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-

-------
                                                                                 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.

-------
    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

-------
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

-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300

RETURN POSTAGE GUARANTEED
                                                                                         Third-Class
                                                                                         Bulk Rate
                    IERL016906a
                    US EPA  REGION  V
                    LIBRARY
                    230  S DEARBORN ST
                    CHICAGO  IL 60604

-------