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31-01-2009, 12:03 AM

The science and technology of deep refrigeration processing occurring at temperatures lower than about 150 k. is the field of cryogenics. The name cryogenics is evolved from Greek word ?kryos? meaning icy cold. Phenomena that occurs at cryogenic temperatures include liquefaction and solidification of ambient gases; loss of ductility and embrittlement of some structural materials such as carbon steel; increase in thermal conductivity to a maximum value, followed by further decrease in temperature. Cryogenics is the low temperature (150 K) refrigeration. It explains the properties of cryogens used and their principles. Storage methods and handling techniques are covered. Cryogenics are applied in different fields of production, transportation, medicine, aerospace, physics research etc. Rocket propulsion is imparting force to a flying vehicle such as missile or spacecraft. Different types of rockets and their parts are explained. Cryogenics has future applications in many fields like superconductivity and propulsion fields. Cryogenics is being applied to variety of research areas; a few of which are: food processing and refrigeration, space craft life supporting system, space simulation, microbiology, medicine, surgery, electronics, data processing and metal working. Rocket propulsion is the process of imparting a force to flying vehicle such as a missile, by momentum of ejected matter. The matter, called propellant, is stored in the vehicle and ejected at high velocity. In chemical rocket, the propellants are chemical compounds that undergo a chemical combustion reaction releasing the energy for thermodynamically accelerating and ejecting the gaseous reaction products at high velocities. Chemical rocket propulsion is thus differential from other types of rocket propulsion which use nuclear, solar or electrical energy as their power source and which may use mechanism other than adiabatic expansion of a gas for achieving high ejection velocities.
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21-03-2010, 01:55 PM

please read please read topicideashow-to-CRYOGENICS--1264 and topicideashow-to-CRYOGENICS-AND-ITS-SPACE-APPLICATIONS-full-report for more about cryogenics technical information
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18-02-2011, 02:20 PM

.doc   Cryogenic_Grinding.DOC (Size: 130.5 KB / Downloads: 138)
The term “Cryogenics” originates from Greek word which means creation or production by means of cold. As prices for energy and raw materials rise and concern for the environment makes safe waste disposal difficult and Costly, resource recovery becomes a vital matter for today’s business. Cryogenic grinding technology can efficiently grind most tough materials and can also facilitate Cryogenic recycling of tough composite materials and multi component scrap. The heart of this technology is the CRYO-GRIND SYSTEM. It employs a cryogenic process to embrittle and grind materials to achieve consistent particle size for a wide range of products. The cryogenic process also has a unique capability for recycling difficult to separate composite materials.
Cryogenic grinding is a method of powdering herbs at sub-zero temperatures ranging from 0 to minus 70°F. The herbs are frozen with liquid nitrogen as they are being ground. This process does not damage or alter the chemical composition of the plant in any way. Normal grinding processes which do not use a cooling system can reach up to 200°F. These high temperatures can reduce volatile components and heat-sensitive constituents in herbs. The cryogenic grinding process starts with air-dried herbs, rather than freeze-dried herbs.
Solid materials are ground or pulverized by way of hammer mills, attrition mills, granulators or other equipment. A smaller particle size is usually needed to enhance the further processing of the solid, as in mixing with other materials. A finer particle also helps in melting of rubber and plastics for molding. However, many materials are either very soft or very tough at room temperatures. By cooling to cryogenic temperatures with liquid nitrogen, these may be embrittled and easily fractured into small particles.
A scientifically controlled study using four herbs was conducted at Frontier Herbs in the Fall of 1996, comparing cryogenic grinding methods with normal grinding methods. The herbs tested included feverfew, goldenseal, valerian and echinacea. In all cases the cryogenically ground herb contained greater amounts of the constituents tested. Feverfew herb showed the greatest difference, with the cryogenically ground herb containing 21.8% higher levels of parthenolide, the primary active constituent. Valerian root showed an 18.7% increase in valerenic acid when cryogenically ground. Goldenseal root showed a 16.4% increase in berberine and 10.7% increase in hydrastine. Lastly, Echinacea purpurea root showed a 12.1% increase in total phenolic content in the cryogenically ground root. Test results were obtained by HPLC (high performance liquid chromatography) methods.
Cryogenic grinding was shown to significantly affect active constituent levels in herbs. Test results showed an average increase of 15.6% in constituents tested in four medicinal herbs when they were ground cryogenically. The range was 10.7% to 21.8%, indicating that some herbs are affected more than others by the temperatures at which they're ground
The major areas in which cryogenics find its applications are : -
1. Gas Industry – in air separation. The volume of production of nitrogen and Oxygen by cryogenic separation of air is the important of the separation of air, refrigeration and separation. In the separation column, the difference in the boiling points of the constituents of air is used to separate them out.
2. As the source of gas. For example, the breathing oxygen needed for the pilots of the fighter aircraft is supplied by vaporizing liquid oxygen on board. In this way is a weight reduction of 65% and space reduction of 85%.
3. In space research – as rocket propellant and for space simulation. The most important advantage of cryogenic fuels is that these have very high specific impulse when compared to other fuels (specific impulse is kgs of thrust produced per kg of propellant per sec). The value is approximately 500 for cryogenic fuels whereas it is about 250 for alcohol oxygen mixture.
4. In biology – for preservation and in treatment of diseases.
5. In food industry – for food handling and processing
6. In electronics – both semiconductor and superconductor electronics for better signal to noise ratio speed etc
7. In miscellaneous applications such as cryogenic grinding , freezing pipelines for repairs, shrink fitting, fire fighting, etc
8. In medicine – Magnetic Resonance Imaging, Magnetic Resonance Spectroscopy (MRS), Magneto Cardio Graphy (MCG), etc.
9. In nuclear and high – energy physics
10. Metal fabrication
Since almost all materials embrittle when exposed to cold temperatures, cryogenic size reduction utilizes the cold energy available from liquid nitrogen to cool, embrittle and inert materials prior to and or during the grinding process. All materials which due to their specific properties at ambient temperatures are elastic, have low melting points, contain volatile or oily substances, have low combustion temperatures and are sensitive to oxygen, are ideal candidates for cryogenic size reduction.
Physical properties of liquid nitrogen is produced by the separation of air into its components in an air separation plant and is distributed in vacuum insulated transport vessels to the end user where it is stored in a vacuum insulated storage vessel till it is used. At atmospheric pressure liquid nitrogen is at a temperature of –320 deg F and possesses a latent energy content of 94 BTU/LB resulting in a total cooling energy content of 179.6 BTU/LB. Nitrogen is anon-flammable, non toxic and inert gas which makes up 78.09% of the air we breathe. It has the characteristics of an inert gas, except at highly elevated temperatures, and does not form any compound under normal temperatures and pressure. Drawn from the liquid phase, nitrogen generally has a purity of 99.998 % with a dew point less than – 100 deg F and is very dry.
Liquid Nitrogen at 77.6 K is used to embrittle a material prior to size reduction. Once brittle the material is much easier to grind. When CRYO-GRIND system is used to recycle composite or multi component materials, two separate phenomena occur. First, since each component generally would have a different coefficient of thermal contraction, high thermal stresses are created at the interface between the components due to rapid cryogenic cooling. Second, because each component material embrittles at different temperatures, it allows selective embritlement, which further enhances separation effectiveness. The most brittle components will undergo greater size reduction. Through careful control of thermal stress and embritlement with operating temperature, cleaner separation and recovery of individual components are achieved
Cryogenic Grinding System
When using the system, measurable and repeatable results are obtained for lab or productions calculations. Mills range in size from 7-1/2 HP to 200 HP. With our cryogenic grinding unit an understanding develops with interaction of equipment components and operating parameters. Factors such as consistent feed rate, precise temperature measurement, mill operating parameters and pressure control are critical to the evaluation of cryogenic grinding and cryogenic grinding systems.

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