Investigation of Material Transport in Cement-rotary Kilns
1964 Volume 13 Issue 4 Pages 293-299
Details
1964 Volume 13 Issue 4 Pages 293-299
Investigations were carried out on two wet-process rotary kilns of different sizes for the purpose of studying the material residence time, the rate of the charge in various sections of the kilns, and further the mixing character of raw meal in the kilns.
These investigations were performed by adding a radioactive tracer to the raw meal at the kiln inlet. As a tracer, approximately 100 millicuries of 140La2O3, after being premixed with 10 kg of raw meal, was used in one test. Behaviours of the tagged raw meal in the kiln were observed through the kiln shell with thirteen scintillation detectors installed along the kiln axis. And two more scintillation detectors were set at the clinker belt conveyer and the circulating dust conveyer.
Some other notices performing these tests are as follows :
In the preliminary tests, it was confirmed by the double tracer method with cobalt oxide that 140La2O3 takes same behaviours in the kiln as raw meal. 140La2O3 was prepared by irradiation of high purity lantan oxide in the atomic reactor.
Recording of measuring results was done with the aid of the automatic connection changing circuit, which operates between six scintillation detectors and two ratemeters. And all scintillation detectors were jacketed with water, to protect them against radiating heat from kiln or hot material.
The following are observed from these tests :
1. The rate of the charge increases gradually from the preheating zone towards the calcination zone, where it reaches over 3 m/min, and is remarkably reduced in the burning zone.
2. The material residence time of main group of the tracer is unexpectedly short. But the circulating dust remains considerably long time in the kiln.
3. The mixing of raw meal is promoted in the region of the chain zone, the lower part. of calcination zone and burning zone. Further, in the kiln 2, the flow of tracer is disturbed severely because of many inverse spiral grooves set of the surface of the fire-bricks stretched the kiln inside.
