Apparatus and process for water conditioning
a technology of apparatus and water conditioning, applied in the field of apparatus and process for water conditioning, can solve the problems of reducing the quality of the water in the system, unsuitable for continued use, and more difficult to treat, so as to reduce the amount of blowdown required, reduce the level of potentially scaling metal ions, and effectively control the effect of scale build-up
Inactive Publication Date: 2010-02-04
CHEMETICS INT
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Benefits of technology
[0026]The present invention is an improved water conditioning process that integrates chemical treatment and physical operations to maintain scale inhibition while reducing the amount of blow-down required from water systems. The process involves combinations of buffers and conditioners matched to effectively control scale build-up in the system and also to remove a portion of the potentially scaling metal ion as precipitated solid salts in a side-stream. The return of side-stream treated water containing lowered levels of potentially scaling metal ions reduces the need for blow-down from the system to prevent scaling.
[0027]The buffers are selected to have the correct balance of properties such that they are capable of binding metal ions in solution as soluble complexes to prevent scaling in the system and subsequently rapidly release the metal ions, e.g. calcium and / or magnesium in the soluble complexes for reaction with the conditioners in the side-stream. Additional desirable properties for the buffers may include positive impact on the characteristics of a precipitated fluid bed formed when the soluble complex is broken, low environmental toxicity and low impact on corrosion of metal parts in the system.
[0028]The conditioners are selected to have the correct balance of properties such that they are capable of rapidly breaking the soluble buffer-metal ion complexes and are also capable of rapidly forming precipitated salts of the metal ions which can be removed as solids from the side-stream. Additional desirable properties for the conditioners may include positive impact on the characteristics of the precipitated fluid formed when the soluble complex is broken. For example, the solids formed may be more fluid due to the use of the conditioner or the solids may contain less water thereby generating less solids.
Problems solved by technology
These concentration processes can reduce the quality of the water in the system to the point where it is unsuitable for continued use.
Some of the problems made more difficult to treat due to reduced water quality caused by concentration processes may include corrosion, microbiological growth and fouling due to sedimentation of preformed insoluble components (mud, silt and some insoluble organic material) introduced into the system and scaling which is the deposition of components precipitated from solution due to concentration processes in the system.
Scale inhibition is often the limiting technology determining how high the concentration process can be operated.
These processes often reduce introduction of components that can cause sedimentation fouling.
Pre-treatment for make-up water for open re-circulating cooling water systems is limited.
In some regions precipitation softening is practiced to some degree for open re-circulating cooling water systems but is not widespread and make-up water from evaporative desalination processes is even more limited.
Complete pre-treatment is not economically viable for most open re-circulating cooling water systems because of the large volumes of water needed.
When un-inhibited scale formation rates become too large even high levels of the threshold inhibitor are ineffective.
Although this is widely applied in open re-circulating cooling water, its use is declining because safety and handling concerns related to concentrated mineral acids make it an undesirable choice in many situations.
Sulfuric acid, the most common acid used, also adds sulfate anions to the system which can cause problems of calcium sulfate scale formation.
Other issues related to mineral acid use involve the potential for severe corrosion problems if overfed.
Binding positively charged metal ions, such as calcium and magnesium, with binding agents in soluble complexes makes them unavailable for reaction with counter ions such as hydroxide, carbonate, bicarbonate or sulfate.
Stoichiometric addition of binding agents has not been practiced in open re-circulating cooling water systems historically due to cost.
Blow-down from the system limits the concentration of these components to acceptable levels.
Adapting these pre-treatment unit operations to side-stream operation has met with limited success.
Their use must be customized to the system and water characteristics of each system and react poorly to operational variability.
For example, although side-stream softening has been used for many years in a number of cooling systems, it is not used frequently because the process can be difficult to control, especially with water sources that have variable constituent chemistry, and the control of cycles of concentration can be difficult in cooling systems, as discussed in a report entitled “Use of Degraded Water Sources as Cooling Water in Power Plants,” dated October, 2003, prepared for the California Energy Commission, by the Electric Power Research Institute (EPRI).
Precipitation softening typically requires high capital investment, high degrees of operator training to control the processes and the handling of several softening chemicals.
Design ‘scalability’ is an issue both in terms of space requirements and component matching to get proper residence times, settling characteristics etc.
Side-stream reverse osmosis is energy intensive and tends to remove many of the treatment program additives.
When a water containing calcium bicarbonate is heated, as in cooling of air conditioning systems or other equipment, the heat in the heat exchanger, will strip off one molecule of carbon dioxide, rendering the remaining calcium salt to calcium carbonate (limestone), also known as “scale.” This precipitate, the scale, is less soluble in warm water than in cool water and has very poor thermal conductivity, thus reducing heat exchanger efficiency.
Also, water with high concentrations of solids are “wasted” or “blown down” through the system drain to a sewer or ditch, and this must be replaced with makeup water as well.
Various combinations of chemicals and inorganic acids are used, but, for example, the current state-of-the-art limits a cooling system using makeup water with 150 parts per million hardness, to a concentration ratio of less than 6, when the total circulating system has a total maximum alkalinity of 600 ppm.
In addition, the relatively high concentration of sulfuric acid renders it potentially corrosive.
Sulfuric acid can also be hazardous to handle.
Method used
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example 1
[0153]An exemplary embodiment of the apparatus and processes of the present invention is illustrated by a first example with respect to the evaporative cooling system 10 shown schematically in conjunction with an exemplary embodiment of my invention 40 in FIG. 2.
[0154]Confidential and experimental tests of this exemplary embodiment were conducted over a period of weeks on an evaporative cooling system 10 servicing a multi-story office building. Prior to the installation of my invention, the hardness of the evaporative cooling system water at a time shortly before blowdown through the drain 24 was typically about 850 ppm. Following blowdown and the addition of makeup water, the hardness was typically 765 ppm. The highest concentration ratio achieved by the owners in prior treatments was approximately 5.5, and the cooling system's blowdown volume was approximately 20 percent of the evaporation in gallons per day.
[0155]In this first example, my process was enabled using the configurati...
example 2
[0172]An exemplary embodiment of the apparatus and processes of the present invention is illustrated by a second example with respect to the evaporative cooling system 10 shown schematically in FIG. 2. In this example, the controller 80 is installed and connected as described above. The controller is microprocessor based and is configured to receive the pH value measured by the supply line pH monitor for the evaporative cooling water entering the tank, and to cause the conditioner injection pump 64 to inject conditioner from the conditioner supply 62 when the pH is shown by the pH measurement to be less than the 9.2-9.4 optimum range, or about to fall from such range. Subsequent measurements communicated to the controller, indicating the pH has returned to the predetermined desired level, cause the controller to signal the conditioner injection pump to cease injection.
[0173]Similarly, the controller 80 in this exemplary embodiment is configured to receive the pH value measured by th...
example 3
[0177]An exemplary embodiment of the apparatus and processes of the present invention is illustrated by a third example with respect to the evaporative cooling system 10 shown schematically in FIG. 2. In this example, the glycolic acid was replaced by a 10 percent citric acid solution. The substitution worked in the process although it was noted that significantly increased volumes of citric acid and increased chemical handling were required, when compared to glycolic acid.
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Abstract
Conditioning processes and equipment for removing hardness from water circulated in a system. A sidestream is routed to a reactor and back. A buffer is added to the circulated water, in some embodiments in a sidestream exiting the reaction chamber, forming soluble metal complexes with metal ions of the type that cause scaling. A conditioner is added to the sidestream water which breaks the soluble metal ion-buffer complexes and precipitates and accumulates the released metal ion as a solid for accumulation and disposal. In some embodiments a polymer is added, a corrosion inhibitor blend is added and / or pre-mixed with the buffer, and a chlorine generator removes sodium chloride from the buffered sidestream, and makes chlorine gas, hydrogen gas, and sodium hydroxide for use in the process or for disposal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of, and is a continuation in part of, U.S. patent application Ser. No. 11 / 879,656, filed Jul. 17, 2007, which claims the benefit of, and is a continuation in part of, U.S. patent application Ser. No. 11 / 645,875, filed Dec. 27, 2006, which claims the benefit of, and is a continuation in part of, U.S. patent application Ser. No. 11 / 085,337, filed Mar. 21, 2005, now issued as U.S. Pat. No. 7,157,008, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 568,134, filed May 5, 2004, and claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 648,097 filed Jan. 28, 2005, the inventor for all applications being Samuel Rupert Owens.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]The field of the invention is water treatment, or, more specifically, my invention relates to the treatment of water used in systems wherein water is circulated for repeated use, such as evap...
Claims
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IPC IPC(8): C02F5/02C02F5/08C02F5/10C02F101/12
CPCC02F1/20C02F2303/08C02F1/4674C02F1/5236C02F1/56C02F1/66C02F1/683C02F1/76C02F5/02C02F5/04C02F5/08C02F2103/023C02F2209/001C02F2209/003C02F2209/05C02F2209/055C02F2209/06C02F2301/024C02F2301/026C02F2301/043C02F1/4604
InventorOWENS, SAMUEL RUPERT
OwnerCHEMETICS INT