Fermentation apparatus for reducing greenhouse gas emissions while recovering carboxylic acids

Abstract

A fermentation apparatus for reducing greenhouse gas emissions while recovering carboxylic acids, comprising a fermentation container (1), a sludge feeding assembly (2), a decanting assembly (3), a hydraulic circulation assembly (4), a heating and thermal insulation assembly (5), a stirring assembly (6), a chemicals dosing and regulation assembly (7), and a monitoring electric control assembly (9). The apparatus is used to ferment primary sludge or excess sludge from a wastewater treatment plant to recover carboxylic acids; by controlling the operation of the fermentation apparatus and reaction parameters, a carboxylic acid mixed solution is produced, thereby significantly reducing emissions of greenhouse gases such as methane generated during fermentation; and the recovered carboxylic acid mixed solution is dosed into a biological reaction tank for application.

Description

A fermentation device for recovering carboxylic acids while reducing greenhouse gas emissions Technical Field

[0001] This invention relates to the field of municipal drainage, and more specifically to a fermentation apparatus and method for recovering carboxylic acids while reducing greenhouse gas emissions. Background Technology

[0002] Driven by the national "dual-carbon" strategy, reducing energy consumption in wastewater treatment plants has become a crucial task for modern wastewater treatment facilities. Currently, many wastewater treatment plants add large amounts of additional carbon sources, such as methanol, acetic acid, sodium acetate, propionic acid, and glucose, due to insufficient carbon sources required for nitrogen and phosphorus removal. In recent years, the requirements for effluent quality have been continuously increasing across regions, leading to a gradual increase in the demand for carbon sources and a significant increase in energy consumption at wastewater treatment plants. Furthermore, the large amount of sludge generated during wastewater treatment is difficult to handle and dispose of, and the issue of sludge resource utilization urgently needs to be addressed.

[0003] Recent research indicates that sludge produced by wastewater treatment plants (mainly including sludge from pretreatment and excess sludge from biological treatment) contains abundant carbohydrates, proteins, and fats, all of which are slow-moving organic carbon sources. If converted into efficient organic carbon sources (such as carboxylic acids like acetic acid, propionic acid, butyric acid, and valeric acid), it can significantly promote nitrogen and phosphorus removal in biological reactors. Furthermore, by adjusting pH and the concentration of trace elements in the wastewater, the metabolic balance of functional microorganisms in the reactor can be regulated, thereby inhibiting the metabolic activity of non-functional microorganisms (such as methanogenic bacteria), preventing the emission of greenhouse gases such as methane, and achieving the goals of carbon reduction and carbon neutrality. Therefore, utilizing sludge to prepare efficient organic carbon sources—carboxylic acids—is particularly important for promoting the low-carbon operation of wastewater treatment plants.

[0004] Currently, research on sludge fermentation, both domestically and internationally, mainly focuses on the mechanisms of acid production under different fermentation conditions, emphasizing theoretical analysis. However, the development of equipment for practical engineering applications has been relatively slow. The requirements of microorganisms for pH and temperature during anaerobic sludge fermentation are complex. In large-scale engineering applications, existing equipment is mostly limited to pretreatment with chemicals, or only considers the equipment form to meet fermentation conditions, resulting in high costs for chemical dosing and temperature control. For example, the invention patent application number 202211043645.4, "A method for preparing carbon source from primary sedimentation sludge in wastewater treatment plants," only pretreats the sludge by adjusting the pH to the isoelectric point; the utility model patent application number 202321878183.8, "A device for anaerobic fermentation of residual sludge to produce acid based on potassium ferrate," pretreats the sludge by adding chemicals. These technologies weaken the process control of the sludge fermentation itself and have not yet been widely applied in engineering.

[0005] In summary, there is still a lack of a fermentation device in this field that integrates hydraulic condition optimization and substrate metabolism regulation functions to achieve efficient and low-cost recovery of carboxylic acids while reducing greenhouse gas emissions. Summary of the Invention

[0006] The purpose of this invention is to improve the internal hydraulic conditions of the sludge anaerobic fermentation device and regulate the substrate metabolism, thereby optimizing the process parameters. This allows the sludge produced by the wastewater treatment plant to ferment more efficiently, energy-savingly, and with low carbon emissions in the fermentation device, producing a high-quality carbon source. This high-quality carbon source can then be reused in the wastewater treatment plant's biological reaction tank, thereby significantly improving the nitrogen and phosphorus removal efficiency of the biological reaction tank, reducing the amount of external carbon source added to the biological reaction tank, and reducing greenhouse gas emissions, thus achieving the goal of cost reduction and efficiency improvement.

[0007] To achieve the above objectives, this invention provides a fermentation device for recovering carboxylic acid while reducing greenhouse gas emissions. The device includes a fermentation container, a sludge inlet assembly, a decanting assembly, a hydraulic circulation assembly, a heating and insulation assembly, a stirring assembly, a reagent control assembly, and a monitoring and electrical control assembly. The fermentation container has a sludge inlet and a hydraulic circulation inlet on its lower side wall, a hydraulic circulation outlet on its upper middle side wall, and a carboxylic acid outlet on its upper side wall. The sludge inlet assembly is connected to the sludge inlet and extends into the fermentation container. The decanting assembly is located at the top of the fermentation container and connected to the carboxylic acid outlet to decant the fermented carboxylic acid from the top of the fermentation container and transport it to a biological reaction tank. The hydraulic circulation assembly is connected to the hydraulic circulation inlet and outlet, and uses a circulation pump to suck and return the sludge within the fermentation container. The sludge is agitated; the heating and insulation component is installed on the side wall of the fermentation container for heating and insulation of the sludge inside the fermentation container; the stirring component uses multi-stage blades installed inside the fermentation container to fully stir the sludge; the reagent control component is connected to the fermentation container and delivers the reagent into the fermentation container; the monitoring and control component includes a controller and a monitoring instrument installed in the fermentation container. The monitoring instrument continuously monitors the temperature, pH value, and water quality of the sludge inside the fermentation container. The controller adjusts the process parameters of the sludge feeding component, hydraulic circulation component, heating and insulation component, stirring component, and reagent control component in real time according to the monitoring results to ensure that the temperature of the sludge inside the fermentation container is stably maintained at 35-55℃ and that a predetermined concentration of carboxylic acid is produced; the concentration S of the produced carboxylic acid is... V The calculation formula is:

[0008]

[0009] S V The concentration of carboxylic acid produced, expressed as COD; S P S represents the concentration of organic matter in the sludge to be treated, expressed as COD; hN1 represents the concentration of hydrolysis products, including protein, fat, and carbohydrates, expressed as COD; N2 represents the variable frequency output power of the circulating pump's hydraulic stirring; N3 represents the variable frequency output power of the agitator's mechanical stirring; a represents the agitator's stirring intensity adjustment coefficient; k represents the concentration of hydrolysis products. m,h X represents the maximum specific utilization rate of the hydrolysis products. h K represents the concentration of carboxylic acid-producing microorganisms. S,h K is the half-saturation constant for the growth of carboxylic acid-producing bacteria. I,h k is the coefficient representing the effect of carboxylic acid concentration on the growth of carboxylic acid-producing bacteria. m,v X represents the maximum specific utilization rate of carboxylic acid. v The concentration of methanogenic microorganisms; k is the maximum specific substrate removal rate constant; k d,h k represents the endogenous decay rate of carboxylate-producing microorganisms. d,v The intrinsic decay rate of methanogenic microorganisms.

[0010] Furthermore, the sludge feeding assembly includes a sludge feeding pipe, an adjustable flow rate sludge feeding pump, and a sludge feeding pipe support. The sludge feeding pipe extends into the fermentation vessel through a sludge inlet on the side wall until its outlet is located in the central area of ​​the fermentation vessel. The sludge feeding pipe support is located below the sludge feeding pipe. The sludge feeding pump is connected to the inlet of the sludge feeding pipe and is used to pump primary sludge or residual sludge generated by the wastewater treatment facility. The monitoring and control assembly adjusts the flow rate of the sludge feeding pump in the sludge feeding assembly in real time according to the monitoring results, controlling the sludge fermentation residence time in the fermentation vessel to be 5-8 days, so that the sludge feeding flow rate matches the carboxylic acid production efficiency.

[0011] Furthermore, a slag discharge port is provided on the upper side wall of the fermentation vessel, and the carboxylic acid outlet is connected to the biological reaction tank of the wastewater treatment facility for transporting the clarified carboxylic acid liquid from fermentation to the biological reaction tank; the decanting assembly includes a decanter, carboxylic acid pipeline, skimmer, and scum collection tank; the decanter includes a rectangular or annular decanting trough, the opening of which is located at the top of the fermentation vessel, where the carboxylic acid produced by sludge fermentation clarifies and stratifies at the top of the sludge, and the clarified liquid overflows into the wastewater treatment facility through the opening of the decanting trough. The decanting tank is described above; one end of the carboxylic acid pipeline is connected to the body of the decanting tank, and the other end is connected to the carboxylic acid outlet; the skimmer is installed on the top of the fermentation vessel and driven by a skimmer motor, used to skim the scum on the surface of the carboxylic acid clarified liquid into the scum collection tank; the opening of the scum collection tank is 0.5-5cm higher than the surface of the carboxylic acid clarified liquid, the body of the scum collection tank is inclined downwards, and the lowest point is connected to the scum discharge port, through which the collected scum is discharged from the fermentation vessel.

[0012] Furthermore, the hydraulic circulation assembly includes a circulation pump, a circulation sludge inlet main pipe, a circulation sludge inlet distribution head, circulation sludge inlet branch pipes, and a circulation sludge outlet pipe; the circulation sludge inlet distribution head is located in the central area of ​​the bottom of the fermentation vessel, and the circulation sludge inlet branch pipes are radially and evenly connected around the circulation sludge inlet distribution head; one end of the circulation sludge inlet main pipe is connected to the circulation sludge inlet distribution head, and the other end extends out from the hydraulic circulation inlet; the circulation pump is located outside the fermentation vessel, and the inlet of the circulation pump is connected to the outlet of the circulation sludge inlet main pipe, and the outlet of the circulation pump... The outlet is connected to the circulating sludge discharge pipe located in the upper part of the fermentation container; the circulating sludge discharge pipe enters the fermentation container from the hydraulic circulation outlet and has multiple circulating sludge discharge ports; when the circulating pump is working, it draws sludge from the bottom of the fermentation container through the circulating sludge inlet branch pipe and the circulating sludge inlet main pipe, and then pressurizes and pumps the sludge to the circulating sludge discharge pipe and sprays it out at high speed through the circulating sludge discharge ports. The working flow rate of the circulating pump is 10-50 times "the effective volume of the fermentation container ÷ 24", so as to realize the hydraulic circulation of sludge in the fermentation container and optimize the hydraulic flow state of sludge.

[0013] Furthermore, the heating and insulation component includes a heating device and an insulation layer; the heating device is an electric heating cable wrapped around the sludge inlet pipe of the sludge inlet component and / or the side wall of the fermentation container, or a hot water coil heated by a water source heat pump, and / or a heating structure installed inside the fermentation container; the insulation layer is installed on the side wall of the fermentation container to reduce heat loss from the fermentation container; the monitoring and control component adjusts the heating and insulation component in real time to keep the temperature of the sludge in the fermentation container stably maintained at 35-55℃.

[0014] Furthermore, a mixer mounting hole is provided on the top surface of the fermentation container; the mixing assembly includes a frequency-adjustable speed mixer, multi-stage blades, a rotating shaft, and a heat transfer circulation pipe; the mixer is eccentrically installed in the mixer mounting hole, and its rotating shaft extends into the fermentation container; the multi-stage blades are installed in the lower middle part of the rotating shaft, evenly divided into 2-5 layers, for fully mixing the sludge in the fermentation container; the rotation speed of the multi-stage blades is 20-60 r / min; each layer of multi-stage blades includes multiple blades, a hydraulic support rod, and a flexible connector, the multiple blades are connected by the flexible connector, and the included angle between the multiple blades is adjusted by the extension and retraction of the hydraulic support rod; when it is necessary to increase the sludge mixing intensity, the included angle between the multiple blades is increased; conversely, the included angle is decreased.

[0015] Furthermore, the stirring assembly also includes a heat transfer circulation pipe, which runs through the rotating shaft and the plurality of impellers. The heat transfer circulation pipe includes a heat inlet pipe and a heat return pipe connected to the heat inlet pipe. A heat transfer medium supplied by a water source heat pump flows into the heat inlet pipe, and heat is conducted to the sludge through the rotating shaft and the plurality of impellers. Cooling water flows back to the water source heat pump from the heat return pipe.

[0016] Furthermore, the reagent control component includes a dosing device, a dosing delivery pipe equipped with a metering pump, and a dosing tank; the dosing tank is located outside the fermentation vessel and is connected to the dosing device located inside the fermentation vessel via a dosing delivery pipe passing through the fermentation vessel; the reagent in the dosing tank includes one or more of alkaline solution, acidic solution, and trace element solution; the monitoring and control component adjusts the flow rates of the alkaline solution, acidic solution, and trace element solution in the reagent control component in real time via the metering pump, so that the pH value of the sludge in the fermentation vessel is maintained at 8-10, and the concentration of trace elements in the sludge is maintained at: Cu 2+ 20-65 mmol / L; Mn 2+ 2.5-6.0 mmol / L; B 3+ 15.0-28.5 mmol / L, Mo 6+ 4.0-6.2 mmol / L; W 6+ 7.0-12.2 mmol / L; Ni 2+ 3.0-5.5 mmol / L; Co 2+ 10.0-18.3 mmol / L; Zn 2+ 25.5-35.0 mmol / L; Ca 2+ , 10.5-30.5 mmol / L.

[0017] Furthermore, the dispensing device is a ring-shaped dispensing device, which is located 20-100cm below the liquid surface in the fermentation container. The ring-shaped dispensing device has multiple nozzles for uniformly spraying the agent into the sludge.

[0018] Furthermore, the reagent control component also includes an inert gas storage tank, an inert gas delivery pipe, and an inert gas stripping nozzle; the inert gas storage tank is located inside the dosing tank and is connected to the inert gas delivery pipe; the end of the inert gas delivery pipe is horizontally positioned at the bottom of the fermentation container and has several inert gas stripping nozzles evenly distributed thereon; the inert gas stripping nozzles spray nitrogen, helium, or argon at a predetermined flow rate to strip residual dissolved oxygen in the sludge and maintain an anaerobic environment for sludge fermentation.

[0019] Furthermore, the fermentation device also includes a venting assembly, with a venting port at the bottom of the fermentation container; the venting assembly includes multiple venting branch pipes, a venting transfer box, and a venting pipe; the inlet of the venting branch pipe faces downward and is 3-30cm away from the bottom surface of the fermentation container; the venting transfer box is a hollow box, and its side wall is connected to the multiple venting branch pipes; one end of the venting pipe is connected to the venting transfer box, and the other end extends out from the venting port, used to completely vent the sludge and carboxylic acid in the fermentation container during device maintenance.

[0020] Furthermore, the fermentation vessel has multiple instrument monitoring ports on its side wall, which are evenly distributed along the side wall from high to low at a certain rotation angle. The monitoring instruments are embedded in the instrument monitoring ports and include a thermometer, a pH meter, and a water quality monitoring probe. The thermometer, pH meter, and water quality monitoring probe are used to continuously monitor the temperature, pH value, and water quality of the sludge in the fermentation vessel. The water quality monitoring probe can simultaneously monitor the concentrations of organic matter COD, total nitrogen TN, total phosphorus TP, total organic acid ions, acetate, propionate, butyrate, and valerate in the sludge. The controller adjusts the flow rate of the circulation pump in the hydraulic circulation assembly and the speed of the agitator in the stirring assembly in real time, so that the data monitored by the thermometer, pH meter, and water quality monitoring probe at different locations tend to be consistent.

[0021] Compared with existing technologies, the fermentation device of the present invention, which recovers carboxylic acid while reducing greenhouse gas emissions, has at least the following advantages:

[0022] 1. High degree of automation and real-time monitoring

[0023] This invention investigated the carboxylic acid concentration S V The calculation formula, through monitoring the electronic control components, can continuously monitor the temperature, pH and water quality inside the fermentation vessel, and adjust the operating parameters of each component in real time according to the monitoring results to ensure that the device is in the best operating condition. The high degree of automation and real-time monitoring function improve the operational stability and ease of operation of the device, and reduce manual intervention and operational errors.

[0024] 2. Substrate metabolism regulation and greenhouse gas emission reduction

[0025] This invention combines hydraulic circulation and reagent regulation. The hydraulic circulation component achieves uniform disturbance and reflux of sludge, thereby improving the completeness and efficiency of the sludge fermentation process. Substrate metabolism regulation includes adjusting the pH, temperature, and trace element concentration in the fermentation unit to ensure the stability and optimization of the fermentation environment. This promotes the conversion of sludge into efficient organic carbon sources (such as acetic acid, propionic acid, butyric acid, valeric acid, and other carboxylic acids). By adding these efficient organic carbon sources to the bioreactor, the abundance of phosphorus removal (e.g., Flavobacterium, Abscis, and Tauraceae, with an increase of 15%-49%) and key denitrification microorganisms (e.g., Microbes, Ternopilio, and Pseudomonas, with an increase of 6%-12%) can be significantly improved. The expression of key genes for nitrogen and phosphorus removal (e.g., encoding polyphosphoric acid kinase, PHA synthase, and NO reductase) can be enhanced, promoting nitrogen and phosphorus removal. This achieves metabolic balance regulation of functional microorganisms in the reactor, inhibits the metabolic activity of non-functional microorganisms (e.g., methanogenic bacteria), avoids the emission of greenhouse gases such as methane, and achieves the goal of carbon reduction and carbon neutrality.

[0026] 3. Integrated fermentation and product decanting separation

[0027] The integrated design of the fermentation vessel with decanting components and a skimmer enables efficient separation and direct utilization of fermentation products. The decanting component transports the clarified carboxylic acid solution produced during fermentation to the biological reaction tank, promoting nitrogen and phosphorus removal. The remaining sludge after fermentation continues into the existing sludge treatment process. This design simplifies the operation, reduces secondary treatment steps, and allows fermentation products to be directly and efficiently applied to the wastewater treatment system.

[0028] 4. Energy-saving and environmentally friendly insulation design

[0029] This invention employs insulation equipment to maintain the temperature inside the fermentation container between 35-55℃, fully utilizing the heat generated during sludge fermentation without requiring a large amount of additional heat energy input. This invention provides multiple low-energy-consumption insulation and heat exchange methods, which can be selected according to actual needs. Compared to existing technologies that require high-energy-consumption additional heating, this invention significantly reduces energy consumption, saves resources, and improves the environmental friendliness and economy of the device.

[0030] 5. No additional microbial strains required.

[0031] The integrated device of this invention can operate automatically after startup, without the need for additional microbial inoculants. It achieves efficient sludge fermentation through its own system circulation and regulation. This not only reduces operating costs but also minimizes the use of chemical agents and potential environmental impact, making the entire treatment process greener and more environmentally friendly. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0033] Figure 1 is a cross-sectional view of the fermentation device of the present invention for recovering carboxylic acid while reducing greenhouse gas emissions.

[0034] Figure 2 is a plan view of the fermentation device of the present invention for recovering carboxylic acids while reducing greenhouse gas emissions.

[0035] Figure 3 is a pipeline plan view of the hydraulic circulation component of the present invention.

[0036] Figure 4 is a pipeline plan view of the mud inlet assembly and venting assembly of the present invention.

[0037] Figure 5 is a structural diagram of the stirring assembly of the present invention.

[0038] Figure 6 is a schematic diagram of the stirring assembly of the present invention in different operating states.

[0039] Figure 7 is a structural diagram of the decanting tank of the present invention.

[0040] Figure 8 is a diagram of the lifting angle of the paddle in Embodiment 2 of the present invention.

[0041] Figure 9 is a process flow diagram of the actual application of the present invention.

[0042] Figure 10 shows the effect of adding the carboxylic acid produced in this invention to the biological reaction tank on key genes for nitrogen and phosphorus removal.

[0043] Figure 11 shows the effect of the carboxylic acid produced in this invention on key microorganisms for phosphorus removal after being added to the biological reaction tank.

[0044] Figure 12 shows the effect of adding the carboxylic acid produced in this invention to the denitrification tank on key denitrification microorganisms.

[0045] Attached reference numerals: 1-Fermentation vessel, 101-Sludge inlet, 102-Carboxylic acid outlet, 103-Vent port, 104-Slag discharge port, 105-Hydraulic circulation inlet, 106-Hydraulic circulation outlet, 107-Maintenance manhole, 108-Agitator mounting hole, 109-Exhaust port, 110-Breathing port, 111-Sampling port, 112-Instrument monitoring port, 113-Supporting angle plate;

[0046] 2-Sludge inlet assembly, 21-Sludge inlet pipe, 22-Sludge inlet pipe support, 23-Sludge inlet pipe outlet;

[0047] 3-Decanting assembly, 31-Decanter, 311-Decanting tank, 32-Carboxylic acid pipeline, 33-Supporting baffle, 34-Skimmer, 35-Scum collection tank;

[0048] 4-Hydraulic circulation components, 41-Circulation pump, 42-Circulation sludge inlet main pipe, 43-Circulation sludge inlet distributor, 44-Circulation sludge inlet branch pipe, 45-Circulation sludge inlet pipe support, 46-Circulation sludge outlet pipe, 47-Circulation sludge outlet, 48-Circulation sludge outlet pipe support.

[0049] 5-Heating and insulation components, 51-Heating facilities, 52-Insulated corrugated steel sheet, 53-Insulation ring;

[0050] 6-Stirring assembly, 61-Stirrer, 611-Connecting device, 62-Multi-stage blades, 621-Blade, 622-Hydraulic support rod, 623-Flexible connector, 63-Shaft, 631-Heat inlet pipe, 632-Heat return pipe, 64-Shaft end, 65-Heat transfer circulation pipe;

[0051] 7-Pharmaceutical control component, 71-Annular dosing device, 72-Pharmaceutical delivery pipe, 73-Pharmaceutical nozzle, 74-Metering pump, 75-Pharmaceutical tank, 76-Inert gas storage chamber, 77-Inert gas delivery pipe, 78-Inert gas stripping nozzle;

[0052] 8-Vent assembly, 81-Vent branch pipe, 82-Vent transfer box, 83-Vent pipe;

[0053] 9-Monitoring electrical control components, 91-Thermometer, 92-pH meter, 93-Water quality monitoring probe. Detailed Implementation

[0054] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0055] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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. Example

[0056] Please refer to Figure 1. The present invention provides a fermentation device for recovering carboxylic acid while reducing greenhouse gas emissions, which includes a fermentation container 1, a sludge feeding assembly 2, a decanting assembly 3, a hydraulic circulation assembly 4, a heating and insulation assembly 5, a stirring assembly 6, a reagent control assembly 7, a venting assembly 8, and a monitoring and electrical control assembly 9.

[0057] Please refer to Figures 2-4. Fermentation container 1 is located on the ground near the wastewater treatment facility and is used to hold the sludge produced by the facility and ferment it into carboxylic acids that are easily utilized by the microorganisms in the biological reaction tank. The sludge inlet assembly 2 is connected to the lower part of fermentation container 1 and is used to transport the primary or residual sludge from the wastewater treatment facility into fermentation container 1. The decanting assembly 3 is located at the top of fermentation container 1 and is used to decant the fermented carboxylic acids from the top of fermentation container 1 and transport them to the biological reaction tank, thereby promoting the denitrification and phosphorus removal process of the microorganisms in the biological reaction tank. The hydraulic circulation assembly 4 is located inside fermentation container 1 and uses a circulation pump 41 to agitate the sludge within fermentation container 1, improving the hydraulic circulation flow of the sludge. The heating and insulation assembly 5 is used to heat the sludge in fermentation container 1 to a suitable temperature and reduce heat loss from the sludge. The stirring assembly 6 uses multi-stage impellers to agitate the sludge. The sludge in fermentation container 1 is thoroughly stirred to ensure uniform sludge distribution. The reagent control component 7 regulates the growth and metabolic environment of microorganisms in the sludge by delivering reagents into fermentation container 1, thereby promoting the efficiency of carboxylic acid production and improving the quality of the produced carboxylic acid. The venting component 8 is located at the bottom of fermentation container 1 and is used to completely vent the sludge in fermentation container 1 during maintenance. The monitoring and control component 9 continuously monitors the temperature, pH, and water quality of the sludge in fermentation container 1 and adjusts the process parameters of sludge feeding component 2, hydraulic circulation component 4, heating and insulation component 5, stirring component 6, and reagent control component 7 in real time based on the monitoring results to ensure that the fermentation device is in optimal operating condition.

[0058] Fermentation vessel 1 is made of 304 or SS316 stainless steel and is cylindrical or egg-shaped. The lower part of the side wall of fermentation vessel 1 has a mud inlet 101, a hydraulic circulation inlet 105, a vent 103, and a maintenance manhole 107. The upper middle part of the side wall has a hydraulic circulation outlet 106, and the upper part of the side wall has a carboxylic acid outlet 102 and a slag discharge outlet 104. Multiple sampling ports 111 and multiple instrument monitoring ports 112 are evenly distributed from the lower to the upper part of the side wall of fermentation vessel 1, with the sampling ports 111 and instrument monitoring ports 112 evenly distributed along the side wall of fermentation vessel 1 from high to low at a certain rotation angle. Each sampling port 111 is connected to a sampling tube, and the sampling tube is equipped with a shut-off valve. A maintenance manhole 1 is also provided on the top surface of fermentation vessel 1. 07. A mixer mounting hole 108, an exhaust port 109, and a vent 110 are also provided. The exhaust port 109 is used to discharge the gas generated in the fermentation container 1. The vent 110 is used to maintain the gas pressure balance in the fermentation container 1. An automatic exhaust check valve is provided at the top of the exhaust port 109, so that the gas in the fermentation container 1 can only go out and not go in. A reverse air intake check valve is provided at the top of the vent 110, so that the gas can only enter the fermentation container 1 and cannot go out. A support corner plate 113 is provided on the bottom surface of the fermentation container 1 to support the entire device firmly on the ground. The top surface of the fermentation container 1 is provided with a box top plate, box top reinforcing steel bars, and box top fence structure, so that the staff can carry out maintenance on the device through the maintenance manhole 107 on the top of the fermentation container 1.

[0059] The sludge inlet assembly 2 is connected to the lower part of the fermentation vessel 1, and includes a sludge inlet pipe 21, an adjustable flow rate sludge inlet pump, and a sludge inlet pipe support 22. The sludge inlet pipe 21 is connected to the sludge inlet 101 at the lower side wall of the fermentation vessel 1 and extends into the fermentation vessel 1 through the sludge inlet 1 until the sludge inlet pipe outlet 23 is located in the central area of ​​the fermentation vessel 1. The sludge inlet pipe support 22 is supported below the sludge inlet pipe 21. The sludge inlet pump is located outside the fermentation vessel 1 and is connected to the inlet of the sludge inlet pipe 21. It is used to pump the primary sludge or residual sludge generated by the wastewater treatment facility. The moisture content of the primary sludge or residual sludge is 95%-99.5%. The flow rate of the sludge inlet pump can be adjusted according to the operating requirements of the fermentation device. The monitoring and control assembly 9 adjusts the flow rate of the sludge inlet pump in the sludge inlet assembly 2 in real time according to the monitoring results, controlling the sludge fermentation residence time in the fermentation vessel 1 to be 5-8 days, so that the sludge inlet flow rate matches the carboxylic acid production efficiency.

[0060] The decanting assembly 3 is located at the top of the fermentation vessel 1 and includes a decanter 31, a carboxylic acid pipeline 32, a support baffle 33, a skimmer 34, and a scum collection tank 35. The decanter 31 includes a rectangular or annular decanting trough 311 (see Figure 7). The opening of the decanting trough 311 is located at the top of the fermentation vessel 1. The carboxylic acid produced by sludge fermentation is clarified and stratified at the top of the sludge. The clarified liquid at the top overflows into the decanting trough 311 through the opening. One end of the carboxylic acid pipeline 32 is connected to the body of the decanting trough 311, and the other end is connected to the carboxylic acid pipeline. The outlet 102 is connected to the raw reaction tank of the wastewater treatment facility, and is used to transport the fermented carboxylic acid clarified liquid to the raw reaction tank; the skimmer 34 is set on the top of the fermentation vessel 1 and is driven by the skimmer motor 341, and is used to skim the scum on the surface of the carboxylic acid clarified liquid into the scum collection tank 35; the opening of the scum collection tank 35 is 0.5-5cm higher than the liquid surface, the tank body of the scum collection tank 35 is inclined downward, and the lowest point is connected to the scum discharge port 104. The collected scum is discharged from the fermentation vessel 1 through the scum discharge port 104.

[0061] The hydraulic circulation assembly 4 includes a circulation pump 41, a circulation sludge inlet main pipe 42, a circulation sludge inlet distributor 43, a circulation sludge inlet branch pipe 44, a circulation sludge inlet pipeline support 45, a circulation sludge outlet pipe 46, a circulation sludge outlet 47, and a circulation sludge outlet pipeline support 48. The circulation sludge inlet main pipe 42, the circulation sludge inlet distributor 43, and the circulation sludge inlet branch pipe 44 are all located at the bottom of the fermentation vessel 1 and connected sequentially. The circulation sludge inlet distributor 43 is located in the central area of ​​the bottom of the fermentation vessel 1. The circulation sludge inlet branch pipes 44 are radially and evenly connected around the circulation sludge inlet distributor 43. The circulation sludge inlet pipeline support 45 provides support for the circulation sludge inlet branch pipes 44 from below. One end of the circulation sludge inlet main pipe 42 is connected to the circulation sludge inlet distributor 43, and the other end extends out from the hydraulic circulation inlet 105. The circulation pump 41 is located outside the fermentation vessel 1. The outlet of the circulating pump 41 is connected to the outlet of the circulating sludge inlet main pipe 42, and the outlet of the circulating pump 41 is connected to the circulating sludge outlet pipe 46 located in the upper part of the fermentation vessel 1. The circulating sludge outlet pipe 46 enters the fermentation vessel 1 from the hydraulic circulation outlet 106 and has multiple circulating sludge outlets 47. When the circulating pump 41 is working, it draws sludge from the bottom of the fermentation vessel 1 through the circulating sludge inlet branch pipe 44 and the circulating sludge inlet main pipe 42, then pressurizes and pumps the sludge to the circulating sludge outlet pipe 46, and then sprays it out at high speed through the circulating sludge outlets 47, realizing the hydraulic circulation of sludge in the fermentation vessel 1 and optimizing the hydraulic flow state of the sludge. The circulating sludge outlet pipe support 48 is located in the upper middle part of the fermentation vessel 1 and is used to support the circulating sludge outlet pipe 46. The working flow rate of the circulating pump 41 (in m³ / s) is... 3 / h), take the effective volume V (m³) of fermentation vessel 1. 3 The ratio of 10 to 50 times "÷24(h)" makes the residence time of sludge in fermentation vessel 1 5 days under the condition of continuous influent of primary sedimentation sludge and decanting of carboxylic acid.

[0062] The heating and insulation component 5 includes a heating device 51 and an insulation layer. The heating device 51 is an electric heating cable or a hot water coil supplied by a water source heat pump wrapped around the sludge inlet pipe 21 of the sludge inlet component 2 and / or the side wall of the fermentation container 1, and / or a heating structure installed inside the fermentation container 1. The insulation layer is installed on the side wall of the fermentation container 1 to reduce heat loss from the fermentation container 1. The insulation layer can be an insulated corrugated steel sheet 52, which is installed on the side wall of the fermentation container 1 and fixed with insulation rings 53. There are multiple insulation rings 53, which are evenly arranged at certain intervals in the height direction outside the fermentation container 1 to effectively fix the insulated corrugated steel sheet 52. The heating structure installed inside the fermentation container 1 can take various forms, such as a heat transfer circulation pipe type for heating method one and an electric heating cable type for heating method two. The monitoring and control component 9 adjusts the heating and insulation component 5 in real time to keep the temperature of the sludge inside the fermentation container 1 stable at 35-55℃.

[0063] Please refer to Figures 1 and 5-8. The stirring assembly 6 includes a frequency-adjustable speed mixer 61, multi-stage impellers 62, a rotating shaft 63, a shaft end 64, and a heat transfer circulation pipe 65. The mixer 61 is eccentrically mounted in the mixer mounting hole 108 on the top surface of the fermentation vessel 1, and its rotating shaft 63 extends into the fermentation vessel 1. The multi-stage impellers 62 are evenly divided into 2-5 layers, all located in the lower middle part of the fermentation vessel 1, for thoroughly stirring the sludge in the fermentation vessel 1. The mixer 61 is a frequency-adjustable design and is connected to the rotating shaft 63 through a connecting device 611, allowing the speed to be adjusted as needed. Specifically, the frequency of the mixer 61 can be adjusted between 100% and 30%, preferably, the frequency can be dynamically adjusted between 15Hz and 50Hz. The connecting device 611 can be a rotary joint or a slip ring depending on the heating method. The multi-stage blades 62 rotate at a speed of 30 r / min. The multi-stage blades 62 are evenly spaced and fixed to the rotating shaft 63, with the shaft end 64 located at the bottom of the shaft 63. Each layer of multi-stage blades 62 includes multiple blades 621, a hydraulic support rod 622, and a flexible connector 623. The multiple blades 621 are connected by the flexible connector 623, as shown in Figure 6. The included angle between the multiple blades 621 can be adjusted by extending and retracting the hydraulic support rod 622. When it is necessary to increase the sludge mixing intensity, the included angle between the multiple blades 621 is increased; conversely, the included angle is decreased. In this embodiment, the included angle between the multiple blades 621 in the first layer is 180°, the included angle between the multiple blades 621 in the second layer is 90°, and the included angle between the multiple blades 621 in the third layer is 60°. The angle adjustment process also has the function of separating impurities and breaking up fibrous entanglements.

[0064] When the heating structure inside the fermentation vessel 1 is a heat transfer circulation pipe, the heat transfer circulation pipe runs through the rotating shaft 63 of the stirring assembly 6. It includes a heat inlet pipe 631 and a heat return pipe 632 connected to the heat inlet pipe 631. Both the rotating shaft 63 and the impeller 62 are hollow, filled with heat-conducting oil or water as the heat transfer medium. Hot water or steam supplied by a water source heat pump flows into the heat inlet pipe 631, transferring heat through the heat transfer medium in each blade 621 of the rotating shaft 63 and impeller 621 to the outer surface of the rotating shaft 63 and impeller 621, and then to the sludge, thus providing internal heating. The cooled heat transfer medium then flows back to the water source heat pump from the heat return pipe 632. Furthermore, the user can select the heat transfer medium according to the actual fermentation needs. Due to the characteristics of the medium, heat-conducting oil is preferred as the heat transfer medium for high-temperature fermentation (55℃), while water is preferred for medium-temperature fermentation (35℃). When using this heating method, the mixer 61 is connected to the rotating shaft 63 through a rotary joint, and the rotation of the outer shell of the rotating shaft 63 does not conflict with the heat transfer circulation tube.

[0065] When the heating structure inside the fermentation vessel 1 is an electric heating cable type, the electric heating cable 634 is wound around the inside of the rotating shaft 63 and the paddle 621, serving as a heat transfer medium to directly conduct heat to the outer surface of the rotating shaft 63 and the paddle 621, and then to the sludge, thus achieving internal heating. The electric heating cable 634 can be arranged in various ways; it can be wound around the middle of the rotating shaft 63 and the paddle 621, or it can be embedded in the middle of the rotating shaft 63 and the paddle 621 in a leaf-like pattern. Furthermore, the user can configure it according to the volume of the fermentation vessel 1 and the selected size of the agitator 61. Specifically, the connection between the rotating shaft 63 and the paddle 621 adopts a flexible connection to ensure that the heating effect is not affected when the paddle 621 is raised or lowered. When using this heating method, the agitator is connected to the rotating shaft through a slip ring, and the rotation of the rotating shaft 63 does not affect the power supply and heat transfer of the electric heating cable.

[0066] The reagent control component 7 includes an annular dosing device 71, a dosing delivery pipe 72 equipped with a metering pump 74, a dosing tank 75, an inert gas storage chamber 76, an inert gas delivery pipe 77, and an inert gas stripping nozzle 78. The dosing tank 75 is located outside the fermentation vessel 1 and is connected to the annular dosing device 71 located inside the fermentation vessel 1 via the dosing delivery pipe 72 passing through the fermentation vessel 1. The annular dosing device 71 is positioned 20-100 cm below the liquid surface inside the fermentation vessel 1, and has multiple nozzles 73 distributed on it for uniformly spraying the reagent into the sludge. The reagent in the dosing tank 75 includes one or more of alkaline solution, acid solution, and trace element solution. The inert gas storage chamber 76 is located inside the dosing tank 75 and is connected to the inert gas delivery pipe 77. The end of the inert gas delivery pipe 77 is water... A number of inert gas stripping nozzles 78 are evenly distributed at the bottom of the fermentation container 1. These nozzles can spray nitrogen, helium, or argon at appropriate flow rates to strip residual dissolved oxygen from the sludge, maintaining an anaerobic environment for fermentation. A metering pump 74 pumps the reagents from the dosing tank 75 to the dosing delivery pipe 72 at an appropriate flow rate. The reagents are then evenly sprayed into the sludge through several reagent nozzles 73 distributed on the annular dosing device 71, and subsequently thoroughly mixed with the sludge under the action of the hydraulic circulation component 4 and the stirring component 6. The monitoring and control component 9 adjusts the flow rates of the alkaline solution, acid solution, and trace element solution in the reagent control component 7 in real time via the metering pump 74, maintaining the pH value of the sludge in the fermentation container 1 at the optimal range of 8-10 and maintaining the concentration of trace elements in the sludge at the following concentration: Cu 2+ 20-65 mmol / L; Mn 2+ 2.5-6.0 mmol / L; B 3+ 15.0-28.5 mmol / L, Mo 6+ 4.0-6.2 mmol / L; W 6+ 7.0-12.2 mmol / L; Ni 2+ 3.0-5.5 mmol / L; Co 2+ 10.0-18.3 mmol / L; Zn 2+ 25.5-35.0 mmol / L; Ca 2+10.5-30.5 mmol / L. Based on years of work experience, the inventors discovered through experiments that trace elements are key components of the active centers of various microbial reductases and key genes for denitrification and phosphorus removal. These elements each have their own functions, and some elements also have synergistic effects. They can improve the hydrolysis of soluble proteins, fats, and polysaccharides during fermentation and promote the regulation of intracellular enzyme activity of microorganisms that synthesize carboxylic acids from hydrolysis products. When the pH of the sludge in fermentation vessel 1 is maintained within the optimal range of 8-10 and the above-mentioned trace element composition, the activity of acid-producing bacteria (expressed as ATP) increases by an average of 1.3-1.5 times. Specifically: the added Cu 2+ Mn 2+ B 3+ Zn 2+ and Co 2+ It can effectively promote the formation of acetic acid, increasing its concentration by 1.3-1.9 times, and the added Cu... 2+ Mo 6+ Ni 2+ and Zn 2+ It can effectively promote the formation of propionic acid, increasing its concentration by 1.5-1.8 times, and the added Cu... 2+ Ca 2+ W 6+ and Co 2+ It can effectively promote the formation of butyric acid, valeric acid, and hexanoic acid, increasing their concentration by 1.1-1.6 times. The overall combination of trace elements can effectively increase the overall concentration of carboxylic acids such as acetic acid, propionic acid, butyric acid, valeric acid, and hexanoic acid, increasing the carboxylic acid concentration (calculated as COD) by 1.2-1.4 times. Ultimately, it promotes the nitrogen and phosphorus removal effect in wastewater treatment and reduces the accumulation of intermediate products such as greenhouse gases generated during the reaction process. The above-mentioned optimal pH value and trace element composition range have been repeatedly verified in municipal sludge from a wastewater treatment plant in Shanghai, Zhejiang, Jiangsu, and Chongqing, confirming their typicality and universality. The acid and alkali solutions and trace element solutions are concentrated solutions, which can be prepared in large quantities at once as needed, avoiding repeated operations. The dosage of the acid and alkali solutions and trace element solutions is calculated based on sensor data and built-in controller logic.

[0067] The venting assembly 8 includes multiple venting branch pipes 81, a venting transfer box 82, and a venting pipe 83. The inlet of the venting branch pipe 81 faces downward and is 3-30cm away from the bottom surface of the fermentation container 1. The venting transfer box 82 is a hollow box, and its side wall is connected to multiple venting branch pipes 81. One end of the venting pipe 83 is connected to the venting transfer box 82, and the other end extends out from the venting port 103. It is used for periodic sludge discharge and to completely vent the sludge and carboxylic acid in the fermentation container 1 during equipment maintenance.

[0068] The monitoring and control component 9 includes a thermometer 91, a pH meter 92, a water quality monitoring probe 93, and a controller. The thermometer 91, pH meter 92, and water quality monitoring probe 93 are embedded in different instrument monitoring ports 112 to continuously monitor the temperature, pH value, and water quality of the sludge in the fermentation vessel 1. The water quality monitoring probe 93 can simultaneously monitor the concentrations of organic matter COD, total nitrogen TN, total phosphorus TP, total organic acid ions, acetate ions, propionate ions, butyrate ions, and valerate ions in the sludge. The controller of the monitoring and control component 9 can adjust the process parameters of the sludge feeding component 2, the hydraulic circulation component 4, the heating and insulation component 5, the stirring component 6, and the reagent control component 7 in real time according to the monitoring results to ensure that the temperature of the sludge in the fermentation device is stably maintained at 35-55℃ and that a predetermined concentration of carboxylic acid is produced. The fermentation vessel 1 can be operated in batch or continuous mode, both of which are achieved by adjusting the sludge feeding and discharging rates through the monitoring and control component 9.

[0069] The concentrations of organic matter (COD) and carboxylic acid (S) in fermentation vessel 1 were as follows: V The calculation formula is:

[0070]

[0071] S V The concentration of carboxylic acid produced, expressed as COD; S P S represents the concentration of organic matter in the sludge to be treated, expressed as COD; h N1 represents the concentration of hydrolysis products, including protein, fat, and carbohydrates, expressed as COD; N2 represents the variable frequency output power of the circulating pump's hydraulic stirring; N3 represents the variable frequency output power of the agitator's mechanical stirring; a represents the agitator's stirring intensity adjustment coefficient; k represents the concentration of hydrolysis products. m,h X represents the maximum specific utilization rate of the hydrolysis products. h K represents the concentration of carboxylic acid-producing microorganisms. S,h K is the half-saturation constant for the growth of carboxylic acid-producing bacteria. I,h k is the coefficient representing the effect of carboxylic acid concentration on the growth of carboxylic acid-producing bacteria. m,v X represents the maximum specific utilization rate of carboxylic acid. v The concentration of methanogenic microorganisms; k is the maximum specific substrate removal rate constant; k d,h k represents the endogenous decay rate of carboxylate-producing microorganisms. d,v The intrinsic decay rate of methanogenic microorganisms.

[0072] The controller of the monitoring and control component 9 can calculate the carboxylic acid concentration produced using the above formula based on the properties of the sludge fed into the fermentation vessel (composition of proteins, carbohydrates, and amino acids), the activity and endogenous decay rate of carboxylic acid-producing microorganisms and methanogenic microorganisms, the output power and intensity adjustment coefficient of the variable frequency agitator, etc. It can also dynamically adjust the operating parameters of the fermentation unit according to the required carboxylic acid concentration. For example, it can adjust the reaction process within the fermentation vessel by adjusting the angle of each impeller of the agitator, or generate a carboxylic acid mixture with a specific ratio by adjusting the ratio and concentration of the fed sludge proteins, carbohydrates, and amino acids (which can generate acetic acid:propionic acid concentrations of 1:1, 2:1, etc., to adjust the bioreactor). When the recovered carboxylic acid is mainly acetic acid (in actual experiments, it accounts for up to 78% of the total carboxylic acid, and propionic acid is less than 18%), this fermentation unit increases the acetic acid yield by an average of 4.5 times and reduces greenhouse gas emissions by an average of 82% compared to traditional technology. When the recovered carboxylic acid is mainly propionic acid (which accounts for up to 63% of the total carboxylic acid), this fermentation unit increases the propionic acid yield by an average of 3.2 times and reduces greenhouse gas emissions by an average of 71% compared to traditional technology.

[0073] This invention also provides a fermentation method for recovering carboxylic acids while reducing greenhouse gas emissions, comprising the following steps:

[0074] Step 1: Set up the fermentation device for recovering carboxylic acid and reducing greenhouse gas emissions of the present invention on the ground near the sewage treatment facility; the fermentation device is the fermentation device mentioned above, which will not be described in detail here. There are no particular restrictions on the relative position and specific distance between the fermentation device and the sewage treatment facility. The actual terrain should be taken into account to facilitate construction and save labor and materials.

[0075] Step 2: Using the sludge inlet assembly 2 connected to the lower part of the fermentation container 1, the sludge to be treated is transported into the fermentation container 1. The sludge to be treated is the primary sedimentation sludge or residual sludge produced by the sewage treatment facility, with a moisture content of 95%-99.5%. The sludge inlet flow rate is adjusted according to the operating requirements of the device. Generally, the sludge fermentation residence time in the fermentation container is controlled to be 5-8 days.

[0076] Step 3: The sludge in fermentation container 1 is agitated by the hydraulic circulation component 4 through suction and return, thus improving the hydraulic circulation flow of the sludge. The sludge in fermentation container 1 is heated and kept warm by the heating and insulation component 5. The sludge in fermentation container 1 is thoroughly stirred by the stirring component 6 to ensure uniform sludge distribution. The agent control component 7 is used to deliver the agent into fermentation container 1 to regulate the growth and metabolism environment of microorganisms in the sludge, thereby improving the efficiency of carboxylic acid production during fermentation and enhancing the quality of the produced carboxylic acid.

[0077] When the circulating pump 41 is working, it draws sludge from the bottom of the fermentation vessel 1 through the circulating sludge inlet branch pipe 44 and the circulating sludge inlet main pipe 42, and then pressurizes the sludge and pumps it to the circulating sludge outlet pipe 46, where it is ejected at high speed through the circulating sludge outlet 47. The working flow rate of the circulating pump 41 is measured in cubic meters per second (m³). 3 / h takes the effective volume of fermentation container 1 (m³) 3 The sludge is 10-50 times larger than 24h, which enables hydraulic circulation of sludge in fermentation container 1 and optimizes the hydraulic flow state of sludge.

[0078] Step four: The temperature, pH value, and water quality of the sludge in fermentation container 1 are continuously monitored by the monitoring and control component 9. Based on the monitoring results, the process parameters of the sludge feeding component 2, hydraulic circulation component 4, heating and insulation component 5, stirring component 6, and reagent control component 7 are adjusted in real time to ensure that the fermentation device is in optimal operating condition to produce a predetermined concentration of carboxylic acid. The optimal operating condition includes: a sludge fermentation residence time of 8 days in fermentation container 1; a stable sludge temperature of 35°C in fermentation container 1 with uniform sludge distribution; a pH value of 10 in fermentation container 1; and a trace element concentration of Cu in the sludge. 2+ 20-65 mmol / L; Mn 2+ 2.5-6.0 mmol / L; B 3+ 15.0-28.5 mmol / L, Mo 6+ 4.0-6.2 mmol / L; W 6+ 7.0-12.2 mmol / L; Ni 2+ 3.0-5.5 mmol / L; Co 2+ 10.0-18.3 mmol / L; Zn 2+ 25.5-35.0 mmol / L; Ca 2+ , 10.5-30.5 mmol / L;

[0079] Step 5: The carboxylic acid clarified liquid produced by fermentation is decanted from the top of fermentation vessel 1 through decanting component 3 and transported to the biological reaction tank of wastewater treatment facility to promote the denitrification and phosphorus removal process.

[0080] Furthermore, the monitoring and control component 9 calculates the carboxylic acid concentration produced by the fermentation vessel 1 according to the process parameters and the above formula, or dynamically adjusts the process parameters of the fermentation device according to the predetermined carboxylic acid concentration.

[0081] In this embodiment, the average moisture content of the primary or residual sludge from the wastewater treatment plant entering the fermentation device is 97%-98%, and the sludge fermentation residence time in the fermentation container is controlled to be 5 days. The flow rate of the circulating pump 41 in the hydraulic circulation component 4 and the rotation speed of the mixer 61 in the stirring component 6 are adjusted in real time to ensure that the data monitored by the thermometer 91, pH meter 92, and water quality monitoring probe 93 at different locations are consistent. Simultaneously, the heating and insulation component 5 is adjusted in real time to maintain the sludge temperature in the fermentation container 1 at a stable 35°C. Furthermore, the flow rate of the metering pump 74 in the reagent control component 7 is adjusted in real time to maintain the sludge pH value in the fermentation container 1 at 10 and maintain the trace element concentration in the sludge at: Cu 2+ 40 mmol / L; Mn 2+ 3.0 mmol / L; B 3+ 20.0 mmol / L, Mo 6+ 5.0 mmol / L; W 6+ 9.0 mmol / L; Ni 2+ 4.0 mmol / L; Co 2+ 15.0 mmol / L; Zn 2+ 30.0 mmol / L; Ca 2+ 20.0 mmol / L.

[0082] The fermentation unit implemented in this example, which recovers carboxylic acids while simultaneously reducing greenhouse gas emissions, can continuously produce a mixed supernatant of carboxylic acids with a COD concentration of 19807 mg / L. The concentrations of acetate, propionate, butyrate, and valerate are 6932 mg / L, 3960 mg / L, 3896 mg / L, and 3373 mg / L, respectively. This carboxylic acid is continuously transported to a processing capacity of 15,000 m³ / h. 3 After adding an anoxic tank to the reaction tank of the wastewater treatment plant, the COD of the anoxic tank can be steadily increased by 58.1 mg / L, which significantly promotes nitrogen and phosphorus removal and saves a lot of external carbon source. The direct economic benefits of saving carbon source are RMB 1.31 million per year, while the indirect economic benefits of reducing greenhouse gas emissions such as methane are RMB 5 million per year. Example

[0083] This embodiment describes a fermentation device for recovering carboxylic acid while reducing greenhouse gas emissions. Its basic structure and usage are the same as in Embodiment 1. Specifically:

[0084] Fermentation container 1 is made of 304 or SS316 stainless steel and is cylindrical or egg-shaped.

[0085] The inlet pipe 21 is connected to an inlet pump for pumping municipal sludge or kitchen waste. The sludge and kitchen waste entering the device have a moisture content of 95%-97%. The flow rates of the inlet pump and the outlet pump can be adjusted according to the operating requirements of the device, so that under the condition of continuous batch feeding of primary sedimentation sludge and decanting to discharge carboxylic acid, the residence time of sludge in the fermentation container 1 is 8 days, and the temperature of sludge in the fermentation container 1 is stably maintained at 35℃.

[0086] The opening of the scum collection tank 35 is 0.5-5cm above the liquid surface.

[0087] The heating facility 51 may take the form of an electric heating cable or a hot water coil heated by a water source heat pump wrapped around the mud inlet pipe 21 or the side wall of the fermentation vessel 1, or a heating rod installed inside the fermentation vessel 1.

[0088] The multi-stage blades 62 are divided into three layers, all located in the middle and lower part of the fermentation container 1, for fully stirring the sludge in the fermentation container 1; the heat-conducting circulation pipe 65 dissipates heat into the sludge through the rotating shaft 63 and each blade 621 via the hot steam flowing inside the pipe, thus playing a heating role.

[0089] In this embodiment, the multi-stage blades gradually change the lifting angle of the blades as the fermentation time progresses, as shown in Figure 8.

[0090] The annular dosing device 71 is positioned 20-100cm below the liquid surface inside the fermentation container 1.

[0091] The reagents in the dosing tank 75 include alkaline solution, acid solution, or trace element solution; the acid or alkaline solution adjusts the optimal pH value in the fermentation vessel to pH=10; the trace element solution uses a flow pump to control the concentration of trace elements in the fermentation vessel to: Cu 2+ 60 mmol / L; Mn 2+ 6.0 mmol / L; B 3+ 28.0 mmol / L, Mo 6+ 6.0 mmol / L; W 6+ 12.0 mmol / L; Ni 2+ 5.0 mmol / L; Co 2+ 18.0 mmol / L; Zn 2+ 35.0 mmol / L; Ca 2+ 30.0 mmol / L; the inert gas stripping nozzle 78 can spray helium gas at an appropriate flow rate to strip the dissolved oxygen remaining in the sludge and maintain the anaerobic environment for sludge fermentation.

[0092] The inlet of the venting branch pipe 81 faces downwards, with a distance of 3-30cm between it and the bottom surface of the fermentation container 1.

[0093] The fermentation unit implemented in this example, which recovers carboxylic acids while simultaneously reducing greenhouse gas emissions, can continuously produce a mixed supernatant of carboxylic acids with a COD concentration of 37,931 mg / L. The concentrations of acetate, propionate, butyrate, and valerate are 8,638 mg / L, 8,891 mg / L, 8,327 mg / L, and 8,576 mg / L, respectively. This carboxylic acid is continuously transported to a processing capacity of 50,000 m³ / h. 3 After adding sludge fermentation broth to the biological reactor of the wastewater treatment plant, the expression of key genes for nitrogen and phosphorus removal was enhanced. The key phosphorus removal genes mainly include: pPK (encoding polyphosphoric acid kinase), which catalyzes the conversion of ATP into polyphosphate; and phaC (encoding PHA synthase), responsible for the synthesis of poly-β-hydroxybutyrate (PHA), which allows polyphosphate-accumulating bacteria to provide energy by storing PHA under anaerobic conditions. The key nitrogen removal gene is norC (encoding NO reductase), which reduces NO to N₂O under anoxic or anaerobic conditions. As shown in Figure 10, after adding sludge fermentation broth, the abundance of both key phosphorus removal genes in the aerobic and anaerobic tanks was significantly increased.

[0094] After the recovered carboxylic acid was added to the biological reactor of the wastewater treatment plant, the overall COD of the influent increased by 59.6 mg / L, which significantly promoted nitrogen and phosphorus removal and saved a large amount of external carbon source. The direct economic benefits of saving carbon source reached RMB 6.63 million per year, while the indirect economic benefits of reducing greenhouse gas emissions such as methane reached RMB 15 million per year. Example

[0095] The fermentation device for recovering carboxylic acid and reducing greenhouse gas emissions in this embodiment has the same basic structure and usage as in Embodiment 1, and its specific implementation method is as follows:

[0096] Fermentation container 1 is made of 304 stainless steel and is cylindrical in shape.

[0097] The front end of the sludge inlet pipe 21 is connected to a sludge inlet pump, which is used to pump the primary sludge or residual sludge in the sewage treatment facility; the moisture content of the primary sludge or residual sludge is 98%; the flow rate of the sludge inlet pump can be adjusted according to the operating requirements of the device, so that under the condition of continuous primary sludge inlet and carboxylic acid decanting, the sludge residence time in the fermentation vessel 1 is 6 days, and the temperature of the sludge in the fermentation vessel 1 is stably maintained at 35℃.

[0098] The opening of the scum collection tank 35 is 3cm above the liquid surface.

[0099] The heating device 51 is in the form of a heating rod installed inside the fermentation vessel 1.

[0100] The multi-stage blades are divided into 2-5 layers, all located in the lower middle part of the fermentation container 1.

[0101] The annular dosing device 71 is positioned 20-100cm below the liquid surface inside the fermentation container 1.

[0102] The reagents in the dosing tank 75 include alkaline solution, acid solution, or trace element solution; the acid or alkaline solution adjusts the optimal pH value in the fermentation vessel to pH=10; the trace element solution uses a flow pump to control the concentration of trace elements in the fermentation vessel to: Cu 2+ 65 mmol / L; Mn 2+ 2.5 mmol / L; B 3+ 15.0 mmol / L; Co 2+ 10.0 mmol / L; Zn 2+ 25.5 mmol / L; the inert gas stripping nozzle 78 can spray helium gas at a suitable flow rate to strip the residual dissolved oxygen in the sludge and maintain the anaerobic environment for sludge fermentation.

[0103] The inlet of the venting branch pipe 81 faces downwards, with a distance of 20cm between it and the bottom surface of the fermentation container 1.

[0104] The fermentation unit implemented in this example, which recovers carboxylic acids while reducing greenhouse gas emissions, can continuously produce a carboxylic acid mixture with a COD concentration of 28971 mg / L. The carboxylic acid mixture contains acetate, propionate, butyrate, and valerate at concentrations of 10138 mg / L, 8691 mg / L, 2657 mg / L, and 2877 mg / L, respectively, as a supernatant of the carboxylic acid mixture.

[0105] The process flow of the fermentation device for recovering carboxylic acid and reducing greenhouse gas emissions, implemented according to this example, is shown in Figure 9. The fermentation device collects all primary sludge and residual sludge from the primary sedimentation tank and sludge thickening tank of the sewage treatment plant for fermentation to recover carboxylic acid. The reaction parameters are controlled to avoid the production of greenhouse gases such as methane during sludge fermentation. The generated carboxylic acid is added to the biological reactor to achieve the coordinated removal of pollutants such as COD, N, and P and greenhouse gases such as CO2, N2O, and NO from the sewage.

[0106] As shown in Figure 11, the carboxylic acid is continuously transported to a processing capacity of 30,000 m³. 3In a wastewater treatment plant's biological reactor (including anaerobic, anoxic, and aerobic tanks) with a daily feed rate of / d, the addition of sludge fermentation broth significantly increased the abundance of key phosphorus removal microorganisms in the anaerobic tank. These included *Flavobacterium*, *Candidatus Accumulibacter*, *Thauera*, and *Dechloromonas*, with abundances increasing by 115%-149% compared to the control group. Simultaneously, the addition of this carboxylic acid also increased the abundance of key denitrifying microorganisms, primarily *Hyphomicrobium*, *Terrimonas*, and *Pseudomonas*, as shown in Figure 12. After adding sludge fermentation broth, the abundance of these key denitrifying microorganisms in the reactor increased by 106%-112% compared to the control group. The new process generates carboxylic acids, enabling clean and efficient treatment of wastewater through biological reactions. Fermentation broth containing a certain amount of propionic acid (accounting for over 30% of total carboxylic acids) achieves better nitrogen and phosphorus removal rates (average increases of 25.4% and 31.3%, respectively), and less CO2, N2O, NO, and sludge production (average reductions of 71.1%, 65.3%, 23.4%, and 43.1%, respectively), allowing wastewater treatment plants to reduce chemical carbon source additions by 38-100%. The process principle is as follows: the fermentation broth contains trace elements such as propionic acid and copper ions. Propionic acid enables functional microorganisms to synthesize more polyhydroxyvalerate (PHV) during the anaerobic stage, resulting in a better match between the rate of energy and reducing power generated by oxidation and decomposition during the aerobic and anoxic stages and the rate of phosphorus absorption and denitrification. This promotes phosphorus absorption and denitrification while reducing CO2, N2O, and NO production. Copper ions are key components of the active centers of various denitrification reductases, promoting denitrification and reducing the accumulation of intermediate products. The input of this carboxylic acid can stably increase the COD of the bioreactor by 57.2 mg / L, significantly promote nitrogen and phosphorus removal, and save a large amount of external carbon source input. The direct economic benefits of saving carbon source amount to RMB 3.23 million per year, while the indirect economic benefits of reducing greenhouse gas emissions such as methane amount to RMB 8 million per year.

[0107] Table 1. Experimental parameters for each embodiment (trace element concentration unit mmol / L)

[0108] Group Fermentation Residence Time Cu 2+ Mn 2+ B 3+ Mo 6+ W 6+ Ni 2+ Co 2+ Zn 2+ Ca 2+pH value and temperature: Example 15 d: 40 3.0 20.0 5.0 9.0 4.0 15.0 30.0 20.0 10 35℃; Control group 15 d: ---------- 35℃; Example 28 d: 60 6.0 28.0 6.0 12.0 5.0 18.0 35.0 30.0 10 35℃; Control group 28 d: ---------- 35℃; Example 36 d: 65 2.5 15.0 4.0 7.0 3.0 10.0 25.5 10.5 10 35℃; Control group 36 d: ---------- 35℃

[0109] Table 2. Experimental results for each example and control group (concentration unit: mg / L)

[0110] Experimental Results: COD (Acetate, Propionate, Butyrate, Valate) Example 1: 198076932396038963373; Control Group: 1142313952264332472195; Example 2: 379318638889183278576; Control Group: 2260945853623161276098; Example 3: 2897110138869126572877; Control Group: 3201556453533723192501

[0111] In summary, the fermentation device of the present invention for recovering carboxylic acid and reducing greenhouse gas emissions is used to collect and process all primary sedimentation and residual sludge from sewage treatment plants for fermentation and recovery of carboxylic acid. It can also mix urban kitchen waste and sludge for fermentation to produce carboxylic acid. By controlling the operation of the fermentation device and reaction parameters, a carboxylic acid mixture with a specific ratio is produced, which significantly reduces the emission of greenhouse gases such as methane produced during fermentation. The recovered carboxylic acid mixture can be added to the biological reactor of sewage treatment plants to achieve clean and ultra-clean sewage treatment and synergistic and efficient removal of greenhouse gases such as CO2, N2O, and NO during the reaction process. Alternatively, the supernatant can be separated to purify and recover carboxylic acid industrial products to achieve resource recovery.

[0112] Compared to the commonly used purchased acetic acid chemicals as a supplementary carbon source in wastewater treatment plants, the fermentation broth produced by the fermentation device of this invention, which utilizes organic waste such as sludge and kitchen waste and contains a certain amount of propionic acid (accounting for more than 30% of the total carboxylic acid), achieves better nitrogen and phosphorus removal rates (average increases of 25.4% and 31.3%, respectively), while producing less N2O, CO2, and sludge (average reductions of 71.1%, 23.4%, and 43.1%, respectively). The mechanism by which the increased proportion of propionic acid significantly improves wastewater treatment efficiency is as follows: propionic acid enables the functional microorganisms in wastewater treatment to synthesize more polyhydroxyvalerate (PHV) during the anaerobic stage. This results in a better match between the rate of energy and reducing power generated by oxidation and decomposition during the aerobic and anoxic stages and the rate of phosphorus absorption and denitrification, promoting phosphorus absorption and denitrification while reducing CO2 and N2O production.

[0113] Compared with existing technologies, the fermentation apparatus and method for recovering carboxylic acids while reducing greenhouse gas emissions of the present invention have at least the following advantages:

[0114] 1. Substrate metabolism regulation and greenhouse gas emission reduction

[0115] This invention combines hydraulic circulation and reagent regulation. The hydraulic circulation component achieves uniform disturbance and reflux of sludge, thereby improving the completeness and efficiency of the sludge fermentation process. Substrate metabolism regulation includes adjusting the pH, temperature, and trace element concentration in the fermentation unit to ensure the stability and optimization of the fermentation environment. This promotes the conversion of sludge into efficient organic carbon sources (such as acetic acid, propionic acid, butyric acid, valeric acid, and other carboxylic acids). By adding these efficient organic carbon sources to the bioreactor, the abundance of phosphorus removal (e.g., Flavobacterium, Abscis, and Tauraceae, with an increase of 15%-49%) and key denitrification microorganisms (e.g., Microbes, Ternopilio, and Pseudomonas, with an increase of 6%-12%) can be significantly improved. The expression of key genes for nitrogen and phosphorus removal (e.g., encoding polyphosphoric acid kinase, PHA synthase, and NO reductase) can be enhanced, promoting nitrogen and phosphorus removal. This achieves metabolic balance regulation of functional microorganisms in the reactor, inhibits the metabolic activity of non-functional microorganisms (e.g., methanogenic bacteria), avoids the emission of greenhouse gases such as methane, and achieves the goal of carbon reduction and carbon neutrality.

[0116] 2. Integrated fermentation and product decanting separation

[0117] The integrated design of the fermentation vessel with decanting components and a skimmer enables efficient separation and direct utilization of fermentation products. The decanting component transports the clarified carboxylic acid solution produced during fermentation to the biological reaction tank, promoting nitrogen and phosphorus removal. The remaining sludge after fermentation continues into the existing sludge treatment process. This design simplifies the operation, reduces secondary treatment steps, and allows fermentation products to be directly and efficiently applied to the wastewater treatment system.

[0118] 3. Energy-saving and environmentally friendly insulation design

[0119] This invention employs insulation equipment to maintain the temperature inside the fermentation container between 35-55℃, fully utilizing the heat generated during sludge fermentation without requiring a large amount of additional heat energy input. This invention provides multiple low-energy-consumption insulation and heat exchange methods, which can be selected according to actual needs. Compared to existing technologies that require high-energy-consumption additional heating, this invention significantly reduces energy consumption, saves resources, and improves the environmental friendliness and economy of the device.

[0120] 4. High degree of automation and real-time monitoring

[0121] This invention investigated the carboxylic acid concentration S VThe calculation formula, through monitoring the electronic control components, can continuously monitor the temperature, pH and water quality inside the fermentation vessel, and adjust the operating parameters of each component in real time according to the monitoring results to ensure that the device is in the best operating condition. The high degree of automation and real-time monitoring function improve the operational stability and ease of operation of the device, and reduce manual intervention and operational errors.

[0122] 5. No additional microbial strains required.

[0123] The integrated device of this invention can operate automatically after startup, without the need for additional microbial inoculants. It achieves efficient sludge fermentation through its own system circulation and regulation. This not only reduces operating costs but also minimizes the use of chemical agents and potential environmental impact, making the entire treatment process greener and more environmentally friendly.

[0124] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A fermentation apparatus for recovering carboxylic acid while reducing greenhouse gas emission, characterized by, The fermentation vessel includes a fermentation container (1), a mud inlet assembly (2), a decanting assembly (3), a hydraulic circulation assembly (4), a heating and insulation assembly (5), a stirring assembly (6), a reagent control assembly (7), and a monitoring and electrical control assembly (9). The fermentation container (1) has a mud inlet (101) and a hydraulic circulation inlet (105) on its lower side wall, a hydraulic circulation outlet (106) on its upper side wall, and a carboxylic acid outlet (102) on its upper side wall. The mud inlet assembly (2) is connected to the fermentation container. The sludge inlet (101) extends into the fermentation vessel (1); the decanting assembly (3) is located at the top of the fermentation vessel (1) and connected to the carboxylic acid outlet (102) to decant the fermented carboxylic acid from the top of the fermentation vessel (1) and transport it to the biological reaction tank; the hydraulic circulation assembly (4) is connected to the hydraulic circulation inlet (105) and the hydraulic circulation outlet (106), and uses a circulation pump (41) to pump and return the sludge to the fermentation vessel (1) to achieve the desired effect. The stirring component (5) is installed on the side wall of the fermentation container (1) to heat and keep the sludge in the fermentation container (1); the stirring component (6) uses multi-stage blades (62) installed in the fermentation container (1) to fully stir the sludge; the agent control component (7) is connected to the fermentation container (1) and delivers the agent to the fermentation container (1); the monitoring and control component (9) includes a controller and a monitoring instrument installed in the fermentation container (1). The monitoring instrument continuously monitors the temperature, pH value and water quality of the sludge in the fermentation container (1). The controller adjusts the process parameters of the sludge feeding component (2), the hydraulic circulation component (4), the heating and insulation component (5), the stirring component (6) and the agent control component (7) in real time according to the monitoring results to ensure that the temperature of the sludge in the fermentation container (1) is stably maintained at 35-55℃ and a predetermined concentration of carboxylic acid is produced; the concentration of the produced carboxylic acid S V The calculation formula is: S V The concentration of carboxylic acid produced, expressed as COD; S P S represents the concentration of organic matter in the sludge to be treated, expressed as COD; h N1 represents the concentration of hydrolysis products, including protein, fat, and carbohydrates, expressed as COD; N2 represents the variable frequency output power of the circulating pump's hydraulic stirring; N3 represents the variable frequency output power of the agitator's mechanical stirring; a represents the agitator's stirring intensity adjustment coefficient; k represents the concentration of hydrolysis products. m,h X represents the maximum specific utilization rate of the hydrolysis products. h K represents the concentration of carboxylic acid-producing microorganisms. S,h K is the half-saturation constant for the growth of carboxylic acid-producing bacteria. I,h k is the coefficient representing the effect of carboxylic acid concentration on the growth of carboxylic acid-producing bacteria. m,v X represents the maximum specific utilization rate of carboxylic acid. v The concentration of methanogenic microorganisms; k is the maximum specific substrate removal rate constant; k d,h k represents the endogenous decay rate of carboxylate-producing microorganisms. d,v The intrinsic decay rate of methanogenic microorganisms.

2. The apparatus for recovering carboxylic acid while reducing greenhouse gas emission according to claim 1, wherein: The sludge inlet assembly (2) includes a sludge inlet pipe (21), an adjustable flow sludge pump, and a sludge inlet pipe support (22). The sludge inlet pipe (21) extends into the fermentation container (1) through the sludge inlet (101) on the side wall of the fermentation container (1) until the sludge inlet pipe outlet (23) is located in the central area of ​​the fermentation container (1). The sludge inlet pipe support (22) is supported below the sludge inlet pipe (21). The sludge inlet pump is connected to the inlet of the sludge inlet pipe (21) and is used to pump the primary sludge or residual sludge generated by the wastewater treatment facility. The monitoring and control assembly (9) adjusts the flow rate of the sludge inlet pump in the sludge inlet assembly (2) in real time according to the monitoring results, and controls the sludge fermentation residence time in the fermentation container (1) to be 5-8 days, so that the sludge inlet flow rate matches the carboxylic acid production efficiency.

3. The apparatus for recovering carboxylic acid while reducing greenhouse gas emission according to claim 1, characterized by: The fermentation vessel (1) has a slag discharge port (104) on the upper side wall. The carboxylic acid outlet (102) is connected to the biological reaction tank of the wastewater treatment facility to transport the clarified carboxylic acid liquid from fermentation to the biological reaction tank. The decanting assembly (3) includes a decanter (31), a carboxylic acid pipeline (32), a skimmer (34), and a scum collection tank (35). The decanter (31) includes a rectangular or annular decanting trough (311). The opening of the decanting trough (311) is located at the top of the fermentation vessel (1). The carboxylic acid produced by sludge fermentation is clarified and stratified at the top of the sludge. The clarified liquid at the top overflows into the decanting trough (311) through the opening of the decanting trough (311). Tank (311); one end of the carboxylic acid pipeline (32) is connected to the tank body of the decanting tank (311), and the other end is connected to the carboxylic acid outlet (102); the skimmer (34) is set on the top of the fermentation container (1) and driven by the skimmer motor (341) to skim the scum on the surface of the carboxylic acid clarified liquid into the scum collection tank (35); the opening of the scum collection tank (35) is 0.5-5cm higher than the surface of the carboxylic acid clarified liquid, the tank body of the scum collection tank (35) is inclined downward, and the lowest point is connected to the scum discharge port (104). The collected scum is discharged from the fermentation container (1) through the scum discharge port (104).

4. The apparatus for recovering carboxylic acid while reducing greenhouse gas emission according to claim 1, characterized by: The hydraulic circulation assembly (4) includes a circulation pump (41), a circulation sludge inlet main pipe (42), a circulation sludge inlet distribution head (43), a circulation sludge inlet branch pipe (44), and a circulation sludge outlet pipe (46); the circulation sludge inlet distribution head (43) is located in the central area of ​​the bottom of the fermentation vessel (1), and the circulation sludge inlet branch pipe (44) is radially and evenly connected around the circulation sludge inlet distribution head (43); one end of the circulation sludge inlet main pipe (42) is connected to the circulation sludge inlet distribution head (43). The other end is connected to the hydraulic circulation inlet (105); the circulation pump (41) is located outside the fermentation container (1), the inlet of the circulation pump (41) is connected to the outlet of the circulation mud inlet pipe (42), and the outlet of the circulation pump (41) is connected to the circulation mud outlet pipe (46) located in the upper part of the fermentation container (1); the circulation mud outlet pipe (46) enters the fermentation container (1) from the hydraulic circulation outlet (106) and has multiple circulation mud outlets (47).

5. The apparatus for recovering carboxylic acid while reducing greenhouse gas emission according to claim 1, characterized by: The heating and insulation component (5) includes a heating device (51) and an insulation layer; the heating device (51) is an electric heating tape or a hot water coil heated by a water source heat pump wrapped around the sludge inlet pipe (21) of the sludge inlet component (2) and / or the side wall of the fermentation container (1), and / or a heating structure set inside the fermentation container (1); the insulation layer is set on the side wall of the fermentation container (1) to reduce the heat loss of the fermentation container (1); the monitoring and control component (9) adjusts the heating and insulation component (5) in real time so that the temperature of the sludge in the fermentation container (1) is stably maintained at 35-55℃.

6. The apparatus for recovering carboxylic acid while reducing greenhouse gas emission according to claim 1, characterized by: The fermentation container (1) has a mixer mounting hole (108) on its top surface; the mixing assembly (6) includes a frequency-adjustable speed mixer (61), multi-stage blades (62), a rotating shaft (63), and a heat transfer circulation pipe (65); the mixer (61) is eccentrically installed in the mixer mounting hole (108), and its rotating shaft (63) extends into the fermentation container (1); the multi-stage blades (62) are installed in the lower middle part of the rotating shaft, and are evenly divided into 2-5 layers for fully mixing the sludge in the fermentation container (1); The rotational speed of the multi-stage blades (62) is 20-60 r / min; each multi-stage blade (62) includes multiple blades (621), a hydraulic support rod (622) and a flexible connector (623). The multiple blades (621) are connected by the flexible connector (623). The included angle between the multiple blades (621) is adjusted by the extension and retraction of the hydraulic support rod (622). When it is necessary to increase the sludge mixing intensity, the included angle between the multiple blades (621) is increased; otherwise, the included angle is decreased.

7. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 6, characterized in that: The stirring assembly (6) further includes a heat transfer circulation pipe (65), which is connected to the rotating shaft (63) and the plurality of blades (621). The heat transfer circulation pipe (65) includes a heat inlet pipe (631) and a heat return pipe (632) connected to the heat inlet pipe (631). A heat transfer medium supplied by a water source heat pump flows into the heat inlet pipe (631) and conducts heat to the sludge through the rotating shaft (63) and the plurality of blades (621). Cooling water flows back to the water source heat pump from the heat return pipe (632).

8. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 1, characterized in that: The reagent control component (7) includes a dosing device, a dosing delivery pipe (72) equipped with a metering pump (74), and a dosing tank (75). The dosing tank (75) is located outside the fermentation container (1) and is connected to the dosing device located inside the fermentation container (1) through the dosing delivery pipe (72) passing through the fermentation container (1). The reagent in the dosing tank (75) includes one or more of alkaline solution, acid solution, and trace element solution. The monitoring and control component (9) adjusts the flow rate of alkaline solution, acid solution, and trace element solution in the reagent control component (7) in real time through the metering pump (74) so ​​that the pH value of the sludge in the fermentation container (1) is maintained at 8-10, and the concentration of trace elements in the sludge is maintained at: Cu 2+ 20-65 mmol / L; Mn 2+ 2.5-6.0 mmol / L; B 3+ 15.0-28.5 mmol / L, Mo 6+ 4.0-6.2 mmol / L; W 6+ 7.0-12.2 mmol / L; Ni 2+ 3.0-5.5 mmol / L; Co 2+ 10.0-18.3 mmol / L; Zn 2+ 25.5-35.0 mmol / L; Ca 2+ , 10.5-30.5 mmol / L.

9. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 8, characterized in that: The dispensing device is a ring-shaped dispensing device (71), which is located 20-100cm below the liquid surface in the fermentation container (1). The ring-shaped dispensing device (71) has multiple dispensing nozzles (73) for uniformly spraying the agent into the sludge.

10. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 8, characterized in that: The reagent control component (7) further includes an inert gas storage tank (76), an inert gas delivery pipe (77), and an inert gas stripping nozzle (78); the inert gas storage tank (76) is located inside the dosing tank (75) and is connected to the inert gas delivery pipe (77); the end of the inert gas delivery pipe (77) is horizontally positioned at the bottom of the fermentation container (1) and is evenly distributed with several inert gas stripping nozzles (78).

11. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 1, characterized in that: The fermentation device also includes a venting component (8), and a venting port (103) is provided at the bottom of the fermentation container (1); the venting component (8) includes multiple venting branch pipes (81), a venting transfer box (82) and a venting pipe (83); the inlet of the venting branch pipe (81) faces downward and is 3-30cm away from the bottom surface of the fermentation container (1); the venting transfer box (82) is a hollow box, and its side wall is connected to the multiple venting branch pipes (81); one end of the venting pipe (83) is connected to the venting transfer box (82), and the other end passes through the venting port (103).

12. The fermentation apparatus for recovering carboxylic acid and simultaneously reducing greenhouse gas emissions according to claim 1, characterized in that: The fermentation container (1) has multiple instrument monitoring ports (112) on its side wall. The instrument monitoring ports (112) are evenly distributed along the side wall of the fermentation container (1) from high to low at a certain rotation angle. The monitoring instruments are embedded in the instrument monitoring ports (112) and include a thermometer (91), a pH meter (92) and a water quality monitoring probe (93). The thermometer (91), pH meter (92) and water quality monitoring probe (93) are used to continuously monitor the temperature, pH value and water quality of the sludge in the fermentation container (1). The controller adjusts the flow rate of the circulation pump (41) in the hydraulic circulation component (4) and the speed of the mixer (61) in the stirring component (6) in real time, so that the data monitored by the thermometer (91), pH meter (92) and water quality monitoring probe (93) at different positions tend to be consistent.

Images