| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1992: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
Gas injection into a bath from an immersed rotating. L-shaped nozzle has been proposed for intensifying the bath stirring and for obtaining better bubble dispersion behavior. Cold model experiments under various nozzle rotating rates and gas injection conditions were made to investigate their effects on the bath mixing. The experimental results of mixing time are compared with previous ones obtained gas injection stirring.
The present results are summarized as follows.
(1) The bath mixing is intensified by the circumferential circulating flow due to the nozzle rotation and by the vertical circulating flow due to the gas injection. Which of the two flows has a larger effect on the mixing can be examined by the dependence of mixing time on the bath depth. However, the contributions of the two powers to the bath mixing changes largely with the experimental conditions, so that quantitative estimation of the mixing time on the basis of mixing power density under widely ranged experimental conditions is quite difficult.
(2) In the case of L/D=0.279 (L : elbow length of the L-shaped nozzle, and D : bath diameter), the effects of various parameters on the mixing time, t_<mix>, can be given by the following equation.
t_<mix> Q^<-0.276>R^<-0.245>H^<0.119>D^<1.26>
where Q is the gas flow rate, R is the rotating rate, and H is the bath depth.
(3) When the bath is shallow, the mechanical stirring gives better bath mixing than the gas injection stirring. But there is a limitation to the intensification of bath mixing by increasing rotating rate of the immersed nozzle.
(4) The present process can disperse bubbles widely in the bath, and the bath mixing is better than that by the conventional gas injection stirring. In the case of high rotating rate and shallow bath, the gas injection increases the mixing time, and hence gives a bad influence on the bath mixing.
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