Mathematical modeling of a continuous fluidized bed dryer

Garnavi, L.; Kasiri, Norollah; Hashemabadi, Seyed Hassan

doi:10.1016/j.icheatmasstransfer.2006.02.014

Cited by 18 publications

(8 citation statements)

References 10 publications

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“…However, since industrial fluidized bed dryers use bubbling fluidized beds, there is limited use of this model. The steady-state, onedimensional two-phase models (suspension of particles and bubbles) of Harrison and Davidson [34][35][36] were widely used successfully [37][38][39][40]. A more elaborate one-dimensional two-phase model that also incorporates the RTD of solids was also developed [29,41].…”

Section: Back-mixed Continuous Fluidized Bed Modelsmentioning

confidence: 99%

Fluidized Bed Dryers — Recent Advances

Daud¹

2008

adv powder technol

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Although industrial fluidized bed dryers have been used successfully for the drying of wet solid particles for many years, the development of industrial fluidized bed dryers for any particular application is fraught with difficulties such as scaling-up, poor fluidization and non-uniform product quality. Scaling-up is the major problem and there are very few good, reliable theoretical models that can replace the expensive laboratory work and pilot-plant trials. This problem is mainly due to the different behavior of bubbles and mixing regimes in fluidized bed dryers of different size. Simple transformation of laboratory batch drying data to continuous back-mixed dryers using the residence time distribution of the solids is insufficient to account for the complex flow and heat and mass transfer phenomena occurring in the bed. Although time scaling using temperature driving forces and solids mass flux for the same change in moisture content in the batch and continuous dryers has been successful in predicting moisture content profiles in the continuous dryer at the constant rate period, it does not take into account solid mixing. Two-phase Davidson-Harrison models have been used in modeling of the continuous back-mixed dryer with various degrees of success. On the other hand, the three-phase Kunii-Levenspiel model is seldom used in modeling fluidized bed dryers because it is too complex to handle. A combination of multi-phase models and residence time distribution could improve predicting power for back-mixed dryers because this combination takes into account both the bubbles and solid mixing phenomena. Incremental models were widely used to model continuous plug flow fluidized bed dryers, but the cross-flow of drying medium has not been sufficiently modeled except by the author. In some incremental models, axial dispersion is modeled using the Peclet number, Pe. A combination of an incremental model with an axial dispersion and cross-flow model of drying medium would improve predicting power. Poor fluidization of Geldart group C particles could be improved by the assistance of external means such as vibration, agitation, rotation and centrifugation. Both vibrated and agitated fluidized bed dryers have been successfully used in industry, but rotating or centrifugal fluidized bed dryers are still not available for industrial use. Nomenclature A bed area (m 2 ) E(t) RTD curve (-) ε bed porosity (-) F dry basis solid flow rate (kg/h) f falling rate drying factor ( • C) G dry basis gas flow rate (kg/h) h bed height (m) L total length of dryer (m) m B mass of bed (kg) N V local solids dying rate (kg/h/m 2 ) NTU number of transfer units (-) Nu nusselt number (-) Pe Peclet number (-)Pr Prandtl number (-) Re p particle Reynolds number (-) T G local gas temperature ( • C) T GI initial gas temperature ( • C) T i inlet gas tenmperature ( • C) T o exhaust gas temperature ( • C) T S local solids temperature ( • C) T wb wet bulb temperature ( • C) t time (s) τ residence time (s) X dry basis solids moisture content (kg/kg) X i inle...

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Section: Back-mixed Continuous Fluidized Bed Modelsmentioning

confidence: 99%

Fluidized Bed Dryers — Recent Advances

Daud¹

2008

adv powder technol

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“…Additionally, the bubble gas is considered with a plug flow like behavior meaning that the heat and mass transport between suspension and bubble is calculated along the fluidized bed dryer height. Garnavi et al [9] included changing bubble sizes along the dryer height, which corresponds more to the general understanding of bubbling fluidized beds. More recently, population-based models are used to describe the drying in fluidized beds to keep tracking of the drying for particles of different size possible [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Process Design of a Multistage Drying Process via Flowsheet Simulation

Buchholz

Haus

Blesinger

et al. 2021

Chemie Ingenieur Technik

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This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.Multistage drying processes including spray drying and fluidized bed unit operations are challenging to design due to the dependencies of the preceding process steps. Flowsheet simulation offers the possibility to simulate a complete process by the application of suitable short-cut models. In this contribution a novel model for a spray dryer based on a population balance approach is presented. Furthermore, a dynamic model for a fluidized bed dryer is introduced. Experimental data is used for validation and parameter optimization. The calibrated models are then used to design an industrial drying process of multiple drying stages.

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“…L Garnavi et al [2006], develop ed a mathematical model based on the two-phase t heory of fluidization is presented for the continuou s fluidized bed dryers.…”

Section: Introductionmentioning

confidence: 99%

“…The results obtained from vari ations in the superficial Rakesh Verma* 1 and Bharat Raj Singh 2 gas velocity imply that the pe rformance of the fluidized bed dryer is largely affected by the drying at the constant rate drying stage [1] .…”

Section: Introductionmentioning

confidence: 99%

Study of Fluidized Bed Drying Method Used For Safe Storage of Rice And Its Analyais

Verma¹,

Singh²

2012

SMSJ

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Rice is used as a staple food by more than 60 percent of world population. The method used for Cooking of rice for eating purpose is most common and popular. Rice starch is used in making ice cream, custard powder, puddings, gel, distillation of potable alcohol, etc. It is used in confectionery products like bread, snacks, cookies and biscuits. The defatted bran is also used as cattle feed, organic fertilizer (compost), and medicinal purpose and in wax making. Rice is used as animal feed, fuel, mushroom bed, for mulching in horticultural crops and in preparation of paper and compost. Rice yields have been increasing since the 1960s, but since the 1990s, growth in rice production has been slower than population growth. Indeed, it is anticipated that rice production will need to increase by 30% by 2025 in order to sustain those who need it for sustenance. In the present work fluidized bed drying method used for safe storage of rice and analysis of rice conditions and we find that inlet air temperature has the most important effect on the drying rate of material, increasing the inlet air temperature increases the drying rate of the material. Inlet material flow rate has the most important effect on thermal efficiency. Increasing the inlet material flow rate increases the efficiency but decreases the drying rate. At lower flow rate of material, efficiency is low.

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Mathematical modeling of a continuous fluidized bed dryer

Cited by 18 publications

References 10 publications

Fluidized Bed Dryers — Recent Advances

Fluidized Bed Dryers — Recent Advances

Process Design of a Multistage Drying Process via Flowsheet Simulation

Study of Fluidized Bed Drying Method Used For Safe Storage of Rice And Its Analyais

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