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 1 ------- 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 2 ------- 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 3 ------- 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 4 ------- 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 5 ------- 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 6 ------- 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 7 ------- 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 8 ------- 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. 9 ------- 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) ------- |