GB2611696A - Method for producing high-efficiency organic liquid fertilizer by using biogas slurry and apparatus therefor - Google Patents

Abstract

The present application provides a method for producing a high-efficiency organic liquid fertilizer by using a biogas slurry and an apparatus therefor. The method comprises the following steps: S1. primary treatment of raw materials, performing primary deodorization and sterilization on the biogas slurry by using a ferrate and a bacteriostatic agent, and performing filtering to obtain a primary treatment solution; S2. re-treatment of the raw materials, further deodorizing the primary treatment solution by using micro-nano bubble water, removing suspended fine particle insoluble substances, and performing filtering to obtain a biogas slurry stock solution; and S3. liquid fertilizer production, freely mixing, according to set different formulae, the biogas slurry stock solution with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution, and a medium and trace element mother liquor, so as to obtain a biogas slurry liquid fertilizer suitable for different crops and having comprehensive nutrients. The present invention also provides an apparatus used for the method for producing a high-efficiency organic liquid fertilizer by using a biogas slurry. The method provided by the present invention is simple in process, low in construction cost, and high in automation degree; the biogas slurry fertilizer prepared by using the method has an increased commercial value, has comprehensive nutrients, is flexible in formula, and can achieve the maximum utilization of the biogas slurry.

Description

METHOD FOR PRODUCING HIGH EFFICIENCY ORGANIC LIQUID FERTILIZER BY USING BIOGAS SLURRY AND APPARATUS THEREFOR

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent application claims the priority of Chinese Patent Application No. 202110609342.3 filed with the China National Intellectual Property Administration on June 1, 2021, and entitled "Method for producing efficient organic liquid fertilizers from biogas slurry and device thereof', the disclosure of which is incorporated by reference herein in its entirety as part of the present application.

TECHNICAL FIELD

[0002] The present disclosure relates to the technical field of resourceful utilization of agricultural wastes, and in particular relates to a method for producing efficient organic liquid fertilizers from biogas slurry and a device thereof

BACKGROUND

[0003] Biogas slurry refers to the residues of various organic matters such as human and livestock excreta, and straw after anaerobic fermentation. With the large-scale and intensified development of aquaculture industry in China, the main treatment mode for a large amount of feces of livestock and poultry produced in the breeding industry at present generally employs biogas engineering, i.e., high-concentration organic wastewater is treated by means of anaerobic biodegradation. The existing mode for treating biogas slurry can be divided into low-cost natural ecological purification, high-cost plant treatment, and high-additional value development and exploitation, but such treatment process may greatly increase the treatment cost. On the other hand, although the biogas slurry is a byproduct during anaerobic digestion, it is also an environment-friendly fertilizer capable of being widely used in agricultural production and an important element of the resource utilization of agricultural waste advocated by the state.

100041 With the continuous improvement of the automation degree of agricultural production, fertilizer consumption shows a trend of high concentration, liquid and compound. Liquid fertilizers account for nearly 40% of the total in the United States. Almost all fields in Israel, which has a high degree of water and fertilizer integration, use liquid fertilizers. In addition, liquid fertilizers are used in large quantities in the United Kingdom, Belgium, the Netherlands and other countries. Biogas slurry is an excellent liquid fertilizer with the main composition of water. Biogas slurry has dual function in crop growth, one is as a biological fertilizer containing nitrogen, phosphorus, potassium and various trace elements, and the other is as a biological pesticide containing amino acids, growth hormones and antibiotics. Numerous studies have shown that biogas slurry is a high-quality and fully effective organic fertilizer. On the basis of ensuring crop quality improvement and yield increase, the biogas slurry can replace or partially replace chemical fertilizer, and has an extensive application range, which can be used not only as base fertilizer, but also as topdressing or foliar fertilizer.

[0005] In foreign countries, the commercial fertilizer produced from biogas slurry is generally prepared by concentrating the biogas slurry by means of multi-effect steam, with high equipment investment cost is high, which is difficult to popularize and apply in a large area in China at present. There is a big difference between the commercial fertilizers produced from the biogas slurry at home and abroad. In China, the commercial biogas slurry fertilizer is guaranteed to meet the national and industrial standards by adding auxiliary materials (mainly inorganic nutrients) to biogas slurry. However, the biogas slurry has complex composition, and contains a large number of microorganisms, salt ions and solid suspensions, and direct field application may easily lead to blockage of irrigation equipment. Meanwhile, incomplete deodorization of the biogas slurry has also caused the low marketability of the liquid fertilizer containing biogas slurry, resulting in low enthusiasm of fertilizer enterprises in production. In Chinese patent CN105819589A, a method for deodorizing biogas slurry is disclosed. Only ferrate and bacteriostatic agent are used for deodorization, but the ferrate deodorization mainly refer to oxidize malodorous substances such as hydrogen sulfide (H2S), methyl mercaptan (CH3SH), methyl sulfur (CH3)2S), ammonia gas (NH), etc., while the odor-causing substances in the biogas slurry include not only hydrogen sulfide, ammonia gas, but also indole, Volatile phenol, etc., the odor in the biogas slurry cannot be completely removed by only using the ferrate deodorization. Meanwhile, the biogas slurry fertilizer prepared by using the method is original liquid of biogas slurry, which needs to be diluted when used, and requires a large amount of water to be added when used for irrigation. Therefore, a new biogas slurry treatment mode needs to be studied for the treatment of the biogas slurry, thus acquiring treated biogas slurry which is more thoroughly in deodorization and more water-saving in use.

SUMMARY

100061 A technical problem to be solved by the present disclosure is to overcome the defects and shortcomings of existing biogas slurry fertilizers, provide a method for producing efficient organic liquid fertilizers from biogas slurry. After oxidative deodorization and multiple filtering, the biogas slurry is further subjected to deodorization and impurity removal by micro-nano bubble water to obtain original liquid of biogas slurry. The original liquid of biogas slurry is compounded to obtain liquid fertilizers with different nutrient ratios.

[0007] A first objective of the present disclosure is to provide a method for producing efficient organic liquid fertilizers from biogas slurry.

100081 A second objective of the present disclosure is to a device used in a method for producing efficient organic liquid fertilizers from biogas slurry.

100091 The objectives above of the present disclosure are achieved through the following technical solutions: 100101 A method for producing efficient organic liquid fertilizers from the biogas slurry comprises the following steps: [0011] SI: primary treatment of raw materials: carrying out primary deodorization and sterilization on biogas slurry by using ferrate and bacteriostatic agent, and filtering to obtain primary treated liquid; 100121 S2: retreatment of raw materials: further deodorizing the primary treated liquid by using micro-nano bubble water, removing suspended fine-particle insoluble matters, and filtering to obtain original liquid of biogas slurry; and [0013] S3: production of liquid fertilizers: freely compounding the original liquid of biogas slurry with nitrogen solution, phosphorus solution, potassium solution, organic solution and medium-trace element mother liquor according to different set formulas, thus obtaining biogas slurry-containing liquid fertilizers with comprehensive nutrients suitable for different crops.

100141 Bubbles having a diameter less than 100 gm are called micron bubbles, and bubbles having a diameter less than 100 nm are called nano bubbles. The diameter of the micro-nano bubble is between that of the micron bubbles and that of the nano bubbles, referring to the bubbles having the diameter between tens of microns and hundreds of nanometers when the bubbles are generated. Compared with ordinary bubbles, the micro-nano bubbles have the characteristics of long staying time in water, high mass transfer efficiency, high interface potential, free radical release, and the like. The surface of the micro-nano bubbles has a negative charge which is higher than that of the ordinary bubbles. In general, the surface charge of micro-nano bubbles is -50 my to 30 my, which may produce particularly dense and delicate bubbles in biogas slurry water, and has no phenomenon of breakage due to increased fusion. Positively charged substances in the water may be adsorbed by utilizing the negative electricity of the micro-nano bubbles, thus removing organic suspended solids or pollutants from the water, and achieving the purification effect of solid-liquid separation. Some studies have also found that the micro-nano bubbles have strong oxidizing property, which may inactivate the bacteria. The odor-producing substances in the biogas slurry treatment process are mainly composed of ammonia gas, hydrogen sulfide, indole, and Volatile phenol. Most of odor-producing substances are organic compounds, all of which have active groups easy to undergo chemical reactions, especially easy to be oxidized. In according with the present disclosure, the purpose of rapid deodorization may be achieved by double oxidation of the micro-nano bubbles and the ferrate. In addition, the micro-nano bubbles may also inactivate the bacteria so as to reduce the reproduction of harmful microorganisms in the biogas slurry. In accordance with the present disclosure, an odor source in the biogas slurry may be rapidly removed through double oxidation of the micro-nano bubbles and the ferrate, thus the deodorization is sufficient. Meanwhile, the water demand for liquid fertilizer production is also saved by using the micro-nano bubble water. The liquid fertilizers prepared by using the method of the present disclosure have nutrient value and marketability, and capacity of satisfying requirements of various irrigation facilities. The method is easy in operation, simple in technique, low in cost, and capable of maximizing the utilization of biogas slurry.

100151 Preferably, the primary treatment of raw materials in the step Si comprises: adding the ferrate which accounts for 0.001% to 0.02% of the mass of the biogas slurry into the biogas slurry to mix and react for 5 h to 12 h, and then adding the bacteriostatic agent which accounts for 0.001% to 0.02% of the mass of the biogas slurry for primary deodorization and sterilization.

[0016] Preferably, the filtering in the step S1 is to carry out double filtering by a first filter screen and a second filter screen.

[0017] Further preferably, apertures of the filter screens in the step Si are 850 pm and 250 pm, respectively.

100181 Preferably, in the step Si, the ferrate is potassium ferrate or sodium ferrate, and the bacteri ostati c agent is 2-bromo-2-nitro-1,3-propanediol.

[0019] Preferably, in the step S2, the retreatment of raw materials comprises: mixing the micro-nano bubble water and the primary treated liquid, and a mixing volume ratio of the micro-nano bubble water to the biogas slurry is 2 to 5: 1.

[0020] Preferably, in the step S2, the micro-nano bubble water is from circulating water produced by a nano bubble generator, and a gas source of the nano bubble generator is air.

[0021] Preferably, in the step S2, the filtering refers to filter by a disc filter.

[0022] Further preferably, in the step S2, the filtering precision is 106 pm.

100231 Preferably, the nitrogen solution in the step S3 comprises urea solution and urea ammonium nitrate solution. The phosphorous solution is monoammonium phosphate solution. The potassium solution is potassium chloride solution.

[0024] A device used in a method for producing efficient organic liquid fertilizers from biogas slurry is composed of a biogas slurry treatment device and a liquid fertilizer mixing device. The biogas slurry treatment device comprises: a nano bubble generator 1, a bubble water pond 2, a filter pond 3, a first filter screen 4, a second filter screen 5, a slag discharge port 6, a first valve 7, a second valve 8, a first centrifugal pump 9, a first stirring unit 10, a biogas slurry treating pond 11, a second centrifugal pump 12, and a filter assembly 13. The liquid fertilizer compounding device comprises a biogas slurry raw material tank 14, a first pneumatic valve 15, a third centrifugal pump 16, a nitrogen solution tank 17, a second pneumatic valve 18, a fourth centrifugal pump 19, a phosphorus solution tank 20, a third pneumatic valve 21, a fifth centrifugal pump 22, a potassium solution tank 23, a fourth pneumatic valve 24, a sixth centrifugal pump 25, a medium-trace element tank 26, a fifth pneumatic valve 27, a seventh centrifugal pump 28, a second stirring unit 29, a mixing tank 30, a flowmeter 31, an eighth centrifugal pump 32, an electromagnetic valve 33, a manual controller 34, and a remote-control terminal 35. One end of the bubble water pond 2 is connected to the nano bubble generator 1, and the other end of the bubble water pond is connected to the first valve 7. The first filter screen 4, the second filter screen 5 and the slag discharge port 6 are arranged in the filter pond 3, the slag discharge port 6 is arranged at the bottom of the filter pond 3, and the second valve 8 is connected to one end, close to filtrate, of the filter pond 3. The first valve 7 and the second valve 8 are commonly connected to the first centrifugal pump 9, and are connected to the biogas slurry treating pond 11 by the first centrifugal pump 9, and the first stirring unit 10 is installed in the biogas slurry treating pond 11. The biogas slurry treating pond 11 is connected to one end of the filter assembly 13 by the second centrifugal pump 12, and the other end of the filter assembly 13 is connected to a feeding port of the biogas slurry raw material tank N. A discharge port of the biogas slurry raw material tank 14 is connected to a charging port of the mixing tank 30 by a main pipeline, and the first pneumatic valve 15 and the third centrifugal pump 16 are arranged close to the discharge port of the biogas slurry raw material tank 14. The nitrogen solution tank 17, the phosphorus solution tank 20, the potassium solution tank 23 and the medium-trace element tank 26 are respectively connected to the main pipeline by branch pipelines, and the branch pipelines are provided with the second pneumatic valve 18 and the fourth centrifugal pump 19, the third pneumatic valve 21 and the fifth centrifugal pump 22, the fourth pneumatic valve 24 and the sixth centrifugal pump 25, as well as the fifth pneumatic valve 27 and the seventh centrifugal pump 28, respectively. The second stirring unit 29 is installed above the mixing tank 30. The mixing tank 30 is connected to the electromagnetic valve 33 by the eighth centrifugal pump 32, and the flowmeter 31 is further arranged between the mixing tank 30 and the eighth centrifugal pump 32. The biogas slurry treatment device further comprises a terminal control. The terminal controller comprises the hand controller 34 and/or the remote-control terminal 35, and is configured to control the valves so as to control the amount of the liquid discharged from the tanks.

[0025] Preferably, the filter pond 3 is designed in a high-low drop manner, and the middle thereof is separated using filter screens. The filter screens comprise the first filter screen 4 and the second filter screen 5.

[0026] Further preferably, apertures of the first filter screen 4 and the second filter screen 5 are 850 pm and 250 pm, respectively.

[0027] Preferably, the biogas slurry treating pond 11 may also be configured to carry out aerobic fermentation, or mixed cultivation with the aerobes, as required.

[0028] Preferably, the filter assembly 13 is a disc filter, with the filtering precision of 106 pm. [0029] Preferably, the system remote-control terminal 35 is configured to perform automatic control by using PLC programming.

[0030] Preferably, the mixing and blending tank 30 is provided with a weighing device so as to control the adding amount of different raw materials.

100311 Preferably, the terminal controller 35 may be configured to automatically calculate the required amounts of the liquid fertilizers prepared from different raw materials according to the field data collected by the agronomist.

[0032] A specific use method of the device above is described as follows: 100331 The collected biogas slurry subjected to anaerobic fermentation is directly injected into the filter pond 3, then ferrate and bacteriostatic agent are added into the filter pond 3 for oxidative deodorization and bacteria breeding prevention, respectively. The biogas slurry is primarily filtered by the first filter screen 4 with the aperture of 850 pm and the second filter screen 5 with the aperture of 250 pm, and the primarily filtered biogas slurry is injected into the biogas slurry treating pond 11 by controlling the second valve 8 and the first centrifugal pump 9. A water source in the bubble water pond 2 is a water source continuously treated by the nano bubble generator 1, a dissolved oxygen concentration in the water reaches saturation concentration, and the dissolved oxygen content in the water approaches to 4 ppm. Micro-nano bubble water is injected into the biogas slurry treating pond 11 by controlling the first valve 7 and the first centrifugal pump 9, and then is left to stand after being stirred with the biogas slurry sufficiently, thus further removing an odorous substance source from the biogas slurry and removing suspended fine insoluble particles from the biogas slurry. The treated biogas slurry is injected into the filter assembly 13 with an aperture of 106 pm by the second centrifugal pump 12, and then flows into the biogas slurry raw material tank 14 after being filtered. The open/close of the pneumatic valves for the biogas slurry raw material tank 14, the nitrogen solution tank 17, the phosphorus solution tank 20, the potassium solution tank 23 and the medium-trace element tank 26 as well as the operation of various tank centrifugal pumps are controlled by the hand controller 34 or the remote-control terminal 35 so as to inject the raw materials into the mixing tank 30 to be mixed. The second stirring unit 29 is arranged above the mixing tank 30 to guarantee that different materials may be mixed uniformly; meanwhile, the mixing tank is loaded with a weighing device to control the adding amount of different raw materials, and the liquid fertilizer of the required formula can be obtained by continuously stirring the raw materials for more than half an hour. Finally, the finished biogas slurry fertilizer is discharged through the eighth centrifugal pump 32 for commercial package or is directly conveyed to the field. The flowmeter 31 is configured to control the extraction amount of the finished fertilizer, and the electromagnetic valve 33 is configured to control the discharging. [0034] Compared with the prior art, the present disclosure has the following beneficial effects: [0035] (1) The present disclosure provides a method for producing efficient organic liquid fertilizers from biogas slurry. The ferrate and the micro-nano bubble water are used for sufficient deodorization, so the odor-producing substances decrease remarkably before and after biogas slurry treatment, the content of hydrogen sulfide decreases by 100%, and the content of indole and Volatile phenol decrease by 84.67% and 77.65%, respectively, indicating that the deodorization is sufficient, and the marketability of the biogas slurry is improved. Different biogas slurry fertilizers are prepared according to different growth requirements of crops, with comprehensive nutrients, flexible formula, high degree of automation, flexible use and wide application range.

[0036] (2) The method provided by the present disclosure is simple in production process and relatively low in construction cost. The biogas slurry fertilizers prepared by using the method can satisfy requirements of various irrigation facilities, and achieve the maximum utilization of the biogas slurry. No waste liquid is generated in the production process of fully utilizing the biogas slurry, and the use of micro-nano bubble water greatly saves the water source consumed in the production of liquid fertilizers. To achieve the recycling of agricultural waste resources, an effective way is provided to fundamentally solve the problem of biogas slurry utilization, and achieve "waste" to treasure as well as efficient utilization.

[0037] (3) The present disclosure provides an arrangement of a method for producing efficient organic liquid fertilizers from biogas slurry. The device has simple equipment, is suitable for industrial and large-scale production of efficient biogas slurry organic liquid fertilizer in the areas with concentrated aquaculture, and can improve the comprehensive utilization benefit of biogas slurry.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 is a structure diagram of a device used in a method for producing efficient organic liquid fertilizers from biogas slurry in accordance with an embodiment 1 of the present disclosure. In FIG, 1: 1-nano bubble generator; 2-bubble water pond; 3-filter pond; 4-first filter screen; 5-second filter screen; 6-slag discharge port; 7-first valve; 8-second valve; 9-first centrifugal pump; 10-first stirring unit; 11-biogas slurry treating pond; 12-second centrifugal pump; 13-filter assembly; 14-biogas slurry raw material tank; 15-first pneumatic valve; 16-third centrifugal pump; 17-nitrogen solution tank; 18-second pneumatic valve; 19-fourth centrifugal pump; 20-phosphorus solution tank; 21-third pneumatic valve; 22-fifth centrifugal pump; 23-potassium solution tank; 24-fourth pneumatic valve; 25-sixth centrifugal pump; 26-medium-trace element tank; 27-fifth pneumatic valve; 28-seventh centrifugal pump; 29-second stirring unit; 30-mixing tank; 31-flowmeter; 32-eighth centrifugal pump; 33-electromagnetic valve; 34-hand controller; 35-remotecontroller.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present disclosure is further described below with reference to the accompanying drawings of the specification and specific embodiments, but the embodiments are not intended to limit the present disclosure in any form. Unless otherwise specified, the reagents, methods and equipment used in the present disclosure are conventional reagents, methods and equipment in the technical field.

100401 Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

[0041] Embodiment 1 A device used in a method for producing efficient organic liquid fertilizers from the biogas slurry [0042] A device used in a method for producing efficient organic liquid fertilizers from biogas slurry is composed of a biogas slurry treatment device and a liquid fertilizer mixing device. The biogas slurry treatment device comprises: a nano bubble generator 1, a bubble water pond 2, a filter pond 3, a first filter screen 4, a second filter screen 5, a slag discharge port 6, a first valve 7, a second valve 8, a first centrifugal pump 9, a first stirring unit 10, a biogas slurry treating pond 11, a second centrifugal pump 12, and a filter assembly 13. The liquid fertilizer compounding device comprises a biogas slurry raw material tank 14, a first pneumatic valve 15, a third centrifugal pump 16, a nitrogen solution tank 17, a second pneumatic valve 18, a fourth centrifugal pump 19, a phosphorus solution tank 20, a third pneumatic valve 21, a fifth centrifugal pump 22, a potassium solution tank 23, a fourth pneumatic valve 24, a sixth centrifugal pump 25, a medium-trace element tank 26, a fifth pneumatic valve 27, a seventh centrifugal pump 28, a second stirring unit 29, a mixing tank 30, a flowmeter 31, an eighth centrifugal pump 32, an electromagnetic valve 33, a manual controller 34, and a remote-control terminal 35. One end of the bubble water pond 2 is connected to the nano bubble generator 1, and the other end of the bubble water pond is connected to the first valve 7. The first filter screen 4, the second filter screen 5 and the slag discharge port 6 are arranged in the filter pond 3, the slag discharge port 6 is arranged at the bottom of the filter pond 3, and the second valve 8 is connected to one end, close to filtrate, of the filter pond 3. The first valve 7 and the second valve 8 are commonly connected to the first centrifugal pump 9, and are connected to the biogas slurry treating pond 11 by the first centrifugal pump 9, and the first stirring unit 10 is installed in the biogas slurry treating pond 11. The biogas slurry treating pond 11 is connected to one end of the filter assembly 13 by the second centrifugal pump 12, and the other end of the filter assembly 13 is connected to a feeding port of the biogas slurry raw material tank N. A discharge port of the biogas slurry raw material tank 14 is connected to a charging port of the mixing tank 30 by a main pipeline, and the first pneumatic valve 15 and the third centrifugal pump 16 are arranged close to the discharge port of the biogas slurry raw material tank 14. The nitrogen solution tank 17, the phosphorus solution tank 20, the potassium solution tank 23 and the medium-trace element tank 26 are respectively connected to the main pipeline by branch pipelines, and the branch pipelines are provided with the second pneumatic valve 18 and the fourth centrifugal pump 19, the third pneumatic valve 21 and the fifth centrifugal pump 22, the fourth pneumatic valve 24 and the sixth centrifugal pump 25, as well as the fifth pneumatic valve 27 and the seventh centrifugal pump 28, respectively. The second stirring unit 29 is installed above the mixing tank 30. The mixing tank 30 is connected to the electromagnetic valve 33 by the eighth centrifugal pump 32, and the flowmeter 31 is further arranged between the mixing tank 30 and the eighth centrifugal pump 32. The biogas slurry treatment device further comprises a terminal control. The terminal controller comprises the hand controller 34 and/or the remote-control terminal 35, and is configured to control the valves so as to control the amount of the liquid discharged from the tanks.

[0043] A use method of the device above is described as follows: [0044] The collected biogas slurry subjected to anaerobic fermentation is directly injected into the filter pond 3, then ferrate and bacteriostatic agent are added into the filter pond 3 for oxidative deodorization and bacteria breeding prevention, respectively. The biogas slurry is primarily filtered by the first filter screen 4 with the aperture of 850 jun and the second filter screen 5 with the aperture of 250 j.tm, and the primarily filtered biogas slurry is injected into the biogas slurry treating pond 11 by controlling the second valve 8 and the first centrifugal pump 9. A water source in the bubble water pond 2 is a water source continuously treated by the nano bubble generator 1, a dissolved oxygen concentration in the water reaches saturation concentration, and the dissolved oxygen content in the water approaches to 4 ppm. Micro-nano bubble water is injected into the biogas slurry treating pond 11 by controlling the first valve 7 and the first centrifugal pump 9, and then is left to stand after being stirred with the biogas slurry sufficiently, thus further removing an odorous substance source from the biogas slurry and removing suspended fine insoluble particles from the biogas slurry. The treated biogas slurry is injected into the filter assembly 13 with an aperture of 106 pm by the second centrifugal pump 12, and then flows into the biogas slurry raw material tank 14 after being filtered. The open/close of the pneumatic valves for the biogas slurry raw material tank 14, the nitrogen solution tank 17, the phosphorus solution tank 20, the potassium solution tank 23 and the medium-trace element tank 26 as well as the operation of various tank centrifugal pumps are controlled by the hand controller 34 or the remote-control terminal 35 so as to inject the raw materials into the mixing tank 30 to be mixed. The second stirring unit 29 is arranged in the mixing tank 30 to guarantee that different materials may be mixed uniformly; meanwhile, the mixing tank is loaded with a weighing device to control the adding amount of different raw materials, and the liquid fertilizer of the required formula can be obtained by continuously stirring the raw materials for more than half an hour. Finally, the finished biogas slurry fertilizer is discharged through the eighth centrifugal pump 32 for commercial package or is directly conveyed to the field. The flowmeter 31 is configured to control the extraction amount of the finished fertilizer, and the electromagnetic valve 33 is configured to control the discharging. [0045] Embodiment 2 A method for producing efficient organic liquid fertilizers from biogas slurry 100461 A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: [0047] (1) Primary treatment of raw materials: potassium ferrate which accounts for 0.005% of the mass of the biogas slurry is added into a filter pond, the potassium ferrate and the biogas slurry, after being mixed, react for 10 h to carry out oxidative deodorization; after the deodorization is finished, bacteriostatic agent 2-bromo-2-nitro-1,3-propanediol which accounts for 0.01% of the mass of the biogas slurry is added to prevent harmful microorganisms from breeding again; and meanwhile, the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 pm and 250 pm so as to obtain primary treated liquid. 100481 (2) Re-treatment of the raw materials: a water source containing a large amount of micro-nano bubbles is prepared by using a nano bubble generator, the water source rich in micro-nano bubbles and the primary treated liquid of the biogas slurry are injected into a mixing pond in a volume ratio of 5: 1, are mixed by using a stirrer and then left to stand for 24 h. Odorous substances and suspended fine-particle insoluble matters are sufficiently removed by using the micro-nano bubbles, and then the retreated biogas slurry is injected into a disc filter set with the filtering precision of 106 pm by a pump © to obtain original liquid of biogas slurry after being filtered. [0049] (3) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

[0050] Embodiment 3 A method for producing efficient organic liquid fertilizers from biogas slurry [0051] A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: [0052] (1) Primary treatment of raw materials: potassium ferrate which accounts for 0.01% of the mass of the biogas slurry is added into a filter pond, the potassium ferrate and the biogas slurry, after being mixed, react for 10 h to carry out oxidative deodorization; after the deodorization is finished, bacteriostatic agent 2-bromo-2-nitro-1,3-propanediol which accounts for 0.01% of the mass of the biogas slurry is added to prevent harmful microorganisms from breeding again; and meanwhile, the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 um and 250 Inn so as to obtain primary treated liquid. [0053] (2) Re-treatment of the raw materials: a water source containing a large amount of micro-nano bubbles is prepared by using a nano bubble generator, the water source rich in micro-nano bubbles and the primary treated liquid of the biogas slurry are injected into a mixing pond in a volume ratio of 5: 1, are mixed by using a stirrer and then left to stand for 24 h. Odorous substances and suspended fine-particle insoluble matters are sufficiently removed by using the micro-nano bubbles, and then the retreated biogas slurry is injected into a disc filter set with the filtering precision of 106 [tm by a pump (1) to obtain original liquid of biogas slurry after being filtered. 100541 (3) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

[0055] Embodiment 4 A method for producing efficient organic liquid fertilizers from biogas slurry 100561 A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: [0057] (1) Primary treatment of raw materials: potassium ferrate which accounts for 0.005% of the mass of the biogas slurry is added into a filter pond, the potassium ferrate and the biogas slurry, after being mixed, react for 10 h to carry out oxidative deodorization; after the deodorization is finished, bacteriostatic agent 2-bromo-2-nitro-1,3-propanediol which accounts for 0.01% of the mass of the biogas slurry is added to prevent harmful microorganisms from breeding again; and meanwhile, the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 um and 250 Inn so as to obtain primary treated liquid. [0058] (2) Re-treatment of the raw materials: a water source containing a large amount of micro-nano bubbles is prepared by using a nano bubble generator, the water source rich in micro-nano bubbles and the primary treated liquid of the biogas slurry are injected into a mixing pond in a volume ratio of 2: 1, are mixed by using a stirrer and then left to stand for 24 h. Odorous substances and suspended fine-particle insoluble matters are sufficiently removed by using the micro-nano bubbles, and then the retreated biogas slurry is injected into a disc filter set with the filtering precision of 106 [tm by a pump 11i) to obtain original liquid of biogas slurry after being filtered. 100591 (3) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

[0060] Embodiment 5 A method for producing efficient organic liquid fertilizers from biogas slurry [0061] A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: 100621 (1) Primary treatment of raw materials: potassium ferrate which accounts for 0.01% of the mass of the biogas slurry is added into a filter pond, the potassium ferrate and the biogas slurry, after being mixed, react for 10 h to carry out oxidative deodorization; after the deodorization is finished, bacteriostatic agent 2-bromo-2-nitro-1,3-propanediol which accounts for 0.01% of the mass of the biogas slurry is added to prevent harmful microorganisms from breeding again; and meanwhile, the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 i_tm and 250 i_tm so as to obtain primary treated liquid. 100631 (2) Re-treatment of the raw materials: a water source containing a large amount of micro-nano bubbles is prepared by using a nano bubble generator, the water source rich in micro-nano bubbles and the primary treated liquid of the biogas slurry are injected into a mixing pond in a volume ratio of 2: 1, are mixed by using a stirrer and then left to stand for 24 h. Odorous substances and suspended fine-particle insoluble matters are sufficiently removed by using the micro-nano bubbles, and then the retreated biogas slurry is filtered by a disc filter set with the filtering precision of 106 iam to obtain original liquid of biogas slurry.

[0064] (3) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

100651 Comparative example 1 [0066] A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: [0067] (1) Primary treatment of raw materials: potassium ferrate which accounts for 0.02% of the mass of the biogas slurry is added into a filter pond, the potassium ferrate and the biogas slurry, after being mixed, react for 10 h to carry out oxidative deodorization; after the deodorization is finished, bacteriostatic agent 2-bromo-2-nitro-1,3-propanediol which accounts for 0.01% of the mass of the biogas slurry is added to prevent harmful microorganisms from breeding again; and meanwhile, the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 ifm and 250 lint so as to obtain primary treated liquid; and the primary treated liquid is further filtered by a disc filter set with the filtering precision of 106 1..tm to obtain original liquid of biogas slurry.

100681 (2) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

100691 Comparative example 2 100701 A method for producing efficient organic liquid fertilizers from biogas slurry comprises the following steps: [0071] (1) Primary treatment of raw materials: the biogas slurry after anaerobic fermentation is subjected to double filtering by using double filter screens having apertures of 850 pm and 250 jtm so as to obtain primary treated liquid.

[0072] (2) Re-treatment of the raw materials: a water source containing a large amount of micro-nano bubbles is prepared by using a nano bubble generator, the water source rich in micro-nano bubbles and the primary treated liquid of the biogas slurry are injected into a mixing pond in a volume ratio of 6: 1, are mixed by using a stirrer and then left to stand for 24 h. Odorous substances and suspended fine-particle insoluble matters are sufficiently removed by using the micro-nano bubbles, and then the retreated biogas slurry is filtered by a disc filter set with the filtering precision of 106 um to obtain original liquid of biogas slurry.

100731 (3) Production of liquid fertilizers: the original liquid of the biogas slurry is used as a raw material for producing the liquid fertilizer, and is freely mixed with a nitrogen solution, a phosphorus solution, a potassium solution, an organic solution and mother liquor of medium and trace elements according to different set formulas, thus obtaining the biogas slurry-containing liquid fertilizers, which have comprehensive nutrients suitable for different crops and can be applied to various irrigation facilities. The nitrogen solution is the urea solution, the phosphorus solution is monoammonium phosphate solution, the potassium solution is potassium chloride solution, and the medium-trace element solution is a mixed solution of various medium-trace elements.

[0074] Embodiment 6 Influence of biogas slurry treatment method on nutrient content of biogas slurry [0075] 1. The influence of the biogas slurry treatment method on odorous substance production of the biogas slurry 100761 Related compositions which produce the odor before and after biogas slurry treatment in embodiments 2 to 5 were analyzed, the concentration of ammonia gas was determined by Nessler colorimetry; the concentration of hydrogen sulfide was determined by iodometry; the concentration of indole was determined by TIPLC; and the concentration of Volatile phenol was determined by 4-AAP spectrophotometry.

[0077] The change of the content of the odor-producing substances before and after biogas slurry treatment is as shown in Table 1.

[0078] Table 1: Change of the content of odor-producing substances before and after biogas slurry treatment Initial concentration (mg/L) Concentration after treatment (mg/L) Ammonia Hydrogen Indole Volatile Ammonia Hydrogen Indole Volatile phenol gas sulfide phenol gas sulfide Embodiment 2 32.06 0.052 0.137 2.64 18.10 0 0.021 0.59 Embodiment 3 32.06 0.052 0.137 2.64 16.32 0 0.011 0.44 Embodiment 4 32.06 0.052 0.137 2.64 19.36 0 0.019 0.52 Embodiment 5 32.06 0.052 0.137 2.64 19.06 0 0.017 0.50 Comparative example 1 32.06 0.052 0.137 2.64 26.18 0.035 0.058 0.96 Comparative example 2 32.06 0.052 0.137 2.64 28.75 0.040 0.071 1.31 [0079] As can be seen from Table 1, the content of the odor-producing substance sources such as ammonia gas, hydrogen sulfide, indole and volatile phenol before and after the biogas slurry treatment decreased significantly. Under the combined deodorization, no hydrogen sulfide was detected in the treated biogas slurry, its content decreased by 100%. The content of indole and volatile phenol also decreased significantly. It was also found from the comparative examples that the deodorization effect obtained by using a higher amount of potassium ferrate or the water source rich in micro-nano bubbles alone was lower than that obtained by combined use of potassium ferrate and the water source rich in micro-nano bubbles in small amount.

100801 2. The influence of the biogas slurry treatment method on the nutrient content of the biogas 10 slurry [0081] The nutrient content in the biogas slurry before and after biogas slurry treatment in the embodiments 2 to 5 was analyzed, the total nitrogen concentration was determined by a titrimetric method after distillation; the total phosphorus concentration was determined by ascorbic acid chromogenic spectrophotometry; and the total organic carbon concentration was determined by di chromate titration.

[0082] The change of the nutrient content before and after biogas slurry treatment is as shown in Table 2 100831 Table 2: Change of nutrient content before and after biogas slurry treatment Before treatment (mg/L) After treatment (mg/L) Total Total Total Total Total Total nitrogen phosphorous organic nitrogen phosphor organic carbon OLIS carbon Embodiment 2 1106.36 35.82 1210.26 735.68 17.39 589.46 Embodiment 3 1106.36 35.82 1210.26 691.34 16.28 498.26 Embodiment 4 1106.36 35.82 1210.26 1015.67 29.05 1035.33 Embodiment 5 1106.36 35.82 1210.26 998.29 27.15 979.46 Comparative example 1 1106.36 35.82 1210.26 986.15 26.53 1003.75 Comparative example 2 1106.36 35.82 1210.26 1072.12 31.37 1082.56 [0084] As can be seen from Table 2, the nutrient content before and after biogas slurry treatment showed a downward trend. Due to a large dilution rate in the embodiment 2 and the embodiment 3, the nutrient content decreased greatly. As can be seen from the comparative examples, the nutrient content after treatment also showed a downward trend, but the decrease range was limited. 100851 3. The influence of the biogas slurry treatment method on the number of microorganisms in the biogas slurry [0086] The number of microorganisms in the biogas slurry before and after biogas slurry treatment in embodiments 2 to 5 was analyzed, and was determined by a dilution-plate method. [0087] The change of the number of microorganisms before and after biogas slurry treatment is shown in Table 3 100881 Table 3: Change of the number of microorganisms before and after biogas slurry treatment Before treatment (CFU/L) After treatment (CFU/L) Bacteria Fecal colifonn Bacteria Fecal colifonn Embodiment 2 6.95 *105 204 136 Negative Embodiment 3 6.95 10 204 115 Negative Embodiment 4 6.95 10 204 206 Negative Embodiment 5 6.95* l0 204 181 Negative Comparative example 1 6.95* 105 204 732 29 Comparative example 2 6.95*105 204 1.35*105 44 100891 As can be seen from Table 3, the number of microorganisms decreased significantly after biogas slurry treatment, especially in the combined deodorization treatment, fecal Escherichia coli was not detected. However, it can also be seen that the mixing ratio of potassium ferrate and nano-bubble water had little effect on the microorganisms. It was also found from the comparative examples that a large number of residual microorganisms still existed in the biogas slurry under the single treatment mode, which may cause certain risks to the later application. Comparatively speaking, the application safety factor of the biogas slurry fertilizer under the combined treatment mode was higher.

[0090] Embodiment 7 Field application test of biogas liquid fertilizer

[0091] (1) Test background

100921 Test location: Xiupo Village, Huashi Town, Fangcheng District, Fangchenggang City, Guangxi Zhuang Autonomous Region [0093] Test time: March 2020 to August 2020 [0094] Test crop: Watermelon [0095] Test soil: Sandy soil [0096] Irrigation facility: Trickle irrigation 100971 Test scheme: In this test, a total of two treatments of the liquid compound fertilizer prepared from the biogas slurry in the embodiment 2 of the present disclosure, solid compound fertilizers and the conventional fertilization (only compound fertilizer) was provided. Conventional fertilization adopts "Garsoni" high-intensity element water-soluble fertilizer (N:P:K is 16: 16: 16) of Chengdu Wintrue Holding Co., Ltd., which is widely used by local farmer households.

[0098] The formula of the liquid compound fertilizer prepared from the biogas slurry is as follows: 20 parts of treated original liquid of biogas slurry, 7 parts of nitrogen solution, 4 parts of phosphorus solution, 8 parts of potassium solution and 0.1 part of medium-trace element solution are sufficiently and uniformly mixed, and then a proper amount of water is added. The liquid fertilizer is injected into irrigation pipelines in the field by a fertilizer injection pump, and an EC (electric conductivity) value of the liquid fertilizer in the field is ensured to be below 4 at the same time. The conventional fertilization is that a large amount of water-soluble granulated fertilizers is poured into a fertilizer dissolving pool, dissolved and then applied to the field through trickle irrigation, [0099] (2) Test results are as shown in Table 4 and Table 5.

[0100] Table 4 Influence of biogas slurry fertilizer and conventional fertilizer on root growth of watermelon Total root length Total root surface area The number of root (cm) (cm') tips (number) Biogas slurry fertilizer 2769.38 235.77 2909 Conventional fertilizer 1895.92 160.29 1916 Table 5 Influence of biogas slurry fertilizer and conventional fertilizer on the yield of watermelon Weight of single Yield per mu Increase rate (%) fruit (kg) (kg) Biogas slurry 33.56 fertilizer 1.59 3283 Conventional 1.27 2458 fertilizer [0101] As can be seen from Table 4 and Table 5, the biogas slurry fertilizer remarkably promoted the root growth of the watermelon, and significantly increased the total root length, the total root surface area and the number of root tips compared with the conventional fertilizer. Compared with the conventional fertilizer, the total root length, the total root surface area and the number of root tips of the watermelon with the biogas slurry fertilizer increased by 46.07%, 47.09% and 51.83%, respectively; and the biogas slurry fertilizer also had significantly yield-increasing effect for the watermelon, and the yield increase rate reached 33.56%.

[0102] When the biogas slurry fertilizer prepared by using the method is used for irrigation, the filter and the water dropper are not blocked, and the irrigation facilities run normally.

101031 The above embodiments are preferred embodiments of the present disclosure, but the embodiments of the present disclosure are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principle of the present disclosure should be equivalent replacement methods, which are encompassed in the scope of protection of the present disclosure.

Claims (8)

1. WHAT IS CLAIMED IS: 1. A method for producing efficient organic liquid fertilizers from biogas slurry, comprising the following steps: Sl: primary treatment of raw materials: carrying out primary deodorization and sterilization on biogas slurry by using ferrate and bacteriostatic agent, and filtering to obtain primary treated liquid; S2: retreatment of raw materials: further deodorizing the primary treated liquid by using micro-nano bubble water, removing suspended fine-particle insoluble matters, and filtering to obtain original liquid of biogas slurry; and S3: production of liquid fertilizers: freely compounding the original liquid of biogas slurry with nitrogen solution, phosphorus solution, potassium solution, organic solution and medium-trace element mother liquor according to different set formulas, thus obtaining biogas slurry-containing liquid fertilizers with comprehensive nutrients suitable for different crops.
2. 2. The method according to claim 1, wherein the primary treatment of raw materials in the step S1 comprises: adding the ferrate which accounts for 0.001% to 0.02% of the mass of the biogas slurry into the biogas slurry to mix and react for 5 h to 12 h, and then adding the bacteriostatic agent which accounts for 0.001% to 0.02% of the mass of the biogas slurry for primary deodorization and sterilization.
3. 3. The method according to claim 1, wherein the filtering in the step Si is to carry out double filtering by two filter screens.
4. 4. The method according to claim 1, wherein apertures of the two filter screens are 850 pm and 250 pni, respectively.
5. 5. The method according to claim 1 or 2, wherein in the step S1, the ferrate is potassium ferrate or sodium ferrate, and the bacteriostatic agent is 2-bromo-2-nitro-1,3-propanediol.
6. 6. The method according to claim 1, wherein in the step S2, the retreatment of raw materials comprises: mixing the micro-nano bubble water and the primary treated liquid, and a mixing volume ratio of the micro-nano bubble water to the biogas slurry is 2 to 5: 1.
7. 7. A device used in a method for producing efficient organic liquid fertilizers from biogas slurry, consisting of a biogas slurry treatment device and a liquid fertilizer compounding device; the biogas slurry treatment device comprises: a nano bubble generator (1), a bubble water pond (2), a filter pond (3), a first filter screen (4), a second filter screen (5), a slag discharge port (6), a first valve (7), a second valve (8), a first centrifugal pump (9), a first stirring unit (10), a biogas slurry treating pond (11), a second centrifugal pump (12), and a filter assembly (13); the liquid fertilizer compounding device comprises a biogas slurry raw material tank (14), a first pneumatic valve (15), a third centrifugal pump (16), a nitrogen solution tank (17), a second pneumatic valve (18), a fourth centrifugal pump (19), a phosphorus solution tank (20), a third pneumatic valve (21), a fifth centrifugal pump (22), a potassium solution tank (23), a fourth pneumatic valve (24), a sixth centrifugal pump (25), a medium-trace element tank (26), a fifth pneumatic valve (27), a seventh centrifugal pump (28), a second stirring unit (29), a mixing tank (30), a flowmeter (31), an eighth centrifugal pump (32), an electromagnetic valve (33), a manual controller (34), and a remote-control terminal (35); one end of the bubble water pond (2) is connected to the nano bubble generator (1), the other end of the bubble water pond is connected to the first valve (7); the first filter screen (4), the second filter screen (5) and the slag discharge port (6) are arranged in the filter pond (3); the slag discharge port (6) is arranged at the bottom of the filter pond (3), and the second valve (8) is connected to one end, close to filtrate, of the filter pond (3); the first valve (7) and the second valve (8) are commonly connected to the first centrifugal pump (9), and are connected to the biogas slurry treating pond (11) by the first centrifugal pump (9), and the first stirring unit (10) is installed in the biogas slurry treating pond (11); the biogas slurry treating pond (11) is connected to one end of the filter assembly (13) by the second centrifugal pump (12), the other end of the filter assembly (13) is connected to a feeding port of the biogas slurry raw material tank (14); a discharge port of the biogas slurry raw material tank (14) is connected to a charging port of the mixing tank (30) by a main pipeline, and the first pneumatic valve (15) and the third centrifugal pump (16) are arranged close to the discharge port of the biogas slurry raw material tank (14); the nitrogen solution tank (17), the phosphorus solution tank (20), the potassium solution tank (23) and the medium-trace element tank (26) are respectively connected to the main pipeline by branch pipelines, and the branch pipelines are provided with the second pneumatic valve (18) and the fourth centrifugal pump (19), the third pneumatic valve (21) and the fifth centrifugal pump (22), the fourth pneumatic valve (24) and the sixth centrifugal pump (25), as well as the fifth pneumatic valve (27) and the seventh centrifugal pump (28), respectively; the second stirring unit (29) is installed above the mixing tank (30); the mixing tank (30) is connected to the electromagnetic valve (33) by the eighth centrifugal pump (32), and the flowmeter (31) is further arranged between the mixing tank (30) and the eighth centrifugal pump (32); a terminal controller comprises the hand controller (34) and/or the remote-control terminal (35), and is configured to control the valves so as to control the amount of the liquid discharged from the tanks.
8. 8. The method according to claim 7, wherein apertures of the first filter screen (4) and the second filter screen (5) are 850 pm and 250 um, respectively.