OPTIMIZATION OF BIOCHEMICAL REACTORS - AN ANALYSIS OF DIFFERENT APPROXIMATIONS OF FED-BATCH OPERATION

In this work we analyse the fed-batch operation of a biochemical react or. In the first part of the work we consider a repeated fed-batch ope ration. The reaction is assumed to follow Haldane kinetics, i.e. it is characterised by substrate inhibition. The feed rate of the substrate is chosen as the control variable. The entire duration of the operati on is divided into different subintervals. We optimise the system perf ormance by approximating the feed flow rate using (i) discrete pulses, (ii) a constant flow rate over different sub-intervals. In the first strategy the equations lend themselves to an analytical solution. For the second case we use a shooting method coupled with a sequential qua dratic programming technique to obtain the constant flow rates in the different sub-intervals. This has been analysed for two scenarios: (i) equal duration of sub-intervals and (ii) unequal duration of sub-inte rvals. The objective here is to maximise the biomass production over o ne cycle. The effect of converting a non-linear constraint to a linear constraint by reformulating the problem on the numerical convergence has also been investigated. In the second part of this work we have ex tended our method to investigate a non-repeated fed-batch reactor oper ation. Here the objective is to maximise the product formed. (C) 1997 Elsevier Science Ltd.