某700 MW锅炉水冷壁高温腐蚀原因分析及其防治措施

针对某电厂700 MW对冲式燃烧锅炉水冷壁腐蚀严重问题,对该锅炉高温腐蚀产生的原因进行了分析。在现场割取了腐蚀的水冷壁管,对其腐蚀垢层进行了X射线衍射(XRD)、能量色散X射线谱(EDS)和扫描电镜(SEM)分析,结果发现腐蚀产物中主要含有ZnS、FeS、Fe₇S₈、Fe₃O₄和α-FeOOH,推定此炉主要为硫化物型高温腐蚀,并制定了该锅炉的防治措施。     

350MW超临界锅炉水冷壁腐蚀分析

某发电公司350MW超超临界锅炉水冷壁出现大面积腐蚀现象,通过扫描电镜及X射线衍射确定腐蚀产物元素组成和主要成分,分析其生成原理并提出防治措施。     

超临界对冲燃烧式机组水冷壁高温区腐蚀原因分析

针对某国产600 MW超临界锅炉长周期运行后高温区侧墙螺旋水冷壁腐蚀情况,利用电镜能谱、X射线荧光光谱、物相分析对水冷壁管外壁附着物进行分析。分析结果表明:水冷壁外壁附着物包含大量FeS,硫元素质量百分比平均在26.7%。水冷壁管的金相组织为铁素体加珠光体,烟气侧硫化物型高温腐蚀是导致水冷壁管腐蚀减薄的直接原因。建议通过防腐喷涂、燃烧调整、贴壁风改造等措施防止水冷壁高温腐蚀减薄。     

电站锅炉水冷壁管向火面外壁腐蚀原因分析

本文通过对锅炉水冷壁管管向火面外壁腐蚀产物的Ｘ射线衍射和扫描电镜的分析，阐述了水冷壁管向火面外壁腐蚀产物为双层结构。其外层灰白色物相为ＦｅＳ，内层灰黑色物相为Ｆｅ１－ｘ和Ｆｅ３Ｏ４。综合试验分析结果认为：由于水冷壁管表面有碱式硫酸盐化合物的存在，当环境为缺氧气氛时，能产生游离态的活性硫，硫与铁反应生成ＦｅＳ。     

锅炉水冷壁爆管原因分析

通过宏观和微观观察、化学成分、腐蚀产物(扫描电镜及能谱、X射线衍射)等分析,结合锅炉运行工况对某厂一流化床锅炉发生的水冷壁管爆管进行了原因分析。结果表明,垢下碱性腐蚀是水冷壁爆管失效的主要原因。垢下高浓度的碱浓缩产生碱腐蚀,造成水冷壁管壁厚减薄和基体金属沿晶界腐蚀并形成微裂纹,在内压作用下最终导致爆管。     

垃圾焚烧发电锅炉第一烟道水冷壁腐蚀分析

由于生活垃圾成分复杂,生活垃圾焚烧发电锅炉的水冷壁的高温腐蚀问题也更为复杂,腐蚀会导致管壁过薄,对锅炉运行产生严重的安全隐患。文中通过对某台垃圾焚烧发电锅炉的腐蚀情况进行研究,并分析该台垃圾焚烧发电锅炉水冷壁腐蚀产物的元素含量,结合垃圾成分,运行中焚烧炉出口O_2/CO的含量,推断该锅炉水冷壁的腐蚀主要为高温Cl腐蚀。并针对水冷壁的腐蚀,采用涂覆Cr-Ni防腐材料对该锅炉第一烟道水冷壁进行了表面防腐,经半年的运行观察,该防腐涂层的防腐效果较好。     

火力发电机组锅炉水冷壁结垢的分析及诊断

文中结合多台火力发电机组锅炉水冷壁的检查情况,归纳了造成水冷壁管腐蚀结垢的常见原因。通过对原位腐蚀(垢下腐蚀、氧腐蚀)、腐蚀产物和杂质迁移沉积、停机期间的空气腐蚀等造成水冷壁结垢的机理及表征分析,总结了不同腐蚀类型在表面形貌、对金属基体的影响、腐蚀产物化学成分组成等方面的表象特征,提出了运用宏观检查、金属金相检查、化学成分分析等多种手段综合诊断火力发电机组锅炉水冷壁腐蚀结垢原因的技术要点和方法。     

1060 MW超超临界锅炉螺旋式上升水冷壁的高温腐蚀研究

采用X射线衍射、扫描电镜、能谱分析,对某电厂1060 MW超超临界锅炉水冷壁的高温腐蚀进行检测分析。结果表明,在不同区域形成的腐蚀产物的形态特征是不同的。有煤灰沉积区域的腐蚀比没有煤灰沉积区域的腐蚀更严重,未燃尽的煤灰沉积在管表面受热分解,煤中的Fe S2受热分解能够生成单质S会进一步加剧水冷壁管氧化膜的破坏,同时,管壁氧化膜的破裂和脱落为沉积在管壁表面的碳元素提供了渗碳可能性,使腐蚀性物质更容易扩散到水冷壁基体。因此,加装风帽和吹灰器在有助于改善水冷壁管表面附近的还原性气氛的同时,需要采用合理的吹灰方式和科学的吹灰间隔,及时清除受热面的积灰。     

红土镍矿选择性还原-熔分制备镍铁合金

以硅镁型红土镍矿主要原料,采用选择性还原工艺将矿中镍氧化物、铁氧化物还原成金属态,将获得的金属化球团熔融分离得到高品位镍铁合金。通过单因素实验考察了各影响因素对实验结果的影响,得到选择性还原-熔分处理红土镍矿最佳工艺参数:还原时间18 min、还原温度1 250℃、碱度R=1、内配碳(C/O原子比)0.6、熔分温度1 500℃、熔分时间30 min,在此条件下可获得镍品位16.2%、铁品位82.3%、镍收得率96.1%的镍铁合金;利用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)对最佳实验参数获得产物进行微观分析,发现加入的石灰石与复杂矿相反应可释放出简单镍氧化物和铁氧化物,促进还原反应的进行,镍基本完全熔解于镍铁合金相中,部分铁存在于磁铁矿相、赤铁矿相。     

电厂煤飞灰颗粒物的物理化学特征

对某台300MW燃煤电站锅炉电除尘器前后的飞灰进行取样,使用激光粒度仪测定粒度分布,使用X射线衍射仪(XRD)和扫描电镜(SEM)研究颗粒中的矿物成分及其微观形貌特征,同时使用电子探针对电除尘器后飞灰的单颗粒进行成分分析．结果表明：通过电除尘装置排入大气的颗粒物平均粒径为2．5μm左右;飞灰粗颗粒中有较多硅铝氧化物和粘土矿物,而细颗粒中则含有较多金属氧化物,且粗颗粒中石英所占矿物相比例相当高;电除尘器前的飞灰形貌类型种类较多,电除尘器后飞灰形貌类型简单,主要是圆球或圆形的颗粒;电除尘器后飞灰单个颗粒间组分随粒径变化的有Si、Al、Ca和S,而元素Fe和Ti的含量较恒定．     

Investigation on high temperature corrosion of water-cooled wall tubes at a 300 MW boiler

Because of the updated requirement on ultra-low NOx emission (<50 mg/Nm³), most of Chinese coal-fired boilers have to be operated at a low NOx combustion mode. However, for high-sulfur coal, water-cooled wall tubes probably suffer severe corrosion in such a strong reduction atmosphere. This work aims to investigate the high temperature corrosion behavior of water-cooled wall tubes inside a 300 MW boiler unit. A short length of corroded water-cooled wall tube was cut down and was analyzed by various characterization methods to further figure out the detailed corrosion mechanism. The typical corrosion products can be distinguished by blue, black and pale-green. Results showed that blue and black color products were mainly consisted of iron sulfides and iron oxides while the pale-green ones were identified as zinc sulfide. Along the radial direction, a layered structure of corrosion products can be observed. The formation of inner layer resulted from the reaction between iron oxide and hydrogen sulfide. The sulfur element displays a gradual increase trend while the Fe element gives out an opposite trend along the radially outward direction. The intermediate layer comes from the fly ash deposition and the outer layer is formed via condensation and deposition of ferrous sulfide gas on the water-cooled wall. The corrosion in this power plant is typical sulfide type for large amounts of Fe and S element were found in the corrosion products.     

储油罐内壁铁锈硫化及氧化反应

储罐内壁铁锈在低温有水的条件下与储罐中的硫化氢气体反应生成硫铁化物．硫铁化物的氧化放热是引起含硫油品储罐着火的主要原因．采用X-射线衍射仪鉴定铁锈成份,对铁锈主要成分室温下进行硫化及硫化产物的氧化实验,绘制硫化及硫化产物氧化反应温度-时间曲线,并鉴定分析硫化产物及硫化产物的氧化产物,研究对含硫储罐自燃的作用．结果表明,铁锈主要成分为Fe2O3和Fe3O4,室温硫化产物均为FeS,但FeS形状与其来源有关．形状、致密性不同,致使氧化自燃性不同．Fe2O3硫化产物比Fe3O4硫化产物的氧化自燃性高,对引发储罐自燃的危险性大．     

自然环境中硫化铁的自燃机理及影响因素

采用自然氧化实验系统,在自然条件下,对Fe_3O_4、Fe_2O_3以及Fe(OH)_3的混合物硫化后生成的硫铁化合物进行氧化实验,研究硫化铁在自然环境中的自燃倾向性。实验结果表明,硫化产物活性很高,具有较高的自然氧化活性,对硫化铁氧化升温特性的影响因素的研究表明,硫化时间长、空气中暴露面积大,能够加速硫化铁升温过程,而含有油品、一定的水分以及较小的暴露面积则降低了硫化铁的自燃倾向性。     

Effect of vinylene carbonate (VC) as electrolyte additive on electrochemical performance of Si film anode for lithium ion batteries

The effect of VC as electrolyte additive on the electrochemical performance of Si film anode was studied in this paper. The charge/discharge test, scanning electron microscopy (SEM), electrochemical impedance spectrum (EIS), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to investigate the cycle performance and SEI layer of Si film anode. It was found that the SEI layer formed in VC-containing electrolyte possessed better properties. It was impermeable to electrolyte and its impedance kept almost invariant upon cycling. The presence of VC in electrolyte brought out the VC-reduced products and decreased the LiF content in SEI layer. The major components of SEI layer were similar in VC-free and VC-containing electrolytes, which contained lithium salt (e.g. ROCO₂Li, Li₂CO₃, LiF), polycarbonate and silicon oxide. It was newly found that silicon oxide could be formed in SEI layer of Si film anode due to the reaction of lithiated silicon with permeated electrolyte in both VC-free and VC-containing electrolytes.     

Influence of inhibitors on corrosion and anodic behaviour of different grades of aluminium in alkaline media

The electrochemical properties of different grades of aluminium are said to be dependent on the presence of minor amounts of iron and silicon impurities. This investigation aims mainly at addressing the influence of different inhibitors (e.g., sodium stannate, sodium citrate and calcium oxide combinations) on properties such as corrosion, anodic behaviour and anode utilization efficiency of different grades of aluminium in alkaline media.     

The dependence of anti-corrosion behaviors of iron sulfide films on different reactants

As the product of hydrogen sulfide corrosion, iron sulfide compound can be used as hydrogen permeation barrier. In this study, chemical vapor deposition was used to synthesize iron sulfide films on the surface of X80 steel with different sulfur sources, and the effects of different sulfur sources on the products were studied. The film was characterized by its morphology, composition and performance. The results show that the hydrogen resistance of our product and the bonding degree between the substrate and the film are strongly relevant with the compactness of the films. When we used TBDS as sulfur source, the highest impendance and the smallest hydrogen permeation current (0.53 μA/cm²) was obtained, which is due to the better adhesion and dense structure compare to the other two sulfur sourses.     

Characteristics of scales from the Milos geothermal plant

Samples of scales have been studied using X-ray diffraction, elemental analysis and scanning electron microscopy. Analyses have also been made of brine and steam samples. The scale consists of heavy metal sulfides and silicon compounds which account for 90–100% of the deposited mass. The composition of the scale depends on the location with respect to the fluid flashing point. Samples in the vicinity of this point largely consist of metal sulfides (PbS, ZnS and CuFeS₂), while the percentage of silica and possibly of other silicon compounds tends to increase farther downstream.In all the samples, a significant part of the iron is not in the form of sulfide and is possibly bound into the silica matrix by some kind of “ion-bridging”. It is also observed that a silicon — rich layer adheres to the metal surface, even in places where sulfides are the main contituents of the scale.     

Corrosion characteristics of 316L as transpiring wall material in supercritical water oxidation of sewage sludge

Systematical corrosion tests of austenitic stainless steel 316L exposed to sewage sludge SCWO (supercritical water oxidation) were conducted in a batch stirred reactor with hydrogen peroxide as oxidant. Experiment conditions such as temperature, oxidation coefficient, pH value, corrosion medium, were chosen mainly keeping in mind the place and environment of reactions (i.e. surrounding transpiring wall). The exposed samples were ultimately analyzed by weight measurement, scanning electron microscopy in conjunction with energy dispersive spectroscopy, and X-ray diffraction analysis. The results show that severe pitting corrosion occurred as the sample was exposed to complicated environments, and different oxides including Fe₃O₄, FeCr₂O₄ and MoO₃ were found on the sample surface. The corrosion rate at all test conditions (360–450 °C pH = 5.2–10.05, oxidation coefficient of 0–2.0, sewage sludge or its SCWO reactor effluent) was in the range of 0.12–0.66 mm/y, and it increased as temperature and OC increased at supercritical conditions. Moreover, potential corrosion mechanism of 316L in sewage sludge SCWO is proposed, and influences of operating parameters on 316L corrosion properties are summarized. 316L and reactor effluent could be considered as transpiring wall material and transpiring water in sewage sludge SCWO with transpiring wall reactor, respectively.     

High-temperature corrosion of water-wall tubes in oxy-combustion atmosphere

Oxy-combustion is one of the most promising technology for CO₂ capture in coal-fired power plants. However, under oxy-combustion conditions, the concentrations of acid gas species are significantly increased due to the introduction of the flue gas recycle, which aggravates the high-temperature corrosion of heat exchanger materials in boilers. In this study, the early-stage high-temperature corrosion (0–16 h) of two representative water-wall tube materials (20G, 12Cr1MoV) is experimentally tested in a lab-scale furnace with the simulated oxy-combustion atmosphere. The effects of material, temperature, CO₂, H₂O, SO₂, H₂S and CO atmospheres on high-temperature corrosion behaviors is investigated. The micro-morphologies and compositions of corrosion layers are characterized by scanning electron microscope with energy dispersive X-ray spectra (SEM-EDS) and X-ray diffraction (XRD). Kinetic analysis shows that the high concentration of CO₂ accelerates high-temperature corrosion of water wall materials. In the simulated oxy-fuel combustion atmosphere (CO₂/O₂/SO₂), the mass gain rate can be enhanced by 10%–30% compared to the conventional air combustion atmosphere (N₂/O₂/SO₂), and the major composition of oxide scale is magnetite. In a reducing oxy-fuel atmosphere (CO₂/CO/SO₂/H₂S), the major components of oxide scale are magnetite and ferrous sulfide. The high concentration of moisture in the atmosphere accelerated the corrosion rate by 10–30%. For both model alloys, the corrosion kinetics obey the parabolic law. Water-wall tube material 12Cr1MoV appears superiority in corrosion resistance compared with 20G material.     

The Influence of Sulfurization of Rust in Oil Tanks

Abstract

Hydrogen sulfide reacts with the corrosion products (Fe₂O₃) in oil tanks to form iron sulfides. The oxidation and released heat of iron sulfides can lead to spontaneous combustion of iron sulfides and fire of oil tanks. In this article, the simulating production process of iron sulfides in oil tanks and the effects of flow rate of hydrogen sulfide, environmental temperature and setting time on the quantities and types of iron sulfides are studied.