CONVERTING FROM STEADY-STATE TO DYNAMIC SIMULATION

CONVERTING FROM STEADY-STATE TO DYNAMIC SIMULATION 

We are now ready to get into the details of converting a steady-state simulation into a dynamic one. Basically, the additional information that must be provided is the physical 

It is important when specifying the control valves to select the correct valid phase. If the stream is aU liquid, select Liquid-Only in the Valid Phases under Flash options on the Operation page tab of the valve block. If the stream is all vapor, select Vapor-Only. Some valves have both phases (particularly when the inlet is liquid at its bubble point temperature and pressure, which means flashing occurs when the pressure decreases as the fluid flows through the valve) and Vapor-Liquid should be selected. Numerical problems can occur in Aspen Dynamics if these valid phases are not correct. 

The propane/isobutane column developed in Chapter 3 is used in this chapter as a numerical example. The control valves all have pressure drops of about 3 atm. The column 

Distillation Design and Control Using Aspen Simulation, Second Edition. William L. Luyben. 2013 John Wiley Sons, Inc. Published 2013 by John Wiley Sons, Inc. 

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CONVERTING FROM STEADY-STATE TO DYNAMIC SIMULATION TC control 20% feed disturbances... 

The steady- and non steady-state simulation of an industrial ammonia converter is presented. The reactor includes two adiabatic radial-flow catalyst beds in series. An interbed (gas-gas) heat exchanger is used to preheat the feed stream. The steady-state results showed good agreement with plant data. The influence of different disturbances (feed composition and temperature, reactor pressure) on the dynamic evolution of the main variables is analysed. The open-loop and closed-loop operation is compared from the standpoint of the reactor stability. 

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