See Product Details

OmegaBond™ Advanced Tubing Technologies - For Urea

OVERVIEW

OmegaBond™ products are robust, advanced tubing designs for use in corrosive chemical processes and other applications. OmegaBond™ technology can be applied to the extremely corrosive urea process. These products incorporate new enabling materials and materials joining technologies and are identified under a new brand known as OmegaBond™ advanced tubing technology. The new tubing designs enable the application of multiple and/or dissimilar metals in a single tube.

The advantages of this new material technology are a solution to corrosion and erosion issues observed in urea stripper equipment. Advantages of OmegaBond™ technology include:

• Superior corrosion resistance of the zirconium inner-liner (zero corrosion rate)
• Directly weldable into a titanium clad tubesheet without affecting the tube liner bond strength
• No passivation air requirements
• Useful in existing titanium-tubed units
• Eliminates urea solution seepage between the liner and tube because of the extrusion (metallurgically) bonded zirconium inner-liner

ZIRCONIUM VERSUS OTHER MATERIALS FOR UREA APPLICATIONS

Zirconium has been used in urea applications for more than 30 years. Its alloys are well known as one of the most resistant materials for use in these environments. Urea is currently produced commercially in large quantities from the starting components of carbon dioxide and ammonia. These processes operate at extremely high pressures of 150 bar and high temperatures approaching 230°C. In these conditions, the carbon dioxide and ammonia are combined to form ammonium carbamate, which is extremely corrosive to most materials. Typical materials used in these conditions include duplex stainless steels, titanium and zirconium.

Many of the stainless steels experience significant corrosion where ammonium carbamate is present. Even where the duplex stainless steels, such as 25Cr-22Ni-2Mo, have a "manageable" corrosion rate, they still must continue to be passivated (coated) in operation. This is accomplished using air or oxygen sparged into the unit to ensure formation of an oxide layer, which imparts the corrosion resistance. Air or oxygen in these high pressure, high temperature units can present explosive hazards.

Although the improvement of certain stainless steels has allowed the reduction of passivation air, the total elimination of passivation air has not been achieved. Titanium, which is another typical material in urea strippers, does not require additional passivation air, but will experience erosion/corrosion in these severe conditions. Zirconium, however, has excellent resistance with no corrosion rate in this environment.

There are currently hundreds of very large urea strippers in fertilizer production facilities throughout the world. Many of these units utilize either duplex stainless steel or titanium tubing, both of which are experiencing corrosion problems and must be replaced in the near future.

OmegaBond™ advanced tubing technology is currently available in three designs. One design consists of lining a titanium tube with a thin liner of zirconium by creating a metallurgical bond between the titanium and the zirconium. The titanium tube of this extrusion bonded tube can then be welded directly to a titanium tubesheet. (Refer to Figure 1.)

A second design concept of the OmegaBond™ technology consists of using a solid zirconium tube with an extrusion-bonded tube inertia welded onto either end. This allows a titanium outer surface to be welded directly to a titanium tubesheet without producing detrimental zirconiumtitanium welds at the tube to tubesheet strength weld.

A third design concept of the OmegaBond™ technology consists of using a solid zirconium tube with solid titanium ends thereby allowing the titanium tube to be directly welded to the titanium tubesheet.

OMEGABOND™ EXTRUSION BONDED TECHNOLOGY

The extrusion bonded technology utilizes multiple steps of metallurgical processing, which begins by meticulous cleaning of components and assembling titanium billets and zirconium tubes, and subsequent hot extrusion and cold pilgering to produce a metallurgically bonded zirconium-lined titanium tube. This tube can be flattened, formed and welded without damage to the bond layer.

OMEGABOND™ INERTIA WELDED TECHNOLOGY

OmegaBond™ manufacturing consists of using solid or extrusion-bonded tube and employing solid-state joining techniques, such as inertia welding, to join titanium ends to a full length zirconium tube. This produces strong weld joints without using a detrimental weld. Fusion welding of dissimilar metals, for example zirconium to titanium fusion welding, often leads to a tube or other product with poor mechanical and corrosion properties.