Pressure drop in packed beds

To calculate the pressure drop in a packed bed, the semi-empirical Ergun equation [54] may be used 

Arrhenius pre-exponential factor A, B reactants C molar heat capacity 

N molar flux (i.e. molar flow rate per unit area) 

G denotes overall mass transfer coefficient in gas film H hydraulic 

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Material balances, often an energy balance, and occasionally a momentum balance are needed to describe an adsorption process. These are written in various forms depending on the specific application and desire for simplicity or rigor. Reasonably general material balances for various processes are given below. An energy balance is developed for a fixea bed for gas-phase application and simphfied for liquid-phase application. Momentum balances for pressure drop in packed beds are given in Sec. 6. 

The allowable pressure drop influences the choice of the particle size and helps determine the column length. Equations for estimating the pressure drop in packed beds are given in Section 6. 

Although several attempts have been made to correlate data of pressure drop in packed beds in accordance with the general theory of granular beds, no useful generalization has been achieved. In any event, all manufacturers make available such data measured for their packings, usually only for the air-water system. Samples of such data are in Figures 13.37, 13.38, and 13.40. 

Levaf has correlated experimental data to obtain the following empirical equation for estimating pressure drop in packed beds under preloading conditions with simultaneous counterflow of liquid and gas ... 

The differential form of the design equation [i.e,. Equation (2-17)] must be u d when analyzing reactors that have a pressure drop along the length of the reactor. We discuss pressure drop in packed-bed reactors in Chapter 4. Integrating with the limits W = 0 at 2( = 0 gives... 

This chapter focuses attention on reactors that are operated isotherraally. We begin by studying a liquid-phase batch reactor to determine the specific reaction rate constant needed for the design of a CSTR. After iilustrating the design of a CSTR from batch reaction rate data, we carry out the design of a tubular reactor for a gas-phase pyrolysis reaction. This is followed by a discussion of pressure drop in packed-bed reactors, equilibrium conversion, and finally, the principles of unsteady operation and semibatch reactors. 

Differential form of Ergun equation for the pressure drop in packed beds... 

CALCULATE THE TOTAL PRESSURE DROP IN PACKED BED, DELTP. 

In Leva s correlation for pressure drop in packed beds of particles, lower pressure drops are predicted for larger shape factors. For particles of the same volume per particle, the pressure drop per unit length is proportional to < , to the — 3 power where a increases from I to 2 as the flow increases from the laminar to the turbulent regime. 

An empirical correlation for pressure drop in packed beds at high Reynolds number > 1000) is the Burke-Plummer equation ... 

Hicks, R. E., Pressure drop in packed beds of sphere, Ind. Eng. Chem. Fundam., 9, 500, 1970... 

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