Three-phase separation flash separator

Three-phase separators, commonly called freewater knockouts, are used to separate and remove any free water phase that may be present. Because flow enters the three-phase separator either directly from a producing wdl, or a separator operating at a higher pressure, the vessel must be designed to separate gas that flashes from the liquid as wdl as oil and water. 

Depending on the fluid compositions, either a two- or three-phase separator can be used. Normally, the flash separator should not have any hydrocarbon liquid however, due to poor upstream separation, the separator may have a tiiree-phase fluid. A two-phase separator is adequate in most cases, though, depending on the requirements, a three-phase separator is also used. In case of a three-phase separator, the glycol-water is fed to the regenerator column, and the hydrocarbon phase is drained to the oily water system. 

The term two-phase flow covers an extremely broad range of situations, and it is possible to address only a small portion of this spectrum in one book, let alone one chapter. Two-phase flow includes any combination of two of the three phases solid, liquid, and gas, i.e., solid-liquid, gas-liquid, solid-gas, or liquid-liquid. Also, if both phases are fluids (combinations of liquid and/or gas), either of the phases may be continuous and the other distributed (e.g., gas in liquid or liquid in gas). Furthermore, the mass ratio of the two phases may be fixed or variable throughout the system. Examples of the former are nonvolatile liquids with solids or noncondensable gases, whereas examples of the latter are flashing liquids, soluble solids in liquids, partly miscible liquids in liquids, etc. In addition, in pipe flows the two phases may be uniformly distributed over the cross section (i.e., homogeneous) or they may be separated, and the conditions under which these states prevail are different for horizontal flow than for vertical flow. 

Fig. 17 (B) shows flash-induced absorbance changes measured at 480 as well as 580 nm. The anteima transients described above were again subtracted to yield the net signals. These new results show more clearly complete electron transfer from photosystem I to ferredoxin. Furthermore, some new features emerge in the transients at 580 nm. At higher time resolution, Setif and Bottin found three fast, first-order components in the absorbance changes with ty, of 500 ns, 20 jus and 100 jus, respectively. Separately measured spectra in the 460-600 nm region show that the three phases are all attributable to electron transfer from [FeS-A/B] to Fd. The different phases have been accounted for on the basis of structurally different, Fd-binding sites in the PS-I reaction center Possible sites may be seen in the newly determined, three-dimensional structure of the PS-I reaction center . ...

The predictions of three-phase equilibria considered so far were done as two separate two-phase calculations. Although applicable to the examples here, such a procedure cannot easily be followed in a three-phase flash calculation in which the temperature or pressure of a mixture of two or more components is changed so that three phases are formed. In this case the equilibrium relations and mass balance equations for all three phases must be solved simultaneously to find the compositions of the three coexisting phases. It is left to you (Problem 11.3-7) to develop the algorithm for such a calculation. 

Decomposition in elementary simulation blocks. Example an azeotropic distillation column may be decomposed in reboiled stripping column, heat exchanger, three-phase flash separator and reflux splitter. 

In this case, the vapor is 94 mol% H2, for which a vapor separation section may not be needed. The organic-rich liquid phase (LI) is sent to a liquid separation section to recover a combined methanol and toluene stream for recycle to the reactor, ethylbenzene as a byproduct, and styrene as the main product. The water-rich liquid phase (L2) is sent to another liquid separation section to recover methanol for recycle to the reactor and water, which is sent to wastewater treatment to remove small quantities of soluble organic components. It is important to note that a two-phase flash calculation would produce erroneous results. If in doubt, perform a three-phase flash calculation, rather than a two-phase flash calculation. 

This effluent is cooled to 38°C and enters a flash-decanter vessel at 278 kPa. Three phases leave that vessel. The vapor phase (hydrogen rich) is sent to the vapor separation system. The aqueous phase (mostly water, with some methanol) is sent to the aqueous stream separation system. The organic-rich phase is sent to the organic stream separation system, which you will design. To obtain the composition of the feed to your section, use a simulator with the UNIFAC method to perform a three-phase flash for the above conditions. If the resulting organic liquid stream contains small amounts of hydrogen and water, assume they can be completely removed at no cost before your stream enters your separation section. 

Example of multiphase flash and stability analysis. We will, in detail, discuss the stability analysis of a three-component system of Ci/CO /nCif at T = 294.0K and P — 67 bar with — 0.05. 2 co.> = 0.90, and = 0.05. At fixed temperature and pressure, from the phase rule F — c - -2 — p, there can be a maximum of three phases when the interface between the phases is flat. The first question is what types of phases may exist—gas, liquid, or solid. As we will see in Chapter 5, a solid phase does not exist for the above system. Therefore one might expect (1) a single gas phase or a single liquid phase, (2) gas and liquid phases, (3) liquid and liquid phases, or (4) gas-liquid-liquid phase separation. The difficulty in liquid-liquid (L-L) and vapor-liquid-liquid (V-Lr-L) and higher-phase equilibria (for more than three components) is how many phases should be considered for flash calculations. One approach is to determine whether one, two, or more phases are to be considered without prior knowledge of the true number of phases. In certain cases, as we will see in the next chapter, it is possible from thermodynamic stability analysis to determine the true number of phases a priori without performing a flash. However, in general, we do not know the true number of phases. One may, therefore, follow a sequential approaches outlined next for the Ci/C02/nCiQ example. 

Ebullated bed processes are offered for license by Axens (IFF) ABB Lummus. In ebullated bed reactors, hydrogen-rich recycle gas bubbles up through a mixture of oil and catalyst particles to provide three-phase turbulent mixing. The reaction envirorunent can be nearly isothermal, which improves product selectivity. At the top of the reactor, catalyst particles are disengaged from the process fluids, which are separated in downstream flash drums. Most of the catalyst goes back to the reactor. Some is withdrawn and replaced with fresh catalyst. 

Many hydrocarbon mixtures contain a small amount of water. In the processing of such mixtures, three phases are frequently encountered a vapor phase (j = i>), a hydrocarbon liquid phase (j = h) and a water phase (J = w). Consider the case of flash separation of such a hydrocarbon-water mixture. Define... 

To a —78 °C solution of (4/C5/ )-2-[(.S )-l-chloro-2-propcnyl]-4,5-dicyclohcxyl-l, 3,2-dioxaborolanc (6) (theoretically 2.0 mmol) in THF are added 0.20 mL (2.0 mmol) of benzaldehydc. The mixture is allowed to reach r.t. overnight and is then treated with 0.30 g (2.0 mmol) of triethanolamine. After stirring for 3 h, 15 mL of sat. aq NH4C1 are added. The phases are separated and the aqueous phase is extracted with three 20-mL portions of diethyl ether. The combined extracts are dried over MgS04 and concentrated. The oily residue is purified by flash chromatography (silica gel, petroleum ether/diethyl ether 6 1) yield 0.26 g (79%) >99% ee [capillary GC of the carbamates obtained with (5 )-(l-isoCyanoethyl)benzene],... 

Calculations for all three cases have been performed for the system described in Tables VII and VIII and Figure 6. In this case the raw feed gas was flashed at 66°C and 138 bars with sufficient water to assure that the gas leaving the separator was water saturated. Each of the calculational philosophies described above was used to predict the phase behavior of the systems at each pressure temperature point in the pipeline. The results of these calculations are summarized in Tables IX through XI and Figures 7 through 10. 

Enantiomeric purity was determined to be 96-98% by 1H NMR analysis of the Mosher esters4 of the alcohols 4 and ent-4 obtained by reduction of the aldehydes 5 and ent-5. To an ice-cold solution of aldehyde 5 (0.10 g, 0.44 mmol) in 5 mL of methanol was added solid sodium borohydride (33 mg, 0.88 mmol). After the mixture was stirred for 30 min at this temperature, the TLC in (7 3) cyclohexane-ethyl acetate showed the clean formation of the alcohol 4. The mixture was treated with 0.05 mL of acetone and concentrated to dryness under reduced pressure. The residue was partitioned between water (10 mL) and ethyl acetate (10 mL) and the phases were separated. The aqueous phase was extracted with three 10-mL portions of ethyl acetate. The combined organic phases were dried with anhydrous sodium sulfate and concentrated under reduced pressure. The residue was purified by flash... 

Z,Z)-Divinyl Tellurium4 To a stirred suspension of 0.383 g (3 mmol) tellurium in 15 ml ethanol kept under nitrogen are added in small portions 0.34 g (9 mmol) of sodium borohydride. The mixture is heated and 0.32 g (8 mmol) sodium hydroxide, 15 m/ water and 5 ml tetrahydrofuran arc added. The mixture is refluxed until all the tellurium has disappeared. When the refluxing mixture has turned yellow (3 to 6 h), it is cooled to 20°, diluted with 50 m/ethyl acetate, and washed with three 30-m/portions of a saturated aqueous solution of ammonium chloride and then with three 30-m/-portions of brine. The organic phase is separated, dried with anhydrous magnesium sulfate, and filtered. The solvent is evaporated from the filtrate on a rotary evaporator at 20 torr. The residue is flash-chromatographcd on silica gel with mixtures of hexane and ethyl acetate. 

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