Biogas upgrading biomethane system

Abstract

The utility model discloses a kind of biogas purification biological natural gas systems, comprising: sequentially connected pretreatment device, purification device and post-treatment device;The pretreatment device includes biogas storage tank, desulfurization device and first stage water separator tank;The purification device contains pre-boosting module, cooling module, second stage water separator, flash evaporation gas recovery tank, biogas compressor, compressor rear buffer tank, carbon removal tower front buffer tank, carbon removal tower, tower top high-efficiency water separator;The post-treatment device contains dehydration device, online detection module, pressure regulating metering pry.The utility model realizes high methane recovery rate, low energy consumption, stable operation by optimizing each process link, and ensure the high-quality output of biological natural gas.

Description

Technical Field

[0001] This utility model belongs to the field of biogas extraction, and more specifically, it relates to a biogas purification and biogas natural gas system. Background Technology

[0002] Biogas is a renewable and clean energy source, primarily derived from anaerobic fermentation systems. However, biogas typically contains various impurities such as sulfides, carbon dioxide, and moisture, limiting its direct application. Traditional biogas purification processes suffer from low methane recovery rates, poor equipment operational stability, and high energy consumption. Therefore, developing an efficient, stable, and energy-saving biogas purification process for biomethane is of significant practical importance. Based on this, we propose a biogas purification system for biomethane. Utility Model Content

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing a biogas purification and biomethane system. By optimizing each process step, it achieves high methane recovery rate, low energy consumption, stable operation, and ensures high-quality biomethane production.

[0004] To achieve the above objectives, this utility model provides the following technical solution: A biogas purification and biogas production system includes: A pretreatment device, a purification device, and a posttreatment device are connected in sequence; the pretreatment device includes a biogas storage tank, a desulfurization device, and a first-stage water separator tank. The purification device includes a pre-pressurization module, a cooling module, a second-stage water separator, a flash vapor recovery tank, a biogas compressor, a compressor post-buffer tank, a decarbonization tower pre-buffer tank, a decarbonization tower, and a tower top high-efficiency water separator; The post-processing device includes a dehydration device, an online detection module, and a pressure regulating and metering skid.

[0005] Preferably, the Roots blower in the pre-pressurization module pressurizes the desulfurized and dehydrated biogas to 40-55 kPa, and after being cooled to 15-20°C by the biogas cooler, it enters the second-stage water separator, where it undergoes physical dehydration through a high-efficiency demister.

[0006] Preferably, the decarbonization unit includes a pressure and temperature coordinated control structure: buffered biogas enters the decarbonization tower at 0.6-0.9MPa and 8-15℃, and the process water and biogas in the tower flow in opposite directions to exchange gas and liquid, selectively absorbing and removing CO2; The biogas generated after decarbonization is further separated into liquid water by a high-efficiency water separator at the top of the tower before being transported to the dehydration unit; all buffer tanks ensure that the gas flow is stable before entering the decarbonization tower.

[0007] Preferably, the system also includes a decarbonization wastewater treatment and flash evaporation recovery unit; The decarbonization wastewater treatment and flash evaporation recovery unit includes a flash evaporation tower, a flash vapor recovery tank, a regeneration tower, and a process water pump connected in sequence; by recovering 3-6% of the inlet gas volume of flash vapor, the overall methane recovery rate of the system is significantly improved.

[0008] Preferably, the outlet of the regeneration tower adopts a water diversion control system. A portion of the regenerated process water is pressurized by the process water pump and directly returned to the decarbonization tower for recycling. The other portion is diverted to the chiller unit to form a refrigeration cycle. The decarbonization tower water temperature is maintained in the range of 8-15℃ through load regulation. This refrigeration cycle provides a cold source for system cooling.

[0009] Preferably, the online detection module includes a multi-parameter analyzer that continuously monitors the methane content, hydrogen sulfide concentration, carbon dioxide concentration, oxygen content, and dew point parameters of the dehydrated biogas in real time; gas is only allowed to enter the pressure regulating and metering skid and be connected to the medium-pressure gas pipeline network after pressure reduction, filtration, metering, and odorization treatment when all parameters meet the preset quality standards.

[0010] Preferably, the system's biogas purification process is as follows: Pretreatment stage: The biogas produced by the anaerobic fermentation system is buffered and stabilized, desulfurized and impurities are removed, and liquid water is separated. Compression and dehydration stage: Pre-pressurization, cooling and heat-reduction, and efficient separation of gaseous water are carried out on the desulfurized biogas; Deep decarbonization stage: Dehydrated biogas is mixed and compressed with recovered flash vapor, and carbon dioxide is absorbed by process water in a countercurrent manner under specific pressure and temperature conditions; Flash regeneration stage: The decarbonization process water is subjected to reduced pressure flash evaporation to recover methane, air regeneration to desorb carbon dioxide, and the regenerated process water is treated separately. Quality control phase: Multi-component online analysis and detection of biogas after decarbonization and dehydration; Grid connection and output phase: Pressure regulation, metering, and odorization treatment are carried out on qualified biogas. Wastewater treatment stage: Collect the contaminated liquid from the system and perform gas-liquid separation to prevent methane gas from entering the sewer system. Technical effects and advantages of this utility model: Compared with traditional technologies, the biogas purification and biomethane system provided by this utility model ensures the stable operation of the entire system, reduces equipment failures and downtime, and improves production efficiency through processes such as buffering, high-efficiency desulfurization, water separation, cooling and dehydration, compressor compression, decarbonization, flash evaporation, and regeneration. Attached Figure Description

[0011] Figure 1 This is a diagram of the biogas purification and biogas natural gas system architecture of this utility model; Figure 2 This is a process flow diagram for the biogas purification and biogas production of this utility model. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this utility model clearer, the following detailed description is provided in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the protection scope of this utility model.

[0013] This utility model provides, for example Figure 1 The biogas purification and biogas system shown includes a pretreatment unit, a purification unit and a posttreatment unit connected in sequence. The pretreatment device includes a biogas storage tank for buffering and stabilizing biogas pressure and flow, a desulfurization device for efficiently removing sulfides to below safe levels, and a first-stage water separator tank equipped with a high-efficiency demister to remove liquid water through physical separation. The purification device includes a pre-pressurization module with a Roots blower to pressurize the biogas to 40-55 kPa, a cooling module with a biogas cooler to cool the biogas to 15-20℃, a second-stage water separator equipped with a high-efficiency demister for preliminary dehydration, a flash vapor recovery tank, a biogas compressor to compress the mixed flash vapor biogas to 0.9 MPa in two stages, a buffer tank after the compressor, a buffer tank before the decarbonization tower, a decarbonization tower that absorbs CO2 through countercurrent contact with process water at 0.6-0.9 MPa and 8-15℃, and a high-efficiency water separator at the top of the tower. The post-treatment device includes a dehydration unit, an online detection module for real-time analysis of methane, hydrogen sulfide, carbon dioxide, oxygen content and dew point, a pressure regulating and metering skid for filtration, pressure reduction to 0.3-0.4 MPa, metering and odorization.

[0014] The Roots blower in the pre-pressurization module pressurizes the desulfurized and dehydrated biogas to 40-55 kPa. After being cooled to 15-20℃ by the biogas cooler, it enters the second-stage water separator, where it undergoes physical dehydration through a high-efficiency demister. This pre-pressurization and cooling process significantly reduces the processing load of the subsequent biogas compressor by reducing the biogas volume, and the cooling and dehydration steps effectively reduce the water saturation and reduce the risk of compressor failure. The decarbonization unit includes a pressure and temperature coordinated control structure: buffered biogas enters the decarbonization tower at 0.6-0.9 MPa and 8-15℃, where process water and biogas flow counter-currently for gas-liquid exchange, selectively absorbing and removing CO2; the biogas generated after decarbonization is further separated into liquid water by a high-efficiency water separator at the top of the tower before being transported to the dehydration unit; all buffer tanks ensure a stable airflow state before entering the decarbonization tower. It also includes: a decarbonization wastewater treatment and flash evaporation recovery unit, which comprises a flash evaporation tower connected in sequence, with the pressure controlled at 0.3-0.5 MPa, used to desorb dissolved gas from CO2-rich process water and release flash vapor with a CH4 content of approximately 70%; a flash vapor recovery tank collects and reuses the flash vapor for mixing before the compressor; a regeneration tower uses air to aerate and regenerate the flashed process water, releasing CO2 gas; and a process water pump pressurizes part of the regenerated solution to 0.7-1.2 MPa and returns it to the decarbonization tower; by recovering 3-6% of the flash vapor from the inlet air volume, the overall methane recovery rate of the system is significantly improved. The process water outlet of the regeneration tower is controlled by a flow control system: part of the regenerated process water is pressurized by the process water pump and directly returned to the decarbonization tower for recycling; the other part is diverted to the chiller unit to form a refrigeration cycle, and the decarbonization tower water temperature is maintained in the range of 8-15℃ through load regulation; this refrigeration cycle provides a cold source for system cooling. The online detection module includes a multi-parameter analyzer that continuously monitors the methane content, hydrogen sulfide concentration, carbon dioxide concentration, oxygen content, and dew point parameters of the dehydrated biogas in real time. Gas is only allowed to enter the pressure regulating and metering skid and be connected to the medium-pressure gas pipeline network after pressure reduction, filtration, metering, and odorization treatment when all parameters meet the preset quality standards. The system also features a wastewater discharge and safety assurance structure: wastewater generated in each stage of the system is collected in a wastewater tank for centralized treatment; the wastewater tank has a gas-liquid separation function, and the separated methane-containing gas is treated separately or safely discharged from the flash evaporator top CO2 and regeneration tower top CO2 to ensure that methane does not enter the sewer; the pressure regulating and metering skid has a built-in pressure reducing valve to precisely control the outlet pressure to 0.3-0.4MPa, and is equipped with an odorant injection device and flow meter.

[0015] In addition, this embodiment also proposes as follows: Figure 2 The biogas purification process for biogas production, shown below, is implemented using the aforementioned system and includes the following steps: S1. Pretreatment and desulfurization: Biogas from the anaerobic fermentation system is sequentially passed through a biogas storage tank to buffer and stabilize the pressure and flow rate, a desulfurization device to remove sulfides to a safe level, and a first-stage water separator tank (with a built-in high-efficiency demister) to physically separate and remove liquid water. The first-stage water separator removes liquid water through gravity settling and mechanical demistering. The desulfurization device efficiently removes sulfur, ensuring that the hydrogen sulfide concentration is below the standard limit for urban gas pipeline networks. S2. Pre-pressurization and Cooling Dehydration: The pre-pressurization unit pressurizes biogas to 40-55 kPa using a Roots blower. The pressurized biogas is then cooled to 15-20℃ by a biogas cooler. The cooled gas enters the second-stage water separator (with a built-in high-efficiency demister) for physical dehydration, removing approximately 70% of the gaseous moisture. Specifically, the pre-pressurization process, after achieving 40-55 kPa pressurization with a Roots blower, cools the biogas to 15-20℃ using a dedicated biogas cooler. Combined with the high-efficiency demister, this reduces the gaseous water saturation, resulting in an 80% reduction in compressor unit failure rate. S3. Biogas Compression and Decarbonization: Dehydrated biogas and recovered flash vapor are mixed in a flash vapor recovery tank, then compressed to 0.9 MPa in two stages by a biogas compressor. The gas flow is stabilized by passing through a buffer tank after the compressor and a buffer tank before the decarbonization tower. It then enters the decarbonization tower (controlled pressure 0.6-0.9 MPa, temperature 8-15℃). Process water and biogas come into countercurrent contact to absorb CO2. After decarbonization, the gas passes through a high-efficiency water separator at the top of the tower to separate liquid water. It is then sent to a dehydration unit for deep dehydration. After the flash vapor and dehydrated biogas are mixed in the flash vapor recovery tank, they are compressed to 0.9 MPa in two stages by a biogas compressor. The gas is then stably input into the decarbonization tower after the flow rate and pressure are balanced by multiple buffer tanks. The decarbonization process operates under a pressure of 0.6-0.9 MPa and a temperature of 8-15℃. Process water comes into countercurrent contact to absorb at least 90% of the CO2. A high-efficiency water separator is installed at the top of the tower to intercept residual liquid water. S4. Decarbonization wastewater treatment: The CO2-rich process water discharged from the decarbonization tower is depressurized to 0.3-0.5 MPa and enters the flash evaporator, where flash vapor with a CH4 content of 70% is desorbed. The recovered amount accounts for 3-6% of the inlet air. The flash vapor is collected in the flash vapor recovery tank and returned to step S3 for mixing. The effluent from the flash evaporator is then depressurized and enters the regeneration tower, where air aeration separates and CO2 escapes. The operating pressure of the flash evaporator is 0.3-0.5 MPa, and the flash vapor recovery rate is controlled at 3-6% of the inlet air. The flash vapor is collected in the recovery tank and then fed into the main process, achieving a comprehensive methane recovery rate of 99%. S5. Reclaimed water circulation treatment: The process water discharged from the regeneration tower is divided into two paths: the first path is pressurized to 0.7-1.2MPa by a process water pump and returned to the decarbonization tower; the second path enters the chiller unit to maintain the refrigeration cycle, and the temperature of the decarbonization tower water is controlled at 8-15℃ by adjusting the refrigeration load; the process water flow after CO2 desorption in the regeneration tower is dynamically adjusted according to the operating load: the process water returning to the decarbonization tower is pressurized to 0.7-1.2MPa by a pump; the process water entering the chiller unit has its temperature of the decarbonization tower controlled by the refrigeration load. S6. Product detection and grid connection: After dehydration, biogas is tested by an online analyzer for methane, hydrogen sulfide, carbon dioxide, oxygen content and dew point. Qualified gas enters the pressure regulating and metering skid for filtration, pressure reduction to 0.3-0.4 MPa, metering and odorization, and then connected to the medium-pressure gas pipeline network. The online analyzer monitors in real time the methane purity, hydrogen sulfide concentration ≤ standard limit, carbon dioxide concentration ≤ 3%, oxygen content ≤ 1%, and dew point compliance. Only gas that meets all the indicators can enter the pressure regulating and metering skid. S7. Wastewater treatment: Wastewater from the system is collected in a wastewater tank for gas-liquid separation. Methane gas is recovered and treated to prevent it from entering the sewer. The wastewater tank performs sealed gas-liquid separation on the system wastewater. The separated methane gas is connected to the main process through a recovery pipeline, and the liquid is discharged after being treated to render it harmless.

[0016] In summary, this application has the following effects: High methane recovery rate: By optimizing decarbonization, regeneration and other process steps, as well as flash steam recovery process, this invention can increase the methane recovery rate to 99%, realizing the efficient utilization of biogas resources and increasing the production of biomethane.

[0017] Stable operation: Through processes such as buffering, high-efficiency desulfurization, water separation, cooling and dehydration, compressor compression, decarbonization, flash evaporation, and regeneration, the stable operation of the entire system is ensured, reducing equipment failures and downtime, and improving production efficiency.

[0018] High-quality biogas production: The biogas processed by the process of this utility model has a high content of methane (CH4) as its main component, and has undergone strict quality testing to ensure the high quality of the biogas, which meets the requirements for integration into the medium-pressure gas pipeline network.

[0019] Energy saving and consumption reduction: The pre-pressurization and biogas cooling process reduces the processing capacity of the biogas compressor and lowers energy consumption, reducing the system power consumption to 0.4 kWh / m3 biogas; the flash steam recovery process improves the methane recovery rate and reduces resource waste; the refrigeration cycle is used to meet the system's cooling needs, further improving energy utilization efficiency and reducing production costs.

[0020] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A biogas purification and biogas natural gas system, characterized in that, include: A pretreatment device, a purification device, and a posttreatment device are connected in sequence; the pretreatment device includes a biogas storage tank, a desulfurization device, and a first-stage water separator tank. The purification device includes a pre-pressurization module, a cooling module, a second-stage water separator, a flash vapor recovery tank, a biogas compressor, a compressor post-buffer tank, a decarbonization tower pre-buffer tank, a decarbonization tower, and a tower top high-efficiency water separator; The post-processing device includes a dehydration device, an online detection module, and a pressure regulating and metering skid.

2. The biogas purification and biogas production system according to claim 1, characterized in that: The Roots blower in the pre-pressurization module pressurizes the desulfurized and dehydrated biogas to 40-55 kPa. After being cooled to 15-20°C by the biogas cooler, the biogas enters the second-stage water separator, where it undergoes physical dehydration through a high-efficiency demister.

3. The biogas purification and biogas production system according to claim 1, characterized in that: The decarbonization unit includes a pressure and temperature coordinated control structure: buffered biogas enters the decarbonization tower at 0.6-0.9MPa and 8-15℃, and the process water and biogas in the tower flow in opposite directions to exchange gas and liquid, selectively absorbing and removing CO2. The biogas generated after decarbonization is further separated into liquid water by a high-efficiency water separator at the top of the tower before being transported to the dehydration unit; all buffer tanks ensure that the gas flow is stable before entering the decarbonization tower.

4. The biogas purification and biogas production system according to claim 1, characterized in that, The system also includes a decarbonization wastewater treatment and flash evaporation recovery unit; The decarbonization wastewater treatment and flash evaporation recovery unit includes a flash evaporation tower, a flash vapor recovery tank, a regeneration tower, and a process water pump connected in sequence; by recovering 3-6% of the inlet gas volume of flash vapor, the overall methane recovery rate of the system is significantly improved.

5. A biogas purification and biomethane system according to claim 4, characterized in that, The outlet of the regeneration tower adopts a water diversion control system. Part of the regenerated process water is pressurized by the process water pump and directly returned to the decarbonization tower for recycling. The other part is diverted to the chiller unit to form a refrigeration cycle. The decarbonization tower water temperature is maintained in the range of 8-15℃ through load regulation. This refrigeration cycle provides a cold source for system cooling.

6. A biogas purification and biogas production system according to claim 1, characterized in that, The online detection module includes a multi-parameter analyzer that continuously monitors the methane content, hydrogen sulfide concentration, carbon dioxide concentration, oxygen content, and dew point parameters of the dehydrated biogas in real time. Only when all parameters meet the preset quality standards is the gas allowed to enter the pressure regulating and metering skid and, after pressure reduction, filtration, metering, and odorization treatment, be connected to the medium-pressure gas pipeline network.

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