An experimental investigation of the residence time distribution of solids in multistage fluidisation
TL;DR: In this paper, the cross-flow model was matched with the experimental data taken subsequently on the residence time distribution of solids in a multistage fluidised bed, and conditions for smooth fluidisation were suggested.
About: This article is published in Chemical Engineering Science.The article was published on 1975-01-01. It has received 15 citations till now. The article focuses on the topics: Residence time distribution.
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TL;DR: In this article, a simplified theory for a bubble column is applied to understand particle circulation in the fluidized catalytic beds, and it is possible to analyze flow patterns of bubbles and emulsion.
Abstract: Publisher Summary Flow properties of the fluidized catalyst bed (FCB) are different from those of other conventional fluidized beds. The different treatment required is very significant for research and development on fluidized catalytic beds. This chapter discusses the factors affecting the flow properties. These properties include particle size distribution, also heat and mass transfer, and mixing properties. In the FCB, the dilute phase plays an important role in advancing the catalytic reaction when reaction rates are high. This factor provides a basis for identifying the appropriate reaction model and clarifying the effect of the dilute phase on selectivity and stability. The simplified theory for a bubble column is applied to understand particle circulation in the FCB. As a result, it is possible to analyze flow patterns of bubbles and “emulsion.” This chapter considers the uses of fluidized beds for catalytic reactions, using a viewpoint quite different from studies directed toward the physical handling of solid particles or toward gas–solid noncatalytic reaction. Particle size distribution has a great effect on most aspects of fluidization. Fluid beds are usually operated in the turbulent-flow region to obtain good contact and sufficient throughput of reactant gas. The uniformity and contact efficiency of a fluid bed can be improved by immersion of a surface within the bed.
80 citations
TL;DR: In this paper, the simulation of bubbling fluidized beds (BFB) residence time distribution (RTD) based on the structure-based drag model is conducted for the single and binary gas-solid phases systems, a comparison of computed results with experimental data proves that their model is applicable to both systems with better accuracy.
22 citations
TL;DR: In this paper, a numerical investigation of the solids residence time distribution and the fluidized structure of a multi-compartment fluidized bed, in which the flow pattern is proved to be close to plug flow by using computational fluid dynamics (CFD) simulations.
19 citations
TL;DR: In this paper, the authors compare curve-fitting with and without the constraint τ = μ, and show that consistently better results are obtained when the constraint is relaxed prior to curvefitting.
Abstract: Parameters in residence time distribution (RTD) models are commonly estimated by least-squares curve-fit in the time domain. Two procedures suggested in the literature for this purpose involve (i) fixing τ (the mean residence time) as equal to μ (first moment of the experimental response) prior to curve-fitting and (ii) estimating τ along with other model parameters by curve-fitting. In this work these two procedures, i.e., curve-fitting with and without the constraint τ = μ, are compared. Four models in conjunction with eight sets of RTD data are considered. The results indicate that consistently better results are obtained when the constraint τ = μ is relaxed prior to curve-fitting. This is particularly so for models with fewer parameters like the dispersion model.
19 citations
TL;DR: In this paper, the authors demonstrate a method for measuring the biomass residence time over the conversion period at a given air flowrate and a given amount of biomass in a bubbling bed using the variation of bed temperature and fluid pressure recorded over time.
18 citations
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...In addition, the proposed model for xchar is developed based on the ideal plug flow which gives the desirable flow pattern for any continuous fluidized bed [33,34]....
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...By plug flow, it is assumed that all particles have the same residence time thereby reducing the instability that arises due to gas flow [33,34]....
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TL;DR: In this paper, a three-parameter mathematical model for expressing the residence time distribution in multistage systems is proposed, in which a fraction of the feed short-circuits each stage consists of an active backmix region and a dead region with cross-flow of the material between the two regions.
25 citations
11 citations
9 citations