Carbonated pericalse refractories with functional additives

Functional additives have been developed constituting an integrated multiphase ingredient in the form of finely dispersed powder obtained by sintering the components of the B₂O₃-C-Al system at temperatures up to 1450°C. The introduction of such additives into the composition of carbonated periclase refractories improves the level of their functional parameters. __________ Translated from Novye Ogneupory, No. 6, pp. 58–62, June, 2007.     

Temporary preservative binders for lime and lime-periclase refractories

It is established that in order to increase the atmospheric resistance of compacts from lime and lime-periclase clinkers the temporary binder should contain high-molecular-weight resin and fatty acids, which form water-insoluble salts on the CaO surface, and surface-active substances in addition to a hydrophobic plasticizer. The requisite amounts of the acid-containing component and the binder itself are calculated. Translated from Ogneupory, No. 3, pp. 18–21, March. 1995.     

Kinetics of joint grinding of quartzite with new kinds of mineralizing additives in the production of dinas refractories

The effect of various calcium- and iron-bearing additives on disintegration of quartzite in joint grinding is studied. The grindability of quartzite mixtures with mineralizing additives virtually does not differ from that of quartzite. This makes it possible to simplify the production process of dinas refractories by introducing the mineralizing additives right into the tube grinder in preparing the fine component of the charge. The properties of the dinas articles stabilize due to the higher degree of homogeneity of the quartzite mixture. A kinetic equation describing the variation of the content of the coarse fraction in grinding quartzite with mineralizing additives is suggested. The properties of specimens fabricated by joint grinding of quartzite with lime screenings and pyrite cinders fully meet the requirements on dinas refractories used for lining coke ovens.     

Dinas refractories based on the lime bond for coke furnaces

Conclusions Tests on dinas refractories with a lime bond in the structure of experimental coke ovens, and the results of a study of their properties after service, confirm their working capability and promise for use in the vertical zone of industrial furnaces.Translated from Ogneupory, No. 7, pp. 36–38, July, 1991.     

Opal-A rich additives used in ancient lime mortars

Ancient stone and brick masonry mortars from three monuments in Konya, Central Anatolia dated to the Anatolian Selçuk Period (12th and 13th centuries AD) were examined for their raw material composition and durability characteristics to understand some characteristics of medieval mortar technology.Optical microscopy, XRD, SEM, EDX, FTIR and TGA analyses revealed that the mortars contained high percentage of lime binder totally carbonated into micritic calcite. Coarse and medium aggregates were mainly composed of sandstone and metamorphic rock fragments, quartz, feldspar and mica minerals. Opal-A was found in considerable amounts in the fine aggregates, likely not derived from the coarser ones but added separately. Pozzolanic activity of the fine aggregates was determined by conductometric measurements. Their ability to form C-S-H was observed by treating them with saturated Ca(OH)₂ solution.Bulk density and total porosity measurements showed that the mortars were highly porous due to the use of high amount of lime. On the other hand, they possessed sufficient mechanical strength. Mechanical properties were determined by point load tests and ultrasonic pulse velocity measurements. They were expressed as uniaxial compressive strength (UCS) and modulus of elasticity (E_mod) in MPa.The results were also discussed in terms of durability characteristics of the mortars. They were expressed with the use of uniaxial compressive strengths in dry and wet states, and total porosity values. The mortars were considered to have high durability to wetting and drying cycles but had poor durability to the crystallization of water-soluble salts.     

含炭耐火材料用硼化物添加剂

综述了近几年国外研究含炭耐火材料防氧化而采用的一些含硼添加剂，介绍了这些添加剂的特性及其防止碳氧化的基本原理。     

The service of refractories in sintering machine ignition furnaces

Conclusions In the service of chamotte roof burner blocks and wall parts in sintering machine ignition furnaces, impregnation of their surface layer with iron and calcium oxides contained in the sinter charge occurs with an increase in the working zone of the refractory in the quantity of glassy phase as the result of the formation of a low-melting (1070°C) eutectic in the CaO-FeO-Al₂O₃-SiO₂ system. This leads to contraction and fusion of the surface layer, which with sharp variations in temperature fails by spalling. This process occurs most intensely in the burner blocks, which are under more severe service conditions. Failure of the mullite roof refractory also occurs by spalling but primarily as the result of its insufficient original heat resistance. To increase the service life of the furnace as a whole high heat resistant mullite-corundum refractories must be used in the roof, including for the burners.Translated from Ogneupory, No. 8, pp. 53–56, August, 1986.     

麦尔兹石灰窑悬挂缸耐火材料的技术改进

从结构和原材料分析华塑公司3座麦尔兹石灰窑悬挂缸浇注料脱落的原因,提出了技术改进方案,介绍了具体处理措施及改进后的效果。     

石灰窑耐火材料脱落原因及改进措施

分析了石灰窑耐火材料脱落原因,采取了重新选择耐材材质、设计砖型、新型隔热材料应用及改进措施等,实现了石灰窑耐火材料使用寿命的延长,使石灰窑筒体煅烧带表面温度降低到350℃以下,最终降低了石灰生产成本。     

Effect of additives on the thermal-shock resistance of corundum-zircon refractories

Conclusions It is established that the addition of 0.1–1.0% of Bi₂O₃ increases 2–7 and 1.5-fold, respectively, the resistance of a material to the nucleation and spread of destructive cracks; CoO₂ in amounts up to 0.1% has virtually no effect on the total thermal-shock resistance but increases threefold the resistance to the nucleation of destructive cracks.The addition of SnO₂ produces a slight decrease in both the number of heat cycles withstood before the appearance of the first visible crack and in the total thermal-shock resistance of the specimens before total destruction.It is established that the favorable effect of the Bi₂O₃ additive can be reduced to the fact that it melts, forming a thin film of melt on the surface of the corundum and zircon grains; this facilitates the formation of denser structures and, after evaporation, the formation of fine discontinuous microcracks.Translated from Ogneupory, No. 6, pp. 39–42, June, 1981.     

Phase composition of sintered lime refractories with TiO2 additions

Conclusions A study of mixtures of CaO and TiO₂ fired at 1770 K with various heating rates confirmed the presence of three binary compounds in the system CaO-TiO₂: CaTiO₃, Ca₃Ti₂O₇, and Ca₄Ti₃O₁₀.Mixtures of CaO and TiO₂ of the same composition but fired at different rates develop calcium titanates that are stoichiometrically different: with a heating rate of 50 K/h Ca₃TiO₇ and Ca₄Ti₃O₁₀ are formed; and at 300 K/h — -mainly calcium monotitanate CaTiO₃, with a small amount of Ca₃Ti₂O₇.The features of the crystallochemical structure of calcium titanate indicating that the structure of Ca₃Ti₂O₇ and Ca₄Ti₃O₁₀ can be perceived as alternating layers of CaTiO₃ and CaO mean that we can assume that the first crystal phase developing in the solid-phase sintering in mixtures CaO-TiO₂ is CaTiO₃. Subsequently, during slow heating gradual ordering of the structure of calcium titanates occurs, leading to the formation of equilibrium with a high concentration of CaO (> 88%) in the association of Ca₃Ti₂O₇ and Ca₄Ti₃O₁₀.With increase in the CaO content in calcium titanate there should be an increase in the resistance of lime refractories to atmospheric hydrolysis. The sintering schedule of lime refractories and especially lime clinker should therefore ensure the formation of titanates and solid solutions most highly enriched with CaO.Translated from Ogneupory, No. 2, pp. 15–17, February, 1993.     

Properties of lime and lime-periclase refractories on a ceramic binder

Lime specimens obtained by clinker technology from sintered lime clinker with a relative density exceeding 75% of the theoretical value using TiO₂ as a sintering addition are investigated. It is established that the heat resistance of lime specimens is 25 heat cycles without fracture and the loss of strength after 20 – 25 heat cycles is insignificant. Posthydration investigation of the degradation of the strength of specimens has shown that the critical hydration level is 2%, after which the strength begins to fall sharply.Translated from Ogneupory, No. 2, pp. 2 – 5, February, 1995.