|
Last update: Saturday 22nd of November 2008 Quench »
QuenchA 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). 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. Role of quenching in scrubbingOccasionally, 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. 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. 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. 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. 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. External links
Quench Mp3 DownloadsDownload audio files (mp3 and wma) with Quench Songs using these download websites. The list will be updated perciodically.Quench RingtonesYou can get any Quench ringtone you like (realtone, polyphonic, mono tone, mp3 ringtone) using the next service:
Pick Carrier, Confirm your Phone number and choose the ringtones you want to receive Quench Music VideosMusic Plate music videos with myspace codes, see Quench music videos section search for music videos and get your myspace music code.Quench LyricsGet full Quench lyrics on music plate Quench lyrics page. Use the search option if the target page is not correctly displayed.
Quench in the news
Motivation - we all have it. In fact, everything we do is driven by some type of motivation. The motivation to settle a hungry stomach. The motivation to rest a weary body. And the motivation to quench thirst are all different forms of motivation. However, we can’t be motivated to do something you don’t want to do. A Nootropic drug is one that stimulates the brain. popularly referred to as "smart drugs", are substances which boost human cognitive abilities. The antioxidant or free radical quenching properties of CoQ10 serve to greatly reduce oxidative damage to tissues (more than vitamin E) Interesting article on whether the Apple Iphone Set New Cell Phone Standards.So whether you are looking to upgrade your current phone or just keep up with the latest technological devices, the iPhone is going to quench your tech thirst. Get ready for the ride.
|
Music Plate Sections:Music Artists and BandsRingtones Lyrics Music Videos Also on Music Plate Right Said Fred Pet Shop Boys Epidemic Jefferson Starship Laughing Man Seal Hitman Sammy Sam John Reuben Punk Barbarians Hoi Polloi Gillian Welch Riders In The Sky Beloved Wall Jump Junior Mo Thugs Candlebox Paradisio Rush Luna Stressed Out American Standard Beck |