Effects of pressure, temperature, and particle shape on the pressure drop in fixed bed

Based on A-S equation, a new expression was derived for pressure drop in fixed bed with gaseous flow. It was indicated by using the proposed expression that the pressure drop is inversely proportional to the pressure level in the bed, and that the overall pressure drop should be obtained by numerical integration. In the case of isothermal gas flow, however, the overall pressure drop can be expressed in an analytical way similar to Ergun equation. Experimental data demonstrated excellent generality of the presented expression for describing the flow rate-pressure drop relation under different pressure levels, while the two coefficients in the expression significantly differ for beds with different-shaped catalyst particles. It was also revealed from the analysis to experimental data that the two coefficients (defined as particle shape coefficients in this paper) reflect the effect of catalyst particle shape (including surface roughness) on pressure drop. For the three kinds of abnormal-shaped catalyst particles used, i.e., ring, wheel shape and honeycomb shape, difference of 2.03 times was found in the pressure drop due to viscous resistance and form drag, and up to 2.7 times due to inertial resistance. It was demonstrated that the Ergun equation will lead to a considerably wrong prediction of pressure drop in industrial fixed-bed reactors with abnormal-shaped catalyst particles operating under high pressures and high temperatures.