Vent condenser

If solvent recovery is maximized by minimizing the temperature approach, the overall heat-transfer coefficient in the condenser will be reduced. This is due to the fact that a large fraction of the heat transfer area is now utilized for cooling a gas rather than condensing a Hquid. Depending on the desired temperature approach the overall heat-transfer coefficients in vent condensers usually range between 85 and 170 W/m K (ca 15 and 30 Btu/h-ft. °F). 

Various solutions have been used. These include orifices to regulate the flow into each tube, a blow-through steam technique with a vent condenser, complete separation of each row of tubes, and inclined tubes. 

Type 77 units are the condenser and reboiler designs. One side is spiral flow and the other side is in cross flow. These SHEs provide veiy stable designs for vacuum condensing and reboiling seiwices. A SHE can be fitted with special mounting connec tions for refliix-type vent-condenser apphcations. The vertically mounted SHE directly attaches on the column or tank. 

Applications The common Heliflow apphcations are tank-vent condensers, sample coolers, pump-seal coolers, and steam-jet vacuum condensers. Instant water heaters, glycoLwater seivdces, and cryogenic vaporizers use the spiral tube s ability to reduce thermally induced stresses caused in these apphcations. 

The noncondensable gases eventually reach the condenser (unless vented from an effect above atmospheric pressure to the atmosphere or to auxiliary vent condensers). These gases will be supplemented by air dissolved in the condenser water and by carbon dioxide given off on decomposition of bicarbonates in the water if a barometric condenser is used. These gases may be removed by the use of a water-jet-type condenser but are usually removed by a separate vacuum pump. 

Provide local exhaust ventilation connected to a disposal system (vent condenser, adsorber, scrubber or incinerator)... 

Reactor vent cooler is RE-1 Reactor vent condenser is RE-2 Reactor recycle pump is RP-1 Level control valv e is Rl C-1 Relief valve is RSV-1... 

Baasel, W. D., Nomograph Solves Vent Condenser Sizing Equations, Petro. Chem. Eng, May (1967), p. 48. 

The oxygen thus released concentrates in the upper zone of the deaerator with other noncondensable gases, passes through a small vent condenser, and then exits the DA through an atmospheric vent together with a limited amount of steam. 

A type of steam-heated open FW heater containing a vent and vent condenser and employed for the elimination of non-condensable gases. Depending upon deaerator design and operation, it is sometimes possible to reduce FW dissolved oxygen (DO) levels to below 0.005 cc/1 (7.2 ppb). 

In larger plants, significant reductions in VOC emissions can usually be made by controlling major sources, such as tank venting, condensers and purges, and by inspection and maintenance of gaskets and shaft seals. 

The reactor vents are due to the non-condensables in both the chlorine and ethylene feeds. In the case of chlorine, the non-condensables are largely the oxygen and inerts (carbon dioxide and nitrogen) as produced from the electrolysers. In the case of ethylene, the non-condensables are largely ethane, which is unreactive. The vent is also saturated with EDC vapour at the vent condenser temperature. 

Gases from the hydrolysis reactors pass through a vent condenser. Liquids from the condenser are returned to the EPDR, and gases are sent to the GPCR in Area 400. 

Aldehydes and Other Low-Boiling Components. As mentioned, a low-boiling fraction, called heads, is normally taken from the vent condenser during the distillation of wine into brandy. The principal impurities removed are acetaldehyde, diethyl acetal, ethyl acetate, and acetalde-hyde-sulfurous acid. 

Approximately 1 of air enters the extractor with each 1 of material. To maintain the extractor under a slight vacuum, the air must be continuously vented from the extractor. At the extractor temperature of 60°C, an equilibrium condition will occur where the vent gas exiting the extractor will contain approximately 10 parts of solvent vapor for every one part of air (see Figure 12). The solvent vapor and air exit the extractor and are typically condensed in an extractor condenser. The extractor condenser is a shell and tube vessel with the vapors typically on the shell side and the coohng water on the tube side. The noncondensable vapors exiting the extractor condenser pass on to the vent condenser. 

The composition of solvent vapor with the air exiting the vent condenser is a result of an equilibrium condition determined by the vent gas temperature. Figure 12 illustrates the equilibrium vapor compositions at various temperatures. For example, at a vent gas temperature of 30°C, the vent gas composition will be slightly greater than one part solvent for every one part air. However, if the vent gas temperature increases to 40° C, then the vent gas composition will be slightly less than two parts solvent for every one part air. Therefore, to minimize the load on the mineral oil system, it is important to minimize the vent gas temperature exiting the vent condenser. Some facilities, particularly in hot and humid climates, install a refrigerated vent gas cooler after the vent condenser to minimize the solvent vapor load on the mineral oil system. 

Air is removed from the system by vent lines connected to all vessels likely to contain some incoming air the extractor, the desolventizer, etc. A slight vacuum, induced by a vent fan, draws noncondensibles from all the condensers and vented vessels into a common header where they pass through a water-cooled vent condenser followed by some device to remove as much solvent vapors as practical and then pass through a flame arrestor before being released to the atmosphere. The simplest, least expensive device is a refrigerated condenser to lower the effluent air temperature. The air leaves the system saturated with solvent vapor the lower the temperature, the less solvent in the air. A more effective method removes the solvent from the air by either absorption or by extraction. 

---