Gas separation: processes – Degasification of liquid – Plural successive degassing treatments
Reexamination Certificate
1999-04-27
2001-08-21
Smith, Duane (Department: 1724)
Gas separation: processes
Degasification of liquid
Plural successive degassing treatments
C095S245000, C095S263000, C095S266000, C096S157000, C210S188000, C210S750000
Reexamination Certificate
active
06277175
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to methods and apparatus for removing trihalomethanes and dissolved oxygen from water in order to render the water potable, and more particularly relates to methods and apparatus for continuously removing trihalomethanes and dissolved oxygen from water prior to using the water to make beverages.
2. Description of the Prior Art
In a typical water treatment system for potable water, the water is disinfected with chlorine. The organics present in water can react with chlorine to form trihalomethanes, among other products. The trihalomethanes (THMs) that are formed during chlorine disinfection of water are chloroform (CHCl
3
), bromodichloromethane (CHCl
2
Br), dibromochloromethane (CHClBr
2
) and bromoform (CHBr
3
). These trihalomethanes are known to be carcinogenic in nature. For the water to be potable, the concentration of trihalomethanes in the water must be very low. Currently, the maximum concentration of trihalomethanes in drinking water that is permitted by regulation is 100 &mgr;g/lit (ppb), both in Canada and the United States (Environment Canada and U.S. Safe Drinking Water Act). However, it appears that in the near future this permissible concentration will be reduced further.
In the beverage industry, the concentration of trihalomethanes in the products is maintained at a level well below the value currently regulated by the federal laws. A typical action level for beverages is 80 ppb or lower. Currently the trihalomethanes from the beverage water are removed by adsorption on activated carbon. The activated carbon also removes residual chlorine. However, the lifetime of an activated carbon bed is much greater when it is used only in dechlorination, rather than both dechlorination and trihalomethane adsorption.
When activated carbon is used to remove trihalomethanes, the carbon bed becomes saturated with trihalomethanes quite quickly. The bed can be regenerated by steaming. Depending on the amount of trihalomethanes in the inlet water and the action level of trihalomethanes in the product water, the carbon bed can require frequent steaming. A large amount of steam is needed in each regeneration of the carbon bed. Further, after some definite number of times of regeneration, the whole carbon bed must be replaced by fresh carbon. On the other hand, if the carbon bed is used solely for the removal of merely chlorine, a carbon tower can typically last several years.
Apparatus for the continuous removal of volatile organic halogenated compounds from a liquid such as water are known, for example, from U.S. Pat. Nos. 4,892,664; 5,004,484; 5,470,478; 5,490,941; and Re. 35,074. A batch process for the removal of volatile organic halogenated compounds from a liquid such as water is known, for example, from U.S. Pat. No. 5,389,126, which could be made to be a continuous process. The disclosed apparatus generally addresses environmental concerns and none is disclosed to be employed in the purification of water for use in the preparation of beverages. Likewise, dissolved oxygen removal systems are known, for example, from U.S. Pat. Nos. 4,565,634; 5,383,958; and 5,766,321, however, no such apparatus is disclosed in combination with apparatus for removing volatile organic halogenated compounds from water.
SUMMARY OF THE INVENTION
In order to aid in the understanding of the present invention, it can be stated in essentially summary form that it is directed to methods and apparatus for removing trihalomethanes (THMs) and dissolved oxygen from water.
More specifically, the apparatus of the present invention includes an air stripping container having an upper portion defining a liquid inlet orifice and a lower portion defining a liquid outlet orifice and a blow air orifice. An air outlet is defined through the air stripping container at the upper portion. Disposed within the air stripping container is a first packing material, disposed generally between the liquid inlet orifice and the liquid outlet orifice and supported on a first packing material support plate. An air blower is disposed in fluid connection with blow air orifice, so that air flow can be provided generally upward through the air stripping container and through the first packing material. Liquid having THMs therein is supplied to the upper portion at the liquid inlet orifice by a supply pump. The supplied liquid is distributed generally uniformly over the cross-sectional area of the air stripping container by a liquid distributor, and wall wipers are disposed at intervals along the interior of the air stripping container. In addition, a mist eliminator is provided within the upper portion. The air blower provides air flow generally upward against the flow of liquid having THMs therein whereby at least some THMs are removed from the liquid as THMs undergo a phase change from liquid to gas and are carried upward with the air, and oxygen is dissolved into the liquid from the air.
The apparatus further includes a vacuum degassing container having an upper region defining a vacuum orifice and a liquid inlet aperture, and a lower region defining a liquid outlet aperture. Disposed within the vacuum degassing container generally between the liquid inlet aperture and the liquid outlet aperture is a second packing material, supported on a second packing material support plate. A transfer pump is disposed in fluid connection between the liquid outlet orifice of the air stripping container and the liquid inlet aperture of the vacuum degassing container, for pumping liquid from which at least some THMs have been removed from the air stripping container to the vacuum degassing container. Liquid is then distributed generally uniformly over the cross-sectional area of the upper region of the vacuum degassing container by a second liquid distributor, and a second mist eliminator is disposed within the other region above the second liquid distributor. A vacuum pump is disposed in fluid connection with the vacuum orifice of the vacuum degassing container, providing a partial vacuum within degassing container so that at least some dissolved oxygen can be removed from the liquid flowing generally downward through the vacuum degassing container.
The flow of liquid through the apparatus at a preselected rate can be controlled by a control means connected to an air stripping container liquid level transmitter and a vacuum degassing container liquid level transmitter, the supply pump, and the transfer pump.
Liquid from which at least some THMs and dissolved oxygen has been removed can be dispensed from the vacuum degassing container through an outlet pump disposed in fluid connection with the liquid outlet aperture.
Apparatus according to the present invention operating on water at a temperature of 25° C. and at flow rates of between about 900 and 1900 liters per minute lowered the THM concentration more than an order of magnitude below current standards to less than 3 parts per billion while lowering the dissolved oxygen concentration to about 1 part per million.
The following portion of the specification, taken in conjunction with the drawing, sets forth the preferred embodiment of the present invention. The embodiment of the invention disclosed herein is the best mode contemplated by the inventors for carrying out the invention in a commercial environment, although it should be understood that various modifications can be accomplished within the parameters of the present invention.
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patent: 4352679 (1982-10-01), Notardonato et al.
patent: 4565634 (1986-01-01), Lydersen
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patent: 4892664 (1990-01-01), Miller
patent: 5004484 (1991-04-01), Stirling et al.
patent: 5383958 (1995-01-01), Battaglia
patent: 5389126 (1995-02-01), Baker et al.
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“Tower Packings”, Product Literature, U.S. Stoneware, p. 10
Halder Raghunath
Lister Jonathan
Brinks Hofer Gilson & Lione
Greene Jason M.
Smith Duane
Sterling Berkefeld Inc.
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