Optimization batch process

It is important to recognize that the batch sizes in Figure 3.16 are representative. However, as discussed subsequently in Section 4.5 and Chapter 12, the batch times and vessel sizes are key design variables in scheduling and optimizing batch processes. 

R. M. Felder, Simulation—A Tool for Optimizing Batch-Process Production, Chem. Eng.,... 

In batch process optimization, one of the principal objectives is to improve equipment utilization through reduction in dead time. This requires both structural and parameter optimization, with many options available. 

Consider changing from batch to continuous operation. Batch processes, by their very nature, are always at unsteady state and thus are difficult to maintain at optimal conditions. 

The purification of value-added pharmaceuticals in the past required multiple chromatographic steps for batch purification processes. The design and optimization of these processes were often cumbersome and the operations were fundamentally complex. Individual batch processes requires optimization between chromatographic efficiency and enantioselectivity, which results in major economic ramifications. An additional problem was the extremely short time for development of the purification process. Commercial constraints demand that the time interval between non-optimized laboratory bench purification and the first process-scale production for clinical trials are kept to a minimum. Therefore, rapid process design and optimization methods based on computer aided simulation of an SMB process will assist at this stage. 

Like enzymes, whole cells are sometime immobilized by attachment to a surface or by entrapment within a carrier material. One motivation for this is similar to the motivation for using biomass recycle in a continuous process. The cells are grown under optimal conditions for cell growth but are used at conditions optimized for transformation of substrate. A great variety of reactor types have been proposed including packed beds, fluidized and spouted beds, and air-lift reactors. A semicommercial process for beer used an air-lift reactor to achieve reaction times of 1 day compared with 5-7 days for the normal batch process. Unfortunately, the beer suffered from a mismatched flavour profile that was attributed to mass transfer limitations. 

Products in Group 3 seem to us to represent the future of practical batch process control. In such systems, modern workstations perform the single-user functions (e.g control system design, set-up, and maintenance operator interface data collection historical reporting) for which they were designed, while powerful multitasking controllers perform actual control. As computer hardware and software standards continue to evolve toward distributed networks of processors optimized for specific kinds of tasks, such systems will, we feel, proliferate rapidly. 

Stefanis, S.K., Livingston, A.G., Pistikopoulos, E.N. (1997) Environmental Impact Considerations in the Optimal Design and Scheduling of Batch Processes. Computers in Chemical Engineering, 21(10), 1073-1094. 

Most accidents in the chemical and related industries occur in batch processing. Therefore, in Chapter 5 much attention is paid to theoretical analysis and experimental techniques for assessing hazards when scaling up a process. Reaction calorimetry, which has become a routine technique to scale up chemical reactors safely, is discussed in much detail. This technique has been proven to be very successful also in the identification of kinetic models suitable for reactor optimization and scale-up. 

Cerda, J., Gutierrez, J., Esplugas, S. and Mata, J., 1990, Ind. Eng. Chem. Res. 29, 590. Charalambides, M.S., 1996, Optimal Design of Integrated Batch Processes , Ph. D. Thesis, University of London, the Imperial College, Department of Chemical Engineering and Chemical Technology, November, London. 

If a batch process manufactures only a single product, then the equipment can be designed and optimized for... 

Batch processes are, by their nature, always in a transitory state. This requires the dynamics of the process to be optimized, and will be considered in Chapter 14. However, the control systems required to put this into practice will not be considered. 

In continuous processes, parameter profiles might be required to be optimized through space. In batch processes, parameter profiles might need to be optimized through time. How can this be achieved ... 

The control variables can be constrained to fixed values (e.g. fixed initial temperature in a temperature profile) or constrained to be between certain limits. In addition to the six variables dictating the shape of the profile, ttotai can also be optimized if required. For example, this can be important in batch processes to optimize the batch cycle time in a batch process, in addition to the other variables. 

However, the designer should not loose sight of the fact that, whilst schedule planning and optimization provides the basis for the design of batch processes, production schedules are often disrupted once production has commenced. For example, what happens if a key item of equipment breaks down and needs to be repaired What happens if... 

Kemp, I.C., Deakin, A.W., 1989. The cascade analysis for energy and process integration of batch processes, Part 1, Chem. Eng. Res. Des., 67 495-509 Kiperstok, A., Sharratt, P.N., 1995. On the optimization of mass exchange networks for the removal of pollutants. Trans. IChemE, 73b 271-277... 

Yao, Z.L., Yuan, X.G., 2000. An approach to optimal design of batch processes with waste minimization. Comput. Chem. Eng., 24 1437-1444. 

Similarly, whole-cell Lactobacillus kefir DSM 20587, which possesses two alcohol dehydrogenases for both asymmetric reduction steps, was applied in the reduction of tert-butyl 6-chloro-3,5-dioxohexanoate for asymmetric synthesis of ft rf-butyl-(31 ,5S)-6-chloro-dihydroxyhexanoate (Figure 7.5), a chiral building block for the HMG-CoA reductase inhibitor [ 17]. A final product concentration of 120 him and a specific product capacity of 2.4 mmol per gram dry cell were achieved in an optimized fed-batch process. Ado 99% was obtained for (3R,5S)- and (3.S, 55)-te/ f-butyl-6-chloro-dihydroxyhexanoate with the space-time yield being 4.7 mmolL-1 h-1. 

The medium composition used in the fed-batch process was optimized, resulting in cell densities near 100 g l-1. By using an exponential feed rate resulting in a growth rate of 0.05 h-1, a maximum biomass concentration of 112 g 1 1 was attained, with a biomass productivity of 1.8 g 1 1 h. The poly(3HAMCL) productivity however was low, 0.34 g 1 1 h, caused by a steady decrease of the poly(3HAMCL) content during the last part of the fermentation [51]. When this optimized medium composition was used in the continuous culture system described above, a maximum biomass concentration of 18 g 1 1 was reached. The PHA content however remained low at approximately 10% [51]. It is still unclear what causes these low PHA contents. 

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