Chemical Engineering June 2010 - 18

A look At r22 rePlAcements
he U.S., among other countries, has passed laws that mandate
commercial facilities to phase out usage of the refrigerant
R22 by 2015. Used extensively throughout the world in HVAC
systems, process chillers and industrial refrigerant plants, R22 contains
hydrochlorofluorocarbons, which are reputed to damage the
ozone layer and contribute to global warming.
The ban prohibits R22 refrigerant usage in various areas of production,
in household equipment and in certain kinds of vehicles.
New refrigeration and air conditioning equipment being manufactured
can no longer contain the chemical. Bans on new R22 refrigerant
in the maintenance and servicing of existing refrigeration
and air conditioning systems takes place this year, while the use of
recycled R22 for the same purposes will be prohibited by 2015.
As the refrigerant is phased out, alternative substances have been
made available. However, R22 replacement " is not a trivial process, "
says Gus Rolotti, director of technical sales and services with
Arkema Inc. (Philadelphia, Pa.). R22 retrofits necessitate modifying
existing heating and cooling/refrigeration systems to accommodate
the replacement, and doing so with minimal process interruption.
He adds that because an existing refrigeration system is already
designed for use specifically with R22, it is likely that users will lose
some capacity when replacing the refrigerant. " Something has to
give, " he says. " If a system is already at the limits of its capacity,
maybe retrofitting with a new refrigerant is not the right option. "
However, if retrofitting appears to be a feasible solution, there
are many alternatives to choose from. Arkema offers several in its
Forane line of refrigerants. The company says Forane 427A is an
effective replacement for R22 in a variety of temperature-critical
refrigeration and air conditioning applications. As a matter of fact,
recently completed R22 retrofit installations using 427A have demonstrated
overall system performance comparable to R22, says the
company. In addition, no adjustments or change-outs to the expansion
valves or other major components were required during any
of the retrofit operations.
One of the retrofits was undertaken in a high-temperature refrigeration
baby-food preparation room at La Mere Poule (SaintLeonard,
Quebec, Canada). Previously, the room was cooled by
an R22 refrigeration system, using a semi-hermetic, reciprocating
compressor with a rooftop-mounted condenser and a ceilingmounted
evaporator assembly. A change of the compressor oil
to POE (polyolester oil), replacement of the system filters, and
deep evacuation were performed. No changes in settings were
required for the expansion valves, pressure controls or other system
components.
T
tower water usage is through reducing
water plume, the cloud of water
vapor produced by a cooling tower
when warm, moist air is cooled by
the ambient air. The SPX ClearSky
Plume-Abatement System (Figure 2)
is another approach to hybrid cooling
towers that focuses on reducing cooling
plumes. The bonus here is that it
can be installed into existing cooling
tower applications, negating the need
for complete system replacement.
According to Lindahl, instead of having
an air-cooled heat exchanger on
top of the wet tower and sharing the
same fan, this system has an air-to-air
heat exchanger above the wet section.
It takes warm air from the wet section
and pulls outside air across the other
side of the heat exchanger and warms
it up before it goes into the tower,
According to La Mere Poule, overall system performance was
nearly indistinguishable from the system's prior performance with
R22. Operating pressures with Forane 427A were close to those
measured for R22 and compressor discharge temperatures and
amperage draw were both lower.
Jon Edmonds, president of Edmonds Engineering Co.,(Birmingham,
Ala.) suggests that natural refrigerants may once again be gaining
popularity as replacements for R22 in the chemical processing and
industries. " Ammonia, carbon dioxide and, to a lesser degree, propane
have renewed interest in industry for use as refrigerants. "
Sometimes referred to as R717, ammonia or NH3, anhydrous
ammonia is commonly found in industrial refrigeration. Ammonia
has the advantage of high latent heat and excellent heat transfer
properties and is readily available at an economical cost when
compared to other commercial refrigerants. From an environmental
standpoint, ammonia has no ozone depletion or global warming
potential and is biodegradable.
Carbon dioxide, also known as CO2 or R744, is undergoing resurgence
for use in low-temperature applications. While its use as
a refrigerant does not contribute to greenhouse gas problems, it is
considered a high-pressure refrigerant. A CO2 refrigeration system
that experiences an emergency shutdown or power outage may
require measures to contain the refrigerant.
Propane is commonly found in large chemical and refining facilities.
As a highly flammable gas, however, its use is restricted to
facilities where requirements of specific area classifications, such as
explosion-proof electrical devices, are reguired.
Edmonds says that while natural refrigerants are making a comeback,
in chemical applications where safety is a hot button issue, a
piggyback system might be in order. This type of set up consists of
ammonia as the primary refrigerant, located in the safe environment
of a protected room where it would condense and cool the
CO2, which would then circulate to remote users.
" This is done to prevent the ammonia from circulating out. If CO2
gets loose, it is still an issue, but not as large and dangerous of an
issue as an ammonia leak, " explains Edmonds.
Rolotti reminds readers that if faced with phasing out R22 or selecting
a refrigerant for a new system, the choice should be based
on the actual requirements of the cooling process, such as what
temperature range is needed, the equipment available for the specific
application and the capacity of the system, including the difference
between winter and summer conditions. Additional criteria
may include safety considerations, familiarity of the chosen refrigerant
and ease of integration into existing infrastructure.
❏
Air Liquide
Process cooling service Providers
Frigel
www.airliquide.com
www.arkema-inc.com
Air Products www.airproducts.com
Arkema
Baltimore Aircoil
www.baltimoreaircoil.com
Edmonds Engineering
www.edmondsengineering.com
which reduces the amount of relative
humidity in the air leaving the tower
so it doesn't make a visible plume.
" This system is also helpful for
chemical processors faced with zero
site discharge requirements, " explains
Lindahl. " Because you're cooling air
that leaves the wet section using outside
air, there's a lot of water that's
condensed in that heat exchanger.
That water can be allowed to fall back
into the tower to reduce the amount of
18 ChemiCal engineering www.Che.Com June 2010
www.frigel.com/NA
Niagara Blower www.niagarablower.com
SPX Cooling Technologies
www.spxcooling.com
SPX Thermal Equipment and Services
www.spx.com
Thermal Care www.thermalcare.com
makeup water that's required to operate
the tower. "
In addition, he says, that clean
water steam can be extracted and
used to dilute wastewater streams or
to improve the quality of plant water.
" This is beneficial to people trying to
stretch the water budget in the plant, "
notes Lindahl.
And for applications such as fluid
loop cooling, direct vapor condensing,
hydrocarbon desuperheating and sub
http://www.airliquide.com http://www.frigel.com/NA http://www.airproducts.com http://www.niagarablower.com http://www.arkema-inc.com http://www.spxcooling.com http://www.baltimoreaircoil.com http://www.spx.com http://www.edmondsengineering.com http://www.thermalcare.com http://www.Che.Com
Chemical Engineering June 2010

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