Overhead Condenser

The overhead condenser was constructed as a double pipe exchanger with condensation in the inner pipe. Chilled water from the shared laboratory network was used as the cooling medium. The duty required at maximum reboiler duty (7.5 kW) was estimated to be 7.3 kW via simulations. This is attained at a cooling water flow of approximately 10 L/min with a chilled water temperature rise of 10°C.

The condenser configuration and dimensions are indicated in Figure 11.5. This results in a heat transfer area of 0.24 m2 and an estimated heat transfer coefficient of 500-600 W/m2/°C (based on rigorous calculations). The condensing temperature is almost independent of the feed-split since the distillate vapour pressure is dominated by the effect of the C4 components. At 950kPag, the condensing temperature is approximately 74°C giving a LMTD of 5 l°C, and a duty of 7.3 kW. Thus, there is no surplus area at design conditions but the maximum chilled water flow is greater than 50 L/min and the LMTD can be increased by raising the pressure. Acceptable operation is also possible with a reduced condenser duty if either the feed rate or the reboiler duty is lowered from the design basis The pressure drops through both the inner and outer pipes are acceptable.

3000 mm

Figure 11.5- Overhead Condenser

12 mm 0

19 mm 0

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