Optimum pressure

For a single stage separator i.e. only one separator vessel, there is an optimum pressure which yields the maximum amount of oil and minimises the carry over of heavy components into the gas phase (a phenomenon called stripping). By adding additional separators to the process line the yield of oil can be increased, but with each additional separator the incremental oil yield will decrease. 

Gas processing facilities generally work best at between 10 and 100 bar. At low pressure, vessels have to be large to operate effectively, whereas at higher pressures facilities can be smaller but vessel walls and piping systems must be thicker. Optimum recovery of heavy hydrocarbons is achieved between 20 bar and 40 bar. Long distance pipeline pressures may reach 150 bar and reinjection pressure can be as high as 700 bar. The gas process line will reflect gas quality and pressure as well as delivery specifications. 

Fig. 4 illustrates the time-dependence of the length of top s water column in conical capillary of the dimensions R = 15 pm and lo =310 pm at temperature T = 22°C. Experimental data for the top s column are approximated by the formula (11). The value of A is selected under the requirement to ensure optimum correlation between experimental and theoretical data. It gives Ae =3,810 J. One can see that there is satisfactory correlation between experimental and theoretical dependencies. Moreover, the value Ae has the same order of magnitude as Hamaker constant Ah. But just Ah describes one of the main components of disjoining pressure IT [13]. It confirms the rightness of our physical arguments, described above, to explain the mechanism of two-side liquid penetration into dead-end capillaries. 

The heat of reaction is approximately 147 kj/mol (35.1 kcal/mol) (23). Optimum yields of ketene [463-51-4] require a temperature of about 730—750°C. Low pressure increases the yield, but not the efficiency of the process. Competitive reactions are... 

The product of this reaction can be removed as an azeotrope (84.1% amide, 15.9% acetic acid) which boils at 170.8—170.9°C. Acid present in the azeotrope can be removed by the addition of soHd caustic soda [1310-73-2] followed by distillation (2). The reaction can also take place in a solution having a DMAC-acetic acid ratio higher than the azeotropic composition, so that an azeotrope does not form. For this purpose, dimethylamine is added in excess of the stoichiometric proportion (3). If a substantial excess of dimethylamine reacts with acetic acid under conditions of elevated temperature and pressure, a reduced amount of azeotrope is formed. Optimum temperatures are between 250—325°C, and pressures in excess of 6200 kPa (900 psi) are requited (4). DMAC can also be made by the reaction of acetic anhydride [108-24-7] and dimethylamine ... 

If ah of the nonfiltration operations are grouped together into a downtime, assumed to be fixed and known, an optimum filtration time in relation to p can be derived by optimizing the average dry cake production obtained from the cycle. Eor constant pressure filtration and where the medium resistance R and the specific cake resistance are constant, the fohowing equation appHes ... 

Paschen s Rule and Breakdown Voltage. As pressure decreases to vacuum conditions, the breakdown voltage (BDV) first decreases, then increases, resulting in a minimum as shown in Figure 1. Table 3 gives BDV data for SF and other dielectrics. For optimum utiUty of a dielectric, a... 

A report on the continuous flash pyrolysis of biomass at atmospheric pressure to produce Hquids iadicates that pyrolysis temperatures must be optimized to maximize Hquid yields (36). It has been found that a sharp maximum ia the Hquid yields vs temperature curves exist and that the yields drop off sharply on both sides of this maximum. Pure ceUulose has been found to have an optimum temperature for Hquids at 500°C, while the wheat straw and wood species tested have optimum temperatures at 600°C and 500°C, respectively. Organic Hquid yields were of the order of 65 wt % of the dry biomass fed, but contained relatively large quantities of organic acids. 

Several types of fluids are used as refrigerants in mechanical compression systems ammonia, halocarbon compounds, hydrocarbons, carbon dioxide, sulfur dioxide, and cryogenic fluids. A wide temperature range therefore is afforded. These fluids boil and condense isotherm ally. The optimum temperature or pressure at which each can be used can be deterrnined from the economics of the system. The optimum refrigerant can be deterrnined only... 

It may be shown (33) that when the inner surface of a cylinder made of components of the same material is subjected to an internal pressure, the bote of each component experiences the same shear stress provided all components have the same diameter ratio. For these optimum conditions,... 

Fig. 9. Yield pressure of multicomponent vessels designed for optimum conditions (34).

Pressure. Within limits, pressure may have Htfle effect in air-sparged LPO reactors. Consider the case where the pressure is high enough to supply oxygen to the Hquid at a reasonable rate and to maintain the gas holdup relatively low. If pressure is doubled, the concentration of oxygen in the bubbles is approximately doubled and the rate of oxygen deHvery from each bubble is also approximately doubled in the mass-transfer rate-limited zone. The total number of bubbles, however, is approximately halved. The overall effect, therefore, can be small. The optimum pressure is likely to be determined by the permissible maximum gas holdup and/or the desirable maximum vapor load in the vent gas. 

Hydrocarbon, typically natural gas, is fed into the reactor to intersect with an electric arc stmck between a graphite cathode and a metal (copper) anode. The arc temperatures are in the vicinity of 20,000 K inducing a net reaction temperature of about 1500°C. Residence time is a few milliseconds before the reaction temperature is drastically reduced by quenching with water. Just under 11 kWh of energy is required per kg of acetylene produced. Low reactor pressure favors acetylene yield and the geometry of the anode tube affects the stabiUty of the arc. The maximum theoretical concentration of acetylene in the cracked gas is 25% (75% hydrogen). The optimum obtained under laboratory conditions was 18.5 vol % with an energy expenditure of 13.5 kWh/kg (4). 

Silica and Alumina. The manufacture of Pordand cement is predicated on the reaction of lime with siUca and alumina to form tricalcium sihcate [12168-85-3] and aluminate. However, under certain ambient conditions of compaction with sustained optimum moisture content, lime reacts very slowly to form complex mono- and dicalcium siUcates, ie, cementitious compounds (9,10). If such a moist, compact mixture of lime and siUca is subjected to steam and pressure in an autoclave, the lime—silica reaction is greatiy accelerated, and when sand and aggregate is added, materials of concrete-like hardness are produced. Limestone does not react with siUca and alumina under any circumstances, unless it is first calcined to lime, as in the case of hydrauhc lime or cement manufacture. 

Condensable Hquids also are recovered from high pressure gas reservoirs by retrograde condensation. In this process, the high pressure fluid from the reservoir produces a Hquid phase on isothermal expansion. As the pressure decreases isotherm ally the quantity of the Hquid phase increases to a maximum and then decreases to disappearance. In the production of natural gas Hquids from these high pressure wells, the well fluids are expanded to produce the optimum amount of Hquid. The Hquid phase then is separated from the gas for further processing. The gas phase is used as a raw material for one of the other recovery processes, as fuel, or is recompressed and returned to the formation. 

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