Cooling tower blow-down

Figure 9-123. Cooling tower blow-down versus number of concentrations in circulating water percent of total circulating water to be wasted to maintain various concentrations. Used by permission of Hensley, J. C. (ed.) Cooling Tower Fundamentals, 2nd Ed. (1985), The Marley Cooling Tower Co., a United Dominion Co.

Boiler feed water and cooling tower blow down recycle for utilities and power generation Cleaning of contaminated surface water and groundwater Potable water from sea or brackish water Pharmaceutical-grade water... 

In addition, the small motor fan attempts to blow air down over the motor and is no match for the much bigger cooling tower fan drawing air up and around the motor. The small fan in this case is useless- even counterproductive. This application needs a TEAO motor. Cooling tower manufacturers sometimes purchase special motors tailored for their application... special grease, seals, slingers, weep hole locations, epoxy coatings, etc.. Such features make an OEM replacement more desirable than an off the shelf replacement. 

CR = cooling range, °F, difFerence between hot water into tower and cold water from the tower, °F B = rate of blow-down, gpm. (Because an acceptable level of concentration has usually been predetermined, the operator is more concerned with the amount of blowdown necessary to maintain the concentration. Equation 9-132.)... 

Example 9-15 Determinii Approximate Blow-down for Cooling Tower (Used by permission of Marley Cooling Tower Co., Inc., from Cooling Tower Fundamentals [144])... 

Performance, 387 Ground Area vs. Height, 391 Pressure Losses, 393 Fan Horsepower for Mechanical Draft Tower, 392 Water Rates and Distribution, 393 Blow-Down and Continuation Build-Up, 394 Example 915 Determining Approximate Blow-Down for Cooling Tower, 395 Pre-... 

Although these units find initial application in areas of limited water, they have not been limited to this situation. In many instances they are more economical than cooling tower systems and have been successfully applied in combination with cooling towers (see Figure 10-184). Economic comparisons should include such items as tower costs, basin, make-up facilities, water treatment, pumps for circulation, power supply, blow down, piping, etc. For small installations of air-cooled units, they should be compared... 

This system normally uses a condenser discharge directly to a hot well and then to a cooling tower, often by gravity. The cooling tower overflow and blow down is discharged to a wastewater treatment facility as part of the plant oily wastewater handling needs. 

Only filtered water should be used for acid cooling and it should not contain more than 50 ppm of dissolved solids. Regular blow downs of cooling tower basins are recommended to control the TDS level. Since the presence of chlorides in cooling water makes it corrosive, the acid coolers can be constructed using corrosion resistance materials like Hastelloy C-276. 

ILLUSTRATIVE EXAMPLE 15.15 Determine the total flowrate of cooling water required for the services listed below in Table 15.2 for a chemical reactor if a cooling tower system supplies the water at 90°F with a return temperature of 115°F. How much flesh water makeup is required if 5% of the return water is sent to blow-down Note that the cooling water heat capacity is 1.00 Btu/lb °F, the heat of vaporization at cooling tower operating conditions is approximately 1030 Btu/lb, and the density of water at cooling tower operating conditions is 62.0 Ib/ft. ... 

---