Mintal Group's High-carbon Ferrochrome 350,000-ton Project Phase Ⅲ Starts Construction

Recently,Mintal Group commenced construction of a stainless steel base materials project with an annual output of 350,000 tons,marking that the Phase I base material project for the supply of basic raw materials for the Mintal’s stainless steel production enters into the implementation phase.This project is also known as Mintal’s high-carbon ferrochrome project phase III with an investment of 900million yuan and occupying an area of 300 mu.

Preparation of potassium chromate by roasting of carbon ferrochrome

The oxidizing roasting process of carbon ferrochrome to prepare potassium chromate in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, mole ratio of potassium carbonate to carbon ferrochrome were studied, and thermodynamics and kinetics were also discussed. It was observed that the reaction temperature and reaction time had a significant influence on the roasting reaction of carbon ferrochrome. The reaction mechanism changed greatly as the temperature varied. A two-stage roasting process was favorable for the roasting reaction, and a chromium recovery rate of 97.06% was obtained through this two-stage roasting method. The chromium residue yielded from this method was only 1/3 of the product. Moreover, the component of Fe in the residue was as high as 55.04%. Therefore, it can be easily recovered to produce sponge iron, realizing complete detoxication and zero-emission of chromium residue.

Novel method to prepare sodium chromate from carbon ferrochrome

An oxidizing roasting process of carbon ferrochrome to prepare sodium chromate in the presence of sodium carbonate and air was investigated. The effects of reaction temperature, reaction time, mole ratio of sodium carbonate to carbon ferrochrome were studied, and thermodynamics and kinetics of the reaction were also discussed. It was observed that there was a sudden increase in reaction rate when the temperature rose to a certain value, and the sample with a smaller grain size could start the sudden increase at a lower temperature. The chromium recovery rate increased with the increase of mole ratio of sodium carbonate to carbon ferrochrome, and it reached up to 99.34% when mole ratio of sodium carbonate to carbon ferrochrome increased to 1.2:1. The chromium residue yielded from this method was only about 1/3 of the product. Moreover, the content of Fe in the residue was as high as 60.41%. Therefore, it can be easily recovered to produce sponge iron, realizing complete detoxication and zero-emission of chromium residue.

Assessment of Reusing Ferrochrome Slag Wastes in Mortar as SCMs

The demand for alternative cementitious materials is on the rise,as the cement causes huge energy consumption and produces greenhouse gas emission.Additionally,there is economic potential for the construction industry to reuse wastes as supplementary building materials.The purpose of this study is to evaluate the potential of utilizing ferrochrome slag wastes in mortar as supplementary cementitious materials (SCMs),thereby achieving this double-sided goal.Thus,the mechanical and physical properties of ferrochrome slag wastes were investigated to be used as admixtures in concrete production.Three different cement mortar specimens were prepared by replacing cement with ferrochrome slag in ratios of 0,30%,and 60% by mass and flexural and compressive strengths of the specimens were determined at the ages of 7,28,56,90,and 180 days.Also,the effects of the ferrochrome slag replacement ratio on workability,setting time and volume expansion were revealed.Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were also investigated to study the microstructural properties of the specimens containing ferrochrome slag.Based on the results,it is concluded that ferrochrome slag wastes have pozzolanic activity,therefore reusing them as SCMs in the cement and concrete industry is convenient.

Research of green cement clinker calcinated from ferrochrome slag

Ferrochrome slag is a kind of industrial waste containing Cr^(6+)and is produced in the process of silico ferrochrome smelting.On the basis of analyzing the chemical composition and mineral composition of ferrochrome slag,this paper has put forward a technology of green portland cement clinker calcinated from ferrochrome slag.In the experiment,physical chemical changes of cement clinker in the burning process of ferrochrome slag were investigated.The effects of calcinating temperature and clinker cooling rate on the solubility value of Cr^(6+)were analyzed.The results indicated that when the calcinating temperature is above 1450℃,and the cooling rate is beyond 120℃/min,Cr^(6+)in cement clinker is almost insoluble.

A novel method to produce potassium chromate from carbon ferrochrome

The oxidizing roasting of carbon ferrochrome in the presence of potassium carbonate and air was investigated. The effects of reaction temperature, reaction time, ratio of alkali-to-ore were studied, together with a discussion of the thermodynamics and macro kinetics. It is observed that the reaction temperature and reaction time have significant influence on the roasting reaction. The reaction mechanism changes greatly as the temperature varies. A two-stage roasting process is favorable for the roasting reaction, and a recovery ratio of 96.51% is obtained through this two-stage roasting method. The chromium residue yielded from this method is quite little, only one third of the product. Moreover, the component of Fe in the residue is as high as 54.28%. Therefore, it can be easily recovered to produce sponge iron, realizing zero-emission of chromium residue.

Effects of Different Calcining Temperatures on the Properties of Ceramsite Prepared by High-carbon Gasification Slag

The structure and characteristics of high-performance lightweight aggregates produced by high-carbon gasification slag were investigated by X-ray diffraction,scanning electron microscopy,thermogravimetry/differential thermogravimetr,differential scanning calorimetry-Fourier transform infrared,and mercury intrusion porosimetry,respectively.The experimental results show that the ceramsite undergoes two weightless stages in the calcining process.With the increase in the calcining temperature,a large number of pores are formed inside the ceramsite,its structure becomes denser,but the calcining temperature band of the ceramsite becomes narrow.The crystalline phase of the ceramsite changes at different calcining temperatures and the mineral phase changes from the earlieralbite,quartz,oligoclase,hematite,etc,to a silica-aluminum-rich glass phase.The 1130℃ is a more suitable calcining temperature,and the cylinder compressive strength of ceramics is 11.59 MPa,the packing density,apparent density,porosity,and water absorption are 939.11 kg/m^(3),1643.75 kg/m^(3),28.11%,and 10.35%,respectively,which can meet the standards for high-strength lightweight aggregates.

有机酸-硫化零价铁处理高浓度含铬废液及铬铁资源化的研究

针对含铬废液净化污泥杂质含量高、铬含量低导致铬回收难的问题,以有机酸-硫化零价铁为铬废液净化剂,在高效去除废液中铬的同时,可净化污泥并直接制备铬铁合金。通过考察零价铁硫化程度、初始废液pH值、不同有机酸摩尔比、硫化零价铁用量等影响因素对废液铬净化与污泥铬富集的影响,探索铬污泥直接制备铬铁合金工艺。研究显示,采用有机酸-硫化零价铁协同处理后,废液总铬质量浓度可由5 324.1 mg/L降低至4.30 mg/L,与未改性零价铁技术相比,铬净化去除率由65.45%提高至99.92%。净化污泥铬铁元素平均质量分数大于46%,在1 500℃,氩气保护气氛下,添加质量分数为30%碳粉即可成功制备铬铁合金。铬铁合金产物中铬铁元素分布均匀,杂质含量较少。XRD分析显示,硫化零价铁的掺入质量增大可降低合金产品中杂相的生成。研究方法为冶金、化工等行业含铬废液的高效净化及资源化处理提供了一条新路径。

高碳铬铁冶炼过程影响因素的研究进展

本文通过总结国内外相关文献,认为影响高碳铬铁冶炼的主要因素为炉料的物理性能、化学性能和化学成分,且炉料的物理性能和化学性能受炉料的化学成分影响。同时,阐述了MgO、Al_(2)O_(3)、SiO_(2)、CaO和碳质还原剂等化学成分对高碳铬铁冶炼的影响,其中碳质还原剂对炉料的电阻率起决定作用;MgO、Al_(2)O_(3)和SiO_(2)等则更多影响冶炼时的熔化性、熔点和黏度等参数。本文还分析了各化学成分对铬铁矿还原的影响,其中Fe、FeO、Fe_(3)O_(4)、SiO_(2)、CaO、NaOH以及硼酸盐等在一定程度上能促进铬铁矿的还原,而MgO则会抑制铬铁矿的还原。此外,归纳总结了镁铝比和炉渣碱度对高碳铬铁冶炼的影响,将镁铝比控制在1.3~1.9,炉渣碱度不超过1.4,可以达到降低冶炼电耗、焦耗和提高铬回收率的效果。

某钢厂含铬污泥冶炼高碳铬铁合金实验研究

镀锌板材在钝化过程中产生大量含铬污泥,严重影响企业的清洁化生产。本文以某钢厂含铬污泥为原料用于制备高碳铬铁合金。结果表明,采用碳化法利用含铬污泥可以直接制备出符合国标的高碳铬铁合金,且铬回收率最高可以达到93%以上。随配碳量的增加,铬的回收率呈先升高后降低的趋势,随钙基脱硫剂的增加,合金中S含量呈先降低后升高的趋势;较为适宜的制备工艺为:当配碳量为1.4:1、钙基脱硫剂用量为含铬污泥质量的15%时,能够得到铬品位61.27%的国标高碳铬铁合金,此时铬回收率可以达到93.43%。

高碳铬铁渣稀浆封层路用性能研究

为解决高碳铬铁渣堆存及开采石料造成的环境污染和破坏问题,以高碳铬铁渣作为集料,分别以不同粒径替代稀浆封层混合料中玄武岩,通过车辙试验、湿轮磨耗试验、冻融劈裂试验、低温弯曲试验、摆式仪测定路面摩擦系数试验对稀浆封层混合料的抗车辙性能、抗水损害性能、低温抗裂性能及抗滑能力进行评价。结果表明:将高碳铬铁渣作为集料替代玄武岩,可明显地提高稀浆混合料的抗车辙性能、低温性能及抗滑能力,4.75 mm~9.5 mm粒径的铬铁渣影响最为显著;铬铁渣的掺入会降低稀浆混合料的抗水损害能力,随着铬铁渣代替量的增加而降低,高碳铬铁渣在稀浆封层中具有一定的适用性。

提高微碳铬铁中铬含量的检验稳定性

采用国家标准测定铬铁中铬含量,对溶样过程中样品称样量、溶样方式、过硫酸铵酸度、磷酸加入试料及冒烟程度、干扰元素等影响因素进行分析对比,最终确定了磷酸溶样过硫酸铵氧化滴定法。该方法操作简便,分析周期短,采用不同标样进行反复验证后,分析结果的准确度和精密度均很高,满足不锈钢的生产需要。

高碳铬铁低碳冶炼工艺研究

介绍了铬粉矿现已成为我国高碳铬铁冶炼的主要原料,随着矿热炉容量的扩大,仍以矿热炉还原熔炼法为主的高碳铬铁冶炼方式允许配入的粉矿占比越来越小。为了实现我国高碳铬铁冶炼深度减碳,本文结合铬矿资源发展,矿热炉大型化,熟料及热料入矿热炉冶炼开展低碳冶炼研究。冶炼实践表明,铬粉矿制成的烧结矿、氧化球团及还原球团分别入炉,使用100%铬还原球团热装入矿热炉,高碳铬铁日产量提高到260 t,电耗降至2 100 kWh/t,渣中铬含量降至3%,还原球团入矿热炉冶炼获得的经济效益最为明显。因此,氧化球团或还原球团热装冶炼,是实现高碳铬铁低碳冶炼的重要技术途径。

复掺矿物掺合料对磷酸镁水泥性能的影响

采用重烧氧化镁、磷酸二氢钾制备磷酸镁水泥,在其中复掺适量的粉煤灰和微碳铬铁粉渣,研究了两种矿物掺合料对磷酸镁水泥工作性能、抗压强度、粘结强度、耐水性能的影响,探究其微观的组分与结构。研究结果表明:掺入矿物掺合料可以有效改善其工作性能,加快磷酸镁水泥早期抗压强度的发展且有利于提高后期强度,增强磷酸镁水泥的粘结强度,同时对MPC材料耐水性的提高起到较大作用。

固废微表处混合料性能研究

为探究高碳铬铁渣固废在微表处混合料中的适用性,将高碳铬铁渣分别以0%和30%的掺量替换常规微表处集料,通过湿轮磨耗试验、改进高温车辙试验和改进低温小梁弯曲试验对比分析高碳铬铁渣掺入后对微表处混合料的耐磨耗性能、水稳定性、高温稳定性和低温抗裂性影响。试验结果表明:与高碳铬铁渣掺量为0%相比,高碳铬铁渣掺入30%后微表处混合料的耐磨耗性能和水稳定性降低,高温稳定性和低温抗裂性增强,说明高碳铬铁渣在微表处应用方面具有一定的适用性。

Spheroidization process in large-deformed high-carbon steel

In this study,the spheroidization process of large-deformed steel under various conditions was researched.Steel with a high carbon content （1.0％ C） was first treated thermomechanically using multipass rolling.Then it underwent spheroidization treatments at different heating temperatures,using various heating times and cooling rates.Spheroidization processes with a lower heating temperature,shorter heating time,or faster cooling rate than those of the traditional process all showed good results,indicating that the spheroidization process was promoted significantly by the large deformation process.Grain refinement and fragmentation of cementite,along with the large deformation process,promoted this spheroidization process.

Effect of RE-Modifier on Microstructure and Mechanical Property of High-Carbon Medium-Manganese Steel

The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.

Can the low-carbon city pilot policy promote the upgrading of high-carbon emitting enterprises? Evidence from China

As a crucial environmental reform system to realize“carbon peaking”and“carbon neutrality”,the pilot policy of low-carbon cities(LCCs)puts pressure and challenges on high-carbon emitting enterprises(HCEEs)while providing opportunities for these firms to take the path of independent transformation.Employing the data of Chinese listed enterprises from 2006 to 2016 and adopting a difference-in-differences(DID)model,we evaluated the impact of LCC construction on the upgrading of HCEEs and its mechanisms.The results indicate that LCC construction enhances the upgrading of HCEEs in the pilot cities.The conclusions remain stable after a series of robustness tests.The mechanism analysis reveals that LCC construction triggers the upgrading of HCEEs by promoting resource allocation efficiency,R&D investment,and green technology innovation.The heterogeneity results indicate that this positive effect is more pronounced for HCEEs in regions with more stringent environmental law enforcement.This study also observes that the upgrading impact is more promi‐nent for state-owned enterprises,enterprises with higher bargaining power,and enterprises whose managers have a long-term vision.The above results provide directions for upgrading HCEEs and replicable evidence for cities in developing economies to fulfill the win-win target of environmental protection and economic transfor‐mation.

Patenting of hot-rolled high-carbon steel and its applications

The patenting process of three hot-rolled steels with carbon mass contents of 0.70%-0. 90% was studied. The effect of the quenching temperature on the cementite lamellar distance in the steel was evaluated on the basis of microstructural characterization and mechanical property tests. The patenting treatment of high-carbon hot- rolled strip and its application in springs were discussed.

Investigation of longitudinal surface cracks in a continuous casting slab of high-carbon steel

Based on a series of related investigations, a mechanism for the formation of longitudinal surface cracks on a continuous casting slab of high-carbon steel was investigated. High-temperature tensile tests performed on slab samples,metallographic and scanning electron microscopy studies, as well as heat flux and shell thickness in continuous casting predicted on the basis of a mathematical model were conducted. The results showed that high- carbon steel exhibited a much lower liquidus temperature and a wider brittle temperature range immediately after solidification compared with those of low-carbon steel. Concentrations of elements K and Na, which are contained in the mold fluxes, were not observed in the cracks during this study. The calculated results showed that the heat flux and the shell thickness were uneven along the mold width and that the shell was thinner and close to the center line of the slab surface. The longitudinal cracks were observed in situ using confocal laser scanning microscopy, to first occur close to the solidification front,where the ductility was extremely low;in addition ,the shell growth was slower than in other regions, which led to a thinner shell and depressed shrinkage owing to a lack of lubrication by the mold fluxes below the meniscus. Furthermore, the pouring temperature of high-carbon steel is - 100 ~C lower than that of low-carbon steel,so the formation of a stable liquid flux near the meniscus within a short time at the beginning of casting is difficult. The amounts of liquid slag film and crystalline slag film were insufficient to provide adequate lubrication between the shell and the mold, which resulted in greater friction force that induced or aggravated cracks. Therefore, the homogeneity of mold fluxes and initial solidification in the mold should be improved to reduce the concentration of slab surface defects.