Lime is a basic industrial chemical that is used as a component in many other chemical processes.
Alkali plants with access to natural soda ash use the "lime-soda process to manufacture caustic soda (sodium hydroxide). Sodium carbonate (soda ash) reacts with a lime slurry to form caustic soda and precipitated calcium carbonate as co-products.
Calcium carbide, the oldest source of acetylene, is formed by mixing quicklime and coke and heating to a temperature of 2000 degrees C. Molten carbide is removed from the furnace continuously, and upon solidifying, is crushed and ground to the desired size. Calcium cyanamide, a nitrogen fertilizer, is made by heating calcium carbide in the presence of nitrogen. Acetylene gas is generated from carbide by adding water, yielding a waste hydrated lime.
Lime is used in the purification of citric acid. Hydrated lime is added to a solution of citric acid that has previously been filtered to remove suspended solids. Calcium citrate is precipitated and removed. Citric acid can later be regenerated from the calcium citrate by reacting it with sulfuric acid to precipitate calcium sulfate.
Lime is used in the two major processes to manufacture magnesia (magnesium oxides): the seawater process and production from brines. In the seawater process, milk of lime precipitates magnesium hydroxide from seawater. Where dolomitic lime is used, up to half of the Mg(OH)2 derives from the lime. So too, in the production of Mg(OH)2 from brine, lime acts as a precipitant.
Calcium hypochlorite bleaches are produced by reacting lime with chlorine. These bleaches are widely used as swimming pool chemicals and in paper production.
Dolomitic lime is reacted with acetic acid to produce calcium magnesium acetate (CMA), a deicing chemical. CMA is not corrosive and is very compatible with the environment. It is much less damaging to road surfaces and to automotive parts than salt. It is effective in melting ice at very low temperatures, and is not toxic to vegetation.
Lime is employed in the manufacture of many other inorganic and organic chemicals and pharmaceuticals. Most of the calcium organic and inorganic salts are produced by reacting the various acids with lime (the base). Among the most important of such inorganic products are calcium phosphates (mono, di, and tri), fluoride, bromide, ferrocyanide, and nitrate. Among the organics are calcium acetate, stearate, oleate, tartrate, lactate, citrate, benzoate, and gluconate.
In addition, lime is used as a neutralizing agent in the manufacture of chrome chemicals (bichromate); for purification of salt brines; to aid in the concentration of glucose and dextrin; to make metallic calcium; as soda-lime, an adsorbent and gas purifier; and for countless other minor or isolated purposes, such as for CO2 absorption, as a desiccant, etc.
Lime is used in the production of ethylene or propylene glycol via the chlorohydrin process. Ethylene gas, obtained readily from petroleum refineries, is chlorinated to form ethylene dichloride, which in turn is reacted with lime to produce ethylene glycol.
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