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.     

某鲕状赤铁矿流化床燃煤还原焙烧-磁选研究

运用小型循环流化床锅炉,针对铁品位为49.20%、磷质量分数为1.16%的湖北某鲕状赤铁矿进行磁化焙烧-磁选试验研究.试验结果表明,将粒径为106～150 μm的鲕状赤铁矿在700 ℃下焙烧15 min,选取磨矿后粒径在74 μm以下的颗粒质量分数为85%的焙烧矿物,运用湿式磁选管在139.22 kA/m的磁场强度下对筛选后的焙烧矿物进行磁选抛尾,可以获得铁品位为55.12%、全铁回收率为70.11%、磷质量分数为0.67%的铁精矿.研究表明,运用循环流化床局部还原性气氛高速磁化焙烧铁矿石是可行的,运用该磁化焙烧-磁选工艺流程可以达到一定的提铁降磷效果.     

冷却方式对焙烧鲕状赤铁矿磨矿性能影响

鲕状赤铁矿有用矿物嵌布粒度细,磨矿成本高,属于典型难选铁矿石。磁化焙烧-磁选工艺是分选此类难选铁矿石的有效方法,研究了不同冷却方式对磁化焙烧矿的磨矿性能产生的影响.鲕状赤铁矿进行磁化焙烧后分别隔绝空气密闭冷却、水淬及空气中自然冷却,进行粒度筛析和磨矿试验.发现焙烧后矿石粒径变粗,从原矿的平均粒径为0.069 9mm至密闭冷却、水冷和自然冷却焙烧矿的0.088 2mm、0.084 3mm、0.087 0mm.相同磨矿条件下,原矿、密闭冷却焙烧矿、水冷焙烧矿和自然冷却焙烧矿-0.045mm含量分别为84.89%、83.89%、76.51%、77.14%.表明磁化焙烧使鲕状赤铁矿变得更为难磨,密闭冷却时磨矿效果最佳,自然冷却次之,水冷最差.     

Effect of coal levels during direct reduction roasting of high phosphorus oolitic hematite ore in a tunnel kiln

The effect of coal levels on phosphorus removal from a high phosphorus oolitic hematite ore after direct reduction roasting have been investigated. Raw ore, coal, and a dephosphorization agent were mixed and the mixture was then roasted in a tunnel kiln. The roasted products were treated by two stages of grinding followed by magnetic separation. XRD and SEM–EDS examination of the products was used to analyze differences in the roasted products. The results show that coal is one of the most important factors affecting the direct reduction roasting process. When the inner coal levels increased from 0% to 15% the iron grade decreased linearly from 94.94% to 88.81% and the iron recovery increased from 55.94% to 92.94%. At the same time the phosphorus content increased from 0.045% to 0.231%. Increasing the inner coal levels also caused more hematite to be reduced to metallic iron but the oolitic structure of the roasted product was preserved in the presence of high coal loading. The phase of the phosphorus in raw ore was not changed after direct reduction roasting. The effect of coal on the phosphorus content in the H-concentrate arises from changes in the difficulty of mechanically liberating the metallic iron from the phosphorus bearing minerals.     

Effect of bastnaesite as reductant on hematite reduction during in-situ suspension magnetization roasting of refractory iron ore under neutral atmosphereOA

The iron tailings of Bayan Obo mines are solid waste,which occupies land area and also causes environmental pollution;however,this waste can be recycled.In this study,based on the characteristics of iron minerals and fluorocarbonate contained in Bayan Obo iron tailings,clean magnetization roasting of iron minerals by bastnaesite from iron tailings during in-situ suspension magnetization roasting in a neutral atmosphere was explored.The results show that for iron tailings with a mass of 12 g, a N...     

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

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 mult...     

Mechanism for suspension magnetization roasting of iron ore using straw-type biomass reductant

As an alternative reductant for fossil fuel in the future, straw-type biomass contributes to emission reduction and green utilization in the suspension roasting process. In this study, the influences of the roasting time, roasting temperature and dose of straw-type biomass after suspension magnetization roasting (SMR) and separation were investigated. The optimal conditions were determined to be a roasting time of 7.5 min with a straw-type biomass dose of 20 wt% and a roasting temperature of 800 ℃, in which an iron grade of 71.07% and recovery of 94.17% were obtained for the iron concentrate. The maximum saturation magnetization under optimal conditions was 35.05 A·m²·g⁻¹, and the gaseous regulation of the biomass revealed that cumulative reducing gas volume was 293.93 mL at the optimal roasting time of 450 s. The transformation of hematite to magnetite was detected by X-ray diffraction (XRD). During microstructure evolution, the outer layer consisting of fissures and tiny holes continuously deepened toward the core.     

鲕状赤铁矿磁化焙烧—磁选—反浮选降磷试验

鄂西宁乡式鲕状赤铁矿嵌布粒度极细,SiO2、Al2O3、P等杂质含量高,用其生产的铁精矿很难达到冶炼要求.针对铁品位为43.76%,磷含量为0.84%的鄂西鲕状赤铁矿进行提铁降磷试验研究,通过对磁化焙烧温度、磁化焙烧时间、还原煤的配比等影响因素的条件试验,确定在焙烧时间60 min,焙烧温度750℃,还原煤11%(质量比)的最佳焙烧条件.焙烧产品磨矿至-0.038 mm占80.54%、用永磁选机进行弱磁选,获得了铁品位54.10%、铁回收率93.19%、磷含量0.80%的粗铁精矿.进行反浮选药剂制度试验,得到了铁品位58.95%、铁综合回收率80%、磷含量0.50%的铁精矿,其最佳浮选药剂制度为NaOH 750 g/t,淀粉800 g/t,石灰500 g/t,RA-715 750 g/t,G310 107.73 g/t,浮选温度30℃.在此浮选制度下,进行一粗一精试验,精选石灰和捕收剂用量减半,可得铁品位59.87%,磷含量降至0.28%,综合回收率71.08%,综合试验结果表明,本文探索的工艺流程具有很大的可行性,能够为鲕状赤铁矿的选矿利用提供参考.     

Thermodynamics of chromite ore oxidative roasting process

To explicate the thermodynamics of the chromite ore lime-free roasting process,the thermodynamics of reactions involved in this process was calculated and the phrases of sinter with different roasting times were studied.The thermodynamics calculation shows that all the standard Gibbs free energy changes of the reactions to form Na2CrO4,Na2O·Fe2O3,Na2O·Al2O3 and Na2O·SiO2 via chromite ore and Na2CO3 are negative,and the standard Gibbs free energy changes of the reactions between MgO,Fe2O3 and SiO2 released f...     

焙烧对石煤钒矿孔结构的影响

分别采用BET法、BJH法和HK法测定了石煤原矿、石煤750℃焙烧渣、1 050℃焙烧渣3种样品的比表面积、中孔和微孔分布.结果表明,石煤原矿中主要以中孔为主,最可几孔径为4 nm,主要为墨水瓶状孔;750℃焙烧3 h,由于有机质氧化,原矿中微孔减少,中孔增加;1 050℃焙烧3 h,孔数量急剧减少,大量中孔和微孔消失,只有少量大孔,比表面积显著减小.     

助磨剂对鄂西高磷鲕状赤铁矿磨矿的影响

鄂西高磷鲕状赤铁矿在微细粒磨矿时黏度非常高,严重影响磨矿效率,导致磨矿能耗大幅上升。用助磨剂六偏磷酸钠和三聚磷酸钠对鄂西高磷鲕状赤铁矿进行降黏度磨矿试验。结果表明,添加两种助磨剂均可降低矿浆的黏度,助磨剂添加量为0.2%时降黏和助磨效果最佳;助磨剂使球磨机的生产能力得到显著提高,其相对增量最高可达144%,磨矿时间为5min时助磨效果最佳。添加助磨剂后磨矿产品中粒度小于38μm的颗粒含量明显增加,两种助磨剂都能有效降低磨矿的能耗,最大能耗降幅为57.14%。     

Fragmentation mechanism of low-grade hematite ore in a high pressure grinding roll

The fragmentation mechanism of low-grade hematite ore in a high pressure grinding roll(HPGR) was studied based on the characteristics of comminuted products at different specific pressure levels. The major properties included the reduction ratio, liberation, specific surface energy, and specific surface area. The results showed that the fracture of low-grade hematite ore in HPGR was an interactive dynamic process in which the interaction between coarse particles of gangue minerals and fine particles of valuable minerals was alternately continuous with increased compactness and compacting strength of materials. Within a range of 2.8–4.4 N/mm~2, valuable minerals were crushed after preferentially absorbing energy, whereas gangue minerals were not completely crushed and only acted as an energy transfer medium. Within a range of 4.4–5.2 N/mm~2, gangue minerals were adequately crushed after absorbing the remaining energy, whereas preferentially crushed valuable minerals acted as an energy transfer medium. Within a range of 5.2–6.0 N/mm~2 range, the low-grade hematite ore was not further comminuted because of the "size effect" on the strength of materials, and the comminution effect of materials became stable.     

红土镍矿干燥焙烧工艺条件选择研究

以红土镍矿为原料,用热重分析(TG)和X射线衍射分析(XRD)等方法,对红土铁矿干燥焙烧条件进行研究.结果表明,在矿石粒度为0~3 mm且小于180目颗粒占25%,配焦粉量8%,焙烧温度850℃,焙烧时间90 min,干燥焙烧效果最佳.     

Study on kinetics of thermal decomposition of low LOI goethetic hematite iron ore

In the present study, the kinetics of thermal decomposition of hydrated minerals associated in natural hematite iron ores has been investigated in a fixed bed system using isothermal methods of kinetic analysis. Hydrated minerals in these hematite iron ores are kaolinite, gibbsite and goethite, which contribute to the loss on ignition(LOI) during thermal decomposition. Experiments in fixed bed have been carried out at variable bed depth(16, 32, 48 and 64 mm),temperature(400-1200 ℃) and residence time(30,45, 60 and 75 min) for iron ore samples. It is observed that beyond a certain critical bed depth(16 mm), 100% removal of LOI is not found possible even at higher temperature and higher residence time. Most of the solid-state reactions of isothermal kinetic analysis have been used to analyze the reaction mechanism. The raw data are modified to yield fraction reacted "α" versus time and used for developing various forms of "α" functions.f(α) is the inverse of first derivative of g(α) with respect to α. The study demonstrates that decomposition of hydrated mineral in hematite follows the chemical kinetics.The estimated activation energy values in all the experimental situations are found to high, of the order of 60 kJ/mol, reinstating that the reactions are indeed controlled by moving phase boundary and random nucleation.     

Flocculation performance and mechanism of hydroxamate flocculants on synthetic hematite or goethite suspension

Suitable amounts of Al(OH)3, Na OH and synthetic hematite or goethite were taken to be digested under the simulated condition of the Bayer process and subsequently diluted with simulative Bayer red mud lotion, then the synthetic hematite or goethite suspension was obtained. The flocculation effect of self-made modified poly(acrylic acids) flocculants containing hydroxamic acid groups(abbreviated as HPAA) on the synthetic hematite or goethite suspension was studied. The experimental results show that with the increase of the dosages of added flocculants, the average settling rate of the synthetic hematite or goethite suspension in the first 1min speeds up, the supernatant solids decrease. It could also be found that there is generally a decrease in the average settling rate of the synthetic hematite or goethite suspension in the first 1 min with increasing solid content of the suspension. When the solid content of hematite or goethite of the suspension is 50 g/L with 240 g/t dosage of HPAA, HPAA has a better flocculation effect on the synthetic goethite suspension than on the synthetic hematite suspension. The adsorption mechanism of HPAA on the surface of hematite or goethite was investigated by Fourier transform infrared spectroscopy(FT-IR) and X-ray photoelectron spectroscopy(XPS).All the results suggest that HPAA is adsorbed on the hematite or goethite surface by a chemisorption, and it has a stronger adsorption on the goethite surface than on the hematite surface.     

Effect of Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> and CaCO<Subscript>3</Subscript> 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 (ε_Fe) 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.     

钢中贝氏体相变热力学

应用综合理论分析的方法研究了钢中贝氏体相变热力学.指出以往的KRC,LFG模型不适于贝氏体相变驱动力的计算.在进行相变热力学分析的基础上,依据γ→αB γ1→BF γ1转变机制设计了新的计算模型,并估算了Bs温度下相变阻力为105 J/mol.指出相变不仅与驱动力有关,而且取决于原子扩散能力.在贝氏体上部温度区,可以依靠界面扩散进行台阶长大;在460 ℃以下的某一段温度,可能以原子热激活跃迁无扩散机制进行贝氏体铁素体形核-长大过程;在Ms点稍上一段温度,可能以切变方式进行.     

低品位铁矿石流化焙烧-磁选提质试验研究

针对我国低品位铁矿石嵌布粒度极细,成分复杂,难提难选的现况,运用循环流化床和磁选管进行劣质铁矿石的流化焙烧 磁选试验研究,试验采用CO、N2的混合气体营造还原性气氛（其中CO体积分数为10%）,将粒径为1 mm以下的新疆某低品位铁矿石（原矿铁品位为9.63%）于850 ℃焙烧10 min,得到强磁性的磁铁矿,将焙烧产物破碎细磨（磨至200 目以下占75%）,利用湿式磁选管在71.66 kA/m的磁场强度下进行弱磁选抛尾,可以得到铁精矿品位为46.25%,全铁回收率为25.52%的选矿指标.研究表明,运用循环流化床焙烧-弱磁选的方法提质铁矿石,可以有效地减少焙烧时间,在保证选矿达标的基础上,有效地降低生产周期.