In cement production, which involves the production of cement clinker in rotary kilns, the main refractories used are magnesia-spinel bricks. These bricks may suffer infiltration by the clinker liquid phase, resulting in the corrosion of the spinel and the formation of low refractoriness mineralogical phases, such as the Q phase (C 20 A 13 M 3 S 3 ), which compromises refractory performance. Thus, the aim of this work is to correlate the infiltration resistance of magnesia-spinel bricks made from different grades of magnesia by clinker collected in three different cement plants (A, B and C). The purity of magnesia, besides its physical properties, strongly influences the properties and the infiltration resistance of magnesia-spinel bricks; as such the use of high grade magnesia is essential for producing high performance refractories.

ResumoA necessidade de melhorar as propriedades dos refratários monolíticos para resistir às condições operacionais cada vez mais severas e instáveis das casas de corrida de Alto-Forno tem sido um grande desafio para os fornecedores de refratários de maneira a garantir a segurança dos canais de corrida e sua disponibilidade para operação. Este trabalho apresenta as propriedades de novos concretos refratários Al2O3-SiC-C (aplicados por vibração ou bombeamento/projeção a úmido) desenvolvidos para resistir ao severo mecanismo de corrosão que ocorre na linha de gusa de canais principais e que exige constante atenção dos operadores das casas de corrida. Testes realizados com os novos concretos refratários em canais de corrida principais de diferentes Altos-Fornos de grande produtividade revelaram uma significativa diminuição da velocidade de desgaste do revestimento refratário na linha de gusa oferecendo uma condição operacional segura e confiável às casas de corrida. Palavras-chave: Canal de corrida; Concreto refratário; Velocidade de desgaste; Resistência a corrosão. REFRACTORY CASTABLES FOR CRITICAL BLAST FURNACE MAIN RUNNER OPERATING CONDITIONS AbstractThe need to improve the monolithic refractories' properties to endure the increasingly severe and unstable Blast Furnace casthouse operating conditions has been a major challenge for refractory suppliers in order to guarantee the runner's safety and its availability for operation. This paper presents the properties of new Al2O3-SiC-C refractory castables (installed by vibrating or pumping/shotcreting) developed to endure the severe corrosion mechanism that occurs at the main runners' metal line which constantly requires a special attention of casthouse operators. Field tests carried out in different large-scale production Blast Furnaces main runners revealed a significant decrease of refractory lining wear speed at the main runner metal line using the new refractory castables developed leading to a safe and reliable Blast Furnace casthouse operation.

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The need to adjust the monolithic refractories to increasingly severe and unstable Blast Furnace casthouse operating conditions has been a major challenge for refractory suppliers in order to guarantee the runner's safety and its availability for operation. This paper presents the properties of a new robust single line Al2O3-SiC-C refractory castable developed to endure the severe operating conditions that main runners are facing in today's Blast Furnace casthouse scenario. Practical results during almost one year of testing revealed a significant lower wear speed of the new refractory lining when compared to a standard product.