Lime applications

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Lime applications describe the use of lime products, lime and lime-based products in various sectors of industry, the environment and agriculture. The areas of application and tasks of lime are varied as natural limestone, as burnt calcium oxide, as slaked hydrated lime or as chemically precipitated calcium carbonate.

definition

The term "lime" is derived from the Latin word "calx". The term "lime" is used in many ways. In the broadest sense, it means the natural rock deposits of calcium carbonate : limestone , marble and chalk as well as dolomite stone of a similar nature - popularly only the element calcium . In a narrower sense, lime is understood to mean the refined products quicklime and slaked lime , also called hydrated lime , which are obtained industrially. Limestone (calcium carbonate) was usually formed millions of years ago from the remains of organisms living in the sea. Lime is produced by burning limestone and, chemically speaking, is the compound calcium oxide .

application areas

Lime and limestone are irreplaceable raw materials. Lime products are indispensable for the iron and steel industry, but also of great importance for environmental technology, the construction industry, the chemical industry, pulp and paper production as well as agriculture, forestry and pond management.

iron and Steel

Around a third of the total quicklime production is supplied to the iron and steel industry. When extracting iron from iron ore, lime first makes the ore lumpy and therefore suitable for blast furnaces. In the blast furnace, lime removes disruptive mineral impurities from the liquid pig iron. Approx. 20 to 30 kg of quicklime and approx. 100–200 kg of limestone are used to produce one ton of pig iron. In steel production, lime removes carbon, silicon, phosphorus and manganese from the raw material and binds the sulfur. Depending on the manufacturing process, 40 to 60 kilograms of quicklime are required to produce one ton of steel.

environmental Protection

  • Lime is used for wastewater purification , drinking water treatment , sewage sludge treatment , flue gas desulphurisation and in the fight against acid rain , because lime can bind toxins and thus render them harmless.
  • In wastewater treatment, germicidal conditions can be set with the help of lime. Lime also lowers the phosphate content of the water. This avoids a depletion of oxygen in the waters.
  • When treating drinking water, lime is used for softening, hardening and neutralization, thus ensuring consistently good water quality.
  • Lime can be used to dewater and solidify sewage sludge. The advantages of the lime process in the sewage process are that plant-available, pure calcium phosphates are created that can be reused as fertilizers.
  • More than 95% of the European incineration plants work with lime products to incorporate harmful gases.
  • Due to the air pollution and the acid rain it causes, many trees suffer from a calcium and magnesium deficiency caused by the acidification of the forest soils. With the help of lime, the pH value can be raised, thereby significantly increasing the resistance of the trees. Therefore, lime-based fertilizers are blown into the forests with helicopters or special vehicles and the nutrients used up are replaced. The forest soils are not only important for plant health, they also filter rainwater and make a decisive contribution to drinking water quality .

Construction industry

Quick lime is used in the manufacture of mortar and plaster . Lime is also of great importance as a component of aerated concrete and sand-lime brick in masonry construction . Limestone with a correspondingly processed surface can be used as natural stone. In road construction , lime is mixed into the soil with special milling machines to improve the soil. It regulates the humidity and makes the road sub-structure more resistant to frost. Lime is also used in all layers of the road surface - be it as a mixture of limestone building materials in the frost protection layer, in the various base layers or in conjunction with bitumen in the asphalt surface .

Industrial applications

  • The chemical industry uses lime for the production of inorganic or organic calcium compounds, as a reactant in chemical syntheses , to change pH values , in chemical reactions, physico-chemical processing processes and for neutralization .
  • From a mixture of quartz sand , soda , potash and limestone , glass is melted in the glass tank at temperatures around 1,450 ° C. As a hardener, lime makes the glass hard and tight.
  • Lime is essential for the sugar industry . The dark gray raw juice, heated to 60 ° C, is mixed with milk of lime . In the process, non-sugar substances, especially protein, flocculate.
  • Soda, an important raw material in modern industry, is made from rock salt and limestone .
  • Lime is used in the production of plastics , rubber articles , alcohols, adhesives, paints and varnishes.
  • Lime products are also required for detergents, cosmetics, pharmaceuticals and some foods.

Pulp and paper

  • Lime is used in the pulp and paper industry to recycle caustic soda for the digestion process as well as for water treatment and wastewater purification . A cycle process is common in the recirculation reaction, so that only part of the lime needs to be added.
  • Natural calcium carbonate is the most commonly used color for coated papers in Europe. Precipitated calcium carbonate is used as a filler in the paper pulp or as a pigment in the coating slip. It gives paper the highest whiteness and density , increases the volume and improves printability and lightfastness .

Agriculture, forestry, horticulture and pond management

  • In addition to its humus content, the fertility and productivity of agriculturally used soil primarily depend on a balanced lime content. Lime fertilizer neutralizes acidic soils, ensures the fertility of arable and grassland soil and loosens the soil structure.
  • Every year, around 300 to 450 kilograms of lime calcium oxide per hectare of agricultural land are required for the neutralization of acids found in the soil and those introduced from outside. The plants extract another 50 kilograms of calcium oxide per hectare as they grow.
  • In animal husbandry, fodder lime ensures healthy bones.
  • In stables and in pond management, the germicidal properties of lime are used to carry out hygiene measures.

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