Symposium CP
Refractory Materials Challenges to Meet Current and Future Industry Needs
ABSTRACTS
CP-1:IL01 Effectiveness and Application of Novel Calcium Magnesium Aluminates in Refractory Bricks and Monolithics
C. Wöhrmeyer, J. Gao, C. Parr, M. Szepizdyn, P. Edwards, C. Deteuf, IMERYS, Oberhausen, Germany
Innovative raw materials are a driving force for more sustainable refractory products with longer service life and lower specific refractory costs. Novel calcium magnesium aluminate (CMA) raw materials support this goal and achieve it in different applications through specific functionalities that are reviewed in this paper. CMA is produced from sintered multi-phase clinker containing micro-MA-spinel and CA-phases. Applied as binder (CMA72) in high alumina castables for steel ladles it has shown its effectiveness against slag penetration and corrosion. The micro-spinel and its unique distribution are the main contributor to this effect. A CMA-based additive (MagArmour), introduced into MgO-C bricks for steel ladles has improved their service life through an in-situ formation of a surface coating on the bricks which better protects them against carbon burnout and slag penetration. MagArmour applied as aggregates in high alumina bricks and monolithics for steel ladles has resulted in significantly lower specific refractory consumption. Here, improved resistance to thermal cycling plays a key role. The micro-porous structure of the MagArmour is at the source of this effect and also results in a density reduction which reduces the heat loss through the refractory lining.
CP-1:IL02 Synthesis of Aluminum Silicon Carbide and its Application
Hatsuo Taira, T. Maeda, S. Uchida, Okayama Ceramics Research Foundation, Bizen, Okayama, Japan
Al4SiC4 is synthesized mainly using metals Al, Si, and natural flake graphite as starting materials. For the purpose of reducing the raw material price, Al4SiC4 was synthesized by replacing the natural flake graphite raw material with carbonized natural ligneous carbon and silicon sludge. The morphology of Al4SiC4 particles which synthesized from ligneous carbons and silicon sludge was characteristic having a hexagonal plate-like structure. We report the results of adding Al4SiC4 to various carbon-containing refractories. Al4SiC4 shows the improvement of the oxidation resistance additive of carbon containing refractories as well as the densification of microstructure.
CP-2:IL01 ATHORNA: An Innovative Device for Monitoring Thermal Shock Behaviour of Refractories Combining Various In-situ Advanced Measurements
M. Huger1, R. Kaczmarek1, R. Oliveira2, M. Mouiya1, 3, J.-C. Dupré4, P. Doumalin4, N. Tessier-Doyen1, Y. TAMRAOUIA3, O. Pop5, 1University of Limoges, UMR CNRS 7315 - IRCER, Centre Européen de la Céramique, Limoges, France; 2University of Coimbra, ISISE Inst., Dept. of Civil Eng., Coimbra, Portugal; 3University Mohammed VI Polytechnic, MSN Dept, Ben Guerir, Morocco; 4University of Poitiers, Pprime Inst., UPR CNRS 3346, Futuroscope Chasseneuil, France; 5University of Limoges, GC2D, Egletons, France
ATHORNA (Advanced measurements for in-situ THermo-mechanical monitORing of large sample uNder thermal grAdient) aims to develop an instrumented thermal shock bench based on innovative measurements, which target the in situ monitoring of thermomechanical behaviour of a refractory material subjected to thermal gradients. The objective is to suddenly heat the centre of the front face of a disk shape sample whose back face is concomitantly monitored by both an infrared camera, and an optical stereo system composed of 2 cameras to ensure an accurate monitoring of deformation field by digital image correlation method (DIC). In addition, the occurrence of any cracks resulting from thermal shock within the specimen is monitored through both: i) six acoustic emission sensors distributed peripherally, in order to allow a spatiotemporal location of acoustic emission events and ii) a direct measurement of local displacement discontinuities using a suitable refined image correlation technique (2P-DIC). Various refractory materials exhibiting significant differences in thermomechanical properties have been investigated. The obtained results in terms of quantitative strain fields evolutions and crack propagation are discussed and interpreted in relation with microstructural design of materials.
CP-2:IL02 In Situ Raman Analysis of Refractory Materials
M.R. AMMAR, ICMN-CNRS, UMR 7374 Univ. Orléans, Orléans, France
Raman spectroscopy is the inelastic scattering of light by matter. Being highly sensitive to the physico-chemical properties of materials as well as the enviromental effect that modifies these properties, it becomes an important tool in a variety of domains. The method is particularly suitable for use in difficult environmental conditions such as those of refractory materials. Owing to its specific characteristics, e.g. the samples can be micrometric in size and particularly the remote of the Raman probe-head by optical fibres. We will focuss here on the use of Raman spectroscopy in situ in specific environments and/or at high or very high (about the 2000°C range) temperatures. The performances of this optical method will be exhibited through some recent examples such as the damage of refractory materials by sp2 carbon in reducing conditions (H2/CO) at 600°C, the characterization of phase transitions, structural modification and chemical transformations of several refractory oxides and sp2 carbon whether by temporal filtering or by spectrally moving away from the maximum of the thermal radiation.
CP-2:L04 Characterization of Aluminium Titanate based Materials: Thermomechanical Properties related to Microstructure
M. MOUIYA1, 2, N. Tessier-Doyen2, Y. Tamraoui1, J. Alami1, M. Huger2, 1Materials Science, Energy and Nanoengineering Dept., University Mohammed VI Polytechnic (UM6P), Ben Guerir, Morocco; 2University of Limoges, Inst. of Research for Ceramics (IRCER), UMR 7315, European Ceramics Center, Limoges Cedex, France
Compared to conventional ceramics, aluminium titanate (Al2TiO5) materials devoted to thermal shock applications exhibit a significant strain before rupture and a high crack growth resistance. Dopants such as SiO2, MgO and Fe2O3 are usually added into a mixture of Al2O3 and TiO2 synthetized at high temperature to inhibit the decomposition of Al2TiO5. Indeed, the strong thermal expansion anisotropy promotes microcracking during cooling and consequently leads to the development of toughening mechanisms very efficient for the improvement thermal shock resistance. The aim of this work was to investigate the thermomechanical properties of a commercial aluminium titanate (AT) material doped with silica through various techniques of characterization operating at high temperature, such as tensile strength, long bar mode method, acoustic emission and dilatometry. The fracture behaviour was also evaluated at room temperature by using Wedge Splitting Test (WST) coupled with 2P-Digital Image Correlation (DIC). A more effective characterization of thermal shock through an instrumented home-made equipment was performed in order to understand the more sensitive parameters involved in the high thermal shock resistance of aluminium titanate refractories.
CP-3:IL01 Refractory Wear and Freeze Lining Formation in Platinum Group Metal Smelters
A. Garbers-Craig, Centre for Pyrometallurgy, Department of Materials Science & Metallurgical Engineering, University of Pretoria, Pretoria, South Africa
PGM (platinum group metal) recovery involves concentration, smelting, converting and refining stages, which are similar to the processing steps in copper and nickel production. The main differences in smelting process conditions between these industries are the higher operating temperatures (slag temperatures up to 1700 degC) and higher matte superheats (up to 650 degC) associated with PGM smelting. The high operating temperatures are the result of the elevated chromium content of the concentrate blend that is fed to the smelter. Higher operating temperatures and higher heat fluxes to the sidewalls have necessitated greater innovation in lining designs and choice of refractory materials. Magnesia-based bricks were used in the sidewalls and hearth of the first PGM smelters. These bricks were subsequently replaced with magnesia-chromite bricks. More recent developments include the use of alumina-chrome bricks in specific areas of the smelter, and with the introduction of sidewall copper cooling, the use of graphite blocks. This paper describes refractory wear mechanisms in the smelter due to slag corrosion and matte penetration. It also describes how wear of the copper coolers are limited through the use of graphite blocks and the role that is played by the attached freeze lining.
CP-3:IL02 Multi-component Refractory Systems Reinforced for Engineering Resilience
D.G. Goski, M.J. Lambert, Allied Mineral Products, Inc., Columbus, OH, USA
Heterogeneous, multi-component refractory systems have been designed to provide increased reliability and more predictable modes of failure. Common failure modes of precast monolithic refractory shapes were analyzed. High temperature reinforcement structures were developed with modelling validation and field testing. The results are application specific solutions using fiber wound inserts in precast refractory shapes components which provide longer operational life and more predictable failures.
CP-3:IL04 Corrosion of Refractories by Metallurgical Slags: Keys Issues and Mechanisms – Steel Ladles Applications
J. Poirier, CEMHTI-CNRS, University of Orleans, Orleans, France
The corrosion mechanisms of MgO-C refractories are different depending on the slag composition. With CaO-SiO2 slag, the dissolution of MgO is predominant. The wear rate depends on the under saturation in MgO of the slag and is reduced when silicates or silico-aluminates of CaO or MgO precipitate at the slag-refractory interface; With CaO-Al2O3 slag, corrosion results from the slag infiltration and erosion of the matrix. The microstructure of the matrix is therefore essential. For the MgO-C qualities with Al, the dissolution of spinel controls corrosion and a slag enriched in Al2O3 is less aggressive. Corrosion also depends on the flow rates of the slag and is significant slowed down if the stirring is less strong and if suspended solids increase the slag viscosity. A few amount of FeO in the CaO-Al2O3 slag gives rise to an additional reaction which involves Mg vapors formed by the reduction of MgO by C. A protective layer of MgO is formed at the hot face,which is why a very deoxidized slag is more aggressive. With rich FeOx slag, the carbon oxidation becomes significant and promotes erosion/corrosion of the matrix. High levels of FeOx (> 30%) have a corrosive effect. At lower levels (10-15%), the iron oxides promote the formation of an magnesio-wustite protective layer.
CP-3:IL05 Self-protecting Mechanism of Magnesia Refractory in Electric Arc Furnace (EAF) Operation Conditions: Challenges of Active Use of Direct Reduced Iron (DRI) as an Alternative iron Source
Jinsung Han, Steelmaking Production Technology Team, Hyundai Steel, Dangjin, South Korea; Jungho Heo, Department of Materials Engineering, KU Leuven, Kasteelpark, Leuven, Belgium; Joohyun Park, Department of Materials Science and Chemical Engineering, Hanyang University, Ansan, South Korea
Interfacial reactions between the EAF slag and the magnesia refractory as a function of DRI addition were investigated at 1550 oC. MgO solubility increases with increasing DRI content by decreasing basicity (i.e., CaO/SiO2 ratio), which is due to an increase in SiO2 supplied from DRI. The measured MgO content was always lower than the theoretical MgO saturation level irrespective of DRI content because the magnesiowüstite (MW) intermediate layer, which formed at the slag/refractory interface, retarded the direct dissolution of the refractory by acting as a self-protective layer. The thickness of the MW intermediate layer and dissolution depth were proportional to DRI content. Several kinetic parameters were estimated, including the dissolution rate constant of the MW intermediate layer, the dissolution rate of the MgO refractory, and the rate constant of MW growth. The slag-refractory interfacial reaction was simulated using thermochemical computing software, FactSageTM7.0. The computations were comparable to our experimental findings. If a large amount of DRI must be used in the EAF process, then MgO content in the slag should be at the saturation limit at first, which accelerates growth of the MW intermediate layer.
CP-4:IL01 New Approach and Numerical Method to Compute Reactive Mass Transport in Porous Media Coupled with Thermomechanical Effects
T. SAYET1, C.-B. Trang1, A. Batakis2, E. de Bilbao3, E. Blond1, 1Univ. Orléans, Univ. Tours, INSA CVL, Laboratory of mechanics Gabriel Lamé, EA7494, Orléans, France; 2Univ. Orléans, Institut Denis Poisson, UMR CNRS 7013, Orléans, France; 3Univ. Orléans, CEMHTI, UPR CNRS 3079, Orléans, France
It is known that the degradation refractory processes are mainly related to high temperatures and aggressive working environments. In industrial plants, refractories are in contact with complex chemical components such as slags, fumes, ashes, etc. An optimal design of the refractories rests on a multiphysics model which accounts for the significant physics that take place in the real process. Many authors have improved the multiphysiques modeling by considering thermomechanical couplings or thermochemical couplings. These approaches often neglect the impact of the reactive transport on the thermomechanical behavior leading to inaccurate stress fields and therefore unreliable lifespan of refractory materials. Classical numerical approaches accounting for the transport phenomena are based on the resolution of partial differential equations that requires a high computational cost and are often subjected to spurious oscillations. In this work, a new approach and numerical method based on gradient percolation theory is sequentially coupled with finite element calculation using User Element subroutine in Abaqus. This numerical method provides a tool able to account for thermal, chemistry, transport and mechanics in order to reach a fully predictive simulation.
CP-4:IL03 Modelling and Simulation of Alumina Dissolution by Slag with Aluminates Formation
E. de Bilbao, CEMHTI, CNRS UPR3079 - Univ. Orléans, Orléans, France
The understanding of the ceramic powders reactivity at high temperature remains for outstanding importance. This is the case of refractory ceramics, operating at high temperature. Nevertheless, their understanding requires the development of new in situ experimental techniques well adapted to these extreme conditions as well as modeling and simulation. This talk will present high-temperature time-resolved XRD techniques used to study phase transformation in solid/liquid reaction. High-temperature X-ray diffraction was used to follow the formation of aluminates monomineral layer formation in the corrosion of alumina by Al2O3-CaO-SiO2 slag. Using a diffractometer equipped with a high temperature chamber and a curved position sensitive detector makes it possible to quantify the contents of CaAl2O4, CaAl4O7, and CaAl12O19 while Al2O3 powder reacts with CaO-Al2O3-SiO2 molten oxides at temperatures up to 1600°C. A numerical simulation was further carried out based on a dissolution model at the interface of the outer layer with the slag combined with a solid diffusion/reaction model occurring through the inner layers and at their interfaces. The modeling allowed to simulate the non congruent dissolution of alumina particles as well as the layer formation/growing.
CP-4:L04 Periodic Thermomechanical Modelling by the Discrete Element Method of Microstructural Aspects within Model Refractory Materials
Q. PLEDEL1, M. HUGER1, D. ANDRE1, P. DOUMALIN2, 1University of Limoges, Institute of Research for Ceramics (IRCER), UMR 7315, European Ceramics Center, Limoges Cedex, France; 2University of Poitier, Institute Pprime UPR 3346, CNRS, ENSMA, Futuroscope Chasseneuil Cedex, France
Refractories are complex materials, subjected to harsh solicitations (high temperature, thermal shock). To withstand such conditions, optimizing their behaviour requires a better understanding of their physical macroscopic properties in relation with microstructural aspects. In this paper, numerical models are carried out in order to better understand the influence of microcracks, resulting from thermal expansion mismatch between constituents, on the non-linear stress-strain behaviour. New developments are implemented on GranOO, a software using the discrete element method (DEM). The description of macroscopic properties of the material is ensured by homogenization methods considering local phenomena taking place at microstructure scale. For that, periodic boundary conditions are applied to a Representative Volume Element representing microstructure. Then, using DEM, a cooling test is applied to the model to reproduce local thermal damage and analyse macroscopic mechanical properties such as Young's modulus and Poisson's ratio as a function of temperature. The anisotropic characteristics of certain local parameters such as thermal expansion coefficient are also under investigation. Such developments ensure a better understanding between microstructure and macroscopic behaviour.
CP-5:IL02 DEM Modelling to Investigate the Impact of Microstructure on Refractory
D. André, T.-T. Nguyen, F. ASADI, M. Huger, University of Limoges, IRCER, UMR CNRS 7315, Limoges, France
The present study aimed at investigating the relationships between the microstructure of refractories and their thermomechanical properties in order to increase their thermal shock resistance. In particular, numerical modeling were carried out in order to better understand the design of microstructure involving damages due to thermal expansion mismatch during processing. For this purpose, experimental results on simplified materials were used as reference for this numerical approach. In order to obtain quantitative results of complex phenomena, new developments of an existing discrete element modeling platform, namely GranOO, were carried out. This DEM approach was then applied to reproduce thermal damages during cooling of simplified materials and to examine their effects on macroscopic properties. The obtained DEM results of evolution of Young’s modulus and thermal expansion coefficient as a function of temperature exhibited similar tendencies with experimental results.
CP-5:IL03 Contributions to Crack Propagation in Coarse Grained Refractories
D. Gruber, H. Harmuth, Chair of Ceramics, Montanuniversitaet, Leoben, Austria
In coarse grained refractories three kinds of crack propagation are observed. Cracks propagate along the interface of grains and matrix, in the matrix and through grains. Microscopic investigations on fractured specimens showed that for refractories with reduced brittleness the share of crack propagation along the interface of grains and matrix is increased. Reason is the micro crack network in brittleness reduced refractories. Finite-Element simulations were carried out to show the formation of micro cracks in the refractories industrial production process and furthermore to investigate the effect of interface properties between grains and matrix on the crack propagation. Simulation results indicate a significant influence of the model parameters specific fracture energy, strength and heterogeneous strength distribution on the crack propagation and on the energy consumption of the entire fracture process. Next to the creation of surface possible sources of energy consumption are friction between crack faces and sliding of grains. Ongoing research is carried out to observe crack propagation in situ and to set up discrete element models to consider mentioned processes in simulation.
CP-5:IL04 Towards Corrosion-resistant Refractories
SHAOWEI ZHANG, University of Exeter, Exeter, UK; JUNFENG CHEN, Wuhan University of Science and Technology, Wuhan, China
During service, refractory materials are required not only to tolerate high temperature and mechanical stresses but also to resist chemical attacks from corrosive liquids such as slags and fluxes. The attack on a refractory is very complicated, involving simultaneous chemical corrosion and physical/mechanical wear, though the former generally shows more serious effects than the latter. The former not only affects negatively the service performance/lives of refractories, but also affects production processes of other target materials and their final quality (e.g., in the case of steel-making). In this talk, the recent work in the presenter's group on refractories corrosion will be reviewed. The presentation starts with a brief background introduction, which is followed by a description of the techniques/methodologies used for corrosion tests (for both aggregates and bulk materials) and simulations. The third part discussed the main corrosion mechanisms and the effects of key factors on corrosion of various systems of refractories (e.g, carbon-containing refractories). Finally, novel strategies for designing more corrosion resistant refractories will be suggested and demonstrated (e.g., engineered corrosion resistant aggregates, and super non-wetting surfaces).
CP-6:IL01 Smart Bubbles for Cleaner Metals and Advanced Insulating Refractories
L.O.Z. Falsetti, T. dos Santos Jr., V.C. Pandolfelli, Materials Engineering Department, Federal University of São Carlos, São Carlos, SP, Brazil
Interfacial energies involved in capturing and removing non-metallic inclusions are analogous to the ones for producing foams stabilised with ceramic particles, a promising method to make porous refractories. Ceramic inclusions, generally deriving from refractory fragments, entrapped slag, or even products from the deoxidation stage, are typically withdrawn through inert gas bubbling along with secondary metallurgy processes. Although kinetic aspects of inclusion removal have been widely studied, little attention has been given to thermodynamic ones. On the other hand, stability of ceramic foams to produce porous refractories has been studied through thermodynamic fundamentals. Therefore, this work points out fundamentals to provide the change in interfacial energies while capturing a particle considering the curvature of the solid and gas phases and the bubble expansion during the attachment. The results suggested a coupled thermodynamic-kinetic limit to the size of particles that can potentially be captured by ascending bubbles and stabilize them for designing better high-temperature insulating ceramics. Alternative techniques to overcome this limit are also presented.
CP-6:IL03 The World of Monolithics: A Review of Last Developments and Way of Installation
P. TASSOT, REFRATECHNIK Steel GmbH, Düsseldorf, Germany
Refractories are the DNA of the iron and steel, cement, foundries, even incineration or petrochemical processes. They have a direct influence on the quality of elaborate grades in the control of solute elements as well as the prevention of non-metallic inclusions. The reduction in term of NOx /CO2 is the latest challenge for productive industries. The first image coming when speaking about refractory materials is bricks that have dominated the market for years, but the higher degree of sophistication and performance of the monolithics in the last decades has strongly contributed to show the wide range of materials as both very attractive on the market and an efficient alternative for the shaped material. Monolithics today have evolved from the simple concrete used in construction with the introduction of high-tech raw materials in their structure, allowing for high mechanical resistance without risk of explosion and high corrosion resistance. Monolithics are usually not ready-to use-materials, and as more sophisticated products, their optimal performance depends critically on the condition of their installation. Innovative devices supporting their installation strongly contribute to the success of these unshaped materials.
CP-6:IL04 Freeze Linings vs Brick Linings in the Non-ferrous Metallurgy
A. Malfliet, S. Van Winkel, L. Zhang, B. Blanpain, Department of Materials Engineering, KU Leuven, Heverlee, Belgium
The freeze lining concept is nowadays an acknowledged alternative to refractory linings to increase the lifetime of metallurgical furnaces. Due to the several advantages it can offer, such as its ability to regenerate and perform under high-intensity conditions, it has found its application in both the ferrous and non-ferrous industry. However, similarly to refractory linings, proper management of the slag composition and temperature is important to ensure the integrity of the freeze lining. In this work, the behavior of refractory linings and freeze linings in non-ferrous metallurgical systems is compared and the ability of a freeze lining to adapt to alternating process conditions is discussed.
CP-6:IL05 Carbon Bonded Foam Structures – Applications as High Temperature Reactive Filters in Combined Refining Filter-systems for Improved Steel Cleanliness
C. Aneziris, T. Wetzig, E. Storti, J. Hubalkova, P. Gehre, TU Bergakademie Freiberg, Germany
There exists an increasing pressure on the metal making and metal using industry to remove solid and liquid inclusions and thereby to improve metal cleanliness. It is well known that size, type and distribution of non-metallic inclusions in metal exert considerable effects on the mechanical properties of the cast products. A new generation of so called combined refining filter systems will be demonstrated based on carbon bonded reactive filters and carbon free oxide active filters. The metal melt comes first in contact with a reactive carbon bonded filter which generates gas bubbles in the melt as well as activates gas bubbles on the surface of the inclusions. As a result a kind of flotation of the inclusions towards the slag on the surface of the melt takes place. Further the high reactivity as well as the gas bubbles contribute to the agglomeration of the fine inclusions to big clusters which flow due to buoyancy forces to the surface of the metal melt. Inclusions which still remain in the melt are filtrated on the surface of oxide based active filters, which do not form gas bubbles but provide on their functionalized surfaces the same chemistry as the inclusions for a sufficient adhesion. With this approach a purification higher than 95 % can be achieved.
CP-6:L06 Field Assisted Sintering of Refractory Composite Materials Nb-/Ta-Al2O3 and the Influence on Material Properties
B. KRAFT, S. Wagner, M.J. Hoffmann, KIT, Karlsruhe, Germany; D. Endler, TU Bergakademie Freiberg, Freiberg, Germany
For several decades the investigation of materials suitable for high-temperature applications has been the subject of an intensive research. This field of interest is still undergoing further progress since the demands for long-term stable materials with ever improving properties and tailored designs are growing. In different industries like metal working or energy sector, an increase in efficiency and sustainability are key factors for a future development. Therefore, a new approach of coarse grained refractory composite materials based on a two step processing of pre-synthesized granules is investigated. The main goal is the development of non-shrinking Nb- and Ta-Al2O3 composite materials with increased thermal shock and creep resistance. This study deals with the first-step processing of fine grained starting powders using Field Assisted Sintering and the investigation of the resulting properties. The materials are examined for their mechanical and electrical properties depending on the composition and processing parameters. The microstructure is analysed to bring the experimental results of the macroscopic properties into context with features of the microscale.
CP-6:L07 Alumina Castables with Addition of Fibers Produced by Electrospinning
E. Storti1, A. Jirícková2, S. Dudczig1, J. Hubálková1, C.G. Aneziris1, 1Institute of Ceramics, Refractories and Composite Materials, TU Bergakademie Freiberg, Freiberg, Germany; 2University of Chemistry and Technology Prague, Department of Inorganic Chemistry, Prague, Czech Republic
In this work, cement-free alumina castables with different fiber additives were produced. The effect of commercial polypropylene fibers was compared to that of magnesium borate precursor fibers produced by electrospinning. The drying behavior of different batches was monitored by means of thermogravimetry. Elastic moduli were estimated in dried, sintered and thermally-shocked samples through the impulse excitation technique. The mechanical strength as cold modulus of rupture (CMOR) was measured by three-point bending tests. The open porosity and bulk density after sintering were assessed by water immersion. The thermal shock resistance was evaluated by heating the samples up to 950 °C and then quenching with compressed air. After 1 or 5 thermal shock cycles, the residual CMOR was determined. The microstructure of fracture surfaces was analyzed by electron scanning microscopy. The possible formation of new phases during thermal treatment was also assessed by means of XRD. Finally, the refractoriness under load was measured.
CP-6:IL09 The NCC Castables: Properties, Benefits and Prospects
HONG PENG, Elkem Silicon Products Development, Kristiansand, Norway
Calcium aluminate cement has been the most used hydraulic binder in unshaped refractory field due to fast setting, high mechanical strength, and good resistance to wide range of chemically aggressive environment. However, there are three major challenges of cement bonded refarctory castable: i) ageing due to the interaction of between cement, or castable mix and moisture from the environment; ii) explosive spalling during dryout caused by removal of free water and dehydration of cement, and iii) low refractoriness at high temperature due to low melting point phase formation with the presence of microsilica. The use of cement-free (CaO-free) binder has been the state-of-art for developing no-cement castables (NCCs) with high performance. Different CaO-free binding systems have been studied for many years, colloidal silica, hydratable alumina, and colloidal alumina to name a few. Colloidal silica has been the most promising alternative binder among colloidal binders in refractory industries. However, the use of colloidal silica-bonded of NCCs has been limited due to long set-time/complex set-behaviour and inadequate development of green strength. Handling, storage and use of liquid colloidal silica are logistic factors that must be dealt with, especially at lower temperatures. This paper reviews the recent advance in no-cement technology, mainly focusing on properties, benefits, and future prospect when calcium aluminate cement is replaced by dry-version silica- and spherical alumina- binder.
CP-7:IL03 Advanced 3D Laser Profile Techniques to Inspect and Analyze Hot Refractory Linings
R. LAMM, MINTEQ International GmbH, Duisburg, Germany
Abstract for Technical Paper at CIMTEC 2021, Germany Key words: Safety, Wear of Refractory, Ladle, 3D-Laserprofile-Measurement, Gap and Crack detection Advanced 3D Laser Profile Techniques to Inspect and Analyze Hot Refractory Linings Laser-measuring system specially designed for extreme hot environment allows immersion of a laser head into a hot vessel with surrounding temperatures up to 1200 °C and surface temperatures up to 1700°C. The system’s laser-beam rapidly scans the lining thickness of the entire surface and is collecting millions of data points in the vessel. Beside detection of gaps and cracks it measures the entire wear of the lining even the critical areas below the slag line which cannot be seen by conventional laser technology from outside the ladle. An unique method to measure refractory lining in hot vessels from inside the vessel allows the evaluation of the entire condition and optimize treatment and maintenance of the refractory lining in the vessel.
CP-8:IL01 Method for Determining the Thermal Expansion Coefficient of Ceramic Bodies and Glazes
W.M. CARTY, H. Lee, M. Ramisetty, Alfred University, Alfred, NY, USA
The Coefficient of Thermal Expansion (CTE) of glazes can be determined from the spacing of the cracks of a crazed glaze. Conversely, if the glaze CTE is known it should also be possible to determine the CTE of a body. The common method, that of making a sample of glaze and measuring the CTE via dilatometry, does not incorporate the body-glaze interaction, that causes a shift in the glaze chemistry, significantly altering the glaze CTE. This approach can be implemented by inking the crazed glaze and scanning the crazing pattern using a scanner. In this manner, the domain size can be equated to an equivalent diameter, to obtain an average CTE and standard deviation. The body-glaze interaction causes a shift in glaze chemistry that is dictated by the glaze application thickness. For a given heat treatment schedule the body-glaze interaction is a constant (but increases with boron in the glaze). This interaction causes an increase in the alumina and silica level in the glaze, reducing the glaze CTE. This means that the glaze application thickness contributes the glaze CTE. It is proposed that standard test tiles could produced that provide a ready quality control tool for determining the CTE of a glaze for industrial processes under production condition.
CP-8:L03 Innovative Refractory Solutions for Lining Furnaces in Energy Intensive Industrial Sectors
D. OLEVANO, P. Miceli, U. Martini, A. Di Donato, V. Ratto, RINA Consulting Centro Sviluppo Materiali S.p.A., Rome, Italy
Energy efficiency of energy intensive industries can be improved by innovative refractories for lining furnaces. Advantages in terms of energy savings as well as increased material life in service with positive impacts on decarbonization can be achieved by new refractory solutions. Innovative refractories were developed for withstanding the stressing operating conditions of three industrial sectors: power generation, ceramic, and steel. The activities of two EU financed projects, namely FLEX FLORES (RFCS No 754032) and VULKANO (H2020 GA No 723803), supported part of the work concerning the development of innovative refractories at higher performance for these sectors. The work explored concepts such as Compositionally Graded Materials, Additive Manufacturing (i.e., AM), and recycling of spent refractories. The refractories have been designed and produced both at lab and industrial scale. Positive results in terms of material performances have been obtained at pilot and demo plant level. This work provides key results arising from funded research and industrial projects and proposes research directions for the future.