Alkaline biological desulfurization apparatus and method

Abstract

This invention discloses an alkaline biological desulfurization device and method. In this invention, the three main containers—the desulfurization tower, the reactor, and the precipitator—are integrated, with at least the reactor and the precipitator combined into one unit. This simplifies the structure and, due to the integration of the precipitator and the reactor, makes reactor level control relatively easy. Furthermore, the interconnectedness further simplifies reactor level control, significantly reducing piping configuration and making the overall structure more compact, thus shortening the flow path of the relevant liquids.

Description

Technical Field

[0001] This invention relates to an alkaline biological desulfurization device for biogas, and also to an alkaline biological desulfurization method for biogas. Background Technology

[0002] Biogas has been widely used as a new energy source, but the sulfur content in biogas feedstock is often excessive, especially in biogas produced by anaerobic fermentation. my country has specific requirements regarding the sulfur content of exhaust gases emitted into the atmosphere after biogas is used for power generation or direct combustion. Furthermore, there are specific requirements for the hydrogen sulfide content of natural gas after biogas is purified. In addition, biogas contains water vapor, which, together with H2S in the biogas, accelerates the corrosion of metal pipes, valves, and other components. Therefore, before industrial or residential use of biogas, it is essential to remove H2S from the biogas as much as possible.

[0003] Currently, commonly used biogas desulfurization methods mainly include dry desulfurization, wet desulfurization, and biological desulfurization (referred to as biological desulfurization). Biological desulfurization has several methods, including alkaline biological desulfurization and acidic biological desulfurization. The desulfurization method involved in this invention belongs to alkaline biological desulfurization. Alkaline biological desulfurization, also known as biocatalytic desulfurization (BDS), is a desulfurization method that utilizes desulfurizing bacteria to convert sulfides into elemental sulfur or sulfates at ambient temperature and pressure. The basic principle of alkaline biological desulfurization is as follows: H2S gas is absorbed by the absorbent liquid in the desulfurization tower through spraying and converted into sulfides. The absorbent liquid containing sulfides is sent to the reactor, where the sulfides are absorbed by desulfurizing bacteria and decomposed, oxidized, and utilized as nutrients. This process provides energy for the growth and reproduction of desulfurizing bacteria simultaneously.

[0004] The biological desulfurization process mainly consists of three stages: (1) The absorption process of H2S gas: Hydrogen sulfide gas is transferred from the gas phase to the liquid phase and is absorbed by the absorption liquid and transformed into sulfides; (2) The adsorption and absorption process of sulfides: Sulfides dissolved in the aqueous solution are absorbed and adsorbed by desulfurizing bacteria and transferred from the aqueous solution into the desulfurizing bacteria; (3) The process of biological oxidation: Sulfides entering the desulfurization bacteria are used as energy or nutrients and are oxidized, decomposed and utilized by enzymes in the bacteria, thereby achieving the purpose of removing H2S.

[0005] Compared with traditional physicochemical desulfurization methods, alkaline biological desulfurization has advantages such as milder conditions, higher hydrogen sulfide removal rate, lower energy consumption, minimal waste liquid generation, no secondary pollution, lower cost, and the ability to generate elemental sulfur for recycling, thus it is widely used. Alkaline biological desulfurization typically includes three main components: a desulfurization tower, a reactor, and a precipitator. These three main components are often relatively far apart, requiring a large footprint and a relatively large number of connecting pipes. Sulfur paste easily accumulates between these pipes, leading to a relatively high system failure rate. Summary of the Invention

[0006] The purpose of this invention is to provide an alkaline biological desulfurization device with a relatively compact overall structure and a relatively low failure rate. This invention also provides an alkaline biological desulfurization method.

[0007] According to a first aspect of the present invention, an alkaline biological desulfurization device is provided, the alkaline biological desulfurization device comprising: The desulfurization tower has an inlet pipe at the bottom for introducing biogas feedstock gas and a connecting port; an outlet pipe at the top for discharging the desulfurized biogas; and a spray desulfurization device is installed in the upper part of the desulfurization tower. The reactor is a biocatalytic desulfurization reactor. The bottom of the reactor is connected to the desulfurization tower through the connecting port, and the reactor is equipped with an aeration assembly distributor and a circulating liquid outlet pipe is connected in the middle. The settler is located inside the reactor, with its top level equal to or higher than the reactor's maximum liquid level, and it has an overflow weir to allow backflow into the reactor via overflow. The desulfurization liquid circulation system has an inlet end connected to the circulating liquid outlet pipe, and an outlet end connected in the first path to the precipitator and in the second path to the spray desulfurization equipment. A sulfur sludge removal device is connected to the bottom of the settler to remove the sulfur sludge that has settled at the bottom of the settler. An alkali replenishment device to add alkali to the desulfurization tower or reactor; and A nutrient solution replenishment device is used to replenish the reactor with the appropriate nutrient solution. Optionally, the spray desulfurization equipment is connected to an external water source.

[0008] Optionally, the lower or lower-middle part of the precipitator has a conical structure that is larger at the top and smaller at the bottom; The sulfur mud discharge device is connected to the lower end of the conical structure.

[0009] Optionally, the pipeline of the sulfur sludge discharge device is equipped with a flow meter to intermittently discharge sulfur sludge through the control of the flow meter or the sulfur sludge pump equipped with the sulfur sludge discharge device. Optionally, the reactor is equipped with a desulfurization liquid distributor that mates with the communication port to disperse the desulfurization liquid on a predetermined cross-section of the reactor.

[0010] Optionally, the desulfurization liquid distributor is stacked below the aeration assembly distributor located inside the reactor.

[0011] Optionally, the aeration distributor has multiple horizontally arranged aeration pipes connected in parallel, which are located at the bottom of the reactor and are provided with aeration holes. The desulfurization liquid distributor is equipped with multiple distribution holes.

[0012] Optionally, the first main body of the aeration pipeline and the second main body of the distribution pipeline are straight pipes; Accordingly, the first subject and the second subject are perpendicular to each other.

[0013] Optionally, a defoaming device is provided above the liquid surface in the reactor. This defoaming device is connected to a given water supply pipe to defoam by spraying.

[0014] Optionally, the reactor is equipped with a liquid level detection device; Accordingly, the reactor is equipped with a drain pipe and a water supply pipe.

[0015] Optionally, the water supply pipe is connected to a soft water supply device; In contrast, the reactor is equipped with a desulfurization liquid conductivity measuring device to control the opening and closing of the water supply pipe based on the conductivity of the desulfurization liquid.

[0016] Alternatively, the lower part of the desulfurization tower is located inside the reactor.

[0017] According to a second aspect of the present invention, an alkaline biological desulfurization method is provided, comprising the following steps: 1) Biogas feedstock is introduced from the bottom of the desulfurization tower, and during the upward movement of the biogas, it is flushed and exchanged with the desulfurization liquid sprayed downward from the top of the desulfurization tower. After desulfurization, the biogas is discharged from the top of the desulfurization tower. 2) The desulfurization liquid enters the reactor through the connection between the reactor and the desulfurization tower and undergoes an oxidation and regeneration reaction with the biocatalytic desulfurization unit. The sulfides contained therein are oxidized into elemental sulfur and the corresponding sulfate ions of sodium sulfate and sodium thiosulfate, while OH⁻ ions are regenerated at the same time. 3) The first part of the desulfurization liquid in the reactor is sent to the precipitator for sedimentation. The supernatant produced by the sedimentation overflows back to the reactor, and the elemental sulfur precipitated at the bottom of the precipitator is discharged from time to time. The second part of the desulfurization liquid is sent to the desulfurization tower for spray desulfurization, forming a circulation of the desulfurization liquid. The reactor is used to regularly replenish nutrient solution for the biological desulfurization unit, and alkali is added periodically, or the timing of alkali addition is determined based on whether the pH value of the desulfurization solution at a predetermined location in the reactor is within a predetermined range.

[0018] Optionally, water replenishment or desulfurization liquid discharge can be carried out based on reactor level monitoring.

[0019] Alternatively, the sulfur sludge in the precipitator can be discharged periodically by using a sludge pump controlled by flow rate.

[0020] Alternatively, the desulfurization tower is connected to the reactor via a desulfurization liquid distributor; The desulfurization liquid distributor is stacked above the aeration distributor in the aeration assembly located inside the reactor to pneumatically agitate the desulfurization liquid.

[0021] Optionally, the desulfurization liquid in the upper layer of the reactor is defoamed and then taken out.

[0022] Optionally, the aeration rate can be adjusted by the aeration control valve to match the oxidation-reduction potential of the desulfurization liquid and control the aeration rate of the gas station entering the reactor.

[0023] According to the alkaline biological desulfurization equipment of this invention, firstly, the three main containers—the desulfurization tower, the reactor, and the precipitator—are integrated, with at least the reactor and the precipitator being combined. The precipitator introduces the desulfurization liquid through a pipeline, but the supernatant is directly returned to the reactor via overflow. This simplifies the structure and, due to the integration of the precipitator and the reactor, makes reactor level control relatively easy. Furthermore, the desulfurization tower and the reactor are connected at the bottom, meaning their liquid levels are essentially level, further facilitating reactor level control. Moreover, the piping configuration between the desulfurization tower and the reactor, and between the precipitator and the reactor, is significantly reduced, making the overall structure more compact and shortening the flow path of the relevant liquids, resulting in relatively good reliability. Additionally, since the desulfurization liquid is also circulated to the top of the desulfurization tower for desulfurization of biogas feedstock, and part of the desulfurization liquid comes from the upper layer of the reactor and contains a certain amount of OH⁻, meaning the desulfurization liquid participating in the desulfurization spray itself has a certain alkalinity, it can remove some hydrogen sulfide first, effectively reducing the load on the desulfurization system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the main structure of an alkaline biological desulfurization device in one embodiment.

[0025] Figure 2 This is a flow chart of an alkaline biological desulfurization equipment in one embodiment. The dashed lines in the figure represent the interconnection control.

[0026] Figure 3 This is a top view of the structural principle of an alkaline biological desulfurization device in one embodiment.

[0027] In the diagram: 1. Liquid level control valve, 2. Drain pipe, 3. Desulfurization liquid distributor, 4. Liquid level gauge, 5. Aeration distributor, 6. Minimum liquid level, 7. Maximum liquid level, 8. Biogas inlet pipe, 9. Differential pressure sensor, 10. Biogas discharge pipe, 11. Desulfurization tower, 12. Soft water spray pipe, 13. Desulfurization liquid spray pipe, 14. Spray control valve, 15. Aeration pipe, 16. Liquid level control valve, 17. Circulating heat exchanger, 18. Desulfurization liquid outlet pipe, 19. Sulfur sludge outlet pipe, 20. Degassing device, 21. Reaction unit. 22. Overflow weir, 23. Sedimenter, 24. Water supply pipe, 25. Flow meter, 26. Aeration control valve, 27. To sludge treatment system, 28. Aeration flux measurement and control valve, 29. Air station, 30. Plate heat exchanger, 31. Alkali supply pipe, 32. Sulfur-containing sludge discharge, 33. From soft water main pipe, 34. From circulating water supply main pipe, 35. To circulating water return main pipe, 36. Alkali system, 37. Sludge pump, 38. Nutrient tank, 39. Desulfurization liquid circulation pump, 40. Nutrient pipe. Detailed Implementation

[0028] To help understand the concept and implementation principle of the present invention, the basic principle of the alkaline biological desulfurization method in the embodiments of the present invention will be explained below.

[0029] Compared with traditional physical and chemical desulfurization methods, biological desulfurization has advantages such as mild conditions, high hydrogen sulfide removal rate, low energy consumption, minimal waste liquid generation, no secondary pollution, lower cost, and the ability to generate elemental sulfur for recycling, thus it is widely used. Depending on the pH value of the absorbent, biological desulfurization can be divided into acid-based biological desulfurization and alkaline biological desulfurization.

[0030] Alkaline biological desulfurization refers to a method of biological desulfurization using desulfurizing bacteria. Because the desulfurization process involves inherent losses, such as alkali loss and nutrient loss of the desulfurizing bacteria, it is necessary to replenish alkali and nutrients required by the desulfurizing bacteria continuously or periodically. It should be noted that the nutritional needs of desulfurizing bacteria are specific and common knowledge in this field, and will not be elaborated upon here.

[0031] The alkaline biological desulfurization method has the following characteristics: (1) High removal efficiency of hydrogen sulfide, up to 99%; (2) No foreign impurity gas mixed into biogas; (3) All sulfides are converted in the bioreactor, 90-95% of sulfides are selectively converted into elemental sulfur, and 90-95% of the washing liquid is regenerated; (4) Minimal consumption of alkali liquid and no need to replenish expensive catalysts; (5) No blockage of the absorption tower; (6) High purity of by-product elemental sulfur; (7) Low maintenance.

[0032] Because the removal rate of hydrogen sulfide is relatively high, such as Figure 1 and Figure 2The biogas exhaust pipe shown can be directly fed into the next process equipment, and the alkaline biological desulfurization equipment has good design conditions for compactness. In the preferred embodiment of the present invention, the desulfurization tower 11, reactor 21 and precipitator 23 are integrated into a single assembly, which not only has a compact overall structure but also relatively convenient piping, especially as... Figure 3 As shown in the diagram, the lower part of the desulfurization tower 11 is located inside the reactor 21, making the connection simpler. The path from the desulfurization tower 11 to the reactor 21 is very short, meaning that the reactor 21 will respond promptly to changes in the liquid level inside the desulfurization tower 11. Conversely, changes in the liquid level inside the reactor 21 can be controlled relatively directly through, for example, a soft water spray pipe 12 connected to the top of the desulfurization tower 11.

[0033] Meanwhile, reactor 21 itself can also be directly connected to a soft water supply pipe to control the liquid level of reactor 21 more quickly.

[0034] It should be noted that, Figure 1 and Figure 2 The piping in the diagram is not configured according to the specific requirements of the product, but is represented in the form of a principle, which is clear and accurate to those skilled in the art.

[0035] In the embodiments of the present invention, desulfurization is mainly achieved through internal circulation, supplemented primarily with soft water, alkaline solution, and nutrients. Although aeration may introduce air, the impurity content in the air is relatively low, and it does not interfere with the desulfurization tower 11, thus having a minimal negative impact on the normal operation of the reactor 21. In other words, virtually no external impurities will be mixed into the biogas.

[0036] As is inherent to the alkaline biological desulfurization method, all sulfides are converted in the bioreactor, with 90-95% of the sulfides selectively converted into elemental sulfur, and 90-95% of the scrubbing liquid (desulfurization liquid) can be regenerated. This also demonstrates... Figure 1 The desulfurization liquid spray pipe 13 shown is the main spray pipe, transporting the vast majority of the spray liquid. The soft water spray pipe 12 shown in the figure serves as an auxiliary pipe, providing a relatively small amount of spraying operation.

[0037] In comparison, alkaline desulfurization often does not require a catalyst, so the corresponding alkaline biological desulfurization equipment is relatively compact. Furthermore, based on the biological desulfurization reaction in reactor 21, OH⁻ can be generated, and the consumption of alkaline solution is relatively low.

[0038] Although the desulfurization liquid participates in the circulation and contains a certain concentration of OH⁻ (the desulfurization liquid participating in the spraying is taken from the upper liquid of reactor 21 and is a lean liquid), when used for the removal of hydrogen sulfide from biogas, a pre-reaction of hydrogen sulfide will occur, but elemental sulfur will not be deposited in the desulfurization tower 11 in advance, and the tower will not be blocked.

[0039] This also shows that the circulating spraying of desulfurization liquid helps to improve the reaction efficiency in reactor 21.

[0040] In addition, elemental sulfur, as a byproduct, is precipitated in precipitator 23 and mixes with a small amount of desulfurization liquid, forming a semi-fluid sulfur sludge. Since there are very few other solid deposits in this process, the purity of the obtained byproduct elemental sulfur is relatively high.

[0041] Due to the compact design adopted in the embodiments of the present invention, the provided alkaline biological desulfurization equipment has a low failure rate and relatively simple maintenance.

[0042] The reaction mechanism equation in the reactor for the alkaline biological desulfurization method according to embodiments of the present invention is as follows: H₂S + OH⁻ → HS⁻ + H₂O 2HS⁻+O2→2S 0 +2OH⁻ 2S 0 +3O₂→2SO₄⁻+2H⁺ + In the chemical formula, S 0 It represents elemental sulfur.

[0043] Reactor 21, or bioreactor, is a crucial component of biogas biological desulfurization, primarily responsible for the adsorption and degradation of sulfides. Its operation involves the following: when the absorbent containing sulfides enters reactor 21, the active desulfurizing bacteria within absorb and oxidize the sulfides. The sulfides are first oxidized to elemental sulfur (S), simultaneously generating OH⁻ ions. The oxidized elemental sulfur does not precipitate under the agitation effect of aeration. Instead, a portion of the desulfurization liquid is forcibly introduced from the upper layer of reactor 21 into the precipitator via the precipitator inlet pipe 17. This active method can be, for example, pump delivery. After this portion of the desulfurization liquid enters the precipitator, the elemental sulfur precipitates, and the supernatant overflows into reactor 21.

[0044] The alkaline solution rich in OH⁻ ions in reactor 21 is pumped by desulfurization liquid circulation pump 39 into desulfurization tower 11, where H₂S gas is absorbed through spraying. Some elemental sulfur is further oxidized to SO₄²⁻ in reactor 21. 2 ⁻, and generate H + This requires the addition of some alkali to neutralize these hydrogen ions.

[0045] The bioreactor unit in reactor 21 is equipped with an aeration system to provide the necessary oxygen for the desulfurizing bacteria within the reactor, while simultaneously increasing the contact area between the bacteria and sulfides to enhance desulfurization efficiency. The bioreactor unit also includes an alkali dosing system and a nutrient salt dosing system to replenish the desulfurization system with alkali and nutrients, used to adjust the pH and alkalinity of the solution and provide the necessary nutrients for the desulfurizing bacteria.

[0046] According to the alkaline biological desulfurization method of this invention, since the desulfurization liquid taken from the upper layer of the reactor is used as the main spray liquid, the main reaction mechanism in the desulfurization tower 11 is as follows: H₂S + OH⁻ → HS⁻ + H₂O H2S + CO3 2 ⁻→HS⁻+HCO3⁻ CO2 + OH⁻ → HCO3⁻ HCO3⁻ + OH⁻ → CO3 2 ⁻+H2O As can be seen from the reaction mechanism of desulfurization tower 11, no solid substances are produced during the reaction process of desulfurization tower 11. Specifically, in the above chemical formula, only a small amount of elemental sulfur is oxidized to hydrogen sulfide ions, and the solid substance formed is only elemental sulfur. Therefore, by-product sulfur with relatively high purity can be obtained based on the precipitation method.

[0047] Since desulfurization is achieved through spraying, no air or oxygen is introduced into the biogas, and the calorific value of the biogas is not reduced.

[0048] Based on the basic principles of alkaline biological desulfurization, the alkaline biological desulfurization equipment provided in the embodiments of the present invention shall be equipped with a desulfurization tower 11, a reactor 21, a precipitator 23, and auxiliary configurations to complete the corresponding circulation, mass transfer, flow guiding, feeding, etc.

[0049] The bottom of the desulfurization tower 11 is connected to an inlet pipe for introducing biogas feedstock gas, such as... Figure 1 The biogas inlet pipe 8 shown is generally located at the bottom of the desulfurization tower 11, below the lower liquid level of the desulfurization tower 11, or it can be located above the lower liquid level of the desulfurization tower 11. The top of the desulfurization tower 11 is equipped with a spray desulfurization device. The part of the spray desulfurization device inside the desulfurization tower 11 is mainly composed of longitudinally and transversely arranged nozzles. For ease of explanation, the part located in the desulfurization tower 11 is referred to as the spray assembly.

[0050] exist Figure 3 As can be seen in the illustrated structure, the desulfurization tower 11 is partially housed within the reactor 21, which is equipped with a desulfurization liquid distributor that mates with the communication port to disperse the desulfurization liquid across a predetermined cross-section of the reactor 21.

[0051] Figure 3In the reactor 21, the desulfurization liquid distributor 3 has multiple horizontally arranged distribution pipelines with distribution holes to ensure that the desulfurization liquid introduced through the connection port is well dispersed within the reactor 21.

[0052] Furthermore, the aeration distributor 5 located below the desulfurization liquid distributor 3 also has multiple horizontally arranged aeration pipes connected in parallel. These multiple aeration pipes are located at the bottom of the reactor, allowing the desulfurization liquid distributor 3 to be stacked on top of the aeration distributor 5. Accordingly, aeration holes are provided on the aeration pipes.

[0053] The aeration generates stirring that directly acts on the desulfurization liquid introduced through the distribution holes, allowing the desulfurization liquid to come into full contact with oxygen and desulfurization bacteria.

[0054] The pipes of the aeration distributor 5 and the desulfurization liquid distributor 3 located in the reactor 21 can be straight pipes, curved pipes, or disc-shaped pipes.

[0055] exist Figure 3 In the illustrated structure, the main body of the aeration pipeline is a straight pipeline, which is referred to as the first main body for ease of description.

[0056] Figure 3 In the middle, the main body of the desulfurization liquid distributor 3 is also a straight pipeline. For ease of description, this straight pipeline is referred to as the second main body.

[0057] exist Figure 3 In this configuration, the first and second main bodies are perpendicular to each other, resulting in a better mixing effect between air and desulfurization liquid.

[0058] Furthermore, in some embodiments, the first body and the second body can be arranged in parallel.

[0059] Figure 3 The aeration distributor 5 has two manifolds, with the first main manifold arranged in parallel between the two manifolds.

[0060] Both manifolds are air inlets to ensure relatively even air output from the aeration holes on the first main body.

[0061] In such Figure 1 In the illustrated structure, the spray assembly is externally connected to a soft water spray pipe 12 and a desulfurization liquid spray pipe 13, with the latter being the main one. The principle of this has been explained in the previous text and will not be repeated here.

[0062] The bottom of the desulfurization tower 11 is also provided with a connecting port for communication with the reactor 21 at the bottom. Based on the principle of communicating vessels, the liquid levels in the desulfurization tower 11 and the reactor 21 are basically the same. Based on the fact that the liquid flows from the connecting port to the reactor 21, it can be known that theoretically the liquid level in the desulfurization tower 11 should be slightly higher than the liquid level in the reactor 21.

[0063] Because the bottom of the desulfurization tower 11 is connected to the bottom of the reactor 21, the bottom surfaces of the desulfurization tower 11 and the reactor 21 can be at approximately the same height. Under these conditions, the liquid level depth inside the desulfurization tower 11 should have a certain measurement, such as 200~1100mm. When the biogas pipeline 8 is connected to the bottom of the desulfurization tower 11, the introduced biogas feed gas first contacts the desulfurization liquid at the bottom of the desulfurization tower 11 and produces a preliminary reaction. Then, the biogas feed gas overflows from the surface of the desulfurization liquid and rises, thereby creating a large area of ​​contact with the sprayed desulfurization liquid and removing H2S from the biogas feed gas.

[0064] like Figure 1 As shown in the figure, the desulfurization tower 11 has a relatively large height relative to the reactor 21. This is to ensure sufficient and prolonged contact between the sprayed desulfurization liquid and the biogas feedstock, so that the biogas discharged from the biogas discharge pipe 10 meets the required standards as much as possible. Furthermore, since the desulfurization tower 11, except for the portion containing the desulfurization liquid, can be essentially considered an empty tower upwards, its relatively high height still contributes to its good stability.

[0065] Furthermore, in a preferred embodiment of the present invention, the bottom of the desulfurization tower 11 can be fixedly connected to the precipitator 23, thereby providing a relatively large supporting base for the relatively tall desulfurization tower 11, thus giving it better overall stability.

[0066] Reactor 21 is a biocatalytic desulfurization reactor. The bottom of reactor 21 is connected to the desulfurization tower 11 through the communication port. The reactor 21 is equipped with an aeration assembly and a circulating liquid outlet pipe is connected at the top to take liquid from the upper layer of the liquid contained in reactor 21.

[0067] It should be understood that aeration is a standard term in the field of engineering technology, referring to the process of forcibly transferring oxygen from the air into a liquid, with the aim of obtaining sufficient dissolved oxygen. In the embodiments of the present invention, as can be seen from the aforementioned chemical formula, aeration is used to oxidize hydrogen sulfide ions to obtain elemental sulfur and reduce OH⁻ to dissolved oxygen.

[0068] From a mechanical perspective, the aeration assembly of the suitable aeration device should facilitate sufficient contact between air and desulfurization liquid. Therefore, the aeration assembly usually has a relatively large number of dispersion holes, such as... Figure 3 The aeration distributor 5 shown has several aeration pipes with dispersion holes to form microbubbles, ensuring sufficient contact between air and the desulfurization liquid. The remaining functions of aeration have been detailed above and will not be repeated here. However, due to the presence of a desulfurization bacteria packing layer in reactor 21, the upper layer of desulfurization liquid in reactor 21 is relatively stable and constitutes a lean liquid.

[0069] Under the stirring effect of aeration and the continuous liquid supply from desulfurization tower 11, elemental sulfur will not precipitate in reactor 21; precipitation of elemental sulfur occurs in precipitator 23. The liquid taken from precipitator 23 is mainly lean liquid, which is forcibly drawn through the desulfurization circulation system. The first outlet of this desulfurization circulation system is then connected to the middle or lower-middle part of precipitator 23. Here, "middle or lower-middle" refers to the outlet of the first outlet. Figure 1 As can be seen in the illustrated structure, the first path corresponds to the precipitator inlet pipe 16 shown in the figure, and its outlet is at... Figure 1 The sediment is biased downward in precipitator 23.

[0070] Since the amount of desulfurization liquid fed into the precipitator 23 is relatively small, most of it is sent to the top of the desulfurization tower 11 for spraying via the second path of the desulfurization circulation system. The precipitator 23 is controlled by liquid flow, which slows down the flow rate to allow sufficient precipitation of elemental sulfur. The precipitator 23 has two outlets: an upper outlet and a lower outlet. The lower outlet is connected to a sulfur sludge removal device. Because sulfur sludge formation takes a long time, the sulfur sludge removal device is not always activated, while the desulfurization liquid introduced via the first path is continuous. Under these conditions, the precipitator 23 will gradually overflow. The liquid overflowing from the precipitator is called the supernatant.

[0071] Accordingly, the precipitator 23 is located inside the reactor 21, and the top of the precipitator 23 is higher than or equal to the maximum liquid level of the reactor 23. Furthermore, the precipitator 23 has an overflow weir, which is generally constructed on the precipitator 23 in the form of a weir. It can also be simply understood as a plate surrounding the upper opening of the precipitator 23, so that the supernatant can be returned to the reactor 21 by means of the overflow weir.

[0072] Figure 2 In the middle, the bottom of the sedimentation tank 23 is connected to the sulfur sludge discharge pipe 19, and the sulfur sludge discharge pipe 19 is equipped with a sulfur sludge pump 37 to periodically discharge the sulfur-containing sludge.

[0073] For the desulfurization liquid, considering the negative correlation between gas solubility and aqueous solution temperature, and also that the temperature inside reactor 21 should not be too low (otherwise the corresponding reaction will be inhibited), the desulfurization liquid temperature should not be too high or too low. In this embodiment of the invention, the desulfurization liquid temperature is controlled within 35~36℃. A temperature sensor is installed inside reactor 21 to monitor the desulfurization liquid temperature in real time. If the desulfurization liquid temperature is below 33℃ or above 42℃, an alarm is triggered and / or a cooling step for the desulfurization liquid is initiated. Cooling is usually necessary, and an alarm can be used as an option.

[0074] The temperature of the desulfurization liquid can be adjusted at the reactor 21 or on the desulfurization liquid path leading to the circulation path. The latter is preferred because the former is mainly used to ensure the efficient operation of the reactor 21.

[0075] exist Figure 2 In the illustrated structure, a plate heat exchanger 30 is used to cool or heat the desulfurization liquid outlet pipe 18. In summer, circulating water is used for cooling, while in winter, steam is used to supplement the heating of the circulating water. The circulating water pipe is replaced with a hot water pipe, which heats the desulfurization liquid through the plate heat exchanger 30. The circulating water interlocks with the cooling tower fan; when the temperature is below 20°C, the cooling tower fan shuts off to reduce energy consumption; when the temperature is ≥25°C, the interlocking fan turns on. The interlocking adjustable parameter determines whether to activate the cooling tower fan. When supplementing heating in winter, the interlocking value can be changed to a higher temperature to prevent the cooling tower fan from turning on.

[0076] To facilitate the collection of precipitates, the lower or lower-middle part of the precipitator 23 is a conical structure that is wider at the top and narrower at the bottom; correspondingly, the sulfur mud discharge device is connected to the lower end of the conical structure.

[0077] As mentioned above, it is better to use an off-time method for the discharge of sulfur sludge in order to reduce the amount of desulfurization liquid discharged when the sulfur sludge is discharged. Accordingly, the pipeline of the sulfur sludge discharge device is equipped with a first control valve to discharge sulfur sludge intermittently through the control of the first control valve or the sulfur sludge pump 37 equipped with the sulfur sludge discharge device.

[0078] In some embodiments, the settler 23 is provided with a flushing pipe at the bottom or the settler 23 is purged by means of the first path to prevent the settler 23 from being blocked when the sulfur sludge pump 37 stops working.

[0079] When equipped with a flushing pipe, the flushing pipe is connected to a soft water supply device.

[0080] In some embodiments, the top of the reactor 21 is provided with a defoaming device, which is connected to a third path of the desulfurization liquid circulation system to defoam by spraying the circulating liquid.

[0081] In addition, a degassing device can be installed on the part of the inlet pipe of the desulfurization circulation system located inside the reactor 21 to avoid cavitation, for example, by the desulfurization liquid circulation pump 39.

[0082] As a corresponding topic, an alkaline biological desulfurization method is provided, mainly implemented using the alkaline biological desulfurization equipment in the embodiments of the present invention. Given the detailed description of the alkaline biological desulfurization equipment and its functions above, the basic steps of the subtractive biological desulfurization method are briefly described below: 1) Biogas feedstock is introduced from the bottom of desulfurization tower 11, and during the upward movement of biogas, it is flushed and exchanged with the desulfurization liquid sprayed downward from the top of desulfurization tower 11. After desulfurization, the biogas is discharged from the top of desulfurization tower 111. 2) After entering the desulfurization liquid through the connection between the reactor 21 and the desulfurization tower 11, the desulfurization liquid undergoes an oxidation and regeneration reaction with the biocatalytic desulfurization unit. The sulfides contained therein are oxidized into elemental sulfur, and OH⁻ ions are regenerated at the same time. The desulfurization liquid is stirred in the reactor 21 by aeration. 3) The first part of the upper desulfurization liquid in reactor 21 is sent to precipitator 23 for precipitation. The supernatant produced by the precipitation in precipitator 23 overflows back to reactor 21. The elemental sulfur precipitated at the bottom of precipitator 21 is discharged from the reactor at regular intervals. The second part of the upper desulfurization liquid is sent to desulfurization tower 11 for spray desulfurization, forming a circulation of desulfurization liquid.

[0083] The reactor 21 is used to periodically replenish nutrients for the biological desulfurization device, and to periodically replenish alkali, or to determine the timing of alkali replenishment based on whether the conductivity of the desulfurization liquid at a predetermined location in the reactor 21 is within a predetermined range.

[0084] Since the conductivity of desulfurization liquid is related to the ion concentration, in other words, the higher the ion concentration, the higher the conductivity, and vice versa, if the conductivity is too high, soft water needs to be added to dilute the desulfurization liquid. Once the conductivity of the desulfurization liquid reaches the predetermined value after adding soft water, the addition of soft water is stopped.

[0085] At this point, another issue needs to be considered: although the current concentration of the desulfurization solution is very high, and soft water should theoretically be added, the liquid level in reactor 21 is too high. Therefore, the issue of draining the solution also needs to be addressed. Figure 1 and 2 In the illustrated structure, a drain pipe 2 is also connected to the bottom of the reactor 21 so that in the event of the above-mentioned problem, part of the desulfurization liquid can be discharged through the drain pipe 2. This part of the desulfurization liquid is sent to the wastewater treatment system and discharged after treatment.

Claims

1. An alkaline biological desulfurization apparatus characterized by comprising: include: The desulfurization tower has an inlet pipe at the bottom for introducing biogas feedstock gas and a connecting port; an outlet pipe at the top for discharging the desulfurized biogas; and a spray desulfurization device is installed in the upper part of the desulfurization tower. The reactor is a biocatalytic desulfurization reactor. The bottom of the reactor is connected to the desulfurization tower through the connecting port, and the reactor is equipped with an aeration assembly distributor and a circulating liquid outlet pipe is connected in the middle. The settler is located inside the reactor, with its top level equal to or higher than the reactor's maximum liquid level, and it has an overflow weir to allow backflow into the reactor via overflow. The desulfurization liquid circulation system has an inlet end connected to the circulating liquid outlet pipe, and an outlet end connected in the first path to the precipitator and in the second path to the spray desulfurization equipment. A sulfur sludge removal device is connected to the bottom of the settler to remove the sulfur sludge that has settled at the bottom of the settler. An alkali replenishment device is used to replenish alkali into the desulfurization tower or reactor; as well as A nutrient solution replenishment device is used to replenish the reactor with the appropriate nutrient solution.

2. The caustic biological desulfurization apparatus according to claim 1, characterized by The spray desulfurization equipment is connected to an external water source.

3. The caustic biological desulfurization apparatus according to claim 1, characterized by The lower or lower-middle part of the precipitator has a conical structure that is larger at the top and smaller at the bottom. The sulfur mud discharge device is connected to the lower end of the conical structure.

4. The caustic biological desulfurization apparatus according to claim 1 or 3, characterized by, The pipeline of the sulfur sludge discharge device is equipped with a flow meter to intermittently discharge sulfur sludge through the control of the flow meter or the sulfur sludge pump equipped with the sulfur sludge discharge device.

5. The caustic biological desulfurization apparatus according to claim 1, characterized by The reactor is equipped with a desulfurization liquid distributor that is connected to the communication port to disperse the desulfurization liquid on a predetermined cross-section of the reactor.

6. The caustic biological desulfurization apparatus according to claim 5, characterized by The desulfurization liquid distributor is stacked below the aeration assembly distributor located inside the reactor.

7. The caustic biological desulfurization apparatus according to claim 6, characterized by The aeration distributor has multiple horizontally arranged aeration pipes connected in parallel. These multiple aeration pipes are located at the bottom of the reactor and are equipped with aeration holes. The desulfurization liquid distributor is equipped with multiple distribution holes.

8. The caustic biological desulfurization apparatus according to claim 7, characterized by The first main body of the aeration pipeline and the second main body of the distribution pipeline are straight pipes; Accordingly, the first subject and the second subject are perpendicular to each other.

9. The caustic biological desulfurization apparatus according to claim 1, characterized by A defoaming device is installed above the liquid surface in the reactor. This defoaming device is connected to a given water supply pipe to defoam by spraying.

10. The caustic biological desulfurization apparatus according to claim 9, characterized by The reactor is equipped with a liquid level detection device; Accordingly, the reactor is equipped with a drain pipe and a water supply pipe.

11. The caustic biological desulfurization apparatus according to claim 10, characterized by The water supply pipe is connected to a soft water supply device; In contrast, the reactor is equipped with a desulfurization liquid conductivity measuring device to control the opening and closing of the water supply pipe based on the conductivity of the desulfurization liquid.

12. The caustic biological desulfurization apparatus according to claim 1, characterized by The lower part of the desulfurization tower is located inside the reactor.

13. An alkaline biological desulfurization method characterized by comprising: Includes the following steps: 1) Biogas feedstock is introduced from the bottom of the desulfurization tower, and during the upward movement of the biogas, it is flushed and exchanged with the desulfurization liquid sprayed downward from the top of the desulfurization tower. After desulfurization, the biogas is discharged from the top of the desulfurization tower. 2) After the desulfurization liquid enters the reactor through the connection between the reactor and the desulfurization tower, it undergoes an oxidation and regeneration reaction with the biocatalytic desulfurization unit. The sulfides contained therein are oxidized into elemental sulfur and the corresponding sulfate ions of sodium sulfate and sodium thiosulfate, while OH- ions are regenerated. 3) The first part of the desulfurization liquid in the reactor is sent to the precipitator for sedimentation. The supernatant produced by the sedimentation overflows back to the reactor, and the elemental sulfur precipitated at the bottom of the precipitator is discharged from time to time. The second part of the desulfurization liquid is sent to the desulfurization tower for spray desulfurization, forming a circulation of the desulfurization liquid. The reactor is used to regularly replenish nutrient solution for the biological desulfurization unit, and alkali is added periodically, or the timing of alkali addition is determined based on whether the pH value of the desulfurization solution at a predetermined location in the reactor is within a predetermined range.

14. The caustic biological desulfurization method according to claim 13, characterized by, Based on the reactor's liquid level monitoring, make-up water or discharge of desulfurization liquid is carried out.

15. The caustic biological desulfurization method according to claim 13, characterized by, The sulfur sludge in the sedimentation tank is discharged on a timed basis by a sludge pump controlled by flow rate.

16. The alkaline biological desulfurization method according to claim 13, characterized in that, The desulfurization tower is connected to the reactor via a desulfurization liquid distributor; The desulfurization liquid distributor is stacked above the aeration distributor in the aeration assembly located inside the reactor to pneumatically agitate the desulfurization liquid.

17. The alkaline biological desulfurization method according to claim 13, characterized in that, The desulfurization liquid in the upper layer of the reactor is taken after defoaming treatment.

18. The alkaline biological desulfurization method according to claim 13, characterized in that, The aeration rate is adjusted by the aeration control valve to match the oxidation-reduction potential of the desulfurization liquid and control the aeration rate of the gas station entering the reactor.

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