Non Linear Advanced Process Control Using Rigorous On-Line Model

Filippo Zerbini, HPS, Honeywell , Monza, Italy

Advanced Process Controls (APC) based on multivariable technology are a very commonly used solution to achieve optimal control of linear processes such as almost all the refinery related process units, from distillation towers to the most complex catalitic reactors like FCC and CCR. For non linear processes or multi-grade processes like in the polymer industry the APC have been always be a tough topic.

Also in ethilene  production linear APC are commonly used to control the hot (reaction) and cold (separation) sections; in some instances units like quench tower have different seasonal behaviour due to environmental conditions being very different i.e. from summer to winter. In this case APC do have some limitation or require different "models" to be switched on and off to use the right gains relevant to the environmental conditions. 

We analze the possibility to create a rigorous first principle process model which is running in real time, fed by actual process data, and calculating the best set of parameters (controller gains) to be downloaded to the APC in real time; this model is then able to "driive" the APC always with the most approrpriate parameters and smoothly following seasonal differences.

This is optimizing APC running helping to achieve even more profitability beyond the one usually provided by normal APC.   

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