Life of refractories in the lining of a cyclone reactor

Conclusions Tests of refractories in the linings of cyclone reactors for the production of industrial carbon showed that mullite-corundum, corundum, and zirconium-containing refractories, which are recommended for wide use, possess the longest life. Alumina-silicon carbide, kaolin-base chamotte, chamotte-graphite, and silicon carbide parts fail rapidly in the reactor linings and are not suitable for these service conditions. Disthene-sillimanite and kaolin-base chamotte (with a mullite-corundum binder) parts showed satisfactory results in service and occupy an intermediate place in life between the first and second groups of refractories.Translated from Ogneupory, No. 2, pp. 46–50, February, 1985.     

锆刚玉莫来石-碳化硅复合材料的显微结构

采用OM、SEM、TEM及EDAX等手段研究了锆刚玉莫来石-碳化硅复合材料的显微结构。结果表明,ZrO_2及SiC均匀地分散于刚玉/莫来石构成的基质中。刚玉-刚玉(或莫来石)及莫来石-莫来石的晶间表面多数存在非晶质薄膜,但也有刚玉-莫来石两相直接结合的相界因扩散而形成固溶层。ZrO_2-刚玉(或莫来石)及SiC-刚玉(或莫来石)的相表面因相间扩散形成固溶层或扩散层而皆属直接结合。在刚玉和莫来石晶体里观察到有晶内ZrO_2存在,其形成原因可能是在烧结过程中,刚玉或莫来石晶体再结晶长大而包裹ZrO_2微粒所致。     

定形耐火材料的高温耐磨性研究

用高温耐磨试验装置研究了高铝砖、刚玉砖、氮化硅结合碳化硅砖和黏土结合碳化硅砖4种定形制品在高温下的耐磨性。结果表明:耐火制品的磨损量随温度的变化曲线可分为两种类型,非氧化物材料(氮化硅结合碳化硅砖)的磨损量-温度曲线接近水平直线,即在整个试验温度区域中(25~1 400℃)磨损量几乎没有变化;氧化物(或氧化物结合)耐火制品(高铝砖、刚玉砖和黏土结合碳化硅砖)在一定温度范围内磨损量变化不大,温度达到某值以上,磨损量大幅度降低,此温度对应为该种材料开始塑性变形温度。高铝砖、刚玉砖、黏土结合碳化硅砖磨损量开始明显下降的温度点分别为800、1 000和600℃。影响不同材质耐火砖的高温耐磨性的因素有物相组成、玻璃相性质以及工艺因素等。     

Mullite-corundum refractories with silicon carbide for linings of transportable mixers

Investigations of the technology of mullite-corundum refractories containing silicon carbide and used for linings of transportable mixers are described. It is shown that an addition (10%) of silicon carbide to a mullite-corundum mixture ensures a high slag resistance. Mixers lined with mullite-corundum refractories with silicon carbide have shown high service properties, namely, 720 pourings of cast iron with 5 hot repairs. Translated from Ogneupory, No. 3, pp. 26–29, March, 1995.     

Vibration milling of silicon carbide and sintered corundum

The paper reports a study concerned with size reduction of corundum grog, sintered corundum (VK-94-1 ceramic waste), and silicon carbide. Corundum and silicon-carbide powders with a specific surface area of 17 and 12 m²/g were obtained. They can serve as fillers for fire-resistant polymer-ceramic composites. Also, the silicon carbide powder can be used as a finely divided additive to heat-stable corundum ceramic products. Translated from Steklo i Keramika, No. 6, pp. 17–20, June, 1997.     

高温炭黑反应炉炉衬选材分析

从抵抗高温气流冲蚀、抗炭黑粒子化学侵蚀和抵抗炉气杂质化学侵蚀等三个方面对高纯刚玉砖、刚玉莫来石砖、铬刚玉砖、高铬砖和氧化锆砖作了分析比较。分析认为,在燃烧室和喉管采用高纯刚玉砖和铬刚玉砖,反应段和急冷段采用高纯刚玉砖较好;而氧化锆砖在整个反应炉各段使用都是可行的。高铬砖因抗炭黑粒子化学侵蚀性差,不适合使用于高温炭黑反应炉     

Silicon carbide refractories with a sialon binder

An investigation concerning molding of silicon carbide refractories with a sialon binder was carried out. It is shown that the alumina-containing component plays an important role in the synthesis of the sialon binder. A corundum addition to the composition of silicon carbide refractories ensures higher parameters for the refractory as compared to a mullite addition. With an increase in the content of crystalline silicon the strength of silicon carbide refractories grows sharply due to the increased amount of -sidalon. Refractories with elevated contents of sialon in the binder have better resistances to alkali, slag, and molten metal than refractories with binders containing silicon nitride.Translated from Ogneupory, No. 4, pp. 2–4, April, 1995.     

Materials based on highly concentrated ceramic binding suspensions (HCBS). Corundum and corundum-mullite ceramic castables based on plasticized hcbs of bauxite

HCBS of roasted Chinese bauxite, plasticized with additives of refractory clay, and corundum or bauxite filler are used for the production of pressed ceramic castables of corundum and mullite-corundum compositions with 93–95% and 80–85% A1₂,O₃, respectively. The optimum clay additive does not exceed 1–2%. The ceramic castables have a porosity of 15–18% and an ultimate compressive strength of 100–200 MPa after treatment at 1200–1300°C. As compared to traditional corundum refractories they are characterized by a finer capillary structure and a higher mechanical strength attained at a diminished (by a factor of 2–3) pressing pressure and a lower (by 400- 500°C) firing temperature.     

Strength properties of refractory mortar with an aluminoboro-phosphate bond during the cementing of mullite-corundum and fireclay products

Conclusions Studies were made of a refractory mortar of mullite-corundum-zircon composition with an aluminoboronphosphate bond possessing a high adhesive capacity and thermal-shock resistance. The refractory mortar can be recommended for preparing articles of block construction using blocks of corundum, mullite-corundum, and mullite compositions.Translated from Ogneupory, No. 2, pp. 15–17, February, 1988.     

高强度刚玉碳化硅浇注料的研制

以棕刚玉和碳化硅为主要原料、铝酸钙水泥为结合剂,制备出了一种高强度的刚玉碳化硅浇注料。通过优化颗粒级配,调整水泥和复合微粉的加入量,测定试样在各种因素影响下的常温和高温强度。结果表明,研制出的刚玉碳化硅浇注料既具有较高的常温强度,又具有很高的高温强度。     

Effect of nickel nitrate on phase changes in mullite and mullite — Corundum refractories when heated in oxidizing and reducing conditions

Conclusions During heating in oxidizing atmospheres of mullite-corundum specimens with an addition of nickel nitrate at 500–900°C, NiO is formed, and an increase in temperature from 900 to 1500°C is characterized by the development of nickel spinel, NiAl₂O₄, the quantity of which increases with an increase in the content of the Ni(NO₃)₂ · 6H₂O, and the firing temperature.The high temperature diffractometric method showed that in the system 3Al₂O₃ · 2SiO₂-NiO heating in oxidizing conditions, and commencing at 1000°C, NiO decomposes the mullite with the formation of aluminonickel spinel, whose quantity rapidly increases with further temperature rise. At 1500°C the mullite is preserved in small quantities.The nickel spinel, formed as a result of heating to 1300°C the mullite-corundum refractory containing 25% Ni(NO₃)₂ · 6H₂O during firing in the silicon carbide mixture and in the hydrogen atmosphere at 1400°C for 30 min, in the main decomposes with the separation of metallic nickel and corundum. However, x-ray patterns confirm that in these conditions the nickel spinel is not completely decomposed.Translated from Ogneupory, No.5, pp.32–36, May, 1972.     

An investigation of different forms of refractories for the service conditions in coke ovens

Conclusions Investigations of different forms of refractories established that it is desirable to use refractory parts with high heat resistance (MK-80 mullite-corundum, silicon carbide, chamotte-cordierite) as extreme roof and hearth parts in place of chamotte ones for increasing the life and providing reliability in service of these elements of the coke oven lining. The most promising for these purposes from the economic point of view and taking into consideration high heat resistance, resistance to reduction, and minimum thermal expansion are chamotte-cordierite parts.Translated from Ogneupory, No. 2, pp. 36–37, February, 1991.     

Tests of mullite-corundum refractories based on fused mullite in the roof of an electric steel-melting furnace

Mullite-corundum refractories based on 63 – 90% fused mullite have been produced and tested in the roof of a 50-ton electric arc furnace. It has been established that their wear resistance is no worse than that of heat-resistant mullite-corundum bricks of grade MK-80 produced according to TU 14-80405-82. The tested refractories were worn due to their saturation with oxides from the molten products and the interaction of the latter with the structural components of the refractory. This promoted the decomposition of mullite into corundum and a glass phase with aftercompaction ands spalling of the refractory.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 31 – 35, December, 1996.     

Slag Resistance of Refractories for Direct Reduction of Laterite Nickel Ores in Rotary Kilns

Aiming at prolonging the service life of refractories for direct reduction of laterite nickel ores in rotary kilns, the slag resistance of ten materials(corundum bricks, chrome corundum bricks, silicon nitride bonded silicon carbide bricks, high alumina silicon carbide bricks, high alumina bricks, magnesia chrome bricks, magnesium aluminate spinel bricks, spinel chrome corundum bricks, chrome corundum castables and magnesia alumina chrome composite spinel bricks) was evaluated by rotary slag tests, which simulate the service conditions in rotary kilns. The corroded residual bricks were analyzed by SEM and EDS. The results show that the magnesia alumina chrome composite spinel brick possesses the advantages of magnesium aluminate spinel bricks and chrome corundum bricks; MgO-rich spinel can absorb the penetrated ferric oxide, and forms a dense zeylanite layer, which prevents the penetration of the molten laterite nickel ores; therefore, it is an ideal lining of rotary kilns for direct reduction of laterite nickel ores.     

锆棕刚玉碳化硅导轨砖的研制

应用复相改性和ZrO_2韧化机理研制的锆棕刚玉碳化硅导轨砖具有高强耐磨、抗高温及热震和表面光滑的优异性能,在洛阳拖拉机厂等机械热处理炉的使用结果表明,它比金属导轨具有明显的优越性,是一项节材节能长寿优质的新产品.     

冲击参数对氧化铝基耐火材料常温耐磨性的影响

参照GB/T18301《耐火材料常温耐磨性试验方法》,分别以标准碳化硅砂(36#)、电熔白刚玉砂(36#)和石油支撑剂用陶粒为磨损介质,采用不同压力(300kPa、448kPa和600kPa)的压缩空气和不同量(1kg、2kg)的磨损介质对普通高铝砖(LZ-65和LZ-75)、高炉用高铝砖、磷酸盐结合高铝砖、高纯刚玉砖、刚玉莫来石砖、铬刚玉砖、赛隆结合刚玉砖、微孔刚玉砖和塑性相复合刚玉砖等10种氧化铝基耐火材料进行了磨损实验。结果表明:(1)随着冲击气体压力的增大,10种材料的磨损量都增加,但由于这些材料在组成和结构上的差异,其磨损量增加的幅度存在明显差异。(2)由于磨损介质的颗粒形状和体积密度不同,在相同的冲击气体压力下,磨损介质的流动速度不同,对材料的磨损量也不同,其中,采用碳化硅时磨损量最大,采用白刚玉时次之,采用陶粒时最小。(3)当磨损介质碳化硅砂用量增加1倍时,材料的磨损量增加,但不同材料的磨损量增加幅度不同,其中微孔刚玉砖和磷酸盐结合高铝砖分别增加了1.84倍和1.26倍,而高纯刚玉砖和高炉用高铝砖增加的不足0.4倍。(4)耐火材料的常温耐磨性能取决于其强度和结构的致密性,强度和致密度较高的材料耐磨性能较好。     

HIGH TEMPERATURE LOAD AND FUSION TESTS OF FIRE BRICK FROM THE PACIFIC NORTHWEST IN COMPARISON WITH OTHER WELL-KNOWN FIRE BRICK1

Seventeen samples of fire-clay brick from the Pacific Northwest have been tested with twenty-seven other commercial brands of fire clay, silica, magnesia, chromite, zirconia, diaspore, silicon carbide and crystalline alumina, as well as china clay and crystalline sillimanite products made at the University of Washington. The tests show that the fire-clay brick of the Pacific Northwest vary considerably in quality. According to the high temperature load test, the majority of the local brick are among the upper grades, some are to be classed with the best fire-clay brick and one equal to the best diaspore brick. The brick tested is not the best which can be made from Pacific Northwest materials, for the kaolins in eastern Washington and northwestern Idaho give opportunity for the production of an all-kaolin fire brick. A method is suggested for testing super-refractory materials under load at high temperatures similar to the standard load test for fire clay and silica brick except that the temperatures are measured by cones, and are raised until 10% linear deformation of the brick is obtained. The rate of heating and soaking varies with the brick under test, and the principles learned from the cone fusion test are used in the application of heat. A numerical value, expressing the area under the cone-shrinkage curve, affords an easy method for comparing the high temperature load resistance of various refractories. The brick which are best able to resist deformation at high temperatures are composed of crystalline materials which have developed a recrystallized bond of the same composition. These are crystalline silica, silicon carbide, corundum and sillimanite, and they resist deformation at temperatures close to their melting points. Amorphous materials like fire clay, diaspore, bauxite or even the very refractory crystalline materials lie chromite and periclase, which depend on amorphous silicates for a bond or are contaminated with silicate impurities. will fail with the softening of the bond of the amorphous impurities. The cone fusion of the brick as a whole can not be depended upon to indicate the resistance to load at high temperatures.     

Future application of aluminosilicate refractories for aluminum electrolyzers. Part 4. Wettability of aluminosilicate refractories with molten industrial electrolyte and sodium fluoride

Optical microscopy is used to determine wetting angles for aluminosilicate refractories with molten industrial electrolyte and NaF. Kinetic wetting parameters and interaction of electrolyte with refractory are determined. It is shown that removal of silicon from refractory also occurs in the form of silicon monoxide. It is established that aluminosilicate refractories, prepared with addition of mullite-corundum chamotte, are wetted worse by fluoride salts, but the corrosion resistance of them is better than for refractories prepared by normal technology. __________ Translated from Novye Ogneupory, No. 1, pp. 17–21, January 2008.     

Corundum-silicon carbide-bearing concrete parts made using a liquid glass binder

Conclusions Using the method of simplex-grid experimental planning and the generalized function of desirability, we determined the range of optimum composition of liquid glass bonded corundum-silicon carbide-bearing concretes possessing the specified properties.The improved service characteristics of the corundum-silicon carbide-containing concrete products owe to their phase composition: the content of nonoxidized silicon carbide, the formation of secondary mullite from the products of oxidation of silicon carbide and the fine fractions of corundum, and due to the presence of virtually unaltered coarse corundum grains that are introduced by the corundum waste products of the Yurginsk abrasives factory.Evaluation tests are being carried out on the experimental corundum-silicon carbide-bearing concrete products that were placed in the lining of a soaking pit of the Krivorozhstal' steel plant and a recuperator of the Petrovsk factory.Translated from Ogneupory, No. 1, pp. 4–10, January, 1988.     

Thermal conductivity of corundum,high-alumina,magnesia, zirconium,and chromate refractories in the 400–1800°c range

Conclusions The temperature relationship of the thermal conductivity of corundum, mullite-corundum, magnesia, zirconium, and chromate refractory parts in the range of average temperatures of 400–1800°C was determined. Data is presented on their porosity, density, and chemical composition.Translated from Ogneupory, No. 5, pp. 16–20, May, 1982.