Flowsheet synthesis

The secondary reactions are parallel with respect to ethylene oxide but series with respect to monoethanolamine. Monoethanolamine is more valuable than both the di- and triethanolamine. As a first step in the flowsheet synthesis, make an initial choice of reactor which will maximize the production of monoethanolamine relative to di- and triethanolamine. 

Laroche L, Bekiaris N, Andersen HW and Morari M (1992) Homogeneous Azeotropic Distillation Separability and Flowsheet Synthesis, Ind Eng Chem Res, 31 2190. 

Consider a simple process in which FEED is reacted to PRODUCT via the reaction in Equation 13.1. The flowsheet synthesis is started at the reactor. The effluent from the reactor contains both PRODUCT and unreacted FEED that must be separated. Unreacted FEED is recycled to the reactor via a pump if the recycle is liquid, or a compressor if the recycle is vapor. 

There are parts of the flowsheet synthesis problem that can be predicted without having to study actual designs. These are the layers of the process onion relating to the... 

Total Flowsheet Synthesis. Several approaches to total flowsheet synthesis appear inthe literature. The first was the AIDES system developed by Siirola, Powers and Rudd (1971). A second is the BALTAZAR system by Mahalec and Motard (1977a,b). ... 

Another class of total flowsheet synthesis algorithms is that of "embedding," where (as stated earlier) a superstructure is invented which contains all the desired flowsheet arrangements as substructures within it. Optimization is used to remove those portions of the superstructure which are not worthwhile, leaving the optimal flowsheet. 

The flowsheet synthesis of continuous chemical-like process can be performed following a systematic strategy known as the hierarchical approach. The procedure, initially proposed by Jim Douglas and coworkers in the decade 1980-90 [1, 2], describes the conceptual design process as a logical sequence of analysis and synthesis steps grouped in levels. Each level involves a flowsheet development mechanism based on design decisions. The result is not a unique solution but a collection of alternative flowsheets from which an evaluation procedure eliminates the less attractive ones. 

Figure 2.13 illustrates the variation of the economic potential during flowsheet synthesis at different stages as a function of the dominant variable, reactor conversion. EPmin is necessary to ensure the economic viability of the process. At the input/output level EP2 sets the upper limit of the reactor conversion. On the other hand, the lower bound is set at the reactor/separation/recycle level by EP3, which accounts for the cost of reactor and recycles, and eventually of the separations. In this way, the range of optimal conversion can be determined. This problem may be handled conveniently by means of standard optimization capabilities of simulation packages, as demonstrated by the case study of a HDA plant [3]. 

Tier II environmental assessment is employed for flowsheet synthesis on a smaller number of design alternatives. This provides an opportunity to evaluate the impacts of separation and other units in the process in addi-... 

This book is intended for use by students in senior design courses in which dynamics and control are incorporated with the traditional steady-state coverage of flowsheet synthesis, engineering economics, and optimization. A modern chemical engineering design course should include all three aspects of design (steady-state synthesis, optimization, and control) if our students are going to be well-prepared for what they will deal with in industry. 

Most of the applications discussed here were based on algorithmic systematic generation approaches to process synthesis. There also exist a number of heuristic rule-based or expert-systems-based approaches including PIP for total flowsheet synthesis, SPLIT for separation schemes (Wahnschafft et ai, 1991),... 

Flowsheet synthesis Solvent and catalyst selection Recycling decisions Location of sensors... 

A different approach to process synthesis is offered by means-ends method. It is based on the observation that the purpose of material processing is to apply various operations in such a sequence that the differences in properties between the raw materials and the products are systematically eliminated. As a result, the raw materials are transformed into the desired products. The means-ends method starts with an initial state and successively applies transformation operators to produce intermediate states with fewer differences until the goal state is reached. The hierarchy for the reduction of property differences is as follows identity, amount, concentration, temperature, pressure, and finally form. This property changing method has its limitations, as it ignores the influences and the impacts on other properties. Moreover, the search method takes an opportrmistic approach, which cannot guarantee the generation of a feasible flowsheet. The means-ends analysis approach has been used as a systematic process synthesis method for overall process flowsheet synthesis, as well as for the more detailed case of a separation system to resolve the concentration differences in nonideal systems that include azeotropes. 

In contrast to these generic tools, the second group of domain-specific software tools addresses certain tasks during the design process in the chemical engineering domain. They can roughly be classified as data retrieval, synthesis, and analysis tools. A typical example for data retrieval tools are physical property systems [1048, 1053[. Synthesis tools include flowsheet synthesis [951, 1039], plant layout and pipe routing [955], model development ]54, 558] or even solvent selection [7.37]. The most prominent examples of analysis tools are process simulators for steady-state ]518, 556, 1046] and dynamic simulation ]288, 518, 916]. 

The Development of (PIP Expert System) an Interactive User Interface for Chemical Flowsheet Synthesis The Falcon Project An Application of an Expert System to Fault Diagnosis... 

The correct assignment of the product streams ensures the consistency of the Input/Output material balance. At each stage of the flowsheet synthesis be certain that all products, by-products and impurities leave the process ... 

The methodology for flowsheet synthesis presented in this book combines the Hierarchical Methodology of Douglas with a knowledge-based approach, proposed by Bamicki and Fair (1990, 1992). Since distillation is the main separation method, the reader should be familiar with modem design concepts described in specialised books as written by Kister (1992), and more recently by Stichlmair Fair (1999) and Doherty Malone (2001). For a more detailed treatment of separation techniques, we recommend the book of Seader and Henley (1998). 

The Gas Separation Manager presented in this section includes both Vapour Recovery and Gas Separation systems. The flowsheet synthesis can be decomposed in subsystems following the following split selectors ... 

The current practice has shown that there is a gap between process and control engineers. Filling this gap is a challenge for education. Only very recently plantwide controllability issues have been included in a book dealing with process design (Seider, Seader Lewin, 1999). This chapter aims to give another perspective on the same subject, with emphasis on integrating controllability aspects in flowsheet synthesis. 

Friedler F, Varga JB, Pan LT. Algorithmic approach to the integration of total flowsheet synthesis and waste minimization. In El-Halwagi MM, Petrides DP, editors. AIChE symposium series pollution prevention via process and product modifications, 90 1995. p. 86—97. 

Partin LR. Combinatorial analysis application for flowsheet synthesis of chemical plants. Maple Tech News 1998 5 15-26. 

Further, we call triangles 1-2-13 and 3-2-13 product simplexes Regsmp- This notion has great significance for separation flowsheets synthesis, because for a feed point xp located inside the product simplex one can get all the components and azeotropes that are vertexes of this simplex in a sequence of (n - 1) columns. 

In industry, it is necessary to deal with very complicated mixtures for which structural matrices can serve as an instrument of separation flowsheets synthesis. In Wahnschafft (1997), the example of plant for separation of coal tar in South Africa (20 components, more than 200 azeotropes) consisting of 40 columns is given. 

This chapter is the central one of the book all previous chapters being introductory ones to it, and all posterior chapters arising from this one. Distillation process in inhnite column at finite refiux is the most similar to the real process in finite columns. The difference in results of finite and infinite column distillation can be made as small as one wants by increasing the number of plates. Therefore, the main practical questions of distillation unit creation are those of separation flowsheet synthesis and of optimal design parameters determination (i.e., the questions of conceptual design) that can be solved only on the basis of theory of distillation in infinite columns at finite reflux. 

The geometric distillation theory also allowed the development of the general methods of separation flowsheets synthesis for azeotropic mixtures and design calculation of simple and complex distillation columns, which is examined in the chapters to follow. 

This is especially important for the solution of the task of separation flowsheet synthesis of multicomponent azeotropic mixtures (see Chapter 8) because this, in many cases, uses autoextractive distillation (i.e., to exclude the application of entrainers). 

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