化,掌握精馏分离操作,加深了对煤层气分离理论的理解,极大地提高了教学效率和质量,提升了学生的综合素质。     

Gaussian与Aspen Plus在化工原理课程设计中的应用*

在化工原理课程设计中将某药厂委托的科研项目“二甲硫醚、甲醇和水分离设计项目”转化为典型教学案例,结合现代计算机辅助技术,引入量化计算软件Gaussian和化工模拟软件Aspen Plus分别从微观和宏观上进行萃取精馏分离共沸物的设计。通过Gaussian软件,基于密度泛函理论证实了待分离体系中已有的组分水可改变二甲硫醚与甲醇二元共沸物的相对挥发度,消除2者之间的共沸。继而采用Aspen Plus软件对待分离混合液进行萃取精馏工艺模拟与优化,最后开展工业设计与设备选型。上述实际案例的设计过程,创造性地使用了混合液已有的组分作为萃取剂,通过萃取精馏工艺实现共沸物的分离,弥补了传统萃取精馏因引入萃取剂导致产品携带少量第三组分的缺点,极大地激发了学生学习的兴趣,丰富了课程教学内容,将复杂的萃取精馏过程讲解透彻,促进教学质量的提升,增强学生的工程设计能力,学生多次参加全国大学生化工设计竞赛并取得了优异成绩。     

Study on modification of Cu-based oxygen carrier for chemical looping combustion

Chemical looping combustion (CLC) is a promising technology for segregation of carbon dioxide. CLC uses a metal oxide as an oxygen carrier, which transfers oxygen from the air to the fuel avoiding direct contact between them, thus separating the carbon dioxide and nitrogen. Cu-based oxygen carriers are excellent mediums due to high reactivity, environmental friendliness, and favorable thermodynamics. However, there are agglomeration issues due to low melting point of Cu. To solve this issue, a new preparation method as well as a dispersion reagent and a thermal durability-enhanced reagent were applied simultaneously to the oxygen carrier. The carriers were synthesized using both wet and dry impregnation methods. Based on the initial oxygen loading capability tests, the dry impregnation method received additional investigation. The characterizations of the oxygen carriers were evaluated using thermogravimetric analyzer (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), and surface area analyzer. TG results demonstrate that the enhanced dry impregnation was an effective preparation method, where the mass loss of the oxygen carrier was typically 3.4 %, correlating to almost 17 % loaded CuO. XRD results indicate a new phase, CuAl₂O₄ spinel, formed after the first few redox cycles, which is responsible for promoting the thermal stability of the oxygen carriers. SEM results show that the addition of the dispersants decreased the agglomeration and the enhanced reagent chemicals greatly improved the strength of the carriers. However, the surface area of the oxygen carriers decreased with the addition of the additives. In addition, with the increasing redox cycles, the surface area also decreased while the pore size increased, indicating that small pores were crushed, but the reactivity of the oxygen carriers did not decrease. In conclusion, the oxygen carriers produced in this manner are suitable for multi-cycle tests, and a major hurdle toward reducing greenhouse gases has been achieved.     

Application of PCM thermal energy storage system to reduce building energy consumption

The building sector is known to make a large contribution to total energy consumption and CO₂ emissions. Phase change materials (PCMs) have been considered for thermal energy storage (TES) in buildings. They can balance out the discrepancies between energy demand and energy supply, which are temporally out of phase. However, traditional PCMs need special latent storage devices or containers to encapsulate the PCM, in order to store and release the latent heat of the PCM. The proper design of TES systems using a PCM requires quantitative information and knowledge about the heat transfer and phase change processes in the PCM. In Korea, radiant floor heating systems, which have traditionally been used in residential buildings, consume approximately 55% of the total residential building energy consumption in heating. This article reviews the development of available latent heat thermal energy storage technologies and discusses PCM application methods for residential building using radiant floor heating systems with the goal of reducing energy consumption.     

Chromatographic separation and chemical analysis of polymers formed by penicillin G

To elucidate the chemical structures of penicillin polymers that may elicit an allergic reaction, a 25% aqueous solution of penicillin G potassium was kept standing in the dark at room temperature for 14 days and was then separated by gel filtration chromatography on Sephadex G-25. The fractions of Kav 0.0-0.3, 0.3-0.55 and 0.55-0.75 were designated fractions A, B and C, respectively. Chemical and spectral data indicated that fractions A and B had almost similar chemical structures, but differed in molecular weight. They consisted of equimolar phenylacetyl and thiazolidine moieties and showed a C:N:S ratio almost equal to that of penicillin G. Their degrees of polymerization were 10 for A and 3.2 for B. Comparison of 1H NMR and IR spectra and thin-layer chromatographic RF values with those of authentic standards showed that the main components of fraction C were N- formylpenicillamine , benzylpenilloic acid, benzylpenicilloic acid and benzylpenillic acid.     

Effects of digestion,chemical separation,and deposition on Po-210 quantitative analysis

The purpose of this work was to determine polonium losses from a variety of sample types (soil, cotton fiber, and air filter) due to digestion technique, chemical separation, and deposition method for alpha energy analysis. Results demonstrated that yields from a perchloric acid wet-ash (87 ± 5 %) were similar to that from a microwave digestion (100 ± 7 %), but both were greater than the dry-ash procedure (38 ± 5 %). The polonium was separated from an SRM soil using an AG1X8 ion exchange column and deposited on a Ag disk with a recovery of 83 ± 7 % of polonium-209 (Po-209). Deposition yields without chemical separation averaged 90 ± 5 % of Po-209. The polonium-210 content was successfully measured in the three matrix types and quantitated using alpha spectroscopy.     

Influence of pretreatment and mechanical nanofibrillation energy on properties of nanofibers from Aspen cellulose

Cellulose - The characteristics of cellulose nanofibers (CNFs) depend on many factors such as the raw material, type and intensity of the pre-treatment, and type and severity of the mechanical...     

铜基载氧体与可燃固体废弃物化学链燃烧特性研究

采用机械混合法制备了铜基载氧体,利用两段式管式炉反应平台和磁悬浮热重分析仪分别研究了铜基载氧体与石墨、可燃固体废弃物典型组分及可燃固体废弃物热解气模型物CH₄的化学链燃烧特性。结果表明,机械混合法制备的Cu80Si950载氧体强度高,具有良好的转化率和循环稳定性,是实现可燃固体废弃物化学链燃烧的一种比较理想的载氧体。利用扫描电镜(SEM)、X射线衍射仪(XRD)和颗粒强度测定仪对各个反应阶段载氧体进行分析。结果表明,Cu80Si950载氧体参与反应后表面结构发生巨大改变,机械强度骤降。多次循环之后载氧体结构趋于规则均匀化,形成类似球棒形状的大孔隙率结构,强度保持不变,使得载氧体在长时间使用过程中反应性能得以维持。     

PVC化学链燃烧过程中二噁英生成研究

制备了负载硅溶胶的CaSO₄载氧体,并对其与CH₄、CO和H₂的反应特性进行了研究表征。采用管式炉实验系统,对PVC在基于CaSO₄载氧体的化学链燃烧和空气燃烧两种方式下,二噁英的生成特性进行了实验研究。结果表明,负载了硅溶胶的CaSO₄载氧体与CH₄、CO和H₂反应均接近完全转化,其中,与CH₄和H₂的反应时间显著短于CO。采用化学链燃烧方式可有效抑制PVC燃烧过程二噁英的生成,其生成量和毒性当量分别由空气燃烧中的34 172.5 pg/g及732.8 pg(I-TEQ)/g降到化学链燃烧的2 270.9 pg/g及290.2 pg(I-TEQ)/g,这主要是因为化学链燃烧过程中燃料与O₂不直接接触,显著减少了大分子碳结构的氧化断裂以及HCl向Cl₂的转化,从而抑制了二噁英的低温从头合成反应和前驱物生成反应。     

基于赤铁矿的生物质化学链燃烧过程中氮氧化物的释放特性

在单批次进料固定床上,基于赤铁矿载氧体,研究了还原反应阶段反应温度和水蒸气量对谷壳的氮氧化物释放特性的影响。研究表明,碳转化率随反应温度升高而增加,但随水蒸气量呈先增加后下降,并在水蒸气量为1.0 g/min时达到最大值。在实验条件下,还原阶段未检测到NO₂。随着反应温度由750 ℃升高到900 ℃,NO的生成率增加,而N₂O的生成率先增加后降低,在850 ℃时达到最大值。水蒸气量由0.5 g/min升高到2.0 g/min,N₂O和NO的生成率均增加,且NO增加速率高于N₂O。在反应后的载氧体中,检测到KAlSi₃O₈存在,表明载氧体与生物质中的K元素发生反应。     

Utilisation of separation methods in the analysis of chemical warfare agents

Chemical warfare agents and their degradation products represent a broad group of compounds with different chemical properties (polarity, volatility, thermostability, etc.). These chemicals often have to be detected and determined in complex matrices and therefore highly efficient separation techniques hyphenated to selective and sensitive detectors play an indispensable role. This review offers an overview of selected papers devoted to the title subject. It cannot be considered as a comprehensive literature compilation but should allow the reader to obtain an insight into the application of separation techniques in the important area of human protection and control of chemical weapons.     

物理法COD减排理论极限能耗的热力学分析

首先针对系统的可持续性发展提出了三点本质要求,在此基础上提出了基于减排过程节能机制的热力学框架,并根据热力学第一、第二定律建立了计算物理法脱除有机污染物理论极限能耗的热力学分析方法.此外,以典型有机污染物的脱除为例,分别计算了封闭体系中298.15K和1.01325×105Pa下不同初始浓度、不同种类以及不同COD减排量的有机污染物脱除的理论极限能耗.本文的计算结果表明,废水中有机污染物的减排需要很高的能耗,脱除相同量有机污染物所需的理论极限能耗随着初始浓度的减小而显著增加,且不同种类污染物处理的难易程度和能耗高低相差很大,这充分说明减排与节能有着密不可分的联系,充分考虑污染物的种类、物理化学性质、毒性和浓度将有助于减排政策的科学制定.     

基于Aspen Plus耦合生命周期评价的科研案例在环境工程原理教学中的应用

将化工流程模拟Aspen Plus软件与环境影响评估领域常用的生命周期评价(LCA)进行集成应用,围绕环境工程原理教学中有关化工过程质量能量衡算与环境污染防治内容的协同应用与拓展,构建化工流程模拟-环境风险评估科研案例“苯酐生产流程模拟及环境风险研究”,并将其作为环境工程原理的综合教学案例。教学实践经验表明,通过引入工程相关综合教学案例,不仅使得抽象的理论知识更加生动具体,而且在深化学生对课程理论知识理解的同时,提高学生应用专业知识分析和解决化工生产环境污染工程问题的综合能力和素质,为学生将来步入相关领域工作奠定扎实的基础。     

Physical analysis of the diatomic “chemical” energy components

 The recent “chemical energy component analysis” permits the total energy of a molecule to be presented approximately but to good accuracy as a sum of atomic and diatomic energy contributions. Here the diatomic energy components are further decomposed into terms of different physical origin: electrostatics (in point-charge approximation and the distributed charge corrections), exchange effects, diatomic overlap and atomic basis extension terms. This analysis may provide us with a deeper insight into the factors influencing both the chemical bonds and the nonbonded interatomic interactions. Received: 6 May 2002 / Accepted: 13 November 2002 / Published online: 19 March 2003 Acknowledgements. The authors are indebted to the Hungarian Scientific Research Fund for partial financial support (grant no. OTKA T29716). Correspondence to: I. Mayer e-mail: mayer@chemres.hu