Energy and exergy analysis and optimization of a gas turbine cycle coupled by a bottoming organic Rankine cycle

Journal of Thermal Analysis and Calorimetry - In this study, the numerical analysis of energy and exergy has been performed for a gas turbine cycle coupled with an ORC cycle. Validation of current...     

Design and analysis of a hybrid concentrated photovoltaic thermal system integrated with an organic Rankine cycle for hydrogen production

Journal of Thermal Analysis and Calorimetry - Solar is one of the most promising energy sources because of the abundance of solar radiation in certain parts of the world. One of the main limiting...     

Techno-economic analysis of new integrated system of humid air turbine,organic Rankine cycle,and parabolic trough collector

Journal of Thermal Analysis and Calorimetry - Microgas turbines are one of the most well-known technologies for distributed generation. Unfortunately, their efficiency is not as high as it should...     

Thermodynamic analysis of waste heat recovery from hybrid system of proton exchange membrane fuel cell and vapor compression refrigeration cycle by recuperative organic Rankine cycle

Journal of Thermal Analysis and Calorimetry - According to day-by-day consumption increase, energy high costs and nonrenewable energy destroying effects, clean technologies such as fuel cells lead...     

Exploration and optimization of conditions for quantitative analysis of lignans in Schisandra chinensis by an online supercritical fluid extraction with supercritical fluid chromatography system

An online supercritical fluid extraction with supercritical fluid chromatography system could provide sequential extraction and quantitative analysis of lignans in Schisandra chinensis. Supercritical fluid extraction conditions were optimized at 15 MPa, 50°C, and 4 min with supercritical CO₂ adding 1% methanol; the elution volume and flow rate were set at 6 mL and 2 mL/min to blow extract out of the tank completely. The split‐flow rate was confirmed at 2.5%, which determines injection volume and accuracy of quantitative detection. The factors having negative influences on supercritical fluid chromatography retention in the online system, including sample loading forms and backpressure settings, are discussed in the paper. At last, an extraction‐quantitative method for lignans in Schisandra chinensis was developed, which could be finished within 19.5 min. The total content percentage of four lignans (Schisandrin, Schisandrin A, Schisandrin B and Schisandrol B) in four batches was respectively measured to be 1.42, 1.54, 1.62, and 1.90%.     

Simultaneous voltammetric determination of dopamine and ascorbic acid at an electrode modified with the gold-palladium binary system

The catalytic activities of gold, palladium, and rhodium particles and their binary systems electrodeposited on the surface of a glassy-carbon electrode in the oxidation of dopamine and ascorbic acid are compared. As compared to individual noble metals, the Au-Pd binary system exhibits a higher catalytic activity that manifests itself in a multiple increase in the oxidation current of the mediator and in a decrease in the oxidation potential of the substrate. It is found that dopamine and ascorbic acid can be simultaneously determined by voltammetry at an electrode modified with the Au-Pd binary system. The catalytic currents of substrate oxidation are linear functions of the concentrations in the ranges from (1 × 10^?3 to 1 × 10^?7) M for dopamine and from (5 × 10^?3 to 1 × 10^?6) M for ascorbic acid.     

Development and optimization of organic acid analysis in tobacco with ion chromatography and suppressed conductivity detection

With the aid of a central composite face-centered design, an ion chromatographic method was developed and optimized for analyzing organic acids in tobacco. A Dionex-100 ion chromatograph with an ion suppressor and a conductivity detector, and a Bio-Rad Aminex HPX-87H column were employed. Only 13 analyses were required to optimize two factors: column temperature and eluent strength. Two sets of optimal conditions for separating nine acids were found: 1.8 mM HFBA eluent and 42 °C column temperature, and 0.8 mM HFBA eluent and 50 °C column temperature. The flow-rate was 0.6 ml min⁻¹ and the analysis time was 18 min or less. A sample preparation procedure included extraction of 2 g ground tobacco with 100 ml of 5 mM sulfuric acid solution for 3 h, filtration of the extract, and dilution of the filtrate 10-fold with deionized water.     

Partitioning of organic solutes between the micellar and the aqueous phase as studied with an artificial kidney

The partitioning of $\text{p}$-nitrophenyl acetae and of $\text{p}$-methylphenylsulfonylmethyl methanesulfonate into CTAB micelles in aqueous solution has been quantitatively investigated by means of a Cordis Dow C-Dak 1.30 artificial kidney.     

Comparative analysis and multi-criteria optimization of a supercritical recompression CO2 Brayton cycle integrated with thermoelectric modules

Journal of Thermal Analysis and Calorimetry - Regarding the high expense of the exploiting energy from energy resources, each innovation or modification on the energy systems with the aim of...     

Thermodynamics of binary mixtures containing organic carbonates Part XI. SLE measurements for systems of diethyl carbonate with long n-alkanes: comparison with DISQUAC and modified UNIFAC predictions

Using the available interaction parameters for organic carbonate+alkane mixtures the ability of the DISQUAC and modified UNIFAC group contribution model to predict solid–liquid equilibria (SLE) is investigated. Six sets of the SLE temperatures for diethyl carbonate+n-alkane (octadecane, eicosane, docosane, tetracosane, hexacosane, octacosane) systems have been measured by a dynamic method from 278.65 K to the melting point of the long chain n-alkane. The data have been correlated by three equations: Wilson, UNIQUAC and NRTL. The existence of a solid–solid first-order phase transition in n-alkanes has been taken into consideration in the solubility calculations. The relative standard deviations of the solubility temperature correlation for all measured data vary from 0.31 to 0.34 K and depend on the particular equation used.

The SLE curves are usually well predicted by DISQUAC and modified UNIFAC models with average standard deviation of <1.35 K.     

Analysis of performance of an anaerobic sequencing batch reactor submitted to increasing organic load with different influent concentrations and cycle lengths

The performance of an anaerobic sequencing batch reactor (ASBR) was assessed when submitted to increasing organic load with different influent concentrations and cycle lengths. The 5-L mechanically stirred (75 rpm) ASBR contained 2 L of granular biomass and treated 2 L of synthetic wastewater per cycle. Volumetric organic loads (VOLs) from 0.66 to 2.88 g of chemical oxygen demand (COD)/(L x d) were applied by using influent concentrations from 550 to 3,600 mg of COD/L in 8- and 12-h cycles. Reactor stability was maintained for VOLs from 0.66 to 2.36 g of COD/(L x d), with organic matter removal efficiencies for filtered samples (epsilonF) between 84 and 88%. For VOLs from 0.78 to 2.36 g of COD/(L x d) at an influent concentration of 2,000 mg of COD/L, when cycle length was reduced from 12 to 8 h, epsilonF did not vary, yet showed a very distinct behavior from the other conditions. In addition, two operation strategies were studied for VOLs with approximately similar values of 2.36 and 2.08 g of COD/(L x d). One involved operation with an influent concentration of 2,000 mg of COD/L and an 8-h cycle, whereas the other involved an influent concentration of 2,600 mg of COD/L and a 12-h cycle. Only the former resulted in system stability and efficiency. These results indicate that besides organic load, influent concentration and cycle length play a significant role in ASBR systems.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VIII. Selectivity of the binary systems action

Selectivity of action of binary systems based on an organometallic compound and a transition metal compound in a direct synthesis of organometallic compounds via alkylation of metals with organic halides has been considered. Study of the side reactions in the course of zinc and cadmium powders alkylation (gaseous hydrocarbons evolution) taken as an example has demonstrated that the increase in activity of the binary system components is accompanied by decrease in its selectivity. The intensity of the side reactions is steeply increased above certain temperature determined by the nature of the reactants and components of the binary system. The surface of the alkylated metal containing adatoms and small clusters of the transition metal promotes the side processes.     

Development and optimization of a method for the analysis of low-molecular-mass organic acids in plants by capillary electrophoresis with indirect UV detection

Capillary zone electrophoresis was developed to analyze low-molecular-mass organic acids including oxalic, tartaric, formic, malic, citric, succinic, glutaric, acetic and lactic acid. The influences of some crucial parameters such as buffer concentration, pH value, surfactant concentration and separation temperature, on electrophoretic separation were investigated. Under the conditions of 15 mM phthalate containing 0.6 mM tetradecyltrimethylammonium bromide as the run buffer (pH 5.6); separation voltage -15 kV (-263.2 V/cm) and temperature 25 degrees C, a satisfactory separation of nine organic acids was accomplished within 7 min. The detection limits (S/N=3) ranged from 0.008 to 0.08 microg/ml and the quantification limits ranged from 0.01 to 0.1 microg/ml for electrokinetic injection. The method was successfully applied to analyze organic acids in different parts of Var splendens (an edible vegetable in China). The recoveries of organic acids in real samples ranged from 88 to 121%.     

Silica gel modified with tetraalkylammonium halides as an available and efficient catalyst for the synthesis of cyclic organic carbonates from epoxides and CO2

Russian Chemical Bulletin - Silica gel with the additives of tetraalkylammonium halides serves as an efficient catalyst for the solvent-free insertion of carbon dioxide into epoxides (10–56...     

Potentiometric microdetermination of lead(II) with an ion-selective lead electrode and its application to the analysis of organic lead compounds

Summary A method for the microdetermination of lead(II) by direct potentiometric titration with 0.0025 M sodium molybdate is described. A lead-selective indicator electrode and a double-junction reference electrode are used in conjunction with an expanded-scale pH-meter to detect the end-point. If the titrant is standardized against 1.5 mg of lead(II), accurate results are obtained for 1–2 mg of lead: the absolute error does not exceed 3gmg of lead. The relative standard deviation is 0.05%. The optimum pH for the titration is 5–5.5. In water-organic solvent mixtures the potential break at the endpoint increases, but the electrode response becomes very slow. The titration of lead is also possible in sodium nitrate and/or perchlorate media, so this titration is applicable to the microdetermination of lead in organic lead compounds after wet mineralization with HNO₃ and/or HClO₄. Chloride (up to 1000 times the lead content) and bromide (100 times) do not interfere. Iodide and sulphate interfere. Five organic lead compounds have been analysed successfully: the standard deviation of the absolute error was 0.1%.

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Zusammenfassung Ein Verfahren zur Mikrobestimmung von Blei(II) durch direkte potentiometrische Titration mit 0,0025M Natriummolybdat wurde beschrieben. Eine bleiempfindliche Indikatorelektrode und eine Bezugselektrode mit KNO₃-Zwischenelektrolyt wurde in Kombination mit einem pH-Meter mit gedehnter Skala zur Erkennung des Titrationsendpunktes verwendet. Unter Standardisierung der Maßlösung gegen 1,5 mg Blei(II) werden genaue Resultate im Bereich von 1 bis 2 mg Blei erhalten: der absolute Fehler ist innerhalb ±3g Blei. Die relative Standardabweichung beträgt 0,05%. Das günstigste pH liegt im Bereich 5–5,5. In Wasser-Aceton oder -Methanol nimmt der Potentialsprung am Äquivalenzpunkt stark zu; gleichzeitig wird jedoch das Ansprechen der Elektroden sehr langsam. Die Titration von Blei ist möglich auch in Medien von Natriumnitrat oder/und Natriumperchlorat, was die Anwendung dieser Titration auf die Bleimikrobestimmung in bleihaltigen organischen Verbindungen nach Mineralisierung auf nassem Wege mit HNO₃ oder/und HClO₄ ermöglicht. Chlorid (bis zum 1000fachen Gehalt an Blei) und Bromid (100fache Menge) stören nicht. Iodid und Sulfat stören. Fünf bleihaltige organische Verbindungen wurden erfolgreich analysiert; die Standardabweichung des absoluten Fehlers betrug 0,1%.

     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: IX. Alkylation of aluminum and concluding remarks

Study of aluminum powder alkylation with ethyl bromide in the presence of ethylaluminum sesquibromide and copper(I) iodide has revealed that binary systems based on an organometallic compound and a transition metal compound are efficient promotors of direct synthesis of organoaluminum compounds as well. Major conclusions drawn in a series of studies on non-transition metals (Zn, Cd, and Al) alkylation with organic halides in the presence of the binary systems are summarized.     

Amperometric detection of hydroxypurines at an electrode modified with a composite based on mixed-valence ruthenium and cobalt oxides in flow injection analysis

A composite material based on mixed-valence ruthenium and cobalt oxides, electrodeposited on the surface of a screen printed electrode, exhibits high catalytic activity in the electrooxidation of uric acid, xanthine, and hypoxanthine. Catalysis manifests itself as a decrease in the substrate oxidation overvoltage and an increase in current at the potential of modifier oxidation. A method is proposed for the simultaneous amperometric detection of two-component systems uric acid–xanthine, xanthine–hypoxanthine, and uric acid–hypoxanthine using a screen printed electrode with two working electrodes modified by this composite. The dependence of the analytical signal on the concentration of analytes is linear in the range 5 × 10^–8 to 5 × 10^–3 M for uric acid and xanthine and from 5 × 10^–7 to 5 × 10^–3 M for hypoxanthine.     

Promoting non-transition metal alkylation with organic halides in the presence of binary systems based on an organometallic compound and a transition metal compound: VII. Additional details of the mechanism

Mechanism of metals alkylation with an organic halide in the presence of binary systems has been defined in more detail. It has been shown that the passivating film on the surface of zinc and cadmium is partially preserved in the course of the process, and the reaction in diethyl ether is decelerated due to the competitive adsorption of the organyl halide and diethyl ether on the surface of the reacting metal. The ratelimiting stages of the studied alkylation process have been elucidated basing on the experimental data on the effect of the reagents (organyl halide and alkylated metal) nature on the rate of the steady-state reaction and modeling of the suggested catalytic cycle.