NL2037125B1

NL2037125B1 - Fermentation system with two-phase dry anaerobic digestion

Info

Publication number: NL2037125B1
Application number: NL2037125A
Authority: NL
Inventors: Wang Yu; Liu Shiming; Wang Xun; Xiao Bo; Wang Xiuping; Jia Yongsheng; Huang Lei; Gao Biao; Dai Jinming; Hu Zhiquan
Original assignee: Univ Huazhong Science Tech
Priority date: 2024-02-27
Filing date: 2024-02-27
Publication date: 2024-10-14

Abstract

The present invention is suitable for the field of biogas fermentation technologies, and provides a fermentation system with two-phase dry anaerobic digestion, including: a hydrolysis acidification pool, a methanation pool, a composting reactor and a heat exchange device. Compared with the prior art, first, the present invention combines a biogas fermentation technology with a composting technology, and uses heat generated during composting to provide heat required for biogas fermentation for the hydrolysis acidification pool and the methanation pool, without other additional heating facilities such as an electric heating film and a biogas boiler; second, biogas residues produced in the methanation pool can be used as a raw material for aerobic composting for subsequent production of an organic fertilizer; and third, in a whole reaction system, digestive raw materials flows automatically depending on a self-weight and a pressure difference, without an additional feeding and discharging device.

Description

FERMENTATION SYSTEM WITH TWO-PHASE DRY ANAEROBIC DIGESTION

TECHNICAL FIELD

The present invention belongs to the field of biogas fermentation technologies, and provides a fermentation system with two-phase dry anaerobic digestion.

BACKGROUND

Biogas anaerobic fermentation can convert various breeding wastes and plant wastes to biogas at a low cost. A methane content in the biogas is generally 60%, and the rest is mainly carbon dioxide. After removal of the carbon dioxide, artificial natural gas with the methane content of 90% may be obtained. It can be seen that it is an energy development path pointed out by the nature for human beings. With the improvement of rural living standards in China, treatment on domestic wastes, toilet manures, and agricultural and forestry organic solid wastes has become an urgent task for China to improve the rural living environment and build beautiful and livable villages. Using a dry anaerobic fermentation technology to reduce and recycle the rural domestic wastes, toilet manures, and agricultural and forestry organic wastes is a new way to improve the rural living environment and build the beautiful and livable villages in China. It is also a technical problem that must be solved in treatment on multi-source organic wastes in villages and towns in China.

In order to increase the production capacity of a biogas pool, the dry fermentation technology of mesophilic or thermophilic fermentation is often used. Dry anaerobic fermentation features high gas production, stable gas production, wide material adaptability and capability of using livestock and poultry manures, agricultural and forestry wastes and food wastes as digestive materials. Meanwhile, there is basically no biogas slurry discharged in the whole fermentation process, which avoids secondary pollution. However, the dry fermentation technology often requires medium and high temperatures. If the temperature is lower than 10°C, the activity of fermentation bacteria in the biogas slurry is inhibited, and the ability of the biogas pool producing the biogas is extremely weak. Therefore, in the mesophilic and thermophilic dry fermentation technology, a temperature raise and thermal insulation of the biogas pool are key problems to be solved, and there is a need for additional energy consumption for thermal insulation and temperature raise. At present, the technical methods and measures for thermal insulation of the biogas pool mainly include electric heating film covering, biogas boiler auxiliary heating, solar heating, etc.

In implementation of the above technical solution, the applicant of the present invention finds that the above technical solution has at least the following defects:

The conventional biogas fermentation technology is greatly affected by a climate change; while the use of external energy to supplement and raise the temperature of the biogas pool has the problems of large prophase investment and high operation and maintenance costs, and thus is difficult to be widely used and popularized in villages and towns.

SUMMARY

An objective of the embodiments of the present invention is to provide a fermentation system with two-phase dry anaerobic digestion, aiming to solve the problems mentioned in

Background.

The embodiments of the present invention are such implemented that a fermentation system with two-phase dry anaerobic digestion includes: a hydrolysis acidification pool, containing hydrolysis acidification bacteria and used for performing hydrolysis acidification treatment on materials; a methanation pool, containing methanogenic bacteria, where the methanation pool communicates with the hydrolysis acidification pool for facilitating digestive raw materials after hydrolysis acidification to automatically flow into the methanation pool by means of a self-weight and a pressure difference, and making the digestive raw materials decomposed into biogas slurry, biogas residues and biogas here; a composting reactor, used for performing composting treatment on a mixture of the biogas residues and the biogas slurry produced in the methanation pool and a specific raw material, where heat energy generated during composting is supplied to a heat exchange device; a heat exchange device, using the heat energy from a composting reaction pool to make the hydrolysis acidification pool and the methanation pool keep at a predetermined temperature; a sensor system, including sensors used for monitoring pH values, temperatures, flow rates and pressures are mounted in the hydrolysis acidification pool and the methanation pool; an automatic control unit, including a microcontroller or a programmable logic controller that is used for integrating data from the sensors and achieving automatic control of the system; and a data analysis and optimization module, used for integrating data analysis software, automatically adjusting working parameters according to real-time data provided by the sensors and optimizing a fermentation process.

The fermentation system with two-phase dry anaerobic digestion further includes: a remote monitoring system that can be connected by means of the Internet, allowing an operator to remotely view and control a state of the fermentation system with two-phase dry anaerobic digestion; an intelligent fault diagnosis module, integrated with an intelligent diagnosis algorithm, and used for timely discovering and reporting a potential problem of the system, where the module relies on the real-time data provided by the sensor system for fault analysis; and a user interface, providing an intuitive user interface to make the operator easily access to state information, a warning, and a diagnostic report of the system.

System integration: the monitoring and diagnosis system is integrated with the components of the above fermentation system with two-phase dry anaerobic digestion to achieve comprehensive system monitoring and intelligent management.

Preferably, a predetermined proportion of the biogas slurry is added to the materials entering the hydrolysis acidification pool; and sediments and scum produced in the hydrolysis acidification pool and the biogas residues produced in the methanation pool are jointly transferred to the composting reactor for composting treatment.

Preferably, sources of heat energy of the heat exchange device further include a biogas boiler, solar energy or electric energy.

Preferably, the heat exchange device includes: a heat exchanger, used for acquiring heat energy generated by the composting reactor during composting; a first medium circulation container, communicating with the heat exchanger, where a medium with a first temperature value generated in the heat exchanger is supplied to the first medium circulation container; a second medium circulation container, communicating with the heat exchanger, where a medium with a second temperature value in the second medium circulation container is supplied to the heat exchanger, and the first temperature value is larger than the second temperature value; a first jacket, arranged on an outer surface of the hydrolysis acidification pool, where the first jacket communicates with the first medium circulation container and the second medium circulation container; a heat exchange coil, arranged inside the hydrolysis acidification pool, where the heat exchange coil communicates with the first medium circulation container and the second medium circulation container; and a second jacket, arranged on an outer surface of the methanation pool, where the second jacket communicates with the first medium circulation container and the second medium circulation container.

Preferably, the heat exchange device has a heat exchange mode of wall-type heat exchange, and includes an in-barrel heat exchanger and an out-barrel heat exchanger; the in- barrel heat exchanger includes a heat exchange coil and a central main pipe heat exchanger with circulating branch pipes; the central main pipe heat exchanger with the circulating branch pipes includes a central main pipe and the circulating branch pipes; and the central main pipe is of a hollow round pipe structure, and the circulating branch pipes are of a hollow sheet structure.

Preferably, the first medium circulation container and the second medium circulation container communicate with the heat exchanger, the first jacket and the second jacket by means of a medium pipeline; and a thermal insulating layer with a thickness larger than or equal to 50 mm and a thermal conductivity smaller than or equal to 0.04 Kj/(M-H-°C}) is arranged on an outer surface of each of the composting reactor, the first medium circulation container, the second medium circulation container and the medium pipeline.

Preferably, the thermal insulating layer on the outer surface of the composting reactor is an insulation sleeve; the insulation sleeve is a jacket of a segmented and open-close structure, and keeps a distance from the composting reactor at 5-10 mm; and the heat exchanger and the insulation sleeve do not rotate with the composting reactor.

Preferably, the first jacket is welded to the outer surface of the hydrolysis acidification pool, and the second jacket is welded to the outer surface of the methanation pool; and a medium inlet communicating with the first medium circulation container is arranged at a lower end of each of the first jacket, the second jacket and the heat exchange coil, and a medium outlet communicating with the second medium circulation container is arranged at an upper end of each of the first jacket, the second jacket and the heat exchange coil.

Preferably, an automatic control valve is formed in each of the medium inlets of the first jacket, the second jacket and the heat exchange coil.

Preferably, the first jacket covers all or part of the outer surface of the hydrolysis acidification pool; and the second jacket covers all or part of the outer surface of the methanation pool.

Preferably, the second jacket is not arranged on the outer surface of the methanation pool.

Preferably, the heat exchange coil is coiled by a stainless steel hollow water pipe, having a coil spacing of 50-500 mm, and a coil diameter being 1/2-2/3 of a diameter or a width of the hydrolysis acidification pool.

Preferably, the composting reactor uses a sealed reaction chamber in a form of rotary kiln structure; and the sealed reaction chamber includes: a chamber body; and a drive piece, used for driving the chamber body to rotate.

Preferably, the composting reactor is inclined relative to a horizontal plane, with an inclination angle of 0.1-1 degree.

Preferably, the hydrolysis acidification pool is of a horizontal structure, is inclined underground, and forms an inclination angle of 0.01-1 degree relative to the horizontal plane.

Preferably, the hydrolysis acidification pool is in a type of a long cylinder or a U-shaped groove.

Preferably, the hydrolysis acidification pool is formed by welding of a stainless steel sheet or an enameling steel sheet.

Preferably, a hydraulic retention time of the hydrolysis acidification pool lasts for 4-8 d.

Preferably, the hydrolysis acidification pool is provided with: a material inlet and a gas outlet; a first stirring device used for stirring the materials;

a digestive solution discharge hole used for discharging a digestive solution, a sediment discharge hole used for discharging the sediments and a scum discharge hole used for discharging the scum; and at least one or more of the following detection devices, including: 5 a first temperature detection device, used for detecting a temperature in the hydrolysis acidification pool; a first pressure detection device, used for detecting a pressure in the hydrolysis acidification pool; a first pH detection device, used for detecting a pH value of the materials in the hydrolysis acidification pool; a first ORP detection device, used for detecting an ORP value of the materials in the hydrolysis acidification pool; and a first liquid level detection device, used for detecting a height of the materials in the hydrolysis acidification pool.

Preferably, the hydrolysis acidification pool is further provided with a first high pressure protection device, a first manhole and a first observation hole.

Preferably, a first stirring shaft of the first stirring device is transversely or longitudinally arranged; a first stirring blade of the first stirring device has a length without exceeding 1/2 of the diameter or the width of the hydrolysis acidification pool; and stirring is performed regularly for 3-4 times a day for 5-20 min each time in the hydrolysis acidification pool.

Preferably, the hydrolysis acidification pool is internally provided with a plurality of first baffles, whose heights do not exceed a height of the first stirring shaft.

Preferably, the digestive solution discharge hole is arranged at 1/2-1/3 of a liquid level height of the digestive solution, and communicates with the methanation pool by means of a siphon pipe; the siphon pipe is a hollow bend pipe similar to an arch bridge; and connection between the siphon pipe and the hydrolysis acidification pool or the methanation pool adopts a live knot way such as flange connection and quick joint connection.

Preferably, the sediment discharge hole is formed in a bottom of the hydrolysis acidification pool, and is connected with a screw discharging machine by means of a valve and a pipeline; and a static pressure generated by a vertical distance between a top of a discharge pipe of the screw discharging machine and a liquid level height in the hydrolysis acidification pool is 5-10 kPa larger than an internal pressure of the hydrolysis acidification pool.

Preferably, the scum discharge hole is arranged at the liquid level of the digestive solution, has a height not exceeding 20-50 mm of the liquid level height of the digestive solution, and communicates with a sealed scum pool by means of a valve and a pipeline.

Preferably, a second thermal insulating layer is arranged on a surface of each of the hydrolysis acidification pool and the methanation pool.

Preferably, the methanation pool is of the horizontal structure, is inclined underground, and forms an inclination angle of 0-0.05 degree relative to the horizontal plane.

Preferably, the methanation pool is in the type of the long cylinder or the U-shaped groove.

Preferably, the methanation pool is formed by welding of a stainless steel sheet or an enameling steel sheet.

Preferably, the methanation pool is internally provided with a plurality of second baffles, whose heights do not exceed 1/4-1/2 of the liquid level height of the digestive solution in the methanation pool.

Preferably, a hydraulic retention time of the methanation pool lasts for 15-30 d.

Preferably, the methanation pool is provided with: a digestive solution feeding hole, a discharge hole and a biogas outlet; a second stirring device used for stirring the mixture; an acidolysis adjustment dosing device, used for adjusting a pH value in the methanation pool; and at least one or more of the following detection devices, including: a second temperature detection device, used for detecting a temperature in the methanation pool; a second pressure detection device, used for detecting a pressure in the methanation pool; a second pH detection device, used for detecting a pH value of the materials in the methanation pool; a second ORP detection device, used for detecting an ORP value of the materials in the methanation pool; and a second liquid level detection device, used for detecting a height of the materials in the methanation pool.

Preferably, the discharge hole communicates with a filter press; and the filter press uses plate frame pressure filtration or stacked screw pressure filtration.

Preferably, the second stirring device is a mechanical stirring device, a biogas stirring device ar a biogas slurry stirring device.

Preferably, biogas stirring is to pump out the biogas above the liquid level of the digestive solution in the methanation pool by means of a biogas pump, and introduce the biogas into the methanation pool from a bottom and a lateral lower side, thereby generating a strong gas reflux, driving sinking sludge to float upward, and promoting methane gas to be smoothly separated from the digestive solution.

Preferably, there is a need for at least one outlet and three injection holes for biogas stirring.

Preferably, biogas slurry stirring is to pump the biogas slurry from the bottom of the methanation pool by means of a sludge pump and inject it tangentially from a lateral upper side

(lower than the height of the digestive solution), thereby forming a strong circumferential flow inside the methanation pool, and then playing a role of biogas slurry stirring.

Preferably, there is a need for at least one biogas slurry outlet and two biogas slurry injection holes in each set of biogas slurry stirring.

Preferably, there is a need for arranging one or more sets of biogas stirring and biogas slurry stirring between every two baffles and in a region isolated by the baffles and feeding and discharging ends.

Preferably, for biogas stirring and biogas slurry stirring, during stirring, a moving speed of the digestive solution in the methanation pool does not exceed 0.5 m/s.

Preferably, biogas stirring and biogas slurry stirring are performed for 3-4 times a day for 5- 10 min each time.

Preferably, biogas stirring and biogas slurry stirring may be arranged separately or simultaneously.

Preferably, in a case that the hydrolysis acidification bacteria and the methanogenic bacteria perform mesophilic anaerobic digestion, the first temperature value is 40-55°C, and the second temperature value is 30-35°C; and in a case that the hydrolysis acidification bacteria and the methanogenic bacteria perform thermophilic anaerobic digestion, the first temperature value is 65-70°C, and the second temperature value is 50-55°C.

Preferably, the fermentation system with two-phase anaerobic digestion further includes: a feeding container, where the feeding container communicates with the hydrolysis acidification pool by means of a material pipeline; the material pipeline is provided with a gravity automatic control valve; the feeding container is provided with a third stirring device used for mixing the materials inside.

Preferably, a static pressure generated by a difference between a bottom of a feeding container and the liquid level height in the hydrolysis acidification pool is larger than or equal to 10 kPa.

The fermentation system with two-phase dry anaerobic digestion provided by the embodiments of the present invention includes: the hydrolysis acidification pool which contains the hydrolysis acidification bacteria used for hydrolysis acidification treatment on the materials; the methanation pool which contains the methanogenic bacteria, and communicates with the hydrolysis acidification pool to be used for acquiring the digestive solution in the hydrolysis acidification pool and decomposing it into the biogas slurry, the biogas residues and the biogas containing methane; the composting reactor which is used for performing composting treatment on the biogas residues produced in the methanation pool and supplying the heat energy generated during composting to the heat exchange device; and the heat exchange device which uses the heat energy supplied by the composting reactor to make the hydrolysis acidification pool and the methanation pool keep at the predetermined temperature.

Compared with the prior art, the present invention combines a biogas fermentation technology with a composting technology, and uses heat generated during composting to provide heat required for biogas fermentation for the hydrolysis acidification pool and the methanation pool, without other additional heating facilities such as an electric heating film and a biogas boiler; and biogas residues produced in the methanation pool can be used as a raw material for aerobic composting for subsequent production of an organic fertilizer, thereby greatly lowering the cost of biogas fermentation, and ensuring normal gas production throughout the year. Therefore, the present invention facilitates popularization and application of the biogas production technology in villages and towns.

In addition, in the embodiments of the present invention, a traditional vertical biogas reactor is changed into the horizontal structure, to make the whole hydrolysis acidification pool and methanation pool placed underground. Size construction of a container is not limited; the construction cost is low; and meanwhile, a dead weight of fermentation raw materials is effectively used, thereby lowering energy consumption of mechanical stirring, and solving the problems of high solid content, poor fluidity, and difficulty in feeding and conveying of the dry fermentation materials.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an architecture diagram of a fermentation system with two-phase dry anaerobic digestion provided by an embodiment of the present invention;

FIG. 2 is an architecture diagram of a remote monitoring system, an intelligent fault diagnosis module and a user interface provided by an embodiment of the present invention;

FIG. 3 is a schematic structural diagram of a fermentation system with two-phase dry anaerobic digestion provided by an embodiment of the present invention;

FIG. 4 is amain view of a hydrolysis acidification pool provided by an embodiment of the present invention;

FIG. 5 is a lateral view of a hydrolysis acidification pool provided by an embodiment of the present invention;

FIG. 6 is a cutaway view A-A in figure 2;

FIG. 7 is a cutaway view B-B in figure 2;

FIG. 8 is a main view of a methanation pool provided by an embodiment of the present invention;

FIG. 9 is a lateral view of a methanation pool provided by an embodiment of the present invention;

FIG. 10 is a cutaway view C-C in figure 8; and

FIG. 11 is a cutaway view D-D in figure 6.

Reference numerals in the drawings: 1, composting reactor; 2, hydrolysis acidification pool; 3, methanation pool; 101, feeding container; 102, heat exchanger; 105, first thermal insulating layer; 115, first medium circulation container; 120, second medium circulation container; 200, gas outlet, 208, second thermal insulating layer; 212, digestive solution discharge hole; 215, sediment discharge hole; 218, first pH detection device; 220, first ORP detection device; 225, first stirring shaft, 228, first baffle; 230, first manhole; 235, first temperature detection device interface; 250, first stirring blade; 240, material inlet; 242, material pipeline; 250, first stirring device; 255, heat exchange coil; 268, first jacket; 408, explosion-proof opening; 410, biogas outlet; 415, defoaming hole; 418, discharge hole; 420, second pH detection device interface; 421, second ORP detection device interface; 425, siphon pipe; 428, reagent inlet; 430, digestive solution feeding hole; 438, second temperature detection device interface; 440, biogas slurry stirring hole; 445, second baffle; 465, second jacket; and 485, second manhole.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the particular embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

A working principle of a fermentation system with two-phase dry anaerobic digestion provided by the present invention is as follows: 1) Hydrolysis acidification pool

Principle: materials enter the hydrolysis acidification pool first. In this stage, complex organic matters (such as proteins, fats, and cellulose) are decomposed into small molecules such as amino acids, fatty acids, and sugars by hydrolysis acidification bacteria.

Process: hydrolysis is an enzyme catalysis process, in which macromolecules are decomposed into soluble small molecules. Subsequently, these small molecules are acidified and converted to intermediate products such as volatile fatty acids (VFAs). 2) Methanation pool

Principle: the hydrolytically acidified materials automatically flow into the methanation pool.

Here, methanogenic bacteria further convert the intermediate products such as the volatile fatty acids to biogas, which includes the main components of methane and carbon dioxide.

Process: this stage mainly involves two bacterial communities: acid-producing bacteria and the methanogenic bacteria. The acid-producing bacteria first convert the VFAs to acetic acid, hydrogen and the carbon dioxide, and then, the methanogenic bacteria convert these products to the methane. 3) Composting reactor

Principle: biogas residues and biogas slurry produced in the methanation pool are mixed with specific raw materials, and then sent to the composting reactor. Here, organic matters are further decomposed by means of microbial activity to generate heat energy.

Process: during composting, the organic matters are further decomposed under the effect of microorganisms, so as to release heat energy. This process not only reduces an amount of wastes, but also produces mature compost that can be used as a soil amendment. 4) Heat exchange device

Principle: heat energy generated by the composting reactor is transmitted by means of the heat exchange device, to be used for maintaining appropriate temperatures of the hydrolysis acidification pool and the methanation pool.

Process: in this way, the system can maintain the required temperature self-sufficiently and improve the overall energy efficiency and the treatment efficiency. 5) Intelligent monitoring and control

Sensors: they monitor pH values, temperatures, flow rates and pressures of the hydrolysis acidification pool and the methanation pool in real time, so as to ensure the system to operate under the best conditions.

Microcontroller or PLC: it integrates and analyzes data from sensors, automatically adjusts operating parameters and optimizes the whole fermentation process.

Remote monitoring and fault diagnosis: a state of the system is remotely monitored in real time, and an intelligent algorithm is used for fault diagnosis and early warning, so as to ensure stable and efficient operation of the system.

The fermentation system with two-phase dry anaerobic digestion provided by the present invention makes full use of the energy of organic materials by means of staged treatment, and achieves self-energy circulation and intelligent management at the same time, thereby improving the energy efficiency and the treatment effect.

The specific implementation of the present invention is described in detail below in conjunction with the particular embodiments.

Embodiment 1

As shown in figure 1, one embodiments of the present invention provides a fermentation system with two-phase dry anaerobic digestion, including: a hydrolysis acidification pool 2, containing hydrolysis acidification bacteria and used for performing hydrolysis acidification treatment on materials; a methanation pool 3, containing methanogenic bacteria, where the methanation pool 3 communicates with the hydrolysis acidification pool 2; digestive raw materials after hydrolysis acidification automatically flow into the methanation pool 3 by means of a self-weight and a pressure difference, and are decomposed into biogas slurry, biogas residues and biogas; a composting reactor 1, used for performing composting treatment on a mixture of the biogas residues and the biogas slurry produced in the methanation pool 3 and a specific raw material, where heat energy generated during composting is supplied to a heat exchange device; and a heat exchange device, using the heat energy supplied by the composting reactor 1 to make the hydrolysis acidification pool 2 and the methanation pool 3 keep at a predetermined temperature.

In the embodiment of the present invention, sources of the materials may be kitchen wastes, agricultural straws, breeding manures, etc. These materials are mixed, then placed in the hydrolysis acidification pool 2, and hydrolytically acidified into the digestive raw materials (including a digestive solution, sediments and scum) under the effect of the hydrolysis acidification bacteria. The produced digestive raw materials enter the methanation pool 3, and are decomposed into biogas slurry, biogas residues and biogas containing methane under the effect of the methanogenic bacteria. The produced biogas residues, part of the biogas slurry and the specified raw material are sent to the composting reactor 1 for composting treatment together (the sediments and the scum may also be sent together). The heat energy generated during composting is supplied to the hydrolysis acidification pool 2 and methanation pool 3 by means of the heat exchange device for thermal insulation of the hydrolysis acidification pool 2 and the methanation pool 3, so as to ensure that the hydrolysis acidification bacteria and methanogenic bacteria always keep high activity and can continuously produce a large quantity of biogas. The designated raw materials mentioned here may be organic wastes such as the kitchen wastes, the agricultural straws, and the breeding manures.

Compared with the prior art, the present invention combines the biogas fermentation technology with the composting technology, and uses the heat generated during composting to provide heat required for biogas fermentation for the hydrolysis acidification pool 2 and the methanation pool 3, without other additional heating facilities such as the electric heating film and the biogas boiler; and the biogas residues produced in the methanation pool 3 can be used as the raw material for aerobic composting for subsequent production of an organic fertilizer, thereby greatly lowering the cost of biogas fermentation, and ensuring normal gas production throughout the year. Therefore, the present invention facilitates popularization and application of the biogas production technology in villages and towns.

As a preferred embodiment of the present invention, a predetermined proportion of the biogas slurry is added to the materials entering the hydrolysis acidification pool; and the sediments and the scum produced in the hydrolysis acidification pool and the biogas residues produced in the methanation pool are jointly transferred to the composting reactor for composting treatment.

Specifically, an amount of the biogas slurry added depends on a solid content of the raw materials. Generally, the solid content of the materials is controlled at 20-28 % after the biogas slurry is added.

As a preferred embodiment of the present invention, sources of heat energy of the heat exchange device further include a biogas boiler, solar energy or electric energy.

Specifically, if the construction cost is within a tolerable range, it is also feasible to use the biogas boiler, the solar energy or the electric energy as the source of the heat energy for the heat exchange device.

As shown in figure 1, as a preferred embodiment of the present invention, the heat exchange device includes: a heat exchanger 102, used for acquiring heat energy generated by the composting reactor 1 during composting; a first medium circulation container 115, communicating with the heat exchanger 102, where a medium with a first temperature value generated in the heat exchanger 102 is supplied to the first medium circulation container 115; a second medium circulation container 120, communicating with the heat exchanger 102, where a medium with a second temperature value in the second medium circulation container 120 is supplied to the heat exchanger 102, and the first temperature value is larger than the second temperature value; a first jacket 268, arranged on an outer surface of the hydrolysis acidification pool 2, where the first jacket 268 communicates with the first medium circulation container 115 and the second medium circulation container 120; a heat exchange coil 255, arranged inside the hydrolysis acidification pool 2, where the heat exchange coil 255 communicates with the first medium circulation container 115 and the second medium circulation container 120; and a second jacket 465, arranged on an outer surface of the methanation pool 3, where the second jacket 465 communicates with the first medium circulation container 115 and the second medium circulation container 120.

Specifically, pumping devices are arranged between the heat exchanger 102 and the first medium circulation container 115, between the first medium circulation container 115 and the first jacket 268, between the first medium circulation container 115 and the second jacket 465, between the first jacket 268 and the second medium circulation container 120, between the second jacket 465 and the second medium circulation container 120, and between the second medium circulation container 120 and the heat exchanger 102 respectively, to be used for cyclic transmission of the medium. In this embodiment, the medium selected may be gas (air, nitrogen, carbon dioxide and other gases) and liquid (water, heavy oil, lubricating oil, heat transfer oil and other liquids). Correspondingly, the heat exchanger 102 may use an air heat exchanger 102, a water heat exchanger 102 and an oil heat exchanger 102. For economic considerations, the medium selected is generally water, and the heat exchanger 102 selected is the water heat exchanger 102. During operation of the heat exchange device, the heat exchanger 102 acquires the heat energy generated during composting of the composting reactor 1; the acquired heat energy heats the medium; the heated medium is stored in the first medium circulation container 115, and pumped to the first jacket 268, the heat exchange coil

255 and the second jacket 465 by means of the pumping devices, to provide heat required for biogas fermentation for the hydrolysis acidification pool 2 and the methanation pool 3; and the medium with a descended temperature after heat release enters the second medium circulation container 120, is pumped back to the heat exchanger 102 by means of the pumping device, and is heated again in the heat exchanger 102. With such cycle, the temperatures in the hydrolysis acidification pool 2 and the methanation pool 3 are ensured to always be kept within high active temperature ranges of the hydrolysis acidification bacteria and the methanogenic bacteria, so that the system of the present invention can normally produce a large quantity of biogas throughout the year.

As a preferred embodiment of the present invention, the heat exchange device 102 has a heat exchange mode of wall-type heat exchange, and includes an in-barrel heat exchanger 102 and an out-barrel heat exchanger 102; the in-barrel heat exchanger 102 includes a heat exchange coil 255 and a central main pipe heat exchanger 102 with circulating branch pipes; the central main pipe heat exchanger 102 with the circulating branch pipes includes a central main pipe and the circulating branch pipes; and the central main pipe is of a hollow round pipe structure, and the circulating branch pipes are of a hollow sheet structure.

As a preferred embodiment of the present invention, the first medium circulation container 115 and the second medium circulation container 120 communicate with the heat exchanger 102, the first jacket 268 and the second jacket 465 by means of a medium pipeline; and a first thermal insulating layer 105 with a thickness larger than or equal to 50 mm and a thermal conductivity smaller than or equal to 0.04 Kj/(M-H-°C) is arranged on an outer surface of each of the composting reactor 1, the first medium circulation container 115, the second medium circulation container 120 and the medium pipeline.

As a preferred embodiment of the present invention, the first thermal insulating layer 105 on the outer surface of the composting reactor 1 is an insulation sleeve; the insulation sleeve is a jacket of a segmented and open-close structure, and keeps a distance from the composting reactor 1 at 5-10 mm; and the heat exchanger 102 and the insulation sleeve do not rotate with the composting reactor 1.

As a preferred embodiment of the present invention, the first jacket 268 is welded to the outer surface of the hydrolysis acidification pool 2, and the second jacket 465 is welded to the outer surface of the methanation pool 3; and a medium inlet communicating with the first medium circulation container 115 is arranged at a lower end of each of the first jacket 268, the second jacket 465 and the heat exchange coil 255, and a medium outlet communicating with the second medium circulation container 120 is arranged at an upper end of each of the first jacket 268, the second jacket 465 and the heat exchange coil 255.

As a preferred embodiment of the present invention, an automatic control valve is formed in each of the medium inlets of the first jacket 268, the second jacket 465 and the heat exchange coil 255.

Specifically, the first jacket 268 and the second jacket 465 are both a thin layer of space welded to the outer surfaces of the hydrolysis acidification pool 2 and the methanation pool 3; and each of them is provided with a water inlet near a lower part and a water outlet at an upper end (taking the medium as water as an example). Hot water enters from the lower part, fully fills the jackets, and then flows out from the upper outlet. The automatic control valves can automatically control circulation and stop of circulating hot water according to the temperatures and the industrial control requirements in the hydrolysis acidification pool 2 and the methanation pool 3. In general, a temperature of the hot water needs to be 5-10°C higher than a reaction temperature of the digestive solution in the methanation pool 3.

As a preferred embodiment of the present invention, the first jacket 268 covers all or part of the outer surface of the hydrolysis acidification pool 2; and the second jacket 465 covers all or part of the outer surface of the methanation pool 3.

As a preferred embodiment of the present invention, the second jacket 465 is not arranged on the outer surface of the methanation pool 3.

As a preferred embodiment of the present invention, the heat exchange coil 255 is coiled by a stainless steel hollow water pipe, having a coil spacing of 50-500 mm, and a coil diameter being 1/2-2/3 of a diameter or a width of the hydrolysis acidification pool 2.

As a preferred embodiment of the present invention, the composting reactor 1 uses a sealed reaction chamber in a form of rotary kiln structure; and the sealed reaction chamber includes: a chamber body; and a drive piece, used for driving the chamber body to rotate.

Specifically, the drive piece selected may be a motor. The motor drives the composting reactor 1 to rotate, so that the biogas residues in the composting reactor 1 can be fully composted, and the heat energy generated can also be fully released and acquired by the heat exchange device.

As a preferred embodiment of the present invention, the composting reactor 1 is inclined relative to a horizontal plane, with an inclination angle of 0.1-1 degree.

As a preferred embodiment of the present invention, the hydrolysis acidification pool 2 is of a horizontal structure, is inclined underground, and forms an inclination angle of 0.01-1 degree relative to the horizontal plane.

Specifically, current limited biogas production still has a problem of a limited capacity of a biogas tank and a too low volume productivity (output value). At present, most of biogas pools widely used at home and abroad are vertical with a high cost and a construction volume limited by a height, so that they are difficultly built to a height or a depth of 100 m Therefore, it can only shorten the retention time of the process, which results in an incomplete reaction, a low energy conversion rate, and a large pollution load of the biogas slurry. The retention period of biogas fermentation in China generally lasts for 10-15 d, and only 7 d sometimes. In Germany, the retention period of biogas fermentation generally lasts for 28-45 d even under the condition of mesophilic anaerobic fermentation at a high temperature.

Due to the limited biogas volume, low biogas conversion efficiency, and low biogas production, the economic benefit of energy utilization cannot be achieved. For example, one chemical reactor of 1 cubic meter may produce 1 ton of chemical materials per day, with a value of more than 15000 yuan generally. However, a biogas reactor of 1 cubic meter (normal temperature} can only produce 0.7 cubic meter of biogas per day on average, with a value of 1.5 yuan, and its volume productivity is only one ten-thousandth of that of a chemical reactor. In order to obtain the value of the chemical reactor of 1 cubic meter in one day, the reactor of the biogas pool needs to be of 10,000 cubic meters. The biogas pool of 10,000 cubic meters needs a current cost of about 15 million yuan, but its annual output value is only about 5.5 million yuan per year. An input-output ratio is too low, and a commercial value is small.

The embodiment of the present invention is similar to an underground river by horizontally arranging the hydrolysis acidification pool 2 underground, so it is called “underground river type”. After being crushed, the dry fermentation materials (with a solid content larger than 20%) are squeezed into the underground river by the gravity from an upstream inlet of the underground river, and slowly creeps downstream. After anaerobic fermentation, the biogas is produced. The biogas residues after biogas production are brought out from a downstream outlet of the underground river by gravity or discharge equipment. In the embodiment of the present invention, the traditional vertical biogas reactor is changed into the horizontal structure, to make the whole hydrolysis acidification pool 2 arranged underground. The temperature in the container is less affected by the climate change; the key technology of fluidized continuous feeding and discharging of materials is solved at the same time; and the problem of difficult biogas production and residue discharge in a pit, the limited capacity of the vertical biogas pool, a high construction cost, and a large effect on the temperature in the pool by temperature changes in the four seasons are solved, which paves the way for large-scale biogas production.

Compared with the prior art, size construction of the hydrolysis acidification pool 2 is not limited; the construction cost is low; and meanwhile, a dead weight of the fermentation raw materials is effectively used, thereby lowering energy consumption of mechanical stirring, and solving the problems of high solid content, poor fluidity, and difficulty in feeding and conveying of the dry fermentation materials.

As a preferred embodiment of the present invention, the hydrolysis acidification pool 2 may be various types of a long cylinder, a U-shaped groove and the like (to prevent material aggregation/dead angle).

As a preferred embodiment of the present invention, the hydrolysis acidification pool 2 is formed by welding of a stainless steel sheet or an enameling steel sheet. If the stainless steel sheet is used, it is necessary to make anti-corrosion treatment on its inner wall.

As a preferred embodiment of the present invention, a hydraulic retention time of the hydrolysis acidification pool 2 lasts for 48 d.

As shown in figures. 2-5, as a preferred embodiment of the present invention, the hydrolysis acidification pool 2 is provided with: a material inlet 240 and a gas outlet 200; a first stirring device 250 used for stirring the materials; a digestive solution discharge hole 212 used for discharging a digestive solution, a sediment discharge hole 215 used for discharging the sediments and a scum discharge hole used for discharging the scum; and at least one or more of the following detection devices, including: a first temperature detection device, used for detecting a temperature in the hydrolysis acidification pool 2; a first pressure detection device, used for detecting a pressure in the hydrolysis acidification pool 2; a first pH detection device, used for detecting a pH value of the materials in the hydrolysis acidification pool 2; a first ORP detection device, used for detecting an ORP value of the materials in the hydrolysis acidification pool 2; and a first liquid level detection device, used for detecting a height of the materials in the hydrolysis acidification pool 2.

Specifically, the hydrolysis acidification pool 2 is provided with a first pH detection device interface, a first ORP detection device interface, and a first temperature detection device interface 235, through which the first pH detection device, the first ORP detection device, and the first temperature detection device are mounted respectively.

As shown in figures. 2-5, as a preferred embodiment of the present invention, the hydrolysis acidification pool 2 is further provided with a first high pressure protection device, a first manhole 230 and a first observation hole.

As shown in figures. 2-5, as a preferred embodiment of the present invention, a first stirring shaft 225 of the first stirring device 250 is transversely or longitudinally arranged, a first stirring blade 250 of the first stirring device 250 has a length without exceeding 1/2 of the diameter or the width of the hydrolysis acidification pool 2; and stirring is performed regularly for 3-4 times a day for 5-20 min each time in the hydrolysis acidification pool 2.

Specifically, the hydrolysis acidification pool 2 uses mechanical stirring (drying fermentation, high solid content and poor fluidity).

As a preferred embodiment of the present invention, the hydrolysis acidification pool 2 is internally provided with a plurality of first baffles 228, whose heights do not exceed a height of the first stirring shaft 225.

Specifically, the hydrolysis acidification pool 2 has different internal visual length-diameter ratios, and is provided with three or more first baffles 228. The baffles intercept sludge and bacteria, prolongs the retention time of the materials, and plays a role in supporting the first stirring shaft 225 at the same time.

As a preferred embodiment of the present invention, the digestive solution discharge hole 212 is arranged at 1/2-1/3 of a liquid level height of the digestive solution, and communicates with the methanation pool 3 by means of a siphon pipe 425; the siphon pipe 425 is a hollow bend pipe similar to an arch bridge; and connection between the siphon pipe 425 and the hydrolysis acidification pool 2 or the methanation pool 3 adopts a live knot way such as flange connection and quick joint connection.

Specifically, the digestive solution discharge hole 212 is located at a lower middle part of the liquid level of the digestive solution, and is connected with the methanation pool 3 by means of the siphon pipe 425. The acidified digestive solution automatically flows into the methanation pool 3 by means of the discharge hole under a self-weight and a pressure difference between the hydrolysis acidification pool 2 and the methanation pool 3.

As a preferred embodiment of the present invention, the sediment discharge hole 215 is formed in a bottom of the hydrolysis acidification pool 2, and is connected with a screw discharging machine by means of a valve and a pipeline; and a static pressure generated by a vertical distance between a top of a discharge pipe of the screw discharging machine and a liquid level height in the hydrolysis acidification pool 2 is 5-10 kPa larger than an internal pressure of the hydrolysis acidification pool 2.

Specifically, the sediment discharge hole 215 is arranged at the bottom; and high-density impurities such as sands are present in the hydrolytically acidified materials, and discharged regularly by means of the sediment discharge hole 215. After the sediments discharged are subjected to pressure filtration, the pressure filtered sediments and the biogas residues are sent for aerobic composting together, and a press filtrate is pumped into the methanation pool 3 for fermentation to produce the biogas.

As a preferred embodiment of the present invention, the scum discharge hole is arranged at the liquid level of the digestive solution, has a height not exceeding 20-50 mm of the height of the liquid level of the digestive solution, and communicates with a sealed scum pool by means of a valve and a pipeline.

As shown in figure 1, as a preferred embodiment of the present invention, second thermal insulating layers 208 are arranged on surfaces of the hydrolysis acidification pool 2 and the methanation pool 3.

As a preferred embodiment of the present invention, the methanation pool 3 is of the horizontal structure, is inclined underground, and forms an inclination angle of 0-0.05 degree relative to the horizontal plane.

Specifically, the methanation pool 3 is horizontally inclined, and is contrastively parallel to the hydrolysis acidification pool 2, that is, the digestive solution discharge hole 212 of the hydrolysis acidification pool 2 is parallel to the digestive solution feeding hole 430 of the methanation pool 3 or vice versa. A height of a bottom of the digestive solution discharge hole 212 of the hydrolysis acidification pool 2 is higher than that of the digestive solution feeding hole 430 of the methanation pool 3, and their height difference is larger than an internal pressure difference of 0.5-10 kPa of the above two during normal operation.

Furthermore, compared with the prior art, size construction of the methanation pool 3 is not limited; the construction cost is low; and meanwhile, the dead weight of the fermentation raw materials is effectively used, thereby lowering energy consumption of mechanical stirring, and solving the problems of high solid content, poor fluidity, and difficulty in feeding and conveying of the dry fermentation materials.

As a preferred embodiment of the present invention, the methanation pool 3 may be various types of a long cylinder, a U-shaped groove and the like (to prevent material aggregation/dead angle).

As a preferred embodiment of the present invention, the methanation pool 3 is formed by welding of a stainless steel sheet or an enameling steel sheet. If the stainless steel sheet is used, it is necessary to make anti-corrosion treatment on its inner wall.

As a preferred embodiment of the present invention, the methanation pool 3 is internally provided with a plurality of second baffles 445, whose heights do not exceed 1/4-1/2 of the liquid level height of the digestive solution in the methanation pool 3.

Specifically, the methanation pool 3 has different internal visual length-diameter ratios, and is provided with three or more second baffles 445. The second baffles 445 intercept sludge and bacteria, and prolong the retention time of the digestive solution.

As a preferred embodiment of the present invention, a hydraulic retention time of the methanation pool 3 lasts for 15-30 d.

As shown in figures. 6-9, as a preferred embodiment of the present invention, the methanation pool 3 is provided with: a digestive solution feeding hole 430, a discharge hole 418 and a biogas outlet 410; a second stirring device used for stirring the mixture; an acidolysis adjustment dosing device, used for adjusting a pH value in the methanation pool 3; and at least one or more of the following detection devices, including: a second temperature detection device, used for detecting a temperature in the methanation pool 3; a second pressure detection device, used for detecting a pressure in the methanation pool 3;

a second pH detection device, used for detecting a pH value of the materials in the methanation pool 3; a second ORP detection device, used for detecting an ORP value of the materials in the methanation pool 3; and a second liquid level detection device, used for detecting a height of the materials in the methanation pool 3.

Specifically, the methanation pool 3 is provided with a second pH detection device interface, a second ORP detection device interface, and a second temperature detection device interface 438, through which the second pH detection device, the second ORP detection device, and the second temperature detection device are mounted respectively. An acidolysis adjustment dosing device is arranged near the digestive solution feeding hole 430, and adds an adjustment reagent to the methanation pool 3 by means of the reagent inlet 428. For example, in a case of excessive acidification in the methanation pool 3, or a serious imbalanced pH value in the methanation pool 3, a certain amount of adjustment reagent may be added appropriately, so as to improve the growth environment of microorganisms in the methanation pool 3.

In addition, an explosion-proof opening 408 and a defoaming hole 415 are further formed in the methanation pool 3, to be used for preventing an overpressure explosion and clearing foams on a surface of the biogas slurry in the methanation pool 3.

As shown in figures. 6-9, as a preferred embodiment of the present invention, a second manhole 485 and a second observation hole are further formed in the methanation pool 3.

As a preferred embodiment of the present invention, the discharge hole communicates with a filter press; the filter press uses plate frame pressure filtration or stacked screw pressure filtration.

Specifically, the discharge hole communicates with the filter press. After pressure filtration, the biogas slurry is separated from the biogas residues, and quantitatively sent to the methanation pool 3 by means of a sewage pump. The biogas residues are sent to the composting reactor 1 by means of a sealed or semi-sealed belt conveyor system for composting and drying to prepare an organic fertilizer.

As a preferred embodiment of the present invention, the second stirring device is a mechanical stirring device, a biogas stirring device or a biogas slurry stirring device.

Specifically, a biogas slurry stirring hole 440 is formed in the methanation pool 3; and various methods such as mechanical stirring, biogas stirring and biogas slurry stirring, preferably, biogas stirring and biogas slurry stirring, may be used.

As a preferred embodiment of the present invention, biogas stirring is to pump out the biogas above the liquid level of the digestive solution in the methanation pool 3 by means of a biogas pump, and introduce the biogas into the methanation pool 3 from a bottom and a lateral lower side, thereby generating a strong gas reflux, driving sinking sludge to float upward, and promoting methane gas to be smoothly separated from the digestive solution.

As a preferred embodiment of the present invention, there is a need for at least one outlet and three injection holes for biogas stirring.

As a preferred embodiment of the present invention, biogas slurry stirring is to pump out the biogas slurry from the bottom of the methanation pool 3 by means of a sludge pump and inject it tangentially from a lateral upper side (lower than the height of the digestive solution), thereby forming a strong circumferential flow inside the methanation pool, and then playing the role of biogas slurry stirring.

As a preferred embodiment of the present invention, there is a need for at least one biogas slurry outlet and two biogas slurry injection holes in each set of biogas slurry stirring.

As a preferred embodiment of the present invention, there is a need for arranging one or more sets of biogas stirring and biogas slurry stirring between every two baffles and in a region isolated by the baffles and feeding and discharging ends.

As a preferred embodiment of the present invention, for biogas stirring and biogas slurry stirring, during stirring, a moving speed of the digestive solution in the methanation pool 3 does not exceed 0.5 m/s.

As a preferred embodiment of the present invention, biogas stirring and biogas slurry stirring are performed for 3-4 times a day for 5-10 min each time.

As a preferred embodiment of the present invention, biogas stirring and biogas slurry stirring may be arranged separately or simultaneously.

As a preferred embodiment of the present invention, in a case that the hydrolysis acidification bacteria and the methanogenic bacteria perform mesophilic anaerobic digestion, the first temperature value is 40-55°C, and the second temperature value is 30-35°C; and in a case that the hydrolysis acidification bacteria and the methanogenic bacteria perform thermophilic anaerobic digestion, the first temperature value is 65-70°C, and the second temperature value is 50-55°C.

As shown in figure 1, as a preferred embodiment of the present invention, the fermentation system with two-phase anaerobic digestion further includes: a feeding container 101, where the feeding container 101 communicates with the hydrolysis acidification pool 2 by means of a material pipeline 242; the material pipeline 242 is provided with a gravity automatic control valve; the feeding container 101 is provided with a third stirring device used for mixing the materials inside.

Specifically, the feeding container 101 may be of a square structure, a circular structure or other structures; and anaerobic digestion materials are mixed in the feeding container 101 according to a certain ratio after being crushed. The feeding container 101 is provided with the third stirring device, which may ensure uniform mixing of the materials with different solid contents, so as to facilitate the mixed material to flow into the hydrolysis acidification pool 2 by means of its dead weight.

As a preferred embodiment of the present invention, a static pressure generated by a height difference between a bottom of the feeding container 101 and the liquid level in the hydrolysis acidification pool 2 is larger than or equal to 10 kPa. Preferably, the height difference between the bottom of the feeding container 101 and the liquid level in the hydrolysis acidification pool 2 is larger than or equal to 20 kPa.

Embodiment 2

This embodiment uses the fermentation system with two-phase anaerobic digestion in embodiment 1 to perform actual fermentation. A fermentation process is as follows:

Residual heat generated by a reaction of composting raw materials in the composting reactor 1 heats the medium (water) to 60-85°C by means of the heat exchanger 102; and the medium flows into the first medium circulation container 115, is subjected to heat exchange by means of the first jacket 268 and the heat exchange coil 255 of the hydrolysis acidification pool 2 and the second jacket 465 of the methanation pool 3, then returned to the second medium circulation container 120, and finally pumped into the heat exchanger 102 of the composting reactor 1 for heating.

After being primarily crushed, the kitchen wastes and the agricultural straws are sent to the feeding container 101 in a ratio of 1: 1: 1 with the breeding manures; the quantitative biogas slurry discharged from the methanation pool 3 is added, to control the solid content (TS) at 20- 28%, and a C/N ratio in a range of (20-30): 1; and uniform stirring is performed to obtain the hydrolysis acidification raw materials with certain fluidity. The above-mentioned raw materials automatically flow into the hydrolysis acidification pool 2 by means of the material pipeline 242 {the hydrolytically acidified slag liquid accounting for 20-30% of an effective volume is pre- added in the container, to provide a bacterium source for hydrolysis acidification, or is domesticated by inoculated biogas slurry for more than 60 d to make a pH value smaller than 6). Circulating hot water at 60-65°C heats the digestive solution by the heat exchanger 102 to 55-60°C (thermophilic hydrolysis acidification ) or 40-45°C (mesophilic hydrolysis acidification ) gradually.

In order to ensure smooth feeding, the height difference between the bottom of the feeding container 101 and the liquid level of the hydrolysis acidification pool 2 is larger than or equal to 1500 mm, so that the static pressure of the materials inside the material pipeline 242 is slightly higher than the internal pressure of 1-10 kPa of the container of the hydrolysis acidification pool 2. In the hydrolysis acidification pool 2, the digestive raw materials are gradually digested and degraded, and gradually moved to the digestive solution discharge hole 212 under the stirring and a self-weight push flow. After 48 d, the digestive raw materials pass through the digestive solution discharge hole 212 and automatically flow into the methanation pool 3 by means of the siphon pipe 425. In order to prevent a “short circuit” of the digestive raw materials, the digestive raw materials flow into the methanation pool 3 before they are completely degraded. The hydrolysis acidification pool 2 is provided with a plurality of first baffles 228 inside; and the first baffles 228 have the effect of intercepting the hydrolysis acidification bacteria at the same time.

A small amount of high-density impurities such as bone debris, sands and gravels in the digestive raw materials will deposit at the bottom of an outlet end of the hydrolysis acidification pool 2 over time, and it is necessary to regularly use a screw discharging machine to discharge the impurities from the sediment discharge hole 215. As the same as feeding, the static pressure of the liquid level of the digestive solution discharge hole 212 should be higher than the internal pressure of 1-10 kPa of container of the hydrolysis acidification pool 2, so as to ensure that gas and the digestive solution in the container of the hydrolysis acidification pool 2 do not leak from the digestive solution discharge hole 212. Meanwhile, hydrolytically acidified gas is discharged directly by means of the gas outlet 200 after being deacidified and deodorized. In normal operation, an optimization process of the hydrolysis acidification pool 2 is as follows: temperatures are 38 + 3°C (mesophilic fermentation) and 58 + 3°C (thermophilic fermentation); hydraulic retention times last for 5-8 d (mesophilic fermentation) and 4-6 d (thermophilic fermentation); a pH value is 4.5-6.0; 350 mV < ORP < 250 mV; and 0 kPa < pressure < 1.5 kPa. At this time, the hydrolytically acidified gas includes the components: larger than 82% of carbon dioxide, and smaller than 0.1% of methane; and in the digestive raw materials, 18 g/L < VFAs < 2.8 g/L.

After the digestive solution flows into the methanation pool 3, most of the fatty acid organic matters are converted to biogas with a high methane content under the effect of methanogenic bacteria and the optimization conditions. The methanation pool 3 uses biogas slurry stirring or biogas stirring. During biogas slurry stirring, under the effect of the biogas slurry pump, the biogas slurry is pumped out by means of the biogas slurry stirring hole 440 at a lateral upper side, and flows in the methanation pool 3 from the bottom and another stirring hole at the lateral upper side. During biogas slurry stirring, the biogas slurry flows out of and into a biogas container tangentially, so that the digestive raw materials form a strong circumferential flow under biogas slurry stirring. Biogas stirring uses a similar arrangement to biogas slurry stirring.

There is a difference in that the biogas is pumped out from a gas gathering region above the methanation pool 3 by means of a fuel gas pump, and then injected into the digestive raw materials by means of three inlets formed in the bottom and side walls. In order to ensure that the digestive solution can automatically flow into the methanation pool 3 smoothly, in terms of an elevation arrangement, a tail of the hydrolysis acidification pool 2 is 200-800 mm higher than a head of the methanation pool 3, so as to balance the internal pressure difference between the hydrolysis acidification pool 2 and the methanation pool 3.

The biogas produced by the methanation pool 3 is discharged by means of the biogas outlet 410, subjected to desulfurization and other purification processes, and then sent to a gas storage cabinet, or may also be further decarbonized to produce artificial natural gas. The biogas slurry flows out by means of the discharge hole 418, and is pressure filtered; the biogas residues are sent for composting; and the biogas slurry converges into the biogas slurry container; and then a part of the biogas slurry is sent to the feeding container 101 by means of the biogas slurry pump, so as to adjust the solid content of the digestive raw materials, and the remaining part is sent for composting.

An optimization process of the methanation pool 3 is as follows: temperatures are 35 + 2°C (mesophilic fermentation) and 53 + 2°C (thermophilic fermentation); hydraulic retention times last for 20-30 d (mesaphilic fermentation) and 15-30 d (thermophilic fermentation); a pH value is 6.8-7.8; 450 mV < ORP < 600 mV; and 0.5 kPa < pressure < 1.8 kPa. At this time, the biogas includes the components: larger than 65% of methane, and smaller than 23% of carbon dioxide accounted.

What is described above is merely preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should all fall within the scope of protection of the present invention.

Claims

CONCLUSIONS

1. A fermentation system with a two-stage dry anaerobic digestion comprising: — a hydrolysis acidification bath, containing hydrolysis acidification bacteria and used for carrying out a hydrolysis acidification treatment on materials; — a methanisation bath, containing methanogenic bacteria, the methanisation bath being connected to the hydrolysis acidification bath to facilitate digestion raw materials after hydrolysis acidification to flow automatically into the methanisation bath by means of its own weight and a pressure difference, thereby decomposing the digestion raw materials into a biogas slurry, biogas residues and biogas; — a composting reactor, used for carrying out a composting treatment on a mixture of the biogas residues and the biogas slurry formed in the methanisation bath and a specific feedstock, the heat energy generated during composting being supplied to a heat exchanger; — a heat exchanger which uses the heat energy of a composting reaction bath to maintain the hydrolysis acidification bath and the methanisation bath at a predetermined temperature; — a sensor system, comprising sensors for monitoring pH values, temperatures, flow rates and pressures, mounted in the hydrolysis acidification bath and the methanisation bath; — an automatic control unit, comprising a microcontroller or a programmable logic controller used for integrating data from the sensors and automatically controlling the system; and — a data analysis and optimisation module, used for integrating software for data analysis, automatically adjusting operating parameters based on real-time data provided by the sensors and optimising the fermentation process.

2. The two-stage dry anaerobic digestion digestion system according to claim 1, comprising: — a remote monitoring system connectable through the Internet, which enables an operator to remotely view and control the condition of the two-stage dry anaerobic digestion digestion system; — an intelligent fault diagnosis module integrated with an intelligent diagnosis algorithm used for timely detecting and reporting a potential problem of the system, the module being based on the real-time data from the sensor system for fault analysis; and — a user interface, which provides an intuitive user interface to allow the operator to easily access status information, a warning and a diagnosis report of the system.

3. The two-stage dry anaerobic digestion digestion system according to claim 1, wherein — a predetermined portion of the biogas slurry is added to the materials entering the hydrolysis acidification bath; and — sediments and foam produced in the hydrolysis acidification bath and the biogas residues produced in the methanization bath and the remaining biogas slurry are jointly transferred to the composting reactor for composting treatment.

4. The two-stage dry anaerobic digestion fermentation system according to claim 1, wherein the heat exchanger comprises: — a heat exchanger used for obtaining heat energy generated by the composting reactor during composting; — a first medium circulation vessel in communication with the heat exchanger, wherein a medium having a first temperature value generated in the heat exchanger is supplied to the first medium circulation vessel; — a second medium circulation vessel in communication with the heat exchanger, wherein a medium having a second temperature value in the second medium circulation vessel is supplied to the heat exchanger, wherein the first temperature value is greater than the second temperature value; — a first jacket disposed on an outer surface of the hydrolysis acidification bath, wherein the first jacket is in communication with the first medium circulation vessel and the second medium circulation vessel; — a heat exchange coil disposed in the hydrolysis acidification bath, wherein the heat exchange coil is in communication with the first medium circulation vessel and the second medium circulation vessel; and — a second jacket disposed on an outer surface of the methanization bath, the second jacket being in communication with the first medium circulation vessel and the second medium circulation vessel.

5. The fermentation system with a two-stage dry anaerobic digestion according to claim 4, wherein

— the first medium circulation vessel and the second medium circulation vessel are connected to the heat exchanger, the first jacket and the second jacket by means of a medium pipeline; — a first thermal insulation layer having a thickness greater than or equal to 50 mm and a thermal conductivity less than or equal to 0,04 Kj/{M-H-°C)} is applied to an external surface of each of the composting reactor, the first medium circulation vessel, the second medium circulation vessel and the medium pipeline; and — a second thermal insulation layer is applied to a surface of each of the hydrolysis acidification bath and the methanisation bath.

6. The fermentation system with a two-stage dry anaerobic digestion according to claim 4, wherein — in the case where the hydrolysis acidifying bacteria and the methanogenic bacteria perform mesophilic anaerobic digestion, the first temperature value is 40 - 55°C, and the second temperature value is 30 - 35°C; and — in the case where the hydrolysis acidifying bacteria and the methanogenic bacteria perform thermophilic anaerobic digestion, the first temperature value is 65 - 70°C, and the second temperature value is 50 - 55°C.

7. The two-stage dry anaerobic digestion fermentation system according to claim 1, wherein — the composting reactor uses a closed reaction chamber in the form of a rotary kiln structure; and — the closed reaction chamber comprises a chamber body and a drive piece for rotating the chamber body.

8. The two-stage dry anaerobic digestion fermentation system according to claim 1, wherein — the composting reactor is inclined with respect to a horizontal plane, with an angle of inclination of 0,1 - 1°; — the hydrolysis acidification bath and the methanation bath both have a horizontal structure; — the hydrolysis acidification bath and the methanation bath are inclined underground, wherein — the angle of inclination of the hydrolysis acidification bath with respect to the horizontal plane is 0,01 - 1°, and — the angle of inclination of the methanation bath with respect to the horizontal plane is 0 - 0,05°.

9. The two-stage dry anaerobic digestion digestion system according to claim 1, wherein the hydrolysis acidification bath comprises: — a material inlet and a gas outlet; — a first agitator for agitating the materials; — a digestion solution discharge port for discharging a digestion solution, a sediment discharge port for discharging sediment and a foam discharge port for discharging foam; and — at least one or more of the following detection devices, comprising: — a first temperature detection device used to detect the temperature in the hydrolysis acidification bath; — a first pressure detection device used to detect the pressure in the hydrolysis acidification bath; — a first pH detection device used to detect the pH value of the materials in the hydrolysis acidification bath; — a first ORP detection device used to detect the ORP value of the materials in the hydrolysis acidification bath; and — a first liquid level detection device used to detect the level of the materials in the hydrolysis acidification bath.

10. The two-stage dry anaerobic digestion fermentation system according to claim 1, wherein the methanization bath is provided with: — a feed opening for the digestion solution, a discharge opening and a biogas outlet; — a second agitator for agitating the mixture; — a dosing device for acidolysis adjustment used to adjust the pH value in the methanization bath; — and at least one or more of the following detection devices, comprising: — a second temperature detection device, used to detect a temperature in the methanization bath; — a second pressure detection device used to detect the pressure in the methanization bath; — a second pH detection device used to detect the pH value of the materials in the methanization bath; — a second ORP detection device used to detect the ORP value of the materials in the methanization bath; and

— a second liquid level detection device used to detect the level of the materials in the methanization bath.

11. The two-stage dry anaerobic digestion fermentation system of claim 1, further comprising a feed vessel, wherein — the feed vessel is connected to the hydrolysis acidification bath by a material conduit; — the material conduit is provided with an automatic gravity control valve; and — the feed vessel is provided with a third agitator for mixing the materials contained therein.