Process and Equipment Changes for Cleaner Production in
Federal Facilities
by
Larry G. Jones and Charles H. Darvin
U. S. Environmental Protection Agency
National Risk Management Research Laboratory
Research Triangle Park, NC 27711
Elizabeth Hill
P.O. Box 12194
Research Triangle Institute
Research Triangle Park, NC 27709
ABSTRACT
EPA's National Risk Management Research Laboratory (NRMRL) has actively participated in
the Strategic Environmental Research and Development Program (SERDP) to develop
innovative technologies and processes for the reduction of environmental pollution. Technology
developments from two of the more noteworthy projects conducted by NRMRL for SERDP are
currently in general use by military and commercial facilities. The specific technologies include
an innovative paint spray booth design and the large scale use of n-methyl-2-pyrrolidone (NMP)
as a paint stripping and surface cleaning agent. These engineering development and
demonstration programs have led to significant cost and pollutant discharge reductions from the
applicable facilities. This paper describes the effectiveness of these processes and estimates the
resulting cost and pollution reductions achieved.
INTRODUCTION
During the decade of the nineties, the U. S. Environmental Protection Agency (EPA) and the
various services of the Department of Defense (DoD) conducted joint research and development
(R&D) efforts aimed at reducing the discharge of hazardous and toxic pollutants from military
production and maintenance facilities. These efforts were mutually beneficial to both DoD and
EPA. They provided the opportunity to demonstrate viable and compliant discharge technologies
and concepts to facilitate the non-polluting production and maintenance of military equipment by
the services and by private industry. The facilities at which these cooperative programs were
conducted provided not only convenient and accessible demonstration and evaluation sites but
also locations with operations, equipment, and pollution problems typical of those found across
the services and at typical commercial manufacturing plants.
Two of the more significant processes in manufacturing which have received a great deal of
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attention in these joint efforts are surface cleaning and coating. Both processes have the
tendency to produce multimedia pollution, including water, solid waste, and air pollution. Thus,
major research efforts have been conducted with emphasis on reducing or eliminating the
multimedia discharges from these industrial processes. This paper will discuss two of these joint
DoD/EPA projects. But more important, it will provide some insight in the development of these
technologies and how they might fit into an overall pollution control strategy. It should be
recognized that pollution control has not only a technology component but also an economic
component which must be considered when developing viable and efficient pollutant reduction
technologies. Both the technology and the economic issue drive the application and acceptance
of a given technology concept.
LARGE SCALE DEMONSTRATION OF N-METHYL-2- PYRROLIDONE
(NMP) FOR PAINT STRIPPING
The EPA and the various services of the DoD have cooperated to develop and demonstrate the
viability of new technologies to address pollution problems that appear at numerous military-
related facilities. One of these programs was conducted and completed at the U. S. Marine
Corps Logistic Base (MCLB), at Albany, GA, with the installation and demonstration of the use
of n-methyl-2- pyrrolidone (NMP) as a replacement for solvent cleaning and degreasing of large
vehicle engines and parts.
Prior to the design and fabrication of equipment for the program, laboratory studies were
conducted to assess the potential of NMP as a substitute for methylene chloride to strip Chemical
Agent Resistant Coating (CARC) from coated surfaces. The preliminary laboratory studies
showed NMP to have a number of desirable qualities. They include: (1) the capability to strip a
broad range of coatings including CARC from vehicle surfaces, (2) its non-flammability at
typical operating temperature1, and (3) its consideration by EPA not to be a hazardous air
pollutant under Title m, Section 112 of the Clean Air Act.2 NMP is not classified under the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or the
Resource Conservation and Recovery Act (RCRA) as a hazardous substance or waste,
respectively.2 Considering these properties, it was anticipated that it might be possible to use
these chemical qualities in a large scale production scenario such as in a paint stripper for
military equipment. A program was therefore developed whose objective was to demonstrate
and evaluate at full scale an integrated CARC paint stripping process using NMP as the stripping
agent.
Methylene Chloride Process Equipment Paint Stripping
A production size immersion tank which formerly used methylene chloride as the stripping agent
was modified for the program. The tank had a surface area of 13.3 m2 (143 ft2) with the depth of
methylene chloride in the tank at approximately 0.76 m (30 in.). The tank contained a 2 to 3 in.
(0.05 to 0.08 m) layer of water floating over the methylene chloride which served as a seal to
reduce methylene chloride emissions. The tank was charged with 8.33 m3 (2200 gal.) of
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methylene chloride.
The first step in the stripping process was the immersion of the coated part in the methylene
chloride at room temperature for approximately 1 to 2 hours. This was followed by a three-stage
tap water rinse in separate tanks. Water from the first rinse stage was used to supply the
methylene chloride water seal in the immersion tank. After rinsing, the parts were air dried.
NMP Process Equipment and Paint Stripping
An immersion tank, equivalent in dimension to the methylene chloride tank used for the baseline
evaluation and with a surface area of approximately 143 ft2, was modified. The tank was
retrofitted with steam heating elements, recirculating and rinse pumps, and an NMP distillation
unit for NMP recovery. The modified tank was charged with 7.91 m3 (2090 gal.) of technical
grade NMP.
The NMP stripping steps were similar to those of the methylene chloride process. However, the
rinsing, the processing time, and the stripper temperature varied from the methylene chloride
process. The NMP is heated to a average temperature of 66 °C (150 °F), because cold NMP will
not strip paint from the surface efficiently. A process controller automatically monitored and
maintained the operating temperature automatically. The parts were soaked in NMP for
approximately 2 to 3 hours. The first stage rinse was done over the soak tank with a high
pressure NMP rinse. The NMP rinse liquid was drained into the immersion tank to reduce any
losses that may have occured due to evaporation or drag out. A final high pressure water rinse
was completed in the rinse tank.
Stripping Effectiveness and Process Emissions
Stripping Effectiveness
Parts stripped with NMP were required to be equivalent to or better in appearance and residual
paint retention than those stripped with methylene chloride. Upon completion of training of
MCLB personnel, the NMP process was shown to be capable of removing multiple layers of
CARC and to strip parts to the base metal within 3 to 4 hours. Unlike methylene chloride, NMP
also successfully removed Plastisol® coating and softened epoxy-based topcoats with extended
soaking. The Plastisol® removal process was formerly carried out in a hot alkaline bath followed
by scraping and abrasive blasting. Thus, the use of NMP exceeded the capability of methylene
chloride for removal of Plastisol®, and in all other cases it was found to be equivalent to or better
than the methylene chloride process.
Emissions
The vapor pressure for NMP is significantly lower than for methylene chloride at their operating
temperatures during stripping. Table 1 presents the vapor pressures at the operating temperatures
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for methylene chloride and NMP.
Table 1. Methylene chloride and NMP data for stripping process
Solvent
Temperature
°C (°F)
Vapor Pressure
mm Hg1-2--'
Emissions Rate
mVhr (gal./hr)ab
Methylene chloride
25 (77)
440
4.4(1.16)
NMP
25 (77)
0.5
Not determined
NMP
66(150)
4.8
1.36 (0.36)
a.	Methylene chloride emissions rate based on historical solvent consumption data.
b.	NMP emissions rate based on consumption during evaluation program.
The NMP-based process operates at an elevated temperature of approximately 66 °C (150 °F).
However, due to the significant difference between the vapor pressures of the two solvents, the
resulting emissions of NMP still remain well below those of methylene chloride at room
temperature. Based on results of the evaluations, the emissions of NMP as liquid volume were
reduced by approximately 70 percent from the former stripping operation. Annual losses of
NMP were projected for the demonstration site to be a maximum of 58 barrels or 0.01 m3 (3,135
gal.) based on the 6 week demonstration and evaluation program. This is compared to an
estimated yearly loss rate of 185 barrels or 38.51 m3 (10,175 gal.) for methylene chloride.
The major advantage of the NMP stripping process is that it permits the removal of a broad range
of coatings using a non-hazardous solvent. Although other stripping agents may have been
applicable to the stripping of individual coatings, none had the broad applicability of NMP. This
capability allowed its use for most stripping requirements at the MCLB, Albany, GA.
NMP Process Cost
Based on the results of the demonstration program, the capital cost to install the NMP technology
was significantly greater than that for the methylene chloride stripping technology at MLBC, at
Albany, GA. As shown in Table 2, the capital cost for the NMP installation was more than 6
times that of the methylene chloride process installation. This difference in cost is due primarily
to the need for thermal control and solvent recycling systems to enhance the stripping capability
and efficiency of NMP. These are not required for the methylene chloride process. The
additional equipment for the NMP processing, which is not required for the methylene chloride
process, includes a heater, storage tanks, a vacuum distillation system, and automation
electronics for the heat and immersion monitoring and control system.
The annual cost for NMP stripping, however, compared favorably to that of the methylene
chloride process. The NMP process annual cost was determined to be approximately 3 percent
less than that for the methylene chloride process. This results from the cost avoidances achieved
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with lower NMP solvent consumption and lower NMP stripping waste disposal costs. It was
estimated that the annual replacement volume for NMP would be 7.54 MT (16,600 lbs),
compared to a total replacement of the methylene chloride volume of 33.14 MT (73,000 lbs).
Based on cost per pound of $1.82 and $0.54 for NMP and methylene chloride, respectively, the
solvent consumption cost is approximately 24 percent less for NMP than for methylene chloride.
As the cost of methylene chloride increases due to increased regulation, the cost comparison
should become even more favorable for NMP.
The NMP process waste disposal cost was approximately 47 percent less than for methylene
chloride due to the NMP's being classified as non-hazardous. A summary of the capital and
annual costs is shown in Table 2.
Table 2. Summary of capital and annual cost.4
Process
Capital Cost ($)
Annualized Cost ($)
Methylene Chloride Stripping
25,136
86,100
NMP Stripping
166,260 •
84,044
Regulatory Impact
The replacing of methylene chloride with NMP will reduce the amount of tracking and reporting
required. Most important, unlike methylene chloride, NMP is not a hazardous air pollutant
(HAP) under Section 112 of the Clean Air Act, 1990 (CAA). Thus, replacing methylene chloride
with NMP immediately eliminates one source of HAPs. The use of NMP will still result in air
emissions of a volatile organic compound (VOC) and may be subject to regulation depending on
the volume released to the atmosphere.
Methylene chloride is classified as a Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA) hazardous substance. NMP is not. However, under Executive
Order 12856 both methylene chloride and NMP are required to be included in a facility's annual
Toxic Release Inventory (TRI) report of chemicals listed under Section 113 of the Superfund
Amendments and Reauthorization Act (SARA) Title III. Table 3 summarizes the regulations
impacting the use of methylene chloride and NMP.
Table 3. Regulations impacting the use of methylene chloride and NMP
Chemical
Section-112,
CAA
Hazardous Substances
CERCLA
RCRA
Code
Toxic Chemical
SARA
Methylene Chloride
yes
454 kg (1,000 lb)
U080
yes
NMP
not listed
not listed
not listed
yes
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Development of Spray Booth Design to Reduce Exhaust Rates
The second program was the installation and demonstration of an innovative spray booth design
that significantly reduced the capital and operating costs of controlling emissions from the
painting of large military vehicles and components. A secondary but less obvious pollution
prevention benefit of this technology development is a reduction in the use of utilities needed to
operate the booth.
The painting process represents one of the largest sources of VOC emissions in both military
equipment maintenance and industrial manufacturing. Approximately 17 percent of industrial
VOC emissions can be attributed to painting and coating operations.5 Military equipment
production and maintenance coating processes suffer from the same emissions control obstacle
found in similar commercial facilities: the high cost of controlling emissions from painting
operations. The emissions from spray booths can be controlled via end-of-pipe air pollution
control (APC) technologies; e.g., carbon adsorption or thermal oxidization. On the surface,
however, these do not represent the concept of pollution prevention. Yet, if the painting process
is analyzed from a systems standpoint, it can be concluded that an improvement in booth
operating efficiency in terms of energy usage may contain a pollution prevention element.
Typically the spray booth serves two purposes during the painting process. First, it collects and
removes paint overspray and solvents from the painting area. A second purpose is to condition
the incoming air; e.g., cooling in the summer and heating in the winter depending on
geographical location and ambient temperature. Whether heating or cooling the incoming spray
booth air, pollution typically will be generated by fossil-fuel-fired utility sources which must
produce the energy needed for air conditioning. The amount of energy used for air movement
and conditioning the air throughput impacts the amount of pollution at the utility source. Thus
any modification in the spray booth design or operation that results in a reduction of energy
required for air movement, heating, or cooling should be considered to be a pollution prevention
measure.
A joint program between the DoD and the EPA was completed in 1997 to demonstrate a unique
spray booth design that significantly reduced the volume of air supplied to and discharged from
the paint spray booth. A demonstration of the booth design was conducted at the MCLB at
Barstow, CA. Two spray booths, one new and one specially modified to evaluate a unique
exhaust flow reduction concept, were constructed for the program. The booths used an air
recirculation scheme coupled with a unique split-flow design that discharged a smaller volume of
pollutant-rich air from the booth. Figure 1 is a general schematic of the booth design.
The recirculation/flow partitioning design takes advantage of the stratification of the pollutants in
the booth and their tendency to settle in the lower regions of the booth.6 A fraction of the air
volume passing through the booth is withdrawn from the lower regions of the booth and directed
to an end-of-pipe control system. However, the major portion of the air passing through the
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Figure 1. Recirculation Split-Flow Spray Booth Design
FRESH
MAKEUP
AIR

BYPASS
DUCT--
w
PARTITION
EXHAUST AIR
TO APCS
INTAKE FILTER
EXHAUST FILTER
booth is recirculated back to the booth without requiring any additional conditioning. Thus, only
the makeup air equivalent to the exhausted air flow requires conditioning. Table 4 presents the
flow reductions achieved in the demonstration booths. A 60 percent or greater air supply
reduction was achieved with the modifications to the test booths.
Table 4. Summary of flow reduction for each booth.7
Booth
Initial Booth Air Supply and Exhaust
Flow Rate
m3/min (cfm)
Final Booth Air Supply and Exhaust
Flow Rate
mVmin (cfm)
1
1,500 (53,000)
566 (20,000)
2
1,784 (63,000)
518 (20,500)
Total
3,284(116,000)
1,084 (40,500)
Based on the exhaust reductions from the booths shown in Table 4, an equivalent total reduction
of 2200 m3/min (75,500 cfm) in fresh air input that required conditioning was achieved. Using
the demonstration site at Barstow, CA, with extremes in temperature from season to season
ranging up to 49 °C (120 °F) and higher in the summer and below 0 °C (32 °F) in winter as an
example, the amount of energy saved in conditioning the inlet air can be significant. Based on
the 2200 mVmin reduction in flow rate and operating an average of 100 days annually, 6 hours
per day when the air temperature to the booth might require raising or lowering an average of
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25°C (45 °F), the fuel energy consumption will be at least 38.4 MBtu/h (40.50 MJ/h). That
energy to operate the booth must be provided by the combustion of fossil fuels in many
geographical locations in the U. S., resulting in the generation of combustion pollution to support
process.
The demonstration represented not only a pollution prevention opportunity but also an economic
opportunity Over the 6-hour, 100-day period the projected energy cost savings are as much as
$91,000 per year. Although the energy and economic savings vary depending on the air-
conditioning requirements and the time of booth usage, any reduction in the air throughput will
reduce the burden on the local utility to produce the power to support the painting operation. In
addition, the reduction of makeup air flow results in a corresponding reduction in ventilation
equipment capital cost. Therefore, modifying the processing equipment can prevent pollution,
although not necessarily at the production site.
The painting facility design concept has been applied to a number of DoD facilities and is
presently used, being considered, or planned for installation at painting facilities throughout the
U.S. military services. These include both paint spray booths and an expansion of the concept to
include aircraft paint hangers. In the case of the aircraft paint hanger, at least two military and
three commercial facilities have been constructed, with additional facilities under consideration
at this time.
Summary
The NMP surface cleaning and spray booth development programs represent only two of a
number of joint R&D efforts which have benefitted both DoD and EPA. Not only did the
cooperative research and engineering development result in cost savings for conducting R&D
programs by the agencies, but it provides tangible technology benefits to both parties. They
identified to DoD viable pollution reduction concepts and strategies that can be applied to
numerous DOD maintenance facilities throughout the world. Because of EPA's involvement,
the requirements regarding the distribution and disposition of pollutants are considered early in
the design and development stages of the concepts. Thus, the manufacturing processes and
equipment design become an integral part of the resulting pollution control strategy.
The joint R&D efforts provided EPA scientists and engineers the opportunity to research, design,
develop, build, operate, and evaluate innovative and emerging pollution prevention technology
concepts in an industrial environment. The programs were carried out in a real world production
scenario as provided by the military production and maintenance facilities which mimic
commercial operations to a significant degree. These and other programs help appraise and
validate technically and economically viable technologies to meet pollution reduction goals of
the Agency.
As a cooperative effort, production rates, schedules, and procedures can be negotiated and
modified for the purpose of the research without impacting the general work routine of the
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facility. Thus, the results can typically be transferred to commercial industry with assurance that
the developments, demonstrations, and evaluations were conducted in a similar production
scenario. The results of the studies resulted in a win, win scenario for each of the participating
agencies.
References
1.	Material Safety Data Sheet No. M7114, N-methyl Pyrrolidone, Mallinckrodt Baker, Inc.,
January 17, 1999, http://www.jtbaker.com/msds/.
2.	Whitfield, J. K., Ramsey, G. H., Adams, N. H., Nunez, C. M., and Gillum, D. E.
Demonstration of n-methyl pyrrolidone (NMP) as a pollution prevention alternative to
paint stripping with methylene chloride; Journal of Cleaner Production, 1999; Vol. 7, pp
331-330.
3.	Material Safety Data Sheet No. AG09956-5, Methylene Chloride, American Cyanamid
Co., June 2, 1997, http://siri.uvm.edu/msds/.
4.	Elion, J.M., Flanagan, J.B., Turner, J.H., Hanley, J.T., and Hill, E.A. Pollution Prevention
Demonstration and Evaluation of Paint Application Equipment and Alternatives to
Methylene Chloride and Methyl Ethyl Ketone; Air Pollution Prevention and Control
Division, Research Triangle Park, NC, EPA-600/R-96-117 (NTIS PB97-104632),
September 1996.
5.	Nizich, S.V., Pierce, T., Pope, A.A., Carlson, P., and Barnhard, B. National Air Pollutant
Emission Trends: 1900-1996; Office of Air Quality Planning and Standards, Research
Triangle Park, NC. EPA-454/R-97-011 (NTIS PB98-153158), December 1997.
6.	Darvin, C.H. Stratification of Particulate and VOC Pollutants in Horizontal Flow Paint
Spray Booths; proceedings, 14Ih Annual Army Environmental R&D Symposium,
Williamsburg, VA, CETHA-TE-TR-80055. November 1989.
7.	Ayer, J., and Proffitt, D. Demonstration of a Paint Spray Booth Emission Control Strategy
Using Recirculation/Partitioning and UV/Ozone Pollutant Emission Control, Volume 1;
Air Pollution Prevention and Control Division, Research Triangle Park, NC. EPA-600/R-
98-016a (NTIS PB98-124316), February 1998.
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TVTt>TV/roT DTD td aqa TECHNICAL REPORT DATA
IN rU-Vi rU-<_ tti ir to *± (Please read Instructions on the reverse before completing)
1. REPORT NO. 2.
EPA/600/A-00/038
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Process and Equipment Changes for Cleaner
Production in Federal Facilities
5. REPORT DATE
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
L.G.Jones and C. H. Darvin (EPA), and E.Hall (RTI)
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Research Triangle Institute
P. O. Box 12194
Research Triangle Park, North Carolina 27709
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-D4-0120
12. SPONSORING AGENCY NAME AND ADORESS
EPA, Office of Research and Development
Air Pollution Prevention and Control Division
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Published paper; 9/93-2/98
14. SPONSORING AGENCY CODE
EPA/600/13
15.supplementary notes ^PPCD project officer is Charles H. Darvin, Mail Drop 61, 919/
541-7633. For presentation at AWMA meeting, Salt Lake City, UT, 6/18-22/00.
16. abstract"j*paper discusses process and equipment changes for cleaner production
in federal facilities. During the 1990s, DoD and EPA conducted joint research and
development, aimed at reducing the discharge of hazardous and toxic pollutants
from military production and maintenance facilities. Two significant manufacturing
processes that have received a great deal of attention in these joint efforts, are sur-
face cleaning and coating. Both tend to produce multimedia polluation, including
water, solid waste, and air pollution. Major research has been conducted to reduce
or eliminate the multimedia discharges from these industrial processes. Pollution
control has not only a technology component but also an economic component which
must be considered when developing viable and efficient pollutant reduction technolo-
gies. Both the technology and the economic issues drive the application and accep-
tance of a given technology concept.
17. KEY WORDS AND DOCUMENT ANALYSIS
a. DESCRIPTORS
b.IDENTIF1ERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Prevention
Cleaning
Cleaning Agents
Toxicity
Stationary Sources
Pollution Prevention
Pyrrolidones
13 B
14G
13H
11K
06T
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)

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