scholarly journals Thermodynamic modelling of roasting of molybdenum sulphide concentrate with calcium hydroxide

2022 ◽  
Vol 25 (6) ◽  
pp. 773-781
Author(s):  
D. S. Aleshin ◽  
A. G. Krasheninin ◽  
P. V. Zaitseva ◽  
I. N. Tanutrov
Keyword(s):  
Calcium Hydroxide ◽  
Thermodynamic Modelling ◽  
Effect Of Temperature ◽  
Molar Ratio ◽  
Temperature Range ◽  
Gaseous Products ◽  
System Pressure ◽  
Mass Ratios ◽  
Process Operation ◽  
Molybdenum Concentrate

This work aims to determine the conditions for the CaMoO4, CaSO4, Ca(ReO4)2 formation during oxidation of MoS2 and ReS2 in the presence of Ca(ОН)2. The concentrate from the Yuzhno-Shameyskoye deposit in the Sverdlovsk region, having 37% wt. Мо and 0.005% wt. Re, was selected as a feedstock for thermodynamic modelling of sweet roasting in the presence of Ca(OH)2. To determine the optimal amount of calcium-containing additives, the thermodynamic modelling was carried out using the following mass ratios: molybdenum concentrate: Ca(OH)2 = 1:0.8, 1:1, 1:1.2 and 1:1.5 in the temperature range of 100–800°С, with a step of 100°С, system pressure of 0.1 MPa in the air (molar ratio: molybdenum concentrate + Ca(OH)2: air = 1:5). The content of all sample components in moles was entered into the HSC 6.1 software package. The main reactions associated with the sweet roasting of molybdenum concentrate in the presence of calcium hydroxide were shown. It was established that the main phases formed as a result of roasting comprise CaSO4, CaSO3, MoO3, CaMoO4, CaMoO3 and CaReO4. The effect of temperature on the formation of the main gaseous products was studied under different mass ratios of molybdenum concentrate and Ca(OH)2. It was found that up to 600°C, with molybdenum concentrate to Ca(OH)2 ratio of 1:1, the concentrations of released sulphurous anhydride are lower than the maximum permissible concentrations. The calculated thermodynamic data was used for modelling the roasting process of molybdenum concentrate with calcium hydroxide. An optimal ratio necessary for the successful process operation was established: molybdenum concentrate: Ca(OH)2 = 1:1 by weight. Thermodynamic modelling showed that, in the temperature range of 100–600°С when using Ca(OH)2, no rhenium and molybdenum loss is observed, the release of sulfur is less than 10 mg/m3.

Reaction Synthesis of Cr2AlC Ceramics Powders

2012 ◽  
Vol 624 ◽  
pp. 13-16
Author(s):  
Chun Long Guan ◽  
Zi Ping Zhang ◽  
Ying Chun Shan ◽  
Chun Hua Wang
Keyword(s):  
Effect Of Temperature ◽  
Molar Ratio ◽  
Reaction Synthesis ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Solid Reaction ◽  
X Ray ◽  
Temperature Range

Polycrystalline Cr2AlC was fabricated by a solid reaction synthesis of a mixture of Cr, Al and graphite powders in a flowing or the atmosphere in the temperature range of 700 to 1450 °C. The products for identification and analysis were characterized by X-ray diffraction (XRD). The effects of the composition of the initial elemental powders and temperature of purity and formation of Cr2AlC were examined. It is found that the co-existence of Cr7C3 with Cr2AlC is attributed to the surplus of carbon in the starting powders at 1350 °C, selecting the starting materials with a Cr: Al: C molar ratio of 2: (1.1-1.6): 1. For sample obtained from the starting elemental powders with the Cr: Al: C molar ratio of 2: 1.2: 0.94, no other phases but Cr2AlC were detected. In addition, the effect of temperature on the formation of Cr2AlC ceramic powders was carried out.

Acetylene chemisorption at palladium: Effect of temperature and structure of the surface

1984 ◽  
Vol 49 (6) ◽  
pp. 1448-1458
Author(s):  
Josef Kopešťanský
Keyword(s):  
Work Function ◽  
Atomic Hydrogen ◽  
Effect Of Temperature ◽  
Thermally Stable ◽  
Template Effect ◽  
Temperature Range ◽  
Adsorbed Layers ◽  
Different Types ◽  
Adsorption Complexes ◽  
Low Coverage

The effect of temperature and structure of the palladium surfaces on acetylene chemisorption was studied along with the interaction of the adsorbed layers with molecular and atomic hydrogen. The work function changes were measured and combined with the volumetric measurements and analysis of the products. At temperature below 100 °C, acetylene is adsorbed almost without dissociation and forms at least two different types of thermally stable adsorption complexes. Acetylene adsorbed at 200 °C is partly decomposed, especially in the low coverage region. Besides the above mentioned effects, the template effect of adsorbed acetylene was studied in the temperature range from -80° to 25 °C. It has been shown that this effect is a typical phenomenon of the palladium-acetylene system which is not due to surface impurities.

scholarly journals Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

2021 ◽  
Author(s):  
Nico Vogler ◽  
Philipp Drabetzki ◽  
Mathias Lindemann ◽  
Hans-Carsten Kühne
Keyword(s):  
Calcium Hydroxide ◽  
Bound Water ◽  
Reference Method ◽  
Microscopic Analysis ◽  
Limestone Powder ◽  
Gravimetric Analysis ◽  
Sample Material ◽  
Accelerated Carbonation ◽  
Temperature Range ◽  
Carbonation Process

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation – co-precipitation method

2020 ◽  
Vol 18 (5-6) ◽  
Author(s):  
Buyan-Ulzii Battulga ◽  
Tungalagtamir Bold ◽  
Enkhsaruul Byambajav
Keyword(s):  
Synergetic Effect ◽  
Space Velocity ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Molar Ratio ◽  
Alumina Support ◽  
Co Methanation ◽  
Temperature Range ◽  
Co Precipitation ◽  
Catalyst Distribution

AbstractNi based catalysts supported on γ-Al2O3 that was unpromoted (Ni/γAl2O3) or promoted (Ni–Fe/γAl2O3, Ni–Co/γAl2O3, and Ni–Fe–Co/γAl2O3) were prepared using by the impregnation – co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H2/CO = 3 and in the temperature range between 130 and 350 °C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni–Co/γAl2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 °C). The temperatures for the 20% CO conversion over Ni–Co/γAl2O3, Ni–Fe/γAl2O3, Ni–Fe–Co/γAl2O3 and Ni/γAl2O3 catalysts were 205, 253, 263 and 270 °C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of β type nickel species which had an appropriate interacting strength with alumina support in the Ni–Co/γAl2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni–Fe/γAl2O3. Moreover, it was found that there was no synergetic effect from the binary Fe–Co promotors in the Ni–Fe–Co/γAl2O3 on catalytic activity for CO methanation.

Densities and molar volumes of the Ca(NO3)2-CaBr2-H2O system

1980 ◽  
Vol 45 (1) ◽  
pp. 17-20 ◽  
Author(s):  
Zdeněk Kodejš ◽  
Ivo Sláma
Keyword(s):  
Calcium Nitrate ◽  
Molar Ratio ◽  
Molar Volumes ◽  
Temperature Range

Molar volumes and densities of mixtures consisting of water, calcium nitrate, and calcium bromide have been determined in the range of molar ratio of water within 3 to 18 and in the temperature range of 20 to 80° C. The obtained results have been described by an equation derived under the assumption that additivity of molar volumes of the components is valid.

scholarly journals Konsentrasi Katalis dan Suhu Optimum pada Reaksi Esterifikasi menggunakan Katalis Zeolit Alam Aktif (ZAH) dalam Pembuatan Biodiesel dari Minyak Jelantah

2013 ◽  
Vol 14 (3) ◽  
pp. 219 ◽  
Author(s):  
Dwi Kartika ◽  
Senny Widyaningsih
Keyword(s):  
Physical Properties ◽  
Natural Zeolite ◽  
Oil And Gas ◽  
Catalyst Concentration ◽  
Waste Cooking Oil ◽  
Effect Of Temperature ◽  
Molar Ratio ◽  
Cooking Oil ◽  
Biodiesel Synthesis ◽  
Directorate General

Transesterification of waste cooking oil into biodiesel using KOH catalyst with and without esterification process usingactivated natural zeolite (ZAH) catalyst has been carried out. Activation of the zeolite was done by refluxing with HCl 6Mfor 30 min, followed calcining and oxydized at 500oC for 2 hours, consecutively. The transesterification without esterificationprocess were done using KOH catalyst 1% (w/w) from oil and methanol weight and oil/methanol molar ratio 1:6 at 60oC. Theesterification reaction was also done using ZAH catalyst then continued by transesterification using KOH catalyst inmethanol media. In order to study the effect of ZAH catalyst concentration at constant temperature, the catalysts werevaried, i.e. 0, 1, 2, and 3% (w/w). To investigate the effect of temperature, the experiments were done at various temperaturefrom 30, 45, 60, and 70oC at constant catalyst concentration. The conversion of biodiesel was determined by 1H-NMRspectrometer and physical properties of biodiesel were determined using ASTM standard methods. The results showedthat the transesterification using KOH catalyst without esterification produced biodiesel conversion of 53.29%. The optimumcondition of biodiesel synthesis via esterification process were reached at 60oC and concentration of ZAH catalyst of2% (w/w), that could give biodiesel conversion = 100.00%. The physical properties were conformed with biodiesel ASTM2003b and Directorate General of Oil and Gas 2006 specification.

THE EFFECT OF TEMPERATURE ON THE RATE AND VARIATION OF OPERCULAR MOVEMENT IN FUNDULUS DIAPHANUS DIAPHANUS

1947 ◽  
Vol 25d (2) ◽  
pp. 91-95
Author(s):  
Benjamin N. Kropp
Keyword(s):  
Constant Temperature ◽  
Beat Frequency ◽  
Nervous Activity ◽  
Respiratory Movement ◽  
Effect Of Temperature ◽  
Temperature Range ◽  
Sources Of Variation ◽  
Fundulus Diaphanus

The rates of opercular beat of 16 specimens of Fundulus diaphanus diaphanus were recorded over a temperature range from 4.3° to 17.5 °C. in order to determine how this respiratory movement varied with temperature and some of the sources of variation in rate. While the rate of beat varies directly as the temperature, over a period of several hours at any constant temperature continuous recordings of the rate show recurring cycles of rise and fall in beat frequency that are chiefly responsible for the scatter of the observations. Both the duration of a cycle and the limits of rise and fall for each cycle are definitely set by the temperature. The possible dependence of these phenomena upon central nervous activity is discussed.

Mitochondrial membrane fluorescence and temperature adaptation in Schistocephalus solidus (Cestoda: Pseudophyllidea)

Parasitology ◽  
1985 ◽  
Vol 90 (1) ◽  
pp. 131-135 ◽  
Author(s):  
R. W. Walker ◽  
J. Barrett
Keyword(s):  
Gasterosteus Aculeatus ◽  
Arrhenius Plot ◽  
Gallus Domesticus ◽  
Temperature Adaptation ◽  
Effect Of Temperature ◽  
Acclimation Temperature ◽  
Membrane Composition ◽  
Mitochondrial Membranes ◽  
Temperature Range ◽  
Schistocephalus Solidus

The fluorescent probe 1-anilino-8-naphthalene suiphonic acid (ANS) was used to investigate the effect of temperature on the physical state of the mitochondrial membranes of adult and larval schistocephalus solzdus together with that of their hosts Gasterosteus aculeatus and Gallus domesticus. Arrhenius plots of ANS/membrane fluorescence for S. solidus plerocercoids was linear over the temperature range 15 to 58 °C, while that for the adult was biphasic with a discontinuity at 39·9 °C. This was interpreted as a physical change which occurred in the adult membrane but not in the plerocercoid membrane and pointed to an alteration in membrane composition during infection. Gasierosteus aculeatus showed a linear Arrhenius plot for membrane fluorescence, irrespective of acclimation temperature. Gallus domesticus showed a discontinuity in the Arrhenius plot for membrane fluorescence at 46·9 °C, outside the normal physiological temperature range.

NQR Relaxation Studies on Halogenomethyl Groups in Halogenoacetates

1998 ◽  
Vol 53 (6-7) ◽  
pp. 480-483 ◽  
Author(s):  
Maria Zdanowska-Fnjczek
Keyword(s):  
Room Temperature ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Effect Of Temperature ◽  
Relaxation Theory ◽  
Temperature Range ◽  
Spin Lattice ◽  
Relaxation Studies

Abstract The effect of temperature on the chlorine NQR spin-lattice relaxation times in CsH(ClH2-CCOO)2 , KH(Cl3 CCOO) 2 and N(CH3)4 H(ClF2CCOO)2 has been studied in the temperature range 77 K to room temperature. The results were discussed on the basis of NQR relaxation theory.

scholarly journals Effect of Temperature, Pressure, and Chemical Composition on the Electrical Conductivity of Schist: Implications for Electrical Structures under the Tibetan Plateau

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 961 ◽  
Author(s):  
Wenqing Sun ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Changcai Liu ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
High Pressures ◽  
High Conductivity ◽  
Effect Of Temperature ◽  
The Tibetan Plateau ◽  
Temperature Range ◽  
Electrical Conductivities ◽  
Conductivity Anomalies ◽  
Lower Temperature Range ◽  
Lower Temperature

The experimental study on the electrical conductivities of schists with various contents of alkali ions (CA = K2O + Na2O = 3.94, 5.17, and 5.78 wt.%) were performed at high temperatures (623–1073 K) and high pressures (0.5–2.5 GPa). Experimental results indicated that the conductivities of schist markedly increased with the rise of temperature. Pressure influence on the conductivities of schist was extremely weak at the entire range of experimental temperatures. Alkali ion content has a significant influence on the conductivities of the schist samples in a lower temperature range (623–773 K), and the influence gradually decreases with increasing temperature in a higher temperature range (823–1073 K). In addition, the activation enthalpies for the conductivities of three schist samples were fitted as being 44.16–61.44 kJ/mol. Based on the activation enthalpies and previous studies, impurity alkaline ions (K+ and Na+) were proposed as the charge carriers of schist. Furthermore, electrical conductivities of schist (10−3.5–10−1.5 S/m) were lower than those of high-conductivity layers under the Tibetan Plateau (10−1–100 S/m). It was implied that the presence of schist cannot cause the high-conductivity anomalies in the middle to lower crust beneath the Tibetan Plateau.

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