Pressure driven heat-up curves – A numerical and experimental investigation

Abstract

Furnace walls and bottoms frequently consist of a refractory concrete, which has to be replaced from time to time due to abrasion. After relining, the furnace has to reach its operating temperature again. During this heat-up process, there is a risk of explosive spalling caused by the pore pressure build-up inside the wet concrete. These explosions may be very dangerous to the crew and the furnace-site. Those risks are reduced till today by the aid of empirically developed heat-up instructions (heat-up curves). The application of these curves doesn't really prevent explosive spalling and it is very time-consuming. To improve the first heat-up procedure, the empirically developed heat-up curves are replaced by optimized ones developed by the aid of numerical modeling. These curves are characterized by a constant maximum pressure during the heat-up drying period, and they bring a significant reduction of both, the heat-up time and the maximum pressure inside the concrete. Furthermore their dependency on wall thickness and pressure limit is investigated, as well as effects of previously not expected conditions which can occure during the heat-up of concrete under industrial conditions. Additionally, an optimized heat-up curve is used to dry a concrete brick in a laboratory experiment showing the practical applicability. Good agreement is obtained for the predicted pressure and temperature devolutions and the measured ones.