Part 1 can be read by clicking here.
Furnace
Environment
The furnace environment can have a
detrimental effect on refractories. If the furnace is processing metals other
than steel or aluminum (e.g., certain compositions of brass, bronze or alloy
steel), the refractory may retain lead, chrome or nickel – metals that are
subject to stricter environmental regulations. In glass-melting furnaces and
other vessels where sodium is a constituent, accumulation of sodium oxide can
cause the refractory’s melting temperature to decline, thereby reducing its
value as a recycling feedstock. Spent refractory ceramic fiber (RCF) materials
can be a good source of relatively pure aluminosilicates, but these materials
can represent a handling hazard due to the presence of crystalline silica,
which could pose an inhalation risk.
Uses
for Recycled Refractories
The most common re-use for spent refractory
is “grog” or “aggregate” in new brick or tile. A certain percentage of ground,
pre-fired material is frequently added to such products to reduce shrinkage and
improve quality. Other construction uses for recycled refractories include: roofing
granules, landscape material, soil stabilization, slag conditioner and fuel
source (in the case of carbonaceous refractories).
In some instances,
chrome-magnesite brick can be recycled as a feed source of chromium for the
production of ferroalloys. Refractories used in high-temperature processing of
precious metals (e.g., silver, gold, platinum) are quite often recycled to
recover high-value materials that have penetrated into the lining.
Testing
Before Shipping
If hazardous constituents (including
radioactivity) in the spent refractory are possible, the furnace user should
have samples tested before engaging in discussions with recyclers or landfills.
Having a shipment rejected by the recipient can add significant unanticipated
cost to what could otherwise be a smooth transaction.
From the opposite
perspective, a furnace user shouldn’t assume that his spent refractory has only
one available fate – disposal at a hazardous-waste landfill. Armed with
favorable test results, the user may find that recycling is a much lower-cost
option than disposal as a hazardous waste. In fact, materials rich in Al2O3
can even bring a substantial return at current market prices.
According to Dr.
Manuel Dekermenjian, principal consultant at Environ and co-lecturer at USC
with this columnist, “Recycling and re-use options for industrial materials,
including spent refractory, are often overlooked despite their financial,
regulatory and environmental payback potential. Knowledge of the material’s
chemical composition is the most powerful tool in deciding the most favorable
fate for spent refractory.”
