Chemical Engineering December 2014 - 48

Feature Report
Identifying improvements
Some energy inefficiencies are endemic
to the industry, and it does
not require much effort to identify
opportunities to improve them. This
is particularly true of certain types
of routine maintenance activities.
For example, over time, a steam
system will develop leaks and a certain
percentage of its steam traps
will fail, and boilers and furnaces
need periodic tune-ups to remain
in top condition. The question is
not whether these situations create
opportunities to improve energy
efficiency, but rather how large the
opportunities are, and what are the
best ways to capture them. Many
steam-trap vendors provide services
to maintain steam-trap populations
(Figure 3), and there are also companies
that specialize in repairing
steam leaks and tuning up furnaces
and boilers.
Identifying most other types of
energy-efficiency improvements requires
a more concerted effort. Here
are some effective approaches:
High-level site audits. High-level
site audits can be used as a first
step to identify where energy is
used across a facility. This exercise
will sometimes find specific inefficiencies,
but its main purpose is to
highlight and quantify major energy
users, so they can be subjected
to more detailed evaluation later.
Site assessments. Site assessments
are typically carried out by
a team of specialists that spends a
period of time at a facility examining
the operation of the main energy
systems and major energy-consuming
equipment. A typical team
might include specialists in fired
heaters, steam and power systems,
rotating equipment, distillation
operations, heat exchangers, and
process design, although other specialties
may participate, depending
on the needs of the site. The team's
role is to identify inefficiencies and
define opportunities that generally
include improvements in operating
practices and maintenance, as well
as facility upgrades.
PFD reviews. Process flow diagram
(PFD) reviews [5] are structured
brainstorming sessions designed to
Courtesy of TLV
FIGURE 3. Many steam-trap vendors provide services to maintain steam-trap populations
within process facilities
tease out opportunities to improve
plant operations and upgrade facilities.
The procedure for a PFD
review is similar to that customarily
used for hazard and operability
(HAZOP) studies. Plant operations
and technical support personnel,
with assistance from energy-efficiency
specialists, review each of
the main streams, equipment items
and systems to identify inefficiencies
and areas of opportunity.
Heat-integration studies. Heatintegration
studies, focusing on
improving heat recovery, are also a
major source of improvement opportunities
on many sites. Some heatintegration
opportunities are very
simple and can easily be identified
in a PFD review. However, some
are more complex, and specialized
techniques - most commonly pinch
analysis [6] - are needed to capture
them.
Steam-system modeling. Steamsystem
modeling and realtime optimization
are also widely used to
identify inefficiencies in steam systems,
and to define improvements
both in operating strategies and facilities
(Figure 4).
Lengthy research and development
programs are generally
needed to create breakthrough technologies
- although occasionally
they appear serendipitously. Typically
only companies with strong
research and development programs
can venture into this field,
although an alert energy manager
should always be on the lookout for
breakthroughs that are relevant to
his or her technology.
Employee suggestions yield many
very attractive energy-efficiency opportunities.
Employees are most familiar
with the processes and practices
of their site, and many of them
- including some who do not have
a strong technical background -
have the ability to " think outside the
box. " These people represent a very
fruitful resource, and their input
into energy management should
be encouraged. Some companies do
this with competitions that reward
the best ideas, either monetarily or
in other ways. Welcoming and acting
on employee suggestions is a
visible and valuable way to change
corporate and site culture.
Evaluating opportunities
Coming up with an idea is important,
but it is only one step along
the efficiency path. Opportunities
must be screened to quantify their
benefits and to estimate their implementation
costs. They should also be
tested for unintended consequences
(for example, adverse effects on production)
and for safety implications.
First, the use of quick screening
methods is effective in eliminatChemiCal
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Chemical Engineering December 2014

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