Oxide Lime

CHEMICAL NAME = calcium oxide CAS NUMBER = 1305-78-8 MOLECULAR FORMULA = CaO MOLAR MASS = 56.0 g/mol COMPOSITION = Ca(71.4%) 0(28.6%) 

Calcium oxide is a white caustic crystalline alkali substance that goes by the common name lime. The term lime is used both generically for several calcium compounds and with adjectives to qualify different forms of lime. This entry equates lime, also called quicklime or burnt lime, with the compound calcium oxide. Hydrated lime, made by combining lime with water, is calcium hydroxide and is often referred to as slaked lime (Ca(OH)2). Dolomite limes contain magnesium as well as calcium. Limestone is the compound calcium carbonate. The term lime comes from the Old English word lim for a sticky substance and denotes lime s traditional use to produce mortar. Calx was the Latin word for lime and was used to name the element calcium. 

Calcium oxide dates from prehistoric times. It is produced by heating limestone to drive off carbon dioxide in a process called calcination CaCO , —-— CaO, + CO ,At tem-peratures of several hundred degrees Celsius, the reaction is reversible and calcium oxide will react with atmospheric carbon dioxide to produce calcium carbonate. Efficient calcium oxide production is favored at temperatures in excess of 1,000°C. In prehistoric times limestone was heated in open fires to produce lime. Over time, lined pits and kilns were used to produce lime. Brick lime kilns were extensively built starting in the 17th century and the technology to produce lime has remained relatively constant since then. 

Modern lime kilns operate at approximately 1,200°C to 1,300°C. Limestone, which has been crushed and screened into pieces with diameters of several inches, is fed into the top of the kiln. Air fed into the kilns bottom fluidizes the limestone, allowing for greater reaction 

Both lime and slaked limes are use to reduce sulfur emissions, which contribute to acid precipitation, from power plants, particularly coal-fired plants. By using lime, more than 95% of the sulfur can be eliminated from the emissions. Calcium oxide reacts with sulfur dioxide to produce calcium sulfite CaOfe) + S02( — CaS03(). Sulfur dioxide is also removed by spraying limewater in the flue gas. Limewater, also called milk of lime, is a fine suspension of calcium hydroxide in water. Other pollutants removed with lime include sulfur trioxide, hydrofluoric acid, and hydrochloric acid. 

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CHIYODA thoroughbred 121 process forced oxidation lime spray drying... 

The choice of selected raw materials is very wide, but they must provide calcium oxide (lime), iron oxide [1309-37-1/, siHca, and aluminum oxide (alumina). Examples of the calcereous (calcium oxide) sources are calcium carbonate minerals (aragonite [14791-73-2] calcite [13397-26-7] limestone [1317-65-3] or mad), seasheUs, or shale. Examples of argillaceous (siHca and alumina) sources are clays, fly ash, mad, shale, and sand. The iron oxide commonly comes from iron ore, clays, or mill scale. Some raw matedals supply more than one ingredient, and the mixture of raw matedals is a function of their chemical composition, as deterrnined by cost and availabiHty. 

Calcium oxide (lime) Rotary kilns, vertical and shaft kilns, fluidized bed furnaces Particulate matter Cyclones plus secondary collectors (baghouse, ESP, wet scrubbers, granular bed filters, wet cyclones)... 

Alkali Ammonia Biocides Sodium hydroxide (caustic soda) Potassium hydroxide (caustic potash) Calcium oxide (lime) Calcium hydroxide Sodium, potassium and calcium carbonates Ammonia (q.v.)... 

Calcium Oxide (lime, Quicklime, Burnt Lime, Calx, Unslaked Lime, Fluxing Lime). CaO, mw 56.08, white or greyish-white lumps or powd, mp 2580°, bp 2850°, d 3.25-3.40g/cc. SI sol in w with formation of calcium hydroxide and evolution of large amts of heat sol in acids, and insol in ethanol. Coml prepn consists of heating calcium carbonate in kilns at 1000—1100° until all of the C02 is driven off. Lab prepn is by burning calcium carbonate or calcium oxalate at about 800° using a quartz crucible in an electric furnace... 

The production of steel begins when iron ore is fed into a blast furnace (Fig. 16.39). The furnace, which is approximately 40 m high, is continuously replenished from the top with a mixture of ore, coke, and limestone. Each kilogram of iron produced requires about 1.75 kg of ore, 0.75 kg of coke, and 0.25 kg of limestone. The limestone, which is primarily calcium carbonate, undergoes thermal decomposition to calcium oxide (lime) and carbon dioxide. The calcium oxide, which contains the Lewis base O2", helps to remove the acidic (nonmetal oxide) and amphoteric impurities from the ore ... 

Potassium hydroxide (caustic potash) Calcium oxide (lime)... 

Sulfur dioxide can be removed from power plant exhaust gas by a scrubber s tem. One common method involves the reaction of SO2 with calcium oxide (lime) to form calcium sulfite S02(g) + CaO( ) CaS03 ( ) Unfortunately, scrubber systems are expensive to operate, and the solid CaS03 is generated in large enough quantities to create significant disposal problems. 

Removing a product from a system at equilibrium also makes Q < and leads to the formation of additional products. This behavior is commonly used to advantage in chemical synthesis. For example, calcium oxide (lime), an important material in the construction industry, is made by heating calcium carbonate in a furnace to about 1100 K CaCOs ( ) CaO (s) + CO2 (g) = (pco2 = 10 at 1100 K... 

Nickel sulfate can be produced from either pure or impure sources. The pure source involves the reaction of pure nickel or nickel oxide powder (combined or separately) with sulfuric acid to produce nickel sulfate that is filtered and crystallized to produce a solid product. The impure raw material may be spent industrial liquor that contains a high percentage of nickel sulfate. The impurities in the liquor are precipitated by sequential treatment with oxidizers lime and sulfides can later be filtered out. The treated liquor, which is a pure solution of nickel sulfate, can be packaged in a drum or further crystallized and dried to produce solid nickel sulfate. Nickel sulfate is used mainly in the metal plating industries. Other uses include dyeing and printing of fabrics and production of patina, an alloy of zinc and brass. 

Many metal hydroxides are insoluble. For example, when MgO is made into a slurry, the white suspension is known as milk of magnesia. Calcium oxide (lime) is produced by heating limestone (calcium carbonate) at high temperature. 

The specimen Scheerer analyzed was given to him by Professor B. M. Keilhau (51). Using a very small sample, Scheerer made an appioximate quantitative analysis, from which he reported the presence of tantalic and titanic acids, yttria, uranous, cerous, and lanthanum oxides, lime, magnesia, and water. He named the mineral euxenite because of... 

It can be shown that the oxygen we breathe combines with carbon (from our food) to make carbon dioxide by a natural process of oxidation. Lime water" is normally clear, but turns cloudy when carbon dioxide is passed through it. The air around us contains only a trace of carbon dioxide, and so does not cause lime water to change color. But the air we breathe out, when bubbled through lime water, will turn it milky, because of the carbon dioxide present. 

Ca- and Mg-oxides (lime, periclase [MgO]) may occur as small crystals embedded within the glass or they may be located on its surface depending on temperature and furnace conditions where the minerals formed. Low-temperature minerals such as anhydrite (CaS04) may form on the surface of the fly ash grains after they have left the high-temperature zones in the furnace (Linton et al. 1977 Soroczak et al 1987 Ainsworth et al. 1993 Fishman et al. 1999). 

Specifically, to react calcium oxide (lime) with water to form calcium... 

The colour of the ash, its solubility in hydrochloric acid, and its neutrality or alkalinity are noted a qualitative analysis may be made, with reference especially to the silica, alumina, ferric oxide, lime, magnesia, alkalies, phosphates, carbonates, sulphates and chlorides. 

Hydroxides of reactive metals show no decomposition when they are heated. The hydroxides of moderately reactive metals do decompose to produce the metal oxide and water. This process is used to convert calcium hydroxide (slaked lime) into calcium oxide (lime). 

Some calcium oxide (lime) is added to remove these solid oxides as slag. The slag may be skimmed or poured off the surface. 

When calcium carbonate is heated strongly it thermally dissociates (breaks up reversibly) to form calcium oxide (lime) and carbon dioxide. 

Decomposition. A decomposition reaction can be considered to be the reverse of a combination reaction. In a decomposition reaction, one substance (the reactant) decomposes to form two or more products. For example, calcium carbonate (limestone) decomposes at high temperatures to calcium oxide (lime) and carbon dioxide. This reaction is used industrially to produce large quantities of lime. 

Confusion can arise because the names or formulae of compounds can be used lo denote either phases or components this applies especially to CaO and MgO. Here and elsewhere, we shall generally use chemical or mineral names of oxides (e.g. calcium oxide, magnesium oxide, lime, periclase) for phases and formulae (e.g. CaO, MgO) for components. Mineral names or prefixed formulae (e.g. a-AljOj) are never used for components. 

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