Page 416 - Design of Simple and Robust Process Plants

9.7 Pragmatic Approach to Operation Optimization 403
The qualification of the different quality levels are:

Reactor model
± H is for a kinetic reactor model which includes product distribution and
properties like a polymer reactor model or a complex multi-component reac-
tion model (e.g., for cracking of hydrocarbons).
± M is for a kinetic reactor model which predicts product distribution (e.g., a
styrene reactor model; no product quality involved).
± L is for a conversion reactor model (e.g., a hydrogenation reactor), fixed bed
or a CSTR type, for full conversion or any model of reasonable quality that
can be bought. However, validation might still be an extensive effort which
might bring it into the M level (be aware that the models ultimately need to
be equation-based in case the source is not made available ± at least access to
the derivatives is a requirement).
± NA is for a polishing reactor (e.g., chemisorption for low impurity levels), not
being a constraint nor have any significant contribution to the operational
cost.

Performance meter
± H In case operation optimization is going to be implemented, to what ever
extent off-line or closed loop, a performance meter is a requirement. Its use
will not be restricted to performance measurement, but it will also include
the necessarily model validation.
± M When process stability and constraint control is to be implemented, the
meter gives a clear picture of the contribution of these improvements. Opera-
tional activities where the number of DOFs for operation are limited in a sta-
bilized process
± L When no optimization or control improvements are planned and opera-
tional DOFs are restricted.
± NA

Process model
± H is for complex process plants with many unit operations(over 12), includ-
ing internal utility generation such as refrigeration (e.g., olefin plants, refi-
neries, propylene oxide/styrene plants, but also smaller plant with multiple
unit operations).
± M is for medium process plants with 8±12 unit operations (e.g., butadiene
extraction plants, hydro dealkylation plants).
± L for simple processes with a low number of unit operations (e.g., glycol
plants, ethyl-benzene plants), process models which might be bought from
technology suppliers, and ultimately need to be equation-based and written
for a standard flowsheeter.
± NA is for simple units which might be optimized by self-optimizing control.
System.