Applications of Zircadyne® Zirconium

One of the major applications for Zircadyne® metal is as a structural material in the chemical processing industry. Zircadyne® metal exhibits excellent resistance to corrosive attack in most organic and inorganic acids, salt solutions, strong alkalis, and some molten salts (see Zircadyne® Corrosion Properties Brochure). 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® heat exchangers for use in the production of rayon by a large chemical producer. This experience has led to the expanded use of Zircadyne® exchangers by a broad spectrum of the chemical process industry. More and more chemical companies are realizing the cost effectiveness of Zircadyne® 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® is replacing many graphite heat exchangers.

The comparison of Zircadyne® metal 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® metal 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® equipment can be cleaned by a broad range of cleansing solutions varying from weak to strong acids or alkalis.

Columns
Zircadyne® metal 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 Zirconiumis used for the most severe applications, such as sulfuric acid at concentrations above 55 wt.% With its higher strength, Zircadyne® 705 Zirconiumcan allow significant cost savings over 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® columns, constructed by Nooter Corporation, stands 123 feet tall and is approximately 11 feet in diameter.

Chemical Processing Applications

Reactor Vessels
In the fabrication of reactor vessels and stands for corrosive media at high concentrations and temperatures, Zircadyne® metal 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® metal 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® metal solve the most difficult corrosion problems in reactor vessels and tanks. Zircadyne® 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® metal 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® 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® product in ancillary components of their process. To supply these necessary components, Wah Chang has developed qualified sources to supply all Zircadyne® products which are not produced in our shops.

Wah Chang produces seamless Zircadyne® 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® metal is easily rolled and welded into large diameter pipe.

Zircadyne® tubing is commonly stocked in 1/2" through 1-1/2" diameters in all popular wall thicknesses. Pipe fittings can be supplied in ells, tees, reducers, and stub ends.

Long, reliable Zircadyne® 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 Wah Chang supplies the basic Zircadyne® metal.

Packings
Zircadyne® metal is lighter than stainless alloys. With nil corrosion allowance, very thin materials of Zircadyne® metal 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® alloys are: Zircaloy-2, Zircaloy-4, Zr-2.5Nb which have excellent corrosion resistance to high temperature steam and water, and good mechanical strength.