The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and completely enclosed by land: on the north by Southern Europe and Anatolia, on the south by North Africa and on the east by the Levant. Although the sea is sometimes considered a part of the Atlantic Ocean, it is identified as a separate body of water. Geological evidence indicates that around 5.9 million years ago, the Mediterranean was cut off from the Atlantic and was or desiccated over a period of some 600,000 years, the Messinian salinity crisis, before being refilled by the Zanclean flood about 5.3 million years ago. It covers an approximate area of 2.5 million km2, representing 0.7 % of the global ocean surface, but its connection to the Atlantic via the Strait of Gibraltar-the narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Spain in Europe from Morocco in Africa- is only 14 km wide. In oceanography, it is sometimes called the Eurafrican Mediterranean Sea or the European Mediterranean Sea to distinguish it from mediterranean seas elsewhere.
The Mediterranean Sea has an average depth of 1,500 m and the deepest recorded point is 5,267 m in the Calypso Deep in the Ionian Sea. The sea is bordered on the north by Europe, the east by Asia, in the south by Africa, it is located between latitudes 30° and 46° N and longitudes 6° W and 36° E. Its west-east length, from the Strait of Gibraltar to the Gulf of Iskenderun, on the southwestern coast of Turkey, is 4,000 km; the sea's average north-south length, from Croatia's southern shore to Libya, is 800 km. The sea was an important route for merchants and travellers of ancient times that allowed for trade and cultural exchange between emergent peoples of the region; the history of the Mediterranean region is crucial to understanding the origins and development of many modern societies. The countries surrounding the Mediterranean in clockwise order are Spain, Monaco, Slovenia, Croatia and Herzegovina, Albania, Turkey, Lebanon, Egypt, Tunisia and Morocco. In addition, the Gaza Strip and the British Overseas Territories of Gibraltar and Akrotiri and Dhekelia have coastlines on the sea.
The Ancient Greeks called the Mediterranean ἡ θάλασσα or sometimes ἡ μεγάλη θάλασσα, ἡ ἡμέτερα θάλασσα, or ἡ θάλασσα ἡ καθ'ἡμᾶς. The Romans called it Mare Mare Internum and, starting with the Roman Empire, Mare Nostrum; the term Mare Mediterrāneum appears later: Solinus used it in the 3rd century, but the earliest extant witness to it is in the 6th century, in Isidore of Seville. It means'in the middle of land, inland' in Latin, a compound of medius, -āneus; the Latin word is a calque of Greek μεσόγειος, from μέσος and γήινος, from γῆ. The original meaning may have been'the sea in the middle of the earth', rather than'the sea enclosed by land'; the Carthaginians called it the "Syrian Sea". In ancient Syrian texts, Phoenician epics and in the Hebrew Bible, it was known as the "Great Sea" or as "The Sea". Another name was the "Sea of the Philistines", from the people inhabiting a large portion of its shores near the Israelites. In Modern Hebrew, it is called HaYam HaTikhon'the Middle Sea'. In Modern Arabic, it is known as al-Baḥr al-Mutawassiṭ'the Middle Sea'.
In Islamic and older Arabic literature, it was Baḥr al-Rūm'the Sea of the Romans' or'the Roman Sea'. At first, that name referred to only the Eastern Mediterranean, but it was extended to the whole Mediterranean. Other Arabic names were Baḥr al-šām'the Sea of Syria' and Baḥr al-Maghrib'the Sea of the West'. In Turkish, it is the Akdeniz'the White Sea'; the origin of the name is not clear, as it is not known in earlier Greek, Byzantine or Islamic sources. It may be to contrast with the Black Sea. In Persian, the name was translated as Baḥr-i Safīd, used in Ottoman Turkish, it is the origin of the colloquial Greek phrase Άσπρη Θάλασσα. Johann Knobloch claims that in Classical Antiquity, cultures in the Levant used colours to refer to the cardinal points: black referred to the north, yellow or blue to east, red to south, white to west; this would explain both the Turkish Akdeniz and the Arab nomenclature described above. Several ancient civilizations were located around the Mediterranean shores and were influenced by their proximity to the sea.
It provided routes for trade and war, as well as food for numerous communities throughout the ages. Due to the shared climate and access to the sea, c
A steel mill or steelworks is an industrial plant for the manufacture of steel. It may be an integrated steel works carrying out all steps of steelmaking from smelting iron ore to rolled product, but may describe plants where steel semi-finished casting products are made, from molten pig iron or from scrap. Since the invention of the Bessemer process, steel mills have replaced ironwork, based on puddling or fining methods. New ways to produce steel appeared later: from scrap melted in an electric arc furnace and, more from direct reduced iron processes. In the late 19th and early 20th centuries the world's largest steel mill was the Barrow Hematite Steel Company steelworks located in Barrow-in-Furness, United Kingdom. Today, the world's largest steel mill is in South Korea. An integrated steel mill has all the functions for primary steel production: iron making, steel making, roughing rolling/billet rolling product rolling; the principal raw materials for an integrated mill are iron ore and coal.
These materials are charged in batches into a blast furnace where the iron compounds in the ore give up excess oxygen and become liquid iron. At intervals of a few hours, the accumulated liquid iron is tapped from the blast furnace and either cast into pig iron or directed to other vessels for further steel making operations; the Bessemer process was a major advancement in the production of economical steel, but it has now been replaced by other processes such as the basic oxygen furnace. Molten steel is cast into large blocks called blooms. During the casting process various methods are used, such as addition of aluminum, so that impurities in the steel float to the surface where they can be cut off the finished bloom; because of the energy cost and structural stress associated with heating and cooling a blast furnace these primary steel making vessels will operate on a continuous production campaign of several years duration. During periods of low steel demand, it may not be feasible to let the blast furnace grow cold, though some adjustment of the production rate is possible.
Integrated mills are large facilities that are only economical to build in 2,000,000-ton per year annual capacity and up. Final products made by an integrated plant are large structural sections, heavy plate, wire rod, railway rails, long products such as bars and pipe. A major environmental hazard associated with integrated steel mills is the pollution produced in the manufacture of coke, an essential intermediate product in the reduction of iron ore in a blast furnace. Integrated mills may adopt some of the processes used in mini-mills, such as arc furnaces and direct casting, to reduce production costs. A minimill is traditionally a secondary steel producer, it obtains most of its iron from scrap steel, recycled from used automobiles and equipment or byproducts of manufacturing. Direct reduced iron is sometimes used with scrap, to help maintain desired chemistry of the steel, though DRI is too expensive to use as the primary raw steelmaking material. A typical mini-mill will have an electric arc furnace for scrap melting, a ladle furnace or vacuum furnace for precision control of chemistry, a strip or billet continuous caster for converting molten steel to solid form, a reheat furnace and a rolling mill.
The mini mill was adapted to production of bar products only, such as concrete reinforcing bar, angles, channels and light rails. Since the late 1980s, successful introduction of the direct strip casting process has made mini mill production of strip feasible. A mini mill will be constructed in an area with no other steel production, to take advantage of local markets, resources, or lower-cost labour. Mini mill plants may specialize, for example, in making coils of rod for wire-drawing use, or pipe, or in special sections for transportation and agriculture. Capacities of mini mills vary: some plants may make as much as 3,000,000 tons per year, a typical size is in the range 200,000 to 400,000 tons per year, some old or specialty plants may make as little as 50,000 tons per year of finished product. Nucor Corporation, for example, annually produces around 9,100,000 tons of sheet steel from its four sheet mills, 6,700,000 tons of bar steel from its 10 bar mills and 2,100,000 tons of plate steel from its two plate mills.
Since the electric arc furnace can be started and stopped on a regular basis, mini mills can follow the market demand for their products operating on 24-hour schedules when demand is high and cutting back production when sales are lower. Foundry List of steel producers Steel § Steel industry McGannon, Harold E.. The Making and Treating of Steel: Ninth Edition. Pittsburgh, Pennsylvania: United States Steel Corporation. Travel Channel video 1 of the Homestead Works An extensive picture gallery of all methods of production in North America and Europe History of steelworks in Scotland Trends in EAF quality capability 1980-2010
Electric arc furnace
An electric arc furnace is a furnace that heats charged material by means of an electric arc. Industrial arc furnaces range in size from small units of one ton capacity up to about 400 ton units used for secondary steelmaking. Arc furnaces used in research laboratories and by dentists may have a capacity of only a few dozen grams. Industrial electric arc furnace temperatures can be up to 1,800 °C, while laboratory units can exceed 3,000 °C. Arc furnaces differ from induction furnaces in that the charge material is directly exposed to an electric arc and the current in the furnace terminals passes through the charged material. In the 19th century, a number of men had employed an electric arc to melt iron. Sir Humphry Davy conducted an experimental demonstration in 1810; the first successful and operational furnace was invented by James Burgess Readman in Edinburgh, Scotland in 1888 and patented in 1889. This was for the creation of phosphorus. Further electric arc furnaces were developed by Paul Héroult, of France, with a commercial plant established in the United States in 1907.
The Sanderson brothers formed The Sanderson Brothers steel Co. in Syracuse, New York, installing the first electric arc furnace in the U. S; this furnace is now on display at Station Square, Pennsylvania. "electric steel" was a specialty product for such uses as machine tools and spring steel. Arc furnaces were used to prepare calcium carbide for use in carbide lamps; the Stassano electric furnace is an arc type furnace that rotates to mix the bath. The Girod furnace is similar to the Héroult furnace. While EAFs were used in World War II for production of alloy steels, it was only that electric steelmaking began to expand; the low capital cost for a mini-mill—around US$140–200 per ton of annual installed capacity, compared with US$1,000 per ton of annual installed capacity for an integrated steel mill—allowed mills to be established in war-ravaged Europe, allowed them to compete with the big United States steelmakers, such as Bethlehem Steel and U. S. Steel, for low-cost, carbon steel "long products" in the U.
S. market. When Nucor—now one of the largest steel producers in the U. S.—decided to enter the long products market in 1969, they chose to start up a mini-mill, with an EAF as its steelmaking furnace, soon followed by other manufacturers. Whilst Nucor expanded in the Eastern U. S. the companies that followed them into mini-mill operations concentrated on local markets for long products, where the use of an EAF allowed the plants to vary production according to local demand. This pattern was followed globally, with EAF steel production used for long products, while integrated mills, using blast furnaces and basic oxygen furnaces, cornered the markets for "flat products"—sheet steel and heavier steel plate. In 1987, Nucor made the decision to expand into the flat products market, still using the EAF production method. An electric arc furnace used for steelmaking consists of a refractory-lined vessel water-cooled in larger sizes, covered with a retractable roof, through which one or more graphite electrodes enter the furnace.
The furnace is split into three sections: the shell, which consists of the sidewalls and lower steel "bowl". The roof supports the refractory delta in its centre, through which one or more graphite electrodes enter; the hearth may be hemispherical in shape, or in an eccentric bottom tapping furnace, the hearth has the shape of a halved egg. In modern meltshops, the furnace is raised off the ground floor, so that ladles and slag pots can be maneuvered under either end of the furnace. Separate from the furnace structure is the electrode support and electrical system, the tilting platform on which the furnace rests. Two configurations are possible: the electrode supports and the roof tilt with the furnace, or are fixed to the raised platform. A typical alternating current furnace is powered by a three-phase electrical supply and therefore has three electrodes. Electrodes are round in section, in segments with threaded couplings, so that as the electrodes wear, new segments can be added; the arc forms between the charged material and the electrode, the charge is heated both by current passing through the charge and by the radiant energy evolved by the arc.
The electric arc temperature reaches around 3000 °C, thus causing the lower sections of the electrodes to glow incandescently when in operation. The electrodes are automatically raised and lowered by a positioning system, which may use either electric winch hoists or hydraulic cylinders; the regulating system maintains constant current and power input during the melting of the charge though scrap may move under the electrodes as it melts. The mast arms holding the electrodes can either carry heavy busbars or be "hot arms", where the whole arm carries the current, increasing efficiency. Hot arms can be made from copper-clad steel or aluminium. Large water-cooled cables connect the bus tubes or arms with the transformer located adjacent to the furnace; the transformer is installed in a vault and is wa
Titanium dioxide known as titanium oxide or titania, is the occurring oxide of titanium, chemical formula TiO2. When used as a pigment, it is called titanium white, Pigment White 6, or CI 77891, it is sourced from ilmenite and anatase. It has a wide range of applications, including paint and food coloring; when used as a food coloring, it has E number E171. World production in 2014 exceeded 9 million metric tons, it has been estimated that titanium dioxide is used in two-thirds of all pigments, pigments based on the oxide has been valued at $13.2 billion. Titanium dioxide occurs in nature as the well-known minerals rutile and brookite, additionally as two high pressure forms, a monoclinic baddeleyite-like form and an orthorhombic α-PbO2-like form, both found at the Ries crater in Bavaria. One of these is known as akaogiite is an rare mineral, it is sourced from ilmenite ore. This is the most widespread form of titanium dioxide-bearing ore around the world. Rutile is the next contains around 98 % titanium dioxide in the ore.
The metastable anatase and brookite phases convert irreversibly to the equilibrium rutile phase upon heating above temperatures in the range 600–800 °C. Titanium dioxide has eight modifications – in addition to rutile and brookite, three metastable phases can be produced synthetically, five high-pressure forms exist: The cotunnite-type phase was claimed by L. Dubrovinsky and co-authors to be the hardest known oxide with the Vickers hardness of 38 GPa and the bulk modulus of 431 GPa at atmospheric pressure; however studies came to different conclusions with much lower values for both the hardness and bulk modulus. The oxides are commercially important ores of titanium; the metal can be mined from other minerals such as ilmenite or leucoxene ores, or one of the purest forms, rutile beach sand. Star sapphires and rubies get their asterism from rutile impurities present in them. Titanium dioxide is found as a mineral in magmatic rocks and hydrothermal veins, as well as weathering rims on perovskite.
TiO2 forms lamellae in other minerals. Molten titanium dioxide has a local structure in which each Ti is coordinated to, on average, about 5 oxygen atoms; this is distinct from the crystalline forms. Spectral lines from titanium oxide are prominent in class M stars, which are cool enough to allow molecules of this chemical to form; the production method depends on the feedstock. The most common mineral source is ilmenite; the abundant Rutile mineral sand can be purified with the chloride process or other processes. Ilmenite is converted into pigment grade titanium dioxide via either the sulfate process or the chloride process. Both Sulfate and Chloride Processes produce the titanium dioxide pigment in the rutile crystal form, but the Sulfate Process can be adjusted to produce the anatase form. Anatase, being softer, is used in paper applications; the Sulfate Process is run as a batch process. Plants using the Sulfate Process require ilmenite concentrate or pretreated feedstocks as suitable source of titanium.
In the sulfate process Ilmenite is treated with sulfuric acid to extract iron sulfate pentahydrate. The resulting synthetic rutile is further processed according to the specifications of the end user, i.e. pigment grade or otherwise. In another method for the production of synthetic rutile from ilmenite the Becher Process first oxidizes the ilmenite as a means to separate the iron component. An alternative process, known as the Chloride process converts ilmenite or other titanium sources to Titanium tetrachloride via reaction with elemental chlorine, purified by distillation, reacted with oxygen to regenerate chlorine and produce the Titanium dioxide. Titanium dioxide pigment can be produced from higher titanium content feedstocks such as upgraded slag and leucoxene via a chloride acid process; the five largest TiO2 pigment processors are in 2019 Chemours, Cristal Global, Venator-Huntsman and Tronox, the largest one. Major paint and coating company end users for pigment grade titanium dioxide include Akzo Nobel, PPG Industries, Sherwin Williams, BASF, Kansai Paints and Valspar.
Global TiO2 pigment demand for 2010 was 5.3 Mt with annual growth expected to be about 3-4%. For specialty applications, TiO2 films are prepared by various specialized chemistries. Sol-gel routes involve the hydrolysis of titanium alkoxides, such as titanium ethoxide: Ti4 + 2 H2O → TiO2 + 4 EtOHThis technology is suited for the preparation of films. A related approach that relies on molecular precursors involves chemical vapor deposition. In this application, the alkoxide is volatilized and decomposed on contact with a hot surface: Ti4 → TiO2 + 2 Et2O The most important application areas are paints and varnishes as well as paper and plastics, which account for about 80% of the world's titanium dioxide consumption. Other pigment applications such as printing inks, rubber, cosmetic products and food account for another 8%; the rest is used in other applications, for instance the production of technical pure titanium and glass ceramics, electrical ceramics, metal patinas, electric conductors and chemical intermediates.
Titanium dioxide is the most used white pigment because of its brightness and high refractive index, in whi
In chemistry, the adjective ferrous indicates a compound that contains iron in the +2 oxidation state as the divalent cation Fe2+. It is opposed to "ferric", which indicates presence of iron in a +3 oxidation state, such as the trivalent cation Fe3+; this usage has been replaced by the IUPAC nomenclature, which calls for the oxidation state being indicate by Roman numerals in parentheses, such as iron oxide for ferrous oxide, iron oxide for ferric oxide, iron oxide for the oxide Fe3O4 that contains both forms of iron. Outside chemistry, ferrous means "containing iron"; the word is derived from the Latin word ferrum. Ferrous metals include alloys of iron with other metals. "Non-ferrous" is used to describe metals and alloys that do not contain an appreciable amount of iron. The term "ferrous" is applied only to metals and alloys; the adjective ferruginous is used instead to refer to non-metallic substances that contain iron, such as "ferruginous water". Ferromagnetism Steelmaking Ferrous metal recycling Iron oxide Iron bromide
Magnesite is a mineral with the chemical formula MgCO3. Iron, manganese and nickel may occur as admixtures, but only in small amounts. Magnesite occurs as veins in and an alteration product of ultramafic rocks and other magnesium rich rock types in both contact and regional metamorphic terrains; these magnesites are cryptocrystalline and contain silica in the form of opal or chert. Magnesite is present within the regolith above ultramafic rocks as a secondary carbonate within soil and subsoil, where it is deposited as a consequence of dissolution of magnesium-bearing minerals by carbon dioxide in groundwaters. Magnesite can be formed via talc carbonate metasomatism of peridotite and other ultramafic rocks. Magnesite is formed via carbonation of olivine in the presence of water and carbon dioxide at elevated temperatures and high pressures typical of the greenschist facies. Magnesite can be formed via the carbonation of magnesium serpentine via the following reaction: 2 Mg3Si2O54 + 3 CO2 → Mg3Si4O102 + 3 MgCO3 + 3 H2O.
However, when performing this reaction in the laboratory, the trihydrated form of magnesium carbonate will form at room temperature. This observation led to the postulation of a "dehydration barrier" being involved in the low-temperature formation of anhydrous magnesium carbonate. Laboratory experiments with formamide, a liquid resembling water, have shown how no such dehydration barrier can be involved; the fundamental difficulty to nucleate anhydrous magnesium carbonate remains when using this non-aqueous solution. Not cation dehydration, but rather the spatial configuration of carbonate anions creates the barrier in the low-temperature nucleation of magnesite. Magnesite has been found in modern sediments and soils, its low-temperature formation is known to require alternations between precipitation and dissolution intervals. Magnesite was detected on planet Mars itself. Magnesite was identified on Mars using infra-red spectroscopy from satellite orbit. Controversy still exists over the temperature of formation of this magnesite.
Low-temperature formation has been suggested for the magnesite from the Mars-derived ALH84001 meteorite. The low-temperature formation of magnesite might well be of significance toward large-scale carbon sequestration. Magnesium-rich olivine favors production of magnesite from peridotite. Iron-rich olivine favors production of magnetite-magnesite-silica compositions. Magnesite can be formed by way of metasomatism in skarn deposits, in dolomitic limestones, associated with wollastonite and talc. Similar to the production of lime, magnesite can be burned in the presence of charcoal to produce MgO, which, in the form of a mineral, is known as periclase. Large quantities of magnesite are burnt to make magnesium oxide: an important refractory material used as a lining in blast furnaces and incinerators. Calcination temperatures determine the reactivity of resulting oxide products and the classifications of light burnt and dead burnt refer to the surface area and resulting reactivity of the product as determined by an industry metric of the iodine number.'Light burnt' product refers to calcination commencing at 450 °C and proceeding to an upper limit of 900 °C - which results in good surface area and reactivity.
Above 900 °C, the material loses its reactive crystalline structure and reverts to the chemically inert'dead-burnt' product-, preferred for use in refractory materials such as furnace linings. Magnesite can be used as a binder in flooring material. Furthermore, it is being used as a catalyst and filler in the production of synthetic rubber and in the preparation of magnesium chemicals and fertilizers. In fire assay, magnesite cupels can be used for cupellation as the magnesite cupel will resist the high temperatures involved. Magnesite can be cut and polished to form beads that are used in jewelry-making. Magnesite beads can be dyed into a broad spectrum of bold colors, including a light blue color that mimics the appearance of turquoise. Research is proceeding to evaluate the practicality of sequestering the greenhouse gas carbon dioxide in magnesite on a large scale. People can be exposed to magnesite in the workplace by inhaling it, skin contact, eye contact; the Occupational Safety and Health Administration has set the legal limit for magnesite exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.
The National Institute for Occupational Safety and Health has set a recommended exposure limit of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. Smithsonian Rock and Gem ISBN 0-7566-0962-3