Mathematical modeling of the zinc pressure leach process

A comprehensive mathematical model is described for the zinc pressure leaching process. Generic kinetic expressions were derived from experimental data found in the literature for the following reaction events: (1) dissolution of marmatite, (Zn,Fe)S, (2) oxidation of ferrous to ferric, and (3) precipitation of lead jarosite. Aqueous solution properties, oxygen solubility, density, enthalpy, and vapor pressure, were correlated with solution composition and temperature. Subsequently, a kineticsbased model for simultaneous sulfide dissolution and iron precipitation in a multistage, three-phase reactor was developed. The population balance method was used for sulfide mineral material balances, and apparent equilibrium was assumed for iron precipitation. A gas-phase material balance was included, which allows for prediction of oxygen utilization. The model was solve for a particular operation of the Cominco Ltd. (Trail, BC) autoclave, and prediction results were shown to be in very good comparison with actual plant performance.     

哈德逊湾加压浸出中铁的控制

世界上第一个锌两段加压浸出冶炼厂于1993年在加拿大弗林弗隆的哈德逊湾矿业公司投产运行。该工艺成功运行的一个关键条件就是时溶液中铁的控制。因为铁作为氧化反应的载体,加快了硫化锌的氧化速度。同时,因为锌电解新液中对铁含量要求非常低,所以浸出后液的除铁工序也是必不可少的。在铁沉降的同时,溶液中其他一些有害元素,如:砷、锑、氟等也被一同沉降下来。本文回顾了目前哈德逊湾冶炼厂两段酸浸的主要工艺流程。同时,特别就浸出过程中铁的行为与分布做了重点描述。     

高海拔下锌的高浸出率——谢里特为中国西部矿业公司进行的锌氧压浸出研究

西部矿业(WMC)甘河精炼厂海拔高,WMC矿山生产的精矿舍铁高,这两点是WMC为其新的锌精炼厂选择氧压浸出工艺的关键因素.谢里特公司在萨斯喀彻温堡用WMC从中国青海省提供的精矿样品进行了氧压漫出试验,本论文描述了该试验的结果.小型间断氧压浸出试验和四天连续扩大试验的结果都进行了报告.连续扩大试验包括两段氧压漫出、中和及除铁的连续操作,产出无铁硫酸锌溶液.氧压浸出取得了大于98%的锌浸出率,同时产出含有约9g/L硫酸和2g/L铁的溶液.中和及除铁后,溶液约合170g/L锌和<10mg/L的铁.从锌精矿原料到元素硫副产品的总硫回收率约为85%,从中和渣中可回收原料中75～80%的锢.试验结果显示了谢里特锌氧压浸出工艺的技术和经济优势,并且为工程设计提供了所需数据.     

Mineralogical characterization of silver flotation concentrates made from zinc neutral leach residues

Silver flotation concentrates prepared from high-silver (1480 ppm Ag) and low-silver (300 ppm Ag) neutral leach residues have been examined mineralogically to determine the phases present and to elucidate the behavior of silver during zinc processing. The flotation concentrates consist principally of sphalerite although lesser amounts of zinc ferrite and PbSO₄, as well as traces of other phases, also are present. In the high-silver flotation concentrate, silver occurs mostly as Ag₂S or (Ag, Cu)₂S rims on sphalerite although (Ag, Cu)₂S inclusions within sphalerite also are present. Trace amounts of a Cu-Ag-S-Cl phase are present on rare copper oxide grains, and this silver-bearing phase may be a fine mixture of Ag₂S, AgCl, and Cu₂S. In the low-silver flotation concentrate, silver occurs mostly as Ag₂S although traces of silver-bearing CuS and Cu₂S also are present. The Ag₂S occurs as <1 μm particles disseminated in elemental sulfur-silica gel patches, as discontinuous rims or isolated patches on sphalerite grains, and as tiny free particles. Silver chloride was not detected. These studies suggest that silver dissolves during neutral leaching and subsequently reacts with sphalerite or other sulfides to form silver sulfide.     

Mineralogical characterization of silver flotation concentrates made from zinc neutral leach residues

Silver flotation concentrates prepared from high-silver (1480 ppm Ag) and low-silver (300 ppm Ag) neutral leach residues have been examined mineralogically to determine the phases present and to elucidate the behavior of silver during zinc processing. The flotation concentrates consist principally of sphalerite although lesser amounts of zinc ferrite and PbSO₄, as well as traces of other phases, also are present. In the high-silver flotation concentrate, silver occurs mostly as Ag₂S or (Ag, Cu)₂S rims on sphalerite although (Ag, Cu)₂S inclusions within sphalerite also are present. Trace amounts of a Cu-Ag-S-Cl phase are present on rare copper oxide grains, and this silver-bearing phase may be a fine mixture of Ag₂S, AgCl, and Cu₂S. In the low-silver flotation concentrate, silver occurs mostly as Ag₂S although traces of silver-bearing CuS and Cu₂S also are present. The Ag₂S occurs as <1 μm particles disseminated in elemental sulfur-silica gel patches, as discontinuous rims or isolated patches on sphalerite grains, and as tiny free particles. Silver chloride was not detected. These studies suggest that silver dissolves during neutral leaching and subsequently reacts with sphalerite or other sulfides to form silver sulfide.     

Purification of zinc calcine leach solutions by exchange extraction with the zinc salt of “versatic” acid

Trivalent iron present in zinc sulphate solutions obtained by the leaching of zinc calcine with sulphuric acid can be removed by exchange extraction using a solution of the zinc salt of “Versatic” 10. Valuable metals, such as cobalt and copper, are not co-extracted and so may be recovered in the normal way.Contaminants, such as arsenic, in the solutions which may be harmful in the further course of the process can be effectively removed by coprecipitation with a a small amount of iron hydroxides.     

Materials science under extreme conditions of pressure and strain rate

Solid-state dynamics experiments at very high pressures and strain rates are becoming possible with high-power laser facilities, albeit over brief intervals of time and spatially small scales. To achieve extreme pressures in the solid state requires that the sample be kept cool, with T _sample<T _melt. To this end, a shockless, plasma-piston “drive” has been developed on the Omega laser, and a staged shock drive was demonstrated on the Nova laser. To characterize the drive, velocity interferometer measurements allow the high pressures of 10 to 200 GPa (0.1 to 2 Mbar) and strain rates of 10⁶ to 10⁸ s⁻¹ to be determined. Solid-state strength in the sample is inferred at these high pressures using the Rayleigh-Taylor (RT) instability as a “diagnostic.” Lattice response and phase can be inferred for single-crystal samples from time-resolved X-ray diffraction. Temperature and compression in polycrystalline samples can be deduced from extended X-ray absorption fine-structure (EXAFS) measurements. Deformation mechanisms and residual melt depth can be identified by examining recovered samples. We will briefly review this new area of laser-based materials-dynamics research, then present a path forward for carrying these solid-state experiments to much higher pressures, P>10³ GPa (10 Mbar), on the National Ignition Facility (NIF) laser at Lawrence Livermore National Laboratory. This article is based on an invited presentation given in the symposium “Dynamic Deformation: Constitutive Modeling, Grain Size, and Other Effects: In Honor of Prof. Ronald W. Armstrong,” March 2–6, 2003, at the 2003 TMS/ASM Annual Meeting, San Diego, California, under the auspices of the TMS/ASM Joint Mechanical Behavior of Materials Committee.     

锌焙砂常规浸出条件下CU2+行为分析

本文通过理论分析,提出以锌焙砂为原料的常规两段浸出湿法炼锌工艺中,制约铜回收率提高的主要因素是浸出液中Cu2+的再次水解沉淀,并通过试验验证了这一结论.     

Comparative hygienic evaluation of nonionogenic surface-active agents with regard to stability and transformation

The authors discuss measures preventing intraoperative allergic reactions in patients subjected to cardiopulmonary bypass surgery. A retrospective analysis of the incidence of allergic reactions in 1330 patients operated on the heart showed that cardiosurgical patients are liable to anaphylaxis because of intraoperative administrations of numerous drugs (besides anesthetics), specifically, antibiotics, protamine, etc., blood components, solutions. Comparison of the incidence of anaphylactic and anaphylactoid reactions allowed the authors to recommend corticosteroids to be added to anesthesiological protocols with prophylactic purpose. A new corticosteroid betamethasone is more effective than traditional prednisolone in equivalent doses as regards prevention and alleviation of allergic reactions in cardiosurgical patients.     

Psychomotor effects of dopamine infusion under decreased glutathione conditions

Administration of buthionine sulfoximine (BSO) selectively inhibits glutathione (GSH) biosynthesis, thereby inducing a GSH deficiency. Because GSH plays a critical role in intracellular antioxidant defense, decreased GSH levels in the brain may result in less oxidative stress (OS) protection. Thus, the pro-oxidant effects of dopamine (DA), which rapidly oxidizes to form reactive oxygen species, may increase. In this study, the behavioral consequences of reduced OS protection were examined by administering BSO (3.2 mg in 30 microl Ringer's solution, intracerebroventricularly) every other day for 12 d to male Fischer 344 rats. In addition, DA (15 microl of 500 microM) was administered every day; when given on the same day as BSO, it was either 1 h after BSO (BSO + DA group) or 1 h before BSO (DA + BSO group). Tests of psychomotor behavior--rod walking, wire suspension, and plank walking--were performed five times during the experiment. BSO + DA administration, but not DA + BSO, impaired performance by decreasing latency to fall in the rod and plank walk tests compared to a vehicle only (Ringer's) group. Therefore, depletion of GSH with BSO, followed by DA treatment, produced deficits in psychomotor behavior. These deficits are similar to those seen in aged rats, suggesting that the oxidation of DA coupled with a reduced capacity to respond to OS may be responsible for the induction of age-related motor behavioral deficits.     

Equilibrium vapour pressure of mercury from dental amalgam under loading conditions

Earlier studies have failed to establish a consensus on the amount of mercury vapour released from dental amalgam restorations. The purpose of this study was to accurately and quantitatively measure the equilibrium mercury vapour pressure from dental amalgam. The vapour pressure was measured using a quartz crystal microbalance as a function of the load from 0-5.4 MPa. Auger spectra were collected of the as-formed and argon ion sputter cleaned dental amalgam surface. For the as-formed surface the mercury vapour density is zero with no load and increases to 0.6 microg m(-3) at 5.4 M Pa. Following cleaning the mercury, vapour density increased to a maximum value of 15 microg m(-3). The Auger spectra of the as-formed surfaces were dominated by features associated with carbon and oxygen. These spectral results in concert with the mercury vapour density measurements indicate that the oxide film on the as-formed surfaces inhibited the release of mercury vapour. The results of this experiment provide an upper limit for the amount of mercury vapour released by dental amalgams. Under conditions simulating the oral cavity this value would be reduced by oxides that form on the surface of dental amalgam restorations.     

Kinetics of the dissolution of zinc-magnesium ferrites in sulphuric acid solutions related to zinc leach processes

The presence of sparingly soluble zinc and magnesium ferrites in roasted zinc concentrates can cause problems during leaching. This study aimed at the determination of the dissolution kinetics of zinc ferrite-magnesium ferrite solid solutions. The investigations have been performed for the (Zn_1?xMg_x)Fe₂O₄ powder specimens (x = 0, 0.25, 0.50, 0.75 and 1) in solutions of 100–200 g/l H₂SO₄ at 323–363 K. Dissolution of all specimens has been found to be chemically controlled and homothetic, being described by the “unreacted-core shrinking” model. The dissolution rate constant of zinc ferrite was about seven times higher than that of magnesium ferrite (e.g. 3.83·10^?6 against 0.53·10^?6 mol/m²s in 100 g/l H₂SO₄ at 363 K). The relation between rate constant and the x value was not linear. The activation energy was not dependent on the x value and amounted to ca. 75 kJ/mol. The results have important relevance to the “magnesium problem” often experienced in roach-leach processes in hydrometallurgy.     

Evaluation and selection of extractants for the separation of copper and zinc from chloride leach liquor

The paper describes the bench-scale studies on the solvent extraction separation of copper and zinc from chloride liquors resulting from the low temperature chlorination of a lead-zinc sulphide concentrate. Various possible extractants were evaluated and the selection of the most suitable reagent was based on the effect of total chloride and equilibrium pH on extraction and discrimination, scrubbing and stripping. Acorga P5300 was the most suitable extractant for copper and TBP was selected for zinc.     

Prediction of the effects of surface-active elements on gas-liquid metal kinetics

Equations have been developed for calculating the fraction of free surface, 1-θ_T, when two or more surface-active elements (S, O,Se,etc.) are present in liquid iron or its alloys. It is shown that equations of the form k =A Vl-θ_T -B well describe the essentially linear plots which represent the variation of rate constant k with concentration of surface-active elements in more than 30 researches on absorption and desorption of nitrogen in stirred liquid iron and its alloys. To normalize the effect of variation in metallodynamic properties from researcher to researcher, a second relation has been developedwhich describes a dimensionless rate constant for nitrogen k _N ^F (with range0 to 1) given by k _N ^F = CVl-θ_T-D, where C and D are small constants. The relation k _N ^F = 1.19 Vl-θ_T-0.19 is a fair representation of the absorption and desorption behaviors in the 1550 ° to 1600 ° range for all the many iron and iron alloy cases examined. Although these two relations are largely empirical they and the simple linear graphs involved provide potentially valuable new methods of rate prediction. There is some evidence that the behavior of hydrogen with liquid Fe, Cu, and Ni is analogous.     

Alerting effects of methylphenidate under basal and sleep-deprived conditions.

Six men and 3 women on each of 4 days received 10 mg of methylphenidate or placebo (2 times a day) at 0800 and 1200 after 8 hr or 0 hr of sleep. Sleep latency was measured by the Multiple Sleep Latency Test (MSLT) at 0930, 1130, 1330, 1530, and 1730. Participants also completed divided-attention and auditory vigilance tasks at 1000 and 1400 and the Profile of Mood States (POMS) and the Addiction Research Center Inventory (ARCI) after the 0930 and 1330 latency tests. The drug increased mean latency on the MSLT in both sleep conditions. Performance only showed drug effects after prior sleep deprivation. On the POMS, the drug increased Vigor and reduced Fatigue and Depression scale scores, primarily after sleep deprivation. The drug increased the ARCI Amphetamine and Morphine-Benzedrine scores only in the basal state. The ARCI Pentobarbital score was increased by sleep deprivation and decreased by the drug. (PsycINFO Database Record (c) 2010 APA, all rights reserved)