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| Semi fluidization |
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In chemical industries, mixing is a most crucial unit operation. It helps to maximize conversion to some extent. Fluidization is one of the best way to achieve mixing. In conventional fluidization, back-mixing, surface erosion and solid particle attrition are most common problems. To overcome this disadvantage, we can convert conventional fluidized bed into Semi-fluidized bed.
In packed bed reactor, channeling, non-uniform bed temperature and segregation of solids are common problems. Semi-fluidized bed has taken care of both packed & conventional fluidized bed disadvantages.
We can convert fluidized bed into semi-fluidized bed with providing sufficient space for fluidized bed expansion and arresting escape of solid particles by restraint in the top. Top restraint (grid) is specially to retain all solid particles & to have negligible pressure drop across it.
Early development
Since 1958, numbers of patents claimed relating to industrial application of semi-fluidized bed. Hydrodynamics, filtration, reaction kinetics and mass transfer studies are published in various research papers & journals.Observations
The maximum and minimum bed height should be taken correctly during operation or experiment of Semi – fluidization. The variables which affect the height of the top packed bed are- Initial static bed height,
- Superficial gas velocity and
- Superficial liquid velocity
Applications
We always find different situations in chemical process where there is contact of fluid phase with solids-for examples- Drying
- Adsorption
- Reaction kinetics
- Solid catalysed reactionsHeat transfer
In these all cases, mixing increase the contact efficiency of fluid-solid phase.
Chlorination & vapor phase oxidation of hydrocarbons are fast exothermic reactions where Semi-fluidized bed technique can be use. Bioreactor is also well-known process where it can be use.
Such devices are of considerable industrial importance as evidenced by their wide use in chemical, petrochemical and bio-chemical processing.
Three phase fluidized bed is also one of the most excellent method of fluidization. It is also called liquid air fluidized bed, where liquid and air (gas) both phase pass upward through bed of solid phase. It is very important topic to study in Chemical reaction engineering. In recent years, it is applicable to aerobic waste water treatment and fermentation processes.
Chlorination & vapor phase oxidation of hydrocarbons are fast exothermic reactions where Semi-fluidized bed technique can be use. Bioreactor is also well-known process where it can be use.
Such devices are of considerable industrial importance as evidenced by their wide use in chemical, petrochemical and bio-chemical processing.
Three phase fluidized bed is also one of the most excellent method of fluidization. It is also called liquid air fluidized bed, where liquid and air (gas) both phase pass upward through bed of solid phase. It is very important topic to study in Chemical reaction engineering. In recent years, it is applicable to aerobic waste water treatment and fermentation processes.
References
- Roy, G K, et al. “Hydrodynamics of Regular Particles in a Liquid-Solid Semifluidized Bed.” Powder Technology, 2009, doi:http://dx.doi.org/10.1016/j.powtec.2009.07.022.
- Das, B S, and B Patanaik. “Hydrodynamic study of three phase semi fluidized bed with irregular and homogeneous binary mixtures.” ethesis.nitrkl.ac.in/1824/1/final_thesis01.pdf.
- Deepika J, et al. “Hydrodynamics studies on semi-fluidized bed reactor using internals.” International Journal of Engineering Research and General Science, vol. 3, no. 2, ser. 2, Mar. 2015, pp. 33–34. 2, pnrsolution.org/Datacenter/Vol3/Issue2/207.pdf.
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