Why are the results obtained from simulations using PORII7.1 and PORII8.1 different?
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After using PORII7.1 to simulate the acetaldehyde distillation column and achieving the design requirements, the minimum reflux ratio calculated was 1.5. When the same data were input into PORII8.1 to meet the same design requirements, the minimum reflux ratio calculated by PORII8.1 was 3.5. Why is there such a large difference? . . . I would like to seek advice from the experts here. . . Thank you. . . $ Generated by PRO/II Keyword Generation System $ Generated on: Wed Feb 11 11:09:49 2009 TITLE DIMENSION SI, TEMP=C, VISCOSITY=CP, SURFACE=D/CM, STDTEMP=0, & STDPRES=101.325 SEQUENCE SIMSCI CALCULATION RVPBASIS=APIN, TVP=37.778 COMPONENT DATA LIBID 1,ACETALD/2,ETHANOL/3,FORMIC/4,ACETIC/5,EOAC/6,H2O, & BANK=PROCESS,SIMSCI THERMODYNAMIC DATA METHOD SYSTEM=NRTL, PHI=HOCV, ENTHALPY(V)=HOCV, DENSITY(V)=HOCV, & ENTROPY(V)=HOCV, SET=NRTL01, DEFAULT STREAM DATA PROPERTY STREAM=S1, TEMPERATURE=65, PHASE=M, RATE(WT)=36465.1, & COMPOSITION(WT)=1,16/2,16/3,0.2/4,0.2/5,0.15/6,67.45 PROPERTY STREAM=S3, TEMPERATURE=163, PHASE=M, RATE(WT)=6000.01, & COMPOSITION(WT)=6,100 UNIT OPERATIONS COLUMN UID=T1 PARAMETER TRAY=30,CHEMDIST=50 FEED S1,8/S3,30 PRODUCT OVHD(WT)=S2,5833.01, BTMS(M)=S4, SUPERSEDE=ON CONDENSER TYPE=BUBB DUTY 1,1,,CONDENSER PRINT COMPOSITION=WT, PROPTABLE=ALL, SUMMARY=WT, & TEFFICIENCY, DIAGRAM ESTIMATE MODEL=CONVENTIONAL, RRATIO(L)=3 PRESSURE 1,220/30,260 SPEC STREAM=S2,PCT(WT), COMP=1,WET, VALUE=99.9 SPEC STREAM=S4,PCT(WT), COMP=1,WET, VALUE=0.01 VARY DUTY=1 VARY FEED=S3 TSIZE SECTION(1)=2,30,VALVE, DMIN=381, FF=70 VLLECHECK CHECK=OFF END REFLUX RATIOS -------- REFLUX RATIOS -------- MOLAR WEIGHT STD L VOL --------- --------- --------- REFLUX / FEED STREAM S1 0.1302 0.2559 0.3004 REFLUX / FEED STREAM S3 0.5995 1.4647 1.8654 REFLUX / TOTAL FEED 0.1070 0.2178 0.2587 REFLUX / LIQUID DISTILLATE 1.5985 1.5985 1.5985 $ Generated by PRO/II Keyword Generation System $ Generated on: Wed Feb 11 11:11:47 2009 TITLE DIMENSION SI, TEMP=C, ENERGY=KCAL, HTCOEF=KC/H, VISCOSITY=CP, & SURFACE=D/CM SEQUENCE SIMSCI COMPONENT DATA LIBID 1,ACETALD/2,ETHANOL/3,FORMIC/4,ACETIC/5,EOAC/6,H2O, & BANK=OLILIB,SIMSCI,PROCESS ASSAY CONVERSION=API94, CURVEFIT=IMPROVED, KVRECONCILE=TAILS THERMODYNAMIC DATA METHOD SYSTEM=NRTL, TRANSPORT=NONE, PHI=HOCV, ENTHALPY(V)=HOCV, & DENSITY(V)=HOCV, ENTROPY(V)=HOCV, SET=NRTL01, DEFAULT STREAM DATA PROPERTY STREAM=S1, TEMPERATURE=65, PHASE=M, RATE(WT)=36465.1, & COMPOSITION(WT)=1,16/2,16/3,0.2/4,0.2/5,0.15/6,67.45 PROPERTY STREAM=S4, TEMPERATURE=163, PHASE=M, RATE(WT)=6999.98, & COMPOSITION(M)=6,1 UNIT OPERATIONS COLUMN UID=T1 PARAMETER TRAY=30,CHEMDIST=80 FEED S1,8/S4,30 PRODUCT OVHD(WT)=S2,5833.01, BTMS(M)=S3 CONDENSER TYPE=BUBB DUTY 1,1,,CONDENSER PRINT COMPOSITION=WT, PROPTABLE=ALL, TEFFICIENCY, DIAGRAM ESTIMATE RRATIO(L)=3 PRESSURE 1,220/30,260 SPEC ID=COL1SPEC1, STREAM=S2,PCT(WT), COMP=1,WET, VALUE=99.9 SPEC ID=COL1SPEC2, STREAM=S3,PCT(WT), COMP=1,WET, VALUE=0.01 VARY DNAME=CONDENSER VARY FEED=S4 TSIZE SECTION(1)=2,30,VALVE, DMIN=381 VLLECHECK CHECK=OFF END REFLUX RATIOS -------- REFLUX RATIOS -------- MOLAR WEIGHT STD L VOL --------- --------- --------- REFLUX / FEED STREAM S1 0.2897 0.5692 0.6664 REFLUX / FEED STREAM S4 0.9792 2.3925 3.0369 REFLUX / TOTAL FEED 0.2235 0.4598 0.5465 REFLUX / LIQUID DISTILLATE 3.5560 3.5560 3.5560 http://bbs.hcbbs.com/viewthread.php?tid=387015&extra=page%3D1&frombbs=1 The simulation process can be found at the link above; please help analyze it. This post was last edited by suiran983527 on 2009-2-12 10:13
It shouldn’t differ by so much; it would be best to provide the inp file.
There will be differences, but not that much. You’d better check your input again; if it doesn’t involve any trade secrets, it’s advisable to upload the INP file so that others can take a look at it for you. :)
After reviewing your output files, it can be seen that for version 7.1, the stream at the bottom of the tower, S3, has the following properties: PROPERTY STREAM=S3, TEMPERATURE=163, PHASE=M, RATE(WT)=6000.01, & COMPOSITION(WT)=6,100. For version 8.1, the stream at the bottom of the tower, S4, has the following properties: PROPERTY STREAM=S4, TEMPERATURE=163, PHASE=M, RATE(WT)=6999.98, & COMPOSITION(M)=6,1. In other words, there is more water in version V8.1 compared to version V7.1. You require that the acetald concentration at the top of the tower be 99.9%
Why do different versions give such vastly different results for the same settings!
I don’t have version 8.1 at hand; I’ll talk about it for now. It might not be correct, so I hope everyone can offer their guidance
So what’s the difference between the results you got using 7.1 and mine?
Yesterday, I didn’t have PRO/II v8.0 software at hand, so I merely glanced at the output results and drew a conclusion casually; however, after copying the two simulation processes to my computer, I realized I was wrong – the flow rate of water entering the bottom of the tower, whether it was 6000 or 7000, had no impact on the return flow rate. After a thorough analysis conducted 15 minutes later, it was found that the molar flow rates of the material streams in versions V7.0 and V8.0 did not match; it was suspected that the components had been forcibly modified, but no signs of such modifications were detected upon closer inspection. By checking the Fixed Properties option in the Component Properties of versions V7.0 and V8.0, it can be seen that there is a significant difference in the value for Standard Liquid Density; this is the fundamental reason behind the difference in their reflux ratios. This phenomenon is caused by the reversed priority assigned to the PROII x.0:SIMSCI database and the PROII x.0:PROCESS database in the Databank Search Order of Component Selection. This is the result of minor differences in the SIMSCI and PROCESS databases being amplified during the calculation process.
Thank you for helping to find the cause. Then, shall we go by that calculation simulation?
Thank you to the friend from Jiangsu up there for their reply; the problem has been solved!
Borrowing the answer from the post “PROII: The Applicability of Databanks” to reply to OLILIB: The electrolyte databases from OLI Systems (mainly inorganic salt solution systems)； The electrolyte system technology for all simulation software mostly comes from OLI Corporation. PROCESS: Databases from the early versions of PROII, with data sources primarily coming from the US PPDS. SIMSCI: All subsequent updates to the component libraries in the PROII version are available in the SIMSCI library, which offers the most comprehensive and up-to-date information; the main data source is DIPPR.