&EPA

United States

Environmental Protection

Agency

EPA/540/F-95/503

March 1995

SUPERFUND INNOVATIVE

TECHNOLOGY EVALUATION

Emerging Technology Bulletin

Waste Vitrification Through Electric Melting

Ferro Corporation

Technology Description: The objective of vitrification technology is to convert contaminated soils, sludges, and sediments

into an oxide glass, rendering them suitable for landfilling as a

nonhazardous material. The technology uses joule heating to

melt the waste matrix, destroying organic compounds in the

process, and encapsulating the inorganic constituents in a leach

resistant form.

Figure 1 shows a schematic of the process. An oxide glass

mixture is mixed with the soil in ratios determined in part by the

contaminants to be vitrified. The glass mixture acts as a fixation

medium and facilitates the flow of current between the electrodes

until the soil reaches a temperature and viscosity sufficient to

conduct the current and produce melting. As the thermal gradient 

approaches organic materials, these materials vaporize. The cold

layer of feed at the top of the melter acts as a counterflow

scrubber condensing volatiles and keeping them in the melting

process. Combustion products escaping the melt are processed

in an off-gas collection system.

Waste Applicability: Vitrification stabilizes inorganic components found in hazardous waste. The high temperature involved

in glass production (about 1500o

C) decomposes anthracene,

bis(2-ethylhexyl phthalate) and pentachlorophenol in waste. The

decomposition products can easily be removed from the low

volume of melter off-gas. The technology can be applied to soil,

sludges, and sediments.

Test Results: Several glass compositions were developed for

vitrification of soils contaminated with organic and inorganic components. Ten replicates of the glass were processed from EPA

synthetic soil matrix (SSM) and glass making materials, and

subject to Toxicity Characteristic Leaching Procedure (TCLP)

testing. SSM and glass making additives were processed in a

laboratory-scale unit at temperatures of 1500-2000o

C. Materials

were processed at the rate of 17 Ib/hr. The laboratory melter was

operated in a variety of electrode configurations with an energy

usage of 3.3 to 3.5 kilowatt hours per kilogram of material

processed. The feed was composed of 67% soil and 33% glass

making additives. During these tests, measurements were taken

to monitor the process and assess the quality of the vitrified

product. The results of the TCLP Analyses for these replicates

are presented in Table 1.

The results of this study show that

vitrification technology was able to:

the Ferro Corporation waste

1)

2)

3)

utilize glass compositions tailored to the waste being treated

to vitrify hazardous soils and sludges,

produce a vitrified product that can pass TCLP requirements

for the release of seven toxic, inorganic components,

continuously produce the target glass composition from an

input of typical soils contaminated with organic and inorganic

species, plus glass making materials.

Figure 1. Electric furnace vitrification.

Printed on Recycled Paper
Table 1. TCLP Analyses Results For Further Information Contact:

TLCP Analyte Concentration, ppm Randy A. Parker

U.S. EPA Risk Reduction Engineering Laboratory

Metal

z

Cr

E

Ni

Zn

Remediation Limit

5

:

z

5

5

Mean of Glass Replicates

<0.100

<0.O1O

0.019

0.355

0.130

<0.010

0.293

26 West Martin Luther King Drive

Cincinnati, OH 45268

(513) 569-7271 (Fax: 569-7620)

United States

Environmental Protection Agency

Center for Environmental Research Information

Cincinnati, OH 45268

Official Business

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$300

BULK RATE

POSTAGE & FEES PAID

EPA

PERMIT No. G-35

EPA/540/F-95/503