Calcium-magnesium oxide from dolomite

Rules are provided to aid decision making at each step. The procedure is illustrated with examples including separation of amino acids, p- and / -cresols, chorobenzoic acids, calcium carbonate and magnesium oxide from dolomite, and the production of salt. 

Thermal Properties. Because all limestone is converted to an oxide before fusion or melting occurs, the only melting point appHcable is that of quicklime. These values are 2570°C for CaO and 2800°C for MgO. Boiling point values for CaO are 2850°C and for MgO 3600°C. The mean specific heats for limestones and limes gradually ascend as temperatures increase from 0 to 1000°C. The ranges are as follows high calcium limestone, 0.19—0.26 dolomitic quicklime, 0.19—0.294 dolomitic limestone, 0.206—0.264 magnesium oxide, 0.199—0.303 and calcium oxide, 0.175—0.286. 

Basic Open Hearth A version of the Open Hearth process for steelmaking in which the hearth is made from calcined dolomite (calcium and magnesium oxides). The sulfur and phosphorus impurities in the raw materials are converted to basic slag, which is separated from the molten steel. First operated in 1882 at Alexandrovsky, near St. Petersburg, Russia, and at Le Creusot, France. It was the major steelmaking process in the world in the first half of the 20th century. See Thomas. 

Metallic magnesium is produced by either chemical or electrolytic reduction of its compounds. In chemical reduction, magnesium oxide is obtained from the decomposition of dolomite. Then ferrosilicon, an alloy of iron and silicon, is used to reduce the MgO at about 1200°C. At this temperature, the magnesium produced is immediately vaporized and carried away. The electrolytic method uses seawater as its principal raw material. The first stage is the precipitation of magnesium hydroxide with slaked lime (calcium hydroxide) ... 

Fig. 2 Basic schematic of a wet scrubber column. Absorbent slurry percolates down through the packing, while the flue gases flow upward. The most common absorbents for sulfur oxides are limestone (calcium carbonate), lime (calcium hydroxide), and magnesium-enhanced lime made from dolomite. The sulfur-bearing sludge for some scrubbers is market-grade gypsum, but for other scrubbers it is a waste product that must be landfilled.

Starting from iron acetate or iron nitrate salts and following the neutral and oxidative pathways, a separated analysis of iron (2+, 2.5+, 3+)-calcium oxide and iron (2+, 2.5+, 3+)-magnesium oxide will be useful also to clarify the nature of the iron-dolomite interaction. The Fe/substrate catalysts have been characterized by X-Ray diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Oxidation (TTO), and Mdssbauer analysis. XRD and TPR experimental conditions, as well as the microreator used in catalytic tests, have been described previously [Di Felice et al., 2009], whereas Mossbauer spectroscopy and TPO are briefly illustrate here. 

Even unpolluted rain can contain both acids and bases. For example, carbon dioxide naturally present in air dissolves in rain to form carbonic acid (H2CO3), the weak acid responsible for the fizz in soda pop. If there were no other substances in rain, CO2 would lower the acidity from neutral (pH 7.0) to weakly acidic (pH 5.6). Unpolluted rain also contains small amounts of acid sulfate and acid nitrate that are produced in the stratosphere. These acids would further lower the natural pH of rain to about 5.4. Several alkaline substances partly neutralize the acidity in rain Ammonia, which is naturally present in the air, dissolves in rain to form ammonium salts. Soil dust containing alkaline minerals such as limestone (calcium carbonate) and dolomite (magnesium carbonate) can dissolve in rain and raise its pH. Fly ash from coal combustion contains calcium and magnesium oxides, which also are alkaline. The pH of rain therefore reflects the competing influence of several different substances. 

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. 

The above-listed features of the formation of X-ray amorphous and crystalline products are observed in the decompositions of many other compounds. Haul and Schoning [41] applied an X-ray method (line-width technique) to study the structure of the decomposition products of dolomite as a function of temperature. The experiments were carried out both in vacuum and in a CO2 environment. In vacuum, decomposition proceeded to the CaO and MgO oxides, and in a CO2 environment, to CaCOs and MgO. This difference is reasonable. It originates from the calcium carbonate being more stable than the magnesium carbonate (the enthalpies of formation of CaCOs and MgCOg at 800 K are —1,154 and —1,045 kJ mol respectively). The size of the crystallites formed in vacuum [41] increased monotonically from 6nm for MgO and 13 nm for CaO to 120-140 nm with the temperature increasing within the range 700-1,000° C. (Oversaturation decreases in these conditions from 10 to 10 for MgO, and from 10 to 10 for CaO.)... 

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