DETERMINATION OF GAS TRANSIT TIME BY RADIO-ACTIVE TRACER RADON IN A DRIVING 1, 000 TON BLAST-FURNACE
Masao Serizawa, Yoshio Kuzuhara, Yoshikazu Takahashi, Keniiro Kanbara, Kazuo Miyakawa
A series of tests on the measurement of the gas transit time and the distribution of the gas in operation of a 1, 000 ton blast furnace were carried out using radioactive tracer at Hirohata Works of the Fuji Iron and Steel Co. As soon as the radon contained in a gold tube was detonated into the furnace by the electrical burster container fitted up one tuyere latch of the furnace, a series of gas samples were caught at 0.7 second intervals by the gas sampler installed at the top of the furnace. The gas samples were transfered first into the flasks and subsequently analyzed for their radio-active content by the pulsed-ionization chamber method.
The samples were simultaneously withdrawn through four steel tubes inserted above the stockline at a center and three different positions near the furnace wall.
Some preliminary tests in 1955 and a series of forty experiments from August to October in 1956, were performed successfully, and the furnace conditions were taken into consideration in relation to their results.
Some results obtained from these tests are as follows.
(1) By using the pulsed ionization chamber method gas radioactivity was detected much more precisely than by the Geiger-Müller counter method. The radon as much as 0.6m.C. is sufficient to analyze the gas radioactivity, and under the favorable conditions it is counted beyoud 1, 000cpm.
(2) The transit time of the gas determined from a series of thirty experiments is shown in Table 4, the average and the 95% confidence limit obtained by statical analysis as to the center of the furnace and the vertical point of the inwall above the tuyere through which the radon is projected. It is observed that the transit time of the gas is faster in the center of the furnace than near the furnace wall by these results; 3-5 seconds to reach the maximum radio-activity at the center against over 5-6 seconds at the inwall, and the transit time varies more at the center than at the inwall, and the gas flow is influenced by pig tapping or slag tapping.
(3) As shown in Fig. 5, experimental results seem to be assorted into four types on therelative curves between the gas radioactivity and the transit time. It will be recognized that these figures and the furnace conditions are substantially related, that is to say, when the furnace condition is stable the figure is often found out as A type, and under instable condition as C or D.