On Some Fundamental Aspects of Operational Parameters of Direct Reduction in Rotary Kiln

A rotary kiln for the reduction of iron oxides in solid state is essentially a continuous gas/solid reactor operating on either counter-current, or co-current flow of solids and gases. The factors affecting isothermal condi-tion in the reaction zone and heat transfer are indicated. Limited rate of heat release, poor heat transfer and leng-thy and rotation, the output can be increased by increa-sing the diameter. The degradation due to self grinding increases with diameter, while exhaust gas velocity is decreased lowering entrainment of solids. For reasonable reaction rate, an appropriate temperature profile has to be maintained. The reaction temperature is dependant on softening temperature of solids. The reactivity of fuel and reducibility of the ore are the rate determining fact-ors. The degree of metallization depends on the particle
size and reducibility of the ore, temperature profile and reactivity of the fuel. All these factors should be consi- dered in designing a rotary kiln pilot plant and parti-cularly for evolving a commercial prototype.