Air-Cooled Overhead Condensers

Air-Cooled Overhead Condensers Air-cooled overhead condensers (AOC) have been designed and installed above distiUation columns as integral parts of distiUation systems. The condensers generally have incliued tubes, with air flow over the finned sur ces induced by a fan. PrevaUing wind affec ts both structural design and performance. 

Air finfan overhead condensers. Table 8.34 gives the modular cost of the overhead condensers and product coolers. Since this plant is to be installed in Saudi Arabia, cooling tower water is not available. Also, cooling water is not necessary since the products will be stored in spherical tanks requiring 150 to 180°F cooling. This is easy to obtain, even in Saudi Arabia, with air finfan coolers. The square feet of surface area shown in Table 8.34 is the bare tube surface area of each cooler. Please note this is not the extended surface of the outside tube area, but rather the outside bare tube surface area in square feet. Figure 8.4 was used to find the base cost of these air coolers. 

Sulfurchlorination of unsaturated compounds or mercaptans is normally carried out at atmospheric pressure in a glass-lined reaction vessel because of the potential to Hberate HCl during the reaction. The sulfurchlorination vessel is equipped with a cooling jacket or coils (very exothermic reaction), a nitrogen or dry air sparging system, an overhead condenser, and a caustic or bleach scmbber. If one of the reactants (olefin or mercaptan) is alow boiling material, ie, isobutylene, a glass-lined pressure vessel is recommended. 

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... 

Evaluate the effects of choosing trays, random packing, or systematic packing. It is recommended that the top column pressure be set for the lowest reasonable overhead pressure consistent with the use of a water- or air-cooled condenser. In this case, pressure would be 50 mmHg, corresponding to a temperature of 53°C (127°F). 

Description Fresh and recycle cumene is oxidized (1) with air to form cumene hydroperoxide (CHP) using new oxidizer treatment technology to reduce organic acid formation and improve selectivity. Overhead vapors are cooled and condensed to recover cumene. Spent air is treated to absorb and recover residual hydrocarbons. 

The usual problem with air-cooled condensers is insufficient air flow. Calculate the overhead condenser duly from process side data. Next, measure the air inlet and outlet temperatures and calculate the volume of air being moved. 

In the final design stage of a project, the question has arisen as to whether to use a water-cooled exchanger or an air-cooled exchanger in the overhead condenser loop of a distillation tower. The information available on the two pieces of equipment is provided as follows ... 

The VPS overhead consists of steam, inerts, condensable and non-condensable hydrocarbons. The condensables result from low boiling material present in the reduced crude feed and from entrainment of liquid from the VPS top tray. The noncondensables result from cracking at the high temperatures employed in the VPS. Inerts result from leakage of air into the evacuated system. Steam and condensable hydrocarbons are condensed using an overhead water-cooled condenser. The distillate drum serves to separate inerts and non-condensables from condensate, as well as liquid hydrocarbons from water. Vacuum is maintained in the VPS using steam jet ejectors. 

C. (R,R)-N,N -Bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamine. A 2-L, three-necked, round-bottomed flask equipped with a mechanical overhead stirrer, reflux condenser, and an addition funnel is charged with 29.7 g of (R,R)-1,2-diammoniumcyclohexane mono-(+)-tartrate salt (0.112 mol), 31.2 g of potassium carbonate (0.225 mol, 2 eq), and 150 mL of water. The mixture is stirred until dissolution is achieved, and 600 mL of ethanol is added. The cloudy mixture is heated to reflux with a heating mantle and a solution of 53.7 g (0.229 mol, 2.0 eq) of 3,5-di-tert-butylsalicylaldehyde in 250 mL of ethanol is then added in a slow stream over 30 min (Note 19). The addition funnel is rinsed with 50 mL of ethanol and the mixture is stirred at reflux for 2 hr before heating is discontinued. Water, 150 mL, is added and the stirred mixture is cooled to <5°C over 2 hr and maintained at that temperature for another hour. The yellow solid is collected by vacuum filtration and washed with 100 mL of ethanol. After the solid is air dried, it is dissolved in 500 mL of methylene chloride. The organic solution is washed with 2 x 300 mL of water, followed by 300 mL of saturated aqueous sodium chloride. The organic layer is dried over sodium sulfate, and filtered to remove the drying agent. The solvent is removed by rotary evaporation to yield the product as a yellow solid, mp 200-203°C (Notes 20 and 21). 

Atmospheric air at the rate of 6.1 million SCFD is compressed to 160 psig in a two-stage compressor JJ-1 that is provided with an intercooler and a knockout drum. Then it proceeds to a packed tower T-l where it is scrubbed with recirculating caustic soda solution. Overhead from T-l is cooled to 14°F in a refrigerated exchanger. After removal of the condensate, this stream proceeds to a dryer system that consists principally of two vessels F-l and F-2 packed with solid desiccant. 

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