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New approaches benefit China's smelting operations

(China Daily)
Updated: 2008-06-30 14:04

In a previous Alcoa energy column, the global aluminum giant shared with partners and competitors its approaches to reducing emissions created during production processes. This week Alcoa showcases examples of the firm's efforts. Although Alcoa has no smelting operations in China, the company shares approaches that can be used in the Chinese aluminum industry:

Brazil: waste into products

Production wastes from Alcoa's Brazilian refineries and smelters are being diverted from landfills and converted into commercially viable products - minimizing their environmental impact and providing new sources of revenue.

One of Alcoa's key sustainability goals is to have zero landfilled waste by 2015. To help achieve that goal, the company has developed a global framework for evaluating and then commercializing its industrial waste for re-use in other industries. There are six stages to the process - concept development, feasibility and lab work, testing, pilot plant demonstration, plant re-use demonstration and implementation.

In Brazil, Alcoa's department of applications, development and special product sales has made significant progress in converting a number of major refining and smelting wastes into commercial products.

Carbon cryolite, a byproduct of the Soderberg smelting process, is now used as an alternative fuel in cement making. Alcoa's Pocos de Caldas smelter sells about 1,000 metric tons of the material each month, which will allow it to eliminate all of its stored cryolite - which the smelter has not produced since 2003 - by mid-2009.

Since 2004, Pocos de Caldas has been selling all of its aluminum oxide dust, fine particles produced in the refining process, collected from the calciner department at the refinery as an alumina source for the enrichment of chamot - an inexpensive refractory aggregate.

A second application for dust is being developed for the Alcoa smelter in Sao Lus, Brazil, which is located too far from most refractory producers. Sao Lus is currently selling the coal dust generated from its boilers as another alternative fuel source for the cement industry. Almost 12,000 tons of the dust is being diverted from the landfill each year.

The Brazilian locations are also investigating several potential commercial applications for bauxite residue, the largest volume waste of the refining process. They are working closely in this effort with Alcoa's Australian researchers, who are also developing processes to convert the residue into a raw material for a variety of applications. Primary initiatives include converting the residue for use in the ceramic tile, agriculture, and cement industries.

Australia: improved practices

Alcoa is working at its Australian operations to reduce emissions through improvements in technology and operating practices. Since 2002, Alcoa's Point Henry and Portland Aluminium smelters have reduced their fluoride air emissions by 49 percent through improvements in emission management systems, real-time laser-based monitoring technology and operating practices.

The Point Henry smelter reported increased emissions of polycyclic aromatic hydrocarbons (PAHs) in 2005. The facility investigated the reason for the increase and carried out an overhaul of the carbon bake operation. Subsequent monitoring in November 2005 found this work had reduced carbon bake PAH emissions by 75 percent.

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