What is lime?
Lime is the everyday name for a variety of chemical compounds that contain calcium. The most common is limestone, a type of rock that is made up primarily of calcium carbonate.
The limestone found in the ground has formed over a long period – between 80 and 2,000 million years in Swedish limestone quarries – from the remains of marine organisms, such as algae, mussels and corals, that have settled as loose material on the seabed and have compressed and cemented together over time, creating hard rock.
How lime is produced
Limestone is quarried in calcareous areas around the world. Sweden has lots of limestone deposits in areas such as Dalarna, Värmland, Närke, Västergötland and Skåne, as well as on the islands of Gotland and Öland.
The limestone is crushed into different fractions, with the intended application determining the size of the crushed stone. Crushed limestone is used without further processing but can also be processed further. This involves placing the limestone in lime kilns where it is burned at very high temperatures in a calcination process to form calcium oxide (CaO), known as burnt lime.
The burnt lime can then be mixed with water. The reaction of the calcium oxide with water produces calcium hydroxide, or slaked lime Ca(OH)2. Depending on the amount of water added to the process, slaked lime is produced in the form of either dry powder or a paste.
Types of lime
Limestone crushed into different fractions is used for agriculture and gardening but also for lake and wetland liming. Crushed lime is also used in the manufacture of paper, paint, asphalt, brick, concrete, metals and more.
Burnt lime is used in the production of iron, steel and cellulose, as well as in the treatment of water and flue gases and in the mining industry.
Depending on the amount of water added to the process, slaked lime is produced in the form of either dry powder or as a paste. Slaked lime is used for water and flue gas treatment and in the building materials industry.
The mineral dolomite is a carbonate rock that is closely related to limestone. Dolomite is formed when limestone is subjected to dolomitization, a process where calcium ions are replaced by magnesium ions. Dolomite is used in agriculture but also as a filler in the paints and plastics industry.
Various fractions of burnt dolomite and also burnt lime are used in steel production to form slag and protect the steel against oxidation. In this process, impurities that are harmful to steel are collected in the slag. Burnt dolomite also protects the fireproof lining in the steel furnace, converter or ladle furnace.