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A lime kiln is a
kiln A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or Chemical Changes, chemical changes. Kilns have been used for millennia to turn objects m ...
used for the
calcination Calcination is thermal treatment of a solid chemical compound (e.g. mixed carbonate ores) whereby the compound is raised to high temperature without melting under restricted supply of ambient oxygen (i.e. gaseous O2 fraction of air), generally f ...
of
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
(
calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...
) to produce the form of
lime Lime most commonly refers to: * Lime (fruit), a green citrus fruit * Lime (material), inorganic materials containing calcium, usually calcium oxide or calcium hydroxide * Lime (color), a color between yellow and green Lime may also refer to: Bo ...
called ''quicklime'' (
calcium oxide Calcium oxide (formula: Ca O), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature. The broadly used term '' lime'' connotes calcium-containing ...
). The
chemical equation A chemical equation is the symbolic representation of a chemical reaction in the form of symbols and chemical formulas. The reactant entities are given on the left-hand side and the Product (chemistry), product entities are on the right-hand side ...
for this
reaction Reaction may refer to a process or to a response to an action, event, or exposure. Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law * Chain reaction (disambiguation) Biology and ...
is: CaCO3 + heat →
CaO Cao or CAO may refer to: Mythology *Cao (bull), a legendary bull in Meitei mythology Companies or organizations * Air China Cargo, ICAO airline designator CAO * CA Oradea, Romanian football club * CA Osasuna, Spanish football club * Canadian ...
+ CO2 This reaction can take place at anywhere above , but is generally considered to occur at (at which temperature the
partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...
of CO2 is 1
atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
), but a temperature around (at which temperature the partial pressure of CO2 is 3.8 atmospheres) is usually used to make the reaction proceed quickly.Parkes, G.D. and Mellor, J.W. (1939). ''Mellor's Modern Inorganic Chemistry'' London: Longmans, Green and Co. Excessive temperature is avoided because it produces unreactive, "dead-burned" lime. Slaked lime (
calcium hydroxide Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca( OH)2. It is a colorless crystal or white powder and is produced when quicklime ( calcium oxide) is mixed with water. Annually, approxim ...
) can be formed by mixing quicklime with water.


History


Pre-pottery Neolithic


In plaster, proto-pottery, and mortar

Because it is so readily made by heating limestone, lime must have been known from the earliest times, and all the early civilizations used it in building
mortars Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a village i ...
and as a stabilizer in mud renders and floors. According to finds at 'Ain Ghazal in Jordan, Yiftahel in Israel, and Abu Hureyra in Syria dating to 7500–6000 BCE, the earliest use of lime was mostly as a binder on floors and in plaster for coating walls. This use of plaster may in turn have led to the development of proto-pottery, made from lime and ash. In mortar, the oldest binder was mud. According to finds at Catal Hüyük in Turkey, mud was soon followed by clay, and then by lime in the 6th millennium BCE.


Lime use in agriculture and coal

Knowledge of its value in
agriculture Agriculture encompasses crop and livestock production, aquaculture, and forestry for food and non-food products. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated species created ...
is also ancient, but agricultural use only became widely possible when the use of coal made it cheap in the coalfields in the late 13th century, and an account of agricultural use was given in 1523. The earliest descriptions of lime kilns differ little from those used for small-scale manufacture a century ago. Because land transportation of minerals like limestone and coal was difficult in the pre-industrial era, they were distributed by sea, and lime was most often manufactured at small coastal ports. Many preserved kilns are still to be seen on quaysides around the coasts of Britain.


Types of kilns

Permanent lime kilns fall into two broad categories: "flare kilns" also known as "intermittent" or "periodic" kilns; and "draw kilns" also known as "perpetual" or "running" kilns. In a flare kiln, a bottom layer of coal was built up and the kiln above filled solely with chalk. The fire was alight for several days, and then the entire kiln was emptied of the lime. In a draw kiln, usually a stone structure, the chalk or limestone was layered with wood, coal or coke and lit. As it burnt through, lime was extracted from the bottom of the kiln, through the draw hole. Further layers of stone and fuel were added to the top.


Early kilns

The common feature of early kilns was an egg-cup shaped burning chamber, with an air inlet at the base (the "eye"), constructed of brick. Limestone was crushed (often by hand) to fairly uniform lumps – fine stone was rejected. Successive dome-shaped layers of limestone and wood or coal were built up in the kiln on grate bars across the eye. When loading was complete, the kiln was kindled at the bottom, and the fire gradually spread upwards through the charge. When burnt through, the lime was cooled and raked out through the base. Fine ash dropped out and was rejected with the "riddlings". Only lump stone could be used, because the charge needed to "breathe" during firing. This also limited the size of kilns and explains why kilns were all much the same size. Above a certain diameter, the half-burned charge would be likely to collapse under its own weight, extinguishing the fire. So kilns always made 25–30
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...
s of lime in a batch. Typically the kiln took a day to load, three days to fire, two days to cool and a day to unload, so a one-week turnaround was normal. The degree of burning was controlled by trial and error from batch to batch by varying the amount of fuel used. Because there were large temperature differences between the center of the charge and the material close to the wall, a mixture of underburned (i.e. high
loss on ignition Loss on ignition (LOI) is a test used in inorganic analytical chemistry and soil science, particularly in the analysis of minerals and the chemical makeup of soil. It consists of strongly heating ( "igniting") a sample of the material at a specif ...
), well-burned and dead-burned lime was normally produced. Typical fuel efficiency was low, with 0.5 tonnes or more of coal being used per tonne of finished lime (15 MJ/kg).


Industrial scale production

Lime production was sometimes carried out on an industrial scale. One example at Annery in North
Devon Devon ( ; historically also known as Devonshire , ) is a ceremonial county in South West England. It is bordered by the Bristol Channel to the north, Somerset and Dorset to the east, the English Channel to the south, and Cornwall to the west ...
,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
, near
Great Torrington Great Torrington (often abbreviated to Torrington, though the villages of Little Torrington and Black Torrington are situated in the same region) is a market town in Devon, England. Parts of it are sited on high ground with steep drops down to ...
, was made up of three kilns grouped together in an 'L' shape and was situated beside the
Torrington canal The Rolle Canal (or Torrington Canal) in north Devon, England, extends from its mouth into the River Torridge at Landcross 6 miles southwards to the industrial mills and corn-mills at Town Mills, Rosemoor, Great TorringtonLost can ...
and the
River Torridge The River Torridge is a river in Devon in England; it rises near Meddon. The river describes a long loop through Devon farming country where its tributaries the Lew and Okement join before meeting the Taw at Appledore and flowing into the Bristol ...
to bring in the limestone and coal, and to transport away the calcined lime in the days before properly
metalled A road surface (British English) or pavement (North American English) is the durable surface material laid down on an area intended to sustain vehicular or foot traffic, such as a road or walkway. In the past, gravel road surfaces, macadam, ho ...
roads existed.Griffith, R. S. Ll. (1971). ''Annery Kiln, Weare Gifford.'' Grenville College project. Supervisor Mr. B. D. Hughes. Sets of seven kilns were common. A loading gang and an unloading gang would work the kilns in rotation through the week. A rarely used kiln was known as a "lazy kiln".Hood, James (1928). ''Kilmarnock Water and Craufurdland'' Kilm Glenf Ramb Soc. Annals. 1919 – 1930. P. 126.


Australia

In the late 19th and early 20th centuries the town of Waratah in
Gippsland Gippsland () is a rural region in the southeastern part of Victoria, Australia, mostly comprising the coastal plains south of the Victorian Alps (the southernmost section of the Great Dividing Range). It covers an elongated area of east of th ...
,
Victoria Victoria most commonly refers to: * Queen Victoria (1819–1901), Queen of the United Kingdom and Empress of India * Victoria (state), a state of Australia * Victoria, British Columbia, Canada, a provincial capital * Victoria, Seychelles, the capi ...
,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
produced a majority of the quicklime used in the city of
Melbourne Melbourne ( , ; Boonwurrung language, Boonwurrung/ or ) is the List of Australian capital cities, capital and List of cities in Australia by population, most populous city of the States and territories of Australia, Australian state of Victori ...
as well as around other parts of Gippsland. The town, now called Walkerville, was set on an isolated part of the Victorian coastline and exported the lime by ship. When this became unprofitable in 1926 the kilns were shut down. The present-day area, though having no town amenities as such, markets itself as a tourist destination. The ruins of the lime kilns can still be seen today. File:Limestone kiln ruins at Walkerville, Victoria, Australia.jpg, alt=Limestone kiln ruin at Walkerville, Victoria, Australia, Limestone kiln ruin at Walkerville, Victoria, Australia File:Limestone kiln ruins viewed from Limeburners track at Walkerville, Victoria, Australia.jpg, alt=Limestone kiln ruin as seen from bushwalking track, Walkerville, Victoria, Australia, Limestone kiln ruin as seen from bushwalking track, Walkerville, Victoria, Australia A lime kiln also existed in Wool Bay,
South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
. File:Wool Bay lime Kiln.JPG, alt=Limestone kiln ruin at Wool Bay, South Australia


Ukraine

File:Lime kilns in Manzhykiv Kut, Ukraine — Вапняні печі у Манжиковому Куті 08.jpg, Old lime kilns in Manzhykiv Kut, Ukraine File:Lime kilns in Manzhykiv Kut, Ukraine — Вапняні печі у Манжиковому Куті 16.jpg, Old lime kilns in Manzhykiv Kut, Ukraine File:Lime kilns in Manzhykiv Kut, Ukraine — Вапняні печі у Манжиковому Куті 15.jpg, Old lime kilns in Manzhykiv Kut, Ukraine File:Lime kilns in Manzhykiv Kut, Ukraine — Вапняні печі у Манжиковому Куті 13.jpg, Old lime kilns in Manzhykiv Kut, Ukraine


United Kingdom

The large kiln at Crindledykes near
Haydon Bridge Haydon Bridge is a village in Northumberland, England, which had a population of 2,184 in the 2011 census. Its most distinctive features are the two bridges crossing the River Tyne, River South Tyne: the picturesque original bridge after which ...
, Northumbria, was one of more than 300 in the county. It was unique to the area in having four draw arches to a single pot. As production was cut back, the two side arches were blocked up, but were restored in 1989 by
English Heritage English Heritage (officially the English Heritage Trust) is a charity that manages over 400 historic monuments, buildings and places. These include prehistoric sites, a battlefield, medieval castles, Roman forts, historic industrial sites, Lis ...
. The development of the national rail network made the local small-scale kilns increasingly unprofitable, and they gradually died out through the 19th century. They were replaced by larger industrial plants. At the same time, new uses for lime in the
chemical A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combin ...
,
steel Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high Young's modulus, elastic modulus, Yield (engineering), yield strength, Fracture, fracture strength a ...
and
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...
industries led to large-scale plants. These also saw the development of more efficient kilns. A lime kiln erected at
Dudley Dudley ( , ) is a market town in the West Midlands, England, southeast of Wolverhampton and northwest of Birmingham. Historically part of Worcestershire, the town is the administrative centre of the Metropolitan Borough of Dudley. In the ...
, West Midlands (formerly
Worcestershire Worcestershire ( , ; written abbreviation: Worcs) is a Ceremonial counties of England, ceremonial county in the West Midlands (region), West Midlands of England. It is bordered by Shropshire, Staffordshire, and the West Midlands (county), West ...
) in 1842 survives as part of the
Black Country Living Museum The Black Country Living Museum (formerly the Black Country Museum) is an open-air museum of rebuilt historic buildings in Dudley, West Midlands (county), West Midlands, England. It is located in the centre of the Black Country, west of Birming ...
which opened in 1976, although the kilns were last used during the 1920s. It is now among the last in a region which was dominated by coalmining and limestone mining for generations until the 1960s. Image:LimeKilnFroghall.JPG, alt=19th century limekilns at Froghall, 19th century limekilns at
Froghall Froghall is a village situated approximately ten miles to the east of Stoke-on-Trent and two miles north of Cheadle in Staffordshire, England. Population details as taken at the 2011 Census can be found under Kingsley. Froghall sits in the C ...
Image:Lime Kiln 1.jpg, alt=A preserved lime kiln in Burgess Park, London, A preserved lime kiln in
Burgess Park Burgess Park is a public park situated in Camberwell in the London Borough of Southwark. It is close to Walworth to the north, Bermondsey to the east and Peckham to the south. At , it is the largest park in the borough. Unlike most other park ...
, London File:Forrabury and Minster - old lime kiln, Boscastle - geograph.org.uk - 842707.jpg, alt=Old lime kiln, Boscastle, Cornwall, Old lime kiln, Boscastle, Cornwall Image:Broadstone limekiln stonework detail.JPG, alt=A large limekiln at Broadstone, Beith, Ayrshire., A large limekiln at Broadstone, Beith, Ayrshire Image:Annery Kiln, Weare Gifford 1.jpg, The
Annery kiln Annery kiln is a former limekiln of the estate of Annery, Monkleigh, Annery, in the parish of Monkleigh, North Devon. It is situated on the left bank of the River Torridge near Half-Penny Bridge, built in 1835,Scrutton, Sue, Lord Rolle's Canal, G ...
in Devon, England Image:Limekiln Crindledykes 1992.jpg, alt=Large 19th-century single limekiln at Crindledykes near Housesteads Northumbria, Large 19th-century single limekiln at Crindledykes near
Housesteads Housesteads Roman Fort was an auxiliary fort on Hadrian's Wall, at Housesteads, Northumberland, England. It is dramatically positioned on the end of the -long crag of the Whin Sill over which the Wall runs, overlooking sparsely populated hil ...
Northumbria Northumbria () was an early medieval Heptarchy, kingdom in what is now Northern England and Scottish Lowlands, South Scotland. The name derives from the Old English meaning "the people or province north of the Humber", as opposed to the Sout ...
Image:Dumbarton castle and lime kiln.jpg, alt=Dumbarton castle in 1800 and functioning lime kiln with smoke in the foreground., Dumbarton castle in 1800 and functioning lime kiln with smoke in the foregroundStoddart, John (1800), ''Remarks on Local Scenery and Manners in Scotland.'' Pub. Wiliam Miller, London. Facing p. 212.


Other countries

File:Antoing JPG04.jpg, Old lime kilns,
Antoing Antoing (; ) is a city and Municipalities in Belgium, municipality of Wallonia located in the Hainaut (province), province of Hainaut, Belgium. The municipality consists of the following districts: Antoing, Bruyelle, Calonne, Wallonia, Calonne, ...
, Belgium File:FornosdaCal1.jpg, Lime kilns, Oeiras, Portugal File:Kalkofen Untermarchtal, Baden-Württemberg.jpg, Lime kiln Untermarchtal,
Baden-Württemberg Baden-Württemberg ( ; ), commonly shortened to BW or BaWü, is a states of Germany, German state () in Southwest Germany, east of the Rhine, which forms the southern part of Germany's western border with France. With more than 11.07 million i ...
File:Old lime kiln of 1906 at Simplon, Namibia (2017).jpg, Lime kiln from 1906 at Simplon,
Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...
File:Lime Kilns - Vojtěšská huť Koněv - in Kladno.jpg, Lime Kilns in Kladno, Czechia, operable until 1975.


Modern kilns


Shaft kilns

The theoretical heat (the standard
enthalpy Enthalpy () is the sum of a thermodynamic system's internal energy and the product of its pressure and volume. It is a state function in thermodynamics used in many measurements in chemical, biological, and physical systems at a constant extern ...
) of reaction required to make high-calcium lime is around 3.15 MJ per kg of lime, so the batch kilns were only around 20% efficient. The key to development in efficiency was the invention of continuous kilns, avoiding the wasteful heat-up and cool-down cycles of the batch kilns. The first were simple shaft kilns, similar in construction to
blast furnace 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. In a ...
s. These are counter-current shaft kilns. Modern variants include regenerative and annular kilns. Output is usually in the range 100–500 tonnes per day.


Counter-current shaft kilns

The fuel is injected part-way up the shaft, producing maximum temperature at this point. The fresh feed fed in at the top is first dried then heated to 800 °C, where de-carbonation begins, and proceeds progressively faster as the temperature rises. Below the burner, the hot lime transfers heat to, and is cooled by, the combustion air. A mechanical grate withdraws the lime at the bottom. A fan draws the gases through the kiln, and the level in the kiln is kept constant by adding feed through an airlock. As with batch kilns, only large, graded stone can be used, in order to ensure uniform gas-flows through the charge. The degree of burning can be adjusted by changing the rate of withdrawal of lime. Heat consumption as low as 4 MJ/kg is possible, but 4.5 to 5 MJ/kg is more typical. Due to temperature peak at the burners up to 1200 °C in a shaft kiln conditions are ideal to produce medium and hard burned lime.


Regenerative kilns

These typically consist of a pair of shafts, operated alternately. First, when shaft A is the "primary" and B the "secondary" shaft, the combustion air is added from the top of shaft A, while fuel somewhat below via burner lances. The flame is top-bottom. The hot gases pass downward, cross to shaft B via the so-called "channel" and pass upward to exhaust of shaft B. At same time in both shafts cooling air is added from the bottom to cool the lime and to make exhaust of gases via the bottom of the kiln impossible via maintaining a positive pressure. The combustion air and cooling air leave the kiln jointly via exhaust on top of shaft B, preheating the stone. The direction of flow is reversed periodically (typically 5–10 times per hour) shaft A and B changing the role of "primary" and "secondary" shaft. The kiln has three zones: preheating zone on the top, burning zone in the middle, and cooling zone close to the bottom. The cycling produces a long burning zone of constant, relatively low temperature (around 950 °C) that is ideal for the production of high quality soft burned reactive lime. With exhaust gas temperatures as low as 120 °C and lime temperature at kiln outlet in 80 °C range the heat loss of the regenerative kiln is minimal, fuel consumption is as low as 3.6 MJ/kg. Due to these features the regenerative kilns are today mainstream technology under conditions of substantial fuel costs. Regenerative kilns are built with 150 to 800 t/day output, 300 to 450 being typical.


Annular kilns

These contain a concentric internal cylinder. This gathers pre-heated air from the cooling zone, which is then used to pressurize the middle annular zone of the kiln. Air spreading outward from the pressurized zone causes
counter-current flow Countercurrent exchange is a mechanism between two flowing bodies flowing in opposite directions to each other, in which there is a transfer of some property, usually heat or some chemical. The flowing bodies can be liquids, gases, or even solid ...
upwards, and co-current flow downwards. This again produces a long, relatively cool calcining zone. Fuel consumption is in 4 to 4.5 MJ/kg range and the lime is typically medium burned.


Rotary kilns

Rotary kilns started to be used for lime manufacture at the start of the 20th century and now account for a large proportion of new installations if energy costs are less important. The early use of simple rotary kilns had the advantages that a much wider range of limestone size could be used, from fines upwards, and undesirable elements such as
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
can be removed. On the other hand, fuel consumption was relatively high because of poor heat exchange compared with shaft kilns, leading to excessive heat loss in exhaust gases. Old fashioned "long" rotary kilns operate at 7 to 10 MJ/kg. Modern installations partially overcome this disadvantage by adding a preheater, which has the same good solids/gas contact as a shaft kiln, but fuel consumption is still somewhat higher, typically in range of 4.5 to 6 MJ/kg. In the design shown, a circle of shafts (typically 8–15) is arranged around the kiln riser duct. Hot limestone is discharged from the shafts in sequence, by the action of a hydraulic "pusher plate". Kilns of 1000 tonnes per day output are typical. The rotary kiln is the most flexible of any lime kilns able to produce soft, medium, or hard burned as well as dead-burned lime or dolime.


Gas cleaning

All the above kiln designs produce exhaust gas that carries an appreciable amount of dust. Lime dust is particularly corrosive. Equipment is installed to trap this dust, typically in the form of
electrostatic precipitator An electrostatic precipitator (ESP) is a filterless device that removes fine particles, such as dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit. In c ...
s or bag filters. The dust usually contains a high concentration of elements such as
alkali metal The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
s,
halogen The halogens () are a group in the periodic table consisting of six chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and the radioactive elements astatine (At) and tennessine (Ts), though some authors would ...
s and sulfur.


Carbon dioxide emissions

The lime industry is a significant
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
emitter. The manufacture of one tonne of calcium oxide involves decomposing calcium carbonate, with the formation of 785 kg of CO2 in some applications, such as when used as mortar; this CO2 is later re-absorbed as the mortar goes off. If the heat supplied to form the lime (3.75 MJ/kg in an efficient kiln) is obtained by burning fossil fuel it will release CO2: in the case of coal fuel 295 kg/t; in the case of natural gas fuel 206 kg/t. The electric power consumption of an efficient plant is around 20
kWh A kilowatt-hour (unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a common b ...
per tonne of lime. This additional input is the equivalent of around 20 kg CO2 per ton if the electricity is coal-generated. Thus, total emission may be around 1 tonne of CO2 for every tonne of lime even in efficient industrial plants, but is typically 1.3 t/t.EU Emissions Trading Scheme
National Archives Gov UK
However, if the source of heat energy used in its manufacture is a fully renewable power source, such as solar, wind, hydro or even nuclear; there may be no net emission of CO2 from the calcination process. Less energy is required in production per weight than
portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar (masonry), mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in th ...
, primarily because a lower temperature is required.


Other emissions


See also

* List of lime kilns ** List of lime kilns in the United States *
Limepit A limepit is either a place where limestone is quarried, or a man-made pit used to burn lime stones in the same way that Lime kiln, modern-day kilns and furnaces constructed of brick are now used above ground for the Calcium carbonate#Calcination ...


References


External links


An authoritative discussion of lime and its uses (US context)

Lime Kilns at Newport Pembrokeshire West Wales


* ttp://www.sic-lime.it/en/default.asp?Subs=430&Liv1=414 The Lime Physical-Chemical Process
Lime Kiln Digital Collection
a
Sonoma State University Library
Wainmans Double Arched Lime Kiln – Made Grade II Listed Building – 1 February 2005 Details & Image
Wainmans Double Arched Lime Kiln - Made Grade II Listed Building
{{DEFAULTSORT:Lime Kiln History of chemistry Kilns Firing techniques
Kiln A kiln is a thermally insulated chamber, a type of oven, that produces temperatures sufficient to complete some process, such as hardening, drying, or Chemical Changes, chemical changes. Kilns have been used for millennia to turn objects m ...