High Temperature Rapid Activity Of Calcined Lime

Limestone-steelmaking could save energy and low carbon compared to steel-making using active lime.Because of the high temperature in converter (the temperature of the bottom of converter after tapping is between 1250—1400℃, while the calcining temperature is 1050—1200℃), the calcined lime in this temperature has enough activity to form slag or not which is the key to popularize the process of limestone steelmaking. We study the activity change law of limestone calcining in short time and high temperature in converter after tapping, and analyze the material balance and heat balance in this condition, thus we get the feasibility of using this method. All these work pave a road to the popularizing of limestone calcining directly in place of active lime in converter.In this paper, firstly we study the lime activity change law in conditions of high temperature (1250—1400℃) and short time (5—15minutes). We choose 1250℃,1300℃, 1350℃and 1400℃as the calcining temperature,5min, 10min and 15min as the calcining time and 12—15mm and 0—0.5mm as the limestone size. And the influence of salt as an additive on activity of 0—0.5mm limestone calcining is studied. The research results shows when 12—15mm limestone grain is calcined in condition of 1300—1400℃and 7minutes, the activity of lime is more than 335ml and it increases when the calcining temperature is going up. When the calcining time exceeds 12min, lime calcined under 1350—1400℃is over-burnt and its activity decreases significantly. Enlarging the size of limestone sample makes the activity decrease. In the condition of 1400℃, limestone sample made of powder is easier over-burnt than that made of grain.Maintaining the internal thermal equilibrium is most important for the no external heat source converter.In this paper, the calculation and comparison of material's heat balance of limestone steelmaking and active lime steelmaking is followed. We define absorbing heat/emitting heat as heat absorbing ratio during slagging. By computation, the ratio of limestone steelmaking is lower than active lime steelmaking. So limestone steelmaking is applicable in industry, and in place of active lime steelmaking is feasibility from the standpoint of energy balance.