Drug – bio-affecting and body treating compositions – Inorganic active ingredient containing – Elemental sulfur or compound thereof
Reexamination Certificate
1999-11-17
2001-10-23
Pryor, Alton (Department: 1616)
Drug, bio-affecting and body treating compositions
Inorganic active ingredient containing
Elemental sulfur or compound thereof
C424S615000, C424S665000, C424S722000, C424S723000
Reexamination Certificate
active
06306441
ABSTRACT:
BACKGROUND
Bromine-based biocides have proven biocidal advantages over chlorination-dechlorination for the microbiological control of cooling waters and disinfection of waste treatment systems. The water treatment industry recognizes these advantages to be cost-effective control at higher pH values, almost no loss in biocidal activity in the presence of ammonia, and effective control of bacteria, algae and mollusks.
A common way of introducing bromine based biocides into a water system is through the use of aqueous NaBr in conjunction with NaOCl bleach. The user feeds both materials to a common point whereupon the NaOCl oxidizes the bromide ion to HOBr/OBr
−
. This activated solution is then introduced directly into the water system to be treated. The feeding of the two liquids in this fashion is necessary because the HOBr/OBr
−
mixture is unstable and has to be generated on-site just prior to its introduction to the water. Furthermore, the feeding, and metering of two liquids is cumbersome, especially as the system has to be designed to allow time for the activation of bromide ion to occur. Consequently many biocide users have expressed the need for a single-feed, bromine-based biocide. Molecular bromine chloride is deemed to meet these demands. It is a liquid at room temperature and can be fed directly to the water system, where immediate hydrolysis occurs to yield HOBr.
BrCl+H
2
O→HOBr+HCl
Bromine chloride is a fuming, red liquid or gas, with a boiling point of 5° C., and a vapor pressure of 1800 mm at 25° C. It corrodes most metals in the presence of water.
It can be seen that certain characteristics of bromine chloride—especially its corrosiveness, high vapor pressure and fuming tendencies—necessitate care and skill in its handling and use.
An economically acceptable way of stabilizing high concentrations of aqueous solutions of bromine chloride is described in U.S. Pat. No. 5,141,652 to Moore, et al. The solution is prepared from bromine chloride, water and a halide salt or hydrohalic acid. These solutions were found to decompose at a rate of less than 30% per year and in cases of high halide salt concentration, less than 5% per year. Moreover, solutions containing the equivalent of 15% elemental bromine could be prepared. Unfortunately, the relatively high acidity of these solutions and their tendency to be corrosive and fuming impose limitations on their commercial acceptance.
The commonly-owned copending continued prosecution application referred to at the out-set describes, inter alia, a new process of forming concentrated aqueous solutions of biocidally active bromine and in so doing, provides novel and eminently useful concentrated aqueous biocidal solutions of bromine chloride. Such solutions are formed by a process which comprises mixing (a) bromine chloride with (b) an aqueous solution of alkali metal salt of sulfamic acid (preferably the sodium salt), the resulting solution having a pH of at least about 7, e.g., in the range of 7 to about 14, and preferably above 7 to about 14. Most preferably the pH is in the range of about 13.0 to about 13.7. The amounts of (a) and (b) used are such that (i) the content of active bromine in the solution is at least 100,000 ppm (wt/wt) and (ii) the atom ratio of nitrogen to active bromine from (a) and (b) is greater than 0.93, and preferably is greater than 1.
SUMMARY OF THE INVENTION
One objective of this invention is to enable the process of the commonly-owned copending application to be carried out not only in a commercially-feasible manner, but in addition, in an exceptionally efficient manner on a continuous basis. Other objectives may appear hereinafter.
In one of its embodiments this invention provides a process of producing a concentrated liquid biocide composition which process comprises:
A) continuously feeding into mixing apparatus (i) bromine chloride and (ii) an aqueous solution of alkali metal salt of sulfamic acid (preferably a sodium salt of sulfamic acid), proportioned to produce an aqueous product having an active bromine content of at least 100,000 ppm (wt/wt), and an atom ratio of nitrogen to active bromine from (i) and (ii) greater than 0.93 (preferably greater than 1); and
B) withdrawing said product from said mixing apparatus at a rate sufficient to enable the continuous feeding in A) to be maintained.
In other embodiments, the bromine chloride is continuously formed from equimolar amounts of bromine and chlorine, and at least a portion of the bromine chloride being continuously produced is used as the continuous feed of bromine chloride in step A) above. Thus in plant facilities where bromine chloride is required or desired for use(s) in addition to that required to maintain the continuous feed of (i) in step A) above, the continuous production of the bromine chloride can be scaled up to serve all such uses.
A preferred embodiment includes, in addition to steps A) and B) as described above, the following concurrent operation, namely, continuously, but alternately, withdrawing from at least one and then from at least one other of at least two reaction vessels, an aqueous solution of alkali metal salt of sulfamic acid at a rate that maintains said stream of (ii) in A), and during the time the solution is being withdrawn from said at least one of at least two reaction vessels, forming additional aqueous solution of alkali metal salt of sulfamic acid in said at least one other of at least two reaction vessels from which solution is not then being withdrawn. In this way, aqueous alkali metal sulfamate solution can be continuously withdrawn from one or more tanks (“Tank(s) I”) to serve as the continuous feed of (ii) in A), while forming more of such solution in one or more other tanks (“Tank(s) II”), so that when Tank(s) I is/are depleted, the system is switched to Tank(s) II which then serve(s) as the supply for the continuous feed of (ii) in A) until depleted, and by that time more of such solution has been formed in Tank(s) I. Thus by alternating the supply and the production from one tank (or group of tanks) to another tank (or group of tanks) and switching back and forth between the filled tanks as the supply, the continuous feed of the aqueous alkali metal sulfamate solution can be maintained without material interruption. A particularly preferred embodiment of this invention is a process which comprises:
A) continuously feeding into mixing apparatus (i) a bromine chloride stream identified below in C), and (ii) a separate feed stream of an aqueous solution of alkali metal salt of sulfamic acid identified below in D), in proportions that produce an aqueous product having an active bromine content of at least 100,000 ppm (wt/wt), and an atom ratio of nitrogen to active bromine from (i) and (ii) greater than 0.93;
B) withdrawing the aqueous product from the mixing apparatus at a rate sufficient to enable the continuous feeding in A) to be maintained;
C) continuously contacting bromine and chlorine in a vessel in equimolar quantities such that bromine chloride is produced, and continuously withdrawing from this vessel a bromine chloride product stream at a rate that maintains the feed of (i) in A), at least a portion of this bromine chloride product stream constituting the bromine chloride stream (i) of A); and
D) continuously, but alternately, withdrawing from at least one and then from at least one other of at least two reaction vessels, an aqueous solution of alkali metal salt of sulfamic acid at a rate that maintains the stream of (ii) in A), and during the time the solution is being withdrawn from at least one of the reaction vessels, forming additional aqueous solution of alkali metal salt of sulfamic acid in at least one other of the reaction vessels from which solution is not then being withdrawn.
The above and other embodiments and features of this invention will be still further apparent from the ensuing description, the accompanying drawing, and/or the appended claims.
REFERENCES:
patent: 3152073 (1964-10-01), Morton
patent: 3170883 (1965-02-01), Owen et al.
patent
Moore, Jr. Robert M.
Wilson, Jr. R. Woodrow
Albemarle Corporation
Pryor Alton
Spielman, Jr. E. E.
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