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Unformatted text preview: ut of the second separator is only 86.8% pure. However, we want purity greater than 90%, as given in the problem statement. 7. In the Data Browser, click on the Flowsheeting Options folder and open the Design Spec option. 8. Click New and name the design specification “PURITY”. Page 5 of 10 9. Click the Define tab to specify the dependent variable. In this case, we will set the dependent variable as the purity (mass fraction) of the water product stream. Click New, and name the new variable “WATER”. Click OK. In the Variable Definition window that appears, select MASS‐FRAC in the Reference section. Select the water product in the Stream field, and “WATER” in the Component field. Click Close. 10. Click on the Spec tab to specify a target value for the dependent variable. In the Spec field, type “WATER”, the dependent variable that we just defined in the Define tab. Type “0.90” into the Target field, the numeric value that we desire for the dependent variable. Type “0.001” into the Tolerance field; we will use a tolerance of 0.1%. (Remember: the tolerance is defined as the acceptable closeness of the Aspen solution to the target value.) 11. Click on the Vary tab to input the information for the independent variable that will be varied; in our case we will vary the mass flow rate of the new MIBK stream (MIBK2). In the Type field, select MASS‐FLOW. Select “MIBK2” for the Stream field, and “METHY‐01” for the Component field inputs. 12. The Manipulated Variable Limits section allows you to input the range over which you would like to vary the independent variable. Input a variable range of 20‐
100 lbs/hr into the appropriate fields. (Note: The original specified value of the independent variable must lie within the range. For example, we used a value of 50 lbs/hr.) If you leave the Step size field blank, Aspen PlusTM uses default values. 13. The Simulation Status bar should read “Required Input Complete”. If it does not, reinitialize. 14. Run the simulation. 15. Open the Run Control Panel to see how many iterations Aspen PlusTM made to reach the desired s...
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- Spring '08