|
Modern batteries are often promoted on their environmental
qualities. Lithium-based batteries fall into this category. While
nickel-cadmium presents an environmental problem on careless
disposal, this chemistry continues to hold an important position
among rechargeable batteries. Power tools are almost exclusively
powered by nickel-cadmium. Lead-acid batteries continue to service
designated market niches and these batteries also need to be
disposed of in a proper manner. lithium-ion would simply be too
fragile to replace many of these older, but environmentally
unfriendly, battery chemistries. The Lead-acid battery has led the way in recycling. The automotive
industry should be given credit in organizing ways to dispose of
spent car batteries. In the USA, 98% of all Lead acid batteries are
recycled. In comparison, only one in six households in North America
recycles batteries.

FLOWCHART: Lead ACID BATTERY RECYCLING PROCESS
Although nickel-metal-hydride is considered environmentally
friendly, this chemistry is also being recycled. The main derivative
is nickel, which is considered semi-toxic. Nickel-metal-hydride also
contains electrolyte that, in large amounts, is hazardous.
Most lithium batteries are non-rechargeable and are used in cameras,
hearing aids and defense applications. For proper disposal, the
batteries must first be fully discharged to consume the metallic
lithium content.
Battery recycling Plant require that the batteries be sorted
according to chemistries. Some sorting must be done prior to the
battery arriving at the recycling Plant. Nickel-cadmium,
nickel-metal-hydride, lithium-ion and Lead acid are placed in
designated boxes at the collection point. Battery recyclers claim
that if a steady stream of batteries, sorted by chemistry, were
available at no charge, recycling would be profitable. But
preparation and transportation add to the cost.
The recycling process starts by removing the combustible material,
such as plastics and insulation, with a gas fired thermal oxidizer.
Gases from the thermal oxidizer are sent to the plant's scrubber
where they are neutralized to remove pollutants. The process leaves
the clean, naked cells, which contain valuable metal content.
The cells are then chopped into small pieces, which are heated until
the metal liquefies. Non-metallic substances are burned off; leaving
a black slag on top that is removed with a slag arm. The different
alloys settle according to their weights and are skimmed off like
cream from raw milk.
Cadmium is relatively light and vaporizes at high temperatures. In a
process that appears like a pan boiling over, a fan blows the
cadmium vapor into a large tube, which is cooled with water mist.
This causes the vapors to condense and produces cadmium that is
99.95 percent pure.
Current battery recycling methods requires a high amount of energy.
It takes six to ten times the amount of energy to reclaim metals
from recycled batteries than it would through other means. |