Complex distillation processes computer simulation

It can be seen from the previous description that the design of both a cold-feed stabilizer and a stabilizer with reflux is a rather complex and involved procedure. Distillation computer simulations are available that can be used to optimize the design of any stabilizer if the properties of the feed stream and desired vapor pressure of the bottoms product are known. Cases should be run of both a cold-feed stabilizer and one with reflux before a selection is made. Because of the large number of calculations required, it is not advisable to use hand calculation techniques to design a distillation process. There is too much opportunity for computational eiToi. 

Simulation, Modeling, and Design Feasibility Because reaction and separation phenomena are closely coupled in a reactive distillation process, simulation and design are significantly more complex than those of sequential reaction and separation processes. In spite of the complexity, however, most commercial computer process modeling packages offer reliable and flexible routines for simulating steady-state reactive distillation columns, with either equilibrium or kinetically controlled reaction models... 

The book may be used for a methodical study of the subject or as a reference for solving day-to-day problems. It follows a logical flow of ideas within each chapter and from one chapter to the next yet each chapter is quite self-contained for quick reference. The discussion starts with fundamental principles, prediction of thermodynamic properties, the equilibrium stage, and moves on to the different types of multistage and complex multistage and multicolumn processes, batch distillation, and membrane separation operations. Although computer simulation is a central theme of this book, no previous experience in the use of simulation software is required. 

The economical design and operation of batch distillation systems must take into account many factors, most of which are time dependent. The mathematical complexity of the process provides a strong incentive for using computer simulation to solve the problem. 

Within the past few years the advances made in hydrocarbon thermodynamics combined wtih increased sophistication in computer software and hardware have made it quite simple for engineers to predict phase equilibria or simulate complex fractionation towers to a high degree of accuracy through software systems such as SSI s PROCESS, Monsanto s FLOWTRAN, and Chemshare s DISTILL among others. This has not beem the case for electrolyte systems. 

The chapter is organized as follows In section 2, we first review basic results on I/O-controllability of linear systems. In section 3, a new t)fpe of I/O-controllability index is introduced, the Robust Performance Number. In section 4, I/O-controllability analysis by optimization is presented. Sections 5 and 6 contain two case studies an air separation plant and a reactive distillation column where these tools are applied to select the best control structure and quantify the process I/O-controllability. The evaluations of the control structures are validated by simulations with low order controllers which can easily be obtained from the analysis, in particular from the computed or estimated attainable performance of the chosen structure, using the procedure described in [9, 42, 29]. So the construction of practically relevant controllers of minimal complexity is seamlessly integrated with the analysis. 

Foams have many industrial applications. The large gas-liquid interfacial area available is exploited in foam fractionation to efficiently separate surface active substances, such as proteins. However, when foam formation interferes with physical and chemical processes, stabilizing gradients must be avoided. Bubbles play an important role in chemical reactors, distillation, froth flotation, and aeration. In low-gravity environments surface tension gradients may provide the primary mechanism for bubble motion itself. The advent of modern computers has enabled simulations of complex interfadal motions to be performed, yielding information that is difficnlt to obtain by experiment or theoretical analysis. 

It is difficult to analyze batch distillation without using computers due to the two reasons stated before (a) the process is time varying, and one has to resort to complex numerical integration techniques and different simulation models for obtaining the transients, and (b) this ever-changing process also provides flexibility in operating and configuring the column in numerous ways. Based on the current state of the... 

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