A biogas slurry resource classification and recovery system and method thereof

Abstract

The present invention relates to the technical field of biogas slurry recycling and utilization, and specifically to a biogas slurry resource classification recycling system and method thereof, including a biogas slurry pond, a DUMF1 membrane module, a DUMF2 membrane module, and a DUMF3 membrane module. The biogas slurry in the biogas slurry pond is successively subjected to concentration treatment by the DUMF1 membrane module and the DUMF2 membrane module. The concentrated water of the DUMF1 membrane module and the DUMF2 membrane module is mixed and introduced into the DUMF3 membrane module. After concentration treatment by the DUMF3 membrane module, humic acid with a target concentration is obtained. The DUMF1 membrane module, the DUMF2 membrane module, and the DUMF3 membrane module adopt decolorizing membranes with different filtration pore diameters. This biogas slurry resource classification recycling system not only uses multiple processes and multiple membrane separation technologies to recycle high-concentration humic acid, but also can recycle inorganic salts such as nitrogen, phosphorus, potassium, and ammonia to produce liquid inorganic fertilizers, and utilize the alkalinity in the biogas slurry to synthesize micro calcium carbonate, nano calcium carbonate, and recover substances such as black calcium carbonate, realizing the comprehensive and full recycling and utilization of biogas slurry resources.

Description

Technical Field

[0001] The present invention relates to the technical field of biogas slurry recycling, and particularly to a biogas slurry resource classification recycling system and its method. Background Art

[0002] At present, the problems of global energy shortage and environmental pollution are becoming increasingly prominent, and biomass energy has gradually become a renewable energy source that has received extensive attention. As an important form of biomass energy, biogas slurry has broad application prospects in the fields of agriculture, animal husbandry, etc. Traditional waste treatment methods often adopt landfill or incineration, which have problems such as incomplete utilization of energy and occupation of land resources. The biogas slurry recycling system can convert waste into biogas and biogas slurry. The biogas can be purified and used for power generation or heating; while the biogas slurry is rich in nutrients such as organic nitrogen, phosphorus, and potassium, and can be used as a high-quality organic fertilizer to achieve double benefits of energy and environmental protection.

[0003] The existing biogas slurry recycling system has a relatively simple concentration treatment process for biogas slurry. In the case of a relatively low concentration of the original biogas slurry, it may lead to a relatively low concentration of humic acid recovered after the existing biogas slurry recycling system concentrates the biogas slurry, and it cannot meet the expected standard for recycling use. Summary of the Invention

[0004] The purpose of the present invention is to provide a biogas slurry resource classification recycling system and its method to solve the problems raised in the above background art.

[0005] To achieve the above purpose, one aspect of the present invention provides the following technical solution:

[0006] A biogas slurry resource classification recycling system, the biogas slurry resource classification recycling system includes a biogas slurry pool, a DUMF1 membrane module, a DUMF2 membrane module, and a DUMF3 membrane module. The biogas slurry in the biogas slurry pool is sequentially concentrated by the DUMF1 membrane module and the DUMF2 membrane module. The concentrated water of the DUMF1 membrane module and the DUMF2 membrane module is mixed and introduced into the DUMF3 membrane module, and humic acid with a target concentration is obtained after being concentrated by the DUMF3 membrane module. The DUMF1 membrane module, the DUMF2 membrane module, and the DUMF3 membrane module adopt decolorizing membranes with different filtration pore sizes.

[0007] Preferably, the biogas slurry resource classification and recovery system further includes an AUMF1 membrane module. The water outlet end of the biogas slurry tank is connected to the water inlet end of the AUMF1 membrane module. The concentrated water end of the AUMF1 membrane module is connected to the inlet of the black calcium reactor. The water production end of the AUMF1 membrane module is connected to the water inlet end of the first storage water tank. The water outlet end of the first storage water tank is connected to the water inlet end of the DUMF1 membrane module through a filtering and reduction component. The concentrated water end of the DUMF1 membrane module is connected to the water inlet end of the second storage water tank. The water production end of the DUMF1 membrane module is connected to the water inlet end of the third storage water tank.

[0008] Preferably, a first water supply pump and a multi-media filter are sequentially connected between the biogas slurry tank and the AUMF1 membrane module, and a second water supply pump is connected between the AUMF1 membrane module and the black calcium reactor.

[0009] Preferably, the biogas slurry resource classification and recovery system further includes an AUMF2 membrane module. The water outlet end of the third storage water tank is connected to the water inlet end of the AUMF2 membrane module. The water production end of the AUMF2 membrane module is connected to the water inlet end of the fourth storage water tank.

[0010] Preferably, a third water supply pump and a nano-calcium carbonate reactor are sequentially connected between the third storage water tank and the AUMF2 membrane module. There is a reflux channel between the concentrated water end of the AUMF2 membrane module and the nano-calcium carbonate reactor. A fourth water supply pump and a nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery component are sequentially connected between the AUMF2 membrane module and the fourth storage water tank.

[0011] Preferably, the biogas slurry resource classification and recovery system further includes a nanofiltration membrane module. The water outlet end of the fourth storage water tank is connected to the water inlet end of the nanofiltration membrane module through a filtering and reduction component. The concentrated water end of the nanofiltration membrane module is connected to the water inlet end of the fifth storage water tank. The water production end of the nanofiltration membrane module is discharged to the outside. The water outlet end of the fifth storage water tank is connected to the water inlet end of the DUMF2 membrane module through a filtering and reduction component. The concentrated water end of the DUMF2 membrane module is connected to the water inlet end of the second storage water tank. The water production end of the DUMF2 membrane module is connected to the water inlet end of the fourth storage water tank.

[0012] Preferably, the water outlet end of the second storage water tank is connected to the water inlet end of the DUMF3 membrane module through a filtering and reduction component. The concentrated water end of the DUMF3 membrane module is connected to the water inlet end of the sixth storage water tank. The water production end of the DUMF3 membrane module is connected to the water inlet end of the fourth storage water tank.

[0013] Preferably, the filtering and reduction component includes a fifth water supply pump, a security filter and a booster pump connected in sequence. A reducing agent tank and a scale inhibitor tank are also connected between the security filter and the booster pump.

[0014] Preferably, the filtration pore size of the DUMF1 membrane module is 500 - 800 molecular weights, the filtration pore size of the DUMF2 membrane module is 400 - 600 molecular weights, the filtration pore size of the DUMF3 membrane module is 300 - 500 molecular weights, and the target concentration is greater than 30000 mg / L.

[0015] The embodiment of the present invention also provides a method for classified recycling of biogas slurry resources, using the biogas slurry classified recycling system as described above, including the following steps:

[0016] S1. The biogas slurry in the biogas slurry pond is filtered through a multi-media filter, and the filtered biogas slurry enters the AUMF1 membrane module for filtration and impurity removal. The produced water of the AUMF1 membrane module enters the first storage water tank for storage and standby, and the concentrated water of the AUMF1 membrane module enters the black calcium reactor to recover black calcium carbonate;

[0017] S2. The produced water in the first storage water tank enters the DUMF1 membrane module for concentration treatment. The produced water of the DUMF1 membrane module enters the third storage water tank for storage and standby, and the concentrated water of the DUMF1 membrane module enters the second storage water tank for storage and standby;

[0018] S3. The biogas slurry in the third storage water tank enters the nano-calcium carbonate reactor to recover micron calcium carbonate and nano-calcium carbonate. The produced water of the nano-calcium carbonate reactor enters the AUMF2 membrane module for filtration and impurity removal. The concentrated water of the AUMF2 membrane module is refluxed to the nano-calcium carbonate reactor for purification treatment. The produced water of the AUMF2 membrane module enters the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery module to recover inorganic salts such as nitrogen, phosphorus, potassium and ammonia, and is made into liquid inorganic fertilizer. The produced water of the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery module enters the fourth storage water tank for storage and standby;

[0019] S4. The produced water in the fourth storage water tank enters the nanofiltration membrane module for filtration. The produced water after nanofiltration treatment is directly discharged, and the concentrated water of the nanofiltration membrane module enters the fifth storage water tank for storage and standby;

[0020] S5. The concentrated water in the fifth storage water tank enters the DUMF2 membrane module for concentration treatment. The concentrated water of the DUMF2 membrane module enters the second storage water tank and is mixed with the concentrated water of the DUMF1 membrane module for standby. The produced water of the DUMF2 membrane module enters the fourth storage water tank for reflux treatment;

[0021] S6. The concentrated water mixed in the second storage water tank enters the DUMF3 membrane module for further concentration treatment. After the concentrated water is concentrated to the concentration, it enters the sixth storage water tank for storage. The produced water of the DUMF3 membrane module enters the fourth storage water tank for reflux treatment.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] In the biogas slurry resource classification and recovery system provided by the embodiment of the present invention, the biogas slurry in the biogas slurry tank is successively concentrated by the DUMF1 membrane module and the DUMF2 membrane module. The concentrated water of the DUMF1 membrane module and the DUMF2 membrane module is mixed and introduced into the DUMF3 membrane module for further concentration treatment, so that humic acid with a concentration greater than 30,000 mg / L can be obtained through multi-stage concentration, improving the biogas slurry concentration effect and the recovery quality of humic acid. At the same time, the biogas slurry resource classification and recovery system can also recover inorganic salts such as nitrogen, phosphorus, potassium, and ammonia to produce liquid inorganic fertilizers, and use the alkalinity in the biogas slurry to synthesize microcalcium carbonate, nanocalcium carbonate, and recover substances such as black calcium carbonate, realizing the comprehensive and full recovery and utilization of biogas slurry resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic structural diagram of a biogas slurry resource classification and recovery system provided by an embodiment of the present invention;

[0025] Figure 2 FIG. is one of the partial views of a biogas slurry resource classification and recovery system provided by an embodiment of the present invention;

[0026] Figure 3 FIG. is the second partial view of a biogas slurry resource classification and recovery system provided by an embodiment of the present invention;

[0027] Figure 4 FIG. is a schematic structural diagram of a filtration and reduction component of a biogas slurry resource classification and recovery system provided by an embodiment of the present invention;

[0028] Figure 5 FIG. is a flowchart of a biogas slurry resource classification and recovery method provided by an embodiment of the present invention.

[0029] DESCRIPTION OF REFERENCE NUMERALS: 1, biogas slurry tank; 2, DUMF1 membrane module; 3, DUMF2 membrane module; 4, DUMF3 membrane module; 5, AUMF1 membrane module; 6, black calcium reactor; 7, first storage water tank; 8, second storage water tank; 9, third storage water tank; 10, first water supply pump; 11, multi-media filter; 12, second water supply pump; 13, AUMF2 membrane module; 14, fourth storage water tank; 15, third water supply pump; 16, nano calcium carbonate reactor; 17, fourth water supply pump; 18, nitrogen, phosphorus, potassium, and ammonia inorganic fertilizer recovery component; 19, nanofiltration membrane module; 20, fifth storage water tank; 21, sixth storage water tank; 22, fifth water supply pump; 23, security filter; 24, booster pump; 25, reducer tank; 26, scale inhibitor tank. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Figure 1 A schematic structural diagram of a biogas slurry resource classification and recovery system provided for an embodiment of the present invention. Figure 2 One of the partial views of a biogas slurry resource classification and recovery system provided for an embodiment of the present invention. Figure 3 The second partial view of a biogas slurry resource classification and recovery system provided for an embodiment of the present invention. An embodiment of the present invention provides a biogas slurry resource classification and recovery system. As Figures 1 to 3 shown, the biogas slurry resource classification and recovery system may include a biogas slurry pond 1, a DUMF1 membrane module 2, a DUMF2 membrane module 3, and a DUMF3 membrane module 4. The biogas slurry in the biogas slurry pond 1 is sequentially concentrated by the DUMF1 membrane module 2 and the DUMF2 membrane module 3. The concentrated water of the DUMF1 membrane module 2 and the DUMF2 membrane module 3 is mixed and introduced into the DUMF3 membrane module 4. After being concentrated by the DUMF3 membrane module 4, humic acid with a target concentration is obtained. The DUMF1 membrane module 2, the DUMF2 membrane module 3, and the DUMF3 membrane module 4 adopt decolorizing membranes with different filtration pore sizes.

[0032] After the biogas slurry in the biogas slurry pond 1 of the biogas slurry resource classification and recovery system provided by the embodiment of the present invention is sequentially concentrated by the DUMF1 membrane module 2 and the DUMF2 membrane module 3, the concentrated water of the DUMF1 membrane module 2 and the DUMF2 membrane module 3 is mixed and introduced into the DUMF3 membrane module 4, and is continuously concentrated by the DUMF3 membrane module 4, so that humic acid with an expected target concentration can be obtained through multi-stage concentration, improving the biogas slurry concentration effect and the recovery quality of humic acid.

[0033] In an embodiment of the present invention, as Figure 1 and Figure 2As shown in the figure, the biogas slurry resource classification and recovery system further includes an AUMF1 membrane module 5. The water outlet end of the biogas slurry pond 1 is connected to the water inlet end of the AUMF1 membrane module 5. The concentrated water end of the AUMF1 membrane module 5 is connected to the inlet of the black calcium reactor 6. The water production end of the AUMF1 membrane module 5 is connected to the water inlet end of the first storage water tank 7. The water outlet end of the first storage water tank 7 is connected to the water inlet end of the DUMF1 membrane module 2 through a filtration and reduction component. The concentrated water end of the DUMF1 membrane module 2 is connected to the water inlet end of the second storage water tank 8. The water production end of the DUMF1 membrane module 2 is connected to the water inlet end of the third storage water tank 9. The concentrated water of the AUMF1 membrane module 5 enters the black calcium reactor 6 for the recovery of black calcium carbonate. The water produced by the AUMF1 membrane module 5 is stored in the second storage water tank 8 for future use after being concentrated by the first stage of the DUMF1 membrane module 2.

[0034] Furthermore, a first water supply pump 10 and a multi-media filter 11 are sequentially connected between the biogas slurry pond 1 and the AUMF1 membrane module 5 of the biogas slurry resource classification and recovery system. A second water supply pump 12 is connected between the AUMF1 membrane module 5 and the black calcium reactor 6. The multi-media filter 11 can remove most of the suspended solids and impurities in the biogas slurry.

[0035] In an embodiment of the present invention, as Figure 1 and Figure 3 shown in the figure, the biogas slurry resource classification and recovery system further includes an AUMF2 membrane module 13. The water outlet end of the third storage water tank 9 is connected to the water inlet end of the AUMF2 membrane module 13. The water production end of the AUMF2 membrane module 13 is connected to the water inlet end of the fourth storage water tank 13.

[0036] Furthermore, a third water supply pump 15 and a nano calcium carbonate reactor 16 are sequentially connected between the third storage water tank 9 and the AUMF2 membrane module 13. There is a reflux channel between the concentrated water end of the AUMF2 membrane module 13 and the nano calcium carbonate reactor 16. A fourth water supply pump 17 and a nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery component 18 are sequentially connected between the AUMF2 membrane module 13 and the fourth storage water tank 13. The biogas slurry in the third storage water tank 9 enters the nano calcium carbonate reactor 16 for the recovery of micron calcium carbonate and nano calcium carbonate. The AUMF2 membrane module 13 is used to filter the biogas slurry after the recovery of micron calcium carbonate and nano calcium carbonate to remove the fine calcium carbonate particles remaining in the reaction of the biogas slurry. The concentrated water of the AUMF2 membrane module 13 is refluxed to the calcium carbonate reactor 16 for purification treatment to improve the recovery rate of micron calcium carbonate and nano calcium carbonate. The water produced by the AUMF2 membrane module 13 enters the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery component 18 for the recovery of inorganic salts such as nitrogen, phosphorus, potassium and ammonia to make liquid inorganic fertilizer. The water produced by the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery component 18 enters the fourth storage water tank 13 for storage and future use.

[0037] Through the above technical solution, the biogas slurry resource classification and recovery system provided by the embodiment of the present invention can recover inorganic salts such as nitrogen, phosphorus, potassium, and ammonia to produce liquid inorganic fertilizers, and use the alkalinity in the biogas slurry to synthesize micron calcium carbonate, nano calcium carbonate, and recover black calcium carbonate and other substances, realizing the comprehensive and full recovery and utilization of biogas slurry resources.

[0038] In an embodiment of the present invention, as Figure 1 and Figure 3 shown, the biogas slurry resource classification and recovery system further includes a nanofiltration membrane module 19. The water outlet end of the fourth storage water tank 13 is connected to the water inlet end of the nanofiltration membrane module 19 through a filtration and reduction component. The concentrated water end of the nanofiltration membrane module 19 is connected to the water inlet end of the fifth storage water tank 20. The water production end of the nanofiltration membrane module 19 discharges to the outside. The water outlet end of the fifth storage water tank 20 is connected to the water inlet end of the DUMF2 membrane module 3 through a filtration and reduction component. The concentrated water end of the DUMF2 membrane module 3 is connected to the water inlet end of the second storage water tank 8. The water production end of the DUMF2 membrane module 3 is connected to the water inlet end of the fourth storage water tank 13. The biogas slurry in the fourth storage water tank 13 enters the nanofiltration membrane module 19 for filtration. The clarified liquid after nanofiltration treatment of the biogas slurry reaches the first-class A discharge standard and can be directly discharged or reused as reclaimed water. The concentrated water of the nanofiltration membrane module 19 enters the fifth storage water tank 20, and then enters the DUMF2 membrane module 3 through a filtration and reduction component for secondary concentration treatment. The concentrated water of the DUMF2 membrane module 3 enters the second storage water tank 8 and is mixed and stored for use with the concentrated water that enters the second storage water tank 8 after the first-stage concentration treatment by the DUMF1 membrane module 2.

[0039] As Figure 1 and Figure 3 shown, in an embodiment of the present invention, the water outlet end of the second storage water tank 8 of the biogas slurry resource classification and recovery system is connected to the water inlet end of the DUMF3 membrane module 4 through a filtration and reduction component. The concentrated water end of the DUMF3 membrane module 4 is connected to the water inlet end of the sixth storage water tank 21. The water production end of the DUMF3 membrane module 4 is connected to the water inlet end of the fourth storage water tank 13. The biogas slurry subjected to the first-stage concentration treatment and the biogas slurry subjected to the second-stage concentration treatment in the second storage water tank 8 are mixed and then enter the DUMF3 membrane module 4 for tertiary concentration treatment to obtain humic acid with the expected target concentration through multi-stage concentration treatment and store it in the sixth storage water tank 21.

[0040] Figure 4 It is a schematic structural diagram of the filtration and reduction component of a biogas slurry resource classification and recovery system provided by an embodiment of the present invention. As Figure 4As shown, in an embodiment of the present invention, the filtration and reduction component of the biogas slurry resource classification and recovery system includes a fifth water supply pump 22, a security filter 23, and a booster pump 24 that are connected in sequence. A reductant tank 25 and a scale inhibitor tank 26 are also connected between the security filter 23 and the booster pump 24. The reductant tank 25 and the scale inhibitor tank 26 respectively add reductant and scale inhibitor to the conveying pipeline. Among them, the reductant is used to reduce the oxidizing substances in the biogas slurry to protect the membrane element; the scale inhibitor is used to prevent the scaling and pollution of CaCO3, CaSO4, BaSO4, SrSO4, SiO2, and iron oxide.

[0041] In an embodiment of the present invention, the DUMF1 membrane module 2, DUMF2 membrane module 3, and DUMF3 membrane module 4 of the biogas slurry resource classification and recovery system can all adopt spiral wound membranes made of polyamide. Among them, the filtration aperture of the DUMF1 membrane module 2 is 500 - 800 molecular weights, the operating pressure is 1.5 - 1.8 Mpa, and the average flux is 20 L / m2·h; the filtration aperture of the DUMF2 membrane module 3 is 400 - 600 molecular weights, the operating pressure is 1.8 - 2.2 Mpa, and the average flux is 18 L / m2·h; the filtration aperture of the DUMF3 membrane module 4 is 300 - 500 molecular weights, the operating pressure is 2.0 - 2.5 Mpa, and the average flux is 15 L / m2·h; the AUMF1 membrane module 5 and AUMF2 membrane module 13 can adopt submerged curtain membranes made of PVDF, with a pore size of 0.1 micron, and the operating pressure is -0.1 - 0 Mpa. Among them, the average flux of the AUMF1 membrane module 5 is 12 L / m2·h, and the average flux of the AUMF2 membrane module 13 is 15 L / m2·h; the nanofiltration membrane module 19 adopts a spiral wound membrane made of polyamide, the filtration aperture is 150 - 300 molecular weights, the operating pressure is 2.0 - 2.5 Mpa, and the average flux is 25 L / m2·h.

[0042] The target concentration of humic acid can be selected within a relatively wide range. Preferably, the target concentration of humic acid is greater than 30000 mg / L.

[0043] Figure 5 It is a flowchart of a method for classifying and recovering biogas slurry resources provided for the embodiment of the present invention. As Figure 5 shown, the embodiment of the present invention also provides a method for classifying and recovering biogas slurry resources. Using the biogas slurry resource classification and recovery system as described above, it includes the following steps:

[0044] S1. The biogas slurry in the biogas slurry tank 1 is filtered by a multi-media filter. The filtered biogas slurry enters the AUMF1 membrane module 5 for filtration and impurity removal. The produced water of the AUMF1 membrane module 5 enters the first storage water tank 7 for storage and standby. The concentrated water of the AUMF1 membrane module 5 enters the black calcium reactor 6 to recover black calcium carbonate;

[0045] S2. The biogas slurry in the first storage water tank 7 enters the DUMF1 membrane module 2 for concentration treatment. The produced water of the DUMF1 membrane module 2 enters the third storage water tank 9 for storage and standby, and the concentrated water of the DUMF1 membrane module 2 enters the second storage water tank 8 for storage and standby;

[0046] S3. The biogas slurry in the third storage water tank 9 enters the nano-calcium carbonate reactor 16 to recover micron calcium carbonate and nano-calcium carbonate. The produced water of the nano-calcium carbonate reactor 16 enters the AUMF2 membrane module 13 for filtration and impurity removal. The concentrated water of the AUMF2 membrane module 13 is refluxed to the nano-calcium carbonate reactor 16 for purification treatment. The produced water of the AUMF2 membrane module 13 enters the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery module 18 to recover inorganic salts such as nitrogen, phosphorus, potassium and ammonia, and is made into liquid inorganic fertilizer. The produced water of the nitrogen, phosphorus, potassium and ammonia inorganic fertilizer recovery module 18 enters the fourth storage water tank 13 for storage and standby;

[0047] S4. The biogas slurry in the fourth storage water tank 13 enters the nanofiltration membrane module 19 for filtration. The produced water after nanofiltration treatment is directly discharged, and the concentrated water of the nanofiltration membrane module 19 enters the fifth storage water tank 20 for storage and standby;

[0048] S5. The biogas slurry in the fifth storage water tank 20 enters the DUMF2 membrane module 3 for concentration treatment. The concentrated water of the DUMF2 membrane module 3 enters the second storage water tank 8 to be mixed with the concentrated water of the DUMF1 membrane module 2 for standby, and the produced water of the DUMF2 membrane module 3 enters the fourth storage water tank 13 for reflux treatment;

[0049] S6. The mixed biogas slurry in the second storage water tank 8 enters the DUMF3 membrane module 4 for further concentration treatment. After the concentrated water is concentrated to a certain concentration, it enters the sixth storage water tank 21 for storage, and the produced water of the DUMF3 membrane module 4 enters the fourth storage water tank 13 for reflux treatment.

[0050] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biogas slurry resource classification and recovery system, characterized in that: The biogas slurry resource classification and recovery system comprises a biogas slurry tank (1), a DUMF1 membrane module (2), a DUMF2 membrane module (3) and a DUMF3 membrane module (4). After the biogas slurry in the biogas slurry tank (1) is concentrated by the DUMF1 membrane module (2) and the DUMF2 membrane module (3) in sequence, the concentrated water of the DUMF1 membrane module (2) and the DUMF2 membrane module (3) is mixed and passed into the DUMF3 membrane module (4). After treatment, humic acid of target concentration is obtained, the DUMF1 membrane assembly (2), the DUMF2 membrane assembly (3) and the DUMF3 membrane assembly (4) use decolorizing membranes with different filtration pore sizes; the DUMF1 membrane assembly (2), the DUMF2 membrane assembly (3) and the DUMF3 membrane assembly (4) use a roll membrane made of polyamide material, wherein the filtration pore size of the DUMF1 membrane assembly (2) is 500-800 molecular weight, the operating pressure is 1.5-1.8Mpa, and the average flux is 20L / m 2 h; the filtration pore size of the DUMF2 membrane module (3) is 400-600 molecular weight, the operating pressure is 1.8-2.2 MPa, and the average flux is 18 L / m 2 h; the filtration pore size of the DUMF3 membrane module (4) is 300-500 molecular weight, the operating pressure is 2.0-2.5 MPa, and the average flux is 15 L / m 2 ·h; The biogas slurry resource classification and recovery system further comprises an AUMF1 membrane assembly (5); the water outlet of the biogas slurry pool (1) is connected to the water inlet of the AUMF1 membrane assembly (5); the concentrated water end of the AUMF1 membrane assembly (5) is connected to the inlet of a black calcium carbonate reactor (6); the water production end of the AUMF1 membrane assembly (5) is connected to the water inlet of a first storage water tank (7); the water outlet of the first storage water tank (7) is connected to the water inlet of the DUMF1 membrane assembly (2) via a filtration reduction assembly; the concentrated water end of the DUMF1 membrane assembly (2) is connected to the water inlet of a second storage water tank (8); and the water production end of the DUMF1 membrane assembly (2) is connected to the water inlet of a third storage water tank (9); the concentrated water of the AUMF1 membrane assembly (5) enters the black calcium carbonate reactor (6) for recovering black calcium carbonate; A first water supply pump (10) and a multi-media filter (11) are sequentially connected between the biogas slurry pool (1) and the AUMF1 membrane assembly (5); and a second water supply pump (12) is connected between the AUMF1 membrane assembly (5) and the black calcium reactor (6); The biogas slurry resource classification and recovery system further comprises an AUMF2 membrane assembly (13), the water outlet of the third storage water tank (9) is connected to the water inlet of the AUMF2 membrane assembly (13), and the water production end of the AUMF2 membrane assembly (13) is connected to the water inlet of the fourth storage water tank (14); the AUMF1 membrane assembly (5) and the AUMF2 membrane assembly (13) adopt an immersed curtain membrane made of PVDF material, with a pore size of 0.1 micron and an operating pressure of -0.1-0 MPa, wherein the average flux of the AUMF1 membrane assembly (5) is 12 L / m 2 h, the average flux of the AUMF2 membrane module (13) is 15 L / m 2 ·h; A third water supply pump (15) and a nano-calcium carbonate reactor (16) are sequentially connected between the third storage water tank (9) and the AUMF2 membrane assembly (13); a reflux channel is provided between the concentrated water end of the AUMF2 membrane assembly (13) and the nano-calcium carbonate reactor (16); and a fourth water supply pump (17) and a nitrogen, phosphorus, potassium, and ammonia inorganic fertilizer recovery assembly (18) are sequentially connected between the AUMF2 membrane assembly (13) and the fourth storage water tank (14).

2. The biogas slurry resource classification and recovery system according to claim 1 is characterized in that: The biogas slurry resource classification and recovery system also includes a nanofiltration membrane assembly (19); the water outlet of the fourth storage water tank (14) is connected to the water inlet of the nanofiltration membrane assembly (19) via a filtration reduction assembly; the concentrated water end of the nanofiltration membrane assembly (19) is connected to the water inlet of the fifth storage water tank (20); the water production end of the nanofiltration membrane assembly (19) is discharged to the outside; the water outlet of the fifth storage water tank (20) is connected to the water inlet of the DUMF2 membrane assembly (3) via a filtration reduction assembly; the concentrated water end of the DUMF2 membrane assembly (3) is connected to the water inlet of the second storage water tank (8); and the water production end of the DUMF2 membrane assembly (3) is connected to the water inlet of the fourth storage water tank (14).

3. The biogas slurry resource classification and recovery system according to claim 2 is characterized in that: The water outlet of the second storage water tank (8) is connected to the water inlet of the DUMF3 membrane assembly (4) via a filtration reduction assembly, the concentrated water end of the DUMF3 membrane assembly (4) is connected to the water inlet of the sixth storage water tank (21), and the produced water end of the DUMF3 membrane assembly (4) is connected to the water inlet of the fourth storage water tank (14).

4. The biogas slurry resource classification and recovery system according to claim 3 is characterized in that: The filtration and reduction assembly comprises a fifth water supply pump (22), a safety filter (23) and a booster pump (24) connected in sequence, and a reducing agent tank (25) and a scale inhibitor tank (26) are further connected between the safety filter (23) and the booster pump (24).

5. The biogas slurry resource classification and recovery system according to any one of claims 1 to 4, characterized in that: The filtration pore size of the DUMF1 membrane component (2) is 500-800 molecular weight, the filtration pore size of the DUMF2 membrane component (3) is 400-600 molecular weight, the filtration pore size of the DUMF3 membrane component (4) is 300-500 molecular weight, and the target concentration is greater than 30,000 mg / L.

6. A biogas slurry resource classification and recovery method, characterized in that: The biogas slurry resource classification and recovery system according to claim 4 comprises the following steps: S1, the biogas in the biogas pool (1) is filtered through a multi-media filter, the filtered biogas enters the AUMF1 membrane module (5) for filtration and impurity removal, the produced water of the AUMF1 membrane module (5) enters the first storage water tank (7) for storage and standby use, and the concentrated water of the AUMF1 membrane module (5) enters the black calcium carbonate reactor (6) for recovery of black calcium carbonate; S2, the biogas slurry in the first storage water tank (7) enters the DUMF1 membrane module (2) for concentration treatment, the produced water of the DUMF1 membrane module (2) enters the third storage water tank (9) for storage and standby use, and the concentrated water of the DUMF1 membrane module (2) enters the second storage water tank (8) for storage and standby use; S3, the biogas slurry in the third storage water tank (9) enters the nano calcium carbonate reactor (16) to recover micron calcium carbonate and nano calcium carbonate, the produced water of the nano calcium carbonate reactor (16) enters the AUMF2 membrane assembly (13) to be filtered and removed, the concentrated water of the AUMF2 membrane assembly (13) is returned to the nano calcium carbonate reactor (16) for purification, the produced water of the AUMF2 membrane assembly (13) enters the nitrogen, phosphorus, potassium, ammonia inorganic fertilizer recovery assembly (18) to recover nitrogen, phosphorus, potassium, ammonia inorganic salts and make liquid inorganic fertilizer, the produced water of the nitrogen, phosphorus, potassium, ammonia inorganic fertilizer recovery assembly (18) enters the fourth storage water tank (14) for storage and standby use; S4, the biogas slurry in the fourth storage water tank (14) enters the nanofiltration membrane assembly (19) for filtration, the produced water after the nanofiltration treatment is directly discharged, and the concentrated water from the nanofiltration membrane assembly (19) enters the fifth storage water tank (20) for storage and standby use; S5, the biogas slurry in the fifth storage water tank (20) enters the DUMF2 membrane module (3) for concentration treatment, the concentrated water of the DUMF2 membrane module (3) enters the second storage water tank (8) and is mixed with the concentrated water of the DUMF1 membrane module (2) for standby use, and the produced water of the DUMF2 membrane module (3) enters the fourth storage water tank (14) for reflux treatment; S6. The mixed biogas slurry in the second storage water tank (8) enters the DUMF3 membrane module (4) for further concentration treatment. After the concentrated water is concentrated to a certain concentration, it enters the sixth storage water tank (21) for storage. The produced water of the DUMF3 membrane module (4) enters the fourth storage water tank (14) for reflux treatment.

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