REDUCTION OF HAZARDOUS WASTE AND CHEMICAL USAGE BY A LITHOGRAPHIC PRINTER
SUMMARY
A lithographic printing company in Atlanta, GA installed a rag centrifuge and solvent recovery still to recover blanket wash. The system recovers ten gallons per day saving $12,900 annually.
BACKGROUND
The printer is a medium sized company employing approximately 150 people. Press cleaning is done by hand wiping blankets and rollers on the cold set presses with rags. Approximately 23 gallons of solvent-based blanket wash and about 1,000 rags are used per day. Little free liquid waste is generated from press cleaning; essentially all waste solvent is contained in the rags. The blanket wash has a density of 6.9 pounds per gallon. The volatile organic compound (VOC) content is approximately 6.4 pounds per gallon. Approximately 0.5 pounds per gallon are conditioning and other nonvolatile chemicals.
PROCESS MODIFICATIONS
In 1994, collection and recovery programs were implemented. New safety cans were placed around the presses to collect and reduce drying of rags. A centrifuge and solvent still were also installed. Rags are collected daily and spun in the centrifuge. The spun rags are sent to a laundry for cleaning. The solvent is distilled, generating clean solvent that can be reused for cleaning blankets after adding a conditioning chemical. The conditioning chemical prevents damage to the blanket and is available from Prisco, the manufacturer of the blanket wash, still, and centrifuge. The solvent still only recovers volatile portions of the blanket wash.
RESULTS
Approximately 43 percent of the blanket wash used by the printer is now recovered. The amount of new blanket wash purchased has been reduced, saving almost $13,000 annually. Additional benefits include reduced fugitive emissions and cleaner rags being sent to the laundry, thus reducing water pollution. Some specific information on the amount of solvent recovered and economic payback is provided on the back.
| Number of rags used per day | 1,000 |
| Amount of blanket wash used per day | 23 gallons |
| Amount of solvent recovered from the centrifuge per day | 15 gallons |
| Amount of solvent recovered from distillation unit | 10 gallons |
| Value of distilled blanket wash ($5.00 per gallon) | $50 per day |
| Annual value of distilled blanket wash | $12,900 |
| Cost of centrifuge | $17,000 |
| Cost of still | $4,500 |
| Safety cans | $1,200 |
| Other handling equipment | $5,000 |
| Lab analysis of distilled solvent | $2,500 |
| Total cost | $30,200 |
Simple Payback (total cost/cost saved per year) = $30,200/($12,900/year) = 2.3 years