Process and Simulation Flowsheets

Process flowsheets are the language of chemical processes. Like a work of art, they describe an existing process or a hypothetical process in sufficient detail to convey the essential features. 

Analysis, or simulation, is the tool chemical engineers use to interpret process flowsheets, to locate malfunctions, and to predict the performance of processes. The heart of analysis is the mathematical model, a collection of equations that relate the process variables, such as stream temperature, pressure, flow rate, and composition, to surface area, valve settings, geometrical configuration, and so on. The steady-state simulators solve for the unknown variables, given the values of certain known quantities. 

There are several levels of analysis. In order of increasing complexity, they involve material balances, material and energy balances, equipment sizing, and profitability analysis. Additional equations are added at each level. New variables are introduced, and the equation-solving algorithms become more complicated. 

Fortunately, most chemical processes involve conventional process equipment heat exchangers, pumps, distillation columns, absorbers, and so on. For these process units, the equa- 

To use a flowsheet simulator effectively, it is very helpful to distinguish between process flowsheets and the so-called simulation flowsheets associated with process simulators. These distinctions are drawn in the next subsections. 

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