Empirical correlations for axial dispersion coefficient and Peclet number in fixed-bed columns

Area of Science:

• Chemical Engineering
• Fluid Dynamics
• Mass Transfer

Background:

• Axial dispersion is a key parameter in fixed-bed reactors, influencing process efficiency.
• Existing correlations like Chung and Wen and De Ligny have limitations, omitting molecular diffusion or bed voidage.
• Accurate modeling of axial dispersion is crucial for optimizing packed-bed column design and operation.

Purpose of the Study:

• To develop a new, more comprehensive, and accurate correlation for the axial dispersion coefficient in fixed-bed columns.
• To address the limitations of existing empirical correlations by including molecular diffusion and bed voidage.
• To provide an improved basis for calculating the Peclet number in packed-bed systems.

Main Methods:

• Compilation and analysis of experimental data on axial dispersion from existing literature.
• Development of a new empirical correlation for the axial dispersion coefficient.
• Validation of the new correlation against experimental data and comparison with established correlations.
• Derivation of a new Peclet number correlation based on the developed axial dispersion coefficient correlation.

Main Results:

• A novel correlation for the axial dispersion coefficient was established, incorporating both molecular diffusion and bed voidage.
• The new correlation demonstrates improved accuracy and comprehensiveness compared to Chung and Wen and De Ligny correlations.
• The derived Peclet number correlation results in an average of 12% lower values than the Chung and Wen correlation.
• Significant reductions in Peclet number values were observed compared to the De Ligny correlation in many cases.

Conclusions:

• The newly developed axial dispersion coefficient correlation offers a more accurate representation of transport phenomena in fixed-bed columns.
• Incorporating molecular diffusion and bed voidage leads to a superior predictive model for packed-bed reactors.
• The findings provide enhanced tools for engineers to optimize the design and performance of fixed-bed systems.