Soda ash roasting of titania slag product from Rosetta ilmenite

A soda ash roasting process for upgrading titania slag product of Rosetta ilmenite to a high grade titanium dioxide (TiO₂) is presented. The roasting process was carried out at moderate to high temperatures to yield a reaction product that would be easily decomposed by subsequent leaching procedures. Factors affecting the roasting process; namely the soda ash ratio to the slag material, the roasting time and temperature were studied. The optimised conditions used a Na₂CO₃ to slag ratio of 0.55:1 at a roasting temperature of 850 °C for 0.5 h duration period. The impurities associated with the roasted slag were subjected to leaching with water and dilute hydrochloric acid solution leaving synthetic rutile (TiO₂) as insoluble residue. To improve the quality of the synthetic rutile, an alkaline leaching step was added to remove the excess silica present in the treated titania slag. This method is capable of producing high purity synthetic rutile assaying about 97% TiO₂.     

Effect of ultrasound on kinetics of scheelite leaching in sodium hydroxide

Abstract

This paper deals with the dissolution of scheelite in sodium hydroxide, in the absence and presence of ultrasound. The experimental data agreed quite well with the shrinking core model. The leaching rate was controlled by surface chemical reaction, with an apparent activation energy of 80 mol kg^?1 in both cases, but the reaction order was reduced from 1·3 to 0·8 in the presence of ultrasound. The effect of ultrasound is mainly focused on the pre-exponential factor A in the Arrhenius equation, which embraces the collision factor. The kinetics equations of the processes are established.

Cet article porte sur la dissolution de la schéelite dans l’hydroxyde de sodium, en absence ou en présence d’ultrasons. Les données expérimentales étaient en très bon accord avec le modèle de rétrécissement du noyau. La réaction chimique superficielle contrôle la vitesse de lixiviation, avec une énergie d’activation apparente de 80 mol kg^?1 dans les deux cas, mais l’ordre de la réaction était réduit de 1·3 à 0·8 en présence d’ultrasons. L’effet des ultrasons est principalement centré sur le facteur pré-exponentiel A de l’équation d’Arrhenius, qui comprend le facteur de collision. On a respectivement établi les équations cinétiques des procédés.     

矿渣-硅灰协同强化钢渣水化反应机理

 强化钢渣水化过程、激发钢渣胶凝活性对提高钢渣资源利用率具有重要意义。选取矿渣、硅灰作为复合激发剂,采用正交试验设计方法,研究钢渣粒度、矿渣与硅灰添加量对钢渣胶凝活性的影响,并针对钢渣胶凝试块3 d、28 d水化产物进行表征分析以揭示矿渣、硅灰协同强化钢渣水化的机理。正交试验结果表明,硅灰由于其高反应活性能够有效促进钢渣3 d龄期的水化,而矿渣中玻璃相的潜在活性使其对钢渣28 d龄期的水化影响更加显著,当硅灰添加量为2%、矿渣添加量为15%时,钢渣的3 d、28 d胶凝活性分别提高18.34%、28.26%;XRD、TG-DTA和SEM分析结果表明,硅灰的晶种效应、火山灰效应和微集料填充效应与矿渣中活性相对较高的铝氧四面体在钢渣高碱性的液相体系中能够协同强化水化反应,使复合胶凝体系中生成更多的C-S-H凝胶和AFt晶体,C-S-H凝胶紧密包裹AFt晶体,两者交错生长形成复杂密实的网络结构,从而提高胶凝材料的力学性能,达到激发钢渣胶凝活性的目的。将钢渣、矿渣、硅灰复合掺合料应用到混凝土中,结果表明,当复合掺合料替代水泥20%时混凝土力学性能和抗碳化性能均得到最大限度提升,其中3 d、28 d力学性能相比纯水泥混凝土分别提高31.53%、25.88%,3 d、28 d抗碳化性能相比纯水泥混凝土分别提高18.75%、24.11%。     

Oxidation kinetics of vanadium-bearing LD converter slag by mechanical activation

A thermogravimetric investigation was performed to evaluate the kinetic and thermodynamic parameters and the influence of mechanical activation on oxidation of vanadium-bearing LD (Linz–Donawitz) converter slag. Results indicate that the particle size of d_0.5 significantly decreased from 29?μm to 0.266?μm after activation, and the specific surface area based on the BET model increased from 1.324?m²/g to 3.289?mm²/g. Thermogravimetric investigations were separately performed at 650, 700, 750, 800, 850, 900, 950 and 1000°C. Two distinct stages in the oxidation process were identified. The first stage was controlled by nucleation and growth and the second stage was controlled by 3D diffusion. However, the first stage relatively contributed more to the entire process than the second stage. Kinetic study also reveals that mechanical activation exhibited a significant effect on the oxidation of LD converter slag. Mechanical activation significantly reduced the roasting temperature and shortened the roasting time. The corresponding apparent activation energy E_a and frequency factor A changed from 13.01?kJ/mol to 6.59?kJ/mol and 0.247?min^?1 to 0.141?min^?1 for unmilled and milled slags, respectively.     

水洗洁净处理对钢渣SMA性能影响的研究

介绍了路用钢渣集料洁净技术,利用洁净工艺前后的钢渣集料分别配制了钢渣沥青玛碲脂碎石混合料(SMA),得到用水清洗后钢渣最佳配合比为:1号(钢渣10~16mm)∶2号(钢渣5~10mm)∶3号(玄武岩3~5mm)∶4号(玄武岩3mm)∶5号(石灰岩矿粉)=38∶36∶8∶8∶10,最佳油石比为6.4;没有用水清洗钢渣最佳配合比为:1号∶2号∶3号∶4号∶5号=34∶38∶10∶8∶10,最佳油石比为6.4。研究了钢渣洁净技术对钢渣SMA性能影响,发现洁净技术有利于发挥钢渣SMA性能。     

钨酸钠溶液氢氧化钙苛化-沉淀白钨的研究

钨酸钠溶液氢氧化钙苛化-沉淀白钨工艺是实现钨矿NaOH分解试剂回收,以至黑钨和黑白钨混合矿绿色冶炼的技术途径;研究了不同温度下钨酸钠溶液氢氧化钙苛化-沉淀白钨反应的平衡常数和标准自由能变化,分析了氢氧化钠和钨酸钠的活度系数对反应平衡的影响;工艺研究表明:温度和钨酸钠溶液浓度对白钨沉淀率的影响非常显著.当氢氧化钙用量为1.4倍理论量,温度100℃,钨酸钠溶液钨浓度为105 g/L,保温时间为2 h,搅拌速度为350 r/min,白钨沉淀率可达96%以上.与传统工艺采用氯化钙作为沉淀剂相比,氢氧化钙沉淀白钨所需的理论量倍数较大、反应的时间较长、搅拌速度更快.     

凌钢钢渣处理生产实践

介绍了凌钢钢渣处理生产工艺流程、主要设备性能参数及钢渣处理关键技术环节,包括高温钢渣运输、焖渣效果控制、磁选设备安装和布置等,同时介绍了钢渣处理所回收产品的种类和用途,指出钢渣处理过程中存在的问题并提出了解决措施。实践结果表明:凌钢钢渣处理生产线经多次技改后,工艺布置合理,处理效果好,运行费用低,有效解决了钢渣外排带来的经济损失以及环保问题。     

Separation of zinc from spent zinc-carbon batteries by selective leaching with sodium hydroxide

Physical methods such as crushing and sieving followed by magnetic separation steps were applied to separate non-magnetic material (88.4 wt.%) from zinc-carbon spent batteries. The oversize material was processed by eddy current separation to recover zinc sheet, carbon rods, and plastics. The undersize fraction (− 2.36 mm) with a metal composition of 15.5% Zn, 17.5% Mn, and 1.4% Fe was used for the leaching experiments under different conditions such as concentration of sodium hydroxide, temperature, agitation speed, and pulp density. Selective leaching using 4 mol dm^− 3 NaOH at 100 g dm^− 3 solid/liquid ratio, 80 °C and 200 rpm gave a zinc extraction of 82% and a manganese extraction of less than 0.1%. An overall zinc recovery was about 88.5% by the processes described in this study.     

Challenges in the use of stainless steel slag

Stainless steel melting shops of Outokumpu Group are located in Finland,Sweden and England(UK). In all of the countries the European Union legislation is the same,but in practice the plants face different technical,economical and administrative challenges in developing sustainable treatments and use of by-products. Due to availability of good natural construction materials,the use of slag and other industrial by-products has been quite small in Northern Europe.Blast furnace slag has been completely utilized,while slag from stainless steel processes has earlier been regarded as waste.Steering of the metallurgical melt phase,slag cooling,treatment and metal recovery processes are the main technical challenges for increasing the sustainable use of stainless steel slag. Moreover,product properties have to fulfill standards and customer requirements.Dry or water-cooled EAF slag aggregates are typically used in road construction.Outokumpu has developed light mineral slag aggregates which are cooled in rapid water process.During this process,a specific structure and mineralogy is formed in the slag and leaching from the material decreases.In many regulatory discussions,it seems that there is not enough relevant scientific data from harmful compounds.Limit values are based only on laboratory tests and model estimations,not on the material use itself or real nature.A risk-based approach is needed when environmental acceptance is not clear.Limit values based on content are not applicable because environmental or health risks depend on the release or leaching of substances from the material.This is the case especially with metals.     

Experimental study on glass-ceramics preparation from hot steel slag

When liquid steel slag produced from steelmaking process was treated into the post-cold slag by conventional methods,the great deal of slag heat was dissipated into the environment,causing a lot of energy waste and environmental pollution.In this study,a novel approach of direct utilization of hot steel slag as a raw material and slag heat for the production of glass-ceramics was proposed and experimentally tested.In order to simulate liquid slag from steelmaking electric furnace,40%water-quenched slag was remelted at 1 450℃and then mixed with 60%melting additives（silica powder,alumina powder and sodium oxide, etc.）and subsequently melted together at 1 500℃for 1 h into modified liquid slag which was cast,heat-treated, annealed and transformed into glass-ceramics.The heat-treated glass samples were investigated using differential thermal analysis（DTA）,X-ray diffraction（XRD）,and scanning electron microscopy（SEM）. The results show that dominant crystalline phase is diopside[CaFe（SiO₃）₂]and the shape of the crystal is like the granule,diameter is about 0.2 -0.6μm.A glass-ceramic with nucleation temperature of 695℃for two hours and crystallization temperature of 893℃for one hour and 1 163℃for half-hour exhibited the best combination of properties.This method of slag mixed with melting additives to adjust the composition of the parent glass is important for the industrial production of glass-ceramics by direct utilization of hot steel slag.     

含铬特殊钢渣中总铬及六价铬浸出特性及影响

 含铬特殊钢渣中六价铬具有强氧化性和高毒性,研究不同条件下渣中总铬及六价铬的浸出行为及特征并进行环境风险评估,对后续无害化及资源化利用具有重要的意义。浸出试验结果表明,渣中总铬和六价铬的浸出量随粒度和浸出时间增加而提高,随液固比(即浸提剂溶液体积与待测固体试样质量的比值)增加而降低;六价铬浸出量随体系pH值升高而增加,当pH=11时六价铬浸出量达到最高值2.92 mg/L;总铬浸出量随pH值升高呈现先降低后增加的趋势,当pH=7时,总铬达到最小浸出量2.49 mg/L。经标准浸出程序测定,钢渣中铬及六价铬浸出量分别为4.71和3.36 mg/L,符合固废堆存限值(GB 5085.3—2007),堆存风险较小,但高于行业利用限值(HJ/T 301—2007),需对其进行无害化处理后再进行后续资源化利用。     

钢渣处理与综合利用技术

结合国内外钢渣处理与利用现状,分析评述了钢渣余热自解热闷工艺、浅盘热泼工艺、风淬工艺、水淬工艺、滚筒处理工艺等钢渣处理工艺,及钢渣作为钢铁冶炼熔剂、用作建筑材料、筑路材料、回收废钢、钢渣微粉等资源综合利用技术。建议在电炉氧化渣水淬工艺、高磷铁水冶炼脱磷处理及钢渣加工设备等方面加强研究和改进。     

钢渣处理工艺的选择

论述了钢渣的不同利用途径.系统介绍了钢渣处理采用的主要技术,分析了各种技术的应用发展情况、达到的效果及存在的问题.重点介绍了风淬法、热闷法、宝钢滚筒法和嘉恒法,同时还比较分析了几种典型工艺的优缺点.对于钢厂如何科学、合理地选择钢渣处理工艺有一定参考意义.     

Effect of slag composition on steel cleanliness in interstitial-free steel

Ladle slag affects steel cleanliness at the end of the Ruhrstahl-Hereaeus (RH) and holding process.The relationship between composition of ladle slag, total oxygen (TO) and inclusions was investigated using X-ray fluorescence (XRF), infrared absorption, and SEM+EDS methods.The results indicate that TO in steel at the end of RH increases linearly with increasing FeO content in slag.TO is lower when wCaO/wAl2 O3 (C/A)=1.5-2.0 than that of C/A=1.0-1.4 under an approximate content of FeO.During the holding process, irregular Al2 O3 inclusions are newly generated due to slag reoxidation.Additionally, Al2 O3-Tix O inclusions are newly generated in the steel when the content of FeO is higher.By combining experimental and thermodynamic calculation results, it is determined that the slag has a good melting property within the zone of C/A=1.2-1.8 and adsorption capacity of Al2 O3 when the content of SiO2 in slag is controlled at 4%-6%.The increase in the C/A ratio and the decrease of FeO content in slag can slow down the reoxidation rate.     

Study on the properties and application of the steel slag special fine aggregate

The physical properties,grading stability and application stability of the steel slag special fine aggregate(diameter≤0.8 mm) at Baosteel were analyzed in this study,and the mechanical and working properties were studied when the aggregate was applied to concrete.The result shows that the aggregate has special advantages of hardness and wear-resistance,so it can be used as an excellent road surface material.The concrete mixed with the steel slag special fine aggregate exhibits good mechanical properties and working properties,which is safe and reliable.     

宝钢滚筒型渣处理装置用钢球磨损分析

通过对滚筒型渣处理装置内钢球磨损原因进行分析,找出了钢球磨损的影响因素和临界状态,发现16Mn钢球发生物理变化的温度临界点在700～800℃。通过滚筒冷却工艺、进渣工艺和放散蒸汽工艺的改进,降低了滚筒钢球的消耗。     

A novel process of preparing glass-ceramics directly from molten steel slag

A novel process technology to prepare glass-ceramics directly from molten steel slag(MSS) is proposed in the study.The liquid-solid mixing method was used to adjust the components of the MSS and glass-ceramics was obtained.The effects of heat-treatment conditions on the microstructure,physical and mechanical properties of samples were studied.Economical benefits of the novel process were analyzed.The results show that heat-treatment is a very effective approach to achieving crystallization.The dominant crystal phase in products is diopside [(Mg6Al2Fe2)Ca(Si1.5Al5)O2].The shape of the crystallization is like a granule.The glass-ceramic samples exhibited good mechanical properties and presented chemical stability.The economic benefits of the process are remarkable due to less energy consumption compared with conventional glass-ceramics production methods.     

Study on rapid stabilization of steel slag powder

Dry ball milling and wet ball milling were used to treat converter slag with particle size < 10 mm and the converter slag powder was stabilized by H₂O only and H₂O coupled with CO₂.respectively.Results showed that when CO₂ &H₂O was used,the free-calcium oxide（f-CaO） content in converter slag decreased significantly and after an-hour treatment the f-CaO content was reduced to 3%;however,when only treated by H₂O without CO₂, f-CaO needed 3-hour stabilization to decrease its content to 3%.When f-CaO in converter slag powder was treated by CO₂ &H₂O,its main reaction products were CaCO₃ and then Ca（OH）₂;however,when only H₂O was used, the f-CaO content decreased gently and the main products were Ca（OH）₂.     

转炉钢渣处理技术的开发和应用

经一年来的生产实践表明,本钢研发的转轮式钢渣水淬处理方法安全可靠,钢渣处理效率高达8t／min,钢渣分离度好,工艺布置紧凑,主体设备结构简单,占地面积小,钢渣粒化液压倾翻渣罐速度可调,粒化周期可控范围大,时间在5～15min内,水淬后的钢渣粒度均匀,小于5mm的比例达95％以上,有利于钢渣的进一步应用。     

不锈钢板坯连铸结晶器内钢/渣界面行为模拟及卷渣分析

基于湍流模型与多相流模型的耦合,应用液面追踪技术(VOF),实现了对不锈钢板坯连铸结晶器内流体流动及钢/渣界面行为的模拟计算,并用水模拟结果进行了对比验证,在此基础上计算出实际的钢/渣界面特征及界面上钢/渣行为.通过分析水口的侧孔形状、出口倾角、水口浸入深度、结晶器宽度以及拉速对钢/渣界面特征及界面上钢/渣行为影响规律,指出了钢/渣界面行为与卷渣是密切相关的,进而探讨了钢/渣界面及卷渣形成的机理.