A coupling method of complexing iron and biological desulfurization

Abstract

The present application belongs to the field of gas purification, and relates to a method for removing hydrogen sulfide from gas by wet oxidation reduction, in particular, the present application is the coupling of complex iron and biological desulfurization technology. The new complexing agent can complex the iron ions in the solution and provide nutrition for the biological bacteria, the sulfur produced by the complex iron desulfurization technology is used as the fixed bed of the biological bacteria, under the double action of the bacterial catalytic regeneration and the iron ion oxidation regeneration of the rich liquid absorbing hydrogen sulfide in the regeneration tower, the efficiency of the conversion of hydrogen sulfide into sulfur is improved, the speed of the conversion of ferrous iron into ferric iron is accelerated, the oxidation regeneration time is shortened, and the oxidation degradation and the generation rate of side reactions of the complexing agent are reduced.

Description

Technical Field

[0001] This invention belongs to the field of gas purification technology and relates to a wet oxidation-reduction method for removing hydrogen sulfide from gas. Specifically, this invention is a coupling of complexed iron and biological desulfurization technology. It uses a wet oxidation method to remove hydrogen sulfide from the gas. During the absorption process, the hydrogen sulfide in the gas is converted into sulfide ions. The rich solution that has absorbed hydrogen sulfide enters the oxidation regeneration process. Microorganisms and air oxidation regeneration realize the oxidation of sulfides into elemental sulfur and the oxidation of divalent iron into trivalent iron. The regenerated solution is recycled. Background Technology

[0002] As is well known, industrial raw material gases containing hydrogen sulfide can cause corrosion of pipelines and equipment, poisoning of catalysts, and affect product quality; emissions of waste gases containing hydrogen sulfide and mercaptans can cause serious environmental problems.

[0003] The main methods for removing hydrogen sulfide are: (1) Dry desulfurization, such as iron oxide method, zinc oxide method and activated carbon method. (2) Alkylamine method. (3) Wet oxidation method, such as ADA method, biological method, 888 method and complexed iron method. (4) Physical solvent method, such as low temperature methanol method and NHD method.

[0004] Wet oxidation-reduction desulfurization generally uses vanadium or iron as catalysts. Representative processes using vanadium as a catalyst include the Stretford process (ADA process), tannin process, and 888 process. Iron-based processes include the LO-CAT process and SulFerox process. These methods involve degradation of the complexing agent during desulfurization (CN11564705A), resulting in higher production and operating costs. The sulfur produced during the complexed iron desulfurization process is hydrophobic and can easily clog pipes, distributors, and tower packing, affecting the normal operation of the desulfurization unit.

[0005] Biological desulfurization refers to a process that utilizes the biological oxidation of sulfur bacteria to oxidize sulfides and organic sulfur into elemental sulfur or sulfuric acid, thereby removing sulfur from the gas stream. Currently, publicly available reports on biological methods for removing gaseous sulfides focus on purifying single components.

[0006] Examples include the removal of hydrogen sulfide from biogas (CN101780373A, CN203090734U), the removal of organic sulfur from fuel oil (CN101703883A), and the removal of carbon disulfide from exhaust gas (CN1470313A).

[0007] CN101935566A discloses a combined biological desulfurization method for natural gas, which uses an acidic iron ion biological method to remove hydrogen sulfide and a bio-trickling filtration method to remove organic sulfur. It can remove both inorganic and organic sulfur simultaneously, but it is ineffective against carbon dioxide. Furthermore, the strongly acidic medium causes severe corrosion to the equipment, thus requiring higher standards for the equipment materials.

[0008] Industrial applications such as shell-paques technology have lower desulfurization costs compared to complexed iron, as no expensive complexing agent is added and only nutrient solution and alkali are needed for operation. However, it has disadvantages such as long regeneration time, high side reaction productivity (5-10%), and waste liquid discharge during the production process. Summary of the Invention

[0009] The purpose of this invention is to propose a coupling method of complexed iron and biological desulfurization, which solves the shortcomings of existing technologies such as low regeneration efficiency, high cost, poor stability of desulfurization efficiency, and high energy consumption.

[0010] The technical concept of this invention is to propose a method for removing hydrogen sulfide gas and recovering sulfur from the raw material gas stream through a coupled purification technology of complexed iron and biological desulfurization. A novel complexing agent is used that can both complex iron ions in the solution and provide nutrients for the bacteria, while the sulfur produced by the complexed iron desulfurization technology serves as a fixed bed for the bacteria.

[0011] The main technical solution of this invention is a coupling method of complexed iron and biological desulfurization, characterized by using an alkaline complexed iron desulfurization solution to remove hydrogen sulfide from the gas. During the absorption process, the hydrogen sulfide in the gas is converted into hydrosulfide ions. The rich solution that has absorbed hydrogen sulfide enters an oxidation regeneration tank containing biological bacteria, where hydrosulfide ions are oxidized to generate sulfur, and ferrous ions are oxidized to ferric ions. The regenerated solution is then pressurized and circulated into an absorption tower for absorption.

[0012] Generally, the complexing agent is one or a mixture of lactic acid, glucose, and pyrophosphate.

[0013] The complexed ion is an iron ion, with an iron ion content of 1-10 g / L, preferably 3-6 g / L.

[0014] The dosage of the complexing agent is: lactic acid 2-10 g / L, glucose 5-20 g / L and / or pyrophosphate 2-15 g / L.

[0015] The bacterial species are alkalophilic thiobacilli, including a group of bacteria composed of denitrifying thiobacilli, thiobacilli excreting thiobacilli, and thiobacilli naplesii.

[0016] The dosage of the biological desulfurization nutrient solution is as follows: Na2CO3 1-5 g / L, KNO3 0.5-1.5 g / L, MgSO4 0.2-0.6 g / L, NaHCO3 5.0-20.0 g / L and / or NH4Cl 0.2-0.8 g / L.

[0017] The sulfur produced during the desulfurization process of complexed iron is used as a carrier for solidifying biological strains.

[0018] Preferably, the sulfur generated during the desulfurization process of complexed iron is added to a culture solution containing biological bacteria for soaking, and the solidified sulfur is transferred to an oxidation regeneration tank.

[0019] More preferably, take a rich solution containing 10% sulfur from the desulfurization of complexed iron, add 100 ppm of sulfur surfactant and stir to make the sulfur particles come into contact with the sulfur surfactant components, causing the sulfur particles to aggregate into sulfur particles of 20-100 micrometers. After standing for 30 minutes, filter the settled complexed iron desulfurization solution through an 800-mesh filter screen, add the separated sulfur particles to a culture solution containing biological inoculum and soak for 24 hours, and transfer the solidified sulfur to an oxidation regeneration tank.

[0020] The method of this invention initially uses complexing agents such as EDTA, HETA, and NTA for the complexed iron. During the oxidation and regeneration of the complexing agent, some of it will be oxidized and degraded. The longer the oxidation time, the greater the degradation of the complexing agent. The sulfur produced during the desulfurization process of complexed iron is hydrophobic sulfur particles that can easily clog equipment and pipelines, affecting the long-term operation of the desulfurization unit. Currently, biological desulfurization technology utilizes sulfur bacteria to desulfurize hydrogen sulfide-containing gases, mainly through three typical processes: biofilter process, bioscrubbing process, and biotrickling filtration process. Among them, the simple-to-operate biotrickling filtration process is more widely used. In the biofilter process, commonly used filter media include peat, soil, and compost. Sulfur bacteria can ensure normal growth in this filter media layer. Gas is continuously introduced into the biofilter, and nutrients are either not added or added in small amounts. The bioscrubbing process includes two stages: the first stage is the absorption process of H2S, and the second stage is the biological oxidation process of H2S in the liquid phase. The packing material is activated sludge, and the absorbent is generally an aqueous solution with added inorganic salts and other components.

[0021] The method of this invention, in the regeneration tower, improves the efficiency of hydrogen sulfide conversion to sulfur under the dual action of bacterial catalytic regeneration and iron ion oxidation regeneration, accelerates the conversion of ferrous iron to ferric iron, shortens the oxidation regeneration time, and reduces the oxidation degradation of complexing agents and the generation rate of side reactions. Another objective of this invention is that during the regeneration process, the complexed iron produces hydrophobic sulfur, and the biological bacteria produce hydrophilic sulfur. The hydrophobic sulfur produced by the complexed iron has a particle size of 20-100 micrometers, serving as a bed for solidified bacteria and simultaneously as sulfur crystal nuclei. The hydrophilic sulfur is adsorbed on the surface, and the two types of sulfur aggregate together, reducing the viscosity of the sulfur particles and effectively preventing sulfur blockage, ultimately achieving a balance between environmental and economic benefits.

[0022] The method of this invention can be used in the removal of hydrogen sulfide and sulfur recovery processes from coal gas, natural gas and refinery gas. Detailed Implementation

[0023] The following examples will further illustrate the content of this invention.

[0024] The implementation method involves a gaseous fluid containing carbon dioxide and hydrogen sulfide entering the lower part of the absorption tower through the inlet. This fluid comes into counter-current contact with the absorbent sprayed from the top of the tower to remove hydrogen sulfide from the gas. The treated purified gas is then discharged from the top of the absorption tower. The rich liquid, which absorbs acidic gases, enters the lower part of the oxidation regeneration tower from the bottom of the absorption tower via a rich liquid pump. After being distributed from the bottom of the biological regeneration tower by an air distributor via a blower, oxidation regeneration occurs from bottom to top, achieving fluidization of sulfur particles from fixed desulfurization bacteria. Sulfide-containing microorganisms and ferric ions in the absorbent liquid are catalytically oxidized to generate elemental sulfur. Regenerated air exits from the top of the biological regeneration tower. The sulfur-containing regenerated sulfur slurry enters the bottom of the oxidation tower, where it undergoes sedimentation and centrifugation processes to recover sulfur resources. The upper clear liquid is returned to the absorption tower for recycling via a lean liquid pump.

[0025] Example 1: Weigh 234 grams of ferrous lactate, heat and dissolve it in 10 liters of water, gradually add NaOH to adjust the pH of the solution to 8, do not add biological bacteria or nutrient solution to the oxidation regeneration tank, and conduct a desulfurization test according to the method of the example.

[0026] (2) Test conditions Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.2g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 5g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0–20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 6 mg / Nm³. 3 The content of by-reaction salts in the desulfurization liquid was sampled and analyzed. The measured values ​​of lactic acid and sodium thiosulfate in the desulfurization liquid at different desulfurization times are shown in Table 1. Fe at different regeneration times 2+ The content determination is shown in Table 2.

[0027] Table 1. Determination data of lactic acid and sodium thiosulfate Desulfurization time (hours) Lactic acid (g / L) Sodium thiosulfate (g / L) 0 17.5 0. 05 24 14.9 8.6 36 13.1 12.4 48 8.8 16.2 .

[0028] Table 2 Regeneration efficiency at different regeneration times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 4.0 2 5 3.2 20% 3 10 2.2 45% 4 15 1.8 55% 5 20 1.0 75% .

[0029] Example 2: Weigh 117 g of ferrous lactate and 223 g of ferrous gluconate, heat and dissolve them in 10 liters of water, gradually add NaOH to adjust the pH of the solution to 8, do not add biological bacteria or nutrient solution to the oxidation regeneration tank, and conduct a desulfurization test according to the method of the example.

[0030] (2) Test conditions Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.3g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 6g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0-20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 5 mg / Nm³. 3 The content of by-reaction salts in the desulfurization solution was sampled and analyzed. Table 3 shows the measured values ​​of lactic acid, glucose, and sodium thiosulfate in the desulfurization solution at different desulfurization times. Fe content at different regeneration times... 2+ The content determination is shown in Table 4.

[0031] Table 3. Determination data of lactic acid, glucose, and sodium thiosulfate. Desulfurization time (hours) Lactic acid (g / L) Glucose (g / L) Sodium thiosulfate (g / L) 0 8.8 19.4 0. 03 24 7.6 16.7 8.1 36 6.8 14.7 12.1 48 4.8 9.9 15.7 .

[0032] Table 4 Regeneration efficiency at different regeneration times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 3.9 2 5 3.0 22% 3 10 2.0 48% 4 15 1.6 59% 5 20 0.9 77% .

[0033] Example 3: Weigh 71.5 g of ferrous pyrophosphate and 223 g of ferrous gluconate, heat and dissolve in 10 liters of water, gradually add NaOH to adjust the pH of the solution to 8, do not add biological bacteria or nutrient solution to the oxidation regeneration tank, and conduct a desulfurization test according to the method of the example.

[0034] (2) Test conditions Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.3g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 4.5 g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0-20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 8 mg / Nm³. 3 The content of by-reaction salts in the desulfurization liquid was sampled and analyzed. The measured values ​​of pyrophosphate, glucose, and sodium thiosulfate in the desulfurization liquid at different desulfurization times are shown in Table 5. Fe at different regeneration times 2+ The content determination is shown in Table 6.

[0035] Table 5. Determination data of pyrophosphate, glucose, and sodium thiosulfate Desulfurization time (hours) Pyrophosphate (g / L) Glucose (g / L) Sodium thiosulfate (g / L) 0 4.4 19.4 0. 04 24 3.6 16.5 8.4 36 3.2 14.4 12.5 48 2.1 9.7 15.9 .

[0036] Table 6 Regeneration efficiency at different regeneration times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 3.9 2 5 3.1 20% 3 10 2.2 44% 4 15 1.7 56% 5 20 1.0 74% .

[0037] Example 4: Take 5L of rich liquid containing approximately 10% sulfur from the desulfurization of complexed iron, add 100ppm of sulfur surfactant and stir to allow the sulfur particles to come into contact with the sulfur surfactant components, causing the sulfur particles to aggregate into sulfur particles of 20-100 micrometers. After standing for 30 minutes, filter the settled desulfurization liquid through an 800-mesh filter screen. Add the separated sulfur particles to a culture medium containing bacterial inoculum and soak for 24 hours to complete the immobilization process. After solidification, transfer the sulfur to an oxidation regeneration tank and add the following nutrient solution: KNO3 0.6 g / L, MgSO4 0.4 g / L, NaHCO3 10.0 g / L, NH4Cl 0.5 g / L. Oxidize in the oxidation regeneration tank tower by introducing air for 8 hours.

[0038] Example 5: The experimental conditions differed from those in Example 1 in that solidified microorganisms were added to the oxidation tower and nutrient solution was replenished.

[0039] (2) Test conditions Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.2g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 5g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0–20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 5 mg / Nm³. 3 The content of by-reaction salts in the desulfurization solution was sampled and analyzed. Table 7 shows the measured values ​​of lactic acid and sodium thiosulfate in the desulfurization solution at different desulfurization times. Fe content at different regeneration times... 2+ The content determination is shown in Table 8. Compared with Comparative Example 1, after 48 hours of reaction, the lactic acid content increased from 8.8 g / L to 10.4 g / L, an increase of 18%, while the sodium thiosulfate content decreased from 16.2 g / L to 13.1 g / L, a decrease of 19%. The regeneration efficiency of ferrous iron increased by an average of 5%.

[0040] Table 7. Determination data of lactic acid and sodium thiosulfate Desulfurization time (hours) Lactic acid (g / L) Sodium thiosulfate (g / L) 0 17.4 0. 05 24 15.3 6.9 36 13.9 9.7 48 10.4 13.1 .

[0041] Table 8 Regeneration efficiency at different times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 3.9 2 5 2.9 26% 3 10 2.0 49% 4 15 1.5 61% 5 20 0.8 79% .

[0042] Example 6: The test conditions differed from those in Example 2 in that the solidified microorganisms were added to the oxidation tower and nutrient solution was replenished. The desulfurization test was conducted according to the method described in the example.

[0043] Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.3g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 6g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0-20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 4 mg / Nm³.3 The content of by-reaction salts in the desulfurization liquid was sampled and analyzed. The measured values ​​of lactic acid, glucose, and sodium thiosulfate in the desulfurization liquid at different desulfurization times are shown in Table 9. Fe at different regeneration times 2+ The content determination is shown in Table 10. Compared with Comparative Example 2, after 48 hours of reaction, the lactic acid content increased from 4.8 g / L to 5.8 g / L (an increase of 21%), the glucose content increased from 9.9 g / L to 11.6 g / L (an increase of 17%), the sodium thiosulfate content decreased from 15.7 g / L to 12.1 g / L (a decrease of 23%), and the regeneration efficiency of ferrous iron increased by an average of 6.5%.

[0044] Table 9. Determination data of lactic acid, glucose, and sodium thiosulfate. Desulfurization time (hours) Lactic acid (g / L) Glucose (g / L) Sodium thiosulfate (g / L) 0 8.7 19.2 0. 05 24 7.8 17.3 6.3 36 7.0 15.4 9.5 48 5.8 11.6 12.1 .

[0045] Table 10 Regeneration efficiency at different times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 3.8 2 5 2.8 27% 3 10 1.7 55% 4 15 1.3 66% 5 20 0.6 84% .

[0046] Example 7: The test conditions differed from those in Example 3 in that the solidified microbial inoculum was added to the oxidation tower and nutrient solution was replenished. The desulfurization test was conducted according to the method described in the example.

[0047] Test gas flow rate: 2.0 Nm 3 / Hour Liquid flow rate: 20 liters / hour H2S content: 11.3g / Nm 3 CO2 content: 5% (v / v) Total Fe content: 4.5 g / L Absorption temperature: ~40°C o C Regeneration temperature: ~40 o C Regeneration reaction time: 0-20 minutes The solution has a pH of 8.0. (3) Experimental results Under the above experimental conditions, after continuous ventilation for 48 hours, the average hydrogen sulfide content in the purified gas was measured to be 8 mg / Nm³. 3 The content of by-reaction salts in the desulfurization liquid was sampled and analyzed. The measured values ​​of pyrophosphate, glucose, and sodium thiosulfate in the desulfurization liquid at different desulfurization times are shown in Table 11. Fe at different regeneration times 2+The content determination is shown in Table 12. Compared with Comparative Example 3, after 48 hours of reaction, the pyrophosphate content increased from 2.1 g / L to 2.5 g / L, an increase of 19%; the glucose content increased from 9.7 g / L to 10.8 g / L, an increase of 11%; the sodium thiosulfate content decreased from 15.9 g / L to 12.6 g / L, a decrease of 21%; and the regeneration efficiency of ferrous iron increased by an average of 5.5%.

[0048] Table 11 Determination data of pyrophosphate, glucose, and sodium thiosulfate Desulfurization time (hours) Pyrophosphate (g / L) Glucose (g / L) Sodium thiosulfate (g / L) 0 4.4 19.3 0. 03 24 3.8 17.4 7.1 36 3.5 15.4 10.1 48 2.5 10.8 12.6 .

[0049] Table 12 Regeneration efficiency at different times Serial Number Regeneration time (minutes) <![CDATA[Fe 2+ (g / L) Regeneration efficiency % 1 0 3.9 2 5 2.9 26% 3 10 2.0 49% 4 15 1.5 62% 5 20 0.8 79% .

[0050] Example 8: 100 ml of the sulfur-containing solution after desulfurization and regeneration in Examples 1, 2, 3, 5, 6, and 7 were added to Buchner funnels with filter cloths, and filtered using a vacuum pump to obtain sulfur paste with a water content of ~50%. The filtration times for these examples are shown in Table 13. In Examples 1, 2, and 3, the sulfur without added bacteria was hydrophobic, resulting in high viscosity sulfur particles that were difficult to filter. In Examples 5, 6, and 7, the hydrophilic sulfur generated by the bacterial strains had low viscosity and was easy to filter. The filtration times for Examples 5, 6, and 7 were reduced by 50% compared to Examples 1, 2, and 3.

[0051] Table 13 Sulfur Filtration Time in Different Examples Example Filtering time (minutes) 1 22 2 25 3 21 5 12 6 11 7 11 .

[0052] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A coupling method for complexed iron and biological desulfurization, characterized in that: An alkaline complexed iron desulfurization solution is used to remove hydrogen sulfide from the gas, converting it into sulfide ions during absorption. The rich solution containing absorbed hydrogen sulfide is then fed into an oxidation regeneration tank containing microorganisms, where sulfide ions are oxidized to sulfur, and ferrous ions are oxidized to ferric ions. The regenerated solution is then pressurized and circulated into an absorption tower for further absorption. The sulfur produced during the complexed iron desulfurization process is used as a carrier for the solidification of the microorganisms. A rich solution containing 10% sulfur from the complexed iron desulfurization process is taken, and 100 ppm of sulfur surfactant is added and stirred. The sulfur particles are brought into contact with the sulfur surfactant, causing them to aggregate into sulfur particles of 20-100 micrometers. After standing for 30 minutes, the settled complexed iron desulfurization liquid is filtered through an 800-mesh filter. The separated sulfur particles are added to a culture medium containing biological strains and soaked for 24 hours. After solidification, the sulfur is transferred to an oxidation regeneration tank. The biological strains are alkalophilic thiobacilli, including a group composed of denitrifying thiobacilli, thiodibacilli, and thiobacilli naples. The complexing agent is one or a mixture of lactic acid, glucose, and pyrophosphate.

2. The method as described in claim 1, characterized in that... The complex ion is an iron ion, with an iron ion content of 1-10 g / L.

3. The method as described in claim 2, characterized in that... The iron ion content is 3-6 g / L.

4. The method as described in claim 1, characterized in that... Dosage of complexing agents: lactic acid 2-10 g / L, glucose 5-20 g / L and / or pyrophosphate 2-15 g / L.

5. The method as described in claim 1, characterized in that: The dosage of biological desulfurization nutrient solution is as follows: Na2CO3 1~5 g / L, KNO3 0.5~1.5 g / L, MgSO4 0.2~0.6 g / L, NaHCO3 5.0~20.0 g / L and / or NH4Cl 0.2~0.8 g / L.