United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-014 July 1983
Project Summary
Evaluation of the Union Carbide
PURASIV HR Vapor Recovery
System
C. S. Parmele, H. S. Basdekis, and M. R. Clark
The objective of this study was to
evaluate a new fluidized-bed adsorp-
tion technology developed in Japan,
licensed by Union Carbide, and now
being marketed in the United States as
PURASIV* HR Vapor Recovery System.
The engineering evaluation was devel-
oped by performing field tests on a full-
scale PURASIV HR unit at Polaroid
Corporation, Wartham, Massachusetts.
The data from the tests supplemented
operating information from a PURASIV
HR system at General Motors Corpora-
tion, Fremont, California Capital and
operating costs were then developed
for both PURASIV HR and fixed-bed
adsorption systems, and these two
types of adsorption systems were then
compared.
The PURASIV HR technology can be
viable for adsorption applications and
can compete economically with fixed-
bed systems, especially at flow rates
above 5,000 scfm, where the higher
capital costs for the PURASIV HR sys-
tem can be offset by savings in steam
and electricity costs. Selection of the
better system should be based on an
integrated evaluation of the benefits
and drawbacks for each type of system.
Neither type of system should be ex-
cluded apriori from a given application
based on costs (in the range of flow
rates of 5,000 to 100,000 scfm and
inlet VOC concentrations of 0.1 to 1.0
Ib VOC/1,000 SCF) without an evalua-
tion of site-specific aspects of the
existing tradeoffs.
Although the PURASIV HR system
has been promoted for controlling
emissions of water-soluble and reac-
tive solvents, it is not uniquely quali-
fied for these applications. Water will
be present in the solvents desorbed
from PURASIV HR systems as well as
from fixed-bed systems, and similar
precautions to minimize conditions
that could lead to bed fires must be
taken in designing and operating either
type of adsorption system. Processing
conditions which eliminate or mini-
mize the possibility of bed fires are
inherent in the process design for the
PURASIV HR systems. The basic de-
sign of a fixed-bed system must be
modified to provide these conditions.
This Project Summary was developed
by EPA's Industrial Environmental Re-
search Laboratory. Cincinnati, OH. to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Background
Steam-regenerated fixed-bed adsorp-
tion technology has often been applied for
solvent recovery/emission control. One
drawback to this technology is the inherent
contact of water with solvents during the
regeneration step. When suitable recov-
ered solvents cannot be produced by de-
canting them from the condensed steam,
additional costs are generated by addi-
tional recovery steps, such as distillation.
A new approach to vapor-phase adsorp-
tion using a fluidized-bed adsorber was
developed in Japan. Since this approach
allows the use of nitrogen to regenerate
the carbon, it may reduce the need for
additional steps to separate the water-
miscible solvents from the water. This
technology, licensed by Union Carbide, is
currently being marketed in the United
States as the PURASIV® HR Vapor Re-
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steam/lb carbon for regeneration. The •
inlet concentration shown in this figure as
0.1 Ib VOC/1000 scf corresponds to a
concentration of about 450 ppm for a
compound with a molecular weight of 80
Ib/lb mole.
Figure 2 shows that annual costs for
generic systems (including capital-related
charges) are almost the same for these
two types of adsorption systems. The
differences between the annual costs for
the two types of adsorption systems are
within the error bounds of the calcula-
tions. Significant differences between the
annual costs existed only for the cases at
the lowest flow rate (where costs for
PURASIV HR systems were higher) and at
inlet VOC concentrations above 0.5 Ib/
VOC 1,000 scf (2250 ppm) when 1.0 Ib
steam/lb carbon was needed for regener-
ation of fixed-bed systems (where costs
for fixed-bed systems were higher).
As is shown in Figure 3, both types of
adsorption systems can be cost effective
when the inlet concentration is greater
than 0.1 Ib VOC/1000 scf (^450 ppm)
covery System. The PURASIV HR pro-
cess uses a new type of beaded activated
carbon specifically developed to resist
attrition, a major disadvantage of previous-
ly developed continuous-flow adsorption
processes The advantages of this f luidized-
bed adsorption system are that it is re-
ported able to desorb the organic from the
carbon with reduced water contamination,
to make use of inert gases during regen-
eration, and to consume relatively low
energy.
The objective of this study was to per-
form an engineering evaluation of the
PURASIV HR technology. First the data
available from commercial installations in
the United States were reviewed and a site
suitable for field sampling was identified.
Field sampling tests were then conducted
to assess the performance and economics
of the PURASIV HR system. Inlet and
effluent concentrations, mass emission
rate,and quality of recovered solvent were
determined during the tests. Reliability,
cost effectiveness, and energy require-
ments were also assessed.
Figure 1 presents installed capital costs
(all in 1980 dollars) for "basic" vapor-
phase adsorption systems as a function of
flow rate. These cost data are for "basic"
adsorption systems, because they include
only the battery limits costs of the ad-
sorption equipment They do not include
costs for any auxiliary equipment that
might be required for pretreatment of the
inlet gas, for wastewater treatment or for
purification of the recovered solvent
Installed capital costs for PURASIV HR
systems are 40 percent higher than the
capital costs for comparable fixed-bed
systems, because the PURASIV HR sys-
tem is different from a conventional fixed-
bed system. However, the higher capital
costs can be offset by lower operating
costs. This is illustrated in Figure 2, which
shows the annual cost per scfm as a
function of flow rate and type of adsorp-
tion system. Curve 1 represents basic
PURASIVHRsystems,Curve2 represents
fixed-bed systems using 1.0 Ib/steam/lb
carbon for regeneration, and Curve 3 rep-
resents fixed-bed systems using 0.3 Ib
Summary and Conclusions
This engineering evaluation has shown
that the PURASIV HR adsorption tech-
nology can be viable for solvent recovery/
emission control applications and can
compete with fixed-bed systems in some
applications. However, it is difficult to
categorically exclude one type of adsorp-
tion system (fixed-bed or PURASIV HR)
from a given application without evaluat-
ing the specific aspects of the many exist-
ing tradeoffs. For example, PURASIV HR
systems require less energy (for desorp-
tion) and less electrical power(to move the
solvent-laden air through the adsorption
system) than fixed-bed systems, but these
cost savings are sometimes offset by
higher capital costs and higher carbon
replacement costs due to shorter carbon
lifetime and higher carbon prices.
The PURASIV HR system has been
promoted for controlling emissions of
water soluble and reactive solvents (such
as ketones, aldehydes, esters, and organic
acids) because steam is not the regenerat-
ing fluid and conditions inside the equip-
ment minimize the possibility of a bed fire.
However, fixed-bed systems can also be
considered for these applications because
the solvent from the PURASIV HR unit
may still contain enough water (5 to 10
percent when regeneration conditions
have been properly adjusted) to require
furthertreatment Also, fixed-bed systems
are designed and operated so that the
possibility of a bed fire is greatly reduced.
10.000
I
J.OOO -
-------
I
1
c
c
80
70
60
50
40
30
20
10
(1) Annual cost of basic PURASIV HR System.
(2) Annual cost of basic fixed-bed adsorption system excluding solvent
recovery equipment and using 1.0 Ib steam/Ib C for regeneration.
13) Annual cost of basic fixed-bed adsorption system excluding solvent
recovery equipment and using 0.3 Ib steam/Ib C for regeneration.
Inlet Concentration -
0.1 Ib VOC
1000 scf
1000
5000 10.0OO
Flow Rate (scfm)
50,000
100,000
Figure 2. Annual cost per scfm vs. flow rate.
and the flow rate is above 5,000 scfm. For
these cases, there are enough adsorbed
volatile organic compounds (VOC) over
which to spread the operating costs so
that the cost/lb VOC is near or below the
range of replacement costs for typical
solvents ($0.20 to 0.40/lb VOC). The
values for cost parameters used to obtain
these results are shown in Table \.
Mechanical problems such as erosion of
the equipment and excessive carbon losses
due to attrition have not been experienced
with the PURASIV HR systems. Such
problems have been overcome by replac-
ing the granular activated carbon that was
used in other continuous-flow adsorption
systems with the spherical, beaded ac-
tivated carbon developed in Japan.
The beaded activated carbon often has a
shorter lifetime than granular activated
carbon, possibly because there is usually
less carbon in a PURASIV HR system and
circulation of the carbon exposes all of it to
the irreversibly adsorbed materials. These
two factors suggest that the beaded car-
bon may become poisoned faster than
granular carbon in fixed-bed systems. The
impact of shorter lifetime on operating
costs was reduced at Polaroid by thermally
regenerating the carbon.
Pretreatment considerations are gener-
ally the same for fixed-bed and PURASIV
HR systems because the same principles
of adsorption influence the operation of
both systems. However, the PURASIV HR
system is more susceptible to conditions
that cause the carbon to agglomerate
(sticky solids or liquids) because the ag-
glomerated carbon particles quickly inter-
fere with the circulation of the carbon. The
PU RASIV H R system is also susceptible to
"shot" upsets of high VOC concentrations
because locally high VOC concentrations
can lead to condensation in the desorption
section.
The outlet concentration from a PURASIV
HR system is influenced most by the
condition of the carbon after regeneration.
At Polaroid, the outlet concentration was
'\5 to 20 ppm using new carbon. By
comparison, carbon which had been in
service for nine months yielded an outlet
concentration of 45 to 70 ppm. The re-
generation process may be optimized to
some extent if the carbon and nitrogen
flow rate and/or the desorption tempera-
ture are independently adjusted. From
this standpoint more flexibility is available
for designing and operating a PURASIV
HR system than for a fixed-bed system.
Recommendations
PURASIV HR systems should be consid-
ered as an alternate to fixed-bed adsorp-
tion systems for solvent recovery/VOC
emission control applications. Selection of
the type of adsorption system should not
be based on one or two features of either
system, but rather on an integrated evalua-
tion of all the benefits and drawbacks of
each type of system.
Neither type of adsorption system should
be categorically excluded from applica-
tions that include water-soluble or reactive
solvents, because neither type of system
is uniquely qualified forthese applications.
Water will be present in the desorbed
solvent from either type of system, but
there is likely to be more with fixed-bed
systems. Also, precautions must be taken
in designing and operating either type of
adsorption system to minimize the con-
ditions that can lead to bed fires. Pro-
cessing conditions which eliminate or
minimize the possibility of bed fires are
inherent in the process design for the
PURASIV HR system. The basic design of
a fixed-bed system must be modified to
provide these conditions.
Liquids should not contact the carbon in
PURASIV HR systems, because the car-
bon distribution and circulation will be
drastically affected.
When the carbon must be replaced
frequently, methods to prevent the loss of
adsorption capacity should be evaluated.
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1.0 -
I
a
.§>
§
0.1
0.01
(1) Operating costs of basic PURASIV HR System.
(21 Operating costs of basic fixed-bed adsorption system excluding solvent
recovery equipment using 1.0 Ib steam/Ib C for regeneration.
(3) Operating costs of basic fixed-bed adsorption system excluding solvent
recovery equipment using 0.3 Ib steam/Ib C for regeneration.
0.1 Ib VOC
\
These methods include pretreatment to
remove from the inlet stream the materials
that cause loss of capacity or periodic
treatment of the carbon via solvent re-
generation or thermal reactivation.
On-line sampling equipment should be
checked frequently. Carbon fines should
be specifically excluded from the sampling
equipment to ensure that the analyzer is
receiving a representative sample from the
process.
woo
10,000
Flow (scfm)
100.000
Figure 3. Operating costs per Ib VOC adsorbed vs. flow rate.
Table 1.
Values of Cost Parameters
Fixed costs
Maintenance labor plus materials, 6%
Capital recovery, 18%a
Taxes, insurances, administration charges, 5%
Utilities
Electric power
Steam
Cooling water
Chilled cooling water
Nitrogen
Beaded carbon replacement cost
Granular carbon replacement cost
29% installed capital
$0.04/kWh
$4.00/1000 Ib
$0.10/1000 gal
$0.90/1000 gal
$0.40/1000 scf
$4.00/lb
$1.00/lb
aBased on 10-year life and 12% interest
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C. S. Parmele, H. S. Basdekis, and M. R. Clark are with IT Enviroscience, Inc.,
Knoxville, TN 37923.
Ronald J. Turner is the EPA Project Officer (see below).
The complete report, entitled "Evaluation of the Union Carbide PURASIV HR
Vapor Recovery System," (Order No. PB 83-193 599; Cost: $ 11.50. subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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