Silica Brick Research Articles

Natural Radioactivity in Clay Ceramics and their Raw Materials in Latvia

Natural radionuclides K-40, and Th-232, U-238 (Ra-226) decay chain products contained in building materials are the main source of radiation dose received by population and the only source of indoor radiation exposure. Present work contains results of the study of natural radionuclide activity level in clay, clay ceramics and silica bricks used in Latvia. Obtained data show that radionuclide content in different clay products can differ up to five times. However, determined activity index values for all tested materials, except fireproof bricks, were below radionuclide concentration level permitted by EU and Latvian national regulations. Comparison with analogous data from other North European and Baltic countries shows that average concentrations of natural radionuclides and activity index values for clay and clay bricks used in Latvia are on the same level as in other countries, except Sweden.

The solution of the reliability problem in the repair process of the plates of the silica bricks press boxes

The solution of the reliability problem in the repair process of the plates of the silica bricks press boxes

SECONDARY MINERAL RESOURCES FOR REFRACTORY PRODUCTION. PART I. SILICA TECHNOLOGICAL MATERIALS

An option for the technological refractory raw materials chemical and mineral classification is proposed. Four largescale secondary man-made mineral formations of mostly siliceous composition are regarded in the article. The non-waste technology for the reject products handling which gives the enriched raw materials for preparation of the ZKV-97 quartzite aggregate, building rocks, gravel and sand was developed. The fitness was determined of the silica wastes fine-grained fraction (the concentration tailings) for the preparation of the molding materials, filter building materials, as well as for acting in the way of the raw materials for container glass and other items. It was shown that the using molding sand's regeneration products can be applied for the high quality coke silica bricks preparation. The integrated study of micro silica was carried out and on base of this investigation the promising trends of its utilization were proposed. Ill. 5. Ref. 9. Tab. 10.

Refractories for Coke Oven Wall – Operator’s Perspective

After a successful campaign of more than 40 years, the walls of Coke Plant 2 of Tata IJmuiden are being replaced. Our paper addresses the issues of the selection and sourcing of the refractory materials for the new walls. Material properties formalised in the specification are reviewed. Those are compared with the properties of alternative silica refractories available on the market. Both conventional silica bricks and relatively new fused silica blocks are evaluated. The discussion is based on thermo-physical data obtained in-house and from plant experience. It is argued that, due to specific lining design and material properties, the coke oven wall refractories are not off-the shelf products that can be sourced on a short notice from any supplier. An extensive pre-order effort is mandatory before the acceptable material and supplier are selected and the order is placed.

Use of Spent Molding Sand in the Production of Refractories

The composition and products of reclamation of spent molding sand made of quartz sand and a pulverized fraction and the potential for its use as a component of a raw mixture of silica brick articles are considered. Results of laboratory and commercial tests employing the technology used in the production of silica brick for coke ovens and the determination of the properties of articles produced from the addition of products from the reclamation of “burnt Earth” are presented.

The analysis of the silicosis misdiagnosis in the silica bricks industry

目的 探讨硅砖生产行业矽肺病误诊原因，为减少误诊提供供参考依据。 方法 筛选2000年1月至2015年1月间硅砖生产行业发生的矽肺病患者358例，选择矽肺病确诊的首次住院病历，按照患者的性别、年龄、院外就诊医疗机构、院外就诊过程及诊断、入院初步诊断、出院诊断及后前位高仟伏胸片等类别进行统计分析。 结果 2000年1月至2015年1月在我院确诊的硅砖生产行业矽肺病患者共计358例，其中发生误诊者82例；矽肺Ⅲ期误诊率最高为68.51%；乡镇卫生院误诊率为42.68%,区（县）级医院误诊率为25.60%，居各类医院的前2位。主要误诊为肺结核50.00%，其次为肺癌25.60%。误诊原因主要是对此类矽肺X线诊断经验不足最多见（53.66%），其次为病史遗漏（21.95%）。 结论 提高矽肺X线诊断能力，规范诊治是减少误诊的关键。

Preparation of Iron Oxide Pigment from Metallurgical Production Dust for Use in Construction

A simple technology is proposed for preparing red iron oxide pigment from metallurgical industry ironcontaining waste dust. The raw material base and profitability of its manufacture are analyzed. Pigment chemical and coloring properties are studied, and some properties of silica brick and concrete colored with this pigment are provided.

Features of Initial Heating of Glass-Founding Furnaces

Requirements for the management of the initial heating of glass-founding furnaces are formulated. Features of thermal expansion of periclase, silica brick, and baddeleyite-corundum articles used in the refractory lining of furnaces and regenerators are considered. An economic temperature-time initial run-up graph of furnaces is presented. The temperatures at which furnace warm-up is transferred to the main burners and build up of the melting chamber with melt commences are determined.

History, Present State and Future of Czech Silica Bricks

This article discusses the history and progress of silica materials production in the Czech Republic over the last 30 years, including descriptions of production capacity, characteristics and quality of individual product types as well as technological changes in the production of silica-based material. Current operational conditions and material applications are summarized. The last chapter of the article focuses on development of new kinds of silica materials and their possible utilization by customers, especially in the field of glass production.

Practice of Energy-Saving Renovation on Tunnel Kiln for Silica Brick by New Mode

Tunnel kiln was reformed according to energy-saving mode, which was energy utilization diagnosis and analysis and energy-saving reconstruction. First, thermal performance was diagnosed, and the basic data for energy-saving reconstruction was provided through the test of tunnel kiln. Then the main factors of low thermal efficiency was found .Second the thermal balance was calculated in drying and sintering process, which determined the form of waste heat recovery and utilization system. Finally the reconstruction was implemented by three energy-saving technologies .It caused energy-saving rate reached 44%.

Possibilities of Reducing the Apparent Porosity of Silica Bricks for the Coke Batteries

Silica is used for lining of the upper parts of glass furnaces and their regenerators and for lining of the lids of arc furnaces and for the coke oven batteries construction. Silica bricks represent 60% of refractory material used for a coke battery construction. Coke ovens are generally the largest oven aggregates, where silica material is used. The whole coke oven battery may reach the length up to 80 m due to the chamber sizes. A single coke oven battery contains up to 50.000 tons of refractories [1]. From the material science point of view, the durability of silica bricks depends on numerous parameters including first of all porosity and mineral composition. Microstructure of silica bricks changes during their application due to the heat load, repeated heating and cooling, and direct contact with the oven atmosphere. The paper discusses the possibility of reducing the apparent porosity and increasing of bulk density of coke oven silica bricks. It describes the effects of an iron dust, microsilica and influence of the compaction pressure on the coke oven silica microstructure. Functional characteristics of the material prepared according to the new standard recipes are compared with the properties of standard silica products.

Clinical analysis of silicosis complicated with spontaneous pneumothorax on silica brick production industry

目的 探讨硅砖生产行业矽肺并发自发性气胸的临床特点及预防思路.方法 对住院治疗的硅砖生产行业矽肺患者79例中并发自发性气胸15例患者的临床资料进行分析.结果 本组硅砖生产行业矽肺自发性气胸的并发率18.99％(15/79);以矽肺Ⅲ期为主14例.左侧气胸3例,右侧气胸8例,双侧气胸4例;闭合型气胸7例,开放型气胸6例,张力型气胸2例;低体重指数(BMI)者15例;低血清白蛋白者14例.15例患者肺复张时间9～86 d,平均30d.治愈13例,好转2例.随访2～0.5年有4例因肺心病、呼吸衰竭死亡.结论 硅砖生产行业矽肺并发自发性气胸的基础疾病重,发生气胸后恢复慢,易复发.建议增加胸部HRCT、BMI及血清白蛋白作为动态观察必检项目。

Elastic anomalies in tridymite- and cristobalite-based silica materials

Cristobalite and tridymite are the main SiO2 phases in silica bricks, a widespread refractory product. The elastic properties of cristobalite at room temperature have been extensively studied, because it is known for auxetic behavior, i.e. negative Poisson ratios, whereas the elastic properties of tridymite are essentially unknown. Here we show that silica brick materials, consisting almost entirely of tridymite and cristobalite, exhibit remarkable anomalies in the temperature dependence of the Young modulus: in the intermediate temperature range between approximately 50 and 250°C these materials become very compliant, with stiffness minima of around 60% of the room temperature values, with a broad transition region at the low-temperature end, a sharp transition at the high-temperature end and a precisely reproducible hysteresis during heating and cooling. Furthermore, it is shown that Young's moduli at around 800°C can be more than three times as high as the room temperature values.

Effect of Additive on Phase Composition and Microstructure of Silica Brick Matrix

The silica matrix specimens were prepared by adding microsilica and MoSi2 powder. The mixture were pressed to cylinder and then sintered at 1200oC, 1250oC, 1300oC and 1400oC for 8h respectively. The phase compositions of specimens were analyzed by X-ray diffusion and the tridymite crystal morphology and grain sizes were observed by SEM. The results show that with the addition amount of MoSi2 powders increase, the intensity of tridymite diffraction peaks first strengthen slightly and then decrease, becoming more and more amorphous process, while the diffraction peaks of residual quartz phase enhance. When adding 2.5% MoSi2, the precipitation of CaMoO4 phase reduces the O/Si ratio in the liquid phase, and promotes the generation of tridymite, so the number of tridymite increase, but the crystal size decreases. With the sintering temperature increase, the intensity of tridymite diffraction peaks increase, the residual quartzite amount reduces.

Growth and Morphology of β-Si<sub>3</sub>N<sub>4</sub> Nano-Belts by Carbothermal Reduction Nitridation of Used Silica Refractory Brick

Silicon nitride (β-Si3N4) nano-belts had been synthesized by used silica bricks and carbon powder as raw materials through carbothermal reduction nitridation. The morphology and microstructure of β-Si3N4 nano-belts were characterized by scanning electron microscopy (SEM/HRSEM), energy disperse spectrum (EDS) and X-ray diffraction (XRD). Results showed that the well-crystallized β-Si3N4 nano-beltes were grown with thinness of 50-150nm and width of 3-5μm. The relatively purer β-Si3N4 were prone to be thin films with thinness of 150nm, while the as-grown SiCN (impurityβ-Si3N4with C elements) were presented as nanorods with cross section length of 150*150nm. Orientation growth mechanism by grain dislocation and vapor-solid (VS) mechanism were both involved in the growth of nanostructures of β-Si3N4 nano-beltes and SiCN nanorods.

Synthesis of Fiber-Like SiС by Carbothermal Reduction of Used Silica Bricks

Fiber-like SiC had been synthesized using used silica bricks and carbon powder as raw materials by carbothermal reduction. A new kind of beaded SiC also had been found in the specimen. The result showed that well-crystallized β-SiC fibers began to appear at 1550 °C with excessive of 100 wt% content of carbon. While at 1600 °C for 6 h with excessive of 100 wt% content of carbon, the as-synthesized SiC fibers were grown with some beads in the fiber strings. The beaded SiC consisted of strings with diameters of less than 0.5 μm (or even 0.1μm) and periodic beads with diameters of 0.5-1.0 μm. Vapor-solid (VS) mechanism and vapor-liquid-solid (VLS) mechanism were also discussed in the synthesizing process of fiber-like SiC. This kind of fiber-like SiC may used as reinforce materials in ceramic composites, the fracture toughness of brittle ceramics can be effectively improved via the incorporation of strong SiC fibers into the matrix due to crack deflection, bridging and fiber pull-out. Moreover, these toughening mechanisms do not diminish as temperature increases.

Phase Behavior of Silica Brick Used in Carbothermal Reduction

In this study we observed the phase behavior of silica brick used in the process of carbothermal reduction. At 1550°C, there are liner β-SiC in clumps huddled together; At 1550°C, short line clumps changed into filamentous, mixed together. There are many particles and some β-SiC lines and few filamentous β-SiC at 1600°C . Different ratio of carbon coke also effect the phase behavior. From the results we obtained SiC powders. SiC refractory powders were prepared via carbothermal reduction method using used silica bricks as raw materials. The effects of carbon content, temperature and holding time on the phase composition and microstructure were analyzed. XRD and SEM analyses show that: β-SiC refractory powders were synthesized at 1600°C for 6 h with100 wt% excessive of carbon content. With the increase of carbon content, the reaction temperature and holding time, content of β-SiC gradually increased while that of cristobalite decreased.

Silica crown refractory corrosion in glass melting furnaces

The critical parameters of silica refractories, such as compressive strength, bulk, density, quantity of silica, microstructure and porosity were evaluated of unused and used bricks to line the crowns of glass furnaces, when the rate of corrosion of crowns were about 2 times greater. The change of these parameters, the chemical composition and formation of the microcracks in the used silica refractories material were studied. It was established that the short time at service of container glass furnace crown can be related to low quality of silica brick: high quantity of CaO and impurities, low quantity of silica, low quantity of silica, transferred to tridymite and cristobalite and formation of 5-10 ?m and more than 100 ?m cracks in the crown material. The main reason of corrosion high quality silica bricks used to line the crown of electrovacuum glass furnace is the multiple cyclic change of crown temperature at 1405 - 1430?C range in the initial zone of crown and at 1575 - 1605?C range in the zone of highest temperatures.

Recycling crushed concrete fines to produce lime–silica bricks

Concrete and building rubble waste from demolished buildings presents an environmental problem in terms of disposal and use. The amount of structural waste generated in Kuwait in 1996 was around 2 Mt, 30% of which was concrete. Recyclable concrete amounted to 764 kt in 2002, and this is expected to exceed 1·21 Mt in 2020 as many old buildings will be demolished. This paper presents research carried out to assess the suitability of crushed concrete for use in the manufacture of lime–silica bricks. The results show that fine powder obtained from crushed concrete contains adequate amounts of lime (Ca(OH)2) as a result of the hydration process, which may react with silica under high temperature and pressure to produce lime–silica bricks. The paper describes the production process, including autoclaving time and temperature, along with the specific gravity, compressive strength and absorption of the resulting bricks. The properties of the bricks were compared with specification requirements, and were found to satisfy and even exceed specifications. The effects of adding different ratios of lime, slag, fly ash and silica fume on brick properties were assessed and the results are reported.

Effect of TiO<sub>2</sub> on the Thermal Conductivity of Eco-Friendly Silica Bricks Fabricated by Yellow River Silt

Silt from the Yellow River was mixed with a certain amount of SiO2 powder to fabricate eco-friendly silica bricks and different amounts of TiO2 were added to ameliorate the thermal conductivity of the bricks. Results showed that the phases of as-fabricated silica bricks are cristobalite and tridymite with cristobalite predominating. With increasing amounts of TiO2, the bulk density and thermal conductivity of the samples increase. Although the bulk density (1.65~1.76 g/cm3 ) than the ideal density 1.85 g/cm3, the thermal conductivity is significantly ameliorated. The thermal conductivity of the sample with 1.5% TiO2 addition is 2.11 W/m.°C, which is nearly three times higher than that of commercial silica bricks (0.8 W/m.°C).