Method for the separation of biological sulphur compounds

Abstract

This invention proposes a method for separating biosulfur, comprising: (1) adding an organic flocculant to a mixing tank containing a biosulfurization solution and stirring to obtain a mixed solution; wherein the organic flocculant is selected from at least one of galactosamine, N-acetylglucosamine, and mannosamine; (2) transferring the mixed solution to a settling tank and allowing it to stand to form a supernatant and a bottom precipitate; and (3) separating the supernatant and the bottom precipitate in the settling tank. The method of this invention can achieve efficient separation of biosulfur, with a biosulfur flocculation rate of 95–99 wt%. This invention also provides the application of at least one of galactosamine, N-acetylglucosamine, and mannosamine in the separation of biosulfur.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and purification, specifically to a method for separating biological sulfur. Background Technology

[0002] In biological desulfurization processes, sulfur-containing compounds are converted into elemental sulfur particles by sulfur bacteria. These sulfur particles need to be separated promptly to avoid reducing the efficiency of the biological desulfurization process. However, these sulfur particles are extremely small, typically 1–3 micrometers in size, and exist in a colloidal state in solution, making them difficult to aggregate and settle. Therefore, technological development is needed to promote sulfur aggregation and sedimentation.

[0003] Flocculation technology is widely used in water treatment units across many industries. The flocculation effect directly impacts the water quality indicators after treatment. Generally, flocculants are needed when the particles in wastewater exhibit both agglomeration and settling stability. Types of flocculants include inorganic salt flocculants, inorganic polymeric flocculants, organic polymeric flocculants, and microbial flocculants. Different types of flocculants are required for different pollutants in different water qualities. Current desulfurization processes generally use inorganic salt flocculants, including ferric sulfate, aluminum ferric sulfate, and aluminum sulfate, which achieve water quality standards after flocculation. However, these flocculants are not observed in the use of biological sulfur solutions. Generally, the use of inorganic flocculants can have adverse effects on the bacteria contained in biological sulfur solutions.

[0004] Chinese patent application CN103172156A discloses a sulfur recovery coagulation inclined plate sedimentation device and a method for separating biological sulfur using it, addressing only the problems of difficulty in separating biological sulfur from effluent and low biological sulfur recovery efficiency in existing desulfurization processes. This patent application uses inorganic salt flocculants (such as polyaluminum chloride) for biological sulfur separation. However, this patent application uses a large amount of inorganic salt flocculant for biological sulfur separation and does not consider the impact of polyaluminum chloride on bacteria contained in the biological sulfur solution. Summary of the Invention

[0005] Therefore, the purpose of this invention is to address the technical problems existing in the prior art by providing a method for the separation of bio-sulfur, which can achieve efficient separation of bio-sulfur. Furthermore, this invention also provides the application of at least one of galactosamine, N-acetylglucosamine, and mannosamine in the separation of bio-sulfur.

[0006] The objective of this invention is achieved through the following technical solutions.

[0007] On one hand, the present invention provides a method for separating biological sulfur, comprising:

[0008] (1) An organic flocculant is added to a mixing tank containing a biological desulfurization solution and stirred to obtain a mixed solution; wherein the organic flocculant is selected from at least one of galactosamine, N-acetylglucosamine, and mannosamine;

[0009] (2) The mixed solution is transferred to a settling tank and allowed to stand, forming a supernatant and a bottom precipitate; and

[0010] (3) Separate the supernatant and the bottom sediment in the settling tank.

[0011] The inventors of this application have discovered that using at least one of galactosamine, N-acetylglucosamine, and mannosamine as an organic flocculant for the separation of biological sulfur can not only achieve highly efficient separation of biological sulfur (the biological sulfur flocculation rate can reach 95-99 wt%), but also the organic flocculant used does not affect the activity of bacteria in the supernatant, allowing the supernatant to be returned to the biological desulfurization system for recycling, which is environmentally friendly.

[0012] In some embodiments, the sulfur content in the biological desulfurization solution is 0.1–0.3 wt%; and / or, the sulfur particle size is 1 μm–6 μm; and / or, the pH value is 8–9.

[0013] In this invention, the term "sulfur particle size" refers to the average particle size D50 of sulfur.

[0014] In some embodiments, the biological desulfurization solution originates from a biological desulfurization unit, and the biological sulfur separation method further includes returning the supernatant to the biological desulfurization unit. This achieves the recycling of the supernatant for use.

[0015] In addition, the present invention does not have special requirements for the biological desulfurization unit (process), and the method of the present invention can process materials containing biological sulfur (e.g., aqueous solutions) obtained from conventional biological desulfurization units.

[0016] In some embodiments, the organic flocculant is selected from one or two of galactosamine, N-acetylglucosamine, and mannosamine. For example, the organic flocculant may be galactosamine, or two of galactosamine, N-acetylglucosamine, and mannosamine.

[0017] When the organic flocculant is selected from two of galactosamine, N-acetylglucosamine, and mannosamine, the present invention can use any ratio. However, in some preferred embodiments, the weight ratio of the two organic flocculants selected from galactosamine, N-acetylglucosamine, and mannosamine is 1:4 to 4:1, for example, 1:4, 1:3.5, 1:3, 1:2.5, 1:2, 1:1.5, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or a range thereof.

[0018] In some preferred embodiments, the organic flocculant includes a first organic flocculant and a second organic flocculant, or is composed of a first organic flocculant and a second organic flocculant. The first organic flocculant is galactosamine, and the second organic flocculant is selected from N-acetylglucosamine and mannosamine. The weight ratio of the first organic flocculant to the second organic flocculant is 1:2.5 to 2.5:1, preferably 1:1 to 2.5:1, and more preferably 1.5:1 to 2.5:1. The inventors of this application have found that using the above combination of organic flocculants not only results in a high flocculation rate but also a short residence time of the material in the settling tank and high separation efficiency. In some specific embodiments, the second organic flocculant is N-acetylglucosamine.

[0019] In some embodiments, the amount of the organic flocculant is 0.005 to 0.1 wt% based on the mass of the biological desulfurization solution. For example, the amount of the organic flocculant is 0.005 wt%, 0.006 wt%, 0.008 wt%, 0.01 wt%, 0.015 wt%, 0.02 wt%, 0.025 wt%, 0.03 wt%, 0.035 wt%, 0.04 wt%, 0.045 wt%, 0.05 wt%, 0.055 wt%, 0.06 wt%, 0.065 wt%, 0.07 wt%, 0.075 wt%, 0.08 wt%, 0.085 wt%, 0.09 wt%, 0.095 wt%, 0.1 wt%, or a range thereof, based on the mass of the biological desulfurization solution.

[0020] In some preferred embodiments, the amount of organic flocculant used is 0.008 to 0.06 wt%, preferably 0.01 to 0.05 wt%, based on the mass of the biological desulfurization solution.

[0021] In some embodiments, the stirring conditions in step (1) include: a stirring speed of 100 r / min to 200 r / min; and / or a temperature of 30 to 40°C.

[0022] In some implementations, the conditions for settling in step (2) include: a temperature of 30 to 40°C; and / or a time of 10 to 60 minutes.

[0023] The settling time in step (2) can be determined based on the composition of the organic flocculant used. For example, the settling time can be 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes or a range thereof.

[0024] In some preferred embodiments, the organic flocculant is composed of a first organic flocculant and a second organic flocculant, wherein the first organic flocculant is galactosamine and the second organic flocculant is N-acetylglucosamine, and the weight ratio of the first organic flocculant to the second organic flocculant is 1:2.5 to 2.5:1, preferably 1:1 to 2.5:1, more preferably 1.5:1 to 2.5:1, and the settling time in step (2) is 10 to 30 minutes, preferably 10 to 20 minutes.

[0025] In some embodiments, the biosulfur separation method further includes feeding the bottom sediment in the settling tank into a centrifuge for separation to recover the biosulfur.

[0026] In some preferred embodiments, the biosulfur separation method further includes purifying and recovering the biosulfur.

[0027] In this invention, the purification process includes extraction and separation of recovered bio-sulfur. Conventional extraction solvents can be used for extraction. Examples of suitable extraction solvents include, but are not limited to, carbon disulfide, toluene, and tetrachloroethylene.

[0028] On the other hand, the present invention provides at least one of galactosamine, N-acetylglucosamine, and mannosamine, preferably one or two, as an organic flocculant in the separation of biological sulfur.

[0029] In some embodiments, the organic flocculant includes a first organic flocculant and a second organic flocculant, or is composed of a first organic flocculant and a second organic flocculant. The first organic flocculant is galactosamine, and the second organic flocculant is selected from N-acetylglucosamine and mannosamine. The weight ratio of the first organic flocculant to the second organic flocculant is 1:2.5 to 2.5:1, preferably 1:1 to 2.5:1, and more preferably 1.5:1 to 2.5:1.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] A) Using at least one of galactosamine, N-acetylglucosamine, and mannosamine as an organic flocculant for the separation of biological sulfur can not only achieve efficient separation of biological sulfur (the biological sulfur flocculation rate can reach 95-99 wt%), but also the organic flocculant used does not affect the bacterial activity in the supernatant, so that the supernatant after biological sulfur separation can be returned to the biological desulfurization system for recycling, which is environmentally friendly.

[0032] B) The supernatant after separation can be returned to the biological desulfurization system for recycling. Furthermore, the organic flocculant used in the method of the present invention does not affect the bacterial activity in the solution, allowing the solution after biological sulfur separation to be returned to the biological desulfurization system for recycling, and the organic flocculant is easily removed from the recovered biological sulfur agglomerates, which is beneficial for subsequent sulfur purification. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a bio-sulfur separation process according to an embodiment of the present invention;

[0034] Among them, V01 is the mixing tank; V02 is the settling tank; and M01 is the centrifuge. Detailed Implementation

[0035] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0036] Determination of sulfur content

[0037] In this invention, the sulfur content in the biological desulfurization solution is determined using the sulfite method, as detailed in the literature Reduction of produced elementary sulfur indenitrifying sulfide removal process. Environmental biotechnology, 2011, 90: 1129-1136.

[0038] The biological desulfurization solution used in the following examples comes from the sulfur recovery treatment unit of the biological desulfurization system of Sinopec Nanjing Chemical Research Institute Co., Ltd. The desulfurizing bacteria are denitrifying thiobacillus and sulfur-excreting thiobacillus. The sulfur in the biological sulfur solution is mainly in the S8 form, the sulfur content is 0.22wt%, the pH value is 8-9, and the sulfur particle size D50 is 5μm.

[0039] Example 1

[0040] Reference Figure 1 The bio-desulfurization solution from the bio-desulfurization system was transported to mixing tank V01. Galactosamine was added to mixing tank V01 and stirred at a speed of 150 r / min. The amount of galactosamine added was 0.01 wt% based on the mass of the bio-desulfurization solution to be treated. The bio-desulfurization solution was then transported to settling tank V02 for static settling and separation for 10 minutes, forming a supernatant and a bottom precipitate. The supernatant (i.e., overflow liquid) was removed by overflow, and the bottom precipitate was sent to centrifuge M01 for centrifugal separation. The bio-sulfur flocculation rate was calculated based on the sulfur content in the bio-desulfurization solution and the supernatant, and the flocculation rate was 95.7%.

[0041] Referring to the parameters in Table 1, biological sulfur was separated according to the above method, and the results are shown in Table 1.

[0042] Table 1. Parameters and results of biological sulfur separation

[0043]

[0044]

[0045] As shown in Table 1, the method of the present invention exhibits a high flocculation rate when using one or two of galactosamine, N-acetylglucosamine, and mannosamine as flocculants. Furthermore, using a combination of two of the above organic flocculants can further improve the flocculation rate. In particular, the combination of galactosamine and N-acetylglucosamine not only has a high flocculation rate but also allows for rapid sedimentation and high separation efficiency.

[0046] Example 2

[0047] With an organic flocculant addition of 0.03 wt%, biosulfur separation was performed according to the method in Example 1. The supernatant in settling tank VO2 was returned to the biological desulfurization system for biological desulfurization testing. Examples 2-6 and 2-7 employed the same method as Examples 1-8 for biosulfur separation.

[0048] The specific details of the biological desulfurization test are as follows:

[0049] The feed gas pressure is 0.1 MPa, and the hydrogen sulfide concentration in the feed gas is 2000 mg / m³. 3 The flow rate is 1 Nm 3 The solution circulation rate is 10 L / h, the supernatant is used as the biological desulfurization solution, and the absorption temperature is 30℃.

[0050] The desulfurization rate was calculated according to the following formula I, and the results are shown in Table 2.

[0051] η=(C1-C2) / C1*100% Equation I

[0052] Wherein, C1 is the hydrogen sulfide concentration in the raw gas, and C2 is the hydrogen sulfide concentration in the purified gas.

[0053] Table 2 Test results of Example 2

[0054]

[0055]

[0056] As can be seen from Table 2, when using the organic flocculant of the present invention, the desulfurization rate can reach more than 98.0% after the supernatant is returned to the biological desulfurization system for recycling, which is higher than the desulfurization rate after the supernatant is returned to the biological desulfurization system for recycling when using organic flocculants such as polyacrylamide and sodium alginate.

[0057] The above results show that the organic flocculant used in the method of the present invention has little effect on the bacterial activity in the biological desulfurization solution, and the bacteria still have a high sulfurization effect when recycled.

[0058] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. Methods for separating biological sulfur, including: (1) An organic flocculant is added to a mixing tank containing a biological desulfurization solution and stirred to obtain a mixed solution; wherein the organic flocculant is selected from at least one of galactosamine, N-acetylglucosamine, and mannosamine; (2) The mixed solution is transferred to a settling tank and allowed to stand, forming a supernatant and a bottom precipitate; and (3) Separate the supernatant and the bottom sediment in the settling tank.

2. The method for separating biological sulfur according to claim 1, characterized in that, The sulfur content in the biological desulfurization solution is 0.1–0.3 wt%, and the sulfur particle size is 1 μm–6 μm. And / or, the biological desulfurization solution comes from the biological desulfurization unit, and the biological sulfur separation method further includes: returning the supernatant to the biological desulfurization unit.

3. The method for separating biological sulfur according to claim 1, characterized in that, The organic flocculant is selected from one or two of galactosamine, N-acetylglucosamine, and mannosamine; And / or, based on the mass of the biological desulfurization solution, the amount of the organic flocculant is 0.005 to 0.1 wt%, preferably 0.008 to 0.06 wt%, more preferably 0.01 to 0.05 wt%.

4. The method for separating biological sulfur according to claim 3, characterized in that, The organic flocculant includes a first organic flocculant and a second organic flocculant, or is composed of a first organic flocculant and a second organic flocculant. The first organic flocculant is galactosamine, and the second organic flocculant is selected from N-acetylglucosamine and mannosamine. The weight ratio of the first organic flocculant to the second organic flocculant is 1:2.5 to 2.5:1, preferably 1:1 to 2.5:1, and more preferably 1.5:1 to 2.5:

1.

5. The method for separating biological sulfur according to any one of claims 1-4, characterized in that, The stirring conditions in step (1) include: a stirring speed of 100 r / min to 200 r / min; and / or a temperature of 30 to 40 °C.

6. The method for separating biological sulfur according to any one of claims 1-5, characterized in that, The conditions for standing in step (2) include: a temperature of 30 to 40°C; and / or a time of 10 to 60 minutes.

7. The method for separating biological sulfur according to any one of claims 1-5, characterized in that, The biosulfur separation method further includes sending the bottom sediment in the settling tank into a centrifuge for separation to recover the biosulfur.

8. The method for separating biological sulfur according to claim 7, characterized in that, The biosulfur separation method further includes purifying and recovering the biosulfur.

9. The method for separating biological sulfur according to claim 8, characterized in that, The purification includes extraction, separation, and recovery of bio-sulfur; preferably, extraction is performed using an extraction solvent, which is preferably selected from carbon disulfide, toluene, and tetrachloroethylene.

10. At least one of galactosamine, N-acetylglucosamine, and mannosamine, preferably one or two, as an organic flocculant in the separation of biological sulfur.

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