Abstract:
A method and system treat contaminated water. In one embodiment, the method comprises treating contaminated water by introducing a methylmorpholine-N-oxide solution to a vessel. The vessel contains the contaminated water and iron oxide. The contaminated water comprises contaminants. In addition, the methylmorpholine-N-oxide solution comprises methylmorpholine-N-oxide and water. The method further comprises contacting the methylmorpholine-N-oxide solution with the contaminated water. In addition, the method comprises treating the contaminated water by allowing the methylmorpholine-N-oxide to react with the contaminants in the presence of the iron oxide.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/650,561 filed on Oct. 12, 2012 which is a non-provisional application that claims the benefit of U.S. Application Ser. No. 61/546,481 filed on Oct. 12, 2011, which are incorporated by reference herein in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to the field of decontamination and more specifically to the field of decontaminating water in vessels using methylmorpholine-N-oxide. 
     Background of the Invention 
     Refineries and petrochemical plants are commonly contaminated with dangerous and reactive sulfur compounds such as H 2 S and pyrophoric iron sulfides. These compounds are typically mitigated or removed as part of decontamination procedures, for instance, prior to vessel (e.g., large storage tanks) entry by individuals. A conventional approach to decontamination is to use hydrogen sulfide scavengers (e.g., liquid scavengers) such as triazine, acrolein, or formaldehyde. Such scavengers may rely on non-oxidative complexation and may be an economical approach for H 2 S mitigation. Liquid scavengers may tie up H 2 S as water-soluble compounds that may be discharged to wastewater treatment facilities. However, such scavengers have drawbacks. For instance, some of the reaction products may not be water-soluble, and some of the treatment chemicals may have associated toxicity or environmental restrictions in certain locations. In addition, only acrolein typically neutralizes pyrophoric iron sulfides. Triazine treatments may raise the pH of effluent streams and as a result, may promote the formation of scales on metal surfaces. Formaldehyde reactions with H 2 S typically produce water insoluble products. Acrolein benefits may be tempered by its toxicity. 
     Other methods have been developed and demonstrated to be effective at oxidizing and eliminating H 2 S and pyrophoric iron sulfide. Such methods include using permanganate (e.g., potassium permanganate), persulfate, sodium nitrite, ozone, hypochlorite, adducts of peroxide such as perborates and percarbonates, and long-chain amine oxides. The oxidizing chemicals may irreversibly convert H 2 S to harmless water soluble forms of sulfur, which may be compatible with effluent discharge. Each of these scavengers and oxidizing compounds (i.e., oxidizing chemicals) have certain drawbacks. For instance, considering the strong oxidizers, persulfates may be corrosive. Hypochlorite may form dangerous chlorine compounds. Ozone and permanganate may require field mixing, and permanganate decontaminations may be further complicated by large amounts of reaction solids that are typically processed at additional cost. Sodium nitrite may produce ammonia as a by-product, which may stall the sulfide oxidation before it is complete. For perborates and percarbonates, field mixing or solutions prepared with stabilizing agents are typically used. Percarbonates, as with permanganate, may also be exothermic in their reaction, which may be particularly dangerous if hydrocarbon vapors are present. It is to be understood that long-chain amine oxides often include large volumes and may produce excessive foam. Permanganate produces solid manganese dioxide as a reaction product that is typically processed at added cost. Treatments using strong oxidizers are typically accomplished in small sequential batches outside the storage vessel in order to control the associated exotherm. As a result, these treatments may involve considerable time and therefore cost. However, these compounds may also react violently with hydrocarbon components that may be present in sour sludge. Strong oxidizers (i.e., permanganate, percarbonate, persulfate) may be quite non-selective in their reaction and may react with many of the hydrocarbon components that may exist in the sludge that typically is contained in storage vessels. As a result, these type treatments are typically accomplished in small sequential batches outside the vessel in time-consuming fashion. 
     Mild oxidizers such as amine oxides and nitrites may also be effective at irreversibly oxidizing hydrogen sulfide to harmless forms of sulfur while having limited or no effect on hydrocarbons, which is unlike the strong oxidizers. Such mild oxidizers may normally be added directly to the storage vessel since associated reactions are non-exothermic. Such mild oxidizers also have drawbacks. For instance, typical long-chain amine oxides may pose foaming issues due to their surfactancy. These amine oxides may also have limited efficiency for large amounts of H 2 S, since they are typically diluted in water to prevent gel formation. Nitrites may also have drawbacks, as their reaction with hydrogen sulfide produces ammonia. As a result, the nitrite oxidation reaction may be accompanied by a rise in pH, which at some point may cease the oxidation before it is complete. 
     Consequently, there is a need for improved methods and products for decontaminating vessels such as sour water tanks. 
     BRIEF SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS 
     These and other needs in the art are addressed in one embodiment by a method for treating contaminated water. The method includes introducing a methylmorpholine-N-oxide solution to a vessel. The vessel contains the contaminated water and iron oxide. The contaminated water comprises contaminants. The methylmorpholine-N-oxide solution comprises methylmorpholine-N-oxide and water. The method further comprises contacting the methylmorpholine-N-oxide solution with the contaminated water. In addition, the method comprises treating the contaminated water by allowing the methylmorpholine-N-oxide to react with the contaminants in the presence of the iron oxide. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
         FIG. 1  illustrates an embodiment of a methylmorpholine-N-oxide water treatment method; 
         FIG. 2  illustrates an embodiment of a methylmorpholine-N-oxide water treatment method having a heat exchanger on the recycle; 
         FIG. 3  illustrates reaction time versus temperature; and 
         FIG. 4  illustrates reaction time versus temperature. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  illustrates an embodiment of methylmorpholine-N-oxide water treatment method  5 . In an embodiment, methylmorpholine-N-oxide water treatment method  5  treats contaminated water by decontaminating the water by removing a portion or all of the contaminants from the water. 
     In embodiments as shown in  FIG. 1 , the contaminated water is disposed in a vessel  10 . Vessel  10  may include any type of vessel that may contain water. In an embodiment, vessel  10  is a tank. In embodiments, the water is contaminated with contaminants. Without limitation, examples of contaminants include hydrogen sulfide, iron sulfides, or any combinations thereof. In an embodiment, the contaminant comprises hydrogen sulfide. In some embodiments, the iron sulfides comprises pyrophoric iron sulfides. The pyrophoric iron sulfides may include any pyrophoric iron sulfides. In embodiments, the pyrophoric iron sulfides comprise pyrite, troilite, marcasite, pyrrhotite, or any combinations thereof. 
       FIG. 1  shows an embodiment of methylmorpholine-N-oxide water treatment method  5  in which methylmorpholine-N-oxide  20  is introduced to vessel  10 . Methylmorpholine-N-oxide  20  may be introduced to vessel  10  by any suitable means. Without limitation, examples of such suitable means include a drum pump, tank truck, and the like. Methylmorpholine-N-oxide  20  may be introduced in any suitable form for removing the contaminants from the contaminated water. In embodiments, methylmorpholine-N-oxide  20  is in a methylmorpholine-N-oxide solution comprising methylmorpholine-N-oxide and water. The methylmorpholine-N-oxide solution may have the methylmorpholine-N-oxide in any desired amount. In some embodiments, the methylmorpholine-N-oxide may be in a very concentrated form. Without being limited by theory, such very concentrated form may allow the methylmorpholine-N-oxide to be applied in small, efficient amounts. The concentrated form may include any desirable concentration. In an embodiment, the concentration of methylmorpholine-N-oxide in the water is between about 1 weight volume % and about 60 weight volume %, alternatively between about 10 weight volume % and about 20 weight volume %, further alternatively between about 5 weight volume % and about 60 weight volume %, and alternatively between about 50 weight volume % and about 60 weight volume %. In embodiments, the concentration of methylmorpholine-N-oxide in the water may be any individual weight volume % in the above ranges or any smaller range of weight volume % that is included in the above ranges. In an embodiment, the concentration of methylmorpholine-N-oxide in the water is between about 50 weight volume % and about 60 weight volume %. In an embodiment, the methylmorpholine-N-oxide is a short-chain amine oxide. In embodiments, the methylmorpholine-N-oxide has the molecular formula C 5 H 11 NO 2 . In vessel  10 , methylmorpholine-N-oxide  20  contacts the contaminated water. In embodiments, methylmorpholine-N-oxide  20  is not heated before introduction to vessel  10 . In embodiments, the amount of methylmorpholine-N-oxide  20  added to vessel  20  provides a mole ratio of methylmorpholine-N-oxide:hydrogen sulfide in vessel  20  from about 1.0 mole methylmorpholine-N-oxide:1.0 mole hydrogen sulfide to about 3.0 mole methylmorpholine-N-oxide:1.0 mole hydrogen sulfide, or any range or mole ratio therebetween. 
     In further embodiments as shown in  FIG. 1 , steam  15  is also added to vessel  10 . Steam  15  is added to increase the temperature of the contaminated water in vessel  10 . In embodiments, steam  15  is added to vessel  10  in amounts to increase the temperature of the contaminated water to a temperature from about 75° F. to about 212° F., alternatively from about 90° F. to about 180° F., and alternatively from about 100° F. to about 140° F. In embodiments, the temperature may be any individual temperature in the above ranges or any smaller range of temperatures that is included in the above ranges. Any suitable psig steam may be used. In embodiments, the steam is 150 psig or less. In an embodiment, the steam is 50 psig steam or 150 psig steam. 
     In embodiments, the methylmorpholine-N-oxide reacts with the contaminants in the presence of iron oxide (i.e., rust). Without being limited by theory, the presence of iron oxide catalyzes the amine oxide (i.e., methylmorpholine-N-oxide) to convert reactive sulfide to elemental sulfur and thiosulfate reaction products irreversibly. Any suitable iron oxide may be used. In embodiments, the iron oxide includes hydrated iron oxide, anhydrous iron oxide, or any combinations thereof. In an embodiment, the iron oxide is hydrous iron oxide. In embodiments, the iron oxide includes ferrous or ferric oxides that are hydrated. In an embodiment, the iron oxide is Fe 2 O 3 7H 2 0, Fe 2 O 3 .10H 2 0, or any combinations thereof. The iron oxide may be present in vessel  10  in any amount suitable to catalyze the reaction between the amine oxide and the contaminants. In an embodiment, vessel  10  has iron oxide in the contaminated water in an amount from about 100 ppm iron oxide to about 1,000 ppm iron oxide. In embodiments, the iron oxide may be present in any individual amount in the above range or any smaller range of amounts that is included in the above range. In embodiments, no iron oxide is added to vessel  10  as methylmorpholine-N-oxide water treatment method  5  uses the iron oxide already present in vessel  10 . In other embodiments, iron oxide is added to vessel  10 . Without being limited by theory, the reaction to remove the contaminants (i.e., reactive sulfide) from the contaminated water comprises methylmorpholine-N-oxide, steam, and iron oxide. The reaction is allowed to occur for a sufficient time to allow the contaminants to be removed (i.e., converted) from the water. In embodiments, the reaction is allowed to occur from about one hour to about fifty hours, alternatively from about one hour to about twenty-five hours. In embodiments, the reaction time may be any individual time in the above times or any smaller time ranges that are included in the above ranges.  FIG. 3  illustrates examples of reaction time versus temperature. Without being limited by theory, it is to be understood that the higher the temperature, the less reaction time may be used. In embodiments, the reaction is allowed to occur for a sufficient time to substantially remove all of the contaminants (i.e., convert substantially all of the reactive sulfide to elemental sulfur). In some embodiments, the reaction produces substantially no foaming. And, in some embodiments, the reaction also does not generate ammonia. In an embodiment, the reaction is non-exothermic. In other embodiments, surfactants are not added to the contaminated water or methylmorpholine-N-oxide  20 . 
     After the desired reaction time occurs (i.e., sulfide conversion is about complete), the water  35  (i.e., treated water) may be drawn off from vessel  10  and nonhazardous products  25  may also be removed from vessel  10 . Water  35  may be sent to any desired location such as a water treatment plant. In embodiments, water  35  has no reactive sulfides. Nonhazardous products  25  include nonhazardous sulfur reaction products along with other native solids in vessel  10  (i.e., sludge). Nonhazardous products  25  may be removed from vessel  10  by an suitable means. In an embodiment, the means include a centrifuge. In embodiments, the liquid portion of the effluent passing from the centrifuge may then be routed to a treatment facility or any other desirable location. 
     In some embodiments (not illustrated), steam is not added to vessel  10 . 
     In an embodiment as shown in  FIG. 1 , methylmorpholine-N-oxide water treatment method  5  may also include re-circulation  30 . Re-circulation  30  is re-circulation of contaminated water. In some embodiments, contaminated water containing introduced methylmorpholine-N-oxide  20  (i.e., a mixture of contaminated water and methylmorpholine-N-oxide) is re-circulated. Without limitation, re-circulation  30  facilitates distribution of methylmorpholine-N-oxide  20  in contaminated water. In an embodiment, from about one volume of the total amount of contaminated water and methylmorpholine-N-oxide solution in vessel  10  to about two vessel  10  volumes of the total amount of contaminated water and methylmorpholine-N-oxide solution in vessel  10  are re-circulated. In embodiments, re-circulation  30  may include re-circulation of any volume or range of volumes less than two. 
     In embodiments as shown in  FIG. 2 , methylmorpholine-N-oxide water treatment method  5  includes heat exchanger  40 , which adds heat to re-circulation  30 . Without limitation, adding the heat increases the reaction. 
     To further illustrate various illustrative embodiments of the present invention, the following examples are provided. 
     EXAMPLES 
     Example 1 
     A purpose of this Example 1 was to determine the extent of reaction of morpholine-N-oxide on H 2 S in sour water at varying mole ratios. The experiments of this Example 1 were conducted at 40° C. and 60° C. 
     At all mole ratios (morpholine-N-oxide:H 2 S) down to and including 1:0:1.0, the destruction of H 2 S was complete at 60° C. after 24 hours. Elemental sulfur was a visible product. This S° was present as platelets (“flakes”). 
     After 24 hours at 40° C., the reaction was complete only at a mole ratio of 3.0:1.0, although nearly complete reactions were recorded at ratios of 2.0:1.0 and 1.8:1.0. Reactions at lower mole ratios were variously incomplete and consistent with the lower loadings. 
     After 48 hours at 40° C., the reaction was complete at all mole ratios except for the lowest loading (1.0:1.0). The product S° was variously present as a milky suspension and flaked solids. 
     For the experiment, a pint of archived sour water at pH˜8.5 was used with an H 2 S content at 9,985 mg/liter (0.293 M/lit). The molecular weight of the solid morpholine-N-oxide was 126.0. 
     A morpholine-N-oxide stock solution was prepared by dissolving 5.00 grams in 100.0 mls distilled water (0.397 M/lit). To each of several screw-capped sample vials, 2.0 mls of the sour water and a dash of powdered iron rust were added. The vials were then diluted with ˜15 mls of distilled water and the following volumes of morpholine-N-oxide were added. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Sample Makeup 
               
               
                 [Morpholine-N-oxide] = 0.397 M/lit 
               
               
                 [H 2 S] = 0.293 M/lit (@ pH ~8.5) 
               
               
                 ~0.5 gm Fe 2 O 3 •xH 2 O 
               
             
          
           
               
                   
                 Volume morpholine-N-oxide stock 
                 Mole ratio (N-oxide:H 2 S) 
               
               
                   
                   
               
               
                   
                 1.477 mls 
                 1.0:1 
               
               
                   
                 1.772 mls 
                 1.2:1 
               
               
                   
                 2.067 mls 
                 1.4:1 
               
               
                   
                 2.363 mls 
                 1.6:1 
               
               
                   
                 2.658 mls 
                 1.8:1 
               
               
                   
                 2.953 mls 
                 2.0:1 
               
               
                   
                 4.430 mls 
                 3.0:1 
               
               
                   
                   
               
             
          
         
       
     
     Three such series were prepared. Each series was treated as follows: series 1: heated at 40° C. for 24 hours (static), series 2: heated at 40° C. for 48 hours (static), series 3: heated at 60° C. for 24 hours (static). 
     At termination of the reaction periods, the entire contents of each reaction vial were emptied into 20 mls of sulfide anti-oxidant buffer, and each was titrated with 0.100 M/lit Pb ++ , according to ULI Procedure LP1005. The results are shown below. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Reaction of Morpholine-N-oxide on H 2 S for 24 Hours @ 40° C. 
               
             
          
           
               
                 Sample 
                 mls Pb ++   
                 Gms H 2 S Titrated 
                 Gms H 2 S Added 
                 % Reacted 
               
               
                   
               
               
                 1.0:1 
                 1.9 
                 0.00019 
                 0.000585 
                 68% 
               
               
                 1.2:1 
                 1.8 
                 0.00018 
                 0.000585 
                 69% 
               
               
                 1.4:1 
                 1.7 
                 0.00017 
                 0.000585 
                 71% 
               
               
                 1.6:1 
                 0.7 
                 0.00007 
                 0.000585 
                 88% 
               
               
                 1.8:1 
                 0.4 
                 0.00004 
                 0.000585 
                 93% 
               
               
                 2.0:1 
                 0.3 
                 0.00003 
                 0.000585 
                 95% 
               
               
                 3.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100%  
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Reaction of Morpholine-N-oxide on H 2 S for 48 Hours @ 40° C. 
               
             
          
           
               
                 Sample 
                 mls Pb ++   
                 Gms H 2 S Titrated 
                 Gms H 2 S Added 
                 % Reacted 
               
               
                   
               
               
                 1.0:1 
                 0.4 
                 0.00004 
                 0.000585 
                  93% 
               
               
                 1.2:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.4:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.6:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.8:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 2.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 3.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                   
               
             
          
         
       
     
     Elemental sulfur, present as small platelets, had been precipitated during reaction. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Reaction of Morpholine-N-oxide on H 2 S for 24 Hours @ 60° C. 
               
             
          
           
               
                 Sample 
                 mls Pb ++   
                 Gms H 2 S Titrated 
                 Gms H 2 S Added 
                 % Reacted 
               
               
                   
               
               
                 1.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.2:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.4:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.6:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 1.8:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 2.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                 3.0:1 
                 0.0 
                 0.00000 
                 0.000585 
                 100% 
               
               
                   
               
             
          
         
       
     
     Elemental sulfur, present as small platelets, had been precipitated during reaction. 
     Example 2 
     A purpose of this example was to determine if a lower ratio than 1.0:1.0 of 4-methylmorpholine-N-oxide:sulfide will completely remove sulfide from solution. The experiments were conducted at 40° C. and 60° C. 
     At a mole ratio of 0.7:1.0 (N-oxide:sulfide), the oxidation and removal of sulfide appeared to be 98%-99% complete. 
     A pint of archived sour water at pH˜8.5 was used and that had an H 2 S content at 8,016 mg/liter (0.250 M/lit). A sample of solid 4-methylmorpholine-N-oxide was determined to have a molecular weight of 126.0. 
     A 4-methylmorpholine-N-oxide stock solution was prepared by dissolving 5.00 grams in 100.0 mls distilled water (0.397 M/lit). To each of four screw-capped sample vials, 2.0 mls of the sour water and a dash of powdered iron rust were added. The vials were diluted to ˜20 mls with distilled water after adding 0.822 mls of 4-methylmorpholine-N-oxide, which amounted to a reaction ratio of 0.7:1.0. 
     Two of the samples were placed in a 40° C. bath for a reaction time of 48 hours. The other two were placed in a 60° C. bath for 24 hours. At termination of the reaction periods, the entire contents of a reaction vial from each bath were emptied into 20 mls of sulfide anti-oxidant buffer and each was titrated with 0.100 M/lit Pb ++ , according to ULI Procedure LP1005. 
     The sample reacted at 40° C. required 0.10 mls of the Pb ++  titrant, and the sample reacted at 60° C. required 0.05 mls. These analysis results calculated to 99% and 98% destruction of sulfide in the tests. 
     The second samples from these reactions were acidified with H 2 SO 4 . This was done in order to determine if there was any odor of residual H 2 S. There was no odor of H 2 S. Instead, there was the unmistakable odor of SO 2 . A common reaction product of N-oxides with S =  is thiosulfate. When thiosulfate is acidified, it disproportionates, forming SO 2 . 
     Elemental sulfur, present as small platelets, had been formed during both reactions. 
     Example 3 
     Two large sour water tanks (about 20,000 m 3 ) were respectively 80% and 75% filled. Methylmorpholine-N-oxide with added temperature of 50° C. was found to reduce hydrogen sulfide to 0 ppm in 19 hours or less. 
     During the course of testing, discoveries were made about the catalytic effect of the voluminous corrosion solids in the tank. When such solids were present, methylmorpholine-N-oxide trials at ambient temperatures were found to be complete with hydrogen sulfide at 0 ppm after 24 hours treatment time. Other trials where the solids were removed prior to methylmorpholine-N-oxide treatment demonstrated that methylmorpholine-N-oxide reduced hydrogen sulfide to 0 ppm in six days at ambient conditions. 
     A sample of the first tank was taken and found to be black from suspended corrosion solids (Fe 2 O 3 +FeS). Various analyses were conducted in order to determine H 2 S content so that a methylmorpholine-N-oxide dose could be calculated. Prior readings were 800-900 ppm H 2 S. A test using a Chemets sulfide colorimetric test kit estimated 400-500 ppm H 2 S. Iodometric titration gave an H 2 S result of 600-700 ppm on the whole sample, and 400-500 ppm H 2 S on filtered sample. 
     The first demonstration was performed under standard conditions where treatments were assisted by heating at 50° C. Two different dosage levels were prepared using newly-made as well as eight month old formulation. One sample was run at ambient conditions. The test make-ups are below in Table 5. 
     
       
         
               
               
               
               
               
             
           
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                   
                 methylmorpholine-N- 
                   
                   
               
               
                   
                 First Tank 
                 oxide:H 2 S mole ratio 
                 Temp (° C.) 
                 Start 
               
               
                   
                   
               
             
             
               
                   
                 15 
                 1.5:1   
                 50 
                 14:30 
               
               
                   
                 15 
                 3:1 
                 50 
                 14:30 
               
               
                   
                 15 
                 3:1 
                 50 
                 14:30 
               
               
                   
                 15 
                 3:1 
                 50 
                 14:30 
               
               
                   
                   
               
             
          
         
       
     
     After 19 hours under the test conditions described above, the heated samples were observed to be completely reacted (H 2 S=0 ppm). Also, the ambient sample was mostly reacted as evidenced by a cloudy yellow solution, which is typical for that course of the reaction. 
     Verification of the completion of H 2 S oxidation was seen in the lead acetate test strips. A dark strip was untreated, the clear strip included the three heated samples with H 2 S=0 ppm, and another strip was the ambient sample that was seen to be much lighter. A subsequent test with Chemets colorimetric sulfide kit indicated the H 2 S levels in the ambient sample to be well below 100 ppm H 2 S. 
     The ambient tests were surprising. This test suggested that the presence of significant amounts of corrosion material were such a sufficient catalyst for timely methylmorpholine-N-oxide reaction that heat was not necessary. 
     Lab trials were initiated to study the effectiveness of methylmorpholine-N-oxide at low dose rates and under ambient conditions. The sample array was intended to study the reaction rate of methylmorpholine-N-oxide with and without the catalytic solids and also varying dose rates. One sample represented the most extreme test of methylmorpholine-N-oxide—ambient conditions with no solids present and a methylmorpholine-N-oxide:H 2 S ratio of 1:1 (i.e., the lowest theoretical dose rate possible). Test parameters were summarized in Table 6. 
     
       
         
               
               
               
               
             
           
               
                 TABLE 6 
               
               
                   
               
               
                 Mole ratio 
                   
                   
                   
               
               
                 methylmorpholine-N- 
               
               
                 oxide:H 2 S 
                 Solids Level 
                 Temperature 
                 Start 
               
               
                   
               
             
             
               
                   1:1 
                 Minimal 
                 Ambient 
                 10:00 
               
               
                 1.5:1 
                 Minimal 
                 Ambient 
                 10:00 
               
               
                 1.5:1 
                 Abundant - Sx Shaken 
                 Ambient 
                 10:00 
               
               
                   
               
             
          
         
       
     
     After 24 hours of exposure, methylmorpholine-N-oxide was found to produce complete eradication of H 2 S in the sample with solids as evidenced. This was consistent with the ambient test with solids above. Also, the higher dose sample with no solids looked to be turning a darker shade of yellow, which indicated some initial progress in reaction. 
     Both of the samples with no solids present were also seen to progressively react with all the H 2 S as well, at much longer reaction times. A summary of the results is included in Table 7. 
     
       
         
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 Solids Present 
                 Mole Ratio 
                 Time to H 2 S = 0 ppm 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Yes 
                 1.5:1 
                 24 
                 hours 
               
               
                 No 
                 1.5:1 
                 6 
                 days 
               
               
                 No 
                 1:1 (theoretical minimum) 
                 12 
                 days 
               
               
                   
               
             
          
         
       
     
       FIG. 4  illustrates a complete performance summary of methylmorpholine-N-oxide for total H 2 S eradiation under different conditions. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations may be made herein without departing from the spirit and scope of the invention as defined by the appended claims.