Reflux drum, boot

Dryout by circulation should be performed under positive pressxu-e (5,296) otherwise, water from drains will be sucked back into the column when a drain is opened. Circulation for dryout must be carried out at a rate high enough to ensure adequate sweeping of water to the low points. Dryout is considered complete when column temperatvme exce 250 to 350°F (or the maximum desirable temperature), no more water comes out of drains (especially the drain on the reflux drum boot), and when pump suction is steady. 

Avoiding refluxing of the component back into the column A typical example is the reflux drum boot technique, commonly applied in hydrocarbon separations where water is the impurity. The boot may be an integral part of the drum (Fig. 13.4), or a separate drum located at ground level. Some guidelines for boot sizing are in Sec. 15.14. 

Separation of small quantities of water from water-insoluble organics. This is usually achieved using a reflux drum boot. A boot can be integral (Fig. 15.16) or external in the latter case, it can be located at ground level and piped to the reflux drum. 

Column internals and reboiler tubes severely corroded after the water drawoff control valve on the reflux drum boot plugged. Manual draining was too in-conaistait to prevent water (saturated with H2S) refluxing into the tower. Contimious water flushing with an external water source prevented recurrence. 

The most neglected, but most important, feature of the reflux drum shown in Fig. 26.3 is the riser, a piece of pipe 4 to 12 in high, protruding from the bottom of the drum. You see, water first settles to the bottom of the drum. The water then runs along the bottom of the drum into the water draw-off boot. 

Water is drained off the boot to maintain an interface level between water and hydrocarbon in the boot. These interface level controllers, especially on reflux drum water draw-off boots, are typically set locally. The operator finds the visible interface level in the boot s gauge glass, and then sets the local interface level controller, to hold the level half way down the boot. Level taps in the lower portion of any vessel, tend to plug. This is especially true with the level taps in water draw-off boots. You need to blow out these taps on some frequent basis, because a high boot interface level can push water into the tower s reflux pump. 

Both a gas stream and a liquid distillate are removed from the reflux drum. In addition, since live steam is fed into the bottom of the column and separates into an aqueous phase in the reflux dmm, a water stream is removed from a small boot at the bottom of this drum that serves as a decanter. The stripping steam flow rate is 5000 Ib/h and its temperature is 400 °F. Both the gas and the liquid products contain some water. The water decanted is 2441b/h. 

Fig. 21.5 shows two waste-heat boilers that are generating superheated, 150-psig steam from a fractionator hot oil pumparound. After years of trouble-free operations, water was observed in the gas-oil pumparound return stream. The symptoms of the water infiltration into the fractionator were an increase in the fractionator pressure and an increase in the water production from the fractionator reflux drum s draw-off boot. 

A three-phase with boot design is used where water load is low (typically, reflux drums). The boot section is used to hold the water, and the cylindrical section is used to hold the condensate. In this design, the interface level is kept within the boot, though a design with the interface in the cylindrical section is also possible. The separator.exe design only considers interface level within the boot. 

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