A continuous dry method biological natural gas production device and process

Abstract

The present application belongs to the technical field of biomass energy production process, and particularly relates to a continuous dry method biogenic natural gas production device and method. The device can include a wet material storage pool, a dry material storage pool, a feed mixing bin, a screw conveyor, an adjusting pool, a pH adjusting tank, a first-stage continuous rotary fermentation device, a first-stage strain culture tank, a second-stage continuous rotary fermentation reactor, a solid-liquid separator, a second-stage strain expansion tank, an organic fertilizer production workshop, a discharge device, a desulfurization tower, a biogas gas cabinet, a CO2 storage tank, a membrane separation device and a natural gas storage tank. The present application improves the biogas production rate, volumetric gas production rate and agricultural waste resource utilization level by improving the multi-element raw material ratio, synchronous pretreatment, hierarchical rotary dry anaerobic fermentation, CO2 biological methanation, fermentation system instability early warning, biological carbon capture and storage and other technologies, obtaining green clean energy, and helping to improve the rural environment and achieve the carbon neutralization target.

Description

TECHNICAL FIELD

[0001] The application discloses a continuous dry method biological natural gas production device and process, and belongs to the technical field of biomass energy production processes. BACKGROUND

[0002] China is the world's largest producer and consumer of agricultural products, and the amount of agricultural waste resources generated annually is huge. Including about 900 million tons of collectable straw, and about 3.8 billion tons of total livestock manure, but the utilization rate of biogas is less than 10%. Greenhouse gases produced during straw burning and natural biomass decomposition are also the main source of agricultural carbon emissions in China. Biological natural gas can effectively replace fossil fuels and is recognized as a green renewable energy source. Utilizing straw, livestock manure, kitchen waste and other materials to produce biological natural gas is beneficial to solving the rural environmental and greenhouse gas emission problems in China and is of great significance to achieving the "double carbon" goal.

[0003] At present, the anaerobic fermentation method of biogas in China mainly uses CSTR wet fermentation, which is mature in technology, but also has many shortcomings such as low volumetric gas production rate, high energy consumption, high water consumption, large amount of biogas slurry production and difficulty in handling. Foreign advanced biological natural gas projects mostly use dry fermentation technology with a solid content of more than 20%. Continuous dry fermentation mainly uses long-axis stirring plug flow reactors, which have poor flowability of high-solid materials, difficulty in large-scale equipment, and poor adaptability to various complex biomass materials.

[0004] In addition, the existing biogas anaerobic fermentation system generally uses a single-stage fermentation reactor to complete the multi-stage fermentation process, and uses a single parameter for temperature, pH, carbon-nitrogen ratio, etc. in different fermentation stages; the inoculum uses backflow biogas slurry, lacks control means and instability early warning mechanism for the anaerobic microorganisms in the fermentation system, limits the improvement of volumetric gas production rate and methane production rate; the process automatic control precision is low; and the generated CO2 lacks effective collection, which cannot maximize the carbon negative emission benefits of the biomass energy carbon capture and storage (BECCS) technology. SUMMARY

[0005] To solve the above problems, the application designs a process system for continuous dry fermentation to produce biological natural gas, which uses a two-stage rotary drum fermentation tank as the main production unit. At the same time, a multi-element raw material mixing and pretreatment system, an inlet and outlet system, an engineering bacteria expansion and tracing monitoring system, a biogas purification and purification system, and a CO2 recovery system are matched with the rotary reactor. Compared with the existing biogas fermentation power, the process can greatly improve the volumetric gas production rate and methane production rate of the reactor, reduce the production cost of biological natural gas, and improve the carbon emission reduction benefits of the process.

[0006] The raw materials are pretreated before fermentation, reducing the residence time of the materials in the reactor. The biogas fermentation process is divided into two stages of acid production and methane production. The backflow sludge and steam flow are used to adjust the different temperature, moisture content, pH and carbon-nitrogen ratio parameters in the two-stage reactor, so that each stage can achieve the best fermentation efficiency. The rotary cylinder and the material lifting plate structure are used to replace the traditional long shaft stirrer, which avoids many defects of the plug flow reactor in engineering scale-up and improves the adaptability to the raw materials. Through the special design of the temperature control system, the efficient heat and mass transfer of the biomass raw materials in the anaerobic fermentation process can be realized. The GFP gene labeled engineering bacteria are added to the raw materials to improve the pretreatment efficiency, and the biomass of the fermentation system is traced and monitored to early warn the system instability. The hydrogen-feeding methane-producing bacteria are added to the backflow sludge to increase the methane content in the biogas and maximize the volumetric gas production rate of the reactor. Through effective collection of the generated CO2, the economic benefit and carbon negative emission benefit of the process are further improved, which is conducive to the large-scale commercial operation of the dry continuous fermentation process for producing bio-natural gas from agricultural waste.

[0007] The application provides a continuous dry bio-natural gas production process and device, which comprises a wet material storage pool, a dry material storage pool, a feed mixing bin, an adjusting pool, a first-stage continuous rotary fermentation device, a second-stage continuous rotary fermentation reactor, a desulfurization tower, a biogas gas tank, a membrane separation device and a natural gas storage tank,

[0008] The wet material storage pool and the dry material storage pool store multiple raw materials with different moisture contents, respectively, and are connected to the inlet of the feed mixing bin through pipelines or belts. The outlet of the feed mixing bin is connected to the inlet of the adjusting pool. The outlet of the adjusting pool is connected to the feed inlet of the first-stage continuous rotary fermentation reactor. The discharge outlet of the first-stage continuous rotary fermentation reactor is connected to the feed inlet of the second-stage continuous rotary fermentation reactor (for example, connected to the lower floor through a metal hose). The discharge bin of the second-stage continuous rotary fermentation reactor is connected to the desulfurization tower through a pipeline. The outlet of the desulfurization tower is connected to the inlet of the biogas gas tank. The outlet of the biogas gas tank is connected to the inlet of the membrane separation device. The gas outlet in the hollow fiber membrane tube of the membrane separation device is connected to the natural gas storage tank.

[0009] Preferably, the device of the application can further comprise a pH adjusting tank for adjusting the acidity and alkalinity of the feed raw materials.

[0010] Preferably, the device of the application can further comprise a first-stage bacterial strain culture tank connected to the adjusting pool.

[0011] Preferably, in the device of the present application, the bottom discharge port of the secondary continuous rotary fermentation reactor discharge bin is connected to the inlet of the solid-liquid separator, for example, through a belt conveyor to the inlet of the solid-liquid separator, the solid discharge port of the solid-liquid separator is connected to the organic fertilizer production workshop, the liquid outlet of the solid-liquid separator is respectively connected to the inlet of the secondary enhanced strain propagation tank and the biogas slurry reflux port of the primary rotary fermentation device discharge bin, and the outlet of the secondary enhanced strain propagation tank is connected to the biogas slurry reflux pipeline.

[0012] Preferably, the production device of the present application can further comprise a CO2 storage tank connected to the permeate gas outlet of the membrane separation device.

[0013] The primary continuous rotary fermentation reactor comprises a rotary drum fermentation tank, a screw feeder for feeding the rotary drum fermentation tank, a feed seal and a discharge seal for ensuring an anaerobic fermentation environment, a supporting device for supporting the rotary drum fermentation tank, a steam jacket wrapped outside the rotary drum fermentation tank and used for heating the rotary drum fermentation tank, a driving device for driving the rotary drum fermentation tank to rotate, and an automatic temperature control device for controlling the temperature in the rotary drum fermentation tank, and a discharge bin for discharge and / or exhaust.

[0014] The rotary drum fermentation tank has a rotation speed of 0.3-3 rpm, a filling coefficient of 0.3-0.7, and an inclination angle of 0.5-3° between the fermentation tank body and the horizontal direction, and the feed inlet is higher than the discharge outlet. A plurality of lifting plates are arranged in the rotary drum fermentation tank, extending from the inner wall of the rotary drum fermentation tank to the center of the rotary drum fermentation tank, and are spaced apart along the circumferential direction of the inner wall, preferably uniformly and equidistantly distributed, and arranged in 30-50 groups. The number of lifting plates in each group along the same circumferential section can be 4-12, preferably 6-10, and the length (radial direction of the rotary drum fermentation tank) is 0.2-0.3 times, preferably about 0.25 times, the diameter of the cylinder. The lifting plate structure is paddle-shaped, with the short side connected to the inner wall of the fermentation tank, the short side width being 0.075-0.015 times, preferably 0.01 times, the diameter of the fermentation tank cylinder, and the long side width being 4-8 times, preferably 5 times, the short side width. The residence time of the biomass raw material in the rotary drum fermentation tank is adjusted by changing the inclination angle of the cylinder and the rotation speed.

[0015] Preferably, the feeding device comprises a screw feeder and a feed sealing bin, both of which are connected through flanges and are fixed components, and the screw feeder is provided with a feed inlet at the front end.

[0016] Preferably, the feed seal and the discharge seal have the same structure, both of which are two-seal structures, comprising a mechanical seal composed of a pair of dynamic and static ring friction pairs and a sealing felt covering the gap between the fixed cylinder and the rotating cylinder. The dynamic and static rings are pressed by a sealing pressure plate and a spring, and the sealing gap is less than 1 mm.

[0017] The support device comprises a supporting wheel and a base such as a cement base, the supporting wheel is arranged on the base and is rotatable, a supporting ring is fastened to the outer periphery of the rotating drum fermentation tank, the supporting ring of the rotating drum fermentation tank is in linear contact with the supporting wheel, the supporting wheel is supported on the base by supporting wheel bearings, generally two groups, each group is located at the feeding side and the discharging side of the rotating drum fermentation tank respectively, each group is symmetrically arranged and is distributed on the two lateral sides of the rotating drum fermentation tank, and the supporting wheel is at an angle of 30°±10° with the vertical center line, preferably 30°.

[0018] Preferably, the steam jacket is fixed to the base by a saddle, the gap between the steam jacket and the cylinder of the rotating drum fermentation tank is 2-5 cm, the heating mode is radiation heat transfer, and a temperature control valve for controlling the steam flow is arranged on the inlet pipeline of the steam jacket.

[0019] The automatic temperature control device comprises a plurality of temperature probes arranged in the circumferential direction and extending into the rotating drum fermentation tank at different depths, a wireless temperature collector and a PLC (programmable logic controller). The plurality of temperature probes are used to measure the average temperature in the cylinder of the rotating drum fermentation tank, the measured temperature is transmitted to the PLC through the wireless temperature collector, the PLC sends a temperature control signal to the temperature control valve, and the steam flow in the steam jacket is adjusted according to the difference between the required fermentation temperature and the measured temperature.

[0020] The driving device can be a variable frequency motor or a fixed frequency motor with a speed reducer, the driving device drives the driving gear to rotate through a worm, the driving gear is arranged on the outer wall of the cylinder, for example, covering the entire circumference, and cooperates with the main gear on the rotating drum fermentation tank, so as to drive the rotating drum fermentation tank to rotate.

[0021] The discharging bin is a fixed component and is fixed to the base such as a cement base by an ear seat, generally in the shape of a box or a cylinder, the lower part is in the shape of an inverted cone (the lower part is usually a tapered part, for example, in the shape of an inverted truncated cone), and the side inlet of the discharging bin is in communication with the outlet of the rotating drum fermentation tank. A backflow biogas slurry inlet is arranged at the upper part of the discharging bin, and a double-layer flap valve is arranged at the lower outlet, the valve plate of the flap valve is opened by the accumulation of material gravity and is closed without gravity.

[0022] The primary fermentation device is mainly used for the pretreatment and acid production stage of anaerobic fermentation, and no gas is discharged during the period, and the secondary fermentation device is used for the methane production stage. The difference between the secondary continuous rotary fermentation reactor and the primary continuous rotary fermentation reactor lies in that the biogas outlet is arranged at the upper part of the discharging bin instead of the backflow biogas slurry inlet, and the rest of the structures are the same. The length ratio of the primary rotating drum fermentation tank to the secondary rotating drum fermentation tank is 1:1-1:2.5, preferably 1:1.5-1:2.

[0023] The application further provides a continuous dry method biogas production method using the above-mentioned continuous dry method biogas production device, comprising the following steps:

[0024] Step one, the multi-element biomass raw materials are classified and stored, the wet materials (preferably various types of livestock and poultry manure, kitchen garbage, etc.) are stored in a wet material storage pool, the dry materials (preferably, crushed crop silage straw, dry straw, and other lignocellulosic raw materials) are stored in a dry material storage pool, and the lignocellulosic raw materials are pretreated during storage. The pretreatment method can adopt an existing method for destroying the structure of lignin fibers, including one or more of biological methods, chemical methods, and physical methods.

[0025] Step two, the raw materials in the wet material storage pool are preferably transported to the feed mixing bin by a slurry pump, and the raw materials in the dry material storage pool are preferably transported to the feed mixing bin by a belt conveyor for premixing. After mixing, the solid content of the biomass raw materials is 18% to 45%, preferably 20% to 25%, and the carbon-nitrogen ratio is 20:1 to 30:1, preferably 25:1. After premixing, the raw materials are transported to a conditioning pool to adjust the pH of the raw materials to 6.0 to 8.5, preferably 6.8 to 7.4.

[0026] Preferably, the seed solution of anaerobically cultured GFP fluorescent protein marker Clostridium thermocellum is added in the conditioning pool.

[0027] Step three, the biomass raw materials enter a primary continuous rotary fermentation reactor for anaerobic acid-producing fermentation, perform spiral motion in the rotary drum fermentation tank, and gradually transfer to a discharge bin, and then enter a secondary continuous rotary fermentation reactor for methanogenic fermentation. The primary fermentation temperature is 30 to 35 DEG C, preferably 32 to 34 DEG C, the fermentation period is 2 to 10 days, preferably 3 to 7 days, the secondary fermentation temperature is 50 to 55 DEG C, preferably 53 to 55 DEG C, and the fermentation period is 5 to 20 days, preferably 6 to 12 days.

[0028] Step four, after biogas desulfurization, methane and CO2 are separated by a membrane separation device to obtain natural gas and industrial CO2 products, respectively. The products meet the biological natural gas standard and the industrial liquid CO2 standard, respectively.

[0029] The method can further include step five, after fermentation, the biogas residue is separated by solid-liquid separation, and the solid part is used for producing organic fertilizer. Preferably, the separated biogas slurry and the added engineering bacteria are mixed as a bacteria solution and then backflow to the outlet of the primary continuous rotary fermentation reactor, and part of the biogas slurry is used for hydrogen-producing methanogen expansion culture. The proportion of the biogas slurry used for expansion culture accounts for 3 to 10%, preferably 5 to 8%, of the total backflow biogas slurry. The engineering bacteria can be a high-temperature methanogen group, preferably a hydrogen-feeding methanogen group, which is screened and separated from the microbial community of the fermentation biogas slurry.

[0030] Advantages of the present application:

[0031] The present application has many advantages such as energy saving, water saving, high gas production efficiency, and high automation degree, which is beneficial to realize efficient resource utilization of agricultural organic waste.

[0032] (1) The process system of the present invention is based on the design of a continuous rotary fermentation reactor. The drum structure is applied to materials with high solid content, which overcomes many defects of the long shaft stirring structure, can effectively improve the volumetric gas production rate, adapt to complex biomass raw materials, and is easy to scale up in engineering.

[0033] (2) Two-stage reactors were designed for anaerobic acid production and methanogenic fermentation processes, respectively. Different fermentation microbial groups and operating parameters such as temperature, pH, and moisture content were adopted to improve fermentation efficiency and reduce production energy consumption.

[0034] (3) It has strong adaptability to raw materials and is suitable for co-fermentation of various organic wastes. The pretreatment process of raw materials is carried out in the storage unit, which reduces the residence time of materials in the reactor and reduces the energy consumption of pretreatment.

[0035] (4) GFP gene-marked strains were used to trace the microbial biomass and metabolic activity during anaerobic fermentation, and engineered strains were added to achieve partial biomethanation of H2 / CO2, thereby increasing the methane yield in biogas. (5) Temperature control, pH adjustment, online monitoring of biogas components, and early warning of fermentation system instability were employed.

[0036] The automated control of the entire production process has improved the level of digitalization in engineering.

[0037] (6) Membrane separation technology facilitates the collection of CO2 from biogas as an industrial byproduct, maximizing the carbon-negative emission benefits of biogas engineering as a BECCS technology. Attached Figure Description

[0038] Figure 1 This is a flow chart of the continuous dry biogas production process described in this invention.

[0039] Figure 2 This is a schematic diagram of the continuous rotary fermentation reactor described in this invention.

[0040] Figure 3 This is a schematic diagram of the cross-sectional structure of the continuous rotary fermentation reactor AA.

[0041] Figure 4 Schematic diagram of feed seal and discharge seal of continuous rotary fermentation reactor.

[0042] Figure 5 This is a diagram showing the sealing connection of the feed seal for a continuous rotary fermentation reactor.

[0043] Figure 6 This is a diagram showing the sealing connection for the discharge seal of a continuous rotary fermentation reactor.

[0044] Figure 7 This is a schematic diagram of the lifting plate structure of a continuous rotary fermentation reactor.

[0045] Numbering on the map:

[0046] 1-Wet material storage tank, 2-Dry material storage tank, 3-Feed mixing bin, 4-Screw conveyor, 5-Equalization tank

[0047] 6-pH adjustment tank, 7-primary continuous rotary fermentation reactor, 8-primary microbial culture tank, 9-secondary continuous rotary fermentation reactor, 10-solid-liquid separator, 11-secondary microbial culture expansion tank, 12-organic fertilizer production workshop, 13-discharge belt conveyor, 14-desulfurization tower, 15-biogas holder, 16-membrane separation device, 17-CO2 storage tank, 18-natural gas storage tank. Detailed Implementation

[0048] The present invention will be described in detail below.

[0049] This invention provides a continuous dry biogas production apparatus, such as... Figure 1 As shown, it includes a wet material storage tank 1, a dry material storage tank 2, a feed mixing bin 3, a regulating tank 5, a primary continuous rotary fermenter 7, a secondary continuous rotary fermenter 9, a desulfurization tower 14, a biogas holder 15, a membrane separator 16, and a natural gas storage tank 18.

[0050] The wet material storage tank 1 and the dry material storage tank 2 store multi-element raw materials with different moisture contents. The wet material storage tank 1 generally stores one or more of the following: livestock and poultry manure such as cow manure, pig manure, sheep manure, horse manure, chicken manure, duck manure, kitchen waste, etc. The solid content is generally below 30 wt%, especially below 20 wt%, and the carbon-nitrogen ratio is 10-20. The dry material storage tank 2 generally stores one or more of the following: silage straw, yellow silage straw, dry straw from crops (such as corn, rice, sorghum, wheat). The solid content is generally greater than 30 wt%, especially above 40 wt% or 50 wt%, and the carbon-nitrogen ratio is 50-70. The dry material storage tank 2 is connected to the feed inlet via a pipe or belt. The mixing silo 3 has an inlet, and its outlet is connected to the inlet of the equalization tank 5 via a screw conveyor 4. The outlet of the equalization tank 5 is connected to the inlet of the primary continuous rotary fermentation unit 7. The discharge port of the primary continuous rotary fermentation unit 7 is connected to the inlet of the secondary continuous rotary fermentation reactor 9 on the lower floor via a metal hose. The exhaust port of the discharge silo of the secondary continuous rotary fermentation reactor 9 is connected to the desulfurization tower 14 via a pipeline. The outlet of the desulfurization tower 14 is connected to the inlet of the biogas holder 15. The outlet of the biogas holder 15 is connected to the inlet of the membrane separator 16. The gas outlet in the hollow fiber tube of the membrane separator 16 (e.g., via a compressor) is connected to the natural gas storage tank 18.

[0051] The process system of this application may further include a pH adjustment tank 6 for changing the acidity or alkalinity of the materials in the adjustment tank 5.

[0052] The process system of this application may further include a primary microbial culture tank 8 connected to an equalization tank 5.

[0053] The process system of the present application can further comprise a bottom discharge port of a secondary continuous rotary fermentation reactor discharge bin connected to an inlet of a solid-liquid separator 10 via a discharge belt conveyor 13, a solid discharge port of the solid-liquid separator connected to an organic fertilizer production workshop 12 for aerobic composting production of organic fertilizer. A liquid outlet of the solid-liquid separator is respectively connected to an inlet of a secondary enhanced strain propagation tank 11 and a biogas slurry reflux port of a discharge bin of a primary rotary fermentation device 7, and an outlet of the secondary enhanced strain propagation tank 11 is connected to a biogas slurry reflux pipeline.

[0054] The process system of the present application can further comprise a CO2 storage tank 17, for example connected to a permeate gas outlet of the membrane separation device 16 via a compressor.

[0055] In the present application, the primary continuous rotary fermentation device 7, as shown in Figure 2 and Figure 3 , comprises a primary rotary drum fermentation tank 73, a feeding device for feeding the material into the rotary drum fermentation tank 73, a feeding seal and a discharge seal for ensuring an anaerobic fermentation environment, a supporting device for supporting the rotary drum fermentation tank, a steam jacket 75 wrapped outside the rotary drum fermentation tank and used for heating the rotary drum fermentation tank, a driving device 79 for driving the rotary drum fermentation tank 73 to rotate, and an automatic temperature control device 77 for controlling the temperature in the rotary drum fermentation tank, a discharge bin 78 for discharging and / or exhausting.

[0056] The rotary drum fermentation tank has a rotation speed of 0.3-3 rpm, a filling coefficient of 0.3-0.7, and an inclination angle of 0.5-3° between the fermentation tank body and the horizontal direction, and the feeding port is higher than the discharge port. A plurality of lifting plates 7301 are arranged in the rotary drum fermentation tank, extending from the inner wall of the rotary drum fermentation tank 73 to the center of the rotary drum fermentation tank 73, and are divided into a plurality of groups and distributed axially along the inner wall at intervals, preferably uniformly and equidistantly, and arranged in 30-50 groups. The number of lifting plates in each group along the same circumferential section can be 4-12, and the length (radial direction of the rotary drum fermentation tank) is 0.2-0.3 times, preferably 0.2-0.25 times, of the diameter of the cylinder. The lifting plate structure is paddle-shaped, as shown in Figure 3 、 Figure 7 , with the short side connected to the inner wall of the fermentation tank, the short side width being 0.075-0.015 times, preferably 0.01 times, of the diameter of the fermentation tank cylinder, and the long side width being 4-8 times, preferably 5-6 times, of the short side width. The residence time of the biomass raw material in the rotary drum fermentation tank is adjusted by changing the inclination angle of the cylinder and the rotation speed.

[0057] The inner diameter of the rotary drum fermentation tank is generally 3-6 meters, and the length of the rotary drum fermentation tank is generally 50-100 meters.

[0058] As shown in Figure 4As shown, the feeding device includes a screw feeder 71 and a feeding seal chamber 72, both of which are connected by flanges, are fixed parts, are supported by a feeder support 7102 and a feeding seal support 7201, and the front end of the screw feeder 71 is provided with a feeding port 7101.

[0059] The feeding seal structure of the primary and secondary drum fermentors is the same, and the feeding seal of the primary drum fermentor is described. The feeding seal includes a feeding seal chamber 72, a first dynamic friction ring 73042, a first static friction ring 73041, and a front end gland flange 7304, as shown in Figure 5 As shown, the feeding seal chamber 72 is a cylindrical fixed part, one end of which extends into the inlet end opening of the drum fermentor 73, and the other end is connected to the end of the screw feeder 71. The first dynamic friction ring 73042, the first static friction ring 73041, and the front end gland flange 7304 are sequentially arranged outwardly at the port of the drum fermentor 73. The first static friction ring 73042 is fixed to the outer wall of the cylinder of the feeding seal chamber 72, and the first dynamic friction ring 73042 rotates with the cylinder of the drum fermentor. A plurality of feeding seal pressure plates 7202 are fixed around the outer periphery of the feeding seal chamber 72. The feeding seal pressure plates 7202 further press the feeding seal chamber 72 against the front end gland flange 7304 through first spring connecting pieces 72021. The front end gland flange 7304 is provided with a variable diameter section covering the first dynamic friction ring 73042 and the first static friction ring 73041. The variable diameter section further covers a section of the first sealing felt 73043 and is in close contact with the outer wall of the inlet end of the drum fermentor 73. The dynamic friction ring is pressed tightly by the spring connecting piece and the static friction ring. During rotation, the dynamic and static friction rings form a friction pair. The sealing gap is less than 1 mm, which prevents gas leakage. The feeding seal pressure plates 7202 and the feeding seal chamber 72 are connected by bolts, and the sealing gap is adjusted by the spring connecting pieces 72021 and the bolts.

[0060] Preferably, the feeding seal pressure plates 7202 are arranged in a ring on the feeding seal chamber 72, and the number is 8-20. The front end flange gland 7304 is provided with two seals. The inner seal is a mechanical seal composed of the first static friction ring 73041 and the first dynamic friction ring 73042. The first static friction ring 73041 is made of PTFE, and the first dynamic friction ring 73042 is a hard alloy composite layer, which is compounded on the front end of the cylinder of the drum fermentor 73. The outer seal increases a section of the first sealing felt 73043 behind the variable diameter section of the flange, which reduces the leakage of gas from the first sealing point.

[0061] Preferably, the screw feeder extends into the feeding port and is connected by a flange. The screw feeder is fixed to the cement foundation by the support 7102. The feeding seal chamber is further provided with a feeding seal support 7201, which is fixed to the cement foundation and serves to fix the feeding seal chamber.

[0062] As shown in Figure 6As shown, the discharge seal includes a rear flange cover 7305, a second dynamic friction ring 73052, a second static friction ring 73051, a second sealing felt 73053, a discharge seal pressing plate 7804 and a second spring connecting piece 78041. The discharge bin 78 is provided with a cylindrical connecting section extending into the outlet opening of the rotating drum fermentation tank 73. The second dynamic friction ring 73052, the second static friction ring 73051 and the front flange cover 7305 are sequentially arranged outward from the outlet opening of the rotating drum fermentation tank 73. The second static friction ring 73051 is fixed to the outer wall of the connecting section of the discharge bin 78. The second dynamic friction ring 73052 rotates with the drum body of the rotating drum fermentation tank 73. A plurality of discharge seal pressing plates 7804 are fixed around the outer periphery of the discharge section of the discharge bin 78. The discharge seal pressing plate 7804 further presses the discharge bin against the rear flange cover 7305 through the second spring connecting piece 78041. The rear flange cover 7305 is provided with a variable diameter section covering the second dynamic friction ring 73052 and the second static friction ring 73051. The variable diameter section further covers a section of the second sealing felt 73053 and is attached to the outer wall of the outlet of the rotating drum fermentation tank 73. The second dynamic friction ring is pressed by the second spring connecting piece and the second static friction ring. The dynamic and static rings form a friction pair during rotation. The sealing gap is less than 1 mm, which prevents gas leakage. The discharge seal pressing plate 7804 and the discharge bin 78 are connected by bolts. The sealing gap is adjusted by the second spring connecting piece 78041 and the bolts.

[0063] Preferably, the discharge seal pressing plates 7804 are annularly arranged on the discharge bin, with a number of 8-20. Two seals are arranged in the rear flange cover 7305. The inner seal is a mechanical seal composed of the second static friction ring 73051 and the second dynamic friction ring 73052. The second static friction ring 73051 is made of PTFE. The second dynamic friction ring 73052 is a hard alloy composite layer, which is combined with the rear end of the drum body of the rotating drum fermentation tank 73. The outer seal increases a section of the second sealing felt 73053 at the rear of the variable diameter section of the flange, which reduces the gas leakage from the first leakage point.

[0064] The feed seal and the discharge seal ensure the anaerobic environment in the fermentation tank and increase the reliability of the seal.

[0065] The support device includes a carrier wheel 74 and a cement base 710. The carrier wheel 74 is rotatably arranged on the cement base 710. The support ring 7302 is fastened to the outer periphery of the first rotating drum fermentation tank 73. The support ring 7302 of the rotating drum fermentation tank 73 is in line contact with the carrier wheel 74. The carrier wheel 74 is supported on the base by carrier wheel bearings 7401. Generally, there are two groups, each with two symmetrically arranged groups, which are distributed on the transverse sides of the rotating drum fermentation tank. For example, each group can be arranged near the two ends of the rotating drum fermentation tank 73. The included angle between the support wheel and the center line is 30°±10°, preferably 30°.

[0066] The steam jacket is fixed on the cement base 710 by a saddle 7502, and the gap between the cylinder of the rotating drum fermenter 73 and the steam jacket is 2-5 cm. The heating mode is radiation heat transfer. A temperature control valve 7501 is arranged on the inlet pipeline of the steam jacket 75 to adjust the flow of steam.

[0067] The automatic temperature control device 77 includes a plurality of temperature probes extending into the rotating drum fermenter 73 at different depths, a wireless temperature collector, and a PLC (programmable logic controller). The plurality of temperature probes are used to measure the average temperature in the cylinder of the rotating drum fermenter 73. The measured temperature is transmitted to the PLC through the wireless temperature collector, and the PLC sends a temperature control signal to the temperature control valve 7501. According to the temperature difference between the required fermentation temperature and the actual measured temperature, the flow of steam in the steam jacket 75 is adjusted.

[0068] The driving device 79 can be a variable frequency motor or a fixed frequency motor with a speed reducer. The driving device drives the driving gear 76 through a worm, and the driving gear is arranged on the outer wall of the cylinder and covers the entire circumference. It cooperates with the main gear on the rotating drum fermenter 73 to drive the rotating drum fermenter 73 to rotate.

[0069] The discharge bin 78 is a fixed component, which is fixed to the base by an ear seat 7803, and is generally box-shaped or cylindrical. The lower part is inverted conical (the lower part is usually tapered, such as inverted truncated conical). The side inlet of the discharge bin 78 is in communication with the outlet of the rotating drum fermenter 73. The upper part (usually the side opposite to the side connected to the outlet of the rotating drum fermenter 73) of the discharge bin 78 is provided with a backflow biogas inlet 7801, and the lower outlet is provided with a double-layer flap valve 7802. The valve plate of the flap valve 7802 is opened by the accumulation of material gravity, and is closed under the action of gravity.

[0070] The primary fermentation device is mainly used for pretreatment and acid production stage of anaerobic fermentation, and no gas is discharged during the period. The secondary fermentation device is used for methane production stage. The difference between the structure of the secondary continuous rotating drum fermentation reactor and the structure of the primary continuous rotating drum fermentation reactor 7 is that the biogas outlet is arranged on the upper part of the discharge bin 78 of the secondary continuous rotating drum fermentation device instead of the backflow biogas inlet 7801, which is used for discharging biogas. The rest of the structure is the same. The length ratio of the primary and secondary rotating drum fermenters is 1:1-1:2.5, preferably 1:1.5-1:2.

[0071] In a specific implementation, the entire fermentation system is sterilized by passing steam into the system before production. The multiple biomass raw materials are classified and stored. Livestock and poultry manure, kitchen waste, and the like are stored in a wet material storage tank 1. Crop silage straw, dry straw, and the like are stored in a dry material storage tank 2 after being crushed. During the storage process, alkali pretreatment, acid pretreatment, or biological pretreatment is used to preliminarily decompose the lignocellulose raw materials and remove part of the lignin. The raw materials in the wet material storage tank 1 are delivered to a feed mixing bin 3 by a slurry pump, and the raw materials in the dry material storage tank 2 are delivered to the feed mixing bin 3 by a belt conveyor. After mixing, the solid content of the biomass raw materials is 18% to 45%, preferably 20% to 25%, the carbon-nitrogen ratio is 20:1 to 30:1, and preferably 22:1 to 28:1, for example, about 25:1. After the preliminary mixing, the raw materials are delivered to a two-layer conditioning tank 5 by a screw conveyor 4.

[0072] A culture medium with cellobiose and urea as carbon and nitrogen sources is added to a primary strain culture tank 8, and Clostridium thermocellum (DSM5812, German Collection of Microorganisms and Cell Cultures) marked with GFP fluorescent protein is anaerobically cultured. The seed liquid is added to the conditioning tank 5 to improve the biomass degradation efficiency and monitor the biomass in the fermentation process through the tracing of the fluorescent protein to provide an early warning system for instability. An acid or alkali is added to the pH adjustment tank 6 according to the pH value of the mixed raw materials to adjust the pH of the raw materials to 6.0 to 8.5, and preferably 6.8 to 7.4.

[0073] The lower part of the conditioning tank 5 is connected to the feed inlet of a primary rotary fermentation device 7. The biomass raw materials enter the primary rotary drum fermentation tank. The rotation speed of the fermentation tank is 0.3 to 3 rpm, the filling coefficient is 0.3 to 0.7, the inclination angle of the primary rotary drum fermentation tank 73 with respect to the horizontal direction is 0.5 to 3°, the feed inlet is higher than the discharge outlet of the tank body, and the material is ensured to move in a spiral manner in the primary rotary drum fermentation tank 73 and gradually transfer to the discharge bin 78. The primary fermentation is mainly an acid-producing anaerobic fermentation process. The fermentation temperature is 30 to 35°C, and preferably 32 to 34°C. After 3 to 7 days of fermentation, the material enters the discharge bin. The double-layer flap valve 7802 in the lower part of the discharge bin 78 automatically opens and resets under the action of gravity, and the material falls into a two-layer secondary continuous rotary fermentation reactor. The rotation speed, filling coefficient, and downward inclination angle of the secondary rotary drum fermentation tank are the same as those of the primary rotary drum fermentation tank 73 to ensure that the material does not block. The secondary fermentation is a methane-producing process. The fermentation temperature is 50 to 55°C, and preferably 53 to 55°C. The fermentation time is 6 to 12 days.

[0074] After fermentation, the biogas residue enters the discharge bin 78, is transported to the solid-liquid separator 10 by the discharge belt conveyor 13, the separated solids enter the organic fertilizer production workshop 12, and after aerobic fermentation and drying, the organic fertilizer product is obtained, and a small part of the separated biogas slurry is branched to the secondary strain expansion tank 11, the hydrogen-producing methanogenic bacteria (mainly Methanosaeta and Methanosarcina) are expanded and cultured, the expanded seed liquid is mixed with the unbranched biogas slurry, the separated biogas slurry and the added engineering strain are mixed as the bacteria liquid and then backflow to the first-stage rotating fermentation device discharge bin backflow biogas slurry inlet 7801, the proportion of the biogas slurry for expansion accounts for 3-10% of the total backflow biogas slurry, and preferably 5-8%. The flow rate of the seed liquid is adjusted by the outlet flow valve of the secondary strain expansion tank 11, and the addition of the engineering strain can convert part of the CO2 generated in the fermentation process into methane, thereby improving the methane yield, and the opening degree of the flow valve is adjusted according to the methane content in the discharged gas monitored online.

[0075] The gas outlet of the secondary continuous rotating fermentation reactor discharge bin 78 is periodically opened to discharge biogas, the biogas is purified by the desulfurization tower 14 and then enters the biogas gas tank for storage 15, the biogas is then purified by the membrane separation device 16, the CO2 gas mainly permeates through the hollow fiber membrane, the gas is compressed, dried and liquefied to obtain an industrial CO2 product, which is stored in the CO2 storage tank 17, and the permeated gas is a biological natural gas product, which is compressed and stored in the natural gas storage tank 18.

[0076] Embodiment

[0077] The fresh corn straw is crushed into particles with a diameter of 2 mm and a length of about 20 mm, KOH is added at a proportion of 1.5% of the mass of the raw material, and the mixture is uniformly mixed and compacted for storage in a dry material storage pool. During storage, the leachate is discharged and recycled every day after recovering the alkali and lignin, and the leachate is repeatedly washed with water. After being stored in the silo for 15 days, the material is taken out, and the storage time is at most 300 days to meet the production needs throughout the year. The cow dung is pre-dehydrated in a wet material storage pool and mixed with the ensiled corn straw in a feed pre-mixing pool. After mixing, the average solid content is 26%, and the carbon-nitrogen ratio of the raw material is 25:1. The mixture is sent to a conditioning pool by a screw conveyor, inoculated with GFP fluorescent protein-labeled Clostridium thermocellum (DSM5812, German strain preservation center), the inoculation amount is 0.2% of the amount of the raw material feed, and then sent to a first-stage continuous rotating fermentation device after adjusting the pH to 7.2. The material is mixed and acid-producing fermented under the action of the rotating cylinder and the lifting plate, the fermentation temperature is 33°C, the volume of the fermentation tank is 1050 m 3 , the rotating speed is 1 rpm, the horizontal downward inclination is 1.5°, the filling coefficient is 0.6, and the hydraulic retention time is 3 days. After that, the material enters a second-stage rotating fermentation tank for methanogenic fermentation. The volume of the second-stage fermentation tank is 1800 m 3 , the rotating speed and the horizontal downward inclination are the same as those of the first-stage fermentation tank, the fermentation temperature is 55°C, the hydraulic retention time is 5 days, and the volumetric gas production rate is 4.4 m 3 / m 3• d. The methane content in the biogas is 65%, and the biogas is purified by chemical absorption method and stored in a biogas tank. The biogas is pressurized to 1.4 MPa, purified by a hollow fiber membrane, and the CO2 content in the permeate gas is greater than 99%. The permeate gas is collected, pressurized and liquefied as an industrial grade CO2 product, and the retentate gas is a bio-natural gas product with a methane content of 98%. The steam heat in the plant is provided by a natural gas boiler, the self-use rate of natural gas is 4%, and the rest is pressurized and sold as CNG. The daily supply of natural gas is 8000 Nm 3 The fluorescence value of the digested residue is sampled and analyzed, and compared with the fluorescence value of the feedstock to monitor whether the fermentation system is unstable. The solid part of the digested residue is used to produce organic fertilizer, and the organic fertilizer contains 73% of solid content, 38% of organic matter content, and 7.5% of total nitrogen, phosphorus and potassium. 6% of the separated digested liquid is introduced into a secondary strain expansion tank to expand the hydrogen-feeding methanogen population (mainly Methanocella and Methanosarcina). During the expansion process, 1.1 liters of hydrogen gas are introduced into each liter of digested liquid, and the mixed seed liquid and the remaining digested liquid are added to the discharge port of the primary fermentation tank.

[0078] Comparative Example 1

[0079] The same conditions as in the example are used, the fermentation tank uses a long-axis stirring type fermentation device, the fermentation temperature is 55°C, and the fermentation time is extended to 11 days. The volumetric gas production rate is 3.0 m 3 / m 3 ·d.

[0080] Comparative Example 2

[0081] The same conditions as in the example are used, a single-stage continuous rotary fermentation device is used, the fermentation temperature is 55°C, and the volumetric gas production rate is 4.2 m 3 / m 3 ·d, and the steam energy consumption increases by 14%.

[0082] Comparative Example 3

[0083] The same conditions as in the example are used, and no hydrogen-feeding methanogenic engineering bacteria are added, and the methane content in the biogas is reduced from 65% to 55%.

[0084] Obviously, the above examples are only examples for the sake of clarity, and are not limitations on the embodiments. Based on the above description, other different forms of changes or variations can also be made by those of ordinary skill in the art. It is not necessary or possible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A continuous dry biogas production unit, characterized in that... It includes a wet material storage tank (1), a dry material storage tank (2), a feed mixing bin (3), an equalization tank (5), a primary continuous rotary fermentation reactor (7) for the pretreatment and acid production stage of anaerobic fermentation, a secondary continuous rotary fermentation reactor (9) for the methanogenic stage, a desulfurization tower (14), a biogas holder (15), a membrane separation device (16), and a natural gas storage tank (18). Among them, the wet material storage tank (1) and the dry material storage tank (2) store multi-element raw materials with different moisture contents respectively. They are connected to the inlet of the feed mixing silo (3) through pipes or belts. The outlet of the feed mixing silo (3) is connected to the inlet of the regulating tank (5). The outlet of the regulating tank (5) is connected to the feed inlet of the first-stage continuous rotary fermentation reactor (7). The discharge port of the first-stage continuous rotary fermentation reactor is connected to the feed inlet of the second-stage continuous rotary fermentation reactor (9). The exhaust port of the discharge silo of the second-stage continuous rotary fermentation reactor is connected to the desulfurization tower (14) through a pipe. The outlet of the desulfurization tower is connected to the inlet of the biogas holder (15). The outlet of the biogas holder (15) is connected to the inlet of the membrane separation device (16). The gas outlet in the hollow fiber membrane tube of the membrane separation device is connected to the natural gas storage tank (18). Add anaerobic cultured GFP fluorescent protein-labeled Clostridium thermocellum seed solution to the conditioning tank. The continuous dry biogas production unit further includes a pH adjustment tank (6) for adjusting the acidity or alkalinity of the feedstock; The continuous dry biogas production unit further includes a primary culture tank (8) connected to the equalization tank. The bottom discharge port of the secondary continuous rotary fermentation reactor is connected to the inlet of the solid-liquid separator (10) via a belt conveyor. The solid discharge port of the solid-liquid separator is connected to the organic fertilizer production workshop (12). The liquid outlet of the solid-liquid separator is connected to the inlet of the secondary enhanced microbial culture tank (11) and the biogas slurry return port of the primary rotary fermentation unit discharge silt, respectively. The outlet of the secondary enhanced microbial culture tank is connected to the biogas slurry return pipeline. The continuous dry biogas production unit further includes a CO2 storage tank (17) connected to the permeate gas outlet of a membrane separation unit (16); The primary continuous rotary fermentation reactor includes a rotary drum fermenter (73), a feeding device for feeding materials into the rotary drum fermenter, a feeding seal and a discharging seal for ensuring an anaerobic fermentation environment, a support device for supporting the rotary drum fermenter, a steam jacket (75) wrapped around the outside of the rotary drum fermenter and used for heating the rotary drum fermenter, a drive device (79) for driving the rotary drum fermenter to rotate, an automatic temperature control device (77) for controlling the temperature inside the rotary drum fermenter, and a discharge hopper (78) for unloading and / or venting. The secondary continuous rotary fermentation reactor differs from the primary continuous rotary fermentation reactor in that a biogas outlet is set at the top of the discharge hopper to replace the reflux biogas slurry inlet for discharging biogas. The rest of the structure is the same. The length ratio of the rotary drum fermenter in the primary continuous rotary fermentation reactor to the rotary drum fermenter in the secondary continuous rotary fermentation reactor is 1:1 to 1:2.

5. The feeding device includes a screw feeder (71) and a feeding sealed chamber (72), which are connected by a flange and are both fixed components. The screw feeder has a feed port at the front end. The feed seal and discharge seal have the same structure, both being a two-seal structure, including a mechanical seal consisting of a pair of dynamic and static ring friction pairs and a sealing felt covering the gap between the fixed cylinder and the rotating cylinder. The dynamic and static rings are pressed together by a sealing plate and a spring, and the sealing gap is less than 1mm.

2. The continuous dry biogas production apparatus according to claim 1, characterized in that, The length ratio of the rotary fermenter in the primary continuous rotary fermentation reactor to that in the secondary continuous rotary fermentation reactor is 1:1.5 to 1:

2.

3. The continuous dry biogas production apparatus according to claim 1, characterized in that, The rotary drum fermenter rotates at a speed of 0.3~3 rpm, with a filling coefficient of 0.3~0.

7. The inclination angle between the fermenter body and the horizontal direction is 0.5~3°. The feed inlet is higher than the discharge outlet. Inside, there are lifting plates (7301) that extend radially from the inner wall of the rotary drum fermenter toward the center of the rotary drum fermenter. They are evenly distributed along the circumference of the inner wall, with 30~50 sets. Each set of lifting plates has 4~12 pieces along the same circumferential cross section, and the length is 0.2~0.3 times the diameter of the cylinder.

4. The continuous dry biogas production apparatus according to claim 3, characterized in that, The lifting plate has a paddle-type structure, with its short side connected to the inner wall of the fermentation tank. The width of the short side is 0.015 to 0.075 times the diameter of the fermentation tank, and the width of the long side is 4 to 8 times the width of the short side; and / or The residence time of biomass feedstock in the rotary drum fermenter can be adjusted by changing the tilt angle of the drum and the rotation speed.

5. The continuous dry biogas production apparatus according to claim 3, characterized in that, The length is 0.25 times the diameter of the cylinder.

6. The continuous dry biogas production apparatus according to claim 1, characterized in that, The support device includes a support roller (74) and a base (710). The support roller (74) is mounted on the base (710) and can rotate. The support ring (7302) is fastened to the outer periphery of the rotary drum fermenter. The support ring (7302) of the rotary drum fermenter is in line contact with the support roller (74). The support roller (74) is supported on the base (710) by the support roller bearing. There are two sets, with two symmetrically arranged in each set, distributed on the transverse sides of the rotary drum fermenter. The angle between the support roller and the vertical center line is 30°±10°.

7. The continuous dry biogas production apparatus according to claim 1, characterized in that, The steam jacket (75) is fixed to the base by the saddle (7502), and the gap between it and the cylinder of the rotary drum fermenter is 2~5cm. The heating method is radiative heat transfer. The inlet pipe of the steam jacket is equipped with a temperature control valve (7501) for controlling the steam flow.

8. The continuous dry biogas production apparatus according to claim 1, characterized in that, The automatic temperature control device includes several temperature probes extending into the rotary fermenter at different depths along the circumference, a wireless temperature acquisition device, and a programmable logic controller (PLC). The temperature probes are used to measure the average temperature inside the rotary fermenter. 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 and adjusts the steam flow in the steam jacket according to the required fermentation temperature and the measured temperature difference.

9. The continuous dry biogas production apparatus according to claim 1, characterized in that, The drive device (79) is a variable frequency motor or a fixed frequency motor plus a reducer. The drive device drives the active gear to rotate through the worm gear. The active 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, thereby driving the rotary fermenter to rotate.

10. The continuous dry biogas production apparatus according to claim 1, characterized in that, The unloading hopper (78) is a fixed component, which is fixed to the base by the ear seat. 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. The upper part of the unloading hopper is equipped with a reflux biogas slurry inlet, and the lower outlet is equipped with a double-layer flap valve (7802). The flap valve plate opens by the accumulation of material gravity and closes when there is no gravity.

11. A method for producing continuous dry biogas using the continuous dry biogas production apparatus according to any one of claims 1-10, comprising the following steps: Step 1: Store wet biomass raw materials in a wet storage tank and dry biomass raw materials in a dry storage tank. Lignocellulose raw materials are pretreated during storage. The pretreatment method is to destroy the lignin fiber structure, including one or more of the following: biological method, chemical method, and physical method. Step 2: The raw materials in the wet material storage tank and the raw materials in the dry material storage tank are transported to the feed mixing silo for premixing. After mixing, the solid content of the biomass raw materials is 18%~45%, and the carbon-nitrogen ratio is 20:1~30:

1. After premixing, the raw materials are transported to the equalization tank to adjust the pH of the raw materials to 6.0~8.

5. Step 3: The biomass raw material enters the primary continuous rotary fermentation reactor for anaerobic acid production fermentation. It moves in a spiral motion in the rotary fermenter and is gradually transferred to the unloading hopper. Then it enters the secondary continuous rotary fermentation reactor for methanogenic fermentation. The primary fermentation temperature is 30~35℃ and the fermentation cycle is 2~10 days. The secondary fermentation temperature is 50~55℃ and the fermentation cycle is 5~20 days. Step 4: After biogas desulfurization, methane and CO2 are separated by a membrane separation device to obtain natural gas and industrial CO2 products, respectively.

12. The continuous dry biogas production method according to claim 11, characterized in that, In step two, the solid content of the mixed biomass feedstock is 20%~25%, the carbon-nitrogen ratio is 25:1, and the pH of the feedstock is adjusted to 6.8~7.4; In step three, the primary fermentation temperature is 32~34℃ and the fermentation period is 3~7 days. The secondary fermentation temperature is 53~55℃ and the fermentation period is 6~12 days.

13. The continuous dry biogas production method according to claim 11, further comprising: Step 5: After fermentation, the biogas residue is separated into solid and liquid components. The solid portion is used to produce organic fertilizer. The separated biogas slurry is mixed with the added engineered bacteria and used as an inoculum to be returned to the outlet of the first-stage continuous rotary fermentation reactor. A portion of the biogas slurry is used for hydrogenation and expansion of the engineered bacteria. The proportion of biogas slurry used for expansion accounts for 3-10% of the total returned biogas slurry.

14. The continuous dry biogas production method according to claim 13, characterized in that, The engineered bacterial strain is a thermophilic methanogenic bacteria.

15. The continuous dry biogas production method according to claim 14, characterized in that, The engineered strain is a hydrogen-eating methanogenic bacteria group, which was screened and isolated from the microbial community of fermentation slurry.

Images