Method for purifying natural gas

Abstract

The invention relates to the field of gas purification, and discloses a method for purifying natural gas, which comprises the following steps: (1) in the presence of a microbial agent, converting organic sulfur contained in crude natural gas into hydrogen sulfide and a first inorganic sulfur-containing solution in a first alkaline aqueous solution; (2) contacting the obtained hydrogen sulfide with a second alkaline aqueous solution to obtain a second inorganic sulfur-containing solution and purified natural gas; (3) mixing the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution, and purifying to obtain a purified barren solution; wherein the content of hydrogen sulfide in the crude natural gas is 2000-6000 mg / m < 3 >, the content of carbonyl sulfide is 70-300 mg / m < 3 >, and the content of methyl mercaptan is 25-110 mg / m < 3 >; the microbial agent comprises pseudomonas and / or rhodococcus. The process has relatively high treatment efficiency on natural gas with relatively high concentration of hydrogen sulfide and organic sulfur, hydrogen sulfide, carbonyl sulfide and methyl mercaptan.

Description

Technical Field

[0001] The invention relates to the field of gas purification, and in particular to a method for purifying natural gas. Background Art

[0002] In addition to inorganic sulfur, the extracted natural gas usually contains organic sulfur. The types of organic sulfur include carbonyl sulfide and methyl mercaptan. These organic sulfur impurities are usually removed by chemical methods such as hydrodesulfurization, but the investment in hydrodesulfurization equipment is large and the operating cost is high.

[0003] Hydrodesulfurization is a typical chemical method for treating organic sulfur. Its main purpose is to convert organic sulfur into hydrogen sulfide and then separate the hydrogen sulfide. The advantage of hydrodesulfurization is that it is not affected by the type, size and distribution of sulfur and can remove most of the sulfur. The disadvantage is that the economic cost is high and the equipment is complicated. Compared with the large investment and high operating costs of hydrodesulfurization equipment, the biological desulfurization process has mild operating conditions, which can reduce energy consumption and emissions, and ultimately convert most of the sulfur in natural gas into biosulfur. However, most of the current treatment technologies deal with low concentrations of hydrogen sulfide and organic sulfur, and the treatment efficiency still needs to be improved.

[0004] CN112899193A discloses a biological desulfurization mixed bacteria system, which includes Thioalkalivibrio, Thiomicrospirillum and Halobacterium halophilum. The mixed bacteria system can treat gas containing organic sulfur and hydrogen sulfide. CN112899193A proposes that the concentration of hydrogen sulfide after purification is lower than 15ppm, but the concentration of organic sulfur after purification is not found.

[0005] Therefore, there is an urgent need for a method for purifying natural gas that can efficiently remove composite natural gas with high concentrations of hydrogen sulfide and organic sulfur. Summary of the invention

[0006] The purpose of the present invention is to overcome the problem of low processing efficiency in the prior art when using microbial methods to purify natural gas containing high concentrations of hydrogen sulfide and organic sulfur, and to provide a method for purifying natural gas containing organic sulfur by microbial methods. This method treats inorganic sulfur and organic sulfur separately, has high purification efficiency, and has mild operating conditions, which can reduce energy consumption and emissions.

[0007] In order to achieve the above object, the present invention provides a method for purifying natural gas, the method comprising the following steps: (1) in the presence of a microbial agent, in a first alkaline aqueous solution, converting organic sulfur contained in raw natural gas into hydrogen sulfide and a first inorganic sulfur-containing solution; (2) contacting the obtained hydrogen sulfide with a second alkaline aqueous solution to obtain a second inorganic sulfur-containing solution and purified natural gas; (3) mixing the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution and purifying them to obtain a purified lean liquid; wherein:

[0008] The content of hydrogen sulfide in the crude natural gas is 2000-6000 mg / m 3 , the content of carbonyl sulfide is 70-300mg / m 3 , the content of methyl mercaptan is 25-110mg / m 3 ;

[0009] The microbial agent comprises Pseudomonas and / or Rhodococcus.

[0010] Through the above technical solution, the beneficial effects of the present invention are:

[0011] Pseudomonas and / or Rhodococcus are used as microbial agents, and the natural gas purification process of the present invention is adopted to first convert organic sulfur into hydrogen sulfide under the action of a biocatalyst, and then treat the hydrogen sulfide. For natural gas with a high concentration of hydrogen sulfide and organic sulfur (the content of hydrogen sulfide is 2000-6000 mg / m 3 , the content of carbonyl sulfide is 70-300mg / m 3 , the content of methyl mercaptan is 25-110mg / m 3 ), hydrogen sulfide, carbonyl sulfide and methyl mercaptan all have high treatment efficiency, and the operating conditions are mild, which can reduce energy consumption and emissions.

[0012] In a preferred embodiment of the present invention, the composite bacterial agent of Pseudomonas stretzschleri, Rhodococcus erythropolis and Rhodococcus erythropolis can promote the conversion of carbonyl sulfide and methyl mercaptan in raw natural gas into hydrogen sulfide, thereby further improving the purification efficiency of carbonyl sulfide and methyl mercaptan. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a process flow chart of purifying natural gas in a specific embodiment of the present invention.

[0014] Description of Reference Numerals

[0015] T01 trickling filter T02 absorption tower R01 bioreactor P01 lean liquid pump DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The present invention provides a method for purifying natural gas, the method comprising the following steps: (1) in the presence of a microbial agent, in a first alkaline aqueous solution, converting organic sulfur contained in raw natural gas into hydrogen sulfide and a first inorganic sulfur-containing solution; (2) contacting the obtained hydrogen sulfide with a second alkaline aqueous solution to obtain a second inorganic sulfur-containing solution and purified natural gas; (3) mixing the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution and purifying them to obtain a purified lean liquid; wherein:

[0018] The content of hydrogen sulfide in the crude natural gas is 2000-6000 mg / m 3 , the content of carbonyl sulfide is 70-300mg / m 3 , the content of methyl mercaptan is 25-110mg / m 3 ;

[0019] The microbial agent comprises Pseudomonas and / or Rhodococcus.

[0020] The hydrolase contained in Pseudomonas and Rhodococcus can break the groups in carbonyl sulfide and methyl mercaptan in the presence of water to generate hydrogen sulfide. Using a microbial agent containing Pseudomonas and / or Rhodococcus, the natural gas purification process of the present invention is adopted to first convert organic sulfur into hydrogen sulfide under the action of a biocatalyst, and then treat the hydrogen sulfide. For natural gas with a high concentration of hydrogen sulfide and organic sulfur (the content of hydrogen sulfide is 2000-6000 mg / m 3 , the content of carbonyl sulfide is 70-300mg / m 3 , the content of methyl mercaptan is 25-110mg / m 3 ), hydrogen sulfide, carbonyl sulfide and methyl mercaptan all have high treatment efficiency.

[0021] According to the present invention, the inorganic sulfur in the first inorganic sulfur-containing solution obtained after the conversion mainly includes sodium sulfide and sodium hydrosulfide; the inorganic sulfur in the second inorganic sulfur-containing solution obtained after hydrogen sulfide and the second alkaline aqueous solution are contacted mainly includes sodium sulfide and sodium hydrosulfide.

[0022] According to the present invention, preferably, the Pseudomonas is selected from at least one of Pseudomonas aeruginosa, Pseudomonas strechingensis and Pseudomonas alcaligenes; and / or the Rhodococcus is selected from Rhodococcus erythropolis and / or Rhodococcus erythropolis.

[0023] According to the present invention, preferably, the microbial agent is a composite agent of Pseudomonas and Rhodococcus.

[0024] According to the present invention, preferably, the microbial agent is a composite agent of Pseudomonas stretzschneri, Rhodococcus erythropolis and Rhodococcus erythropolis. Using the composite agent of Pseudomonas stretzschneri, Rhodococcus erythropolis and Rhodococcus erythropolis as a microbial agent can promote the conversion of carbonyl sulfide and methyl mercaptan in raw natural gas into hydrogen sulfide, thereby further improving the purification efficiency of carbonyl sulfide and methyl mercaptan.

[0025] The inventors found that the conversion efficiency of carbonyl sulfide and methyl mercaptan in natural gas by strains of Pseudomonas stutzeri, Rhodococcus erythropolis and Rhodococcus erythropolis from different sources is very similar, that is, the strain sources of Pseudomonas stutzeri, Rhodococcus erythropolis and Rhodococcus erythropolis have little effect on the conversion efficiency of carbonyl sulfide and methyl mercaptan.

[0026] According to the present invention, preferably, the flow rate of the raw natural gas is 1Nm 3 / h, the dosage of the first alkaline aqueous solution is 5-15 L / h, preferably 8-12 L / h.

[0027] According to the present invention, preferably, in step (1), the temperature of the conversion is 30-40° C. and the time is 0.1-0.3 h.

[0028] According to the present invention, preferably, the pH value of the first alkaline aqueous solution is 8-10.

[0029] According to the present invention, preferably, the pH value of the second alkaline aqueous solution is 8-10.

[0030] According to the present invention, preferably, in step (2), the flow rate of the raw natural gas is 1Nm 3 / h, the dosage of the second alkaline aqueous solution is 40-60 L / h, preferably 45-55 L / h.

[0031] According to the present invention, preferably, hydrogen sulfide and the second alkaline aqueous solution are contacted in an absorption tower.

[0032] According to the present invention, preferably, in step (3), the purification method comprises: in the presence of oxygen, the first inorganic sulfur-containing solution, the second inorganic sulfur-containing solution and aerobic bacteria are contacted for aeration regeneration, wherein the aerobic bacteria are selected from at least one of Thiobacillus ferrooxidans, Thiobacillus denitrificans and Thiobacillus thiooxidans. The aerobic bacteria Thiobacillus ferrooxidans, Thiobacillus denitrificans and Thiobacillus thiooxidans can absorb and oxidize the inorganic sulfur components in the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution in the presence of oxygen to generate elemental biological sulfur and a small amount of sulfate, thereby obtaining a purified lean solution.

[0033] According to the present invention, preferably, the aerobic bacteria are dispersed in a third alkaline aqueous solution with a pH value of 8-10.

[0034] According to the present invention, preferably, the flow rate of the raw natural gas is 1Nm 3 / h, the amount of aerobic bacteria is 5-50g, and the amount of the third alkaline aqueous solution is 50-200L.

[0035] According to the present invention, preferably, the temperature of the aeration regeneration is 30-40°C and the time is 2-10h.

[0036] Furthermore, the temperature of the aeration regeneration is 34-36°C.

[0037] According to the present invention, preferably, the aeration regeneration is carried out in a bioreactor, and the bioreactor is preferably an airlift bioreactor.

[0038] According to the present invention, preferably, in step (1), the conversion is carried out in a trickling tower, the bed of the trickling tower is filled with a carrier, and the microbial agent is attached to the carrier.

[0039] According to the present invention, preferably, the method for attaching the microbial agent to the carrier comprises: inoculating a seed solution containing the microbial agent on the carrier;

[0040] The total concentration of live bacteria in the seed solution is 10 6 -10 10 CFU / mL, preferably 10 8 -10 10 CFU / mL.

[0041] Preferably, the volume of the carrier is 1m 3 The inoculation amount of the seed solution is 30-60L.

[0042] According to the present invention, preferably, the ratio of the live bacterial concentrations of Pseudomonas stretzschneri, Rhodococcus erythropolis and Rhodococcus erythropolis contained in the seed solution is 1:(80-120):(0.1-10).

[0043] According to a specific embodiment of the present invention, the live bacterial concentrations of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis contained in the seed solution are independently 10 6 -9×10 9 Preferably, the live bacterial concentrations of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis in the seed solution are 10 6 -10 8 CFU / mL, 10 8 -9×10 9 CFU / mL and 10 6 -10 8 CFU / mL.

[0044] According to the present invention, preferably, the average particle size of the carrier is 3 mm-20 mm.

[0045] According to the present invention, preferably, the average pore size of the carrier is 500-2000 μm, and the porosity is 30-70%.

[0046] According to the present invention, preferably, the specific surface area of ​​the carrier is 500-1500m 2 / m 3 .

[0047] According to the present invention, preferably, the carrier is selected from at least one of ceramsite, activated carbon, calcium alginate microbeads and zeolite.

[0048] According to the present invention, preferably, the inlet pressure of the raw natural gas in the trickling tower is 1-5 MPa, preferably 2-4 MPa.

[0049] According to the present invention, preferably, the method further comprises: in step (3), a part of the purified lean liquid is returned to the trickling filter as the first alkaline aqueous solution of the next cycle to participate in the conversion, and another part is returned to the absorption tower as the second alkaline aqueous solution of the next cycle to participate in the absorption of hydrogen sulfide. After aeration regeneration, most of the aerobic bacteria in the bioreactor settle at the bottom of the bioreactor. In order to minimize the number of aerobic bacteria that return to the trickling filter and the absorption tower together with the purified lean liquid, it is more preferred that a part of the purified lean liquid is returned to the trickling filter from the upper part of the bioreactor, and another part is returned to the absorption tower.

[0050] According to the present invention, preferably, the flow rate of the raw natural gas is 1Nm 3 / h, the flow rate of the purified lean liquid returned to the trickling tower is 5-15L / h, preferably 8-12L / h; the flow rate of the purified lean liquid returned to the absorption tower is 40-60L / h, preferably 45-55L / h.

[0051] According to the present invention, the first alkaline aqueous solution, the second alkaline aqueous solution and the third alkaline aqueous solution can each independently be an aqueous sodium carbonate solution, an aqueous sodium bicarbonate solution, an aqueous potassium carbonate solution or an aqueous potassium bicarbonate solution.

[0052] The second aspect of the present invention provides a device for purifying natural gas, the device comprising: a trickling tower T01, an absorption tower T02 and a bioreactor R01 connected in sequence; wherein:

[0053] The trickling tower T01 is used to contact the raw natural gas with the biocatalyst to convert the organic sulfur contained in the raw natural gas into hydrogen sulfide and the first inorganic sulfur-containing solution;

[0054] The absorption tower T02 is used to contact the obtained hydrogen sulfide with the second alkaline aqueous solution to obtain a second inorganic sulfur-containing solution and purified natural gas;

[0055] The bioreactor R01 is used to mix and purify the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution to obtain a purified lean solution;

[0056] The top of the trickling tower T01 is connected to the bottom of the absorption tower T02, the bottom of the trickling tower T01 and the bottom of the absorption tower T02 are respectively connected to the bioreactor R01, and the bioreactor R01 is respectively connected to the top of the trickling tower T01 and the top of the absorption tower T02.

[0057] According to a specific embodiment of the present invention, Figure 1 A method for purifying natural gas using the device provided by the present invention is described, and the method comprises the following steps:

[0058] Step (1): The bed of the trickling tower T01 is filled with a carrier, and the microbial agent is attached to the carrier. The crude natural gas enters the trickling tower from the bottom and flows from bottom to top. The first alkaline aqueous solution flows from top to bottom through the bed of the trickling tower T01 filled with the carrier and attached with the microbial agent, so that the organic sulfur contained in the crude natural gas is converted into hydrogen sulfide and a first inorganic sulfur-containing solution under the action of the microbial agent. The obtained hydrogen sulfide flows out from the top of the trickling tower and enters the absorption tower T02 from the bottom. The obtained first inorganic sulfur-containing solution flows into the bioreactor R01 from the bottom of the trickling tower T01;

[0059] Step (2): After the hydrogen sulfide obtained in step (1) enters the absorption tower T02, it flows toward the upper part of the absorption tower T02, and the second alkaline aqueous solution flows into the absorption tower T02 from the upper part. The second alkaline aqueous solution contacts the hydrogen sulfide in reverse. After absorbing the hydrogen sulfide, the second alkaline aqueous solution, i.e., the second inorganic sulfur-containing solution, flows out from the bottom of the absorption tower T02 and enters the bioreactor R01. The generated purified natural gas flows out from the top of the absorption tower T02;

[0060] Step (3): In the presence of oxygen, in the third alkaline aqueous solution, the first inorganic sulfur-containing solution obtained in step (1) and the second inorganic sulfur-containing solution obtained in step (2) are respectively introduced into the bioreactor R01 and mixed, and are contacted with the aerobic bacteria in the bioreactor R01 for aeration regeneration. Under the action of the aerobic bacteria, the inorganic sulfur components in the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution are absorbed and oxidized by the aerobic bacteria. A portion of the obtained purified lean liquid is returned to the trickling filter T01 via the lean liquid pump P01 as the first alkaline aqueous solution of the next cycle to participate in the conversion reaction, and the other portion is returned to the absorption tower T02 as the second alkaline aqueous solution of the next cycle for the absorption of hydrogen sulfide.

[0061] According to a preferred embodiment of the present invention, the alkaline substances in the first alkaline aqueous solution, the second alkaline aqueous solution and the third alkaline aqueous solution are the same. When purifying natural gas, an alkaline aqueous solution with a pH value of 8-10 is first prepared in a bioreactor, and aerobic bacteria are dispersed in the alkaline aqueous solution, and then a part of the alkaline aqueous solution dispersed with aerobic bacteria is pumped into a trickling filter as the first alkaline aqueous solution to participate in the conversion reaction, and a part is pumped into an absorption tower as the second alkaline aqueous solution to contact with hydrogen sulfide, and the remaining alkaline aqueous solution in the bioreactor is used as the third alkaline aqueous solution to participate in aeration regeneration.

[0062] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, all methods are conventional methods; and the reagents and materials used, unless otherwise specified, can be obtained from commercial sources.

[0063] The contents of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in crude natural gas and purified natural gas were determined according to GB / T13610 and GB / T-11060.6 methods.

[0064] Example 1

[0065] according to Figure 1 The crude natural gas is purified by the process flow. The contents of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in the crude natural gas are shown in Table 1.

[0066] The specific steps of raw natural gas purification are:

[0067] Step (1): preparing a sodium carbonate aqueous solution (the sodium carbonate content in the sodium carbonate aqueous solution is 10 g / L and the pH value is 8) in an airlift bioreactor R01, and dispersing aerobic bacteria (Thiobacillus thiooxidans) in the sodium carbonate aqueous solution so that the aerobic bacteria content is 5 g based on the volume of the sodium carbonate aqueous solution being 100 L, then pumping a portion of the sodium carbonate aqueous solution from the upper part of the airlift bioreactor R01 into a trickling filter T01 as a first alkaline aqueous solution to participate in the conversion reaction, and a portion of the sodium carbonate aqueous solution is pumped into an absorption tower T02 as a second alkaline aqueous solution to contact with hydrogen sulfide, and the remaining alkaline aqueous solution in the airlift bioreactor R01 participates in aeration regeneration as a third alkaline aqueous solution; the flow rate of the sodium carbonate aqueous solution pumped into the trickling filter T01 is 10 L / h, and the flow rate of the sodium carbonate aqueous solution pumped into the absorption tower T02 is 50 L / h;

[0068] The bed of trickling tower T01 is filled with a carrier (average particle size of 10 mm, average pore size of 1000 μm, porosity of 50%, specific surface area of ​​1000 m 2 / m 3 The composite microorganism is a combination of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis, and the total concentration of live bacteria in the seed liquid is 6×107 CFU / mL, the ratio of the live bacterial concentration of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis is 1:1:1. The raw natural gas enters from the lower part of the trickling tower T01 and flows from bottom to top. The first alkaline aqueous solution flows from top to bottom through the bed of the trickling tower T01 filled with a carrier and attached with composite microorganisms, so that the organic sulfur contained in the raw natural gas is converted into hydrogen sulfide and the first inorganic sulfur-containing solution under the action of the composite microorganisms. The obtained hydrogen sulfide flows out from the top of the trickling tower T01 and enters the absorption tower T02 from the bottom. The obtained first inorganic sulfur-containing solution flows into the bioreactor R01 from the bottom of the trickling tower T01;

[0069] Step (2): After the hydrogen sulfide obtained in step (1) enters the absorption tower T02, it flows toward the upper part of the absorption tower T02, and the second alkaline aqueous solution flows into the absorption tower T02 from the upper part. The second alkaline aqueous solution contacts the hydrogen sulfide in reverse. After absorbing the hydrogen sulfide, the second alkaline aqueous solution, i.e., the second inorganic sulfur-containing solution, flows out from the bottom of the absorption tower T02 and enters the bioreactor R01. The generated purified natural gas flows out from the top of the absorption tower T02;

[0070] Step (3): In the presence of oxygen, in the third alkaline aqueous solution, the first inorganic sulfur-containing solution obtained in step (1) and the second inorganic sulfur-containing solution obtained in step (2) are respectively introduced into the bioreactor R01 and mixed, and are contacted with aerobic bacteria (Thiobacillus thiooxidans) in the bioreactor R01 for aeration regeneration. Under the action of the aerobic bacteria, the inorganic sulfur components in the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution are absorbed and oxidized by the aerobic bacteria. A portion of the obtained purified lean solution is returned from the upper part of the bioreactor R01 to the trickling filter T01 as the first alkaline aqueous solution of the next cycle to participate in the conversion reaction, and the other portion is returned to the absorption tower T02 as the second alkaline aqueous solution of the next cycle for the absorption of hydrogen sulfide;

[0071] In step (1), the flow rate of raw natural gas is 1Nm 3 / h, the inlet pressure of the crude natural gas in the trickling tower T01 is 3MPa, the dosage of the first alkaline aqueous solution is 10L / h; the conversion temperature is 30°C, and the time is 0.1h;

[0072] In step (2), the dosage of the second alkaline aqueous solution is 50 L / h;

[0073] In step (3), the temperature of aeration regeneration is 35°C and the time is 2h; the amount of aerobic bacteria is 5g, and the amount of the third alkaline aqueous solution is 150L; the flow rate of the purified lean liquid returning to the trickling filter T01 is 10L / h, and the flow rate of the purified lean liquid returning to the absorption tower T02 is 50L / h.

[0074] Embodiment 2-7

[0075] The crude natural gas was purified according to the method of Example 1, except that the contents of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in the crude natural gas were different. The compositions of the crude natural gas of Examples 2-7 are shown in Table 1.

[0076] Example 8

[0077] The crude natural gas was purified according to the method of Example 1, except that the type of composite microorganism was different. Specifically, in step (1), Pseudomonas stretzschneri was replaced with Pseudomonas aeruginosa, which was inoculated on the carrier to obtain purified natural gas.

[0078] Example 9

[0079] The crude natural gas was purified according to the method of Example 1, except that a combination of Pseudomonas alcaligenes and Rhodococcus erythropolis was used as the composite microorganism. Specifically, in step (1), the seed liquid of the composite microorganism was inoculated on the carrier, and the total concentration of live bacteria in the seed liquid was 6×10 7 CFU / mL, the ratio of the live bacterial concentration of Pseudomonas alcaligenes to that of Rhodococcus erythropolis was 1:1. Purified natural gas was obtained.

[0080] Example 10

[0081] The crude natural gas was purified according to the method of Example 1, except that the composite microorganism was a combination of Pseudomonas aeruginosa, Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis. Specifically, in step (1), the seed liquid of the composite microorganism was inoculated on the carrier, and the total concentration of live bacteria in the seed liquid was 6×10 7 CFU / mL, the ratio of the live bacterial concentrations of Pseudomonas aeruginosa, Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis was 1:2:2:1. Purified natural gas was obtained.

[0082] Embodiment 11

[0083] The crude natural gas was purified according to the method of Example 1, except that the amount of composite microorganisms used was different, and the ratios of Pseudomonas styraciflua, Rhodococcus erythropolis and Rhodococcus erythropolis were different. Specifically, in step (1), the total concentration of live bacteria in the seed solution was 1.02×10 9 CFU / mL, the ratio of the live bacterial concentrations of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis is 1:100:1, that is, the live bacterial concentration of Pseudomonas strechingensis is 10 7 CFU / mL, the concentration of live Rhodococcus erythropolis is 10 9 CFU / mL, the total concentration of live Rhodococcus erythropolis is 10 7 CFU / mL. Purified natural gas was obtained.

[0084] Example 12

[0085] The crude natural gas was purified according to the method of Example 1, except that the amount of the first alkaline aqueous solution used was different. Specifically, in step (1), the flow rate of the sodium carbonate aqueous solution pumped into the trickling tower T01 was 15 L / h; in step (3), the flow rate of the purified lean liquid returned to the trickling tower T01 was 15 L / h. Purified natural gas was obtained.

[0086] Embodiment 13

[0087] The crude natural gas was purified according to the method of Example 1, except that the amount of the first alkaline aqueous solution used was different. Specifically, in step (1), the flow rate of the sodium carbonate aqueous solution pumped into the trickling tower T01 was 8 L / h; in step (3), the flow rate of the purified lean liquid returned to the trickling tower T01 was 8 L / h. Purified natural gas was obtained.

[0088] Embodiment 14

[0089] The crude natural gas was purified according to the method of Example 1, except that the amount of the second alkaline aqueous solution used was different. Specifically, in step (1), the flow rate of the sodium carbonate aqueous solution pumped into the absorption tower T02 was 60 L / h; in step (3), the flow rate of the purified lean liquid returned to the absorption tower T02 was 60 L / h. Purified natural gas was obtained.

[0090] Embodiment 15

[0091] The crude natural gas was purified according to the method of Example 1, except that the amount of the second alkaline aqueous solution used was different. Specifically, in step (1), the flow rate of the sodium carbonate aqueous solution pumped into the absorption tower T02 was 40 L / h; in step (3), the flow rate of the purified lean liquid returned to the absorption tower T02 was 40 L / h. Purified natural gas was obtained.

[0092] Example 16

[0093] The crude natural gas was purified according to the method of Example 1, except that the carrier to which the biocatalyst was attached had an average particle size of 30 mm, an average pore size of 2300 μm, a porosity of 20%, and a specific surface area of ​​450 m 2 / m 3 , and obtain purified natural gas.

[0094] Comparative Example 1

[0095] The crude natural gas was purified according to the method of Example 1, except that the composite microorganism was a combination of Pseudomonas aeruginosa, Pseudomonas stutzeri and Pseudomonas alcaligenes. Specifically, in step (1), the total concentration of live bacteria in the seed solution was 6×10 7 CFU / mL, the ratio of the live bacterial concentrations of Pseudomonas aeruginosa, Pseudomonas stutzeri and Pseudomonas alcaligenes was 1:1:1. Purified natural gas was obtained.

[0096] Comparative Example 2

[0097] The crude natural gas was purified according to the method of Example 1, except that the contents of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in the natural gas were different. Specifically, the content of hydrogen sulfide in the crude natural gas was 6200 mg / m 3 , the content of carbonyl sulfide is 330mg / m 3 , the content of methyl mercaptan is 120mg / m 3 . Get purified natural gas.

[0098] Test Case

[0099] The contents of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in the purified natural gas of each embodiment and comparative example were measured. The results are shown in Table 1.

[0100] Table 1

[0101]

[0102] From the results in Table 1, it can be seen that for natural gas with high concentrations of hydrogen sulfide and organic sulfur, the purification method of the present invention is used. In Examples 1-16, both hydrogen sulfide and organic sulfur have high treatment efficiency, with a removal rate of hydrogen sulfide of more than 99.8, a removal rate of carbonyl sulfide of more than 50%, and a removal rate of methyl mercaptan of more than 59%. The microbial agent used in Comparative Example 1 only contains Pseudomonas, and the content of hydrogen sulfide, carbonyl sulfide and methyl mercaptan in the natural gas treated in Comparative Example 2 is too high, and the purification efficiency of organic sulfur is significantly reduced. It shows that the biocatalyst of the present invention has a high treatment efficiency for natural gas of a specific composition.

[0103] In addition, Example 8 replaces Pseudomonas schrenkigensis with Pseudomonas aeruginosa, Example 9 uses a combination of Pseudomonas alcaligenes and Rhodococcus erythropolis as a composite microorganism, and Example 10 uses a combination of Pseudomonas aeruginosa, Pseudomonas schrenkigensis, Rhodococcus erythropolis and Rhodococcus erythropolis as a composite microorganism. Compared with Example 1, the purification efficiency of organic sulfur is reduced. Example 11 uses a composite microorganism with a preferred dosage and combination ratio to convert organic sulfur. Compared with Example 1, the purification efficiency of organic sulfur is higher. It shows that the combination mode, proportion of microorganisms in the biocatalyst and the dosage of the biocatalyst have a great influence on the purification efficiency of organic sulfur. In addition, Examples 12 and 13 change the dosage of the first alkaline aqueous solution, Examples 14 and 15 change the dosage of the second alkaline aqueous solution, and Example 16 changes the parameters of the carrier to which the biocatalyst is attached. Compared with Example 1, the purification efficiency of organic sulfur is reduced.

[0104] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for purifying natural gas, characterized in that: The method comprises the following steps: (1) in the presence of a microbial agent, in a first alkaline aqueous solution, converting organic sulfur contained in raw natural gas into hydrogen sulfide and a first inorganic sulfur-containing solution; (2) contacting the obtained hydrogen sulfide with a second alkaline aqueous solution to obtain a second inorganic sulfur-containing solution and purified natural gas; (3) mixing the first inorganic sulfur-containing solution and the second inorganic sulfur-containing solution and purifying them to obtain a purified lean liquid; wherein: The content of hydrogen sulfide in the crude natural gas is 2000-6000 mg / m 3 , the content of carbonyl sulfide is 70-300mg / m 3 , the content of methyl mercaptan is 25-110mg / m 3 ; The microbial agent comprises Pseudomonas and / or Rhodococcus.

2. The method according to claim 1, characterized in that The Pseudomonas is selected from at least one of Pseudomonas aeruginosa, Pseudomonas stutzeri and Pseudomonas alcaligenes; and / or The rhodococcus is selected from Rhodococcus erythropolis and / or Rhodococcus erythropolis; Preferably, the microbial agent is a composite agent of Pseudomonas and Rhodococcus; Preferably, the microbial agent is a composite agent of Pseudomonas strechingensis, Rhodococcus erythropolis and Rhodococcus erythropolis.

3. The method according to claim 1 or 2, characterized in that: The flow rate of the crude natural gas is 1Nm 3 / h, the dosage of the first alkaline aqueous solution is 5-15L / h, preferably 8-12L / h; Preferably, in step (1), the temperature of the conversion is 30-40°C and the time is 0.1-0.3h; Preferably, the pH value of the first alkaline aqueous solution is 8-10.

4. The method according to any one of claims 1 to 3, characterized in that: The pH value of the second alkaline aqueous solution is 8-10; Preferably, in step (2), the flow rate of the crude natural gas is 1 Nm 3 / h, the dosage of the second alkaline aqueous solution is 40-60L / h, preferably 45-55L / h; Preferably, hydrogen sulfide and the second alkaline aqueous solution are contacted in an absorption tower.

5. The method according to any one of claims 1 to 4, characterized in that: In step (3), the purification method comprises: in the presence of oxygen, contacting the first inorganic sulfur-containing solution, the second inorganic sulfur-containing solution and aerobic bacteria for aeration regeneration, wherein the aerobic bacteria are selected from at least one of Thiobacillus ferrooxidans, Thiobacillus denitrificans and Thiobacillus thiooxidans; Preferably, the aerobic bacteria are dispersed in a third alkaline aqueous solution with a pH value of 8-10.

6. The method according to claim 5, characterized in that The flow rate of the crude natural gas is 1Nm 3 / h, the amount of aerobic bacteria is 5-50g, and the amount of the third alkaline aqueous solution is 50-200L; Preferably, the temperature of the aeration regeneration is 30-40°C and the time is 2-10h; Preferably, the aerated regeneration is carried out in a bioreactor, and the bioreactor is preferably an airlift bioreactor.

7. The method according to any one of claims 1 to 6, characterized in that: In step (1), the conversion is carried out in a trickling filter, the bed of the trickling filter is filled with a carrier, and the microbial agent is attached to the carrier; Preferably, the method for attaching the microbial agent to the carrier comprises: inoculating a seed solution containing the microbial agent on the carrier; The total concentration of live bacteria in the seed solution is 10 6 -10 10 CFU / mL, preferably 10 8 -10 10 CFU / mL; Preferably, the volume of the carrier is 1m 3 The inoculation amount of the seed solution is 30-60L; Preferably, the ratio of the live bacterial concentrations of Pseudomonas stretzschneri, Rhodococcus erythropolis and Rhodococcus erythropolis contained in the seed solution is 1:(80-120):(0.1-10).

8. The method according to claim 7, characterized in that The average particle size of the carrier is 3mm-20mm; Preferably, the average pore size of the carrier is 500-2000 μm, and the porosity is 30-70%; Preferably, the specific surface area of ​​the carrier is 500-1500m 2 / m 3 ; Preferably, the carrier is selected from at least one of ceramsite, activated carbon, calcium alginate microbeads and zeolite.

9. The method according to any one of claims 1 to 8, characterized in that: The method further comprises: in step (3), a part of the purified lean liquid is returned to the trickling tower, and another part is returned to the absorption tower.

10. The method according to claim 9, characterized in that The flow rate of the crude natural gas is 1Nm 3 / h, the flow rate of the purified lean liquid returned to the trickling tower is 5-15L / h, preferably 8-12L / h; the flow rate of the purified lean liquid returned to the absorption tower is 40-60L / h, preferably 45-55L / h.

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