Effect of Na2CO3 and CaCO3 on Coreduction Roasting of Blast Furnace Dust and High-phosphorus Oolitic Hematite

Iron was recovered from blast furnace dust and high-phosphorus oolitic hematite in the presence of Na2CO3 and CaCO3 additives. The functions of Na2CO3 and CaCO3 during the coreduction roasting process were investigated by XRD and SEM-EDS analyses. Results indicate that these additives not only hinder the reduction of fluorapatite, CaCO3 also decreases the P content of direct reduced iron（DRI） by increasing the reduction alkalinity. P remains as fluorapatite in the slag, which can be removed by grinding and magnetic separation under optimal conditions. The Na2CO3 promotes hematite reduction and improves the iron recovery（εFe） by replacing the FeO from fayalite, which results in quick growth and aggregation of metallic iron and improvement of ε（Fe） in DRI. A DRI with 91.88 mass% Fe, and 0.065 mass% P can be achieved at a recovery of 87.86 mass% under the optimal condition.

Strengthening iron enrichment and dephosphorization of high-phosphorus oolitic hematite using high-temperature pretreatment

The efficient development and utilization of high-phosphorus oolitic hematite is of great strategic significance for the sustainable supply of iron-ore resources in China.In this paper,the mechanism of high-temperature pretreatment for enhancing the effect of iron enrichment and dephosphorization in the magnetization roasting–leaching process was studied by X-ray diffraction(XRD),vibration sample magnetometer(VSM),scanning electron microscopy and energy dispersive spectrometry(SEM–EDS).Compared with the process without high-temperature pretreatment,the iron grade of the magnetic separation concentrate after high-temperature pretreatment had increased by 0.98%,iron recovery rate had increased by 1.33%,and the phosphorus content in the leached residue had decreased by 0.12%.High-temperature pretreatment resulted in the dehydration and decomposition of hydroxyapatite,the dehydration of limonite and the thermal decomposition of siderite,which can produce pores and cracks and weaken the compactness of the ore,improve the magnetization characteristics of roasted ore,and strengthen the iron enrichment and dephosphorization during the magnetization roasting and leaching process.

Direct Reduction of High-phosphorus Oolitic Hematite Ore Based on Biomass Pyrolysis

Direct reduction of high-phosphorus oolitic hematite ore based on biomass pyrolysis gases （CO, H2, and CH4 ）, tar, and char was conducted to investigate the effects of reduction temperature, iron ore-biomass mass ratio, and reduction time on the metallization rate. In addition, the effect of particle size on the dephosphorization and iron recovery rate was studied by magnetic separation. It was determined that the metallization rate of the hematite ore could reach 99.35 % at iron ore-biomass mass ratio of 1 ： 0.6, reduction temperature of 1100℃, and reduction time of 55 min. The metallization rate and the aggregation degree of iron particles increase with the increase of reduction temperature. The particle size of direct reduced iron （DRI） has a great influence on the quality of the iron concentrate during magnetic separation. The separation degree of slag and iron was improved by the addition of 15 mass% sodium carbonate. DRI with iron grade of 89.11%, iron recovery rate of 83.47%, and phosphorus content of 0.28% can be obtained when ore fines with particle size of -10μm account for 78.15%.

Magnetizing Roasting Mechanism and Effective Ore Dressing Process for Oolitic Hematite Ore

Magnetizing roasting of oolitic hematite ore from western Hubei Province was investigated.The mechanism for reduction roasting of oolitic hematite ore was discussed and analyzed.It is found that flash magnetizing roasting-magnetic separation process is a promising approach for the processing of oolitic hematite ore from western Hubei Province.

Phase transformation in suspension roasting of oolitic hematite ore

Suspension roasting followed by magnetic separation is a promising method to upgrade oolitic hematite ore.An oolitic hematite ore was roasted using suspension roasting technology at different temperatures.The phase transformation for iron minerals was investigated by XRD and Mossbauer spectrum,and the characteristics of roasted product were analyzed by VSM and SEM-EDS.Results indicate that the magnetic concentrate is of 58.73% Fe with iron recovery of 83.96% at 650 °C.The hematite is rapidly transformed into magnetite during the roasting with transformation ratio of 92.75% at 650 °C.Roasting temperature has a significant influence on the phase transformation of hematite to magnetite.The transformation ratio increases with increased temperature.After roasting,the magnetic susceptibility is significantly improved,while iron ore microstructure is not altered significantly.

Migration behaviors and kinetics of phosphorus during coal-based reduction of high-phosphorus oolitic iron ore

To understand the migration mechanisms of phosphorus(P)during coal-based reduction,a high-phosphorus oolitic iron ore was reduced by coal under various experimental conditions.The migration characteristics and kinetics of P were investigated by a field-emission electron probe microanalyzer(FE-EPMA)and using the basic principle of solid phase mass transfer,respectively.Experimental results showed that the P transferred from the slag to the metallic phase during reduction,and the migration process could be divided into three stages:phosphorus diffusing from the slag to the metallic interface,the formation of Fe P compounds at the slag metal interface and P diffusing from the slag metal interface to the metallic interior.The reduction time and temperature significantly influenced the phosphorus content of the metallic and slag phases.The P content of the metallic phase increased with increasing reduction time and temperature,while that of the slag phase gradually decreased.The P diffusion constant and activation energy were determined and a migration kinetics model of P in coal-based reduction was proposed.P diffusion in the metallic phase was the controlling step of the P migration.

Application of multi-stage dynamic magnetizing roasting technology on the utilization of cryptocrystalline oolitic hematite:A review

A large number of studies have shown that oolitic hematite is an iron ore that is extremely difficult to utilize because of its fine disseminated particle size, high harmful impurity content and oolitic structure.To recover iron from oolitic hematite, we developed a novel multistage dynamic magnetizing roasting technology. Compared with traditional magnetizing roasting technologies, this novel technology has the following advantages: firstly, the oolitic hematite is dynamically reduced in a multi-stage roasting furnace, which shortens the reduction time and avoids ringing and over-reduction;secondly, the novel dynamic magnetizing roasting technology has strong raw material adaptability, and the size range of raw materials can be as wide as 0–15 mm;thirdly, the roasting furnace adopts a preheating-heating process, and the low-calorific value blast furnace gas can be used as the fuel and reductant, which greatly reduces the cost. The actual industrial production data showed that the energy consumption in the roasting process can be less than 35 kg of standard coal per ton of raw ore. The iron grade of the concentrate and iron recovery reached 65% and 90%, respectively.

Process mineralogy and characteristic associations of iron and phosphorus-based minerals on oolitic hematite

The chemical compositions,mineralogical characteristics,as well as dissemination of iron-and phosphorus-based minerals were studied for the E’xi oolitic hematite from western Hubei Province in China by using chemical analysis,optical microscope,electron probe micro-analyzer(EPMA)and energy dispersive spectroscopy(EDS).It is found that this kind of oolitic hematite ore contains 47.71%TFe,10.96%SiO_2,as well as 0.874%P,with hematite as the dominant Fe-bearing minerals,and quartz,chamosite,illite and cellophane as main gangue minerals.The microscope examination showed that the ore has an oolitic structure,with some ooids principally formed by a series of concentric layers of hematite collophanite around nucleus that is hematite in the association with collophanite.Based on the EPMA and EDS analysis,it can be known that some ooids are primarily composed of hematite and collophanite.The separation can be achieved through fine grinding for those collophanite laminae with a higher P content.However,the dissemination of two minerals at the interface will result in the difficulty in effective separation.Besides,some ooids are made of chamosite with some nucleus formed of quartz,which is principally finely disseminated with hematite.In view of the close association and dissemination of iron-and phosphorus-based minerals in the ooids,it is found that the process of stage-grindings and stage-separations can be adopted to effectively increase the iron recovery and decrease the P content in the concentrate to some extent.

Corrosion and Penetration Resistance of Corundum Bricks to High Phosphorus Oolitic Hematite Reducing Materials

The paper aims at investigating whether corundum bricks can be used for the bottom, of the direct reduction furnace of high phosphorus oolitic hematite. The reducing materials including high phosphorus oolitic hematite, bitumite, Ca（OH） 2 and Na2CO3 at a mass ratio of 1：0. 15：0. 15：0. 03 were mixed and pressed into carbon containing cylindrical specimens with the size of Ф15 mm × 20 mm. The specimens were placed on the corundum bricks and reduced in a high temperature tube furnace at 1 200 ℃ for 40, 60, 80, 140 and 220 min, respective- ly. The corrosion and penetration resistance of corundum. bricks to high phosphorus oolitic hematite reducing materials were analyzed with XRD, SEM and EDS. It shows that the reducing slag formed in the reduction process corrodes the surface of corundum bricks to form a product layer of anorthite and hercynite, retarding the further corrosion of the reducing slag; the reducing slag which has penetrated into the interior of the brick goes through the gaps between the particles and generates anorthite and hercynite, filling the gaps and hindering the reducing slag penetration.

Application of Wood Char in Processing Oolitic High-phosphorus Hematite for Phosphorus Removal

Phosphorus removal from oolitic high-phosphorus hematite using direct reduction followed by melting sep aration was investigated. At the direct reduction stage, highly volatile wood char was prepared by carbonizing jujube wood at 673 K for 2 h and was used as reducing agent. The results of the direct reduction tests show that at a tem- perature of 1373 K, a char mixing ratio of 0.8, and a reduction time of 10-25 min, the briquettes reached a metal- lization degree of 80% -84% and a residual carbon content of 0.13 -1.98 mass%. Phosphorus remained in the gangue as calcium phosphate after reduction. The results of the melting separation tests show that residual carbon in reduced briquette negatively affects the phosphorus content （W[p]） in hot metal. When the reduced briquettes ob- tained under the aforementioned conditions were used for melting separation, hot metal suitable for basic oxygen steelmaking （w[p]〈0.4 mass%） could not be obtained from metallic briquettes with a residual carbon content more than 1.0 mass~. In contrast, it could be obtained from metallic briquettes with residual carbon content less than 0.35 mass% by mixing with 2%-4% Na2CO3.

还原剂及脱磷剂对高磷鲕状赤铁矿直接还原-磁选影响的研究进展

这是一篇矿业工程领域的文章。综述了还原剂及脱磷剂对高磷鲕状赤铁矿直接还原的影响,从煤和其他还原剂两个方面归纳了还原剂对高磷鲕状赤铁矿还原影响的研究现状,从单一脱磷剂和组合脱磷剂两种使用方式总结了脱磷剂的研究进展。指出了高磷鲕状赤铁矿直接还原-磁选工艺存在的问题,根据目前存在问题提出了未来针对高磷鲕状赤铁矿直接还原-磁选研究方向的建议。

国外某高磷鲕状铁矿选矿试验研究

国外某高磷鲕状铁矿石主要铁矿物为磁铁矿和赤褐铁矿,有害杂质硫含量较低,伴生杂质硅、铝、磷含量较高。为降低该高磷鲕状铁矿石中的磷矿物含量,提前抛出部分含磷高的尾矿,进行了多粒级干式预选试验研究,探索预选抛废的可行性,同时对磨选工艺进行了阶段磨矿磨矿细度试验。试验确定了原矿阶段磨矿—弱磁选流程,最终获得了产率47.42%、铁品位64.45%、磷品位0.501%、铁回收率53.19%的铁精矿,有效降低了铁精矿中的磷含量,为合理开发利用该铁矿资源提供了参考依据。

Reduction of Carbon-bearing Pellets of Oolitic Hematite in a Shaft Furnace

When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each other at high temperatures;and the separation of phosphorus from iron is difficult.To solve these problems,experiments were conducted on oolitic hematite reduction in a resistance furnace and semi-industrial test shaft furnace.The results showed that the metallization rate reached 90% or greater under the conditions of a reduction temperature of 1 150℃,an atmosphere of simulated flue gas,and a reduction time between 1.5and 2.0h.The problem of high-temperature bonding among pellets can be solved by increasing the strength of the pellets,coating their surface with a surface transfer agent and maintaining an even temperature inside the shaft furnace.The basicity of the ore blend exerted no obvious effect on the magnetic concentrate and phosphorus content.The phosphorus content in the magnetic concentrate can be further reduced by improving the grinding capacity of the ball mills used in the experiments.On the basis of the experimental results related to oolitic hematite reduction with carbon-bearing pellets in a shaft furnace,the experimental requirements were satisfied with an average 88.27%total Fe content and 0.581% P content in the pellets.

Slag/metal Separation Process of Gas-reduced Oolitic High-phosphorus Iron Ore Fines

Slag/metal separation process of the highly reduced oolitic high-phosphorus iron ore fines was investigated. Samples were prepared using the reduced ore fines （metallization rate： 88%） and powder additives of CaO and Na2CO3. Slag/metal separation behavior tests were conducted using a quenching method and the obtained metal parts were subjected to direct observation as well as microstructure examination with SEM and EDS; iron recovery and phosphorus distribution tests were conducted using a Si-Mo high temperature furnace and the obtained metal parts were examined by ICP-AES analysis and mass measurement. Thermodynamic calculation using coexistence theory of slag structure was also performed. Results show that temperature for slag/metal separation must be higher than 1823 K and a satisfying slag/metal separation of the highly reduced ore fines needs at least 4 min; phosphorus con- tent of hot metal is mainly determined by thermodynamics; temperature of 1823-1873 K and Na2CO3 mixing ratio of about 3 % are adequate for controlling phosphorus content to be less than 0.3 mass% in hot metal; temperature, time and Na2CO3 mixing ratio do not have significant effect on iron recovery, and iron recovery rate could be higher than 80% as long as a good slag/metal separation result is obtained.

高磷鲕状赤铁矿还原焙烧中脱磷剂CaCO_(3)作用影响因素研究

为揭示褐煤用量和焙烧温度对CaCO_(3)作用效果的影响机制,以褐煤为还原剂、CaCO_(3)为脱磷剂对国外某高磷鲕状赤铁矿进行了直接还原焙烧试验。热力学计算、X射线衍射(XRD)和扫描电镜(SEM-EDS)分析表明,Ca-CO_(3)的作用效果是其分解的CaO和CO_(2)共同作用的效果总和。CaO的主要作用是促进铁矿物中的磷生成磷灰石并抑制磷灰石的还原,减少铁橄榄石和铁尖晶石的生成;CO_(2)可促进煤的气化反应,加快铁氧化物的还原。而褐煤用量和焙烧温度会影响CaO的反应程度,进而影响CaCO_(3)的作用效果。由于低褐煤用量和高焙烧温度时焙烧过程的熔融程度高,可促进CaO的固相反应,因此CaCO_(3)的作用效果好。试验研究发现,在CaCO_(3)用量28%、褐煤用量20%、焙烧温度1200℃时,得到的直接还原铁产品的脱磷率高达92%。

高磷鲕状赤铁矿侧吹熔炼试验研究

针对高磷鲕状赤铁矿现有冶炼工艺难以生产低磷铁水的问题,本文提出采用富氧侧吹还原熔炼技术处理高磷鲕状赤铁矿冶炼低磷铁水,在原料分析、热力学计算的基础上,进行了还原熔炼试验,并对还原体系进行了平衡计算,得到以下结论。矿物分析表明,该矿石具有典型的鲕状结构,鲕粒中赤铁矿主要分布在与脉石矿物形成的同心环状包裹构造的壳层中,铁、磷难以进行物理分离。热力学计算表明,高磷鲕状赤铁矿在1450~1600℃温度范围内进行还原时,磷以单质磷形式还原进入金属铁相,不能以磷氧化物形式挥发;仅在CaO存在的条件下,H_(2)O及CO_(2)才与Fe_(3)P反应,使磷以Ca_(3)(PO_(4))_(2)形式进入渣中。还原熔炼试验表明,矿热炉工艺中铁水中的磷含量大于1.0%,而侧吹炉还原工艺中铁水中磷含量可降低到0.45%。平衡计算表明,随着O_(2)/CH_(4)的增加和配炭比的降低,Fe的回收率减少;生铁中w[C]随着生铁中w[P]降低而降低。该研究表明,富氧侧吹还原技术具有熔池搅拌能力强、氧势及温度可灵活控制的优势,可强化铁中除磷、渣中留磷的冶炼条件,实现含磷铁基矿物的高效、短流程冶炼。本文研究结果为富氧侧吹工艺处理高磷鲕状赤铁矿的工业应用及推广提供理论基础和工艺参数指导。

重庆某高磷鲕状赤铁矿石提铁降磷试验研究

重庆巫山桃花高磷鲕状赤铁矿石铁品位较高,赤褐铁占总铁的97.71%,矿石有害成分磷含量较高。为了确定该矿石的开发利用工艺,进行了选矿试验研究。结果表明,矿石在磨矿细度为-0.075 mm占85%、SSS—I—500型双频双立环脉动高梯度磁选机2次粗选背景磁感应强度分别为0.77和0.80 T,脉动冲次均为60 Hz,2次常温反浮选粗选、粗选尾矿1粗1精2扫流程常温反浮选扫选情况下进行全流程试验,获得了铁品位为54.39%、磷含量为0.25%、铁回收率为74.96%的精矿。研究结果说明,针对高磷鲕状赤铁矿,采用强磁选—反浮选工艺能较好地降低磷含量,提高铁品位。

微波流态化预处理鲕状赤铁矿的创新技术:分离特性和机理

鲕状赤铁矿具有资源储量大、铁品位低、嵌布粒度细、矿物成分复杂等特点,传统选矿工艺难以有效利用。本文提出了一种新的微波流态化预处理工艺(MFP)来强化鲕状赤铁矿的分离。采用扫描电子显微镜、振动样品磁强计和激光粒度分析仪研究了MFP对焙烧磁选和浸出的影响。结果表明,与常规电炉预处理(EFP)相比,MFP焙烧产物的磁性显著提高,其磁选精矿的铁品位从56.88%提高到58.72%;回收率从88.89%提高到89.32%,浸出渣的磷含量从0.17%降至0.11%,MFP使磷浸出率从83.06%提高到89.77%。MFP可以强化微裂纹的形成和生长,从而增加矿石的比表面积和可磨性。

高磷鲕状赤铁矿氢基矿相转化强化提铁脱磷高效利用技术研究

本文针对高磷鲕状赤铁矿工艺矿物学特性及其难以利用传统选矿技术进行分选的难点,创新提出氢基矿相转化−磁选−酸浸高效提铁脱磷的新技术,探明了高磷鲕状赤铁矿氢基矿相转化过程中还原温度、还原时间、还原剂浓度等对分选效果的影响规律,通过技术优化获得了铁精矿铁品位65.05%、铁总回收率81.86%、磷含量0.081%的技术指标;采用XRD、VSM、XPS、SEM等检测分析手段探明了矿物物相、磁学特性、微观结构的演变规律,查明了铁矿物转化程度与分离效果之间的匹配机制,查明了高磷鲕状赤铁矿氢基矿相转化及分选过程中铁、磷等组份的富集迁移规律。研究成果为高磷鲕状赤铁等复杂难选铁矿高效利用提供了新技术借鉴和理论支撑。

Mn^2＋和Fe^3＋的致色作用：来自意大利白垩纪远洋红色灰岩的启示

本文首先详细研究了含Mn2+和Fe3+的致色矿物菱锰矿、鲕状赤铁矿、云母赤铁矿和镜铁矿的可见光吸收光谱及其一阶导数谱,鲕状赤铁矿、云母赤铁矿和镜铁矿的可见光吸收一阶导数谱的红光区的吸收谷的位置的变化表明随赤铁矿结晶度的降低,吸收谷由586.4nm移至577.4nm,而菱锰矿展示出了Mn2+的因电子跃迁产生的四个典型吸收及其一阶导数谱上577nm的吸收谷的强度比赤铁矿相应谷的强度低一个数量级,表明其电子跃迁的致色机理与赤铁矿的染色机理完全不同。依据赤铁矿的结晶度和鲕状赤铁矿与大洋红层中赤铁矿的沉积成因相似的原则遴选出鲕状赤铁矿为含Fe3+致色矿物,依据菱锰矿是和方解石具有相似结构且为红色的原则选取菱锰矿为含锰致色矿物,并佐以化学纯氧化镁为基体配制了一系列的含菱锰矿、鲕状赤铁矿和菱锰矿及鲕状赤铁矿的两相或三相混合物。详细研究了三类混合物的可见光吸收光谱的一阶导数谱,发现含菱锰矿和含鲕状赤铁矿在573nm附近均存在一吸收谷,鲕状赤铁矿的重量分数低至0.05%时仍可见一明显吸收谷且该吸收谷移至565nm附近,菱锰矿在低至0.50%时也可见这一吸收且在低至0.11%时仍可显示出菱锰矿的信息,其575nm的吸收峰未见偏移;混合物可见光一阶导数吸收谱上鲕状赤铁矿的575nm附近的吸收谷的强度随鲕状赤铁矿的重量分数的升高而增强,而所有的配制混合物中该吸收谷的位置低于577.4nm的事实也表明为使致色矿物和氧化镁混合均匀的研磨降低了赤铁矿的结晶度。本研究表明Mn2+的电子跃迁激发和细小、结晶差的赤铁矿的染色共同造就了意大利白垩纪远洋红色灰岩的红色。