Metal

Smelting and refining furnace for copper and copper alloys

The new tilting rotary furnace with a single opening and integrated post-combustion of the flue gases reduces emissions of dust, dioxins and total carbon significantly. As it is now also possible to melt scrap metal containing a higher quantity of organic matter, the furnace consumes much less energy.

Summary

Initial situation

KME Germany AG & Co. KG manufactures a wide range of copper and copper alloy products for customers from a large variety of industries at their Osnabrück site.

KME used three rotary furnaces in the copper smelting and refining process. Due to their design, these furnaces produce large quantities of fugitive emissions (dust) and consume high amounts of specific energy, as the hot combustion gases they generate are hardly used for energy within the process.

It was impossible to process material with a higher degree of organic contamination in the rotary furnaces.

The flue gases can only be captured and treated when end-of-pipe technology such as thermal post-combustion is applied.

The aim of the project was to develop a process that offered the following advantages over the best available copper fire-refining technology and to test this on a large scale:

  • A significant reduction in captured and fugitive emissions, and especially in PM10 particles
  • The removal of oxygen from the melt by the injection of gas through porous plugs rather than using the poling method
  • The efficient use of contaminated copper scrap in order to produce copper
  • A post-combustion of pollutants (e.g. organic matter, PCDD/F) that is integrated as far as possible into the process
  • Greater energy efficiency
  • A minimisation of the cost of purifying waste gases

Technical solution and findings

Reduction of emissions:

  • The rotary furnace with two openings was replaced by a tilting rotary furnace with just one opening. Returning the exhaust air across the burner flame makes it possible to capture the flue gases (fugitive emissions) very effectively during the charging and smelting processes
  • Integrated post-combustion: returning the flue gases across the furnace flame helps to reduce the level of pollutants such as organic matter and PCDD/F
  • Substituting the process of green poling with gas poling reduces the proportion of fugitive emissions
  • Operating the burners with pure oxygen instead of ambient air during the smelting phase reduces the quantity of flue gases produced; the higher flame temperature shortens the smelting phase

Energy savings:

  • It is now possible to use about four times the quantity of impure scrap metal than previously and refine it directly as DHP copper; it is no longer necessary to send the scrap metal through a secondary refinery, a less energy-efficient process involving an anode furnace and subsequent electrolysis
  • After commissioning of the refining furnace, specific gas consumption fell by more than 30%

Limitations: Injecting inert gas into the melt to reduce the oxygen content is extremely time-consuming and therefore not economically viable.

Conclusions

As a result of the findings made to date, the refining furnace is mainly used as a smelting unit; used at this stage of the process it is superior to the rotary furnace in terms of both operation and the environment.

Source: Final report

Project Participants

Implementing Institutions

KME Germany AG & Co. KG

More Project Information

Project title: Schmelz- und Raffinationsofen für Kupfer- und Kupferlegierungen

Project number: 20093

Project period: 2008 - 2011

Project region: Germany (Lower Saxony)

Project contact:

Frau Fischer
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+49 (340) 2103 3067
+49 (340) 2104 3067

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Source: Environmental library of the Federal Environment Agency (UBA)