Melt corrosion of oxide and oxide–carbon refractories

Abstract

reactant contact the refractories' composition, physical texture, and product transport nature of the bond Penetration and dissolution mechanisms are phase (which is the first to be penetrated by liquid), reviewed for predominantly single phase oxide, two phase oxide, and oxide-carbon composite and the characteristics of melt and reaction products refractories by liquid silicates. Theoretical models affect the rate of the reaction. Consequently, to underof these processes, as well as static (sessile drop, stand the corrosion mechanisms, refractories microdipping, and crucible) and dynamic (rotating finger structures (in particular, composition and texture of and rotary slag) experimental tests, along with grain and bond phases, the linkage of grain to bond, their practical limitations are considered. Direct and internal or residual stress), melt properties (congruent or homogeneous) attack involves (especially composition and viscosity as a function of dissolution of a solid into a liquid with no temperature), and their wetting and interaction at intermediate solid phase leading to active high temperatures should be examined together. corrosion. Indirect (incongruent or heterogeneous) Almost all liquid metals do not wet ceramics while attack leads to formation of one or more new solid phases at the original solid/liquid interface. This almost all slags, glasses, and fluxes do, so attack at may lead to passive corrosion. Examples of direct the slag line, where the less dense (typically silicate) and indirect attack in a range of refractory-liquid liquid floats on the denser metal liquid, is frequently systems are described highlighting the critical a problem. Carbon based ceramics are not wetted by influence of the composition and hence viscosity silicate liquids, behaviour which has led to their of the local liquid adjacent to the solid. Penetration extensive use in iron-and steelmaking refractories.and corrosion can be controlled either through the Wetting behaviour gives an indication of penetration local liquid composition via the refractory or the (simple permeation via open porosity without chemibulk liquid or by microstructural control of the cal reaction) but not attack or corrosion (penetration refractory by, for example, internal generation of and chemical reaction). This review begins by examindense layers or external deposition/generation of passive coatings. IMR/325 ing simple theoretical treatments of these phenomena. Much research has examined refractories in different

Placas de refratários aluminosos do sistema de válvula gaveta em panela de aciaria: avaliação e estudo de caso

“…Esta fase indicou reação entre o óxido de ferro e o óxido de magnésio, sendo o primeiro advindo possivelmente da oxidação do ferro metálico (após lingotamento) e/ou da escória, e o segundo proveniente da escória (e/ou do revestimento refratário). É interessante destacar a ausência de compostos característicos da corrosão entre escória e a placa como os aluminatos de cálcio, os quais possuem baixa temperatura de fusão e são comumente encontrados na corrosão de refratários aluminosos [18]. A ausência de compostos formados a partir de componentes da estrutura da placa (Al 2 O 3 ) indica somente uma reação na face exterior (magnesioferrita), provavelmente sem grandes consequências à estrutura da peça, desde que sua infiltração seja pequena.…”

Materials Challenges for Advanced Combustion and Gasification Fossil Energy Systems

“…The mechanisms of slagrefractory interactions causing refractory degradation include chemical dissolution, mechanical erosion, and structural spalling. [30] The nature of the mineral matter was found to vary with different fuels, imparting different chemical and physical properties to the slag. High chrome oxide refractory liners are used to line gasifiers because of their superior resistance to attack.…”

Degradation of Alumina and Magnesia Chrome refractory bricks in Portland cement kiln – Corrected version*

“…These interactions are severe and make the brick more sensitive to thermal shock, mechanical stress and erosion, which can lead to a loss of integrity of the brick structure. Chemical degradation is due to mutually observable phenomena in the brick and in the liquid phase as the dissolution of refractory components in the liquid slag [2], the diffusion of slag components in refractory phases [3,4], and the formation of new phases [5,6]. This later phenomenon is particularly desirable in the event that the new formed phases lead to more stabilization by volume expansion of the brick and densification which can be achieved during temperature variations in atmosphere kiln.…”

“…Furthemore, Diouri and al. [7], showed that the infiltration of cement phases, especially ȕ-Ca 2 More recent study of Recio Dominguez and all. [9] has revealed that the attack take place due to the action of the potassium, sulphur, lime and chlorine.…”