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PL
W pracy zbadano kinetykę przemiany przechłodzonego austenitu trzech stali typu TRIP(Transformation Induced Plasticity), o zróznicowanym stężeniu węgla w zakresie 0,076-0407%. Dla temperatury końca walcowania równej temperaturze Ac3+50stopniC zaproponowano przebiegi chłodzenia pasma blachy optymalne z punktu widzenia uzyskiwanych wasności wytrzymałościowych i plastycznych, wskutek przemiany metastabilnego mechanicznie austenitu nieprzemienionego. Podstawą technologii obróbki cieplnej stali typu TRIP dla walcowni gorącej blach były temperatury krytyczne Ms, Ac3 i Ar1k oraz krytyczne szybkości chłodzenia, ustalone na podstawie wykonywanych wykresów CTPc.
EN
The kinetic of over-cooled austenite of three kind of tRIP steels were investigated. As a main difference in chemical composition was carbon concentrion 0,076-0,407%. Fox fixed temperature of finish rolling Ac3+50stopniC the suitable cooling rates were proposed. It was designed to get optimum mechanical properties and ductility of dhit strips. It can be achived as a result of phase transformation of metastabe austenite. The heat treatment of these TRIP steels designed due to critical temperatures (Ms, Ac3 and Ar1k) and to critical cooling rates which were established using TTc diagrams.
PL
W pracy zamieszczono wykresy CTPc dwóch nowych stali martenzytyczno-bainitycznych i jednego staliwa ledeburytycznego, przeznaczonych na walce do walcowania na gorąco. Cechą charakterystyczną nowych stali jest ich wielka hartowność. Umożliwia ona uzyskanie w walcach o średnicy 1300 mm chłodzonych w powietrzu, struktury złożonej z martenzytu i bainitu dolnego na głębokości do 350 mm. Stwarza to możliwość osiągnięcia wielkich wytrzymałości i odporności na pękanie równoeż w walcach bruzdowych. Dla jednej z nowych stali zbadano wpływ temperatury austenityzowania na kinetykę przemian fazowych przechłodzonego austenitu. W przypadku staliwa wykazano natomiast brak wpływu temperatury austenityzowania na kinetyke przemian przechłodzonego austenitu. Wykresy te mogą być wykorzystane do optymalizacji obróbki cieplnej tego gatunku staliwa, dla zwiększenia jego odporności na pękanie.
EN
In the paper two CCT diagrams of new martensitic-bainitic steels and one ledeburitic cast steel intended for rools for hot rolling are published. The characteristic feature of new steels is their graet hardenability. It enables getting in 1300 mm diameter rolls cooled in air, the structure consisting of martensite and lower bainite at the bainite at the depth up to 350 mm. This creates the possibility of getting great strength and fracture toughness also in shaped rolls. The influence of austenitizing temperature on the kinetics of phase transformations of overcooled austenite was researched for one of new steels.However, in the case of ledeburitic cast steel lack of austenitizing temperature's influence on the kinetics of transformations of the overcooled austenite has been proved. These diagrams, can be used to optimise heat treatment of this kind of ledeburitic cast steel to increase its fracture toughness.
EN
The oxidation kinetics of diphenyl, dialkyl and methyl phenyl sulphides has been investigated under pseudo-first-order conditions with quinolinium fluorochromate (QFC), a newly developed Cr(VI) reagent in acetonitrile medium. p- Toluene sulphonic acid (TsOH) is used for catalyzing the reaction. Initial-rate methods are used for determining the orders with respect to reactants in dialkyl sulphides. The oxidation is first-order with respect to [QFC] and second-order dependence is observed on [TsOH]. [Sulphide] has no effect on the reaction rate. Diphenyl sulphide (DPS) oxidation follows the rate law, v = k2Rrl [S][Ox][TsOH]. Acrylonitrile retards the rate of oxidation significantly in diphenyl sulphides indicating the involvement of free radical cation sulphur intermediate in the rate-limiting step. The Michaelis-Menten dependence each on [sulphide] and [TsOH] can be well explained by a two-pathway mechanism in methyl phenyl sulphide oxidation. The derived rate law, v = k1[Ox][TsOH] -+ k3[OX][S] is consistent with experimental observations.
4
Content available remote CFD analysis of mixing intensity in jet stirred reactors
100%
EN
The homogeneous stirred reactor designed for kinetic studies of the combustion of hydrocarbons with intensive internal recirculation in high temperature combustion chamber is described. The originality of our reactor lies in its construction which allows to intensively mix fuel and flue gases, measure gas temperature as well as obtain samples which can be used to investigate diffusion flames. The cylindrical construction enables to use the reactor in laboratory cylindrical electrically heated ovens. The CFD analysis of the reactors, the mixing parameters (turbulent Peclet number and mixing level) and the volume average temperature in the reactors were elaborated on the basis of the typical dimensions of classical reactors to kinetics research as well as the own reactor design. The results of the analysis allow to reveal advantages of our construction.
EN
A pseudo-second order rate equation describing the kinetics of the adsorption of 1,2-dichloropropane from aqueous solution onto the activated carbon at different initial concentrations, adsorbent dose, temperature, particle diameter and the rate of stirring have been developed. The rate constant was calculated. The rate constant correlation in a good mixing conditions was described as a function of the temperature.
EN
Coal flotation is a complex multiphase process governed by different sub-processes and interphase interactions. The coal cleaning efficiency by flotation is largely affected by many different physical and chemical factors that can be roughly classified into three main group: coal feed properties, pulp chemical and rheological properties, and machine and operational properties. A great number of flotation kinetic model have been proposed in literature but a vast majority uses three parameters to describe the flotation kinetics, which are the ultimate recovery, the flotation rate constant, and flotation time. The models expand on the classical theory of flotation proposed by Zuniga (1935) that is based on the assumption that the particle–bubble collision rate is first-order with respect to the number of particles in the system, while bubble concentration remains constant. The flotation rate constant is directly proportional to available bubble surface area and probability of flotation, which is strongly dependent on particle size. Therefore, particle size is one of the most important parameters in coal flotation because it affects gas bubble mineralization and froth stability, bubble size distribution and air holdup, bubble-particle collision, attachment, and detachment rates, and reagent adsorption. Numerous researchers have studied the effect of particle size on flotation kinetics over years. This paper provides a comprehensive review of coal flotation kinetics models with a special focus on the effect of particle size on coal kinetic rate, recovery, and product quality. A particular emphasis will be put on research findings reported over the last three decades.
EN
Glutathione reductase (GR, E.C 1.6.4.2) is a flavoprotein that catalyzes NADPH-dependent reduction of oxidized glutathione (GSSG) to reduced glutathione (GSH). The aim of this study was to investigate in vitro effects of phenolic compounds isolated from Sideritis brevibracteata on bovine kidney GR. The Sideritis species are widely found in nature and commonly used as medicinal plants. 7-O-glycosides of 8-OH-flavones (hypolaetin, isoscutellarein and 3'-hydroxy-4'-O-methylisoscutellarein) were isolated from aerial parts of Sideritis brevibracteata. These compounds inhibited bovine kidney cortex GR in a concentration-dependent manner. Kinetic characterization of the inhibition was also performed.
EN
Ethylene diamine phosphate (EDP), as a synthetic organic reagent, was used for the first time to leach malachite, and a new method of using organic amine to leach copper oxide ore was developed. The effects of stirring speed, particle size, reagent concentration, and reaction temperature on EDP-dissolution malachite were investigated. Results showed that malachite rapidly dissolved in EDP solution. The malachite-dissolving rate also increased with increased reagent concentration, increased reaction temperature, and decreased particle size. Stirring speed exhibited nearly no effect on EDP-induced malachite dissolution. The leaching kinetics was found to follow the shrinking-core model, and dissolution was controlled by surface chemical reaction with an activation energy of 52.63kJ×mol−1. A semiempirical rate equation was obtained to describe the dissolution process expressed as 1-(1-XCu)1/3=0.0149(CEDP)0.7814 × (Pmalachite)−0.7982×exp(−6.3308/T) ×t.
9
Content available Adsorption of penicillin by decaffeinated tea waste
88%
EN
Removal of penicillin has been investigated using decaffeinated tea waste (DCTW). Decaffeination of tea waste was investigated using different methods. Results indicate that ozonation was the most effective process for removal of penicillin. Batch adsorption experiments were completed at various temperatures (20, 30, and 40°C), DCTW dosages (2, 4, 6, 8, and 10 g per 250 mL), penicillin concentrations (4, 10, and 14 mg/L), and pH (3, 7, and 10) conditions. Studies showed that adsorption reaches equilibrium within 40 min. The main factor affecting adsorption of penicillin was the solution pH, with maximum adsorption occurring at pH 3. Higher adsorbent dosages and lower penicillin concentrations also resulted in higher percentages of penicillin removal. Results show that data obeyed the pseudo-first-order kinetic and Freundlich isotherm models. This process proves that low-cost DCTW could be used as a high performance adsorbent for removing penicillin from aqueous solutions.
EN
Dyeing operations in industries like textiles, paper, and leather are significant contributors to environmental pollution due to the release of harmful dyes. The current study aimed to examine the use of oil palm trunk (OPT) treated with phosphoric acid (PAOPT) to remove malachite green (MG) dye from aqueous solutions through batch adsorption experiments. Spectroscopic and quantitative tests were used to characterise the PAOPT adsorbent. The effects of initial solution pH (3–6), PAOPT dosage (0.02–0.10 g), and adsorption duration (0–120 min) were studied. The adsorption rate of MG followed a pseudo-second-order kinetic model with a high regression correlation (R2 ) and a low chi-squared value (χ2 ). The single-layer adsorption of PAOPT for MG was determined to be 217.23 mg/g at a pH of 6, 0.02 g PAOPT mass, 20 min contact time, and 298 K. The percentage of MG desorption from the loaded PAOPT using distilled water and 0.01 M HCl was 0% and 19.65%, respectively, indicating the possible involvement of electrostatic interactions between the dye and PAOPT, π-π interaction and hydrogen bonding. The experimental results of the current study and the assessment with other stated adsorbents indicate that PAOPT could be used as a cost-effective alternative adsorbent for MG removal.
EN
The [2+3] cycloaddition of triphenylnitrone to trans-1-nitroprop-1-ene proceeds according to concerted mechanism, in spite of pi-deficient character of dipolarophile and strongly shielded one of the reaction centers in molecule of 1,3-dipole. This mechanism is indicated by the obtained values of activation parameters and weak kinetic solvent effect.
12
Content available remote Adsorption of penicillin by decaffeinated tea waste
88%
EN
Removal of penicillin has been investigated using decaffeinated tea waste (DCTW). Decaffeination of tea waste was investigated using different methods. Results indicate that ozonation was the most effective process for removal of penicillin. Batch adsorption experiments were completed at various temperatures (20, 30, and 40°C), DCTW dosages (2, 4, 6, 8, and 10 g per 250 mL), penicillin concentrations (4, 10, and 14 mg/L), and pH (3, 7, and 10) conditions. Studies showed that adsorption reaches equilibrium within 40 min. The main factor affecting adsorption of penicillin was the solution pH, with maximum adsorption occurring at pH 3. Higher adsorbent dosages and lower penicillin concentrations also resulted in higher percentages of penicillin removal. Results show that data obeyed the pseudo-first-order kinetic and Freundlich isotherm models. This process proves that low-cost DCTW could be used as a high performance adsorbent for removing penicillin from aqueous solutions.
EN
The study was aimed to determine the hydrodynamic of water seepage through a porous bed saturated with different amounts of high viscosity liquids. An attempt was made to describe the process of seepage through beds saturated with oils using the theory of outflow of a liquid from the tank. It was assumed that the discharge coefficient will represent changes of flow resistance during the process. It was found that the dependence of this factor on time is linear. In the second part of this work kinetics of the seepage process was investigated. Dependence of oil concentrations, eluted from the deposit with the flowing water, on time has been evaluated. Thanks to these studies it was possible to determine the effectiveness of an elution of high viscosity liquids from porous beds using water as the washing out liquid.
EN
The textile industry is very important because its products are widely used by society, however, this activity has a great contribution to the contamination of water resources due to its effluents that contain large amounts of colorants, among which is the blue of methylene (MB) and methyl orange (MO) that can cause damage to the health of living being. For this reason the present study concerned the removal of these dyes by adsorption using Eichhornia Crassipes (Water lily) with different treatments. The results show that the chemisorption removal process using two sites per dye molecule having an exothermic nature for the water-treated lily and for the NaOH-treated lily is endothermic. The maximum adsorption capacities of 228.9 mg/g for MB (60 °C) and 155.38 mg/g (30 °C) for MO with the NaOH treatment were achieved. The SEM analysis shows that there are significant changes in the surface due to the treatments. The XRD patterns indicate that with the pretreatment with NaOH the crystallinity of WL increases while the treatment with water maintains the presence of amorphous cellulose. In the FTIR spectra, the bands corresponding to different functional groups such as lignin, cellulose and hemicellulose that participate in the adsorption of both dyes are observed.
EN
The catalytic epoxidation reaction of 1-octene with tert-butyl hydroperoxide in the presence of disilicides MoSi2,WSi2, VSi2, TiSi2, TaSi2 and HfSi2 was studied. The kinetics of this process in the presence of themost effective catalystMoSi2 was investigated. The effect of reactant and reaction product concentrations on the process catalyzed by MoSi2 was examined. The kinetic scheme was proposed and the kinetic parameters of the process were calculated. The equation for the reaction rate as well as the equation that connects the current concentrations of hydroperoxide with the reaction time and allows to calculate the theoretical kinetic curves for tert-butyl hydroperoxide consumption were derived.
16
75%
EN
In this study a possibility of obtaining sorbents from basketry wastes has been investigated. Therefore, adsorption of cadmium ions on wicker bark of Salix americana has been studied. The obtained experimental results were described by the Freundlich equation and adsorption kinetics by the pseudo-second order equation. The effect of pH on cadmium ions adsorption by S. americana was also investigated. It has been found that for the pH values ranging from 2 to 7 cadmium removal from the solution was held at almost constant level.
Karbo
|
2002
|
tom Nr 9
272-275
EN
Paper present the influence of pressure on the kinetics of NO, N(2)O and N(2) emission during char combustion. A heterogeneous NO and N(2)O formation and destruction mechanism is presented in a form suitable for modelling in broad range of char combustion conditions. The reaction rate constants of the kinetic equations were found to be independent of the combustion pressure. The model was verified on basis of experiments in a pressurised combustor, up to 1,5 MPa. It has been found that the conversion of char-N into NO decreases, while into N(2)O increases with the total combustion pressure, that is reproduced well by the heterogeneous mathematical model.
PL
Ciśnieniowe techniki spalania węgla są zaliczane do przyszłościowych czystych technologii węglowych, umożliwiających obniżenie przede wszystkim emisji dwutlenku węgla w rezultacie wzrostu sprawności procesu. Publikowane badania wskazują również na możliwość obniżenia emisji tlenków azotu NO(x) i tlenku węgla CO z komór spalania. W publikacji zebrano niezbędne informacje do modelowania emisji NO, N(2)O i N(2) podczas spalania karbonizatów przy podwyższonym ciśnieniu w celu zwiększenia dokładności opisu mechanizmu tworzenia tlenków azotu. Przedstawiono wpływ ciśnienia na kinetykę tworzenia i rozpadu NO i N(2)O z azotu zawartego w paliwie. Eksperymenty spalania prowadzono w ciśnieniowym reaktorze, w atmosferze 21% O(2) w He, przy ciśnieniu roboczym do 1,5 MPa dla karbonizatu ze wzbogaconego węgla SIERSZA o ziarnistości 0,9 mm. W trakcie badań zaobserwowano, że ze wzrostem całkowitego ciśnienia spalania konwersja azotu paliwowego do NO spada, natomiast konwersja do N(2)O wzrasta, co jest dość dobrze opisane poprzez matematyczny model spalania.
20
75%
EN
The homogeneous stirred reactor designed for kinetic studies of the combustion of hydrocarbons with intensive internal recirculation in high temperature combustion chamber is described. The originality of our reactor lies in its construction which allows to intensively mix fuel and flue gases, measure gas temperature as well as obtain samples which can be used to investigate diffusion flames. The cylindrical construction enables to use the reactor in laboratory cylindrical electrically heated ovens. The CFD analysis of the reactors, the mixing parameters (turbulent Peclet number and mixing level) and the volume average temperature in the reactors were elaborated on the basis of the typical dimensions of classical reactors to kinetics research as well as the own reactor design. The results of the analysis allow to reveal advantages of our construction.
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