Runback Specs Aspen

( Partial (enter 2 specifications) c Total (enter 1 specification only) H Block CDU (PetroFrac) Pumparounds P-2 - Data Browser j 0 Setup Ril Pumparounds ffi - E) P-l fi P-2 1--fla Strippers jO Heaters Coolers Runback Specs j Efficiencies Design Specs Q Condenser Hcurves jO Reboiler Hcurves fflTray Sizing Q Tray Rating -Pumparound results summary Draw stage EE Return stage Temperature Pressure Vapor fraction Heat duty Mole flow Mass flow StdVol flow

Petroleum Fractions

In the chemical industry, we deal with compositions (mole fractions). In petroleum refining, we deal with boiling point ranges. For example, suppose that we take a sample of heating oil and place it in a heated container at atmospheric pressure. The temperature at which the first vapor is formed is called the initial boiling point. This corresponds to the bubblepoint of a mixture of specific chemical components. If we continue to heat the sample, more and more material is vaporized. The 5 point...

Info

Getting the simulation to converge to this steady state is quite difficult. The calculated compositions of the reflux and recycle are compared to the guessed values. The reflux composition is quite close 84.4 14.0 1.6 mol B E W calculated versus 84.4 14.1 1.5 mol assumed. The recycle composition is somewhat different 4.7 41.6 53.7 mol calculated versus 7.2 47.1 45.7 mol assumed. Changing these compositions to the calculated values and rerunning the program...

Steadystate Design Of Preflash Column

The first petroleum fractionator simulated is a simple distillation column that removes some of the light material in the crude. Figure 11.16 gives the Aspen Plus flowsheet of this unit. There are two crude feedstreams that are combined and heated in a furnace in which the feed is partially vaporized before entering the bottom of the column. There is no reboiler. Live steam is introduced in the bottom of the column to strip out some of the light components in the bottoms stream, which is fed to...

Control Of Sidestream Columns

In this chapter we study distillation columns that have more than the normal two product streams. These more complex configurations provide savings in energy costs and capital investment in some systems. Sidestream columns are used in many ternary separations, and the examples in this chapter illustrate this application. However, a sidestream column can also be used in a binary separation if different purity levels are desired. For example, two grades of propylene products are sometimes...

Thermal Condition Q

Minimum Number Trays Plot

Increasing product purities does not have a significant effect on the required reflux ratio. 5. Increasing the liquid to vapor ratio in a section of a column increases the separation that occurs in that section. These effects apply to all types of separations and distillation columns. Before we go through a specific example, we need to discuss some of the limiting conditions. The minimum number of trays for a specified separation corresponds to total reflux operation. If the column is run...

Specifying Chemical Components And Physical Properties

N m2 , which are quite inconvenient for most chemical processes because typical pressures are very large numbers in pascals 1 atm 101,325 Pa . Therefore we will use pressures in atmospheres in most of the examples. However, make sure that you select the correct units when you enter data. The second preliminary item is to indicate what properties we want to see for all the streams. The defaults do not include compositions in mole fractions, which are very useful in distillation calculations. To...

Relative Volatility

One of the most useful ways to represent VLE data is by employing relative volatility, which is the ratio of the y x values vapor mole fraction over divided by liquid mole fraction of two components. For example, the relative volatility of component L with respect to component H is defined in the following equation The larger the relative volatility, the easier the separation. Relative volatilities can be applied to both binary and multicomponent systems. In the binary case, the relative...

Nc

Figure 2.16 Ternary analysis using DISTIL setting feed and reflux ratio. Figure 2.16 Ternary analysis using DISTIL setting feed and reflux ratio. Detailed results are plotted on the ternary diagram given in Figure 2.19. The feed, distillate, and bottoms points have been labeled. They lie on a straight line the heavy dashed line , as required by the overall component balances. The liquid compositions on all the trays in the stripping and rectifying trays are shown. Residue curves are added by...

Jnjx

Figure 5.11 Methyl acetate flowsheet. A guess for the reflux ratio of 2 is made, and the simulation is run. The resulting product compositions are 2.475 x 103 mol H2O and 61.98 mol MeAc in the distillate and 3.356 x 107 mol MeAc in the bottoms. To drive the bottoms methyl acetate composition to the specified 0.1 mol , we set up a Design Spec Vary manipulating distillate flowrate and click the N button. The column does not converge after the default 25 iterations. Clicking Convergence under the...

Columns With Partial Condensers

All the distillation columns considered up to this point in the book have used total condensers, where the distillate product is a liquid. However, many industrial columns have partial condensers in which the distillate product is removed as a vapor stream. This is commonly employed when there are very light components in the feed to the column that would require a high column pressure or a low condenser temperature to completely condense these very volatile components. The use of a partial...

Finding The Optimum Feed Tray And Minimum Conditions

Now that the pressure has been determined and the product specifications attained, we need to go back and find the optimum feed tray. In addition, the minimum reflux ratio and the minimum number of trays can be determined. These will be useful for heuristic optimization, which is discussed in detail in Chapter 4. In most distillation columns, the major operating cost is reboiler energy consumption. Of course, if refrigeration were used in the condenser, this heat removal expense would also be...

Fundamentals Of Vaporliquid Phase Equilibrium

Distillation occupies a very important position in chemical engineering. Distillation and chemical reactors represent the backbone of what distinguishes chemical engineering from other engineering disciplines. Operations involving heat transfer and fluid mechanics are common to several disciplines. But distillation is uniquely under the purview of chemical engineers. The basis of distillation is phase equilibrium, specifically, vapor-liquid phase equilibrium VLE and in some cases...

Design Degrees Of Freedom

Mccabe Thiele Diagram Ethanol Water

The design of a distillation column involves many parameters product compositions, product flowrates, operating pressure, total number of trays, feed tray location, reflux ratio, reboiler heat input, condenser heat removal, column diameter, and column height. Not all of these variables are independent, so a degrees of freedom analysis is useful in pinning down exactly how many independent variables can and must be specified to completely define the system. A rigorous degrees-of-freedom analysis...

Residue Curves For Ternary Systems

Pentane Diagram

Residue curve analysis is quite useful in studying ternary systems. A mixture with an initial composition xi 0 and x2 o gt is placed in a container at some fixed pressure. A Figure 1.19 Azeotrope composition and temperatures. Figure 1.19 Azeotrope composition and temperatures. vapor stream is continuously removed, and the composition of the remaining liquid in the vessel is plotted on the ternary diagram. Figure 1.21 gives an example of how the compositions of the liquid Xj and the vapor y...

Ternary Diagrams

Ternary Diagram

Three-component systems can be represented in two-dimensional ternary diagrams. There are three components, but the sum of the mole fractions must add to unity. Therefore, specifying two mole fractions completely defines the composition. A typical rectangular ternary diagram is given in Figure 1.10. The mole fraction of component 1 is shown on the abscissa the mole fraction of component 2, on the ordinate. Both of these dimensions run from 0 to 1. The three corners of the triangle represent the...

Approximate Multicomponent Methods

Mccabe Thiele Problems

Many years before the availability of computers for rigorous analysis, several simple approximate methods were developed for analyzing multicomponent systems. These methods are still quite useful for getting quick estimates of the size of a column Figure 2.13 Summary of calculated results. Figure 2.13 Summary of calculated results. number of trays and the energy consumption reflux ratios and the corresponding vapor boilup and reboiler heat input . 2.3.1 Fenske Equation for Minimum Number of...

Vle Nonideality

Diagram Ethanol

Liquid-phase ideality activity coefficients g 1 occurs only when the components are quite similar. The benzene toluene system is a common example. As shown in the sixth and seventh columns in Figure 1.5, the activity coefficients of both benzene and toluene are very close to unity. However, if components are dissimilar, nonideal behavior occurs. Consider a mixture of methanol and water. Water is very polar. Methanol is polar on the OH end of the molecule, but the CH3 end is nonpolar. This...

Exporting To Aspen Dynamics

Aspen Plus

Aspen Dynamics uses the steady-state information generated in Aspen Plus, but they are two different programs with different files. The Aspen Plus file is filename.apw, and there is also a backup file, filename.bkp, that is generated. The latter file can be used to upgrade to newer versions of Aspen Plus. The information from Aspen Plus is exported into Aspen Dynamics by generating two additional files. The first is a filename.dynf file that is used in Aspen Dynamics and is modified to...

Set Reflux Ratio to 12 Times Minimum Reflux Ratio

The other common distillation economic heuristic is to select a reflux ratio that is 20 larger than the minimum reflux ratio. The minimum reflux ratio found in Chapter 3 from the simulation was 2.9. Multiplying this by 1.2 gives an actual reflux ratio of 3.48. This is very close to the reflux ratio 3.49 that we found was necessary in Chapter 3 for a 32-stage column. It is interesting to compare the minimum reflux ratio found in the simulation with that predicted by the Underwood equations....

Ethanol Dehydration

Distillation Column Azeotrope

For our second nonideal system we study a process that has extremely nonideal VLE behavior and has a complex flowsheet. The components involved are ethanol, water, and benzene. Ethanol and water at atmospheric pressure form a minimum-boiling homogeneous azeotrope at 351 K of composition 90 mol ethanol. Much more complexity is introduced by the benzene water system, which forms two liquid phases with partial miscibility. The flowsheet contains two distillation columns and a decanter. There are...

Ternary Column Design

Methanol Meac

Let us consider a numerical case in which there are several design objectives 1. The concentration of the methyl acetate in the distillate should be fairly close to the azeotropic composition because this stream is sent for further processing. It may be sent to another distillation column operating at a higher pressure that shifts Figure 5.8 a Specifying ternary diagram parameters b ternary diagram c ternary diagram with residue curves. Figure 5.8 a Specifying ternary diagram parameters b...

More Complex Distillation Systems

Aspen Plus Azeotrope

In the example distillation system considered in Chapters 3 and 4 we studied the binary propane isobutane separation in a single distillation column. This is a fairly ideal system from the standpoint of vapor-liquid equilibrium, and it has only two components, a single feed and two product streams. In this chapter we will show that the steady-state simulation methods can be extended to multicomponent nonideal systems and to more complex column configurations. Other methods of analysis can also...