6 Fermentation and Biochemical Engineering Handbook Figure l is an example of chemostat equipment that we call a single-stage continuous culture. Typical homogeneous continuous culture systems are shown in Fig. 2 Table 4. Classification of continuous fermentation processes 1. without feedback control a. Turbidostat lIlm WIllI Vent Broth eservoir reservoir Broth (a)single-stage continuous culture b)Level controller system Figure 1. Chemostat System. V: Operation volume. F: Feed rate of medium
6 Fermentation and Biochemical Engineering Handbook Figure 1 is an example of chemostat equipment that we call a single-stage continuous culture. Typical homogeneous continuous culture systems are shown in Fig. 2. Table 4. Classification of continuous fermentation processes 1. Without feedback control a. Chemostat 2. With feedback control a. Turbidostat b. Nutristat c. Phauxostat i F Med i urn reservoir Air Motor 1 Broth re servo i r (a1Single-stage continuous culture system f (bltevel controller Figure 1. Chemostat System. V: Operation volume. F: Feedrate ofmedium. Sf: Concentration of limiting substrate
Fermentation Pilot plant (a)single-stage continuous operat ion (b)single-stage continuous operation with feedback (c)Multi-stage continuous operation: simple chain (d)Multi-stage continuous operation: Multiple substrate addition Figure 2. Homogeneous systems for continuous fermentation
Fermentation Pilot Plant L r I 11 1 I I mM - 0 7 - _N_v (a)Single-stage m c o n t i n u o u s o p e r a t i o n Figure 2. Homogeneous systems for continuous fermentation
8 Fermentation and Biochemical Engineering Handboot 1.3 Application of Computer Control and Sensing Technologies for Fermentation Process The application of direct digital control of fermentation processes began in the 1960s. Since then, many corporations have developed computer-aided fermentation in both pilot and commercial plants. Unfortu nately, these proprietary processes have almost never been published, dueto corporate secrecy. Nevertheless, recent advances in computer and sensing technologies do provide us with a great deal of information on fermentation This information can be used to design optimal and adaptive process controls In commercial plants, programmable logic controllers and process computers enable both process automation and labor-savings. The present and likely future uses of computer applications to fermentation processes in pilot and industrial plants are summarized in table 5. In the table, open circles indicate items that have already been discussed in other reports while the open triangles are those topics to be elaborated here Table 5. Computer Applications to Fermentation Plants Pilot scale Production scale Fut Sequence control Feedback control Data acquisition imation state variables Advanced control △ Modelling Scheduling
8 Fermentation and Biochemical Engineering Handbook 1.3 Application of Computer Control and Sensing Technologies for Fermentation Process The application of direct digital control of fermentation processes began in the 1960’s. Since then, many corporations have developed computer-aided fermentation in both pilot and commercial plants. Unfortunately, these proprietary processes have almost never been published, due to corporate secrecy. Nevertheless, recent advances in computer and sensing technologies do provide us with a great deal of information on fermentation. This information can be used to design optimal and adaptive process controls. In commercial plants, programmable logic controllers and process computers enable both process automation and labor-savings. The present and likely future uses of computer applications to fermentation processes in pilot and industrial plants are summarized in Table 5. In the table, open circles indicate items that have already been discussed in other reports while the open triangles are those topics to be elaborated here. Table 5. Computer Applications to Fermentation Plants Sequence control Feedback control Data acquisition Estimation of state variables Advanced control Optimized Control Modelling Scheduling Pilot Scale Present Future Production Scale Present Future A few cases A A
fermentation Pilot plant The acquisition of data and the estimation of state parameters on commercial scales will undoubtedly become increasingly significant Unfortunately, the advanced control involving adaptive and optimize controls have not yet been sufficiently investigated in either the pilot or industrial scale Adaptive control is of great importance for self-optimization of fermentation processes, even on a commercial scale, because in ordinary fermentation the process includes several variables regarding culture condi tions and raw materials. We are sometimes faced with difficulties in the mathematical modelling of fermentation processes because of the complex reaction kinetics involving cellular metabolism. The knowledge-based controls using fuzzy theory or neural networks have been found very uset for what we call the"black box processes. Although the complexity of the process and the number of control parameters make control problems in fermentation very difficult to solve, the solution of adaptive optimization strategies is worthwhile and can contribute greatly to total profits. In order to establish such investigations, many fermentation corporations have been building pilot fermentation systems that consist of highly instrumented fermenters coupled to a distributed hierarchical computer network for on-and off-line data acquisition, data analysis, control and modelling. An example of the hierarchical computer system that is shown in Fig. 3 has become as common in the installation of large fermentation plants as it is elsewhere in the chemical industry. Figure 4 shows the details of a computer communi- cation network and hardware As seen in Fig 3, the system is mainly divided into three different functional levels. The first level has the YEWPACK package instrumenta tion systems(Yokogawa Electric Corporation, Tokyo), which may consist of an operators console (UOPC or UOPS)and several field control units (UFCU or UFCH) which are used mainly for on-line measurement, alarm, sequence control, and various types of proportional-integral-derivative(PID) controls. Each of the field control units interfaces directly with input/output signals from the instruments of fermenters via program controlle conditioners. In the second level, YEWMAC line computer systems (Yokogawa Electric Corporation, Tokyo) are dedicated to the acquisiti storage, and analysis of data as well as to documentation, graphics, optimi zation, and advanced control. a line computer and several line controllers constitute a YEWMAC. The line controller also governs the local area network formed with some lower level process computers using the bsc multipoint system. On the third level, a mainframe computer is reserved for modelling, development of advanced control, and the building of a data base
Fermentation Pilot Plant 9 The acquisition of data and the estimation of state parameters on commercial scales will undoubtedly become increasingly significant. Unfortunately, the advanced control involving adaptive and optimized controls have not yet been sufficiently investigated in either the pilot or industrial scale. Adaptive control is of great importance for self-optimization of fermentation processes, even on a commercial scale, because in ordinary fermentation the process includes several variables regarding culture conditions and raw materials. We are sometimes faced with difficulties in the mathematical modelling of fermentation processes because of the complex reaction kinetics involving cellular metabolism. The knowledge-based controls using fuzzy theory or neural networks have been found very useful for what we call the “black box” processes. Although the complexity of the process and the number of control parameters make control problems in fermentation very difficult to solve, the solution of adaptive optimization strategies is worthwhile and can contribute greatly to total profits. In order to establish such investigations, many fermentation corporations have been building pilot fermentation systems that consist of highly instrumented fermenters coupled to a distributed hierarchical computer network for on-and off-line data acquisition, data analysis, control and modelling. An example of the hierarchical computer system that is shown in Fig. 3 has become as common in the installation of large fermentation plants as it is elsewhere in the chemical industry. Figure 4 shows the details of a computer communication network and hardware. As seen in Fig. 3, the system is mainly divided into three different functional levels. The first level has the YEWPACK package instrumentation systems (Yokogawa Electric Corporation, Tokyo), which may consist of an operator’s console (UOPC or UOPS) and several field control units (UFCU or UFCH) which are used mainly for on-line measurement, alarm, sequence control, and various types of proportional-integral-derivative (PID) controls. Each of the field control units interfaces directly with input/output signals from the instruments of fermenters via program controllers and signal conditioners. In the second level, YEWMAC line computer systems (Yokogawa Electric Corporation, Tokyo) are dedicated to the acquisition, storage, and analysis of data as well as to documentation, graphics, optimization, and advanced control. A line computer and several line controllers constitute a YEWMAC. The line controller also governs the local area network formed with some lower level process computers using the BSC multipoint system. On the third level, a mainframe computer is reserved for modelling, development of advanced control, and the building of a data base
10 Fermentation and Biochemical Engineering Handbook Finally, the mainframe computer communicates with a company computer via a data highway. This is used for decision-making, planning, and other managerial functions. The lower level computer, shown as the first level in Fig. 3, is directly interfaced to some highly-instrumented fermenters Figure 5 illustrates a brand new fermenter for fed-batch operation. Control is originally confined to pH, temperature, defoaming, air flow rate, agitation speed, back pressure, and medium feed rate. Analog signals from various sensors are sent to a multiplexer and A/D converters. After the computer stores the data and analyzes it on the basis of algorithms, the computer sends the control signals to the corresponding controllers to control the fermentation process MAINFRAME COMPUTER LINE COMPUTOR 3 quISiTiOn Graphy ic display LIME CONTROLLER Sophist icated contre ■■■■■■■■■■■■■■■■■■■■■■■■■■■■■■国■■■■■■■■■■■■薯■■ DATA HIGHWAY Level I OPERATOR OPERATOR CONSOLE CONSOLE PID cor UFCU: Field control unlt Figure 3. Configuration of distributed hierarchical computer system for fermentation
IO Fermentation and Biochemical Engineering Handbook DATA HIOHWAY Finally, the mainframe computer communicates with a company computer via a data highway. This is used for decision-making, planning, and other managerial functions. The lower level computer, shown as the first level in Fig. 3, is directly interfaced to some highly-instrumented fermenters. Figure 5 illustrates a brand new fermenter for fed-batch operation. Control is originally confined to pH, temperature, defoaming, air flow rate, agitation speed, back pressure, and medium feed rate, Analog signals from various sensors are sent to a multiplexer and ND converters. After the computer stores the data and analyzes it on the basis of algorithms, the computer sends the control signals to the corresponding controllers to control the fermentation process. level m MAINFRAME COMPUTER Figure 3. Configuration of distributed hierarchical computer system for fermentation pilot plant. Optimi zit ion VEWMAC 300 LINE COMPUTOR tevei II Data aquisition LINE CONTROLLER 3600-M$A Optimization Sophisticated control I ! UFCU