Vapor hydrocarbon

Compilation of physical properties for 321 heavy hydrocarbons. Vapor pressures at low pressures. ... 

Solubility increases with temperature. This increase is, however, smaller than the increase in hydrocarbon vapor pressure. 

In the standard method, the metal enclosure (called the air chamber) used to hold the hydrocarbon vapors is immersed in water before the test, then drained but not dried. This mode of operation, often designated as the wet bomb" is stipulated for all materials that are exclusively petroleum. But if the fuels contain alcohols or other organic products soluble in water, the apparatus must be dried in order that the vapors are not absorbed by the water on the walls. This technique is called the dry bomb" it results in RVP values higher by about 100 mbar for some oxygenated motor fuels. When examining the numerical results, it is thus important to know the technique employed. In any case, the dry bomb method is preferred. 

Adsorption may occur from the vapor phase rather than from the solution phase. Thus Fig. Ill-16 shows the surface tension lowering when water was exposed for various hydrocarbon vapors is the saturation pressure, that is, the vapor pressure of the pure liquid hydrocarbon. The activity of the hydrocarbon is given by its vapor pressure, and the Gibbs equation takes the form... 

The value of m, also known as equiHbrium K value, is widely employed to represent hydrocarbon vapor—Hquid equiHbria in absorption and distillation... 

Vapor Pressures and Adsorption Isotherms. The key variables affecting the rate of destmction of soHd wastes are temperature, time, and gas—sohd contacting. The effect of temperature on hydrocarbon vaporization rates is readily understood in terms of its effect on Hquid and adsorbed hydrocarbon vapor pressures. For Hquids, the Clausius-Clapeyron equation yields... 

Product Hterature on hydrocarbon vapor recovery systems, John Zink Co., Tulsa, OHa., 1990. 

Groundwater contaminated with chlorinated hydrocarbons is being remediated by a conventional air stripper or a rotary stripper, producing an air stream containing the halogenated hydrocarbon vapors and saturated with water vapor (45), which is then passed through a catalyst bed. 

This procedure has been applied to the absorption of C5 and lighter hydrocarbon vapors into a lean oil, for example. 

This cany-off of film drops, which may also occur with breakiug foam, in certain cases can partially convert water pollution into air pollution. if such is the case, it may be desirable to recirculate the gas. Such recirculation is also indicated if hydrocarbon vapors or other volatiles are incorporated in the gas stream to improve adsorptive selectivity [Maas, Sep. Sci., 4, 457 (1969)]. 

Fire can also resiilt from the combining of such oxidizers as chlorine and various hydrocarbon vapors oxygen is not required for a fire to take place. 

Evaporative emissions from the fuel tank and carburetor have been controlled on all 1971 and later model automobiles sold in the United States. This has been accomplished by either a vapor recovery system which uses the crankcase of the engine for the storage of the hydrocarbon vapors or an adsorption and regeneration system using a canister of activated carbon to trap the vapors and hold them until such time as a fresh air purge through the canister carries the vapors to the induction system for burning in the combustion chamber. 

Roofs of tanks have to be exchanged for floating types to minimize the dangerous atmosphere of hydrocarbon vapor-air mixture which may explode by sparking due to the static electricity. 

Fuels such as diesel and kerosene readily absorb hydrocarbon vapors, the total uptake and absorption rate depending on both chemical and physical factors. If a soluble test gas is introduced above a charged test oil the concentration of flammable test gas therefore decreases with time. Liquid mist and spray produced by charged liquid increase the absorption rate relative to a quiescent liquid surface. As discussed in A-5-4, absorption could lead to an underestimation of test gas MIE near the liquid surface unless the rate of test gas introduction is sufficiently high to offset the rate of removal. Table 3-8.1.2 shows solubilities of a selection of gases in a mineral-based transformer oil at ambient temperature and pressure [200]. 

Onboard Refueling Vapor Recovery (OR ) regulations were fust proposed m 1987 but were met with a litany of technical and safety issues that delayed the requirement. The 1990 CAA amendments required the implementation of ORVR and the EPA regulation requires passenger cars to first have the systems starting in 1998. The ORVR test will be performed in a SHED and will require that not more than 0.2 grams of hydrocarbon vapor per gallon of dispensed fuel be released from the vehicle. 

As initially discussed in Section 3, carbon canisters are used in the automotive emission control system to temporarily store hydrocarbon vapors. The vapors are later purged into the air charge stream of the air induction system, thus regenerating the carbon canister. Carbon canister design is dependent on the characteristics of the vapors sent to the canister and the amount of purge air available. In the following section, factors that affect the performance of the evaporative emission control system will be discussed. 

Hydrocarbon vapor migration within the carbon canister is a significant factoi during the real time diurnal test procedure. The phenomenon occurs after the canister has been partially charged with fuel vapors. Initially the hydrocarbons will reside primarily in the activated carbon that is closest to the fuel vapor source. Over time, the hydrocarbons will diffuse to areas in the carbon bed with lower HC concentration. Premature break through caused by vapor migration for twc different canisters is shown in Fig. 17. The canister with the L/D ratio of 5.0 shows substantially lower bleed emissions than the canister with an L/D ratio of 3.0. 

Steam is then injected into the full coke drum to remove hydrocarbon vapors, water is injected to cool the coke, and the coke is removed. Typically, high pressure water jets are used to cut the coke from the drum. 

Fluidized-bed catalytic cracking units (FCCUs) are the most common catalytic cracking units. In the fluidized-bed process, oil and oil vapor preheated to 500 to SOOT is contacted with hot catalyst at about 1,300°F either in the reactor itself or in the feed line (called the riser) to the reactor. The catalyst is in a fine, granular form which, when mixed with the vapor, has many of the properties of a fluid. The fluidized catalyst and the reacted hydrocarbon vapor separate mechanically in the reactor and any oil remaining on the catalyst is removed by steam stripping. 

The spent catalyst is withdrawn from the bottom of the reactor and stripped with steam to vaporize the hydrocarbons remaining on the surface. Stripping also removes most of the hydrocarbon vapors which are entrained between the particles of catalyst. Without stripping, hydrocarbon products would be carried to the regenerator and needlessly burned consuming much of the regeneration air, and decreasing yield of useful products. 

For hydrocarbon vapors, values for P,/P, can be obtained from Figure 11, which is sufficiently accurate under all conditions for PR valve calculations. The ratio of specific heats, K, for a particular substance, varies with pressure and... 

For mixtures of hydrocarbon vapor/hydrogen/steam, see "Sizing for Hydrocarbon Vapor/ Hydrogen/Steam Mixtures," below. 

Sizing for Hydrocarbon Vapor/Hydrogen/Steam Mixtures... 

When an average K for a hydrocarbon vapor/hydrogen/steam mixture is required, the following procedure for estimating this K-value is recommended ... 

Figure 13. Safety valve orifice area required for hydrocarbon vapor release.

They are effective as a means of removing heavy hydrocarbon vapors from emergency release streams, thus minimizing condensation problems in downstream equipment. 

---