Cooling towers

Cooling tower blowdown can be reduced by improving the energy efficiency of processes, thus reducing the thermal load on cooling towers. Alternatively, cooling water systems can be switched to air coolers, which eliminates the problem altogether. 

Cool flames Cooling crystallizers Cooling towers... 

W. S. Norman, Mbsorption, Disti/htion and Cooling Towers Longmans, Green Co., Ltd. (Wiley) New York, 1962. 

The utihty iadustry utilizes fans typically from 6.7—10 m diameter ia banks of 8 to 12 fans ia wet cooling towers. These towers cool the water used to condense the steam from the turbiaes. Many towers may be needed ia large plants requiring as many as 50 to 60 fans 12 m in diameter. These fans typically utilize velocity recovery stacks to recoup some of the velocity pressure losses and convert it to useful static pressure work. 

Water Treatment Industrial CleaningPipplications. Boiler and cooling tower waters are treated with lignosulfonates to prevent scale deposition (78). In such systems, lignosulfonates sequester hard water salts and thus prevent their deposition on metal surfaces. They can also prevent the precipitation of certain iasoluble heat-coagulable particles (79). Typical use levels for such appHcatioas range from 1—1000 ppm. 

Antimicrobials. In slightly alkaline aqueous solutions, nitro alcohols are useful for the control of microorganisms, eg, in cutting fluids, cooling towers, oil-field flooding, drilling muds, etc (8—15) (see INDUSTRIAL ANTIMICROBIAL AGENTS Petroleum). However, only... 

Water Purification reservoirs, swimming pools, cooling towers... 

Alkyl or aryl phosphonates, which contain a carbon—phosphoms bond, are comparatively more stable. They are of interest as antiscaling additives and corrosion inhibitors for cooling towers and heat exchangers (see Dispersants Water, industrial water treatment), surfactants (qv), sequestrants, and textile-treating agents. Trialkyl phosphites are usehil as esterification (qv) reagents. 

Phosphonic acid is an intermediate in the production of alkylphosphonates that are used as herbicides and as water treatment chemicals for sequestration, scale inhibition, deflocculation, and ion-control agents in oil weUs, cooling tower waters, and boiler feed waters. For example, aqueous phosphonic acid reacts with formaldehyde and ammonium chloride in the presence of hydrochloric acid to yield aminotri(methylenephosphonic acid) [6419-19-8]. 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Cooling Towers. The cooling tower location relative to the prevailing wind direction should be such that the wind hits the short side or the side perpendicular to the inlet louvers. This helps balance the air flow to the two inlet sides. 

Vented risers should be provided on most cooling towers to release only light hydrocarbon leakage from the cooling water before the spray header. No ignition or source of spark should be within 30 m of the vented riser. 

Plant layout and noise suppression material are two general noise abatement methods. Plant layout does not affect noise levels at any given point however, noise can be abated by screening off a section of the plant. An example of this is to orient cooling towers with their closed faces toward the critical location. This method must also consider wind direction to balance air draft. Tankage can be located to act as a noise screen. 

Fixed investment includes cooling tower, boiler feedwater treatment, raw water ammonia storage as minimum off-sites requirement. 

Other energy considerations for cooling towers include the use of two-speed or variable-speed drives on cooling-tower fans, and proper cooling-water chemistry to prevent fouling in users (see Water, industrial water treatment). Air coolers can be a cost-effective alternative to cooling towers at 50—90°C, just below the level where heat recovery is economical. 

Fig. 8. Transverse cross-sectional view of double-flow induced-draft cooling tower. Courtesy of The Madey Co.

The thermal design of cooling towers follows the same general procedures already presented. Integration of equation 35 is usually done numerically using the appropriate software, mass-transfer coefficients, saturation enthalpies, etc. In mechanical-draft towers the air and water dows are both suppHed by machines, and hence dow rates are fixed. Under these conditions the design procedure is straightforward. 

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