Fin fans

Surface Condensers Surface condensers (indirect-contact condensers) are used extensively in the chemical-process industiy. They are employed in the air-poUution-equipment industry for recoveiy, control, and/or removal of trace impurities or contaminants. In the surface type, coolant does not contact the vapor condensate. There are various types of surface condensers including the shell-and-tube, fin-fan, finned-hairpin, finned-tube-section, ana tubular. The use of surface condensers has several advantages. Salable condensate can be recovered. If water is used for coolant, it can be reused, or the condenser may be air-cooled when water is not available. Also, surface condensers require less water and produce 10 to 20 times less condensate. Their disadvantage is that they are usually more expensive and require more maintenance than the contac t type. 

Amine-stripper overhead condensers are typically air-cooled, fin-fan exchangers. Their duty can be determined from the concepts in Chapter 3 as required to cool the overhead gases and condense the overhead steam... 

The amine cooler is typically an air-cooled, fin-fan cooler, which low-er.s the lean amine temperature before it enters the absorber. The lean amine entering the absorber should be approximately 10°F warmer than the sour gas entering the absorber. Lower amine temperatures may cause the gas to cool in the absorber and thus condense hydrocarbon liquids. Higher temperatures would increase the amine vapor pressure and thus increase amine losses to the gas. The duty for the cooler can be calculated from the lean-amine flow rate, the lean-amine temperature leaving the rich/lean exchanger and the sour-gas inlet temperature. 

On several other occasions, the draft from fin-fans has made fires worse. And the fans could not be stopped because the Stop buttons were too near the fire. The Stop buttons should be located (or duplicated) at least 10 m away. 

Check pressure drop between Fin-Fans and Trim Coolers... 

Fin fan supports should be fireproofed up to their full load bearing height. 

Spraying water on fin-fan air coolers is generally not a good idea. It is really effective only in dry climates with low humidity. The evaporation of water by the dry air cools the surface of the fins that is, the latent heat of vaporization of the water, robs sensible heat from the tubes. 

Deionized- water Cooler A finned fan-type cooler. would be sufficient to provide the estimated 300 kW cooling duty. 

The second modification to the flowscheme is that steam condensate from the ammonia vaporizer has been fed directly into the vapour/liquid separator, from where it may be drawn for waste-heat boiler feed. This route is in preference to feeding the condensate (at 250°C) back into the deionized-water circuit. By re-routing to the vapour/liquid separator, the heat duty of the waste-heat boiler can be reduced, and hence its size and cost are lower. The duty on the deionized-water fin-fan cooler and the economizer throughput are reduced. Both of these modifications result in a lower capital cost. 

The ion-exchange unit for treatment of scheme water to deionized water is outside the process flowsheet shown in Figure 4.1. The flowrate through this unit is 2338 kg, equal to the make-up water requirement. Also required is a fin/fan-type cooler for the circuit itself, so that the temperature of the return deionized-water stream can be lowered from 40°C to 20°C... 

Fin/fan heat duty = (Total warm water) CP (T, - Tout)... 

SPECIFICATIONS FOR FIN FAN HEAT EXCHANGERS FLUOR GRISCOM RUSSELL... 

Table 2.9 Revamp options for heat exchangers and fin fan (or air) coolers. Equipment - Objective Options...

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