Sequential batch operation

Assuming that the annual production requirement has been established, one of the first problems faced in process design is to choose a process cycle so that material and energy balances on a time basis can be worked out and all of the necessary flow sheets prepared. Questions related to a 24-hr or 8 hr/day operation and production by sequential batch operation or on a steady-state continuous basis must be resolved. 

As an example of the first strategy outlined above, the simulation of sequential batch operation with immobilized penicillin acylase is presented. Penicillin acylase is inhibited by both products, being phenylacetic acid a competitive inhibitor and 6-aminopenicillanic acid a non-competitive inhibitor (lllanes et al. 1994). Simulation was done by solving differential Eq. 5.6, which represents the material balance with the corresponding kinetic expression (Eq. 3.43), and Eq. 5.76, which represents the two-phase series type enzyme inactivation kinetics. The scheme for this situation is presented in Fig. 5.20. 

Eq. 6.2.6 was solved analytically to obtain the operation curve of the reactor (X vs t). Lumped kinetic parameters were determined by non-linear regression of experimental data using the numerical method of Newton-Raphson with first-order Taylor series expansion. Lumped parameters were smooth functions of temperature all parameters were adequately fitted to second order polynomials except for D that required a fourth order polynomial. The model can be used for reactor temperature optimization and can be extended to prolonged sequential batch operation provided that a sound model for enzyme inactivation is validated (Illanes et al. 2005b). 

Even though results were satisfactory and fulfill the established requirements, operational stability of the enzyme was tested in sequential batch operation, where the biocatalyst was recovered after each batch by in-situ filtration. Results were disappointing since most of the enzyme (about 90%) was desorbed during operation... 

If there is no consumption of reagent in a traditional sequential batch operation, the pH response is integrating and the pH loop will continuously oscillate across the split range point. 

Process data for the same polymer recipe were analyzed for 50 noncon-secutive, sequential batches. As before, the data were preprocessed to remove outliers and sorted to reflect normal operation. The data are sampled at 1-minute intervals during production of each batch. Fillering and normalization of the data is done prior to analysis. The final polymer quality... 

Lourenco ND, Novais JM, Pinheiro HM (2001) Effect of some operational parameters on textile dye biodegradation in a sequential batch reactor. J Biotechnol 89 163-174... 

The sequential batch reactor (SBR) consists of a vessel operated under batch conditions according to the time schedule reported in Fig. 3. The symbols Fill, React, Settle, Draw and Idle refer to the typical sequential phases of operation loading, reaction, biophase settling, discharging and the idle time. The reaction period may be split into two sub-phases an anaerobic phase and an aerobic phase. The aerobic sub-phase is devoted to convert products of the azo-dye anaerobic... 

Bioreactors are operated in discontinuous mode, with a sequential or continuous feed of the substrate (fed-batch operation) or in continuous mode. The choice of the operating mode depends mainly on the reaction characteristics ... 

In general, an objective function in the optimization problem can be chosen, depending on the nature of the problem. Here, two practical optimization problems related to batch operation maximization of product concentration in a fixed batch time and minimization of batch operation time given amount of desired product, are considered to determine an optimal reactor temperature profile. The first problem formulation is applied to a situation where we need to increase the amount of desired product while batch operation time is fixed. This is due to the limitation of complete production line in a sequential processing. However, in some circumstances, we need to reduce the duration of batch run to allow the operation of more runs per day. This requirement leads to the minimum time optimization problem. These problems can be described in details as follows. 

Fig. 5.21 Simulation of sequential batch reactor operation with immobilised penicillin acylase at pH 7.8 and 40 C (K = 6.5mM Kj = 56.5mM K2 = 59.3 V = 625 pmol/min/g. a) considering full protection by catalytic modulators (all n, = 1 all n( = 1) b) not considering modulation (till n = 0 all nj = 0) c) with experimentally determined vtilues for modulation factors (Illanes et al. 1996)...

Table 63.4 Results of Sequential Batch Reactor Operation with Lipase QL Immobilized in Butyl Sepabeads at 0.03 g enzyme/g wood sterols 5 mol acyl agent/mol wood sterols, 70°C, 50 mbar and 0.75 aw...

COD (chemical oxygen demand) removed [27]. The process can be operated in either a batch [28] or continuous [29] mode within a single unit, where adsorption, separation, and regeneration occur either continuously within different zones of the unit or sequentially in batch operation. 

For precise modelling of batch operations a formalism that describes the system behaviour at this level of details is needed. Such formalism must allow analysing the interactions of the different process units and steps that allows developing the best co-ordination control system (Fig. 4). The Petri Net and Sequential Function Chart (SFC) have been used to adequately represent and develop the co-ordination system of batch processes. 

The total batch time and the recoveries of the three products are pretty much the same with the wide 10°C mismatches of temperature upward or downward (101.73 or 81.73°C). Only when this setpoint is set to be too low at 71.73°C does the batch operation fail with the organic phase totally refluxed but still not able to reach the temperature setpoint. At this low temperature setpoint value causing total refluxing of the organic phase, Strategy A discussed in Section 13.3.2 should be implemented with two sequential steps in the batch sequence (aqueous product recovery step and followed by the entrainer-acetic acid recovery step). However, because our proposed procedure only allows for simultaneous recovery of the three products, the batch operation failed. 

Develop an information flow diagram, a sequential function chart, and binary and ladder logic diagrams for this batch operation. Assume the batch proceeds uninterrupted (i.e., do not consider the case where the operator could accidentally activate the hand switch after the batch sequence starts). 

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