Bubble point pressure limitations

The quantity of gas-forming molecules (light molecules) in the liquid phase at reservoir temperature is limited only by the pressure and the quantity of light molecules present. A black oil is said to be saturated when a slight decrease in pressure will allow release of some gas. The bubble-point pressure is a special case of saturation at which the first release of gas occurs. 

Equation 8-16 can be integrated under the assumption that c0 remains constant as pressure changes. Our future use of this equation will be related to bubble-point pressure, so we will use a lower limit of... 

When the wetting fluid is expelled from the largest pore, a bulk gas flow will be detected on the downstream side of the filter system (Fig. 7). The bubble point measurement determines the pore size of the filter membrane, i.e., the larger the pore the lower the bubble point pressure. Therefore, filter manufacturers specify the bubble point limits as the minimum allowable bubble point. During an integrity test, the bubble point test has to exceed the set minimum bubble point. 

It is essential that the microbiological particle passage test is performed as part of the development of new sterile formulations. Because of its very specialized nature, the test is normally performed only by the filter manufacturers, who then provide limits for secondary physical tests (e.g., bubble point, pressure decay, forward flow, etc.), which can be applied to verify the pore size rating and integrity of the membrane filters. 

Second, solubility gas components is limited by the value of the bubble-point pressure which is that max pressure, at which volatiles of water begin to segregate and form subsurface gas. As in this case P = P, according to equations (2.279) and (2.297), for underground gas and water are valid equalities... 

Below the bubble-point, pressure gas percolates out of the oil phase, coalesces and displaces the crude oil. The gas phase, which is much less viscous and thus more mobile than the oil phase, fingers through the displaced oil phase. In the absence of external forces, the primary depletion inefficiently produces only 10 to 30 percent of the original oil in place. In the secondary stage of production, water is usually injected to overcome the viscous resistance of the crude at a predetermined economic limit of the primary depletion drive. The low displacement efficiencies, 30 to 50 percent, of secondary waterfloods are usually attributed to vertical and areal sweep inefficiencies associated with reservoir heterogeneities and nonconformance in flood patterns. Most of the oil in petroleum reservoirs is retained as a result of macroscopic reservoir heterogeneities which divert the driving fluid and the microscopically induced capillary forces which restrict viscous displacement of contacted oil. This oil accounts for approximately 70 percent, or 300 x 10 bbl, of the known reserves in the United States. 

GN2 over GHe, both of which act to limit the performance enhancing effect of evaporation on the bubble point pressure. 

In controlled venting operation, the quench tank pressure is maintained at a desired level by a pressure controller/control valve system or pressure relief valve. This mode of operation is used when the discharge mixture bubble point is close to or below the maximum ambient temperature and it is desired to limit the maximum quench tank pressure. 

In many practical cases, the conditions for criticality described in the previous sections are only necessary to ensure safe operation. Such conditions do not guarantee, indeed, that the maximum allowable temperature in the reactor, Tma, is not exceeded. For instance, this upper temperature limit can be imposed, in liquid systems, by the bubble point of the reacting solution or by the decomposition temperature of some compounds in it, or, in gaseous systems, by the maximum internal pressure the vessel can comply with. 

Measurements of solid solubilities in supercritical pentane were, in principle, identical to the bubble point or dew point measurements described above. The equilibrium pressure and corresponding solid solubility at a fixed temperature were determined from the measured pressure and known mixture composition in the cell when the last crystal of solid dissolved. These measurements were limited at low solubilities by the low porphyrin loadings, and at high solubilities by the dark purple color of the fluid phase which obscured observation of the solid phase. 

If one independent variable is the temperature or pressure and the only product is a saturated liquid (i.e., the other independent variable is the vapor fraction set at the zero limit), then the operation is a bubble point flash. The dependent variables are the pressure or temperature, the heat duty, and the liquid and vapor compositions. Since the liquid is the only product, its composition is identical to the feed composition. The vapor composition refers to the composition of a vapor at equilibrium with the liquid. Although its rate is zero, its composition is determinable and is equal to the composition of the first vapor bubble resulting from infinitesimal vaporization. Bubble points are not feasible at all temperatures and pressures. As discussed in... 

In a dew point flash, the fraction vapor is set at the unity limit, at a specified temperature or pressure. The dependent variables are the pressure or temperature, the heat duty, and the liquid and vapor compositions. The only product is a saturated vapor with composition equal to that of the feed. The equilibrium liquid composition corresponds to the first liquid drop resulting from infinitesimal condensation. As in the bubble point flash, dew points can exist only within certain ranges of temperature and pressure. Referring to Figure 2.1, no dew points can exist at temperatures above the cricondentherm or at pressures above the cricondenbar. At temperatures or pressures where retrograde condensation can occur, there can be two dew points a normal dew point and a retrograde dew point. 

Stream Information. Directed arcs that represent the streams, with flow direction from left to right wherever possible, are numbered for reference. By convention, when streamlines cross, the horizontal line is shown as a continuous arc, with the vertical line broken. Each stream is labeled on the PFD by a numbered diamond. Furthermore, the feed and product streams are identified by name. Thus, streams 1 and 2 in Rgure 3.19 are labeled as the ethylene and chlorine feed streams, while streams 11 and 14 are labeled as the hydrogen chloride and vinyl-chloride product streams. Mass flow rates, pressures, and tempera-mres may appear on the PFD directly, but more often are placed in the stream table instead, for clarity. The latter has a column for each stream and can appear at the bottom of the PFD or as a separate table. Here, because of formatting limitations in this text, the stream table for the vinyl-chloride process is presented separately in Table 3.6. At least the following entries are presented for each stream label, temperature, pressure, vapor fraction, total and component molar flow rates, and total mass flow rate. In addition, stream properties such as the enthalpy, density, heat capacity, viscosity, and entropy, may be displayed. Stream tables are often completed using a process simulator. In Table 3.6, the conversion in the direct chlorination reactor is assumed to be 100%, while that in the pyrolysis reactor is only 60%. Furthermore, both towers are assumed to carry out perfect separations, with the overhead and bottoms temperatures computed based on dew- and bubble-point temperatures, respectively. 

This linear relationship between the total pressure, P, and the mole fraction, x, of the most volatile species is a characteristic of Raoult s law, as shown in Figure 7.18a for the benzene-toluene mixture at 90°C. Note that the bubble-point curve (P-x) is linear between the vapor pressures of the pure species (at x, = 0, 1), and the dew-point curve (P-yJ lies below it. When the (x, yi) points are graphed at different pressures, the familiar vapor-liquid equilibrium curve is obtained, as shown in Figure 7.18b. Using McCabe-Thiele analysis, it is shown readily that for any feed composition, there are no limitations to the values of the mole fractions of the distillate and bottoms products from a distillation tower. 

The region in which vapor and liquid may coexist in a binary system is limited by the vapor pressure curves of the pure components and the critical line. In Figure 5.9 the vapor pressure curves of the pure compounds of the system ethane-heptane are shown together with the PT-curves of different fixed compositions of the liquid and the vapor phase. The intersections of the dew point and the bubble point curve for a given temperature and pressure mark the VLE for the chosen compositions in the liquid and the vapor phase. The critical points of a binary system can be found where a loop in Figure 5.9 is tangential to the envelope critical curve, also called critical locus. 

The bubble-point method gives only limited information and a another method was developed that combines the bubble-point concept with the measurement of the gas flow through the emptied pores. Here at first the gas flow is measured through a dry membrane as a function of the pressure and generally a straight line obtained (see figure IV - 8). Then... 

Screen channel LAD performance in high-pressure propellant tanks may be affected by the degree of propellant subcooling and type of gas used during pressurization or liquid expulsion. Therefore it was ensured that bubble point data was collected over the widest possible range of thermal conditions inside a LOX propellant tank, consistent with the limitations of the test hardware. Therefore, the purpose of this chapter is to conduct an in-depth analysis on these high-pressure bubble point tests to understand parameters that affect LAD performance in an elevated pressure environment. 

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