Method for scavenging hydrogen sulphide and mercaptans using a composition comprising MMA and / or MEA triazine and an amino compound

Abstract

The present invention relates to a method for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group in a liquid or gaseous stream, comprising contacting said stream a composition comprising: - monoethanolamine triazine and / or monomethylamine triazine, and - at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of said amino compound(s) lies within the range from 1:1 to 100:1. The present invention also concerns an additive composition useful for scavenging hydrogen sulphide and organic compounds.

Description

[0001] The present invention relates to a method for scavenging hydrogen sulphide and organic compounds comprising at least one sulfhydryl group in a liquid or gaseous stream while reducing fouling and unwanted solid deposits. The method comprises contacting said stream with a composition comprising monoethanolamine triazine (also known as "MEA triazine") and / or monomethylamine triazine (also known as "MMA triazine") as well as a particular amino compound as defined below.

[0002] The invention also relates to compositions useful for implementing such a method.

[0003] The present invention also relates to the use of the compositions of the invention for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group in a liquid or gaseous stream.

[0004] The invention also relates to the use of said amino compound for preventing or reducing the formation of deposits in scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group with monoethanolamine triazine and / or monomethylamine triazine.

[0005] Hydrogen sulphide (H 2 S) is a colourless and fairly toxic, flammable and corrosive gas which has a characteristic odour at a very low concentration. Hydrogen sulphide dissolves in liquid and gaseous streams such as hydrocarbon and water streams and can also be present in the vapour phase above liquid streams as well as in hydrocarbon gas such as LPG and natural gas. The hydrogen sulphide emissions can be harmful to workers operating in the drilling, production, transport, storage, and processing of such streams. It would therefore be desirable for the workers' comfort and safety to reduce or even eliminate the hydrogen sulphide emissions during the handling of said products.

[0006] Legislation has been in place for years, imposing strict regulations on hydrogen sulphide levels of hydrocarbon streams in pipelines, in storage and shipping containers.

[0007] Similar problems arise with organic compounds comprising a sulfhydryl group (-SH) such as mercaptans R-SH, thiocarboxylic acids RC(O)SH, dithiocarboxylic acids RC(S)SH, with R denoting a hydrocarbon chain. Such sulfhydryl-containing compounds are very corrosive, and are likely to release hydrogen sulphide.

[0008] A variety of chemical scavengers are available to reduce the concentration of hydrogen sulphide and sulfhydryl-containing compounds in liquid and gaseous streams containing them, in particular aqueous streams and hydrocarbon streams such as gas, crude oils and refined products. Some of the most common methods for treating hydrogen sulphide consist in contacting them with a chemical scavenger such as compounds containing a triazine group, glyoxal, as well as metal-based scavengers. Glyoxal has been used extensively as hydrogen sulphide scavenger but suffers from a major drawback since aqueous glyoxal solutions are highly corrosive and cannot be used for a gas tower application. Monoethanolamine triazine (MEA-triazine) and monomethylamine triazine (MMA triazine) have recently become common chemical scavengers used for treating hydrogen sulphide from hydrocarbon streams.

[0009] However, the use of MEA-triazine and of MMA triazine as hydrogen sulphide scavengers has the drawback of leading to the formation of solid deposits. In the case of MEA-triazine, the deposits probably at least for a part thereof result from the further reaction and polymerization of MEA-dithiazine which is the product of reaction of MEA-triazine with H 2 S. The deposits mainly contain stable and water-insoluble solid compounds which can precipitate and accumulate, especially in the devices and installations used for extracting and transporting petroleum products.

[0010] As non-limitative examples of devices which may be damaged by such a fouling, mention may be made of artificial lift systems and pumps used in oil production wells, such as Progressive Cavity Pumps (often denoted PCP), Rod Lifts, Plunger Lifts, and Electric Submersible Pumps (often denoted ESPs).

[0011] Electric Submersible Pumps are particularly advantageous as they can handle a wide range of flow rates, especially from moderate to high volumes of oil, fulfil a large string of lift requirements, and be implemented in harsh environments.

[0012] However, these electric submersible pumps display a specific geometry that is very sensitive to solid fouling which may cause the pumps to malfunction.

[0013] It bespeaks that when such fouling occurs, operators need to stop the oil production for several days and initiate a chemical treatment for cleaning the pumps, especially the pumps internals including their surfaces.

[0014] Such a maintenance operation is time-consuming, so as the costs as the oil production must be halted for a long period of time and the cleaning treatment must be carried out several times, and risks damaging not only the pumps but also any part of the oil production installation. Indeed, the oil production installation and / or the electric submersible pumps may be impaired, especially during shutdown, cleaning, and / or restarting.

[0015] This maintenance operation may also have the drawback of having to be performed several times.

[0016] Hence, fouling or deposit formations linked with the hydrogen sulphide elimination treatments necessary in oil production may hinder oil productivity, lead to heavy financial losses, and shorten the lifetime of the pumps and / or the oil production installations. In addition, fouling can build-up on the surfaces of any part of the oil production installation in the same conditions as in the ESPs.

[0017] Thus, there remains a continuous need for improving existing methods for eliminating hydrogen sulphide and other compounds comprising a sulfhydryl group in an efficient, economic and safe manner, not only in crude oil extraction systems but in all situations where hydrogen sulphide and / or sulfhydryl compounds need to be removed. In particular, there remains a need for reducing the formation of unwanted deposits in methods involving MEA-triazine and MMA-triazine as scavenging agents.

[0018] The Applicant has now discovered that the combination of MEA-triazine and / or MMA-triazine with a particular amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane was particularly efficient for scavenging hydrogen sulphide and organic compounds comprising at least one sulfhydryl group, while reducing the formation of unwanted deposits.

[0019] Therefore, the present invention relates to a method for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group such as mercaptans in a liquid or gaseous stream, wherein said stream is contacted with a composition comprising: monoethanolamine triazine and / or monomethylamine triazine, and at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.

[0020] The method of the present invention allows achieving efficient scavenging of hydrogen sulphide and organic compounds comprising at least one sulfhydryl group in a short contact time, while preventing or reducing fouling as well as formation of unwanted deposits, with regard to prior art scavenging compositions comprising MEA-triazine or MMA-triazine.

[0021] In particular, the formation of deposits, especially water-insoluble solid deposits, can be greatly reduced.

[0022] Additionally, the efficiency of MEA-triazine and MMA-triazine as scavenging agents is substantially increased.

[0023] The invention also relates to an additive composition comprising: monoethanolamine triazine and / or monomethylamine triazine in a total amount ranging from 25% to 80% by weight, relative to the total weight of the composition, and at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.

[0024] The additive composition may be diluted or dispersed in a liquid vehicle.

[0025] The present invention also relates to the use of the composition of the invention for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group in a liquid or gaseous stream.

[0026] The invention also relates to the use of at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane for preventing or reducing the formation of deposits in the scavenging of hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group with monoethanolamine triazine and / or monomethylamine triazine.

[0027] In the following, and at least one other indication, the limits of a value range are included within this range, particularly in the expressions "between" and "ranging from ... to ...".

[0028] Moreover, the expressions "at least one" and "at least" used in the present description are respectively equivalent to the expressions "one or more" and "more than or equal to".

[0029] Finally, in a manner known per se, C N compound or group designates a compound or a group containing in its chemical structure N carbon atoms.The triazines

[0030] The present invention uses monoethanolamine triazine, also commonly referred to as MEA triazine and / or monomethylamine triazine also commonly referred to as MMA triazine.

[0031] The complete name of monomethylamine triazine is hexahydro-1,3,5-tris(methyl)-s-triazine.

[0032] The complete name of monoethanolamine triazine is hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine and the developed formula is the following:

[0033] Monoethanolamine triazine is preferred.

[0034] The composition contains a total amount of monomethylamine triazine and / or monoethanolamine triazine ranging from 25% to 80% by weight, preferably from 30 to 75% by weight, more preferably from 35% to 70% by weight, even more preferably from 40 to 70% by weight, and better still from 45 to 70% by weight, relative to the total weight of the composition.

[0035] According to a preferred embodiment, the composition contains an amount of monoethanolamine triazine ranging from 25% to 80% by weight, preferably from 30 to 75% by weight, more preferably from 35% to 70% by weight, even more preferably from 40 to 70% by weight, and better still from 45 to 70% by weight, relative to the total weight of the composition.The amino compounds

[0036] The present invention uses at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane.

[0037] These three amino compounds are very well known and easily available. In a manner known per se: Ammonium hydroxide is a salt of formula NH 4 OH or NH 3 .H 2 O; Ammonium persulfate is a salts of formula (NH 4 ) 2 S 2 O 8 ; and Tris(hydroxymethyl)aminomethane, also known as TRIS and as 2-amino-2-(hydroxyméthyl)propane-1,3-diol, is a compound of formula :

[0038] Mixtures of two or three of the above compounds are also contemplated in the present invention.

[0039] The additive composition preferably contains a total amount of the above described amino compound(s) ranging from 1 to 20% by weight, preferably from 2 to 15% by weight and more preferably from 4 to 12% by weight, relative to the total weight of the composition.

[0040] The weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1, preferably from 2:1 to 30:1, more preferably from 4:1 to 20:1.

[0041] According to a preferred embodiment, said at least one compound is ammonium hydroxide.

[0042] The additive composition preferably contains a total amount of ammonium hydroxide ranging from 1 to 20% by weight, preferably from 2 to 15% by weight and more preferably from 4 to 12% by weight, relative to the total weight of the composition.

[0043] The weight ratio between the amount of monoethanolamine triazine and the total amount of ammonium hydroxide preferably lies within the range from 1:1 to 100:1, preferably from 2:1 to 30:1, more preferably from 4:1 to 20:1.

[0044] According to another embodiment, aid at least one compound is ammonium persulfate.

[0045] The additive composition preferably contains a total amount of ammonium persulfate ranging from 1 to 20% by weight, preferably from 2 to 15% by weight and more preferably from 4 to 12% by weight, relative to the total weight of the composition.

[0046] The weight ratio between the amount of monoethanolamine triazine and the total amount of ammonium persulfate preferably lies within the range from 1:1 to 100:1, preferably from 2:1 to 30:1, more preferably from 4:1 to 20:1.

[0047] According to another embodiment, said at least one compound tris(hydroxymethyl)aminomethane.

[0048] The additive composition preferably contains a total amount of tris(hydroxymethyl)aminomethane ranging from 1 to 20% by weight, preferably from 2 to 15% by weight and more preferably from 4 to 12% by weight, relative to the total weight of the composition.

[0049] The weight ratio between the amount of monoethanolamine triazine and the total amount of tris(hydroxymethyl)aminomethane preferably lies within the range from 1:1 to 100:1, preferably from 2:1 to 30:1, more preferably from 4:1 to 20:1.

[0050] The additive composition of the invention may be diluted or dispersed in a liquid vehicle which facilitates its use and its dispersion within the medium to be treated.

[0051] The invention therefore encompasses a diluted composition comprising the additive composition as defined above and a liquid vehicle.Liquid vehicles

[0052] By liquid, it is meant a compound or a mixture of compounds which is in liquid form at ambient temperature (20°C) and atmospheric pressure (1,013.10 5< Pa).

[0053] According to a preferred embodiment, the liquid vehicle consists of water or a mixture of water with one or more organic solvent(s).

[0054] Such organic solvents may in particular be chosen from (poly) oxyalkyl ethers, such as butyl carbitol (diethylene glycol monobutyl ether), polyethylene glycols, as well as mixtures thereof.

[0055] The choice of the liquid vehicle mainly depends on the final use of the composition. When the composition is intended to be used for scavenging hydrogen sulphide and / or sulfhydryl-containing compounds in an aqueous stream, water may be a vehicle of choice. When the composition is intended to be used for scavenging hydrogen sulphide and / or sulfhydryl-containing compounds in a hydrocarbon stream or in a mixture of water and hydrocarbons (such as a mixture of crude oil and brine), a mixture of water and of organic solvent may be preferred.

[0056] The diluted composition of the invention advantageously contains an amount of liquid vehicle ranging from 30 to 90% by weight, preferably from 40 to 85% by weight, more preferably from 50 to 80% by weight, relative to the total weight of the composition.Defoamer

[0057] The composition of the invention may further comprise at least one defoamer, preferably at least one silicone-based defoamer.

[0058] The defoamers are preferably chosen from polydimethylsiloxane polymers, more preferably from grafted polydimethylsiloxane polymers.

[0059] The composition of the invention may contain an amount of defoamer ranging from 0.1 to 2% by weight, relative to the total weight of the composition.Uses

[0060] The present invention also encompasses the use of a composition as described above for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group in a liquid or gaseous stream.

[0061] The organic compounds comprising at least one sulfhydryl group are especially chosen from mercaptans, thiocarboxylic acids and dithiocarboxylic acids.

[0062] The liquid or gaseous stream may be a monophasic stream such as in particular an aqueous stream or an organic stream, or a multiphasic stream containing both water and hydrocarbons (such as for instance oil / water or oil / water / gas or gas / water).

[0063] According to a preferred embodiment, the composition of the invention is used for scavenging hydrogen sulphide (H 2 S) and mercaptans (compounds of formula RSH) in a hydrocarbon containing stream.

[0064] The mercaptans which need to be eliminated are typically those of formula RSH wherein R is an alkyl or alkenyl group containing from 1 to 8, preferably from 1 to 6 and more preferably from 1 to 4 carbon atoms.

[0065] The hydrocarbon containing streams are typically selected from crude petroleum oils, hydrocarbon fractions and residues deriving from the distillation thereof, light petroleum gas (LPG) and natural gas, as well as mixtures thereof with aqueous phases such as brine.

[0066] Such streams contain H 2 S and / or mercaptans in total amounts which may range for example from 1 to 10 000 ppm by weight.

[0067] The present invention also concerns the use of at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane for preventing or reducing the formation of solid deposits in the scavenging of hydrogen sulphide (H 2 S) and / or mercaptans with monoethanolamine triazine and / or monomethylamine triazine, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.Method

[0068] The method of the invention comprises contacting said a liquid or gaseous stream with a composition as disclosed herein.

[0069] As described above, the liquid or gaseous stream may be monophasic such as in particular an aqueous stream or an organic stream, or multiphasic such as a stream containing both water and hydrocarbons (such as for instance oil / water or oil / water / gas or gas / water).

[0070] According to a preferred embodiment, the stream contains hydrocarbons. The stream may be especially selected from crude petroleum oils, hydrocarbon fractions and residues deriving from the distillation thereof such as in particular fuel oils and heavy fuel oils, light petroleum gas (LPG) and natural gas, as well as mixtures thereof with aqueous compositions such as brine.

[0071] The amount of additive composition used per amount of stream depends on the concentration of active components (MEA-triazine and / or MMA-triazine and amino compounds) as well as the total content of hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group in the liquid or gaseous stream.

[0072] The composition is contacted with the liquid or gaseous stream for a time sufficient to achieve an effective scavenging and removal of hydrogen sulphide and of organic compounds comprising at least one sulfhydryl group.

Claims

1. Method for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group such as mercaptans in a liquid or gaseous stream, wherein said stream is contacted with a composition comprising: - monoethanolamine triazine and / or monomethylamine triazine, and - at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.

2. The method of claim 1, wherein the composition comprises monoethanolamine triazine.

3. The method according to anyone of claims 1 and 2, wherein said at least one amino compound is ammonium hydroxide.

4. The method according to anyone of claims 1 to 3, wherein, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 2:1 to 30:1, preferably from 4:1 to 20:1.

5. Additive composition comprising: - monoethanolamine triazine and / or monomethylamine triazine in a total amount ranging from 25% to 80% by weight, relative to the total weight of the composition, and - at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.

6. The composition of claim 5, wherein the total amount of monoethanolamine triazine and / or monomethylamine triazine ranges from 30 to 75% by weight, preferably from 35% to 70% by weight, even more preferably from 40 to 70% by weight, and better still from 45 to 70% by weight, relative to the total weight of the composition.

7. The composition as defined in anyone of claims 5 and 6, comprising monoethanolamine triazine.

8. The composition as defined in anyone of claims 5 to 7, wherein said at least one amino compound is ammonium hydroxide.

9. The composition as defined in anyone of claims 5 to 8, wherein the total amount of said amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane ranges from 1 to 20% by weight, preferably from 2 to 15% by weight and more preferably from 4 to 12% by weight, relative to the total weight of the composition.

10. The composition as defined in anyone of claims 5 to 9, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 2:1 to 30:1, preferably from 4:1 to 20:1.

11. A diluted composition comprising the additive composition as defined in anyone of claims 5 to 10 and a liquid vehicle, which preferably consisting of water or a mixture of water with one or more organic solvent(s).

12. The composition as defined in claim 11, wherein the amount of liquid vehicle ranges from 30 to 90% by weight, preferably from 40 to 85% by weight, more preferably from 50 to 80% by weight, relative to the total weight of the composition.

13. Use of a composition as defined in anyone of claims 1 to 12 for scavenging hydrogen sulphide and / or organic compounds comprising at least one sulfhydryl group such as mercaptans in a liquid or gaseous stream.

14. Use of at least one amino compound chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane for preventing or reducing the formation of solid deposits in the scavenging of hydrogen sulphide and / or mercaptans with monoethanolamine triazine and / or monomethylamine triazine, wherein the weight ratio between the total amount of monoethanolamine triazine and / or monomethylamine triazine and the total amount of amino compound(s) chosen from ammonium hydroxide, ammonium persulfate and tris(hydroxymethyl)aminomethane lies within the range from 1:1 to 100:1.

Images