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.     

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...     

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.     

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     

Electrophoretic and chromatographie separation and fluorimetric analysis of polynuclear phenols. Application to air pollution

Summary Thin-layer Chromatographic and low-voltage and high-voltage electrophoretic procedures are described for a large number of polynuclear aromatic and heteroaromatic phenols. Location methods of various types are described. In particular, theo-phthalaldehyde and 3-methyl-2-benzothiazolinone hydrazone methods give brilliant colors. For some of the phenols phthalaldehyde gives brilliant yellow or orange fluorescence colors. With the help of separation and location techniques and fluorimetric examination of methanolic and alkaline solutions the following phenols were identified in coal-tar-pitch: 1-naphthol, 2-naphthol, 2-hydroxybiphenyl, 4-hydroxybiphenyl, 2-fluorenol, 3-fluorenol, 2-hydroxydibenzofuran and 2-hydroxycarbazole. 2-Fluorenol was also found in a particulate sample from Manhattan (New York City) air. In addition, a large number of unidentified fluorescent spots, characterized as phenols, were found in coal-tar-pitch and various airborne particulate samples from urban areas.

---

Zusammenfassung Die Dünnschichtchromatographie, die Niederspannungs- und Hochspannungselektrophorese einer großen Anzahl von cyklischen und heterooyklischen Phenolen und deren Lokalisierung wurde beschrieben.Besonders mit o-Phthalaldehyd und mit 3-Methyl-2-benzothiazolinonhydrazon erhält man leuchtende Farben. Mit manchen Phenolen gibt Phthalaldehyd ein leuchtendes Gelb oder orange Fluoreszenz. Durch Trennung, Lokalisierung und fluorimetrische Prüfung methanolischer und alkalischer Lösungen wurden folgende Phenole in Kohlenteerrückständen nachgewiesen:-Naphthol,-Naphthol, 2-Hydroxydiphenyl, 4-Hydroxydiphenyl, 2-Fluorenol, 3-Fluorenol, 2-Hydroxydibenzofuran und 2-Hydroxycarbazol. 2-Fluorenol wurde auch in einer Luftprobe von Manhattan (N. Y.) gefunden. Außerdem wurden zahlreiche fluoreszierende, aber nicht näher identifizierte Flecken bei der Aufarbeitung von Kohlenteerrückständen und verschiedenen Luftproben gefunden, die von Phenolen herrühren.

     

Multi-element analysis of manganese nodules by atomic absorption spectrometry without chemical separation

Five manganese nodules, including the USGS reference nodules A-1 and P-1, were analyzed for Co, Cu, Fe, K, Mg, Mn, Na, Ni and Zn without prior chemical separation by using a simultaneous multi-element atomic absorption spectrometer with an air—cetylene flame. The nodules were prepared in three digestion matrices. One of these solutions was measured using sixteen different combinations of burner height and air/acetylene ratios. Results for A-1 and P-1 are compared to recommended values and results for all nodules are compared to those obtained with an inductively coupled plasma. The elements Co, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn are simultaneously determined with a composite recovery for all elements of 100 ± 7%, independent of the digestion matrices, heights in the flame, or flame stoichiometries examined. Individual recoveries for Co, K, and Ni are considerably poorer in two digests than this composite figure, however. The optimum individual recoveries of 100 ± 5% and imprecisions of 1–4%, except for zinc, are obtained when Co, K, Mn, Na and Ni are determined simultaneously in a concentrated digest, and in another analytical sequence, when Cu, Fe, Mg, Mn and Zn are measured simultaneously after dilution. Determination of manganese is equally accurate in the two sequences; its measurement in both assures internal consistency between the two measurement sequences. This approach improves analytical efficiency over that for conventional atomic absorption methods, while minimizing loss of accuracy or precision for individual elements.     

Study on chemical species of inorganic elements in some marine algae by neutron activation analysis combined with chemical and biochemical separation techniques

The compositional changes of inorganic elements on freshwater leaching of 35 species of Chinese algae were studied by the determination of the element contents in marine algae using instrumental neutron activation analysis. It was found that alkali metals and chlorine mainly exist as ions in algae, in which, water-soluble K and Na exist as chlorides. While, other elements exist as the states of both ions and organic combination in which the water leaching ratios of alkaline earth metals are the lowest. The combination of trace elements with various organic macromolecules inSargassum kjellmanianum was also studied using neutron activation analysis combined with chemical and biochemical separation techniques. The results indicate that the concentration of many trace elements, such as Zn, Fe, Sc, Th are earths in protein are quite high, and some trace elements can also be combined by pigment and polyphenol. Alkaline earth metal mainly bind with alginic acid inSargassum kjellmanianum.     

Identification of unknown nuclear reaction products using gas phase separation and chemical pattern analysis

A method for the fast separation of short-lived nuclides in the gas phase is described. The attribution of new γ-lines to a certain element is possible by the variation of the chemical and physical separation parameters and the determination of the “yield” of a line, compared with the “yields” of well known nuclides.     

Gas chemical methods for the separation of elements in radioisotope production and activation analysis

Summary Liquid-liquid extraction is used for one-atom-at-a-time separations of transactinide elements from heavy-ion reaction product mixtures. It is suitable for this purpose because it is fast, provided that a chemical system with negligible kinetics is used, and it can be used for continuous separations. It is, however, not quite easy to determine the uncertainties of the measured distribution coefficients or complex formation constants. In this paper methods for such estimates will be discussed.