Hot blast

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Blast furnace (left), and three Cowper stoves (right) used to preheat the air blown into the furnace. Carrie Furnace No. 7, U.S. Steel Homestead Works, Blast Furnace Plant, Along Monongahela River, Homestead (Allegheny County, Pennsylvania).jpg
Blast furnace (left), and three Cowper stoves (right) used to preheat the air blown into the furnace.
Hot blast furnace: note the flow of air from the stove in the background to the two blast furnaces, and hot air from the foreground furnace being drawn off to heat the stove. Modern blast furnaces (Wonder Book of Engineering Wonders, 1931).jpg
Hot blast furnace: note the flow of air from the stove in the background to the two blast furnaces, and hot air from the foreground furnace being drawn off to heat the stove.

Hot blast refers to the preheating of air blown into a blast furnace or other metallurgical process. As this considerably reduced the fuel consumed, hot blast was one of the most important technologies developed during the Industrial Revolution. [1] Hot blast also allowed higher furnace temperatures, which increased the capacity of furnaces. [2] [3]

Contents

As first developed, it worked by alternately storing heat from the furnace flue gas in a firebrick-lined vessel with multiple chambers, then blowing combustion air through the hot chamber. This is known as regenerative heating. Hot blast was invented and patented for iron furnaces by James Beaumont Neilson in 1828 at Wilsontown Ironworks [ citation needed ] in Scotland, but was later applied in other contexts, including late bloomeries. Later the carbon monoxide in the flue gas was burned to provide additional heat.

History

Invention and spread

James Beaumont Neilson, previously foreman at Glasgow gas works, invented the system of preheating the blast for a furnace. He found that by increasing the temperature of the incoming air to 300 degrees Fahrenheit, he could reduce the fuel consumption from 8.06 tons to 5.16 tons with further reductions at even higher temperatures. [4] He, with partners including Charles Macintosh, patented this in 1828. [5] Initially the heating vessel was made of wrought iron plates, but these oxidized, and he substituted a cast iron vessel. [4]

On the basis of a January 1828 patent, Thomas Botfield has a historical claim as the inventor of the hot blast method. Neilson is credited as inventor of hot blast, because he won patent litigation. [1] Neilson and his partners engaged in substantial litigation to enforce the patent against infringers. [5] The spread of this technology across Britain was relatively slow. By 1840, 58 ironmasters had taken out licenses, yielding a royalty income of £30,000 per year. By the time the patent expired there were 80 licenses. In 1843, just after it expired, 42 of the 80 furnaces in south Staffordshire were using hot blast, and uptake in south Wales was even slower. [6]

Other advantages of hot blast were that raw coal could be used instead of coke. In Scotland, the relatively poor "black band" ironstone could be profitably smelted. [5] It also increased the daily output of furnaces. In the case of Calder ironworks from 5.6 tons per day in 1828 to 8.2 in 1833, which made Scotland the lowest cost steel producing region in Britain in the 1830s. [7]

Early hot blast stoves were troublesome, as thermal expansion and contraction could cause breakage of pipes. This was somewhat remedied by supporting the pipes on rollers. It was also necessary to devise new methods of connecting the blast pipes to the tuyeres, as leather could not longer be used. [8]

Ultimately this principle was applied even more efficiently in regenerative heat exchangers, such as the Cowper stove (which preheat incoming blast air with waste heat from flue gas; these are used in modern blast furnaces), and in the open hearth furnace (for making steel) by the Siemens-Martin process. [9]

Independently, George Crane and David Thomas, of the Yniscedwyn Works in Wales, conceived of the same idea, and Crane filed for a British patent in 1836. They began producing iron by the new process on February 5, 1837. Crane subsequently bought Gessenhainer's patent and patented additions to it, controlling the use of the process in both Britain and the US. While Crane remained in Wales, Thomas moved to the US on behalf of the Lehigh Coal and Navigation Company and founded the Lehigh Crane Iron Company to utilize the process. [10]

Anthracite in ironmaking

Hot blast allowed the use of anthracite in iron smelting. It also allowed use of lower quality coal because less fuel meant proportionately less sulfur and ash. [11]

At the time the process was invented, good coking coal was only available in sufficient quantities in Great Britain and western Germany, [12] so iron furnaces in the US were using charcoal. This meant that any given iron furnace required vast tracts of forested land for charcoal production, and generally went out of blast when the nearby woods had been felled. Attempts to use anthracite as a fuel had ended in failure, as the coal resisted ignition under cold blast conditions. In 1831, Dr. Frederick W. Gessenhainer filed for a US patent on the use of hot blast and anthracite to smelt iron. He produced a small quantity of anthracite iron by this method at Valley Furnace near Pottsville, Pennsylvania in 1836, but due to breakdowns and his illness and death in 1838, he was not able to develop the process into large-scale production. [10]

Anthracite was displaced by coke in the US after the Civil War. Coke was more porous and able to support the heavier loads in the vastly larger furnaces of the late 19th century. [2] :90 [13] :139

Steel

For steel the hot blast temperature can be from 900 °C to 1300 °C (1600 °F to 2300 °F) depending on the stove design and condition. The temperatures they deal with may be 2000 °C to 2300 °C (3600 °F to 4200 °F). Oil, tar, natural gas, powdered coal and oxygen can also be injected into the furnace at tuyere level (near the base) to combine with the coke to release additional energy which is necessary to increase productivity. [14]

Related Research Articles

Coke (fuel) A grey, hard and porous fuel with high carbon content and few impurities.

Coke is a grey, hard, and porous fuel with a high carbon content and few impurities, made by heating coal or oil in the absence of air — a destructive distillation process. It is an important industrial product, used mainly in iron ore smelting, but also as a fuel in stoves and forges when air pollution is a concern.

Anthracite A hard, compact variety of coal that has a submetallic luster

Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals.

Blast furnace type of metallurgical furnace used for smelting to produce industrial metals

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David Thomas was a native of Wales who was influential in the birth of the Industrial Revolution in the US.

Anthracite iron

Anthracite iron or Anthracite 'Pig Iron' is the substance created by the smelting together of anthracite coal and iron ore, that is using Anthracite coal instead of charcoal to smelt iron ores — and was an important historic advance in the late-1830s enabling great acceleration the industrial revolution in Europe and North America.

Bloomery early form of iron smelter

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Reverberatory furnace metallurgical furnace

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James Beaumont Neilson Scottish inventor of the hot-blast process for smelting iron

James Beaumont Neilson was a Scottish inventor whose hot-blast process greatly increased the efficiency of smelting iron.

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A tuyere or tuyère is a tube, nozzle or pipe through which air is blown into a furnace or hearth.

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Cornwall Iron Furnace United States historic place

Cornwall Iron Furnace is a designated National Historic Landmark that is administered by the Pennsylvania Historical and Museum Commission in Cornwall, Lebanon County, Pennsylvania in the United States. The furnace was a leading Pennsylvania iron producer from 1742 until it was shut down in 1883. The furnaces, support buildings and surrounding community have been preserved as a historical site and museum, providing a glimpse into Lebanon County's industrial past. The site is the only intact charcoal-burning iron blast furnace in its original plantation in the western hemisphere. Established by Peter Grubb in 1742, Cornwall Furnace was operated during the Revolution by his sons Curtis and Peter Jr. who were major arms providers to George Washington. Robert Coleman acquired Cornwall Furnace after the Revolution and became Pennsylvania's first millionaire. Ownership of the furnace and its surroundings was transferred to the Commonwealth of Pennsylvania in 1932.

Cold blast

Cold blast, in ironmaking, refers to a furnace where air is not preheated before being blown into the furnace. This represents the earliest stage in the development of ironmaking. Until the 1820s, the use of cold air was thought to be preferable to hot air for the production of high-quality iron; this effect was due to the reduced moisture in cool winter air.

Charcoal iron is the substance created by the smelting of iron ore with charcoal.

Cupola furnace

A cupola or cupola furnace is a melting device used in foundries that can be used to melt cast iron, Ni-resist iron and some bronzes. The cupola can be made almost any practical size. The size of a cupola is expressed in diameters and can range from 1.5 to 13 feet. The overall shape is cylindrical and the equipment is arranged vertically, usually supported by four legs. The overall look is similar to a large smokestack.

Pulverized coal injection is a method for improving the performance of a blast furnace.

Sinter plants agglomerate iron ore fines (dust) with other fine materials at high temperature, to create a product that can be used in a blast furnace. The final product, a sinter, is a small, irregular nodule of iron mixed with small amounts of other minerals. The process, called sintering, causes the constituent materials to fuse to make a single porous mass with little change in the chemical properties of the ingredients. The purpose of sinter are to be used converting iron into steel.

History of the iron and steel industry in the United States aspect of history

The US iron and steel industry has paralleled the industry in other countries in technological developments. In the 1800s, the US switched from charcoal to coke in ore smelting, adopted the Bessemer process, and saw the rise of very large integrated steel mills. In the 20th century, the US industry successively adopted the open hearth furnace, then the basic oxygen steelmaking process. Since the American industry peaked in the 1940s and 1950s, the US industry has shifted to small mini-mills and specialty mills, using iron and steel scrap as feedstock, rather than iron ore.

KM2 and KM3 are Early Iron Age complex industrial archaeological sites in Tanzania, excavated by a team led by archaeologist Peter Schmidt in the late 1970s and 1980s. The excavations aimed at better understanding the iron smelting process and its ritual aspects in East Africa. At the KM2 and KM3 sites, Schmidt tested the hypothesis that the high combustion temperature of furnaces, discovered to be between 1350 to 1400 degree Celsius, was caused by the preheating of air blasts. Preheating has been suggested to be a distinct feature of African Early Iron Age smelting techniques by ethnographic observations of the Haya people of northwestern Tanzania.

References

  1. 1 2 Belford, Paul (2012). "Hot blast iron smelting in the early 19th century" (PDF). Historical Metallurgy. Historical Metallurgy Society. 46 (1): 32–44.
  2. 1 2 Landes, David S. (1969). The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present. Cambridge, New York: Press Syndicate of the University of Cambridge. p. 92. ISBN   0-521-09418-6.
  3. Ayres, Robert (1989). "Technological Transformations and Long Waves" (PDF): 21<Fig. 7 shows C/Fe ratio time series>Cite journal requires |journal= (help)
  4. 1 2 W.K.V. Gale, British iron and steel industry (David and Charles, Newton Abbot 1967), 55-8.
  5. 1 2 3 "Neilson, James Beaumont (1792–1865)". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/19866.(Subscription or UK public library membership required.)
  6. C.K. Hyde, Technological change and the British iron industry 1700-1870 (Princeton University Press, 1977), 154-5.
  7. C.K. Hyde, Technological change and the British iron industry 1700-1870 (Princeton University Press, 1977), 151.
  8. W.K.V. Gale, The Black Country iron industry (David and Charles, Newton Abbot 1966), 71-5.
  9. W.K.V. Gale, British iron and steel industry (David and Charles, Newton Abbot 1967), 98-100.
  10. 1 2 Bartholomew, Craig L.; Metz, Lance E. (1988). Bartholomew, Ann (ed.). The Anthracite Industry of the Lehigh Valley. Center for Canal History and Technology. ISBN   0-930973-08-9.
  11. Rosenberg, Nathan (1982). Inside the Black Box: Technology and Economics . Cambridge, New York: Cambridge University Press. p.  88. ISBN   0-521-27367-6.
  12. Landes 1969, p. 82.
  13. Rosen, William (2012). The Most Powerful Idea in the World: A Story of Steam, Industry and Invention. University Of Chicago Press. ISBN   978-0226726342.
  14. "How a Blast Furnace Works". Archived from the original on 2017-09-26. Retrieved 2017-02-07.