Non Condensibles Beer Column

FIGURE 8.1.18 TEfifERftTUftE CyCLE , CASE 1

CASE STUDY No. 2 Heavies in Inlet Line (Reference 2? author had similar experience).

INSTALLATION A vertical thermosyphon reboiler, processing a mixture of two components - a high boiler and a low boiler (Figure 8.1.2).

PROBLEM Heat transfer and circulation rate deteriorated with time. Neither fouling nor composition variations appeared to be the cause.

The problem was diagnosed to a lack of outlet for residue. It accumulated at the base of the reboiler and reduced temperature difference.

SOLUTION Install a draw-off line to periodically remove residue from the base of the reboiler.

Vertical Thermosiphon Reboiler

FIGURE S.I.2 COLUMN AND RCSOtltR RRRftflGCrfEitTj ewe z (aaseo on rep 2.)

CASE STUDY No. 3 Film Boiling (Reference 3)

INSTALLATION Vertical thermosvphon using Dowtherm which entered at | 725°F as the heating medium. The process liquid entered at 440°F and the two-phase mixture left the reboiler at 550°F. (Figure 8.1.3).

PROBLEM Reboiler would only achieve a fraction of the design duty. The problem was caused by film boiling. Dowtherm entering from the bottom side of the reboiler with a temperature difference of about 300°F caused film boiling.

SOLUTION Reverse the heating medium flow direction to avoid film j boiling.

FIGURE 8.1.3 COLUMN BMO REBOILER ARRANGEMENT, CflSE 3 (BASED ON A6F 3 )

LLOUiO Bowman 725"?

FIGURE 8.1.3 COLUMN BMO REBOILER ARRANGEMENT, CflSE 3 (BASED ON A6F 3 )

CAST STUDY No. 4 Poor Venting on Heating Side (References 4,5) |

INSTALLATION Vertical thermosyphon reboilers of two distillation columns in a sequence of 3 columns separating recycle reactants in the C- range under pressure. Thermosyphons were heated in both cases by condensing Cg streams. The arrangement is shown in Figure 8.1.4.

PROBLEM Insufficient heat transfer. This resulted from the top vent being ineffective, as it was simply venting incoming vapor. The exchanger had a series of baffles guiding the non-condensibles towards the condensate outlet, but there was no vent there. Moreover, non-condensibles could not be entrained in the effluent liquid because the bubble rise velocity in the pipe exceeded the liquid velocity. The condensate piping acted as a vapor trap and the vent on the receiver was ineffective.

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