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Flash Smelting and Flash Converting

Outotec® Flash Smelting Process combined with Kennecott-Outotec® Flash Converting Process is an integrated smelting solution resulting in low investment and operating costs with the most effective emission control.

The Kennecott-Outotec® Flash Converting process is the result of successful development work carried out jointly by Kennecott Utah Copper Corporation and Outotec. The process is an innovative application of the Outotec® Flash Smelting technology.

Compared to the conventional copper smelting route, the Flash Smelting-Flash Converting concept provides several advantages such as:

  • High recovery of copper and other valuable metals
  • Low investment and operating costs for smelter and acid plant
  • Continuous process, since smelting and converting are decoupled, resulting in high on-line availability
  • High sulfur recovery, only one continuous high strength SO2 stream to the acid plant
  • Improved in-plant hygiene, compact equipment, no ladle transportation of molten materials

Today Outotec® Flash Smelting has achieved a clear leading position as the world’s number one primary copper smelting technology.

Outotec® Flash Smelting

The Flash Smelting process is based on utilization of the feed material’s internal energy for smelting. Finely ground sulfidic copper concentrate is mixed with oxygen-enriched air to form a rapidly reacting suspension in the reaction shaft of the Outotec®Flash Smelting Furnace. Sulfide compounds of the feed ignite, oxidize and release heat, acting as a fuel for the process and no external energy is needed for smelting. In the settler of the furnace, molten droplets separate from the gas stream and settle at the bottom of the furnace as distinct matte and slag layers, based on their specific densities.

The molten high-grade matte produced in the Flash Smelting Furnace is led through covered launders directly to granulation, where the matte is dispersed and granulated by means of high-pressure water jets. The Flash Smelting slag is directed to a slag cleaning furnace or slag concentrator for copper recovery. The matte granules are ground into a grain size suitable for completing the oxidation reactions in the Flash Converting Furnace.

Kennecott - Outotec® Flash Converting

The Kennecott -Outotec® Flash Converting Process is very similar to the Outotec® Flash Smelting process. The oxidation of matte proceeds under highly oxidizing conditions so that the sulfidic matte converts to metallic copper. For oxidation of fine matte particles, high oxygen enrichment or even pure technical oxygen can be used. The Flash Converting Furnace can operate autogenously even with high matte grades without using additional fossil fuels.

The sulfur content of blister copper is controlled by the oxygen-to-matte ratio in the feed. Either silica or lime-based slag can be used. The copper content of the slag produced in the Flash Converting Furnace is relatively high but its quantity is low. So, it can be fed back into the primary Flash Smelting Furnace directly in granulated form, thus no separate slag treatment is needed.

Blister copper produced in the Flash Converting Furnace contains some sulfur. Final sulfur removal is carried out in anode furnaces by air oxidization.

Flash Smelting and Flash Converting Furnaces produce process gas rich in SO2. As a result of the high oxygen enrichment, the volume of the gas is small. Furnace off-gases are cooled down in the heat recovery boiler, which also collects part of the dust load. The rest of the particulates are captured in the electrostatic precipitator. Normally all dust is recycled back into the furnace. After the cooling and cleaning steps, the gas is directed to the sulfur recovery plant for sulfur recovery.

Outotec provides complete tailored process solutions for customers’ needs. Decades of experience in the supply of Flash Smelting plants have resulted in extensive metallurgical know-how that ensures the most profitable process choice and its optimal performance. Outotec’s life-cycle technology partnership with the customer spans from the early stages of the process solution design all through the supply and commissioning of the entire process chain with integrated process control and holistic service and support concept. Continuous research and development ensure that the customer is provided with the latest advancements in process and equipment solutions.