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Sulphide Stress Cracking

Sulphide stress cracking

Sulphide stress cracking (SSC), or sulphide stress corrosion cracking (SSCC), is a special corrosion type, a form of stress corrosion cracking. Susceptible alloys, especially steels, react with hydrogen sulfide, forming metal sulfides and elementary hydrogen, which gets absorbed in metal and leads to hydrogen embrittlement. High content of nickel in the steels greatly improves their resistance to SSC. This type of corrosion is worst at temperatures around 80°C (176°F). Sulphide stress cracking has special importance in gas and oil industry, as the materials being processed there (natural gas and crude oil) often contain considerable amount of hydrogen sulfide. Equipment that comes in contact with such high-sulphur materials has to be rated for sour service. Category:Corrosion

Stress corrosion cracking

Stress corrosion cracking (SCC) is the unexpected sudden failure of normally ductile metals subjected to a constant tensile stress in a corrosive environment, especially at elevated temperature. This type of corrosion often progresses rapidly. The stresses can result of the service loads, or can be caused by the type of assembly or residual stresses from fabrication (eg. cold working); the residual stresses can be relieved by annealing. Certain austenitic stainless steels and aluminium alloys crack in the presence of chlorides, mild steel cracks in the present of alkali (boiler cracking) and copper alloys crack in ammoniacal solutions (season cracking). This limits the usefulness of stainless steel for containing water with higher than few ppm content of chlorides at temperatures above 50 °C. Worse still, high-tensile structural steels crack in an unexpectedly brittle manner in a whole variety of aqueous environments, especially chloride. With the possible exception of the latter, which is a special example of hydrogen cracking, all the others display the phenomenon of subcritical crack growth, i.e. small surface flaws propagate (usually smoothly) under conditions where fracture mechanics predicts that failure should not occur. That is, in the presence of a corrodent, cracks develop and propagate well below KIc. In fact, the subcritical value of the stress intensity, designated as KIscc, may be less than 1% of KIc, as the following table shows: Alloy KIc SCC environment KIscc MN/m3/2 MN/m3/2 ------------------------------------------------------ 13Cr steel 60 3% NaCl 12 18Cr-8Ni 200 42% MgCl2 10 Cu-30Zn 200 NH4OH, pH7 1 Al-3Mg-7Zn 25 Aqueous halides 5 Ti-6Al-1V 60 0.6M KCl 20 The subcritical nature of propagation may be attributed to the chemical energy released as the crack propagates. That is, :elastic energy released + chemical energy = surface energy + deformation energy The crack initiates at KIscc and thereafter propagates at a rate governed by the slowest process, which most of the time is the rate at which corrosive ions can diffuse to the crack tip. As the crack advances so K rises (because crack length appears in the calculation of stress intensity). Finally it reaches KIc , whereupon fast fracture ensues and the component fails. One of the practical difficulties with SCC is its unexpected nature. Stainless steels, for example, are employed because under most conditions they are 'passive', i.e. effectively inert. Very often one finds a single crack has propagated while the rest of the metal surface stays apparently unaffected.

See also


- Fracture mechanics

External links


- [http://www.key-to-metals.com/Article17.htm Stress corrosion cracking of aluminum alloys] Category:Corrosion

Steels

Steel is a metal alloy whose major component is iron, with carbon being the primary alloying material. Carbon acts as a hardening agent, preventing iron atoms, which are naturally arranged in a lattice, from sliding past one another. Varying the amount of carbon and its distribution in the alloy controls qualities such as the hardness, elasticity, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also more brittle. One classical definition is that steels are iron–carbon alloys with up to 1.5 percent carbon by weight; alloys with higher carbon content than this are known as cast iron. Currently there are several classes of steels in which carbon is replaced with other alloying materials, and carbon, if present, is undesired. A more recent definition is that steels are iron-based alloys that can be plastically formed (pounded, rolled, etc.).

Iron and steel

plastically Iron, like most metals, is not found in the Earth's crust in a native state. Iron can be found in the crust only in combination with oxygen or sulfur. Typically Fe2O3—the form of iron oxide found as the mineral hematite, and FeS2—Pyrite. Iron oxide is a soft sandstone-like material with limited uses on its own. Iron is extracted from ore by removing the oxygen by combining it with a preferred chemical partner such as carbon. This process, known as smelting, was first applied to metals with lower melting points. Copper melts at just over 1000 °C, while tin melts around 250 °C. Both temperatures could be reached with ancient methods that have been used for at least 6000 years (since the Bronze Age). Since the oxidation rate itself increases rapidly beyond 800 °C, it is important that smelting take place in a fairly oxygen-free environment. Unlike copper and tin, liquid iron dissolves carbon quite readily, so that smelting results in an alloy containing too much carbon to be called steel. Bronze Age Even in the narrow range of concentrations that make up steel, mixtures of carbon and iron can form into a number of different structures, or allotropes, with very different properties; understanding these is essential to making quality steel. At room temperature, the most stable form of iron is the body-centered cubic structure ferrite or α-iron, a fairly soft metallic material that can dissolve only a small concentration of carbon (no more than 0.021 wt% at 910 °C). Above 910 °C ferrite undergoes a phase transition from body-centered cubic to a face-centered cubic configuration, called austenite or γ-iron, which is similarly soft and metallic but can dissolve considerably more carbon (as much as 2.04 wt% carbon at 1146 °C). As carbon-rich austenite cools, the mixture attempts to revert to the ferrite phase, resulting in an excess of carbon. One way for carbon to leave the austenite is for cementite to precipitate out of the mix, leaving behind iron that is pure enough to take the form of ferrite, and resulting in a cementite-ferrite mixture. Cementite is a stochiometric phase with the chemical formula of Fe3C. Cementite forms in regions of higher carbon content while other areas revert to ferrite around it. Self-reinforcing patterns often emerge during this process, leading to a patterned layering known as pearlite due to its pearl-like appearance, or the similar but less beautiful bainite. Perhaps the most important allotrope is martensite, a chemically metastable substance with about four to five times the strength of ferrite. Martensite has a very similar unit cell structure to austenite, and identical chemical composition. As such, it requires extremely little thermal activation energy to form. The heat treatment process for most steels involves heating the alloy until austenite forms, then quenching the hot metal in water or oil, cooling it so rapidly that the transformation to ferrite or perlite does not have time to take place. The transformation into martensite, by contrast, occurs almost immediately, due to a lower activation energy. Martensite has a lower density than austenite, so that the transformation between them results in a change of volume. In this case, expansion occurs. Internal stresses from this expansion generally take the form of compression on the crystals of martensite and tension on the remaining ferrite, with a fair amount of shear on both constituents. If quenching is done improperly, these internal stresses can cause a part to shatter as it cools; at the very least, they cause internal work hardening and other microscopic imperfections. At this point, if its carbon content is high enough to produce a significant concentration of martensite, the metal resembles spring steel: extremely hard, but very brittle. Often, steel undergoes further heat treatment at a lower temperature to destroy some of the martensite (by allowing enough time for cementite, etc., to form) and help settle the internal stresses and defects. This softens the steel, producing a more ductile and fracture-resistant metal. Because time is so critical to the end result, this process is known as tempering, source of the term tempered steel. Other materials are often added to the iron-carbon mixture to tailor the resulting properties. Nickel and manganese in steel add to its tensile strength and make austenite more chemically stable, chromium increases the hardness and melting temperature, and vanadium also increases the hardness while reducing the effects of metal fatigue. Large amounts of chromium and nickel (often 18 and 8 %, respectively) are added to stainless steel so that a hard oxide forms on the metal surface to inhibit corrosion. Tungsten interferes with the formation of cementite, allowing martensite to form with slower quench rates, resulting in high speed steel. On the other hand sulfur, nitrogen, and phosphorus make steel more brittle, so these commonly found elements must be removed from the ore during processing. When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable. To become steel, it must be melted and reprocessed to remove the correct amount of carbon, at which point other elements can be added. Once this liquid is cast into ingots, it usually must be "worked" at high temperature to remove any cracks or poorly mixed regions from the solidification process, and to produce shapes such as plate, sheet, wire, etc. It is then heat-treated to produce a desirable crystal structure, and often "cold worked" to produce the final shape. In modern steelmaking these processes are often combined, with ore going in one end of the assembly line and finished steel coming out the other. These can be streamlined by a deft control of the interaction between work hardening and tempering.

History of iron and steelmaking

Iron was in limited use long before it became possible to smelt it. The first signs of iron use come from Ancient Egypt and Sumer, where around 4000 BC small items, such as the tips of spears and ornaments, were being fashioned from iron recovered from meteorites (see Iron: History). About 6% of meteorites are composed of an iron-nickel alloy, and iron recovered from meteorite falls allowed ancient peoples to manufacture small numbers of iron artifacts. Meteoric iron was also fashioned into tools in precontact North America. Beginning around the year 1000, the Thule people of Greenland began making harpoons and other edged tools from pieces of the Cape York meteorite. These artifacts were also used as trade goods with other Arctic peoples: tools made from the Cape York meteorite have been found in archaeological sites more than 1000 miles (1600 km) away. When the American polar explorer Robert Peary shipped the largest piece of the meteorite to the American Museum of Natural History in New York City in 1897, it still weighed over 33 tons. The name for iron in several ancient languages means "sky metal" or something similar. In distant antiquity, iron was regarded as a precious metal, suitable for royal ornaments.

The Iron Age

ton Beginning between 3000 BC to 2000 BC increasing numbers of smelted iron objects (distinguishable from meteoric iron by their lack of nickel) appear in Anatolia, Egypt and Mesopotamia (see Iron: History). The oldest known samples of iron that appear to have been smelted from iron oxides are small lumps found at copper-smelting sites on the Sinai Peninsula, dated to about 3000 BC. Some iron oxides are effective fluxes for copper smelting; it is possible that small amounts of metallic iron were made as a by-product of copper and bronze production throughout the Bronze Age. In Anatolia, smelted iron was occasionally used for ornamental weapons: an iron-bladed dagger with a bronze hilt has been recovered from a Hattic tomb dating from 2500 BC. Also, the Egyptian ruler Tutankhamun died in 1323 BC and was buried with an iron dagger with a golden hilt. An Ancient Egyptian sword bearing the name of pharaoh Merneptah as well as a battle axe with an iron blade and gold-decorated bronze haft were both found in the excavation of Ugarit (see Ugarit). The early Hittites are known to have bartered iron for silver, at a rate of 40 times the iron's weigh, with Assyria. Iron did not, however, replace bronze as the chief metal used for weapons and tools for several centuries, despite some attempts. Working iron required more fuel and significantly more labor than working bronze, and the quality of iron produced by early smiths may have been inferior to bronze as a material for tools. Then, between 1200 and 1000 BC, iron tools and weapons displaced bronze ones throughout the near east. This process appears to have begun in the Hittite Empire around 1300 BC, or in Cyprus and southern Greece, where iron artifacts dominate the archaeological record after 1050 BC. Mesopotamia was fully into the Iron Age by 900 BC, central Europe by 800 BC. The reason for this sudden adoption of iron remains a topic of debate among archaeologists. One prominent theory is that warfare and mass migrations beginning around 1200 BC disrupted the regional tin trade, forcing a switch from bronze to iron. Egypt, on the other hand, did not experience such a rapid transition from the bronze to iron ages: although Egyptian smiths did produce iron artifacts, bronze remained in widespread use there until after Egypt's conquest by Assyria in 663 BC. Iron smelting at this time was based on the bloomery, a furnace where bellows were used to force air through a pile of iron ore and burning charcoal. The carbon monoxide produced by the charcoal reduced the iron oxides to metallic iron, but the bloomery was not hot enough to melt the iron. Instead, the iron collected in the bottom of the furnace as a spongy mass, or bloom, whose pores were filled with ash and slag. The bloom then had to be reheated to soften the iron and melt the slag, and then repeatedly beaten and folded to force the molten slag out of it. The result of this time-consuming and laborious process was wrought iron, a malleable but fairly soft alloy containing little carbon. Wrought iron can be carburized into a mild steel by holding it in a charcoal fire for prolonged periods of time. By the beginning of the Iron Age, smiths had discovered that iron that was repeatedly reforged produced a higher quality of metal. Quench-hardening was also known by this time. The oldest quench-hardened steel artifact is a knife found on Cyprus at a site dated to 1100 BC.

Developments in China

Archaeologists and historians debate whether bloomery-based ironworking ever spread to China from the West. Around 500 BC, however, metalworkers in the southern state of Wu developed an iron smelting technology that would not be practiced in Europe until late medieval times. In Wu, iron smelters achieved a temperature of 1130°C, hot enough to be considered a blast furnace. At this temperature, iron combines with 4.3% carbon and melts. As a liquid, iron can be cast into molds, a method far less laborious than individually forging each piece of iron from a bloom. Cast iron is rather brittle and unsuitable for striking implements. It can, however, be decarburized to steel or wrought iron by heating it in air for several days. In China, these ironworking methods spread northward, and by 300 BC, iron was the material of choice throughout China for most tools and weapons. A mass grave in Hebei province, dated to the early third century BC, contains several soldiers buried with their weapons and other equipment. The artifacts recovered from this grave are variously made of wrought iron, cast iron, malleabilized cast iron, and quench-hardened steel, with only a few, probably ornamental, bronze weapons. During the Han Dynasty (202 BC–AD 220), Chinese ironworking achieved a scale and sophistication not reached in the West until the eighteenth century. In the first century, the Han government established ironworking as a state monopoly and built a series of large blast furnaces in Henan province, each capable of producing several tons of iron per day. By this time, Chinese metallurgists had discovered how to puddle molten pig iron, stirring it in the open air until it lost its carbon and became wrought iron. (In Chinese, the process was called chao, literally, stir-frying.) Also during this time, Chinese metallurgists had found that wrought iron and cast iron could be melted together to yield an alloy of intermediate carbon content, that is, steel. According to legend, the sword of Liu Bang, the first Han emperor, was made in this fashion. Some texts of the era mention "harmonizing the hard and the soft" in the context of ironworking; the phrase may refer to this process.

India

Perhaps as early as 300 BC, although certainly by AD 200, high quality steel was being produced in southern India by what Europeans would later call the crucible technique. In this system, high-purity wrought iron, charcoal, and glass were mixed in crucibles and heated until the iron melted and absorbed the carbon. The resulting high-carbon steel, called پولاد (pulâd) in Persian and wootz by later Europeans, was exported throughout much of Asia. A solid pillar of rust-resistant steel forged in 4th century AD and now standing for many centuries next to the Kutab Minar in Delhi is a testimony of the steel manufaturing skills of Indian artisans. The famous Damascus sword was made of steel imported from India.

Middle East

By the 9th century, smiths in the Abbasid caliphate had developed techniques for forging wootz to produce steel blades of unusual flexibility and sharpness (Damascus steel). The secret of forging this kind of steel was lost, even in the Middle East, by around 1600, and only recently have metallurgists found methods for reproducing its properties.

Ironworking in medieval Europe

The middle ages in Europe saw the construction of progressively larger bloomeries. By the 8th century, smiths in northern Spain had developed a style that become known as a Catalan forge, a furnace about 1 meter (3 feet) tall, capable of smelting up to 150 kg (350 lb) of iron in each batch. In succeeding centuries, smiths in the Frankish empire and later the Holy Roman Empire scaled up this basic design, increasing the height of the flue to as tall as 5 meters (16 feet) and smelting as much as 350 kg (750 lb) of iron in each batch. These larger furnaces required more draft than could be provided by human power, and forging the large blooms that resulted was also beyond the capabilities of a single man. To this end, waterwheels were employed to power the bellows and hammers. Eventually, the scaling up of the bloomery reached a point where the furnace was hot enough to produce cast iron. Although the brittle cast iron may initially have been a nuisance to the smith, as it was too brittle to be forged, the spread of cannon to Europe in the 1300s provided an application for iron casting, cast iron cannonballs. The oldest known blast furnace in Europe was constructed at Lapphyttan in Sweden, sometime between 1150 and 1350. Other early European blast furnaces were built throughout the Rhine valley: blast furnaces were in operation near Liège (a city in modern-day Belgium) in the 1340s, and at Massevaux in France by 1409. The first English blast furnace was not built until 1496, when Henry VII commissioned a new ironworks at Newbridge, in a part of Sussex known as the Weald. Despite this late start, the production of English iron foundries rapidly grew, in no small part due to foreign craftsmen hired by Henry to bring the craft of iron casting to England. In 1543, William Levett, a Wealden ironmaster, and Peter Baude, a French craftsman in Henry VIII's employ, cast the Weald's first one-piece iron cannon. English iron cannons gained a reputation for being superior to, and less expensive than, the bronze cannons made elsewhere in Europe, and at least initially, efforts to copy them outside the Weald failed. The superiority of English cannons over Spanish ones has been credited as one factor in England's 1588 defeat of the Spanish Armada. In 1619, Jan Andries Moerbeck, a Dutch ironmaster, began importing Wealden iron ore for comparison to the ore available on the Continent. One difference he observed was that the English ore contained some calcareous material, and soon after, Dutch ironmasters introduced the use of limestone as a flux in the blast furnace. This practice improved the separation of slag from the cast iron and improved the quality of Continental cast iron.

Ironworking in early modern Europe

Dutch Also by the early 1600s, ironworkers in western Europe had found a means (called cementation) to carburize wrought iron without individually forging each piece. Wrought iron bars and charcoal were packed into stone boxes, then held at a red heat for up to a week. During this time, carbon diffused into the iron, producing a product called cement steel or blister steel. For many years the best steels could be produced by buying expensive iron ore from Sweden. Although it was not understood at the time, Swedish ore had very low phosphorus content compared to most ores (notably those in England), which allowed for a finer and stronger crystal structure. Sales of Swedish ore generated considerable trade income, and local development helped the country become the industrialised nation it remains to this day. By the 18th century, deforestation in western Europe was making ironworking and its charcoal-hungry processes increasingly expensive. In 1709 Abraham Darby began smelting iron using coke, a refined coal product, in place of charcoal at his ironworks at Coalbrookdale in England. Although coke could be produced less expensively than charcoal, coke-fired iron was initially of inferior quality compared to charcoal-fired iron. It was not until the 1750s, when Darby's son refined the coking process to reduce the amount of sulfur in the coke that coke-fired furnaces became widespread. Another 18th-century European development was the reinvention of the puddling furnace. In particular, the form of coal-fired puddling furnace developed by the British engineer Henry Cort in 1784 made it possible to convert cast iron into wrought iron in large batches, finally rendering the ancient bloomery obsolete. Wrought iron produced using this method became a major metal in the English midlands' emerging toy industry. The combination of the blast furnace and the puddling furnace allowed iron to be produced at either end of the carbon spectrum, depending on the user's needs. As for alloys of intermediate carbon content (that is, steel), crucible steel was rediscovered in the 1740s by Benjamin Huntsman in Handsworth in England. In his process, wrought iron and cast iron were heated in small ceramic crucibles, melting together to form steel. While producing steel superior to cement steel, the crucible steel process remained relatively expensive in both time and fuel, and could not be used in any sort of modern industrial scale. The strong steels produced were however in high demand for specialty products such as cutlery and weapons. Sheffield's Abbeydale Industrial Hamlet has preserved a waterwheel powered, scythe-making works dating from Huntsman's times. It is still operated for the public, several times per year, using crucible steel made on the Abbeydale site.

Industrial steelmaking

Abbeydale Industrial Hamlet The problem of mass-producing steel was solved in 1855 by Henry Bessemer, with the introduction of the Bessemer converter at his steelworks in Sheffield, England. (An early converter can still be seen at the city's Kelham Island Museum). In the Bessemer process, molten pig iron from the blast furnace was charged into a large crucible, and then air was blown through the molten iron from below, igniting the dissolved carbon from the coke. As the carbon burned off, the melting point of the mixture increased, but the heat from the burning carbon provided the extra energy needed to keep the mixture molten. After the carbon content in the melt had dropped to the desired level, the air draft was cut off: a typical Bessemer converter could convert a 25-ton batch of pig iron to steel in half an hour. In 1867, the German-British engineer Sir William Siemens introduced an improved puddling furnace – the regenerative furnace – that used brick heat exchangers to preheat the incoming air and conserve fuel. The next year Pierre and Émile Martin, French ironmasters who had licensed Siemens' furnace design, developed a method for measuring the carbon content of molten iron. Thus, the decarburization could be stopped at the steel stage rather than proceeding all the way to wrought iron. This open-hearth process coexisted in industrial practice with the Bessemer process for many years, but eventually proved more economical and displaced it. Reasons for this include its ability to recycle scrap metal in addition to fresh pig iron, its greater scalability (up to hundreds of tons per batch, compared to tens of tons for the Bessemer process), and the more precise quality control it permitted. quality control Initially, only ores low in phosphorus and sulfur could be used for quality steelmaking; ores rich in those elements yielded brittle metals little better than cast iron. This problem was solved in 1878 by Percy Carlyle Gilchrist and his cousin Sidney Gilchrist Thomas at the ironworks at Blaenavon in Wales. Their modified Bessemer process used a converter lined with limestone or dolomite, and additional lime was added to the molten metal as a flux. This added basic material removed phosphorus and sulfur from the steel as insoluble calcium or magnesium phosphates and sulfates. This development expanded the range of iron ores that could be used to make steel, especially in France and Germany, where high-phosphorus ores abounded. These developments increased the availability and decreased the price of steel; 22 thousand tonnes were produced in 1867, 500 thousand in 1870, 1 million in 1880 and 28 million by 1900. Today, worldwide annual production is around 1.1 billion tonnes. This widespread availability of inexpensive steel powered the industrial revolution and modern society as we know it. It also led to the introduction of newer "niche" steels (such as stainless steel), all of them dependent on the wide availability of inexpensive iron and steel and the ability to alloy it at will.

Types of steel

Alloy steels were known from antiquity, being nickel-rich iron from meteorites hot-worked into useful products. In a modern sense, alloy steels have been made since the invention of furnaces capable of melting iron, into which other metals could be thrown and mixed.
- Carbon steel
- Damascus steel, which was famous in ancient times for its durability and ability to hold an edge, was created from a number of different materials (some only in traces), essentially a complicated alloy with iron as main component.
- Stainless steels and surgical stainless steels contain a minimum of 10.5% chromium, often combined with nickel, to resist corrosion (rust). Some stainless steels are nonmagnetic.
- Tool steels
- HSLA Steel (High Strength, Low Alloy)
- Advanced High Strength Steels
- Ferrous superalloys Though not an alloy, there exists also galvanized steel, which is steel that has gone through the chemical process of being hot-dipped or electroplated in zinc for protection against rust.

Production methods


- Crucible technique or puddling - the original steel making technique, developed in India as wootz, used in the Middle East as Damascus steel and independently redeveloped in Sheffield by Benjamin Huntsman in 1740, and Pavel Anosov in Russia in 1837.
- Bessemer process, the first commercial-scale steel production process
- Open hearth furnace
- Basic oxygen steelmaking
- Electric arc furnace a form of secondary steelmaking from scrap, though the process can also use direct-reduced iron

References


- [http://www.geology.ucdavis.edu/~cowen/~GEL115/index.html Essays on geology, history, and people]
- [http://www.staff.hum.ku.dk/dbwagner/KoreanFe/KoreanFe.html Early iron in China, Korea, and Japan]
- [http://www.davistownmuseum.org/toolPreBlastFurnace.html Precursors of the blast furnace]
- [http://members.lycos.nl/cvdv/historycastiron.htm Early progress in the melting of iron]
- [http://www.tilthammer.com/bio/index.html Steel City founders]

See also


- Steel producers

External links


- [http://www.soas.ac.uk/art/tanavoli.html Exhibition of Persian Steel]
- [http://www.ae.msstate.edu/vlsm/materials/alloys/steel.htm Steel Alloys and Their Classification]
- [http://www.ce.berkeley.edu/~paulmont/CE60/quench/ Quenched & Tempered Steel Alloys]
- [http://www.key-to-steel.com/Articles/Art12.htm Quench hardening of steel]
- [http://cic.nist.gov/vrml/cis2.html CIMsteel Integration Standards] Category:Alloys
- ja:鋼 simple:Steel

Hydrogen

|- | Critical temperature || 32.19 K |- | Critical pressure || 1.315 MPa |- | Critical density || 30.12 g/L (Bohr radius) Hydrogen (Latin: hydrogenium, from Greek: hydro: water, genes: forming) is a chemical element in the periodic table that has the symbol H and atomic number 1. At standard temperature and pressure it is a colorless, odorless, nonmetallic, univalent, highly flammable diatomic gas. Hydrogen is the lightest and most abundant element in the universe. It is present in water, all organic compounds (rare exceptions exist, like buckminsterfullerene) and in all living organisms. Hydrogen is able to react chemically with most other elements. Stars in their main sequence are overwhelmingly composed of hydrogen in its plasma state. The element is used in ammonia production, as a lifting gas, as an alternative fuel, and more recently as a power source of fuel cells. Despite its ubiquity in the universe, hydrogen is surprisingly hard to produce in large quantities on the Earth. In the laboratory, the element is prepared by the reaction of acids on metals such as zinc. The electrolysis of water is a simple method of producing hydrogen, but is economically inefficient for mass production. Large-scale production is usually achieved by steam reforming natural gas. Scientists are now researching new methods for hydrogen production; if they succeed in developing a cost-efficient method of large-scale production, hydrogen may become a viable alternative to greenhouse-gas-producing fossil fuels. One of the methods under investigation involves use of green algae; another promising method involves the conversion of biomass derivatives such as glucose or sorbitol at low temperatures using a catalyst. Yet another method is the "steaming" of Carbon, whereby hydrocarbons are broken down with heat to release hydrogen.

Basic features

Hydrogen is the lightest chemical element; its most common isotope comprises just one negatively charged electron, distributed around a positively charged proton (the nucleus of the atom). The electron is bound to the proton by the Coulomb force, the electrical force that one stationary, electrically charged nanoparticle exerts on another. The hydrogen atom has special significance in quantum mechanics as a simple physical system for which there is an exact solution to the Schrödinger equation; from that equation, the experimentally observed frequencies and intensities of the hydrogen's spectral lines can be calculated. Spectral lines are dark or bright lines in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. At standard temperature and pressure, hydrogen forms a diatomic gas, H2, with a boiling point of only 20.27 K and a melting point of 14.02 K. Under extreme pressures, such as those at the center of gas giants, the molecules lose their identity and the hydrogen becomes a liquid metal. Under the extremely low pressure in space—virtually a vacuum—the element tends to exist as individual atoms, simply because there is no way for them to combine. However, clouds of H2 and singular hydrogen atoms are said to form in H I and H II regions and are associated with star formation, however the existence of singular hydrogen atoms is disputed.. Hydrogen plays a vital role in powering stars through the proton–proton and carbon–nitrogen cycle. These are nuclear fusion processes, which release huge amounts of energy in stars and other hot celestial bodies as hydrogen atoms combine into helium atoms. H2 is highly soluble in water, alcohol, and ether. It has a high capacity for adsorption, in which it is attached to and held to the surface of some substances. It is an odorless, tasteless, colorless, and highly flammable gas that burns at concentrations as low as 4% H2 in air. It reacts violently with chlorine and fluorine, forming hydrohalic acids that can damage the lungs and other tissues. When mixed with oxygen, hydrogen explodes on ignition. A unique property of hydrogen is that its flame is completely invisible in air. This makes it difficult to tell if a leak is burning, and carries the added risk that it is easy to walk into a hydrogen fire inadvertently. See also: hydrogen atom.

Applications

Large quantities of hydrogen are needed in the chemical and petrolium industries, notably in the Haber process for the production of ammonia, which by mass ranks as the world's fifth most highly produced industrial compound. Hydrogen is used in the hydrogenation of fats and oils (into items such as margarine), and in the production of methanol. Hydrogen is used in hydrodealkylation, hydrodesulfurization, and hydrocracking. The element has several other important uses.
- The element is used in the manufacture of hydrochloric acid, in welding processes, and in the reduction of metallic ores.
- It is an ingredient in rocket fuels.
- It is used as the rotor coolant in electrical generators at power stations, because it has the highest thermal conductivity of any gas.
- Liquid hydrogen is used in cryogenic research, including superconductivity studies.
- Since hydrogen is 14.5 times lighter than air, it was once widely used as a lifting agent in balloons and airships. However, this use was curtailed when the Hindenburg disaster convinced the public that the gas was too dangerous for this purpose.
- Deuterium, an isotope of hydrogen (hydrogen-2), is used in nuclear fission applications as a moderator to slow neutrons, and in nuclear fusion reactions. Deuterium compounds have applications in chemistry and biology in studies of reaction isotope effects.
- Tritium (hydrogen-3), produced in nuclear reactors, is used in the production of hydrogen bombs, as an isotopic label in the biosciences, and as a radiation source in luminous paints. There are no "hydrogen wells" or "hydrogen mines" on Earth, so hydrogen cannot be considered a primary energy source like fossil fuels or uranium. Hydrogen can however be burned in internal combustion engines, an approach advocated by BMW's experimental hydrogen car. However, it is currently difficult and dangerous to store and handle in sufficient quantity for motor fuel use. Hydrogen fuel cells are being investigated as mobile power sources with lower emissions than hydrogen-burning internal combustion engines. The low emissions of hydrogen in internal combustion engines and fuel cells are currently offset by the pollution created by hydrogen production. This may change if the substantial amounts of electricity required for water electrolysis can be generated primarily from low pollution sources such as nuclear energy or wind. Research is being conducted on hydrogen as a replacement for fossil fuels. It could become the link between a range of energy sources, carriers and storage. Hydrogen can be converted to and from electricity (solving the electricity storage and transport issues), from bio-fuels, and from and into natural gas and diesel fuel. All of this can theoretically be achieved with zero emissions of CO2 and toxic pollutants.

History

Hydrogen was first produced by Theophratus Bombastus von Hohenheim (1493–1541)—also known as Paracelsus—by mixing metals with acids. He was unaware that the explosive gas produced by this chemical reaction was hydrogen. In 1671, Robert Boyle described the reaction between two iron fillings and dilute acids, which results in the production of gaseous hydrogen. In 1766, Henry Cavendish was the first to recognize hydrogen as a discrete substance, by identifying the gas from this reaction as "inflammable" and finding that the gas produces water when burned in air. Cavendish stumbled on hydrogen when experimenting with acids and mercury. Although he wrongly assumed that hydrogen was a compound of mercury—and not of the acid—he was still able to accurately describe several key properties of hydrogen. Antoine Lavoisier gave the element its name and proved that water is composed of hydrogen and oxygen. One of the first uses of the element was for balloons. The hydrogen was obtained by mixing sulfuric acid and iron. Harold C. Urey discovered Deuterium, an isotope of hydrogen, by repeated distilling the same sample of water. For this discovery, Urey received the Nobel prize for in 1934. In the same year, the third isotope, tritium, was discovered. Because of its relatively simple structure, hydrogen has often been used in models of how an atom works.

Electron energy levels

The ground state energy level of the electron in a Hydrogen atom is 13.6 eV, which is equivalent to an ultraviolet photon of roughly 92 nm. With the Bohr Model the energy levels of Hydrogen can be calculated fairly accurately. This is done by modeling the electron as revolving around the proton, much like the earth revolving around the sun. Except the sun holds earth in orbit with the force of gravity, but the proton holds the electron in orbit with the force of electromagnetism. Another difference between the Earth-Sun system and the Electron-Proton system is that, in this model, due to quantum mechanics the electron is allowed to only be at very specific distances from the proton. Modeling the hydrogen atom in this fashion yields the correct energy levels and spectrum.

Occurrence

quantum mechanics.]] Hydrogen is the most abundant element in the universe, making up 75% of normal matter by mass and over 90% by number of atoms. This element is found in great abundance in stars and gas giant planets. It is very rare in the Earth's atmosphere (1 ppm by volume), because being the lightest gas causes it to escape Earth's gravity, though when compounds are considered, it is the tenth most abundant element on Earth. The most common source for this element on Earth is water, which is composed two parts hydrogen to one part oxygen (H2O). Other sources include most forms of organic matter (currently all known life forms) including coal, natural gas, and other fossil fuels. Methane (CH4) is an increasingly important source of hydrogen. Throughout the Universe, hydrogen is mostly found in the plasma state whose properties are quite different to molecular hydrogen. As a plasma, hydrogen's electron and proton are not bound together, resulting in very high electrical conductivity, even when the gas is only partially ionised. The charged particles are highly influenced by magnetic and electric fields, for example, in the Solar Wind they interact with the Earth's magnetosphere giving rise to Birkeland currents and the aurora. Hydrogen can be prepared in several different ways: steam on heated carbon, hydrocarbon decomposition with heat, reaction of a strong base in an aqueous solution with aluminium, water electrolysis, or displacement from acids with certain metals. Commercial bulk hydrogen is usually produced by the steam reforming of natural gas. At high temperatures (700–1100 °C), steam reacts with methane to yield carbon monoxide and hydrogen. :CH4 + H2O → CO + 3 H2 Additional hydrogen can be recovered from the carbon monoxide through the water-gas shift reaction: :CO + H2O → CO2 + H2

Compounds

The lightest of all gases, hydrogen combines with most other elements to form compounds. Hydrogen has an electronegativity of 2.2, so it forms compounds where it is the more nonmetallic and where it is the more metallic element. The former are called hydrides, where hydrogen either exists as H- ions or just as a solute within the other element (as in palladium hydride). The latter tend to be covalent, since the H+ ion would be a bare nucleus and so has a strong tendency to pull electrons to itself. These both form acids. Thus even in an acidic solution one sees ions like hydronium (H3O+) as the protons latch on to something. Although exotic on earth, one of the most common ions in the universe is the H3+ ion. Hydrogen combines with oxygen to form water, H2O, and releases a lot of energy in doing so, burning explosively in air. Deuterium oxide, or D2O, is commonly referred to as heavy water. Hydrogen also forms a vast array of compounds with carbon. Because of their association with living things, these compounds are called organic compounds, and the study of the properties of these compounds is called organic chemistry. organic chemistry

Forms

Under normal conditions, hydrogen gas is a mix of two different kinds of molecules which differ from one another by the relative spin of the nuclei. These two forms are known as ortho- and para-hydrogen (this is different from isotopes, see below). In ortho-hydrogen the nuclear spins are parallel (form a triplet), while in para they are antiparallel (form a singlet). At standard conditions hydrogen is composed of about 25% of the para form and 75% of the ortho form (the so-called "normal" form). The equilibrium ratio of these two forms depends on temperature, but since the ortho form has higher energy (is an excited state), it cannot be stable in its pure form. In low temperatures (around boiling point), the equilibrium state is comprised almost entirely of the para form. The conversion process between the forms is slow, and if hydrogen is cooled down and condensed rapidly, it contains large quantities of the ortho form. It is important in preparation and storage of liquid hydrogen, since the ortho-para conversion produces more heat than the heat of its evaporation, and a lot of hydrogen can be lost by evaporation in this way during several days after liquefying. Therefore, some catalysts of the ortho-para conversion process are used during hydrogen cooling. The two forms have also slightly different physical properties. For example, the melting and boiling points of parahydrogen are about 0.1 K lower than of the "normal" form.

Isotopes

Hydrogen is the only element that has different names for its isotopes. (During the early study of radioactivity, various heavy radioactive isotopes were given names, but such names are no longer used, although one element, radon, has a name that originally applied to only one of its isotopes.) The symbols D and T (instead of 2H and 3H) are sometimes used for deuterium and tritium, although this is not officially sanctioned. (The symbol P is already in use for phosphorus and is not available for protium.) ;1H The most common isotope of hydrogen, this stable isotope has a nucleus consisting of a single proton; hence the descriptive, although rarely used, name protium. The spin of a protium atom is 1/2+. ;2H The other stable isotope is deuterium, with an extra neutron in the nucleus. Deuterium comprises 0.0184%–0.0082% of all hydrogen (IUPAC); ratios of deuterium to protium are reported relative to the VSMOW standard reference water. The spin of a deuterium atom is 1+. ;3H The third naturally occurring hydrogen isotope is the radioactive tritium. The tritium nucleus contains two neutrons in addition to the proton. It decays through beta decay and has a half-life of 12.32 years. Tritium occurs naturally due to cosmic rays interacting with atmospheric gases. Like ordinary hydrogen, tritium reacts with the oxygen in the atmosphere to form T2O. This radioactive "water" molecule constantly enters the Earth's seas and lakes in the form of slightly radioactive rain, but its half-life is short enough to prevent a buildup of hazardous radioactivity. The spin of a tritium atom is 1/2+. ;4H Hydrogen-4 was synthesized by bombarding tritium with fast-moving deuterium nuclei. It decays through neutron emission and has a half-life of 9.93696x10-23 seconds. The spin of a hydrogen-4 atom is 2-. ;5H In 2001 scientists detected hydrogen-5 by bombarding a hydrogen target with heavy ions. It decays through neutron emission and has a half-life of 8.01930x10-23 seconds. ;6H Hydrogen-6 decays through triple neutron emission and has a half-life of 3.26500-22 seconds. ;7H In 2003 hydrogen-7 was created ([http://physicsweb.org/articles/news/7/3/3 article]) at the RIKEN laboratory in Japan by colliding a high-energy beam of helium-8 atoms with a cryogenic hydrogen target and detecting tritons—the nuclei of tritium atoms—and neutrons from the breakup of hydrogen-7, the same method used to produce and detect hydrogen-5.

See also


- Antihydrogen
- Deuterium
- Fuel cell
- Hydrogen atom
- Hydrogen bomb
- Hydrogen bond
- Hydrogen car
- Hydrogen cycle
- Hydrogen economy
- Hydrogen line
- Hydrogen molecule
- Hydrogen spectral series
- Hydrogen station
- Liquid Hydrogen
- Periodic table
- Photohydrogen
- Tritium

References

# # # # # #
- [http://www.riken.go.jp/engn/r-world/research/lab/wako/ribeam/ RIKEN Beam Science Laboratory, Japan - Heavy hydrogen research]
- [http://chartofthenuclides.com/default.html Nuclides and Isotopes] Fourteenth Edition: Chart of the Nuclides, General Electric Company, 1989 ;Book references:
-
-
-
-

External links


- [http://www.hydropole.ch/Hydropole/Intro/Phasediag.gif Hydrogen phase diagram.]
- [http://www.compchemwiki.org/index.php?title=Hydrogen Computational Chemistry Wiki] Category:Nonmetals Category:Fuels Category:Chemical elements ko:수소 ms:Hidrogen ja:水素 simple:Hydrogen th:ไฮโดรเจน

Nickel

:This article is about the element nickel. See also nickel (U.S. coin) and nickel (Canadian coin). Nickel is a metallic chemical element in the periodic table that has the symbol Ni and atomic number 28.

Notable characteristics

Nickel is a silvery white metal that takes on a high polish. It belongs to the iron group, and is hard, malleable, and ductile. It occurs combined with sulfur in millerite, with arsenic in the mineral niccolite, and with arsenic and sulfur in nickel glance. On account of its permanence in air and inertness to oxidation, it is used in the smaller coins, for plating iron, brass, etc., for chemical apparatus, and in certain alloys, as German silver. It is magnetic, and is very frequently accompanied by cobalt, both being found in meteoric iron. It is chiefly valuable for the alloys it forms. Nickel is one of the five ferromagnetic elements. Because of the precise alloy used, the US "nickel" coin is not ferromagnetic, while the Canadian coin of the same name is, up to and including the year 1958. The most common oxidation state of nickel is +2, though 0, +1 and +3 Ni complexes are observed. The unit cell of nickel is an FCC with a lattice parameter of 0.356 nm giving a radius of the atom of 0.126 nm.

Applications

About 65 percent of the nickel consumed in the Western World is used to make austenitic stainless steel. Another 12 percent goes into superalloys. The remaining 23% of consumption is divided between alloy steels, rechargeable batteries, catalysts and other chemicals, coinage, foundry products, and plating. The five-cent Canadian and US coin is only 25% nickel. The largest consumer of nickel is Japan, which uses 169,600 tonnes per year (2005) . Applications include but are not limited to:
- Stainless steel and other corrosion-resistant alloys.
- Nickel steel is used for armour plates and burglar-proof vaults.
- The alloy Alnico is used in magnets.
- Mu-metal has an especially high magnetic permeability, and is used to screen magnetic fields.
- Monel metal is a copper-nickel alloy highly resistant to corrosion, used for ship propellers, kitchen supplies, and chemical industry plumbing
- Smart wire, or shape memory alloys, are used in robotics.
- Rechargeable batteries, such as nickel metal hydride batteries and nickel cadmium batteries.
- Coinage. In the United States and Canada, nickel is used in five-cent coins called nickels. See also clad.
- In electroplating.
- In crucibles for chemical laboratories.
- Finely divided nickel is a catalyst for hydrogenating vegetable oils.

History

Nickel use is ancient, and can be traced back as far as 3500 BCE. Bronzes from what is now Syria had a nickel content of up to two percent. Further, there are Chinese manuscripts suggesting that "white copper" (e.g. baitung) was used in the Orient between 1400 and 1700 BC. However, because the ores of nickel were easily mistaken for ores of silver, any understanding of this metal and its use dates to more contemporary times. Minerals containing nickel (e.g. kupfernickel, or false copper) were of value for colouring glass green. In 1751, Baron Axel Frederik Cronstedt was attempting to extract copper from kupfernickel (now called niccolite), and obtained instead a white metal that he called nickel. The first nickel coin of the pure metal was made in 1881.

Biological role

Many but not all hydrogenases contain nickel in addition to iron-sulfur clusters. Nickel centres are a common element in those hydrogenases whose function is to oxidise rather than evolve hydrogen. The nickel centre appears to undergo changes in oxidation state, and evidence has been presented that the nickel centre might be the active site of these enzymes. A nickel-tetrapyrrole coenzyme, Co-F430, is present in the methyl CoM reductase and in methanogenic bacteria. The tetrapyrrole is intermediate in structure between porphyrin and corrin. Changes in redox state, as well as changes in nickel coordination, have recently been observed. There is also a nickel-containing carbon monoxide dehydrogenase. Little is known about the structure of the nickel site. Due to studies on chicks and rats (the latter of which are relatively close to humans genetically), nickel is apparently essential for proper liver function.

Occurrence

The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe,Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni,Mg)3Si2O5(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: (Ni,Fe)9S8. In terms of supply, the Sudbury region of Ontario, Canada, produces about 30 percent of the world's supply of nickel. The Sudbury deposit is located in an area with evidence of a massive meteorite impact event early in the geologic history of Earth. Other deposits are found elsewhere in Canada, as well as in Russia, New Caledonia, Australia, Cuba, and Indonesia. A recent development has been the exploitation of a deposit in western Turkey, especially convenient for European smelters, steelmakers and factories. The deposits in tropical areas are typically laterites which are produced by the intense weathering of ultramafic igneous rocks and the resulting secondary concentration of nickel bearing oxide and silicate minerals. Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth's core.

Extraction and Purification

Nickel can be recovered using extractive metallurgy. Oxy-hydroxide ores are treated using hydrometallurgy, and from sulfide mineral concentrates using pyrometallurgical or hydrometallurgical techniques. Sulfide mineral concentrates are produced by applying the froth flotation process. Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of >95% purity. Final purification to >99.99% purity is performed by reacting Nickel and carbon monoxide to form Nickel carbonyl. This gas is passed into a large chamber at a higher temperature in which tens of thousands of nickel spheres are maintained in constant motion. The Nickel carbonyl decomposes depositing pure nickel onto the nickel spheres. The resultant carbon monoxide is re-circulated through the process. The largest producer of nickel is Russia which extracts 267,000 tonnes of nickel per year. Australia and Canada are the second and third largest producers, making 207 and 189.3 thousand tonnes per year.

Compounds


- Kamacite is a naturally occurring alloy of iron and nickel, usually in the proportion of 90:10 to 95:5 although impurities such as cobalt or carbon may be present. Kamacite occurs in nickel-iron meteorites.

Isotopes

Naturally occurring nickel is composed of 5 stable isotopes; 58-Ni, 60-Ni, 61-Ni, 62-Ni and 64-Ni with 58-Ni being the most abundant (68.077% natural abundance). 18 radioisotopes have been characterised with the most stable being 59-Ni with a half-life of 76,000 years, 63-Ni with a half-life of 100.1 years, and 56-Ni with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lifes that are less than 60 hours and the majority of these have half lifes that are less than 30 seconds. This element also has 1 meta state. Nickel-56 is produced in large quantities in type Ia supernovae and the shape of the light curve of these supernovae corresponds to the decay of nickel-56 to cobalt-56 and then to iron-56. Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 76,000 years. 59Ni has found many applications in isotope geology. 59Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide 60Fe (half-life = 1.5 Myr). Because the extinct radionuclide 60Fe had such a long half-life, its persistence in solar_system materials at high enough concentrations may have generated observable variations in the isotopic composition of 60Ni. Therefore, the abundance of 60Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history. The isotopes of nickel range in atomic weight from 48 amu (48-Ni) to 78 amu (78-Ni). Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron. [http://skyandtelescope.com/news/article_1502_1.asp]

Precautions

Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well. Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air. Sensitised individuals may show an allergy to nickel affecting their skin. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 a report in the journal Nature researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction.

References


- [http://periodic.lanl.gov/elements/28.html Los Alamos National Laboratory – Nickel]

Notes


- Production and consumption figures are from, The Economist: Pocket World in Figures 2005, Profile Books (2005), ISBN 1-86197-799-9

External links


- [http://www.webelements.com/webelements/elements/text/Ni/index.html WebElements.com – Ni]
- [http://www.nature.com/cgi-taf/DynaPage.taf?file=/nature/journal/v419/n6903/abs/419132a_fs.html&filetype=&_UserReference=C0A804ED4653F39333F43C407C6F3D7FE5CE Article in Nature on nickel emitted by euro coins]
- [http://www.lme.co.uk London Metal Exchange]
- [http://www.enickel.co.uk European Nickel plc]
- [http://www-cie.iarc.fr/htdocs/monographs/vol49/nickel.html IARC Monograph "Nickel and Nickel compounds"]
- [http://www.specialmetalswelding.com/publica/joining.pdf Tutorial - joining nickel alloys (pdf format)] Category:Chemical elements Category:Transition metals ja:ニッケル th:นิกเกิล

Oil industry

The Oil industry brings to market what is currently considered the lifeblood of nearly all other industry, if not industrialized civilization itself. Oil accounts for 40 % of the United States' energy supply and a comparable percentage of the world’s energy supply. The US currently consumes 7.5 billion barrels (1.2 km³) of oil per year, while the world consumes 30 billion barrels (4.8 km³) per year. The U.S., and most of the world, are net importers of the resource.

Infrastructure

The Industry can be divided into two broad themes: Upstream producers and Downstream transporters (tanker, Pipeline transport), refiners, retailers, and consumers. Oil companies are generally categorized as "majors and "independents". Most work in the oil field or on an oil well (upstream) is contracted out to drilling contractors and oil field service companies and the service personnel work under the watchful gaze of the client oil company, which may be a "major" or an "independent".

Impact

Petroleum is one of the non-renewable natural resources and the industry is faced with the spectre of the inevitable eventual depletion of the world's oil supply. By the very definition of non-renewable resources, oil exploration alone will not stave off future shortages of the resource. Resource economists argue that oil prices will rise as demand increases relative to supply, and that this will spur further exploration and development. However, this process will not increase the amount of oil in the ground, but will rather temporarily prolong production as higher prices make it economical to extract oil that was previously not economically recoverable. The Hubbert peak theory, also known as peak oil http://www.grist.org/news/maindish/2005/11/03/simmons/, is an influential theory concerning the long-term rate of conventional oil production and depletion.

See Also


- Petroleum
- Abiogenic petroleum origin
- History of the petroleum industry
- OPEC
- List of oil fields
- List of oil-producing states.
- List of petroleum companies.
- Energy crisis: 1973 energy crisis, 1979 energy crisis.
- Fossil fuel.
- Greenhouse gases.
- Future energy development.
- Oil imperialism.
- Oil price increases of 2004
- Oil price increases of 2005
- Oil refinery.
- Oil supplies.
- Oil well.
- Olduvai theory (not strictly about oil, but it basically assumes that oil and gas are the only significant energy sources).
- Peak oil.
- Petroleum disasters.
- Process Industry.
- Renewable energy.
- Thermal depolymerization. Category:Petroleum

Natural gas

Natural gas (commonly refered to as gas in many countries, but note that gas is also an American and Canadian shortening of gasoline) is a gaseous fossil fuel consisting primarily of methane. It is found in oil fields and natural gas fields, as well as—in smaller quantities—in coal beds. When methane-rich gasses are produced by the anaerobic decay of non-fossil organic material, these are referred to as biogas. Sources of biogas include swamps (swamp gas), marshes (marsh gas), landfills (landfill gas), sewage sludge and manure (by way of anaerobic digesters) and flatulence (most notably in cattle.) Methane is an extremely efficient greenhouse gas which may contribute to enhanced global warming when free in the atmosphere, and such free methane, would then be considered a pollutant rather than a useful energy resource. However, methane in the atmosphere reacts with ozone, producing carbon dioxide and water, so that the greenhouse effect of released methane is relatively short-lived. Also, natural gas, when burned, produces much less greenhouse gas than more carboniferous fuel sources, such as coal. As a pollutant, significant biological sources of methane are termites, cattle (ruminants) and cultivation (estimated emissions are 15, 75 and 100 million tons per year respectively). Landfill gas, which is approximately equal parts methane and carbon dioxide, also contains trace volatile organic compounds (VOCs), many of which are known to be precursors to photochemical smog. Because landfill gas contains these trace compounds, The US Federal Clean Air Act (Part 40 of the Federal Code of Regulations) requires landfill owners to estimate the quantity of VOCs emitted. If the estimated VOC emissions exceeds 50 metric tons, then the landfill owner is required to collect the landfill gas, and treat it to remove the entrained VOCs. Usually, treatment is by combustion of the landfill gas. Because of the remoteness of landfill sites, it is sometimes not economically feasible to produce electricity from the gas.

Chemical composition and energy content

Chemical composition

The primary component of natural gas is methane (CH4), the shortest and lightest hydrocarbon molecule. It may also contain heavier gaseous hydrocarbons such as ethane (C2H6), propane (C3H8) and butane (C4H10), as well as other sulphur containing gases, in varying amounts, see also natural gas condensate. Organosulfur compounds and Hydrogen sulfide (H2S see acid gas) are common contaminants, which must be removed prior to most uses. Gas with a significant amount of sulfur impurities is termed "sour". Natural gas is tasteless and odorless. However, before gas is distributed to end-users, it is odorized by adding mercaptans, to assist in leak detection. Natrual gas is, in itself, harmless to the human body -- unlike carbon monoxide, for instance, it is not a poison. Natural gas can kill, however if it is present in large concentrations -- and thus reduces the amount of oxygen available in the air, such that the amount of oxygen remaining won't sustain life. Natural gas can also kill through an explosion. Natural gas is lighter than air, and so tends to dissipate. But when natural gas is contained, such as within a house or in a tent (perhaps put over a house for fumigation) gas concentrations can reach explosive proportions and trigger very powerful blasts that can level houses, and even neighborhoods. Methane has a Lower Explosive Limit of 5% in air, and an Upper Explosive Limit of 15%. Explosive concerns with compressed natural gas used in vehicles are almost non-existant, due the the escaping nature of the gas, and the need to maintain concentrations between 5% and 15% to trigger explosions.

Energy content and statistics

Combustion of one cubic metre of commercial quality natural gas yields 38 MJ (10.6 kWh). Equivilently, one cubic foot of natural gas produces just over 1000 British Thermal Units (BTUs). In the USA, at retail, natural gas is often sold in units of therms (th), which equals 100,000 BTU. Wholesale transactions are generally done in decatherms (DTh), or in thousand decatherms (MDth), or in million decatherms (MMDth). A million decatherms is roughly a billion cubic feet of natural gas. The US uses roughly 60,000 billion cubic feet, or 60 tera decatherms (TDth), each year.

Storage and transport

cubic metre The major difficulty in the use of natural gas is transportation and storage. Natural gas pipelines are economical, but are impractical across oceans. Many existing pipelines in North America are close to reaching their capacity prompting some politicians in colder climates to speak publicly of potential shortages. Liquefied natural gas tankers are also used, but have higher cost and safety problems. In many cases, as with oil fields the natural gas which is recovered in the course of recovering petroleum cannot be profitably sold, and is simply burned at the oil field (known as flaring). This wasteful practice is now illegal in many countries, especially since it adds greenhouse gas pollution to the earth's atmosphere, and since a profitable method may be found in the future. Instead, the gas is instead re-injected back into the formation for later recovery. This is known as Underground Gas Storage (UGS). It also assists oil pumping by keeping underground pressures higher. In Saudi Arabia, in the late 1970s, a "Master Gas System" was created, ending the need for flaring. The natural gas is used to generate electricity and heat for desalinization. Natural gas is often stored in underground caverns formed inside salt domes as Compressed Natural Gas (CNG), or in tanks as Liquefied Natural Gas (LNG).

Natural gas crisis

Many politicians and prominent figures in North America have spoken publicly about a possible natural gas crisis. This includes former Secretary of Energy Spencer Abraham, Chairman of the Federal Reserve Alan Greenspan, Ontario Minister of Energy Dwight Duncan. The natural gas crisis is typically described by the increasing price of natural gas in the U.S. over the last few years due to the decline in indigenous supply and the increase in demand for electricity generation. Indigenous supply has not truly fallen -- but it has leveled off (no matter how many new straws we put into the ground, we still get about the same amount of natural gas each year). But because of the continuing growth in demand, and the temporary but dramatic hit to production that came from Hurricanes Katrina and Rita, the price has become so high that many industrial users, mainly in the petrochemical industry, have closed their plants causing loss of jobs. Greenspan has suggested that a solution to the natural gas crisis is the importation of LNG. This solution is both capital intensive and politically charged due to the NIMBY syndrome and the public perception that LNG terminals are explosive risks, especially in the wake of the 9/11 terrorist attacks in the United States. The U.S. Department of Homeland Security is responsible for maintaining their security, and the security arrangements during the 2004 Democratic Convention in Boston, Massachusetts, home to one of only six LNG terminals in the United States, were extraordinarily tight. Infrastructure issues to establish new or expanded LNG terminals are non-trivial, to say the least, especially when taken together with high capitalization needs of each subsystem. LNG terminals require a very spacious—at least 38.5m deep—harbor, as well as being sheltered from wind and waves. These "suitable" sites are thus deep in well populated seaports, which are also burdened with right of way concerns for LNG pipelines, or conversely, required to also host the LNG expansion plant facilities and end use (petrochemical) plants amidst the high population densities of major cities (with the associated fumes, multiple serious risks to safety). Typically, to attain "well sheltered" waters, suitable harbor sites are well up rivers or estuaries, which are unlikely to be dredged deep enough. Since these very large vessels must move slowly and ponderously in restricted waters, the transit times to and from the terminal become costly, as multiple tugs and security boats shelter and safeguard the large vessels. Operationally, LNG tankers are (for example, in Boston) effectively given sole use of the harbor, forced to arrive and depart during non-peak hours, and precluded from occupying the same harbor until the first is well departed. These factors increase operating costs and make capital investment less attractive. To substantially increase the amount of LNG used to supply natural gas to North America, not only must "re-gasification" plants be built on North American shores -- difficult for the reasons stated above -- someone also must but substantial, new liquification stations in Indonesia, the Middle East, and Afreca, in order to concetrate the gas generally assoicated with oil production in those areas. A substantial explansion of the fleet of LNG tankers also must occur to move the hugh amount of fuel needed to make up for the coming shortfall in North America.

Uses

Power generation

Natural gas is important as a major source for electricity generation through the use of gas turbines and steam turbines. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Environmentally, natural gas burns cleaner than other fossil fuels, such as oil and coal, and produces fewer greenhouse gases. For an equivalent amount of heat, burning natural gas produces about 30% less carbon dioxide than burning petroleum and about 45% less than burning coal. [http://www.naturalgas.org/environment/naturalgas.asp#greenhouse] Combined cycle power generation using natural gas is thus the cleanest source of power available using fossil fuels, and this technology is widely used wherever gas can be obtained at a reasonable cost. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not price-competitive. Also, Natural gas is said to peak around the year 2030, 20 years after the peak of oil. It is also projected that the world's supply of natural gas should finish in the mid 2080's(2085).

Natural gas vehicles

Compressed natural gas (and LPG) is used as a clean alternative to other automobile fuels. As of 2003, the countries with the largest number of natural gas vehicles were Argentina, Brazil, Pakistan, Italy, and India. The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines, partially due to the fact that natural gas engine function using the Otto Cycle, but research is on its way to improve the process (Westport-Cycle). Here is a link to a general discription of this technology. http://www.nesea.org/greencarclub/factsheets_naturalgas.pdf#search='explosion%20ratio%20natural%20gas'

Residental domestic use

Westport-Cycle Natural gas is supplied to homes where it is used for such purposes as cooking and heating/cooling. CNG is used in rural homes without connections to piped-in public utility services, or with portable grills.

Fertilizer

Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.

Other

Natural gas is also used in the manufacture of fabrics, glass, steel, plastics, paint, and other products.

Sources

Natural gas is commercially produced from oil fields and natural gas fields. Gas produced from oil wells is called casinghead gas or associated gas. Natural gas can also be produced by treating coal chemically, although coal gasification is not economic at current gas prices. The biggest natural gas field is located in Urengoy, Russia, with a reserve of 10.0 · 1012 m³. See also List of natural gas fields.

Possible future sources

One experimental idea is to use the methane gas that is naturally produced from landfills to supply power to cities. Tests have shown that methane gas could be a financially sustainable power source. There are plans in Ontario to capture the biogas, methane gasses rising from the manure of cattle caged in a factory farm, and to use that gas to provide power to a small town. There is also the possibility that with the source separation of organic materials from the waste stream that by using an anaerobic digester, the methane can be used to produce useable energy. This can be improved by adding other organic material (plants as well as slaughter house waste) to the digester.

Safety

In any form, a concentrated, rotten-egg like scent (such as mercaptan/ethanethiol) is deliberately added to the otherwise colorless and odorless gas, so that leaks can be detected by smell before an explosion occurs. In mines, sensors are used and mining apparatus has been specifically developed to avoid ignition sources (e.g. the Davy lamp). Adding scent to natural gas began after the 1937 New London School explosion. The buildup of gas in the school went unnoticed, and killed three hundred students and faculty when it ignited. Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and boats are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast will be enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, disintegrating one or more buildings in the process. The gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if weather conditions are right. Also, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low. Contrary to popular belief, natural gas and the odorant that's added to it is non-toxic, though some gas fields yield 'acid gas' or 'sour gas' containing hydrogen sulfide. This untreated gas is toxic. Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir. This in turn may lead to subsidence at ground level. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations etc.

See also


- Future energy development
- CO2
- Liquefied natural gas (LNG)
- Compressed natural gas (CNG)

External links

Natural gas vehicles


- [http://www.iangv.org/jaytech/default.php?PageID=130 International Natural Gas Vehicle Statistics]
- [http://www.naftc.wvu.edu Alternative Fuel Vehicle Training] From the National Alternative Fuels Training Consortium.
- [http://www.iangv.org IANGV - International Association for Natural Gas Vehicles]

North America


- [http://www.energyquest.ca.gov/transportation/CNG.html What is Compressed Natural Gas?]
- [http://www.wokr13.tv/news/local/story.aspx?content_id=B841A1FA-0DAA-4EA3-88E5-EFB409DF3F38 Could CNG work in America?]
- [http://www.naturalgas.org/index.asp Natural Gas Supply Association]
- [http://www.gastechnology.org/webroot/app/xn/xd.aspx?it=enweb&xd=gtihome.xml Institute of Gas Technology]

South Asia


- India: [http://cities.expressindia.com/fullstory.php?newsid=85665 How New Delhi used CNG to ease pollution]

Pollution and allergy


- [http://www.geocities.com/RainForest/6847/#quote1 Pollutant chemical pollutant chemical that can worsen both classical allergy and chemical sensitivity]. Category:Natural gas ms:Gas asli ja:天然ガス simple:Natural gas

Category:Corrosion

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غزة

غزة هي أكبر مدينة في قطاع غزة، في الجنوب الغربي لفلسطين على شاطئ البحر اللأبيض المتوسط، يقدر عدد سكانها بـ 400.000 نسمة. تولت السلطة الفلسطينية ادارة المدينة تطبيقا لاتفاق اوسلو سنة 1993 بعد ان كانت تتخذها قوات الجيش الاسرائيلي مقرا لها أثناء احتلال قطاع غزة ما بين 1967 و1994.

نبذة تاريخية

تدل الوثائق التاريخية على استمرار الناس بالعيش في مدينة غزة على مدار أكثر من 3000 عام، كانت أول مرة ذكر فيها في مخطوطة للفرعون تحتمس الثالث (القرن 15 ق.م)، وكذلك ورد اسمها في الواح تل العمارنة. بعد 300 سنة من الاحتلال الفرعوني للمدينة نزلت قبيلة من الفلسطيننين وسكنت المدينة والمنطقة المجاورة لها، عام 635 م دخل المسلمون العرب المدينة وأصبحت مركزا اسلاميا مهما وخاصة انها مشهورة بوحود قبر للجد الثاني للنبي (ص) هاشم بن عبد مناف فيها ولذلك أحيانا تسمى غزة هاشم. وكانت المدينة مسف