Pressure vessels vapor-liquid

A pressure vessel contains liquid water and water vapor in equilibrium at 300(°F). The total mass of liquid and vapor is 2(lbm). If the volume of vapor is 100 times the volume of liquid, what is the total enthalpy of the contents of the vessel ... 

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... 

Subsection B This subsection contains rules pertaining to the methods of fabrication of pressure vessels. Part UW is applicable to welded vessels. Service restric tions are defined. Lethal service is for lethal substances, which are defined as poisonous gases or liquids of such a nature that a very small amount of the gas or the vapor of the liquid mixed or unmixed with air is dangerous to life when inhaled. It is stated that it is the user s responsibility to advise the designer or manufacturer if the service is lethal. All vessels in lethal service shall have all butt-welded joints fully radiographed, and when practical, joints shall be butt-welded. All vessels fabricated of carbon or low-aUoy steel shall be postweld-heat-treated. 

Figure 12.1 is a simplified representation of the cavitation process. Figure 12. L4 represents a vessel containing a liquid. The vessel is closed by an air-tight plunger. When the plunger is withdrawn (B), a partial vacuum is created above the liquid, causing vapor bubbles to form and grow within the liquid. In essence, the liquid boils without a temperature increase. If the plunger is then driven toward the surface of the liquid (C), the pressure in the liquid increases and the bubbles...

The feed flow is often not controlled but is rather on level control from another column or vessel. The liquid product flow s (distillate and bottoms) are often on level rather than flow control. Top vapor product is, however, usually on pressure control. The reflu.x is frequently on FRC, but also may be on column TRC or accumulator level. 

An old 100-m pressure vessel, a vertical cylinder, designed for a gauge pressure of 5 psi (0.3 bar), was being used to store, at atmospheric pressure, a liquid of flash point 40°C. The fire heated the vessel to above 40°C and ignited the vapor coming out of the vent the fire flashed back into the tank, where an explosion occurred. The vessel burst at the bottom seam, and the entire vessel, except for the base, and contents went into orbit like a rocket [4]. 

An entirely different diesel hazard is compression of a pocket of air and flammable vapor trapped in a vessel or pipeline by a column of liquid. If the pressure of the liquid rises, the air is compressed, and the heat developed may heat the vapor above its auto-ignition temperature [13]. 

This section addresses the effects of BLEVE blasts and pressure vessel bursts. Actually, the blast effect of a BLEVE results not only from rapid evaporation (flashing) of liquid, but also from the expansion of vapor in the vessel s vapor (head) space. In many accidents, head-space vapor expansion probably produces most of the blast effects. Rapid expansion of vapor produces a blast identical to that of other pressure vessel ruptures, and so does flashing liquid. Therefore, it is necessary to calculate blast from pressure vessel mpture in order to calculate a BLEVE blast effect. 

Method for Explosively Flashing Liquids and Pressure Vessel Bursts with Vapor or Nonideal Gas... 

In the preceding subsections, bursting vessels were assumed to be filled with ideal gases. In fact, most pressure vessels are filled with fluids whose behavior cannot be described, or even approximated, by the ideal-gas law. Furthermore, many vessels are filled with superheated liquids which may vaporize rapidly, or even explosively, when depressurized. 

Rgure 6.29. Calculation of energy of flashing liquids and pressure vessel bursts filled with vapor or nonideal gas. 

Failure followed by inunediate combustion Runaw ay chemical reaction before failure Runaway nuclear reaction before failure BLEVEs (boiling liquidexpanding vapor explosion pressure vessel containing a flash-evaporating liquid) External Heating Immediate combustion after release No combustion after release... 

A boding liquid-expanding vapor explosion occurs when a pressure vessel containing a liquid is heated to a temperature liigh enough to cause tlie metal to lose strength and rupture. The source of tlie heat is nonnally another fire near tlie vessel. The effects of a BLEVE depend on whether tlie liquid in tlie vessel is flammable. If the liquid is flammable, it may eitlier cause a fire, which radiates heat, or fonii a vapor cloud, which could result in a second explosion. 

Storage Vessels Vapor pressure of liquid at maximum ambient temperature plus 30° F. (usually 110° to 140° F.)... 

Boiling-liquid expanding-vapor explosion (BLEVE) A BLEVE occurs if a vessel that contains a liquid at a temperature above its atmospheric pressure boiling point ruptures. The subsequent BLEVE is the explosive vaporization of a large fraction of the vessel contents possibly followed by combustion or explosion of the vaporized cloud if it is combustible. This type of explosion occurs when an external fire heats the contents of a tank of volatile material. As the tank contents heat, the vapor pressure of the liquid within the tank increases and the tank s structural integrity is reduced because of the heating. If the tank ruptures, the hot liquid volatilizes explosively. 

A storage vessel contains liquid benzene at 100°F. The vessel vapor space is inerted with pure nitrogen to a total pressure of 1/2-in of water gauge. Assume that the vapor space is saturated with benzene vapor. 

A physical explosion, for example, a boiler explosion, a pressure vessel failure, or a BLEVE (Boiling Liquid Expanding Vapor Explosion), is not necessarily caused by a chemical reaction. Chemical explosions are characterized as detonations, deflagrations, and thermal explosions. In the case of a detonation or deflagration (e.g., explosive burning), a reaction front is present that proceeds through the material. A detonation proceeds by a shock wave with a velocity exceeding the speed of sound in the unreacted material. A... 

Gas production and subsequent pressure-time histories can be investigated successfully only in pressure vessels such as the VSP. If the gaseous product dissolves partly in the reaction mixture (i.e., the vapor-liquid equilibrium is changed), careful investigations of the pressure effect within the possible variations of the operating conditions are necessary. Pressurized vessels are also useful to investigate any mass transfer improvement for gas-liquid or gas-dissolved (suspended) solid reactions. 

---