Page 23 - Design of Simple and Robust Process Plants

6 Chapter 1 Introduction
In this report, it was argued that such an objective had to be achieved through the
development of fundamental process models, in static as well as dynamic state. The
application of these models for control design as well as operation optimization is
considered as apparent.
The above discussion mainly concentrates on the operational requirements of a
process plant. The plant of the 21st century has more extended characteristics which
should bring it close to a domestic refrigerator. The definition of the simple and
robust plant for the 21st century plant, as adopted in this book is:
An optimal designed safe and reliable plant, operated hands-off at the most economical
conditions.

Such a competitive plant can be achieved by striving for the following objectives:
. Plants must be captured in fundamental models statically as well as dynami-
cally, to achieve understanding, design and operational support.
. Design optimization must be applied based on computerized flowsheet eva-
luations including process synthesis tools with economic objectives, respect-
ing the safety, environmental and sustainability constraints.
. Plants should be reliable and maintenance-free, and achieve a schedule of 4±
5 years between turn-arounds.
. Plants must be safe, environmentally sound, and ± if required ± automati-
cally fall in a fail-safe mode.
. Operational activities such as start, stop and regeneration should be fully
automatic, and be tested with simulations before actual operation.
. Control should be robust and hands-off, with an adequate disturbance rejec-
tion capability. The control design must be based on dynamic models.
. Optimized operation based on mathematical models should be performed
on-going in relation to the site and the business.
Simple and robust plants are low-cost plants. The ratio of annual profit per invest-
ment is the ultimate economic performance yardstick for each investment. World-
wide, this is the basis for comparison of economic operations. The sensitivity of the
economic performance for the investment in a facility is demonstrated in the follow-
ing example.

revenues cost†=year
Annual profit/investment = 100 %
investment
The direct fixed capital (DFC) of a process plant is 10 MM
The site-related capital is 0.1 ” DFC is 1 MM
Total investment is 1.1 ” DFC = 11 MM

Revenues are 20 MM/year
Variable cost (raw material + energy cost) are 16 MM/year