Flow-sheeting ASPEN PLUS

Fig. 8.3-2. Aspen-Plus flow sheet used for simulation comparisons The equipment list is reported in Table 8.3-1.

In 2006, GA participated in a study conducted by the Savannah River National Laboratory (Summers, 2006). The S-I process was coupled to a VHTR with a required helium return temperature near 600°C. To efficiently match temperature requirements with available heat, a design was developed to supply HI decomposition section energy with recovered heat from the sulphuric acid decomposition section. For the purposes of comparison and analysis in this paper, the GA flow sheets will refer to this design, and CEA flow sheets will refer to a design in which helium supplies heat to both acid decomposition sections. CEA uses ProSimPlus for flow sheet analysis, and GA uses Aspen Plus . A previous study (Buckingham, 2008) showed that the two process simulators give similar calculated results when the same unit operations and stream compositions are modelled, although different thermodynamic models are used for the calculations. 

Ideally you would have calculated the equilibrium in the reactor, too. Then you would have three interacting iterations, and it would be the rare problem that Excel could solve. The difficulty is that, during the iterations, the values may be physically unrealistic. Then, the equilibrium relation or the Rachford-Rice equation gives even more unrealistic values. Programs such as Aspen Plus can realize this and take precautionary steps to avoid it. As the flow sheet gets more and more complicated, and involves more and more thermodynamics, the power of Aspen Plus is welcome. See Chapters 6 and 7 for examples. 

Using available data (technical literature, laboratory data, pilot-scale data, etc.), generate process flow sheets, material and energy balances, and equipment capital costs using ASPEN Plus process simulation computer software. 

Sheets("Data from Aspen Plus").Range("Cl") = Aoetene Flow Rate.Value... 

The flow-sheeting program Aspen Plus is used to design the FP-FC system, which produces 100 W of electricity. The process has been modeled and simulated for a standard set of conditions shown in Table 15.3 and subsequently the process... 

Finally, specify the makeup feed stream input to the second mixer to have a temperature of 35°C and pressure of 2 bar. To be an effective makeup stream, the flow rates of MDEA and H2O must equal the flow rates of those two components lost via the CO2 product and clean syngas streams. Although trivial to compute at the moment, once the recycle loop is closed, this number must be computed for each flow sheet convergence iteration in order to be able to physically achieve a steady state and prevent eventual dry-up of the solvent. Unlike ProMax, which has a Make-up/Blow-down block to handle this specific scenario. Aspen Plus has more generic tools that can be used instead. For example, a calculator block can be added that computes and sets the inlet composition and flow rate of the makeup feed stream for every flowsheet iteration. To do this, first configure the makeup stream to have a mole flow of H2O and MDEA of 1 kmol/h each. These are strictly dummy variables. However, it is critical that the Total Flow Rate is left blank. By specifying it in this manner, we are creating a specification in which the calculator block will be able to directly overwrite the dummy numbers of 1 kmol/h with its own calculations just before the second Mixer block executes. 

In a new case in Aspen Plus, add benzene and toluene components and select the appropriate fluid package. Select Peng-Robinson EOS as a proper fluid package for hydrocarbons. The process flow sheet is shown in Figure 1.44. 

Start the Aspen program, select Aspen Plus User Interface, and when the Connect to Engine window appears, use the default Server Type Local PC. Select Pipe under the Pressure Changes tab from the Equipment Model Library and then click on the flow sheet window where you would like the piece of equipment to appear. In order to add material streams to the simulation, select the material stream from the Stream Library. When the material stream option is selected, a number of arrows will appear on each of the unit operations. Red arrows indicate a required stream and blue arrows indicate an optional stream. 

The shell and tube heat exchange design using Aspen Plus is done as that in Example 4.4. The process flow sheet and stream table properties are shown in Figure 4.37. The Exchanger details are shown in Figure 4.38. 

Process flow sheet and stream table generated by Aspen Plus. 

The process flow sheet for a PFR in Aspen Plus is constructed in the same way as previous examples. In the data browser, specify the feed stream properties. Specify inlet reactions stoichiometry and parameters as shown in Figure 5.48 for the first reaction. For the thermodynamic data, Peng-Robinson is selected. The reactor is considered isothermal. The process flow sheet and stream property table are both shown in Figure 5.49. 

After the required data are entered, the system is ready to be run. The Aspen Plus simulation results are shown in Figure 7.17. The packed-bed diameter is obtained from design specifications of the Flow sheeting options in the Browser menu. 

Using Aspen Plus the process flow sheet and stream table compositions are shown in Figure 8.25, as a base model NRTL was used. The extraction column consists of three equilibrium stages. 

Process flow sheet with Stream Table of Example 8.2 using Aspen Plus. 

Process flow sheet and Stream Table of Example 8.4 (Aspen Plus). 

The Aspen Plus process flow sheet, stream table weight, and mass fractions are shown in Figure 8.46. 

Process flow sheet with Aspen Plus. 

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