Batch processes optimisation

Aim of this work was to optimise enzymatic depolymerization of pectins to valuable oligomers using commercial mixtures of pectolytic enzymes. Results of experiments in continuous and batch reactor configurations are presented which give some preliminary indications helpful to process optimisation. The use of continuous reactors equipped with ultrafiltration membranes, which assure removal of the reaction products, allows to identify possible operation policy for the improvement of the reaction yield. 

One of the most attractive features of the IL/CO2 approach to homogeneous catalysis is the development of continuous processes [7]. Consequently it needs to be demonstrated that the combination of a suitable IL and compressed CO2 can offer more potential for process optimisation than just a simple protocol for batch-wise catalyst recycling. As an example we were able to activate, tune and immobilise Ni catalyst 13 in a continuous-flow system for the hydroviny-lation of styrene (Scheme 3). Styrene is co-dimerised with ethene yielding 3-substituted 1-butenes [26,27]. We could show that this powerful carbon-carbon bond-forming reaction can be achieved with high enantioselectivity in batch-wise operation and in continuous-flow systems. 

After the process optimisation (Scheme 7), the final results gave similar yields to the ones reported in batch trials [19]. The overall conclusion was positive as the continuous reaction procedure afforded more constant yields, a safer handling of... 

A reaction simulation program, REACTION, which will run on a personal computer, and which is specifically adapted for the non-steady states prevailing in batch reactions, is described and illustrated by a typical reaction model. Among uses of the program for rapidly studying reaction engineering, process optimisation, control systems, scale-up and staff training requirements, are included thermal stability and process safety studies. 

Optimal Control of Batch Processes Using Particle Swam Optimisation with Stacked Neural Network Models... 

An optimal control strategy for batch processes using particle swam optimisation (PSO) and stacked neural networks is presented in this paper. Stacked neural networks are used to improve model generalisation capability, as well as provide model prediction confidence bounds. In order to improve the reliability of the calculated optimal control policy, an additional term is introduced in the optimisation objective function to penalise wide model prediction confidence bounds. PSO can cope with multiple local minima and could generally find the global minimum. Application to a simulated fed-batch process demonstrates that the proposed technique is very effective. 

Keywords Batch processes. Neural networks. Particle swam optimisation. Reliability. 

Retrofit analysis Debottlenecking Batch processes planning and scheduling Data reconciliation Fault diagnosis Real time optimisation Fleat and mass and momentum Modeling... 

A useful approach to process optimisation is to identify all the critical process parameters that could potentially affect product quality or performance and prepare a Process Optimisation Protocol. Typically, data used to identify critical process parameters will be derived from laboratory or pilot-scale batches, and do not need to be confirmed on full-scale batches unless the control of the particular parameter can only be evaluated on a production scale. There is good incentive to use the production facilities at the earliest opportunity, drug availability permitting, to iron out any transfer difficulties. Manufacture of the stability batches to support Phase III studies, and also the Phase III clinical batches, at the final commercial site should minimise any questions from the FDA during PAI about possible differences between R D and Production process used. 

At later development stages, when process optimisation has been completed and clinical batches are being manufactured under replicated conditions, the regulatory authorities will expect more process validation. The actual process used and results obtained must be documented so that it can be duplicated. Normally, the product must meet predetermined product specifications and acceptance criteria on three occasions. The benefit of validating the process successfully is to reduce the amount of product testing. 

Batch processes are inherently dynamic and more difficult to monitor, control and optimise than steady state, continuous processes. Quality control of the product in a dynamic process is more difficult to achieve. Also, process safety is more difficult to achieve in a dynamic system than in continuous production. 

The batch process reactor system adds more flexibility but is probably the biggest contributor to waste generation. A detailed breakdown of the unit operations will give clear indications to the areas of manipulation which give most impact on waste minimisation. A step by step breakdown, as used in a Hazard and Operability (HAZOP) study, is applicable to optimising batch processes with respect to waste minimisation. 

In addition, the use of specialised plant, or indeed modification of a batch process to continuous process operation, may help in optimisation. Recovery/recycling, whilst important in the overall process efficiency, can be considered to be part of a distinctly separate study by the process development chemist. If satisfactory progress is not made by these approaches then consideration has to be given to the identification of a... 

In the pharmaceutical and food industry high-value-added products are manufactured mainly in batch process units. The heart of units is generally a jacketed stirred tank in which not only chemical transformation, but distillation, crystallisation, etc. can also be performed. As the aim of pharmaceutical industry is to produce high quality and purity products, the optimisation and control of operating conditions is the most efficient approach to produce efficiently, as well as to reach specific final conditions of the product in terms of quality and quantity (Cezerac, 1995). The S88.01 batch control standard defines three types of control needed for batch processing (ECES, 1997) ... 

Because of the increasing trend toward the production of low-volume/high-cost materials batch and semibatch processes become more and more important. In today s competitive markets, this implies the need for consistent high quality and improved performance. Over the last few years there has been growing interest in techniques for the determination of optimal operation policies for batch processes. Dynamic simulation has become a widely used tool in the analysis, optimisation, control structure selection and controller design. Some of the most recent work has been concerned with the mathematical optimisation of batch process performance (Li, 1998, Li et al., 1998). 

The synthesis of fine chemicals or pharmaceuticals, widely carried out in batch processes, implies many successive reaction and separation steps. Thus, synthesis optimisation is often restricted to the determination of the optimal operating conditions of each step separately. This approach is based on the use of reliable optimisation tools and has involved the development of various optimal control studies in reaction and distillation (Toulouse, 1999 Furlonge, 2000). 

Any water which may be contaminated with VCM, for example water used for the cleaning of reactors containing VCM, transfer lines and suspension or latex stock tanks, must be passed through a water stripper to remove VCM. This may be either continuous, consisting of a packed column or a column equipped with trays, or be a batch process. The VCM removal is optimised by the correct combination of residence time and temperature. The removed VCM is sent to the recovery plant and the aqueous effluent to a water treatment facility. 

Batch polymerisation is realised in autoclave reactors which operate on a cycle of phases at increased levels of temperature where the time and pressure parameters are carefiilly adjusted in order to gradually convert the monomer into polymer. The design of the plant is realised in order to optimise the sequences of different autoclaves, giving better continuity to production. The low quantity of product produced per each batch operation and the higher flexibility of the process, make the batch process suitable for the production of speciality polyamides. Batch polymerisation is also suitable for producing copolymers of polyamide 66 and polyamide 6, using partially caprolactam as the raw material together with nylon salt. 

In general the initial charge contains a seed, which is used principally to avoid the lack of reproducibility of the nucleation stages when the seed is produced in situ. In addition, it should be remarked that nucleation is very scale sensitive (Meuldijk et aL, 2003). Besides the seed latex, the initial charge in a semi-batch process contains a fraction of the total amount of water to be used, surfactant and initiator. Under some circumstances certain amount of the monomer(s) can also be present. The rest of the formulation ingredients are fed to the reaction mixture at a constant flow rate. Note that in many cases time-dependent feed rates are used. These feed rate profiles can be calculated by using empirical knowledge of the process or by application of optimisation techniques based on mathematical models. 

---