Cenospheres

The residue often seen floating atop the bodies of
water around Kingston consists of cenospheres,
which are hollow balls of sand-like material that
are created in a coal-fired boiler when molten silica
solidifies around a bubble of flue gas to form a
sphere. The gas bubbles cause the cenospheres to
be so lightweight that they float on water. They are
typically collected by skimming the surface of an ash
pond. Cenospheres by themselves are not harmful
to the environment, but they can mix with other
debris and materials. TVA will further test and study
the cenospheres to assess any materials that may be
bound to the inert spheres. The size of the particles
ranges from about 20 to 600 microns, which is about
the same range of sizes as is found in the diameter of
human hair.

TVA has used a variety of methods to remove the
cenospheres from the water. Skimmer booms have
been placed in the water to contain the particles
on the surface of the water. Vacuum trucks on

barges, backhoes, and hand tools have then
been used to remove the cenospheres from the
water surface. Trucks transport the recovered
cenospheres to holding cells adjacent to the
settling pond on the Kingston plant site.

These lightweight, rigid, waterproof materials are
useful in a variety of products, primarily as fillers.
TVA sells the censopheres harvested from ash
ponds at its Kingston, Bull Run, Johnsonville, and
Widows Creek plants for use in manufactured
products such as ceramic tile, cement, flooring,
epoxy fillers, bowling balls, golfing equipment,
flotation devices, and cosmetics.

Page Updated June 16, 2009 3:08 PM