Performance of High Thermal Conductivity Dense Silica Bricks and Their High Thermal Conductivity Mechanism

High thermal conductivity dense silica bricks have the higher thermal conductivity than ordinary silica bricks,which is conducive to the realization of energy saving and emission reduction in the iron and steel industry.The performance of ordinary silica bricks and high thermal conductivity dense silica bricks was compared,and the high thermal conductivity mechanism was analyzed.The results show that(1)compared with ordinary silica bricks,high thermal conductivity dense silica bricks have the characteristics of higher thermal conductivity,lower apparent porosity,higher tridymite content,higher compressive strength,and higher thermal expansion;(2)by increasing the tridymite content and reducing the porosity,the close packing of honeycombα-tridymite improves the density and continuity of the SiO_(2)frame structure of the silica bricks,and the larger area perpendicular to the heat transfer direction improves the thermal conductivity of the bricks;(3)the densification of the silica bricks also increases the thermal expansion of the bricks,but they still meet the standard requirements.

Thermal Conductivity of Compressed Earth Bricks Strengthening by Shea Butter Wastes with Cement

Currently, in a context of sustainable development, the economic and environmental challenges incite, to valorize local materials such as clays and agro-industrial waste. It is in this approach that a new category of compressed earth bricks (BTC) stabilized with shea meal (TK) and cement was proposed. The purpose of this paper is to investigate the effect of shea meal rate on the thermal conductivity properties of cement stabilized earth bricks. A lateritic clay (Lat) mainly composed of kaolinite (38.44%), quartz (24.94%), goethite (12.28%), hematite (4.44%) and illite (19.9%) was used to make bricks. Different mix designs made up of lateritic clay and 5% cement were studied. The shea meal is added as a partial lateritic clay replacement in different proportions. The thermal conductivity was determined by hot disk method and correlated to both porosity and density of elaborated materials. The results obtained show that the thermal conductivity and density of bricks decrease respectively from 0.72 W·m-1·K-1 to 0.52 W·m-1·K-1 and from 2.77 g·cm-3 to 2.52 g·cm-3. The presence of shea meal within the material generates pore formation, which may partly explain the improvement of the thermal insulation properties. A positive correlation was noted between density and thermal conductivity of these materials.

Indispensability and Vulnerability of Magnesia-carbon Bricks for Steelmaking Process

The manufacturing techniques of magnesia-carbon bricks in China have been documented from raw materials,production(process and facilities)to performance and wear issues in the ladle.Magnesia-carbon bricks made of ordinary fused magnesia is the prevailing material used in the slagline of the ladle,but its service life is substantially lower than the bricks based on large-periclase-crystal fused magnesia.In two types of fused magnesia,the average values of periclase crystal size are in double for their difference.It is suggested that large-periclase-crystal fused magnesia should be used for manufacturing magnesia-carbon bricks for the slagline of the ladle by abandoning ordinary fused magnesia,in order to have a prolonged service life,increase the availability of the ladle and reduce the number of downtimes of the ladle.Free phenol in resin produced in China should be as low as that of resin made in Europe,to improve production environment and reduce smoke emission during the ladle preheating.There are large spaces to promote the productivity of magnesia-carbon bricks in China,with high intensity mixers and hydraulic presses.Expansion controlled magnesia-carbon bricks in the ladle depend on the optimized combination of sintered magnesia,Carbores and antioxidants as the matrix,to minimize the premature wear of vertical cracks and joint opening formed in the ladle lining.

Effect of Polyethylene Terephthalate Plastic Waste on the Physico-Mechanical and Thermal Characteristics of Stabilized Laterite Bricks

The present work investigated the effect of polyethylene terephthalate (PET) plastic waste on the physico-mechanical and thermal properties of cement-stabilized laterite bricks to see the durability of the modified bricks (CSLB). Samples were formulated by mixing laterite, cement, and different percentages of PET (0%, 3%, 5%, and 7%) by volume. The bricks were produced using the M7MI Hydraform standard interlocking block and kept in the shade for a curing period of 28 days. The addition of 3% to 5% PET to the laterite stabilized with 10% cement results in a decrease in both dry and wet compressive strength, which is determined using the Controlab compression machine. However, the obtained results are in concordance with the standards. The thermal conductivity of CSLB, determined using the box method with the EI700 measurement cell, decreases as the PET content of the mixture increases. A decrease in bulk density from 1.67 to 1.58 g/cm3 was observed.

Thermal Properties of Earth Bricks Stabilised with Cement and Sawdust Residue Using the Asymmetrical Hot-Plane Method

This paper presents an experimental study of the characterisation of local materials used in the construction and thermal insulation of buildings. These materials are compressed earth bricks stabilised with cement and sawdust. The thermal conductivity, diffusivity, effusivity, and specific heat of earth-based materials containing cement or sawdust have been determined. The results show that the blocks with earth + sawdust are better thermal insulators than the blocks with simple earth. We observe an improvement in thermal efficiency depending on the presence of sawdust or cement stabilisers. For cement stabilisation, the thermal conductivity increases (λ: 1.04 to 1.36 W·m-1·K-1), the diffusivity increases (from 4.32 × 10-7 to 9.82 × 10-7 m2·s-1), and the effusivity decreases (1404 - 1096 J·m-2·K-1·s-1/2). For sawdust stabilisation, the thermal conductivity decreases (λ: 1.04 to 0.64 W·m-1·K-1), the diffusivity increases (from 4.32 × 10-7 to 5.9 × 10-7 m2·s-1), and the effusivity decreases (1404 - 906 J·m-2·K-1·s-1/2). Improving the structural and thermal efficiency of BTC via stabilisation with derived binders or cement is beneficial for the load-bearing capacity and thermal performance of buildings.

Finite Element Modeling Of Low Heat Conducting Building Bricks

Heat conduction through conventional and interlocking building bricks with cavities was studied in this work. Heat transfer analysis was carried out using MATLAB? partial differential equation toolbox. Regular and staggered hole arrangements were studied. Results showed that four staggered holed interlocking bricks were effective in thermal resistance into the bricks and increasing the holes beyond four did not give any thermal resistance advantage. For the conventional bricks staggered holes did not give any thermal resistance advantage but the four-holed bricks were also adjudged to be effective in thermal resistance into the brick surface. Increasing the number of holes beyond four in conventional bricks did give some thermal resistivity advantage but very minimal. Structural strengths of holed bricks were not considered in this study.

一种促进建筑节能的多功能砖及其设计研究

现代建筑形式多样,建筑全寿命期间的能耗居高不下。为响应我国建筑领域绿色节能碳减排计划,设计一种符合绿色节能理念的新型多功能砖。该型砖结构特殊,砖模一体,孔洞和凸台嵌套设计,增加了墙体强度;墙体中空,可填充保温材料,阻隔墙体热传导,从而实现建筑节能目的。试制产品经过测试,与同类型节能建筑产品比较,在墙体强度、墙体导热率性能上具有优势。该产品可降低建筑后期能耗,实现建筑绿色节能目的,为建筑领域节能减排作出贡献。

Properties,Performance and Quality Control of Recycled MgO-C Bricks

Properties, section structure and service results of recycled MgO-C bricks and new MgO-C bricks for ladle slag line of Baosteel were analyzed and compared, and the measures of improving stability and quality of recycled MgO-C bricks were summarized. The results show that： （1） High quality recycled MgO-C materials can be produced by scientific, meticulous and strict management for every process such as dismantling furnace, selection, removing impurity and slag, stacking and homogenization ; （2） Using high quality recycled materials and reasonable production technique, recycled MgO-C bricks with better properties and service efficiency than those of new MgO-C brick can be produced; （3） Service efficiency of recycled MgO - C bricks is good because of its high density, good oxidation resistance and reasonable structure.

Development of a Thermoplastic Magnesia Carbon Brick ——“A Cold Process Flexible System”

Conventional resin bonded MgO-C bricks, which are manufactured via cold mixing process, harden and attain brittleness during carbonization of resin due to the formation of isotropic glassy carbon. They do not exhibit thermo-plasticity, which can facilitate the release of huge amount of stresses generated during preheating or in operation. On the contrary, pitch bonded MgO-C bricks, show better pyro-plasticity due to formation of an anisotropic and graphitized coke structure during carbonization of pitch. Hence, pitch bonded bricks show a superior structural spalling resistance in comparison to resin-bonded bricks. One of the drawbacks of pitch-bonded bricks is that the manufacturing requires a hot mixing process and hot pressing facility. This paper describes how a combination of above two processes was optimized to make a MgO-C brick via cold process. These bricks exhibit a low Modulus of Elasticity and thereby facilitate release of stresses during operation. Normal coal tar pitch is considered as an environmental hazard due to the presence of polyaromatic hydrocarbons like benzopyrene B [ a ] P. So, a special binder with a low B[ a ] P was selected, which is eco-friendly in nature. Such bricks were made in our plant in China and supplied to an integrated steel plant in Europe for their ladle. The bricks supplied have given encouraging life.

焦炉用耐火材料的改进及应用

简述了焦炉结构,分析了焦炉所用传统耐火材料存在的不足,介绍了一些新型耐火材料的性能特点及其在焦炉蓄热室、烟道、燃烧室、炭化室、加煤孔、上升管、炉门、热回收焦炉布风器等部位的应用,并对比分析了使用效果。生产实践结果表明:新型耐火材料的应用,对焦炉的节能、环保、使用寿命都具有积极影响,有助于焦化企业的环保升级、降本增效。

基于ABAQUS的水泥窑低导热复合耐火砖结构设计及性能预测

为有效降低回转窑筒体表面散热损失,减少水泥生产标准煤耗,开发新型低导热耐火砖成为研发的重点。本文借助有限元仿真技术,以力学性能和隔热性能为观测点,对新型低导热耐火砖的结构进行优化设计并模拟预测了窑内的使用效果。结果表明,低导热气凝胶材料与传统耐火砖以T型结构复合,既满足耐火砖工程应用力学性能要求,同时可有效降低回转窑表面温度约70℃,具有潜在的应用价值。

Production and Characterization of Porous Insulating Fired Bricks from Ifon Clay with Varied Sawdust Admixture

The effect of compositions of saw dust admixture on thermal conductivity and other mechanical/refractory properties of Ifon Clay was investigated. The raw clay gotten from Ifon in Ondo state was first processed to very fine particles and characterized using SEM/EDX, XRD and XRF. Sawdust from mahogany tree procured from a saw mill in Akure the State capital of Ondo State was also dried to remove moisture present. A composite mixture of this dried saw dust with the processed clay was made at various proportions of the saw dust, with a little addition of water for plasticity. Sam- ples of cylindrical dimensions were then produced from the mounting press by the process of compaction with a very high pressure. The samples were dried and then finally fired in the furnace at 1000?C for a final curing. Properties which include thermal shock resistance, bulk density, cold crushing strength, thermal conductivity and porosity were obtained by the appropriate standard test methods. The microstructures of the fired samples were also characterized with SEM using back scattered secondary imaging. The results show that the amount of sawdust admixture affects the properties variously;porosity increases with percentage increase in sawdust admixture while the thermal conductivity and other properties of the sample reduce with percentage increase in sawdust admixture. It was concluded that for structural insulating bricks where compressive strength is important the sawdust admixture should not exceed 10 to 15 percent.

高导热BNNS/ANF复合绝缘纸的结构设计及性能分析

随着电力设备逐渐向高电压、大容量、高集成化方向发展,对其绝缘材料的导热性能提出了更高的要求。本文借鉴天然珍珠母的仿生结构,以耐高温的1维芳纶纳米纤维(ANF)组成骨架网络,以高导热的2维氮化硼纳米片(BNNS)为功能基元,构筑复合绝缘纸。首先,利用柠檬酸锂充当表面活性剂,将六方氮化硼(h–BN)通过超声与水热反应相结合的方法剥离成BNNS,并对其微观形貌及分散特性进行研究;然后,采用浓碱去质子化法剥离Kevlar纤维(AF)制得(ANF);分别以ANF、BNNS为纳米基元,通过真空辅助抽滤技术制备出BNNS/ANF复合绝缘纸,并对其微观形貌结构、导热性能、力学性能、击穿性能进行了分析。结果表明:所剥离制备的薄层BNNS具有高长径比,BNNS与ANF之间均匀堆积形成致密的砖泥结构,这种砖泥结构有助于改善复合绝缘纸的击穿性能和力学性能;当BNNS填充质量分数为20%时,BNNS/ANF复合绝缘纸的标准击穿场强达到313.04 kV/mm,抗拉强度达到216.64 MPa,分别是纯ANF绝缘纸的166.47%和126.38%;此外,BNNS在ANF网络中定向分布形成连续导热的桥联,显著提高了复合绝缘纸的导热性能,当BNNS填充质量分数为30%时,复合绝缘纸的热导率达到5.31 W/(m·K),是纯ANF绝缘纸的211.55%。该复合绝缘纸具有高导热性、良好的力学性能以及优异的电绝缘性,能有效解决设备绝缘散热问题,有望在电气设备中推广应用。

Thermal Characteristics of Earth Blocks Stabilized by Rice Husks

The objective of this study is to determine the thermal characteristics of bricks produced from clay soils in Chad using the asymmetric plane method. Indeed, in Sahelian countries like Chad, temperature variations are excessive. The study of the thermal behavior of a recyclable local material with low environmental impact could not only improve thermal comfort in homes, but also help mitigate the effects of climate change. It is in this context that this study is envisaged. Before carrying out these measurements, we first produced different formulations of soil blocks 0%, 1% 1.5%, 2% and 2.5% by mass of rice husks (1.25 mm sieve refusal). Brick specimens of dimensions 10 cm × 10 cm × 1 cm were developed at 0 day, 7 days and 14 days of maturation of the formulated pastes. After, those bricks were submitted after drying to the measurements of various thermal parameters: in particular the conductivity, the effusivity, the volumetric capacity and the diffusivity. The obtained results show that the addition of rice husks to clay soils improves conductivity by 13% to 49%, effusivity by 19% to 24%, volumetric capacity by 23% to 27%, and diffusivity by 47% to 58% for the Moundou soils, depending on the maturation period. For the N’Djamena soil, these thermal characteristics are improved from 11% to 38%, from 11% to 13%, from 40% to 47% and from 39% to 40% respectively.

砖肥对土壤电导率及烤烟根系分布的影响

紫色土分布区域降雨集中、土壤养分淋失严重,导致土壤肥力下降、根区养分供应不足、根系发育不良等问题,提升土壤养分的供应强度有利于优化根系空间分布格局和促进根系生长。将原料肥和有机物料混匀后,利用1400 kg/cm^(2)的强大压力将其压制成砖肥(BF),同时,设置原料肥和有机物料物理混合(CK)为对照。于关键生育期测定垄向截面不同土层深度和离烟株不同远近距离的格点位置的土壤电导率(EC)、不同直径的根系组成和根系生物量,采用Logistic模型、指数模型拟合根系空间分布关键参数和生物量累积关键参数,研究砖肥对烤烟根区电导率及根系生长的影响。结果表明:在烤烟根系主要分布区,即主根系半径12.5 cm处,深度2.5~12.5 cm的土壤剖面,BF处理的EC比CK高90.5~281.6μS/cm;主根系半径17.5 cm处,深度2.5~17.5 cm的土壤剖面,BF的EC比CK高160.1~392.2μS/cm。在主根系15~20 cm水平半径内,BF的根系重量比CK提高150%;分布在10~15 cm深度土层的根系重量提高了26.5%,并且土壤剖面10~20 cm之间的侧根伸展性更强、分布更广。移栽后75、90和105 d,BF的田间根系生物量分别比CK提高12.7、11.9和9.7 g/株,烟叶生物量分别比CK高24.5、13.6和17.1 g/株,根系和烟叶生物量最大累积速率分别比CK提高了43.5%和15.7%。对于淋失严重的土壤,施用砖肥可以提高养分供应强度、优化根系分布格局和促进烤烟生长发育。

矿热炉用不同品位镁砖的对比研究

矿热炉用碱性耐火制品,以镁质砖为主。镁含量不同的镁砖其基质间的硅酸盐相组成和含量也不同,通过对原料的微观结构,成品砖的导热系数、线膨胀及静态抗渣实验的分析,对不同镁含量的镁砖有更清晰的认知。

用玉米芯和废玻璃增强低温烧制黏土砖的孔隙率和强度分析

本研究旨在探讨玉米芯和废玻璃是如何提高低温烧制黏土砖的孔隙率和强度的。本试验中使用的黏土砖样品是用10%的玉米芯制成的,废玻璃是回收的窗户玻璃,然后以0、5%、10%、15%和20%的比例加入黏土混合物中。绿色黏土混合物在900℃、1000℃和1100℃下烧制,对烧制的黏土砖进行了物理和热性能测试。结果表明:低温下添加玉米芯和废玻璃可以提高黏土砖的孔隙率和强度,因为玉米芯增加了砖的孔隙率,而废玻璃作为助熔剂,促进了砖的烧结,形成了矿物钠长石,提高了砖的强度。含10%玉米芯和20%废玻璃的样品在900℃下烧制,符合mw级黏土砖的强度和吸水率要求,导热系数为0.81W/m·K。

焙烧炭砖孔结构和热导率与硅粉加入量的关系

以电煅无烟煤(5～3、3～1、≤1及≤0.088 mm,w(固定碳)=95.17%,w(挥发分)=0.37%,w(灰分)=4.14%)、鳞片石墨(≤0.147和≤0.074 mm,w(固定碳)=96.5%)、棕刚玉粉(≤0.074 mm,w(A l2O3)=93.5%,w(TiO2)=2.3%)和硅粉(≤0.043 mm,w(Si)=96.37%)为原料,固定骨料与细粉的质量比为60∶40,细粉中硅粉和电煅无烟煤细粉总量固定为14%(质量分数),改变硅粉加入量(质量分数)分别为3%、5%、8%、10%、14%,以液态热塑性酚醛树脂为结合剂,乌洛托品作固化剂制成炭砖,于1 400℃3 h埋炭焙烧,借助于X射线衍射仪、压汞仪、激光导热仪、扫描电子显微镜和能谱分析仪等测试手段,研究了不同硅粉加入量的焙烧炭砖的孔结构及热导率。结果表明:因炭砖焙烧过程单质硅原位反应形成β-SiC、Si2N2O和石英等陶瓷相,填充、阻隔或封闭了气孔,故硅粉加入量控制着试样内部的气孔分布、平均孔径和孔径<1μm气孔的孔容积率;受材料组成和孔结构变化影响,炭砖的热导率也发生相应变化;随硅粉加入量增加,试样中孔径分布范围由宽变窄,平均孔径逐渐减小,<1μm孔的容积率增加,气孔呈微孔化趋势;当试样中硅粉加入量超过8%时,气孔的平均孔径<0.3μm,<1μm孔容积率超过70%,试样的热导率急剧下降。

赤泥陶瓷保温砖的制备及结构与性能

利用2种赤泥成功地制备了具有保温功能的陶瓷砖。其中烧结法赤泥和拜尔法赤泥的总掺量达质量分数60%以上,制备的样品具有较高的抗压和抗折强度及较低的导热系数。利用XRD、SEM等测试手段分析了样品的理化性能与微观结构。结果表明:烧结法赤泥添加量为24%,拜尔法赤泥添加量为36%时,样品的最佳烧成温度为1 040℃,气孔率为41.57%,吸水率为23.13%,体积密度为1.80 g/cm3,抗折强度为14.97 MPa,抗压强度为53.84 MPa,导热系数为0.88 W/(m.K)。样品的晶相组成为SiO2、Fe2O3、Ca3Fe2Si3O12、Ca2Al2SiO7、CaMgSi2O6。

第二代新型干法水泥工艺用耐火材料的配置技术

围绕第二代新型干法水泥工艺要求耐火材料具有节能降耗、绿色环保、长寿高效的功能和特点,介绍了与之相适应的低导热多层复合莫来石砖、镁铁尖晶石砖、预制件、浇注料、火泥等耐火材料的性能及其在第二代新型干法水泥工艺的配置技术。