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Design and operation of batch processes
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Section 3 Rapporteurs’ DESIGN Automation
Review
AND OPERATION
and Control
OF HATCH PROCESSES
MICHEL D. RENARD Systems, Merck &Co., Inc., P.O. Box 2000, Rahway, (Receivedfh
publication
Mr. Chairman, Ladies and Gentlemen ; First of all, on behalf of my Company I would like to express our gratitude to Dr. Rippin for having invited a representative of our Automation and Control department to report at the session on Design and Operation of Batch Processes. As is apparent from a quick review of the papers presented in this Symposium, interest given by the process control industry and the universities to the use of computers in Batch Processes is still minimal (6 papers out of a total of 115). We at Merck are cognizant of this reality since the very existence of our department was necessitated by the need to develop inhouse capabilities for applying computers to the design and operations of batch chemical plants. On the surface, it might be surprising that 21 years after the installation of the first process control computer, not more progress has been made toward developing global approaches to the design and operation of batch processes with computers. After all, when you get right down to it, all the actions that are required to operate equipment in a batch plant can be reduced to five elementary ones: to open and close valves, to turn motors on and off and to manipulate control valves. Computers have been able to do that much for quite a while now. Of course, in large multipurpose batch chemical plants, one typically finds several thousand valves and several hundred control valves. But that is nothing extraordinary; refineries for example are furnished with many times more than these numbers, and computers are routinely in use there. What then are some of the reasons why batch processing has remained the step child of the process automation technology as compared with continuous one ?
8 February
NJ 07065, U.S.A.
1980)
In comparison, batch processes tend to be used in industries characterized by a fragmented production: short campaigns (therefore small volume) of a relatively large array of products, each requiring a different process. As a result, in those industries, automation can only be financially justified in specific instances as for example : --dedicated facilities, producing the same product, year in, year out, with small or no process changes so that reprogramming and relearning by operating personnel are at a minimum ; -spot automation; that is, using a computer for finer control of a specific part of the plant to eliminate a bottleneck; -assisting in complex control strategies where the computer can help alleviate costly operator mistakes. In the case of the pharmaceutical industry, additional factors have made automation of batch processes an attractive proposition and a necessity. First, given the trend towards specialization by pharmaceutical firms in their fields of research-and the trend towards worldwide marketing-production volumes have increased making automation benefits financially interesting. Second, increased legislation by the regulatory agencies requires one to collect large quantities of data about the conditions of production, and of ccgrse computers are very much at home in this role. Third, increased competition on a world-wide basis and the rapid introduction of ever better drugs have made it more difficult to predict the product life of a new drug. As a hedge against the risk to be left with idle plants when a competitor’s product takes over the market, where possible, companies are building multiproduct facilities which offer the flexibility of producing a mix of different products with the same equipment. But this flexibility carries with it much added complexity in the design and operation of these plants and computers have proven to be very helpful there. However: given the large cost of developing computer-assisted techniques that can be routinely used by engineers, few companies are able to afford the necessary investment. The pooling of resources which would be helpful is unfortunately hampered by the need to protect trade secrets regarding the processes.
ECONOMIC FACTORS
For the suppliers of instrumentation equipment, continuous processes constitute a much larger market than batch processes (SO vs 20%) and continuous process plants represent as a whole a much larger asset base than those of the batch type. As a result more resources have been invested in the research or development of automation techniques towards the former than the latter. Continuous processes are found in industries characterized by large volumes of single products and generally smaller profit margins per unit of volume. There, even moderately sophisticated automation brings about huge benefits because even a fraction of a percent in throughput or yield improvement translates into very substantial operating and inventory cost reductions. Therefore, automation investments on an industry by industry basis are more attractive for the continuous type processes.
PROCESS CONSIDERATIONS
For continuous processes it is economical to build special purpose plant equipment which is designed to fit more closely with the process. Such equipment requires less manipulation of controlling elements. And since the strategy ofcontinuous processes consists of maintaining conditions at steady state, general purpose algorithms can be applied more widely from process to process. 9
Rapporteurs’ review
10
Batch processes are carried out within a variety of more general purpose plants equipment. This requires increased manipulation of the controlling elements and there is less opportunity of generalizing operating procedures or control algorithms. In the world of continuous control, deviation from steady state is viewed as a process upset, a distraction from the objective. For this reason, start-up and shutdown of operations are considered control and operational nightmares. In comparison, a batch plant is constantly starting up and shutting down its various equipment, and the strategy of control consists in changing the state of controlling variables, based upon both events and time (the sequencing problem). In addition, the control problem is superimposed with a scheduling problem aimed at reducing dead times and maximizing equipment utilization. Furthermore, since the batch process involves the simultaneous operation of an array of different equipment each in a different way, at each stage of the process, a large number of activities must be conducted in simultaneity (the parallelism problem). For all the above reasons, it is much more difficult to develop automated methods for batch processes than continuous ones.
TECHNOLOGICAL
LIMITATION
In 1971, Mr. Jaakko Numminen, Minister of Education, Finland, noted in the opening address of the 3rd international ISA Conference, in Helsinki, that the slow progress made in using computers in process control was largely due to the fact that it was very difficult to adapt machines that were designed to keep track of inventory and compute payroll for use in the control of a chemical reaction ! Of course during the intervening decade much was done by the computer manufacturers to bring to market a fantastic array of computers and associated interfacing devices better adapted to the needs of real time control applications. However, for the batch process, impedence factors still exist today that gave a slow start to the use of computers in the process industry at large, 10 years ago. Machine Architecture. The general purpose nature of the architecture of computers is simply not well geared for modeling or controlling batch processes. Specifically, something better is needed to solve the sequencing and parallelism problems mentioned above. What is needed are true multi-engine sequencing machines, with high-level languages, easy to customize for each class ofapplication. For fast communication between the engines, we also need built-in distributed data storage and management facilities. Man/Machine Interface. Of course great progress was achieved in this area with the introduction of colored cathod-ray tubes and colored plotters for visualization of conditions and trending of variables. But shortcomings still exist which affect the batch process. They are (1) limitation in the size of those devices to economically represent the large number of variables or control elements characteristic of batch equipment, and (2) inadequacy of input devices (keyboards, touch pads, etc.) to permit the operator to perform a large number of control actions per unit of time with a minimal number of hand motions.
Sensing Elements. The lack of certain sensors still means that too much information is needed from the field operator, thus requiring resort to ‘manual steps’ and thereby defeating the advantages gained by an otherwise automated operation. I will now proceed to introduce the papers at this session in the perspective of the general comments given above. I have attempted to group them in four categories even though the topics sometimes overlap.
1. PLANT DESIGN In the course of the above discussion I compared the characteristics of the continuous process vs those of the batch type. But the real world is not that well divided and frequently in a given production facility material flows from equipment operated in a ‘continuous’ mode to equipment of a ‘batch’ nature. At the intersection of those two worlds some interesting control or operational problems arise. In Paper 3.4 (K. Oi, H. ltoh and I. Mughi), the case of a process stream going from several parallel batch units to a continuous unit is considered. Specifically, a model is presented to compute the relationship between the margin of safety (in volume) of the storage section which absorbs the fluctuations of flow between continuous and batch units, and the scheduling of starting instants of the batch units. Noting that in practice the size of the storage unit is always selected to provide a margin of safety, the author develops a theory which demonstrates how to manipulate the starting instants of the batch units to make use of the margin of volume safety to increase the throughput of the whole. This paper constitutes original theoretical work and illustrates the need for a computer to solve this class of problems. The result of this work has been successfully applied to the scheduling of waste flows that fluctuate periodically from several production units into a waste treatment plant. In Paper 3.S (T. Takamatsu. 1. Hashimoto and S. Hasebe), a model is presented that characterizes the situation of a parallel batch unit and associated storage tanks located between two continuous units. The relation between the value of storage tank capacities and scheduling of the batch unit is given. The problem solved here is of great value since this arrangement of equipment is often found in industrial plants, for example in fermentation. Resulting calculations allow one to derive minimum storage tank capacity while maintaining constant flow rates ofinput and output streams. 2. PROCESS DESIGN The next two.papers discuss strategies for optimal control of classic operations that have a wide range of utilization in the process industry. In the first one (Paper 3.1 by H. Egly, V. Ruby and B. Seid). a dynamic process model is developed on a computer for evaluation of different strategies in conducting discontinuous rectifications in the presence of superimposed reactions. Results of the theory are applied to practical cases. It is found that by applying the optimization techniques with the help of a process control computer, improvements in capacity of 507/, have been achieved along with energy savings of 3tX40%. This paper is quite timely in our era of energy conservation, as it positively shows that computers can help us solve yet another challenge.
Rapporteurs’
A classic operation encountered in the synthesis of chemicals is the heating of a batch to reaction temperature and subsequent control of the temperature while the reaction is in progress. In paper 3.2 (P. Hugo and W. Schaper) a strategy of temperature control for strong exothermic reactions is presented. Four necessary phases are selected: (a) a heating period until the reaction catches on, (b) an adiabatic phase, (c) a phase of maximum cooling during which the reaction reaches the maximum allowable temperature and (d) a controlled cooling phase until reaction completes. Since a theoretical modeling of the ideal temperature is too complex, an empirical curve is developed from laboratory experiments during which the reacting materials are brought to an empirically determinable maximum temperature as quickly as possible with the help of a computer. The aim is to determine the optimal time at which to apply maximum cooling. Results show that by applying this strategy it is possible to increase batch size from l-2 to 10 M3 with reproducible results in an industrial environment. 3. OPERATION
EVALUATION
An obvious problem faced by the technical management of industrial firms is the decision related to automation investments. This topic is very complex since the advantages of automation vary among industries, according to not only the types of processes concerned but also the geographic location of the plant. The first major obstacle is that it is very difficult to isolate the benefits brought about by the computer itself from those contributed by the other steps, which by themselves carry additional costs and benefits, but which must be taken so that a computer can be used to start with. For example, the largest labor savings come from the installation of remote operators and sensors for centralized operation. (Replacing leg and muscle power by finger power.) But the benefits of centralization by themselves may not justify the cost of remote instrumentation. Adding a computer to the scheme opens up the possibility for additional benefits that were not possible before such as : -more accurate control -better equipment utilization -reproducibility of quality -yield improvement -throughput increase -record keeping plus a long list of intangible advantages. However none of these can be realized with the computer alone, therefore some fraction of the centralization cost must be weighed against the computerization benefits. But how much? The second major difficulty is that when alternatives are analyzed for the construction of a new plant, each employing different degrees of automation, one will choose one of them and build that one only. It’s only after the facility is in routine operation that accurate operating information can be developed. But rarely can one find facilities in use that are identical to the other alternatives considered, against which to make true comparisons. And this does not mention the fact that company management rarely wants to spend the money necessary to develop the audits.
11
reriebv
This situation makes it very difficult to develop accurate data about the advantages of the new technologies with which we are all involved in a way that will satisfy hard nosed financial controllers. This is an area where useful research could be applied. Without it one can gain some useful information from the published experience of others. As a case in point is paper 3.6 (E. Lahteemaki, E. Jutila and M. Paasila). The benefits of process control automation in paper mills based on the experience gained in 20 installations are presented. Results indicate payback periods from 3 months to 2 years due to capacity improvement of 10-35 “/,, yield improvement of 0.2-1.5 %, energy savings of 8-32 ‘, and reduction in the use of raw material from 2 to 7 “<. 4. PRODUCTION
PLANNING
As mentioned earlier in the general comments section, effective management ofa multi-product batch processing plant requires more careful attention than for the single product plant. In addition to the daily operating difficulties which can be alleviated by using a computer for the control of the process, the plant manager is faced with careful planning in order to assure maximum equipment utilization in a long term optimal production plan. Paper 3.7 (A. Mauderli and D. W. T. Rippin) describes a computer package for the Production Planning and Scheduling for Multi-Purpose Batch Chemical Plants. The package helps identify an optimal production plan for a given period by selecting the arrangement of campaigns that either maximizes profits or minimizes the time required to produce specified amounts of given products. tool for the This program is a welcome Pharmaceutical Industry where multi-product batch plants are more widely used. Coming in the footsteps of the MULTIBATCH computer program, which was also developed at Eidgenossis-he Technische Hochschule, Zurich, this new work is another example of the excellent contribution to the automation of Batch E’rocesses by this prestigious institution. I should like to congratulate the authors of the papers which I had the honour to review. I hope that their work will encourage others to tackle the challenging problems posed by batch production. But beyond technical challenge, economic necessities require further development in the field. For, even if the batch processing industry represents only onefifth of the process industry taken as a whole, the potential savings from productivity gains and reduction of capital investments that could be achieved by more automation are quite large. And it seems that in the 80’s the world is going to need every bit ofefficiency it can get to move our industrial civilization forward. But it will take a concentrated effort from the companies in the respective industries to define what their needs are, and for the universities to undertake the necessary research, so that we will start to define the problems further before solving them; as opposed to force fitting existing solutions to needs. Only then will we be able to specify the automation equipment which the batch process industry needs and expect from the computer manufacturers to build it. It has not happened from the computer experts learning about the process. It may happen as the Chemical Engineer learns more about computers.
Section 3 Rapporteurs’ DESIGN Automation
Review
AND OPERATION
and Control
OF HATCH PROCESSES
MICHEL D. RENARD Systems, Merck &Co., Inc., P.O. Box 2000, Rahway, (Receivedfh
publication
Mr. Chairman, Ladies and Gentlemen ; First of all, on behalf of my Company I would like to express our gratitude to Dr. Rippin for having invited a representative of our Automation and Control department to report at the session on Design and Operation of Batch Processes. As is apparent from a quick review of the papers presented in this Symposium, interest given by the process control industry and the universities to the use of computers in Batch Processes is still minimal (6 papers out of a total of 115). We at Merck are cognizant of this reality since the very existence of our department was necessitated by the need to develop inhouse capabilities for applying computers to the design and operations of batch chemical plants. On the surface, it might be surprising that 21 years after the installation of the first process control computer, not more progress has been made toward developing global approaches to the design and operation of batch processes with computers. After all, when you get right down to it, all the actions that are required to operate equipment in a batch plant can be reduced to five elementary ones: to open and close valves, to turn motors on and off and to manipulate control valves. Computers have been able to do that much for quite a while now. Of course, in large multipurpose batch chemical plants, one typically finds several thousand valves and several hundred control valves. But that is nothing extraordinary; refineries for example are furnished with many times more than these numbers, and computers are routinely in use there. What then are some of the reasons why batch processing has remained the step child of the process automation technology as compared with continuous one ?
8 February
NJ 07065, U.S.A.
1980)
In comparison, batch processes tend to be used in industries characterized by a fragmented production: short campaigns (therefore small volume) of a relatively large array of products, each requiring a different process. As a result, in those industries, automation can only be financially justified in specific instances as for example : --dedicated facilities, producing the same product, year in, year out, with small or no process changes so that reprogramming and relearning by operating personnel are at a minimum ; -spot automation; that is, using a computer for finer control of a specific part of the plant to eliminate a bottleneck; -assisting in complex control strategies where the computer can help alleviate costly operator mistakes. In the case of the pharmaceutical industry, additional factors have made automation of batch processes an attractive proposition and a necessity. First, given the trend towards specialization by pharmaceutical firms in their fields of research-and the trend towards worldwide marketing-production volumes have increased making automation benefits financially interesting. Second, increased legislation by the regulatory agencies requires one to collect large quantities of data about the conditions of production, and of ccgrse computers are very much at home in this role. Third, increased competition on a world-wide basis and the rapid introduction of ever better drugs have made it more difficult to predict the product life of a new drug. As a hedge against the risk to be left with idle plants when a competitor’s product takes over the market, where possible, companies are building multiproduct facilities which offer the flexibility of producing a mix of different products with the same equipment. But this flexibility carries with it much added complexity in the design and operation of these plants and computers have proven to be very helpful there. However: given the large cost of developing computer-assisted techniques that can be routinely used by engineers, few companies are able to afford the necessary investment. The pooling of resources which would be helpful is unfortunately hampered by the need to protect trade secrets regarding the processes.
ECONOMIC FACTORS
For the suppliers of instrumentation equipment, continuous processes constitute a much larger market than batch processes (SO vs 20%) and continuous process plants represent as a whole a much larger asset base than those of the batch type. As a result more resources have been invested in the research or development of automation techniques towards the former than the latter. Continuous processes are found in industries characterized by large volumes of single products and generally smaller profit margins per unit of volume. There, even moderately sophisticated automation brings about huge benefits because even a fraction of a percent in throughput or yield improvement translates into very substantial operating and inventory cost reductions. Therefore, automation investments on an industry by industry basis are more attractive for the continuous type processes.
PROCESS CONSIDERATIONS
For continuous processes it is economical to build special purpose plant equipment which is designed to fit more closely with the process. Such equipment requires less manipulation of controlling elements. And since the strategy ofcontinuous processes consists of maintaining conditions at steady state, general purpose algorithms can be applied more widely from process to process. 9
Rapporteurs’ review
10
Batch processes are carried out within a variety of more general purpose plants equipment. This requires increased manipulation of the controlling elements and there is less opportunity of generalizing operating procedures or control algorithms. In the world of continuous control, deviation from steady state is viewed as a process upset, a distraction from the objective. For this reason, start-up and shutdown of operations are considered control and operational nightmares. In comparison, a batch plant is constantly starting up and shutting down its various equipment, and the strategy of control consists in changing the state of controlling variables, based upon both events and time (the sequencing problem). In addition, the control problem is superimposed with a scheduling problem aimed at reducing dead times and maximizing equipment utilization. Furthermore, since the batch process involves the simultaneous operation of an array of different equipment each in a different way, at each stage of the process, a large number of activities must be conducted in simultaneity (the parallelism problem). For all the above reasons, it is much more difficult to develop automated methods for batch processes than continuous ones.
TECHNOLOGICAL
LIMITATION
In 1971, Mr. Jaakko Numminen, Minister of Education, Finland, noted in the opening address of the 3rd international ISA Conference, in Helsinki, that the slow progress made in using computers in process control was largely due to the fact that it was very difficult to adapt machines that were designed to keep track of inventory and compute payroll for use in the control of a chemical reaction ! Of course during the intervening decade much was done by the computer manufacturers to bring to market a fantastic array of computers and associated interfacing devices better adapted to the needs of real time control applications. However, for the batch process, impedence factors still exist today that gave a slow start to the use of computers in the process industry at large, 10 years ago. Machine Architecture. The general purpose nature of the architecture of computers is simply not well geared for modeling or controlling batch processes. Specifically, something better is needed to solve the sequencing and parallelism problems mentioned above. What is needed are true multi-engine sequencing machines, with high-level languages, easy to customize for each class ofapplication. For fast communication between the engines, we also need built-in distributed data storage and management facilities. Man/Machine Interface. Of course great progress was achieved in this area with the introduction of colored cathod-ray tubes and colored plotters for visualization of conditions and trending of variables. But shortcomings still exist which affect the batch process. They are (1) limitation in the size of those devices to economically represent the large number of variables or control elements characteristic of batch equipment, and (2) inadequacy of input devices (keyboards, touch pads, etc.) to permit the operator to perform a large number of control actions per unit of time with a minimal number of hand motions.
Sensing Elements. The lack of certain sensors still means that too much information is needed from the field operator, thus requiring resort to ‘manual steps’ and thereby defeating the advantages gained by an otherwise automated operation. I will now proceed to introduce the papers at this session in the perspective of the general comments given above. I have attempted to group them in four categories even though the topics sometimes overlap.
1. PLANT DESIGN In the course of the above discussion I compared the characteristics of the continuous process vs those of the batch type. But the real world is not that well divided and frequently in a given production facility material flows from equipment operated in a ‘continuous’ mode to equipment of a ‘batch’ nature. At the intersection of those two worlds some interesting control or operational problems arise. In Paper 3.4 (K. Oi, H. ltoh and I. Mughi), the case of a process stream going from several parallel batch units to a continuous unit is considered. Specifically, a model is presented to compute the relationship between the margin of safety (in volume) of the storage section which absorbs the fluctuations of flow between continuous and batch units, and the scheduling of starting instants of the batch units. Noting that in practice the size of the storage unit is always selected to provide a margin of safety, the author develops a theory which demonstrates how to manipulate the starting instants of the batch units to make use of the margin of volume safety to increase the throughput of the whole. This paper constitutes original theoretical work and illustrates the need for a computer to solve this class of problems. The result of this work has been successfully applied to the scheduling of waste flows that fluctuate periodically from several production units into a waste treatment plant. In Paper 3.S (T. Takamatsu. 1. Hashimoto and S. Hasebe), a model is presented that characterizes the situation of a parallel batch unit and associated storage tanks located between two continuous units. The relation between the value of storage tank capacities and scheduling of the batch unit is given. The problem solved here is of great value since this arrangement of equipment is often found in industrial plants, for example in fermentation. Resulting calculations allow one to derive minimum storage tank capacity while maintaining constant flow rates ofinput and output streams. 2. PROCESS DESIGN The next two.papers discuss strategies for optimal control of classic operations that have a wide range of utilization in the process industry. In the first one (Paper 3.1 by H. Egly, V. Ruby and B. Seid). a dynamic process model is developed on a computer for evaluation of different strategies in conducting discontinuous rectifications in the presence of superimposed reactions. Results of the theory are applied to practical cases. It is found that by applying the optimization techniques with the help of a process control computer, improvements in capacity of 507/, have been achieved along with energy savings of 3tX40%. This paper is quite timely in our era of energy conservation, as it positively shows that computers can help us solve yet another challenge.
Rapporteurs’
A classic operation encountered in the synthesis of chemicals is the heating of a batch to reaction temperature and subsequent control of the temperature while the reaction is in progress. In paper 3.2 (P. Hugo and W. Schaper) a strategy of temperature control for strong exothermic reactions is presented. Four necessary phases are selected: (a) a heating period until the reaction catches on, (b) an adiabatic phase, (c) a phase of maximum cooling during which the reaction reaches the maximum allowable temperature and (d) a controlled cooling phase until reaction completes. Since a theoretical modeling of the ideal temperature is too complex, an empirical curve is developed from laboratory experiments during which the reacting materials are brought to an empirically determinable maximum temperature as quickly as possible with the help of a computer. The aim is to determine the optimal time at which to apply maximum cooling. Results show that by applying this strategy it is possible to increase batch size from l-2 to 10 M3 with reproducible results in an industrial environment. 3. OPERATION
EVALUATION
An obvious problem faced by the technical management of industrial firms is the decision related to automation investments. This topic is very complex since the advantages of automation vary among industries, according to not only the types of processes concerned but also the geographic location of the plant. The first major obstacle is that it is very difficult to isolate the benefits brought about by the computer itself from those contributed by the other steps, which by themselves carry additional costs and benefits, but which must be taken so that a computer can be used to start with. For example, the largest labor savings come from the installation of remote operators and sensors for centralized operation. (Replacing leg and muscle power by finger power.) But the benefits of centralization by themselves may not justify the cost of remote instrumentation. Adding a computer to the scheme opens up the possibility for additional benefits that were not possible before such as : -more accurate control -better equipment utilization -reproducibility of quality -yield improvement -throughput increase -record keeping plus a long list of intangible advantages. However none of these can be realized with the computer alone, therefore some fraction of the centralization cost must be weighed against the computerization benefits. But how much? The second major difficulty is that when alternatives are analyzed for the construction of a new plant, each employing different degrees of automation, one will choose one of them and build that one only. It’s only after the facility is in routine operation that accurate operating information can be developed. But rarely can one find facilities in use that are identical to the other alternatives considered, against which to make true comparisons. And this does not mention the fact that company management rarely wants to spend the money necessary to develop the audits.
11
reriebv
This situation makes it very difficult to develop accurate data about the advantages of the new technologies with which we are all involved in a way that will satisfy hard nosed financial controllers. This is an area where useful research could be applied. Without it one can gain some useful information from the published experience of others. As a case in point is paper 3.6 (E. Lahteemaki, E. Jutila and M. Paasila). The benefits of process control automation in paper mills based on the experience gained in 20 installations are presented. Results indicate payback periods from 3 months to 2 years due to capacity improvement of 10-35 “/,, yield improvement of 0.2-1.5 %, energy savings of 8-32 ‘, and reduction in the use of raw material from 2 to 7 “<. 4. PRODUCTION
PLANNING
As mentioned earlier in the general comments section, effective management ofa multi-product batch processing plant requires more careful attention than for the single product plant. In addition to the daily operating difficulties which can be alleviated by using a computer for the control of the process, the plant manager is faced with careful planning in order to assure maximum equipment utilization in a long term optimal production plan. Paper 3.7 (A. Mauderli and D. W. T. Rippin) describes a computer package for the Production Planning and Scheduling for Multi-Purpose Batch Chemical Plants. The package helps identify an optimal production plan for a given period by selecting the arrangement of campaigns that either maximizes profits or minimizes the time required to produce specified amounts of given products. tool for the This program is a welcome Pharmaceutical Industry where multi-product batch plants are more widely used. Coming in the footsteps of the MULTIBATCH computer program, which was also developed at Eidgenossis-he Technische Hochschule, Zurich, this new work is another example of the excellent contribution to the automation of Batch E’rocesses by this prestigious institution. I should like to congratulate the authors of the papers which I had the honour to review. I hope that their work will encourage others to tackle the challenging problems posed by batch production. But beyond technical challenge, economic necessities require further development in the field. For, even if the batch processing industry represents only onefifth of the process industry taken as a whole, the potential savings from productivity gains and reduction of capital investments that could be achieved by more automation are quite large. And it seems that in the 80’s the world is going to need every bit ofefficiency it can get to move our industrial civilization forward. But it will take a concentrated effort from the companies in the respective industries to define what their needs are, and for the universities to undertake the necessary research, so that we will start to define the problems further before solving them; as opposed to force fitting existing solutions to needs. Only then will we be able to specify the automation equipment which the batch process industry needs and expect from the computer manufacturers to build it. It has not happened from the computer experts learning about the process. It may happen as the Chemical Engineer learns more about computers.