3.3 Batch Reactor

  • For batch reactor, conversion (\(X_A\)) is a function of the time of reaction (\(t_R\)). Time of reaction (\(t_R\)) is the usual measure of processing rate in case of batch reactor.

    Note that the time appearing in the batch reactor’s performance equation is the time of reaction, \(t_R\). Time of reaction (\(t_R\)) is also called the contact time. The time of reaction in a batch reactor is inversely proportional to the rate of reaction (see the performance equations).

    The total cycle time for a batch operation [\(t_{\text{(total batch cycle)}}\)] is usually longer than the reaction time (\(t_R\)) because one has to account for the times necessary to charge the reactants (\(t_f\)), heat the reactants before they are charged if necessary (\(t_h\)), emptying (\(t_e\)) and cleaning between batches (\(t_c\)), etc. \[t_{\text{(total batch cycle)}}=t_R+t_f+t_h+t_e+t_c\]

  • Under isothermal conditions, the rate of reaction is a function of the concentration of materials available for reaction.

    As the reaction proceeds (increase in reaction time), more and more amount of reactant material is getting used up. Hence, at very high conversion levels (very large time scales), there is a little amount of reactant available for the reaction to go on. This would make the rate of reaction insignificant and hence the reaction time requirement escalates. i.e., \[(-r_A) \rightarrow 0 \ \text{ as } \ t_R \rightarrow \infty\] This is why reactions other than zero order and fractional order will never go to completion.