Process synthesis methodologies

A number of experimental chemical process synthesis procedures have been developed with a hierarchical architecture based on both the hierarchical structure of the chemical innovation process and the physical property hierarchy. Examples include PIP (Kirkwood et al, 1988) and BALTAZAR (Mahalec and Motard, 1977). This hierarchical approach is also evident in the Pinch Technology Onion Diagram (Linnhoff and Ahmad, 1983). The hierarchical approach is also the foundation for the two early textbooks on process synthesis methodology (Rudd et al, 1973 Douglas, 1988). 

While the model of abstract refinement is quite satisfactory for the hierarchical planning of the process synthesis methodology, it is quite cumbersome and possibly incorrect as a model to describe the intricate web of design actions from one milestone to the next. Instead, the transformational model (Balzer et al., 1976 Scherlis and Scott, 1983 Stephanopoulos, 1989) provides a more appropriate vehicle. This model converts specifications into designs through a series of correctness-... 

Despite a fair amount of effort to find a process synthesis methodology that can headle the above problems. 

There are msny efforts now underway to develop procedures for incoiporating heat integration into process synthesis methodology several of the references for this section should be examined for more information. 

More recant efforts to develop computer-aided process synthesis methodologies can be cbeincterized as either sequential modular, simultaneous modular, or equation oriented, Sequeatial-modular approaches are ben for steady-state simulation where process inputs are defined and process para met ara ate available. The best feature of sequential-modular approaches is that they are flowsheet oriented, bot they are not as flexible as the other methodologies in parfonuing design and optimization tasks.39... 

There is no doubt that, in many instances, relatively smtple approaches are still anfficient to accomplish particular control objectives. However, for example, in the case of separation sequences that involve complex flow arrangements and thermal onapling, more advanced process control strategies will be necessary. As process synthesis methodologies improve, control strategy evaluation and process design and... 

In recent years a considerable amount of literature has appeared in chemical engineering journals on the subject of process synthesis. Nishida et al. reviewed the current state of the art as it applies to cheiiucal processes. If process synthesis methodology were developed fully, one could invoke a computer program which, with minimal input, would select not only the separation method of choice but also would determine how the various unit operations should be connected together to form the entire flowsheet. At the present time, however, process synthesis methodology for separation processes is in the earty stages of research. 

Process simulation is now a powerful tool for process design. As process synthesis methodology matures, it is reasonable to expect process simulation to be a powerful subset of process synthesis. Before that becomes a reality, however, much must be done to currently available process simulation packages. More separation operations must be incorporated into the simulation packages with their associated cost calculations. The most serious deficiency in the simulation software, however, is the absence of short-cut computations of sufficient accuracy to lead to valid conclusions. 

---