Sequential engineering approach

The sequential modular approach to process simulation solves system equations in blocks corresponding to the unit operations that make up the process. The block diagram for the process looks very much like the traditional process flowchart. Since engineers are accustomed to viewing chemical processes as sequences of unit operations, they lend to feel comfortable with this approach. 

Ihese difficulties vanish if the system equations are simply collected and solved for all unknown variables. Several powerful equation-solving algorithms are available in commercial programs like Maple , Mathematica , Matlab , Mathcad , and E-Z Solve that make the equation-based approach competitive with the sequential modular approach. Many researchers in the field believe that as this trend continues, the former approach will replace the latter one as the standard method for flowsheet simulation. (Engineers are also working on simultaneous modular methods, which combine features of both sequential modular and equation-based approaches. We will not deal with these refinements here, however.)... 

Hillestad, M., and T. Hertzberg, Dynamic Simulation of Chemical Engineering Systems by the Sequential Modular Approach, Comput. Chem. Eng., v. 10, p. 377 (1986). 

Many companies still take the risk of considering the different phases of complex products creation as sequential tasks. They assume that the periodical information exchange between the disciplines is sufficient. This can lead in most cases to inconsistencies. Instead, a concurrent engineering approach is to be followed, ensuring a traceability between all the models and phases involved [69]. 

This book demonstrates the application of biological sciences in engineering with theoretical and practical aspects. The seventeen chapters give more understanding of the knowledge related to the specified field, with more practical approaches and related case studies with original research data. It is a book for students to follow the sequential lectures with detailed explanations, and solves the actual problems in the related chapters. 

The Newton/sparse matrix methods now used by electrical engineers have become the solution method of choice. Hutchison and his students at Cambridge were among the first chemical engineers to publish this approach, in the early 1970s. They used a quasi-linear model rather than a Newton one, but the ideas were really very similar. (It appears that the COPE flowsheeting system of Exxon was Newton based it existed in the mid-1960s but slowly evolved into a sequential modular system. One must assume the Newton method failed to compete.)... 

Hong, W., Wang, S., Li, P., Wozny, G., Biegler, L.T., A Quasi-Sequential Approach to Large-Scale Dynamic Optimization Problems, AlChe Journal 52, No. 1 (255), 2006. Dorneanu, B., Bildea, C.S., Grievink, L, On the Application of Model Reduction to Plantwide Control, IT " European Symposium on Computer Aided Process Engineering, Bucharest, Romania, 2007. 

In the period 1970-80 s the major engineering bureaus, as well as some large manufacturing companies in refining and petrochemical industries developed in-house flowsheeting programs. Mostly adopted the modular sequential architecture. However, some were based on the equations oriented approach, as SPEEDUP at Imperial College in London (UK) and TISFLO at DSM in The Netherlands. 

---