The effects of highly porous refractory materials on steel ladle heat loss

The purpose of this research was to investigate methods of lowering the energy requirements and improve overall thermal efficiency during steel melting. A low thermal conductivity, low density, alumina based refractory material developed at UMR with porosity in excess of 75% was tested for its potential to reduce heat losses in the ladle. The performance of the new material was compared to low density magnesia and 70% alumina castable, two of the most widely used materials in steel foundries. Laboratory scale trials were conducted using a 45 kg (liquid steel capacity) foundry ladle constructed from pre-cast lining inserts with thermocouples attached at various locations and depths. In order to study the effects of the thermal state of the ladle lining prior to tap on the heat loss, each lining was preheated to four different conditions (no pre-heat, 400°C, 700°C and 900°C). Molten metal was tapped at 1650°C and held until the temperature dropped to 1335°C. During the holding time, the temperatures of the molten metal and nine lining locations were monitored. Metal holding time and the rate of heat loss for each insert during the holding period were calculated. In addition to the standard trials, one additional trial was completed using a calcium silicate based backup insulation lining. The study showed the possibility of significant decrease in the tapping temperature (decreased energy usage) based on using low density porous refractory ceramic in place of traditional alumina castable or low density magnesia linings. Additional insulation was found to play a major role in further reducing heat losses --Abstract, page iii