Page 329 - Design of Simple and Robust Process Plants

8.3 Automation of Operation 315
. Consistency and accessibility of the software for interpretation of its opera-
tional state and its transient operation.
. Requests for operation attention to see keep them alert..
. Overview of the actual process plant using television monitors.
Instruments for observation are important, as these are planned to inform operators
at an early stage if there are deviations from the normal operation. This information
can be split into measurements of the process and unit operations, and the follow-
ing information should be readily available:

. The operational state ± that is, the state or its transient operational step at
which the process or unit is functioning.
. The line-up ± this is especially important for batch operations as well as con-
tinuous processes if different line-ups are involved.
. The condition of a units ± this should not be confused with the fact as to
whether the unit at the desired quality specification (such information is
available from the controlled variables).
. The performance of the process
The operational state of the different units needs to be clear at a single glance for the
operator. For clarification, the following questions may cross his/her mind:
± During a batch reaction, what recipe are we producing, what is the current
feeding steps and which are planned for the reaction?
± During start-up, which units are in reversible operation, and which transition
steps are active?

For line-up, these have questions might be:
± Which loading stations, storage tank or feed tanks are lined up?
± Which adsorber is lined up for regeneration?

The operational condition is, next to its quality performance as measured by the con-
trolled variables, directly traceable from some measurements in the units, these
being quite sensitive to small operational variations:
± Whether the condition from a distillation column can be read from a pres-
sure-compensated temperature measurement in the column. This might
warn operation of any build-up of intermediate component(s) or of any
change(s) in feed composition.
± What is the location of temperature front in the absorber? A decrease in inlet
concentration might create a breakthrough due to the characteristics of the
absorption isotherm.
± How does the radial temperature profile appear for the packed bed reactor?
± How steady is the process? For steady-state, optimization measurements are
installed to verify the steady-state of the process before the optimization
sequence commences (see Chapter 9).