A biogas desulfurization system based on three-phase separation and in-situ tail gas treatment

Abstract

The application discloses a biogas desulfurization system based on three-phase separation and on-site tail gas treatment, and belongs to the technical field of biogas purification and desulfurization, and comprises a biological desulfurization tower, a biological regeneration reactor, an external three-phase separator, an aeration system, an on-site waste gas treatment device, a desulfurization tower spray pump, a reactor spray pump, an external discharge pump, a first communication pipe and a second communication pipe; the biological desulfurization tower is communicated with the biological regeneration reactor through the first communication pipe, so as to deliver a sulfur-containing solution to the biological regeneration reactor; the biological regeneration reactor is communicated with the external three-phase separator through the second communication pipe; the application forms a circulation system through the biological desulfurization tower, the biological regeneration reactor and the external three-phase separator, combines the on-site tail gas treatment and the inert gas pressure flushing structure, realizes gas-liquid-solid separation and stable operation, is convenient to maintain, reduces the risk of cavitation, blockage and waste gas diffusion, and designs and applies a lifting diffuser suitable for the working condition of sulfur-containing sludge and combined with a self-control system.

Description

Technical Field

[0001] This invention relates to the field of biogas purification and desulfurization technology, specifically a biogas desulfurization system based on three-phase separation and on-site tail gas treatment. Background Technology

[0002] Biogas, an important renewable energy source, is widely derived from the anaerobic fermentation process of livestock and poultry waste, agricultural straw, and organic waste. Its main component is methane, accompanied by a certain concentration of hydrogen sulfide (H2S). Hydrogen sulfide is highly corrosive and toxic. If it enters power generation equipment or purification systems directly without treatment, it will not only cause severe corrosion to the equipment but also affect combustion efficiency and the safety of subsequent gas utilization. Therefore, desulfurization treatment is usually required before biogas can be utilized as a resource.

[0003] Currently, the most widely used desulfurization process is the alkaline biological desulfurization process. This process absorbs hydrogen sulfide with alkaline solution and regenerates the absorbent through aeration in a biological regeneration reactor. It has advantages such as relatively low operating costs and strong adaptability. However, in practical engineering applications, this type of system still has the following problems: First, in traditional systems, the gas-liquid separation structure is mostly integrated inside the bioregeneration reactor, making it difficult to fully remove the gas entrained in the solution. This results in a high gas content in the circulating liquid, which can easily cause problems such as cavitation of the circulating pump, flow fluctuations, and unstable system operation, while also reducing regeneration efficiency. Secondly, the exhaust gas generated by the existing aeration system usually needs to be transported to a remote centralized treatment device through pipelines. Due to the dispersed layout of biogas treatment sites, the exhaust gas transportation distance is long and the pipeline system is complex, which is prone to problems such as interface leakage, corrosion and aging, resulting in local exhaust gas leakage, which not only affects the surrounding environment, but also increases the project investment and maintenance costs. Furthermore, existing alkaline desulfurization systems are prone to increased system pressure loss due to impurity deposition, packing scaling, or blockage of aeration devices during long-term operation. This usually requires periodic shutdowns for manual cleaning or component replacement, which not only affects the continuous operation of the system but also increases maintenance costs and labor input.

[0004] Based on this, the present invention designs a biogas desulfurization system based on three-phase separation and on-site tail gas treatment to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a biogas desulfurization system based on three-phase separation and on-site tail gas treatment to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a biogas desulfurization system based on three-phase separation and on-site tail gas treatment, comprising: a biological desulfurization tower, a biological regeneration reactor, an external three-phase separator, an aeration system, an on-site waste gas processor, a desulfurization tower spray pump, a reactor spray pump, an external discharge pump, a first connecting pipe, and a second connecting pipe. The biological desulfurization tower is connected to the biological regeneration reactor via a first connecting pipe; The bioregeneration reactor is connected to an external three-phase separator via a second connecting pipe; The external three-phase separator is connected to the biological desulfurization tower and the biological regeneration reactor via a spray pump to form a circulation loop; The aeration system is installed inside the bioregeneration reactor, and its gas outlet is connected to the on-site waste gas processor installed at the top of the bioregeneration reactor. Several booster aerators are provided to supply the oxygen required for the reaction. The external three-phase separator is used for gas-liquid-solid separation of the solution, and its bottom is connected to an external discharge pump to discharge solids; A pressure sensor is installed on the outlet pipe of the biological desulfurization tower and connected to an inert gas flushing system, which is used to flush the biological desulfurization tower when the detected pressure exceeds a set threshold. The system consists of a desulfurization tower, a reactor, and a three-phase separator, forming a circulating system. Combined with on-site tail gas treatment and pressure flushing, it achieves gas-liquid-solid separation and stable operation, reducing the risks of cavitation, blockage, and exhaust gas escape.

[0007] A preferred biogas desulfurization method based on this system includes step S1: passing sulfur-containing biogas into a biological desulfurization tower for spray absorption to obtain a sulfur-containing solution; S2. The sulfur-containing solution is transported to a biological regeneration reactor and regenerated by aeration through an aeration system; S3. The regenerated solution is transported to an external three-phase separator for gas-liquid-solid separation. The separated liquid is returned to the biological desulfurization tower and biological regeneration reactor, and the solid is discharged through an external pump. S4. The exhaust gas generated by aeration is introduced into an on-site waste gas processor installed at the top of the bioregeneration reactor for treatment before being discharged. S5. During operation, monitor the outlet pressure of the biological desulfurization tower. When the pressure exceeds the set threshold, start the inert gas flushing system for flushing. The process flow from absorption, regeneration, and three-phase separation to tail gas treatment and pressure flushing achieves efficient removal of hydrogen sulfide and solution recycling, improving treatment continuity and system operation stability. By improving the aeration method, the blockage problem of aeration pipeline in the bioregeneration reactor is solved. The improved aeration method and external three-phase separator simplify the internal structure of the bioregeneration reactor, achieve a thorough gas-liquid mixing effect, and solve the problem of insufficient local aeration. By setting up an automatic control system, not only is fully automatic operation achieved, but also blockage warning is provided for key pipelines of the process unit.

[0008] Preferably, the aeration system includes an aeration blower and a liftable aerator, wherein the liftable aerator can be removed from the top of the bioregeneration reactor; The system employs an aeration blower and a liftable aerator structure. The aerator is made of ABS material, and the air supply pipeline is made of SS316L material. Each air supply branch is equipped with a stainless steel ball valve to distribute the gas. This allows the aeration device to be disassembled and maintained online, reducing the probability of blockage, decreasing the frequency of downtime for maintenance, and improving the reliability and ease of maintenance of the equipment.

[0009] Preferably, the on-site exhaust gas processor is fixedly installed on the top of the bioregeneration reactor and directly connected to the gas outlet at the top of the bioregeneration reactor; The exhaust gas processor is installed at the top of the reactor and directly connected to the top outlet of the bio-regeneration reactor, enabling on-site treatment of exhaust gas, reducing the need for long-distance transportation, and lowering pipeline complexity and the risk of exhaust gas leakage.

[0010] Preferably, the external three-phase separator is located outside the bioregeneration reactor and is used to remove dissolved gases from the solution; An external three-phase separator degasses the solution, allowing dissolved gases in the circulating liquid to be fully released, reducing cavitation in the circulating pump, and improving system stability and separation efficiency.

[0011] Preferably, in step S5, the set threshold is a preset pressure upper limit, and the flushing duration is a preset time interval; By setting pressure thresholds and flushing time intervals, automatic flushing control can be achieved when pressure is abnormal, reducing the risk of blockage, maintaining stable system pressure loss, and improving continuous operation capability.

[0012] Preferably, in step S2, the regeneration reaction rate is controlled by adjusting the aeration intensity of the aeration system; Adjusting the aeration intensity controls the regeneration reaction rate, allowing the system to flexibly adjust its operating status according to working conditions, thereby improving reaction efficiency and reducing unnecessary energy consumption.

[0013] Preferably, the system further includes a liquid alkali pump, a trace element pump, and a water quality analysis unit, used to control the addition of alkali and trace elements based on the test results; The liquid alkali pump, trace element pump, water quality and analysis combination unit are set in the system circulation pipeline to achieve on-demand addition of alkali solution, avoid overuse, reduce operating costs and improve system control accuracy.

[0014] Preferably, the system further includes a heat exchanger, which is disposed on the outlet pipe of the reactor spray pump; A heat exchanger is installed in the reactor circulation pipeline to regulate and control the system temperature, ensuring stable reaction conditions and thus improving desulfurization efficiency and system adaptability.

[0015] Preferably, the external three-phase separator is equipped with a liquid level detection device and a water supply valve, and water is supplied through the water supply valve when the liquid level is lower than the set value; The system is equipped with a liquid level detection and automatic water replenishment mechanism to maintain a stable liquid level in the three-phase separator and prevent system operation interruption.

[0016] The system is equipped with a water quality analyzer, a biogas outlet pressure sensor, a flow meter for the spray pipeline of the bioregeneration reactor to monitor the spray flow and prevent defoaming failures caused by nozzle blockage, an external three-phase separator level sensor, and an automatic water supply valve to enable automatic operation and fault warning of the system.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: Firstly, by setting up an independent external three-phase separator outside the bio-regeneration reactor, the regeneration liquid is separated into gas, liquid, and solid phases. This allows the dissolved gas in the solution to be fully removed before entering the circulation system, thereby effectively reducing the gas content of the circulating liquid, reducing cavitation during the operation of the circulating pump, avoiding flow instability and equipment vibration caused by gas entrainment, and improving the overall operational stability and regeneration efficiency of the system. Secondly, unlike the built-in degassing method in existing technologies, it avoids uneven aeration in some areas of the bioregeneration reactor, which would affect the regeneration efficiency; the external three-phase separator simplifies the internal structure of the bioregeneration reactor and enables a fully mixed aeration state. Thirdly, the exhaust gas generated by the aeration system is directly introduced into the on-site waste gas processor set on top of the bio-regeneration reactor for treatment. Compared with the traditional method of centrally transporting the exhaust gas to a remote treatment system, this significantly shortens the exhaust gas transport path, reduces the complexity of pipeline layout and investment costs, and reduces the risk of exhaust gas emission caused by pipeline leakage or aging. This helps to improve the on-site environment and enhance the environmental protection and safety of the system operation. Fourth, unlike existing technologies that transport the exhaust gas from the bioregeneration reactor to a centralized waste gas treatment system, this avoids the situation where a malfunction in the defoaming device in the bioregeneration reactor leads to the generation of foam inside the reactor, which would then be further drawn into the waste gas delivery pipeline, causing a significant impact. Fifth, a pressure sensor is installed on the outlet pipeline of the biological desulfurization tower and linked to the inert gas flushing system. By monitoring the system pressure in real time, the flushing operation is automatically triggered when the pressure rises abnormally, thereby removing any blockages or deposits that may form in time, reducing system pressure loss, avoiding frequent shutdowns for maintenance, improving the continuous operation capability of the device, reducing manual intervention, and improving the overall reliability and economy of operation. Sixth, a complete and concise automatic control system was designed, including a flow meter installed on the reactor spray pump pipeline. When the flow meter output flow shows a decreasing trend, an alarm is triggered to remind operators to promptly check and clear any blockages to avoid defoaming failures. The system also includes a system level and automatic water replenishment interlock to prevent the system level from exceeding or falling below the limit. Furthermore, when the biogas outlet pressure shows an increasing trend, an inert gas flushing system is used to clear the packing material and reduce the desulfurization tower pressure. This automatic control system not only achieves basic automatic control functions but also provides early warning for key process steps. Seventh, the optimized aerator features a large-diameter flow outlet, solving the problem of sulfur blockage. The flow components are made of high-polymer ABS, which is anti-aging. Unique bubble cutting and swirling technology prevents scaling. Replacement is simple, requiring no changes to the existing main pipeline or production shutdown, allowing for live-line modification and installation. Installation time is short, saving 60% of the construction period, making it particularly suitable for renovation projects. It has a long service life, requiring no replacement for over 10 years. This differs from traditional microporous aeration discs, which are prone to blockage under current operating conditions due to complex piping arrangements. These discs are made of rubber and have a short service life, requiring replacement only every 2-3 years (according to engineering application data provided by some aeration equipment manufacturers). Furthermore, blockages can create aeration dead zones. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of this embodiment; Figure 2 This is a schematic diagram comparing the effects of the aerator in this embodiment with those of a traditional aerator.

[0020] The attached diagram lists the components represented by each number as follows: 1. Biological desulfurization tower; 2. Biological regeneration reactor; 3. External three-phase separator; 4. Aeration system; 5. On-site waste gas processor; 6. Desulfurization tower spray pump; 7. Reactor spray pump; 8. External discharge pump; 9. Liquid alkali pump; 10. Trace element pump; 11. Water quality analysis unit; 12. Heat exchanger; 13. Water supply valve; 14. Pressure sensor; 15. Inert gas flushing system; 16. Connecting pipe; 17. Connecting pipe; 41. Liftable aerator. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Please see Figure 1 The present invention provides a technical solution: a biogas desulfurization system based on three-phase separation and on-site tail gas treatment; Example 1: The core circulation unit consists of a biological desulfurization tower 1, a biological regeneration reactor 2, and an external three-phase separator 3. The biological desulfurization tower 1 is connected to the biological regeneration reactor 2 through the first connecting pipe 16. The desulfurization tower 1 is connected to the external three-phase separator 3 through the desulfurization tower spray pump 6, so that the sulfur-containing solution after absorption enters the biological regeneration reactor 2. An aeration system 4 is provided in the bioregeneration reactor 2, preferably including an aeration blower and a liftable aerator 41, for introducing air into the solution for bioregeneration. The regenerated solution enters the external three-phase separator 3 through the second connecting pipe 17, where gas-liquid-solid separation is completed: gas is released and discharged, solid is discharged through the external discharge pump 8, and liquid is lifted into the desulfurization tower 1 through the desulfurization tower spray pump 6. The exhaust gas generated during the aeration process enters the on-site waste gas processor 5 installed at the top of the reactor through the pipeline for treatment before being discharged. A pressure sensor 14 is installed on the outlet pipeline of the desulfurization tower. When the detected pressure exceeds the set value (e.g., 3~10 kPa), the inert gas flushing system 15 is activated for short-term flushing (e.g., 30~120 s) to reduce the risk of blockage. The flushing cycle can be set to periodic triggering or triggering based on pressure changes, with each flushing session lasting a short time interval (e.g., 1 to 5 minutes). This method allows for online cleaning of the packing material without shutting down the system, reducing the risk of blockage, maintaining system pressure loss within a reasonable range, and thus improving the system's continuous operation capability.

[0023] Compared to the traditional method that requires periodic shutdowns to clean the packing material, this embodiment can reduce the number of shutdowns for cleaning, shorten maintenance time, and help improve the continuity and utilization efficiency of the biogas treatment process.

[0024] The system may also include: a liquid alkali pump 9 linked with a water quality analyzer 11 to regulate pH (e.g., maintain at 8-9), a heat exchanger 12 to maintain the reaction temperature (e.g., 25-30°C), and a water supply valve 13 for liquid level compensation; In this embodiment, the system operation method includes: S1: The biogas containing H2S is introduced into the desulfurization tower and absorbed by alkaline spraying; S2: The sulfur-containing solution enters the biological regeneration reactor 2 and is regenerated through the aeration system 4; S3: The regenerated liquid enters the external three-phase separator 3 to complete gas-liquid-solid separation, with liquid refluxed and solid discharged; S4: The aeration exhaust gas enters the on-site waste gas processor 5 for treatment; S5: The system operates stably through pressure monitoring and inert gas flushing control.

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms should be interpreted broadly. For example, a term can refer to a fixed connection, a detachable connection, or an integral part; a term can refer to a mechanical connection or an electrical connection; a term can refer to a direct connection or an indirect connection through an intermediate medium; a term can refer to the internal connection of two components or the interaction between two components. Unless otherwise explicitly limited, those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biogas desulfurization system based on three-phase separation and on-site tail gas treatment, characterized in that, include: Biological desulfurization tower (1), biological regeneration reactor (2), external three-phase separator (3), aeration system (4), on-site waste gas processor (5), desulfurization tower spray pump (6), reactor spray pump (7), external discharge pump (8), first connecting pipe (16) and second connecting pipe (17). The biological desulfurization tower (1) is connected to the biological regeneration reactor (2) through the first connecting pipe (16) to transport the sulfur-containing solution to the biological regeneration reactor (2). The bioregeneration reactor (2) is connected to an external three-phase separator (3) via a second connecting pipe (17); The external three-phase separator (3) uses the biological desulfurization tower spray pump (6) to transport the sulfur-containing solution to the biological desulfurization tower (1) for spraying, so as to capture hydrogen sulfide in the gas and form a circulating liquid loop at the same time. The aeration system (4) is installed inside the biological regeneration reactor (2), and the gas outlet of the biological regeneration reactor (2) is connected to the on-site waste gas processor (5) at its top. The external three-phase separator (3) is used to separate the solution into gas, liquid and solid phases. Its bottom is connected to the external discharge pump (8) to discharge the solids generated by the entire process system and achieve element balance. A pressure sensor (14) is installed on the outlet pipe of the biological desulfurization tower (1) and connected to an inert gas flushing system (15) for flushing the biological desulfurization tower (1) when the detected pressure exceeds a set threshold. The aeration system (4) includes several liftable aerators (41), which are connected to the top aeration system (4) delivery pipes via flanges. Each gas delivery branch is equipped with a ball valve for disassembly and lifting.

2. The biogas desulfurization method of the biogas desulfurization system according to claim 1, characterized in that: The steps include: S1, passing sulfur-containing biogas into a biological desulfurization tower (1) for spray absorption to obtain a solution containing sulfides, and reducing the alkalinity of the solution; S2. The sulfur-containing solution is transported to the bio-regeneration reactor (2) and aerated and regenerated through the aeration system (4). The regeneration yields a solution containing hydroxide ions and elemental sulfur, and the alkalinity of the solution is restored. S3. The regenerated solution is transported to an external three-phase separator (3) for gas-liquid-solid separation. The liquid is returned to the alkaline biological desulfurization tower (1) for reabsorption of hydrogen sulfide. It is also returned to the biological regeneration reactor (2) for defoaming spraying to prevent biological foam generated in the biological regeneration reactor due to changes in the treatment load. The solid generated after passing through the external three-phase separator (3) is discharged as a solid solution containing sulfur element through an external discharge pump (8). S4. The exhaust gas generated by aeration is introduced into the on-site waste gas processor (5) installed on the top of the bio-regeneration reactor (2) for treatment before being discharged. S5. During operation, the gas pressure of the biological desulfurization tower (1) is monitored. When the pressure exceeds the set threshold, the inert gas flushing system (15) is started for flushing.

3. The biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The aeration system (4) includes an aeration blower and a liftable aerator (41), which can be removed from the top of the bioregeneration reactor (2).

4. The biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The on-site exhaust gas processor (5) is fixedly installed on the top of the bioregeneration reactor (2) and directly connected to the gas outlet at the top of the bioregeneration reactor (2).

5. A biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The external three-phase separator (3) is located outside the bio-regeneration reactor (2) and is used to remove dissolved gases from the solution.

6. The biogas desulfurization method according to claim 2, characterized in that: In step S5, the set threshold is a preset pressure upper limit, and the flushing duration is a preset time interval.

7. The biogas desulfurization method according to claim 2, characterized in that: In step S2, the regeneration reaction rate is controlled by adjusting the aeration intensity of the aeration system (4).

8. A biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The system also includes a liquid alkali pump (9), a trace element pump (10), and a water quality analysis unit (11) for controlling the addition of alkali and trace elements based on the test results.

9. A biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The system also includes a heat exchanger (12), which is located on the outlet pipe of the reactor spray pump (7).

10. A biogas desulfurization system based on three-phase separation and on-site tail gas treatment according to claim 1, characterized in that: The external three-phase separator (3) is equipped with a liquid level detection device and a water supply valve (13), and water is supplied through the water supply valve (13) when the liquid level is lower than the set value.

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