Reduction of chromium oxides in stainless steel dust

The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.

Self-reduction Mechanism of Coal Composite Stainless Steel Dust Hot Briquette

To efficiently recycle valuable metals such as chromium and nickel in stainless steel dust, self-reduction ex- periments were carried out to study the reduction mechanism of metal oxides in coal composite stainless steel dust hot briquette, which is defined as a CCSB here. Self-reduction of CCSB is proceeded by volatile matter and fixed carbon contained within CCSB. Experiments were performed to study the effects of temperature and carbon to oxygen （C/OCoal） ratio on self reduction of CCSB. At 1400 and 1450℃, volatile matter in coal used for experiment could take the place of about 40℃ of fixed carbon in coal. Under the present experimental conditions, reduction product of chromium appears as FeCr2O2, Cr2O3, Cr7C3 , and [Cr] in turn during reduction. To evaluate the formation of met al nuggets in self reduction process of CCSB, metal nuggets containing chromium and nickel were observed in outside of reduction products under various conditions, and thermodynamic equilibrium calculation was carried out for possi hie products and formation of molten metal by fixed carbon. SEM and EDS analyses were made for metal nugget and slag in reduced product. The results reveal that it is reasonable to achieve the metal nuggets at 1450℃, 0.8 of C/OCoal ratio and 20 min of reduction time. The nugget formation can indicate one innovative process for comprehensive utilization of stainless steel dust.

Recovery rates of iron, nickel, and chromium via iron-bath reduction of stainless steel dust briquettes based on corundum crucible erosion balance analysis

The leaching of chromium from stainless steel dust （SSD） is deleterious to the environment. To address this issue, the reduction of SSD briquettes can be employed to effectively extract chromium. The recovery rates of iron, chromium, and nickel via ironbath reduction of SSD briquettes were determined using X-ray fluorescence spectroscopy, X-ray diffraction, and scanning electron microscopy measurements. First, the effects of basicity and contents of silicon, iron, CaF2, and carbon on the recovery rates of the three metals were analyzed using the slag amount prediction model, which was originally established from the A1203 balance of corundum crucible erosion behavior. Second, the effect of feeding mode, i.e., whether steel scrap and SSD briquettes were simultaneously added, on the recovery rates was discussed in detail. Third, the iron-bath reduction of SSD briquettes was thermodynamically analyzed. The results indicated that the recovery rates of the three metals are greater than 95% those of using a basicity of 1.5 and 6.0% CaF2, 15% carbon, and 7% ferrosilicon. The recovery rate of chromium increases twofold with the addition of ferrosilicon. The feeding mode of adding briquettes and steel scrap simultaneously is better for recovery of metals and separation of the metal and slag than the feeding mode of adding steel scrap firstly and then briquettes.

Basic properties of steel plant dust and technological properties of direct reduction

Basic physicochemical properties of the dust from Laiwu Iron and Steel Co. Ltd. were studied. It is found that C, Zn, K, Na, etc. exist in the fabric filter dust, off gas （OG） sludge, fine ash in converter, and electrical field dust in sinter. Among these, OG sludge gives the finest particle, more than 90% of which is less than 2.51 mm. The dust can lead to a serious negative influence on the production of sintering and blast furnaces （BF） if it is recycled in sintering. The briquette and reduction experimental results showed that the qualified strength could be obtained in the case of 8wt% molasses or 4wt% QT-10 added as binders. Also, more than 75% of metallization ratio, more than 95% of dezincing ratio, as well as more than 80% of K and Na removal rates were achieved for the briquettes kept at 1250℃ for 15 min during the direct reduction process. SEM observation indicated that the rates of indirect reduction and carbonization became dominating when the bri-quettes were kept at 1250℃ for 6 min.

Influence of the Steel-making Dust on High Temperature and Fatigue Performance of Asphalt Mortars

To research the possibility of steel-making dust as a kind of mineral filler in asphalt mixture, two steel-making dusts and one ordinary mineral filler were adopted. The specific density, specific surface area, fineness modulus and mineralogy component of the dusts were tested. Scanning electron microscopy(SEM) was carried out to research the microstructure of the dusts; dynamic shear rheological(DSR) test and time sweep test were used to research the high temperature and fatigue performance of asphalt mortars containing steel-making dust. The experimental results indicate that, compared with ordinary mineral filler, steel-making dusts have more active ingredients, difference surface characteristics and micro-structure. Furthermore, the high temperature and fatigue performance of steel-making dusts corresponding asphalt mortars are superior to those of reference group. Therefore, the steel-making dust would be an alternative to the ordinary mineral filler to improve the performance of asphalt mortars and reduce the harm of the dusts to the environment at the same time.

Volatilization of zinc and lead in direct recycling of stainless steel making dust

The volatilization of zinc and lead from the stainless steel making dust pellets in the direct recycling procedure was conducted by using a thermo-gravimetric analyzer and a Tamman furnace in the nitrogen atmosphere respectively. The results show that the temperature has a significant effect on the volatilization rates of zinc and lead, and the carbon content in the pellets has no effect on the volatilization process. The volatilization of zinc is controlled by the chemical reaction between zinc oxide and carbon monoxide, while the volatilization of lead is controlled by the evaporation from liquid phase to the atmosphere. The volatilization of zinc and lead mainly happen at about 1 000 ℃ according to non-isothermal experiment.

The sustainability of valuable metals—recycling of residues from stainless steel production

The European stainless steel producers generate 20 -30 kg dust per ton of produced stainless steel.The dust formed during various stages of the production process contains valuable metals such as Cr,Ni and Mo.In general this dust is considered as a hazardous waste.If not taken care of the dust will be an environmental risk causing potential problems such as leaching of heavy metals into groundwater and pollution of land and air.By applying techniques for recycling the dust the problem is minimized and valuable metals are recovered and re-used as raw material in the steel making process,leading to a significant reduction of the consumption of natural resources to decelerate the climate change and ensure a sustainable development.One of the business segments of Befesa Zinc S.L.U.,a subsidiary company of Abengoa,is the recycling of dusts and other residues containing nickel,chromium and molybdenum from the stainless steel industry.The technologies applied are submerged arc reduction smelting(Befesa Valera S.A.S.,Gravelines,France) and plasma reduction smelting(Befesa ScanDust AB,Landskrona,Sweden).Stainless steel plant dusts,mill scale and other residues are delivered in closed containers and big bags by ship,rail or truck and stored.After a preparation of the residues and charging into the pyrometallurgical furnace,the metal compounds contained in the charge are reduced to metals in the presence of the carbon added.At Befesa ScanDust,the regularly tapped liquid metal is cast in the form of granules via the Granshot^(?) granulation process.The granulated product has many advantages such as excellent preheating properties and fast melting when added to a metallurgical process.The granules size and shape also makes it very suitable to handle with most raw material handling systems.By granulating the so-called alloyed pig iron(API) a high metallic yield is achieved ensuring maximum recovery of metal and less new dust generation compared to a crushed material.The granules are redelivered to the stainless steel producers or sold on the open market.

Preparation and Properties of Anti-oxidation Inorganic Nano-coating for Low Carbon Steel at an Elevated Temperature

A new kind of anti-oxidation inorganic nano-coating for the common low carbon steel was prepared. It included magnesite mineral, metallurgic dust and silicate adhesive as the main raw materials. The nano-coating could be sprayed directly onto the low carbon steel slab even though with hot surface as far as under 1000 ℃ . And at the same time, a compact thin nano-film was formed, and the film would inhibit the oxygen into the interface of the steel body and decrease the loss of weight because of oxidation. The loss was decreased by about 60% or more. The properties and mechanism of oxidation resistance of the coating were discussed through XRD, TG-DTA and SEM. The experimental results show that many reactions would happen among the companents of the coating and then many microspheres with the size of 80- 100nm generated in the system. By using the heat of the steel body, the silicate adhesive would interact with the microspheres, and the other components of the coating would be soft and sintered so that when the coating was sprayed onto the suface of the steel slab , the intact and compact film could be formed and adhesive with the steel body. Besides the special properties of anti- oxidation, the coating could prevent the volatilization of microelement in the steel such as silicate and carbon at a high temperature. So it can improve the quality and output of steel with this new kind of nano-coating.

某东南沿海电厂钢结构腐蚀影响因素分析

目的 对比腐蚀环境因子分布和钢结构腐蚀事件分布,分析影响火力发电厂钢结构腐蚀的主要环境因素,探讨火力发电厂钢结构腐蚀的机理。方法 以东南沿海某火力发电厂为例,对电厂厂区进行网格化,利用便携式温湿度计进行逐网格温、湿度监测,逐网格收集结构物表面灰尘,并分析其中氯离子、可溶盐、酸碱含量等,开展腐蚀环境监测。统计从2012年至2022年10年间该电厂每一网格内的腐蚀防护工程,如腐蚀防护器件、装备、材料购置等项目的施工或应用次数。结果 温度、湿度及钢结构表面灰尘中氯离子含量、可溶盐含量、灰尘浸渍水p H等因子受海洋环境、厂区结构分布、生产活动多重原因的影响,随距海距离增加呈带状分布,或围绕生产设施点呈辐射分布。结论 环境因子对钢铁结构腐蚀的影响大小顺序为结构物灰尘含盐量>结构物灰尘浸渍水p H>相对湿度>结构物灰尘氯离子含量>温度。电厂钢结构腐蚀机理为雨水或大气凝结水溶出结构物表面灰尘的可溶性盐,含盐水经涂层缺陷输运至金属表面,成为钢铁腐蚀原电池的离子导路,导致钢结构发生电化学腐蚀。

湛江钢铁多工序环境除尘超低排放改造应用现状

本文介绍了湛江钢铁在烧结、球团、焦化、炼铁、炼钢、石灰窑和钢渣处理等关键工序中部署的先进除尘技术和设备,包括防静电超细复合纤维针刺毡布袋除尘器、PTFE涂层塑烧板除尘器、覆膜滤袋除尘器等,这些技术的应用显著提高了除尘效率,减少了粉尘排放,有效提高了公司的环保水平。通过对比改造前后的排放数据,本文展示了湛江钢铁在实现超低排放目标方面取得的突破性进展,总结了实施的环境除尘超低排放改造项目的应用现状与成效。

不锈钢粉尘冷态固结球团强度提升优化研究

2022年不锈钢粗钢年产量达到3197.50万t,生产每吨不锈钢粗钢就会产生18~33 kg粉尘。粉尘中包含大量的铁元素,约占其20%~53%,还含有铬和镍等重金属元素,具有很大的回收价值。以不锈钢粉尘为原料制备了冶金球团,系统研究了水分含量、成型压力、粘结剂种类和粘结剂添加量对不锈钢粉尘球团强度的影响。试验发现当水分添加量为8%、采用5%的蔗糖作为粘结剂、在20 MPa的成型压力下,所得球团的湿球落下强度为5.6次/0.5 m、干球落下强度为12.7次/2 m、干球抗压强度达到了3314 N,均超过了炼钢用尘泥团块的行业标准要求。

包钢球团配加EP灰及酸洗氧化铁皮试验研究

针对白云鄂博铁精矿的特殊性及包钢624 m^(2)带式焙烧工艺铁料结构,进行了配加2%EP灰及2%酸洗氧化铁皮的制备氧化球团矿试验研究,结果表明:配加2%EP灰后,可实现膨润土配比降低0.5%,为了保证球团矿抗压强度≥2 500 N,焙烧温度需提高20~30℃;配加2%氧化铁皮后,生球性能小幅改善,为了保证球团矿抗压强度≥2500 N,焙烧温度需提高50~60℃;配加少量酸洗氧化铁皮或EP灰,其化学成分及还原性能可以满足高炉生产需求。

钢铁企业含锌尘泥回转窑处置设计原理及工业实践

钢铁企业产生的含锌尘泥主要是高炉、转炉、电炉除尘系统收集的除尘灰或湿式除尘产生的污泥,该含锌尘泥含有大量的锌元素等杂质,直接返回钢铁冶炼流程会影响高炉等设备的正常运行并造成锌资源浪费。回转窑工艺因成熟稳定、投资及运行成本低、原料适应性强,已成为处置含锌尘泥的主流工艺。随着“固废不出厂”等理念的深入推进,含锌尘泥回转窑处置技术也将在钢铁企业中得到广泛的应用。本文主要介绍某钢铁企业1.5×10^(5)t/a含锌尘泥回转窑处置生产线的设计原理、工艺流程和实际运行情况。该生产线设计采用具有“低碳、稳定、协同、智能、环保”的新型回转窑处置技术,有效解决了回转窑易结圈问题、智能控制水平较高、原料的适用性广泛,且具有工序能源消耗低、锌回收率高、窑渣铁金属化率高等特点,可实现含锌尘泥的资源化综合利用。项目投产后,运行稳定,生产指标达到或超过设计要求,取得了良好的经济效益。

转底炉工艺处理不锈钢除尘灰可行性分析

中国是不锈钢生产大国,生产不锈钢需要大量的铬矿,长期依赖进口,且伴随着不锈钢的生产产出大量的不锈钢除尘灰,其中富含铁、铬等有价元素,目前没有较为成熟的综合利用工艺。通过整理分析目前国内外处理不锈钢除尘灰的工艺,论证优缺点,综合考虑建议采用压球+转底炉预处理+电炉/矿热炉的工艺处理不锈钢除尘灰。转底炉工艺预处理从理论和实践中可以获得含有大量铁金属单质、少量铬金属单质和高还原度的三价铬氧化物的炉料是可行的。相较于不锈钢除尘灰直接用于矿热炉,转底炉预处理不锈钢除尘灰获得的炉料用于矿热炉可以降低工序能耗、提高利用系数等效益,每处理一吨不锈钢除尘灰成本降低约30%以上,经济性提升显著。

塑烧板除尘器在H型钢生产中的应用和研究

首钢长治钢铁有限公司轧钢厂H型钢生产线除尘系统采取塑烧板除尘器,该除尘器是一种高效节能的烟气净化设备,具有除尘效率高、处理烟气量大、使用寿命长等特点,针对该除尘系统的工艺流程、设备参数以及运行过程中的问题及维护要点进行了研究分析,以确保除尘系统后期的稳定运行。

钢铁企业车间粉尘特性及控制研究

钢铁行业车间粉尘浓度对于操作人员、车间设备都有较大危害,为了降低车间粉尘浓度,对某钢铁企业的生产情况、规模及工艺进行分析,并设置不同采样点对烧结、炼铁、炼钢及轧钢车间的粉尘特性进行了研究,基于实验情况对烧结、炼铁及炼钢车间的粉尘控制工艺分析后,结果验证了该控制技术的可行性,为后续粉尘浓度降低研究提供了基础。

火法处理钢铁粉尘中有价元素研究现状及展望

针对国内外钢铁冶金粉尘的化学组成和各有价元素的赋存状态,本文比较了国内外提取钢铁冶金粉尘有价元素的工艺现状,并基于热力学基本原理,着重分析了火法处理工艺的影响因素及存在的问题。在此基础上,围绕钢铁冶金粉尘协同资源化问题,提出高效利用粉尘自身所含碳素资源,采用火法富集—湿法分离提取—尾渣资源化工艺是我国冶金行业未来实现钢铁冶金粉尘全量资源化的一条有效途径。

真空碳热还原温度对电炉钢渣自粉化的影响

为解决电炉钢渣易磨性差,文章采用理论计算结合真空碳热还原的方法对电炉钢渣进行还原研究。通过理论计算确定电炉钢渣中各组分随还原温度升高时的变化情况,从而设定真空碳热还原实验的还原温度区间。实验结果表明,随着还原温度的不断升高电炉钢渣自粉化效果呈现出一个先上升后下降的趋势,同时Fe不断被还原出来并表现出明显的聚集效果有利于后续的分离回收。最佳还原条件为:配碳量16%,碱度R=1,保温60 min,1450℃下电炉钢渣的自粉化率达到93.8%,试样中粒径小于89.2μm颗粒占比高达90%。相较于传统电炉钢渣自粉化研究,在常压空气气氛下,还原温度高达1600℃时,电炉钢渣自粉化率仅达到49.97%,真空碳热还原具有粉化率高还原温度低的明显优势。

可控移动式顶抽除尘罩系统在不锈钢连铸切割中的应用

为解决不锈钢铸坯在线切割时产生的金属粉尘污染工作环境的问题,设计并制作了一套可控移动式顶抽除尘罩系统,在保证除尘效果的前提下,有效实施对切割区域的散热,保证切割机和辊道系统的正常使用。

钢铁行业尘泥回收利用及处理技术分析

在总结钢铁行业尘泥主要来源及污染特征的基础上,对钢铁行业现有钢铁尘泥综合利用及处理技术进行详细分析,深入探讨了物理法、湿法、火法和火法—湿法联合处理的工艺原理以及在实际应用中的优缺点,并对未来钢铁行业尘泥处理的发展方向进行展望,以期为相关人员提供参考。