A quench refers to a rapid cooling. In polymer chemistry and materials science, quenching is used to prevent low-temperature processes such as phase transformations from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and kinetically accessible. For instance, it can reduce crystallinity and thereby increase toughness of both alloys and plastics (produced through polymerization). Heat flow along perfectly insulated wire Conduction is the transfer of heat or electric current from one substance to another by direct contact. ... Polymer chemistry or macromolecular chemistry is a multidisciplinary science that deals with the chemical synthesis and chemical properties of polymers or macromolecules. ... The Materials Science Tetrahedron, which often also includes Characterization at the center Materials science is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... Crystallinity is the degree of structural order in a solid, often represented by a fraction or percentage. ... An alloy is a homogeneous mixture of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... This article or section does not cite any references or sources. ... This is the article about the process. ...

In metallurgy, it is most commonly used to harden steel by introducing martensite, in which case the steel must be rapidly cooled through its eutectoid point, the temperature at which austenite becomes unstable. In steel alloyed with metals such as nickel and manganese, the eutectoid temperature becomes much lower, but the kinetic barriers to phase transformation remain the same. This allows quenching to start at a lower temperature, making the process much easier. High-speed steel also has added tungsten, which serves to raise kinetic barriers and give the illusion that the material has been cooled more rapidly than it really has. Even cooling such alloys slowly in air has most of the desired effects of quenching. Metallurgy is a domain of materials science and of materials engineering that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their mixtures, which are called alloys. ... The steel cable of a colliery winding tower. ... Martensite, named after the German metallurgist Adolf Martens, is a class of hard minerals occurring as lathe- or plate-shaped crystals. ... Eutectoid transformation occurs when a solid solution decomposes into a fixed two solid constituents at a fixed temperature. ... Iron-carbon phase diagram, showing the conditions under which austenite (γ) is stable in carbon steel. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic and silvery with a gold tinge Standard atomic weight 58. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Standard atomic weight 54. ... High speed steel (HSS) is a material usually used in the manufacture of machine tools. ... General Name, Symbol, Number tungsten, W, 74 Chemical series transition metals Group, Period, Block 6, 6, d Appearance grayish white, lustrous Standard atomic weight 183. ...

Role of quenching in scrubbing

Occasionally, hot exhaust gas is quenched or cooled by water sprays before entering the scrubber. Hot gases (those above ambient temperature) are often cooled to near the saturation level. The word scrubber can mean:- The part of a rebreather breathing set which absorbs the carbon dioxide which the individual using the breathing set breathes out. ... Look up Saturation in Wiktionary, the free dictionary. ...

If not cooled, the hot gas stream can evaporate a large portion of the scrubbing liquor, adversely affecting collection efficiency and damaging scrubber internal parts. If the gases entering the scrubber are too hot, some liquid droplets may evaporate before they have a chance to contact pollutants in the exhaust stream, and others may evaporate after contact, causing captured particles to become reentrained. In some cases, quenching can actually save money. The word scrubber can mean:- The part of a rebreather breathing set which absorbs the carbon dioxide which the individual using the breathing set breathes out. ... Many of the compounds which are dangerous to the environment can also be harmful to humans in the long-term range and come from mineral and fossil sources or are produced by humans themselves. ... A particle is Look up Particle in Wiktionary, the free dictionary In particle physics, a basic unit of matter or energy. ...

Cooling the gases reduces the temperature and, therefore, the volume of gases,permitting the use of less expensive construction materials and a smaller scrubber vessel and fan.

A quenching system can be as simple as spraying liquid into the duct just preceding the main scrubbing vessel, or it can be a separate chamber (or tower) with its own spray system identical to a spray tower. Figure 1 - Countercurrent-flow spray tower Spray towers, or chambers, are constructed very simply - consisting of empty cylindrical vessels made of steel or plastic and nozzles that spray liquid into the vessels. ...

Quenchers are designed using the same principles as scrubbers. Increasing the gas-liquid contact in them increases their operational efficiency. Small liquid droplets cool the exhaust stream more quickly than large droplets because they evaporate more easily. Therefore, less liquid is required. However, in most scrubbing systems, approximately one-and-a-half to two and- a-half times the theoretical evaporation demand is required to ensure proper cooling (Industrial Gas Cleaning Institute 1975). Evaporation also depends on time - it does not occur instantaneously. The word scrubber can mean:- The part of a rebreather breathing set which absorbs the carbon dioxide which the individual using the breathing set breathes out. ...

Therefore, the quencher should be sized to allow for an adequate exhaust stream residence time. Normal residence times range from 0.15 to 0.25 seconds for gases under 540°C (1000°F) to 0.2 to 0.3 seconds for gases hotter than 540°C (Schifftner 1979).

Quenching with recirculated scrubber liquor could potentially reduce overall scrubber performance, since recycled liquid usually contains a high level of suspended and dissolved solids. As the liquid droplets evaporate, these solids could become reentrained in the exhaust gas stream. To help reduce this problem, clean makeup water can be added directly to the quench system rather than adding all makeup water to a common sump. ^[1] The word scrubber can mean:- The part of a rebreather breathing set which absorbs the carbon dioxide which the individual using the breathing set breathes out. ... A sump is a low area that collects an often-undesirable liquid(s) such as water or chemicals. ...

External links

• J.L. Becker Company - Manufacturer of quenching and other heat treating systems & components

References

1. ^ *US EPA Air Pollution Training Institute developed in collaboration with North Carolina State University, College of Engineering (NCSU)