A Calculation of Pressure Drop in

2 Design of a Fixed Bed Reactor According to the One-Dimensional Pseudohomogeneous Model 

This design example is suggested from hydrocarbon oxidation processes such as benzene oxidation into maleic anhydride or the synthesis of phthalic anhydride from o-xylene. These strongly exothermic processes are carried out in multitubular reactors cooled by molten salt that is circulating around the tubes and that exchanges heat to an internal or external boiler. The length of the tubes is 3 m and their internal diameter is 2.54 cm. One reactor may contain 2500 tubes in parallel and even 10,000 or more in the latest versions. In German processes the 

The operating pressure is nearly atmospheric. The phthalic anhydride production from such a reactor with 2500 tubes is 1650 tons/yr. It follows that with this catalyst a typical mass flow velocity of the gas mixture is 4684 kg/m h. With a mean fluid density of 1293 kg/m this leads to a superficial fluid velocity of 3600 m/h. A typical heat of reaction is 1,285,409 kj/kmol, and the specific heat is 0.992 kj/kg K. In this example the kinetic equation for the hydrocarbon conversion will be considered in first approximation to be pseudo-first order, due to the large excess of oxygen  

More complex rate equations for this type of reaction will be used in a later example given in Section 11.7.5. 

The continuity equation for the hydrocarbon, in terms of partial pressures and the energy equation, may be written, for constant density. 

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Example 11.5.1.A Calculation of Pressure Drop in Packed Beds... 

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