Number range CHAPTERDiminishing Materials Use and Air Pollutants in
Foundries via an Integrated Advanced Oxidation Process

Fred S. Cannon, Robert C. Voigt, James Furness

This research has been evaluating a novel advanced oxidation (AO)
process that can be applied in foundries so as to diminishes air
pollutants while also reducing the amount of clay and coal that a
foundry needs to use. Results at a half dozen foundries have shown that
VOC's are diminished by 15-65%, while coal and clay use has been
diminished by 10-30%. Moreover, results at a full-scale test foundry
have shown that with the AO process, total emissions remained below 20
ppmv, in accordance with the new EPA emissions standard. In nanoscale
analysis, we have learned that AO-treated green sand contains more pores
in the 4-100 A range than does non-AO green sand, which can be
attributed to AO delaminating the clay and converting the coal to
activated carbon. Also, AO-treated greensand adsorbs more m-xylene than
non-AO-treated greensand. When AO is applied to greensand, the AO cleans
the clay surface, enabling it to sorb more water; and this makes the
mold stronger for a given amount of clay. Less clay also means less
coal. The combination of all the AO unit operations (hydrogen peroxide,
ozonation, sonication) generates twice as much OH\* (0.4-0.9 mg/L) as is
generated by just hydrogen peroxide.

This research has been evaluating a novel advanced oxidation (AO)
process that can be applied in foundries so as to diminishes air
pollutants while also reducing the amount of clay and coal that a
foundry needs to use. In this process, AO-enriched water is blended with
the sand, clay, and coal that comprise a green sand mold. When molten
metal is poured into this mold and the metal is cooled, the mold
releases less volatile organic compounds than it would if non-AO water
were used. The advanced oxidation process includes hydrogen peroxide
(100-500 ppm), ozone (to saturation), hydrosonication, acoustical
sonication, and (possibly) underwater plasma. The AO can be applied into
a slurry of bag house dust; and this dust represents recycled
particulate emissions that were captured before they could be released
to the atmosphere.

Results at a half dozen foundries have shown that VOC's are diminished
by 40-65% for non-cored green sands, and by 15-45% for green sands that
include heavy loadings of phenolic urethane core. Concurrently, these
foundries have shown that when employing AO, the foundry can achieve
proper casting quality while employing 10-30% less clay and coal
additions. The installation of AO systems have paid for themselves
within 2-6 months. Moreover, results at a full-scale test foundry have
shown that with the AO process and the materials savings it offers,
total FID emissions remained below 20 ppmv with AO for either cored or
non-cored operations. However, without AO nor these materials savings,
emissions exceeded 20 ppmv at this test foundry. The new EPA emissions
standard is 20 ppmv. An important component of this overall research and
development program has been for the Penn State team to coordinate and
document the parameters that this AO process has been achieving.

The Penn State team is also exploring at the nanoscale why this AO
process can diminish air emissions and materials use. Thus far, we have
learned that AO-treated green sand contains more pores in the 4-100 A
range than does non-AO green sand, and we have discerned that this can
be attributed to AO delaminating the clay while also creating activated
carbon-type pores within the coal. Also, AO-treated greensand adsorbs
more m-xylene than non-AO-treated greensand. When AO is applied to
greensand, the AO cleans the clay surface, enabling it to sorb more
water; and this means that less clay is needed to achieve a targeted
green compressive strength for a given amount of clay.

There is considerable full-scale evidence that when employing AO, less
clay also translates to less coal needed to achieve a desirable metal
finish. It is also well-known that during heating, clay contracts while
coal expands; and we are currently testing the hypothesis that with the
lesser amount of clay, there are physical spacing reasons why there is
likewise a concurrent need for less coal.

Yet further testing at Penn State is appraising the extent to which
various combinations of AO unit operations create advanced operations;
and this research has been driven by the hypothesis that greater OH\*
radical generation will translate to more favorable impact of AO on
green sand properties and emissions. Apparent OH\* generation (as
monitored by hydroxy terephthalic acid formation) is twice as high (up
to 0.4-0.9 mg/L) when hydrogen peroxide has been coupled with ozone,
sonication, and underwater plasma, than when hydrogen peroxide was used
alone. This represents a considerable savings to foundries, since the
ozone, sonication, and underwater plasma can be generated on-site.