Water jacket furnace (metallurgy)

Last updated

A water jacket furnace is a type of blast furnace used to smelt non-ferrous metallic ores, most typically ores of copper or silver-lead. It takes its name from the water jacket arrangement used to cool the lower furnace casing and prolong the life of the furnace hearth. Nearly entirely replaced, by flash smelting of ore concentrates, the water jacket furnace is now virtually an obsolete technology.

Contents

The terminology is also used for an indirect heating device used in the petroleum oil and gas industry, generally known as a water jacket heater [1] or water bath heater, which should not be confused with the metallurgical water jacket furnace.

History

Water jacket furnaces under construction Mounting copper blast furnaces in a workshop.png
Water jacket furnaces under construction

In the mid 19th Century, most non-ferrous smelting was done using reverberatory furnaces. Blast furnaces were used to smelt sulphide copper ore in the Harz Mountains of Germany. The mines at Burra in South Australia tried to adopt the technology, in 1847, but without success because the German furnace design, using horse-powered bellows to provide the air blast, was not well suited to their carbonate copper ore. [2]

The 'water jacket' blast furnace design arose in North America, during the 1870s, [3] and an alternative name for it, in Australia, was 'American water jacket furnace'. [4] The design evolved from earlier German cupola furnace designs, with the distinguishing innovation being a well-controlled cooling of the furnace shell. [3]

Water jacket furnaces began to be common in the later part of the century, from the 1880s, particularly for smelting sulphide ores. Unlike reverberatory furnaces, water jacket furnaces could be made in a factory and then assembled at site. [3]

Not all situations were well-suited to water jacket furnace operation, and some attempts to use them were costly failures, such as at Burraga [5] and at the Overflow Mine at Bobadah, both in New South Wales. [6] However, the furnaces were hugely successful, when well applied, such as at the vast Anaconda Copper Mine, in Butte, Montana, Mt Lyell Mine in Tasmania, and at many other mines.

Water jacket furnaces only ever partially displaced reverberatory furnaces in the copper industry, until both furnace types were displaced, almost entirely, by flash smelting, between around 1949 and 1980. [7]

Technology and application

Smelting

Small round water jacket furnace for silver-lead ore Water-jacket blast furnace for silver-lead ores.png
Small round water jacket furnace for silver-lead ore

A water jacket furnace could be used to reduce non-ferrous oxide ores mixed with coke, to produce metal, but its main use was smelting the more common sulphide ores. The feedstock was the ore, coke and fluxes. When smelting lead sulphide ores, a water jacket furnace produces molten lead and slag. Lead and silver often occur in the same ore body. Separating silver metal from the crude lead produced by a furnace needed a second process of refining, such as the Parkes process.

The pyrometallurgical process of a water jacket furnace, when smelting copper sulphide ores, is fundamentally different to a conventional blast furnace used to make iron, or a water jacket furnace used to make lead. The conventional blast furnace process produces molten metal by reducing the ore, and separating out the silica as slag. Water jacket furnaces, when smelting sulphide copper ores, used an oxidation reaction that produces molten copper matte, which must be further treated in a convertor (similar in concept to a Bessemer convertor) or reverberatory furnace to produce copper metal. The product of that conversion process is known as blister copper. [3]

The smelting of sulphide ores in a water jacket furnace can be viewed as concentrating the non-ferrous metallic portion of the ore, as matte, and separating out some impurities, such as silica and iron, in the mainly iron silicate slag, and much of the sulphur, as sulphur dioxide in the off-gas. The molten slag and matte separated, with the denser matte accumulating at the bottom of the furnace. [3]

Depending upon the composition of the ore being smelted, the choice of a suitable flux was particularly important. [8] Fluxes used could be limestone, iron oxide, or silica (quartz), depending upon what was needed to create slag and to minimise the loss of copper with that slag. When both 'basic' (oxide or carbonate) ores and 'siliceous' ores were available, feeding the furnaces with a mixture of the two copper ore types reduced the amount of other fluxes needing to be added. [9] [10]

Advantages and disadvantages

Rectangular cross-section water jacket furnace. Water Jacket Furnace (Australian Town & Country Journal, 15 July 1893 p24).jpg
Rectangular cross-section water jacket furnace.

Water jacket furnaces had some advantages over reverberatory furnaces. Fuel consumption was lower. Sulphide ores could be smelted without first roasting the ore. Production per furnace was generally higher. Low grade ore could be smelted, because the water jacket furnace could more readily discharge large amounts of molten slag. Because solidified slag is unsuitable to backfill the voids (stopes) created by underground mining, disposal of large volumes of slag, from smelting of low grade ores, was a significant problem. Some mines treated molten slag with water to create granulated slag, which could be used to backfill stopes. [11] Otherwise, the molten slag was dumped and large slag dumps accumulated near the smelter, becoming a lasting legacy of smelting operations. [12] Smelting of low grade ores became less prevalent, once the froth flotation process was used to produce ore concentrates.

Another advantage of the water jacket furnace was that, while out of service, the bottom of the furnace, if so designed, could be 'dropped' for cleaning it up or for repair. Over time, a significant amount of copper material would accumulate in the bottom of a reverberatory furnace which could not be accessed without effectively demolishing the furnace. [13]

A disadvantage of the water jacket furnace was that it could not handle fine ore well and was so was better suited to lump ore. Fines tended to either choke the furnace or were blown into flue by the air blast. Eventually, the second problem, only, would be solved by capturing the flue dust and recycling it. [3]

An initial disadvantage of the water jacket furnace was its use of coke as fuel. It could not use the cheaper fuels such as firewood or fine raw coal that could be used to fire a reverberatory furnace. That disadvantage was offset by lower overall fuel consumption. In the first years of the 20th Century, the perfection of a technique known as pyritic smelting greatly reduced coke consumption, when smelting suitable ores such as chalcopyrite, by optimizing the use of the sulphur in the ore itself, as a fuel. [14]

Water jacket furnaces needed blowers and a cooling water supply, and were more complex to build and operate than the reverberatory furnaces. Water jacket furnaces, like other blast furnaces, are best operated continuously, and smelters that used them had to work continuously too.

Differences from conventional blast furnace

The design of water jacket furnaces differ from the conventional blast furnaces used for smelting iron ore, which use a hot blast. Water jacket furnaces typically used a cold air blast, typically provided by a positive-displacement blower, such as a Roots blower. Preheating of the air blast was used on some water jacket furnaces. [15] The horizontal cross-section of water jacket furnaces was usually rectangular—although circular and oval cross-section ones did exist [4] —whereas conventional blast furnaces always have a circular horizontal cross-section. In some larger furnace designs, molten metal and molten slag were tapped at the opposite narrow ends of the rectangular base. Water jacket furnaces typically had a higher number of smaller tuyeres than a conventional blast furnace. Typically, the feedstock was fed into a water jacket furnace through a sliding door arrangement in the side of the upper furnace structure, [4] but not via the top itself as in a blast furnace for iron. At the top of a water jacket furnace there was a fixed flue. The off-gas contained a large proportion of sulphur dioxide and was not suitable to be recycled, as done in a blast furnace making iron, which generates blast furnace gas. Dust carried in the flue gas was often collected, as it had a significant metallic content.

Other applications

A variant of the water jacket furnace was used to smelt lead-zinc ores using the Imperial Smelting Process. In that case, the furnace was completely sealed, to allow the zinc to be recovered, from flue gases, in its vapour phase. [16]

Water jacket furnaces were used to reprocess copper smelter slag that still contained a significant amount of copper, especially slag from smelting high-grade copper ore in reverberatory furnaces.

Although rarely done, small water jacket furnaces have been used to recover gold from quartz rock—particularly if the ore was very rich in gold or sulphide ores of other metals were also present—as an alternative to crushing the rock and extracting the gold using other methods. [17] [18] However, it was a very inefficient method of extracting gold. [19]

Where gold and silver were present in copper ores, the precious metals were present in the copper matte produced by a water jacket furnace. The precious metals could later be separated from blister copper, using electrolytic copper refining, and delivered in the form of dore bullion.

Demise

As the typical average ore grades of copper mines declined, ore smelting became uneconomic and was largely superseded by a process consisting of ore concentration, especially using froth flotation, and smelting of ore concentrates. The water jacket furnace was less well suited to that new regime—especially large ones that had been used to smelt low grade ores—and, after the introduction of flash smelting, from around 1949, had fallen out of favour by 1980. [7] It is now a largely forgotten technology.

See also


Related Research Articles

<span class="mw-page-title-main">Smelting</span> Use of heat and a reducing agent to extract metal from ore

Smelting is a process of applying heat and a chemical reducing agent to an ore to extract a desired base metal product. It is a form of extractive metallurgy that is used to obtain many metals such as iron, copper, silver, tin, lead and zinc. Smelting uses heat and a chemical reducing agent to decompose the ore, driving off other elements as gases or slag and leaving the metal behind. The reducing agent is commonly a fossil-fuel source of carbon, such as carbon monoxide from incomplete combustion of coke—or, in earlier times, of charcoal. The oxygen in the ore binds to carbon at high temperatures, as the chemical potential energy of the bonds in carbon dioxide is lower than that of the bonds in the ore.

<span class="mw-page-title-main">Wrought iron</span> Iron alloy with a very low carbon content

Wrought iron is an iron alloy with a very low carbon content in contrast to that of cast iron. It is a semi-fused mass of iron with fibrous slag inclusions, which give it a wood-like "grain" that is visible when it is etched, rusted, or bent to failure. Wrought iron is tough, malleable, ductile, corrosion resistant, and easily forge welded, but is more difficult to weld electrically.

<span class="mw-page-title-main">Chalcopyrite</span> Copper iron sulfide mineral

Chalcopyrite ( KAL-kə-PY-ryte, -⁠koh-) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green-tinged black.

<span class="mw-page-title-main">Slag</span> By-product of smelting ores and used metals

The general term slag may be a by-product or co-product of smelting (pyrometallurgical) ores and recycled metals depending on the type of material being produced. Slag is mainly a mixture of metal oxides and silicon dioxide. Broadly, it can be classified as ferrous, ferroalloy or non-ferrous/base metals. Within these general categories, slags can be further categorized by their precursor and processing conditions. Slag generated from the EAF process can contain toxic metals, which can be hazardous to human and environmental health.

<span class="mw-page-title-main">Blast furnace</span> Type of furnace used for smelting to produce industrial metals

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally pig iron, but also others such as lead or copper. Blast refers to the combustion air being supplied above atmospheric pressure.

<span class="mw-page-title-main">Copper extraction</span> Process of extracting copper from the ground

Copper extraction refers to the methods used to obtain copper from its ores. The conversion of copper ores consists of a series of physical, chemical, and electrochemical processes. Methods have evolved and vary with country depending on the ore source, local environmental regulations, and other factors.

<span class="mw-page-title-main">Reverberatory furnace</span> Metallurgical furnace

A reverberatory furnace is a metallurgical or process furnace that isolates the material being processed from contact with the fuel, but not from contact with combustion gases. The term reverberation is used here in a generic sense of rebounding or reflecting, not in the acoustic sense of echoing.

Pyrometallurgy is a branch of extractive metallurgy. It consists of the thermal treatment of minerals and metallurgical ores and concentrates to bring about physical and chemical transformations in the materials to enable recovery of valuable metals. Pyrometallurgical treatment may produce products able to be sold such as pure metals, or intermediate compounds or alloys, suitable as feed for further processing. Examples of elements extracted by pyrometallurgical processes include the oxides of less reactive elements like iron, copper, zinc, chromium, tin, and manganese.

Mount Isa Mines Limited ("MIM") operates the Mount Isa copper, lead, zinc and silver mines near Mount Isa, Queensland, Australia as part of the Glencore group of companies. For a brief period in 1980, MIM was Australia's largest company. It has pioneered several significant mining industry innovations, including the Isa Process copper refining technology, the Isasmelt smelting technology, and the IsaMill fine grinding technology, and it also commercialized the Jameson Cell column flotation technology.

<span class="mw-page-title-main">Chillagoe smelters</span> Heritage listed smelter in Queensland, Australia

The Chillagoe smelters is a heritage-listed refinery at Chillagoe-Mungana Caves National Park, Mareeba Mining District, Chillagoe, Shire of Mareeba, Queensland, Australia. It operated in the early 1900s. It is also known as Chillagoe State Smelters. It was added to the Queensland Heritage Register on 21 October 1992.

<span class="mw-page-title-main">Flash smelting</span> Smelting process for sulfur-containing ores

Flash smelting is a smelting process for sulfur-containing ores including chalcopyrite. The process was developed by Outokumpu in Finland and first applied at the Harjavalta plant in 1949 for smelting copper ore. It has also been adapted for nickel and lead production.

<span class="mw-page-title-main">Archaeometallurgical slag</span> Artefact of ancient iron production

Archaeometallurgical slag is slag discovered and studied in the context of archaeology. Slag, the byproduct of iron-working processes such as smelting or smithing, is left at the iron-working site rather than being moved away with the product. As it weathers well, it is readily available for study. The size, shape, chemical composition and microstructure of slag are determined by features of the iron-working processes used at the time of its formation.

<span class="mw-page-title-main">Lead smelting</span> Process of refining lead metal

Plants for the production of lead are generally referred to as lead smelters. Primary lead production begins with sintering. Concentrated lead ore is fed into a sintering machine with iron, silica, limestone fluxes, coke, soda ash, pyrite, zinc, caustics or pollution control particulates. Smelting uses suitable reducing substances that will combine with those oxidizing elements to free the metal. Reduction is the final, high-temperature step in smelting. It is here that the oxide becomes the elemental metal. A reducing environment pulls the final oxygen atoms from the raw metal.

<span class="mw-page-title-main">ISASMELT</span> Smelting process

The ISASMELT process is an energy-efficient smelting process that was jointly developed from the 1970s to the 1990s by Mount Isa Mines and the Government of Australia's CSIRO. It has relatively low capital and operating costs for a smelting process.

<span class="mw-page-title-main">Bottom-blown oxygen converter</span> Smelting furnace

The Bottom-blown Oxygen Converter or BBOC is a smelting furnace developed by the staff at Britannia Refined Metals Limited (“BRM”), a British subsidiary of MIM Holdings Limited. The furnace is currently marketed by Glencore Technology. It is a sealed, flat-bottomed furnace mounted on a tilting frame that is used in the recovery of precious metals. A key feature is the use of a shrouded lance to inject oxygen through the bottom of the furnace, directly into the precious metals contained in the furnace, to oxidize base metals or other impurities as part of their removal as slag.

Sundown Tin and Copper Mine is a heritage-listed mine at Little Sundown Creek, Stanthorpe, Southern Downs Region, Queensland, Australia. It was built from c. 1897 to 1920s. It was added to the Queensland Heritage Register on 28 July 2000.

<span class="mw-page-title-main">Glassford Creek Smelter Sites</span> Historic site in Queensland, Australia

Glassford Creek Smelter Sites are the heritage-listed remains of a former smelter at Glassford State Forest, off Many Peaks Road, Many Peaks, Gladstone Region, Queensland, Australia. It was built c. 1903. It is also known as Glassford Creek Copper Smelters. It was added to the Queensland Heritage Register on 4 July 2006.

<span class="mw-page-title-main">Metallurgical furnace</span> Device used to heat, melt, or otherwise process metals

A metallurgical furnace, often simply referred to as a furnace when the context is known, is an industrial furnace used to heat, melt, or otherwise process metals. Furnaces have been a central piece of equipment throughout the history of metallurgy; processing metals with heat is even its own engineering specialty known as pyrometallurgy.

<span class="mw-page-title-main">Illewong, New South Wales</span> Ghost town in New South Wales, Australia

Illewong was a mining village, now a ghost town, in the Orana region of New South Wales, Australia. Prior to 1906, it was known as Bee Mountain. The area, in which Illewong once lay, is now part of Cobar, for postal and statistical purposes.

<span class="mw-page-title-main">Great Cobar mine</span> Former copper mine, in New South Wales, Australia

Great Cobar mine was a copper mine, located at Cobar, New South Wales, Australia, which also produced significant amounts of gold and silver. It operated between 1871 and 1919. Over that period, it was operated by five entities; Cobar Copper Mining Company (1871–1875), Great Cobar Copper-Mining Company (1876–1889), Great Cobar Mining Syndicate (1894–1906), Great Cobar Limited (1906–1914), and finally the receiver representing the debentures holders of Great Cobar Limited (1915–1919). Its operations included mines and smelters, at Cobar, an electrolytic copper refinery, coal mine and coke works, at Lithgow, and a coal mine and coke works at Rix's Creek near Singleton.

References

  1. ↑ "Water Jacket Heater/INDIRECT HEATER_Luoyang Runcheng Petrochemical Equipment Co.,LTD.---Focus on ASME Test Separator since 2004". www.lrcoilequipment.com. Retrieved 22 December 2024.
  2. ↑ "Ore Smelting at the Burra Mine". www.burrasa.info. Retrieved 3 December 2024.
  3. 1 2 3 4 5 6 Bell, Peter; McCarthy, Justin (September 2010). "The Evolution of Early Copper Smelting Technology in Australia" (PDF). Journal of Australasian Mining History. 8: 6–10.
  4. 1 2 3 "MODERN COPPER SMELTING". Adelaide Observer . 28 March 1903. p. 31. Retrieved 22 December 2024.
  5. ↑ "Lloyd's Copper Mine". The Sydney Morning Herald. 15 December 1906. p. 6. Retrieved 13 September 2020.
  6. ↑ "OVERFLOW SILVER MINE". Sydney Morning Herald. 29 November 1898. Retrieved 23 October 2021.
  7. 1 2 Graphic from Constraints and Ingenuity: The Case of Outokumpu and the Development of Flash Smelting in the Copper Industry, 22 June 2015, retrieved 4 December 2024
  8. ↑ "Sectional Water Jacket Furnace". Australian Town and Country Journal . 15 July 1893. p. 24. Retrieved 5 December 2024.
  9. ↑ "DOES THE C.S.A. MINE JUSTIFY THE LINE?". Cobar Herald . 5 June 1914. p. 4. Retrieved 5 December 2024.
  10. ↑ "Cobar's Prospects". Western Age . 13 September 1918. p. 3. Retrieved 5 December 2024.
  11. ↑ Bell, Peter; McCarthy, Justin (September 2010). "The Evolution of Early Copper Smelting Technology in Australia" (PDF). Journal of Australasian Mining History. 8: 11–12, 18–19.
  12. ↑ "OLD COBAR". Dubbo Dispatch and Wellington Independent . 2 March 1928. p. 2. Retrieved 25 September 2024.
  13. ↑ "The Queen Bee Mine". Western Age. 2 December 1914. p. 2. Retrieved 10 January 2023.
  14. ↑ Bell, Peter; McCarthy, Justin (September 2010). "The Evolution of Early Copper Smelting Technology in Australia" (PDF). Journal of Australasian Mining History. 8.
  15. ↑ "BLAYNEY COPPER MINE. THE PYRITIC SMELTING AND THE HOT-AIR BLAST". Lithgow Mercury . 16 March 1900.
  16. ↑ Sinclair, Roderick J (2005). The Extractive Metallurgy of Zinc (PDF). Australasian Institute of Mining and Metallurgy. pp. 201–210. ISBN   978-1-920806-34-7.
  17. ↑ "THE CUNNINGAR SMELTING PLANT". The Ballarat Star . 10 December 1885. p. 4.
  18. ↑ "OPENING OF THE CUNINGAR GOLD REEFING WORKS". Goulburn Herald . 10 December 1885. p. 2.
  19. ↑ "John Dye La Monte - The Wrong Man in the Right Place at the Right Time". www.thetreasury.org.nz. Retrieved 5 December 2024.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.