Cleaner Production

The pollution prevention audit started with an analysis of the material flow in the degreasing process. It was shown that by better housekeeping, the need for trichloroethylene degreasing could be reduced by 50%, but this has now been cut to zero. The cutting of aluminum sheets required cutting fluids, which were difficult to remove without the use of chlorinated solvents. A change to biodegradable cutting oils allowed an alkaline degreasing procedure in place of the previous trichloroethylene method.

The degreasing is carried out in a new piece of equipment in the form of a totally enclosed tunnel, 30 m long. The metal products are suspended from an overhead conveyor and then pass through five zones where they are sprayed with various liquids (Figure 1.10). The stages carried out are degreas-ing, water rinse, iron phosphating to aid the adherence of the paint, water rinse, a deionized water rinse, and drying. The liquid runs off the metal items into tanks below, where it is recirculated back to the spray nozzles.

Electrostatic powder painting uses polymer-based paints that do not have any solvent in their formulation. A long-term problem was changing to a different color of paint. This is now accomplished by changing the whole module with containers of different colors. The company has now installed a new electrostatic powder painting line having 12 automatic powder guns. The paint is positively charged relative to the metal items. Now only 5% of the colors have organic solvents and are used only for the painting of short production runs in special colors or for retouching of the automatically sprayed items where necessary. Manual spraying is carried out in a ventilated booth fitted with two electrostatic guns.

NEW DEGREASING PROCESS

Fixed nozzles

NEW DEGREASING PROCESS

Fixed nozzles

Eisenphosphatierung

Recirculating tanks

5. Deionizing water rinse

4. Cold water rinse

3. Iron phosphating

2. Cold water rinse

1. Alkaline degrease

FIGURE 1.10 Schematic of the new degreasing process. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)

Recirculating tanks

5. Deionizing water rinse

4. Cold water rinse

3. Iron phosphating

2. Cold water rinse

1. Alkaline degrease

FIGURE 1.10 Schematic of the new degreasing process. (From Wang, L.K. et al. Case Studies of Cleaner Production and Site Remediation, Training Manual DTT-5-4-95, United Nations Industrial Development Organization, Industrial Sectors and Environment Division, Vienna, Austria, April 1995.)

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