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Almost all fluids can undergo supercritical drying as a physical chemistry process, but the harsh conditions involved will often make it impractical as part of an industrial process. Fluids which do see industrial application of supercritical drying include
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is unavailable. The liquid carbon dioxide is then heated until its temperature goes beyond the critical point, at which time the pressure can be gradually released, allowing the gas to escape and leaving a dried product.
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is inconvenient due to possible heat damage to a sample at its critical point temperature (647 K, 374 °C) and corrosiveness of water at such high temperatures and pressures (22.064 MPa, 3,212 psi).
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To avoid this, the sample can be brought via two possible alternate paths from the liquid phase to the gas phase without crossing the liquid–gas boundary on the phase diagram. In
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region, where the distinction between gas and liquid ceases to apply. Densities of the liquid phase and vapor phase become equal at critical point of drying.
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of the working fluid in order to avoid the direct liquid–gas transition seen in ordinary drying (green arrow) or the two phase changes in
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of these two fluids. The acetone is then washed away with high pressure liquid carbon dioxide, the industry standard now that
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in the liquid body pulls against any solid structures the liquid might be in contact with. Delicate structures such as
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at a finite rate, while the amount of liquid decreases. When this happens within a heterogeneous environment,
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in a precise and controlled way. It is useful in the production of
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Modern Drying
Technology, Volume 3: Product Quality and Formulation
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has similar physical behavior to carbon dioxide, but is a powerful
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is first used to wash away all water, exploiting the complete
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of coffee and in the preparation of biological specimens.
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Evangelos
Tsotsas; Arun S. Mujumdar (29 August 2011).
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Scanning electron microscopy and X-ray microanalysis
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230:showing the supercritical region (light blue) of
125:Supercritical drying (red arrow) goes beyond the
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275:in its supercritical state. Supercritical
172:As the substance in a liquid body crosses
109:Learn how and when to remove this message
331:. John Wiley & Sons. pp. 185–.
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47:adding citations to reliable sources
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174:the boundary from liquid to gas
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356:. John Wiley & Sons.
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352:Grahame Lawes (1987).
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152:(MEMS), the drying of
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58:"Supercritical drying"
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142:critical point drying
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389:Industrial processes
176:(see green arrow in
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43:improve this article
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205:solid–gas boundary
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363:978-8-126-5-17305
338:978-3-527-31558-1
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41:Please help
36:verification
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289:miscibility
378:Categories
312:References
194:silica gel
190:cell walls
99:April 2017
69:newspapers
300:See also
273:oxidizer
285:acetone
158:aerogel
83:scholar
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219:Fluids
160:, the
154:spices
146:liquid
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277:water
265:freon
90:JSTOR
76:books
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62:news
261:psi
253:MPa
182:gas
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