Leaching of hemimorphite in neutral solution at high temperature

The leaching behavior of hemimorphite in neutral solution (NH4 +-Cl--H2O) was investigated at high temperature (T > 100?C) under a range of experimental conditions. Thermodynamic calculations indicate that the tendency of dehydration of silica gel is significantly enhanced with the increasing temperature. It was shown that the temperature, ammonium chloride concentration, or L/S ratio increased resulted in greater leaching efficiency. The following optimized leaching conditions were obtained: stirrer speed 400r/min, NH4Cl concentration 5.5M, L/S ratio 9mL/g at 160?C for 3h. Under these optimized conditions, the average leaching yield of zinc was 97.82%. The silicon was converted to quartz and remained in the residue. This process can be used to dispose willemite and hemimorphite as it solves the problem of silica gel dehydration.

Download Full-text

Investigation of the kinetics of spontaneous combustion of the major coal seam in Dahuangshan mining area of the Southern Junggar coalfield, Xinjiang, China

Scientific Reports ◽

10.1038/s41598-020-79223-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Li Shen ◽

Qiang Zeng

Keyword(s):

Particle Size ◽

High Temperature ◽

Coal Seam ◽

Spontaneous Combustion ◽

Heating Temperature ◽

Characteristic Temperature ◽

Mining Area ◽

Particle Sizes ◽

Coal Oxidation ◽

Increasing Temperature

AbstractIn the present paper, with using diverse methods (including the SEM, the XRD, the TPO, the FTIR, and the TGA) , the authors analysed samples of the major coal seam in Dahuangshan Mining area with different particle sizes and with different heated temperatures (from 50 to 800 °C at regular intervals of 50 °C). The results from SEM and XRD showed that high temperature and high number of pores, fissures, and hierarchical structures in the coal samples could facilitate oxidation reactions and spontaneous combustion. A higher degree of graphitization and much greater number of aromatic microcrystalline structures facilitated spontaneous combustion. The results from TPO showed that the oxygen consumption rate of the coal samples increased exponentially with increasing temperature. The generation rates of different gases indicated that temperatures of 90 °C or 130 °C could accelerate coal oxidation. With increasing temperature, the coal oxidation rate increased, and the release of gaseous products was accelerated. The FTIR results showed that the amount of hydroxide radicals and oxygen-containing functional groups increased with the decline in particle size, indicating that a smaller particle size may facilitate the oxidation reaction and spontaneous combustion of coal. The absorbance and the functional group areas at different particle sizes were consistent with those of the heated coal samples, which decreased as the temperature rose. The results from TGA showed that the characteristic temperature T3 declined with decreasing particle size. After the sample with 0.15–0.18 mm particle size was heated, its carbon content decreased, and its mineral content increased, inhibiting coal oxidation. This result also shows that the activation energy of the heated samples tended to increase at the stage of high-temperature combustion with increasing heating temperature.

Download Full-text

Purification of Eucalyptus globulus water prehydrolyzates using the HiTAC process (high-temperature adsorption on activated charcoal)

Holzforschung ◽

10.1515/hf.2011.065 ◽

2011 ◽

Vol 65 (4) ◽

Cited By ~ 15

Author(s):

Jenny Sabrina Gütsch ◽

Herbert Sixta

Keyword(s):

High Temperature ◽

Room Temperature ◽

Adsorption Process ◽

Value Added ◽

Sustainable Utilization ◽

Pulp And Paper Mills ◽

Paper Mills ◽

Charcoal Adsorption ◽

Increasing Temperature ◽

Value Added Products

Abstract The implementation of biorefinery concepts into existing pulp and paper mills is a key step for a sustainable utilization of the natural resource wood. Water prehydrolysis of wood is an interesting process for the recovery of xylo-oligosaccharides and derivatives thereof, while at the same time cellulose is preserved to a large extent for subsequent dissolving pulp production. The recovery of value-added products out of autohydrolyzates is frequently hindered by extensive lignin precipitation, especially at high temperatures. In this study, a new high-temperature adsorption process (HiTAC process) was developed, where lignin is removed directly after the autohydrolysis, which enables further processing of the autohydrolyzates. The suitability of activated charcoals as a selective adsorbent for lignin under process-relevant conditions (150 and 170°C) has not been considered up to now, because former experiments showed decreasing efficiency of charcoal adsorption of lignin with increasing temperature in the range 20–80°C. In contrast to these results, we demonstrated that the adsorption of lignin at 170°C directly after autohydrolysis is even more efficient than after cooling the hydrolyzate to room temperature. The formation of lignin precipitation and incrustations can thus be efficiently prevented by the HiTAC process. The carbohydrates in the autohydrolysis liquor remain unaffected over a wide charcoal concentration range and can be further processed to yield valuable products.

Download Full-text

Experimental Investigation of Wave Velocity-Permeability Model for Granite Subjected to Different Temperature Processing

Geofluids ◽

10.1155/2017/6586438 ◽

2017 ◽

Vol 2017 ◽

pp. 1-10 ◽

Cited By ~ 2

Author(s):

Guanghui Jiang ◽

Jianping Zuo ◽

Teng Ma ◽

Xu Wei

Keyword(s):

Particle Size ◽

High Temperature ◽

Wave Velocity ◽

Pore Fluid ◽

Rock Matrix ◽

Permeability Model ◽

Wave Velocities ◽

Before And After ◽

Different Temperatures ◽

Increasing Temperature

Understanding the change of permeability of rocks before and after heating is of great significance for exploitation of hydrocarbon resources and disposal of nuclear waste. The rock permeability under high temperature cannot be measured with most of the existing methods. In this paper, quality, wave velocity, and permeability of granite specimen from Maluanshan tunnel are measured after high temperature processing. Quality and wave velocity of granite decrease and permeability of granite increases with increasing temperature. Using porosity as the medium, a new wave velocity-permeability model is established with modified wave velocity-porosity formula and Kozeny-Carman formula. Under some given wave velocities and corresponding permeabilities through experiment, the permeabilities at different temperatures and wave velocities can be obtained. By comparing the experimental and the theoretical results, the proposed formulas are verified. In addition, a sensitivity analysis is performed to examine the effect of particle size, wave velocities in rock matrix, and pore fluid on permeability: permeability increases with increasing particle size, wave velocities in rock matrix, and pore fluid; the higher the rock wave velocity, the lower the effect of wave velocities in rock matrix and pore fluid on permeability.

Download Full-text

A Brief Overview on High Temperature Friction and Wear

STLE/ASME 2010 International Joint Tribology Conference ◽

10.1115/ijtc2010-41297 ◽

2010 ◽

Author(s):

Mustafa Bulut Coskun ◽

Mahmut Faruk Aksit

Keyword(s):

High Temperature ◽

Gas Turbines ◽

Friction And Wear ◽

Oxidation Behavior ◽

Elevated Temperatures ◽

Wear Performance ◽

Large Pressure ◽

Higher Power ◽

Vibratory Motion ◽

Increasing Temperature

With the race for higher power and efficiency new gas turbines operate at ever increasing pressures and temperatures. Increased compression ratios and firing temperatures require many engine parts to survive extended service hours under large pressure loads and thermal distortions while sustaining relative vibratory motion. On the other hand, wear at elevated temperatures limits part life. Combined with rapid oxidation for most materials wear resistance reduces rapidly with increasing temperature. In order to achieve improved wear performance at elevated temperatures better understanding of combined wear and oxidation behavior of high temperature super alloys and coatings needed. In an attempt to aid designers for high temperature applications, this work provides a quick reference for the high temperature friction and wear research available in open literature. High temperature friction and wear data have been collected, grouped and summarized in tables.

Download Full-text

Photosynthetic Capacity, Antioxidant Activity and Molecular Responses in Parthenocissus Quinquefolia (L.) Planch Under High Temperature Stress and Subsequent Recovery

Bangladesh Journal of Botany ◽

10.3329/bjb.v50i2.54103 ◽

2021 ◽

Vol 50 (2) ◽

pp. 433-436

Author(s):

Yuan Xue Tao ◽

Li Fu Ping

Keyword(s):

High Temperature ◽

Antioxidant Enzyme ◽

Temperature Stress ◽

Photosynthetic Capacity ◽

D1 Protein ◽

Temperature Limit ◽

High Temperature Stress ◽

Psii Activity ◽

Increasing Temperature ◽

Parthenocissus Quinquefolia

Photosynthetic capacity and photosystem II (PSII) activity decreased with increasing temperature, whereas antioxidant enzyme activity showed the opposite trend. High temperature stress induced a significant increase in Φf,D, and D1 protein turnover rate. Photosynthetic capacity, PSII activity, and antioxidant enzyme levels in plants treated at 35 and 40°C were restored to control levels upon stress relief, whereas those in plants grown at 45℃ were only partially restored. Therefore, the temperature limit for heat tolerance in Parthenocissus quinquefolia is between 40 and 45℃. Further, it was observed that antioxidant enzymes were crucial for high-temperature stress resistance in P. quinquefolia, with DEGP1 protein playing a major role in the rapid turnover of D1 protein for PSII repair. Bangladesh J. Bot. 50(2): 433-436, 2021 (June)

Download Full-text

SODIUM CHELATES OF ETHYLENEDIAMINETETRAACETIC ACID

Canadian Journal of Chemistry ◽

10.1139/v63-004 ◽

1963 ◽

Vol 41 (1) ◽

pp. 18-20 ◽

Cited By ~ 10

Author(s):

Vladimir Palaty

Keyword(s):

Stability Constant ◽

Stability Constants ◽

Ethylenediaminetetraacetic Acid ◽

Glass Electrode ◽

Neutral Solution ◽

Experimental Conditions ◽

The Stability ◽

Sensitive Method

The stability constant of the sodium chelate of EDTA was determined by means of a sodium-sensitive glass electrode. It appears that a hydrogen chelate of the formula NaHY2− is formed in the neutral solution of EDTA, but is very unstable. The stability constants, pKNaY = −2.61 and pKNaHY = 0.03, are comparable to the value obtained by Schwarzenbach and Ackermann under different experimental conditions by a less sensitive method.

Download Full-text

Effect of pinealectomy on the testicular response of the freshwater snake Natrix piscator to different environmental factors

Canadian Journal of Zoology ◽

10.1139/z89-332 ◽

1989 ◽

Vol 67 (10) ◽

pp. 2352-2357 ◽

Cited By ~ 6

Author(s):

C. Haldar ◽

R. Pandey

Keyword(s):

High Temperature ◽

Pineal Gland ◽

High Humidity ◽

Testicular Function ◽

Experimental Conditions ◽

Gland Weight ◽

Tropical Water ◽

Water Snake ◽

Temperature Regimes ◽

Testicular Weight

The effects of different humidity, photoperiod, and temperature regimes on the testicular function of the tropical water snake Natrix piscator were investigated in both sham-operated and pinealectomized snakes. Moderate humidity (50 ± 5%) had no effect on the testis, but high humidity (85 ± 5%) increased the testicular weight and activity of sham-operated snakes after 3, 6, and 9 weeks. Exposures to 14L:10D or 24L:0D and high temperature (42 ± 2 °C) inhibited testicular weight and activity in sham-operated snakes, whereas exposure to 10L:14D or 0L:24D and a low temperature (20 ± 2 °C) had no effect. Pinealectomized snakes did not respond to any of these experimental conditions, but their testicular weight remained the same as that of the pinealectomized controls under natural environmental conditions. The pineal gland showed an opposite response to that of the testes. Pineal gland weight decreased under high humidity and increased under 14L:10D, 24L:0D, and high temperature. These findings suggest that the ecofactors humidity, photoperiod, and temperature play a role in the regulation of testicular function in this snake, and that the pineal gland is implicated in the mediation of these factors.

Download Full-text

Frictional properties of exhumed fault gouges in DFDP-1 cores, Alpine Fault, New Zealand

10.26686/wgtn.13818845.v1 ◽

2021 ◽

Author(s):

Carolyn Boulton ◽

D Moore ◽

D Lockner ◽

V Toy ◽

John Townend ◽

...

Keyword(s):

New Zealand ◽

Friction Coefficient ◽

White Mica ◽

Rate Dependence ◽

Experimental Conditions ◽

Alpine Fault ◽

Negative Rate ◽

Sample Depth ◽

Fault Gouges ◽

Increasing Temperature

Principal slip zone gouges recovered during the Deep Fault Drilling Project (DFDP-1), Alpine Fault, New Zealand, were deformed in triaxial friction experiments at temperatures, T, of up to 350°C, effective normal stresses, σn′, of up to 156 MPa, and velocities between 0.01 and 3 μm/s. Chlorite/white mica-bearing DFDP-1A blue gouge, 90.62 m sample depth, is frictionally strong (friction coefficient, μ, 0.61-0.76) across all experimental conditions tested (T = 70-350°C, σn′ = 31.2-156 MPa); it undergoes a transition from positive to negative rate dependence as T increases past 210°C. The friction coefficient of smectite-bearing DFDP-1B brown gouge, 128.42 m sample depth, increases from 0.49 to 0.74 with increasing temperature and pressure (T = 70-210°C, σn′ = 31.2-93.6 MPa); the positive to negative rate dependence transition occurs as T increases past 140°C. These measurements indicate that, in the absence of elevated pore fluid pressures, DFDP-1 gouges are frictionally strong under conditions representative of the seismogenic crust.

Download Full-text

Compressibility behavior of Boron (Tincal) added to sand-bentonite mixtures under different temperatures

E3S Web of Conferences ◽

10.1051/e3sconf/202020509007 ◽

2020 ◽

Vol 205 ◽

pp. 09007

Author(s):

Sukran Gizem Alpaydin ◽

Yeliz Yukselen-Aksoy

Keyword(s):

High Temperature ◽

Volume Deformation ◽

Landfill Liners ◽

Low Thermal Expansion ◽

Boron Minerals ◽

Different Temperatures ◽

Increasing Temperature ◽

Waste Repositories ◽

Oedometer Tests ◽

Soil Changes

The importance of thermal behaviour of soils has increased significantly with increasing number of energy structures. There is a need for soils, which show design criteria (strength, permeability, etc.) performance during their life under high temperature or thermal cycles. In the literature studies, it was observed that the volumetric deformation of the soil changes with increasing temperature. Sand-bentonite mixtures generally act as impervious barrier in areas such as nuclear waste repositories, landfill liners etc. These mixtures will be exposed to high temperature; therefore, their engineering performance should not alter under high temperature. Boron is used in the industry for high temperature resistance, flexibility, lightness, power and ease of production. Boron minerals have very low thermal expansion and they are also resistant to thermal shocks. For that reason, the properties of sand-bentonite mixtures can be improved by boron additives at high temperatures. In this study, volume deformation behavior of sand-bentonite mixtures was determined in the presence of tincal. The oedometer tests were performed under room temperature and 80°C.

Download Full-text

Influence of substitution of Portland cement CP-II-Z32 by refractory cement on residual properties of high-temperature concrete

Cerâmica ◽

10.1590/0366-69132020663792913 ◽

2020 ◽

Vol 66 (379) ◽

pp. 330-339

Author(s):

C. da Silva ◽

D. S. S. Godinho ◽

A. Ribeiro ◽

A. Ferronato ◽

A. B. S. dos Santos Neto ◽

...

Keyword(s):

Heat Conduction ◽

High Temperature ◽

Portland Cement ◽

Mechanical Strength ◽

Fire Safety ◽

Residual Properties ◽

Refractory Cement ◽

Lower Heat ◽

Temperature Levels ◽

Increasing Temperature

Abstract Concrete structures must be sized to ensure stability over their lifetime. Moreover, there are criteria that must be followed for fire safety verification. Given this context, this study aimed to evaluate the influence of the partial and integral replacement of CPII-Z32 cement by a refractory cement in concrete compositions related to the residual properties after exposure to different temperature levels. For the tests, cylindrical specimens were molded with cement replacement percentages of 0% (reference), 50%, and 100%, and exposed at 450 °C and 900 °C without load. The results showed a change in the color of the specimens and a reduction of the mechanical strength with increasing temperature. The increase in the percentage of refractory cement resulted in lower heat conduction for the concrete made with this material.

Download Full-text