Distillation RadFrac

Rigorous distillation RadFrac, MultiFrac Distillation, 3-Phase Distillation... 

The simulation is performed with the Radfrac module in ASPEN Plus and the NRTL liquid-activity model [20]. Tracing the RCM (Figure 3.15) shows that acetone and chloroform are unstable nodes, toluene is a stable node and the maximum-boiling azeotrope acetone-chloroform is a saddle. The distillation boundary shows a strong curvature. 

Rmin and the corresponding number of trays calculated ( 2N J. The shortcut models were replaced by rigorous RADFRAC units, where the reflux and distillate feed ratio were adjusted by means of design specifications, in order to meet the desired separation. The trays were sized using Aspen s facilities. Finally, the dimensions of the reflux drum and column sump were found based on a residence time of 5 min and aspect ratio H D = 2 1. Table 9.7 presents the results of distillation column sizing. 

Hydraulic analysis of the Aspen Plus simulator produces thermodynamic ideal minimum flow and actual flow curves for rigorous distillation column simulations. These types of calculations are performed for RADFRAC columns. Using the input summary given in problem 4.48 construct the stage-flow curves. Assess the thermodynamic performance of the column. 

TABLE 6.3. Stream Table for Multicomponent Distillation with RadFrac, Reflux Ratio = 3.44... 

Figure 6.5. Multicomponent distillation with RadFrac, reflux ratio = 3.44. (a) Condenser (b) reboiler.

TABLE 6.4. Multicomponent Distillation with Radfrac, Reflux Ratio = 10... 

This chapter introduced you to the many thermodynamic models available in Aspen Plus. The equations for short-cut distillation were summarized, and the Aspen Plus was used to solve a variety of distillation problems, with either short-cut methods (DSTWU) or plate-to-plate methods (RadFrac). You also learned how to solve gas absorption problems using Aspen Plus. 

Model column B2 in Figure 6.8 using a detailed model, RadFrac. (Hint Use the results from Problem 6.1 to choose key operating parameters.) Prepare a report comparing the output when using DSTWU and RadFrac to model the distillation column. What information was needed for each How do the results compare ... 

RadFrac - rigorous two phase and three phase, absorber, stripper, distillation columns using stages... 

This unit can simulate any type of separation processes, as distillation, absorption, stripping, or extraction columns, modelled as cascade of counter-current equilibrium stages. The model Radfrac in Aspen Plus is particular powerful. It is first built on the inside-out algorithm that increased dramatically the robustness in simulating distillation-based operations (Boston, 1980). Columns with multiple feeds, side streams products, stage heaters or coolers, can be treated, as illustrated in Fig. 3.13. The following capabilities are generally available ... 

As shown in the multimedia CD-ROM that accompanies this textbook, the approximations in Eqs. (10.20) and (10.21) apply for the separation of propane from n-butane in a mixture of five normal paraffins, from ethane to n-hexane. Using both the RADFRAC subroutine in ASPEN PLUS SEPARATIONS Distillation MESH Equations RADFRAC) and the Column object in HYSYS.Plant SEPARATIONS —> Distillation Column Setup), the ap-... 

In the ASPEN PLUS simulation, for each distillation column, use the RADFRAC subroutine in place of the DISTL subroutine. As a result, the reflux ratios change somewhat to achieve the same product specifications using the same number of trays. 

A depropanizer example is provided to illustrate the use of Aspen IPE. The depropanizer is a distillation tower to recover propane and lighter species from a normal-paraffins stream, as shown in Figure 1. The simulation flowsheet and selected results are shown in Appendix I and in the multimedia tutorial on the CD-ROM that contains these course notes ASPEN Tutorials —> Separation Principles -> Flash and Distillation). Also, a copy of the file, RADFRAC.bkp, is provided on the CD-ROM. 

In this section, equipment sizes and costs are estimated for the monochlorobenzene (MCB) separation process, which is discussed in Section 4.4 of the textbook and in the multimedia portion of the CD-ROM (ASPEN Principles of Flowsheet Simulation Interpretation of Input and Output —> Sample Problem) that contains these course notes. Beginning with the file, MCB.bkp, which is available on the CD-ROM, additional mixture properties are added and the DISTL subroutine, used to model the D1 distillation column, is replaced with the RADFRAC subroutine. The reflux ratio computed using the RADFRAC subroutine is 3.35, as compared with 4.29 computed using the approximate DISTL subroutine. Also, the stream flow rates differ slightly (< 1%). Both of the files, MCB-IPE.bkp and MCB-IPE.rep, are on the CD-ROM. 

The expected market price, chemical kinetics and VLE data, and utility costs will be supplied at a later date. Where VLE data are lacking you may use the UNIFAC correlation. Your company has access to ASPEN PLUS which has a reactive distillation subroutine (RADFRAC). 

A light-hydrocarbon mixture is to be separated by distillation, as shown in Figure 9.29, into ethane-rich and propane-rich fractions. Based on the specifications given and use of the Soave-Redlich-Kwong equation for thermodynamic properties, use ASPEN PLUS with the RADFRAC distillation model to simulate the column operation. Using the results of the simulation, with Tq = 80°F, a condenser refrigerant temperature of 0°F, and a reboiler steam temperature of 250°F, calculate the... 

In this chapter we begin at the beginning. We take a simple binary separation and go through all the details of setting up a simulation of this system in Aspen Plus using the rigorous distillation column simulator RadFrac. 

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. 

Steady-state simulations are performed in Aspen Plus using Choa-Seader physical properties. Dynamic simulations are performed in Aspen Dynamic using the rigorous RadFrac distillation column model. 

Lab 3. The goals of this lab are 1) to become familiar with Aspen Plus simulations using RADFRAC for binary distillation systems, and 2) to explore the effect of changing operating variables on the results of the binary distillation. There is no assignment to hand in. However, understanding this material should help you understand the textbook and will help you do later labs. 

Start a blank simulation with general metric units. At the bottom of the flowsheet page click on the tab labeled columns. Use the column simulator RADFRAC. Draw a flowsheet of a single colunm with one feed, a liquid distillate product (red arrow), and a liquid bottoms product. (This is the most common configuration for distillation columns.) Click on the arrow to the right of the RADFRAC button to see alternative sketches of the column. Do not use a packed bed system The screen should look similar to Figure 4-Al. 

G4. You have an ordinary, single feed distillation column separating benzene, toluene, and biphenyl (C12H10, also called diphenyl). There are 15 trays in column and feed location in column is tray 9 (input above stage), reflux ratio is 1.1, pressure is 1.5 atm (operate column at constant pressure), total condenser with saturated liquid reflux, kettle type reboiler, feed flow rate is 200 kmol/h, feed mole fractions benzene = 0.2, toluene = 0.65, and biphenyl = 0.15 feed pressure is 1.5 atm, feed tenderature is 100°C, D = 170 kmol/h, adiabatic column, and use the Peng-Robinson VLE package. Open a new blank file, simulate this system with RADFRAC, and answer the following questions ... 

Lab 5. In this lab we continue to use RADFRAC to explore distillation in more detail and to learn more... 

Lab 6. Use RADFRAC with an appropriate VLE package for this assignment. Use the direct sequence in Figure 11-9A. Do the overall mass balances for both columns to determine both distillate values before lab. 

To draw an absorber, use the RADFRAC icon. Draw a system with a vapor feed at the bottom, a liquid bottoms product, a second feed (liquid) at the top, and a vapor distillate. In the configuration window for the RADFRAC block set ... 

Open Aspen Plus with either a tenplate or a blank flowsheet. When you get to the process flowsheet window, draw either a distillation column (RADFRAC) or a flash distillation (Flash2) with the appropriate feed and product streams. Then click Next and click OK to display the next input. 

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