Refractories Definition & Classification Tina Stendal Svendsen Product Manager 1

Definition of Refractory “ non-metallic ceramic material or product whose chemical and physical properties allow it to be used in a high temperature environment” 2

Application of Refractory Lining of plants for thermal processing (melting, firing and heat- treatment furnaces) e.g.: Iron and steel Cement and lime Glass and ceramics Chemical and petrochemical Heat- and power (waste and biomass) Heat-insulation Functional products: shaped products with an additional function during service 3

Classification due to product type Refractory Monolithics (unshaped) CastablesDenseInsulatingMortars Heat- insulating Bricks (shaped) Functional products 4

Classification due to bond type and cement content Dense castable Hydraulic bond Conventional Traditional castables Gunning ‘high technology’ Low cement 1.0-2,5% CaO Ultra low cement < 1.0% CaO No cement < 0.2% CaO Chemical bond 5

Classification according to type of chemical composition Focus on Alumina-Silicate refractory products based on: Al 2 O 3 (alumina) SiO 2 (sillica) The variants of alumina-silica castables are formulated by: Different amounts of Al 2 O 3 and SiO 2 in raw materials Different crystal structures of raw materials Different properties of raw materials Grain size distribution and matrix products 6

Composition of dense refractory castables Aggregates (> 45 μm) 65-75% Croase; build the foundation of the castable Fine; fill the voids between the croase aggregates Matrix products (< 45 μm) 25-35% Fill the micron size voids, affects workability and strength Binders; hold castable together until thermal sintering occurs Additives; reduces water or control setting time 7

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Raw materials characterization Chamotte (calcined fireclay): 30-45% Al 2 O 3 Alkali resistance Andalusite: 50-60% Al 2 O 3 Shock resistance Bauxite: 80-90% Al 2 O 3 Abrasion resistance Corrundum (alumina): 99% Al 2 O 3 High refractoriness Syntetic mullite (calcined bauxitic clay): 60-80% Al 2 O 3 Strength Silicon carbide: SiC High thermal conductivity 10

High quality refractory raw materials: Are subjected to Calcination (minerals fired at °C) Reduces the amount of impurities Low porosity High density Chemically stable Increased refractoriness Low iron (Fe 2 O 3 ) content (minimize the risk of CO-attack) Low alkali content (minimize the formation of low-melting-temp. glasses) Be aware of recycled materials! 11

Summary Refractory materials can be classified according to e.g. type, cement content, application/installation technique and the main raw material We will focus on Alumina-Silicate castables Dense castables contains approx. 70% aggregates and 30% matrix products The variants of alumina-silicate castables are achieved by a diversity of different raw materials with different properties Both natural minerals and calcined minerals are used Fractions (and optimal particle distribution) are obtained by crushing, sieving and grinding/milling High quality raw materials performs better! 12