Chemical apparatus and process disinfecting – deodorizing – preser – Chemical reactor – With means applying electromagnetic wave energy or...
Reexamination Certificate
2000-12-12
2004-04-20
Mayekar, Kishor (Department: 1741)
Chemical apparatus and process disinfecting, deodorizing, preser
Chemical reactor
With means applying electromagnetic wave energy or...
C204S176000
Reexamination Certificate
active
06723293
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of Invention
This invention relates generally to systems and methods for treating cooling tower water and, more specifically, to a system and method for treating cooling tower water utilizing a high concentration ozone generation apparatus.
BACKGROUND OF THE INVENTION
Cooling towers are utilized in a variety of processes, such as refrigeration and steam power generation, to remove heat generated by the process. Generally, the cooling tower is part of a system in which water is circulated to a heat exchanger, which is located at a part of a system (for example condenser coils in a large refrigeration system) having heat that needs to be removed. The cooling tower water absorbs the heat at the heat exchanger, and the heated water is then piped to the cooling tower, where it is sprayed into the atmosphere and partially evaporated to liberate the heat, and then recovered and returned at a lower temperature to the system, where the process repeats itself.
Because of minerals, biological contaminants and other matter contained in cooling tower water, cooling tower systems are vulnerable to deposits (scaling), biofouling, and other types of damage. For example, calcium bicarbonate present in water of the type typically used in cooling towers will stay in solution to about 2,000 parts per million (ppm). However, when the water is heated, the calcium bicarbonate becomes calcium carbonate, with carbon dioxide being given off. Calcium carbonate is far less soluble than calcium bicarbonate, and will only stay in solution to about 10 parts per million. (This phenomenon is known as inverse solubility—since it is the reverse of the common principle that solubility generally increases as the temperature of the solution is raised.) Calcium carbonate coming out of solution forms deposits in the system, including in particular at the heat exchanger. The formation of deposits on the heat exchanger will reduce the efficiency of the system.
Biological fouling is also a significant problem. Microbiological contaminants can enter a cooling tower system through the water introduced into the system or by being washed from the air during the cooling process. As these contaminants grow, they can interfere with water flow and/or foul the heat exchanger, restricting heat flow. Such contaminants can also destroy cooling tower lumber. More seriously, such contaminants can be harmful to persons. The most notable example has been outbreaks of Legionnaires' disease, affecting people in hotels, hospitals, office buildings, and other locations, who have come into contact with cooled air from an air conditioning system cooled with contaminated cooling tower water.
A number of methods have been developed to treat cooling tower water, so as to address these and related problems. These generally fall into two categories: chemical addition and bleed-off control. With respect to the former, for example, the problem of hardness has been treated by removing the calcium hardness or scale forming mineral from the water prior to its introduction to the system—with lime soda, ion exchange, or reverse osmosis. Another chemical addition method is to keep scale forming minerals in solution by increasing their solubility through the addition of acid to the water. Still another is to add crystal modifying chemicals that will allow the minerals to precipitate out as a non-adhering sludge instead of as a hard deposit. Biofouling has been addressed with the introduction of chemical biocides into the water, including oxidizing chemicals and industrial poisons. Drawbacks to chemical addition treatment methods include that some of the chemicals used are toxic; a chemical treatment that is effective in dealing with one problem (e.g., increasing alkalinity to control corrosion) can aggravate another problem (e.g., increased alkalinity promotes scaling); and cost.
Bleed-off control, the other basic treatment method, addresses problems associated with impurities in cooling tower water by removing a portion of the water contained in the cooling system so as to reduce the concentration of impurities. However, the increasing cost of water has made it desirable to operate a cooling tower with as little bleed as possible.
In recent years, ozone has attracted attention as a treatment method for cooling tower water. Ozone is an unstable molecule comprised of three atoms of oxygen (O
3
) having a high oxidation potential. Its ability to purify water and air is well known. It was used to purify drinking water by the latter part of the 1800's, and today is used for this purpose by most major U.S. cities. Ozone has also been utilized for the purification of other types of water, including waste water and irrigation water. Still further, ozone has been used for purifying the air in food storage facilities going back at least as far as 1909.
The basic principles underlying the use of ozone generation are well established. Clean, dry air consists of approximately 78 percent nitrogen gas (N
2
), approximately 21 percent oxygen gas (O
2
), and less than one percent of hydrogen (H
2
) and other gasses. When air (referred to as the “feed gas” in this context) is irradiated using either an ultraviolet source or corona discharge (the acceleration of electrons between two electrodes, separated by a dielectric material, to collide with a feed gas passed therebetween), some of the O
2
molecules are split to form two short-lived oxygen atoms. These oxygen atoms combine, almost instantaneously, with uncleaved oxygen molecules to form ozone.
Ozone is not the only product of what is generally referred to herein as an ozonation process; i.e., the irradiation of a feed gas to create ozone and other new compounds. The bombarding of the feed gas with electrons causes the all of the component gasses—and not just the oxygen to rearrange—forming a number of beneficial molecular combinations in addition to ozone. These rearranged molecules include nitrates, nitrites, nitrogen oxides, nitric acid, nitrogen based acids, hydrogen peroxide, hydroperoxide, and hydroxyl radicals (NO, NO
2
, NO
3
, N
2
O, N
2
O
5
, HNO
2
, HNO
3
, O, H, OH, HO
2
, H
2
O
2
).
Ozone and certain of the other atoms and molecules formed as a result of ozonation have a number of beneficial uses in the areas of disinfection and water softening—and are therefore particularly useful in the treatment of cooling tower water.
Ultraviolet radiation is disfavored as a method for generating ozone, due to the inability to produce high quantities of ozone at a relatively low cost in this fashion. As a result, most commercial ozone production is accomplished using a corona discharge type of ozone generator.
However, there are numerous problems with prior art corona discharge ozone generators, and thus limitations on their suitability for use in a system and method for treating cooling tower water. Thus, when the feed gas is passed between the electrodes, water or dust present in the feed gas attach themselves to the dielectric surrounding the cathode. These spots tend to attract electrons, with the result that hot spots are formed on the surface of the dielectric—leading eventually to the burning through of the dielectric and consequent failure of the generation apparatus. In the commercial area, ozone generators require constant servicing and, indeed, rebuilding, because of such problems. In the City of Los Angeles, for example, high concentration ozone generators used to treat the city's drinking water are presently required to be rebuilt after approximately ten days of use—a rate that is plainly undesirable. Moreover, prior art devices do not permit the ready manipulation of the ozonation products, for example to produce more ozone and less nitrogen-containing compounds or more nitrogen-containing products and less ozone.
Still further, prior art systems for treating cooling tower water based on ozonation do not utilize a centrifuge to further assist in the process of removing separated materials, resulting in a less efficient process.
U.S. Pat. No. 4,954,321, i
Mayekar Kishor
Nytrox 1, Inc.
Weiss Harry M.
Weiss Jeffrey
Weiss, Moy & Harris P.C.
LandOfFree
System and method for treating cooling tower water does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with System and method for treating cooling tower water, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and System and method for treating cooling tower water will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3226238