Coolers condensers

To prevent such release, off gases are treated in Charcoal Delay Systems, which delay the release of xenon and krypton, and other radioactive gases, such as iodine and methyl iodide, until sufficient time has elapsed for the short-Hved radioactivity to decay. The delay time is increased by increasing the mass of adsorbent and by lowering the temperature and humidity for a boiling water reactor (BWR), a typical system containing 211 of activated carbon operated at 255 K, at 500 K dewpoint, and 101 kPa (15 psia) would provide about 42 days holdup for xenon and 1.8 days holdup for krypton (88). Humidity reduction is typically provided by a combination of a cooler-condenser and a molecular sieve adsorbent bed. 

Dual-Pressure Process. Dual-pressure processes have a medium pressure (ca 0.3—0.6 MPa) front end for ammonia oxidation and a high pressure (1.1—1.5 MPa) tail end for absorption. Some older plants still use atmospheric pressure for ammonia conversion. Compared to high monopressure plants, the lower oxidation pressure improves ammonia yield and catalyst performance. Platinum losses are significantiy lower and production mns are extended by a longer catalyst life. Reduced pressure also results in weaker nitric acid condensate from the cooler condenser, which helps to improve absorber performance. Due to the spHt in operating conditions, the dual-pressure process requires a specialized stainless steel NO compressor. 

Weak Acid. Stainless steels (SS) have exceUent corrosion resistance to weak nitric acid and are the primary materials of constmction for a weak acid process. Low carbon stainless steels are preferred because of their resistance to corrosion at weld points. However, higher grade materials of constmction are required for certain sections of the weak acid process. These are limited to high temperature areas around the gau2e (ca 900°G) and to places in which contact with hot Hquid nitric acid is likely to be experienced (the cooler condenser and tail gas preheater). 

For coolers, condensers, steam heaters and reboilers. The effluent cooling water and condensate are typically discharged as follows ... 

In direct contact heal exchange, there is no wall to separate hot and cold streams, and high rales of heal transfer are achieved. Applications include reactor off-gas quenching, vacuum condensers, desuperheating, and humidification. Water-cooling lowers are a particular example of a direct contact heal e.xchanger. In direct contact cooler-condensers, the condensed liquid is frequently used as the coolant. 

Condenser (a) Condenses all vapors (pure or mixed) entering. (b) Condenses all condensable vapor, cools the gases—termed a cooler-condenser. 

Cooler Condenser Design Lb-Water Program No. 710402 Water Rate Tube Modified Colbiu-n-Hougen, Bras Method Design Calc, for Sec. Coolers—Water Sat d at 110°F TL-in. Cooling Water Pass No. 2 In. °F 48.00 Lb-Gas, Gas Rate HLI, Water 8c Tube Acc-F, Program Tube 92.30 lb hr tube 480.00 Overall Coeff. Accmacy. 10 I.D. Controlled to 0.1 F Pl-Atm, Press, of Sys Gas in Top I.OOO ... 

The method is applicable only to gas-vapor mixtures with the vapor at saturation. However, systems involving superheated mixtures and subcooling can be handled as separate problems and added to the cooler-condenser area requirements to form a complete unit. 

Area Calculated as Cooler-Condenser (Inlet Mixture at Dew Point)... 

Water vapor entering compressor at 104°F and 14.2 psia and entering cooler-condenser at 250°F. 

Water vapor leaving cooler condenser at 104°F and an assumed 31 psia, allowing 3 psi for pressure drop through unit. 

Fair, J. R, Designing Direct-Contact Coolers/Condensers, Chem. Eng, p. 91,June 12, (1972). 

Stream (T)may be Process Fluid being Cooled or Condensed, Or it maybe Brine being Cooled for Use in Process Coolers. Condensers and Miscelloneous Equipment. 

Impervious graphites, that is electro-graphites with appropriate resin impregnation are used in cascade-, shell- apd tube-type coolers, condensers, pre-heaters etc. in a wide variety of chemical plants. Similar resistance to corrosion applies to glassy carbon vessels and pyrolytic carbons and graphites. The corrosion resistance to principal chemical agents is given in Table 18.2. 

In the first part of any steam-condensate system the C02 provides only a small fraction of the total steam-vapor mass, but as the steam condenses, it contributes a greater percentage of the remaining vapor. Toward the end of the run, the carbon dioxide, having a greater partial pressure, dissolves to a greater percentage (in the cooler condensate) and results in a lower pH level. 

In the design of a cooler-condenser for a mixture of vapour and a permanent gas, the method of Colburn and Hougen(66) is considered. This requires a point-to-point calculation of the condensate-vapour interface conditions T( and P . A trial and error solution is required of the equation ... 

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