EP1270704B1 - A process for removing sulfur compounds from hydrocarbon streams - Google Patents
A process for removing sulfur compounds from hydrocarbon streams Download PDFInfo
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- EP1270704B1 EP1270704B1 EP01115343A EP01115343A EP1270704B1 EP 1270704 B1 EP1270704 B1 EP 1270704B1 EP 01115343 A EP01115343 A EP 01115343A EP 01115343 A EP01115343 A EP 01115343A EP 1270704 B1 EP1270704 B1 EP 1270704B1
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G19/00—Refining hydrocarbon oils in the absence of hydrogen, by alkaline treatment
- C10G19/02—Refining hydrocarbon oils in the absence of hydrogen, by alkaline treatment with aqueous alkaline solutions
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G19/00—Refining hydrocarbon oils in the absence of hydrogen, by alkaline treatment
- C10G19/08—Recovery of used refining agents
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/12—Liquefied petroleum gas
Definitions
- This invention relates to a process for removing sulfur compounds such as H 2 S and mercaptans from a hydrocarbon stream.
- the process involves contacting the hydrocarbon stream with a weakly basic aqueous stream such as a sodium bicarbonate solution in order to extract the H 2 S and mercaptans from the hydrocarbon stream.
- the basic stream is now flowed to a reactor containing microorganisms and oxygen in order to convert the H 2 S to sulfur and the mercaptans to disulfides.
- the sulfur and disulfides are separated from the basic stream which can then be recycled and used to treat a fresh hydrocarbon stream.
- Hydrocarbon streams which contain sulfur compounds such as mercaptans are usually referred to as sour hydrocarbon streams.
- sour hydrocarbon streams In order to render these hydrocarbon streams usable, it is common in the oil refining industry to treat these streams in one of two ways.
- One way is to contact the sour stream (usually a liquid stream) with an oxidation catalyst and an alkaline agent in the presence of an oxidizing agent such as air at reaction conditions in order to convert the mercaptans to disulfides.
- Another way to treat these sour hydrocarbon streams is to contact the hydrocarbon stream with a strongly basic solution in order to extract the mercaptans into the basic solution thereby forming mercaptides and then taking the basic solution and regenerating it by contacting it with an oxidizing catalyst, an alkaline agent, and an oxidizing agent such as air to convert the mercaptides to disulfides.
- the disulfides are separated from the basic solution which is recycled and used to extract more mercaptans from a fresh hydrocarbon stream.
- the first type of process is disclosed in a number of U.S. patents, including U.S. Pat. Nos. 3,108,081; 4,156,641; 4,913,802; 4,290,913 and 4,337,147. Processes in which the mercaptans are extracted with an alkaline solution are disclosed in U.S. Patent Nos. 2,853,432; 2,921,020; 2,988,500 and 3,408,287.
- U.S.-A-4,666,689 again discloses contacting hydrocarbon streams with alkaline solutions such as aqueous sodium hydroxide solutions.
- alkaline solutions such as aqueous sodium hydroxide solutions.
- sulfur compounds such as H 2 S are removed from a gaseous effluent. The gaseous waste stream is first contacted with a basic aqueous solution and then the aqueous solution is treated in a bioreactor thereby converting the H 2 S to elemental sulfur in order to regenerate the basic solution. It is disclosed in the '545 patent that an improvement in H 2 S removal is observed when the recirculating basic solution contains from 0.1 to 50 g/l of sulfur.
- US 6, 224, 750 discloses a process for treating a hydrocarbon feedstream comprising sulfur-containing compounds, such as, hydrogen sulfide and mercaptans.
- the process comprises the steps of contacting the hydrocarbon stream with an aqueous basic solution, whereby, the sulfur-containing compounds are extracted into the basic aqueous stream. Subsequently the basic stream is separated from the hydrocarbon stream, and following to this the basic stream is contacted with microorganisms to convert sulfide into elemental sulfur.
- the biological conversion conditions are aerobic and the bacteria employed in this reaction include the oxidizing bacteria of the genera thiobacillus and thiomicrospira. After the conversion reaction the elemental sulfur is separated from the basic solution thereby forming a regenerated basic stream.
- GB 912,926 is related to a process of purifying an acid oil consisting substantially of phenolic compounds and carboxylic acids and containing mercaptans as contaminants. Therefore, an alkaline solution of the acid oil is subjected to an oxidizing treatment with a gas containing free oxygen in the presence of a phthalocyanine sulfonate or carboxylate catalyst and the resulting disulfides are separated as an upper layer or extracted from the alkaline solution.
- Applicants have developed a process whereby a liquid hydrocarbon stream containing both H 2 S and mercaptans is contacted with a weakly basic solution, e.g., bicarbonate solution, to simultaneously remove H 2 S and mercaptans.
- a weakly basic solution e.g., bicarbonate solution
- the basic solution which now contains H 2 S and mercaptans is treated in a bioreactor where the solution is contacted with a sulfide oxidizing bacteria in the presence of oxygen.
- the H 2 S is converted to elemental sulfur while the mercaptans are converted to disulfides.
- the oxygen level in the reactor is controlled in order to obtain these final products.
- the sulfur and disulfides are removed from the aqueous stream which is then recirculated and used to further extract hydrogen sulfide and mercaptans from a fresh liquid hydrocarbon stream.
- the treated liquid hydrocarbon stream now contains substantially less hydrogen sulfide and mercaptans, and can be used in various applications.
- the present invention relates to a process for simultaneously removing H 2 S and mercaptans from a liquid hydrocarbon stream. Accordingly, one embodiment of the invention is a process comprising:
- the basic stream which enters the reactor may also contain some hydrocarbons.
- the Figure is a simplified process flow diagram of one embodiment of the inventionshowing the extraction of H 2 S and mercaptans from a hydrocarbon stream with a weakly basic aqueous stream and the subsequent purification of the aqueous stream.
- the hydrocarbon streams which can be treated by the process of this invention can vary widely and usually contain from 2 to 30 carbon atoms and include both liquid and gaseous streams. Specific examples include what is commonly referred to as liquefied petroleum gas (LPG) which contains mostly C 3 to C 4 hydrocarbons. Other examples include gasoline hydrocarbon streams, naphtha hydrocarbon streams, diesel hydrocarbon streams and streams containing mainly single components such as ethylene or pentanes (C 5 ). Usually these hydrocarbon streams will contain from 5 to 5,000 ppm H 2 S and from 5 to 5,000 ppm mercaptans.
- LPG liquefied petroleum gas
- Other examples include gasoline hydrocarbon streams, naphtha hydrocarbon streams, diesel hydrocarbon streams and streams containing mainly single components such as ethylene or pentanes (C 5 ). Usually these hydrocarbon streams will contain from 5 to 5,000 ppm H 2 S and from 5 to 5,000 ppm mercaptans.
- a weakly basic stream is meant a stream which contains a compound which is weakly dissociated in water (as defined in standard chemistry texts). These compounds include but are not limited to sodium carbonate, sodium bicarbonate, sodium phosphate, ammonium hydroxide, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, etc. Strongly basic, i.e., completely dissociated compounds, such as sodium hydroxide, are not included in the basic compounds which are used to practice the present invention.
- the basic stream for the treatment of the hydrocarbon stream has a pH of 7.5 to 14.
- a basic stream Contacting of the hydrocarbon stream with the weakly basic aqueous stream (hereinafter referred to as a basic stream) can be done by means well known in the art, using vessels which are commonly known as extractors or extraction columns.
- the extractor will contain a number of trays or packed beds in order to increase the contact between the two streams. These trays or beds are generally referred to as equilibrium stages and an extractor will contain from 1 to 20 equilibrium stages.
- the two streams can be contacted either cocurrently or countercurrently.
- the extraction conditions which are used in such extractors include a temperature of 20°C to 50°C, a basic compound to hydrocarbon weight ratio of 30:1 to 0.01:1, and a pressure of 100 to 2500 kPa. It should be pointed out that the strength of the basic stream can be much stronger in the extraction part of the process and then can be diluted with water to a pH of 7.1 to 10.5, which is compatible with the microorganisms in the subsequent part of the process.
- the purified hydrocarbon stream is now separated from the basic stream and collected.
- the hydrocarbon stream can optionally be flowed through an adsorbent bed, e.g., carbon bed, or other type of drying bed in order to remove any residual water and some sulfur compounds from the hydrocarbon stream.
- an adsorbent bed e.g., carbon bed, or other type of drying bed in order to remove any residual water and some sulfur compounds from the hydrocarbon stream.
- the purified hydrocarbon stream pass the copper strip corrosion test as defined by ASTM methods D-130, D-1838 and D-2420.
- the copper strip test is a test which detects the presence of components in the hydrocarbon stream which may be corrosive to copper. Passing the copper strip test, i.e., minimal corrosion, provides assurance that problems will not be experienced with many of the fittings and connections that are commonly used in storage, transportation, etc., which are composed of copper or copper alloys.
- the basic stream which now contains the hydrogen sulfide and mercaptans which have been converted to HS - and mercaptide ions respectively is flowed to a reactor which contains microorganisms such as cultures of the genera Thiobacillus and Thiomicrospira. These microorganisms are described in U.S. Patent 5,354,545, which is incorporated by reference. These bacteria are capable of oxidizing sulfide to elemental sulfur in the presence of oxygen.
- the microorganisms i.e., bacteria
- the sulfide (HS - ) to elemental sulfur.
- the mercaptides (RS - ) are converted to disulfides.
- the mercaptides are converted to disulfides chemically, i.e., without the aid of the bacteria.
- the partial oxidation of the mercaptides to disulfides by the bacteria may be taking place to some extent. That is, although both biological and chemical conversion of the mercaptides to disulfides can both be occurring, it is believed that the primary conversion route is chemical.
- the basic stream In order to carry out the conversion of hydrogen sulfide to sulfur and the mercaptans to disulfides, the basic stream must be contacted with the microorganisms and oxygen for a sufficient time.
- the amount of oxygen fed to the reactor is controlled in order to convert the sulfide ions to elemental sulfur and the mercaptides to disulfides.
- this amount of oxygen which can be derived from air or some other oxygen source, varies from 0.4 to 2.0 moles O 2 /moles S (total sulfur).
- this time can vary from 15 min. to 10 hours and preferably from 2 hrs. to 5 hrs.
- the basic stream can be treated in a batch or continuous process, a continuous process is preferred.
- Other sulfide and mercaptide conversion conditions include a temperature of 20°C to 50°C, a pH of 7.1 to 10.5 and atmospheric pressure (or higher, e.g., 100 to 1,000 kPa).
- hydrocarbons may be present in the basic stream. This is the result of either incomplete separation or the partial solubility of hydrocarbons in the basic stream.
- the amount of hydrocarbons will be small and usually in the range of 1 ppm to 500 ppm by weight. It is surprising that the bacteria can function in the presence of hydrocarbons.
- the basic stream is further processed in order to remove the sulfur and disulfide components in the basic stream. Since the disulfides are not very water soluble, if a sufficient quantity of disulfides is present, a disulfide layer will form at the top of the basic stream or solution. This disulfide layer can be withdrawn by any means known in the art.
- the basic stream is flowed from the reactor to a first separation zone where the elemental sulfur is separated from the aqueous stream usually by filtration or any other method of separating a solid from a liquid, which methods are well known in the art.
- the disulfides are not separated from the basic stream in the reactor.
- concentration of the disulfides is such that only droplets are formed, then they are dispersed throughout the aqueous stream and cannot be siphoned or withdrawn from the aqueous phase.
- the effluent from the first separation zone is flowed to a second separation zone where the disulfide oil is separated from the aqueous stream. This can be done by settling or extraction with a solvent, both of which are well known in the art.
- the purified stream Since a portion of the purified basic stream can be recycled to the extraction step and contacted with a fresh hydrocarbon stream, it is necessary that the purified stream contain less than 0.08 g/l of elemental sulfur. Controlling the sulfur level to this amount will assure that the purified hydrocarbon stream will meet the copper strip corrosion test.
- a hydrocarbon stream containing H 2 S and mercaptan impurities is flowed via line 1 into extraction column 2 where it is contacted with a basic stream which is flowed into column 2 via line 3 .
- H 2 S and mercaptans are extracted from the hydrocarbon stream into the basic stream.
- the purified hydrocarbon stream is removed via line 4 and collected.
- the hydrocarbon stream can be removed via line 5 , flowed to adsorbent bed 6 in order to remove any water impurities and some of the residual sulfur compounds and then withdrawn and collected via line 7 .
- the aqueous stream is removed from extraction column 2 via line 8 and flowed to reactor 9 where it is contacted with a sulfide oxidizing microorganism in the presence of oxygen, thereby converting the H 2 S to sulfur and the mercaptans to disulfides. If the disulfide oil forms a layer on top of the aqueous phase, it is withdrawn via line 10 .
- the aqueous stream is flowed from reactor 9 via line 11 to a first separation zone 12 where the elemental sulfur is separated from the aqueous stream.
- the sulfur is removed via line 13 and the aqueous stream is removed via line 14 .
- a portion or all of the aqueous stream can be recycled via line 15 to extraction column 2 .
- the aqueous stream is removed via line 16 to a second separation zone 17 where the disulfides are separated from the aqueous stream by settling, extraction or other known means.
- the disulfides are now removed via line 18 and the aqueous stream is removed via line 19 . Again, a portion of the aqueous stream can be recycled to extraction column 2 via line 20 .
- a LPG feed stream containing 900 ppm H 2 S and 200 ppm mercaptans was contacted with a sodium bicarbonate solution in a single stage extractor column operated at ambient temperature (24°C), an LPG feed rate of 375g/hr, a bicarbonate solution feed rate of 1080g/hr, a pressure of 1034 kPa (150 psi) and a bicarbonate solution to hydrocarbon weight ratio of 2.8.
- the aqueous stream was separated from the hydrocarbon stream. Analysis of the hydrocarbon stream showed that 100% of the H 2 S and 60% of the mercaptans were extracted from the hydrocarbon stream.
- the aqueous stream was flowed to a bioreactor containing Thiobacillus bacteria.
- This reactor was operated at ambient temperature (24°C), a pH of 9.0 and an O 2 /S mole ratio range of 0.5:1 to 1.0:1.0.
- the effluent from this bioreactor was analyzed and showed that all the H 2 S was converted with a selectivity of 75% to sulfur, a selectivity of 20% to sulfate and a selectivity of 5% to thiosulfate. Greater than 85% of the mercaptans were converted with a selectivity of 75% to disulfides.
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Abstract
Description
- This invention relates to a process for removing sulfur compounds such as H2S and mercaptans from a hydrocarbon stream. The process involves contacting the hydrocarbon stream with a weakly basic aqueous stream such as a sodium bicarbonate solution in order to extract the H2S and mercaptans from the hydrocarbon stream. The basic stream is now flowed to a reactor containing microorganisms and oxygen in order to convert the H2S to sulfur and the mercaptans to disulfides. The sulfur and disulfides are separated from the basic stream which can then be recycled and used to treat a fresh hydrocarbon stream.
- Hydrocarbon streams which contain sulfur compounds such as mercaptans are usually referred to as sour hydrocarbon streams. In order to render these hydrocarbon streams usable, it is common in the oil refining industry to treat these streams in one of two ways. One way is to contact the sour stream (usually a liquid stream) with an oxidation catalyst and an alkaline agent in the presence of an oxidizing agent such as air at reaction conditions in order to convert the mercaptans to disulfides. Another way to treat these sour hydrocarbon streams is to contact the hydrocarbon stream with a strongly basic solution in order to extract the mercaptans into the basic solution thereby forming mercaptides and then taking the basic solution and regenerating it by contacting it with an oxidizing catalyst, an alkaline agent, and an oxidizing agent such as air to convert the mercaptides to disulfides. The disulfides are separated from the basic solution which is recycled and used to extract more mercaptans from a fresh hydrocarbon stream. The first type of process is disclosed in a number of U.S. patents, including U.S. Pat. Nos. 3,108,081; 4,156,641; 4,913,802; 4,290,913 and 4,337,147. Processes in which the mercaptans are extracted with an alkaline solution are disclosed in U.S. Patent Nos. 2,853,432; 2,921,020; 2,988,500 and 3,408,287.
- It is also known that if the liquid hydrocarbon streams contain H2S, that this must be removed separately before the mercaptans are either extracted and oxidized or oxidized to disulfides in one step. This separate process usually involves contacting the stream with either a basic solution or an adsorbent in order to remove the H2S present in the hydrocarbon stream. For example, U.S.-A-4,562,300 discloses a process for extracting mercaptans from hydrocarbon distillates with an alkaline solution having from about 5 to about 50 weight percent of an alkaline. Alkaline materials include sodium hydroxide, lithium hydroxide and potassium hydroxide. These alkaline materials are all very strong bases. U.S.-A-4,666,689 again discloses contacting hydrocarbon streams with alkaline solutions such as aqueous sodium hydroxide solutions. Finally, In U.S. Patent 5,354,545 it is disclosed that sulfur compounds such as H2S are removed from a gaseous effluent. The gaseous waste stream is first contacted with a basic aqueous solution and then the aqueous solution is treated in a bioreactor thereby converting the H2S to elemental sulfur in order to regenerate the basic solution. It is disclosed in the '545 patent that an improvement in H2S removal is observed when the recirculating basic solution contains from 0.1 to 50 g/l of sulfur.
- US 6, 224, 750 discloses a process for treating a hydrocarbon feedstream comprising sulfur-containing compounds, such as, hydrogen sulfide and mercaptans. The process comprises the steps of contacting the hydrocarbon stream with an aqueous basic solution, whereby, the sulfur-containing compounds are extracted into the basic aqueous stream. Subsequently the basic stream is separated from the hydrocarbon stream, and following to this the basic stream is contacted with microorganisms to convert sulfide into elemental sulfur. The biological conversion conditions are aerobic and the bacteria employed in this reaction include the oxidizing bacteria of the genera thiobacillus and thiomicrospira. After the conversion reaction the elemental sulfur is separated from the basic solution thereby forming a regenerated basic stream.
- GB 912,926 is related to a process of purifying an acid oil consisting substantially of phenolic compounds and carboxylic acids and containing mercaptans as contaminants. Therefore, an alkaline solution of the acid oil is subjected to an oxidizing treatment with a gas containing free oxygen in the presence of a phthalocyanine sulfonate or carboxylate catalyst and the resulting disulfides are separated as an upper layer or extracted from the alkaline solution.
- Applicants have developed a process whereby a liquid hydrocarbon stream containing both H2S and mercaptans is contacted with a weakly basic solution, e.g., bicarbonate solution, to simultaneously remove H2S and mercaptans. The basic solution which now contains H2S and mercaptans is treated in a bioreactor where the solution is contacted with a sulfide oxidizing bacteria in the presence of oxygen. The H2S is converted to elemental sulfur while the mercaptans are converted to disulfides. The oxygen level in the reactor is controlled in order to obtain these final products. Subsequently, the sulfur and disulfides are removed from the aqueous stream which is then recirculated and used to further extract hydrogen sulfide and mercaptans from a fresh liquid hydrocarbon stream. The treated liquid hydrocarbon stream now contains substantially less hydrogen sulfide and mercaptans, and can be used in various applications.
- In comparison to U.S.-A-5,354,545 applicants have demonstrated that a weakly basic solution can be used to extract H2S and mercaptans from a liquid hydrocarbon stream. It is also surprising that the bacteria is able to function even when small amounts of hydrocarbons are present in the aqueous stream. Finally, applicants' treated aqueous stream will contain less than 0.08 g/l of elemental sulfur.
- The present invention relates to a process for simultaneously removing H2S and mercaptans from a liquid hydrocarbon stream. Accordingly, one embodiment of the invention is a process comprising:
- a) contacting the hydrocarbon stream with a weakly basic aqueous stream in an extraction column at extraction conditions, thereby extracting H2S and mercaptans into the basic stream;
- b) separating the basic stream from the hydrocarbon stream and collecting a treated hydrocarbon stream, which passes the copper strip test;
- c) flowing the basic stream to a reactor and contacting the stream for a sufficient time with a sulfide oxidizing microorganism, in the presence of sufficient oxygen, to oxidize the H2S to elemental sulfur and oxidize the mercaptans to disulfides;
- d) separating the disulfides from the basic stream and flowing the basic stream to a first separation zone where the elemental sulfur is separated from the basic stream to give a purified basic stream, which contains less than 0.08 g/l of sulfur, and
- e) flowing the basic stream from step (d) to a second separation zone where any remaining disulfides are separated from the purified basic stream by settling or extraction with a solvent.
- The basic stream which enters the reactor may also contain some hydrocarbons.
- These and other objects and embodiments will become more apparent after a detailed description of the invention.
- The Figure is a simplified process flow diagram of one embodiment of the inventionshowing the extraction of H2S and mercaptans from a hydrocarbon stream with a weakly basic aqueous stream and the subsequent purification of the aqueous stream.
- The hydrocarbon streams which can be treated by the process of this invention can vary widely and usually contain from 2 to 30 carbon atoms and include both liquid and gaseous streams. Specific examples include what is commonly referred to as liquefied petroleum gas (LPG) which contains mostly C3 to C4 hydrocarbons. Other examples include gasoline hydrocarbon streams, naphtha hydrocarbon streams, diesel hydrocarbon streams and streams containing mainly single components such as ethylene or pentanes (C5). Usually these hydrocarbon streams will contain from 5 to 5,000 ppm H2S and from 5 to 5,000 ppm mercaptans.
- The hydrocarbon stream which is to be treated is now contacted with a weakly basic aqueous stream at extraction conditions in order to extract H2S and mercaptans into the aqueous stream. By a weakly basic stream is meant a stream which contains a compound which is weakly dissociated in water (as defined in standard chemistry texts). These compounds include but are not limited to sodium carbonate, sodium bicarbonate, sodium phosphate, ammonium hydroxide, potassium carbonate, potassium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, etc. Strongly basic, i.e., completely dissociated compounds, such as sodium hydroxide, are not included in the basic compounds which are used to practice the present invention. In preferred embodiments of the present invention, the basic stream for the treatment of the hydrocarbon stream has a pH of 7.5 to 14.
- Contacting of the hydrocarbon stream with the weakly basic aqueous stream (hereinafter referred to as a basic stream) can be done by means well known in the art, using vessels which are commonly known as extractors or extraction columns. The extractor will contain a number of trays or packed beds in order to increase the contact between the two streams. These trays or beds are generally referred to as equilibrium stages and an extractor will contain from 1 to 20 equilibrium stages. The two streams can be contacted either cocurrently or countercurrently. Typically the extraction conditions which are used in such extractors include a temperature of 20°C to 50°C, a basic compound to hydrocarbon weight ratio of 30:1 to 0.01:1, and a pressure of 100 to 2500 kPa. It should be pointed out that the strength of the basic stream can be much stronger in the extraction part of the process and then can be diluted with water to a pH of 7.1 to 10.5, which is compatible with the microorganisms in the subsequent part of the process.
- The purified hydrocarbon stream is now separated from the basic stream and collected. The hydrocarbon stream can optionally be flowed through an adsorbent bed, e.g., carbon bed, or other type of drying bed in order to remove any residual water and some sulfur compounds from the hydrocarbon stream. It is also necessary that the purified hydrocarbon stream pass the copper strip corrosion test as defined by ASTM methods D-130, D-1838 and D-2420. The copper strip test is a test which detects the presence of components in the hydrocarbon stream which may be corrosive to copper. Passing the copper strip test, i.e., minimal corrosion, provides assurance that problems will not be experienced with many of the fittings and connections that are commonly used in storage, transportation, etc., which are composed of copper or copper alloys.
- The basic stream which now contains the hydrogen sulfide and mercaptans which have been converted to HS- and mercaptide ions respectively is flowed to a reactor which contains microorganisms such as cultures of the genera Thiobacillus and Thiomicrospira. These microorganisms are described in U.S. Patent 5,354,545, which is incorporated by reference. These bacteria are capable of oxidizing sulfide to elemental sulfur in the presence of oxygen.
- In the reactor, the microorganisms, i.e., bacteria, convert the sulfide (HS-) to elemental sulfur. Simultaneously the mercaptides (RS-) are converted to disulfides. Without wishing to be bound by any particular mechanism or theory, it appears that the mercaptides are converted to disulfides chemically, i.e., without the aid of the bacteria. However, the partial oxidation of the mercaptides to disulfides by the bacteria may be taking place to some extent. That is, although both biological and chemical conversion of the mercaptides to disulfides can both be occurring, it is believed that the primary conversion route is chemical.
- In order to carry out the conversion of hydrogen sulfide to sulfur and the mercaptans to disulfides, the basic stream must be contacted with the microorganisms and oxygen for a sufficient time. The amount of oxygen fed to the reactor is controlled in order to convert the sulfide ions to elemental sulfur and the mercaptides to disulfides. Generally this amount of oxygen, which can be derived from air or some other oxygen source, varies from 0.4 to 2.0 moles O2/moles S (total sulfur). Generally this time can vary from 15 min. to 10 hours and preferably from 2 hrs. to 5 hrs. Although the basic stream can be treated in a batch or continuous process, a continuous process is preferred. Other sulfide and mercaptide conversion conditions include a temperature of 20°C to 50°C, a pH of 7.1 to 10.5 and atmospheric pressure (or higher, e.g., 100 to 1,000 kPa).
- It should also be pointed out that some amount of hydrocarbons may be present in the basic stream. This is the result of either incomplete separation or the partial solubility of hydrocarbons in the basic stream. The amount of hydrocarbons will be small and usually in the range of 1 ppm to 500 ppm by weight. It is surprising that the bacteria can function in the presence of hydrocarbons.
- Once conversion of H2S to sulfur and mercaptans to disulfides is accomplished, the basic stream is further processed in order to remove the sulfur and disulfide components in the basic stream. Since the disulfides are not very water soluble, if a sufficient quantity of disulfides is present, a disulfide layer will form at the top of the basic stream or solution. This disulfide layer can be withdrawn by any means known in the art.
- Next, the basic stream is flowed from the reactor to a first separation zone where the elemental sulfur is separated from the aqueous stream usually by filtration or any other method of separating a solid from a liquid, which methods are well known in the art.
- In some instances, the disulfides are not separated from the basic stream in the reactor. For example, if the concentration of the disulfides is such that only droplets are formed, then they are dispersed throughout the aqueous stream and cannot be siphoned or withdrawn from the aqueous phase. In such cases the effluent from the first separation zone is flowed to a second separation zone where the disulfide oil is separated from the aqueous stream. This can be done by settling or extraction with a solvent, both of which are well known in the art. Even if a disulfide layer is withdrawn in the reactor, further purification in a second separation zone may be desirable in order to ensure more complete removal of the disulfides and thus prevent recontamination of the hydrocarbon stream if a portion of the aqueous stream is recycled to the extractor. The purified basic stream can now either be disposed of or at least a portion of it can be recycled to the extractor and contacted with a fresh liquid hydrocarbon stream in order to further extract hydrogen sulfide and mercaptans.
- Since a portion of the purified basic stream can be recycled to the extraction step and contacted with a fresh hydrocarbon stream, it is necessary that the purified stream contain less than 0.08 g/l of elemental sulfur. Controlling the sulfur level to this amount will assure that the purified hydrocarbon stream will meet the copper strip corrosion test.
- The Figure illustrates one embodiment of the invention. Referring now to the Figure: a hydrocarbon stream containing H2S and mercaptan impurities is flowed via line 1 into
extraction column 2 where it is contacted with a basic stream which is flowed intocolumn 2 vialine 3. Inextraction column 2, H2S and mercaptans are extracted from the hydrocarbon stream into the basic stream. The purified hydrocarbon stream is removed via line 4 and collected. Optionally, the hydrocarbon stream can be removed vialine 5, flowed to adsorbent bed 6 in order to remove any water impurities and some of the residual sulfur compounds and then withdrawn and collected vialine 7. - The aqueous stream is removed from
extraction column 2 vialine 8 and flowed toreactor 9 where it is contacted with a sulfide oxidizing microorganism in the presence of oxygen, thereby converting the H2S to sulfur and the mercaptans to disulfides. If the disulfide oil forms a layer on top of the aqueous phase, it is withdrawn vialine 10. - The aqueous stream is flowed from
reactor 9 vialine 11 to afirst separation zone 12 where the elemental sulfur is separated from the aqueous stream. The sulfur is removed vialine 13 and the aqueous stream is removed vialine 14. A portion or all of the aqueous stream can be recycled vialine 15 toextraction column 2. - When the aqueous phase still contains disulfides, the aqueous stream is removed via
line 16 to asecond separation zone 17 where the disulfides are separated from the aqueous stream by settling, extraction or other known means. The disulfides are now removed vialine 18 and the aqueous stream is removed vialine 19. Again, a portion of the aqueous stream can be recycled toextraction column 2 vialine 20. - The following examples are presented in illustration of this invention and are not intended as undue limitations on the generally broad scope of the invention as set out in the appended claims.
- A LPG feed stream containing 900 ppm H2S and 200 ppm mercaptans was contacted with a sodium bicarbonate solution in a single stage extractor column operated at ambient temperature (24°C), an LPG feed rate of 375g/hr, a bicarbonate solution feed rate of 1080g/hr, a pressure of 1034 kPa (150 psi) and a bicarbonate solution to hydrocarbon weight ratio of 2.8. The aqueous stream was separated from the hydrocarbon stream. Analysis of the hydrocarbon stream showed that 100% of the H2S and 60% of the mercaptans were extracted from the hydrocarbon stream.
- Next, the aqueous stream was flowed to a bioreactor containing Thiobacillus bacteria. This reactor was operated at ambient temperature (24°C), a pH of 9.0 and an O2/S mole ratio range of 0.5:1 to 1.0:1.0. The effluent from this bioreactor was analyzed and showed that all the H2S was converted with a selectivity of 75% to sulfur, a selectivity of 20% to sulfate and a selectivity of 5% to thiosulfate. Greater than 85% of the mercaptans were converted with a selectivity of 75% to disulfides.
Claims (9)
- A process for treating a hydrocarbon stream containing H2S and mercaptans comprising:a) contacting the hydrocarbon stream with a basic stream in an extraction column at extraction conditions, thereby extracting H2S and mercaptans into the basic stream; whereby the basic stream is a weakly basic aqueous solution;b) separating the basic stream from the hydrocarbon stream and collecting a treated hydrocarbon stream which passes the copper strip test;c) flowing the basic stream to a reactor and contacting the stream for a sufficient time with a sulfide oxidizing microorganism, at conversion conditions in the presence of sufficient oxygen, to convert the H2S to elemental sulphur and convert the mercaptans to disulfides;d) separating the disulfides from the basic stream and flowing the basic stream to a first separation zone where the elemental sulphur is separated from the basic stream to give a purified basic stream, which contains less than 0.08 g/l of sulphur;e) flowing the basic stream from step (d) to a second separation zone where any remaining disulfides are separated from the purified basic stream by settling or extraction with a solvent.
- The process of claim 1 further characterized in that at least a portion of the purified basic stream from step e) is recycled to the extraction column of step a).
- The process of any of claims 1 or 2 wherein the basic stream enters the reactor with from 1 ppm to 500 ppm by weight of hydrocarbons.
- The process of any of claims 1 to 3, wherein the hydrocarbon stream is a LPG stream containing C3 and C4 hydrocarbons.
- The process of any of claims 1 to 4, wherein the basic stream of step a) has a pH of 7.5 to 14.
- The process of any of claims 1 to 5, wherein the basic stream contains a basic compound selected from the group consisting of sodium carbonate, sodium bicarbonate and ammonium hydroxide.
- The process of any of claims 1 to 6, wherein the extraction conditions of step a) include a temperature of 20°C to 50°C, a basic compound to hydrocarbon weight ratio of 30:1 to 0.01:1, a pressure of 100 to 2500 kPa and the contact time in step c) varies from 15 minutes to 10 hours.
- The process of any of claims 1 to 7, wherein the conversion conditions in step c) include a temperature of 20°C to 50°C, an O2/total S mole ratio of 0.4 to 2.0 and a pH of 7.1 to 10.5.
- The process of any of claims 1 to 8, wherein the hydrocarbon stream is a liquid.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP01115343A EP1270704B1 (en) | 2001-06-26 | 2001-06-26 | A process for removing sulfur compounds from hydrocarbon streams |
AT01115343T ATE340837T1 (en) | 2001-06-26 | 2001-06-26 | METHOD FOR REMOVAL OF SULFUR COMPOUNDS FROM HYDROCARBON FEEDS |
DE60123404T DE60123404D1 (en) | 2001-06-26 | 2001-06-26 | Process for removing sulfur compounds from hydrocarbon feeds |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
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EP01115343A EP1270704B1 (en) | 2001-06-26 | 2001-06-26 | A process for removing sulfur compounds from hydrocarbon streams |
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EP1270704A1 EP1270704A1 (en) | 2003-01-02 |
EP1270704B1 true EP1270704B1 (en) | 2006-09-27 |
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EP01115343A Expired - Lifetime EP1270704B1 (en) | 2001-06-26 | 2001-06-26 | A process for removing sulfur compounds from hydrocarbon streams |
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EP (1) | EP1270704B1 (en) |
AT (1) | ATE340837T1 (en) |
DE (1) | DE60123404D1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
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FR2875236B1 (en) * | 2004-09-10 | 2006-11-10 | Total Sa | METHOD AND INSTALLATION FOR TREATING DSO |
GB2485824B (en) * | 2010-11-25 | 2017-12-20 | The Queen's Univ Of Belfast | Process for removing organic acids from crude oil and crude oil distillates |
EP3034157A1 (en) | 2015-02-19 | 2016-06-22 | Paqell B.V. | Process for treating a hydrogen sulphide and mercaptans comprising gas |
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GB912926A (en) * | 1959-04-24 | 1962-12-12 | Universal Oil Prod Co | Process for purifying phenolic acid oils |
RU2120464C1 (en) * | 1997-09-12 | 1998-10-20 | Всероссийский научно-исследовательский институт углеводородного сырья | Method and installation for deodorizing purification of crude oil and gas condensate from hydrogen sulfide and low-molecular mercaptans |
US6306288B1 (en) * | 1998-04-17 | 2001-10-23 | Uop Llc | Process for removing sulfur compounds from hydrocarbon streams |
US6224750B1 (en) * | 1998-11-02 | 2001-05-01 | Uop Llc | Producing low sulfur hydrocarbons with biologically regenerated caustic |
-
2001
- 2001-06-26 AT AT01115343T patent/ATE340837T1/en not_active IP Right Cessation
- 2001-06-26 DE DE60123404T patent/DE60123404D1/en not_active Expired - Lifetime
- 2001-06-26 EP EP01115343A patent/EP1270704B1/en not_active Expired - Lifetime
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EP1270704A1 (en) | 2003-01-02 |
ATE340837T1 (en) | 2006-10-15 |
DE60123404D1 (en) | 2006-11-09 |
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