MultiFrac model

There are two approaches to using Aspen Plus for the simulation of a DWC. A model can be developed using four RadFrac vessels a rectifier with only a condenser, two absorbers with neither a condenser nor a reboiler, and a stripper with only a reboiler. Interconnecting vapor and liquid streams and splitters are used to model the streams feeding and leaving all vessels. Alternatively, a model can be developed using a MultiFrac model that inherently contains all the vessels and connections. In the following sections, we discuss the use of both approaches. 

BhidtDWC (MultiFrac) Colwiim 2 Setup - Dele Browser 

Fignre 12.5 Column 2 (prefiractionator column with feed side of wall). 

Connect Streams. Probably the most important (and perhaps the most confusing) issue in setting up a MultiFrac Petlyuk column in Aspen Plus is the definition of where the four interconnecting streams (two liquids and two vapors) leave and enter the two columns. There are four Connect Streams. The flow rates of the two streams entering column C2 (one liquid at the top and one vapor at the bottom of the prefractionator) will be specified. The other two streams are dependent variables and will be calculated in the model. 

Qj Connect Sireem Mcun i TnySizing C3 Tray Reting 

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In designing a conventional single column, the RadFrac model in Aspen Plus is used. To use a. MultiFrac model with a Peflyuk configuration, select the appropriate icon and drop it onto the process flow diagram as shown in Figure 12.2. Then feed, distillate, and bottoms material streams are added as shown in Figure 12.3. The model block is labeled DWC. 

The MultiFrac model is somewhat easier to set up and converge than the RadFrac model discussed in the next section. However, the MultiFrac model cannot be exported... 

Based on the specifications given and other specifications of your choice to achieve reasonably good separations, together with use of the Peng-Robinson equation for thermodynamic properties, use ASPEN PLUS with the MULTIFRAC distillation model to simulate the column. Using the results of the simulation, with To = 100 F, calculate the... 

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