Double-pipe reactors flow rate ratio

Figure 4-5 Sensitivity of reactant conversion to changes in flow rate ratio for nonisother-mal plug-flow tubular reactors with exothermic chemical reaction and cocurrent cooling in a concentric double-pipe configuration with radius ratio k = 0.5. The inlet tempoatures are 340 K for the reactive fluid and 335 K for the cooling fluid.

Obviously, thermal runaway occurs in the previous example if the flow rate ratio is unity. However, it is possible to control a double-pipe reactor with = I by decreasing the radius ratio. This is illustrated in Table 4-4 for conditions described in the previous example. Thermal runaway occurs when k > /Ccriticai and the critical radius ratio lies somewhere between 0.10 and 0.15. 

The outer wall of the double-pipe configuration at radius Routside is thermally insulated from the surroundings. Identify the acceptable range of the flow rate ratio parameter xj/ that corresponds to a well-behaved novel reactive system which does not exhibit thermal runaway. The appropriate reactor design equations are summarized in Table 4-6. 

Figure 4-8 Effect of higher flow rate ratios on the conversion of an exothermic reactive fluid in a plug-flow reactor with endothermic cocurrent cooling in a concentric double-pipe configuration with radius ratio k =0.5. Both fluids enter the double-pipe reactor at 340 K.

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