Raising the efficiency of heat-power units due to the use of modern refractory and heat-insulating materials

The timeliness and efficiency of the use of new refractory materials in modern heat-power units and the positive experience in the use of fiber refractory articles in heat-treatment furnaces and steam-generating units are considered. Novel design solutions for linings of heating furnaces operating at a temperature exceeding 1000°C are presented. __________ Translated from Novye Ogneupory, No. 12, pp. 6–9, December, 2007.     

Radiation heating test and development of porous MgAl2O4 ceramics with high thermal shielding effect based on Mie theory

Porous MgAl₂O₄ ceramics designated as THERMOSCATT^TM have diffuse reflectance based on the Mie theory. The reflectance greatly suppresses radiation heat transfer and has low emissivity at 1–5 μm wavelengths. Their thermal conductivity has been measured as less than 0.3 W/(m K) at 1500°C. Furthermore, porous MgAl₂O₄ ceramics have near-zero hemispherical spectral emissivity values at 0.35–5 μm wavelengths. High heat resistance and low emissivity materials in the atmosphere are useful for the innermost layer of industrial furnaces to confine energy efficiently. Additionally, this material is useful as a radiation reflectors, such as in stand-off thermal protection systems. This study elucidated the suppression of radiation transfer in porous MgAl₂O₄ ceramics attributable to low thermal emissivity. Therefore, the thermal insulation performance under radiation heating in vacuum, the emissivity validity evaluation of low-emissivity porous materials using finite element analysis, and microstructure effects on radiation heating performance and mechanical properties were investigated.     

Synthetic Mica Investigations: III, Precision-Controlled Electric Furnaces for Temperatures to 1500°C

Three furnaces using silicon carbide heating elements are described, including (1) a utility furnace for melting and testing, (2) a precisioncontrolled (± 1/2°C.) crystallization furnace, and (3) a rectangular crystallization furnace. Schematic drawings of the furnaces and a simplified wiring diagram for the heating elements are included. One composite controller is described from a functional viewpoint, with a block-diagram presentation. A complete circuit diagram of this controller also is incorporated. The use of saturable core reactors in regulating power to electric furnaces is advocated; reactors permit the control of electricity in a manner similar to adjustment of the flow of water by means of a valve.     

THE THERMAL CONDUCTIVITY OF CARBORUNDUM REFRACTORIES1

Thermal conductivity measurements up to 1350°C of silicon carbide refractory materials have been made, using the water calorimeter method. Data were secured on furnace walls such as those commonly used in practice and results are believed to be accurate to within about 1%. Conductivity measurements were made on seven carborundum single walls and on eight carborundum-fire-clay composite walls. The relation of the thermal conductivity to temperature, chemical composition, and porosity was investigated, as well as the magnitude of the surface and joint effects. The conductivity of carborundum was found to vary with the quantity of heat energy transmitted through the wall. Tables are given showing the coefficients of thermal conductivity and heat flow through various types of walls with a temperature of 1500°C in the combustion chamber. Temperature gradient charts and heat flow curves for various walls are also given together with the practical application of the results in the design of commercial furnaces.     

高湿物料真空连续复合管束烘干设备研制初步探讨

从分析影响烘干设备干燥效果的烘干时间、加热温度、运行距离、物料与加热系统的接触面积入手，研制出高湿物料真空连续复合管束烘干设备。干燥主机采用三个不同直径的同心圆筒组成多级干燥室，各个干燥室内设有一定数量的加热管束，利用真空连续干燥、热能按需分配的原理，延长物料在干燥主机内的烘干时间、运行距离，加大物料与加热系统的接触面积，提高烘干设备的空间利用率。从而有效踺提高了烘干效率，降低烘干成本，改善了物料品质；改变了传统管束烘干设备采用一级干燥室的空间利用率低、热能不被充分利用的局面。     

Thermal energy storage in inorganic salts

The work involved studying the potential of Na₂SO₄, NaCl, KCl, CaCl₂ and some eutectic mixtures of inorganic salt for storing thermal energy. Heat storage materials have wide application in devices such as “off-peak” space heating furnaces. Data reveal Na₂SO₄ to be a better heat storage material than other salts as well as conventional heat storage materials because of its dimorphic nature and high heat of transition. It is estimated that less than 0.29 m³ of Na₂SO₄ would be required for heating a normal sized house on the Canadian Prairies.     

New forms of unmolded refractory materials produced by OOO Keralit

New forms of refractory materials are presented, produced by OOO Keralit: heat-insulating concretes, refractory concretes with low and normal cement contents, torcrete-mixes for heating furnace walls, and magnesia torcrete-mixes for hot repair of arc furnaces. Properties and fields of application for unmolded materials are provided. Translated from Novye Ogneupory, No. 7, pp. 21–23, July 2008.     

Experience of the use of alumosilicate materials on phosphate binders for lining “Aichelin” heat-treatment furnaces

Alumosilicate composite materials on a phosphate binder which provide high operational stability are suggested as substitutes for imported lining elements of Aichelin heat treatment furnaces (Austria). The lining elements are produced by the branch laboratory of the Bashtekhprom enterprise (Ufa). Industrial tests of the articles have given positive results.     

Increase in the operating efficiency of heating units using ceramic fibers and objects based on them

The operating efficiency of heating units using ceramic fibers and objects based upon them is demonstrated: furnace warm-up time and cooling is saved by a factor of five, there is an overall reduction in fuel consumption with the use of light-weight objects in continuously operating furnaces by 10 – 15%, and in periodically operating furnaces by 45%, and there is a reduction in capital expenditure in furnace construction by a factor of 5 – 10 (according to USA data). In addition, use of thermal insulation materials not only saves energy resources, but in many cases it speeds up production processes, improves ecology, and simplifies lining construction.     

Study of the properties of ceramic surfacing material used for restoring coking chamber linings

Properties are given for original raw components and a production scheme is provided for preparing ceramic surfacing for repairing the dinas lining of coking furnaces. Data are presented for x-ray phase and petrographic analyses of ceramic surfacing. Adeformation - temperature diagram is provided. Recommendations are given for use of the proposed compositions for repairing heating units.     

New fields of application of materials and articles from refractory fibers in the Al2O3 — SiO2 system

Basic properties of materials and articles from refractory fibers that save resources, cut heat loss, and reduce the consumption of material for furnaces are presented. A new direction in the development of materials and articles from refractory fibers for converter production is described     

相变介质组成对粉煤灰基高温定形复合相变材料蓄热性能的影响

分别以Al粉、Al-12Si、Al-20Si合金粉为相变介质,粉煤灰为基体材料,采用混合烧结法在空气、真空两种烧结氛围下制备金属/陶瓷基高温定形复合相变材料,探讨相变介质中硅铝相对含量及烧结氛围对材料蓄热性能的影响。结果表明:分别用三种金属粉制备复合相变材料时,Al的氧化难以避免,致使Si的相对含量均超过共晶点组成,凝固时其状态点始终处于共晶相+Si相的两相区,未被氧化的Al都转变成为Al-Si共晶相。空气中烧结有利于Al形成致密氧化膜从而阻止其进一步反应,材料的密度、相变潜热都比真空中烧结高。三种复合相变材料中,由Al粉制备的热稳定性最差,由Al-12Si合金粉制备的相变潜热、保留率最高,热稳定性及蓄热性能突出。     

Construction of renewable roofs for continuous heating furnaces

Constructions are considered for renewable roofs of continuous heating furnaces using different lining materials: chamotte refractories, monolithic refractory concrete, and refractory ceramic fiber. It is established that it is most desirable to use panel roofs using modular blocks made of refractory ceramic fiber. __________ Translated from Novye Ogneupory, No. 11, pp. 23–27, November 2007.     

Decreasing the waste in metal-heating processes

Results of laboratory development and industrial application of general-purpose coatings for the bricklining of heating furnaces are presented. On the basis of the operating characteristics of the coatings, the effectiveness of their use in furnaces is estimated. The best type of coating, IVAKS-2, is selected, which gives a decrease in the fuel consumption in a soaking pit by 10% and lowers the amount of effluents of nitrogen oxides and carbon oxide by 27% and 20%, respectively, thus improving the waste indices of the processes of metal heating. The IVAKS-2 coating is recommended for wide use in high-temperature heating furnaces of metallurgical and mechanical engineering enterprises. Translated from Ogneupory, No. 4, pp. 19 – 22, April, 1994.     

SHS-rolling in a vacuum — an effective method for preparing cermet and intermetallic materials

Results are presented for experiments in studying SHS-rolling realized under conditions of rolling in a vacuum. The starting materials used are powder mixtures of the systems Ti-C, Ti-Al, Ti-C-N-Ni. Optimum heat treatment regimes and compaction of the starting mixtures are determined and parameters are studied for combustion and subsequent plastic deformation in a vacuum, test specimens are prepared in the form of strips of TiC and TiAl and a hard alloy based on TiC and TiN with porosity from 3 to 65%. The new method will make it possible to prepare articles made of synthetic hard materials in the form of strip, sheets, bars and other metallurgical products. __________ Translated from Novye Ogneupory, No. 10, pp. 42–44, October 2007. Self-propagating high-temperature synthesis.     

硫磺回收及尾气处理工艺新型流程

针对硫磺回收及尾气处理Claus +SCOT装置存在的问题进行探讨 ,提出采用非在线加热炉并合理利用自身热源的新型简化流程。对新老流程进行了对比 ,指出了新流程设计中应考虑的问题。     

Development of ceramic material and filtering element technology for disk vacuum filtering units used in dewatering ferrous and nonferrous metal ore concentrates

Question of reducing expenditure for producing a production unit may be resolved by means of filtering elements made of porous permeable ceramic materials with a controlled pore size created using the newest technology. Methodology is presented for creating sector filtering elements made of porous permeable ceramic based on electrocorundum for disk vacuum filtering units used extensively in ferrous and nonferrous ore-dressing plants. Translated from Novye Ogneupory, No. 3, pp. 24 – 28, March 2009.     

Current State of In Situ Measuring Methods for the Control of Firing Processes

A combination of in situ measuring methods and computer simulation is suggested for the optimization of debinding and sintering processes in lab furnaces. From the optical measurement of sintering shrinkage and the mass loss measurement during debinding the respective reaction rates are derived. A high resolution of 1 μm and a reproducibility better than 0.3% were obtained for the optical measurement of sintering shrinkage. The atmospheres in the in situ measuring furnaces have to be closely matched to the production furnaces, to allow a transfer of the optimized heating cycles. A kinetic field method is used to obtain a model-free prediction of the debinding and sintering kinetics. Various other macroscopic in situ measuring methods are discussed, regarding their role during process optimization of ceramics. For example, heat transfer properties, required to calculate temperature and stress distributions during the heat treatment, were obtained by a modified laser-flash technique.     

VACUUM DRYING OF DISPERSED MATERIALS FROM MULTICOMPONENT LIQUID SYSTEMS: VERIFICATION OF MODEL

ABSTRACT

Experimental data on vacuum drying of chemical and microbial synthesis products under laboratory and industrial conditions are presented. Kinetic relations of vacuum drying of dispersed materials with the removal of a multicomponent liquid system are verified on both laboratory and industrial scale dryers under different operating conditions. The results of the research were generalised and a number of empirical relations needed for drying process calculation are given. The relation between heat transfer coefficient and heat flux and motive force for the vacuum drying process is established.     

Temperature measurement with a carbon thermal indicator

Conclusions Temperatures have been measured with carbon indicators under vacuum and in oxidizing and reducing media, as well as in corrosive ones. The method is recommended when traditional methods and devices are expensive or unreliable. The method has been tested in EVP furnaces providing siliciding heating for silicon carbide heaters and can also be used in metallurgy and the refractories industry.Translated from Ogneupory, No. 1, pp. 29–30, January, 1991.