Estimation of Porosity of Emulsion Phase and Interstitial Gas Velocity in Fluidized Bed

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The premises of the two-phase theory of fluidization were examined with a combined probe of the light transmission and the differential pressure methods developed by the authors. The light transmission method composed of Ift, light emitting diode and phototransistor linked up with a bubble elimination circuit can extract the bubble free signal of emulsion phase eeml, from which its solid concentration and thus its local porosity εeml was determined from the intensity of eeml by assuming Lambert-Beer law. The differential pressure method is a pair of pressure taps connected to a pressure transducer which gives the local pressure drop Δp. When those two probes are combined together, the interstitial gas velocity ue in fluidized beds can be estimated by Kozeny-Carman equation since both εeml and Δp are given simultaneously. The premises chosen are as follows: i) εeml should be uniform and be εmf', the porosity at minimum fluidization velocity umf. ii) ue should be uniform and be umf/εmf (or uz should be uniform and be umf, in superficial form since uz=ueεeml). The combined probe method revealed that both εeml and uz were not so uniform as might be expected but distributed axially as well as radially in the bed of solids of two kinds. As a whole, the average εeml at the lower part was larger than εmf and the average uz there was also larger than that at the upper part of the bed. In the bed of cracking catalyst, the decreasing trends of the average εeml, and average uz against the bed height were slightly more obvious than those in the bed of silica sand.
日本混相流学会の論文

Estimation of Porosity of Emulsion Phase and Interstitial Gas Velocity in Fluidized Bed

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日本混相流学会 | 論文

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