Carbide lime

Calcium carbide is produced by reacting quicklime and coke at 1800 to 2100 °C (see section 31.4). The carbide is then reacted with water to form acetylene and calcium hydroxide as a by-product. A few acetylene producers use a dry generation process (otherwise known as the water to carbide process), which results in a powdered hydrated lime, commonly called carbide lime . A high level of control is exercised over the water addition and the calcium carbide/hydrate mixture is agitated continuously to prevent localised over-heating and the formation of undesirable polymerised by-products. 

The dry hydrate is more convenient to handle than the milk of lime produced by the carbide to water wet generation processes (see section 22.9). While it may be less pure than many commercial hydrates, it is used for the production of masonry mortar, acid neutralisation, water purification and water treatment. It has also been calcined to regenerate quicklime for recycling to the carbide furnace [20.2,20.18]. 

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Most carbide acetylene processes are wet processes from which hydrated lime, Ca(OH)2, is a by-product. The hydrated lime slurry is allowed to settle in a pond or tank after which the supernatant lime-water can be decanted and reused in the generator. Federal, state, and local legislation restrict the methods of storage and disposal of carbide lime hydrate and it has become increasingly important to find consumers for the by-product. The thickened hydrated lime is marketed for industrial wastewater treatment, neutrali2ation of spent pickling acids, as a soil conditioner in road constmction, and in the production of sand-lime bricks. 

Carbide lime is a waste lime hydrate by-product from the generation of acetylene from calcium carbide and may occur as a wet sludge or dry powder of widely varying purity and particle size. It is gray and has the pungent odor associated with acetylene (see Hydrocarbons, acetylene). 

Names calcium hydroxide, carbide lime, lime hydrate, hydrated hme, slaked hme CAS 1305-62-0... 

White Knight 100 - acetylene production co-product derived from carbide lime... 

Austria. The Statistische Nachrichten (3), issued monthly, gives statistics on population, labor conditions, production, foreign trade, and wholesale prices. Production figures are given for caustic soda, chlorine, carbon dioxide, calcium carbide, lime-ammonium nitrate, acetylene (dissolved), oxygen, soda crystals, soaps and detergents, cellulose, rayon, and magnesite. 

When selecting a product for agricultural liming, a critical factor is the delivered cost per unit of neutralising value [30.2]. In consequence, when lime is used, inexpensive grades of lime are favoured. TTiese include the fines screened from run-of-kiln lime, which contain more impurities (such as fuel ash, sulfur and clay) than the coarser fractions (see section 17.1.3). Hydrator rejects (section 20.4.3) and carbide lime (section 22.10) are also used. 

In dry generators, the carbide is reacted with a controlled excess of water to produce acetylene, steam and hydrated lime with 1 to 2 % of excess water. Part of the hydrated lime may be calcined to quicklime and recycled to the carbide furnace. The remainder, which acts as a purge for impurities, can be used in many of the applications described for hydrated lime (see also section 20.10). Few details of kilns used for the dehydration of carbide lime appear to have been published. Kampmann [31.4] mentions granulation and briquetting of the hydrate, presumably for feeding into a rotary kiln. Other techniques, such as fluidised bed calcining would also appear to be appropriate (see section 16.4.11). 

This route to trichloroethylene is not widely used, but provides an outlet for carbide lime in works which use the calcium carbide process to generate acetylene (see section 31.4.2). 

Carbide lime is a by-product of acetylene production from calcium carbide. It is principally calcium hydroxide and oceurs either as a wet sludge or a dry powder of varying degrees of purity and partiele size. 

G-1,5 Carbide Lime—Its Value and Its Uses, Describes the use of calcium hydroxide (a byproduct from acetylene generation) in agriculture, building construction, industrial and chemical processes, and miscellaneous uses. (16 pages)... 

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