Furnace Components Research Articles

A yttrium aluminosilicate glass-ceramic to join SiC/SiC composites

In this work, a yttrium aluminosilicate glass-ceramic was employed to join two different SiC/SiC ceramic matrix composites to be used as radiant tube furnace components for energy-intensive industries, such as steelmaking. Two different joining processes are reported. The joints were morphologically characterized using scanning electron microscopy, and they were mechanically tested using the single-lap offset shear test at room temperature, where the failure was caused by the delamination of the composite, thus denoting an excellent adhesion between the glass-ceramic and the SiC/SiC composite.

Design, construction and validation of a simple, low-cost phi meter

The best correlation between the yields of the major toxicants in fire smoke and the fire condition is obtained by expressing the ventilation in terms of the equivalence ratio, phi. Phi meters allow this fuel-air equivalence ratio to be determined during a large-scale fire test. The original design used a platinum catalyst, a large furnace, and required pure oxygen. This work aimed to make a simple, low-cost device which could monitor the equivalence ratio during a large-scale fire test. The current design produces the same quality of measurement with a much smaller footprint and throughput. Benefits include enhanced portability, reduction in sample gas cleaning and drying requirements and lower cost. The work showed that normal furnace components (alumina and silica) provide suitably catalytic surfaces at 900 °C eliminating the requirement for platinum catalysts and the use of pure oxygen. The ISO/TS 19700 steady state tube furnace (SSTF) was used to validate the phi meter measurements as it can both pre-set and independently quantify the equivalence ratio during a test. Long sample collection times were overcome with a larger sampling pump and effluent being split between the phi meter furnace and the exhaust. It is hoped that this simpler, optimized apparatus will encourage more widespread use and lead to better prediction of smoke toxicity.

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel.

Hot-stamped ultrahigh strength steel components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coating may transfer to the furnace components, leading to maintenance costs and operational downtime. A detailed understanding of the coating transformation mechanism is needed to avoid such production issues while ensuring that final intermetallic coatings conform to specifications. We introduce cross-sectional Raman microscopic mapping as a method to rapidly elucidate the coating transformation mechanism. Raman spectroscopic fingerprints for relevant intermetallic compounds were determined using synthesized Al-Fe-Si ternary and Al-Fe binary compounds. These fingerprints were used to map the spatial distribution of intermetallic compounds through cross sections of Al-Si-coated 22MnB5 specimens that were heated at temperatures between 570 and 900 °C. These chemical maps show that the intermetallic fraction of the coating does not grow significantly until formation of η (Al5Fe2) at the steel interface, suggesting that η facilitates extraction of iron from the steel and subsequent diffusion through the coating. Under the heating conditions used here, a series of reactions ultimately lead to a silicon-rich τ2 (Al3FeSi) phase on top of the binary η phase. The technique presented here simplifies structural analysis of intermetallic compounds, which will facilitate prototyping of strategies to optimize hot stamping.

Damage analysis of 800 series materials from reformer tube outlet components

To investigate the failure of 800 series materials from the furnace tube outlet components of the reformers, the test devices such as metallographic microscope, scanning electron microscope, carburizing detector and high temperature endurance testing machine were adopted. The failure mode and failure mechanism of 800 series materials for outlet components of reformer such as pig tail pipe, outlet pipe, stiffenerjoint and collection tube, which had been in service for 1–11 years from 7 petrochemical and chemical fertilizer enterprises were analyzed. The results suggest that the damage of 800 series materials from reformer outlet components in 7 petrochemical and chemical fertilizer enterprises mainly occurred on the base metal. The failure modes included bulging, cracking and fracture, and the principal failure mechanisms were creep and carburizing, respectively. The main factors affecting the failure of 800 series materials in the tube outlet components of reformer were discussed with respect to grain size, metal temperature and stress concentration. Consequently, multiple suggestions were given to avoid premature damage and failure of such components.

Glass-ceramics for joining oxide-based ceramic matrix composites (Al2O3f/Al2O3-ZrO2) operating under direct flame exposure

This work focuses on the joining processes of oxide-based ceramic matrix composites (Al2O3f /Al2O3-ZrO2), which are used as radiant tube furnace components in the steel industry. These components have to operate in harsh environments, and under high temperatures, and they therefore have to resist corrosion, humidity, and combustion. Two glass-ceramics systems, which have Y2Ti2O7 as their main crystalline phase, as well as specific and optimized properties to withstand severe operating conditions, including temperatures of 900 °C, are here proposed as joining materials. The adhesion of the glass-ceramics to the composite was found to be excellent after mechanical and thermal tests in which they were in direct contact with a 900 °C flame and thermal cycling of between 400 °C and 900 °C.

THERMAL AND COMPUTATIONAL FLUID DYNAMICS ANALYSIS OF AN OIL FIRED CRUCIBLE FURNACE DURING SECONDARY ALUMINUM SMELTING

Thermal and computational fluid dynamics (CFD) analysis were explore with knowledge based software such as Solid Works and ANSYS workbench 14.0 for modeling and simulation of an Oil fired crucible furnace used for aluminum secondary smelting. Thermal analysis gives the maximum heat flux and directional heat flux as 8.7596W/mm2 and 8.0349 W/mm2 respectively. CFD simulation shows that the effect of the process parameter on the furnace components is as a result of furnace factors. In brevity theoretical calculations of thermal stress up in the furnace and heat transfer to crucible conform to the modelled results.

Thermal behaviour of vitreous ceramic coatings obtained by electrophoretic deposition for furnace components

In this study, three different vitreous ceramic coatings have been designed to improve radiation heat transfer and thereby increase the thermal efficiency of fired heaters or furnaces working at high temperatures. The vitreous ceramic coatings were produced through Electrophoretic Deposition technique (EPD) of ceramic suspensions. These ceramic formulations were designed based on components which increase emissivity, such as SiO2 and a Black dye (based on chromium, copper and iron oxides), added in 25 wt%. These coatings showed emissivity values around 0.89 at room temperature and around 0.82 at 550 °C in the middle infrared (MIR) spectral range, with slight differences between them. The SiO2 and Black dye additions provide an important protective effect on the coatings’ thermal stability as it was proved by the absorbance level at long times, higher than 85% in the near infrared (NIR) spectral range. These results were also supported by microstructural characterisation, substrate-coatings adhesion strength and thermal stability tests.

Development and Commercialization of High Performance Furnace Components

High-purity mullite (3Al2O3·2SiO2) has excellent mechanical properties at high temperature, such as high flexural strength and excellent creep resistance, and are thus promising as high-temperature structural ceramics. The mechanical properties at high temperature are influenced by factors such as the Al2O3/SiO2 ratio, impurities, and the microstructure; therefore, the relationships among these factors and their effect on the mechanical properties at high temperature have been investigated with respect to improving the properties of high-purity mullite. High-thermal-stability mullite has thus been developed by the control of the Al2O3/SiO2 ratio, the amount of impurities, and the microstructure with high precision. The mechanical properties of this newly developed mullite are superior to those of high - purity mullite with a composition of 3Al2O3·2SiO2. We have successfully applied this mullite for the components of high-performance furnaces such as the roller hearth kiln (RHK) because this mullite has high thermal stability and exhibits better long-term stability at temperatures as high as 1600°C in an oxidizing atmosphere. The RHK with high-thermal-stability mullite components has been widely accepted by the ceramic device industry, which produces advanced materials such as electronic components. High-thermal-stability mullite has thus contributed to the development and stabilization of product properties and efficiency, and offers faster sintering times, all of which contribute significantly to the development of a wide variety of ceramics.

Numerical Prediction of the Flow Structure Inside Components of Industrial Glass Furnace Systems

An important aspect in the glass production industry is related to the heat recovery of the combustion gases. It is usually obtained throughout the use of well-tested technologies, such as regenerative towers with refractory material. For an effective heat recovery, a good distribution of the flow rate at the entrance of the chambers is crucial. The use of Computational Fluid Dynamics (CFD) allows the detailed analysis of the gas evolution during the process; the same would be impractical with experimental measurements, due to prohibitive ambient local conditions. The CFD approach during the design phase typically considers CAD geometries without the level of details related to technological features of the actual installed configuration (i.e. sharp edges vs rounded edges). A brand new built furnace has blunt edges in every connection between 3D walls of refractory blocks. The above edges will be rounded by the erosion-corrosion process due to the harsh chemical/mechanical/thermal environmental conditions inside the plant components (i.e. regenerative chambers, connecting ducts, furnace). The purpose of this work is to evaluate the influence of the geometrical details of the CAD (with focus on the edges connecting adjacent walls), due to technological or erosion aspects, on the flow structure in the furnace components.

Electrochemical Deposition of Tantalum from Ionic Liquids

Tantalum belongs to a class of metals called refractory metals (Niobium, Molybdenum, Tantalum, Tungsten and Rhenium) which are exceptionally resistant to heat and mechanical wear. Due to their tendency to form stable and dense oxide layers, these metals also possess a high resistance towards chemically agressive media. Therefore these metals can be used as protective coatings to build corrosion resistant parts, such as thermowells and valve bodies or for the production of special vacuum furnace components.[1] The electrochemical deposition of refractory metals is a cost-efficient method to coat materials of complex geometries. The negative reduction potential of Ta makes it impossible to use aqueous solutions. Thus ionic liquids (ILs), with an electrochemical window of 5 to 6 V, are promising alternative solvents and have been intensively used in different research fields of electrochemistry during the last years.[2] We have investigated the electrodeposition of Ta using different Ta halides (TaX5, X=F, Cl or Br) and different pyrrolidinium based ILs (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP][TFSI] and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, [BMP][OTf]). We could show that the combination of the precursor and the IL has a strong influence on the electrodeposition process of Ta. Furthermore using IR spectroscopy we found significant differences in the spectra of the different electrolytes which we correlated with results from computated spectra using Density Functional Theory (DFT). The aim of this combined IR/DFT approach is to identify the formed species in our electrolytes. We will present these data together with experimental results from investigations on the reduction mechanism using different electrochemical in-situ techniques (Differential Pulse Voltammetry, Rotating Ring Disk Electrode, Electrochemical Quartz Micro Balance) to show the influence of precursor-IL interaction on the electrodeposition process of Ta from ILs. Literature 1 F. Endres, A.P. Abbott, D. MacFarlane, Electrodeposition from Ionic Liquids, Wiley-VCH, Weinheim, 2008. 2 A. Ispas, B. Adolphi, A. Bund, F. Endres, Phys. Chem. Chem. Phys., 12 (2010) 1793-1803.

Modeling Interface Shape in Czochralski Growth of Sapphire Crystals

AbstractNumerical modeling is applied to investigate the factors affecting the shape of the crystal‐melt interface in Czochralski growth of sapphire crystals having 10 cm in diameter. The modeling is performed for a 2D – axisymmetric furnace configuration, where all the furnace components are included. The shape of the crystal‐melt interface is computed by using the deformable mesh technique. Numerical results show that the conical shape of the interface depends essentially on the internal radiative heat exchanges in the semi‐transparent sapphire crystal, being less influenced by the buoyancy convection. The Marangoni effect enhances the flow near the triple solid‐liquid‐gas point, leading to convex‐concave shape of the growth interface, which is prone to facet formation. Numerically computed shape of the interface is compared to experimental results taken from literature. Applying crystal/crucible rotation has a significant impact on the flow pattern and the shape of the growth interface. Computations performed by applying only crystal rotation at rates higher than a critical value, show a reversed convection at the sample centre, underneath the crystal. This flow affects the shape of the interface, which is less curved and exhibits a convex shape. If the rotation rate is too much increased, the interface shape can be distorted by the intense flow. Application of crucible rotation intensifies the downward flow at the sample centre, leading to increased interface curvature. Rotating both the crystal and crucible in opposite directions generates a complex flow pattern, but has no flattening effect on the interface.

Исследование количества твердых осаждений и пути их уменьшения с целью повышения ресурса узлов и механизмов доменных печей

Исследование количества твердых осаждений и пути их уменьшения с целью повышения ресурса узлов и механизмов доменных печей

Mathematical modelling and parameter identification of a stainless steel annealing furnace

A new, comprehensive mathematical model of continuous annealing furnaces is developed, under consideration of both the radiative and convective heat transfer of the furnace components. Based on measured normal operating data from an industrial stainless steel plant, parameter identification is basically carried out using a nonlinear least-squares optimization algorithm for the whole annealing furnace, to estimate optimal values of uncertain parameters, such as emissivities. Due to the complexity of the model, a sequential approach for parameter identification is proposed and implemented, i.e. the parameter set is divided into different subsets, and the parameter estimation is carried out sequentially in several steps and iterations. The performance of the model with the estimated parameters is then evaluated on a different test data set. It is shown that the obtained model can predict temperature evolutions along the furnace in good agreement to measured data, under both steady-state and transient conditions. The presented model is suitable for controller design and process optimization.

High-temperature piezoelectric crystals ReCa4O(BO3)3: a review.

High-temperature sensors are desirable for structural health monitoring and/or nondestructive evaluation of next-generation turbines, more efficient jet engines, and the furnace components of electrical power plants. Of all the investigated high-temperature piezoelectric materials, rare-earth calcium oxyborate crystals ReCa4O(BO3)3 (ReCOB, Re: rare-earth) exhibit attractive advantages for high-temperature piezoelectric sensing. In this paper, the electroelastic properties of different ReCOB piezoelectric crystals are investigated. The crosstalk between various vibration modes are discussed, from which the optimized crystal cuts are achieved. Furthermore, temperature dependences of the electrical resistivity, dielectric, elastic, piezoelectric, and electromechanical properties of ReCOB crystals are studied. Finally, the thermal properties, including thermal expansion, specific heat, and thermal conductivity at elevated temperatures are studied and compared with commercially available high-temperature piezoelectric crystals.

Variable Scheduling of Wind-based Micro-grid for Electric Arc Furnace Steel Production

The heavy electrical power draw of electric arc furnaces (EAF) proposes them as prime candidates for economically viable decentralized grid operation, provided they are able to operate efficiently and flexibly in response and in anticipation of fluctuations in price and local renewable energy availability. For this purpose, we consider a hypothetical industrial micro-grid consisting of a wind park, a pumped storage reservoir and a micro-EAF with ability to draw power from both the electrical grid and the hydro storage facility. We then investigate the energy savings potential for steel production, given minor load shift flexibility in production scheduling, and further flexibility in terms of the sizing of the reservoir and the generation capacity of the coupled wind park. The numerical methodology involved dynamic simulation of the furnace components, turbines (from realistic wind data), pump, generator and reservoir, and comparison of flexible vs. regular interval spaced production scheduling.

Optimizing the Process of Steel Slab Reheating in Pusher Type Reheat Furnace Prior to Hot Working

Steel reheating prior to hot rolling is a process which is necessary to achieve sound mechanical and chemical properties of the finished steel products. Heating of steel works in reheat furnaces takes place gradually and with specific rates in order to avoid the development of structural defects due to the development thermal stresses. A mathematical two dimensional heat transfer model was constructed in order to calculate steel slab heating profile through the reheat furnace with actual temperature set points of the furnace zones being used as an input to this model. Calculated slab temperatures indicated aggressive heating of the steel in the early stages of heating and that slabs remain at temperatures close to rolling temperatures for longer period of time than necessary. This finding necessitates a readjustment of slab heating strategy in order to protect furnace components and steel from overheating.

Investigation of Freeze Linings in Copper-Containing Slag Systems: Part II. Mechanism of the Deposit Stabilization

A major industrial problem in high-temperature liquid reaction systems is the attack of furnace components by chemically aggressive molten reactants. Freeze-lining technologies involving the deliberate formation of controlled frozen deposits are increasingly being applied to extend the range of liquid bath compositions and process temperatures that can be used; this has resulted in significant increases in process performance and productivity. It has been widely assumed that the interface between the stationary frozen layer and the agitated molten bath at steady state consists of the primary phase, which stays in contact with the bulk liquid at the liquidus temperature, Tliquidus. It has been shown in the current laboratory-based studies through the use of a cold finger technique that, at steady state and in selected ranges of process conditions and bath compositions, the phase assemblage present at the deposit/liquid interface is not that of the primary phase alone. The microstructural observations clearly demonstrate that the temperature of the deposit/liquid bath interface, Tf, can be lower than the liquidus temperature of the bulk liquid, Tliquidus. These observations point to a significant change in the mechanism and behavior of the systems. To explain this phenomenon, it is proposed that the steady-state thickness of freeze linings is not the result of equilibrium freezing but rather represents a state of dynamic equilibrium that is critically dependent on the relative rates of crystallization, mass, and heat transfer processes, occurring close to and at the deposit interface. The mechanisms taking place in the boundary liquid layer involve both partial crystallization/remelting and continuous removal of solids. This finding has important implications for the design of the high-temperature industrial reactors and selection of ranges of melt chemistries and conditions that can be used. This finding means that temperatures below the liquidus can be selected for some processes, resulting potentially in significant savings of energy and increases in throughput of pyrometallurgical reactors. The findings are generic and are not limited to the specific chemical systems reported in the article.

Cast Steels for Creep-Resistant Parts Used in Heat Treatment Plants

Abstract Creep-resistant parts of heat treatment furnaces are in most cases made from high-alloyed chromium-nickel and nickel-chromium iron alloys, both cast and wrought. This paper presents the types of casting alloys used for this particular purpose, since the majority of furnace components are made by the casting process. Standards were cited which give symbols of alloy grades used in technical specifications by the domestic industry. It has been indicated that castings made currently are based on a wider spectrum of the creep-resistant alloy grades than the number of alloys covered by the standards. Alloy grades recommended by the technical literature for individual parts of the furnace equipment were given. The recommendations reflect both the type of the technological process used and the technical tasks performed by individual parts of the furnace equipment. Comments were also made on the role of individual alloying elements in shaping the performance properties of castings.

Sensitivity analyses of furnace material properties in the Czochralski crystal growth method for silicon

Reliability of the numerical simulation results strongly depends on the input data, in particular on the thermo-physical properties of the furnace components, e.g. graphite thermal conductivity and steel surface emissivity. Uncertainties are always involved in the measurement of these parameters. A set of global 2D simulations has been carried out in order to investigate the impact of each property on the growth conditions in Czochralski silicon growth furnaces. The results indicate that steel emissivity and felt conductivity have significant impact on the calculated thermal field and energy consumption.

Electric Arc Furnace Based on Fuzzy Neural Network Control System and MATLAB Simulation

EAF steelmaking is a complex physical and chemical reactions，has Highly nonlinearity, time variability and strong coupling. As the electrode's contact with the charging circuit, charging the collapse of the gasification furnace components and liquid metal boiling and other factors, often result in dramatic fluctuations in arc current. At this point we need to quickly adjust the location of electrodes, so that arc current stable base on this within a certain range. This article in the fuzzy control and neural network’s foundation,will study a kind based on three-phase consciousness electric arc furnace predictive control new method, Using the fuzzy neural network control adjusting electrode, further enhancing the effectiveness of electric arc furnace’synthesis movement.