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Liquid overheated, vaporization

Raoult s law is the basis for steam distillation. Chapter 5, and its reverse, immiscible solvents distillation, also in Chapter 5. When the sum of the individual vapor pressures reaches 760 torr at sea level, the mixture will boil. By adding steam to a liquid, the vapor pressure of the water is quite high compared to the other components, and they will distill at a much lower temperature. This can minimize destruction caused by overheating, and is usually applied to liquids immiscible with water. The reverse, using a liquid such as toluene, can be used to remove large amounts of water from something like a watermelon section prior to additional chemical analysis. [Pg.4]

Boiling liquid, expanding vapor, explosion (BLEVE) The explosion and rupture of a container caused by the expanding vapor pressure as liquids in the container become overheated. [Pg.399]

Among the most damaging of accidents is a Boiling Liquid Expanding Vapor Explosion (BLEVE, pronounced BLEV-ee). This occurs when a pressure vessel containing liquid is heated so that the metal loses strength and ruptures. Typically, this happens when the vessel failure results from overheating upon... [Pg.159]

QUENCH LIQUID SELECTION The choice of the appropriate quench liquid depends on a number of fac tors. Water is usually the first quench hquid to consider, since it is nontoxic, nonflammable, compatible with many effluent vapors, and has excellent thermal properties. If water is selected as the quench liquid, the tank should oe located indoors, if possible, to avoid freezing problems. If the tank has to be located outdoors in a cold climate, the addition of antifreeze is preferable to heat-tracing the tank, since overheating the tank can occur from tracing, thus reducing its effectiveness. [Pg.2299]

If two insoluble liquids are heated, each is unaffected by the presence of the other and vaporizes to an extent determined only by its own nature. Such a mixture always boils at a temperature lower than is true for either substance alone. This effect may be applied to substances that would be damaged by overheating if distilled in the usual fashion. Substances can also be distilled at temperatures below their normal boiling points by partially evacuating the still. The greater the vacuum, the lower the distillation temperature. [Pg.164]

The position of the meniscus within the micro-channel defines the type of temperature distribution. In the first case, when the meniscus is near the outlet, the temperature gradient of the vapor region is small. The rate of evaporation is determined mainly by the heat flux in the liquid region. Therefore, the necessary condition of the evaporation consists of the existence of the region (near the meniscus), where the water is overheated (its temperature is higher than the temperature of boiling). The heat losses to the inlet tank cause the existence of the temperature maximum. [Pg.422]

Typically a BLEVE occurs after a metal container has been overheated above 538 °C (1,000 °F). The metal may not be able to withstand the internal stress and therefore failure occurs. The contained liquid space of the vessel normally acts as a heat absorber, so the wetted portions of the container are usually not at risk, only the surfaces of internal vapor spaces. Most BLEVEs occur when containers are less than 1/2 to 1/3 full of liquids. The liquid vaporization expansion energy is such that container pieces have been thrown as far as 0.8 km (1/2 mile) from the rupture and fatalities from such incidents have occurred up to 244 meters (800 ft.) away. Fireballs may occur at the time of rupture, that are several meters in diameter, resulting in intense heat exposure to nearby personnel. Fatalities due to burns from such incidents have occurred to personnel as much as 76 meters (250 Ft.) away from the point of rupture. [Pg.51]

All the obstacles in the path of distillation progress, however, were not equipment fabrication and design problems. It was discovered very early in the running of sour crudes that the shell still corroded severely at the vapor-liquid interface line and in that portion of the shell in contact with vapors. At the same time severe corrosion in pipe stills and tube stills, along with overheating and coking, resulted in expensive equipment failures. These problems started metallurgists on a chain of developments which produced the corrosion- and heat-resistant alloys used in modern oil heaters and the alloy liners used in distillation columns. [Pg.204]

Figure 3.14. The lower ends of fractionators, (a) Kettle reboiler. The heat source may be on TC of either of the two locations shown or on flow control, or on difference of pressure between key locations in the tower. Because of the built-in weir, no LC is needed. Less head room is needed than with the thermosiphon reboiler, (b) Thermosiphon reboiler. Compared with the kettle, the heat transfer coefficient is greater, the shorter residence time may prevent overheating of thermally sensitive materials, surface fouling will be less, and the smaller holdup of hot liquid is a safety precaution, (c) Forced circulation reboiler. High rate of heat transfer and a short residence time which is desirable with thermally sensitive materials are achieved, (d) Rate of supply of heat transfer medium is controlled by the difference in pressure between two key locations in the tower, (e) With the control valve in the condensate line, the rate of heat transfer is controlled by the amount of unflooded heat transfer surface present at any time, (f) Withdrawal on TC ensures that the product has the correct boiling point and presumably the correct composition. The LC on the steam supply ensures that the specified heat input is being maintained, (g) Cascade control The set point of the FC on the steam supply is adjusted by the TC to ensure constant temperature in the column, (h) Steam flow rate is controlled to ensure specified composition of the PF effluent. The composition may be measured directly or indirectly by measurement of some physical property such as vapor pressure, (i) The three-way valve in the hot oil heating supply prevents buildup of excessive pressure in case the flow to the reboiier is throttled substantially, (j) The three-way valve of case (i) is replaced by a two-way valve and a differential pressure controller. This method is more expensive but avoids use of the possibly troublesome three-way valve. Figure 3.14. The lower ends of fractionators, (a) Kettle reboiler. The heat source may be on TC of either of the two locations shown or on flow control, or on difference of pressure between key locations in the tower. Because of the built-in weir, no LC is needed. Less head room is needed than with the thermosiphon reboiler, (b) Thermosiphon reboiler. Compared with the kettle, the heat transfer coefficient is greater, the shorter residence time may prevent overheating of thermally sensitive materials, surface fouling will be less, and the smaller holdup of hot liquid is a safety precaution, (c) Forced circulation reboiler. High rate of heat transfer and a short residence time which is desirable with thermally sensitive materials are achieved, (d) Rate of supply of heat transfer medium is controlled by the difference in pressure between two key locations in the tower, (e) With the control valve in the condensate line, the rate of heat transfer is controlled by the amount of unflooded heat transfer surface present at any time, (f) Withdrawal on TC ensures that the product has the correct boiling point and presumably the correct composition. The LC on the steam supply ensures that the specified heat input is being maintained, (g) Cascade control The set point of the FC on the steam supply is adjusted by the TC to ensure constant temperature in the column, (h) Steam flow rate is controlled to ensure specified composition of the PF effluent. The composition may be measured directly or indirectly by measurement of some physical property such as vapor pressure, (i) The three-way valve in the hot oil heating supply prevents buildup of excessive pressure in case the flow to the reboiier is throttled substantially, (j) The three-way valve of case (i) is replaced by a two-way valve and a differential pressure controller. This method is more expensive but avoids use of the possibly troublesome three-way valve.
Particularly extractions of fatty substances are carried out with propane in high pressure liquid/liquid mode. Although this extraction medium may be used in supercritical condition, this limiting case of liquid/liquid extraction was considered for design, because the required vaporization heat is maximized. The extraction is operated at a pressure of merely 80 bar and a temperature of 55°C. The further steps are the first decompression, evaporation and overheating to vapour conditions at 15 bar, 65°C followed by the second precipitation at 10 bar, 65°C. Afterwards the vapour will be liquified through condensation, recompressed and - in this case - reheated to extraction conditions. [Pg.622]

Inhalation of fluoropolymer fumes from overheating or burning the resin may cause polymer fume fever . High temperatures, such as in sintering operations, may release APFO vapors, which may condense as a solid or as a liquid solution in the oven, exhaust duct or stack, or on other cool surfaces. [Pg.1941]


See other pages where Liquid overheated, vaporization is mentioned: [Pg.160]    [Pg.342]    [Pg.504]    [Pg.504]    [Pg.200]    [Pg.121]    [Pg.173]    [Pg.214]    [Pg.215]    [Pg.113]    [Pg.16]    [Pg.35]    [Pg.802]    [Pg.16]    [Pg.1140]    [Pg.2339]    [Pg.39]    [Pg.172]    [Pg.128]    [Pg.145]    [Pg.550]    [Pg.75]    [Pg.210]    [Pg.461]    [Pg.108]    [Pg.111]    [Pg.344]    [Pg.963]    [Pg.2044]    [Pg.2094]    [Pg.129]    [Pg.375]    [Pg.1309]    [Pg.2577]   
See also in sourсe #XX -- [ Pg.111 ]




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