Hot briquetting of flue dust

The operation of a 5-tph, fluid bed reactor pilot plant for briquetting blast-furnace flue dust is reported. The design considerations are discussed, and the elements of the machine—fluid bed reactor, cyclone heat exchangers, and briquetting press—are described in detail. The economics of this process—which can use flue dust, millscale, oxygen-furnace slag, and ore fines as feed—are compared to those of a sintering plant.     

黄磷电炉电尘浆提取镓的预处理

根据在电炉还原炼磷过程中,磷灰石中的镓在电尘浆中高度富集,成为可供利用的镓资源,提出了一种提取镓的预处理技术:用浓硫酸熟化电尘,将其中的镓先转化成水溶性化合物,再从预处理物料中浸出镓.考察了预处理过程中电尘的化学和矿物学变化以及影响镓提取率的因素,并给出了适宜的预处理条件;在最佳质量比电尘:水:硫酸=1:1:1,200℃下熟化2 h.实验结果表明,在优化条件下将预处理的电尘在80℃浸出1 h,镓的浸出率可达90%以上.     

Corrosion in flue gas desulfurization plants and other low temperature equipment

A literature study of corrosion problems in flue gas desulfurization (FGD) plants and other low-temperature equipment has been made. The study in question has been limited to coal- and waste-fired plants. The results of the study shall contribute to selection of better materials and an optimization of the flue gas processing in such a way that the corrosion risk will be diminished leading to less costs of operation and maintenance. Before the selection of materials for FGD plants experiences from similar plants, pilot plant data, laboratory results and general recommendations for material selection must be carefully studied. Material recommendations from manufacturers are of great value, especially when selecting organic or inorganic coatings alternatively linings. The choice of an alloy is strongly dependent on the process chemistry, above all the pH and the chloride concentration. In several cases high-alloyed steels, nickel base or titanium alloys are recommended, e.g. nickel base alloys or titanium can be installed either as solid plates, clad plates or attached liners. Properly selected protective linings or coatings of non-metallics applied in a qualified manner and maintained well will, however, perform cost-effectively. Different ways to minimize the corrosiveness of the process environment have also been discussed, e.g. the use of inhibitors but considerable interest has also been devoted to corrosion monitoring.     

Corrosion experience with carbon steel in spray absorption FGD plant

Carbon steel is the traditional material for boiler flue gas ducts and stacks. The introduction of flue gas desulphurisation systems in existing power plant units requires major changes in the flue gas system from boilers to the flue stack. In the semidry spray absorption plant at Studstrupværk power plant carbon steel has been used. This concept was chosen to utilize part of the existing carbon steel ducting and avoid the use of expensive high alloyed materials and coating systems. During the first year of operation emission of fine flakes of rust from the ducting and the stack become a major problem. To overcome this, corrosion testings were performed in laboratory and in the plant. The corrosion problems were found to be related to an atmospheric corrosion with hygroscopic chloride containing deposits. The aim of the tests was to establish the critical humidity for corrosion of carbon steel in FGD plant products and deposits. The examinations cover products and deposits from different operational conditions and parts of the Studstrupværk power plant. The laboratory tests were followed by corrosion probe tests in the plant and full scale operation tests with the plant. The results of this programme showed that carbon steel can be used and corrosion can be kept at a very low level by controlling the humidity of the flue gas below 40% RH with fresh water as process water and down to 30% RH with salt water as process water. In practice this has to be controlled by the temperature difference between the flue gas and the adiabatic saturation temperature of the flue gas. Effective insulation of the ducting has been found to be of outmost importance as the humidity should be measured relative to the surface temperature. Experience from the plant shows that the most severe corrosion is found in cold spots.     

蓄热式辐射管的国内外专利情况及其发展趋势

分析总结了目前国内外有关蓄热式辐射管的发明专利情况,主要从其核心部件即燃烧器的结构、燃烧过程的组织及内部插件等方面进行了评述,并针对现阶段发展状况指出今后该领域主要朝着结构紧凑及具有烟气回流结构的新管型方向发展,为该领域未来的研究和技术开发提供参考和指导。     

不锈钢电弧炉粉尘直接还原回收工艺研究

电弧炉粉尘巳被列为有害废物，直接还原回收粉尘中有价金属不仅可保护环境，而且可充分利用宝贵的金属资源。采用中频感应电炉模拟电弧炉冶炼工艺进行了A、B、C和D系列实验研究。通过气体成分的检测、钢锭和炉渣的成分分析，了解工艺参数对还原过程的影响，认为电弧炉粉尘直接还原回收工艺切实可行，不影响钢产品质量，为该新工艺的生产实践提供了依据。     

Hydrometallurgically recovering zinc from electric arc furnace dusts

The increasing use of zinc-containing scrap for steel production has lead to a high zinc content in the electric arc furnace and converter flue dusts. The cost of disposing of this residue is high due to environmental restrictions. Various recycling processes have been developed for these dusts, but most never reached the pilot plant stage and many investigations were stopped because of metallurgical and economical inefficiencies. While pyrometallurgical methods have to deal with high energy consumption, low zinc yield, and valueless residues, hydrometallurgical processes could offer an economical recycling alternative. This paper describes hydrometallurgical methods for recovering zinc from steel industry dust. These methods can be integrated in the primary zinc-winning process or in galvanization. Investigations of sulfuric-acid leaching show high zinc solubility but also a high iron content in the final liquor. As a result, steps for purification are required that cannot be conducted economically. Alternatively, a NaOH leaching gives a satisfying zinc yield and a very low solubility for the iron that remains in the residue. For more information, contact J. Antrekowitsch, University of Leoben, Nonferrous Metallurgy Department, Franz-Josef-Str. 18, Leoben, Styria A-8700, Austria; +43-3842-402322; fax +43-3842-402627; e-mail antreko@unileoben.ac.at.     

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。     

Sulfate Aerosol Particulates

The condensation of SO₃ vapor to detrimental acid-mist occurs only after substantial flue gas cooling, usually downstream from electrostatic precipitators. This condensation is an equilibrium process depending on gas temperature and water vapor pressure. Smelter plume opacity is related to acidmist and other sulfate aerosol particulate concentration through Mie particulate scattering theory. It is possible to estimate the amounts of sulfate particulate emissions and plume opacity, particularly those resulting from anticipated changes in smelter operations and flue gas treatment. These estimates can be used to determine compliance with current or anticipated regulations on smelter particulate emissions or plume opacity.     

大功率密闭直流电弧炉冶炼钛渣烟气净化工艺研究

根据国内引进的第一台30MW密闭直流电弧炉钛渣生产线的工艺流程,对采用云南省钛铁矿冶炼钛渣过程中产生的烟气进行了气体及烟尘的流量、含量、化学成分等分析。由于产生的烟气具有温度高、含尘量大(1.75%~9.60%)、SO2含量低、CO含量高的特点,选择烟气净化设备时,除了处理能力要符合生产要求,还需要考虑粉尘粒径和烟气温度这两个因素,以实现烟气回收利用的目的。经过研究,烟气净化工艺首先对烟气进行直接水冷使烟气降温,然后选用德国进口涤气机对烟气进行精处理,除尘效率可以达到99.983%。处理净化后的烟气,热值高,气体性质稳定,净化后可安全用于无烟煤/钛渣干燥及渣包/铁包的烘烤,实现节能减排的目标;烟尘可以回收利用。     

工艺气体消耗近于零的气体渗碳法

热处理炉,尤其是渗碳及淬火炉,都是连续不断地向炉内通入工艺气体。尽管工艺气体的消耗相当可观,也是热处理成本的一部分,但到目前为止,所通入的工艺气体都是通过废气口烧掉了。本文所述的技术是将工艺气体催化再生后,再送回热处理炉中,渗碳淬火炉的工艺气体消耗量可节省高达90％。本文重点介绍了新的再生技术的概念、实施以及工业应用的效果。     

A low-cost electro-gen solvent for carbon dioxide sequestration

An innovative concept for one of the lowest-cost carbon dioxide capture methods from power plants and other carbon-dioxide-emitting facilities is provided here. The concept is to use a novel electro-thermo-chemical regeneration approach which will generate a product solution containing hydroxyl ions for absorbing the flue gas CO₂. This may work with existing flue gas desulfurizing equipment to minimize the cost of carbon capture. The process involves the use of low-cost make-up reagents which are capable of providing credits for partial mineralization of CO₂, thus offsetting some of the costs for carbon capture and sequestration. The process presents the possibility of making this a low-cost on-site mineralization with cost offsets.     

建龙钢铁烧结烟气脱硫工艺抉择实践

介绍了建龙钢铁烧结烟气脱硫工艺抉择过程中重点关注的原料特点、烟气参数、选择的原则、选择的依据等因素,较详细地介绍了建龙钢铁石灰-石膏法湿式脱硫工艺流程,并从工程建设角度,对选择该工艺后可能出现的腐蚀和磨损问题进行了应对策略分析。     

热电厂烟气脱硫技术初探

火电厂排放的SO2严重地危害着人类的生存环境,为此,国家重新修订了《火电厂大气污染物排放标准》,强制要求对火电厂排放的烟气,要安装烟气脱硫装置来进行控制。笔者以氧化铝厂配套建设的热电厂锅炉烟气治理为例,分析、比较了几种治理措施的特点,提出了适合的烟气脱硫方法。     

Leaching of gallium from corundum flue dust using mixed acid solution

In order to extract gallium from a high-silica-content flue dust generated in corundum production, a mixed acid solution of H₂SO₄ and HF was used for leaching, and test parameters of the leaching process were optimized. Experimental results show that the leaching rate of gallium was only 38% when H₂SO₄ was used as leaching agent. Composition analysis results of micro areas in this corundum flue dust indicate that the content of gallium in silica-enriched phases was high; this portion of gallium was insoluble in H₂SO₄ solution. The leaching rate of gallium increased significantly with addition of HF due to corrosion of silica. Effects of reaction time, temperature, and concentrations of HF and H₂SO₄ on leaching rates of gallium were investigated. The leaching rate of gallium reached 91% when this corundum flue dust was leached in a mixed acid solution of H₂SO₄ and HF for 4 h, at a temperature of 80 °C, with a liquid-to-solid ratio of 5:1 (mL/g). The optimal concentrations of H₂SO₄ and HF in the mixed acid solution were 1.5 and 6.4 mol/L, respectively.     

Fireside corrosion of superheater materials in chlorine containing flue gas

Corrosion resistance of three types of candidate materials for superheater sections under simulated waste incineration conditions was evaluated. A 9Cr1Mo steel, an AISI 310SS, and the Ni-based alloy Sanicro 28 were tested on a laboratory and on a pilot scale with different flue gas compositions (up to 2500 mg/Nm³ of HCl and 1500 mg/Nm³ of fly ash). Laboratory tests were carried out in a furnace up to 200 h. Metal and gas temperature were kept constant at 500 °C. Pilot scale tests were carried out by using a 0.3 × 0.3 m cross-sectional combustor, with flue gas velocity of 5 m/s. Air-cooled probes, designed to operate at a metal temperature of 500 °C and facing gas temperatures as high as 600 °C, were used for 200 h as maximum test time. Qualitative correspondence was found between results obtained by the two sets of experimental tests, but quantitative values were not comparable. Metallographic evaluations, metal loss measurements, and weight loss analysis evidenced as the most suitable alloy Sanicro28. Maximum metal loss observed was 240, 182, and 107 μm, respectively, for 9Cr1Mo, AISI310SS, and Sanicro 28 under the most aggressive conditions. Intergranular corrosion attack was evidenced for AISI310SS, limiting the choice of materials to 9Cr1Mo and Sanicro 28, depending upon the lifetime expected at the design stage.     

Diagnostic technique for laser micromachining of multi-layer thin films

Excimer laser micromachining was a key process for producing features by removing parts of some photoresist layers. One hurdle was that the lower substrate layer was easily attacked or damaged in laser ablation of the upper photoresist layer. To overcome this, a real-time monitoring scheme of laser micromachining process was proposed on the basis of taking acoustic emissions arising from pulsed laser–material interaction as feedback signals and employing a diagnostic program. It was showed that extracted features (e.g. the RMS values) from sensor signals were indicative of the process. In particular, the feature values tended to have an abrupt change when laser beam approached the interface of consecutive two layers. Relying on this characteristic, we proposed a fuzzy expert system as the core part of the diagnostic program. The effectiveness of the program was verified with tests.     

Purification technology of flue gas from remelting process of aluminum alloy tailings

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有限体积数值模拟技术在宽展挤压模具设计中的运用

介绍了有限体积数值模拟技术,在MSC.Superforge商业应用软件平台上,对某公司铝型材产品FDAWDD7的挤压变形进行了过程模拟,通过工业试验证明,金属流出速度的模拟结果与实际情况比较相符,利用这种技术指导一般的非空心型材挤压模具设计在生产上是可行的。     

表面渗层和CrNiMo涂层材料的露点腐蚀*

基于我国电站锅炉排烟温度普遍偏高、烟气深度冷却利用过程中存在露点腐蚀的现状,文中以耐露点腐蚀材料316L钢作为对比材料,选取普通碳钢进行表面热喷涂和表面渗镍处理后在1000MW机组的锅炉上进行实炉露点腐蚀试验。结果表明:材料的腐蚀层厚度随壁面温度升高而减小;在40～60℃的金属壁面温度范围内,碳钢表面CrNiMo涂层和渗镍层因表面缺陷导致涂层严重腐蚀;在70～90℃的金属壁面温度范围内,腐蚀层厚度随温度变化趋于平稳,表面渗层材料具有和316L钢相当的耐露点腐蚀能力,碳钢表面喷涂CrNiMo耐腐蚀性能更为优越,3种材料均能满足火电厂烟气深度冷却利用的露点腐蚀性环境。