Helium recovery systems reduce cost of fiber production
By ROBERT PEASE
With a sluggish demand for new optical fiber these days, fiber manufacturers are seeking ways to reduce expenditures and control critical assets. They must develop a hedge against future increases in the costs associated with manufacturing fiber as they await an economic recovery that could take several more years.
Helium recovery and recycling provides manufacturers with a significant new tool for reducing operating costs-an important consideration during a period of rising helium prices and uncertain supply. Fiber-optic-cable manufacturing accounts for about 15% of the helium on today's market, and demand is growing. Yet, there are only 12 helium sources in the world, with some nearing exhaustion.
According to the fiber-optic solutions group of BOC, a worldwide industrial gas services company headquartered in the United Kingdom, the supply of helium, which is actually extracted as a byproduct from natural gas, is nearly sold out-with significant new supply sources not expected until at least 2004. The result is a steep increase in helium prices and additional operating costs for optical-fiber manufacturers-and it is spawning new technologies for the recovery and reuse of helium.
Helium in the process
To produce optical fibers, a silica preform is lowered into a furnace situated at the top of a draw tower. As the silica softens and melts, a thin strand of fiber is drawn from the preform. Within the process, the fiber strand is rapidly cooled in a flow of helium before being coated with a resin for additional strength.
"Helium is injected into the annular space between the fiber and the cooling tube at a flow rate necessary to achieve the required fiber temperature," says Art Shirley, director of commercialization and technology for BOC's fiber-optic solutions group. "As the fiber draw speed is increased, proportionally more helium is introduced into the cooling tube to achieve the required temperature."
Several companies, including BOC, Air Products & Chemicals (Allentown, PA), and Praxair (Danbury, CT), offer their own versions of helium recovery systems boasting recovery at a rate of 70-90% at purities in excess of 99%. This savings is huge for fiber producers, particularly in the Asia/Pacific market, since 85% of the world's supply of helium comes from U.S. sources. The supply line to Asia/Pacific markets is extended and expensive.
More than one purpose
Although fiber manufacturing processes vary widely, a typical process uses large amounts of helium. While most commonly used for cooling in the draw process, helium also may be used as a carrier gas in the preform deposition and a sweep gas in preform consolidation. Each process introduces different impurities, contaminant levels, or heat levels into the helium.
Fiber manufacturers can no longer afford to use the "once through" helium flows in their processes. Turnkey systems are being evaluated, including compact systems that include all the hardware as well as the software for controlling and monitoring the recovery of helium. Fiber makers can lease many systems.
"Helium recovery and recycling from industrial processes just makes economic and strategic sense," says Shirley. "It provides fiber manufacturers with onsite control over their source of helium supply and helps them reduce operating costs."
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