new recycling de zincing process

Australia-based scrap metal recycler CMA Corp. and German machinery manufacturer Scholz AG have developed unique recycling equipment for the "environmentally friendly removal" of zinc from galvanized steels. Use of the patented Meretec Technology is being tested at CMA plant in East Chicago, Ind., and Melbourne, Australia.

The partners say the Meretec technology, developed in the U.S. and England and purchased last year by CMA, represents a significant world breakthrough" in the recycling of zinc-coated galvanized steel that is used widely in applications where rust resistance is needed.

A CMA statement says some steelmaking plants and most foundries can't tolerate zinc in their steel scrap feeds. Yet, an estimated 9 million metric tons of galvanized steel is produced annually. The plan is to use the Meretec process at the pilot plants to recycle enough steel to 3,000 metric tons of hazardous waste (zinc and other coating contaminants) annually. At full capacity, each Meretec plant is expected to recycle 120,000 metric tons of galvanized steel and generate 2,000 metric tons of high grade zinc powder and 118,000 metric tons of clean black steel. A press release says the Meretec technology is a six-step de-zincing process:
1. Shredding: Galvanized scrap from the auto and building industries plus end of life coated products are pulverized into fist sized pieces.
2. Removing the zinc coating: The steel is added to the reactor drum where hot caustic washes the coating from steel.
3. Washing: The steel is washed and a rust inhibitor added to produce, clean melt stock ready for foundries.
4. Purification process: The solution is purified to remove dirt and elements limiting zinc recovery.
5. Electro winning: The solution is electroplated in cells where the zinc is grown and harvested. The solution is returned via the evaporator to the drum and is washed.
6. Separation, washing, packing: The zinc is sent to a centrifuge and drier for drying and packaging.
CMA says each ton of galvanized steel de-zinced by Meretec and recycled saves more than one ton of iron ore, 0.635 metric ton of coal, 0.055 metric ton of limestone and 0.020 metric tons of fresh zinc.