Process for decontamination of hazardous sulfur compounds in sour water tanks

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.

Claims

1. A method for treating contaminants in water, comprising: (A) providing a vessel comprising water, wherein the water comprises hydrogen sulfide; (B) introducing methylmorpholine-N-oxide into the vessel, wherein the amount of methylmorpholine-N-oxide is added to the vessel such that the mole ratio of methylmorpholine-N-oxide:hydrogen sulfide in the vessel is 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; (C) introducing iron oxide into the vessel, wherein the iron oxide is added to the vessel such that the amount of iron oxide present in the water is from about 100 ppm to about 1,000 ppm; (D) allowing the methylmorpholine-N-oxide to react with the hydrogen sulfide as a reaction, wherein the iron oxide catalyzes the reaction between the methylmorpholine-N-oxide and the hydrogen sulfide.

2. The method of claim 1, wherein step (D) irreversibly converts the hydrogen sulfide to elemental sulfur and thiosulfate reaction products.

3. The method of claim 1, further comprising introducing steam into the vessel.

4. The method of claim 3, wherein introducing the steam into the vessel increases the temperature of the water to a temperature from about 75° F. to about 212° F.

5. The method of claim 3, wherein the steam comprises 150 psig steam or less.

6. The method of claim 1, wherein the iron oxide comprises ferrous or ferric oxides that are hydrated.

7. The method of claim 1, wherein the iron oxide comprises Fe.sub.2O.sub.3.7H.sub.2O, Fe.sub.2O.sub.3.10H.sub.2O, or any combinations thereof.

8. The method of claim 1, wherein the methylmorpholine-N-oxide reacts with the hydrogen sulfide from about one hour to about fifty hours.

9. The method of claim 1, further comprising moving the water from the vessel to a treatment plant after performing step (D).

10. The method of claim 1, further comprising removing nonhazardous products comprising nonhazardous sulfur reaction products and native solids from the vessel by way of centrifuge.

11. A method for treating contaminants in water, comprising: (A) providing a vessel comprising water, wherein the water comprises hydrogen sulfide; (B) introducing methylmorpholine-N-oxide into the vessel, wherein the amount of methylmorpholine-N-oxide is added to the vessel such that the mole ratio of methylmorpholine-N-oxide:hydrogen sulfide in the vessel is 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; (C) introducing iron oxide into the vessel, wherein the iron oxide is added to the vessel such that the amount of iron oxide present in the water is from about 100 ppm to about 1,000 ppm; (D) allowing the methylmorpholine-N-oxide to react with the hydrogen sulfide, wherein the iron oxide catalyzes the reaction between the methylmorpholine-N-oxide and the hydrogen sulfide; (E) recirculating the water and methylmorpholine-N-oxide through the vessel, whereby steps (B)-(D) are repeated.

12. The method of claim 11, wherein step (D) irreversibly converts the hydrogen sulfide to elemental sulfur and thiosulfate reaction products.

13. The method of claim 11, wherein step (E) recirculates between about one volume of the total amount of the water and methylmorpholine-N-oxide in the vessel to about two volumes of the total amount of the water and methylmorpholine-N-oxide in the vessel.

14. The method of claim 11, wherein step (E) comprises heating the water and methylmorpholine-N-oxide via a heat exchanger.

15. The method of claim 11, further comprising introducing steam into the vessel.

16. The method of claim 15, wherein introducing the steam into the vessel increases the temperature of the water to a temperature from about 75° F. to about 212° F.

17. The method of claim 15, wherein the steam comprises 150 psig steam or less.

18. The method of claim 11, wherein the iron oxide comprises ferrous or ferric oxides that are hydrated.

19. The method of claim 11, wherein the iron oxide comprises Fe.sub.2O.sub.3.7H.sub.2O, Fe.sub.2O.sub.3.10H.sub.2O, or any combinations thereof.

20. The method of claim 11, wherein the methylmorpholine-N-oxide reacts with the hydrogen sulfide from about one hour to about fifty hours.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:

(2) FIG. 1 illustrates an embodiment of a methylmorpholine-N-oxide water treatment method;

(3) FIG. 2 illustrates an embodiment of a methylmorpholine-N-oxide water treatment method having a heat exchanger on the recycle;

(4) FIG. 3 illustrates reaction time versus temperature; and

(5) FIG. 4 illustrates reaction time versus temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) 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.

(7) 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.

(8) 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.sub.5H.sub.11NO.sub.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.

(9) 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.

(10) 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.sub.2O.sub.3.7H.sub.2O, Fe.sub.2O.sub.3.10H.sub.2O, 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.

(11) 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.

(12) In some embodiments (not illustrated), steam is not added to vessel 10.

(13) 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.

(14) 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.

(15) To further illustrate various illustrative embodiments of the present invention, the following examples are provided.

EXAMPLES

Example 1

(16) A purpose of this Example 1 was to determine the extent of reaction of morpholine-N-oxide on H.sub.2S in sour water at varying mole ratios. The experiments of this Example 1 were conducted at 40° C. and 60° C.

(17) At all mole ratios (morpholine-N-oxide:H.sub.2S) down to and including 1.0:1.0, the destruction of H.sub.2S was complete at 60° C. after 24 hours. Elemental sulfur was a visible product. This S° was present as platelets (“flakes”).

(18) 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.

(19) 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.

(20) For the experiment, a pint of archived sour water at pH-8.5 was used with an H.sub.2S content at 9,985 mg/liter (0.293 M/lit). The molecular weight of the solid morpholine-N-oxide was 126.0.

(21) 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.

(22) TABLE-US-00001 TABLE 1 Sample Makeup [Morpholine-N-oxide] = 0.397M/lit [H.sub.2S] = 0.293M/lit (@ pH ~8.5) ~0.5 gm Fe.sub.2O.sub.3•xH.sub.2O Volume morpholine-N-oxide stock Mole ratio (N-oxide:H.sub.2S) 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

(23) 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).

(24) 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.sup.++, according to ULI Procedure LP1005. The results are shown below.

(25) TABLE-US-00002 TABLE 2 Reaction of Morpholine-N-oxide on H.sub.2S for 24 Hours @ 40° C. Sample mls Pb.sup.++ Gms H.sub.2S Titrated Gms H.sub.2S 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% 

(26) TABLE-US-00003 TABLE 3 Reaction of Morpholine-N-oxide on H.sub.2S for 48 Hours @ 40° C. Sample mls Pb.sup.++ Gms H.sub.2S Titrated Gms H.sub.2S 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%

(27) Elemental sulfur, present as small platelets, had been precipitated during reaction.

(28) TABLE-US-00004 TABLE 4 Reaction of Morpholine-N-oxide on H.sub.2S for 24 Hours @ 60° C. Sample mls Pb.sup.++ Gms H.sub.2S Titrated Gms H.sub.2S 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%

(29) Elemental sulfur, present as small platelets, had been precipitated during reaction.

Example 2

(30) 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.

(31) At a mole ratio of 0.7:1.0 (N-oxide:sulfide), the oxidation and removal of sulfide appeared to be 98%-99% complete.

(32) A pint of archived sour water at pH-8.5 was used and that had an H.sub.2S 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.

(33) 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.

(34) 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.sup.++, according to ULI Procedure LP1005.

(35) The sample reacted at 40° C. required 0.10 mls of the Pb.sup.++ 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.

(36) The second samples from these reactions were acidified with H.sub.2SO.sub.4. This was done in order to determine if there was any odor of residual H.sub.2S. There was no odor of H.sub.2S. Instead, there was the unmistakable odor of SO.sub.2. A common reaction product of N-oxides with S.sup.═ is thiosulfate. When thiosulfate is acidified, it disproportionates, forming SO.sub.2.

(37) Elemental sulfur, present as small platelets, had been formed during both reactions.

Example 3

(38) Two large sour water tanks (about 20,000 m.sup.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.

(39) 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.

(40) A sample of the first tank was taken and found to be black from suspended corrosion solids (Fe.sub.2O.sub.3+FeS). Various analyses were conducted in order to determine H.sub.2S content so that a methylmorpholine-N-oxide dose could be calculated. Prior readings were 800-900 ppm H.sub.2S. A test using a Chemets sulfide colorimetric test kit estimated 400-500 ppm H.sub.2S. Iodometric titration gave an H.sub.2S result of 600-700 ppm on the whole sample, and 400-500 ppm H.sub.2S on filtered sample.

(41) 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.

(42) TABLE-US-00005 TABLE 5 methylmorpholine-N- First Tank oxide:H.sub.2S mole ratio Temp (° C.) Start 15 1.5:1.sup.  50 14:30 15 3:1 50 14:30 15 3:1 50 14:30 15 3:1 50 14:30

(43) After 19 hours under the test conditions described above, the heated samples were observed to be completely reacted (H.sub.2S=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.

(44) Verification of the completion of H.sub.2S oxidation was seen in the lead acetate test strips. A dark strip was untreated, the clear strip included the three heated samples with H.sub.2S=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.sub.2S levels in the ambient sample to be well below 100 ppm H.sub.2S.

(45) 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.

(46) 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.sub.2S ratio of 1:1 (i.e., the lowest theoretical dose rate possible). Test parameters were summarized in Table 6.

(47) TABLE-US-00006 TABLE 6 Mole ratio methylmorpholine-N- oxide:H.sub.2S Solids Level Temperature Start .sup. 1:1 Minimal Ambient 10:00 1.5:1 Minimal Ambient 10:00 1.5:1 Abundant - Sx Shaken Ambient 10:00

(48) After 24 hours of exposure, methylmorpholine-N-oxide was found to produce complete eradication of H.sub.2S 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.

(49) Both of the samples with no solids present were also seen to progressively react with all the H.sub.2S as well, at much longer reaction times. A summary of the results is included in Table 7.

(50) TABLE-US-00007 TABLE 7 Solids Present Mole Ratio Time to H.sub.2S = 0 ppm Yes 1.5:1 24 hours No 1.5:1 6 days No 1:1 (theoretical minimum) 12 days

(51) FIG. 4 illustrates a complete performance summary of methylmorpholine-N-oxide for total H.sub.2S eradiation under different conditions.

(52) 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.