Process mode for the A6G example simulation

The objective of Process mode is to provide an overall mass and energy balance for the process and to estimate the product flowrates and compositions. We switch the following process specifications to meet the design requirements:

• For the SRC1 Source, we calculate the mass flow (W) to set the molar flow (F) to 3256.54 lbmol/h.

• For the D7 Drum:

  • We calculate the heat duty (Duty) to set the drum temperature (T) to 40°F.

  • We set the InletPressures parameter to Balanced so that we can set the pressure (P) in Process mode to 4840 psig. Because the Balanced option forces all feeds to have the same pressure as the drum, we must remove the specification on the XV1 pressure drop (XV1.DP) so that the valve pressure drop is calculated based on the required inlet pressure to the drum (D7.P).

• For the X4 heat exchanger, we calculate the heat duty (Duty) to set the shell-side outlet temperature (Tso) to 85°F.

• For the FDEF heat exchanger, we calculate the heat duty (Duty) to set the tube-side outlet temperature (Tto) to 430°F.

• For the D6 Drum:

  • We calculate the heat duty (Duty) to set the drum temperature (T) to 85°F.

  • We set the InletPressures parameter to Balanced so that we can set the pressure (P) in Process mode to 4660 psig. Because the Balanced option forces all feeds to have the same pressure as the drum, we must remove the specification on the XV2 pressure drop (XV2.DP) so that the valve pressure drop is calculated based on the required inlet pressure to the drum (D6.P).

• For the D8 Drum, we set the InletPressures parameter to Balanced so that we can set the pressure (P) in Process mode to 350 psig. Because the Balanced option forces all feeds to have the same pressure as the drum, we must remove the specifications on the XV3 and XV4 pressure drops (XV3.DP and XV4.DP) so that the valve pressure drops are calculated based on the required inlet pressures to the drum (D8.P).

• For the SP1 splitter, we calculate the outlet flow ratios for the two product streams (OutRatio) to set the RatioSum to 1 and the molar flowrate of the purge stream (Purge.F) to 70 lbmol/h.

• For the CP4 Compressor, we calculate the compressor pressure ratio (Pr) to set the InletPressures parameter for the MX1 mixer (MX1.InletPressures) to Balanced. This allows CP4 to meet the pressure needs of the synthesis loop.

The specification on the molar flowrate of the purge stream (Purge.F) allows us to meet the design requirements defined in the AVEVA PRO/II Simulation example1 that we based this example simulation on. However, specifying the molar flowrate may limit further detailed design and the transition into Fluid Flow and Dynamics modes. A better specification setup is to set the purity constraints in the reactor instead. We do this for the two case studies (Pro 2 and Pro 3 snapshots) included in this simulation. For the case studies, we switch the following additional process specifications:

• We calculate the molar flowrate of the purge stream (Purge.F) to set the combined argon and methane impurity in the reactor feed (Rx_Feed_Inerts) to 0.12 for the first case study (Pro 2 snapshot) and then to 0.16 for the second case study (Pro 3 snapshot).