Residence time measurement of an oil sludge incinerator using nuclear tracer technique

A 1.6 Ton/hr revolving fluidised bed incinerator was recently commissioned in Johor, Malaysia. As part of the commissioning work for the plant, a residence time measurement was conducted by MINT. As there is no nonnuclear technique available at that time to measure the said parameter, a radioactive tracer technique was proposed and applied for the plant testing. The tracer used was Br-82, in the form of KBr in water solution, having an activity of about lOmCi per injection. The method used two detector systems backed by interlocking switch to trigger the injection and detection signal. Two test arrangements were done. The first test arrangement resulted in the so-called two chamber effect due to bad test set up with a diffuse residence time distribution. Incidentally, this test helped to explain a little the flow characteristic in the secondary chamber air plenum and nozzles. The second chamber effect has been eliminated by modifying the injection point and test set up which has given an excellent result. A clear residence time distribution and very sharp peaks were obtained for every tests. The results enable the peak of the residence time to be deducted. The average residence time, measured from peak to peak, was deduced to be 3.28 seconds, compared to the calculated design value of 3.68 seconds at 8500 C. This paper highlights the methodology, discusses the problems, advantages and limitations of the technique compared to established non nuclear techniques