Water
In 2005, the Gerdau Group invested R$ 24.2 million towards preserving Brazil’s water. Water consumption at the Group’s units around the country fell 17%, to 37.5 million cubic meters per year. Water consumption per ton also decreased 12.2%, from 6.21 cubic meters in 2004 to 5.45 cubic meters in 2005.

The Group was able to reduce its consumption by improving the water treatment and recirculation systems. During the year, the water reuse level rose from 95.7% to 95.9%.

This means that only 4.1% of the water used for production came from water basins. Approximately 2% of the water used in the industrial process evaporates and 2% is returned to the rivers after being adequately treated to ensure that it is released into the environment in accordance with the standards set by environmental agencies.  

Water is used mainly during the steelmaking process to cool equipment, a closed-circuit process that allows for the continuous reuse of the natural resource during production. There are two types of cooling systems in use at Gerdau mills. In the first, the water does not mix with the other materials and therefore preserves its physical and chemical characteristics. This is called indirect contact water. Indirect contact water is used to cool the equipment that comes into contact with steel, which is produced at temperatures as high as 1,600ºC (2,900 F). This cooling system includes tanks or pools as well as pumps and cooling towers. When it returns to the first tank, the water has already been cooled down to a temperature of approximately 30ºC (86 F). Special products are added so that the water cools more effectively and also to avoid pipe and equipment oxidation.

The second cooling system is the gray water system, which also operates in a closed tank circuit. When the water comes into direct contact with the steel, a layer of iron oxide (called mill scale) is formed and remains in the water. The mill scale is mechanically removed in a decanter tank and then sent for internal co-processing and reuse by other economic sectors. The water is treated and reused within the production process.

Air
Group investments to reduce atmospheric emissions in the Brazilian facilities totaled R$ 67.4 million.

The main air protection equipment used at Gerdau steel mills is a dust removal system that filters solid particles generated during the steel production process. In 2005, 90,700 tons of particle material was filtered using these systems at the Group’s Brazilian units.

Another 2005 highlight was the installation of the quenching tower at Gerdau Cosigua. This technology boosts the efficiency of the dust removal system and optimizes gas temperature control.