By Ali Bourji, David Ballow and Martha Choroszy, WorleyParsons |
One of the most energy-intensive utilities for many facilities in the chemical process industries (CPI) is the steam system. Traditionally, steam-use optimization has centered on efficient heat transfer and eliminating waste [ 1]. Further optimization can involve a broader look at how steam supply and consumption interact dynamically throughout a large complex. This type of optimization often results in increased interconnectivity and interdependency.
Many CPI facilities have a central steam-production area containing boilers and boiler feedwater treatment, as well as additional steam generators scattered throughout the facility (for example in the petroleum refining sector there are ethylene and catalytic cracking units). If a facility is built in several stages, as is often the case, steam generating systems may be separated by considerable distances. Over these distances, the stability of the integrated steam system could be jeopardized by inappropriate control strategies. How should one go about setting up a control strategy and verifying that it is stable and appropriate for a particular complex?
Figure 1. An effective control strategy can be broken down into four stages
Steady-state modeling and steam balances…