Utilization of nickel slag using selective reduction followed by magnetic separation

In order to utilize slag discarded by nickel plants, the selective recovery of nickel and copper versus iron was investigated by selective reduction, which was achieved by controlling the reduction parameters and magnetic separation process on bench scale. The results show that increasing the basicity （mass ratio of CaO to SIO2） of nickel slag facilitates the enrichment of nickel and copper The process parameters for selective reduction were optimized as follows： basicity of 0.15, reducing at 1200 ~C for 20 min, 5% coal on a dried slag mass base. The grinding-magnetic separation results of reduced briquettes show that concentrate containing 3.25%Ni, 1.20%Cu and 75.26%Fe is obtained and selective enrichment is achieved with a recovery of 82.20%, 80.00% for nickel and copper respectively, while the recovery of iron is only 42.17%. The S and P contents are not reduced obviously and further research may be needed to examine the behaviors of S and P in the process.

Extraction of arsenic from arsenic-containing cobalt and nickel slag and preparation of arsenic-bearing compounds

The arsenic extraction from the arsenic-containing cobalt and nickel slag,which came from the purification process of zinc sulfate solution in a zinc smelting factory,was investigated.The alkaline leaching method was proposed according to the mode of occurrence of arsenic in the slag and its amphoteric characteristic.The leaching experiments were conducted in the alkaline aqueous medium,with bubbling of oxygen into the solution,and the optimal conditions for leaching arsenic were determined.The results showed that the extraction rate of arsenic was maximized at 99.10%under the optimal conditions of temperature 140 ℃,NaOH concentration 150 g/L,oxygen partial pressure 0.5 MPa,and a liquid-to-solid ratio 5：1.Based on the solubilities of As2O5,ZnO and PbO in NaOH solution at 25 ℃,a method for the separation of As in the form of sodium arsenate salt from the arsenic-rich leachate via cooling crystallization was established,and the reaction medium could be fully recycled.The crystallization rate was confirmed to reach 88.9%（calculated on the basis of Na3AsO4） upon a direct cooling of the hot leachate down to room temperature.On the basis of redox potentials,the sodium arsenate solution could be further reduced by sulfur dioxide（SO2） gas to arsenite,at a reduction yield of 92%under the suitable conditions.Arsenic trioxide with regular octahedron shape could be prepared successfully from the reduced solution,and further recycled to the purification process to purify the zinc sulfate solution.Also,sodium arsenite solution obtained after the reduction of arsenate could be directly used to purify the zinc sulfate solution.Therefore,the technical scheme of alkaline leaching with pressured oxygen,cooling crystallization,arsenate reduction by SO2 gas,and arsenic trioxide preparation,provides an attractive approach to realize the resource utilization of arsenic-containing cobalt and nickel slag.

Enhancement of the nickel converter slag-cleaning operation with the addition of spent potlining

The slag cleaning(or matte settling) process was experimentally investigated at 1573 K using a fayalitic nickel converter slag containing spinel and matte/alloy particles.The addition of various amounts of spent potlining(SPL) was studied in terms of its influence on matte settling and the overall metal recoveries.The slags produced were characterized by scanning electron microscopy,energy-dispersive spectroscopy,and wet chemical analysis using inductively coupled plasma optical emission spectrometry.The presence of solid spinel particles in the molten slag hindered coalescence and settling of matte/alloy droplets.Matte settling was effectively promoted with the addition of as little as 2 wt% SPL because of the reduction of spinel by the carbonaceous component of the SPL.The reduced viscosity of the molten slag in the presence of SPL also contributed to the accelerated matte settling.Greater metal recoveries were achieved with larger amounts of added SPL.Fast reduction of the molten slag at 1573 K promoted the formation of highly dispersed metal particles/clusters via accelerated nucleation in the molten slag,which increased the overall slag viscosity.This increase in viscosity,when combined with rapid gas evolution from accelerated reduction reactions,led to slag foaming.

Improvement of carbothermic reduction of nickel slag by addition of CaCO3

The effect of CaCO3 addition on the carbothermic reduction of nickel slag was studied,and the mechanism of CaCO3 in improving the reduction was analyzed.The results showed that when the CaCO3 content added to the slag was increased from 0 to 8 wt.%,initiation temperature of the carbothermic reaction decreased from 1100 to 1000℃,the temperature reaching the maximum reduction rate decreased from 1150 to 1100℃,and the reduction degree of the nickel slag increased from 58%to 88%.The iron particles in the reduced nickel slag were coarsened and the X-ray diffraction intensity of metallic iron peaks increased,confirming that the addition of CaCO3 was beneficial to the reduction of nickel slag and recovery of iron.

Effect of additives on growth of ferronickel grains and metal-slag separation behavior

Na_(2)S,Na_(2)CO_(3),FeO,FeS and carbon were used to regulate the properties of slag or metal fractions,and their effects on metal growth and metal–slag separation behavior were investigated.The growth of ferronickel grains can be enhanced by adding these additives,and Na_(2)S was the most effective.Na_(2)S,Na_(2)CO_(3) and FeO mainly affected the properties of slag,while carbon and FeS affected the metal fraction.The onset temperature of metal–slag separation was 1297℃ for the sample without additive,which was decreased to 1123 and 1101℃ after adding 3.30 wt.%Na_(2)S and 4.47 wt.%Na_(2)CO_(3),respectively.The onset temperature of metal–slag separation was mainly controlled by the slag fraction.The average apparent activation energy of metal grain growth was 125.32 kJ/mol without additive,and it decreased obviously after adding different additives.Na_(2)S also had the most remarkable effect on the decrease in activation energy.

Application of Modified Nickel Slag Adsorbent on the Removal of Pb^(2＋) and Cu^(2＋) from Aqueous Solution

Al（OH）_3 modified nickel slag adsorbent was prepared by sintering technology. The structure of the sample was characterized by BET, XRD, IR, SEM and EDAX. The sample＇s adsorption performance of Pb^（2＋） and Cu^（2＋） from aqueous solution was studied. Results indicated that the adsorbent is a loose and porous mesoporous material. Its surface had mass aluminosilicate, high-activity γ-Al_2O_3 and its p H ranges from 4 to 12 that all have negative charges. The BET surface of the adsorbent is 23.90 m^2/g. Furthermore, its surface contains rich oxygenic functional groups, which could not only provide abundant adsorption sites for Pb^（2＋） and Cu^（2＋）, but also improve the adsorption performance of Pb^（2＋） and Cu^（2＋） from waste water through the complexation of heavy metal ions. The best p H values selected in the adsorption of Pb^（2＋） and Cu^（2＋） are 6 and 5, respectively. With the increase of the initial concentration of simulated solution, the adsorption capacities of Pb^（2＋） and Cu^（2＋） gradually increased but the removal rates showed a downward trend. The competitive adsorption results of Pb^（2＋） and Cu^（2＋） showed that Pb^（2＋） has better preferential adsorption than Cu^（2＋）.

Adsorption of Pb^2+and Cu^2+with Unburned Desulphurization Slag Modified Nickel Slag

Desulphurization slag modified nickel slag adsorbent was prepared by unburned forming technology. The structure of the sample was characterized by BET,XRD,IR,SEM and EDAX. The adsorption performance of Pb^2＋ and Cu^2＋ onto the resultant adsorbent from aqueous solution was studied. Results indicated that the adsorbent possesses a network pore structure formed by the AFt and C–S–H through cross lapping; the adsorbent contains a large number of Si–OH and Al–OH functional groups. The presence of functional groups not only provides abundant adsorption sites for Pb^2＋ and Cu^2＋,but also improves the adsorption performance of Pb^2＋ and Cu^2＋ from waste water through the complexation of heavy metal ions. The result of specific surface area analysis showed that the adsorbent sample possesses mesoporous structure and the BET specific surface area is 27.15 m^2/g. The solution p H values for the adsorption of Pb^2＋ and Cu^2＋ were optimized to be 6 and 5.5,respectively. The adsorption capacities of Pb^2＋ and Cu^2＋ gradually increase,whereas the removal rates of the two metal ions decrease with increasing the initial concentration of simulated solution. The resultant adsorbent gives a higher adsorption capacity for Cu^2＋ than for Pb^2＋ in the single ion solution. However,it shows preferential adsorption of Pb^2＋ rather than that of Cu^2＋. Meanwhile,results of recyclability indicate the remarkable regeneration capacity,re-adsorption ability and reusability performance of the adsorbent sample.

Leaching of magnesium from desiliconization slag of nickel laterite ores by carbonation process

The leaching of magnesium from desiliconization slag of nickel laterite ores by carbonation process was studied.The influence of various parameters was investigated to optimize the conditions and determine the kinetics of the reaction.The results show that with increasing stirring speed,liquid-to-solid ratio and reaction time,and decreasing temperature,the leaching rate of magnesium enhances.The leaching process of the desiliconization slag in the range of 288-298 K is controlled by the surface chemical reaction model.The apparent activation energy is-20.45 kJ/mol,and the kinetics model is obtained.

Slag Resistance of Refractories for Direct Reduction of Laterite Nickel Ores in Rotary Kilns

Aiming at prolonging the service life of refractories for direct reduction of laterite nickel ores in rotary kilns,the slag resistance of ten materials(corundum bricks,chrome corundum bricks,silicon nitride bonded silicon carbide bricks,high alumina silicon carbide bricks,high alumina bricks,magnesia chrome bricks,magnesium aluminate spinel bricks,spinel chrome corundum bricks,chrome corundum castables and magnesia alumina chrome composite spinel bricks)was evaluated by rotary slag tests,which simulate the service conditions in rotary kilns.The corroded residual bricks were analyzed by SEM and EDS.The results show that the magnesia alumina chrome composite spinel brick possesses the advantages of magnesium aluminate spinel bricks and chrome corundum bricks;MgO-rich spinel can absorb the penetrated ferric oxide,and forms a dense zeylanite layer,which prevents the penetration of the molten laterite nickel ores;therefore,it is an ideal lining of rotary kilns for direct reduction of laterite nickel ores.

Recovery of valuable metals from spent lithium ion batteries by smelting reduction process based on FeO-SiO_2-Al_2O_3 slag system

NA novel smelting reduction process based on FeO-SiO2-Al2O3 slag system for spent lithium ion batteries with Al cans was developed, while using copper slag as the only slag former. The feasibility of the process and the mechanism of copper loss in slag were investigated. 98.83% Co, 98.39% Ni and 93.57% Cu were recovered under the optimum conditions of slag former/battery mass ratio of 4.0：1, smelting temperature of 1723 K, and smelting mass ratio of time of 30 min. The FeO-SiO2-Al2O3 slag system for the smelting process is appropriate under the conditions of m（FeO）：m（SiO2）=0.58：1？1.03：1, and 17.19%？21.52% Al2O3 content. The obtained alloy was mainly composed of Fe-Co-Cu-Ni solid solution including small amounts of matte. The obtained slag mainly consisted of fayalite and hercynite. Meanwhile, the mechanism of copper loss is the mechanical entrainment from strip-like fayalite particles in the main form of copper sulfide and metallic copper.

Activity coefficients of NiO and CoO in CaO–Al_2O_3–SiO_2 slag and their application to the recycling of Ni–Co–Fe-based end-of-life superalloys via remelting

To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life（EoL） superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al_2O_3-SiO_2 slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al_2O_3-SiO_2 slag. The activity coefficients of NiO and CoO in CaO-Al_2O_3-SiO_2 slag both show a positive deviation from Raoult＇s law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B =（%CaO）/（%SiO_2） = 1, where B is the basicity. We observed that controlling the slag composition at approximately B = 1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.

Viscosities of Fe_nO-MgO-SiO_2 and Fe_nO-MgO-CaO-SiO_2 slags

The viscosities of molten FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 semi-synthetic slags for nickel flash smelting were mearured in the temperature range of 1 2001 450 ℃ by use of a rotational viscometer. The mass ratio of Fe to SiO2 was fixed at 1.2, calcium oxide and magnesium oxide contents varied in the range of 2%8% and 9%12%（mass fraction）, respectively. The results show that silicate anions become smaller by increasing CaO content, which results in the viscosity decrease of slag. In the case of addition of MgO the viscosity behaviour is complicated. When MgO content is less than 11%, the viscosity increases with the increase of MgO at all temperatures tested . However, when the MgO content is more than 11%, the viscosity decreases slightly for FenO-MgO-CaO-SiO2 system. At higher MgO contents, low-viscosity slags can be obtained by adding CaO. As for a given composition, the viscosity decreased with increasing temperature .The higher the temperature, the more MgO can be added before saturation. The effect of Fe3O4 on the viscosity is quite significant. The viscosity of slag increases to 300 mPa·s at （1 300 ℃） when Fe3O4 content varied from 2.84% to 9.53%. The viscosity values are expressed as the functions of temperature and composition. A comparison between FenO-MgO-SiO2 and FenO-MgO-CaO-SiO2 systems are also given.

Activity coefficient of NiO in SiO_(2)-saturated MnO–SiO_(2)slag and Al_(2)O_(3)-saturated MnO–SiO_(2)–Al_(2)O_(3)slag at 1623 K

As a part of the fundamental study related to the reduction smelting of spent lithium-ion batteries and ocean polymetallic nodules based on MnO–SiO_(2)slags,this work investigated the activity coefficient of NiO in SiO_(2)-saturated Mn O–Si O_(2)slag and Al_(2)O_(3)-saturated Mn O–SiO_(2)–Al_(2)O_(3)slag at 1623 K with controlled oxygen partial pressure levels of 10^(-7),10^(-6),and 10^(-5)Pa.Results showed that the solubility of nickel oxide in the slags increased with increasing oxygen partial pressure.The nickel in the Mn O–Si O_(2)slag and Mn O–Si O_(2)–Al_(2)O_(3)slag existed as Ni O under experimental conditions.The addition of Al_(2)O_(3)in the Mn O–Si O_(2)slag decreased the dissolution of nickel in the slag and increased the activity coefficient of Ni O.Furthermore,the activity coefficient of Ni O(γN_(i O)),which is solid Ni O,in the Si O_(2)saturated Mn O–Si O_(2)slag and Al_(2)O_(3)saturated Mn O–Si O_(2)–Al_(2)O_(3)slag at 1623 K can be respectively calculated asγN_(i O)=8.58w(Ni O)+3.18 andγN_(i O)=11.06w(Ni O)+4.07,respectively,where w(Ni O)is the Ni O mass fraction in the slag.

Study of decomposing carbonyl slag

A new technology was put forward to deal with the carbonyl slag at low acidity and low oxygen pressure in the kettle. With the orthogonal experiments for analyzing the sequence of four factors and some single factor experiments for the best conditions. The best conditions are used for extracting nickel, cobalt and copper and enriching precious metals: the cupric ion concentration is 5 g/L; and pH=6; the sulfur coefficient is 1.4; the oxygen pressure is 0.08 MPa; the time bubbling oxygen is 20 min; the ratio of liquid to solid is 8:1; the leaching time is 2 h; the heating time is 2.5 h. The leaching rates of nickel and cobalt are more than 98% and that of copper is above 97%. Nickel and cobalt can be separated efficiently from copper and precious metals from the carbonyl slag. Moreover, its leaching liquor has less copper. Nickel and cobalt can be reclaimed only once. During the whole process, the leaching rates of Au and Ag are more than 99.9%, while other precious metals are still in the residue without any loss.

氯化挥发法提取电炉冶炼镍铁渣中镁

针对电炉冶炼红土镍矿产生的镍铁渣中镁含量高导致渣无法大宗利用及造成镁资源浪费的问题,文中提出碳共存条件下用CaCl_(2)氯化挥发渣中MgO的技术思路。研究了氯化温度、保温时间、碳及氯化钙添加量等对渣中镁挥发率的影响。研究结果表明:在n(C)/n(Mg)=1.25、n(CaCl_(2))/n(Mg)=1、1300℃保温120 min条件下,镍铁渣中镁的挥发率可以达到67.22%,氯化后渣中MgO含量降低至8.21%。碳共存条件下CaCl_(2)氯化渣中镁的过程是:O_(2)和渣中酸性氧化物使CaCl_(2)分解产出Cl_(2),Cl_(2)与MgO反应生成MgCl_(2),碳的作用是降低Cl_(2)与MgO反应时的反应温度。随着氯化过程的进行,渣中主要物相由Mg_(2)SiO_(4)转变为CaMgSi_(2)O_(6),渣的熔化性温度由最初的1400℃降低至1300℃。

响应曲面法优化二次镍渣微晶玻璃热处理制度

镍渣作为有色冶炼过程产生的冶金废渣,以堆存形式处理,环境影响突出,但含铁量高,是一种极具开发前景的二次利用资源。以二次镍渣为原料制备微晶玻璃,采用响应曲面法并结合Box-Behnke原理设计探讨了核化温度、核化时间、晶化温度、晶化时间及其交互作用对微晶玻璃抗折性能的影响,建立了抗折强度与各因子间的模型。通过模拟优化,确定了最佳热处理工艺参数:核化温度和晶化温度分别为845℃和955℃、核化时间和晶化时间均为80 min。采用最优工艺参数试验验证发现,微晶玻璃主晶相为铁硅灰石和钙长石,抗折强度均值达到126.78 MPa,与模型预测值偏差较小,表明该预测模型可靠有效及工艺优化合理可行。

单组分电炉镍渣基地聚物修补材料制备与性能调控

为利用具有潜在活性的固体废弃物电炉镍渣,制备单组分电炉镍渣基地聚物修补砂浆.基于正交实验和极差分析,通过掺入掺合料并改变碱模数和碱当量等关键影响因素,对地聚物砂浆各项修补性能进行调控,获取满足修补性能的最优配合比,确定各因素对修补性能的影响主次.结果表明,最优配比是矿渣掺量为30%,粉煤灰掺量为30%,碱模数为1.2,碱当量为6.5%,其28 d抗压、抗折强度分别为90.29、9.23 MPa,干燥收缩率为0.56×10-3,14 d拉伸粘结强度为3.64 MPa,满足修补砂浆规范要求.经比较,矿渣掺量对修补砂浆性能调控影响最为显著.

国内外汽轮机转子用镍基合金锻件研制现状

对于650℃等级超超临界汽轮机转子,耐热钢已经无法满足其对抗氧化性能和高温性能的要求,必须采用镍基合金制造。然而镍基合金成分复杂,制造1000 mm以上的锭型难度很大,同时锻造变形温度区间窄、变形抗力大,很难制造1000 mm以上、重量超过10 t的大型转子锻件。本文介绍了国内外超超临界汽轮机高温转子用大型镍基合金的成分特点、冶炼工艺、锻件尺寸、性能水平等,重点阐述了国内大型镍基合金冶炼工艺、锻造、热处理等制造工艺方面的研究现状,指出了国内下一步大型镍基合金锻件的研制重点。

基于调渣提铁的镍冶炼渣熔化温度调控

目前,镍渣提铁工艺存在提铁效率低、工艺实施难度大、成本高等问题。本文通过相图分析、单因素和正交实验等方法,研究了炉渣中主要氧化物含量对半球点温度的影响,得到了有利于提铁的炉渣渣型优化方案。结果表明:当CaO含量(质量分数)为25%、MgO含量为9%、铁硅比为0.8时,该渣型的半球点温度最低。考虑到现行工艺,选择MgO含量为13%、CaO含量为20%、铁硅比为1.0为较优方案,所得炉渣的半球点温度明显低于现行顶吹炉渣的半球点温度。调整后的炉渣中含铁物相由以硅酸亚铁为主转化为以钙铁榴石和铁氧化物为主,有利于后续提铁。

镍冶炼渣中铁资源回收研究现状及发展分析

镍渣为有色冶炼过程中产生的冶金废渣,铁品位高达40%,具有较高的回收利用价值。镍渣中的铁主要以硅酸亚铁形式的化合物为主,难以对其进行有效提取。如何合理利用镍渣,对行业可持续、绿色化发展具有重大意义,是目前的研究热点。本文对镍渣中铁资源回收技术进行了综合分析,针对现有镍渣提铁工艺中存在的问题,提出在镍冶炼过程中加钙以调整镍渣渣型和降低冶炼温度,使铁橄榄石向铁酸钙形式转变,降低后续提铁难度,以期实现镍渣的高值资源化综合利用。