Chemical compositions and methods of using same for remediating low to moderate amounts of sulfur-containing compositions and other contaminants in liquids

Abstract

A treatment composition for remediating for remediating H.sub.2S and other contaminant(s) in contaminated liquids, comprising: 0.1-10.0 weight % collectively of at least one hydroxide compound; 0.01-3.0 weight % collectively of at least one organic acid selected from a group consisting of fulvic acid and humic acid; 0.01-10.0 wt % of a chelating agent; and at least 75% weight of water.

Claims

1. A treatment composition for remediating H.sub.2S and other contaminant(s) in contaminated liquids, comprising: 0.1-10.0 weight % collectively of at least one hydroxide compound; 0.01-3.0 weight % collectively of at least one organic acid selected from a group consisting of fulvic acid and humic acid; 0.01-10.0 wt % of a chelating agent; and at least 75% weight of water.

2. The treatment composition according to claim 1, wherein the chelating agent is EDTA, and the hydroxide compound(s) include at least one of sodium hydroxide and potassium hydroxide.

3. The treatment composition according to claim 1, further comprising 0.001-0.2 weight % of surfactant.

4. The treatment composition according to claim 3, wherein the surfactant comprises sodium lauryl sulphate.

5. The treatment composition according to claim 1, wherein water constitutes at least 90 wt % of the treatment composition.

6. The treatment composition according to claim 1, wherein a pH of the composition is about 14.0.

7. A treatment process for remediating H.sub.2S in a contaminated liquid, comprising steps of adding 0.05-15 ml of the treatment composition according to claim 1/liter of contaminated liquid, and allowing the treatment composition to react with the H.sub.2S and other contaminant(s) in the contaminated liquid for a sufficient time to permit the amounts of the H.sub.2S in the contaminated liquid to be reduced down to less than 5 ppm, wherein an amount of H.sub.2S in the contaminated liquid prior to addition of the treatment composition is in a range of 5 to 2000 ppm.

8. The treatment process according to claim 7, wherein in the adding step 0.5-2.0 ml of the treatment composition is added/liter of the contaminated liquid.

9. The treatment process according to claim 7, wherein the amount of H.sub.2S in the contaminated liquid prior to addition of the treatment composition is in a range of 5 to 500 ppm.

10. The treatment process according to claim 7, wherein the chelating agent is EDTA, and the hydroxide compound(s) include at least one of sodium hydroxide and potassium hydroxide.

11. The treatment process according to claim 7, wherein the treatment composition further comprises 0.001-0.2 weight % of surfactant.

12. The treatment process according to claim 11, wherein the surfactant comprises sodium lauryl sulphate.

13. The treatment process according to claim 7, wherein water constitutes at least 90 wt % of the treatment composition.

14. The treatment process according to claim 7, wherein a pH of the composition is about 14.0.

Description

DETAILED DESCRIPTION OF PRESENT EXEMPLARY EMBODIMENTS

(1) Exemplary embodiments of the present invention will be described below. Primary aspects of the present invention involve use of novel treatment compositions in treatment processes for contaminated liquids containing H.sub.2S wherein the treatment compositions are combined/mixed with the contaminated liquids and permitted to react over a period of time until the amount of H.sub.2S remaining in the liquids is less than 5 ppm.

(2) According to a exemplary embodiment of the present invention, a novel treatment composition for remediating for remediating low to moderate amounts of H.sub.2S and other contaminant(s) in contaminated liquids comprises: a relatively dilute aqueous solution containing mostly water, together with much lower concentrations of hydroxide compound(s) and organic acid(s) than in the treatment solution as disclosed in PCT/US2018/064015, an amount of a chelating agent such as EDTA, and optionally a small amount of surfactant. For example, a treatment composition according to an exemplary embodiment of the present invention may contain at least 70% weight of water, and preferably at least 90% weight of water, together with: 0.1-10.0 weight % collectively of at least one hydroxide compound; 0.01-3.0 weight % collectively of at least one organic acid including as fulvic acid, humic acid and the like; 0.05-10.0 wt % of a chelating agent such as EDTA; and optionally 0.001-0.2 wt % of surfactant such as sodium lauryl sulphate. A pH of the treatment composition may be approximately 14.0.

(3) In the novel treatment composition according to this embodiment of the present invention, the collective concentration of the hydroxide compound(s), the organic acid(s), the chelating agent and/or surfactant may be adjusted within the discussed ranges depending on the amounts of H.sub.2S and other contaminants in the liquid being treated, as well as on other factors including specific reaction rate desired and other contaminants in the liquid being treated.

(4) The novel treatment composition according to this embodiment of the present invention includes hydroxide compound(s) as the primary reactant for reacting with the H.sub.2S in the liquid being treated to remediate same according to the same reactions as discussed in PCT/US2018/064015, e.g., if sodium hydroxide (NaOH) is one of the hydroxide compound(s), the water and NaOH dissociates H.sub.2S to HS— ion at higher pH, which shifts the equilibrium of H.sub.2S gas from oil to water, then, the HS— can react with sodium to form NaHS (sodium bisulfide), or with S.sub.2— to form Na.sub.2S (sodium sulfide), for example, plus water as a byproduct according to the following equations.
H.sub.2S+NaOH.fwdarw.NaHS+H.sub.2O  (1)
NaHS+NaOH.fwdarw.Na.sub.2S+H.sub.2O  (2)

(5) If other hydroxide compounds are included in the treatment solution they will react similarly with the H.sub.2S to remediate same. As noted in PCT/US2018/064015, the treatment composition and associated treatment process may involve use of only one hydroxide such as sodium hydroxide (NaOH) or potassium hydroxide (KOH), but may also involve use of a combination of hydroxides for more completely reacting with most or some of the other contaminants in the petroleum based liquids, noting that there are more than 300 species of sulfur compounds, although hydrogen sulfide H.sub.2S is by far the main contaminant that must be remediated. It should be noted that the diluted treatment composition according to the present invention is also different from the more concentrated treatment composition disclosed in PCT/US2018/064015 in relation to remediating many common contaminants found in crude oil besides H.sub.2S. For example, while the treatment composition disclosed in PCT/US2018/064015 is also very effective at remediating many other sulfur based contaminants besides H.sub.2S, the new dilute treatment composition is not very effective at remediating some other species of undesirable sulfur compounds including ethyl mercaptan (CH.sub.3CH.sub.2SH), dimethyl sulfide (C.sub.2H.sub.6S), isobutyl mercatan (C.sub.4H.sub.10S) and components thereof.

(6) Sodium hydroxide is very effective for use as a hydroxide compound in the treatment solution according to the present invention because it does not harm the petroleum based liquids when used in appropriate amounts, and is relatively inexpensive. Potassium hydroxide is more effective than sodium hydroxide for reacting with some species of sulfides. Hence, the treatment process involving potassium hydroxide (KOH) together with the sodium hydroxide achieves a more complete reaction with all of the sulfides contained in the hydrocarbon based liquids in comparison to just using a concentrated solution of sodium hydroxide. Some other hydroxide compounds that may be suitable for use in the treatment composition and treatment process of the present invention include magnesium hydroxide (Mg(OH).sub.2), ammonium hydroxide (NH.sub.4OH), and manganese hydroxide (Mn(OH).sub.2. Mn(OH).sub.4), but the present invention is not limited to any particular hydroxide compound(s) as long as the compounds are effective for remediating H.sub.2S and other targeted contaminants. Another consideration in selecting the hydroxide compounds is that they should not contain element(s)/component(s) that are also included as a significant contaminant in the liquid being treated. For example, if the liquid contains a significant amount of sodium chloride as a contaminant, then the hydroxide compound(s) in the treatment solution it would be preferred to use a hydroxide other than sodium hydroxide, e.g., potassium hydroxide (KOH), magnesium hydroxide (Mg(OH).sub.2), ammonium hydroxide (NH.sub.4OH), and manganese hydroxide (Mn(OH).sub.2, Mn(OH).sub.4) would be suitable hydroxides for use in this situation. Also, a given hydroxide compound or a given combination of hydroxide compounds may achieve a faster and/or more efficient reaction with H.sub.2S and other contaminants in a given contaminated liquid.

(7) It should be noted that equation (2) above is reversible, so large amounts of water hydrolyze the sodium sulfide (Na.sub.2S) back to NaOH and NaHS. In other words, equation (2) in the reverse direction is a hydrolysis reaction. However, because the treatment composition according to the present invention includes the organic acid(s) such as fulvic acid and humic acid, as well as a chelating agent such as EDTA, these desirably prevent the reactions between the hydroxide compound(s) and H.sub.2S from being reversible.

(8) The organic acids such as fulvic acid and humic acid in the treatment composition are very effective for binding with the sulfur ions, and sulfur based compounds resulting from the remediation of H.sub.2S and other species of sulfur based contaminants in the contaminated liquid and for preventing the resulting surfur compounds and other contaminants from precipitating out of the treated crude oil or other treated liquid. The fulvic acid and humic acid will pick up sulfide ions (HS.sup.− or S.sub.2.sup.−) as a scavenger. There is presently no analytical method for identifying all sulfur species in a reaction of H.sub.2S (including HS.sup.− or S.sub.2.sup.−) with fulvic or humic acid. Fulvic acid is not one molecule, but a mixture of organic molecules of different structures with various aliphatic and aromatic hydrocarbon with carbonyl and hydroxyl functional groups that can react with HS— and S.sub.2—. The same applies to humic acid. In the natural environment, fulvic acid and humic acid are known to pick up sulfur in biogeochemical cycling processes to form organic sulfides, thiols and thiophenes, sulfoxides, polysulfones and sulfonates. Likewise, when sulfur in a contaminated liquid reacts in a solution containing fulvic acid and/or humic acid, the number and complexity of these compounds makes it difficult to speciate and the results will be different based on other variables such as pH, redox potential, and the presence of other compounds in the solution including impurities in contaminated liquid that can react with and/or bond to fulvic acid or humic acid. These organic acids help in two ways, i.e., they bind sulfur as an irreversible scavenger of sulfur (i.e., once bound, a drop in pH does not return the sulfur to H.sub.2S), and it also helps to keep solids in solution (i.e. it is a solubility enhancer).

(9) In the novel treatment composition according to the exemplary embodiment of the present invention, the chelating agent used may be ethylenediaminetriaceticacid (EDTA). EDTA is particularly effective for controlling the pH of the treatment composition to remain above 8 in that EDTA is an alkali base with a PH of 14 and slows the decrease of the pH of the treatment composition as it is used over a period of time. Essentially the EDTA increases the molar concentration performance of the alkali (hydroxide(s)) in the remediation of H.sub.2S and the reaction of other sulfur speciation compounds along with the other reactive contaminants. This is advantageous because the high pH favors reaction between the hydroxide compound(s) and the H.sub.2S in the contaminated liquid, such that a given amount of the treatment composition can be effectively used for remediating more of the H.sub.2S in comparison to an equal amount of treatment composition which does not include EDTA. In other words, the EDTA or other chelating agent effectively increase the reactivity of the other components in the treatment composition and extends the useful life of the treatment composition. Incidentally, EDTA has been conventionally used in other treatment processes as a primary reactant in a method of mitigating H.sub.2S in a contaminated liquid. However, according to the conventional treatment processes involving EDTA the required molar reaction time is long and the molar reaction ratio may be about 1 mole EDTA to 1 mole H.sub.2S, such that high concentrations of H.sub.2S would require large doses of EDTA for a long treatment period, which may not be desirable. While use of a chelating agent such as EDTA is not required for the treatment solution and treatment method according to the present invention to be effective, it may be helpful to achieve a more efficient and cost effective treatment of the contaminated liquids.

(10) The contaminated liquids which may be treated using the treatment composition in a treatment process according to the present invention can be essentially any hydrocarbon based or aqueous based liquids. For example, hydrocarbon based liquids may have a viscosity or API density (the term API as used herein, is an abbreviation for American Petroleum Institute) across a broad range, e.g., from a very dense/viscous substance such as asphaltene to far less viscous/dense substances such as blends of napthas of liquids with an API of about 80. Of course, for some of the very dense/viscous liquids, it may be necessary to heat and/or mix the liquid in order to sufficiently disperse the treatment solution throughout the liquid so that it may sufficiently and efficiently react therewith in a reasonable time.

(11) A treatment process according to an exemplary embodiment of the present invention may involve adding a standard dosage of the inventors' recently proposed treatment composition per unit volume of the contaminated liquid, i.e., a dosage within a range of 0.05-15 ml, preferably 0.5-5.0 ml of the new, dilute treatment composition/liter of contaminated liquid, and then simply letting the treatment composition react with the H.sub.2S and other targeted contaminants for period of time such as 30 minutes-24 hours. The inventors have found that treatment process is very effective for safely and efficiently remediating the low to moderate levels of H.sub.2S, e.g., about 2000 ppm or less, and other targeted contaminants therein down to appropriate levels of less than 5 ppm within such time period without creating precipitates to be released from the treated liquids and without causing any significant problems for the treated liquids. The most appropriate dosage rate within the discussed range for the treatment composition, as well as for each of the components thereof, will be based on specific characteristics of the contaminated liquid being treated, but not so dependent on whether the liquid is a hydrocarbon based liquid or contaminated aqueous solution. Within such range, the most appropriate dosage rate largely depends on: 1) the amount of H.sub.2S and other targeted contaminants in the liquid being treated; 2) the viscosity of the liquid; and 3) the amount of time permitted for reacting the treatment composition with the liquid being treated. Heating and/or mixing of the liquid being treated may also be important considerations because heating and/or mixing of the liquid being treated will typically reduce the viscosity of the liquid and will also reduce the amount of time required for dispersing the treatment composition throughout the contaminated liquid for properly remediating the H.sub.2S and other targeted contaminants in the liquid. The dosage amount of treatment composition and each of its components are substantially, linearly scalable within the discussed range based on these factors.

(12) Other considerations regarding the dosage amount for a given contaminated liquid as discussed in PCT/US2018/064015 regarding the amounts of hydroxide compound(s) and organic acid(s) in the treatment solution also generally apply to the treatment solution according to the exemplary embodiment of the present invention. However, given that the dilute treatment composition according to the exemplary embodiment of the present invention contains a significantly larger proportion of water and less of the reactive compounds than the treatment composition of PCT/US2018/064015, it is important that the total water content of treated hydrocarbon based liquids such as crude oil not exceed 0.5 volume % because this could render the treated crude oil not marketable and valuable. Hence, if the contaminated liquid contains relatively higher amounts of H.sub.2S, e.g., exceeding 2000 ppm, it may be more appropriate to a less diluted version of the treatment composition according to the exemplary embodiment of the present invention or a treatment composition as disclosed in PCT/US2018/064015 rather than a fully treatment composition according to the present invention for treating the contaminated liquid.

Examples

(13) An example of an aqueous treatment composition according to the exemplary embodiment of the present invention may be prepared as follows. In an appropriate size container combine: 20-50 gallons of a concentrated aqueous solution containing 35-55 wt % collectively, preferably 45-55 wt % collectively, of one or more hydroxide compounds such as NaOH and KOH; 2-5 gallons of an aqueous solution containing about 1-10 wt % collectively of one or more organic acids such as fulvic acid and humic acid; 2-5 gallons of an aqueous solution containing 25-50 wt % of EDTA; and optionally 0.1-1 gallon of surfactant such as sodium lauryl sulphate, together with an amount of water to generate 330 gallons of the treatment composition. Again, timing for when some or all the amount of water is added to the other components may be delayed until the other components are brought to a location where the treatment composition is to be added to the contaminated liquid being treated, e.g., at a given oil well.

(14) A example of treatment process using an aqueous treatment composition according to the exemplary embodiment of the present invention to treat crude oil containing about 2000 ppm of H.sub.2S involves the steps of: 1) adding 5 ml of the treatment composition as prepared in the example of the preceding paragraph to a volume of contaminated crude oil contained in a closed vessel such as a tanker truck at a dosage rate of 5 ml of the treatment composition/liter of the crude oil; and 2) allowing the treatment composition to react with the H.sub.2S for a period of 15 minutes to 24 hours or until the concentration of H.sub.2S remaining in the crude oil is less than 5 ppm. Thus treated, the crude oil is safe for being transported to a refinery and the remediated H.sub.2S and other contaminants in the crude oil will remain in the crude oil without precipitating and being released from the treated crude oil.

INTENT OF DISCLOSURE

(15) Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid in understanding of the invention, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how it may later be disguised by variations in form or additions of further improvements. The claims at the end hereof are the chief aid toward this purpose, as it is these that meet the requirement of pointing out the improvements, combinations and methods in which the inventive concepts are found.

(16) The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention may be apparent to those having ordinary skill in the art and are encompassed by the claims appended hereto. For example, while the exemplary embodiment of the treatment composition is a relatively dilute aqueous solution containing a large proportion of water, an alternative treatment composition and treatment process according to the present invention may involves preparing a concentrated version of the treatment composition which is not diluted with water, and then a much smaller volume of the concentrated treatment solution is added per unit of the contaminated liquid, e.g., a dosage of 0.005-1.5 ml, preferably 0.05-0.5 ml of the new concentrated treatment composition is added/liter of contaminated liquid. The effective dosage amounts of the chemical reactants used in this treatment process would be the same as the effective dosage amounts of these chemical reactants used in the treatment process using the diluted treatment composition, but significantly less water would be used-added to the liquid being treated. As another example, it is possible to include other components in the treatment composition of the exemplary embodiment, such as MEA as an anti-scaling agent, an antibacterial such as a sulfite compound, etc.