GEORGIA TECH RESEARCH INSTITUTE ENVIRONMENTAL SCIENCE AND TECHNOLOGY LABORATORY POLLUTION PREVENTION PROJECT

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Quentin Townsend
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1 GEORGIA TECH RESEARCH INSTITUTE ENVIRONMENTAL SCIENCE AND TECHNOLOGY LABORATORY POLLUTION PREVENTION PROJECT Company: Contact: Primary Products: PPG Industries 1377 Oakleigh Drive Marvin Branch Waste Reduction Coordinator House Paints Heavy Duty Maintenance Paints Wastes Generated 1. Wash solvent contaminated with pigments containing heavy metals from rinsing stationary tanks, filling equipment, and grinding equipment. 2. Spent filter cartridges 3. Paint wastes such as off-specification paint and obsolete materials 4. Bag-house dust Spent caustic cleaning solution sludge Empty bags, off-specification containers, and emptied containers from paint which had to be reworked - Non-Hazardous This plant manufactures all of its products in individual batches, and as a result, generates a variety of hazardous and non-hazardous wastes in their operations. Tank and equipment cleaning is the principal source of waste generated in batch formulation. In this particular plant another significant waste stream is bag-house dust. This dust is presently collected and mixed with other paint wastes which are subsequently incinerated off-site. Approximately 25,000 gal/month of wash solvent composed of a variety of chemicals including toluene, xylene, methyl ethyl ketone, and methyl isobutyl ketone are sent off-site to a local reclaimer. Q-1

2 Approximately 200 lbs/week of bag-house dust which may be contaminated with heavy metal pigments are mixed with the paint wastes. This dust may contain lead, barium, chromium, and cadmium and must be considered hazardous. The pigments currently cannot be reincorporated into subsequent paint batches because of contaminants, possibly dirt and gelled resins. Analysis Results for Bag-house Dust Sample: Two different drums Drum 1 Analysis Phase CaSiO 3 / Wollastonite SiO 2, / Quartz CaO (Zn, Ca) Al 2 P 2 H 6 O 12 3H 2 0 Ti0 2 /Rutile C 4 H 4 O 5 Pb/lead acetate UCS for Mg,S,Cl,K,Cr,Mn,Zr,Fe * Weight % major trace Drum 2 Analysis Phase SiO 2 /Quartz Zn TiO 2 /Rutile ZnO CaCO 3 /Calcite CaAl 2 Si 2 O 8 4H 2 O/Gismondine CaFeO 2 PbO/Litharge Weight % major trace trace * Unidentified Crystalline Species Q-2

3 Process Description PPG produces batches of oil-based paints and water-based paints. This plant produces approximately six million gallons of paint per year. The processes for both types of paints are generally similar, although the raw materials vary. The major production difference is the carrying agent: oil-based paints are dispersed in a solvent mixture, while water-based paints are dispersed in water with a surfactant as the dispersing agent. The three major steps involved in the paint manufacturing process are (1) mixing and grinding of raw materials, (2) tinting and thinning, and (3) filling operations. Pigments and additives are purchased in bags and are added manually to the mixing tank. Solvents are pumped into the tank directly from bulk storage containers outside. In most cases grinding and mixing are performed in one production step. For specialty paints, the material is sent to a grinder which contains fine glass beads which disperse pigment to the proper particle size. Vents from the dispersing units capture dust and the empty bags. Empty bags are removed and collected to be compacted. Dust is collected by using a bag-house. The paint is transferred to a holding tank and analyzed. The composition is adjusted as necessary to meet the required specifications for the type of paint being produced. The paint is then filtered to remove any undispersed pigment and foreign particles and is then transferred to a filling operation and dispensed into labeled cans. The cans are placed on pallets and moved into a storage area. Portable tanks are cleaned with a portable cleaning machine which utilizes high pressure nozzles. The equipment holds up to 200 gallons of solvent, but typically only 75 gallons are used. One tank per batch of solvent can be used to clean several tanks. The used solvent from this operation is sent to the appropriate waste storage tank. Stationary holding tanks are cleaned when the subsequent batch to be manufactured is of a different type of material. Spent solvents used to clean tanks and filling equipment are separated depending on whether they can or cannot be reused in a paint formulation. Solvent which cannot be reused is sent to an off-site reclaimer. Solvent which can be reused is kept in three different tanks, depending on the product into which it will go: (1) reds and browns, (2) gray, or (3) white. Wash water is kept in a fourth tank, to be reused in the next batch of latex paint. This segregation of reusable solvent allows it to be used in a larger number of products and, therefore, increases the percentage of wash solvent which is reused. It may also reduce problems associated with potential pigment interactions which result in material settling in the bottom of the wash solvent tanks. Q-3

5 Plant Efforts to Reduce Waste Organizational. The plant has a full-time employee responsible for evaluating pollution prevention options. Wash Solvents. Wash solvent from mixing tanks is incorporated as part of the, solvent requirement for the batch of paint being manufactured.. Where possible, the wash solvent from cleaning holding tanks and filling equipment is collected and used in the next compatible batch of paint as part of the formulation.. A portable tank cleaning machine has replaced the daily cleaning with caustic cleaning solution. The use of caustic solution has been reduced to cleaning each tank once a year. This caustic solution is settled, decanted, and reused.. One more tank was added to the three tanks in the wash recovery system in order to segregate reds and browns from gray. Because of the additional color separation, the wash can be incorporated into a larger number of products, which allows for a larger percentage of the wash to be reused.. Solvents used to clean pull-off tanks are incorporated into the batch. Paint-related Wastes. Pull-off, overruns, and customer returns are worked back into new batches of paint.. Quality control samples are reused in compatible batches.

6 Equipment Modifications. Tanks were modified to completely purge equipment. Flat bottoms were converted to cone-shaped surfaces to remove material more efficiently.. Mechanical pumps were changed to more efficient air pumps.. Wire screen filtering equipment is being installed in order to slowly eliminate. the use of filter bags and cartridges. The wire screen filters can be reused almost indefinitely because they are backwashable. Bag-house Dust. Bag-house dust was used to produce a gray deck enamel but paint proved to be unsatisfactory. The contaminants produced a rough finish. Water. The latex paint has a closed system for water which results in zero discharge. All water from the production of latex paints is reused. Therefore, no process water is discharged from this facility. Recommendations Source Reduction Batch Sequencing Batches should be scheduled in such a way that compatible paints are produced consecutively. This could mean the elimination of an intermediate cleaning step in some cases. Waste Documentation Computerized waste documentation can help track the wastes in the process and can be used to manage solvents that have to be segregated or stored for reuse or distillation. Additional Stock Keeping Units (SKUs) in the plant s current computerized inventory control system could be determined in order to track wastes. Q-6

7 Dedicated Bag-house System for Pigment Loading Area Recycling/Reuse Since all pigment dusts are mixed, the pigments cannot be recycled to the process that generated them. Due to the system already in place, this option is not economically feasible at present but may be considered as an option in the future if replacement is necessary. Note that, even if this system was implemented, it may not solve the problem of contaminants (dirt and gelled resins) in the dust which restrict the reuse of the dust. On-site Distillation of Wash Solvent On-site reclamation has the following benefits:. The transportation of the wastes and the associated risks are minimized because less waste leaves the facility.. More control over the purity of the reclaimed solvent.. Even though the distillation residues require off-site incineration, the fact that the waste volume is considerably reduced, decreases off-site disposal costs. The following conditions must be satisfied before the distillation unit is purchased and installed:. The still should meet technical requirements for reclaiming solvents which have a wide variety of boiling points.. The economics of on-site distillation must be proven to be favorable. This analysis should include technical personnel to operate the still.. The measure should be proven to be an environmentally safer option (short term and long term) compared to the presently employed offsite recycling. Q-7

8 A more detailed analysis of the types of solvents used should be performed b and cost and performance data should be obtained from vendors to determine the technical and economic feasibility of this option. Enclosed is a list of suppliers of distillation equipment and some of their brochures. Some of the difficulties that might be encountered are:. Loss of solvent during distillation process. Low solvent recovery efficiency. Installation problems. Maintenance problems. Permitting If it is not feasible to install and use a solvent recovery unit, it may become feasible to employ the services of an on-site recycling company. Enclosed is information on two companies that provide such services. Separate Gelled Particles from Bag-house Dust A Particle Size Analysis (ASTM D422-63) should be performed to determine what type of equipment is necessary to achieve this separation. Particle Size Analysis is a quantitative determination of a material s particle size distribution and is broadly used in engineering classification of materials. Cyclones can be used to separate solid particles from an air stream and customized cyclones to selectively remove particles of above a certain size can be designed. Even though cyclones are very effective, this customized system may be very expensive. One separation method that may be of particular interest is a vibro-separator. The vibration motion is based on a principle in which motor rotation imparts vibration to an entire screen assembly in both vertical and horizontal planes. These separators are very effective in separating solid material accurately up to five different sizes with a single separator.

9 The following are suppliers of vibrating screens which may be contacted for b further information: 1. Macon Wire, Inc Joycliff Road Macon, Georgia l Contact: Steve Dew (Brochure Enclosed) 2. SWECO, Inc New Buffington Road Florence, KY (606) Analyze Settled Material in Wash Solvent If new procedures initiated by the plant do not eliminate settling, the material should be analyzed to determine its composition. If the analysis indicates that it is primarily pigment, companies that produce sealers, deadners and adhesives that may be interested in using the pigment as filler should be contacted. If it is concluded that the material is primarily resin, the source should be determined before appropriate measures could be taken. Determine if Bag-house Dust Could be Used as a Filler Waste Exchanges could be contacted to locate companies that may be interested in using the bag-house dust as a raw material even though it is hazardous. Waste could be advertised in a Waste Exchange magazine. The following are Waste Exchange Addresses: Southeast Waste Exchange UNCC Station Urban Institute University of North Carolina at Charlotte Charlotte, NC (704) Contact: Maxie May

10 Southern Waste Information Exchange (SWIX) Florida State University/CBTR Institute of Science and Public Affairs Tallahassee, FL (904) Contact: Dr. Roy Herndon Bibliography On-Site Solvent Recovery, American Machinist & Automated Manufacturing, May 1987, p.75. DEWCO Vibro-separators Brochure obtained through Macon Wire, Inc., Macon, GA Guides to Pollution: The Paint Manufacturing Industry. Jacobs Engineering Group, Inc., Pasadena, California. EPA/625/7-90/005. June Guide to Solvent Reduction Alternatives. Toxic Substances Control Division, California Department of Health Services, Los Angeles, California. October Considerations For Selecting a Still for On-Site Recycling. Minnesota Technical Assistance Program MnTap), Minneapolis, MN. March Stabilization/Solidification of CERCLA and RCRA Wastes, EPA/625/6-89/022. U.S. Environmental Protection Agency. Cincinnati, OH. May p. 4-l. Waste Minimization in Metals Parts Cleaning. EPA/530-SW U.S. Environmental Protection Agency. Washington. DC. August p.27.

Hazardous waste management methods that are affordable and. relatively simple to implement are often overlooked as

Hazardous waste management methods that are affordable and. relatively simple to implement are often overlooked as PRACTICAL METHODS FOR HAURWUS WASTE IIANACEMENT IN TYPICAL Sue Sullivan, MPH McLaren Environmental Engineering 2855 S. Pullman Street Santa Ana, California 92705 (714) 756-2667 ABSTIUCT Hazardous waste