Experimental investigation of high-temperature corrosion properties in simulated reducing-sulphidizing atmospheres of the waterwall fireside in the boiler

The presence of reducing atmospheres of the waterwall fireside in the boiler due to extensive use of low-NOx combustion mode caused severe high-temperature corrosion problems. In this study, high-temperature sulphur corrosion properties of two types of low alloyed waterwall steel (15CrMoG and 12Cr1MoVG) in two kinds of reducing-sulphidizing atmospheres were investigated by lab-scale experiments. The experimental atmospheres and temperature were simulated according to field measurements in the boiler of a thermal power plant. The experimental results showed that the reducing-sulphidizing atmosphere with CO was more corrosive, and the CO accelerated the corrosion of H₂S and worsened the corrosion. The CO inhibited the formation of oxide scales, provided some corrosion resistance, and produced the intensely corrosive COS. The corrosivity of the alkali metal chlorides was limited in the reducing-sulphidizing atmosphere without CO, while the corrosion was strongly hindered in the reducing-sulphidizing atmosphere with CO.     

对真空感应炉中二次炼钢用耐火材料的侵蚀性研究

采用一种优化的侵蚀性测试方法,模拟了真空炉内温度、熔渣成分和超低的压力条件,测试在真空感应炉内进行,并且分析了MgO-C砖的损毁机理。通过对测试后样品进行比较性分析,确定了本研究的可靠性。     

A pilot-scale fireside deposit study of co-firing Cynara with two coals in a fluidised bed

Costs of biofuel production from energy crops can be reduced by applying the crop residues in heat and power production. Perennial herbaceous crops like Cynara cardunculus L. are challenging fuels because they tend to have high ash and chlorine contents. Coals, however, are often rich in aluminium silicates and sulphur, and co-firing of these biofuels with coal could be expected to reduce operational problems. In addition, CO₂ emissions are lower than during coal firing alone. Blends of Cynara and two coals, South African bituminous and Spanish sub-bituminous coal, were combusted in a 20 kW bubbling bed pilot reactor to ascertain the ability of the coals to reduce operational problems by alkali capture. The Cynara fuel sample contained almost 2 wt% chlorine. The South African coal was rich in kaolinite capable of capturing alkalies from chlorides to produce alkali aluminium silicate and HCl. The Spanish coal was rich in sulphur (mostly present as FeS₂), and produced high concentrations of SO₂ that partially oxidised to SO₃. The SO₃ can capture alkalies from chlorides by sulphation. Up to 30% Cynara, on energy basis, could be co-fired with Spanish coal without operational problems, whereas the same percentage of Cynara with South African coal led to strong Cl deposition. Co-firing of Cynara with both coals resulted in high HCl emissions (up to 1500 mg/Nm³ in 6% O₂). In addition, co-firing of the Spanish coal led to very high SO₂ emissions (up to about 16,000 mg/N m³ in 6% O₂). Thus, a power plant capable of firing such blends must be equipped with flue gas cleaning equipment for effective SO₂ and HCl capture in the flue gas channel after the superheaters, or else the quality of the Cynara must be markedly improved by changing the harvesting technology and fertilisers, which could be major sources of high ash and chlorine content in the fuel.     

Water vapor corrosion test using supersonic gas velocities

Testing of the corrosion resistance of environmental barrier coating (EBC) systems is necessary for developing reliable coatings. Unfortunately tests under realistic gas turbine conditions are difficult and expensive. The materials under investigation as well as parts of the test setup have to withstand high temperatures (≥1200°C), high pressure (up to 30 bar) as well as the corrosive atmosphere (H₂O, O₂, NO_x). Therefore most lab scale test-rigs focus on simplified test conditions. In this work water vapor corrosion testing of EBCs with a high velocity oxy fuel (HVOF) facility is introduced which combines high temperatures and high gas velocities. It leads to quite high recession rates in short periods of time, which are comparable to results from literature. It was found that high flow velocities can easily compensate low gas pressures. HVOF-testing is a simple and fast way to measure the recession rate of an EBC-system. As proof of concept the recession rates of an oxide/oxide CMC with and without EBC were measured.     

Isothermal corrosion testing of frit furnace refractories

In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al₂O₃ precipitation observed along the frit–refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al₂O₃ precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite.     

Mechanistic prediction of ash deposition in a pilot-scale test facility

A mechanistic approach has been used for assessing the ash deposition tendency and has been used for predicting the ash deposition behavior of Australian bituminous coals in a pilot-scale test furnace. The detailed analysis of mineral matter in coal determined by QemSCAN analytical technique was incorporated into an ash formation model to estimate the character of ash particles. The detailed chemical composition and particle size distribution data of ash particles from the ash formation model were incorporated into a computational fluid dynamics (CFD) code to get the arrival rate and retention ability of each ash particle onto the heat transfer surfaces.The CFD code along with the ash character from the ash formation model was able to simulate trends in ash deposition along the furnace length similar to those in the test furnace. The approach was also able to distinguish coals with high ash deposition potential from low ash deposition problems and the results agreed with those in test furnace.     

氯化氢合成炉腐蚀原因与缓蚀措施

通过对PVC生产过程中氯化氢工序所采用的水冷却夹套式钢制合成炉腐蚀原因的分析，提出了缓解该设备腐蚀的相应措施和需要注意的问题。     

气田加热炉腐蚀机理及防腐措施研究

针对某气田加热炉,进行水质以及腐蚀产物垢样分析,平均腐蚀速率达到0．2688mm／a,加热炉用水总矿化度为339．92mg／L,导致加热炉腐蚀、结垢现象严重。确定出加热炉腐蚀主要为均匀腐蚀、溃疡状腐蚀和斑点腐蚀。为解决这些问题,分析了加热炉内氧腐蚀以及酸腐蚀的腐蚀机理,并在试验的基础上提出了加热炉防腐措施,即对五种酸洗缓蚀剂以及缓蚀阻垢剂进行评价筛选实验,给出了防腐配方：10％盐酸＋1％SH-129,其中盐酸具有润湿性、促进解垢作用和渗透作用;复合SH-129缓蚀剂具有点腐蚀抑制剂、轻质开裂抑制剂和还原辅助剂。试验取得满意的效果,腐蚀速率均在0．076mm／a以下,缓蚀率达到97．32％。筛选出SG-200阻垢剂,在pH值为12．07,其阻垢率为96．81％。在此基础上设计了加热炉的防腐防垢方案,为下一步工作和其他油气田企业提供借鉴。     

Coating evaluation and validation of accelerated test conditions using an in-situ corrosion sensor

An in-situ corrosion sensor was used to obtain electrochemical impedance spectroscopy (EIS) measurements on coated panels under a variety of accelerated laboratory test conditions as well as ambient exposure at a Florida beach. Three studies are reported. The first compared the sensor (EIS) measurements taken in a salt fog chamber to those obtained using a clamp-on cell and the conventional remote electrode/immersion approach. For coatings with minimal edge defects, the two methods gave equivalent results. For coatings with edge defects, the sensor was able to detect the defects provided the surface was wet, as in the salt fog chamber. In contrast, the conventional approach was unable to detect defects unless they were within the confines of the clamp-on cell. In the second case, sensor measurements were used to compare coating degradation during salt fog, a cyclic corrosion test, humidity, and immersion to that occurring at a Florida beach. The cyclic corrosion test showed an excellent correlation with beach exposure while the salt fog and other test showed very little correlation, suggesting that the cyclic test is more valid for discriminating coating performance for seacoast exposure. The sensor also indicated that the test could be short-ened by up to 40% without significantly reducing the validity of the test. In the final example, a series of primers and appliqués were evaluated using the cyclic corrosion test. The sensor EIS results allowed a discrimination between the materials sets even though there was little or no visual difference between the specimens. 10260 Old Columbia Rd., Columbia, MD 21046.     

生物质锅炉氯腐蚀的密度泛函理论研究

氯气的活化氧化腐蚀是生物质锅炉过热器腐蚀的主要原因之一。为探究活化氧化腐蚀循环中FeCl₂与O₂的反应机理,本文利用Material Studio中的DMOl³模块,基于密度泛函和过渡态理论,优化了各反应物、产物、中间体和过渡态的几何构型。通过频率分析证实了中间体和过渡态的真实性。结果表明,FeCl₂与O₂反应生成Fe₃O₄的过程中逐次生成3个Cl₂分子,其中第三个Cl₂逸出生成Fe₃O₄需要吸收高达300.4 kJ/mol的能量,为反应路径的速率决定步骤。     

关于燃气加热炉低温腐蚀的原因与对策

低温腐蚀是困扰燃气加热炉安全运行与炉效提高的主要问题。以某石化公司120万t/a焦化加热炉为例进行了换热计算和腐蚀原因分析,提出了以下改进方法:①提高脱硫工艺温度,降低燃料中的H2S含量;②增加吹灰器;③降低烟气中的水含量;④调整好烟道挡板的位置;⑤控制烟气酸露点温度。     

热媒炉烟气露点腐蚀及防止措施

根据聚酯生产中热媒炉运行出现的问题,指出了烟气露点腐蚀的危害。分析了产生露点腐蚀的原因。提出了针对露点腐蚀所采取的几种措施,实践证明这些措施具有较强的可操作性。     

Modifications to the copper strip corrosion test for the measurement of sulfur-related corrosion

The copper strip corrosion test (CSCT) is used to measure the corrosivity of sulfur compounds in hydrocarbon fluids. The CSCT is performed by immersing a strip of cleaned, polished copper in a hydrocarbon fluid at a specified temperature for a predetermined time, then ‘rating’ the strip against a standard. In this work, instead of using the usual large, oblong strips designed to measure 30 mL fluid samples, we used small circular Cu ‘coupons’ as an alternative method for carrying out CSCTs on microscale samples of fluid. The motivations for reducing the scale include: applicability to small samples, ability to archive the small and inexpensive coupons, reduced waste, and potential for automated analysis using autosampler vials as reaction vessels. Moreover, the symmetric circular geometry facilitates the analysis of the images with mathematical color spaces. Mixtures of n-decane:n-tetradecane with varying concentrations of H₂S (from a distillation column) were used as a source of microscale samples of corrosive fluid to demonstrate the viability of the smaller scale CSCT. Additional experimental details concerning the lighting conditions and digital photography of the coupons, measurement of corrosion using color space, and quantification of the sulfur content of the distillate are also described.     

石灰软化-絮凝法处理地下水硬度动态中试试验研究

采用石灰软化-絮凝法处理华南地区某水厂地下水硬度。动态中试试验采用一体化处理装置,考察石灰软化工艺运行效果,并进一步探索石灰投加量和PAC投加量对试验效果的影响。试验结果表明,Ca(OH)2投加量为299.1³61.3 mg/L、PAC投加量为43.6361.3 mg/L、PAC投加量为43.6⁴8.7 mg/L,处理效果较佳。处理后总硬度(以CaCO3计)降到110mg/L,总碱度(非碳酸盐碱度)降到80 mg/L,符合GB 5749—2006《生活饮用水卫生标准》要求。基于基础设施、设备投资和运行成本的分析表明,石灰软化工艺较离子交换工艺的制水成本减少0.457元/t。     

我国高炉用耐火材料的进展

结合高炉炉身、炉缸、炉底、风口和出铁沟的工作条件,阐述了相应部位用耐火材料的发展进程。     

上海玻璃熔窑的发展历程

用电能熔制玻璃始于1906年,在上世纪40年代由于钼电极的使用而迅速发展.60年代二氧化锡电极的出现,进一步深化了电熔技术在铅玻璃方面的发展.迄今为止,几乎所有玻璃都能采用电能熔化.电熔窑的主要优势有:大大提高熔窑的热效率,把一次能源燃烧间接传热变成内部焦耳热,因此热效率从火焰窑的30%～60%提高到60%～80%,其次大大降低废气及挥发物的排放.由于采用冷顶工艺,配合料的挥发从火焰炉的6%～15%降低到0.5%～2%,考虑到一次能源的不可再生性及价格继续攀升,因此电熔窑得到了广泛应用.目前主要使用于中小型规模、质量要求高的产品.     

新型间接式热风炉的设计开发

介绍了燃煤、燃油 (气 )间接式热风炉的型式 ,分析了新型炉的结构设计原则和新型炉的优点     

Development of a pilot-scale acid gas removal system for coal syngas

The Korean pilot-scale gasification facility consists of a coal gasifier, hot gas filtering system, and acid gas removal (AGR) system. The syngas stream from the coal gasification at the rate of 100–120 Nm³/hr included pollutants such as fly ash, H₂S, COS, etc. The acid gas, such as H₂S and COS, is removed in the AGR system before generating electricity by gas engine and producing chemicals like Di-methyl Ether (DME) in the catalytic reactor. A hydrolysis system was installed to hydrolyze COS into H₂S. The designed operation temperature and pressure of the COS hydrolysis system are 150 °C and 8 kg/cm². After the hydrolysis system, COS was reduced below 1 ppm at the normal operating condition. The normal designed operation temperature and pressure of the AGR system are below 40 °C and 8 kg/cm². Fe-chelate was used as an absorbent. H₂S was removed below 0.5 ppm in the AGR system when the maximum concentration of H₂S was 900 ppm. A small scale COS adsorber was also installed and tested to remove COS below 0.5 ppm. COS was removed below 0.1 ppm after the COS adsorbents such as the activated carbon and ion exchange resin. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

高炉用耐火材料的发展

结合当前国内外高炉对耐火材料的要求，概述了高炉炉身、炉腰、炉腹、炉缸用耐火材料的发展状况。