Abstract
So far we have reported on the physical and chemical analyses of the reduction kiln. The present study is concerned with heat balances including the rate of input energy and that of energy consumption in the kiln. The calculation of thermal balance is necessary not only for efficient and economical operation of the kiln, but also for reasonable improvement of the kiln-process as a reduction device. As the result of measurement of energy balances in several typical operations, we reach the following conclusions:-
The total heat consumption for the kiln reduction amounts to 1.9-2.6×103 kcal per kg of half-reduction iron sand sponge, combustion efficiencies ranging 70-80%, and over-all thermal efficiencies ranging 30-35% on the test kiln. Considerable heat loss amounting to 15-30% of total input is found in the exhaust gas forming CO and soot. However, we find that the heat loss in the kiln-shell is not very large.
Furthermore, by examining the enthalpy curves of raw material in the operation kiln, we find that heat of reduction reacts as buffer for temperature of raw material under radiation of burner flame. Since the dry part of kiln has a high efficiency of heat transference the rate of fuel consumption is not influenced by the moisture content of the charged material. The recovery of avoidable heat loss may contribute to reduction of a considerable amount of heat consumption.
