New Tower Designs

Location Must be located in an area at some distance from the plant proper. This is necessary for air supply considerations and because of problems associated with fogging and drift from discharging air. Noise considerations also tend to dictate site selection. Can be built adjacent to plant buildings, on centers 1.5 (d) where d = base diameter, so that piping costs are reduced. Their position must be chosen so as not to interfere with power plant exhaust plumes. 

Materials of Construction May be constructed of wood, metal or concrete. The structure must be designed to withstand wind or earthquake stress, dead loads such as weight of tower and circulating water and vibrations from mechanical equipment. Constructed of thin concrete shells that have good wind resistance. 

Initial Investment Can be built with less expensive materials like wood, asbestos-cement board and plastic imaterials. Fan cost is higher. Built with relatively expensive materials such as prestressed, precast and reinforced concrete and asbestos-cement for fill. 

Operation Maintenance Costs Pumping head is less, so power cost for the circulating water pumps is less. Power cost for fans is considerable. Cost of maintaining fans and associated drives and transmissions is also significant. Total operating cost will favor natural-draft towers. 

Recirculation, Fogging These are major problems. Design accommodation, restrictions on tower dimensions, orientation with prevailing winds, and added capacity for recirculation can boost tower cost. Because of its elevated discharge, the natural-draft tower rarely has the trouble with recirculation and fogging. 

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For new tower design, packing is the favored choice in 1) low-pressure operation 2) low-pressure drop operation 3) high liquid-to-vapor ratios 4) low liquid-to-vapor ratios 5) ceramic and polymer... 

For new tower design, without overriding process factors, the cheapest overall system (tower, foundation, internals) is normally a sieve or a valve tray. Both have essentially the same capacity. The driving force behind valve tray selection is the flexibility benefit of the valve tray at little additional cost. However, for larger diameters and higher liquid rates, the flexibility advantage of the valve tray is more illusory than factual.f ... 

I had concluded that the FCCU fractionator was entraining black slurry oil into the LCO product because the slurry pumparound section was flooding. But how could a brand-new tower, designed by a reputable engineering contractor, flood at design throughput ... 

Kiihni Tower The extraction towers designed at Kiihni [see Mogh and Biihlmann, in Lo, Baird, and Hanson (eds.). Handbook of Solvent Extraction, Wiley-lnterscience, New York, 1983, sec. 13.5]... 

This value of entrainment is negligible. For a new column design, this would indicate that the tower tvas too large, and a smaller shell should be considered. 

For new towers, the designs will usually develop to utilize the entire tower cross-section. However, for existing towers with perforated trays being installed to replace bubble caps or packing, the optimum active tray area may not utilize the entire cross-section. If the number of holes required is small compared to available area, it is better to group the holes on 2.5 dg to 3.5 do than to exceed these limits. Holes separated by more than 3 in. are not considered effective in tray action so necessary for good efficiency. Blanking strips may be used to cover some holes when more than required have been perforated in the tray. 

Alternate Preliminary Design of New Tower (after References 12 and 19)... 

Dullien, F. A. L. Porous Media Fluid Transport and Pore Structure (Academic Press, New York, 1979). Leva, M. Tower Packings and Packed Tower Design, 2nd edn. (U.S. Stoneware Co., 1953). 

The authors describe how manageable discharge levels can be obtained by sidestream treatment and careful tower design. The permissible tower control limits based on old concepts and with high pH and new concepts requiring the use of organic additives or dispersant are listed. Examples are given. 

Question s most often asked of a fan engineer about axial-flow fans for today s wet cooling towers generally cover performance efficiency corrosion resistance and noise. This article reviews such fundamentals and gives new insight for optimum tower design. 

Given are two examples which show different methods that are used to reduce the quantities of waste water from cooling tower operation. In one case, the treatment technique of an existing facility was modified to reduce waste water production. In the order case, a new plant design included facilities for the minimization of the requirements for waste water disposal. 

The FCT built a small-scale physical model of the preheater tower, up to cyclones lA and IB, having the scale of a laboratory model to an actual plant of 1 35.5. The model was made of transparent acrylic for visibility inside to visualize the flow streams and mixing (Figure 31.20). The existing burners were modeled as slots on the acrylic model, and new FCT design auxiliary model burners were tested as a possible solution. A water-bead modeling reveals the aerod5mamics inside of the riser duct the kiln exhaust was represented by water in the model. For the visualization of flow, neutrally buoyant polystyrene beads follow the water flow accurately and beads allow the flow streams to be visualized ... 

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