A fully-mixed anaerobic reactor stirring system and a process control method thereof

Abstract

This invention discloses a mixing system for a fully mixed anaerobic reactor and its process control method. The mixing system includes an anaerobic reactor, a variable frequency pump, a main ejector, and a secondary ejector. A guide tube is located at the bottom of the anaerobic reactor. The inlet of the variable frequency pump is connected to the inner cavity of the anaerobic reactor via a pipeline. The inlet of the main ejector is connected to the outlet of the variable frequency pump, and the outlet of the main ejector is connected to the inlet of the guide tube. The inlet of the secondary ejector is connected to the air chamber at the top of the inner cavity of the anaerobic reactor via a pipeline, and the outlet of the secondary ejector is connected to the side suction port of the main ejector. The side suction port of the secondary ejector is equipped with an air branch pipe connected to the atmospheric environment. This invention, through a two-stage Venturi ejector and utilizing a dual-medium power source, not only meets the mixing and mass transfer requirements of the materials within the reactor but also introduces trace amounts of air through the ejectors, providing a controllable microaerobic fermentation environment for anaerobic digestion. This improves anaerobic fermentation efficiency while achieving in-situ desulfurization of biogas.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a stirring system for a fully mixed anaerobic reactor and its process control method. Background Technology

[0002] Anaerobic fermentation technology, as a core process for treating high-concentration organic waste, has significant advantages in energy recovery and pollution control. While the current mainstream CSTR reactor can adapt to the treatment requirements of high-suspended solids feedstocks, the technical bottlenecks in its stirring system severely restrict its process efficiency and economics. For example, mechanical stirring relies on high-power motors for continuous operation, with energy costs accounting for 30%-40% of the total system energy consumption, and frequent mechanical failures lead to a surge in maintenance costs; biogas stirring is limited by uneven gas distribution, easily forming material stratification and fermentation dead zones; hydraulic stirring has an inherent defect of insufficient mixing intensity and often needs to be used in conjunction with other methods, further increasing system complexity.

[0003] At the process optimization level, the synergistic effect of micro-oxygen environment on hydrolysis enhancement and in-situ desulfurization of biogas has been proven: dissolved oxygen of 0.1-1.0 mg / L can increase the degradation rate of organic matter by 15%-22% and the hydrogen sulfide removal efficiency to over 90%. However, current micro-oxygen control technology has a dual contradiction: although gas-phase methods can achieve desulfurization, they cannot improve material mixing; in liquid-phase aeration, the oxygen transfer efficiency of traditional bubble methods is less than 30%; and nano-aeration systems increase operating costs by 50%-60% due to the risk of blockage in precision components. More importantly, the current technology system separates the stirring function from the micro-oxygen supply design—mechanical stirring systems cannot integrate gas dispersion units, and aeration devices lack material circulation power, making it difficult for the system to build a stable and controllable micro-oxygen fermentation environment.

[0004] While some related technologies employ jet mixing, their single-stage Venturi structures suffer from a sharp drop in gas-liquid mixing efficiency and fail to break through the technical framework of using only a single mixing medium (liquid or gas). This technological gap directly leads to methane yield fluctuations of 20%-30% in anaerobic systems, and biogas desulfurization costs accounting for as much as 15%-18% of operating expenses. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] Therefore, embodiments of the present invention propose a fully mixed anaerobic reactor stirring system that combines jet stirring and microaerobic aeration to achieve controllable microaerobic anaerobic fermentation.

[0007] The stirred system of the fully mixed anaerobic reactor in this embodiment of the invention includes:

[0008] An anaerobic reactor, wherein a flow guide tube is provided at the bottom of the anaerobic reactor;

[0009] A variable frequency pump, the inlet of which is connected to the inner cavity of the anaerobic reactor via a pipeline;

[0010] The system includes a main injector and a secondary injector. The inlet of the main injector is connected to the outlet of the variable frequency pump, and the outlet of the main injector is connected to the inlet of the guide tube. The inlet of the secondary injector is connected via a pipeline to the air chamber at the top of the inner cavity of the anaerobic reactor, and the outlet of the secondary injector is connected to the side suction port of the main injector. The side suction port of the secondary injector is equipped with an air branch pipe connected to the atmospheric environment. The working fluid is a mixture of anaerobic digestion liquid drawn in by the main injector, outside air drawn in by the secondary injector, and biogas in the anaerobic reactor. After the gas and liquid are mixed in the main injector, the mixture is injected into the anaerobic reactor through the guide tube.

[0011] The fully mixed anaerobic reactor stirring system of this invention, through a two-stage Venturi injector and a dual-medium power source, can not only meet the mixing and mass transfer requirements of materials in the reactor, but also introduce a trace amount of air through the injector, providing a controllable micro-aerobic fermentation environment for anaerobic digestion, thereby improving the efficiency of anaerobic fermentation and achieving in-situ desulfurization of biogas.

[0012] In some embodiments, the diameter of the guide tube is the same as the outlet diameter of the main injector, the guide tube is arc-shaped, the curvature r of the guide tube is 1 / 2 of the radius R of the anaerobic reactor, and the length of the guide tube is the arc length of a 30° section of a full circle.

[0013] In some embodiments, the pipeline between the variable frequency pump and the anaerobic reactor is defined as the inlet pipe, and the inlet height of the inlet pipe is located 1m below the working liquid level in the anaerobic reactor.

[0014] In some embodiments, the pipeline between the auxiliary injector and the anaerobic reactor is defined as a biogas pipe, and the inlet height of the biogas pipe is located at a position 1m above the working liquid level in the anaerobic reactor.

[0015] In some embodiments, the inlet diameter D of the main injector 11 The inlet diameter D of the main injector is the same as the outlet diameter of the variable frequency pump. 11 With respect to the inlet diameter D of the auxiliary injector 21 The relationship between them satisfies 1.5D. 11 ≥D 21 ≥1.2D 11 .

[0016] In some embodiments, the outlet diameter D of the secondary injector23 The diameter D of the side suction port of the main injector 12 same.

[0017] In some embodiments, the nozzle diameter d1 of the main injector is the inlet diameter D. 11 1 / 2, the inlet diameter D of the main injector 11 For the outlet diameter D 13 The length-to-diameter ratio of the throat of the main injector is (8-12):1, and the nozzle diameter d2 of the auxiliary injector is equal to the inlet diameter D. 21 1 / 2, the inlet diameter D of the secondary injector 21 For the outlet diameter D 23 The length-to-diameter ratio of the throat of the secondary injector is (8-12):1.

[0018] In some embodiments, the side suction port diameter D of the secondary injector 22 With the inlet diameter D 21 The relationship between them satisfies D 22 =0.73D 21 .

[0019] In some embodiments, the air branch pipe is equipped with an air flow meter and an electric regulating valve, and the biogas pipe is equipped with a biogas flow meter.

[0020] The embodiments of the present invention also propose a process control method for a fully mixed anaerobic reactor stirring system, which is applicable to the fully mixed anaerobic reactor stirring system described in the above embodiments.

[0021] The process control method for the stirred system of the fully mixed anaerobic reactor according to embodiments of the present invention includes:

[0022] During system operation, oxygen is consumed in both the liquid and gas phases, and the oxygen concentration changes in real time. Its differential equation over time is:

[0023]

[0024] in, , where V is the target value for the gas phase air content, V is the gas chamber volume of the anaerobic reactor, and k is the air consumption rate constant;

[0025] When the system is running stably, to maintain a constant gaseous oxygen concentration over time, the above equation applies:

[0026]

[0027] After the system is running normally, monitor the air flow rate, biogas flow rate, and actual oxygen concentration at different biogas return rates, calculate the k value, and set the concentration of oxygen in the biogas. The target value is below 0.42%. By real-time monitoring of the oxygen concentration in the gas chamber and the biogas return flow, q is adjusted based on PID control. air The quantity satisfies The general formula for equilibrium. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the stirring system of the fully mixed anaerobic reactor according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the guide tube and the direction of liquid flow in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the components of the injector according to an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the main injector according to an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of the auxiliary injector according to an embodiment of the present invention.

[0033] Figure label:

[0034] 11-Anaerobic reactor, 12-Guide cylinder, 13-Biogas overflow pipe, 14-Biogas component analyzer, 101-Liquid inlet, 102-Liquid outlet, 103-Gas chamber.

[0035] 21-Variable frequency pump,

[0036] 31-Main injector, 32-Auxiliary injector, 33-Air branch pipe, 34-Liquid inlet pipe, 35-Biogas pipe, 36-Air flow meter, 37-Electric regulating valve, 38-Biogas flow meter

[0037] 301-Inlet, 302-Outlet, 303-Side suction port, 304-Mixing chamber, 305-Nozzle, 306-Throat, 307-Diffuser tube. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0039] The stirring system of the fully mixed anaerobic reactor according to an embodiment of the present invention is described below with reference to the accompanying drawings.

[0040] like Figures 1 to 5 As shown, the stirring system of the fully mixed anaerobic reactor in this embodiment of the invention includes an anaerobic reactor 11, a variable frequency pump 21, a main ejector 31, and a secondary ejector 32.

[0041] The anaerobic reactor 11 has an inlet 101 and an outlet 102. The bottom of the anaerobic reactor 11 is equipped with a guide tube 12, and the top of the anaerobic reactor 11 is equipped with a biogas overflow pipe 13. A biogas component analyzer 14 is installed on the biogas overflow pipe 13 to test the hydrogen sulfide concentration and the oxygen content in the biogas.

[0042] The inlet of the variable frequency pump 21 is connected to the inner cavity of the anaerobic reactor 11 via a pipeline. The inlet of the main ejector 31 is connected to the outlet of the variable frequency pump 21. The outlet of the main ejector 31 is connected to the inlet of the guide tube 12. The inlet of the auxiliary ejector 32 is connected to the air chamber 103 at the top of the inner cavity of the anaerobic reactor 11 via a pipeline. The outlet of the auxiliary ejector 32 is connected to the side suction port of the main ejector 31. The side suction port of the auxiliary ejector 32 is provided with an air branch pipe 33 that connects to the atmospheric environment.

[0043] Both the main injector 31 and the auxiliary injector 32 are Venturi injectors. The main injector 31 is a gas-liquid injector, and the auxiliary injector 32 is a gas-gas injector. The injector has an inlet 301, an outlet 302, a side suction port 303, and a mixing chamber 304. The injector includes a nozzle 305, a throat 306, and a diffuser 307.

[0044] The main injector 31 is powered by a variable frequency pump 21 at its inlet. The variable frequency pump 21 draws anaerobic digestion liquid from the anaerobic reactor 11 as the working fluid. After being sprayed out at high speed through the nozzle, it forms a negative pressure, which draws the mixed gas in the auxiliary injector 32 into the mixing chamber of the main injector 31. After the gas and liquid are mixed, they enter the anaerobic reactor 11 through the guide tube 12 to achieve the jet stirring effect.

[0045] The auxiliary injector 32 is powered by the pressure of the gas chamber 103 of the anaerobic reactor 11 and the negative pressure of the side suction port generated by the operation of the main injector 31. It uses the biogas in the anaerobic reactor 11 as the working fluid and draws air into the mixing chamber of the auxiliary injector 32. After the biogas and air are mixed, they become the fluid drawn into the main injector 31 and are mixed with the anaerobic digestion liquid in the mixing chamber of the main injector 31.

[0046] It is understood that the mixing system of the fully mixed anaerobic reactor in this embodiment of the invention uses the anaerobic digestion liquid in the anaerobic reactor 11 drawn by the main injector 31 and the mixture of outside air and biogas in the anaerobic reactor 11 drawn by the auxiliary injector 32 as the working fluid, and after the gas and liquid are mixed in the main injector 31, it is sprayed into the anaerobic reactor 11 through the guide tube 12.

[0047] Therefore, by using a two-stage Venturi injector and a dual-medium power source, not only can the mixing and mass transfer requirements of the materials in the reactor be met, but also a small amount of air can be introduced through the injector to provide a controllable micro-aerobic fermentation environment for anaerobic digestion, thereby improving the efficiency of anaerobic fermentation and achieving in-situ desulfurization of biogas.

[0048] In some embodiments, such as Figures 2 to 4 As shown, the diameter of the guide tube 12 is the same as the outlet diameter D of the main injector 31. 13 Similarly, the guide tube 12 is arc-shaped, and the curvature r of the guide tube 12 is 1 / 2 of the radius R of the anaerobic reactor 11. The length of the guide tube 12 is the arc length of a 30° section of a whole circle.

[0049] Understandably, after the guide tube 12 is installed, it enables the fluid entering the anaerobic reactor 11 to be sprayed out in a horizontal direction. Under the combined effect of spraying and suction, the anaerobic digestion liquid in the anaerobic reactor 11 forms a swirling flow to achieve stirring.

[0050] In some embodiments, such as Figure 1 As shown, the pipeline between the variable frequency pump 21 and the anaerobic reactor 11 is defined as the inlet pipe 34, and the inlet height of the inlet pipe 34 is located 1m below the working liquid level L in the anaerobic reactor 11.

[0051] When the feed volume or gas production changes, the liquid level in anaerobic reactor 11 may fluctuate instantaneously. The 1m submersion depth is designed to allow for a safety margin when the liquid level drops, ensuring that the variable frequency pump 21 always draws anaerobic digestate and improving the stability of system operation.

[0052] The pipeline between the auxiliary injector 32 and the anaerobic reactor 11 is defined as the biogas pipe 35. The inlet height of the biogas pipe 35 is located at a position 1m above the working liquid level L inside the anaerobic reactor 11.

[0053] Biogas is mainly concentrated in the gas chamber 103 at the top of the reactor. The position 1m above the liquid level ensures that the biogas pipe 35 is always in the pure biogas layer of the gas phase, preventing the anaerobic digester liquid from entering the auxiliary injector 32 and causing interference in the gas-liquid two-phase flow. This ensures that the auxiliary injector 32 only processes gases (biogas and air) and maintains its mixing efficiency under its design conditions.

[0054] In some embodiments, such as Figures 3 to 5 As shown, the inlet diameter D of the main injector 31 11 The outlet diameter is the same as that of the variable frequency pump 21 to avoid the problem of reduced efficiency of the variable frequency pump 21 caused by the change in diameter.

[0055] The inlet diameter D of the main injector 31 11 With the inlet diameter D of the auxiliary injector 32 21 The relationship between them satisfies 1.5D. 11 ≥D 21 ≥1.2D 11 The inlet diameter of the secondary injector 32 is slightly larger than that of the main injector 31, by increasing the gas passage area (D). 21 ≥1.2D 11 This compensates for the low density characteristics of the gas, ensuring mass flow rate matching between the two injectors. Simultaneously, it limits D... 21≤1.5D 11 To avoid insufficient power of the gas-liquid ejector leading to negative pressure imbalance.

[0056] The outlet diameter D of the auxiliary injector 32 23 The diameter D of the side suction port of the main injector 31 12 Same. The mixed gas (biogas + air) output by the auxiliary injector 32 needs to enter its mixing chamber through the side suction port of the main injector 31. The equal diameter design eliminates turbulence and pressure drop caused by abrupt changes in cross-section, ensuring a stable flow rate of the gas-gas mixture.

[0057] The nozzle diameter d1 of the main injector 31 is equal to the inlet diameter D. 11 1 / 2, the inlet diameter D of the main injector 31 11 For the outlet diameter D 13 The nozzle cross-sectional area of ​​the main injector 31 is reduced to 1 / 4 of the inlet (the area ratio is proportional to the square of the diameter), increasing the flow rate of the anaerobic digester liquid. Utilizing the Bernoulli effect, a high negative pressure is created at the throat, driving the auxiliary injector 32 to draw in the mixed gas. The diffuser diameter of the main injector 31 is increased to 2D. 11 (With a cross-sectional area increased by 4 times), the kinetic energy of high-speed fluid is gradually converted into static pressure energy, reducing energy loss and promoting full mixing of gas and liquid two-phase flow.

[0058] The nozzle diameter d2 of the auxiliary injector 32 is equal to the inlet diameter D. 21 1 / 2, the inlet diameter D of the auxiliary injector 32 21 For the outlet diameter D 23 Half of it. The biogas is accelerated through the nozzle, forming a high-speed jet that draws in air, while simultaneously being diffused to 2D through the diffuser. 21 The flow rate is reduced to prevent excessive gas velocity from causing micro-oxygen bubbles to burst. The low-velocity diffusion section prolongs the gas-gas mixing time, promoting the oxidation reaction of H2S by thiobacilli (residence time ≥ reaction kinetic threshold 0.1 seconds), achieving an elemental sulfur generation rate ≥90%.

[0059] The length-to-diameter ratio of the throat of the main injector 31 is (8-12):1, and the length-to-diameter ratio of the throat of the auxiliary injector 32 is also (8-12):1. The longer throats prolong the gas-liquid / gas-gas contact time, ensuring that the oxygen solubility in the liquid is ≥80% and the mixing uniformity of biogas and air. A length-to-diameter ratio that is too small (<8:1) leads to boundary layer separation and turbulent energy loss; a ratio that is too large (>12:1) increases frictional resistance. This range balances mixing efficiency and energy consumption.

[0060] In some embodiments, such as Figures 3 to 5 As shown, the diameter D of the side suction port of the auxiliary injector 32 is... 22 (That is, the diameter of air branch pipe 33) and the inlet diameter D 21 The relationship between them satisfies D 22=0.73D 21 This ratio ensures that the air content in the gas chamber 103 of the anaerobic reactor 11 is less than 2% under any circumstances in the mechanical design.

[0061] It is important to note that during system operation, in order to ensure that the air entering the system does not affect the anaerobic environment, and because the mixed fluid first enters the liquid phase and then enters the gas phase, it is necessary to ensure that the dissolved oxygen concentration in the liquid phase does not exceed the range that anaerobic microorganisms can tolerate under any circumstances.

[0062] According to Bernoulli's equation, in the secondary injector 32:

[0063]

[0064] Among them, P 21 For the inlet pressure, ρ gas v is the density of biogas 21 The flow velocity in the biogas pipe is 35, g is the acceleration due to gravity, and h is the velocity due to gravity. 21 For import height, P 22 v is the nozzle pressure. 22 h is the jet nozzle velocity. 22 This refers to the height of the nozzle.

[0065] Because the length between the injector inlet and the injection port is limited, i.e., h 21 ≈h 22 The negative pressure at the nozzle can then be calculated as follows:

[0066]

[0067] According to the law of conservation of mass:

[0068] q gas =A 21 v 21 =A 22 v 22

[0069] Among them: A 21 The inlet cross-sectional area of ​​the auxiliary injector is 32.

[0070] A2 is the cross-sectional area of ​​the 32 nozzle of the secondary injector.

[0071] We can obtain:

[0072]

[0073] Therefore, we can conclude that:

[0074]

[0075] The negative pressure value ΔP that the secondary injector 32 can draw in air has been calculated above. Based on Bernoulli's equation, since the air branch pipe 33 is directly connected to the atmosphere, the air velocity outside the pipe opening is approximately 0. As the air branch pipe 33 is installed horizontally, there is no elevation difference. Therefore:

[0076]

[0077] Where, ρ air For air density, v air This refers to the air velocity.

[0078] Therefore, the airflow rate is:

[0079]

[0080] A 22 The cross-sectional area of ​​the air branch pipe is 33.

[0081] The above formula derivation reveals the relationship between biogas from the secondary injector 32 and the intake air, expressed as:

[0082] q air =Kq gas

[0083] in,

[0084]

[0085] A 22 The cross-sectional area of ​​the air branch pipe is 33.

[0086] To ensure safety, the oxygen concentration in the empty tower of anaerobic reactor 11 (i.e., when no oxygen-consuming reaction occurs within anaerobic reactor 11, and biogas and air are mixed and directly discharged) is limited to below 2%. Therefore, the oxygen concentration of the mixed gas is expressed as:

[0087]

[0088] Among them, C air The concentration of air in the mixed gas is expressed as a percentage (%); 0.21 represents the oxygen content in the air, which is 21%.

[0089] We can conclude that K < 0.1053. Substituting this into the K value expression, we can obtain the relationship between the diameter of the air branch pipe 33 and the diameter of the biogas pipe 35 of the auxiliary injector 32:

[0090] D 22 ≤0.73D 21

[0091] This parameter is a key design parameter to ensure the safe operation of the system's controllable microaerobic anaerobic fermentation. To maximize the use of microaerobic conditions for in-situ desulfurization, D is selected during the design phase. 22 =0.73D 21， This relationship is an important design parameter for the fully mixed anaerobic reactor stirring system in this embodiment of the invention.

[0092] Furthermore, the oxidation of hydrogen sulfide by thiobacilli requires an oxygen content in the biogas phase of 0.42%–1.26% (with desulfurization efficiency reaching over 95%), which translates to an air concentration of 2%–6%. Using a commonly used air supply rate of 2% for biological desulfurization (the air supply rate of biological desulfurization towers in large and medium-sized biogas projects in Europe is mostly around 2%), we can determine whether oxygen at this concentration will inhibit methanogens. When the air content in the biogas is 2%, assuming the anaerobic digester does not consume oxygen, according to the ideal gas equation and Henry's law, at 25°C, the oxygen concentration in water is 8.47 mg / L. In the mixture of biogas and air, air accounts for 2%, so oxygen accounts for 2% * 21% = 0.00442. Therefore, the highest dissolved oxygen concentration in the liquid phase at this time is 8.47 * 0.0042 = 0.0356 mg / L, corresponding to an ORP of -300mV to -200mV, which will not inhibit the system's anaerobic digestion. The oxygen environment has an impact. In actual operation, when oxygen-consuming reactions are taking place in the liquid phase environment, the concentration of dissolved oxygen will further decrease. (According to literature data, methanogens will maintain high activity when the dissolved oxygen concentration is ≤0.03mg / L). When the fermentation temperature is 35℃, the oxygen concentration in water is 7.36mg / L, and the dissolved oxygen concentration of the mixed gas in water is 0.0309mg / L. The temperature of mesophilic anaerobic fermentation is about 35℃, which ensures that the anaerobic reaction environment is not inhibited.

[0093] In some embodiments, such as Figure 1 As shown, an air flow meter 36 and an electric regulating valve 37 are installed on the air branch pipe 33. The air flow meter 36 measures the air being drawn in, and the air flow rate is adjusted by the electric regulating valve 37. A biogas flow meter 38 is installed on the biogas pipe 35 to monitor the biogas flow rate.

[0094] The present invention provides a process control method for a fully mixed anaerobic reactor stirring system, applicable to the fully mixed anaerobic reactor stirring system described in the above embodiments.

[0095] The process control method for the stirred system of the fully mixed anaerobic reactor according to embodiments of the present invention includes:

[0096] During system operation, oxygen is consumed in both the liquid and gas phases, and the oxygen concentration changes in real time. Its differential equation over time is:

[0097]

[0098] in, is the target value of gas phase air content, in %; V is the volume of gas chamber 103 of anaerobic reactor 11; k is the air consumption rate constant (including consumption in the gas phase and consumption in the liquid phase), which is affected by a combination of factors such as the oxidation rate of liquid phase substances, the activity of gas phase desulfurization bacteria, and desulfurization load.

[0099] When the system is running stably, to maintain a constant gaseous oxygen concentration over time, the above equation applies:

[0100]

[0101] After the system is running normally, the air flow rate, biogas flow rate, and actual oxygen concentration are monitored at different biogas return rates to calculate the k-value. Because the diameter of the air duct is designed according to the 2% limit, the air regulating valve does not need to be controlled during the initial operation, thus obtaining the k-value under different conditions.

[0102] Setting biogas The target value is below 0.42%. By real-time monitoring of the oxygen concentration and biogas return flow in gas chamber 103, and based on PID control, the opening of the air valve is adjusted to ensure that q air The quantity satisfies The general formula for equilibrium.

[0103] Based on the above formula, a precise process control method for micro-aerobic anaerobic fermentation with a two-stage Venturi ejector and a dual-medium power source can be established.

[0104] In summary, according to Bernoulli's equation, the volume of the mixed fluid can be increased to 3 to 4 times the volume of the liquid by jet mixing. Calculated by volume replacement, the time required for stirring the digestate in the anaerobic reactor 11 once is reduced to 1 / 3 to 1 / 2 of the original time compared with the ordinary circulation method. When the circulation is the same multiple, the jet mixing method saves 50% to 60% of the energy compared with the ordinary circulation mixing method.

[0105] A secondary injector 32 is added to the side intake of the main injector 31 to introduce trace amounts of oxygen into the anaerobic reactor 11, creating a micro-aerobic anaerobic fermentation environment. Micro-oxygen can increase the hydrolysis rate of macromolecular organic matter and some toxic substances, and the smallest jet-stirred bubbles can reach 0.45 mm (450 μm), which is nearly 20 times larger than the specific surface area of ​​bubbles generated by traditional aeration methods, resulting in better mass transfer. By setting the ratio of the air branch pipe 33 to the pipe diameter, it is ensured that the incoming air does not negatively affect the anaerobic environment under any operating condition. The opening of the electric regulating valve 37 is controlled in real time by an algorithm, thereby achieving precise control of the incoming air.

[0106] The introduction of trace amounts of oxygen into the digestate creates a micro-aerobic anaerobic fermentation environment, promoting the rapid degradation of macromolecular organic matter and toxic substances in the wastewater, improving anaerobic fermentation efficiency, increasing biogas production, and enhancing the stability of the anaerobic process. The presence of trace oxygen in both the digestate and biogas phases promotes the natural growth of thiobacilli in both the gas and liquid phases. These thiobacilli utilize oxygen as an electron donor to reduce hydrogen sulfide to elemental sulfur and inhibit sulfate conversion, achieving in-situ desulfurization. The removal rate of hydrogen sulfide can reach approximately 90%, significantly reducing the consumption of desulfurizing agents and operating costs in the biogas treatment process.

[0107] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are 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. Therefore, they should not be construed as limitations on this invention.

[0108] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0109] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication 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.

[0110] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0111] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0112] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A stirring system for a fully mixed anaerobic reactor, characterized in that, include: An anaerobic reactor, wherein a flow guide tube is provided at the bottom of the anaerobic reactor; A variable frequency pump, the inlet of which is connected to the inner cavity of the anaerobic reactor via a pipeline; The system includes a main ejector and a secondary ejector, both of which are Venturi ejectors. The inlet of the main ejector is connected to the outlet of the variable frequency pump, and the outlet of the main ejector is connected to the inlet of the guide tube. The inlet of the secondary ejector is connected via a pipeline to the air chamber at the top of the anaerobic reactor's inner cavity, and the outlet of the secondary ejector is connected to the side suction port of the main ejector. The side suction port of the secondary ejector is equipped with an air branch pipe connected to the atmospheric environment. The working fluid is a mixture of anaerobic digestion liquid drawn in by the main ejector from the anaerobic reactor, outside air drawn in by the secondary ejector, and biogas from the anaerobic reactor. After the gas and liquid are mixed in the main ejector, the mixture is injected into the anaerobic reactor through the guide tube. The diameter D of the side suction port of the secondary ejector is... 22 With the inlet diameter D 21 The relationship between them satisfies D 22 =0.73D 21 .

2. The stirring system for a fully mixed anaerobic reactor according to claim 1, characterized in that, The diameter of the guide tube is the same as the outlet diameter of the main injector. The guide tube is arc-shaped, and the curvature r of the guide tube is 1 / 2 of the radius R of the anaerobic reactor. The length of the guide tube is the arc length of a 30° section of a whole circle.

3. The stirring system for a fully mixed anaerobic reactor according to claim 1, characterized in that, The pipeline between the variable frequency pump and the anaerobic reactor is defined as the inlet pipe, and the inlet height of the inlet pipe is located 1m below the working liquid level in the anaerobic reactor.

4. The stirring system for a fully mixed anaerobic reactor according to claim 1, characterized in that, The pipeline between the auxiliary injector and the anaerobic reactor is defined as the biogas pipe, and the inlet height of the biogas pipe is located at a position 1m above the working liquid level in the anaerobic reactor.

5. The stirring system for a fully mixed anaerobic reactor according to claim 1, characterized in that, The inlet diameter D of the main injector 11 The inlet diameter D of the main injector is the same as the outlet diameter of the variable frequency pump. 11 With respect to the inlet diameter D of the auxiliary injector 21 The relationship between them satisfies 1.5D. 11 ≥D 21 ≥1.2D 11 .

6. The stirring system for a fully mixed anaerobic reactor according to claim 5, characterized in that, The outlet diameter D of the auxiliary injector 23 The diameter D of the side suction port of the main injector 12 same.

7. The stirring system for a fully mixed anaerobic reactor according to claim 6, characterized in that, The nozzle diameter d1 of the main injector is the inlet diameter D. 11 1 / 2, the inlet diameter D of the main injector 11 For the outlet diameter D 13 The length-to-diameter ratio of the throat of the main injector is (8-12):1, and the nozzle diameter d2 of the auxiliary injector is equal to the inlet diameter D. 21 1 / 2, the inlet diameter D of the secondary injector 21 For the outlet diameter D 23 The length-to-diameter ratio of the throat of the secondary injector is (8-12):

1.

8. The stirring system for a fully mixed anaerobic reactor according to claim 1, characterized in that, The air branch pipe is equipped with an air flow meter and an electric regulating valve, and the biogas pipe is equipped with a biogas flow meter.

9. A process control method for a stirred system in a fully mixed anaerobic reactor, characterized in that, The control method is applicable to the stirred system of the fully mixed anaerobic reactor according to any one of claims 1-8, and the control method includes: During system operation, oxygen is consumed in both the liquid and gas phases, and the oxygen concentration changes in real time. Its differential equation over time is: in, This is the target value for the content of gaseous air. This refers to the gas chamber volume of the anaerobic reactor. Let be the air consumption rate constant. For airflow, Biogas flow rate; When the system is running stably, to maintain a constant gaseous oxygen concentration over time, the above equation applies: After the system is running normally, monitor the air flow rate, biogas flow rate, and actual oxygen concentration at different biogas return rates, and calculate the results. Value, setting the biogas content If the target value is below 0.42%, the oxygen concentration in the gas chamber and the biogas return flow are monitored in real time, and adjustments are made based on PID control. The quantity satisfies The general formula for equilibrium.

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