The residence time distribution of the solids in multistage fluidisation, wherein downcomers for transferring the solids from stage to stage are provided to the horizontal perforated plates, is experimentally investigated covering a wide range in process variables using flat, baffle and spiral plates developed in the study. The RTD data is modelled using (i) the multiple parameter model, (ii) the diffusional mixing model and (iii) the fractional tank extension model when it is noted that over certain conditions of operation both spiral and baffle plates indicate near piston-flow for the solids without hampering the fluidisation characteristics. © 1982.

K. Krisrnaiah

Y. Pydisetty

Y. B.G. Varma

Residence time distribution (RTD)

CHEMICAL OPERATIONS - Fluidization

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IIT Madras

Residence time distribution of solids in multistage fluidisation

Chemical Engineering Science

Solids are dried in batch and in continuous fluidized beds corresponding to cross-flow and countercurrent flow of phases covering a wide range in drying conditions. Materials that essentially dry with constant drying rate and then give a falling drying rate approximately linear with respect to solids moisture content (sand) as well as those with an extensive falling rate period with the subsequent falling rate being a curve with respect to the moisture content (mustard, ragi, poppy seeds) are chosen for the study. The performance of the continuous fluidized bed driers is compared with that of batch fluidized bed driers; the performance is predicted using batch kinetics, the residence time distribution of solids, and the contact efficiency between the phases. © 1995, American Chemical Society. All rights reserved.

Industrial and Engineering Chemistry Research

Drying of Solids in Fluidized Beds

The residence time distribution (RTD) of solids in spiral fluidised beds was experimentally investigated, covering as variables the flow rates of the phases, the particle characteristics and the column and plate geometries. The RTD was adequately described by the Fickian diffusion model, indicating that particle dispersion can be predicted from a knowledge of particle diffusivity. Correlations for the particle mean residence times and the particle diffusivity are presented. © 1989.

Powder Technology

Axial dispersion of solids in spiral fluidised beds

The cross-flow model (Chem. Engng Sci. 1973 28 585), proposed by the authors for multistage systems, is matched with the experimental data taken subsequently on the residence time distribution of solids in a multistage fluidised bed. The model parameters are related to the plate geometry and the flow rates of the phases. The model is found to agree with the experimental data of the earlier investigators on single and multistage fluidised beds with a maximum root mean square deviation of 0·05. Based on the data, conditions for smooth fluidisation are suggested. © 1975.

An experimental investigation of the residence time distribution of solids in multistage fluidisation

Staging of a fluidisation column with horizontal screens reduces the axial mixing of the phases and limits the formation and growth of the bubbles. The pressure drop of the fluid and the flow patterns of the phases differ markedly with the mode of operation of the multistage fluidised bed. These aspects with respect to the theoretical models, the experimental data and the range of applicability are discussed along with the correlations to predict the characteristics of the bed. © 1975.

Journal	Chemical Engineering Science
ISSN	00092509
Open Access	No