Column-mounted condensers

Liquid-liquid heat exchange Liquid-liquid heat exchange Column-mounted condensing... 

Use of Desiccants and Chemical Means to Remove Water. Another means to remove the water of esterification is calcium carbide supported in a thimble of a continuous extractor through which the condensed vapor from the esterification mixture is percolated (41) (see Carbides). A column of activated bauxite (Elorite) mounted over the reaction vessel has been used to remove the water of reaction from the vapor by adsorption (42). 

A common form of turbine pump is the vertical pump, which has the pump element mounted at the bottom of a column that serves as the discharge pipe (see Fig. 10-46). Such units are immersed in the liquid to be pumped and are commonly used for wells, condenser circulating water, large-volume drainage, etc. Another form of the pump has a shell surrounding the pumping element which is connected to the intake pipe. In this form, the pump is used on condensate service in power plants and for process work in oil refineries. 

Type 77 units are the condenser and reboiler designs. One side is spiral flow and the other side is in cross flow. These SHEs provide veiy stable designs for vacuum condensing and reboiling seiwices. A SHE can be fitted with special mounting connec tions for refliix-type vent-condenser apphcations. The vertically mounted SHE directly attaches on the column or tank. 

Process designers sometimes like to use dephlegmators or partial condensers mounted directly in the top of the distillation column when the overhead product is taken off as a vapor. They arc particularly popular for corrosive, toxic, or hard-to-handle chemicals since they eliminate a. separate condenser shell, a reflux drum, and a reflux pump. Comment on the relative controllability of the two process systems sketched below. 

A heat exchanger is to be mounted at the top of a fractionating column about 15 m high to condense 4 kg/s of //-pentane at 205 kN/m2, corresponding to a condensing temperature of 333 K. Give an outline of the calculations you would make to obtain an approximate idea of the size and construction of the exchanger required. 

Most of the experiments were carried out in a pilot-scale reactor (Fig. 8.25). For each experiment, four pieces of coated monoliths were stacked carefully in line and mounted in a 2 m- high heated column of 50 mm diameter. The preheated liquid feed was distributed via a spray nozzle. After each pass, the liquid was collected in the liquid-supply vessel and was circulated continuously through the reactor (batch-recycle mode). The preheated countercurrent nitrogen stream was fed after one pass to a condenser to separate the liquid, and then vented. The condensables were collected in a phase separator, from where the water could be tapped off, whilst the... 

The bypassed vapor heats up the liquid there, thereby causing the pressure to rise. WTien the bypass is closed, the pressure falls. Sufficient heat transfer surface is provided to subcool the condensate, (f) Vapor bypass between the condenser and the accumulator, with the condenser near ground level for the ease of maintenance When the pressure in the tower falls, the bypass valve opens, and the subcooled liquid in the drum heats up and is forced by its vapor pressure back into the condenser. Because of the smaller surface now exposed to the vapor, the rate of condensation is decreased and consequently the tower pressure increases to the preset value. With normal subcooling, obtained with some excess surface, a difference of 10-15 ft in levels of drum and condenser is sufficient for good control, (g) Cascade control The same system as case (a), but with addition of a TC (or composition controller) that resets the reflux flow rate, (h) Reflux rate on a differential temperature controller. Ensures constant internal reflux rate even when the performance of the condenser fluctuates, (i) Reflux is provided by a separate partial condenser on TC. It may be mounted on top of the column as shown or inside the column or installed with its own accumulator and reflux pump in the usual way. The overhead product is handled by an alter condenser which can be operated with refrigerant if required to handle low boiling components. 

Most commonly, air is humidified by passage through a spray of water. Small quantities of air are easily dehumidified by adsorbing the water vapor with alumina or silica gel arranged in columns. These are mounted in pairs so that one can be regenerated while the other is in use. Alternatively, the air can be cooled below the dew point. Excess water vapor condenses and the cold saturated air is reheated. 

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