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DIP_simu_06

DIP_simu_06.ppt. Specifications management Design Specifications Control Panel : calculation sequence management. Calculator block: FORTRAN. Open from last class: DIP_MCB_m.apw and DIP_MCB_m.xls. Resume:. DIP_MCB_m.apw.

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DIP_simu_06

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  1. DIP_simu_06.ppt • Specifications management • Design Specifications • Control Panel: calculation sequence management. • Calculator block: FORTRAN

  2. Open from last class: DIP_MCB_m.apw and DIP_MCB_m.xls Resume: DIP_MCB_m.apw

  3. Note: Conversion and Selectivity values are calculated in DIP_MCB_m.xls DIP_MCB_m.apw

  4. Design Specifications Use design specifications to set the CL2 mole flow in the feed stream, in order to meet the gas outlet stream requirements (2%mol of CL2). • /Data /Flowsheeting Options /Design Spec: [New...] • Enter variable Name: CL2-R130 [OK] DIP_MCB_n.apw

  5. Check the design specification: increase the residence time in the first reactor to 3 h and let the design specification to find the new mole flow of CL2 in stream 2. • Errors are reported: there is a lack of CL2 in the feed stream (reactor kinetics are CL2 independent, and more CL2 than the one present in de feed stream may be calculated to react.) • Try increasing the initial estimate of CL2 mole flow in stream 2: 40 kmol/h • Some errors are reported in intermediate iterations, but a solution is finally found. DIP_MCB_o.apw Control Panel: calculation sequence control. • Reinitialize • Step

  6. Also an Stop point may be allocated (right-click) after the reactor. • Calculations evolution may be closely followed using the Step button and loading intermediate results (/Run /Load Results, or /Tools /Options: Run Tab,Interactively load results -> ON). • Results may be displayed using the right-click View/ Report or Results options.

  7. Write a second design specification (CL2-R140) for the second reactor to obtain (xCL2)6=0.02. (NOTE: First, set back the residence time of R-130 to 2.5 h again) • For CL2 mole flow in Vary set the range between 10 and 30 kmol/h, and the initial estimate (stream 5 , CL2 mole flow = 25 kmol/h) DIP_MCB_p.apw Calculate benzene conversion in both reactors. (In Excel use Copy and Paste Links). • Copy Stream results from R-130. • Paste in Excel (link). • Calculate conversion

  8. Write a new design specification (S-R130) to set the selectivity in R-130 to 95%, by varying the residence time. • /Data /Flowsheeting Options /Design Spec: [New...] • Enter variable Name: S-R130 [OK] DIP_MCB_q.apw Errors are reported and a solution is not found. Which elements are at the end of the calculation process reporting problems?

  9. Both reactors are solved sequentially (see the Control Panel). • The first reactor (R-130) and both solvers associated to this reactor (design specifications CL2-R130 and S-R130) are correctly solved. • Error are reported in the second reactor (R-140) and its associated solver ($OLVER02, for design specification CL2-R140).

  10. Design specification CL2-R140 must be deactivated, and different CL2 mole flows in stream 5 must be evaluated to determine the new range. • Activate again the design specification • Set the new range: /Data /Flowsheeting Options /Design Spec: CL2-R140, Input, Vary • Lower: 12 kmol/h • Upper: 20 kmol/h CL2 mole flows in stream 5 = 14,144 kmol/h DIP_MCB_r.apw

  11. Calculator block: FORTRAN Modify design specification S-R130 to set global selectivity instead of R-130 selectivity. Both reactors must be of the same volume to minimize cost. A Calculator Block must be written to set the volume of the second reactor. Change setup specification of R-140 to “Reactor volume & Phase volume fraction”. Any value may be used for the volume, as it will be modified later by the calculator block. Reactor R-140

  12. /Data /Flowsheeting options: Calculator [New...] VOL-R140 [OK]

  13. Design specification S-R130 must be modified and renamed to SELECT. Errors are reported in design specification CL2-R140. Use a higher initial estimate for CL2 mole flow in stream 5 = 20 kmol/h Solution: Reactor volume = 30,47 m3 CL2 mole flow in stream 2 = 21,32 kmol/h CL2 mole flow in stream 5 = 16,82 kmol/h DIP_MCB_s.apw

  14. FORTRAN • FORTRAN code may be used in Aspen in many forms and in FORTRAN blocks. • FORTRAN blocks allow: • Calculate and set input variables before being used (feedforward). • Write information to the Control Panel. • Read/write information from/to external files. • Call external FORTRAN subroutines. • FORTRAN blocks operation modes: • Feed-forward: defining variables or performing actions that affect only downstream units. • Feedback: changing input variables in upstream units. The calculation sequence automatically creates iteration loops for calculation, if the sequence of calculation is determined from reading and writing variables. • FORTRAN code: • Variable names starting with AH and OZ are considered double precision variables. Those starting with I-N are considered as integers. Variable names ZZ and IZ may not be used. • Lines of executable code: starting in column 7. • Comments: C in the first column and the second blank. • Write values to the Control Panel: WRITE (NTERM, *) A • Writing in the report file: WRITE (NRPT, *) A • Interactive input of values: READ (NTERM, *) A

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