Gravity-flow condenser

A gravity-flow condenser uses the hydraulic head of the liquid in the line from the condenser to overcome the pressure drop over the control valve and the difference between the pressure at the top of the distillation column P and the pressure at the bottom of the condenser Pi. The pressure difference is due to the flow of vapor through the vapor line and condenser. When the flow rate of vapor from the top of the column is 14 1.6 Ibm/min, the pressure drop P - Pi is 2 psi. The pressure drop due to the liquid flowing through the liquid return line is negligible. Liquid density is 62.4 lbm/ft ... 

When alloy piping or large bore piping is required, the associated equipment is located together as much as possible to keep the pipe mns short, preferably nozzle-to-nozzle by avoiding the piperack. Items such as elevated overhead condensers are located near the source and destination. Similarly, thermosyphon reboHers need to be placed adjacent to the column they reboH. Where gravity flow is required, these lines must be kept short and sloped. Space allocation for future additions must also be considered. 

An innovation is a direct-contact condenser mounted on the vapor body. A short piece of vertical pipe connects the vapor body with the condenser to minimize piping and pressure drop. This design also eliminates structural steel for support of a separate condenser. For cooling tower applications, the hotwell is elevated to permit gravity flow of water from the hotwell to the top of the cooling tower, thus eliminating the need for a pump. 

Pressure drop is only likely to be a major consideration in the design of vacuum condensers and where reflux is returned to a column by gravity flow from the condenser. 

These designs have provisions for the removal of noncondensable vapors and air, for the prevention of freezing during cold weather. Excessive buildup of noncondensable vapors in the main condenser would prevent effective condensation. Protection against ice formation is usually accomplished by warm air recirculation and/or fan control. Condensed steam from cooling coils flows by gravity to condensate receivers and is pumped back to the feedwater circuit by a condensate pump. 

Because of the elevation difference within the synthesis section, internal synthesis recycle is based on gravity flow. Result Electrical energy requirement is very low. Synthesis-gas condensation in the pool reactor generates steam, which is used in downstream sections within the plant. Process steam consumption is low. 

Film condensation in a vertical tube. To present a theoretical description of film condensation in tubes is much more difficult, since there may arise a strong dynamic interaction between the moving vapor and the flowing condensate film. If the direction of the vapor motion coincides with the direction of the condensate motion due to gravity, then, owing to viscous friction on the phase boundary, the velocity of the film flow increases, its thickness decreases, and the coefficient of convective heat transfer also increases. If the direction of the vapor motion is opposite to that of the condensate flow, then we have the opposite situation. If the vapor velocity increases, then the film may partially separate from the wall and convective heat transfer can increase sharply. 

R. Hashimoto, K. Yanagi, and T. Fujii, Effects of Condensate Flow Patterns upon Gravity-Controlled Condensation of Ethanol and Water Mixtures on a Vertical Surface, Heat Transfer-Japanese Research, 23, pp. 330-348,1994. 

If gravity flow is required from the condenser outlet to a collecting drum, reflux drum or separator, exchangers must be elevated. Examples are shown in Figure 7-67 and 7-68. 

Downstream from the pool condenser, the urea-carbamate liquid enters the vertical reactor, if required, located at ground level. Here, the final part of the urea conversion takes place. The urea solution then leaves the top of the reactor, all by gravity flow via an overflow funnel, before being introduced into the HP stripper. Gases leaving the urea reactor are directed to the pool condenser. 

Hydrocarbon gases condensation Low heat transfer in a horizontal, two-pass, in-tuhe condenser was caused by an undersized condensate line using gravity flow. Ensure adequate condensate removal. 

Piping arrangements are very important [25]. Pressure drops must be very low because of the low absolute pressure on the gas side and the use of flashing gravity flow on the liquid side. Condensate piping between condensers and hotwells should have a... 

Vapor from the reactor flows to a heat exchanger. The pressure in the reactor must be higher than the pressure in the condenser to produce this flow of vapor. The vapor is condensed and the liquid is returned back to the reactor. The condenser is typically mounted high enough above the reactor so that gravity flow can be used to get the liquid back into the... 

Of course, when the reactor vessel is depressurised to near containment pressure, gravity flow from the suppression system and from the flooded reactor cavity will maintain the RV coolant inventory for an unlimited period of time. However, this function would not be strictly necessary for any reasonable recovery period since the core decay heat is removed directly by condensing steam inside the pressure vessel, thus preventing any primary water from leaving the pressure vessel. 

Condensers are usually conventional tubular heat exchangers, generally arranged horizontally with the coolant inside the tubes, but also vertically with the coolant on either side of the tubes [27]. The condenser may be placed above the tower for gravity flow of the condensed reflux to the top tray, but it is usually more convenient for purposes of construction and cleaning to place the condenser nearer the ground and to return the reflux from an accumulator drum [55] to the top tray by pumping. This procedure also provides more pressure drop for operation of control valves on the reflux line. 

Horizontal tube bundle with coolant in tubes (Figure 3.3). The vapor comes up from below and condensate drops into an annular space around the vapor nozzle. The latter has a haf over it to prevent condensate from dropping back down the column. Reflux may return internally via an overflow weir, or externally through a gravity flow line with a control valve. 

Since acrylic polymerizations liberate considerable heat, violent or mnaway reactions are avoided by gradual addition of the reactants to the kettie. Usually the monomers are added by a gravity feed from weighing or measuring tanks situated close to the kettie. The rate of monomer addition is adjusted to permit removal of heat with full flow of water in the condenser and a partial flow in the cooling jacket. Flow in the jacket can be increased to control the polymerization in cases of erroneous feed rates or other unexpected circumstances. A supply of inhibitor is kept on hand to stop the polymerization if the cooling becomes inadequate. 

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