Liquid purification or separation – Processes – Including controlling process in response to a sensed condition
Reexamination Certificate
2002-01-31
2004-02-03
Morrison Hoey, Betsey (Department: 1724)
Liquid purification or separation
Processes
Including controlling process in response to a sensed condition
C210S749000, C210S085000
Reexamination Certificate
active
06685840
ABSTRACT:
FIELD OF INVENTION
This invention is in the field of water treatment products. Specifically, this invention is in the field of water treatment products for use in industrial water systems.
BACKGROUND OF THE INVENTION
Industrial water systems exist so that necessary chemical, mechanical and biological processes can be conducted to reach the desired outcome. Industrial water systems include the following: cooling water systems, including open recirculating, closed and once-through cooling tower water systems; boilers and boiler water systems; petroleum wells, downhole formations, geothermal wells and other oil field applications; mineral process waters including mineral washing, flotation and benefaction; paper mill digesters, washers, bleach plants and white water systems; black liquor evaporators in the pulp industry; gas scrubbers and air washers; continuous casting processes in the metallurgical industry; air conditioning and refrigeration systems; industrial and petroleum process water; indirect contact cooling and heating water, such as pasteurization water; water reclamation and purification systems; membrane filtration water systems; food processing streams (meat, vegetable, sugar beets, sugar cane, grain, poultry, fruit and soybean); and waste treatment systems as well as in clarifiers, liquid-solid applications, municipal sewage treatment and industrial or municipal water systems.
An example of one ubiquitous type of industrial water system is a cooling water system; wherein the cooling water system comprises a cooling tower, heat exchangers, pumps and all necessary piping to move water through the system. Control of a cooling water system is based on balancing the desire to operate the system at the highest concentration cycles possible without incurring detrimental scaling, corrosion, fouling, or microbiological control patterns.
As is the case with many industrial water systems, many cooling water systems use treatment products to control undesirable phenomena such as scaling, corrosion, fouling and microbiological growth. These treatment products include chemical materials such as polymers, phosphates, phosphonates, azoles, zinc, molybdate, biocides, and other materials and are known to people of ordinary skill in the art of cooling water systems.
Treatment products are typically prepared by taking these chemical materials and formulating them into aqueous liquid phase products for distribution to and delivery into a cooling water system. Delivery into a cooling water system can be accomplished by pump feed or edductor feed system or even by manual addition of the treatment product. A cooling water system can be set up to feed treatment product based on either a bleed/feed mechanism where the action of blowdown triggers a chemical feed pump or valve that feeds treatment product; or, in the alternative, the cooling water system feeds treatment product based on timers using a “feeding schedule” or flow meters on the make-up water line trigger the pumping of treatment product based on a certain amount of make-up water being pumped. A limitation of these control methods is that none of these systems measure the treatment product concentration directly online, so if there is a mechanical problem, for example, if a pump fails, a drum empties, or high, low or unknown blowdown occurs, system volume changes or makeup water quality changes; the correct treatment product concentration is not maintained. Because this problem is common, cooling tower systems are typically either overfed with treatment product to ensure the level of treatment product in the system does not drop too low as a result of high variability in product dosage or the treatment product is unknowingly underfed. Both overfeeding and underfeeding of treatment product are undesirable due to cost and performance drawbacks.
One aspect of known control schemes is addition of an inert fluorescent chemical tracer in a known proportion to the active component of the treatment product and feeding this mixture of treatment product and tracer to the cooling water system. Then a fluorometer is used to monitor the fluorescent signal of the inert fluorescent chemical. This technology is commercially available as TRASAR®, which is a registered trademark of Ondeo Nalco Company, Ondeo Nalco Center, 1601 W. Diehl Road, Naperville Ill. 60563, ((630) 305-1000). The fluorescent signal of the inert fluorescent chemical is used to determine how much inert fluorescent tracer is present, and by knowing the amount of inert fluorescent tracer that is present it is possible to determine the amount of treatment product that is present in the cooling tower. If the amount of treatment product that is present is not what is desired then the feed rate of treatment product can be adjusted to provide the desired amount of treatment product.
As water evaporates from a cooling tower, the concentration of undesirable species in the tower increases. Control methods, such as the water conductivity in the tower, may be used to initiate release of water from the tower, in a process known as blowdown. To maintain a constant water volume, additional water having a lower concentration of undesirable species is added to the tower, in a process known as makeup. Blowdown also reduces the amount of inert tracer and treatment chemicals in the system. Decreasing the amount of inert tracer in the system, decreases the fluorescent signal from the inert tracer. When the fluorescent signal from tracer decreases, the tracer control system is set up to feed a fresh mixture of treatment product and inert tracer chemical to compensate for the decrease in inert fluorescent tracer and treatment chemical that was lost in the blowdown.
Another known method of control of product feed to a cooling water system involves the use of another aspect of tracer technology. This involves using a treatment product containing a molecule or polymer that is either inherently fluorescent or that has been “tagged” with a fluorescent moiety. In contrast to the earlier described inert fluorescent tracers, these fluorescent moieties, are not inert, rather, they are supposed to be consumed as they function to treat whatever performance-related condition it is that they are designed to treat. Thus, by measuring the fluorescent signal of the tagged treatment moiety it is possible to determine the amount of consumption of the tagged treatment moiety. By knowing the amount of consumption of the tagged treatment polymer it is possible to use that information to control the feeding of new treatment product containing tagged treatment moieties.
Liquid phase treatment programs have been favored for cooling water treatment because of their relative ease of delivery into a cooling water system and advantages associated with formulating variations of products. Active components can be formulated in the liquid phase and combined with other active components relatively easily. These same advantages of liquid phase product delivery may be offset by other disadvantages associated with delivery and formulation. For example, pump failure due to air lock, loss of prime, or other mechanical reason can lead to insufficient product delivery into a cooling water system. Liquid phase product combinations and concentrations can be limited by inherent raw material incompatibilities such as acid/base behavior or pH dependent solubility. Some combinations of raw materials simply cannot be combined into a desired product formulation. Furthermore, liquid phase products may become unstable with time and temperature, often leading to undesired product component segregation in delivery containers, or worse, sediment and precipitate buildup in delivery tanks and lines. Some formulations are susceptible to microbiological attack and measures must be taken to preclude microbiological growth in a product. These failures can lead to insufficient or undesirable component delivery to the cooling tower system.
One way of circumventing the disadvantages associated with liquid phase product delivery is to deliver products in sol
Breininger Thomas M.
Brumm Margaret M.
Hoey Betsey Morrison
Ondeo Nalco Company
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