Horizontal distillation

Separation of a mixture of dodecanoic and tetradecanoic acids in Jantzen s horizontal distillation apparatus... 

In radiochemistry, the most popular version is TC with a stationary temperature gradient, in which the concentration of a substance and its local distribution depend on the distance or temperature, i.e., c = f x) or c = f T). This means that the volatile compounds remain in the thermochromatographic column. In the literature this method was previously referred to by various jargon terms, e.g., horizontal distillation, separation on the gradient tube, separation on the temperature gradient, etc. 

A common type of distillation contacting device used in refinery applications is the sieve tray. In the early 50 s and for many years before, the bubble cap tray was the mainstay of the distillation field. A sieve tray consists of a flat plate with regularly spaced holes, normally 1/2 to 1 inch in diameter. Liquid flows horizontally across the tray and into a channel, called a downcomer, which leads to the tray below. The sieve tray exhibits good capacity, excellent efficiency, low pressure drop, and good flexibility i.e., it will operate quite efficiently at tower loadings which are 1/2 to 1/3 of design values. 

Water can be trapped behind heat exchanger baffles and then suddenly vaporized by circulation of hot oil. It can also be trapped in dead-ends and U-bends in pipework (see Section 9.1.1). Such U-bends can form when one end of a horizontal pipe is raised by thermal expansion. The trays in a distillation column were damaged during startup when hot gas met water, from previous steaming, dripping down the column [3J. Section 17.12 describes an incident somewhat similar to a foamover. 

A distillation system is to operate with a horizontal overhead condenser. Figure 6-19, and pressures are as marked. The estimated air leakage into the system is 7 Ibs/hr. The molecular weight of the product vapor going out the condenser into the ejector (at 80°F) is 53. The vapor pressure of the condensing vapors is 3 mm Hg abs at 80°F. 

Because reboilers are used extensively with bottoms boiling of distillation columns, the horizontal units have some advantages. ... 

Figure 10-96B. Horizontal thermosiphon reboiler on distillation column shell and tube design, not kettle. Boiling in shell.

The horizontal natural circulation systems do not use a kettle design exchanger, but rather a 1-2 (1 shell side, 2 tube-side passes) unit, with the vaporized liquid plus liquid not vaporized circulating back to a distillation column bottoms vapor space or, for example, to a separate drum where the vapor separates and flows back to the process system and where liquid recirculates back along with make-up feed to the inlet of the horizontal shell and tube reboiler. See Figures 10-96A-C. 

The kettle unit used in the reboiling service usually has an internal weir to maintain a fixed liquid level and tube coverage. The bottoms draw-off is from the weir section. The reboiling handled in horizontal thermosiphon units omits the disengaging space because the liquid-vapor mixture should enter the distillation tower where disengaging takes place. The chiller often keeps the kettle design but does not use the weir because no liquid bottoms draw off when a refrigerant is vaporized. 

A condenser is required to condense n-propanol vapour leaving the top of a distillation column. The n-propanol is essentially pure, and is a saturated vapour at a pressure of 2.1 bara. The condensate needs to be sub-cooled to 45°C. Design a horizontal shell and tube condenser capable of handling a vapour rate of 30,000 kg/h. Cooling water is available at 30°C and the temperature rise is to be limited to 30° C. The pressure drop on the vapour stream is to be less than 50 kN/m2, and on the water stream less than 70 kN/m2. The preferred tube size is 16 mm inside diameter, 19 mm outside diameter, and 2.5 m long. 

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