BFW Pump 4 replaces motor-driven Pump 3. Net 600 psig steam export goes down by
20klb/h, and 600-150 psig steam letdown is reduced by 29klb/h.
Other common optimization“handles”include steam producers, fuel sources, steam
turbines, and a number of cogeneration plant variables.
On-demand steam producers, such as auxiliary boilers and ductfiring on heat
recovery steam generators, can provide excellent handles for reducing cost site-wide
through boiler-to-boiler rebalancing for maximum systemefficiency.Whenmultiple fuel
options such as refinery fuel gas and natural gas are available, the optimization can
negotiate the complexities of differential pricing and constraints to find real-time
operational savings. Even complex constraints are respected, such as the requirement
to consume all refinery fuel gas (discussed in Chapter 20) to avoidflaring.
Steam turbines can provide excellent handles for optimization if their operation can
be adjusted. For example, a steam turbine generator with a manual set point provides the
optimizer with an opportunity to react to changes in the incremental fuel versus
electricity pricing. So, if the price of electricity increases in comparison to the price
of fuel, the steam turbine may be a cost-effective option for either reducing site-wide
power purchases or increasing power sales.
Even extraction/condensing turbines with a constant horsepower requirement to
the process can provide savings by rebalancing the horsepower between the high- and
low-pressure sections of the turbine with the adjustment of other steam equipment in
manual control.
Cogeneration systems with gas turbines and heat recovery steam generators can
react to changes in fuel versus electricity purchase and sales pricing if the power
generation is inmanual control. Excess steamor water injection for power augmentation,
inlet air chilling, and combustion air recirculation all provide additional flexibility in
cogeneration operation and handles the optimization system can use to increase the
savings it provides through real-time recommendations