Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using disinfecting or sterilizing substance
Reexamination Certificate
1999-03-31
2001-08-07
McKane, Elizabeth (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using disinfecting or sterilizing substance
C422S006000, C008S107000, C008S137000, C162S001000, C423S500000, C252S187200
Reexamination Certificate
active
06270722
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to water treatment and, more particularly, to stabilized bromine solutions, method of manufacture and uses thereof for biofouling control.
BACKGROUND OF THE INVENTION
Sodium hypochlorite has been widely used in a variety of industrial and recreational water systems to control biofouling. However, sodium hypochlorite is unstable and must be provided in a stabilized form. There are several methods known in the art for stabilizing hypochlorite (See, e.g., U.S. Pat. Nos. 3,328,294 and 3,767,586).
Bromine is preferred over chlorine for use in water treatment because of its lower volatility and better performance at high pH and amine environments. However, like sodium hypochlorite, sodium hypobromite is unstable in typical storage conditions and must therefore also be provided in a stabilized form. U.S. Pat. Nos. 5,683,654 and 5,795,487, as well as the references disclosed therein, teach various methods for stabilizing sodium hypobromite. The '654 and '487 patents disclose batch methods which utilize sodium hypochlorite and sodium bromide as starting materials, followed by the addition of a stabilizer. WO 97/20909 similarly discloses a process which includes a hypobromite formation step followed by a bromine stabilization step. However, a disadvantage associated with this technique is that unstabilized hypobromite is formed in a separate step at a high concentration and pH. It is known that unstabilized hypobromite degrades quickly under such conditions to form bromate, a non-biocidal compound that is very toxic and a suspected carcinogen.
In addition, WO 97/43392 discloses a process that first forms stabilized chlorine compounds and then converts them to stabilized bromine compounds. However, this type of process is limiting because only hypochlorite-releasing compounds can be used as the oxidizing source.
Therefore, because the demand for stabilized bromine solutions is expected to increase in the future due to its advantages over chlorine, there is a need for other cost-effective methods of manufacturing stabilized bromine which can use a wider range of oxidants and produce a higher strength product at higher yield.
Accordingly, it would be desirable to provide a method of making a stabilized bromine solution which can be carried out as a batch or continuous process and which can produce a higher strength product at higher yield. It would also be desirable to develop a method of making a stabilized bromine solution which is flexible and allows a variety of oxidizers to be utilized.
SUMMARY OF THE INVENTION
The stabilized bromine solutions of the present invention are prepared by combining a bromine source and a stabilizer to form a mixture, adding an oxidizer to the mixture, and then adding an alkaline source to adjust the pH of the mixture to at least 13.
The inventive method is economically appealing because it can be carried out as a batch or continuous process and because it produces a high-strength stabilized bromine solution at higher yield. The method of preparation is also flexible and allows for the utilization of a variety of oxidizers.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a method of making stabilized bromine solutions. In accordance with this invention, a bromine source and a stabilizer are combined to form a mixture, an oxidizer is next added to the mixture and then an alkaline source is added to adjust the pH of the mixture to at least 13.
The bromine sources which may be used in the practice of the present invention include hydrobromic acid, bromine chloride, elemental bromine and alkali or alkaline earth metal bromides, such as sodium bromide, potassium bromide and lithium bromide.
The stabilizers which may be employed in this invention have the chemical formula R—NH—R
1
, wherein R and R
1
are selected from the group consisting of R
2
CO, R
2
SO
2
, R
2
CF
2
, R
2
CHF, H, OH and PO(OH)
2
, and R
2
is an alkyl group or an aromatic group. Suitable stabilizers include saccharin, urea, thiourea, creatine, cyanuric acids, alkyl hydantoins, monoethanolamine, diethanolamine, organic sulfonamides, biuret, sulfamic acid, organic sulfamates and melamine. Sulfamic acid is the most preferred stabilizer.
The oxidizers which may be used include chlorine gas, hypochlorous acid, hypochlorite salt, chlorite, chlorate, elemental bromine, bromine chloride, hydrogen peroxide, persulfate, permanganate and peracetic acid. It is believed that other peroxy compounds can also be used in accordance with this invention.
The alkaline source is preferably an alkali or alkaline earth metal hydroxide. Suitable alkaline sources include sodium hydroxide, lithium hydroxide, potassium hydroxide, magnesium hydroxide and calcium hydroxide.
It is preferred that the molar ratio between the bromine source and the stabilizer be in the range of about 0.2 to 5. The molar ratio between the bromine source and the oxidizer should preferably be in the range of about 0.5 to 2.
The method of the present invention is maintained at a temperature of less than 80° F., and preferably in the range of about 40 to 70° F. The pH of the mixture during the oxidizer addition should be kept below about 7. The present invention can be carried out as either a batch or continuous process.
The stabilized bromine solutions which are prepared in accordance with this invention may be used in a wide variety of commercial applications. These applications include, but are not limited to, the use of the stabilized bromine solution: (1) as the bleaching agent in a method for the laundering of soiled garments in which the soiled garments are washed in an aqueous media containing a detergent and a bleaching agent; (2) as the oxidizing agent in a method for the manufacture of cellulosic materials in which cellulosic fibers are bleached; (3) as the oxidizing and biocidal agent in a method for the control of biofouling in a recreational water system in which an oxidizing and biocidal agent is added to control biofouling; (4) as the oxidizing and biocidal agent in a method for the control of biofouling on a hard surface in which an oxidizing and biocidal agent is applied to the surface to control biofouling on the surface; (5) in a method for the control of biofouling occurring on the surfaces of equipment in contact with produced oil field waters; and (6) in a method for controlling biofouling in an aqueous system.
In another embodiment, the invention is a method of preventing biofouling on the surfaces of equipment in contact with an industrial water system. The method comprises adding an effective biofouling controlling amount of a stabilized bromine solution to the water system, wherein the solution is prepared by combining a bromine source and a stabilizer to form a mixture, adding an oxidizer to the mixture, and then adding an alkaline source to adjust the pH of the mixture to at least 13.
The types of industrial water systems in which the stabilized bromine solution may be used to prevent biofouling include, but are not limited to, cooling water systems, sweetwater systems, gas scrubber systems, air washer systems, evaporative condensers, pasteurizers, produce sanitizer streams, fire protection water systems and heat exchanger tubes.
It is preferred that the amount of stabilized bromine solution which is added to the industrial water system be in the range of about 0.1 ppm to about 2000 ppm and preferably in the range of about 0.5 ppm to about 500 ppm, based on available bromine concentration. The stabilized bromine solution can be added to the water system by any conventional method, i.e., by slug, intermittently or continuously.
In another embodiment, the invention is a method of making a stabilized bromine solution comprising the steps of selecting a bromine source, and then adding a stabilizer and an oxidizer to the bromine source to form a mixture, wherein the stabilizer and the oxidizer are alternately added to the mixture in an amount sufficient to maintain the pH of the mixture between about 0 and 6.9, more preferably
Allain Eric J.
Dallmier Anthony W.
McCoy William F.
Myers Eric R.
Yang Shunong
Breininger Thomas M.
Cummings Kelly L.
McKane Elizabeth
Nalco Chemical Company
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