Computer Simulation


We have applied both steady-state and dynamic modeling to many process control and design applications.


Dynamic Modeling – We have written models using general simulation languages as well as packages specifically designed for modeling chemical, pharmaceutical and petroleum processes like Aspen Hysys.


Steady State Modeling - Often, a lot can be learned from a steady state model.  A benefit of this approach is that it requires less engineering time especially when a steady state model is already prepared.  We have developed techniques to establish the feasibility of a control approach using steady state models.  We have applied this technique extensively to designing controls for distillation columns.  If the proposed controls will not work at all the various steady state conditions that define the normal operating range than there is no need to investigate this approach further.


Example Projects




Power Plant

Wrote a dynamic model for prototyping a MPC application using Aspen Hysys.

Operator Training Simulator

Developed a dynamic model that was run in real-time and linked to a DCS system.

Air Separation Units

Wrote dynamic simulations of air separation units for control strategy testing and to develop initial PID tuning constants.

Oil Refining Training

Gave a training class at a refinery on distillation column control using Hysim.


Used Aspen Plus steady state simulation to design controls for more than 20 different distillation systems.

Relief System Sizing

Wrote a dynamic simulation of a gas pipeline and applied it to size a relief system.

Soil Remediation Process

Developed a dynamic simulation to improve pressure control.  This eliminated exposure of operators to toxic chemicals.

Steam Cogeneration

Wrote a dynamic simulation to test control strategy and to come up with start-up PID controller tuning constants.

Batch Reactor with Distillation

 Developed a dynamic simulation of polymer reaction system with distillation for improved process understanding.


Wrote a dynamic simulation of a fermentation process to solve a control problem.

Process HVAC System

Developed dynamic simulations of a number of film drying processes as part of control upgrade projects.



Simulation Benefits


The benefits of simulation can result in substantial savings.  The savings routinely come from:


· Faster, smoother start-ups

· Improved product quality

· Less frequent emergency trips

· Predicting the impact of process changes before they are implemented

· Reduced environmental incidents and safer operation


Modeling Publications:


Fruehauf P. S. and Hobgood J. V., “Dynamic Simulation of a Steam Generation Process with Co-generation” ISA EXPO/2000 Technology Updates (October 2002).


Fruehauf P. S. and Mahoney D. P., “Distillation Column Control Design Using Steady State Models; Usefulness and Limitations” ISA Transactions, 32, pp. 157-175 (1993)


Fruehauf P. S. and Mahoney D. P., “Improve Distillation-Column Control Design” Chemical Engineering Progress 75 (March 1994).


Mahoney D. P. and Fruehauf P. S., “An Integrated Approach for Distillation Column Control Design Using Steady State and Dynamic Simulation”