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Title:
LOW OR ZERO BLEED WATER DISCHARGE COOLING TOWER SYSTEM
Document Type and Number:
WIPO Patent Application WO/2004/028978
Kind Code:
A1
Abstract:
An improvement in a cooling tower system (70) and operation thereof. The improvement comprises acid treatment of the cooling water, softening of the inlet water and controlling of drift. Drift is controlled by controlling fan (58) speed; controlling fan (58) operation time; adjustment of inlet louver (46) spacing; adjustment of wetfill (30) spacing; adjustment of mist eliminator (38) spacing; spraying of inlet louvers (46) with cooling or other water; and spraying of the mist eliminators (38) with cooling or other water. Water softening may be accomplished by replacing hardness cations with sodium cation or with hydrogen cation. The amount of softening performed is controlled by an adjustable system comprising the water meter/contact timer (78) and the solenoid valve (82). Optionally a filtration subsystem (130, 134) for the cooling water may be included.

Inventors:
Snyder, Milton W. (243 18th Street, Santa Monica, CA, 90402, US)
Application Number:
PCT/US2002/030708
Publication Date:
April 08, 2004
Filing Date:
September 27, 2002
Export Citation:
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Assignee:
Snyder, Milton W. (243 18th Street, Santa Monica, CA, 90402, US)
International Classes:
C02F1/42; F28C1/04; F28F25/00; F28F25/10; F28F27/00; (IPC1-7): C02F1/42
Foreign References:
US6206350B12001-03-27
US6012708A2000-01-11
US5730879A1998-03-24
US5531801A1996-07-02
US5320651A1994-06-14
US4931187A1990-06-05
US3850595A1974-11-26
US3805880A1974-04-23
US3780567A1973-12-25
US3748832A1973-07-31
Attorney, Agent or Firm:
Townsley, Norton R. (Belasco Jacobs & Townsley, Howard Hughes Center 6100 Center Drive, Suite 63, Los Angeles CA, 90045, US)
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Claims:
Claims
1. An improvement in a cooling tower system, said system having a basin of cooling water, a fan, a mist eliminator, wetfill, and a plurality of inlet louvers ; said weffill including a weffill spacing; said inlet louvers having an inlet spacing therebetween; said mist eliminator having an eliminator spacing; said cooling tower system experiencing cooling water losses to atmosphere (drift); said improvement comprising: a) an alkalinity reduction means for minimizing the concentration of carbonate ions in said cooling water; b) a cation exchange means for reducing the hardness of said cooling water; and c) a drift control means for controlling drift.
2. An improvement as claimed in claim 1 in which the concentration of carbonate ions is maintained at a level sufficient to eliminate scale formation in said system.
3. An improvement as claimed in claim 1 in which the concentration of carbonate ions is maintained at zero.
4. An improvement as claimed in claim 1 in which the alkalinity and hardness are adjusted so that the Langelier Scaling Index is kept below +2.
5. An improvement as claimed in claim 1 in which the hardness is kept below about 650 ppm.
6. An improvement as claimed in claim 1 in which said drift control means comprises a fan speed control means for adjusting the operating speed of said fan so that bleed is minimized.
7. An improvement as claimed in claim 1 in which said drift control means comprises a fan timer means for adjusting operation time of said fan so that bleed minimized.
8. An improvement as claimed in claim 1 in which said drift control means comprises said inlet spacing being adjusted so that bleed is minimized.
9. An improvement as claimed in claim 1 in which said drift control means comprises said weffill spacing being adjusted so that bleed is minimized.
10. An improvement as claimed in claim 1 in which said drift control means comprises said eliminator spacing being adjusted so that bleed is minimized.
11. An improvement as claimed in claim 1 in which said drift control means comprises an inlet spray means for spraying said inlet louvers with water.
12. An improvement as claimed in claim 11 in which said water is cooling water.
13. An improvement as claimed in claim 1 in which said drift control means comprises an outlet spray means for spraying said mist eliminator with water.
14. An improvement as claimed in claim 13 in which said water is cooling water.
15. An improvement as claimed in claim 1 in which said alkalinity reduction means is addition of acid.
16. An improvement as claimed in claim 1 in which said alkalinity reduction means is hydrogen cation exchange.
17. An improvement as claimed in claim 1 in which said cation exchange means is replacement of hardness cations with sodium cation.
18. An improvement as claimed in claim 1 in which said cation exchange means is replacement of hardness cations with hydrogen cation.
19. An improvement as claimed in claim 1 further including a means for filtering said cooling water.
20. An improvement in a cooling tower system, said system having a basin of cooling water, a fan, a mist eliminator, weffill, and a plurality of inlet louvers said wetfill including a weffill spacing; said inlet louvers having an inlet spacing therebetween; said mist eliminator having an eliminator spacing; said cooling tower system experiencing cooling water losses to atmosphere (drift); said improvement comprising: a) an acid treatment subsystem for said cooling water. b) a water softener subsystem for said cooling water; and c) a drift control system for said drift.
21. An improvement as claimed in claim 20 in which the pH is kept below approximately 8.6.
22. An improvement as claimed in claim 20 in which said acid treatment and said softening are performed so as to keep the Langelier Scaling Index below +2.
23. An improvement as claimed in claim 20 in which the hardness is kept below 650 ppm.
24. An improvement as claimed in claim 20 in which said drift control system comprises a fan speed controller.
25. An improvement as claimed in claim 20 in which said drift control system comprises a fan operating time timer.
26. An improvement as claimed in claim 20 in which said drift control system comprises said inlet spacing being adjusted so that bleed is minimized.
27. An improvement as claimed in claim 20 in which said drift control system comprises said wetfill spacing being adjusted so that bleed is minimized.
28. An improvement as claimed in claim 20 in which said drift control system comprises said eliminator spacing being adjusted so that bleed is minimized.
29. An improvement as claimed in claim 20 in which said drift control system comprises an inlet spray subsystem adapted to spray said inlet louvers with water.
30. An improvement as claimed in claim 29 in which said water is cooling water.
31. An improvement as claimed in claim 20 in which said drift control system comprises an outlet spray subsystem adapted to spray said mist eliminator with water.
32. An improvement as claimed in claim 31 in which said water is cooling water.
33. An improvement as claimed in claim 20 in which said water softener subsystem replaces hardness cations with sodium cation.
34. An improvement as claimed in claim 20 in which said water softener subsystem replaces hardness cations with hydrogen cation.
35. An improvement as claimed in claim 20 further including filtration subsystem for said cooling water.
36. An improved method of operating a cooling tower system, said system having a basin of cooling water, a fan, a mist eliminator, wetfill, and a plurality of inlet louvers ; said weffill including a wetfill spacing; said inlet louvers having an inlet spacing therebetween; said mist eliminator having an eliminator spacing; said cooling tower system experiencing cooling water losses to atmosphere (drift); said improved method comprising the steps of: a) reducing the concentration of carbonate ions in said cooling water. b) reducing the hardness of said cooling water; and c) controlling drift.
37. An improved method as claimed in claim 36 in which the concentration of carbonate ions is maintained at a level sufficient to eliminate scale formation in said system.
38. An improved method as claimed in claim 36 in which the concentration of carbonate ions is maintained at zero.
39. An improved method as claimed in claim 36 in which the concentration of carbonate ions and hardness are maintained so that the Langelier Scaling Index is kept below +2.
40. An improved method as claimed in claim 36 in which the hardness is kept below about 650 ppm.
41. An improved method as claimed in claim 36 in which said drift control step comprises the steps of adjusting the operating speed of said fan.
42. An improved method as claimed in claim 36 in which said drift control step comprises the steps of adjusting the operation time of said fan.
43. An improved method as claimed in claim 36 in which said drift control step comprises the steps of adjusting said inlet spacing.
44. An improved method as claimed in claim 36 in which said drift control step comprises the steps of adjusting said wetfill spacing.
45. An improved method as claimed in claim 36 in which said drift control step comprises the steps of adjusting said eliminator spacing.
46. An improved method as claimed in claim 36 in which said drift control step comprises the steps of spraying said inlet louvers with water.
47. An improved method as claimed in claim 46 in which said water is cooling water.
48. An improved method as claimed in claim 36 in which said drift control step comprises the steps of spraying said outlet louvers with water.
49. An improved method as claimed in claim 48 in which said water is cooling water.
50. An improved method as claimed in claim 36 in which said carbonate ion reduction is accomplished by addition of acid.
51. An improved method as claimed in claim 36 in which said carbonate ion reduction is accomplished by hydrogen cation exchange.
52. An improved method as claimed in claim 36 in which said hardness reduction is accomplished by replacement of hardness cations with sodium cation.
53. An improved method as claimed in claim 36 in which said hardness reduction is accomplished by replacement of hardness cations with hydrogen cation.
54. An improved method as claimed in claim 36 further including the step of filtering said cooling water.
Description:
Low or Zero Bleed Water Discharge Cooling Tower System Technical Field This invention relates to the field of water treatment and more particularly to the treatment of water used in evaporative recirculating cooling water systems.

Background Art Cooling systems are designed primarily for one function, that is, to remove heat from a process system.

Heat removal can be accomplished in a number of ways. Once-through water systems have been used for many years where sufficient water supply is available and where water agencies allow their use. Spray ponds or lakes have also been used but require substantial surface area for convection and surface evaporation to remove enough heat. Cooling towers on the other hand require substantially less space, have higher efficiency and reduce water usage.

Where large refrigeration machines are used, the condensor coils that liberate heat are located in a water jacket near the compressor. This water is circulated through a piping system to carry away the heat to a cooling tower located a distance away from the condenser or to an evaporative condenser where the refrigerant is located within the spray tower. In the open spray tower system the water is sprayed or dropped in an air stream so that a portion of the water is evaporated, thereby cooling the main body of water in the open spray tower. This cooled water then is used to extract heat from the refrigerant or process.

The cooling and heating of the water is repeated continuously in the spray tower and process system.

Several methods are widely used to chemically treat cooling waters. One such process is the all polymer alkaline treatment program which relies totally on the use of polymers for both scale and corrosion control. The pH of the system's cooling water is allowed to reach values as high as approximately 9. The system is simple in that it may be controlled by adding a single product directly from a container to the cooling water, and the system is capable of maintaining a reasonable amount of control over scale and corrosion. However, in order to properly control the system, an increasing volume of water must be bled from the system to keep dissolved salts within their ranges of solubility, thus preventing scale

formation. This requires large additions of make-up water to keep the concentrations of dissolved solids within a scale free range. Also, this treatment scheme is relatively high in cost and requires other additives to control microbiological fouling of exchange surfaces.

A second commonly used system is one in which the pH and alkalinity of the cooling water are controlled through the addition of strong acids, such as sulfuric acid. This type of system has the advantage of permitting higher concentrations of dissolved salts to build up in the cooling water. This results in considerable savings of water as less make-up water is required as compared to the polymer treatment method. Sulfuric acid additions are capable of scale prevention with added inhibitors and biocides used for corrosion and microbiological growth control. This maintains cleaner and more efficient heat transfer surfaces. While the overall treatment cost is somewhat less than in the all polymer system, this process relies on a hazardous chemical. Thus, safety and environmental concerns tend to make this type of treatment process less attractive.

Cooling towers operate on the principle that the latent heat of vaporization of the water being evaporated subtracts energy from the system, thus, reducing the temperature of the remaining water in the system. Only some of the water is evaporated, however, so the concentrations of salts in the remaining water constantly increase until equilibrium is reached. Common dissolved salts in domestic water are bicarbonates, chlorides and sulfates of calcium, magnesium and sodium. When water containing calcium bicarbonate is heated the heat will strip off one molecule of carbon dioxide, producing calcium carbonate (limestone), according to the equation: Ca (HCOs) 2 + [heat] e CaC03 +CO2 +H20 Unlike most salts, calcium carbonate is less soluble in hot water than in cold water. This is why boiler and condenser scale (calcium carbonate scales) is deposited on hot heat exchange surfaces. Calcium carbonate solubility is also a function of the pH of the water.

Calcium salts are markedly less soluble in high pH systems. Knowing these properties of dissolved solids in cooling waters thus offers several means of control. Controlling the pH will allow more calcium to remain in solution, thus preventing it from becoming a hard scale on heat exchange surfaces. Another method of control is to eliminate or drastically reduce calcium and magnesium from the system entirely. This has in fact been done through the provision of a water softener. While this effectively controls scale, it does not necessarily eliminate the need for acid feed to control pH in conjunction with partial water softening.

Total softness of the make up water in spray towers requires larger equipment to soften the water and thus may be impractical. Furthermore, softened waters are notoriously much more corrosive than un-softened ones. Thus, in these systems, the scaling problem may be eliminated, but at the expense of increased corrosion. Of course, in order to be practical on a wide scale, a water treatment system must be simple and capable of use by plant personnel.

Because of evaporation and addition of chemicals to the cooling water, the total dissolved solids (TDS) of the cooling water constantly increases to a high value until an equilibrium is reached. If the TDS becomes too high, salts will start to deposit on various parts of the tower thus reducing efficiency, which also reduces efficiency of the cooling process. To control TDS, some cooling water is periodically bled from the system and replaced with fresh water.

A number of patents discuss various approaches to controlling the cooling water used in cooling towers US Patent No. 3,299, 619 discloses an improvement in evaporative cooling systems in which a relatively hot stream of water is contacted with atmospheric air to cool the stream, the cooled water is collected, and the water reheated and recycled. The improvement comprises passing at least a portion of the water to a liquid cyclone separator in which foulants are separated.

US Patent No. 3,627, 032 discloses a water treatment system for the water circulation system of a large capacity air-conditioning system which functions to maintain the water in the system in a suitable condition for passage through the heat exchanger and into engagement with the surfaces of the flow system. Makeup water is added to the reservoir of the cooling tower to replace the water lost from evaporation and windage, and chemicals are added to the water in the flow system as the water flows from the heat exchanger to the spray means at the top of the cooling tower.

US Patent No. 3,748, 832 discloses a drift eliminator to prevent airborne water droplets which are generated in a cooling tower from escaping through the discharge outlet by trapping the water droplets in the exhaust air and redirecting the air flow through the drift eliminator. The eliminator blades, hollow in cross-section, include three plane surfaces which incorporate a series of protrusions or sharp ridges for trapping water droplets which impinge on the eliminator blades and prevent same from becoming re entrained in the air.

The blades are formed with a ballistic nose of an air foil type leading edge to reduce

resistance to air movement across the drift eliminator. The drift eliminator blades are assembled into unique panels to reduce field assembly time.

US Patent No. 3,805, 880 discloses equipment in which environmental pollution attributable to the discharge of toxic and other wise polluting additives, such as chromates, phosphates and various biocides, by the common practice of"blowdown,"is avoided. The usual loss of expensive additives from the system is minimized and scaling of the waterside surfaces of the equipment being serviced is obviated. These benefits are achieved in a cooling system wherein an aqueous coolant is circulated to industrial equipment for heat absorption, then to an evaporating zone where heat is removed from the coolant by partial evaporation, then back to the industrial equipment for further heat absorption. Coolant-free solids are removed from the circulating sys tem by bleeding a minor portion of the coolant, separating the solids there from and returning the bleed to the system. The additives are recovered from the solids by water washing, returning the water containing the recovered additives to the circulating system, and maintaining a balanced system by introducing soft make-up water to the coolant without blowdown.

US Patent No. 3,850, 595 discloses a drift eliminator assembly for use in combination with a cooling tower including a plurality of drift eliminator panels secured together in an end to end relationship. Each panel includes a plurality of longitudinally extending drift eliminator blades supported at their respective ends by a pair of side plates. The side plates of longitudinally adjacent panels are secured together defining an integral drain channel there between. The side plates have openings integral there with to permit liquid collected on the blades to pass there through into the drain channel for discharge to a cold water basin.

US Patent No. 3,983, 914 discloses crescent shaped vanes disposed in an evaporative cooling tower so that the vanes generally have their leading edges aligned with a plane which forms an acute angle with a vertical plane and that adjacent vanes form a continuous smooth curve flow path which is generally directed upwardly and changes less than 90 degrees in direction to form an effective, low-pressure drop drift eliminator.

US Patent No. 4,475, 356 discloses an improved method for controlling the blowdown of recirculating water for an industrial cooling system or the like, in direct proportion to the heat load on refrigeration systems. A temperature probe is positioned in the recirculating water which is in communication with a blowdown valve. As the heat load on the system increases the temperature of the cooling water increases and the blowdown valve is then

regulated to release more of the circulating water. Additional makeup water and chemicals may be also supplied to the cooling system to maintain a proper chemical balance. In the preferred embodiment of the invention the probe is positioned between the refrigerant condenser and the cooling tower in the circulating water system. Appropriate chemical feed systems and makeup water can be regulated to function in relation to the amount of blowdown to insure that the desired chemical balance is maintained.

US Patent No. 4,936, 881 discloses a cooling tower having a flue gas outlet extending upwardly above the heat exchanger baffles in which the water from a steam power plant is cooled in counterflow to a rising cooling air stream. The mouth of the duct is formed with a droplet trap supplied with rinse water and cooperates with a collector for the rinse water which is led out of the tower independently of the cooled water of the heat exchanger zone.

US Patent No. 5,040, 377 discloses a new and improved cooling system and method for cooling the air in an enclosed space. The cooling system includes a cooling tower having a plurality of fans arranged to cool a first fluid and a chiller including a condenser thermally coupled to the first fluid, a compressor and an evaporator. The chiller further includes first conduit means for carrying a refrigerant. A chilled fluid loop including second conduit means circulates a second fluid through the evaporator for cooling the second fluid and is arranged to flow air over the second conduit means and into the enclosed space for cooling the air in the enclosed space. Fan control means controls the speed of the cooling tower fans to minimize the total power consumption of the fan motors and the compressor. The fan control means include load determining means for determining the heat transfer load on the chiller, control factor means for generating a control factor which is proportional to the load on the chiller, and speed control means for increasing or decreasing the speed of one or more of the fans responsive to the control factor.

US Patent No. 5,294, 916 discloses an apparatus for controlling the treatment of water that flows through a cooling system. The electrical conductivity of the water is sensed. A valve control opens a system drain valve when the sensed conductivity is greater than a threshold, and closes the drain valve when the conductivity drops below the threshold by a given amount. The water drained form the system is replenished through an inlet and a mechanism measures the volume of water added to the cooling system. Chemicals to treat the water are fed into the system when specified volumes of water have been added. The sensing of conductivity can be inhibited for a certain period following the application of the

chemicals. A possible system malfunction is indicated when the conductivity does not drop below the threshold after the drain valve is open for a given period of time.

US Patent No. 5,730, 879 discloses a process for conditioning recirculated evaporative cooling water in a cooling water system. The process reduces the amount of make-up water required during the operation of this system as compared to conventional water treatment systems. The process includes the steps of determining the pH of saturation. A strong cation exchange media is used in a controlled sidestream and operated so that the pH of the recirculated cooling water is within about a plus or minus 0.4 of the pH of saturation. The system avoids the necessity of storing acid at the water treatment site and also significantly reduces the amount of make-up water required.

All of the above patents are directed to solving a number of problems in cooling tower operation. However, none is directed to operating a cooling tower with minimal or zero bleed. Bleed is the water that is bled out of the system to sanitary sewers, septic tanks and waterways. In these days of water shortages and restrictions on discharges to sanitary sewers, septic tanks and waterways, minimal or zero bleed is rapidly becoming the most important operating parameter for water tower operation.

Development of a water tower system which can be operated with minimal or zero bleed represents a great improvement in the field of water towers and satisfies a long felt need of the plant engineers.

Disclosure of Invention This invention is an improvement in a cooling tower system. The system has a basin of cooling water, a fan, a mist eliminator (sometimes called outlet louvers), wetfill, and inlet louvers. The improvement comprises: an acid treatment subsystem for the cooling water. a water softener subsystem for the cooling water; and a drift control system for adjusting the loss of cooling water to atmosphere.

This system is operated to achieve a maximum Langelier Saturation Index (LSI) of +2. But this depends on the quality of the incoming water. The object is to control the pH and i The Langelier Saturation Index (LSI) is an equilibrium model derived from the theoretical

hardness of the cooling water so as to minimize scaling and salting out of minerals while reducing the amount of water that has to be bled from the system. Preferably, pH is kept above about the mid 7's and hardness is kept below 650 ppm. It is possible to reduce bleed to zero with this system.

The drift control system comprises one or more of the following elements: a fan speed controller. a fan operating time timer. adjustment of inlet louver spacing so that bleed is minimized. adjustment of outlet louver spacing so that bleed is minimized. adjustment of weffill spacing so that bleed is minimized. adjustment of mist eliminator spacing so that bleed is minimized. an inlet spray subsystem adapted to spray the inlet louvers with water; and an outlet spray subsystem adapted to spray the mist eliminators with water.

Water softening may be accomplished by replacing hardness cations with sodium cation or with hydrogen cation. Optionally a filtration subsystem for the cooling water may be included.

This invention also provides an improved method of operating this improved cooling tower system. The improved method comprising the steps of: reducing the concentration of carbonate ions in the cooling water. reducing the hardness of the cooling water; and controlling drift. concept of saturation and provides an indicator of the degree of saturation of water with respect to calcium carbonate. It can be shown that the LSI approximates the base 10 logarithm of the calcite saturation level. The LSI approaches the concept of saturation using pH as a main variable and can be interpreted as the pH change required to bring water to equilibrium. TDS, alkalinity, hardness and temperature are additional variables.

For more information see http ://www. corrosion-doctors. org/NaturalWaters/Langelier. htm

Again, the system is operated to achieve a maxium Langelier scaling index of +2, dependin on the quality of the incoming water. The object is to control the pH and hardness of the cooling water so as to minimize scaling and salting out of minerals while reducing the amount of water that has to be bled from the system. So preferably, pH is kept above about the mid 7's and hardness is kept below 650 ppm. It is possible to reduce bleed to zero with this system.

The drift control step comprises one or more of the following steps: adjusting the operating speed of the fan. adjusting the operation time of the fan. adjusting spacing of the inlet louvers to minimize bleed. adjusting spacing between the outlet louvers to minimize bleed. adjusting spacing between blocks or sheets of wetfill to minimize bleed. adjusting spacing between mist eliminators to minimize bleed. spraying the inlet louvers with cooling water; and spraying the mist eliminators with water.

Preferably carbonate ion reduction is accomplished by addition of acid. Alternatively, carbonate ion reduction may be accomplished by hydrogen cation exchange. Hardness reduction may be accomplished by replacement of hardness cations with sodium cations or with hydrogen cation. Optionally, the cooling water my be filtered.

An appreciation of the other aims and objectives of the present invention and a more complete and comprehensive understanding of it may be achieved by referring to the accompanying drawings and studying the following description of the best mode of carrying out the invention.

Brief Description of Drawings Figure 1 is a partially cut away drawing of a prior art cooling tower illustrating some of the working components.

Figure 2 is a partially cut away drawing of one variety of a prior art cooling tower illustrating vertical cross flow.

Figure 3 is a partially cut away drawing of another variety of a prior art cooling tower illustrating counter flow.

Figure 4 is a partially cut away drawing of another variety of a prior art cooling tower another variety of cross flow.

Figure 5 is a schematic drawing illustrating the inner workings of a typical prior art cooling tower.

Figure 6 is a flow diagram illustrating the water saving cooling tower of this invention. For clarity the fan, wetfill, inlet and outlet louvers, drift eliminators and circulation of cooling water to the heat load are not included.

Figure 7 is a block diagram of the water savings cooling tower of this invention. For clarity the wetfill, inlet and outlet louvers and drift eliminators are not included.

Figure 8A illustrates spraying of the inlet louvers and mist eliminators (outlet louvers) with water from the sump.

Figure 8B illustrates spraying of the inlet louvers and mist eliminators (outlet louvers) with tower water being returned from the heat load.

Figure 8C illustrates spraying of the inlet louvers and mist eliminators (outlet louvers) with fresh (inlet) water.

Figure 9 illustrates controlling the operation of the fan with a speed controller and/or a timer.

Figure 10 illustrates inlet louver spacing.

Figure 11 illustrates weffill spacing.

Figure 11 illustrates mist eliminator spacing.

Best Mode for Carrying Out Invention While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto.

Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.

Cooling towers 10 such as atmospheric towers, induced draft towers, forced-draft towers, and natural draft towers all have a number of parts in common. See Figures 1 and 5.

Sump 14: The cooling tower sump 14 is the collection basin from where water is drawn and circulated to the system.

Screens 18: Cooling tower screens 18 are designed to prevent large debris from going through the pump 22, circulating through the system and potentially reducing water flow which will reduce heat exchange capacity.

Pumps 22: Circulating water pumps 22 move the water through the system, where heat is removed from the process, and return the water to the tower 10.

Tower Distribution System 26: Tower distribution is accomplished through nozzles 32 and sprays 34 at the distribution deck 26.

Tower Fill 30: Tower fill, weffill or packing 30 is made up of splash bars or plastic media which break up the water particles within the tower so intimate air and water contact is accomplished. Wetfill 30 is commercially available. Several varieties are CF-750, CF-1200 and CF-1900, manufactured by Brentwood Industries of Reading, Pennsylvania. Another variety is PLASdek @, manufactured by Munters Corporation, Fort Myers Florida.

Mist Eliminators 38: Mist eliminators or outlet louvers 38 are used to reduce the amount of water lost due to entrainment in the humid hot air leaving the tower.

Inlet Louvers 46: Louvers 46 on the inlet side direct the flow of air into the tower and can reduce water splashing outside the tower.

Fan 58: A fan 58 is needed in most systems to move air through the tower 10, and thus past the fill 30 and mist eliminators 38 so that heat exchange with atmospheric air is efficiently accomplished with controlled water droplets or water loss to atmosphere (drift).

Figures 2-4 illustrate varieties of cooling towers 10 with fans 58 in different locations in order to move the air in different directions.

The way prior art cooling towers work is as follows. Water absorbs heat from the heat load 62 and is pumped into the top 26 of the cooling tower 10. The heated water percolates down over the wet fill 30. Air is moved over the wetfill 30 so that the water is cooled and the heat is removed to atmosphere. The cooled water collects in the sump 14 where it is pumped out to extract heat from the heat load 62 again. Water lost to atmosphere (drift) is controlled to some extent by the exact way the water is introduced into the fill. In other words, whether sprayed or trickled. If sprayed, how many nozzles, and the water pressure and spray pattern. In order to further reduce or control drift there are mist eliminators 38 in the air outlet from the wetfill 30. Air circulation through the tower is controlled by fan 58 and the passage through the tower interior 10.

Figures 6 and 7 illustrate an open spray cooling tower system 70 of this invention. Cooling water is maintained in the sump 14 at a certain level via a float valve 74. As water is lost through evaporation into the atmosphere, make up water is added through line A. Water additions are monitored via a special water meter/contact/timer 78. The water meter portion of this controller 78 keeps track of the amount of water added to the system. The contact/timer portion of this controller periodically opens the inlet solenoid valve 82 for a specific period of time so that inlet water is passed via line B to one or more water softeners 86 and from thence back to the sump 14.

After a specific volume of water has been added to the tower 70, the water meter/contact/timer 78 allows the proper amount of soft water additions to be introduced into the sump 14 via solenoid valve 82 based on the quality of the make up water and the degree of mineral build up designed for the system. The system is operated to achieve the pre-calculated Langelier Scale Index. Water softening can be accomplished by cation or hydrogen ion exchange. While softening is applied to the inlet water, it will be appreciated that the net effect is to soften the cooling water in the sump 14.

Water is sprayed over the inlet louvers 46 and mist eliminators 38. The water may come from the return piping 26 to the top of the tower 70, from a separate pump 90 which withdraws water from the sump 14, or from an external source of water. Figure 8A illustrates a spray manifold 94 for spraying the inlet louvers 46 and a spray manifold 98 for spraying the mist eliminators 38 with water from the sump 14. Figure 8B illustrates a spray

manifold 94 for spraying the inlet louvers 46 and a spray manifold 98 for spraying the mist eliminators 38 with tower water being returned from the heat load. Figure 8C illustrates a spray manifold 94 for spraying the inlet louvers 46 and a spray manifold 98 for spraying the mist eliminators 38 with fresh (inlet) water.

Some water is constantly withdrawn from the sump through line D and passed by a pH probe 102 and a total dissolved solids (TDS) sensor 106. If the pH rises above the pre- designed value, acid is pumped into the sump 14 through line E via conventional technology. The pre-designed pH value depending on the design of the tower 70, the quality of the incoming water and the desired Langelier scaling index. A typical pH value might be, for example, 7.8. However, if hydrogen ion softening is used then the pH probe 102 and acid additions may not be needed. In this case, the hydrogen component of softening is controlled by the pH probe with a tie in to an adjunct solenoid valve controling softener operation.

If the TDS rises above a pre-designed value, corrosion inhibitor is pumped into the sump 14 via conventional technology and the bleed solenoid valve 110 is opened and some water is bled off. Corrosion inhibitors may be selected from organic polymers, phosphates, molybdates, azoles, zinc compounds and silicates. The exact compound employed is dictated by the metallurgy and rules of local agencies regarding what compounds can be discharged from the system 70. There is a water meter 114 on the bleed line F.

Subtracting bleed (outlet) water from make up (inlet) water provides the water lost to evaporation. Drift losses are very small in comparison to other losses : usually less than 0.2% of circulation rate. This is represented by the following equation: Make up = Evaporation + Bleed + Drift This system can be operated so efficiently that no water needs to be bled off.

Three methods of controlling drift have already been mentioned. These are spraying the inlet louvers 46, mist eliminators 38 and weffill 30 with water from the tower system or another source. Operating time, spray pressure and spray pattern are all typically adjustable. Other methods of controlling drift are: 1. Adjusting the operating speed of the fan 58. A speed controller 118, as illustrated in Figure 9, is needed.

2. Adjusting the operation time of the fan 58. A timer 122, as illustrated in Figure 9, is needed. This may be alone or in addition to the speed controller 118.

3. Adjusting the spacing between inlet louvers 46. This is illustrated in Figure 10.

4. Adjusting the spacing between blocks or sheets of weffill 30. This is illustrated in Figure 11.

5. Adjusting the spacing between the mist eliminators 38. This is illustrated in Figure 12.

In practice, what must be done is to design and build a tower 70 or modify an existing tower 70 in which all these drift control parameters are adjustable then, during a preliminary set up period, adjust them so that drift is controlled. The objective of controlling drift is to minimize scale and bleed.

In addition, during this set up period all other operating parameters, such as the periodicity of water softening, and water treatment, in response to pH (alkalinity) and TDS readings, are adjusted so that the concentration of CaCO3, and thus deposits of limestone throughout the system 70, are minimized or eliminated; and so that the TDS are kept at desired values. Eliminating white rust deposits on galvanized steel is accomplished by controlling alkalinity, hardness and chemical passivation.

As will be appreciated by those most familiar with the art to which this invention pertains, set up of a system 70 in accordance with this invention can be conducted by making initial settings of the equipment, monitoring the condition of the cooling water over time and making adjustments to the settings as indicated until optimal control of the cooling water is achieved. In most cases this will necessitate setting various controls, meters and valves and reading various gages. As an alternative, as indicated in Figure 7, lines can be run from all strategic valves, meters and gages to a central automation control unit 126. Such a unit can be programmed, via well known computer automation techniques, to make operation of the system 70 automatic. It is even possible to download data from the controller 126 via a modem to a remote computer, again via will known computer techniques.

Figures 6 and 7 also include a number of shut off valves, which have not been described in detail. The purpose of these valves is to enable maintenance of portions of the system 70

and equipment replacement without the need to completely shut down and drain the entire system 70.

Figure 7 also illustrates that the cooling water can, optionally, be filtered via another pump 130, with appropriate filter 134 to remove airborne dust sized particles to 5 micron size.

The following reference numerals are used on Figures 1 through 12: 10 prior art cooling towers 14 sump 18 screen 22 tower pump 26 water distribution deck 30 wetfill 32 spray nozzle 34 water spray 38 mist eliminator 46 inlet louver 58 fan 62 heat load 70 cooling tower of this invention 74 float valve 78 water meter/contact timer 82 solenoid valve to softening system 86 water softener 94 inlet louver spray manifold

98 mist eliminator spray manifold 102 pH probe 106 TDS sensor 110 outlet or bleed solenoid valve 114 outlet or bleed water meter 118 fan speed controller 122 fan timer 126 automation controller 130 filter pump 134 filter What has been described above is a water treatment system or process for use in open spray evaporative water systems 70 such as Cooling Towers, Fluid Coolers, Evaporative Condensers and other open spray water systems.

The new ideas incorporated in this system 70 reduce bleed water consumption (e. g. discharge to the sanitary sewer or storm drain) to low values and, if desired, to zero. As a side benefit, white rust formation on new galvanized steel metal surfaces can be minimized by maintaining alkalinity and water hardness less than approximately 300 ppm. The hardness level is known to inhibit white rust. However, chemical passivation treatment is also required.

The new system 70 saves significant bleed water as well as prevents mineral scaling in heat exchangers, Elements of this new water saving system 70 include: 1. Alkalinity reduction to minimize or exclude carbonate ions-which is the most common anion in mineral scale-such as calcium carbonate.

Chemical control is achieved by using acid water treatment and/or hydrogen cation exchange.

2. Hardness reduction via cation type water softeners to reduce hardness cations such as calcium-which is the most common cation in mineral scale-such as calcium carbonate.

Sodium softening removes hardness. Hydrogen softening removes hardness and reduces alkalinity.

Control of amount of hardness removal is achieved by a new development using water meter/contact/timer 78 which controls the softening of some make up water via a solenoid valve 82 after a specific volume of un-softened water has passed through the water meter/contact/timer 78.

3. Tower water drift loss increase via controlled conditions to provide a small tower water mineral turnover consistent with tower water chemistry, design capacity of the tower 70 and the surrounding areas which receive drift.

Drift loss increase is innovatively achieved by changing the operating characteristic of the tower by one of several means. These include : A. Tower fan 58 speed increase or operating the fan 58 for longer periods of time than "normal" B. Changing spacing in mist eliminators 38 and/or wetfill 30 and/or inlet louvers 46-all of which affect drift losses C. Spraying the exterior of the inlet louvers 46 & mist eliminators 38 with tower water or other water which affects drift loss & which prevents salt buildup on louvers 46, wetfill 30 or eliminators 38. These areas tend to build up salts due to wetting & drying.

Thus, the present invention 70 has been described herein with reference to a particular embodiment for a particular application. Those having ordinary skill in the art and access to the present teachings will recognize additional modifications, applications and embodiments within the scope thereof.

It is therefore intended by the appended claims to cover any and all such applications, modifications and embodiments within the scope of the present invention.