A continuous dry anaerobic fermentation reactor

Abstract

The application discloses a continuous dry anaerobic fermentation reactor, which comprises a rotating drum fermentation tank, a spiral feeder for feeding materials into the rotating drum fermentation tank, a sealing device for ensuring an anaerobic fermentation environment, a supporting device for supporting the rotating drum fermentation tank, a steam jacket wrapped outside the rotating drum fermentation tank and used for heating the rotating drum fermentation tank, a driving device for driving the rotating drum fermentation tank to rotate, an automatic temperature control device for controlling the temperature in the rotating drum fermentation tank, and a discharging bin for discharging materials and discharging biogas. The application is suitable for high-solid-content dry mesophilic and thermophilic anaerobic fermentation, and heat and mass transfer are intensified in the mode of rotating drum and material lifting plate, so that the reliability of the equipment and the biogas production rate are improved; the special sealing structure ensures the anaerobic environment; the design of the inclined cylinder of the rotating drum fermentation tank ensures that the material transmission and the fermentation process are simultaneously performed; and the automatic discharging and temperature control devices improve the automatic production level of the bio-natural gas.

Description

Technical Field

[0001] This invention discloses a continuous dry anaerobic fermentation reactor, particularly a rotary continuous dry fermentation equipment for biogas production, belonging to the field of biomass energy production equipment technology. Background Technology

[0002] my country is the world's largest producer and consumer of agricultural products, generating a massive amount of agricultural waste annually. As of 2020, my country produced approximately 900 million tons of collectable straw and 3.8 billion tons of livestock and poultry manure annually, with low biogas utilization rates. Biogas can effectively replace fossil fuels and is a recognized green and renewable energy source. Utilizing straw, livestock and poultry manure, and kitchen waste to produce biogas can help address my country's rural environmental and natural gas shortage problems.

[0003] Currently, my country's anaerobic biogas fermentation methods mainly utilize CSTR wet fermentation. While the technology is relatively mature, it also suffers from numerous drawbacks, including low volumetric gas production rate, high energy and water consumption, and large volumes of difficult-to-treat wastewater. At present, most advanced biogas projects abroad employ dry fermentation technologies with a solids content greater than 20%, including batch and continuous processes. Batch fermentation primarily uses composting and leaching, but suffers from difficulties in heat and mass transfer and low fermentation yield. Continuous dry fermentation is further divided into long-shaft plug flow and pneumatic stirring types. Due to limitations in automation control, current continuous dry fermentation projects in my country all utilize long-shaft stirred plug flow reactors.

[0004] The main problems with long-shaft stirred reactors include: 1) Severe wear of the stirring impeller due to direct contact between solid raw materials and the impeller. 2) Failure of the sealing end of the stirring shaft, leading to biogas leakage. 3) Unavoidable dead zones in mechanical stirring, affecting gas production efficiency and increasing equipment corrosion. 4) Limited by the machining capabilities of the long shaft, domestic production and large-scale manufacturing are difficult, and the reactor has poor adaptability to various complex biomass raw materials. Summary of the Invention

[0005] To address the above issues, this invention designs a rotary anaerobic fermentation reactor, which replaces the push-flow long-shaft agitator with a rotary cylinder and lifting plate structure. Through a specially designed temperature control system, it enables efficient heat and mass transfer of biomass raw materials during anaerobic fermentation, improves volumetric gas production rate, and facilitates the large-scale commercial operation of dry continuous fermentation of agricultural waste to produce biogas.

[0006] This invention proposes a continuous dry anaerobic fermentation reactor for the fermentation of biomass feedstocks, specifically employing the following technical solution:

[0007] A continuous dry anaerobic fermentation reactor includes a rotary drum fermenter, a screw feeder for feeding materials into the rotary drum fermenter, feed seals and discharge seals for ensuring the anaerobic fermentation environment, a support device for supporting the rotary drum fermenter, a steam jacket surrounding the rotary drum fermenter and used for heating the rotary drum fermenter, a drive device for driving the rotary drum fermenter to rotate, and a discharge bin for unloading materials and releasing biogas.

[0008] The filling coefficient of the rotary drum fermenter is 0.3 to 0.7, preferably 0.4 to 0.6, the tilt angle of the fermenter body in the horizontal direction is 0.5 to 3°, preferably 1 to 2.5°, and the inlet end is higher than the outlet end.

[0009] The rotary fermenter is equipped with lifting plates of varying radial lengths, extending from the inner wall towards the center of the fermenter. These plates are arranged in several groups, spaced circumferentially along the inner wall, preferably evenly spaced. Each group contains 4 to 12 lifting plates along the same circumferential cross-section. The lifting plates include longer lifting plates and shorter lifting plates. The longer lifting plates are 0.3 to 0.4 times the diameter of the cylinder, preferably about 0.375 times, while the shorter lifting plates are 0.2 to 0.3 times the diameter of the cylinder, preferably about 0.225 times. They are preferably distributed in axial groups and stages at equal intervals. The longer lifting plates are grouped at the front section of the rotary fermenter, occupying 15 to 20% of the total length of the fermenter, and arranged in 5 to 25 groups, preferably 8 to 22 groups, and more preferably 10 to 20 groups. 10-15 groups; short lifting plates are grouped and arranged in the rear section of the rotary drum fermenter, accounting for 80-85% of the total length of the rotary drum fermenter, with 15-50 groups, preferably 20-45 groups, preferably 25-40 groups, and preferably 30-40 groups. The lifting plate structure is paddle type, with the short side (paddle handle) connected to the inner wall of the fermenter. The width of the short side is 0.075-0.015 times the diameter of the fermenter cylinder, preferably 0.01 times. The width of the long side (paddle blade) is 4-8 times the width of the short side, preferably 5 times.

[0010] Preferably, the inner diameter of the rotary drum fermenter is 3 to 6 meters, and the length of the rotary drum fermenter is 50 to 100 meters.

[0011] Preferably, the screw feeder is a fixed component, with a feed inlet at the front end and a biogas slurry return outlet at the rear end.

[0012] Preferably, the feed seal includes a feed sealing chamber, a first dynamic friction ring, a first static friction ring, and a front flange cover. The feed sealing chamber seals the inlet of the screw feeder and the rotary fermenter. The feed sealing chamber is a cylindrical fixed component, with one end extending into the inlet opening of the rotary fermenter and the other end connected to the end of the screw feeder. The first dynamic friction ring, the first static friction ring, and the front flange cover are sequentially arranged outward from the port of the rotary fermenter. The first static friction ring is fixed to the outer wall of the feed sealing chamber cylinder. The first dynamic friction ring rotates with the rotary fermenter cylinder. Multiple feed sealing pressure plates are fixed around the outer periphery of the feed sealing chamber. The feed sealing pressure plates further press the feed sealing chamber tightly against the front flange cover through a first spring connector. The front flange cover has a variable diameter section that covers the first dynamic friction ring and the first static friction ring. The variable diameter section further covers a section of first sealing felt that fits against the outer wall of the fermenter. The dynamic friction ring is pressed together by the spring connector and the static friction ring. During rotation, the dynamic and static friction rings cooperate to form a friction pair, with a sealing gap of less than 1mm, preventing gas leakage. The sealing plate and the feed sealing chamber are connected by bolts, and the sealing gap is adjusted by the spring connector and bolts.

[0013] Preferably, the feed sealing pressure plates are arranged in a ring on the feed sealing chamber, with a quantity of 8 to 20. The front flange cover is provided with two seals. The inner seal is a mechanical seal composed of a first static friction ring and a first dynamic friction ring. Preferably, the first static friction ring is made of PTFE and is fixed to the outer wall of the feed sealing chamber. The first dynamic friction ring is a hard alloy composite layer and is composited to the front end of the drum fermenter body. The outer seal is a section of sealing felt added at the rear of the flange diameter change section, which further reduces the leakage of biogas from the inner sealing point.

[0014] Preferably, the feed sealing chamber is further provided with a feed sealing bracket, which is fixed to the cement foundation and serves to fix the feed sealing chamber.

[0015] Preferably, the discharge seal includes a rear flange cover, a second dynamic friction ring, a second static friction ring, a second sealing felt, a discharge sealing plate, and a second spring connector. The discharge hopper has a cylindrical connecting section that extends into the outlet opening of the rotary fermenter. The second dynamic friction ring, the second static friction ring, and the rear flange cover are sequentially arranged outwards from the outlet opening of the rotary fermenter. The second static friction ring is fixed to the outer wall of the discharge section of the discharge hopper. The second dynamic friction ring rotates with the rotary fermenter. Multiple discharge sealing plates are fixed around the outer periphery of the discharge hopper connecting section. The discharge sealing plates further press the discharge hopper against the rear flange cover via the second spring connector. The rear flange cover has a variable diameter section that covers the second dynamic friction ring and the second static friction ring. The variable diameter section further covers a section of second sealing felt and fits against the outer wall of the outlet of the rotary fermenter. The second dynamic friction ring is pressed against the spring connector and the second static friction ring. During rotation, the dynamic and static rings cooperate to form a friction pair with a sealing gap of less than 1 mm, preventing gas leakage.

[0016] Preferably, the unloading sealing plates are arranged in a ring on the unloading hopper connection section, with a quantity of 8 to 20. The first seal is a mechanical seal composed of a second static friction ring and a second dynamic friction ring. Preferably, the second static friction ring is made of PTFE and is fixed to the rear flange cover, while the second dynamic friction ring is a hard alloy composite layer bonded to the rear end of the rotary fermenter body. The second seal adds a section of second sealing felt at the rear of the flange diameter reduction section to further reduce biogas leakage from the first sealing point. The inlet and outlet seals ensure the anaerobic environment inside the fermenter and increase the reliability of the seal.

[0017] The screw feeder extends into the feed sealing chamber, and the screw feeder and the feed sealing chamber are connected by a flange.

[0018] The refluxed biogas slurry after steady-state fermentation is used as inoculum and to adjust the moisture content of the feed. The biogas slurry after solid-liquid separation at the rear end is pumped and pressurized and returned to the feed end through the biogas slurry return port, which also serves to flush and lubricate the screw feeder.

[0019] The support device includes rollers and a base, such as a cement base. The rotary fermenter is supported on the base by rollers, which are rotatable. A support ring is fastened to the outer periphery of the rotary fermenter. The support ring of the rotary fermenter is in line contact with the rollers. The rollers are supported on the base by roller bearings. There are generally two sets, usually located on the feed side and discharge side of the rotary fermenter, respectively. Two rollers are arranged symmetrically in each set, distributed on both sides of the rotary fermenter. For example, each set can be set near both ends of the rotary fermenter. The angle between the support rollers and the vertical center line is preferably 30±10°, preferably about 30°.

[0020] The automatic temperature control device includes several temperature probes extending to different depths into the rotary fermenter along its circumference, a wireless temperature sensor, a temperature control valve for controlling steam flow, and a PLC (Programmable Logic Controller). The steam jacket is fixedly mounted on the base via a saddle, with a gap of 2-5 cm between it and the rotary fermenter body; heating is achieved through radiative heat transfer. A temperature control valve is installed on the inlet pipe leading to the steam jacket, and several temperature probes are used to measure the average temperature inside the rotary fermenter body. The measured temperature is transmitted to the PLC via the wireless temperature sensor. The PLC sends a temperature adjustment signal to the temperature control valve, adjusting the steam flow in the steam jacket according to the temperature difference between the desired fermentation temperature and the actual measured temperature.

[0021] The drive unit can be a variable frequency motor or a fixed frequency motor plus a reducer. The drive unit drives the drive gear to rotate through a worm gear. The drive gear is set on the outer wall of the cylinder, for example, covering the entire circumference, and cooperates with the main gear on the rotary fermenter, thereby driving the rotary fermenter to rotate. The preferred speed is 0.3 to 3 rpm.

[0022] The discharge device includes a discharge hopper and a discharge conveyor belt. The discharge hopper is a fixed component, secured to a base, such as a cement base, via lugs. It is generally box-shaped or cylindrical, with an inverted cone shape at the bottom (usually tapering gradually, such as an inverted truncated cone). The side inlet of the discharge hopper connects to the outlet of the rotary fermenter. A periodically opening vent is located at the upper part of the discharge hopper (usually on the opposite side to the outlet of the rotary fermenter), and a double-layer flap valve is installed at the lower outlet. The flap valve opens due to the cumulative force of the material's gravity and closes when gravity is absent.

[0023] The biomass raw material fed into the feed inlet is one or a mixture of several of the following: crop silage straw (such as corn silage straw), yellow silage straw, livestock and poultry manure (such as cow dung and pig dung), kitchen waste, and distiller's grains (such as sweet sorghum distiller's grains). For example, it is a combination of at least one of crop silage straw (such as corn silage straw) and yellow silage straw with at least one of livestock and poultry manure (such as cow dung and pig dung), kitchen waste, and distiller's grains (such as sweet sorghum distiller's grains). The mass ratio of the two is preferably 1:3 to 3:1, more preferably 1:2 to 2:1, wherein the solid content of the biomass raw material is greater than 20%.

[0024] In practice, steam is introduced to sterilize the rotary fermenter before fermentation. The motor is started, and biomass feedstock enters the rotary fermenter via a screw feeder. The fermenter, supported by rollers, rotates at 0.3–3 rpm driven by a drive gear, with a filling rate of 0.3–0.7%. Lifting plates of different lengths are used for the acid production and methanogenesis stages, respectively. The lifting plates are longer in the acid production stage, with two sets arranged alternately to reduce the escape of non-product gases with foul odors, such as ammonia, hydrogen sulfide, and organic acids, in the early stages of fermentation. The lifting plates are shorter in the methanogenesis stage to enhance feedstock mixing. The rotary movement of the fermenter and the combined effect of the long and short lifting plates enhance mass and heat transfer, as well as the migration of anaerobic bacteria, increasing fermentation intensity and gas production rate. The rotary fermenter is tilted at an angle of 0.5–3° to the horizontal, with the feed inlet higher than the discharge outlet, ensuring the material undergoes a spiral motion within the fermenter and gradually transfers towards the discharge bin. The fermentation residence time of biomass feedstock in the rotary fermenter is adjusted by changing the tilt angle of the drum and the rotation speed of the fermenter. Typically, the anaerobic fermentation time in the fermenter is 7–25 days, with material transfer to the outlet occurring simultaneously with mixing. Steam enters the steam jacket via a temperature control valve, using radiant heat transfer to maintain a constant temperature inside the fermenter. During fermentation, when the temperature difference detector inside the PLC detects a deviation between the fermenter temperature and the desired temperature from the set value, it sends a temperature adjustment signal to the temperature control valve, regulating the steam flow in the steam jacket to achieve the required fermentation temperature. After fermentation, the biogas residue enters the unloading hopper. The double-layer flap valve at the bottom of the unloading hopper automatically opens and resets under the weight of the material. The fermented biogas residue is then conveyed to the subsequent biogas residue processing section via a discharge conveyor belt. The gas outlet of the unloading hopper is opened periodically to release biogas, which is then desulfurized and purified to obtain biomethane.

[0025] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0026] (1) The present invention adopts a rotary drum fermenter. The rotary structure is much better than mechanical stirring and other structures, avoiding problems such as wear of the stirring paddle and dead corners caused by the instability of solid raw materials, and improving the service life of the equipment.

[0027] (2) The present invention has specially designed a double-layer sealing device suitable for rotary drum fermenters and biogas production. Compared with long-shaft stirring and propulsion equipment, it increases the sealing reliability, ensures the anaerobic fermentation environment, and reduces biogas leakage.

[0028] (3) The present invention uses a steam jacket and an automatic temperature control system, which can be applied to microbial anaerobic fermentation under high temperature conditions and accelerate the fermentation reaction rate.

[0029] (4) The present invention adopts a paddle-type lifting plate structure in the rotary drum fermenter, which enhances mass and heat transfer during continuous fermentation. By arranging the lifting plates with a longer front and shorter back, the generation and escape of non-product gases with foul odors are reduced, gas production efficiency is improved, and the production environment is improved.

[0030] (5) The inclined cylinder design of the rotary drum fermenter of the present invention ensures that material transfer and fermentation processes are carried out simultaneously, thereby improving the level of automated production of biogas. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the continuous dry anaerobic fermentation reactor described in this invention.

[0032] Figure 2 This is a schematic diagram of the cross-sectional structure of the continuous dry anaerobic fermentation reactor AA.

[0033] Figure 3 This is a schematic diagram of the feed seal and discharge seal of a continuous dry anaerobic fermentation reactor.

[0034] Figure 4 This is a diagram showing the sealing connection of the feed seal for a continuous dry anaerobic fermentation reactor.

[0035] Figure 5 This is a diagram showing the sealing connection for the discharge seal of a continuous dry anaerobic fermentation reactor.

[0036] Figure 6 This is a schematic diagram of the material lifting plate structure in a continuous dry anaerobic fermentation reactor.

[0037] 1-Screw feeder, 2-Feed sealing chamber, 3-Rotating fermenter, 4-Support roller, 5-Steam jacket, 6-Drive gear, 7-Automatic temperature control device, 8-Unloading chamber, 9-Discharge conveyor belt, 10-Drive device, 11-Base, 101-Feed inlet, 102-Biogas slurry return inlet, 103-Feeder bracket, 201-Feed sealing bracket, 202-Feed sealing pressure plate, 301-Long lifting plate, 302-Short lifting plate, 303-Support ring, 304-Front flange cover 305-Rear flange cover, 501-Temperature control valve, 502-Steam jacket saddle, 801-Air outlet, 802-Double-layer flap valve, 803-Unloading bin ear seat, 804-Unloading sealing pressure plate, 2021-First spring connector, 8041-Second spring connector, 3041-First static friction ring, 3051-Second static friction ring, 3042-First dynamic friction ring, 3052-Second dynamic friction ring, 3043-First sealing felt, 3053-Second sealing felt. Detailed Implementation

[0038] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples. Figure 1 As shown, a continuous dry anaerobic fermentation reactor includes a rotary drum fermenter 3, a feeding device for feeding materials into the rotary drum fermenter 3, namely a screw feeder 1, a feed seal and a discharge seal for ensuring the anaerobic fermentation environment, a support device for supporting the rotary drum fermenter, a steam jacket 5 wrapped around the outside of the rotary drum fermenter and used for heating the rotary drum fermenter, a drive device 10 for driving the rotary drum fermenter 3 to rotate, a discharge bin 8 for unloading materials and releasing biogas, and an automatic temperature control device 7 for controlling the temperature inside the rotary drum fermenter.

[0039] The rotary fermenter 3 is supported on the base 11 by rollers 4. Inside, there are lifting plates of varying radial lengths. The lifting plates have a paddle-type structure. Figure 2 and Figure 4 As shown, the lifting plates extend radially from the inner wall of the rotary fermenter 3 towards its center, and are divided into several groups evenly distributed along the circumference of the inner wall. The number of lifting plates in each group along the same circumferential cross section can be 4 to 12. The lifting plates include long lifting plates 301 with a longer length and short lifting plates 302 with a shorter length. The long lifting plates are 0.3 to 0.4 times the diameter of the cylinder, preferably 0.375 times, and the short lifting plates are 0.2 to 0.3 times the diameter of the cylinder, preferably 0.225 times. They are distributed in groups and stages at equal intervals. The long lifting plates are grouped and set in the front section of the rotary fermenter (near the feed inlet side), accounting for 15 to 20% of the total length of the rotary fermenter, and arranged in 10 to 20 groups, preferably 10 to 15 groups. The short lifting plates are grouped and set in the rear section of the rotary fermenter (near the discharge outlet side), accounting for 80 to 85% of the total length of the rotary fermenter, and arranged in 25 to 40 groups, preferably 30 to 40 groups. The lifting plate has a paddle-type structure, with its short side (paddle handle) connected to the inner wall of the fermenter. The width of the short side is 0.075 to 0.015 times the diameter of the fermenter cylinder, preferably 0.01 times. The width of the long side (paddle blade) is 4 to 8 times the width of the short side, preferably 5 times. The ratio of the length of the paddle handle (short side) to the length of the paddle blade (long side) (radial dimension of the fermenter) is 1:3 to 3:1, preferably 1:2 to 2:1, and more preferably about 1:1.

[0040] The inner diameter of a rotary drum fermenter is generally 3 to 6 meters, and the length of a rotary drum fermenter is generally 50 to 100 meters.

[0041] like Figure 3 As shown, the screw feeder 1 is a fixed component, fixed by the support 103. It has a feed inlet 101 at the front end and a biogas slurry return inlet 102 at the rear end. The screw feeder extends into the feed sealing chamber 2, and the screw feeder and the feed sealing chamber are connected by a flange.

[0042] The feed seal includes a feed sealing chamber 2, a first dynamic friction ring 3042, a first static friction ring 3041, and a front flange cover 304. The feed sealing chamber 2 seals the screw feeder 1 with the inlet of the rotary fermenter; Figure 3 As shown, the feed sealing chamber 2 is a cylindrical fixed component. One end extends into the inlet opening of the rotary fermenter 3, and the other end is connected to the end of the screw feeder. A first dynamic friction ring 3042, a first static friction ring 3041, and a front flange cover 304 are sequentially arranged outward from the port of the rotary fermenter 3. The first static friction ring 3042 is fixed to the outer wall of the feed sealing chamber 2. The first dynamic friction ring 3042 rotates with the rotary fermenter. Multiple feed sealing pressure plates 202 are fixed around the outer periphery of the feed sealing chamber 2. The feed sealing pressure plates 202 further press the feed sealing chamber against the front flange cover 304 through the first spring connector 2021. The front flange cover 304 has a variable diameter section that covers the first dynamic friction ring 3042 and the first static friction ring 3041. The variable diameter section further covers a section of first sealing felt 3043 and fits against the outer wall of the inlet of the rotary fermenter 3. The dynamic friction ring is pressed by the spring connector and the static friction ring. During rotation, the dynamic and static friction rings cooperate to form a friction pair. The sealing gap is less than 1mm to prevent gas leakage. The sealing pressure plate 202 and the feed sealing chamber are connected by bolts. The sealing gap is adjusted by the spring connector 2021 and the bolts.

[0043] Preferably, the feed sealing pressure plates 202 are arranged in a ring on the feed sealing chamber, with a quantity of 8 to 20. The front flange cover 304 is provided with two seals. The inner seal is a mechanical seal composed of a first static friction ring 3041 and a first dynamic friction ring 3042. The first static friction ring 3041 is made of PTFE and is fixed to the outer wall of the feed sealing chamber 2. The first dynamic friction ring 3042 is a hard alloy composite layer and is composited to the front end of the drum fermenter 3. The outer seal adds a section of first sealing felt 3043 at the rear of the flange diameter change section to reduce biogas leakage from the first sealing point.

[0044] Preferably, the feed sealing chamber is further provided with a feed sealing bracket 201, which is fixed to a cement foundation.

[0045] The discharge seal includes a rear flange cover 305, a second dynamic friction ring 3052, a second static friction ring 3051, a second sealing felt 3053, a discharge sealing pressure plate 804, and a second spring connector 8041. The discharge bin 8 has a cylindrical connecting section that extends into the outlet end opening of the rotary fermenter 3. The second dynamic friction ring 3052, the second static friction ring 3051, and the rear flange cover 305 are sequentially arranged outwards from the outlet end opening of the rotary fermenter 3. The second static friction ring 3051 is connected to the discharge bin 8 via the connecting section. The second dynamic friction ring 3052 rotates with the drum fermenter body. Multiple discharge sealing plates 804 are fixed around the outer periphery of the connecting section of the discharge hopper 8. The discharge sealing plates 804 further press the discharge hopper against the rear flange cover 305 via a second spring connector 8041. The rear flange cover 804 has a variable diameter section covering the second dynamic friction ring 3052 and the second static friction ring 3051. The variable diameter section further covers a section of second sealing felt 3053, which fits against the outer wall of the outlet end of the drum fermenter 3. The second dynamic friction ring is pressed against the second static friction ring by the spring connector. During rotation, the dynamic and static rings cooperate to form a friction pair with a sealing gap of less than 1 mm, preventing gas leakage.

[0046] Preferably, 8 to 20 unloading sealing plates 804 are arranged in a ring on the unloading hopper connecting section. Two seals are installed inside the rear flange cover 305. The first seal is a mechanical seal composed of a second static friction ring 3051 and a second dynamic friction ring 3052. The second static friction ring 3051 is made of PTFE and fixed to the rear flange cover 305. The second dynamic friction ring 3052 is a hard alloy composite layer, laminated to the rear end of the drum fermenter 3. A second sealing felt 3053 is added at the rear of the flange diameter reduction section to reduce biogas leakage from the first leakage point. The inlet and outlet seals ensure the anaerobic environment inside the fermenter and increase the reliability of the seals.

[0047] The refluxed biogas slurry after steady-state fermentation is used as inoculum to adjust the moisture content of the feed. After solid-liquid separation at the rear end, the biogas slurry is pumped and pressurized and returned to the feed end through the biogas slurry return port 102. In engineering applications, the rear end of the feed auger is easily blocked by fibrous materials. The pressurized biogas slurry return also has the function of cleaning the blockage materials, making the feed smoother.

[0048] The support device includes a support roller 4 and a base 11. The support roller 4 is rotatable and mounted on the base 11. A support ring 303 is fastened to the outer periphery of the rotary fermenter 3. The support ring 303 of the rotary fermenter 3 is in line contact with the support roller 4. The support roller 4 is supported on the base by a support roller bearing 401 (e.g., ...). Figure 2 Generally, there are 2 to 3 groups, with two symmetrically arranged in each group, distributed on both sides of the rotary drum fermenter. For example, each group can be set near both ends of the rotary drum fermenter 3, with the angle between the support wheel and the center line being 30±10°, preferably about 30°.

[0049] The automatic temperature control device 7 includes several temperature probes extending to different depths into the rotary fermenter 3, distributed circumferentially; a wireless temperature acquisition device; a temperature control valve 501 for controlling steam flow; and a PLC (Programmable Logic Controller). The steam jacket 5 is fixedly mounted on the base 11 via a steam jacket saddle 502, with a gap of 2-5 cm between it and the cylinder of the rotary fermenter 3. Heating is achieved through radiative heat transfer. A temperature control valve 501 is installed on the inlet pipe leading into the steam jacket 5. Several temperature probes, distributed circumferentially inside the rotary fermenter 3, measure the average temperature inside the cylinder. The measured temperature is transmitted to the PLC via the wireless temperature acquisition device. The PLC sends a temperature adjustment signal to the temperature control valve 501, adjusting the steam flow in the steam jacket 5 according to the temperature difference between the desired fermentation temperature and the actual measured temperature.

[0050] The drive device 10 can be a variable frequency motor or a fixed frequency motor plus a reducer. The drive device 10 drives the drive gear 6 to rotate through the worm gear. The drive gear is set on the outer wall of the cylinder and covers the entire circumference. It cooperates with the main gear on the rotary fermenter 3, thereby driving the rotary fermenter 3 to rotate at a speed of 0.3 to 3 rpm.

[0051] The filling coefficient of the rotary fermenter 3 is 0.3–0.7, and the horizontal inclination angle of the fermenter 3 body is 0.5–3°. A rear flange cover 305 is installed at the outlet end of the fermenter 3 body, i.e., the discharge port, connecting to the discharge device, and the inlet is higher than the outlet. The discharge device is as follows: Figure 1 As shown, it includes a discharge bin 8 and a discharge conveyor belt 9. The discharge bin 8 is a fixed component, generally box-shaped or cylindrical, with an inverted cone shape at the bottom (the bottom usually tapers gradually, such as an inverted truncated cone). The side inlet of the discharge bin 8 is connected to the outlet of the rotary fermenter 3. Figure 2 As shown, the upper part of the unloading hopper 8 (usually the opposite side to the side connected to the outlet of the rotary fermenter 3) is equipped with a periodically open vent 801, and the lower outlet is equipped with a double-layer flap valve 802. The flap valve 802 opens and closes under the action of gravity due to the accumulation of unloading material.

[0052] The biomass raw material fed into feed inlet 1 is one or a mixture of several of the following: crop silage straw, yellow silage straw, livestock and poultry manure, and kitchen waste, wherein the solid content of the biomass raw material is greater than 20%.

[0053] In practice, steam is first introduced into the steam jacket 5 to sterilize the rotary fermenter 3 before fermentation. The motor is started, and the biomass feedstock enters the rotary fermenter 3 through the screw feeder 1. The rotary fermenter 3 is supported by rollers 4 and rotates under the drive gear 6 at a speed of 0.3–3 rpm with a filling rate of 0.3–0.7. Lifting plates 301 and 302 of different lengths are used for the acid production and methanogenesis stages, respectively. The lifting plates 301 are longer and staggered in the acid production stage to reduce the escape of acidic gases, while the lifting plates are shorter in the methanogenesis stage to enhance feedstock mixing. The rotary motion of the rotary fermenter 3 and the combined effect of the lifting plates 301 and 302 enhance mass transfer, heat transfer, and anaerobic bacteria migration, thereby increasing fermentation intensity and gas production rate. The rotary fermenter 3 is tilted at an angle of 0.5–3° to the horizontal, with the inlet 101 higher than the outlet, ensuring that the material moves in a spiral motion within the fermenter 3 and gradually transfers to the discharge bin 8. The fermentation residence time of the biomass raw materials within the fermenter 3 is adjusted by changing the tilt angle and rotation speed. Typically, the anaerobic fermentation time in the fermenter 3 is 7–25 days, with material transfer occurring simultaneously with mixing. Steam is connected to the steam jacket 5 via a temperature control valve 501 to maintain a constant temperature within the fermenter. During fermentation, when the temperature difference detector inside the PLC detects a deviation between the temperature inside the fermenter 3 and the desired temperature from the set value, it sends a temperature adjustment signal to the temperature control valve, regulating the steam flow in the steam jacket to achieve the required fermentation temperature. After fermentation, the biogas residue enters the discharge bin 8. The double-layer flap valve 802 at the bottom of the discharge bin 8 automatically opens and resets under the weight of the material. The fermented biogas residue is then conveyed to the subsequent biogas residue processing section via the discharge conveyor belt 9. The gas outlet 801 of the unloading silo is opened periodically to release biogas, which is then desulfurized and purified to obtain biomethane products.

[0054] Example 1

[0055] The continuous dry anaerobic fermentation reactor of this invention uses corn stalks crushed into powder particles approximately 2 mm in diameter and 20 mm in length. After silage pretreatment, the powder is mixed with pig manure and fed into the downstream biogas slurry. The mass ratio of corn stalks to pig manure in the silage is 1:2, with a solids content of 24%. The premixed raw materials are fed into a rotary drum fermenter via a screw feeder. The fermenter has a diameter of 3.6 meters, a length of 70 meters, a rotation speed of 0.5 rpm, an inclination angle of 0.9°, and a filling coefficient of 0.6. The front end of the fermenter is equipped with 15 sets of long lifting plates 301, with 6 plates in each set, each plate having a length of 0.35 times the cylinder diameter. The front and rear sets of lifting plates are staggered at an angle of 15°. The rear end is equipped with 40 sets of short lifting plates 302, with 6 plates in each set, each plate having a length of 0.25 times the cylinder diameter. The fermentation temperature is stabilized at 38℃±1℃ by adjusting the steam flow rate through radiative heat transfer via a steam jacket. After the raw materials enter the cylinder, they rotate forward in a spiral motion as the inclined cylinder rotates, continuously producing biogas which is then discharged by the exhaust fan. The biogas production is 62 Nm³. 3 / h, volumetric gas production rate 2.1m³ 3 / (m 3 ·d). After 20 days of fermentation, the biomass raw materials enter the unloading silo. After solid-liquid separation, the biogas slurry is recycled, and the biogas residue is further used to produce organic fertilizer.

[0056] Example 2

[0057] The continuous dry anaerobic fermentation reactor of this invention uses a mixture of sweet sorghum distiller's grains and cow manure at a mass ratio of 1:1, with a solids content of 25%. The pH is adjusted before introducing biogas slurry. The premixed raw materials are fed into a rotary fermenter via a screw feeder. The fermenter rotates at 1 rpm, with the cylinder tilted at 1.5° and a filling coefficient of 0.7. Ten sets of long lifting plates 301 are arranged at the front end of the fermenter, with eight plates per set and each plate having a length of 0.375 times the cylinder diameter. The front and rear sets of lifting plates are staggered at a 10° angle. Thirty sets of short lifting plates 302 are arranged at the rear end, with six plates per set and each plate having a length of 0.25 times the cylinder diameter. The fermentation temperature is stabilized at 53℃±1℃ by radiative heat transfer through a steam jacket and adjustment of the steam flow rate. After entering the cylinder, the raw materials move forward in a spiral motion with the tilted cylinder, continuously generating biogas and discharging it from the unloading hopper. The fermentation cycle is 8 days, with a biogas yield of 160 Nm³. 3 / h, volumetric gas production rate 5.4m³ 3 / (m 3 ·d). After 8 days of fermentation, the biomass raw materials enter the unloading silo. After discharge, the materials undergo solid-liquid separation, the biogas slurry is recycled, and the biogas residue is further used to produce organic fertilizer.

[0058] Comparative Example 1

[0059] Comparative Example 1 used the same raw materials, fermenter volume, filling rate, and fermentation temperature as Example 1, but instead used a plug-flow long-shaft stirred dry anaerobic fermentation reactor (the main difference between this plug-flow long-shaft stirred dry anaerobic fermentation reactor and the reactor of this invention is that the cylinder remains stationary and there are no internal lifting plates; the material is stirred by the rotation of the long stirring shaft driving the paddles). Due to the decrease in heat and mass transfer efficiency and the existence of stirring dead zones, the hydraulic retention time increased from 20 days to 25 days, and the biogas production decreased to 46 Nm³. 3 / h, the volumetric gas production rate decreased to 1.6m³. 3 / (m 3 (d) Meanwhile, due to the complexity of biomass raw materials, impurities such as soil, rocks, and plastics may enter the reactor along with the raw materials, increasing the risk of agitator wear and seal failure. After wear, the entire agitator needs to be replaced or repaired, which affects output and increases operating costs.

[0060] Comparative Example 2

[0061] The lifting plates are all the same length, 0.25 times the diameter of the cylinder.

[0062] The initial stage of anaerobic fermentation of biogas is an acid-producing process, during which organic matter degrades into short-chain fatty acids, and nitrogen in the raw materials degrades into ammonia nitrogen. During high-temperature fermentation, small-molecule organic acids, hydrogen sulfide, and ammonia are more easily volatilized, reducing biogas yield and quality, and creating a poor production environment. The staggered arrangement of the long lifting plates extends the raw material mixing time, resulting in higher heat and mass transfer efficiency of the multi-component raw materials during the acid-producing stage. It also increases gas escape resistance, reducing the content of impurities such as hydrogen sulfide and ammonia in the biogas. In Comparative Example 2, the lifting plates were all 0.25 times the cylinder diameter and arranged in parallel, otherwise identical to Example 2. The hydrogen sulfide content in the biogas increased from 0.35% to 1.5%, the ammonia content increased from undetectable to 160 ppm, and the methane content decreased from 58% to 55%.

[0063] The above-described embodiments only illustrate two implementation methods of the present invention, facilitating a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A continuous dry anaerobic fermentation reactor, characterized in that... It includes a rotary fermenter, a screw feeder for feeding materials into the rotary fermenter, feed seals and discharge seals for ensuring an anaerobic fermentation environment, a support device for supporting the rotary fermenter, a steam jacket that surrounds the rotary fermenter and is used to heat it, a drive device for driving the rotary fermenter to rotate, and a discharge bin for unloading and releasing biogas. The filling coefficient of the rotary drum fermenter is 0.3~0.7, the tilt angle of the fermenter body in the horizontal direction is 0.5~3°, and the inlet end is higher than the outlet end. The rotary fermenter is equipped with lifting plates of different radial lengths, which extend radially from the inner wall of the rotary fermenter to the center of the rotary fermenter and are divided into several groups that are distributed circumferentially along the inner wall. The number of lifting plates in each group along the same circumferential cross section is 4 to 12. The lifting plates include long lifting plates and short lifting plates. The radial length of the long lifting plates is 0.3 to 0.4 times the diameter of the cylinder, and the radial length of the short lifting plates is 0.2 to 0.3 times the diameter of the cylinder. The long lifting plates are grouped and arranged in the front section of the rotary fermenter, accounting for 15 to 20% of the total length of the rotary fermenter, and arranged in 5 to 25 groups. The short lifting plates are grouped and arranged in the rear section of the rotary fermenter, accounting for 80 to 85% of the total length of the rotary fermenter, and arranged in 15 to 50 groups. The feed seal includes a feed sealing chamber, a first dynamic friction ring, a first static friction ring, and a front flange cover. The feed sealing chamber seals the inlet of the screw feeder to the rotary fermenter. The feed sealing chamber is a cylindrical fixed component, with one end extending into the inlet opening of the rotary fermenter and the other end connected to the end of the screw feeder. The first dynamic friction ring, the first static friction ring, and the front flange cover are sequentially arranged outward from the port of the rotary fermenter. The first static friction ring is fixed to the outer wall of the feed sealing chamber cylinder. The first dynamic friction ring rotates with the rotary fermenter cylinder. Multiple feed sealing pressure plates are fixed around the outer periphery of the feed sealing chamber. The feed sealing pressure plates press the feed sealing chamber against the front flange cover through a first spring connector. The front flange cover has a variable diameter section that covers the first dynamic friction ring and the first static friction ring. The variable diameter section is covered with a section of first sealing felt, which fits against the outer wall of the inlet of the rotary fermenter.

2. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The radial length of the long lifting plate is 0.375 times the diameter of the cylinder, and the radial length of the short lifting plate is 0.225 times the diameter of the cylinder.

3. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The lifting plate has a paddle-type structure, with its short side connected to the inner wall of the fermentation tank, and the width of its long side being 2 to 10 times the width of its short side.

4. The continuous dry anaerobic fermentation reactor according to claim 3, characterized in that, The width of the long side of the lifting plate is 4 to 8 times the width of the short side.

5. The continuous dry anaerobic fermentation reactor according to claim 4, characterized in that, The width of the short side of the lifting plate is 0.01 times the diameter of the fermentation tank, and the width of the long side of the lifting plate is 5 times the width of the short side.

6. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The screw feeder is a fixed component with a feed inlet at the front end and a biogas slurry return outlet at the rear end.

7. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The inner diameter of the rotary drum fermenter is 3 to 6 meters, and the length of the rotary drum fermenter is 50 to 100 meters.

8. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, Long and short lifting plates are distributed in groups and stages with equal spacing along the axial direction.

9. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The long lifting plates are arranged in 10 to 20 groups; the short lifting plates are arranged in 25 to 40 groups.

10. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The long lifting plates are arranged in 10 to 15 groups; the short lifting plates are arranged in 30 to 40 groups.

11. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, It includes an automatic temperature control device for controlling the temperature inside the rotary fermenter.

12. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The first dynamic friction ring is pressed together by the first spring connector and the first static friction ring. During rotation, the dynamic and static friction rings cooperate to form a friction pair, and the sealing gap is less than 1mm, preventing gas leakage.

13. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The feed sealing pressure plates are arranged in a ring on the feed sealing chamber, with a quantity of 8 to 20. The front flange cover is equipped with two seals: the inner seal is a mechanical seal composed of a first static friction ring and a first dynamic friction ring, and the outer seal is the first sealing felt at the edge of the first flange diameter-changing section, which reduces the leakage of biogas from the inner sealing point.

14. The continuous dry anaerobic fermentation reactor according to claim 13, characterized in that, The first static friction ring is made of PTFE and is fixed to the outer wall of the feed sealing chamber. The first dynamic friction ring is a hard alloy composite layer.

15. The continuous dry anaerobic fermentation reactor according to any one of claims 1 and 12-14, characterized in that, The discharge seal includes a rear flange cover, a second dynamic friction ring, a second static friction ring, a second sealing felt, a discharge sealing plate, and a second spring connector. The discharge hopper is a fixed component. The discharge hopper has a cylindrical connecting section that extends into the outlet opening of the rotary fermenter. The second dynamic friction ring, the second static friction ring, and the rear flange cover are sequentially arranged outward from the outlet opening of the rotary fermenter. The second static friction ring is fixed to the outer wall of the discharge hopper connecting section. The second dynamic friction ring rotates with the rotary fermenter. Multiple discharge sealing plates are fixed around the outer periphery of the discharge hopper connecting section. The discharge sealing plates press the discharge hopper tightly against the rear flange cover through the second spring connector. The rear flange cover has a variable diameter section that covers the second dynamic friction ring and the second static friction ring. The variable diameter section is covered with a section of second sealing felt, which fits against the outer wall of the outlet end of the rotary fermenter.

16. The continuous dry anaerobic fermentation reactor according to claim 15, characterized in that, The second dynamic friction ring is pressed together by the second spring connector and the second static friction ring. During rotation, the dynamic and static rings cooperate to form a friction pair, and the sealing gap is less than 1mm, preventing gas leakage.

17. The continuous dry anaerobic fermentation reactor according to claim 15, characterized in that, The unloading sealing pressure plates are arranged in a ring on the unloading hopper connection section, with a quantity of 8 to 20. Two seals are set inside the rear flange cover. The first seal is a mechanical seal composed of a second static friction ring and a second dynamic friction ring. The second seal is a second sealing felt at the edge of the flange diameter change section to reduce biogas leakage from the inner sealing point.

18. The continuous dry anaerobic fermentation reactor according to claim 17, characterized in that, The second static friction ring is made of PTFE and is fixed to the rear flange cover. The second dynamic friction ring is a hard alloy composite layer.

19. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The support device includes a roller and a base. The rotary fermenter is supported on the base by the roller. The roller is rotatable and is mounted on the base. The support ring is fastened to the outer periphery of the rotary fermenter. The support ring of the rotary fermenter is in line contact with the roller. The roller is supported on the base by the roller bearing. There are two sets of rollers, two in each set, symmetrically arranged on both sides of the rotary fermenter.

20. The continuous dry anaerobic fermentation reactor according to claim 19, characterized in that, Each set of support rollers is located near both ends of the rotary drum fermenter, with the support ring at an angle of 30±10° to the vertical center line.

21. The continuous dry anaerobic fermentation reactor according to claim 11, characterized in that, The automatic temperature control device includes several temperature probes that extend into the rotary fermenter at different depths along the circumference, a wireless temperature acquisition device, a temperature control valve for controlling the steam flow, and a programmable logic controller.

22. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The steam jacket is fixedly installed on the base via a saddle, with a gap of 2-5 cm between it and the drum fermenter. The heating method is radiative heat transfer. A temperature control valve is installed on the inlet pipe of the steam jacket. Several temperature probes are used to measure the average temperature inside the drum fermenter. The measured temperature is transmitted to the programmable logic controller (PLC) via a wireless temperature acquisition device. The PLC sends a temperature adjustment signal to the temperature control valve and adjusts the steam flow rate in the steam jacket according to the temperature difference between the required fermentation temperature and the actual measured temperature.

23. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The drive unit is a variable frequency motor or a fixed frequency motor plus a reducer. The drive unit drives the drive gear to rotate through a worm gear. The drive gear is located on the outer wall of the cylinder and cooperates with the main gear on the rotary fermenter, thereby driving the rotary fermenter to rotate.

24. The continuous dry anaerobic fermentation reactor according to claim 23, characterized in that, The rotation speed of the rotary drum fermenter is 0.3~3 rpm.

25. The continuous dry anaerobic fermentation reactor according to claim 1, characterized in that, The unloading hopper is fixed to the base by ear seats. It is box-shaped or cylindrical with an inverted cone shape at the bottom. The side inlet of the unloading hopper is connected to the outlet of the rotary drum fermenter. A biogas emission port is set at the top of the unloading hopper, and a double-layer flap valve is set at the bottom outlet. The flap valve plate opens by the accumulation of material gravity and closes when there is no gravity.

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