System and method for segmented regulation and control of anaerobic fermentation of biomass based on modified charcoal

Abstract

The invention discloses a system and a method for segmented regulation and control of biomass anaerobic fermentation based on modified biochar. The system comprises a low-temperature biochar preparation system, a biochar modification system, a hydrolytic acidification system, a methane production system, a biogas purification and separation system and a heat utilization system. The low-temperature biochar preparation system is used for preparing low-temperature biochar and providing the low-temperature biochar to the hydrolytic acidification system and the biochar modification system, and the biochar modification system is used for carrying out carbon dioxide high-temperature modification on the low-temperature biochar to obtain modified biochar and providing the modified biochar to the methane production system; the biochar is modified according to different requirements on biochar functions in different stages of anaerobic fermentation, and low-temperature biochar and modified biochar are respectively added in a hydrolytic acidification stage and a methanogenesis stage of anaerobic fermentation, so that accurate intervention of C / N dynamic balance and inhibitor control is realized.

Description

Technical Field

[0001] This invention relates to the resource utilization and anaerobic fermentation technology of biomass organic solid waste, specifically to a system and method for segmented regulation of biomass anaerobic fermentation based on modified biochar. Background Technology

[0002] Using agricultural waste such as straw and livestock manure for anaerobic fermentation to produce biogas, which is then purified and converted into biomethane that meets standards, not only addresses rural non-point source pollution but also promotes sustainable and green energy development. It is currently an energy conversion technology for the effective disposal and high-value utilization of agricultural waste.

[0003] In the direct anaerobic fermentation of livestock and poultry manure, C / N imbalance and the accumulation of inhibitors (such as ammonia nitrogen and VFA) are key issues restricting fermentation efficiency. Traditionally, adding high-carbon biomass such as straw and sawdust can adjust the C / N ratio. However, due to the slow hydrolysis of lignocellulosic biomass such as straw, acidification time is easily prolonged. Furthermore, the low density of biomass reduces the gas production per unit volume of the reactor and causes problems such as floating material crusting. Compared with biomass such as straw, adding biochar can function without degradation, and can simultaneously achieve C / N adjustment and inhibitor control, providing a feasible path for the efficient resource utilization of livestock and poultry manure.

[0004] Chinese invention patent application CN118374550A discloses a magnetic biochar coupling carrier and its preparation method. This method involves pyrolyzing the biogas residue from the anaerobic fermentation of corn stalks and cow manure to obtain biochar. An equal mass of Fe3O4 is then added to the obtained biochar and pyrolyzed again to obtain magnetic biochar. Further enzymatic hydrolysis is then used to obtain the magnetic biochar coupling carrier. Finally, the obtained magnetic biochar coupling carrier is added to an anaerobic fermentation system to promote the hydrolysis process of anaerobic fermentation.

[0005] CN 117023551 A discloses a method for preparing biochar from recycled lignocellulosic biomass and its application. This invention uses the solid residue containing biochar at the end of the anaerobic fermentation process as an additive to improve hydrogen production during anaerobic fermentation. It demonstrates significant resource utilization, is simple to operate, and provides a new perspective for the resource and energy utilization of agricultural waste biomass.

[0006] However, the above patent applications and other existing technologies all involve the one-time addition of biochar. The one-time addition of biochar has the following problems: (1) The adsorption capacity of biochar may be rapidly saturated in the early stage (such as the adsorption of a large amount of ammonia nitrogen), which leads to the re-accumulation of inhibitors in the later stage of methanogenesis; (2) Livestock and poultry manure requires a rapid carbon source in the early stage of degradation, while it requires electron transfer support in the later stage. The functional requirements of biochar are different, which leads to the inability of biochar to play its role well. Therefore, although the one-time addition of biochar can improve the C / N ratio of the system, it cannot dynamically match the functional requirements of biochar in different stages of anaerobic fermentation. Summary of the Invention

[0007] Purpose of the invention: The purpose of this invention is to provide a system and method for segmented regulation of anaerobic fermentation of biomass based on modified biochar. This method modifies biochar to meet the different functional requirements of biochar at different stages of anaerobic fermentation, and adds low-temperature biochar and modified biochar to the hydrolysis acidification stage and the methanogenesis stage of anaerobic fermentation, respectively, to achieve precise intervention in C / N dynamic balance and inhibitor control.

[0008] Technical Solution: This invention provides a system for segmented regulation of anaerobic fermentation of biomass based on modified biochar, comprising a low-temperature biochar preparation system, a biochar modification system, a hydrolysis acidification system, a methanogenesis system, a biogas purification and separation system, and a heat utilization system. The outlet of the low-temperature biochar preparation system is connected to the inlet of the biochar modification system and the inlet of the hydrolysis acidification system, respectively. The outlet of the hydrolysis acidification system is connected to the inlet of the methanogenesis system, and the outlet of the methanogenesis system is connected to the inlet of the biogas purification and separation system. The outlet of the biochar modification system is connected to the inlet of the methanogenesis system. The low-temperature biochar preparation system is used to prepare low-temperature biochar and supply it to the hydrolysis acidification system and the biochar modification system. The biochar modification system is used to perform high-temperature carbon dioxide modification on the low-temperature biochar to obtain modified biochar, which is then supplied to the methanogenesis system. The heat utilization system is used to combust the pyrolysis oil and gas generated by the low-temperature biochar preparation system and the furnace gas generated by the biochar modification system. The resulting high-temperature flue gas is used sequentially as a heat source for the biochar modification system, the low-temperature biochar preparation system, and the anaerobic fermentation system.

[0009] Furthermore, the outlet of the biogas purification and separation system is connected to the inlet of the biochar modification system, which is used to transport the carbon dioxide generated by the biogas purification and separation system to the biochar modification system.

[0010] Furthermore, the low-temperature biochar preparation system includes a rotary jacketed pyrolysis machine, which comprises a kiln head, a kiln body, and a kiln tail. The kiln head is provided with a first biomass inlet, and the kiln tail is provided with a low-temperature biochar outlet and a pyrolysis oil and gas outlet. The inner cavity of the kiln body is provided with a spiral baffle, and the outer side of the kiln body is provided with an annular jacket. A medium-temperature flue gas inlet is provided at one end of the annular jacket near the kiln tail, and a medium-low temperature flue gas outlet is provided at one end of the annular jacket near the kiln head.

[0011] Furthermore, the biochar modification system includes a vertical segmented furnace, with a feeding section at the top, a reaction section in the middle, and a discharge section at the bottom. The feeding section is equipped with a low-temperature biochar inlet and a furnace gas outlet, while the discharge section is equipped with a CO2 inlet and a modified biochar outlet. An annular jacket is provided on the outside of the reaction section, with a high-temperature flue gas inlet near the discharge section and a medium-temperature flue gas outlet near the feeding section.

[0012] Furthermore, the vertical segmented furnace is equipped with a rotatable segmented material plate for the gradual descent of materials, and the descent speed of the materials is controlled by adjusting the rotation speed of the rotatable segmented material plate.

[0013] Furthermore, the hydrolysis acidification system includes a hydrolysis acidification tank, with a second biomass inlet, a first steam inlet, and a low-temperature biochar inlet at the top of the hydrolysis acidification tank, and an acidification residue outlet at the bottom of the hydrolysis acidification tank.

[0014] Furthermore, the methanogenic system includes a methanogenic tank, with an acidification slag inlet at the bottom and a second steam inlet, a modified biochar inlet, and a biogas outlet at the top. The side of the methanogenic tank has biogas residue and biogas slurry outlets.

[0015] Furthermore, the biogas purification and separation system includes a biogas purification system and a biogas separation system. The biogas purification system includes a cyclone separator, a wet desulfurization tower, and a dry desulfurization tower connected in sequence. Each of the cyclone separator, wet desulfurization tower, and dry desulfurization tower is equipped with a corresponding biogas inlet and a purified biogas outlet. The biogas separation system is a membrane separation device, equipped with a purified biogas inlet, a biomethane outlet, and a carbon dioxide outlet. The purified biogas outlet is connected to the purified biogas inlet of the dry desulfurization tower.

[0016] Furthermore, the heat utilization system includes a hot blast stove and a heat exchanger, wherein multiple independent burners are evenly distributed around the hot blast stove; the hot blast stove has a pyrolysis gas inlet, a primary air inlet, a furnace gas inlet, and a high-temperature flue gas outlet; the pyrolysis gas inlet is connected to the pyrolysis oil and gas outlet of the low-temperature biochar preparation system, the furnace gas inlet is connected to the furnace gas outlet of the biochar modification system, and the high-temperature flue gas outlet is connected to the high-temperature flue gas inlet of the biochar modification system; the hot blast stove is used to generate high-temperature flue gas, which enters the biochar modification system and is then heated to become medium-temperature flue gas, which enters the low-temperature biochar preparation system and is then heated to become medium-low temperature flue gas, which enters the heat exchanger and exchanges heat with cold water to generate steam, which is then fed into the hydrolysis acidification system and the methanogenesis system.

[0017] Based on the same inventive concept, the present invention provides a method for segmented regulation of anaerobic fermentation of biomass using modified biochar, applied to the aforementioned system for segmented regulation of anaerobic fermentation of biomass, comprising:

[0018] Low-temperature biochar preparation: After pretreatment, the first biomass is pyrolyzed in a low-temperature biochar preparation system by indirect heating to obtain low-temperature biochar; wherein, the first biomass is one or more of the organic solid wastes such as straw, sawdust, mushroom residue, and sludge.

[0019] Preparation of modified biochar: The low-temperature biochar obtained from the low-temperature biochar preparation system is directly transported to the biochar modification system at high temperature. The low-temperature biochar is modified at high temperature using carbon dioxide generated by the biogas purification and separation system to obtain modified biochar.

[0020] Anaerobic fermentation to produce biogas: Low-temperature biochar is added to the hydrolysis acidification system and modified biochar is added to the methanogenic system; after pretreatment, the second biomass is anaerobically fermented in the hydrolysis acidification system and the methanogenic system in sequence, and the methanogenic system produces biogas, biogas residue and biogas liquid; wherein, the second biomass is one or more of livestock and poultry manure, kitchen waste and organic sludge.

[0021] Biogas purification and separation: The biogas produced by the methanogenic system is purified to remove impurities, and then the methane and carbon dioxide in the biogas are further separated by membrane separation to obtain biomethane and carbon dioxide.

[0022] Heat utilization: The pyrolysis oil and gas generated by the low-temperature biochar preparation system and the furnace gas generated by the biochar modification system are transported through pipelines to the heat utilization system for combustion. The high-temperature flue gas generated is used as the heat source for the biochar modification system, the low-temperature biochar preparation system and the anaerobic fermentation system in sequence.

[0023] Working Principle: This invention obtains low-temperature biochar through low-temperature pyrolysis of biomass (straw, sawdust, mushroom residue, sludge, and other organic solid waste). Then, it utilizes carbon dioxide obtained from the separation of biogas produced during the anaerobic fermentation of livestock and poultry manure to perform high-temperature modification of the low-temperature biochar, increasing its specific surface area and porosity to obtain modified biochar. The resulting biochars (low-temperature biochar and modified biochar) are then added to the hydrolysis-acidification and methanogenesis stages of the anaerobic fermentation of livestock and poultry manure biomass, respectively. This meets the functional requirements of biochar at different stages of anaerobic fermentation, achieving precise intervention in C / N dynamic balance and inhibitor control, improving the fermentation efficiency and system stability of the entire system. It enables the coupled optimization of inhibitor control, C / N dynamic balance, and microbial synergy, representing a key technological path for the efficient resource utilization of livestock and poultry manure through anaerobic fermentation.

[0024] Beneficial effects: Compared with the prior art, the significant technical effects of the present invention are as follows: (1) Compared with the direct addition of biomass, the pyrolysis machine decomposes the lignin and other difficult-to-degrade components in biomass 1, which can avoid the problem of slow biomass degradation; at the same time, the volume of the low-temperature biochar obtained by pyrolysis is greatly reduced, which can increase the effective volume of the anaerobic tank, improve the settling properties of the anaerobic fermentation raw materials, and reduce the problem of scum caused by the direct addition of the original biomass; (2) The low-temperature biochar obtained by the low-temperature biochar preparation system has abundant oxygen-containing functional groups, which can not only be used as a carbon source to adjust the C / N ratio of the system, but also combine with anaerobic biomass to accelerate biomass hydrolysis; at the same time, its weakly acidic surface environment has good compatibility with volatile fatty acids, reducing the inhibition of acid-producing bacteria by pH fluctuations, which is beneficial to (3) The alkaline surface of the modified biochar obtained by the biochar modification system is adapted to methanogens. In addition, its high specific surface area and micropores can adsorb volatile fatty acids, avoid the instantaneous high concentration of acetic acid from inhibiting methanogens, and provide more attachment points for methanogens. At the same time, the high conductivity of the modified biochar can promote direct interspecies electron transfer (DIET), accelerate the acetic acid cracking to produce methanogens, and help improve the methanogen production rate. (4) By using the carbon dioxide generated by biogas separation to modify the low-temperature biochar and feeding the modified biochar back to the methanogen system, the methanogen production efficiency is improved. This not only increases the value of the separated carbon dioxide, but also increases the methanogen production rate of the entire anaerobic fermentation system, greatly improving the overall benefits. Attached Figure Description

[0025] Figure 1 This is a system block diagram of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will now be described in conjunction with specific embodiments and the accompanying drawings.

[0028] like Figure 1 As shown, the system for segmented regulation of anaerobic fermentation of biomass based on modified biochar of the present invention includes a low-temperature biochar preparation system, a biochar modification system, a hydrolysis-acidification system, a methanogenesis system, a biogas purification and separation system, and a heat utilization system. The outlet of the low-temperature biochar preparation system is connected to the inlet of the biochar modification system and the inlet of the hydrolysis-acidification system, respectively. The outlet of the hydrolysis-acidification system is connected to the inlet of the methanogenesis system, and the outlet of the methanogenesis system is connected to the inlet of the biogas purification and separation system. The outlet of the biochar modification system is connected to the inlet of the methanogenesis system. The low-temperature biochar preparation system is used to prepare low-temperature biochar and supply it to the hydrolysis-acidification system and the biochar modification system. The biochar modification system is used to perform high-temperature carbon dioxide modification on the low-temperature biochar to obtain modified biochar, which is then supplied to the methanogenesis system. The outlet of the biogas purification and separation system is connected to the inlet of the biochar modification system and is used to transport the carbon dioxide generated by the biogas purification and separation system to the biochar modification system. The heat utilization system is used to burn the pyrolysis oil and gas generated by the low-temperature biochar preparation system and the exhaust gas generated by the biochar modification system. The high-temperature flue gas generated is used as the heat source for the biochar modification system, the low-temperature biochar preparation system and the anaerobic fermentation system in sequence.

[0029] like Figure 1 and Figure 2 As shown, the main equipment of the low-temperature biochar preparation system is a rotary jacketed pyrolysis machine. The rotary jacketed pyrolysis machine includes a kiln head, a kiln body, and a kiln tail. The kiln head has a first biomass inlet 11, which is connected to a first biomass feeding and conveying system. The kiln tail has a low-temperature biochar outlet 12 and a pyrolysis oil and gas outlet 13. The inner cavity of the kiln body is equipped with spiral baffles to guide the material effectively. An annular jacket is located on the outer side of the kiln body. A medium-temperature flue gas inlet 14 is located at the end of the annular jacket near the kiln tail, and a medium-low temperature flue gas outlet 15 is located at the end of the annular jacket near the kiln head. The drive unit of the rotary jacketed pyrolysis machine has frequency conversion and reverse rotation functions, allowing adjustment of the pyrolysis machine's rotation speed according to the material temperature at the outlet, or reverse operation to ensure complete biomass pyrolysis.

[0030] The main equipment of the biochar modification system is a vertical segmented furnace. The top of the furnace is the feeding section, the middle section is the reaction section, and the bottom section is the discharge section. The feeding section is equipped with a low-temperature biochar inlet 21 and a furnace gas outlet 24, with the low-temperature biochar inlet 21 connected to the low-temperature biochar outlet 12. The discharge section is equipped with a CO2 inlet 22 and a modified biochar outlet 23. An annular jacket is installed outside the reaction section. A high-temperature flue gas inlet 25 is located near the discharge section of the annular jacket, and a medium-temperature flue gas outlet 26 is located near the feeding section of the annular jacket, connected to the medium-temperature flue gas inlet 14. The vertical segmented furnace is equipped with a rotatable segmented material plate for the gradual descent of the material. The descent speed of the material is controlled by adjusting the rotation speed of the rotatable segmented material plate, thereby ensuring sufficient contact between the biochar and carbon dioxide.

[0031] The core equipment of the hydrolysis acidification system is the hydrolysis acidification tank. The top of the tank has a second biomass inlet 31, a first steam inlet 32, and a low-temperature biochar inlet 33, while the bottom has an acidification slag outlet 34. The second biomass inlet 31 is connected to the second biomass feeding and conveying system, and the low-temperature biochar inlet 33 is connected to the low-temperature biochar outlet 12. A stirring device is installed inside the hydrolysis acidification tank to improve the contact and transfer of materials within the tank, thereby enhancing the system's operational stability.

[0032] The core equipment of the methanogenic system is the methanogenic tank. The bottom of the tank has an acidification slag inlet 41, which is connected to the acidification slag outlet 34. The top of the tank has a second steam inlet 42, a modified biochar inlet 43, and a biogas outlet 44. The side of the tank has biogas residue and biogas slurry outlets 45. The modified biochar inlet 43 is connected to the modified biochar outlet 23. A stirring device is installed inside the tank to improve the contact and transfer of materials within the tank, thereby enhancing the system's operational stability.

[0033] The biogas purification and separation system comprises a biogas purification system and a biogas separation system. The core equipment of the biogas purification system includes a cyclone separator, a wet desulfurization tower, and a dry desulfurization tower, while the core equipment of the biogas separation system is a membrane separation device. The cyclone separator, wet desulfurization tower, and dry desulfurization tower are connected sequentially, each equipped with a corresponding biogas inlet 51 and a purified biogas outlet 52. In the biogas purification system, the cyclone separator, wet desulfurization tower, and dry desulfurization tower all function as purification devices. The cyclone separator performs preliminary separation, removing solid particles and entrained droplets; the wet and dry desulfurization towers are desulfurization devices, with the dry desulfurization process also involving dehydration.

[0034] The membrane separation unit has a purified biogas inlet 53, a biogas outlet 54, and a carbon dioxide outlet 55. The purified biogas outlet 52 of the dry desulfurization tower is connected to the purified biogas inlet 53, and the carbon dioxide outlet 55 is connected to the CO2 inlet 22.

[0035] The core equipment of the heat utilization system consists of a hot blast stove and a heat exchanger. Multiple independent burners, at least four in number, are evenly distributed around the hot blast stove to ensure complete combustion of the pyrolysis oil and gas entering and exiting the stove. The hot blast stove has a pyrolysis gas inlet 61, a primary air inlet 62, an exit gas inlet 63, multiple independent burner connection ports 64, and a high-temperature flue gas outlet 65. The pyrolysis gas inlet 61 connects to the pyrolysis oil and gas outlet 13 of the low-temperature biochar preparation system. The primary air inlet 62 is used to introduce primary air. The exit gas inlet 63 connects to the exit gas outlet 24 of the biochar modification system. The independent burner connection ports 64 connect to independent burners. The high-temperature flue gas outlet 65 connects to the high-temperature flue gas inlet 25 of the biochar modification system. The heat exchanger has a medium-low temperature flue gas inlet 66, which connects to the medium-low temperature flue gas outlet 15. The outlet of the heat exchanger is connected to the first steam inlet 32 ​​and the second steam inlet 42.

[0036] The hot blast stove is used to generate high-temperature flue gas. After exiting from the high-temperature flue gas outlet 65, the high-temperature flue gas enters the annular jacket of the vertical segmented furnace through the high-temperature flue gas inlet 25, providing heat to the vertical segmented furnace. Then, it becomes medium-temperature flue gas and escapes from the medium-temperature flue gas outlet 26. The medium-temperature flue gas enters the annular jacket of the rotary jacketed pyrolysis machine through the medium-temperature flue gas inlet 14, providing heat to the rotary jacketed pyrolysis machine. Then, it becomes medium-low temperature flue gas and escapes from the medium-low temperature flue gas outlet 15. The medium-low temperature flue gas enters the heat exchanger through the medium-low temperature flue gas inlet 66. The low-temperature flue gas exchanges heat with cold water in the heat exchanger to generate water vapor. Part of the water vapor is used in the hydrolysis acidification system and the methanogenic system, and the remainder is used to explore other waste heat utilization methods. The tail gas after the medium-low temperature flue gas heat exchange enters the tail gas purification system and is discharged after purification to meet the standards.

[0037] The present invention provides a method for segmented regulation of anaerobic fermentation of biomass based on modified biochar, which specifically includes the following steps:

[0038] S1. Low-temperature biochar preparation: After pretreatment, the first biomass (biomass 1 in the figure) is pyrolyzed in a rotary jacketed pyrolysis machine of the low-temperature biochar preparation system by indirect heating to obtain low-temperature biochar; wherein, the first biomass is one or more of organic solid wastes such as straw, sawdust, mushroom residue, and sludge.

[0039] In this embodiment, the pretreatment process of the first biomass includes crushing and drying; after drying, the moisture content of the first biomass is ≤20% to ensure the low-energy and stable operation of the pyrolysis furnace.

[0040] The pyrolysis temperature of the first biomass is 400-450℃, and the pyrolysis time is 30-60 minutes. The heating source for the rotary jacketed pyrolysis machine is the medium-temperature flue gas exiting the vertical segmented furnace.

[0041] S2. Preparation of modified biochar: The low-temperature biochar obtained from the low-temperature biochar preparation system is directly transported to the biochar modification system at high temperature. The low-temperature biochar is modified at high temperature using carbon dioxide generated by the biogas purification and separation system to obtain modified biochar.

[0042] In this embodiment, the modification temperature of the low-temperature biochar is 750-850℃, and the residence time of the low-temperature biochar in the furnace is 45-90 min. The CO2 flow rate is 100-150 ml / min. The heating method for the low-temperature biochar modification is indirect heating.

[0043] S3. Anaerobic fermentation to produce biogas: Low-temperature biochar is added to the hydrolysis acidification system, and modified biochar is added to the methanogenic system; the second biomass (biomass 2 in the figure) is pretreated and then anaerobically fermented in the hydrolysis acidification system and the methanogenic system in sequence. The methanogenic system produces biogas, biogas residue and biogas liquid; wherein, the second biomass is one or more of livestock and poultry manure, kitchen waste and organic sludge.

[0044] In this embodiment, the pretreatment process of the second biomass mainly refers to the separation of large particulate impurities. The temperature in the hydrolysis acidification system is 20-35℃, the pH is 5.5-6.5, and the residence time is 3-6 days; the amount of low-temperature biochar added in the hydrolysis acidification system is 7-15% of the solid weight.

[0045] In this embodiment, the temperature in the methanogenic system is 30-35°C, the pH is 6.8-7.8, and the residence time is 10-25 days. The amount of modified biochar added to the methanogenic system is 2-5% of the solid weight.

[0046] The biogas residue and biogas slurry produced by the methanogenic system are further stabilized and treated to produce organic fertilizer and liquid fertilizer for resource utilization.

[0047] S4. Biogas purification and separation: The biogas produced by the methanogenic system is purified to remove impurities such as dust, hydrogen sulfide, and moisture. Furthermore, membrane separation is used to separate methane and carbon dioxide in the biogas to obtain biomethane and carbon dioxide.

[0048] In this embodiment, the purification process comprises conventional cyclone dust removal, wet desulfurization, and dry desulfurization processes. The separation of carbon dioxide and methane utilizes advanced membrane separation technology; the high-pressure side pressure is 1-2 MPa, the low-pressure side pressure is 0.1-0.2 MPa, and the membrane separation temperature is 20-40°C. The purity of the separated carbon dioxide is ≥95.5%, and the purity of the separated methane is ≥97.6%.

[0049] S5. Heat Utilization: The pyrolysis oil and gas generated by the low-temperature biochar preparation system and the furnace gas generated by the biochar modification system are transported through pipelines to the hot blast furnace of the heat utilization system for combustion. The high-temperature flue gas generated is used as the heat source for the biochar modification system, the low-temperature biochar preparation system and the anaerobic fermentation system in sequence.

[0050] In this embodiment, the temperature of the high-temperature flue gas entering the annular jacket of the modified biochar system is 900-1000℃, and the exit temperature is 700-800℃. The temperature of the medium-temperature flue gas entering the annular jacket of the low-temperature biochar preparation system is 650-700℃, and the exit temperature is 450-500℃; the temperature of the medium-low temperature flue gas entering the heat exchanger is 400-450℃, and the exit temperature is 120-180℃; the exhaust gas exiting the heat exchanger is finally purified by the flue gas purification system and discharged in compliance with standards.

[0051] This invention utilizes carbon dioxide to modify low-temperature biochar and adds low-temperature biochar and modified biochar in stages according to the functional requirements of biochar at different stages of anaerobic fermentation. This maximizes the function of biochar and enables precise control of different stages of biomass anaerobic fermentation, thereby improving the operational stability and fermentation efficiency of biomass anaerobic fermentation throughout the entire process.

Claims

1. A system for segmented regulation of anaerobic fermentation of biomass based on modified biochar, characterized in that: It includes a low-temperature biochar preparation system, a biochar modification system, a hydrolysis acidification system, a methanogenesis system, a biogas purification and separation system, and a heat utilization system; The outlet of the low-temperature biochar preparation system is connected to the inlet of the biochar modification system and the inlet of the hydrolysis acidification system, respectively. The outlet of the hydrolysis acidification system is connected to the inlet of the methanogenic system, and the outlet of the methanogenic system is connected to the inlet of the biogas purification and separation system. The outlet of the biochar modification system is connected to the inlet of the methanogenic system. The low-temperature biochar preparation system is used to prepare low-temperature biochar and supply it to the hydrolysis acidification system and the biochar modification system. The biochar modification system is used to perform high-temperature carbon dioxide modification on the low-temperature biochar to obtain modified biochar and supply it to the methanogenic system. The heat utilization system is used to burn the pyrolysis oil and gas generated by the low-temperature biochar preparation system and the furnace gas generated by the biochar modification system. The high-temperature flue gas generated is used as the heat source for the biochar modification system, the low-temperature biochar preparation system and the anaerobic fermentation system in sequence.

2. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 1, characterized in that: The outlet of the biogas purification and separation system is connected to the inlet of the biochar modification system, which is used to transport the carbon dioxide generated by the biogas purification and separation system to the biochar modification system.

3. The system for segmented regulation of biomass anaerobic fermentation based on modified biochar according to claim 1, characterized in that: The low-temperature biochar preparation system includes a rotary jacketed pyrolysis machine, which includes a kiln head, a kiln body and a kiln tail. The kiln head is provided with a first biomass inlet (11), and the kiln tail is provided with a low-temperature biochar outlet (12) and a pyrolysis oil and gas outlet (13). The inner cavity of the kiln body is provided with a spiral baffle, and the outer side of the kiln body is provided with an annular jacket. A medium-temperature flue gas inlet (14) is provided at one end of the annular jacket near the kiln tail, and a medium-low temperature flue gas outlet (15) is provided at one end of the annular jacket near the kiln head.

4. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 1, characterized in that: The biochar modification system includes a vertical segmented furnace, with the top of the furnace being the feeding section, the middle section being the reaction section, and the bottom section being the discharge section. The feeding section is provided with a low-temperature biochar inlet (21) and a furnace gas outlet (24), and the discharging section is provided with a CO2 inlet (22) and a modified biochar outlet (23); An annular jacket is provided on the outside of the reaction section. A high-temperature flue gas inlet (25) is provided near the discharge section of the annular jacket, and a medium-temperature flue gas outlet (26) is provided near the feed section of the annular jacket.

5. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 4, characterized in that: The vertical segmented furnace is equipped with a rotatable segmented material plate for the gradual descent of materials, and the descent speed of the materials is controlled by adjusting the rotation speed of the rotatable segmented material plate.

6. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 1, characterized in that: The hydrolysis acidification system includes a hydrolysis acidification tank, with a second biomass inlet (31), a first steam inlet (32), and a low-temperature biochar inlet (33) at the top of the hydrolysis acidification tank, and an acidification slag outlet (34) at the bottom of the hydrolysis acidification tank.

7. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 1, characterized in that: The methanogenic system includes a methanogenic tank, with an acidification slag inlet (41) at the bottom and a second steam inlet (42), a modified biochar inlet (43), and a biogas outlet (44) at the top. A biogas residue and biogas slurry outlet (45) is provided on the side of the methanogenic tank.

8. The system for segmented regulation of biomass anaerobic fermentation based on modified biochar according to claim 1, characterized in that: The biogas purification and separation system includes a biogas purification system and a biogas separation system. The biogas purification system includes a cyclone separator, a wet desulfurization tower, and a dry desulfurization tower connected in sequence. The cyclone separator, the wet desulfurization tower, and the dry desulfurization tower are each provided with a corresponding biogas inlet (51) and a purified biogas outlet (52). The biogas separation system is a membrane separation device, which is provided with a purified biogas inlet (53), a biogas outlet (54), and a carbon dioxide outlet (55). The purified biogas outlet (52) of the dry desulfurization tower is connected to the purified biogas inlet (53).

9. The system for segmented regulation of anaerobic fermentation of biomass based on modified biochar according to claim 1, characterized in that: The heat utilization system includes a hot air furnace and a heat exchanger, wherein multiple independent burners are evenly distributed around the hot air furnace; The hot blast stove has a pyrolysis gas inlet (61), a primary air inlet (62), a furnace gas inlet (63), and a high-temperature flue gas outlet (65); The pyrolysis gas inlet (61) is connected to the pyrolysis oil and gas outlet (13) of the low-temperature biochar preparation system, the furnace gas inlet (63) is connected to the furnace gas outlet (24) of the biochar modification system, and the high-temperature flue gas outlet (65) is connected to the high-temperature flue gas inlet (25) of the biochar modification system. The hot air furnace is used to generate high-temperature flue gas. After entering the biochar modification system, the high-temperature flue gas is heated and becomes medium-temperature flue gas. After entering the low-temperature biochar preparation system, the medium-temperature flue gas is heated and becomes medium-low temperature flue gas. The medium-low temperature flue gas enters the heat exchanger and exchanges heat with cold water to generate water vapor. The water vapor is then fed into the hydrolysis acidification system and the methanogenesis system.

10. A method for segmented regulation of anaerobic fermentation of biomass based on modified biochar, characterized in that, This method is applied to the system of segmented regulation of biomass anaerobic fermentation based on modified biochar as described in claim 1, comprising: Low-temperature biochar preparation: After pretreatment, the first biomass is pyrolyzed in a low-temperature biochar preparation system by indirect heating to obtain low-temperature biochar; wherein, the first biomass is one or more of the organic solid wastes such as straw, sawdust, mushroom residue, and sludge. Preparation of modified biochar: The low-temperature biochar obtained from the low-temperature biochar preparation system is directly transported to the biochar modification system at high temperature. The low-temperature biochar is modified at high temperature using carbon dioxide generated by the biogas purification and separation system to obtain modified biochar. Anaerobic fermentation to produce biogas: Low-temperature biochar is added to the hydrolysis acidification system and modified biochar is added to the methanogenic system; after pretreatment, the second biomass is anaerobically fermented in the hydrolysis acidification system and the methanogenic system in sequence, and the methanogenic system produces biogas, biogas residue and biogas liquid; wherein, the second biomass is one or more of livestock and poultry manure, kitchen waste and organic sludge. Biogas purification and separation: The biogas produced by the methanogenic system is purified to remove impurities, and then the methane and carbon dioxide in the biogas are further separated by membrane separation to obtain biomethane and carbon dioxide. Heat utilization: The pyrolysis oil and gas generated by the low-temperature biochar preparation system and the furnace gas generated by the biochar modification system are transported through pipelines to the heat utilization system for combustion. The high-temperature flue gas generated is used as the heat source for the biochar modification system, the low-temperature biochar preparation system and the anaerobic fermentation system in sequence.

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