Effect of cooling rate on the crystallization behavior of perovskite in high titanium-bearing blast furnace slag

The effect of cooling rate on the crystallization of perovskite in high Ti-bearing blast furnace（BF） slag was studied using confocal scanning laser microscopy（CSLM）. Results showed that perovskite was the primary phase formed during the cooling of slag. On the slag surface, the growth of perovskite proceeded via the successive production of quasi-particles along straight lines, which further extended in certain directions. The morphology and structure of perovskite was found to vary as a function of cooling rate. At cooling rates of 10 and 30 K/min, the dendritic arms of perovskite crossed obliquely, while they were orthogonal at a cooling rate of 20 K/min and hexagonal at cooling rates of 40 and 50 K/min. These three crystal morphologies thus obtained at different cooling rates respectively corresponded to the orthorhombic, cubic and hexagonal crystal structures of perovskite. The observed change in the structure of perovskite could probably be attributed to the deficiency of O^2-, when Ti2O3 was involved in the formation of perovskite.

New Type Regulating Valve Applied in Cooling System of Blast Furnace

A new type regulating valve with the cooling mode of constant temperature difference water supply, temperature difference self operated regulating valve, was introduced into blast furnace cooling system to overcome shortcomings of the cooling mode of constant flow rate water supply. The results show that the temperature difference between inlet and outlet water of cooling wall can be decreased greatly and steadily, and the water supply for blast furnace cooling can be reduced considerably.

Cooling Water Flow Rate Calculation for Hearth of Large Blast Furnaces

The cooling water flow rate for hearth of large blast furnaces was calculated by simulation. The results show that the cooling water flow rate shall be above 4 200m3/ h for hearth of large blast furnaces; to meet requirements of the increasing smelting intensity and to ensure the safety at the end of the first campaign,the designed maximum cooling water flow rate should be 5 900m3/ h; according to the flow distribution stability and the calculated resistance loss,hearth cooling stave pipes with the specification of 76 mm × 6 mm shall be adopted to assure the flow velocity in pipes of hearth cooling stave in the range of 1. 9- 2. 3 m / s.

Numerical simulation on boiling heat transfer of evaporation cooling in a billet reheating furnace

The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.

Analysis of temperature,stress,and displacement distributions of staves for a blast furnace

The temperature of gas flow inside a blast furnace （BF） changes significantly when the blast furnace is under unstable operations, and the temperature and stress distributions of cooling staves （CS） for BF work the same pattern. The effect of gas temperature on the temperature, stress, and displacement distributions of the cooling stave were analyzed as the gas temperature inside the blast furnace rose from 1000 to 1600℃ in 900 s. The results show that both the temperature and temperature gradient of the hot side of CS increase when the gas flow temperature inside BF rises. The temperature gradient of the hot side of CS is greater than that of the other area of CS and it can reach 65℃/mm. In the vertical direction of the hot side of CS, closer to the central part of CS, the stress intensity is greater than that of the other area of the hot side of CS, which causes cracks on the hot side of CS in the vertical di- rection. As the gas temperature increases, the stress intensity rate near the fixed pin increases and finally reaches 45 MPa/s. Fatigues near the fixed pin and bolts are caused by great stress intensity rate and the area around the pin can be damaged easily. The edge of CS bends toward the cold side and the central part of CS shifts toward the hot surface.

Physical Properties of Crushed Air-cooled Blast Furnace Slag and Numerical Representation of Its Morphology Characteristics

Physical properties and geometrical morphologies of crushed air-cooled blast furnace slag （SCR） and crushed limestone （LCR） were comparatively investigated. The shape, angularity, surface texture and internal pore structure of aggregate particles for different size and gradation were numerically represented by sphericity （ψ） and shape index （SI）, angularity number （AN）, index of aggregate particle shape and texture （IAPST）, porosity and pore size, respectively. The results show that SCR is a porous and rough aggregate. Apparent density, void, water absorption and smashing index of SCR are obviously higher than those of LCR with the same gradation, respectively. However, bulk density of SCR is lower than that of LCR with the same gradation. SI, AN, IAPST and porosity of SCR are obviously higher than those of LCR with the same gradation, respectively. The smaller particle size of SCR, the larger of its AN, IAPST and porosity.

Application of Air-cooled Blast Furnace Slag Aggregates as Replacement of Natural Aggregates in Cement-based Materials：A Study on Water Absorption Property

The influence of air-cooled blast furnace slag aggregates as replacement of natural aggregates on the water absorption of concrete and mortar was studied, and the mechanism was analyzed. The interface between aggregate and matrix in concrete was analyzed by using a micro-hardness tester, a laser confocal microscope and a scanning electron microscope with backscattered electron image mode. The pore structure of mortar matrixes under different curing conditions was investigated by mercury intrusion porosimetry. The results showed that when natural aggregates were replaced with air-cooled blast furnace slag aggregates in mortar or concrete, the content of the capillary pore in the mortar matrix was reduced and the interfacial structure between aggregate and matrix was improved, resulting in the lower water absorption of mortar or concrete. Compared to the concrete made with crushed limestone and natural river sand, the initial absorption coefficient, the secondary absorption coefficient and the water absorption capacity through the surface for 7 d of the concrete made from crushed air-cooled blast furnace slag and air-cooled blast furnace slag sand were reduced by 48.9%, 52.8%, and 46.5%, respectively.

Effect of Crushed Air-cooled Blast Furnace Slag on Mechanical Properties of Concrete

Morphology characteristics of mix aggregates with crushed air-cooled blast furnace slag（SCR） and crushed limestone（LCR） with 5-20 mm and 20-40 mm gradation were represented by numerical parameters including angularity number（AN） and index of aggregate particle shape and texture（IAPST）.The effect of mix aggregates containing SCR on compressive strength and splitting tensile strength of concrete was investigated.Fracture characteristics of concrete,interfacial structure between aggregates and matrix were analyzed.The experimental results show that porous and rough SCR increases contact area with matrix in concrete,concave holes and micro-pores on the surface of SCR are filled by mortar and hydrated cement paste,which may increase interlocking and mechanical bond between aggregate and matrix in concrete.SCR can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with LCR.The increase of AN and IAPST of aggregate may enhance mechanical properties of concrete.

Cooling phenomena in blast furnace hearth

Cooling water provides the best protection for refractory in the blast furnace hearth. Stable and suitable water quality and abundant cooling water are the basis for long service life of the hearth. Some phenomena about cooling system in the commercial blast furnaces were described, and reasonable explanations of these phenomena were analyzed. The results show that increasing the amount of cooling water and reducing the inlet temperature of cooling water can increase the cooling effect significantly in the case of water scaling. Heat flux in the blast furnace hearth is the average heat flux of cooling stave, and the erosion of carbon brick is uneven. There is no direct connection between the actual erosion condition and the heat flux in the hearth. The change trend of thermocouple temperature and heat flux in the hearth can reflect whether the gaps exist among the bricks or not, providing an effective guidance for industrial production and the evaluation of safety state in the hearth. And, the film boiling will not occur in the normal cooling system in the blast furnace hearth.

Design and Operation Control for Long Campaign Life of Blast Furnaces

At the beginning of 1990s, Shougang blast furnaces （BFs） No. 2, No. 4, No. 3 and No. 1 were rebuilt se quently for new technological modernization in succession. The campaign life of BFs No. 1, No. 3 and No. 4 reaches 16.4, 17.6 and 15.6 years, respectively, and the hot metal output of one campaign reaches 33.8, 35.48 and 26.37 Mt, respectively; the hot metal output of BF effective volume of one campaign reaches 13328, 13991 and 12560 t/m^3, respectively, which reaches the international advanced level of BF high efficiency and long campaign life. In BF desig-ning, several advanced BF long campaign technologies were adopted. BF proper inner profile was optimized, reasona- ble inner profile was adopted, and closed circulating soften water cooling technology was applied in 4 BFs. Double row cooling pipe high efficiency cooling stave was developed which could prolong the service life of bosh, belly and stack. Hot pressed carbon brick and ceramic cup hearth lining structure were applied and optimized. BF operation was improved continuously to ensure stable and smooth operation of BF. Hearth working condition control was strengthened, burden distribution control technology was applied to achieve reasonable distribution of gas flow, and heat load monitoring was strengthened to maintain BF reasonable working inner profile. Proper maintenance at the end of BF campaign was enhanced. Hearth and bottom service life was prolonged by adding titaniferous material and enhancing hearth cooling. Gunning of lining was carried out periodically for the area above tuyere zone.

MnO对高炉渣等温析晶动力学的影响

文章通过单丝热偶法研究了等温冷却条件下MnO质量分数对调质渣析晶行为的影响规律,分析在不同MnO质量分数下调质渣矿相结构随着温度的演变规律,并在此基础上利用JMA动力学方程建立调质渣在不同MnO质量分数下的析晶动力学模型。实验结果表明,MnO质量分数对调质渣的析晶行为有显著影响,当MnO质量分数从0.17%增至12.24%时,调质渣中晶体逐渐难以析出,但当MnO质量分数提高至16.32%时,调质渣的析晶能力得到加强;与原始高炉渣相比,MnO调质渣的主要析出矿相增加了锰橄榄石相与锰氧化物相;调质渣的析晶方式为表面形核、一维方向生长,根据阿伦尼乌斯公式并通过线性拟合得出,调质渣中MnO质量分数的增加会提高其析晶活化能,当MnO质量分数为12.24%时,活化能最大,为606.2 kJ/mol,但MnO质量分数达到16.32%时,活化能降低至最小,为373.9 kJ/mol。

铜冷却壁长寿的使用维护及结构优化浅析

首钢股份高炉铜冷却壁的长寿使用维护经验,主要是对冷却水温、水量、水压,入炉有害元素及边沿煤气流等进行有效控制,同时对中长期休风和降料面停炉等特殊时段进行专门维护,保障铜冷却壁长期稳定安全运行。针对铜冷却壁在长期使用后可能存在的热面磨损和累积变形,采用热面镶嵌钢砖、本体加强等结构优化设计,能大幅度提高耐磨和挂渣性能,增强抗变形能力,延长在异常工况条件下的使用寿命。认为,只要铜冷却壁设计合理、使用维护得当,就完全能在保障高炉高水平稳定顺行的基础上,实现超过一代炉役的长寿目标。

基于热阻及成本分析的高炉冷却壁多目标优化

本文建立了高炉冷却壁热阻模型,冷却壁热阻包括火积耗散热阻和对流热阻,分别表征其导热性能和换热表面的对流换热性能。分析冷却壁运行过程中的各项成本,包括冷却壁材料成本、运行耗水成本、运行能耗成本以及冷却壁厚度减薄时产生的额外收益。应用遗传算法以冷却壁热阻和成本为目标函数,以冷却壁各结构参数为决策变量,对冷却壁进行多目标优化,获得了Pareto最优解集。优化后的冷却壁与初始冷却壁相比,可在传热性能相当的前提下成本下降79.9%,或在冷却成本相当的前提下,热阻下降27.3%。

新钢7^(#)高炉炉凉事故分析与处理

新钢7^(#)高炉在有上部结厚的情况下计划检修,休风期间炉墙西南结厚物整体坍塌,复风过程因结厚物进入炉缸破坏了热平衡,补加净焦量不够,风口自动吹开,使用质量差的烧结开机料,最终造成炉温大凉。本文通过对高炉炉凉事故起因、处理经过及恢复到正常三个阶段进行了分析,为处理高炉炉凉事故快速恢复提供了宝贵经验。

沙钢2680m^(3)高炉长寿技术特点及铜冷却壁使用效果

沙钢2680m高炉设计及操作遵从炉料膨胀、收缩与炉型相适应的原则,通过设计合理炉型、优化铜冷却壁设计及操作制度等,延长铜冷却壁寿命。炉型设计采用合理的炉腰体积占比(12%~16%);优化炉身上部结构,减少铸铁冷却壁厚度,增加耐材厚度,可降低炉身上部冷却强度,避免边沿气流温度过低影响炉料的干燥和预热;优化铜冷却壁设计,壁体采用侧凸台,加强高炉周向传热的均匀性;优化操作制度,合理调剂上下部制度,增大炉缸活跃区占比,避免软熔带根部位置过低。采用上述措施后,2680m高炉铜冷却壁寿命普遍超过17年,部分达到23年。

酒钢1号高炉冷却壁长寿技术应用简析

酒钢1号高炉大修停炉检查冷却壁基本完好,5~7段铜冷却壁的使用效果明显优于8、9段铸铁冷却壁。1号高炉冷却壁使用效果较好,主要是采用了优化设计炉型、铜冷却壁、增加冷却水量提高冷却强度、联合软水密闭循环冷却系统等技术;同时,存在炉身中下部铸铁冷却壁冷却水流速偏小、冷却强度不足的问题,不易形成稳定的渣皮。认为,铜冷却壁上部的铸铁冷却壁是制约高炉长寿的重要环节,应结合高炉实际原燃料条件和操作制度优化设计,增加炉身下部铜冷却壁的高度,将铜冷却壁延伸至干湿交接部位。

高炉软水密闭循环冷却系统水温调控分析与探讨

介绍了首钢股份4 000 m~3高炉的软水密闭循环冷却系统的工艺流程、系统特点与运行效果。高炉软水密闭循环系统采用闭式冷却塔冷却降温,冷却水采用循环供水方式,通过冷却水量的合理分配,实现对软水的可靠降温。根据十年来的实际运行情况,对软水密闭循环冷却系统水温调控存在的问题进行了整改,有效提升了降温能力,提高了系统的供水安全性。

风冷高炉矿渣的超细粉磨与化学激发联合活化研究

风冷高炉矿渣水化活性低,某企业工业试验中使用风冷高炉矿渣作混合材生产复合水泥时,矿粉在水泥中的掺量通常低于30%。本文提出超细粉磨和化学激发联合活化的技术思路,改造粉磨工艺实现风冷高炉矿渣超细粉磨,并探究了粉磨工艺参数对矿粉粒径和活性指数的影响,当矿粉比表面积为650 m^(2)/kg时,28 d活性指数为88.4%,比原生矿粉提高了26.2%。在化学激发方面则研究了激发剂种类、掺量以及多元复配对矿粉活性的影响,最终以硫酸钠、硫酸铝钾和三乙醇胺为主要成分制备了一款复合激发剂,矿粉粉磨过程引入1.5%复合激发剂即可使7 d活性指数提高16.9%。

高炉重矿渣在高速公路路基工程中的应用研究

采用包钢高炉重矿渣铺筑了路基试验段,测试分析了重矿渣的矿物组成、稳定性、及其作为填筑材料的黏聚力、压缩系数、回弹模量和承载比等性能,研究了粒径大小对最大干密度、最佳含水率的影响规律及施工工艺.结果表明:重矿渣稳定性好,含有C 3S硅酸三钙、C 2S硅酸二钙等硅酸盐材料,具有一定的胶凝活性,有利于提高承载力;重矿渣填筑料压缩系数为0.05 MPa-1,属于低压缩性土,回弹模量为86.7 MPa,黏聚力为13.66 kPa,承载比能满足路基不同深度的强度设计要求.随着重矿渣9.5 mm通过率的减小,其重击实试件的最大干密度和最佳含水率逐渐降低.重矿渣路基试验段的松铺系数为1.1,最佳碾压方式为2遍静压加6遍动压,压实参数满足规范要求,平整度平均值小于20 mm,路用性能优良.

唐钢新区高比例球团矿冶炼高炉的操作炉型控制

唐钢新区高炉设计秉承“现代化、绿色化”理念,采用50%球团矿冶炼,为适应高比例球团矿冶炼,优化炉型设计,冷却设备采用全铸铁冷却壁形式。高比例球团矿冶炼下,因高炉边沿不稳、炉墙易结厚,操作炉型不易控制。通过采取加强原燃料质量控制、合理匹配上下部操作制度、合理控制水温差、快速处理炉墙结厚等措施,高炉保持了较长周期稳定顺行,各项技术指标持续提升。2022年下半年以来,高炉利用系数保持在2.74~2.97(m^(3)·d),从使用效果看,全铸铁冷却壁能够适应高比例球团矿冶炼条件下的高强度冶炼要求。