Carpet Fiber II
August 2, 2009 ISSUE # 213
CARPET FIBER II
A Vincent screw press was installed last year in Dalton, Georgia to dewater recycled carpet fibers. A major carpet producer is using the press in a system which recycles old carpet collected by dealers. This worn carpet comes from households and businesses replacing their carpet flooring.
The recycling center receives whole bundles, still wrapped with duck tape, and methodically separates them into three streams: 99% pure nylon fibers, 99% pure polypropylene (PP) fibers, and trash. After shredding and removal of large and heavy junk, the nylon and PP fiber are separated and purified using over one hundred different hydroclones, centrifuges, and other spinning machines. The relatively large difference in specific gravity between nylon (~1.0) and PP (~0.9) is what makes this operation practical. It is important to note that no chemicals, other than water, are used by the recycling center.
Although it may be practical to recycle carpet into pelletized nylon and PP, government regulations, and perhaps high resin prices, are what make this operation economical. A reliable source at the recycling center expects all carpet ripped from floors in states west of the Mississippi to be recycled rather than discarded into landfills.
After a final, water-bath filtration step, the damp carpet fibers are sent to a Vincent KP-10 screw press. The fibers enter the press at 50% moisture, and, after a light squeeze, the fluffy cake is sent to a dryer at reliable, consistent moisture content. The recycling center is not entirely interested in the moisture content of the press cake, but rather that the fed to the dryer be at a consistent moisture content. Fluctuations in feed consistency can cause an industrial dryer to under-heat or overheat its contents, resulting product being discharged “wet” or burnt, respectively.
The recycling center is also using a screw press to dewater its waste stream. The waste stream contains plenty of fibers along with loads of dust and grit. Because of the abrasive nature of the material, the screw in the Vincent press was coated with a special titanium dioxide hardsurfacing. This suffered premature failure, so we reverted to the conventional weld-applied hardsurfacing.
A 0.010" slot wedgewire screen is used to maximize capture of the fine particles. When the discharge end of the screen wears down, the screen can be reversed for double-the-normal lifetime.
An earlier Pressing News, Number 8 of November 1993, covers this same subject.