Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.9 Fabricated metal products 921
Table 14.9.1. Reported solvent releases from the metal fabricating and finishing
facilities in 1993 [Data from Ref. 1]
Solvent Amount, kg/year Solvent Amount, kg/year
acetone 870,400 2-methoxyethanol 22,800
benzene 1,800 methyl ethyl ketone 4,540,000
n-butyl alcohol 495,000 methyl isobutyl ketone 934,000
sec-butyl alcohol 13,600 tetrachloroethylene 844,000
cyclohexanone 303,000 toluene 3,015,000
1,2-dichlorobenzene 10,900 1,1,1-trichloroethane 2,889,000
dichlorofluoromethane 10,800 trichloroethylene 3,187,000
dichloromethane 1,350,000 trichlorofluoromethane 82,000
ethylbenzene 299,000 1,2,4-trimethylbenzene 262,000
ethylene glycol 99,000 xylene (mixture) 4,814,000
2-ethoxy ethanol 18,600 m-xylene 8,800
isopropyl alcohol 23,400 o-xylene 17,000
methanol 199,000 p-xylene 10
Figure 14.9.1 shows a schematic diagram of the operations in a fabricated metal products
manufacturing process. 1 The diagram shows that solvent emissions, waste waters, and solid
wastes are produced from three operations: the metal cutting and forming process, metal
cleaning, and painting. In metal cutting and forming the major solvents used are
1,1,1-trichloethane, acetone, toluene, and xylene. In surface cleaning, the straight solvents
are used for cleaning or some solvents such as kerosene or glycols are emulsified in water
and the emulsion is used for cleaning. When emulsions are used the amount of solvent is
decreased. Solvents are released due to evaporation, volatilization during storage, and
direct ventilation of fumes. Waste waters are generated from rinse waters. These waste waters
are typically cleaned on-site by conventional hydroxide precipitation. Solid wastes are
generated from waste water cleaning sludge, still bottoms, cleaning tank residues, and
machining fluid residues. In painting, two methods are used: spray painting and
electrodeposition. Painting operations release benzene, methyl ethyl ketone, methyl
isobutyl ketone, toluene, and xylene. Paint cleanup operations also contribute to emissions
and waste generation. The predominant solvents used for equipment cleaning are tetrachloride,
dichloromethane, 1,1,1-trichloroethane, and perchloroethylene. Sources of solid and
liquid waste include components of emission controlling devices (e.g., paint booth
collection system and ventilation filters), equipment washing, paint disposal, overspray,
and excess paint discarded after expiration of paint’s shelf-life.
Table 14.9.1 shows reported solvent releases from metal fabricating and finishing facilities
and Table 14.9.2 shows reported solvent transfers from the same industry.
Xylene, methyl ethyl ketone, trichloroethylene, 1,1,1-trichloroethane, and
dichloromethane are released in the largest quantities. Methyl ethyl ketone, xylene, toluene,