The New Process

The pollution control system that is integrated into the manufacturing process consists of three basic steps:

1. The regeneration and copper recovery system for the primary pickle bath

2. The chemical rinse system

3. The use of hydrogen peroxide plus proprietary additives for the secondary pickle.

Figure 1.1 illustrates the final process. Block A shows the work flow through the new system. After the hot sulfuric acid pickle and the secondary pickle of 2.5% hydrogen peroxide in sulfuric acid, the work passes through a chemical rinse step that neutralizes the acid dragout. It also precipitates any copper salts by reduction of cupric (Cu2+) ions to cuprous (Cu+) ions, which are insoluble at the pH of the chemical rinse. The work then goes to a cold rinse using city water, a hot rinse using deionized water, and finally a lubricant bath prior to the drawing operation.

Block B shows the electrolytic copper recovery cell, which recovers metallic copper and regenerates sulfuric acid from the metal salts in the hot sulfuric acid pickle solution. It was originally felt that trace metals (zinc, tin, lead) would interfere with the recovery of pure copper. By controlling current density at 50 to 100 A/m2, however, pure copper can be recovered while maintaining the copper concentration in the pickle bath at 15 g/L.

The secondary pickle reservoir is also shown in Block B. Copper sulfate accumulates in this bath and eventually crystallizes out. These crystals can be recovered and sold as a copper-rich sludge or added to the electrolytic copper recovery loop.

The chemical rinse reservoir is maintained at the proper pH and composition by the addition of caustic, sodium carbonate, and a reducing agent, in this case hydrazine. The sludge draw off along with the flow from the floor spill neutralization first goes to a sludge filter to recover salvage copper sludge and then to a final sump for discharge.

The rinse flows go to a pH adjustment tank, a settling tank, and finally to the rinsewater sump, where the bulk of the flow is recirculated to the first water rinse tank.

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