TowerKlean® Cooling Water Treatment System
 

Water is the most common medium for removing heat from industrial equipment. The heat transfer capabilities of water are efficient and effective. To further utilize the economics of water cooling, the common practice is to recycle it through the use of a cooling tower. In a cooling tower, the water is exposed to a high velocity of air with the water being spread over a large surface area. The natural evaporation provides the cooling necessary to reuse the water.

As water evaporates, the naturally occurring minerals in the water concentrate. These minerals and contaminants will eventually reach a concentration where they will cause problems and interfere with the performance of both the tower and the cooling system, itself.

The most common and noticeable of these problems is the formation of scale although biological fouling and corrosion can be equally troublesome. In the past, these problems were controlled by the addition of chemicals to the water. Chelaters and complexers were added to control the formation of scale by increasing the solubility of the hardness forming ions of calcium and magnesium, biocides were added to control algae and fungi and corrosion inhibitors were added to protect the equipment.

Through a unique process developed in the mid 1980’s this chemical conditioning is no longer necessary. The discovery involved the galvanic reaction that results when water comes in contact with a bimetallic medium. Research and development of the discovery revealed that a high purity alloy of copper and zinc, in the proper ratio, would alter the oxidation/reduction potential (ORP) of water. This reaction is as common and easily understood as the rusting of iron. All that is really taking place is an exchange of electrons. The same principle applies to the function of any battery. Two dissimilar metals are submerged in an electrolyte and a flow of electrons is created.

When water used in cooling towers is exposed to the reaction medium, this flow of electrons performs several key functions in the control and conditioning of the water. First, is the alteration of the crystalline structure of the scale forming compounds. The most common of these is a form of calcium carbonate called calcite. Calcium is present in nearly all feed waters. When combined with carbon dioxide dissolved from the air and when exposed to heat, this calcite is deposited in the heat exchangers, pipes, pumps, reservoirs and towers used for water cooling.

1.
The calcite is a coarse crystalline material that will continue to grow upon itself until a thick layer of scale is formed. Left uncontrolled this scale can totally foul a heat exchanger. Whether this level of fouling occurs or not, a 0.1” thick deposit will reduce the heat transfer ability by 40%.

When water, containing scale forming levels of calcium is processed by the TowerKlean® system several unique things happen. The ORP is severely affected at the surface of the media and as a result of the electron flow between the copper and zinc, a small amount of zinc ions are sacrificed. These zinc ions, in conjunction with the ORP shock at the surface of the media, play key roles in controlling scale, biological fouling and corrosion.

Within the TowerKlean® reaction column, zinc is sacrificed at a small level. This level is, however, sufficient to perform several key functions. First and probably most notable, the zinc serves as a crystal modifier. Normally, on saturation, calcium hardness will combine with alkalinity (carbonate and bicarbonate) to form the calcite crystal structure of calcium carbonate (CaCO3). In this form, hard scale is deposited on surfaces within the cooling system, beginning in the hottest zones. The zinc ions in the water alter the formation of the calcium carbonate crystal and force it into a different crystalline mineral shape. This mineral is called aragonite. The aragonite crystal is precipitated from the water and remains as a filterable solid, which is then removed with the TowerKlean® filter.

After conditioning with the medium and the subsequent filtration, analyses indicate that the water also attacks the calcium hardness that exists as old deposits. The crystal modification continues to take place causing the old scale to break down and slough off. This material is also removed by the filtration with the exception of some larger particles that may collect in quiet areas of the reservoir.

The next problem area in cooling towers involves the control of biofouling. The medium controls microorganisms in two ways. First, is due to a result of the oxidation reduction potential (ORP) change. The exchange of electrons at the surface of the media sets up an ORP shock that most microorganisms cannot survive. Second, the zinc that is released by the reactions is toxic to both algae and bacteria. Finally, the pH elevation that takes place creates a level that is toxic to bacterial strains such as the Legionella Pneumophilla that is responsible for Legionnaires disease.

Finally, cooling water can contribute to corrosion of metallic surfaces. With increased conductivity due to evaporative water loss, elevated temperatures, high levels of dissolved oxygen and low pH resulting from dissolved carbon dioxide and decomposition of organic material, conditions are ideal for corrosion. The TowerKlean® system protects metallic surfaces by elevating the pH to a non-corrosive range, controlling biological fouling which leads to the generation of organic acids, reducing the conductivity of the water and depositing a corrosion inhibiting film of zinc based compounds.

2.
These areas of control are the same that chemical manufacturers address in providing chemical additives to the water. Until now, the addition of chemicals has been considered the best available technology for cooling systems. Best available, however, does not mean that the process is totally effective or even desirable. Cooling systems can only tolerate a certain level of total dissolved solids. Once that level has been reached, a portion of the water must be blown down and discharged. During this blow down, contaminants are sent down the drain along with a significant portion of the conditioning chemicals. The chemical level must then be replaced.

These chemicals pose their own environmental concerns. The biocides, inhibitors and scale control agents are sent down the drain. In some areas the discharge of these chemicals is prohibited, especially when the discharge is to the surface or ground waters. The high levels of phosphates and biocides pose discharge hazards. In addition, approximately 2% of the total water loss is due to the mist from the cooling tower, itself. This results in non-point source chemical discharges that are coming under close scrutiny.

Next is the expense of chemical usage. Because of the high cost, attempts are often made to minimize their use. This situation leads to inadequate doses of chemical treatment and their related problems. If insufficient dosage is experienced, scale forms, algae blooms occur and corrosion is experienced. When that happens, maintenance time is increased and damage may occur to the equipment.

Many chemical suppliers offer to provide regular monitoring and even make the appropriate adjustments to the feed pumps, themselves. This is an undesirable situation because the end user loses control of the use and expense of the product. Finally, the chemical treatment is seldom 100% effective. Constant monitoring and adjustment is required, over usage is expensive and wasteful and under usage results in failures that are not corrected when the readjustment is made. Scale deposits remain until a cleaning operation is performed.

These effects are eliminated with the TowerKlean® system. Once the system is in place, scale does not occur. In fact, the water conditioning performed by the system will remain in the water and existing scale is attacked. The crystal modifying effect of the conditioned water takes place on old deposits and slowly but surely the scale begins to slough off at the same time that new scale is prevented.

The solution behind the TowerKlean® process is the media and how it is used. The key to successful operation is maintaining a sufficient surface area and exposing the water to this surface continuously. TowerKlean® systems are designed to recirculate the water so the volume is processed every 90 minutes. By doing this, water conditioning is maintained.

3. The TowerKlean system works like this:
Water is drawn from the cooling reservoir into a coarse basket strainer. The strainer contains a basket designed to protect the pump from debris or foreign material that might result in damage.

Next is the self-priming centrifugal pump. This pump transfers the water to the filter chamber that is loaded with a single grade sand media. The filter removes general dirt and debris, along with the precipitated calcium carbonate particles. As pressure increases across the media bed, the filter will backwash automatically on pressure differential. This backwash is also initiated by a time interval from the control panel. The backwash on the TowerKlean system serves several functions.

First, the backwash is necessary to purge the system of accumulated dissolved solids. As water evaporates, dissolved solids remain. It is necessary to remove these solids to prevent concentrations that can lead to corrosion, scaling and other problems. Next, the backwash keeps the filter clean and maintains flow rates. Finally, the precipitated calcium carbonate particles (aragonite crystals) must be removed to prevent their reversion to calcite. This condition can result in cementation of the sand and lead to system failure.

Following filtration, the water is processed by the reaction media. The media bed is fluidized in an up-flow manner. Each patented TowerKlean® reaction column is designed to handle approximately 20 gallons per minute of flow. The design provides media fluidization in the lower reaction chamber while the upper portion of the column is expanded resulting in a flow velocity reduction of approximately 50%. This is necessary to insure that media is not lost back to the reservoir.

Once the water is processed it is returned to the cooling reservoir. Flow is equalized by using a bypass line and flow adjustment valves. The process is continuous and is designed to turn the volume of water within the system every 90 minutes. The self contained pump, filter and reaction column(s) do not interfere with the cooling system and it is unnecessary to treat your entire system at the process flow rate. TowerKlean® water is clean, clear and free of debris and dirt, built around a filter is designed for cooling systems.

In comparing the TowerKlean® system to other control options it must be noted that no other system addresses all of the water treatment needs in cooling tower applications like the TowerKlean®. Chemical controls must use a variety of additives to condition the water against the effects of scale, corrosion and biofouling. Ozone systems are only marginally effective against scale and can contribute to increased corrosion. In addition, they are expensive to purchase and maintain. Magnetic devices are virtually ineffective.

4.
The TowerKlean® system provides the most cost effective package while outperforming any other system on the market. The systems offer superior reliability with no treatment chemicals, either in the system or the blowdown water. The water is safe to discharge to the sewer or to the surface waters.

The equipment is simple, performance is consistent and the media is efficient, effective and recyclable.

The TowerKlean® system represents the only, non-chemical total replacement for chemical water conditioning of cooling towers.

To select the proper model of TowerKlean® contact TowerKlean LLC at
(248) 666-9200, fax at (248) 666-9202.

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