キルン内の原料移動および温度分布

ロータリーキルンによる砂鉄予備還元の検討-II

抄録

In the previous paper we described the installation of a multi-purpose 46 m long kiln with 6 sampling holes and the method of taking samples from a reducing kiln while it is in operation, then showed some results of measuring works.
In this paper we discuss the travel of material and distribution of its temperature. Many literatures are found which investigate the transportation of raw materials, through a rotary kiln in the field of cement industry. From the viewpoint of roasting reaction, the material is composed of a single element for a cement kiln; however, it is always a mixture of 2 elements 'which consist of reducing agent and substrate for a reducing kiln. Then if segregation occurs between 2 elements, it means an interruption of reducing reaction in the kiln.
So the segregation of material is one of the most important facts in the reducing kiln.
After various experiments, researches and observations, we reach the following conclusions;
(1) Segregation occurs because of different repose angles of material grain.
(2) Travelling speed of grain through the rotary kiln is decided by the filling ratio of charge and its local position in the bed.
(3) The grain of iron sand is so fine, and the reducing agent is not so fine, and as the result, the reducing agent has tendency to segregate outside of bed. We call it belt type segregation.
(4) Belt type segregation grows into rippling distribution across the axis of kiln, we call it striped segregation.
It is necessary for reductive roasting with kiln to control the grain size of charge material. In the future reports we shall analyse the segregation quantitatively again.
Generally, a reductive kiln has three zones by the name of drying, heating and reducing zone. Measured distribution of material temperature is almost linear throughout its length, and the rate of heat transfer in the last zone by means of improvement on heat transmission and prevention of segregation in charge material.