Study on metallurgical properties and pellet proportioning technology of stainless steel cold-rolling sludge

With a complicated composition, large rolling sludge has been a focal point concerning neither at home nor abroad have any technologies suitable for bulk utilization of stainless steel cold- production and serious damage to the environment, stainless steel cold- environmental protection for stainless steel enterprises. Up to now, come into being that are not only proper, safe and economical but also rolling sludge. Based on the characteristics of the stainless steel cold- rolling sludge, orthogonal experiments were carried out on pellet proportioning and high-temperature roasting, and major metallurgical properties of sludge pellets were also tested. As the results show, pellets with 30% addition of cold-rolling sludge are qualified regarding their compressive strength, chemical composition and major metallurgical properties. No adverse impact happens to the blast furnace operation when sludge pellets account for 10% of the blast furnace raw materials. Therefore, the technical route applied in this paper is proved simple, feasible and environmentally friendly for cold-rolling sludge treatment.

Recovery of heavy metals from electroplating sludge and stainless steel pickle waste liquid by ammonia leaching method

A coordinative disposal process for treatment of electroplating sludge and stainless steel pickle waste liquid containing Cu, Ni, Zn, Cr and Fe etc., has been developed to recover valuable metals and to eliminate pollution. The recovery of Cu, Ni, Zn and Cr is 94%, 91%, 90% and 95%, respectively. The ammonia was recycled by the simplified process of CaO caustic distillation. The precipitated product of Cu, Ni and Zn obtained from caustic distillation of ammonia was separated by extraction or high\|pressure hydrogen reduction in an autoclave. The qualified metal salt products were obtained through extraction. The rich chromium residue from coordinative disposal was subjected to recover Cr by hydrothermal oxidation in NaOH medium and Fe\-3O\-4 was synthesized by wet methods from the residue produced by extracting Cr. Cr was a stable chemical fixed in Fe\-3O\-4 and harmless. The recovery process has been used in a pilot plant with sludge production capacity of 2000 t/a.

Characterization and recycling of nickel- and chromium-contained pickling sludge generated in production of stainless steel

Pickling sludge generated during the neutralization of pickling wastewater with calcium hydroxide in stainless steel pickling process was characterized using X-ray fluorescence spectrometry,X-ray diffractometry,scanning electron microscopy,thermogravimetry and differential scanning calorimetry,etc.The major compositions of pickling sludge are CaF2,CaSO4,Me(OH)n(M: Fe,Cr,Ni),and the content of CaF2 is high in the sludge.The melting point of pickling sludge is about 1350 °C and the viscosity is about 0.14 Pa·s at 1450 °C,which are comparatively lower than those of normal refining slag.After heat treatment,the contents of sulfur and fluorine in the pickling sludge were reduced,confirming the thermal decomposition of sulfate in the sludge.Fluorine in the sludge is reduced by the gaseous SiF4 and AlF3 generated through the reactions of CaF2 with SiO2 and Al2O3.The preliminary results from the reduction test indicate that the sulfur content in the steel is not affected by the presence of sulfur in the sludge.The recovery of nickel is about 40%,and the chromium content changes marginally due to the protective atmosphere under the reduction condition of chromic oxide.The pickling sludge is a potential auxiliary material for the production of stainless steel.

Fatigue Response of Cold-Rolled Type-304 Stainless Steel Foil

This study presents the fatigue response of 304 stainless steel foil, cold-rolled to a thickness of 3.2 μm with 87 percent cold work at orientations of 0, 45, and 90 degrees to the direction of rolling. Fatigue specimens were fabricated by laminating a supportive layer of 20-μm polyimide film to one side of the foil and patterning 242 crack initiation features by photolithographic process. Progression of fatigue damage was determined through electrical resistance measurement. The fatigue response was demonstrated to be largely affected by anisotropy existing between the rolling direction and the off-axis orientations. Fatigue cracks that traveled in a direction parallel to the elongated grains (cyclic loads applied at 90-degree orientation to foil rolling direction) had the most fatigue response (undesirable characteristic). The construction of the specimens with thin foil supported by a film backing contributed to high fatigue threshold.

Inclusion and its deformation behavior in 304 stainless steel

Non-metallic inclusion is the main reason for the presence of surface defects in cold-rolled steel strip. In this study, the composition, morphology, and size of the non-metallic inclusion in hot-rolled 304 stainless steel strips are analyzed. Cold-rolled 304 stainless steel strips with different cold-rolling reduction have been prepared, and the morphology and size of inclusion in these cold-rolled strips are also analyzed. Furthermore, the deformation behavior of a non-metallic inclusion during the cold-rolling process is studied. The results show that CaO-SiO2- MgO-Al2 O3, a kind of brittle compound oxide,is the main type of inclusion in hot-rolled 304 stainless steel strips. During the cold-rolling process, ductile deformation of this type of inclusion is not obvious, where large inclusions are crushed, and the average size of inclusions in cold-rolled strips decreased while the cold-rolling reduction increased.

Researches on the problems in the production of low nickel austenitic stainless steel

Problems encountered in the production of low nickel austenitic stainless steel have been studied. These problems primarily include the changes to the microstructure of the slab during the heating process, the formation and removal of deformation - induced martensite during cold rolling, and the effects of the annealing process on the surface oxide structure. A reasonable manufacturing process has been proposed on the basis of the research results and high-quality cold-rolled strips of low nickel austenitic stainless steel have been produced.

Pyrometallurgical recycling of stainless steel pickling sludge: a review

Stainless steel pickling sludge (SSPS), generated from the lime neutralization process of spent pickling liquor, is classified as a hazardous waste consisting of abundant metals like Fe, Cr and Ni, and other elements like F, S and Na, etc. Rather than a common disposal in landfill, recovering these metals and other valuable components from SSPS can not only create economic benefits, but also eliminate its adverse impacts on human health and the environment. A review of the formation mechanism and basic properties of SSPS was made, and the technical features, advantages and limitations of a series of pyrometallurgical treatment processes were summarized. Based on these, the main challenges for recycling of SSPS through the existing techniques are demonstrated. The traditional pelletizing/sintering-blast furnace process can only be used as a partial solution. Direct use of SSPS as flux in an argon-oxygen decarburization converter or electric arc furnace is a promising way, but low S sludges are preferred. The STAR process shows excellent recovery for metals, but it also has a low tolerance to the S and F contents in SSPS. And theINMETCO process is highly flexible in treatment of various wastes, whereas it exhibits relatively low Cr recovery and produces poor-quality pig iron. In addition, the feasibility of the rotary kiln-electric furnace, solid -state reduction of chromite and reduction-magnetic separation processes requires further studies. An urgent task at present is to develop a system for scientific classification and separate collection of SSPS in terms of chemical composition, notably S and F contents.

Desulfurization thermodynamics experiment of stainless steel pickling sludge

A technical idea of returning stainless steel pickling sludge to smelting process so as to recycle valuable metals of Fe, Cr, and Ni was proposed, expecting to realize sludge detoxification and resource utilization. Thermodynamics calculation showed that not only most valuable elements including Fe, Cr and Ni, but also the harmful element of sulfur in pickling sludge can be enriched into molten metal. As a result, a theoretical study on desulfurization thermodynamics of sludge pretreatment was conducted, and results indicated that complete desulfurization temperature of pure pickling sludge was above 1400℃. When 0.5-0.8% carbon was added as reducing agent, the complete desulfurization temperature was reduced to 1000℃ or below. Desulfurization roasting experiment indicated that desulfurization rate at 1400℃ under inert environment was 78.74% and maximum desulfurization rate at 1000℃ under reducing environment was 91.62%.

400系不锈钢酸洗污泥资源化利用试验研究

针对400系不锈钢酸洗过程生成的污泥悬浊物数量较大的问题,通过压滤机方式将酸洗污泥进行收集,对收集的酸洗污泥进行成分分析,发现混酸污泥的Cr、Fe元素含量接近高碳铬铁的金属含量。将混酸污泥替代高碳铬铁进行了Cr17型不锈钢冶炼试验,冶炼装置使用坩埚容量为2 kg的中频感应熔装置。通过试验发现,混酸污泥可替代高碳铬铁应用于不锈钢的冶炼生产,但工业化生产前应采取措施保证Cr元素的收得率。

反硝化颗粒污泥处理不锈钢酸洗废水研究

采用以厌氧絮状污泥作为接种污泥的上流式厌氧反应器,通过调整其水力停留时间和水力条件等关键因素培养反硝化颗粒污泥,开展其对不锈钢酸洗废水脱氮研究。研究结果表明,上流式厌氧反应器以甲醇作为碳源运行42 d后,形成了成熟的反硝化颗粒污泥;成熟的反硝化颗粒污泥边缘清晰、表面包裹大量杆菌,单颗污泥沉降速率可达198~273 m/h,粒径为1~6 mm,反硝化速率最高可达2.79 gN/(gVSS·d);在反应器NO_(3)^(-)-N容积负荷为2.0~2.44 kg/(m^(3)·d)时,NO_(3)^(-)-N平均去除率为98.03%,NH_(4)^(+)-N平均去除率为89.76%,TN平均去除率为97.81%;最终出水的氨氮及总氮可同时满足《钢铁工业水污染物排放标准》(GB 13456-2012)的间接排放标准和《污水排入城镇下水道水质标准》(GB/T 31962-2015)的C级排放标准。本工艺相比传统反硝化工艺能够节约碳源30%左右。

超临界水氧化城市污泥中316L不锈钢的腐蚀行为

采用间歇式超临界水氧化装置,对316L不锈钢网状试样和块状试样在超临界水氧化处理城市污泥环境中的腐蚀特性进行了研究。结果表明,试样的腐蚀程度随氧化系数的提高而加剧,碱性条件下网状试样表面有富含Mo和Ni的丝状无机盐生成。与网状试样不同,块状试样在高氧化系数和酸性条件下均表现出点蚀形貌,在酸性条件下腐蚀速率最高达0.17 mm/a,经历高氧化系数(2.0)、酸性(pH=5.2)和碱性(pH=10.05)条件下分别腐蚀10 h后,块状试样表面呈现点蚀形貌,表层氧化物主要为Fe_3O_4-NiFe_2O_4。

不锈钢冷轧污泥配矿压球工艺及冶金性能研究

冷轧污泥成分复杂、产量大、危害严重,已成为不锈钢企业环保治理的难点,国内外尚无妥善安全又经济实用的利用途径。针对不锈钢冷轧污泥的特点,进行了配矿压球、高温焙烧的正交试验,考察了污泥球团的主要冶金性能。结果表明,污泥掺量30%时,球团抗压强度、化学成分和主要冶金性能满足高炉要求;按照10%进行配料,对高炉顺行无影响,是一条工艺简单、技术可行的无害化处理途径。

不锈钢污泥与碱共存条件对水泥熟料烧成的影响

采用不锈钢冷轧脱水污泥参与高碱生料的配料,并通过正交试验研究污泥掺量、烧成温度、碱含量等因素对熟料烧成质量的影响。结果表明其影响顺序为:污泥掺量>烧成温度>碱含量。分析认为,这是因为污泥中既含有较多活性较高的CaO和Fe2O3,同时其中还有具有良好矿化作用的F,Cr,Ni等微量元素;当高碱生料中适量配入不锈钢污泥并与适宜的烧成温度相结合,能显著改善熟料矿物的形成条件,从而有效抑制碱的危害,提高熟料的质量。

不锈钢酸洗废水处理技术分析

介绍了不锈钢酸洗废水的来源、组成、危害及其传统石灰中和的处理方法,通过传统方法处理不锈钢酸洗废水后得到的污泥的处理技术主要有无害化处理、稳定化和资源化三个层次。无害化处理是含铬固体废弃物处理的基本要求,固化、稳定化技术是处理重金属固体废弃物和其它非重金属危险废弃物的重要手段之一,对资源化方向国内外采用氨浸处理污泥的倾向比较大。分析了不锈钢酸洗废水处理技术的研究现状,主要包括化学法、物理化学法和生物化学法,并对不锈钢酸洗废水的治理进行了展望。指出了将不锈钢酸洗废液作为资源,将综合利用与环境治理结合才是最佳的解决途径。

不锈钢酸洗污泥对铁矿粉烧结液相生成的影响

为了有效利用不锈钢生产过程产生的大量不锈钢酸洗污泥,本文采用Factsage热力学软件计算不锈钢酸洗污泥对铁矿粉烧结液相生成特性和CaO-SiO_2-Fe_2O_3-Al_2O_3-MgO-CaF_2体系液相分布的影响,并选用熔点熔速测定仪研究了不锈钢酸洗污泥对铁矿粉液相生成能力的影响规律,建立了液相流动性与不锈钢酸洗污泥液配加比例之间的数学模型,揭示了液相生成量的变化特征。结果表明,实验结果与FactSage计算值基本一致,不锈钢酸洗污泥配加比例小于10%能够有效改善铁矿粉液相生成特征温度,而对铁矿粉液相生成量的影响较小,液相流动性指数与不锈钢酸洗污泥配加比例关系为:y=18. 40305-0. 09139x-0. 02644x^2+9. 07734x^3。

现场试片法测试油田污水腐蚀速率存在的问题探讨

以油田联合站与注水站污水腐蚀速率为研究对象,采用现场挂片的方法,考察了附着油泥对挂片失重及污水腐蚀速率测定结果的影响。结果表明,在所取得的试片中,附着的油泥多,腐蚀速率高,附着的油泥少或无油泥附着的,腐蚀速率低。标准所采用的方法获得的腐蚀速率高低受油泥影响。

不锈钢尘泥球团预还原-熔炼回收有价金属

不锈钢行业每年会产生大量的不锈钢尘泥,其中含有Fe、Cr、Ni等有价元素。目前不锈钢尘泥常用的处理方法如简单填埋和堆存,存在处理不完全、易产生二次污染、处理成本高等问题。本文提出了一种以球团预还原-熔炼来综合利用不锈钢酸洗污泥、除尘灰、氧化铁皮的新工艺。结果表明:不锈钢尘泥球团在预还原温度1250℃,预还原时间80 min,C、Fe质量比为1.5,内配炭量2%的条件下还原时,所得预还原球团抗压强度为685 N,金属化率为82.84%。该预还原球团在配焦量为8%和温度1625℃下熔炼20min,得到铬铁合金中Fe、Cr、Ni含量分别为66.90%、20.28%和0.96%,回收率分别为97.62%、97.91%、96.45%。该工艺可以高效地回收不锈钢尘泥中的有价金属,获得的铬铁合金可作为200系、300系不锈钢冶炼的炉料。

不锈钢酸洗污泥-黏土基陶粒的制备及性能研究

利用热力学软件FactSage中Equilib模块计算不锈钢酸洗污泥掺量的增加对制备陶粒结晶相的影响,得到合适的污泥烧制陶粒的掺量配比,即m(污泥)∶m(黏土)=20∶80;通过陶粒烧制试验,对该配比烧制的陶粒颗粒进行密度与抗压性能测试,得1100℃时烧制陶粒颗粒膨胀性较好,颗粒内部孔洞较为均匀,抗压强度平均为810N;陶粒对重金属Cr、Ni浸出结果显示,浸出液中Cr、Ni元素远小于国标中的限定量,表明陶粒对这两种元素的固化效果较好。

不锈钢酸洗污泥中重金属的浸出试验研究

采用无机酸作为浸出剂对不锈钢酸洗污泥中的重金属进行浸出,在相同条件下,各种酸的浸出效率顺序为:硫酸>盐酸>硝酸.讨论了硫酸浸出酸洗污泥时浸出时间、硫酸浓度、液固比和温度等条件对金属浸出率的影响.结果表明,硫酸浓度和液固比对镍铬的浸出率有较大的影响,而温度的影响较小.在液固比为6∶1、温度为30℃、硫酸浓度为3mol/L以及浸出时间为90min的条件下,污泥中镍、铬、铁和锰的浸出率分别为99.3%,99.2%,99.8%和93.2%,残余污泥中镍铬含量符合排放标准.

不锈钢冷轧废水站污泥脱水系统

介绍了采用板框压滤机处理不锈钢冷轧废水重金属污泥的工艺。设计泥量(以干污泥计)24 t/d,各水处理子系统的污泥,主要以含酸废水处理系统的污泥为主,泵入污泥浓缩池浓缩后,含固率8%～10%的污泥通过变频器控制的偏心单螺杆泵输送至板框压滤机。经过板框压滤机脱水后的泥饼含固率要求大于35%。系统自2007年9月初调试正常以来,运行良好,泥饼含固率稳定在35%以上。