STR Batch Backmix

An STR can be operated batch, semibatch (Section 6.28) and continuous stirred tank reactors (Section 6.29). For all STRs, residence time 600-15 000 s (10 min to 4 h) heat of reaction primarily exothermic reaction rate slow to lengthy. 

High pressure autoclaves 100 L. Flexible. Do not use for gaseous reactions or for very fast reactions in the liquid phase. 

Unique to batch STR Phases L, LL, LcS, GL bio S, L bioS, low capacity 3 L/s but usually 0.3 L/s. Use (i) if the concentrations of all reactants are high (ii) if need good selectivity for consecutive reactions (iii) for low and variable production rate, (iv) a variety of similar products or several products sequentially. Batch STR usually have low fixed capital cost but the product cost is high because of the cycles. Usually batch is better than continuous (Section 6.29) for very slow reactions. If (Da/St) 1. 

Details of other applications and guidelines are given in Sections 6.28, semibatch, and 6.29, CSTR. 

Liquid and liquid-liquid commonly used for polymerizations and dehydrations. Cas-Uquid area per unit volume 20 to 200 m /m can suspend solids, maximum pressure limited by the seal around the rotating mixing shaft. Ha 0.3 and 5 = 150-800. 

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