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High Temperature Hydrogen Attack
High temperature hydrogen attack (HTHA), also called hot hydrogen attack or methane reaction, is a problem which concerns steels operating at elevated temperatures (typically above ) in hydrogen-rich atmospheres, such as refineries, petrochemical and other chemical facilities and, possibly, high pressure steam boilers. It is not to be confused with hydrogen embrittlement. If a steel is exposed to very hot hydrogen, the high temperature enables the hydrogen molecules to dissociate and to diffuse into the alloy as individual ''diffusible'' atoms. There are two stages to the damage: # First, dissolved carbon in the steel reacts with the surface hydrogen and escapes into the gas as methane. This leads to superficial decarburization and a loss of strength in the surface. Initially, the damage is not visible. # Second, the reduction in the concentration of dissolved carbon creates a driving force which dissolves the carbides in the steel. This leads to a loss of strength deeper in the ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant typically need an additional 11% chromium. Because of its high tensile strength and low cost, steel is used in buildings, infrastructure, tools, ships, trains, cars, machines, electrical appliances, weapons, and rockets. Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has relatively little resistance to the iron atoms slipping past one another, and so pure iron is quite ductile, or soft and easily formed. In steel, small amounts of carbon, other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Selective Leaching
In metallurgy, selective leaching, also called dealloying, demetalification, parting and selective corrosion, is a corrosion type in some solid solution alloys, when in suitable conditions a component of the alloys is preferentially leached from the initially homogenous material. The less noble metal is removed from the alloy by a microscopic-scale galvanic corrosion mechanism. The most susceptible alloys are the ones containing metals with high distance between each other in the galvanic series, e.g. copper and zinc in brass. The elements most typically undergoing selective removal are zinc, aluminium, iron, cobalt, chromium, and others. Leaching of zinc The most common example is selective leaching of zinc from brass alloys containing more than 15% zinc (dezincification) in the presence of oxygen and moisture, e.g. from brass taps in chlorine-containing water. Dezincification has been studied since the Civil War era, and the mechanism by which it occurs was under extensive ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrosion
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion. In the most common use of the word, this means electrochemical oxidation of metal in reaction with an oxidant such as oxygen, hydrogen or hydroxide. Rusting, the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal and results in a distinctive orange colouration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term "degradation" is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases. Many structural ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Safety
Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of 4 on the flammability scale because it is flammable when mixed even in small amounts with ordinary air; ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. However, hydrogen has no rating for innate hazard for reactivity or toxicity. The storage and use of hydrogen poses unique challenges due to its ease of leaking as a gaseous fuel, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation. Liquid hydrogen poses additional challenges due to its increased density and the extremely low temperatures needed to keep it in liquid form. Moreover, its demand and use in industry—as rocket fuel, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Embrittlement
Hydrogen embrittlement (HE), also known as hydrogen-assisted cracking or hydrogen-induced cracking (HIC), is a reduction in the ductility of a metal due to absorbed hydrogen. Hydrogen atoms are small and can permeate solid metals. Once absorbed, hydrogen lowers the stress required for cracks in the metal to initiate and propagate, resulting in embrittlement. Hydrogen embrittlement occurs most notably in steels, as well as in iron, nickel, titanium, cobalt, and their alloys. Copper, aluminium, and stainless steels are less susceptible to hydrogen embrittlement. The essential facts about the nature of hydrogen embrittlement have been known since the 19th century. Hydrogen embrittlement is maximised at around room temperature in steels, and most metals are relatively immune to hydrogen embrittlement at temperatures above 150 °C. Hydrogen embrittlement requires the presence of both atomic ("diffusible") hydrogen and a mechanical stress to induce crack growth, although that str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corrosion Engineering
Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to manage corrosion. From a holistic perspective, corrosion is the phenomenon of metals returning to the state they are found in nature. The driving force that causes metals to corrode is a consequence of their temporary existence in metallic form. To produce metals starting from naturally occurring minerals and ores, it is necessary to provide a certain amount of energy, e.g. Iron ore in a blast furnace. It is therefore thermodynamically inevitable that these metals when exposed to various environments would revert to their state found in nature. Corrosion and corrosion engineering thus involves a study of chemical kinetics, thermodynamics, electrochemistry and materials science. General background Generally related to metallurgy or material ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2010 Tesoro Anacortes Refinery Disaster
The 2010 Tesoro Anacortes Refinery disaster was an industrial accident that occurred at the Tesoro Anacortes Refinery in Anacortes, Washington on April 2, 2010. Seven workers received fatal burns in an explosion and ensuing fire when a heat exchanger violently ruptured after a maintenance restart. Explosion At 12:30 a.m. on April 2, while personnel were performing post-maintenance heat exchanger restart operations, a heat exchanger on an adjacent bank catastrophically and violently ruptured. The pressure-containing shell of the heat exchanger burst at its weld seams, expelling a large volume of very hot hydrogen and naphtha, which spontaneously ignited upon contact with the surrounding air. The ensuing explosion was so violent that many in Anacortes felt the shock wave across Fidalgo Bay. A giant fireball lit up the sky above the refinery, and a plume of black smoke was pushed toward the town by a southeast wind. It took about 90 minutes to put the fire out. Aftermath The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the Earth's crust consists of oxides. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements (2nd Edn.), Oxford:Butterworth-Heinemann. . Stoichiometry (the measurable relationship between reactants and chemical equations of a equation or reaction) Oxides are extraordinarily diverse in terms of stoichiometries and in terms of the structures of each stoichiometry. Most elements form oxides of more than one stoichiometry. A well known example is carbon monoxide and carbon dioxide.Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching or higher, about higher than that required to smelt copper. Humans started to master that process in Eurasia during the 2nd millennium BCE and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. That event is considered the transition from the Bronze Age to the Iron A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele. The metal was first isolated in 1781 by Peter Jacob Hjelm. Molybdenum does not occur naturally as a free metal on Earth; it is found only in various oxidation states in minerals. The free element, a silvery metal with a grey cast, has the sixth-highest melting point of any element. It readily forms hard, stable carbides in alloys, and for this reason most of the world production of the element (about 80%) is used in steel alloys, including high-strength alloys and superalloys. Most molybdenum compounds have low solubili ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromium
Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardness. A major development in steel production was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating (electroplating with chromium) together comprise 85% of the commercial use. Chromium is also greatly valued as a metal that is able to be highly polished while resisting tarnishing. Polished chromium reflects almost 70% of the visible spectrum, and almost 90% of infrared light. The name of the element is derived from the Greek word χρῶμα, ''chrōma'', meaning color, because many chromium compounds are intensely colored. Industrial production of chromium proceeds from chromite ore (mostly FeCr2O4) to produce ferro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science Direct
ScienceDirect is a website which provides access to a large bibliographic database of scientific and medical publications of the Dutch publisher Elsevier. It hosts over 18 million pieces of content from more than 4,000 academic journals and 30,000 e-books of this publisher. The access to the full-text requires subscription, while the bibliographic metadata is free to read. ScienceDirect is operated by Elsevier. It was launched in March 1997. Usage The journals are grouped into four main sections: ''Physical Sciences and Engineering'', ''Life Sciences'', ''Health Sciences'', and ''Social Sciences and Humanities''. Article abstracts are freely available, and access to their full texts (in PDF and, for newer publications, also HTML) generally requires a subscription or pay-per-view purchase unless the content is freely available in open access. Subscriptions to the overall offering hosted on ScienceDirect, rather than to specific titles it carries, are usually acquired through a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
