Process Simulation Diagram

In this way, the layout of a complete flowsheet can be done. It may be observed that the flowsheet for simulation is somewhat different from Fig. 2.4 A first conclusion might be drawn the technological flowsheet, commonly called Process Flow Diagram, must be translated in a diagram compatible with the capabilities of the simulator. This new flowsheet will be called here Process Simulation Diagram. 

A real Process Flow Diagram (PFD) must be translated in a scheme compatible with the software capabilities and with the simulation goals. The flowsheet scheme built up for simulation purposes will be called in this book Process Simulation Diagram (PSD). PSD is in general different from PFD. For example, some simple units, as for pressure or temperature change, may be lumped in more complex units (from simulation viewpoint). Contrary, complex units, as distillation columns or chemical reactors, may need to be simulated as small flowsheets. Hence, a preliminary problem analysis is necessary. The steps in defining a simulation problem are ... 

As shown in Chapter 2, the above Process Flow Diagram (PFD) has to be translated in a Process Simulation Diagram (PSD). This example has been worked out with ASPEN Plus , but the approach is similar with other packages. The problem analysis takes into account the following aspects ... 

Figure 3.6 presents the final Process Simulation Diagram of the HDA process. Disregarding the loop created by the flowsheet controller, three recycle loops may be identified heat integration around the reactor, recycle of hydrogen and recycle of toluene. The last two loops have a common part from the mixer up to the flash. As a result, the two loops may be solved by only one tear stream. Hence, we have three loops but only two tear streams, as for example the exit streams from mixer and reactor. However, a further simplification is possible. We may break the loop around the heat... 

A Process Simulation Diagram can be built-up by means of unit operations or simulation blocks. The list below cites the most frequent types, available in any allpurpose simulator ... 

Figure 3. Shift and methanation process flow diagram. (Used with permission of Simulation Sciences Inc.)...

As a typical example from industrial practice we consider the simulation of a process with the reaction of methylphosphinic acid and butanol to methylphosphinic acid butyl ester and water, which was modeled by Gordana Hofmann-Jovic at InfraServ Knapsack [C28]. Because of the lack of experimental data for the binary systems with phosphorous compounds, COSMO-RS was used for the prediction of the binary activity coefficients. Then the results were fitted by an NRTL equation and the entire process was modeled by a commercial process simulator. The resulting phase diagrams were in close agreement with experimental measurements obtained later (Fig. 8.2). 

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. 

Although most process simulation programs feature a graphical user interface (GUI) that creates a drawing that resembles a PED, printouts of these drawings are very seldom used as actual process flow diagrams. The unit operations shown in the process simulation usually do not exactly match the unit operations of the process. The simulation may include dummy items that do not physically exist and may omit some equipment that is needed in the plant but is not part of the simulation. 

Instructions on loading data from a process simulation are given in the Aspen ICARUS Process Evaluator User s Guide (AspenTech, 2002a). When a simulator report file is loaded, IPE generates a block-flow diagram with each unit operation of the simulation shown as a block. These blocks must then be mapped to Icarus project components (pieces of equipment or bulk items). 

Solid-liquid equilibrium phase diagrams play an important role in the design of industrial crystallization processes. The calculation of phase diagrams can be used to validate the activity coefficient model used for process simulation. 

The simulation flow diagram and optimization sequences of the process units for different products were examined. A relational data bases which including input component data base and process parameters data base as well as simulation results data base were developed. In this paper knowledge based process simulation and design of the starch plant were developed. The relational data bases system was linking with simulation models and simulation interface. The obtained results in this paper can be applied in the others domain. 

Fig. 6.5 Comparison between process flow diagram and simulation flowsheet for an HPLC plant.

After the process simulation applying the experimentally validated model, all axial concentration profiles are plotted in a dimensionless diagram using C /Cfeed, and L/Lc as axes. These profiles are taken at the end of a shifting interval from quasi-steady state. Figure 7.5 illustrates that all concentration profiles are completely identical. ... 

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