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Multiple hearth furnace

Efficient and flexible calcination with the multiple hearth furnace

Streamline operations via simultaneous multi-stage processing fine-grained material in a multiple hearth furnace (MHF). Ideal for the thermal treatment of fine and mechanically unstable raw materials or tailings, it precisely maintains temperature profiles and retention times to deliver the highest quality product.

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Key benefits of the multiple hearth furnace

  • Process materials with moisture content over 50%

    The design of the MHF – with its multiple stacked round hearths – means it can process raw materials with very high moisture contents without pre-drying, saving time and energy. It’s a significant advantage over rotary kilns used in the same applications, and particularly important when dealing with very fine flotation concentrates and other valuable ores.

  • Precisely control temperature profiles ± 5°C

    Our multiple hearth furnaces allow close monitoring and control of the temperature profile within the individual hearths, reducing energy consumption and delivering optimal control of the process for maximum production and product quality. It's especially beneficial in applications where overheating of the raw materials has a detrimental impact on product quality.

  • Process particle sizes from 0mm to 40mm

    Able to process a broad range of particle sizes, the MHF offers remarkable flexibility in the types of ores and raw materials it can handle. Most notable, however, is its ability to thermally treat very fine materials under tightly controlled atmospheric and temperature conditions, ensuring these materials are processed consistently and correctly.

  • Zero product loss through internal dust recycling

    Despite often processing very fine materials, no material is lost from the multiple hearth furnace, as 100% of the filter dust can be recycled into the process. This ensures excellent production efficiency and zero product losses – a critical advantage over other calcination technologies.

  • Support mine waste valorisation

    Thanks to its ability to process fine and unstable raw materials, our multiple heath furnaces can play a key role in the extraction of valuable ores from previously discarded fine raw materials and tailings.

Our multiple hearth furnace

The multiple hearth furnace is a reliable and versatile technology with over 70 different applications, including calcining industrial minerals, flotation concentrates and filter cakes, thermally treating ores, biomass, and electronic scrap, and producing and reactivating activated carbon. Its multiple stacked hearths create different zones within the cylindrical furnace, each fulfilling a different purpose: from drying and heating through to calcination or oxidisation. Design parameters vary widely according to the specific applications. Systems delivered have included six to 19 hearths, diameters of 4.5m to 7.8m, and operating temperatures up to 1150°C. MHF can also use a variety of liquid and gaseous fuels, including low-calorific gas, and low-carbon alternatives such as hydrogen and electric heating.  

Downloads for the multiple hearth furnace

Frequently asked questions

FAQs for multiple hearth furnace

Multiple hearth furnaces comprise several circular hearths stacked vertically within a cylindrical shell. Material is fed into the top hearth and descends via holes in the hearth bottoms, being progressively dried, heated, and calcined, reoxidised or oxidised, depending on the application. 

Multiple hearth furnaces, or multiple hearth incinerators, are used to thermally treat a wide range of fine or mechanically unstable materials. Applications include roasting ores and reducing metal oxides, producing or reactivation of activated carbon, calcining chemicals and minerals, incinerating sewage sludge and other waste materials, and treating electronic scrap.

Multiple hearth furnaces may be known as Herreshoff furnaces, Herreshoff-Nichols furnaces, Skinner furnaces, or MULTIPOL furnaces.

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