&EPA
United States
Environmental Protection
Agency
EPA/54QYSR-92/002
Sept. 1992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
The Carver-Greenfield Process
Dehydro-Tech Corporation
A demonstration of the Carver-Green-
field Process8 for extracting solvents
and separating components of wastes
has been evaluated under the Super-
fund Innovative Technology Evaluation
(SITE) program.
Tests were conducted in August 1991
at EPA's research facility in Edison,
NJ, with the use of 650 Ib of drilling-
mud waste from the PAB Oil site in
Abbeville, LA. The waste feed contained
indigenous oil (oil-soluble organic con-
taminants), drilling solids, and water.
The process effectively separated the
waste feed into its constituent solid,
aqueous and organic fractions. This
summary includes a brief description
of the technology, an overview of the
demonstration, analytical results, and
conclusions.
This summary was developed by
EPA's Risk Reduction Engineering
Laboratory in Cincinnati, OH, to an-
nounce the key findings of the Carver-
Greenfield Process SITE demonstration
that is fully documented in two sepa-
rate reports (see ordering information
at back).
Introduction
In response to the Superfund Amend-
ments and Reauthorization Act of 1986
(SARA), the U.S. Environmental Protection
Agency (EPA) established a formal pro-
gram to accelerate the development,
demonstration, and use of new or innova-
tive technologies that offer permanent,
long-term cleanup solutions at Superfund
sites. This SITE program is administered
by the Office of Research and Develop-
ment (ORD) and the Office of Solid Waste
and Emergency Response (OSWER).
The major objectives of the SITE pro-
gram are to develop reliable performance
and cost information. One of the selected
technobgies was the Carver-Greenfield (C-
G) Process, developed by Dehydro-Tech
Corporation (DTC).
During the demonstration, waste feed
from the PAB Oil site was processed using
Isopar-L, a food-grade hydrocarbon with a
boiling point of about 400°F, as the sol-
vent. Approximately 10 Ib of solvent per
pound of waste solids were used for each
of three extractions during the two runs in
the demonstration. The final solids product
was determined to be nonhazardous,
based on extraction by the toxicity char-
Printed on Recycled Paper
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acterfstlc teaching procedure (TCLP) and
chemical analysis of the extract.
Process Description
The C-G Process, shown In Figure 1,
separates wastes into three product
streams: clean dry solids; a water product
substantially free of solids and organics;
and indigenous oil (a concentrated mix-
ture of extracted organics). The process
incorporates several unit operations. In
the first, the prepared feedstock is slurried
with a hydrocarbon-based solvent (often
called "carrier oil") to fluidize the waste
and to extract soluble organic materials
from the solids into the solvent phase.
These are typically synthetic organics, pe-
troleum-based hydrocarbons, or other or-
ganic materials that may contaminate the
solid matrix often called the "indigenous"
oil. The slurry Is also dewatered in an
evaporation step, yielding a water frac-
tion. The solids are separated from the
slurry by centrifugatlon (or other means in
some applications). Multiple solvent ex-
tractions may be performed before final
centrifugation. Residual solvent is then re-
moved from the centrifuged solids by a
combined hydrocarbon evaporation and
stripping operation, to yield a dry, clean
solids product. In the final step, the spent
solvent undergoes fractional distillation to
separate the extracted lighter and heavier
organic components from the solvent. The
recovered solvent is recycled to the f luidi-
zatlon operation, and the extracted "indig-
enous" organic fractions are disposed of.
Several factors affect the C-G Process's
performance in treating waste. Important
among them are the size distribution of
the feed solids, oil-soluble content, water
content, operating parameters, and sol-
vent selection. These criteria, as applied
to the SITE demonstration of the C-G
Process, are discussed below:
Solids Size Distribution: The maxi-
mum size of the solids fed to the process
is restricted to I/4 in. To meet this require-
ment, the PAB Oil site waste was passed
through a l/4-in. screen during excavation
and again before fluidization in the mobile
pilot plant.
Oil-Soluble Content: The C-G Process
can treat soils, wastes, and sludges with
oil-soluble contents from parts per million
(ppm) levels to levels of 75% and higher.
Feeds with higher oil contents may ben-
efit from pretreatment to remove free oils
if they are present. The PAB Oil site waste
contained 7% to 18% oil and did not re-
quire pretreatment.
Water Content: Waste streams with up
to 99% water can be successfully treated
with the C-G Process. Pretreatment (such
as gravity separation) to remove free wa-
ter in high-water-content wastes may be
beneficial to reduce the energy costs of
the process. The PAB Oil site waste con-
tained 20% to 35% water arid did not
require pretreatment.
Operating Parameters: Operating pa-
rameters (e.g., temperatures, pressures,
number of extractions, etc.) for the C-G
Process are set according to the waste
characteristics and product quality require-
ments. For the demonstration, these pa-
rameters were determined from bench-
scale treatability evaluations and process
modifications during the demonstration
using the PAB Oil site waste.
Solvent Selection: The choice of sol-
vent is generally governed by the impuri-
ties in the waste and the processing ob-
jectives. Isopar-L, a food grade oil having
a boiling point around 400°F and consist-
ing predominantly of C^ to C13 iso-paraf-
finic hydrocarbons, was DTC's choice for
the demonstration.
The primary objectives of the C-G Pro-
cess SITE demonstration included the fol-
lowing:
Assess the ability of the process to
effectively separate petroleum-based
hydrocarbon-contaminated soils into
their constituent solids, oil, and water
fractions.
Evaluate the system's reliability in
treating petroleum-based hydrocar-
bon-contaminated soils.
Develop capital and operating costs
for the C-G Process technology that
can be readily used in the Superfund
decision-making process.
Secondary objectives were also defined:
Characterize residuals (water, oil, va-
por, and solids) relative to applicable
standards for final disposal or further
treatment.
Document the important operating
conditions of the C-G Process for ap-
plication to hazardous waste sites.
Waste Feed Handling
oo
Carrier OH
Fluk
1
Feed
1 *" Unnnar ^
Make-up
Carrier Oil
Hzation e=*
^ank
^
.Ji, Recov-
^
3
ŁVc
Steam Boiler
:
Stag
pora
)
io/7
Distillaton
ered for Carrier
(
Carrier Oil Oil Recover)/
LJť-
O/7/Water
Separator
~r
_l
^^
- " ki
Condensed Water
> Discharge to POTW
or Onsite Treatment
Slurry Centrifugation
Cake Desolventization
Final Product
Return to Site
Excavation
L/ghf CVfe
Indigenous Oil
Offsite Disposal
Flgur* 1. Simplified diagram of site remediation by the Carver-Greenfield Process.
2
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Assess the fate and movement of
volatile and semivolatiie organic con-
taminants and metals in the waste.
Overview of the Carver-
Greenfield Process SITE
Demonstration
The demonstration test runs included
(1) a series of trial runs to establish optimal
operating conditions, (2) a blank run, and
(3) two test runs. The pilot plant was oper-
ated in a batch mode, treating approxi-
mately 300 Ib of "oily" solids per test run.
The cleaned solids were tested by the
TCLP test for compliance with relevant
Toxicity Characteristic Rule land applica-
tion limits, and for indigenous total petro-
leum hydrocarbons (TPH) to meet a re-
sidual target level of 0.3% (3 g/kg). The
water fraction analysis conformed with
specific categorical standards for organics
and metals and conventional pollutant pa-
rameters relevant to conventional waste-
water treatment applications.
The operating data collected included
temperature, pressure, and flow measure-
ments throughout the process. The
evaporative extraction operated at 200 to
250°F, under 22 to 23 in. Hg vacuum, to
ensure complete removal of water from
the waste. The two subsequent extractions
operated at atmospheric pressure and
temperatures of 130 to 180°F. The desol-
ventizer temperature was also important,
since the desolventizer is the last point at
which residual solvent and water can be
removed from the solids. The desolven-
tizer temperatures were slightly below the
original projections of 225 to 350°F, which
may have contributed to slightly higher
than projected solvent concentrations on
the final product solids.
Demonstration Results
During the demonstration, a compre-
hensive sampling and analysis program
was undertaken to characterize the waste
feed and products from the process. Sol-
ids, oil, water, and solvent analyses were
interpreted to evaluate the process with
respect to the primary demonstration ob-
jectives. Metals, volatile organic com-
pounds (VOCs), and semivolatiie organic
compounds (SVOCs) were analyzed to
qualitatively determine the fate of these
materials through the process.
Sampling and Analytical
Results
The sampling and analysis program fo-
cused on characterizing the following:
feedstock;
final product (dry solids), including
TCLP results;
recovered oils (centrate and con-
densed oils); and
water product.
Each of these items is discussed be-
low.
Feedstock Characteristics
Soil, oil, and water (SOW); TPH; sol-
vent; VOC; SVOC; and metals were ana-
lyzed. The principal waste characteriza-
tion, with respect to the primary demon-
stration objectives, was with the SOW
analyses, which are summarized in Table
1. The two feedstocks were similar in sol-
ids content but differed in oil and water
content. Both feedstocks were considered
suitable for the C-G Process.
In the feedstock for Test Run 1, xylene
was the only organic compound (VOC or
SVOC) found above detection limits.
Toluene and ethylbenzene (VOCs), and
phenanthrene and 2-methyl naphthalene
(SVOCs), may also have been present at
concentrations less than detection limits.
In the feedstock for Test Run 2, only
ethylbenzene and toluene were above de-
tection limits. Benzene (VOC) and
phenanthrene, 2-methyl naphthalene, and
naphthalene (SVOC), may also have been
present at concentrations less than de-
tection limits.
The most significant metals in both feed-
stocks were aluminum, barium, calcium,
iron, and magnesium. TPH levels ranged
from 80,000 to 150,000 mg/kg; this con-
Table 1. Composition of Waste Feeds
Test Run No. Solids (%) Oil (%)
firmed the oil levels indicated by the SOW
results. The feedstocks had no detectable
Isopar-L and had ignitabilfty levels greater
than 100°C.
Final Solids Product
Characteristics
The final solids product was a dry pow-
der similar to bentonite in appearance.
Isopar-L comprised the bulk of the hydro-
carbon content in the final solids product.
Indigenous TPH levels in the final solids
product of Test Runs 1 and 2 were in
trace amounts. Indigenous TPH removal
efficiency is a calculated value (initial feed
TPH minus final product TPH minus final
product Isopar-L divided by initial feed
TPH) that indicates the C-G Process's oil
removal efficiency. Table 2 summarizes
removal efficiencies for indigenous oil,
TPH, and indigenous TPH observed in
the demonstration.
TCLP analysis of the final solids product
of Test Runs 1 and 2 indicated that treated
solids do not leach metals, VOCs, or
SVOCs above RCRA regulatory limits.
Recovered Oils Characteristics
Centrate produced in both test runs was
a dark liquid with a strong odor. As ex-
pected, analyses showed relatively higher
indigenous oil levels in the first extraction
centrate in both test runs. The first extrac-
tion centrate contained about 87% to 89%
Isopar-L, and the second and third had
Water (%)
1
2
52.35
52.44
17.47
7.26
21.75
34.7
Table 2. Indigenous Oil and TPH Removals
Oil Removal Efficiency (%)
Test Run No.
Indigenous Oil
TPH
Indigenous TPH
1
2
91.8
88.3
94.6
92.6
>99.9
>99.9
Table 3. Oil Removal Efficiency of Extractions
Testl
Test 2
Sample
Location
Feedstock
Extraction A
Extraction B
Extraction C
Final Product
Indigenous
Oil/Solid
(9/9)
0.334
0.084
0.043
0.037
0.014
Fraction of
Total Indigenous
Oil Removed (%)
78.1
12.8
1.88
7.29
Indigenous
Oil/Solid
(9/9)
0.138
0.053
0.020
0.016
0.009
Fraction of
Total Indigenous
Oil Removed (%)
65.9
25.6
3.1
5.4
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levels above 98%. Table 3 summarizes
the oil removal efficiency of each extrac-
tion through desolventization to the final
product.
The condensed solvent product was a
clear liquid in both test runs. VOCs and
SVOCs were not analyzed because of
elevated detection limits in the solvent
matrix. Metals analyses indicated that most
metals were below detection limits. The
condensed solvent can be recycled in the
C-G Process.
Because of scheduling constraints and
equipment limitations, the final distillation
step to demonstrate the separation of sol-
vent from the indigenous oil was canceled.
Therefore, the characteristics of the final
indigenous oil product and solvent pro-
duced after distillation were not deter-
mined. The centrate should, however, be
easily split by fractional distillation to its
constituent heavy oil and solvent compo-
nents; this would allow cost-effective re-
cycling of the recovered solvent and more
efficient disposal of the indigenous oil
fraction.
Water Product Characteristics
The water product produced in Test
Runs 1 and 2 was a clear liquid with a
strong odor, tow suspended solids, low
biochemical oxygen demand (BOD), and
high chemical oxygen demand (COD).
TPH analysis results correlated well with
the COD analysis results in both test runs
to suggest that most of the COD was
related to the presence of Isopar-L and
lighter organics in the water product. Ac-
etone and 2-butanone were detected at
trace levels. No other VOCs or SVOCs
were detected. Metals analyses also
showed only trace amounts. The charac-
teristics of the water product were similar
to dilute municipal wastewater. The water
complied with Organic Chemical, Plastics,
and Synthetic Fibers (OCPSF) industrial
categorical discharge limits with respect
to metals and organics concentrations.
Carver-Greenfield Process
Operational Reliability and
Treatment Costs
The estimated cost per ton for treating
drilling-mud waste from the PAB Oil site,
using a full-scale C-G Process system, is
about $523 per wet ton. Of this total, $221
is C-G Process technology-specific and
$302 is site-specific. Of the $302 per ton
site-specific cost, about $240 is for the
incineration of indigenous oil separated
from the feed. The estimated costs of the
C-G Process are highly site-specific and
difficult to identify without accurate data
from a site remedial investigation report or
waste profile. Variability in the waste char-
acteristics could significantly affect treat-
ment costs. A more detailed discussion of
this technology, including a detailed dis-
cussion of economics by the vendor, is
presented in the Applications Analysis
Report (AAR).
Comments
This section is intended to pu't the dem-
onstration results in perspective with re-
spect to an actual full-scale site remedia-
tion. The batch-operated pilot-plant pro-
cess used in the demonstration differs from
an actual full-scale process unit that would
be used in a site remediation.
Bench-scale and possibly pilot-scale
treatability studies should be done with,
the actual waste material to aid in solvent
selection and to identify critical operating
parameters and extraction-evaporation
sequence. These studies should simulate
continuous or semi-continuous operations
and should incorporate any special start-
up conditions that a full-scale system might
require.
The age and condition of the C-G Pro-
cess pilot-plant equipment somewhat
compromised the efficiency of two critical
unit operations in the demonstration. The
condition of the centrifuge required that
the slurry be double centrifuged after the
last extraction before the final desolventi-
zation. The desolventizer malfunctioned
before the blank run; although operable
during the demonstration, it ran at a lower
temperature than originally planned. This
may have resulted in solvent levels on the
final product that were slightly elevated
over initial projections.
Gross material balances were done on
the blank run and the test runs> to deter-
mine the integrity of the analytical results
and weight measurements. More than
5,500 Ib of materials, including solvent,
were charged to the system in each test
run; more than 96% were recovered. On
a constituent basis, 80% of the solids,
107% of the water, and 96% of the oil
phases charged to the system were re-
covered in Test Run 1. Similarly, 79% of
the solids, 95% of the water, and 93% of
the oil phases charged to the system were
recovered in Test Run 2. The gross mate-
rial balance results suggest that the mea-
surement techniques and analytical meth-
ods sufficiently characterized the move-
ment of materials through the process.
Conclusions
Based on the SITE demonstration re-
sults, the following conclusions can be
made concerning the C-G Process:
1) The C-G Process separated a petro-
leum-oil-contaminated waste drilling
mud into its solids, oil, and water
phases. The C-G Process removed
about 90% of the indigenous oil (as
measured by the SOW procedure).
No detectable levels of indigenous
TPHs were found on the final solids
product from either test run.
2) The final solids product was a dry
powder similar in character to dry
bentonite. Isopar-L solvent, a food
grade oil, comprised the bulk of the
residual oil content on the final solids
product.
3) Values for all metals and organics
were well below the RCRA TCLP lim-
its for characteristic hazardous wastes.
Residues from the C-G Process may
still require disposal as hazardous
materials because of the regulatory
constraints governing the disposal of
Superfund wastes.
4) The C-G Process, as demonstrated
on the PAB Oil site wastes, does not
remove metals bound to the solids
phase. The process may increase the
apparent metals concentration in the
solids fraction by volume reduction.
5) The resulting water product requires
further treatment because of light or-
ganics and solvent. In some cases,
the wastewater may be disposed of
at a local publicly owned treatment
works.
6) A full-scale C-G Process system can
process drilling-mud waste from the
PAB Oil site at an estimated cost of
$523 per wet ton of feed. Of this
total, $221 is C-G Process technol-
ogy-specific and $302 is site-specific.
Of the $302 per ton site-specific cost,
about $240 is for the incineration of
indigenous oil separated from the
feed. Treatment costs are highly site-
specific, and accurate cost estimation
requires data from a site remedial
investigation or waste profile, as well
as specific treatment goals. Variabil-
ity in the waste characteristics or pre-
treatment requirements could signifi-
cantly affect treatment costs.
U.S. Government Printing Office: 1992 648-080/60070
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TTje EPA Project Manager, Laurel J. Staley, is with the Risk Reduction
Engineering Laboratory, Cincinnati, OH 45268 (see below).
The complete report, entitled "Technology Evaluation Report: The Carver-
Greenfield Process, Dehydro-Tech Corporation," (Order No. PB92-
217462AS; Cost: $35.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
A related report, entitled "Applications Analysis Report: The Carver-Greenfield
Process, Dehydro-Tech Corporation" (EPA/540/AR-92/002) is available.
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
EPA/540/SR-92/002
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No, G-35
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