Vapor pressure liquefied gases

Release of a pressurized, liquefied gas to the atmosphere will cause the gas to cool and condense water vapor in ambient air, forming a visible vapor cloud. Firefighters and operators who attempt to move such a cloud away from furnaces and the like with fire hoses and water jet guns are at risk, because of the possibility of a UVCE near them. Plants and governmental agencies who recommend such practices need to reexamine their policies. 

Often a fireball follows a BLEVE ( Boiling Liquid Vapor Cloud Explosion ) (vid. Sect. 10.7), which may occur, for example, if a vessel containing pressure liquefied gas fails. 

The first step in a gas processing plant is to separate the components that are to be recovered from the gas into an NGL stream. It may then be desirable to fractionate the NGL stream into various liquefied petroleum gas (LPG) components of ethane, propane, iso-butane, or normal-butane. The LPG products are defined by their vapor pressure and must meet certain criteria as shown in Table 9-1. The unfractionated natural gas liquids product (NGL) is defined by the properties in Table 9-2. NGL is made up principally of pentanes and heavier hydrocarbons although it may contain some butanes and very small amounts of propane. It cannot contain heavy components that boil at more than 375°F. 

All gases can be liquefied under suitable pressure and temperature conditions and therefore could be called vapors. The term gas is most generally used when conditions are such that a return to the liquid state, i.e. condensation, would be difficult within the scope of the operations being conducted. However, a gas under such conditions is actually a superheated vapor. 

It is impossible to have liquid carbon dioxide at temperatures above 31°C, no matter how much pressure is applied. Even at pressures as high as 1000 atm, carbon dioxide gas does not liquefy at 35 or 40°C. This behavior is typical of all substances. There is a temperature, called the critical temperature, above which the liquid phase of a pure substance cannot exist The pressure that must be applied to cause condensation at that temperature is called the critical pressure. Quite simply, the critical pressure is the vapor pressure of the liquid at the critical temperature. 

Phase changes are characteristic of all substances. The normal phases displayed by the halogens appear in Section II-L where we also show that a gas liquefies or a liquid freezes at low enough temperatures. Vapor pressure, which results from molecules escaping from a condensed phase into the gas phase, is one of the liquid properties described in Section II-I. Phase changes depends on temperature, pressure, and the magnitudes of intermolecular forces. 

Arsine has a high vapor pressure and is difficult to store as a liquefied gas. It is extremely flammable and is also decomposed by light, heat, and contact with various metals. It can explode on contact with warm, dry air. 

E) Normal means 1 atm (760 mm Hg) pressure. Boiling occurs at a temperature at which the substance s vapor pressure becomes equal to the pressure above its surface. On this phase diagram, at 1 atm pressure, there is no intercept on a line separating the liquid phase from the gas phase. In other words, carbon dioxide cannot be liquefied at 1 atm pressure. It is in the liquid form only under very high pressures. At 1.0 atm pressure, solid C02 will sublime — that is, go directly to the gas phase. 

A further aspect of volatility that receives considerable attention is the vapor pressure of petroleum and its constituent fractions. The vapor pressure is the force exerted on the walls of a closed container by the vaporized portion of a liquid. Conversely, it is the force that must be exerted on the liquid to prevent it from vaporizing further (ASTM D323). The vapor pressure increases with temperature for any given gasoline, liquefied pefioleum gas, or other product. The temperature at which the vapor pressure of a liquid, either a pure compound or a mixture of many compounds, equals 1 atm pressure (14.7 psi, absolute) is designated as the boiling point of the liquid. 

Simple evaporation tests in conjunction with vapor pressure measurement give a further guide to composition. In these tests a liquefied petroleum gas sample is allowed to evaporate naturally from an open graduated vessel. Results are recorded on the basis of volume and temperature changes, such as the temperature recorded when 95% has evaporated or the volume left at a particular temperature (ASTM D1837). 

Roberts makes clear that P is intended to be the vapor pressure when the failure occurs. In a BLEVE, this might be the relief valve setting Pq, whereas in a fireball resulting from an impact failure, it will be the vapor pressure at ambient temperature, as is used in FLARE (described in Appendix C). For a fireball following a release of gas (as opposed to liquefied gas), P should be the storage pressure. 

Colorless gas pungent suffocating odor density 2.975 g/L fumes in moist air liquefies at -101°C sohdifies at -126.8° vapor pressure at -128°C is 57.8 torr critical temperature -12.2°C critical pressure 49.15 atm critical volume 115 cm3/mol soluble in water with partial hydrolysis solubdity in water at 0°C 332 g/lOOg also soluble in benzene, toluene, hexane, chloroform and methylene chloride soluble in anhydrous concentrated sulfuric acid. 

Colorless gas strong, pungent odor gas density 2.985 g/L hquid density 1.114 g/mL at 0°C refractive index 1.4538 (at 0°C) vapor pressure 588 torr at 0°C liquefies at 6.8°C freezes at -111.3°C burns with a blue sooty flame reacts... 

Colorless gas almond-like pungent odor hums with a pink flame with hluish tinge density 2.283 g/L liquefies at -21.1°C vapor pressure 635 torr at -25°C solidifies at -27.9°C critical pressure 59.02 atm slightly soluble in water (about 400 mL gas at NTP dissolves in 100 mL water or 0.85 g/100 mfy water) soluble in alcohol and ether. 

Colorless gas moldy odor liquefies at -128.75°C density of hquid 3.116 g/mL vapor pressure at -158°C 96 torr sohdifies at -206.8°C critical temperature -39.15°C critical pressure 44.02 atm critical volume 126 cm /mol very slightly soluble in water. 

Temperature at the critical point (end of the vapor pressure curve in phase diagram) is termed critical temperature. At temperatures above critical temperature, a substance cannot be liquefied, no matter how great the pressure. Pressure at the critical point is called critical pressure. It is the minimum pressure required to condense gas to liquid at the critical temperature. A substance is still a fluid above the critical point, neither a gas nor a liquid, and is referred to as a supercritical fluid. The critical temperature and pressure are expressed in this text in -C and atm, respectively. 

Tests with Aerosol Sprays. One of the chief means of applying concentrated oil sprays is in aerosol form. An aerosol generally remains suspended in the air for some time and is carried by normal wind or air currents. Aerosols are probably best adapted to interior applications but have been used with some success outdoors. They may be produced by liquefied-gas formulations released through capillary nozzles, by steam and air atomization, by centrifugal disks and rotors, by extremely high pressure, and by heat vaporization. 

LPG (liquefied petroleum gas)— propane or (less commonly) butane, obtained by extraction from natural gas or from refinery processes. LPG has a vapor pressure sufficiently low to permit compression and storage in a liquid state at moderate pressures and normal ambient temperatures. Pressurized in metal bottles or tanks. LPG is easily handled and readily lends itself to a variety of applications as a fuel, refrigerant, and propellant in packaged aerosols. LPG is also called LP gas and bottled gas. See natural gas liquids. 

MW 44.06 unstable, ring cleaves readily CAS [75-21-8] used as a fumigant and sterilizing agent, and in the manufacture of many glycol ethers and ethano-lamines colorless gas with ether-like odor liquefies at 10.4°C density 0.88 g/mL at 10°C vapor pressure 1095 torr at 20°C soluble in water and most organic solvents highly flammable, toxic, and severe irritant. 

Actually, the small amount of liquefied gas passing into the bonnet vaporizes and provides a vapor barrier between the liquefied gas and the packing area. In addition, the pressure resulting from the vaporization of the liquid prevents additional liquid from passing into the bonnet area. Excess pressure vents back into the body. 

The partial vapor pressure of each liquefied gas is given by ... 

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