First heat-up of 1D multi-layer walls and 2D geometries consisting of refractory concrete

Abstract Furnaces are frequently lined with low permeability refractory concrete. During the first heat-up process of a relined furnace, high vapour pressures inside the initially wet refractory concrete can result in an explosive destruction of the concrete structure. In this article, the first heat-up process of complex geometries is investigated by modeling and further by a large-scale experiment. The article bases on a previous one, concerning the first heat-up of a one-dimensional single layer wall. The simulation of the first heat-up process of a one-dimensional three-layer wall shows the occurrence of several drying fronts inside the wall. Even if the wall is heated only from one side, two drying fronts appear at both surfaces, moving deeper and deeper inside the wall. Four further drying fronts are arising at the two boundary surfaces, moving in contrawise directions. The simulation shows that the first boundary surface is drying even faster than the first concrete layer, although this layer is arranged in front of that boundary surface. Further the simulation predicts a constant temperature slightly below 100° C at the wall's unheated surface over a large period of time. The model is validated by a large scale experiment which confirms both observations. Further, two more complex geometries are investigated by the aid of a two-dimensional model. One of these geometries, a corner, needs much more time for drying compared with the drying process of a (multilayer-) wall or an exposed edge. This is mainly caused by the slow heat transfer into the corner's core. The second two-dimensional geometry, the (exposed) edge shows the highest pressure maximum of all investigated geometries, caused by the fast heat transfer into the geometry's exposed needle. For both two-dimensional geometries, optimized (pressure-driven) heat-up curves are calculated. These curves are effecting the fastest possible heat-up process without exceeding a given pressure limit. The curves of both geometires are differing significantly from each other and from those ones calculated for a single-layer wall of equal thickness.