Exporting to Aspen Dynamics

Aspen Dynamics uses the steady-state information generated in Aspen Plus, but the two simulators are different programs with different files. The Aspen Plus file is filemme.apwz, and there is also a backup file filename, bkp, which 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.dynffile, which is used in Aspen Dynamics and is modified to incorporate controllers, plots and other features. The second file is a filenamedyn.appdf file that contains all the physical property information to be used in Aspen Dynamics. 

In the propane/isobutane column example, the Aspen Plus files are called Examplel. apwz and Examplel.bkp. The files generated and used in Aspen Dynamics are Examplel. dynfwA Exampleldyn.appdf. Both of these files are needed to run the simulation in Aspen Dynamics. 

Fatal Error M ssagci Exporting Dynamic Simulation 

TRANSLATE USING COMPILED AST PROCEDURES IN DVPtovan Flea 

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The program in Aspen Plus is run and pressure-checked. It is then exported to Aspen Dynamics as a pressure-driven dynamic simulation as was done in Chapter 3 with CSTRs. The Aspen Dynamics file is opened, giving the window shown in Figure 6.37. The default control scheme has a pressure controller manipulating the valve in the reactor exit line. The simulation is run until all variables stop changing. 

Preparing for Export to Aspen Dynamics The dynamic units in the flowsheet are... 

With these elements, ASPEN Plus can perform a sizing run and determine initial values for dynamic simulation, particularly the holdup on each tray. We select a diameter of 2.2 m and sieve trays with 50 mm weir height. Then the operation parameters, sizing elements and initial values are exported to ASPEN Dynamics. 

The usual sizing calculations are performed, the flowsheet is pressure checked, and the file is exported to Aspen Dynamics. Flow controllers are installed on the feed, distillate, and sidestream. Base level is controlled by manipulating bottoms flow rate. Reflux-drum level is controlled by manipulating reflux flow rate. 

The reflux drum and column base are sized to provide 5 min of liquid holdup when half full. The file is pressure checked and exported to Aspen Dynamics. The initial control scheme that opens is shown in Figure 11.26. Note that there is a level controller (LCW1) that pulls off free water from the reflux dmm. The other level controller (LC12) manipulates reflux flow rate to hold the liquid level of the organic phase in the reflux dmm. Since the reflux ratio is only 0.344 in this column, we change the control structure to hold reflux-dmm level with the NAPHTHA flow rate (valve V12). Pressure controller PCI manipulates the valve V14 in the vapor line. 

AbSOrbBr. A column with 11 stages operates at 1 atm pressure at the top. A tray pressure drop of 0.2 psi is specified in order to satisfy the requirement that the specified pressure drop is greater than the pressme drop calculate from the hydraulics when exporting to Aspen Dynamics. The design feed gas is 13,100 kmol/h and is compressed to 1.136 atm and fed at the bottom of the absorber. The specified recovery of carbon dioxide is 90%, which corresponds to an absorber exit gas composition of 1.3 mol% CO2. 

In the original simulation, the stripper was modeled using a normal RadFrac column with a partial condenser and a total reboUer. Serious simulation issues arose when the stripper was exported to Aspen Dynamics. When a normal RadFrac model with condenser and reboiler was used (see Fig. 14.3a), the file could not be initialized in Aspen Dynamics. 

Figure 14.5 shows the Aspen Plus flowsheet with the solvent recycle loop open. The makeup flow rates of water and MEA were estimated from the losses of these components. After exporting to Aspen Dynamics, the block VDUM and the streams CALC and SOLVENT are deleted. Then stream LEAN is connected to mixer Ml. ... 

Figure 14.15 shows the Aspen Plus process flow diagram with the solvent recycle loop open. To close this loop, the amounts of water and solvent lost in the off gas and stripper vapor product streams have to be precisely known. As is often the case, it turned out to be easier to close the loop after exporting to Aspen Dynamics. Figures 14.16 and 14.17 give temperature and CO2 composition profiles in the absorber and in the stripper. 

The Aspen Plus file is exported to Aspen Dynamics as a pressure-driven simulation after reflux-dram and base volumes are specified to provide 5 min of holdup when at 50%... 

The flowsheet is exported to Aspen Dynamics after all the parameters required for a dynamic simulation are specified (equipment sizes), and the flowsheet is pressure checked so that a realistic pressure driven dynamic simulation can be used. Reflux drums and column bases are sized to provide 5 min of holdup when half full. Pump heads and control valve pressure drops are specified to give reasonable plumbing. Typical design control valve pressure drops are 3 bar with the valve half open at design flowrates. 

The Aspen Plus file of this extractive distillation system is exported to Aspen Dynamics after dynamic parameters are specified (equipment sizes). Figure 11.8 shows the control stmcture developed for this system, which is based on the extractive distillation control structure proposed by Grassi. Relay-feedback testing and Tyreus-Luyben tuning of the temperature loops give the controller parameters given in Table 11.2. The temperature controllers have 1 min deadtimes in the loops. Reflux ratios are held constant in each column (3.44 in the extractive column and 1.61 in the methanol column). 

The Aspen Plus files for each of the three extractive distillation systems are exported to Aspen Dynamics after dynamic parameters are specified. Aspen Plus tray sizing is used to fix column diameters. Table 11.4 gives column sizes. Pump heads and valve pressure drops (typically 3 atm) are selected to give reasonable rangeability so that 20% increases... 

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