| Brass, Copper, and Stainless Steel Pickling without using Nitric and Chromic Acids | Italy | 1992 | Full scale |
MANUFACTURE OF FABRICATED METAL PRODUCTS # 21
Background
Industrial brass and copper articles must be treated to eliminate superficial layers of oxide to give them a permanent smart appearance. In the traditional pickling technology, nitric and chromic acid are used with high atmospheric (NOx) and water (metal, nitrate, chromate) pollution hazards. In addition to waste streams treatment before release, gas and liquid disposal costs are also high. An alternative chemical pickling process, using organic peroxides was developed in 1992. It can be set up without plant modification, it is easy to operate and cost and quality effective. The technology is applicable to stainless steel coils, wire rods, tube, and in the treatment of stainless steel.
Cleaner Production Principle
Material substitution; Process modification; Recovery, Reuse and Recycle
Cleaner Production Application
This case study, illustrates a technology that makes use of organic peroxides for brass, copper and stainless steel pickling, lustering and surface passivation. Nitric and chromic acid are then eliminated with a consequent reduction of atmospheric emissions of NOx and elimination of NO3- and CrO4- ions in the waste water. Besides, simplifying the liquid waste purification, the technology makes the water processed reusable and therefore closes the loop. The electrolytic process can be applied to the recovery of metals contained in water out-streams. It has been in operation since 1987.
Environmental and Economic Benefits
The main cleaner production benefits are:
| elimination of atmospheric pollution NOx from nitric acid reaction; |
| cleaner pickling reaction, hazardous material (100 tons/yr of nitric acid and 5 tons/yr are of chromic acid) are replaced by peroxides; |
| sludges reduced to 1/3; |
| closed loop recycling: purified output streams can be recycled to the pickling bath; and |
| resource conservation: less water, reagents, and energy consumption. |
Regarding investment costs, the plant, though designed for the traditional technology, notes that it can manage the new process without modifications. Hence, further investment costs were not necessary for the implementation of the technology.
Considering the cost of the product, treatment, and of loss of metals, the traditional pickling using nitric and chromic acid ran about 100 lire/kilo and using the new technology costs ran 35 lire/kilo.
Constraints
None reported.
Contacts
Review Status
This case study was submitted to UNEP IE in 1994 by Italy's ENEA. It was reviewed and edited by UNEP IE in July 1995.
Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.