Vapor lines

A convenient way of representing the T—x y phase diagram (Eig. 14b) is by projection onto the composition triangle at the base of the figure. It is understood that the temperature varies from point to point on the projected vapor line and on the projected boiling envelope. The latter looks like an isothermal Hquid—Hquid binodal envelope, but is not. Each tie line across the boiling envelope is associated with a different boiling temperature (Eig. 15). 

Fig. 15. Isobaric vapor—liquid—liquid (VLLE) phase diagrams for the ethanol—water—benzene system at 101.3 kPa (D-D) representHquid—Hquid tie-lines (A—A), the vapor line I, homogeneous azeotropes , heterogeneous azeotropes Horsley s azeotropes, (a) Calculated, where A is the end poiat of the vapor line and the numbers correspond to boiling temperatures ia °C of 1, 70.50 2, 68.55 3, 67.46 4, 66.88 5, 66.59 6, 66.46 7, 66.47, and 8, the critical poiat, 66.48. (b) Experimental, where A is the critical poiat at 64.90°C and the numbers correspond to boiling temperatures ia °C of 1, 67 2, 65.5 3, 65.0 ...

Fig. 16. Residue curve map calculated for the ethanol—water—benzene mixture where A is the end poiat of the vapor line I represents a homogeneous...

Make this XS area 5 times larger than the inlet vapor line... 

For partial condenser systems, the pressure can be controlled by manipulating vapor product or a noncondensible vent stream. This gives excellent pressure control. To have a constant top vapor product composition, the condenser outlet temperature also needs to be controlled. For a total condenser system, a butterfly valve in the column overhead vapor line to the condenser has been used. Varying the condenser cooling by various means such as manipulation of coolant flow is also common. 

NPSH, AaSOLOTE VAPOR LINE >0 FFE ENCE AVAILABLE PRESS,PT PRESS FT LOSS.FT " L V.Ff... 

For big vapor lines and condensers (frequent in vacuum systems) always insulate the line, condenser, and top of column. Rain or sudden cold fronts will change column control otherwise. It is possible to have more surface in the overhead line than in the condenser. 

When winterizing is required, the steam tracing and insulation should include the first 7.5 m of the flare stack above the vapor inlet and also in the case of a drum seal, the vapor line from the seal drum to the flare. Where steam injection to one of the smokeless tips, as shown in Figures 11 B and C is used, then the steam ring should remain outside the top of the flare tip (i.e., not internal). Where severe ambient conditions are encountered then it is recommended that the entire seal drum and flare be insulated in addition to steam tracing and open steam injection at base of flare. 

A second trial is required for two main flare headers, one collecting the low-pressure flares (usually 5 to 10 psig) and the other collecting relatively high-pressure flares (usually 15 to 20 psig). The two headers are connected to their individual knock-out drums. The vapor lines from the knock-out drums are combined into a single header connected to the flare stack. 

The final header connecting the vapor line (or lines) from the knock-out drum leading to the flare stack. 

In the DCC unit, the hydroearbon feed is dispersed with steam and eraeked using a hot solid eatalyst in a riser, and enters a fluidized bed reaetor. A known injeetion system is employed to aehieve the desired temperature and eatalyst-to-oil eontaeting. This maximizes the seleetive eatalytie reaetions. The vaporized oil and eatalyst flow up the riser to the reaetor where the reaetion eonditions ean be varied to eomplete the eraeking proeess. The eyelones that are loeated in the top of the reaetor effeet the separation of the eatalyst and the hydroearbon vapor produets. The steam and reaetion produets are diseharged from the reaetor vapor line and enter the main fraetionator where further proeessing ensure the separation of the stream into valuable produets. 

A large distillation column was made in two halves, connected by a 42-in. vapor line containing a bellows. During a shutdown this line was... 

For vapor lines that cannot be slant down conveniently to remove and clean arrester elements, parallel flame arresters are sometimes installed. To be able to switch the flame arresters, snitable isolation valving mnst be installed npstream of the flame arresters, which will allow the switching to be done withont intermpting operations. Care mnst be taken to assnre that... 

High pressure steam lines Low pressure steam lines Vacuum steam lines Compressed air lines Refrigerant vapor lines High pressure Low pressure Refrigerant liquid Brine lines Ventilating ducts Register grilles... 

The air bleed is u.sed to maintain a constant condition. However, a control valve may be used instead. Control or hand valves in the lower pressure vapor lines to an ejector are not recommended, as they must be paid for in system pressure drop and ejector udlity requirements. 

This is satisfactory, although a 2-in. nozzle would have a velocity of 34.3 ft/sec. Because this condenser has entering vapors at the dew point, entrainment of some particles is always a real possibility therefore, a low inlet velocity is preferred. Also, overhead vapor lines should have low pressure drop for vapor at its dew point and a 3-in. line might he indicated when this line is checked. 

The outlet vapor line should be two nominal pipe sizes larger than the liquid inlet. Table 10-33 is helpful to relate exchanger size and pipe connections, although the same standards cannot apply to every design. 

Within 3 ft of point of connection of both fill and vapor lines, extending in all directions. 

High Delta P across the Reactor Ovhd. vapor line... 

Sometimes insufficient differential across the regenerated catalyst slide valve is not due to inadequate pressure buildup upstream of the valve, but rather due to an increase in pressure downstream of the slide valve. Possible causes of this increased backpressure are an excessive pressure drop in the Y or J-bend section, riser, reactor cyclones, reactor overhead vapor line, main fractionator, and/or the main fractionator overhead condensing/cooling system. 

The pressure drop across the reactor cyclones, reactor vapor line, main fractionator, and main column overhead condensing/cooling system can be too high. The pressure drop is primarily a function of vapor velocity. Any plugging can increase the pressure drop. 

Nearly every cat cracker experiences some degree of coking/fouling. Coke has been found on the reactor walls, dome, cyclones, overhead vapor line, and the slurry bottoms pumparound circuit. Coking and fouling always occur, but they become a problem when they impact throughput or efficiency. 

A high fractionator bottoms level, a low riser temperature, and a high residence time in the reactor dome/vapor line are additional operating factors that increase coke buildup. If the main column level rises above the vapor line inlet nozzle, donut shaped coke can form at the nozzle entrance. 

The quality of the FCC feed also impacts coke buildup in the reactor internals and vapor line and fouling/coking of the main column circuit. The asphaltene or the resid content of the feed, if not converted in the riser, can contribute to this coking. 

Follow proper start-up procedures. Introduce feed to the riser only when the reactor system is adequately heated up. Local cold spots cause coke to build up in the reactor cyclones, the plenum chamber, or the vapor line. 

Since the mid-1980s, FCC technology licensors and a number of oil companies have employed a number of RTD s to reduce non-selective post-riser cracking reactions. Two general approaches have been used to reduce post riser cracking. The most widely used approach is direct connection of the cyclones to the riser and on to the reactor vapor line. The second approach is quenching the reactor vapors downstream of the riser-cyclones (rough-cut cyclones). 

RTD s separate the catalyst and the oil vapor immediately at the end of the riser. The cyclone vapor usually discharges directly to the second-stage cyclones and then to the reactor vapor line. The catalyst is directly discharged into the stripper. The reactor is simply a vessel for holding the cyclones. Technologies are offered by ... 

It is known that the three-phase line H G in the binary system H2S-H20 lies below the liquid vapor line (LG) of pure H2S. Likewise, after addition of CHC13 the four-phase line lies... 

Thus, yz is not linearly related to p, and a graph of p against yz is not a straight line. The graph of the vapor line, which is also known as the dew pressure curve, is shown in Figure 8.13 for (y C-C6HnCH3 + V2C-C6H12) as the lower curve at T= 308.15 K. 

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