The effect of the addition of fine andalusite particles in refractory bricks on gaseous corrosion

Abstract

How would you……describe the overall signifi cance of this paper? The corrosion of refractory materials in anode baking furnaces can be reduced by the addition of andalusite in the matrix of the bricks.…describe this work to a materials science and engineering professional with no experience in your technical specialty? This work describes a study of the deterioration of refractory materials used in anode baking furnaces. The major mechanism of the corrosion is gaseous sodium corrosion. A solution to reduce the corrosion by sodium vapors is to add andalusite into the bricks.In the past, the mechanisms of corrosion in refractory materials used in the fl ue wall of anode baking furnaces have been poorly understood. To better understand the processes of degradation, a study of corroded refractories from anode baking furnaces was conducted. This study found that all refractory bricks contain fi ne andalusite particles in the matrix and fi reclay as aggregates. The fi rst stage of corrosion is the penetration of gaseous sodium, coming from recycled anodes, through the porosity of materials. Then, at high temperature, sodium becomes oxidized and is included in the liquid phase. The sodium-rich liquid phase corrodes the refractory material, in particular mullite networks. To understand why the andalusite mineral is used in the refractory materials, a corrosion test able to simulate the gaseous corrosion of materials at laboratory scale was developed. Several recipes, composed of andalusite or fi reclay, were submitted to the corrosion test. The microstructural observations showed that the matrix is more sensitive to corrosion. Thus, the use of a raw material such as andalusite in the matrix is advised in order to reduce the gaseous sodium corrosion of fi reclay based bricks.

Investigation of Spent Refractory Lining in an Anode Baking Furnace

“…An important part in the process of aluminum electrolysis are the production and quality of the pre-baked carbon anodes, where the main production principle is quite similar from plant to plant [1][2][3]. The most significant variation with respect to furnace design is whether the furnace has an open or closed top section [4].…”

“…Due to the high temperature, cryolite contaminations in the anodes will evaporate forming gaseous NaF and NaAlF4. The combination of thermal cycling and chemically harsh environments results in refractory degradation and eventually the need for the refractory wall to be replaced [3,6].…”

“…Investigations of degradation of refractory lining in anode baking furnaces have been reported in several works [1][2][3]6]. These investigations have shown mineralogical changes close to the anode side of the refractory, in addition to blackening of the refractory caused by carbon deposition.…”

“…These investigations have shown mineralogical changes close to the anode side of the refractory, in addition to blackening of the refractory caused by carbon deposition. Gaseous sodium and fluorides were proposed to react with the lining forming a liquid phase, which during cooling forms a glass phase with a lower solidus temperature compared to the original refractory lining [1][2][3]. This mechanism causes the thermomechanical properties of the refractory lining to change, which eventually leads to deformation and degradation of the lining.…”

“…This mechanism causes the thermomechanical properties of the refractory lining to change, which eventually leads to deformation and degradation of the lining. The interaction of similar materials with sodium aluminum fluorides has also been studied in depth in relation to the refractory lining in electrolysis cells [1][2][3][6][7][8][9][10][11][12][13][14][15][16].…”