CPI Zirconium
Zircadyne® Zirconium Applications
One of the major applications for Zircadyne® zirconium is as a
structural material in the chemical processing industry.
Zircadyne® zirconium exhibits excellent resistance to corrosive
attack in most organic and inorganic acids, salt
solutions, strong alkalis, and some molten salts.
In certain
applications, the unique corrosion resistance of Zircadyne®
zirconium can extend its useful life beyond that of the remainder of
the plant. Consequently, maintenance costs are reduced,
and downtime is minimized. Furthermore, an increasingly
important advantage is that Zircadyne® zirconium appears to be
non-toxic and bio-compatible. Some of the more important
areas in the chemical industry where Zircadyne® zirconium is being
used include reboilers, evaporators, tanks, packings,
trays, reactor vessels, pumps, valves and piping.
Heat Exchangers
The outstanding performance of three heat exchangers used
in the production of hydrogen peroxide precipitated the
purchase of several more Zircadyne® zirconium heat exchangers for
use in the production of rayon by a large chemical
producer. This experience has led to the expanded use of
Zircadyne® zirconium exchangers by a broad spectrum of the chemical
process industry. More and more chemical companies are
realizing the cost effectiveness of Zircadyne® zirconium heat
exchangers over other materials because of longer
equipment life, reduced maintenance and downtime,
elimination of corrosion product contaminants, and greater
process efficiency. Because of its greater heat transfer
characteristics an durability, Zircadyne® zirconium is replacing
many graphite heat exchangers.
The comparison of Zircadyne® zirconium with other materials of
construction is not a simple, or direct task. Main factors
must be considered and evaluated. Since corrosion
allowance is not often necessary, the utilization of
thinner material can be realized. In those areas where
Zircadyne® zirconium exhibits exceptional corrosion resistance,
scaling or scale formation is virtually non-existent. As a
consequence, fouling allowance factors may be markedly
reduced or eliminated. Heat exchangers can then be
designed and operated on the basis of the calculated
overall heat transfer coefficient rather that a design
coefficient. The higher design coefficients are the result
of non-corroding, nonfouling, high film coefficient
surfaces. Periodic cleaning is not required on a frequent
basis so that the effective on-stream time is dramatically
increased. Bright, hard surfaces, and intrinsic property
of Zircadyne® zirconium, enables the use of higher than normal
flowrates. Laminar and turbulent conditions affect the
pressure drop and thickness of the stagnant film resulting
in film coefficients for fluids in the turbulent range
substantially higher than those in the laminar region.
Maximum turbulence in correlation with maximum allowable
pressure drop is optimum. Zircadyne® zirconium allows an approach
to this economy.
Since Zircadyne® zirconium owes its unique corrosion resistance
to a tenaciously adherent, inert oxide film, it can be
used to great advantage in condensers. Process media do
not wet the surface of Zircadyne® zicronium. This phenomenon
promotes dropwise condensation. Dropwise heat transfer
coefficients can be four to eight times greater than those
for filmwise condensations. When cleaning becomes
necessary, Zircadyne® zirconium equipment can be cleaned by a broad
range of cleansing solutions varying from weak to strong
acids or alkalis.
Columns
Zircadyne® zirconium is frequently used as a structural material in
the construction of stripper or drying columns. The choice
of Zircadyne® zirconium grades depends on the corrosive media
involved. Zircadyne® 702 zirconium is used for the most severe
applications, such as sulfuric acid at concentrations
above 55 wt.% With its higher strength, Zircadyne® 705
zirconium can allow significant cost savings over Zr 702 when the
corrosivity of the media permits its use. Zircadyne® 702
and 705 zirconium are both qualified for use in the construction of
pressure vessels in accordance with the ASME Boiler and
Pressure Vessel Code. One of the worlds largest Zircadyne® zirconium
columns, constructed by Nooter Corporation, stands 123ft
(37m) tall and is approximately 11ft (3m) in diameter.
Chemical Processing Applications
Reactor Vessels
In the fabrication of reactor vessels and stands for
corrosive media at high concentrations and temperatures,
Zircadyne® zirconium offers a significant economic advantage over
many other materials. Its thermal conductivity, corrosion
resistance, formability, strength, and minimum creep
characteristics under high operational temperatures make
Zircadyne® zirconium the logical choice to replace many other
materials. Zircadyne® zirconium has the ability to withstand alternating
acidic and basic environments is especially important.
Glass and graphite can withstand high temperatures, but
not high pressures. Thermal shock may result in mechanical
breakage which shortens their production life. many other
materials are incapable of handling high temperature
because of the difficulty in achieving high quality
joints.
Steel shells lined with Zircadyne® zirconium solve the most
difficult corrosion problems in reactor vessels and tanks.
Zircadyne® zirconium plates can be welded to form vessels of any
size. When used as a liner in steel vessels, the strength
is enhanced. This can be accomplished either as a loose
lining, as a resistance welded lining, or as an
explosively bonded lining. Large assemblies can be made
with minimal weld joints.
Zircadyne® zirconium resistance to organic acids led to its
acceptance as a construction material for reactors, tanks,
and piping in ethylbenzene reactors. Gas scrubbers and
pickling tanks, resin plants, chlorination systems, batch
reactors, coal degasification reactors and prilling tanks
are but a few of the applications in which Zircadyne® zirconium
will function with superior efficiency compared to many
other common metals.
Piping, Pumps and Valves
Zircadyne® zirconium product has gained recognition as a cost effective
material in piping systems to handle hot, corrosive acids,
and other liquids. Any leading chemical companies have
realized substantial cost savings through the use of
Zircadyne® zirconium product in ancillary components of their process. To
supply these necessary components, ATI Wah Chang has developed
qualified sources to supply all Zircadyne® zirconium products which
are not produced in our shops.
ATI Wah Chang produces seamless Zircadyne® zirconium pipe in
Schedules 5, 10, and 40 in all nominal pipe sizes of
1/2" through 6" diameter. Many sizes are also
available in less expensive welded pipe. Zircadyne® zirconium is
easily rolled and welded into large diameter pipe.
Zircadyne® zirconium tubing is commonly stocked in 1/2" (12.7 mm)
through 1-1/2" (38.1 mm) diameters in all popular wall
thicknesses. Pipe fittings can be supplied in ells, tees,
reducers, and stub ends.
Long, reliable Zircadyne® zirconium piping lines can be
constructed with fewer flanges than non-metallic lines.
This is very effective in addressing concerns for fugitive
emissions. Pumps and valve castings are available from
foundries to which ATI Wah Chang supplies the basic Zircadyne®
zirconium.
Packings
Zircadyne® zirconium is lighter than stainless alloys. With nil
corrosion allowance, very thin materials of Zircadyne®
zirconium can be used to make light, durable random and structural
packings, which dramatically improve process efficiency.
Nuclear Reactor Applications
A major use of Zircadyne® zirconium (on a tonnage basis) is for
structural material in nuclear reactor cores. Because of
its low thermal neutron absorption cross-section and good
strength, Zircadyne® zirconium is ideal in this application. The
thermal neutron absorption crossscetion is the ability of
a material to absorb thermal neutrons. The lower the
thermal neutron absorption, the greater the efficiency of
a nuclear reactor. In this application, reactor grade (low
hafnium) material must be used. The major nuclear grade
Zircadyne® zirconium alloys are: Zircaloy-2, Zircaloy-4, Zr-2.5Nb
which have excellent corrosion resistance to high
temperature steam and water, and good mechanical strength.
|
