Condensers indirect contact

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. 

Pure product recovery (in the case of indirect-contact condensers)... 

Water used as the coolant in an indirect-contact condenser (i.e., shell-and-tube heat exchanger), not in contact with contaminated gas stream, and is reusable after cooling... 

The dewpoint hygrometer detects the dewpoint temperature of air by cooling a surface in contact with the air to the dewpoint temperature. There are several ways to achieve cooling and to observe the formation of condensate on the surface. The early dewpoint hygirometers were cooled simply by applying the vaporization of ether or some other suitable liquid. Condensate formation on the surface was determined visually. Other cooling methods are to use a refrigerant flow in direct or indirect contact with the back of the surface, or to use electricity with a (thermoelectric) Peltier element. 

Condensers and vacuum pumps will be needed for evaporators operated under vacuum. For aqueous solutions, steam ejectors and jet condensers are normally used. Jet condensers are direct-contact condensers, where the vapour is condensed by contact with jets of cooling water. Indirect, surface condensers, are used where it is necessary to keep the condensed vapour and cooling water effluent separate. 

The solution is straightforward. Do not condense the steam by direct contact with cold water, as is done in the barometric condenser. Condense the steam by indirect contact, with the cold surface of the tubes in a shell-and-tube condenser. Hence the name surface condenser, a sketch of which is shown in Fig. 18.2. Compare Fig. 18.1 with the surface condenser. Is there really much difference Other than recovering clean steam condensate for reuse, there is no difference at all. I last used a surface condenser in 1976, on a sulfuric acid plant reactor feed gas boost blower, and it worked just fine. 

A schematic of the 2kD system is shown in Figure 2. The title 2kT> is derived from the design capacity of 2k ton per day charcoal output. The basic trailer-mounted system is comprised of three subsystems 1) a reactor, 2) a recirculating gas loop to bring heat into the reactor by indirect contact of the recirculating gas with hot products of combustion in a heat exchanger and 3) the combustion system. Ancillary subsystems such as a condenser to obtain liquid distillates (shown in sketch) and secondary heat exchangers (not shown) are not critical to the operation of the 24D system. 

Chlorine is produced as a hot, wet cell gas. Its temperature leaving the cells usually is greater than 85°C, and it is saturated with water at its vapor pressure over the anolyte. Nearly all applications require cooling of this gas, which causes partial condensation of the contained water vapor. Two basically different methods of cooling are in common use, based on direct and indirect contact with the coolant. These are dealt with in Sections 9.1.3.3 and 9.1.3.4. Before considering these techniques, we review methods of calculation of heat-transfer rates and the effects of simultaneous mass transfer on the heat transfer process (Sections 9.1.3.1 and 9.1.3.2). 

Typical dryer exhaust emissions are sulfur compounds such as hydrogen sulfide, carbon disulfide, carbonyl sulfide, and methyl and w-propyl mercaptans. In addition to ammonia, the only amine present is trimethyl amine. Since the emissions from the dryers contain considerable moisture at temperature of about 95°C, necessary means should be provided to remove most of this moisture and to cool the air before further odor treatment. Also, there may be dust particles in the cyclone exhaust that should be removed before effective odor measures can be applied. This is normally accomplished by either direct or indirect contact (e.g., shell and tube) water-cooled condensers. The direct-contact type includes cocurrent flow venturi scrubbers and countercurrent... 

Gas from the ethane recovery column is compressed to about 650 psig (S), cooled, and partially condensed by providing reboil heat and by indirect contact with a refrigerant in heat exchanger (6), and then fed into the carbon dioxide recovery colunm (7). 

Barometric condensers are direct contact coolers and condensers. They may be counter flow or parallel flow. Good contact direct cooling is an efficient inexpensive design, being considerably cheaper and more efficient than indirect surface or tubular coolers. 

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