May 19, 1997

An unusual application for a dewatering screw press is found in factories that produce fiberglass wool.  This insulating material is produced in continuous wide (20' or more) blankets.  The factory building we visited was long, over a quarter of a mile.  The wool is formed in a large chamber at one end, and it is either rolled or sheared into panels at the other end.  In between the two ends of the factory the material is coated with a binder resin that is baked on, and the material is then cooled to where it can be handled.

Once running, the equipment is only rarely shut down.  As the material comes from the chamber where the fibers are formed, it is white in color.  It turns to the familiar tan color only after the resin is baked.

Considerable volumes of waste material are created.  Because of impurities, recycling is the exception.  Generally the dry waste is compacted in large industrial compactors. (Marathon is a supplier of these.)  The compacted material is landfilled.

The application for the Vincent press is to dewater waste at the beginning of the process.  The fine strands of fiberglass (angel hair) are formed by injecting molten glass through dies with tiny holes.  The extruded glass goes into a large chamber, surrounded by a hood, where it solidifies.  The hood walls are cooled with a water film, and the glass that hits the walls solidifies and is washed to a collection pit.

The water, fiberglass, and some glass particles the size of marbles accumulate in the pit.  This is pumped to shaker screens to remove a large part of the water.  The tailings from the shaker screens, amounting to only 200 pounds per hour each, were found to contain 90% moisture.  The high water content of the tailings presents a problem in that water drips from them as they are carried through the plant.  Also, they drip water when placed in the compactors along with the dry waste.

By running the tailings from the shaker screens through a screw press, we were able to remove one half to three quarters by weight as water.  This solved the dripping problem. A new problem created was that the water coming from the press contained a significant amount of ground glass.  This was created in the pressing action.  We feared that it would be abrasive; however, only the tan (baked) material is abrasive.

In our first testing, at Knauf Fiber Glass GMBH in Alabama, we were up against a Hycor Helixpress.  Both it and our CP-4 press had problems with the tailings bridging at the inlets to the presses.  This was solved by the addition of sluicing water (available from the shaker screens).

The 8" Hycor machine costs about $20,000 versus $12,000 for our CP-4 press.  In the end the Hycor unit was selected because it was better at passing chunks of glass and other
waste.  It was only later that we were able to resolve this problem in our press with the invention of the Sterile screw (see Pressing News #37).

Subsequently we learned of another identical application at Evanite in Oregon.  They were debating between buying an additional Oberlin machine for about $30,000, or a Hycor.  Their existing Oberlin, which they described as a semi-continuous belt press, produced press liquor with only 3 ppm solids and 45% press cake moisture.  In contrast, the Hycor they tested gave them 600 to 700 ppm in the pressate.  They could not accept the higher solids content in the wastewater, so they stuck with Oberlin.  Their objection to the Oberlin was primarily mechanical deficiencies which they were assured had been corrected.

We declined to test at Evanite because we knew our solids in the press liquor would be excessive.

The advent of the new KP presses gives us an excellent machine for the fiberglass application.  Bridging problems will be minimal because the press will grab anything that
will fall through the 8" pipe inlet.  Plus, the Sterile screw will not jam with large pieces of trash.  Cost is still an advantage as the KP-6 sells for the same as the CP-4.

The only remaining problem is ground glass in the press liquor.  This will have to be removed separately, probably by decanting in a pit.  After all, it is a screw press, not a filter press.

Issue 61