Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Thermodynamics and kinetics of extracting zinc from zinc oxide ore by the ammonium sulfate roasting method  [PDF]
Yi Sun,Xiao-yi Shen,Yu-chun Zhai
- , 2015, DOI: https://doi.org/10.1007/s12613-015-1095-x
Abstract: Thermodynamic analyses and kinetic studies were performed on zinc oxide ore treatment by (NH4)2SO4 roasting technology. The results show that it is theoretically feasible to realize a roasting reaction between the zinc oxide ore and (NH4)2SO4 in a temperature range of 573–723 K. The effects of reaction temperature and particle size on the extraction rate of zinc were also examined. It is found that a surface chemical reaction is the rate-controlling step in roasting kinetics. The calculated activation energy of this process is about 45.57 kJ/mol, and the kinetic model can be expressed as follows: 1 ? (1 ? α)1/3 = 30.85 exp(?45.57/RT)·t. An extraction ratio of zinc as high as 92% could be achieved under the optimum conditions.
Optimization experiment study on Zinc oxide ore leaching zinc

- , 2017,
Abstract: 采用响应曲面法(Response Surface Methodology,RSM),选取Quadratic模型,据此模型进行了Box-Behnken实验设计优化在NH3-(NH4)2SO4-H2O体系浸出氧化锌矿的实验工艺参数,建立了回归方程。 回归分析模型的“Prob>F”值为0.0023,小于0.05,模型模拟精度高,回归方程的全体自变量与因变量之间是显著的,回归方程可信。模型分析发现,液固比、浸出温度、浸出时间三个因素对锌的浸出率影响较为显著,对响应面和等高线图进行分析,液固比和浸出时间的交互作用较为显著。RSM法优化最佳浸出实验参数液固比12.81、浸出温度30℃、浸出时间4.15h、总氨浓度7.5 mol?L-1,预测浸出率86.2%。综合考虑操作的可行性,在采用NH3-(NH4)2SO4-H2O体系浸出氧化锌矿工艺中,选取液固比13、浸出温度30℃、浸出时间4h、总氨浓度7.5 mol?L-1,测得浸出率为86.0%,与理论预测值相比误差为0.23%。
Abstract:Using Response Surface Methodology(RSM), selecting Quadratic model, on the basis of model Box-Behnken experiment design optimization in NH3-(NH4)2SO4-H2O system leaching of zinc oxide ore experiment process parameters, and the regression equation is established.Regression analysis model of "Prob>F" value of 0.0023, less than 0.05, the model of high precision, all between independent variable and dependent variable of the regression equation is significant, regression equation to be trusted. Model analysis found that the liquid-solid ratio, leaching temperature, leaching time, the three factors that affect the leaching rate of zinc is significant, the analysis of the response surface and contour plot, liquid-solid ratio and the leaching time of interaction is significant.RSM analysis ,the optimum leaching conditions were obtained as follows: liquid-solid ratio 12.81, leaching temperature 30 ℃, leaching time of 4.15 h, total ammonia concentration of 7.5 mol?L-1, predicting leaching rate was 86.2%.Considering the feasibility of the operation, in the NH3-(NH4)2SO4-H2O system leaching process of zinc oxide ore, selected liquid-solid ratio 13, leaching time 4h, leaching temperature 30 ℃, total ammonia concentration of 7.5 mol?L-1, measured the leaching rate was 86.0%, compared with the theoretical prediction error is 0.23%
Laboratory Study on the Removal of Fluorine from High Fluorine Bearing Zinc Oxide Ore
Yaozhong LAN,Liaoyuan YE,Rose WSmith,

材料科学技术学报 , 2005,
Abstract: An ever increasing demand for zinc has resulted in worldwide efforts to exploit complex and lean grade reserves of zinc oxide ore. In this study experiments were done on zinc recovery from high-fluorine bearing zinc oxide ore. First the effect of different variables on fluorine removal was investigated. Optimum experimental conditions occurred when the temperature was 1173 K, roasting time was 90 min and air flow was at a velocity of 5 m/min, the fluorine removal from the samples reached over 93%. The results obtained indicate that fluorine removal is not enhanced by adding diluted sulfuric acid or water as a binder. Second the roasted materials were leached with a diluted sulfuric acid,neutralized, flocculated and filtrated. The residual fluorine content in the leached solutions was less than 38 mg/L,which satisfies the requirement of fluorine content in the leached solutions for the production of electrolytic zinc.
Dolochar as a reductant in the reduction roasting of iron ore slimes  [PDF]
Swagat S. Rath,Danda Srinivas Rao
- , 2017, DOI: https://doi.org/10.1007/s12613-017-1526-y
Abstract: The present investigation examines the viability of dolochar, a sponge iron industry waste material, as a reductant in the reduction roasting of iron ore slimes, which are another waste generated by iron ore beneficiation plants. Under statistically determined optimum conditions, which include a temperature of 900°C, a reductant-to-feed mass ratio of 0.35, and a reduction time of 30–45 min, the roasted mass, after being subjected to low-intensity magnetic separation, yielded an iron ore concentrate of approximately 64wt% Fe at a mass recovery of approximately 71% from the feed iron ore slime assaying 56.2wt% Fe. X-ray diffraction analyses indicated that the magnetic products contain magnetite and hematite as the major phases, whereas the nonmagnetic fractions contain quartz and hematite.
SEM/EDS analysis of soil and roasting vessels fragments from ancient mercury ore roasting sites at Idrija area  [PDF]
Tamara Ter?i?
Geologija , 2011,
Abstract: Numerous roasting vessels fragments can be found at ancient roasting site areas in the surroundings of Idrija town, which were used for ore roasting in the first 150 years of Hg production in Idrija. The earthen vessels fragments lay just below the surface humus layer and in some parts they stretch more than 1 meter deep; they arecovered with red (cinnabar) or black (metacinnabar) coatings.SEM/EDS analysis of roasting vessels fragments and soil samples from roasting site areas P{enk and Frbej ene trate was performed in order to characterize the solid forms of Hg in applied sampling material. Mercuric sulphide HgS was found to be the main mercury compound present in the samples. Analysis of earthen vessels fragmentsshowed abundant HgS coatings on the surface of ceramics, forming either crust-like aggregates on matrix or isolated grains. Some well-shaped grains with indicated structure and the size of up to 200 μm could also be observed. In soil HgS was present as powder-like concentrations scattered in soil samples, frequently coating silicate and quartz crystals and clay-minerals. Polycristalline, mercury- and sulphur- rich particles comprising silica, clay mineralsand Al-, Fe- and Mg-oxides that were also observed in the samples were interpreted as soil aggregates infiltrated by mercuric and sulphur vapours and by liquid mercury spilled during roasting. These particles suggest a possible presence of mercury-sulphur associations other than HgS.
Effects of urea and (NH4)2SO4 on nitrification and acidification of Ultisols from Southern China

Deli Tong,Renkou Xu,

环境科学学报(英文版) , 2012,
Abstract: The mechanisms for the effects of ammonium-based fertilizers on soil acidification in subtropical regions are not well understood. Two Ultisols collected from cropland and a tea garden in Anhui and Jiangxi Provinces in subtropical southern China, respectively, were used to study the effects of urea and (NH4)2SO4 on the nitrification and acidification of soils with incubation experiments. Nitrification occurred at very low pH with no N fertilizer added and led to lowering of the soil pH by 0.53 and 0.30 units for the soils from Jiangxi and Anhui, respectively. Addition of urea accelerated nitrification and soil acidification in both Ultisols; while nitrification was inhibited by the addition of (NH4)2SO4, and greater input of (NH4)2SO4 led to greater inhibition of nitrification. Ammonia-oxidizing bacteria (AOB) played an important role in nitrification in cropland soil under acidic conditions. Addition of urea increased the soil pH at the early stages of incubation due to hydrolysis and stimulated the increase in the AOB population, and thus accelerated nitrification and soil acidification. At the end of incubation, the pH of Ultisol from Jiangxi had decreased by 1.25, 1.54 and 1.84 units compared to maximum values for the treatments with 150, 300 and 400 mg/kg of urea-N added, respectively; the corresponding figures were 0.95, 1.25 and 1.69 for the Ultisol from Anhui. However, addition of (NH4)2SO4 inhibited the increase in the AOB population and thus inhibited nitrification and soil acidification. Soil pH for the treatments with 300 and 400 mg/kg of (NH4)2SO4-N remained almost constant during the incubation. AOB played an important role in nitrification of the cropland soil under acidic conditions. Addition of urea stimulated the increase in the AOB population and thus accelerated nitrification and soil acidification; while addition of (NH4)2SO4 inhibited the increase in the AOB population and thus inhibited nitrification.
Recovery of Iron and Zinc from Blast Furnace Sludge

LI Liao-sha,LI Kai-yuan,

过程工程学报 , 2009,
Abstract: The reduction roasting and weak magnetic separation techniques were adopted to recover high grade iron-rich ore from blast furnace sludge, and in the roasting process, CH3COOH solution was used to reclaim zinc in a by-product of Zn(CH3COO)2. The optimum conditions were obtained as follows: temperature 1373.2 K, and time 60 min. Through the reduction roasting, the dezincification rate reached up to 98%, a high grade iron ore with only 0.04% zinc was obtained. By weak magnetic separation 80% iron rich ore was...
Research on the Roasting Process with Calcium Compounds for Silica Based Vanadium Ore

过程工程学报 , 2001,
Abstract: The relation of the optimum amount of additive with the composition of silica based vanadium ore roasted with calcium compounds for was studied. A calculating formula for the roasting load was proposed. The roasting mechanism was explored and it is believed that vanadium exists in the calcifying roasted ore mainly in form of calcium silicon vanadate.
用PEG/(NH4)2SO4双水相体系萃取糖化酶  [PDF]
华侨大学学报(自然科学版) , 1996, DOI: 10.11830/ISSN.1000-5013.1996.04.0407
Abstract: 用PEG(聚乙二醇)/(NH4)2SO4双水相体系从黑曲霉粗酶液中萃取糖化酶.探讨了对糖化酶分配系数、总蛋白分配系数及糖化酶回收率的影响因素.确定萃取糖化酶的最佳操作条件.
用PEG/(NH4)2SO4两水相从全缪液萃取糖化酶  [PDF]
华侨大学学报(自然科学版) , 1999, DOI: 10.11830/ISSN.1000-5013.1999.01.0084
Abstract: PEG(聚乙二醇)600/(NH4)2SO4两水相系统,能有效地从全缪液直接萃取糖化酶.在研究PEG/(NH4)2SO4相图的基础上,探讨了影响糖化酶萃取效果的因素,确定了萃取糖化酶的最佳工艺条件.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.