Oxidation of Fe-Cr-Ni Alloys in a Low Oxygen Partial Pressure Atmosphere to Mitigate Coke Formation

Anti-coking oxide films were prepared on a 25Cr35Ni and 35Cr45Ni alloy surface under the low oxygen partialpressure atmosphere of a H2-H2O mixture. The composition and phase structure of the oxide films were analyzed by energydispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The anti-cokingperformance of a mini tube made of a HP40 (25Cr35Ni) alloy was evaluated on a bench scale pyrolysis and coking test unit.The results showed that the surface Fe and Ni content decreased after the oxidation of the two alloys in a low oxygen partialpressure atmosphere. The oxide films were mainly composed of MnCr_(2)O_(4) and Cr_(2)O_(3). The average mass of coke in the minitube with oxide film decreased by 87% relative to that of a tube without an oxide film when the cracking temperature was 900℃. The ethylene, propylene, and butadiene yields in the pyrolysis tests were almost the same for the mini tubes withand without an oxide film. The oxide film on the alloy surface effectively inhibited catalytic filamentous coke formation.An industrial test showed that the run length of the cracking furnace with the in-situ coating technology was significantlyextended.

Influence of CeO_2 addition on the preparation of foamed glass-ceramics from high-titanium blast furnace slag

Foamed glass-ceramics doped with cerium oxide（CeO_2）were successfully prepared from high-titanium blast furnace slag by one-step sintering.The influence of CeO_2 addition（1.5wt%–3.5wt%）on the crystalline phases,microstructure,and properties of foamed glass-ceramics was studied.Results show that CeO_2 improves the stability of the glass phase and changes the two-dimensional crystallization mechanism into three-dimensional one.XRD analysis indicates the presence of Ca（Mg,Fe）Si_2O_6 and Ca（Ti,Mg,Al）（Si,Al）_2O_（6 ）in all sintered samples.Added with CeO_2,Ti CeO_4 precipitates,and crystallinity increases,leading to increased thickness of pore walls and uniform pores.The comprehensive properties of foamed glass-ceramics are better than that of samples without CeO_2.In particular,the sample added with a suitable amount of CeO_2（2.5wt%）exhibits bulk density that is similar to and compressive strength（14.9 MPa）that is more than twice of foamed glass-ceramics without CeO_2.

Recovery of Fe,V,and Ti in modified Ti-bearing blast furnace slag

A two-stage oxidation—alkali leaching—acid leaching method was proposed to recovery Fe,V,and Ti in modified Ti-bearing blast furnace slag.The optimal experiment conditions of iron extraction were one-stage oxidation time 40 s and holding time 8 min.The recovery rate of iron was 89.93%.The optimum experiment conditions of vanadium extraction were total oxidation time of 126 s,NaOH concentration of 4.0 mol/L,leaching temperature of 95℃,leaching time of 90 min,and the number of cycle was 4.The leaching rate of vanadium was 92.13%.The optimal experiment conditions of titanium extraction were HCl concentration of 4.5 mol/L,leaching temperature of 75℃,and leaching time of 90 min.The TiO_(2)content of synthetic rutile was 98.61%.

Effect of Fe_2O_3 on the crystallization behavior of glass-ceramics produced from naturally cooled yellow phosphorus furnace slag

CaO–Al2O3–SiO2(CAS) glass-ceramics were prepared via a melting method using naturally cooled yellow phosphorus furnace slag as the main raw material. The effects of the addition of Fe2O3on the crystallization behavior and properties of the prepared glass-ceramics were studied by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The crystallization activation energy was calculated using the modified Johnson–Mehl–Avrami equation. The results show that the intrinsic nucleating agent in the yellow phosphorus furnace slag could effectively promote the crystallization of CAS. The crystallization activation energy first increased and then decreased with increasing amount of added Fe2O3. At 4wt% of added Fe2O3, the crystallization activation energy reached a maximum of 676.374 kJ·mol−1. The type of the main crystalline phase did not change with the amount of added Fe2O3. The primary and secondary crystalline phases were identified as wollastonite (CaSiO3) and hedenbergite (CaFe(Si2O6)), respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Indirect mineral carbonation of titanium-bearing blast furnace slag coupled with recovery of TiO_2 and Al_2O_3

Large quantities of CO2 and blast furnace slag are discharged in the iron and steel industry. Mineral carbonation of blast furnace slag can offer substantial CO2 emission reduction and comprehensive utilization of the solid waste. This paper describes a novel route for indirect mineral carbonation of titanium-bearing blast furnace （TBBF） slag, in which the TBBF slag is roasted with recyclable （NH4）2SO4 （AS） at low temperatures and converted into the sulphates of various valuable metals, including calcium, magnesium, aluminium and titanium. High value added Ti-and Al-rich products can be obtained through stepwise precipitation of the leaching solution from the roasted slag. The NH3 produced during the roasting is used to capture CO2 from flue gases. The NH4HCO3 and （NH4）2CO3 thus obtained are used to carbonate the CaSO4-containing leaching residue and MgSO4-rich leaching solution, respectively. In this study, the process parameters and efficiency for the roasting, carbonation and Ti and Al recovery were investigated in detail. The results showed that the sulfation ratios of calcium, magnesium, titanium and aluminium reached 92.6%, 87% and 84.4%, respectively, after roasting at an AS-to-TBBF slag mass ratio of 2：1 and 350℃ for 2 h. The leaching solution was subjected to hydrolysis at 102℃ for 4 h with a Ti hydrolysis ratio of 95.7%and the purity of TiO2 in the calcined hydrolysate reached 98 wt%. 99.7% of aluminium in the Ti-depleted leaching solution was precipitated by using NH3. The carbonation products of Ca and Mg were CaCO3 and （NH4）2Mg（CO3）2·4H2O, respectively. The latter can be decomposed into MgCO3 at 100-200℃ with simultaneous recovery of the NH3 for reuse. In this process, approximately 82.1% of Ca and 84.2% of Mg in the TBBF slag were transformed into stable carbonates and the total CO2 sequestration capacity per ton of TBBF slag reached up to 239.7 kg. The TiO2 obtained can be used directly as an end product, while the Al-rich precipitate and the two carbonation products can act, respectively, as raw materials for electrolytic aluminium, cement and light magnesium carbonate production for the replacement of natural resources.

碳纤维预氧化炉内气流均布装置模拟研究

碳纤维是一种耐高温、高强度、耐腐蚀的新型材料,广泛应用于航空航天、国防军工和民用工业各领域。在碳纤维生产制造过程中,预氧化是其中最为关键的步骤之一。工业生产过程中往往采用预氧化炉进行预氧化,而衡量预氧化好坏的一个关键指标就是预氧化炉内风场均匀性。研究对象是预氧化炉内的气流均布装置,通过ANSYS FLUENT软件对气流通过气流均布装置后的流场分布状况进行研究。通过改变气流均布装置进出风口的几何结构以及气流分布板上开孔位置来实现气流均布。将模拟得到的流场特性与速度压力云图作对比,分析气流均布装置出口处的压力与气流均匀性来获得气流分布效果更优的气流均布装置。模拟获得的优化的气流均布装置结构为:采用双层气流分布板不完全错孔排列的直角进出口结构。

富氧铜侧吹熔池熔炼炉内流场与混匀效率模拟研究

鉴于冶金炉窑的高温与不可见性,大多测量手段受到限制,所以本文采用数值模拟对高温下富氧铜侧吹熔炼炉内的流场与混匀效率进行分析。受浮力影响,侧吹气流具有区域性的特点,主要对气流上升轨迹周围熔体直接搅拌,熔池中心存在低速区域,速度小于0.1 m/s。受侧吹气流反冲作用,壁面高应力区域集中在喷嘴附近以及气泡上浮路径周围,该区域壁面应力是相邻喷枪间壁面应力的2~3倍,炉衬更易受损。通过熔池内环流分布状态,沿喷枪轴线方向将熔池划分为高速喷吹区与环流搅拌区。其中环流搅拌区为主反应区,速度小于1 m/s,但速度分布更加均匀,组分的均混时间为34.10 s。平行环流喷吹技术对熔池的混合效率改善最明显,湍流黏度为原工况的1.51倍,均混时间相对降低62.18%。

蒸汽转化管内壁瘤状物组成与形成机制研究

在一根天然气制甲醇蒸汽转化炉管内壁某位置发现瘤状物,不仅突出于内壁还向炉管内部生长,导致炉管性能受到严重影响。针对此罕见现象,文章采用光学显微镜,扫描电子显微镜和能谱仪等手段对该瘤状物的组织和成分进行观察分析。结果表明:瘤状物的本质为Cr与Fe的氧化物,与基体之间存在不同于常规氧化物的过渡区,且在瘤状物内部观察到许多富碳的疏松结构。推测瘤状物的形成机制与还原-氧化相互共同作用有关。

空气和钛精矿对含钛混合熔渣钙钛矿富集行为的影响

采用XRD、SEM、EDS、Image-J等分析手段,探讨空气和钛精矿对含钛熔渣中钛资源富集行为的影响。通过对含钛混合熔渣改性,熔渣中钙钛矿晶体形状发生变化,降低钙钛矿晶体运动阻力,方便上部钙钛矿晶体向下部迁移和富集,得到高品位人造钙钛矿精矿。结果表明:合适的氧化时间有利于熔渣中的低价钛向高价钛转化,适量的添加钛精矿有利于促进钙钛矿晶体的成核,以球形晶体析出。因此,在较佳氧化时间2 min和较佳钛精矿添加量12%共同作用下,Ti组分以球形钙钛矿晶体富集于改性渣底部,钙钛矿体积分数由25.12%增加到61.50%。

氢基竖炉直接还原技术研究现状及展望

概述了国内外氢基竖炉直接还原工艺的发展现状,总结分析了在我国资源及能源条件下气基竖炉直接还原技术发展需要解决的关键问题,包含氢基竖炉专用氧化球团制备技术、氢基竖炉高效直接还原技术、绿色高效制氢技术。基于钢铁生产全流程考虑矿粉磨选工艺的投入,生产全铁品位高于65%,S、P含量低的纯铁精粉球团,可解决我国直接还原铁优质原料缺少的技术难题;或在氢基竖炉炉料中加入块矿、高炉用球团矿,是直接还原技术发展的方向;在高温还原气制备过程中,积碳导致堵塞设备、管道和阀门等风险,需密切关注;绿色高效制氢技术中,风电制氢技术(PEM)成本将会大幅下降,具有明显市场竞争优势。大幅度降低绿氢的制备成本,将是未来气基竖炉直接还原技术发展的主要推动力,利用过剩的焦炉煤气、石化行业副产氢气资源和局部地区相对丰富的天然气资源生产直接还原铁,为实现气基竖炉向全氢还原过渡提供重要支撑。

SAE1070钢在加热过程中氧化影响因素

SAE1070钢在加热过程中的氧化对其产品质量及加热炉能耗存在较大的影响.结合前人实验结果,提出了SAE1070钢坯氧化层厚度的计算公式,该公式考虑了加热温度、加热时间和氧气体积分数等炉内参数对SAE1070钢坯氧化的影响,还分析了SAE1070钢氧化层的厚度随加热温度、加热时间及氧气体积分数的变化.结果表明:当炉内烟气中氧气体积分数为3%时,SAE1070钢坯形成的氧化层厚度是炉内烟气中氧气体积分数为1%时的1.3倍.设计及实际控制加热炉时,可根据上述研究结果优化其结构及加热过程的控制策略.

蓄热式氧化炉在炼油污水处理厂中的应用

采用蓄热式氧化炉技术高效处理炼油污水处理厂VOCs。介绍了蓄热式氧化炉的应用流程、工艺设计和运行情况。实验结果表明:在蓄热式氧化炉入口气体浓度为甲烷爆炸下限的6.5%~7.0%、炉膛温度为800~820℃的条件下,装置运行效果较好,处理后烟气排放非甲烷总烃、苯、甲苯、二甲苯的平均质量浓度分别为5.28,0.09,0.20,0.02 mg/m^(3),远低于国家排放标准。蓄热式氧化炉具有热效率和净化率高、操作安全可靠、维护工作量少等特点,是炼油污水处理厂VOCs治理的有效途径。

航空煤油加氢装置加热炉CO含量超标问题分析及对策

分析了某石化公司航空煤油加氢装置加热炉运行过程中CO超标的问题,并提出改进措施,在不改变燃烧器本体基础上,通过在线改造燃料气枪,设计出燃料分级低氮低CO燃烧器。结果表明:引起加热炉运行期间产生大量CO的原因主要有加热炉炉膛温度低、燃烧器实际热负荷变动大、燃烧器结构局限性等;经计算流体动力学(CFD)模拟,改造后燃烧器火焰中心的最高燃烧温度为1364.18℃,低于NO_(x)大量生成的温度(1450℃以上),NO_(x),CO排放质量浓度分别为35.00,26.45 mg/m^(3);改造后的燃烧器通过燃料预混耦合燃料分级燃烧的方式,调整2套燃料气枪燃烧负荷,使得火焰燃烧更完全,加热炉总烟气中CO质量浓度由改造前最高(1262 mg/m^(3))降至最低(18.00 mg/m^(3)),同时,烟气中NO_(x),SO_(2)等污染物远低于排放指标。

原料钢坯氧化铁皮控制研究

热轧带钢和原料坯氧化铁皮的厚度对于提高钢产品表面质量、降低生产成本具有重要意义,但原料坯进入加热炉后,氧化铁皮逐渐脱落、堆积,会严重影响加热炉正常运行,若处理不当,还会造成产品表面缺陷。针对此问题,重点分析了原料钢坯氧化铁皮在生产中对加热炉的主要影响,并针对性地制定了优化钢产品化学成分、调整生产工艺参数、制作氧化铁皮清除装置等工艺优化措施,减少了热轧带钢中氧化铁皮的轧入。

降低管式加热炉氮氧化物排放的有效途径

石化装置管式加热炉燃烧过程中产生的氮氧化物伴随着烟气排放至大气中,对环境与人类具有较大的危害。文章介绍了某石化装置管式加热炉烟气中氮氧化物的生成机理与排放浓度计算方法,并以高热负荷管式加热炉NF-503、低热负荷管式加热炉F-101C为例,探讨了低氮燃烧器改造、降低过剩空气系数、降低热空气温度等加热炉氮氧化物减排措施的原理、适用条件与应用效果。研究结论对相关企业管式加热炉氮氧化物减排具有一定的借鉴意义。

制氢装置停开工非氨脱硝剂工业应用总结

制氢装置转化炉燃料气在停工切出PSA(变压吸附)尾气后,开工切入PSA尾气前,使用工厂管网的高压燃料气作燃料,存在外排烟气氧含量较高工况下NO_(x)折算值超标的难题,为此在停、开工过程开展了非氨生物基无触媒脱硝还原剂撬装式技术的工业应用及优化。结果表明:针对制氢装置停、开工过程燃料切换和烟气中高氧量的特殊工况,烟气温度450~850℃的气氛下,实施加剂后,把NO_(x)实测值降至超低,解决了NO_(x)折算值超标的问题,实现转化炉烟气NO_(x)全时合规外排,其中停工过程NO_(x)折算浓度日均值由279 mg/m^(3)下降至129 mg/m^(3)(满足小于180 mg/m^(3)的指标要求);开工过程NO_(x)折算浓度日均值由502 mg/m^(3)下降至104 mg/m^(3)。

原料物理性能对稀土氟盐电解影响的研究

万安级电解炉槽体较大,电解过程中槽底温度低,电解过程难以把控。在使用万安级电解炉进行熔盐电解时,尽量采取少量多次的方式加料,避免原辅料沉底,从而控制金属单耗,保证生产正常稳定运行。但在使用不同厂家提供的化学成分、比重等基本一致的原辅料后,生产情况却不尽相同。因此,针对原辅料的各项物理性能,结合实际生产情况进行研究,以探究原辅料物理性能对稀土熔盐电解的影响。研究结果表明:稀土熔盐电解较大程度受到原辅料的物理性能差异的影响;原辅料粒径越大越不利于电解过程的稳定进行;在不会因表面张力作用出现团聚的情况下,原辅料颗粒比表面积越大越有利于其在高温下熔融和溶解,稀土氟盐电解效果越好。

适用于器件制程的立式扩散/氧化设备设计与验证

针对半导体器件的国产化制造及工艺制程需求,设计了一款适用于200 mm(8英寸)晶圆的立式扩散/氧化设备。介绍了设备的功能特点和几个关键部分的设计要点,并对炉体系统进行了详细论述;设备设计完成后上线进行了流片试验,根据工艺验证结果,该设备满足产品工艺要求,膜厚均匀性均优于±2%。

降低加热炉煤气消耗及氧化烧损的工程技术研究

文中结合轧钢厂加热炉的实际情况,通过分析加热炉煤气消耗的问题和原因,采取了多种措施降低了加热炉煤气消耗及氧化烧损,通过优化燃烧控制,提高加热效率,减少能源浪费,并降低了环境污染,文中的研究成果不仅适用于轧钢厂,也适用于其他钢铁企业的加热炉改造。

辊底式热处理炉炉底辊结瘤分析及改善措施

对无氧化辊底式热处理炉的炉底辊结瘤成因进行分析,并提出了改善措施,旨在有效延长炉底辊结瘤周期。从外部问题、设备问题以及热处理工艺温度3个方面分析了辊底式热处理炉炉底辊结瘤的成因,并在设备维护、热处理工艺和入炉板质量方面提出了改善措施。以山东钢铁集团日照有限公司中厚板厂2#热处理炉为例,验证了该方法的可行性和有效性。