Unformatted text preview: Homework 3 Problem 5 Aspen HYSYS™ Two-Stage Compression with
20 points possible due Friday September 16, 2011 Grader: Israel Problem Statement: Use a process simulator to model a two‐stage compression system with an intercooler. The feed stream consists of 95 mol% hydrogen and 5 mol% methane at 100°F and 30 psia; 440 lbmol/hr is compressed to 569 psia. The outlet temperature of the intercooler is 100°F and its pressure drop is 2 psi. The centrifugal compressors have an isentropic efficiency of 0.9 and a mechanical efficiency of 0.98. Determine the power requirements and heat removed for three intermediate pressures (outlet from the first stage): 100, 130, and 160 psia. Method of Solution: Use the Compressor and Cooler units in HYSYSTM to simulate the process and calculate the power requirements and heat removed. Solution: 1) Open the HYSYSTM program and start a New Case. 2) Open the Fluid Pkgs tab and click Add..., select the SRK fluid property package. 3) Click View to open the Component List View window, and then input the process components. Page 1 of 6 4) After both process components have been added to the list, close the Component List View and Fluid Package windows. 5) Click Enter Simulation Environment. 6) Click on the Compressor icon in the Object Palette, and click again in the PDF window to place it in the workspace. 7) Double‐click on the compressor to specify the streams. Type “Feed” for the Inlet, “S1” as the Outlet, and “Q1” as the Energy stream. 8) Select Parameters from the menu on the left‐hand side; enter 90.00 as the Adiabatic Efficiency. 9) Close the K‐100 Compressor window and double click on the Feed stream. 10) Before entering the Feed conditions, check that the Field Units Set is selected. Select Tools, Preferences…, click the Variables tab and select the Field Unit Set. 11) In the Feed window, enter the temperature, pressure, and molar flow as specified in the problem. Page 2 of 6 12) Click on the Compositions Worksheet and enter the compositions of methane and hydrogen and press enter. The stream should converge. 13) Add a cooler to the PFD by clicking the icon in the object palette and clicking back in the workspace. 14) Also, add the second compressor at this point, to the right of the cooler. The PFD should now look like the the one shown below: 15) Double click on the cooler and select the inlet stream “S1”. Define an outlet stream, “S2”, and an energy stream, “Q2”. Type “Intercooler” in the Name field. Page 3 of 6 16) Click on Parameters on the left‐hand side of the window. Enter a Delta P of 2 psi. The cooler will not yet converge. 17) Double click on the second compressor and select the inlet stream, “S2”. Define a Product stream, “Products”, and an Energy stream, “Q3”. 18) Again, enter an Adiabatic Efficiency of 90.00 under the Parameters option. Close the compressor window. 19) Double click on the “S1” stream. Enter the Pressure as the desired intermediate pressure indicated in the problem statement (100, 130 or 160 psia). 20) Double click on the “S2” stream. Specify the Temperature as 100°F. 21) Double click on the “S3” stream. Specify the final Pressure. The system should now converge. The completed process flow diagram should look similar to the one below. Page 4 of 6 22) Right click anywhere in the workspace and select Add Workbook Table. Select Material Streams and click Select. 23) Before adding an Energy Streams workbook in the same way, click on the workbook icon at the top of the screen. Right click on the Energy Streams tab and select Setup. 24) When the Setup window appears, click Add on the right side and select Power as the variable. Click OK and continue to add the Energy Streams workbook to the workspace. 25) Your tables should look like the ones below for the 100psia intermediate pressure. Page 5 of 6 26) Save the file, change the S1 pressure to 130 psia and resave the file under a new name. Repeat for the final pressure of 160 psia. 27) Compare these results with the results found in problem 1 using Aspen Plus™. Page 6 of 6 ...
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