Chemical Engineering June 2018 - 76

Feature Report
Steam Balancing:
The First Step in
Steam Optimization
The ability to achieve an optimal steam balance can help to improve the overall
thermal cycle efficiency of any steam-production system
200 PSIG steam produced
and delivered to the process
Vent
High pressure steam
Deaerator
Boiler
Feedwater
Condensate return
I
n any chemical process plant that produces
steam, carrying out a steam balance
is the most efficient way to improve
knowledge of all aspects of the overall
steam system, including steam generation,
distribution, end users and condensaterecovery
systems. Carrying out a steam
balance is a necessary first step in any
effort to optimize and manage overall
steam generation.
For instance, the valuable knowledge
gained from developing or updating a steam
balance can help process engineers to develop
a road map that will allow the steam
system to be used in the most efficient way.
Such an effort also provides essential insight
that can be used to increase the overall thermal-cycle
efficiency of the steam-generation
system. Ideally, every plant should strive to
achieve the highest possible thermal-cycle
efficiency; the steam balance provides the
information needed to achieve this objective.
An optimal steam balance ensures that
the end users - that is, the steam-consuming
processes - can consume the correct
amount of energy at the correct steam
pressure and temperature, with the required
steam quality. A system that has achieved an
optimal steam balance has no energy losses
that might otherwise occur from steam leak200
PSIG steam consumed by the process and
returned to the deaerator at 198 PSIG produced
Condensate return
FIGURE 1. Shown here is a perfect steam balance. This scenario
is an aspirational goal for process
age, excessive low-pressure steam venting,
flash steam venting and condensate loss.
Establishing the correct steam balance
can be very challenging because so many
different dynamics are at work in any given
steam system. These include modulating
steam loads, variable production times, unaccountable
losses, insulation inefficiencies,
turbine operation and more.
Figure 1 shows a nearly perfect steam balance
in a system that produces steam at
200 psig and delivers it to the process. The
process consumes the entire 200 psig (latent
energy) of the steam while the condensate
(sensible energy) is removed from the process.
The end user's process requires the
latent energy contained in the steam. When
that latent steam is released, there is no temperature
or pressure variance, and the condensate
that contains the sensible energy
is returned to the deaerator operation at a
pressure of 30 psig or higher. The condensate
system that is operating at 198 psig returns
the condensate (using a high-pressure
return system) back to a high-pressure deaerator
system. This dearator system delivers
the feedwater at an elevated temperature
(198 psig at 387°F) into the boiler.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
JUNE 2018
Heat exchanger
Process
weater in
Process
weater out
IN BRIEF
THE CHALLENGE AT
HAND
ACHIEVING A STEAM
BALANCE
END RESULTS OF A
STEAM BALANCE
WHAT A STEAM BALANCE
PROVIDES
STEPS FOR A STEAM
BALANCE
Kelly Paffel
Inveno Engineering, LLC
67
http://WWW.CHEMENGONLINE.COM
Chemical Engineering June 2018

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