che 1008 chemical engineering equilibrium separations...

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ChE 1008 Chemical Engineering Equilibrium Separations

Spring Term 2003 (03-2) Project Project Overview You have been assigned a new project at your company to do the preliminary design of a new debutanizer column that is fed from an upstream deisobutanizer. In Figure 1, you are given the following column, fed from a flash drum, that has a single feed F, a total condenser and a partial reboiler:

F

D

B

DEBUTFLASH

VAPOR

LIQUID

FEED

Figure 1. Flash and Debutanizer column. The required process specifications for this system are given as attached forms as used by your company. You are required to complete these forms and incorporate them back into a corporate design report, the format of which is attached. You have the Aspen Plus software package, which your company has just received. You have been asked by your supervisor to perform an independent calculation, based upon your McCabe-Thiele expertise, and compare your results to the Aspen results to verify that the Aspen package is functioning properly. You are also required to use an independent data source for your equilibrium data other than Aspen. Your performance report from your supervisor will be based upon your thoroughness in the calculations; statement of assumptions; completion of the calculations; correctness of the calculations; discussion, analyses, and recommendation write-ups; and presentation of the report. The calculations have been broken down into the following separate parts.

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Calculations Part 1 – Multi-Component Feed Temperature You are required to use an independent data source, other than Aspen, for your equilibrium data for the following determinations and/or calculations using Mathcad: 1.) The feed temperature delivered to the column at the feed pressure and fraction of feed vaporized. 2.) The vapor and liquid compositions and the vapor and liquid flow rates fed to the column. 3.) The bubble- and dew-point temperatures of the actual feed mixture based upon independent equilibrium data and the problem specifications. 4.) The minimum and maximum boiling point temperatures of any possible feed mixture based upon the independent equilibrium data. Calculations Part 2 – Binary McCabe-Thiele Method You are required to use an independent calculation and data source for your equilibrium data, other than Aspen, and the McCabe-Thiele method and Mathcad for the following determinations and/or calculations: Hint: You are given a multi-component mixture and the McCabe-Thiele method is applicable to binary separations only. What assumption(s) can you make to enable the use of the McCabe-Thiele graphical method based upon the multi-component system specifications? Remember that your mole fractions need to sum to one. 1.) The mass balance around the column, reboiler, feed stage, and/or condenser based upon the information given in the process specifications to determine L, V, L, V, D, B, xD and xB. Hint: The given n-butane recovery is based upon the amount of n-butane in the distillate and the amount of n-butane in the feed. 2.) The fraction of feed remaining as liquid. 3.) The recovery of isopentane at the bottoms. Recovery is based upon isopentane in the feed. 4.) The top and bottom operating lines for this column based upon your assumptions. 5.) The feed line equation for this column based on the process specifications. 6.) The feed temperature based upon the process specifications. 7.) The vapor and liquid compositions and the vapor and liquid flow rates fed to the column. 8.) The equilibrium curve relationship for this system based upon your assumptions. Hint: How can you obtain an estimate for an equilibrium curve from equilibrium data relationships assuming that the average column temperature is close to the feed stage temperature and pressure? 9.) A y vs. x plot for the n-butane-isopentane binary system. 10.) The McCabe-Thiele graphical stage solution based upon your assumptions showing the equilibrium curve, the operating lines, the feed line, xB, xD, and the staged step-off solution down from the condenser. 11.) The number of theoretical column stages, N, and the reboiler fractional stage from your McCabe-Thiele graphical stage solution.

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12.) The optimum feed stage location, NF, from your McCabe-Thiele graphical stage solution – report as the number of stages down from the condenser. 13.) The minimum number, Nmin, of equilibrium stages, excluding the reboiler, at total reflux using a McCabe-Thiele graphical stage solution. 14.) The pinch point for the binary system indicated on a McCabe-Thiele plot. 15.) The minimum reflux ratio, (L/D)min. Calculations Part 3 – Multi-Component Approximate Methods You are required to use multi-component distillation correlations and Mathcad for the following determinations and/or calculations: 1.) The light key component. 2.) The heavy key component. 3.) All other heavy and light non-key components. 4.) The minimum number, Nmin, of equilibrium stages at total reflux using the Fenske equation. Hint: Use the recovery results of Part 2. 5.) The recoveries, FRdist,i and FRbot,i, and the distillate and bottoms compositions, xdist,i and xbot,i, for all components. 6.) The feed stage, NF, min, at total reflux. 7.) The minimum reflux, (L/D)min using the Underwood equation. Hint: Use the results of the Fenske equation assuming that the distribution of the non-keys at Nmin is the same at minimum reflux. Any HNK component with a distillate fractional recovery less than 99% fractional recovery can be considered to be a non-distributing, non-key component. 8.) The actual number of column stages, N, using the Gilliland correlation. 9.) The actual feed stage location, NF, using the Gilliland correlation and the Fenske equation result – report as the number of stages down from the condenser. Calculations Part 4 – Multi-Component Aspen Plus’ FLASH2 and DSTWU You are required to use Aspen Plus’ Flash2 and DSTWU column calculation procedures and the problem specifications for the following determinations and/or calculations (use the Peng-Robinson equation of state and bottoms recovery determined in Part 2 and note that isopentane is also known as 2-methylbutane): 1.) A flash calculation to determine the TF at the Pcol and f. 2.) The minimum reflux ratio, (L/D)min. for the specified distillation column. 3.) The minimum number of column equilibrium stages, Nmin. 4.) The actual number of equilibrium stages, N. 5.) The feed stage location, NF – report as the number of stages down from the condenser. 6.) The distillate temperature, TD. 7.) The bottoms temperature, TB. 8.) The condenser duty, QC. 9.) The reboiler duty, QR. 10.) A y vs. x plot for the n-butane-isopentane binary system.

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of

UNIT OPERATION FEED/PRODUCT STREAM(S) GLOBAL SPECIFICATIONS Name (Symbol or No.) Type Flow Rate (Units) Temp. (Units) Press. (Units) Condition Notes FEED Inlet 876.3 (kgmol/hr) TBD (oC) TBD (kPa) liquid spec’d to maintain liquid feed VAPOR Outlet TBD (kgmol/hr) TBD (oC) 552 (kPa) sat. vap. spec’d fed to column at column pressure and fraction of feed vaporized LIQUID Outlet TBD (kgmol/hr) TBD (oC) 552 (kPa) sat. liq. spec’d fed to column at column pressure and fraction of feed vaporized

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of

UNIT OPERATION FEED/PRODUCT STREAM(S) GLOBAL SPECIFICATIONS Name (Symbol or No.) Type Flow Rate (Units) Temp. (Units) Press. (Units) Condition Notes Feed (F) Inlet TBD (kgmol/hr) TBD (oC) 552 (kPa) TBD spec’d with flash to the column at column pressure and fraction of feed vaporized Distillate (D) Outlet TBD (kgmol/hr) TBD (oC) 546 (kPa) TBD total condenser spec’d Bottoms (B) Outlet TBD (kgmol/hr) TBD (oC) 593 (kPa) TBD partial reboiler spec’d

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: FEED Composition Units: mole %

STREAM COMPOSITION SPECIFICATIONS

Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 1.369 TBD (oC) TBD (kPa) liquid spec’d to maintain n-butane n-C4 51.124 TBD (oC) TBD (kPa) liquid liquid feed isopentane i-C5 31.061 TBD (oC) TBD (kPa) liquid n-pentane n-C5 1.712 TBD (oC) TBD (kPa) liquid n-hexane n-C6 2.625 TBD (oC) TBD (kPa) liquid n-heptane n-C7 4.462 TBD (oC) TBD (kPa) liquid n-octane n-C8 4.108 TBD (oC) TBD (kPa) liquid n-nonane n-C9 3.539 TBD (oC) TBD (kPa) liquid Total 100.000 Basis: 876.3 kg moles/hr Feed Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: VAPOR Composition Units: mole %


Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 TBD TBD (oC) TBD (kPa) TBD n-butane n-C4 TBD TBD (oC) TBD (kPa) TBD isopentane i-C5 TBD TBD (oC) TBD (kPa) TBD n-pentane n-C5 TBD TBD (oC) TBD (kPa) TBD n-hexane n-C6 TBD TBD (oC) TBD (kPa) TBD n-heptane n-C7 TBD TBD (oC) TBD (kPa) TBD n-octane n-C8 TBD TBD (oC) TBD (kPa) TBD n-nonane n-C9 TBD TBD (oC) TBD (kPa) TBD Total 100.000 Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: LIQUID Composition Units: mole %


Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 TBD TBD (oC) TBD (kPa) TBD n-butane n-C4 TBD TBD (oC) TBD (kPa) TBD isopentane i-C5 TBD TBD (oC) TBD (kPa) TBD n-pentane n-C5 TBD TBD (oC) TBD (kPa) TBD n-hexane n-C6 TBD TBD (oC) TBD (kPa) TBD n-heptane n-C7 TBD TBD (oC) TBD (kPa) TBD n-octane n-C8 TBD TBD (oC) TBD (kPa) TBD n-nonane n-C9 TBD TBD (oC) TBD (kPa) TBD Total 100.000 Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: FEED Composition Units: mole %

STREAM FLOW RATE SPECIFICATIONS

Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 1.369 TBD (kg/mole/hr) TBD (kg/mole/hr) spec’d to maintain n-butane n-C4 51.124 TBD (kg/mole/hr) TBD (kg/mole/hr) liquid feed isopentane i-C5 31.061 TBD (kg/mole/hr) TBD (kg/mole/hr) n-pentane n-C5 1.712 TBD (kg/mole/hr) TBD (kg/mole/hr) n-hexane n-C6 2.625 TBD (kg/mole/hr) TBD (kg/mole/hr) n-heptane n-C7 4.462 TBD (kg/mole/hr) TBD (kg/mole/hr) n-octane n-C8 4.108 TBD (kg/mole/hr) TBD (kg/mole/hr) n-nonane n-C9 3.539 TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: 876.3 kg moles/hr Feed Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: VAPOR Composition Units: mole %


Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-butane n-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) isopentane i-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-pentane n-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-hexane n-C6 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-heptane n-C7 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-octane n-C8 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-nonane n-C9 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Flash Drum 1 Revision No. of Stream Name: LIQUID Composition Units: mole %


Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-butane n-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)isopentane i-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-pentane n-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-hexane n-C6 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-heptane n-C7 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-octane n-C8 TBD TBD (kg/mole/hr) TBD (kg/mole/hr)n-nonane n-C9 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Feed (F) Composition Units: mole %


Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 TBD TBD (oC) 552 (kPa) TBD spec’d at column pressure n-butane n-C4 TBD TBD (oC) 552 (kPa) TBD spec’d from flash drum isopentane i-C5 TBD TBD (oC) 552 (kPa) TBD n-pentane n-C5 TBD TBD (oC) 552 (kPa) TBD n-hexane n-C6 TBD TBD (oC) 552 (kPa) TBD n-heptane n-C7 TBD TBD (oC) 552 (kPa) TBD n-octane n-C8 TBD TBD (oC) 552 (kPa) TBD n-nonane n-C9 TBD TBD (oC) 552 (kPa) TBD Total 100.000 Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Distillate (D) Composition Units: mole %


Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 TBD TBD (oC) 546 (kPa) TBD spec’d at cond. pressure n-butane n-C4 94.400 TBD (oC) 546 (kPa) TBD spec’d distillate isopentane i-C5 TBD TBD (oC) 546 (kPa) TBD composition n-pentane n-C5 TBD TBD (oC) 546 (kPa) TBD spec’d total condenser n-hexane n-C6 TBD TBD (oC) 546 (kPa) TBD n-heptane n-C7 TBD TBD (oC) 546 (kPa) TBD n-octane n-C8 TBD TBD (oC) 546 (kPa) TBD n-nonane n-C9 TBD TBD (oC) 546 (kPa) TBD Total 100.000 Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Bottoms (B) Composition Units: mole %


Component Symbol Composition Temp. (Units) Press. (Units) Condition Notes isobutane i-C4 TBD TBD (oC) 593 (kPa) TBD spec’d at reboil. pressure n-butane n-C4 TBD TBD (oC) 593 (kPa) TBD spec’d partial reboiler isopentane i-C5 TBD TBD (oC) 593 (kPa) TBD n-pentane n-C5 TBD TBD (oC) 593 (kPa) TBD n-hexane n-C6 TBD TBD (oC) 593 (kPa) TBD n-heptane n-C7 TBD TBD (oC) 593 (kPa) TBD n-octane n-C8 TBD TBD (oC) 593 (kPa) TBD n-nonane n-C9 TBD TBD (oC) 593 (kPa) TBD Total 100.000 Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Feed (F) Composition Units: mole %


Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) spec’d from flash drum n-butane n-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) isopentane i-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-pentane n-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-hexane n-C6 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-heptane n-C7 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-octane n-C8 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-nonane n-C9 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Distillate (D) Composition Units: mole %


Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) spec’d from total cond. n-butane n-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) isopentane i-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-pentane n-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-hexane n-C6 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-heptane n-C7 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-octane n-C8 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-nonane n-C9 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calculation By: Date: Customer: In-House Checked By: Date: Unit Operation: Debutanizer Column 1 Revision No. of Stream Name: Bottoms (B) Composition Units: mole %


Component Symbol Composition Liquid (Units) Vapor (Units) Notes isobutane i-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) spec’d at partial reboiler n-butane n-C4 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) isopentane i-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-pentane n-C5 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-hexane n-C6 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-heptane n-C7 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-octane n-C8 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) n-nonane n-C9 TBD TBD (kg/mole/hr) TBD (kg/mole/hr) Total 100.00 TBD (kg/mole/hr) TBD (kg/mole/hr) Basis: Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calc. By: Date: Customer: In-House Chkd’ By: Date: Unit Operation: Flash Drum 1 Revision No. of

DISTILLATION COLUMN

UNIT OPERATION SPECIFICATIONS Specification Value Notes

Type Drum spec’d Inlet Pressure, PF TBD spec’d as liquid Outlet Pressure, Pc 552 (kPa) Inlet Temperature, TF TBD Outlet Temperature, Ts TBD spec’d Fraction Feed Vaporized 0.1334 Streams Inlet 1 (Name) FEED Outlet 1 (Name) VAPOR Outlet 2 (Name) LIQUID Basis: 876.3 kg moles/hr Feed Calculation Method(s): Data Source(s):

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Job No.: ChE 1008 (03-2) Calc. By: Date: Customer: In-House Chkd’ By: Date: Unit Operation: Debutanizer Column 1 Revision No. of

DISTILLATION COLUMN


Type Trayed spec’d Average Operating Pressure, Pc 552 (kPa) spec’d Actual Reflux Ratio, L/D 5 spec’d Minimum Reflux Ratio L/Dmin TBD Actual Column Equil. Stages, N TBD Minimum Column Equil. Stages Nmin TBD total reflux Actual Column Feed Stage, NF TBD down from condenser Minimum Column Feed Stage, NF, min TBD down from condenser Column Feed Stage Temperature, Ts TBD (oC) Distillate Recovery 98.7% n-butane spec’d based upon Bottoms Recovery TBD isopentane feed stream Light Key Component (LK) TBD Heavy Key Component (HK) TBD Heavy Non-Key Component(s) (HNK) TBD Light Non-Key Component(s) (LNK) TBD Streams Inlet (Name) Feed (F) see attached Outlet 1 (Name) Distillate (D) stream composition Outlet 2 (Name) Bottoms (B) specifications Basis: Calculation Method(s): Data Source(s):

Job No.: ChE 1008 (03-2) Calc. By: Date: Customer: In-House Chkd’ By: Date: Unit Operation: Debutanizer Column 1 Revision No. of

COLUMN CONDENSER/REBOILER


Condenser Type Total spec’d Operating Pressure 546 (kPa) spec’d Temperature TBD (oC) Duty TBD (kcal/hr) Reboiler Type Partial spec’d Operating Pressure 593 (kPa) spec’d Temperature TBD (oC) Duty TBD (kcal/hr) Basis: 876.3 kg moles/hr Feed Calculation Method(s): Data Source(s):

Project Report Requirements The following is the report format which must be followed: Signed Letter of Transmittal (to the Instructor) Cover Sheet (project title, your name, and submission date)

I. Project Statement II. Calculation Methodology III. Results

1. Binary Equilibrium Plots 2. McCabe-Thiele Method 3. Multi-Component Approximate Methods 4. Aspen Plus’ DSTWU Method

IV. Discussion V. Recommendations VI. References

Appendices A-1 Multi-Component Feed Temperatures Calculations A-2 Binary McCabe-Thiele Calculations A-3 Multi-Component Approximate Methods Calculations A-4 Multi-Component Flash Calculation – Aspen Plus Flash2 A-5 Multi-Component Distillation – Aspen Plus’ DSTWU

The Project Statement section serves as the introduction to your report. State the problem and what you will be presenting in the report. The Calculation Methodology section should provide a brief explanation of the methods used in the calculations. Reference as necessary – don’t report a lot of equations – but include the key equations. For Results section 1, include plots of y vs. x generated from the equilibrium relationship used in the McCabe-Thiele method and that generated from Aspen. For Results sections 2 through 4, complete a separate set of specification forms for each method and fill in all TBD’s (to be determined). In your Discussion, compare and contrast the methods based on your results. Highlight any assumptions that you made and discuss their implications with respect to your results. Provide your final recommendations in the Recommendations section including which method you would use, why you would use it, and when would you use it. Cite all material used in the solution of your problem in the Reference section. Your appendices should be well organized with your calculations presented in Mathcad worksheet printouts, as well as, printouts of the Aspen report results.

che 1008 chemical engineering equilibrium separations...

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