Traditionally process design has been done using steady state simulators. Many process design decisions requires knowledge about transient response and process interactions. Also process designs based only on steady state simulations may lead to inadequate sizing of some equipment. Dynamic simulation can identify transient process bottlenecks and avoid process design mistakes. Here a few examples:

FURNACES

For units with a lot of heat integration between the preheat section and the separation section, process designers can under-estimate the heat capacity of a furnace during start-up making the steady state almost unachievable.

SECONDARY PROCESS LINES

Recirculation lines can sometimes be under-sized when steady states simulation are used. Dynamic simulation can cover all the process dynamics, from start-up to shutdown.

COMPRESSOR STABILITY

Insufficient hold-up in vessels around compressors may lead to process instabilities during start-up. Dynamic simulation can help prevent these issues.

Dynamic simulators can be used early in a project to identify important operability and control issues. Instead of using only rules of thumb to develop control strategies, a control engineer can easily evaluate, test and tune a control strategy.

Advanced control development can also be performed with a dynamic simulation, avoiding excessive plant testing.

The effect of planned or unplanned disturbances can also be studied with a dynamic model. It allows to see the effect on the plant operability. For example, one might be interested to see the control in action when ambient conditions changes, when a production switch is done or when there is a sudden pressure loss.

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