电厂烟气脱硫系统烟囱的腐蚀与防护研究进展

湿法脱硫工艺已成为国内外电厂主导的烟气脱硫技术.湿法脱硫后烟气具有强腐蚀性,带来严重的设备腐蚀问题.本文介绍了湿法脱硫后烟囱的腐蚀环境、腐蚀机理及其腐蚀行为,综述了国内外电厂脱硫系统烟囱腐蚀控制方法与防腐蚀材料的研究进展,供设计烟囱防腐蚀措施参考,有助于提升国内电厂脱硫设备的腐蚀控制水平.     

烟气脱硫系统的严重腐蚀问题完全能够解决——访中冶集团建筑研究总院教授级高工张大厚

10月15日，由国家电力监管委员会会同国家发展和改革委员会、国家能源局、环境保护部，并商有关部门共同组织编写《2008年电力企业节能减排情况通报》出台。对比去年出台的《2007年电力企业节能减排情况通报》，可见电厂烟气脱硫过程中的防腐蚀工程质量问题，虽由来已久，但有问题越来越严重的趋势。烟气脱硫过程中的防腐蚀工程，是脱硫过程必须的措施，是对电厂减少排放的保障。烟气脱硫中的防腐蚀工程质量事故的频发，必须引起电厂及防腐蚀工作者的高度重视。为此，本刊整理了一些关于烟气脱硫防腐蚀方面的资料，期望能对大家有所帮助。     

国内FGD装置中鳞片衬里防腐蚀失效原因分析

湿法烟气脱硫装置因其处理烟气量大、脱硫率高、运行周期长、运营成本适中,已成为国内外火电厂烟气脱硫的主导装置.但该装置腐蚀环境苛刻,防腐蚀是FGD装置中的一个重要环节,而作为一种普通采用的鳞片衬里材料,在国内的一些应用案例,出现了一些防腐蚀失效甚至失败的情况,本文就一些FGD装置的失效情况进行分析和总结,找出一些原因以及对策,从而为后续烟气脱硫装置的防腐蚀技术提供了可靠的技术借鉴.     

钢铁行业烧结烟气脱硫装置的防腐蚀材料选择探讨

根据我国钢铁行业烧结烟气的特点,对湿法脱硫装置防腐蚀衬里技术及衬里结构优化进行了分析,结合多项工程的实践经验,提出了适合烧结烟气脱硫装置防腐蚀的初步设计方案,供同行参考。     

氨法烟气脱硫装置腐蚀与防护

针对某热电厂氨法烟气脱硫装置防腐蚀设计以及运行中的腐蚀现状,分析了该装置的腐蚀原因。结果表明,脱硫浆液中硫酸根离子、氯离子等对金属设备的酸腐蚀、颗粒物结晶腐蚀和机械冲刷磨损,以及脱硫后低温湿烟气凝结成低浓度酸液对烟囱等设备的露点腐蚀是造成装置腐蚀的主要原因。提出了氨法脱硫装置防腐蚀对策,主要包括合理选用防腐蚀设备材料;严格按照防腐蚀施工工艺标准,确保防腐蚀施工质量;运行中严格控制引起腐蚀的因素,降低设备腐蚀速率。     

非金属衬里材料在烟气脱硫装置上的应用

催化裂化再生装置中产生的烟气是炼油企业污染物的主要来源。根据国家环保标准的要求,炼厂必须采用烟气脱硫装置(FGD)来控制二氧化硫的排放。烟气脱硫装置所处腐蚀环境极为恶劣,若不采取有效的防护措施,将影响整个系统的安全稳定运行。烟气脱硫装置如果整体采用耐蚀合金材料,价格昂贵。介绍了适用于烟气脱硫装置的几种非金属衬里及其性能和应用区域,包括橡胶衬里、玻璃鳞片树脂衬里、耐蚀胶泥、耐蚀砖板衬里、整体玻璃钢等常用非金属衬里,以及聚脲、纳米复合涂料等新型高性能防腐蚀涂料等。橡胶衬里的耐化学腐蚀性和抗介质渗透性较好,但耐温性差,一般用于机械负荷大而内部环境温度较低的区域,如吸收塔内部、浆液系统和烟道。玻璃鳞片树脂衬里的综合性能较好,被广泛应用于烟道、吸收塔等烟气脱硫装置的各个区域。玻璃钢衬里多用于脱硫系统中的输送管道和吸收塔内喷淋管道等部位。胶泥和耐蚀砖板衬里是应用较早的防腐蚀技术,其抗冲击性能差。聚脲和纳米复合涂料是重防腐蚀涂料,是FGD装置腐蚀防护的新技术,虽然在炼厂脱硫装置中有一些应用,但其使用效果还有待证明。     

火力发电厂烟气脱硫后烟囱的腐蚀与防护

随着烟气脱硫技术在火力发电厂的普及,烟气对烟囱的腐蚀性加强,烟囱的腐蚀防护已成为发电厂重点关注的防腐蚀工作之一。通过分析脱硫后烟囱的腐蚀环境和运行环境,分析目前采用的防腐蚀材料的应用情况,对烟囱腐蚀防护设计中需要考虑的因素进行了分析,对烟囱防腐蚀工作提出了建设性意见。     

火力发电厂烟囱涂料防腐蚀工程质量检验方法

随着烟气脱硫技术在火力发电厂的普及,烟气对烟囱的腐蚀性加强,烟囱的保护已成为发电厂的重要工作,烟囱工程质量监督和验收的技术手段急需完善。分析脱硫后烟囱的腐蚀环境和运行环境,结合目前采用的防腐蚀材料应用情况,分析讨论了针对烟囱防腐蚀涂料性能及质量检测评价的关键项目和方法。     

腐蚀控制是影响烟气脱硫装置长周期安全运行的重点——访上海富晨工程有限公司总经理王天堂

问：防腐蚀工作在电厂烟气脱硫过程中，有何作用？答：在国外一个新建项目中，防腐蚀工程会占该项目总投资的20％～30％左右，从这个数据中可以很清楚的得出防腐蚀工程在项目建设中的重要性，这对于脱硫工程（FGD）更是如此。     

烟气净化设备的腐蚀机理与防护方法

介绍了烟气净化设备的腐蚀环境,分析了腐蚀机理：SO2、SO3和HCl等酸性气体组分使烟气露点温度提高,烟气在净化设备表面上凝结析出酸性电解质溶液,形成腐蚀性原电池,发生电化学腐蚀。归纳总结了湿法烟气脱硫装置的各种防腐蚀技术,介绍了新研制的适用于电晕放电烟气净化设备的防腐蚀导电涂料。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.