Multiperiod Operation optimisation

For a fixed column design, Bonny et al. (1996) considered multiperiod operation optimisation but with multiple separation duties. That is why this is presented in this chapter rather than in Chapter 6. The optimisation problem can be stated as ... 

For single separation duty, Mujtaba and Macchietto (1993) proposed a method, based on extensions of the techniques of Mujtaba (1989) and Mujtaba and Macchietto (1988, 1989, 1991, 1992), to determine the optimal multiperiod operation policies for binary and general multicomponent batch distillation of a given feed mixture, with several main-cuts and off-cuts. A two level dynamic optimisation formulation was presented so as to maximise a general profit function for the multiperiod operation, subject to general constraints. The solution of this problem determines the optimal amount of each main and off cut, the optimal duration of each distillation task and the optimal reflux ratio profiles during each production period. The outer level optimisation maximises the profit function by... 

The dynamic optimisation problem formulation is illustrated for representative multiperiod operations. The STNs in Figures 6.1 and 6.2 for binary and ternary mixtures undergoing single separation duty describe the multiperiod operations (see Chapter 3). For other networks, mixtures with larger number of components and other constraints the problem formulation requires only simple modifications of that presented in this section. 

The optimisation problem formulation for the multiperiod operation given in Figure 6.1 can now be written as follows ... 

The reflux ratio is discretised into two time intervals for task 1 and one time interval for task 2. Thus a total of 3 reflux ratio levels and 3 switching times are optimised for the whole multiperiod operation. Three cases are considered, corresponding to different values of the main-cut 1 product. For each case the... 

Multiperiod Campaign Operation Optimisation - Industrial Case Study... 

Logsdon et al. (1990) formulated multiperiod multiple separation duties design and operation optimisation problem for two binary mixtures. Only one distillate product per mixture was considered according to the operation shown in Figure 7.7. 

Mujtaba (1999) considered the conventional configuration of BED processes for the separation of binary close boiling and azeotropic mixtures. Dynamic optimisation technique was used for quantitative assessment of the effectiveness of BED processes. Two distinct solvent feeding modes were considered and their implications on the optimisation problem formulation, solution and on the performance of BED processes were discussed. A general Multiperiod Dynamic Optimisation (MDO) problem formulation was presented to obtain optimal separation of all the components in the feed mixture and the recovery of solvent while maximising the overall profitability of the operation. 

Table 7.6. Multiperiod Optimisation of Design and Operation [Adopted from Logsdon et al., 1990]...

First, two examples using both problems OP1 and OP2 are presented to explain the effects of different solvent feeding modes and path constraint on the operation. In these examples only Task 1 of Figure 10.6 is carried out where component 1 is recovered at a given purity. Then, example 3 using Multiperiod Optimisation Problem (OP) is presented, where all three Tasks of Figure 10.6 are carried out. 

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