1. DC Submerged Arc Furnace (SAF)

DC Submerged Arc Furnace (SAF)

The DC furnace is ideally suited for efficient reduction of both high and low-grade fine ores, using readily available reductants like fine coal and anthracite. Since fine raw materials can be fed directly into a DC furnace, no additional agglomeration facility is needed.

 

Tenova Pyromet is a world leading company in the design and supply of Direct Current (DC) Furnaces for the production of ferroalloys.

The open-bath operation and control philosophy of a DC furnace permits a rapid response to operational changes and fast, consistent control of product quality. A further attribute of a DC arc furnace is the use of a graphite electrode in an open-bath configuration, enabling the furnace to be switched off at short notice and switched on again several hours later , without fear of electrode breakages.

At a time of energy shortages, when both compulsory and voluntary load shedding is becoming a way of life, this is a highly significant operating cost benefit.

Currently, DC arc smelting furnaces ranging in size from 10 MW to 60 MW are in operation for ferroalloy production. Compared to other types of furnace, they have proved to be cost-effective producers. Detailed designs have been completed for DC furnaces, with capacities of 70 MW and higher.Tenova Pyromet is a leading designer and supplier of high-capacity electric submerged-arc smelting furnaces and complete smelting plants for the production of ferroalloys, base metals, slag cleaning and alloy refining.

Tenova, through an exclusive co-operation agreement with GLPS Project Management & Engineering Services, offers the ferroalloy industry DC furnace technology for the smelting of high and low-grade ores, using readily available reductants, such as fine coal and anthracite. Since fine ores can be fed directly into a DC furnace, without the need to conglomerate the ore, this reduces the cost through obviating the need to prepare the material before it can be smelted. Expensive metallurgical coke is not required as a reductant, further reducing the operating cost of the furnace. The reductants used in the process ensure an off-gas that is ideal for use in co-generation plants. The open bath operation and control philosophy of a DC furnace permits rapid response to operational changes and fast, consistent control of product quality.

The DC arc furnace uses a graphite electrode in an open-bath configuration, enabling the furnace to be switched off at short notice and on again, several hours later, without electrode breakages.

DC arc smelting furnaces ranging in size from 10 MW to 60 MW are in operation for ferroalloy production, with detailed designs completed for DC furnaces with capacities of 70 MW and higher

  • Efficiency

    Efficiency

    • Use of fines feed. Fine ores are often of high chemical quality. Extreme fines such as UG2 tailings and baghouse dust can also easily be processed. Since fine ores can be used, there is no need to install expensive plant to conglomerate the ore, before feeding to the furnace.
    • Use of readily available, lower-cost reductants. Coke is not required as a reductant. Consequently, plant operating costs are substantially lower and readily available coal and anthracite can be used.
    • Strong reducing conditions inside the furnace for high product recovery and low sulfur levels. A higher average chrome content in the final product is still possible, even if lower grade raw materials are used. Rapid reaction times due to open-bath operation and direct materials feed into molten bath.
    • Improved control of product grades due to faster reaction times.
    • High tapping temperatures and use of two launders (metal & slag separate) ensure clean alloy and no metal in slag, as well as higher overall recovery.
    • Use of coal and anthracite produces furnace off-gas for electrical power co-generation.
    • Proven high-reliability DC transformer/rectifier system.
  • Environment

    Environment

    • For ferrochrome operations, the off-gas dust contains no hexavalent chrome, thanks to high reducing conditions. This eliminates a major environmental hazard.
  • Value for Money

    Value for Money

    • Currently, DC arc smelting furnaces ranging in size from 10 MW to 60 MW are in operation for ferroalloy production. Compared to other types of furnace, they have proved to be cost-effective producers. Detailed designs have been completed for DC furnaces, with capacities of 70 MW and higher.

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References

  • Yunnan Xinli DC Furnace

    Customer
    Project name
    Yunnan Xinli Nonferrous Metals
    China
    2009

    "Xinli’s furnace is the fifth commercial-scale DC furnace facility for the production of TiO2 slag built world-wide. Given the benefits offered by DC furnaces it is likely that this technology will play an increasingly important role in the future of TiO2 slag production for new smelter plants. A lot of interest is being expressed in this technology from new and existing producers, particularly in China, India and Vietnam."

    The plant comprises one 30MW DC furnace with a single graphite electrode and conductive bottom anode. The furnace off-gas is cooled and cleaned in a wet scrubber, and re-used in other parts of the plant. Upstream of the furnace, the ilmenite and anthracite are dried in fluid bed driers fuelled by furnace gas. The feed of ilmenite and anthracite to the furnace is independently and continuously controlled by accurate feed control systems. The mixed feed is then introduced to the furnace via a hollow electrode and/or peripheral feed chutes.

    The furnace is operated with an open-bath (no unreacted burden) and open-arc. Slag is tapped intermittently into 15 ton slag pots and left to solidify and cool before crushing and milling. Iron is tapped intermittently into 35 ton ladles and then desulphurised and re-carburised before being cast into saleable 7kg ingots drying ilmenite feedstock and crushed slag product.

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Smelters

Tenova Pyromet has in-depth knowledge and understanding of the ferroalloys and base metals smelting process and its technology is applied to a wide range of customer solutions. The company has an extensive reference list of successful projects and applies this technology to the benefit of ferroalloy and base metals customers world-wide.