Lime Kiln 2/3 - quicklime, lime mortar
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- Опубликовано: 13 сен 2024
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A lime kiln is a kiln used to produce quicklime by the calcination of limestone (calcium carbonate). The chemical equation for this reaction is:
CaCO3 + heat → CaO + CO2
This reaction takes place at 900°C (at which temperature the partial pressure of CO2 is 1 atmosphere), but a temperature around 1000°C (at which temperature the partial pressure of CO2 is 3.8 atmospheres) is usually used to make the reaction proceed quickly. Excessive temperature is avoided because it produces unreactive, "dead-burned" lime.
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 and as a stabilizer in mud renders and floors.
Knowledge of its value in agriculture 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 limekilns 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.
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 20-60 mm (1 to 2.5 inch) lumps - fine stone was rejected. Successive dome-shaped layers of coal and limestone 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 coal 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 tonnes 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 under-burned (i.e. high loss on ignition), 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).
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Thank for this!! I'm writing a thesis on lime kilns, great to see one in action.
My 4x great grandfather Christopher Hodgson was listed as lime burner in the 1841 census for Seamer, ( near Scarborough, Yorkshire, England. Thank you for this video. Now I know what he did for his livelihood .
This is amazing.... AND FRIGHTENING, regarding what he said about the homeless people.
excellent about the measures on the layers in the kiln...and yes sometimes coal may not be easily substituted...modern kilns are steel tubes just off horizontal turned by motors slowly assuring even heat distribution and natural gas burners but carbon monoxide is still produced! and the slowly turning tubes wear as do the screws that slowly move the limestone forward and as the limestone breaks down the kilns can off load directly to slaking and cooling areas for continual operations! but for low energy tech the vertical batch burns proved reliable just a bit labor intensive...but a track loader could make short work off loading...and unloading the kilns to slaking ponds! the lime putty could then be barreled and sealed for future use! especially for housing nothing better than limed adobe with a good pair of shoes , gloria, and a rock steady roof today probably engineered metal shingles for ease of repair ! I know to historians this may seem sacrilege! However having a home be generational for over 500 years with built in heating and cooling is the off grid ideal...and the next issues of off grid water treatment for gray water and only black water going to process allows for irrigated gardens etc...leaving municipalities less burdened as would your purse be less burdened! We need to raise our lower classes standards through skill and education soon, or the problem of dependence will be out right unmanageable! Sorry but there it is and it is global...
Great to see a lime kiln in action
Make a container that holds 20 shovels full. Then just fill that save u all the counting and precise shoveling.
This show would be awesome! I have to search netflix for this
Why roasted? Before you said that i was kind of enjoying the video.
For 3 days, and 6 nights. WTF?
try user/gracelessgillett
Hello again class 7