Chemical Engineering March 2023 - 38

Marmon
Industrial
Water
FIGURE 4. The filter elements are coated with resins to remove
ionic contaminants and suspended solids, including iron, copper
and silica. Once the resin is exhausted, the elements can be
cleaned and re-coated
fiber material, are coated on the outside
of the filter septa in a thin layer.
These finely ground resins remove
ionic contaminants while also effectively
removing most suspended
solids. Upon exhaustion (ion breakthrough)
or high pressure drop (solids
loading), the unit is backwashed,
sending the exhausted precoat and
contaminants out to drain. Subsequently,
a new precoat is applied and
the process is repeated.
Precoat filter demineralizers reactimove
iron,
copper,
silica,
vated
corrosion products and salts,
whether soluble or suspended. Systems
of this type have been in operation
since the early 1960s, but
have experienced advancements in
precoating techniques, as well as
improvements in a high-energy airscour
backwash for enhanced septa
cleaning, reducing waste volumes
by over 60% in certain applications.
Figure 4 illustrates the progressive
coating and cleaning process of the
filter elements.
Water conservation
Using precoat filter demineralization
provides a string of benefits, starting
with water conservation. By avoiding
blowdowns, plants can save millions
of gallons of water per year, as well
as the costs associated with treating
both blowdown water and makeup
water, including the related labor
costs. There are also growing regulatory
compliance implications, especially
in water-stressed areas. Some
plants are already facing increased
pressure to reduce water waste, and
every other plant should be preparing
now for this eventuality.
But even in the absence of regu38
lation,
there are stout economic
advantages to installing
this kind of condensate
polisher. A large cost benefit
is that precoat filter demineralization
helps protect
assets. Less contaminated
water will result in less
damage to system components,
extending the life
and performance of those
components and reducing
maintenance requirements.
Plants that do not install a
condensate polisher may
save money in the shortterm,
but pay more in the future for
equipment damage, boiler cleaning
and replacement fees. Though many
natural-gas combined-cycle (NGCC)
plants are still relatively new, corrosion
has already become nearly ubiquitous
in steam boilers and heat-recovery
boilers in those plants without highquality
condensate-polisher systems.
Furthermore, the air-cooled condenser
(ACC) design paradigm contributes
substantial corrosion-product
contamination to cycle water. Data
from the Electric Power Research Institute
(EPRI; Palo Alto, Calif.; www.
epri.com) indicate that four of the top
five causes of HRSG tube failure have
been tied to steam-cycle chemistry
related to flow-accelerated corrosion,
corrosion fatigue, under-deposit corrosion
and pitting.
Returning more high-quality condensate
back to the boiler system
can improve feedwater
quality,
increasing the number of boiler
cycles of concentration, faster
startup times and extending the time
between blowdowns.
For some plants, when it is time to
replace their 40- to 50-year-old boilers,
they are finding that manufacturers
have more stringent condensate-quality
requirements in order to
protect the equipment from contamination
damage. In these scenarios,
plant engineers are turning to condensate
polishers to help them maintain
the water quality specified by the
modern equipment.
Enhanced startup and efficiency
For various
maintenance and repair
reasons, a turbine occasionally
has to be taken offline. When
this happens, the condensate in the
system can become contaminated
very quickly due to the stagnation of
the water inside metal pipes, combined
with the introduction of air into
the system.
When the condensate is highly contaminated,
a blowdown is required
before the system can be restarted,
significantly delaying the achievement
of full generating capacity. During this
startup delay, it can cost the operator
between $25 and $35 per MWh
- a substantial outlay each time the
plant cycles. Further, chemistry fluctuations
make it impossible to determine
how long it will take for the
plant to reach full power each time
it starts, complicating budgeting for
auxiliary power purchase. Systems
that use a precoat filter demineralizer
can avoid this blowdown, resulting
in a process that can return the
turbine to service much more quickly
and less expensively. Additionally, the
elimination and control of harmful impurities,
both dissolved and insoluble,
can improve thermal efficiency (by up
to 1%) and can increase overall plant
efficiency (by approximately 1-3%).
Water scarcity will continue
While the cost of fresh water is among
the smaller pieces of the total cost of
makeup water, this is not likely to remain
so. The average price of water
increased by 60% in the 30 largest
U.S. cities between 2010 and 2019,
according to data compiled by Barclays,
while California water futures
have regularly jumped as much as
300% in recent years. The growing
water crisis is requiring all industries
to rethink their water use, especially
those in essential service sectors that
depend so heavily on water.
■
Edited by Mary Page Bailey
Author
John Yen is the director of strategic
marketing and innovation at
Marmon Industrial Water LLC (30
Technology Drive Suite 2F, Warren,
NJ 07059; Phone: 908-516-1400;
Email: info.graver@marmonwater.
com). With over 30 years of experience
in the water industry, Yen
drives innovation and revenue
growth for the industry through
capital equipment, aftermarket parts and service solutions.
He previously held roles at BASF and Siemens
Water (now Evoqua). He has a B.S.Ch.E. from Rutgers
University and an M.S. degree in management science
from the University of Massachusetts, Lowell.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2023
http://www.epri.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2023

Table of Contents for the Digital Edition of Chemical Engineering March 2023
