A Study on a Reduction in Fuel Consumption in Soaking Pits

Inverted-L Type Heating Method

Abstract

Conventional ordinary methods of heating steel ingots in soaking pits consist in setting the furnace temperature at about 1300°C upon charging hot steel ingots into a soaking pit, feeding the fuel at a maximum flow rate at the early period of heating, and gradually reducing the amount of the fuel when the furnace temperature has reached a set value. When the steel ingots heated for a definite period of time have reached the uniform temperature throughout, the soaking process is completed and they are extracted and rolled. For this reason, large quantities of heat are given off as the sensible heat of exhaust gas and as heat radiation from the furnace. Thus this situation is not desirable from the standpoint of energy-saving. To cope with this high fuel price age after the oil shock, the authors have studied heating methods and developed “the inverted-L type heating method”, a new method entirely different from conventional heating methods.
This method consists in heating steel ingots with the fuel at a minimum definite flow rate required for heat balance until the latent heat of solidification has spread throughout the steel ingots, increasing the fuel flow rate just before extraction, and thereby abruptly heating the surface.
The average unit fuel consumption decreased from 183×10³ kcal/t in 1973 to 111×10³ kcal/t in 1977 when this method was adopted, thus showing a decrease of 34%.