A system and method for preparing organic nutrient soil from urban domestic sewage sludge, and organic nutrient soil and its application

Abstract

The present invention belongs to the technical field of resource utilization of urban domestic sludge and soil fertilizer, and more specifically, relates to a system and method for preparing organic nutrient soil from urban domestic sludge, and organic nutrient soil and its application. The system includes: a pretreatment unit, a high temperature and high pressure reaction unit, a composting and energy recovery unit, an organic nutrient soil extraction unit, an organic nutrient soil shaping unit, and a central monitoring and control unit for controlling the operation of each unit. The sludge treatment process of the present invention can be carried out by automated equipment. The central monitoring and control unit monitors and controls the operating parameters of each unit through a human-machine interface. The operating personnel have no direct contact with the sludge, and the operating conditions are convenient for inspection and adjustment. It solves the problems of low automation level and low degree of industrial operation in the traditional mode, which is greatly affected by the management level and operation level of the operating personnel, making it difficult to effectively control the quality of the treated products, and the quality characteristics fluctuate greatly.

Description

Technical Field

[0001] The present invention belongs to the technical field of resource utilization of urban domestic sludge and soil fertilizer, and more specifically, relates to a system and method for preparing organic nutrient soil from urban domestic sludge, and the organic nutrient soil and its application. Background Art

[0002] As sewage treatment requirements are upgraded, the amount of sludge is increasing day by day. Urban domestic sludge contains a large amount of organic matter, nitrogen, phosphorus and other nutrients. If it is treated and reaches a certain standard for land use, its fertilizer components can be obtained and used as fertilizer, thereby giving full play to the resource attributes of sludge, which is also an important form of nutrient recycling. At present, sludge treatment products used for land use at home and abroad are mainly produced by anaerobic digestion and aerobic fermentation. However, due to the poor biological availability of organic matter in sludge, the degradation rate of traditional anaerobic digestion is relatively low, and it is difficult to ensure that the degree of composting is stable and up to standard. The direct land use of the treated products is not ideal. At the same time, this method has limited energy recovery due to the low gas production rate, low energy efficiency, low system integration, and it is difficult to achieve satisfactory operational stability in the production process. Aerobic fermentation processes require a lot of ventilation and oxygen supply, and ammonia volatilization, odor and other gaseous byproducts escape seriously, which is poor in environmental friendliness. The composting process is greatly affected by factors such as carbon-nitrogen ratio, temperature, and time. The composting time cannot be effectively quantified. The use of a large amount of auxiliary materials and labor input in the composting process leads to increased comprehensive operating costs. At the same time, the fermentation process requires a large area. The above two processes have a low level of automation and a low degree of industrial operation in the traditional mode. They are greatly affected by the management and operation levels of the operators, making it difficult to effectively control the quality of the treated products, and the quality characteristics fluctuate greatly. Summary of the invention

[0003] The purpose of the present invention is to solve the above problems, provide a system and method for preparing organic nutrient soil from urban domestic sludge, organic nutrient soil and its application, through the high integration of technical units and the full automation of the overall system, to form a centralized and effective control of the production process, to ensure the stability of product quality characteristics. The problems of large volume, difficult disposal, unfriendly environment, tight production site, unstable composting and sterilization effect, low energy recovery rate of urban domestic sludge are solved in an industrialized production manner, so as to achieve safe and stable treatment of urban domestic sludge and land resource utilization.

[0004] In order to achieve the above object, the first aspect of the present invention provides a system for preparing organic nutrient soil from urban domestic sludge, the system comprising:

[0005] Pretreatment unit, high temperature and high pressure reaction unit, composting and energy recovery unit, organic nutrient soil extraction unit, organic nutrient soil shaping unit and central monitoring and control unit for controlling the operation of each unit;

[0006] The pretreatment unit includes a slag and sand removal device, a centrifugal concentration device and a pre-dehydration device:

[0007] The slag and sand removal device is used to remove most of the impurities in the primary sludge of urban domestic sewage treatment plants;

[0008] The centrifugal concentrator is used for centrifugal dehydration of the residual activated sludge in the urban sewage treatment plant;

[0009] The pre-dehydration device is used to pre-dehydrate the mixture of materials obtained from the slag and sand removal device and the centrifugal concentration device to obtain pre-dehydrated sludge;

[0010] The high temperature and high pressure reaction unit comprises a conditioning container, a high temperature and high pressure reaction container, and a buffer container:

[0011] The conditioning container is used to receive the first flash steam and the second flash steam supplied by the high-temperature and high-pressure reaction container and the buffer container respectively, so as to preheat and slurry the pre-dehydrated sludge;

[0012] The high temperature and high pressure reaction vessel is used to perform thermal hydrolysis on the material received from the conditioning vessel and generate first flash steam supplied to the conditioning vessel;

[0013] The buffer container is used to receive the material after thermal hydrolysis in the high-temperature and high-pressure reaction container and provide the second flash steam for supplying the conditioning container;

[0014] A first pressure relief valve and a second pressure relief valve are respectively provided on the top of the high-temperature and high-pressure reaction vessel and the cache vessel, for controlling the pressure of the high-temperature and high-pressure reaction vessel and the cache vessel;

[0015] The first pressure relief valve and the second pressure relief valve are respectively connected to the middle and lower parts of the conditioning container through closed pipes;

[0016] The decomposition and energy recovery unit includes an anaerobic reaction container and a biogas storage container:

[0017] The anaerobic reaction container is used for anaerobically composting the sludge raw material from the buffer container;

[0018] The biogas storage container is used to store the biogas obtained from the anaerobic reaction container;

[0019] The organic nutrient soil extraction unit includes an extrusion dehydration device for extruding and dehydrating the product obtained by anaerobic decomposition to obtain organic nutrient soil in the form of fragments and a dehydrated solution;

[0020] The organic nutrient soil shaping unit comprises a crushing device for crushing the organic nutrient soil in block form to obtain granular organic nutrient soil.

[0021] A second aspect of the present invention provides a method for preparing organic nutrient soil from urban sewage sludge, the method utilizing the above-mentioned system, the method comprising:

[0022] 1) using a slag and sand removal device to remove most of the impurities in the primary sludge of the urban sewage treatment plant, using a centrifugal concentrator to centrifugally dehydrate the residual activated sludge of the urban sewage treatment plant, and then pre-dehydrating the mixture of the materials obtained by the slag and sand removal device and the centrifugal concentrator to obtain pre-dehydrated sludge;

[0023] 2) receiving the first flash steam and the second flash steam through the conditioning container to preheat and slurry the pre-dehydrated sludge, so that the temperature of the pre-dehydrated sludge is maintained at 90° C.-97° C., the solid content is maintained at 12%-14%, and the material liquid level in the conditioning container is controlled to be maintained at a height of 60%-70%;

[0024] 3) The preheated and slurried materials are subjected to thermal hydrolysis using a high-temperature and high-pressure reaction vessel. After the reaction is completed, the pressure is first released through the first pressure relief valve on the top of the high-temperature and high-pressure reaction vessel, and the first flash steam enters the middle and lower part of the conditioning container through the pipeline. When the pressure in the high-temperature and high-pressure reaction vessel is less than 0.28MPa, the central monitoring and control unit controls the first pressure relief valve to automatically close, and the mud discharge valve at the bottom of the high-temperature and high-pressure reaction vessel to automatically open, and the materials in the high-temperature and high-pressure reaction vessel are sprayed into the container from the middle and upper interface of the buffer container under their own pressure;

[0025] 4) The second flash steam generated at the top of the buffer container enters the container through the second pressure relief valve through the pipeline from the middle and lower interface of the conditioning container, and the material in the buffer container is pumped to the anaerobic reaction container as needed for anaerobic decomposition, and the biogas obtained by the reaction is stored in the biogas storage container;

[0026] 5) Extruding and dehydrating the anaerobic decomposition product by an extrusion dehydration device to obtain organic nutrient soil in the form of fragments and a dehydrated solution;

[0027] 6) The organic nutrient soil in pieces is crushed and shaped to obtain granular organic nutrient soil.

[0028] The third aspect of the present invention provides organic nutrient soil prepared by the above method.

[0029] The fourth aspect of the present invention provides the application of the above-mentioned organic nutrient soil in the technical field of resource utilization and preparation of soil fertilizer.

[0030] Beneficial effects of the present invention:

[0031] 1. High degree of system automation: The sludge treatment process can be carried out through automated equipment. The central monitoring and control unit monitors and controls the operating parameters of each unit through the human-machine interface. The operating personnel have no direct contact with the sludge, and the operating conditions are easy to check and adjust. This solves the problems of low automation level and low degree of industrial operation in the traditional mode, which is greatly affected by the management and operation level of the operating personnel, making it difficult to effectively control the quality of the treated products, and the large fluctuations in quality characteristics.

[0032] 2. Control strategy based on optimal system performance: The system can centrally control each technical operation unit, comprehensively consider the operation status of each unit, formulate a comprehensive operation parameter system for the entire system, optimize the performance matching and parameter connection between different operation units, so as to cope with the seasonal fluctuations in the properties of the system's imported raw materials, thereby achieving the best system operation effect and ensuring that the quality of the final product meets the standards in a long-term and stable manner.

[0033] 3. The organic nutrient soil product obtained by the above system has a high degree of maturity: the degradation rate of organic matter in the treated sludge can reach 45%-60%, and the maturity (seed germination index) can reach more than 70%, which can well meet the "Municipal Sludge Treatment Stability Standard for Urban Wastewater Treatment Plants" CJ / T510-2017.

[0034] 4. The organic nutrient soil product obtained by the above system has a high degree of sanitation: the sludge passes through the high-temperature and high-pressure reaction unit, undergoes sufficient hydrolysis reaction and flash explosion, and the pathogenic microorganism elimination rate is 99.99%. In addition, the main treatment system is completely closed and there is no possibility of contact with foreign pathogens.

[0035] 5. The organic nutrient soil product obtained by the above system has high organic matter and nutrient content: the organic matter of the product is stable ≥35%, and the total nutrients (N+P2O5+K2O) ≥5%.

[0036] 6. The quality of the organic nutrient soil products obtained by the above system can well meet the following standards: "Agricultural Sludge Pollutant Control Standard" (GB 4284-2018), "Municipal Sewage Treatment Plant Sludge Disposal for Landscaping Mud" (GB / T23486-2009), "Municipal Sewage Treatment Plant Sludge Disposal for Land Improvement Mud" (GB / T 24600-2009), "Municipal Sewage Treatment Plant Sludge Disposal for Forest Land" (CJ / T 362-2011), "Organic Nutrient Soil Preparation by Advanced Anaerobic Digestion of Sewage Sludge" (Q / BDG45045-2017).

[0037] 7. The above system has low comprehensive operating cost: the energy recovered in the form of biogas can fully meet the heat and electricity needs of the whole system. The whole production process does not require external energy input, which greatly reduces the operating cost, and in most cases can achieve net energy output; the organic nutrient soil produced by the system can reduce the transportation cost by about 60%-70% compared with the untreated original sludge (water content 80%); the organic nutrient soil can be effectively utilized as a resource for land utilization, and the product sales can obtain considerable profits.

[0038] 8. The production process of the above system is environmentally friendly: all odors in the production environment are collected and treated, and the working environment is highly acceptable; the filtrate produced during the dehydration process is treated with efficient nitrogen removal and there is no secondary pollution.

[0039] 9. The above system solves the problem of traditional anaerobic digestion, which is affected by the poor biological availability of organic matter in sludge, has a relatively low degradation rate, and it is difficult to ensure that the degree of composting meets the standard stably. The direct land use of the treated products is not ideal. At the same time, this method has limited energy recovery due to the low gas production rate, low energy efficiency, low system integration, and it is difficult to achieve a satisfactory level of operational stability in the production process.

[0040] 10. The above system solves the problems that the traditional aerobic fermentation process requires a lot of ventilation and oxygen supply, ammonia volatilization, odor and other gaseous by-products are seriously emitted, the environment is poor, the composting process is greatly affected by factors such as carbon-nitrogen ratio, temperature, time, etc., the composting time cannot be effectively quantified, the use of a large amount of auxiliary materials and labor input in the composting process leads to increased comprehensive operating costs, and the fermentation process requires a large area of ​​land.

[0041] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0043] Figure 1 A schematic diagram of a system for preparing organic nutrient soil from urban domestic sludge according to an embodiment of the present invention is shown.

[0044] Description of reference numerals:

[0045] 1-slag and sand removal device, 2-centrifugal concentration device, 3-pre-dehydration device, 4-conditioning container, 5-high temperature and high pressure reaction container, 6-buffer container, 7-anaerobic reaction container, 8-biogas storage container, 9-extrusion dehydration equipment, 10-crushing device, 11-steam boiler, 12-power generation equipment, 13-denitrification reaction facility, 14-central monitoring and control unit, 91-dehydrated water, 92-fragmented organic nutrient soil, 93-granular organic nutrient soil, 101-primary sludge of urban sewage treatment plant, 111-high temperature steam, 121-electricity, 201-residual activated sludge of urban sewage treatment plant, 131-sewage treatment system, 1211-system self-use, 1212-external power supply. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0047] A first aspect of the present invention provides a system for preparing organic nutrient soil from urban domestic sludge, the system comprising:

[0048] Pretreatment unit, high temperature and high pressure reaction unit, composting and energy recovery unit, organic nutrient soil extraction unit, organic nutrient soil shaping unit and central monitoring and control unit for controlling the operation of each unit;

[0049] The pretreatment unit includes a slag and sand removal device, a centrifugal concentration device and a pre-dehydration device:

[0050] The slag and sand removal device is used to remove most of the impurities in the primary sludge of urban domestic sewage treatment plants;

[0051] The centrifugal concentrator is used for centrifugal dehydration of the residual activated sludge in the urban sewage treatment plant;

[0052] The pre-dehydration device is used to pre-dehydrate the mixture of materials obtained from the slag and sand removal device and the centrifugal concentration device to obtain pre-dehydrated sludge;

[0053] The high temperature and high pressure reaction unit includes a conditioning container, a high temperature and high pressure reaction container, and a buffer container:

[0054] The conditioning container is used to receive the first flash steam and the second flash steam supplied by the high-temperature and high-pressure reaction container and the buffer container respectively, so as to preheat and slurry the pre-dehydrated sludge;

[0055] The high temperature and high pressure reaction vessel is used to perform thermal hydrolysis on the material received from the conditioning vessel and generate first flash steam supplied to the conditioning vessel;

[0056] The buffer container is used to receive the material after thermal hydrolysis in the high-temperature and high-pressure reaction container and provide the second flash steam for supplying the conditioning container;

[0057] A first pressure relief valve and a second pressure relief valve are respectively provided on the top of the high-temperature and high-pressure reaction vessel and the cache vessel, for controlling the pressure of the high-temperature and high-pressure reaction vessel and the cache vessel;

[0058] The first pressure relief valve and the second pressure relief valve are respectively connected to the middle and lower parts of the conditioning container through closed pipes;

[0059] The composting and energy recovery unit includes an anaerobic reaction vessel and a biogas storage vessel:

[0060] The anaerobic reaction container is used for anaerobically composting the sludge raw material from the buffer container;

[0061] The biogas storage container is used to store the biogas obtained from the anaerobic reaction container;

[0062] The organic nutrient soil extraction unit includes an extrusion dehydration device for extruding and dehydrating the product obtained by anaerobic decomposition to obtain organic nutrient soil in the form of fragments and a dehydrated solution;

[0063] The organic nutrient soil shaping unit comprises a crushing device for crushing the organic nutrient soil in block form to obtain granular organic nutrient soil.

[0064] According to the present invention, the above-mentioned urban domestic sludge specifically refers to the sludge generated during the treatment of urban domestic sewage.

[0065] According to the present invention, the central monitoring and control unit controls the corresponding equipment (unit) through the conventional settings of its human-machine interface, PLC control unit, etc. It is a conventional technical means. Specifically, the corresponding equipment (unit) is provided with sensors, the PLC control unit is communicatively connected and / or electrically connected to each sensor, and controls the corresponding equipment (unit), and each unit is centrally monitored and / or warned and / or adjusts operating parameters through the human-machine interface.

[0066] In the present application, as a preferred solution, the central monitoring and control unit controls the timing cleaning of slag and sand removal and controls the centrifuge speed through a human-machine interface.

[0067] In the present application, as a preferred solution, the conditioning container is provided with a liquid level sensor and a temperature sensor.

[0068] In the present application, as a preferred solution, the high temperature and high pressure reaction vessel is provided with a pressure sensor, a temperature sensor, and a liquid level sensor.

[0069] In the present application, as a preferred solution, the cache container is provided with a liquid level sensor, a pressure sensor, and a temperature sensor.

[0070] In the present application, as a preferred solution, the anaerobic reaction container is provided with a liquid level sensor, a temperature sensor, a flow sensor, and a pH sensor.

[0071] In the present application, as a preferred solution, the biogas storage container is provided with a height sensor (liquid level sensor) to feedback the amount of gas in the biogas storage tank.

[0072] In the present application, as a preferred solution, the human-machine interface can control the material transportation of the organic nutrient soil extraction unit.

[0073] In the present application, as a preferred solution, the extrusion dehydration equipment is provided with a pressure sensor.

[0074] As a preferred solution, the composting and energy recovery unit also includes:

[0075] The steam boiler is connected to the biogas storage container through a closed pipeline; the biogas in the biogas storage container provides energy for the steam boiler, and the high-temperature saturated steam obtained by the steam boiler is used as a heat source for heating the materials in the high-temperature and high-pressure reaction container. The steam boiler is connected to the high-temperature and high-pressure reaction container through a closed pipeline.

[0076] As a preferred solution, the composting and energy recovery unit also includes:

[0077] The power generation equipment utilizes the biogas in the biogas storage container to generate electrical energy, and the electrical energy is used for self-use of the system and / or for external power supply.

[0078] As a preferred solution, the organic nutrient soil extraction unit further includes a denitrification reaction device for denitrifying the dehydrated solution, and the treated dehydrated solution can optionally enter a sewage treatment system for further treatment.

[0079] As a preferred embodiment, the step of denitrification treatment of the desalted water solution by the denitrification reaction equipment comprises: converting ammonia nitrogen in the desalted water solution into nitrogen gas based on the anaerobic ammonium oxidation process.

[0080] As a preferred solution, the slag and sand removal device and the centrifugal concentration device are respectively connected to the pre-dehydration device through pipelines.

[0081] As a preferred solution, the pre-dehydration device, the conditioning container, the high-temperature and high-pressure reaction container, the buffer container, the anaerobic reaction container and the biogas storage container are sequentially connected through closed pipelines.

[0082] As a preferred solution, the anaerobic reaction container and the extrusion dehydration equipment are connected via a closed pipeline.

[0083] As a preferred solution, the extrusion dehydration equipment and the crushing device are connected via a screw conveying device.

[0084] According to the present invention, the slag and sand removing device can specifically adopt a grid slag remover and a cyclone sand removing machine; the centrifugal concentration device can specifically adopt a centrifuge; the pre-dehydration device can specifically adopt a centrifuge; the conditioning container can specifically adopt a vertical cylindrical slurry tank; the high-temperature and high-pressure reaction container can specifically adopt a vertical cylindrical high-temperature and high-pressure reactor; the buffer container can specifically adopt a vertical cylindrical flash buffer tank; the anaerobic reaction container can specifically adopt a cylindrical anaerobic reaction tank with mechanical stirring; the biogas storage container can specifically adopt a double-membrane spherical biogas cabinet; the extrusion dehydration equipment can specifically adopt a high-pressure plate and frame filter press; the crushing device can specifically adopt a hammer crusher; the denitrification reaction facility can specifically adopt a one-stage anaerobic ammonia oxidation reaction tank.

[0085] A second aspect of the present invention provides a method for preparing organic nutrient soil from urban sewage sludge, the method utilizing the above-mentioned system, the method comprising:

[0086] 1) A slag and sand removal device is used to remove most of the impurities in the primary sludge of the urban sewage treatment plant, and a centrifugal concentrator is used to centrifugally dehydrate the residual activated sludge of the urban sewage treatment plant, and then the mixture of the materials obtained by the slag and sand removal device and the centrifugal concentrator is pre-dehydrated to obtain pre-dehydrated sludge; slag and sand removal is beneficial to increase the organic matter content in the sludge and reduce the hidden dangers of equipment wear;

[0087] 2) receiving the first flash steam and the second flash steam through the conditioning container to preheat and slurry the pre-dehydrated sludge, so that the temperature of the pre-dehydrated sludge is maintained at 90° C.-97° C., the solid content is maintained at 12%-14%, and the material liquid level in the conditioning container is controlled to be maintained at a height of 60%-70%;

[0088] 3) The preheated and slurried materials are subjected to thermal hydrolysis using a high-temperature and high-pressure reaction vessel. After the reaction is completed, the pressure is first released through the first pressure relief valve on the top of the high-temperature and high-pressure reaction vessel, and the first flash steam enters the middle and lower part of the conditioning container through the pipeline. When the pressure in the high-temperature and high-pressure reaction vessel is less than 0.28MPa, the central monitoring and control unit controls the first pressure relief valve to automatically close, and the mud discharge valve at the bottom of the high-temperature and high-pressure reaction vessel to automatically open, and the materials in the high-temperature and high-pressure reaction vessel are sprayed into the container from the middle and upper interface of the buffer container under their own pressure;

[0089] 4) The second flash steam generated at the top of the buffer container enters the container through the second pressure relief valve through the pipeline from the middle and lower interface of the conditioning container, and the material in the buffer container is pumped to the anaerobic reaction container as needed for anaerobic decomposition, and the biogas obtained by the reaction is stored in the biogas storage container;

[0090] 5) Extruding and dehydrating the anaerobic decomposition product by an extrusion dehydration device to obtain organic nutrient soil in the form of fragments and a dehydrated solution;

[0091] 6) The organic nutrient soil in pieces is crushed and shaped to obtain granular organic nutrient soil.

[0092] As a preferred solution, the high temperature and high pressure reaction vessel is preferably operated in batch mode.

[0093] According to the present invention, when the pressure in the high-temperature and high-pressure reaction vessel is less than 0.28MPa, the sludge in the reaction vessel is discharged to the buffer container under its own pressure. At this time, flash explosion occurs under the action of the pressure difference between the inside and outside of the sludge cells, the sludge cells are broken, the intracellular nutrients are fully dissolved, the sludge fluidity is significantly improved, and the biodegradability of organic matter in the sludge is significantly improved; when the pressure in the high-temperature and high-pressure reaction vessel drops to 0.1MPa, the sludge in the conditioning container can enter the high-temperature and high-pressure reaction vessel again to enter the next reaction cycle.

[0094] According to the present invention, when the high temperature and high pressure reaction vessel needs to be fed, the material is usually pumped from the bottom of the conditioning vessel to the upper middle portion of the high temperature and high pressure reaction vessel.

[0095] As a preferred embodiment, in step 1), a first agent is added during the centrifugal dehydration process to assist dehydration, the agent includes PAM, and the centrifugal dehydration reduces the moisture content of the remaining activated sludge to 97%-97.5%. The amount of the first agent added is 1‰-2‰ of the dry weight of the remaining activated sludge.

[0096] As a preferred embodiment, in step 1), a second agent is added during the pre-dehydration process to assist in dehydration, the agent includes PAM, and the pre-dehydration reduces the moisture content of the pretreated sludge to 82%-86%. The amount of the second agent added is 3‰-5‰ of the dry weight of the sludge of the mixture of materials obtained from the deslagging and desanding device and the centrifugal concentrator.

[0097] As a preferred embodiment, in step 2), the initial pressure of the first flash steam is 0.6 MPa-0.28 MPa, and the initial pressure of the second flash steam is 0.28 MPa-0.1 MPa.

[0098] As a preferred solution, in step 3), the pressure of thermal hydrolysis is 0.6MPa-1.0MPa, the temperature of thermal hydrolysis is 160℃-180℃, and the time of thermal hydrolysis is 30min-60min. In this process, the solid organic matter of the sludge is dissolved, the macromolecules are hydrolyzed into small molecules, and the pathogens are completely disinfected.

[0099] As a preferred solution, in step 4), the temperature of the anaerobic composting process is 40±0.5°C. After anaerobic composting, the organic matter in the sludge is transformed and utilized by anaerobic microorganisms, the degradation rate can reach 45%-60%, and the gas production rate can reach 250-400m 3 / t dry mud, the residence time can be reduced to 15-18 days.

[0100] According to the present invention, in a specific embodiment, the generated biogas is transported to a biogas cabinet, and after desulfurization, the biogas first enters a steam boiler to produce 1.25MPa saturated steam to supply a high-temperature and high-pressure reaction unit, and the remaining biogas enters a power generation equipment to produce electricity, which is used in an organic nutrient soil production system, and the excess electricity is supplied externally.

[0101] As a preferred embodiment, in step 5), the pressure of extrusion dehydration is 1.5MPa-2.5MPa, and the time of extrusion dehydration is 40min-60min.

[0102] As a preferred solution, in step 5), an organic-inorganic compound dehydrating agent is added to assist dehydration during extrusion dehydration, and the addition ratio is 6%-8% of the dry weight of the anaerobic decomposition product, and the dehydration is performed until the moisture content is ≤60%. The organic-inorganic compound dehydrating agent is an organic-inorganic compound dehydrating agent conventionally used by those skilled in the art, and is a common commercially available product.

[0103] After dehydration, the organic nutrient soil is in solid state, which is convenient for storage and transportation. Compared with untreated raw sludge, the transportation cost can be reduced by about 60%-70%.

[0104] As a preferred solution, in step 6), the particle size of the granular organic nutrient soil 101 obtained is ≤10 mm.

[0105] The third aspect of the present invention provides organic nutrient soil prepared by the above method. After testing, the organic nutrient soil has an organic matter content ≥35%, a total nutrient content (N+P2O5+K2O) ≥5%, and a maturity (seed germination index) that is stable at more than 70%.

[0106] The fourth aspect of the present invention provides the application of the above-mentioned organic nutrient soil in the technical field of resource utilization and preparation of soil fertilizer.

[0107] Embodiment 1:

[0108] This embodiment provides a system and method for preparing organic nutrient soil from urban domestic sludge, and organic nutrient soil and applications.

[0109] Figure 1 The schematic diagram of a system for preparing organic nutrient soil from urban domestic sewage sludge according to an embodiment of the present invention is shown. Figure 1 As shown, the system includes:

[0110] Pretreatment unit, high temperature and high pressure reaction unit, composting and energy recovery unit, organic nutrient soil extraction unit, organic nutrient soil shaping unit and central monitoring and control unit for controlling the operation of each unit;

[0111] The pretreatment unit includes a slag and sand removal device 1, a centrifugal concentration device 2 and a pre-dehydration device 3:

[0112] The slag and sand removal device 1 is used to remove most of the impurities in the primary sludge 101 of the urban domestic sewage treatment plant;

[0113] The centrifugal concentrator 2 is used for centrifugal dehydration of the excess activated sludge 201 of the urban sewage treatment plant;

[0114] The pre-dehydration device 3 is used to pre-dehydrate the mixture of materials obtained by the deslagging and desanding device 1 and the centrifugal concentration device 2 to obtain pre-dehydrated sludge;

[0115] The high temperature and high pressure reaction unit includes a conditioning container 4, a high temperature and high pressure reaction container 5, and a buffer container 6:

[0116] The conditioning container 4 is used to receive the first flash steam and the second flash steam supplied by the high-temperature and high-pressure reaction container 5 and the buffer container 6 respectively, so as to preheat and slurry the pre-dehydrated sludge;

[0117] The high temperature and high pressure reaction vessel 5 is used to perform thermal hydrolysis on the material received from the conditioning vessel 4 and generate first flash steam supplied to the conditioning vessel 4;

[0118] The buffer container 6 is used to receive the material after thermal hydrolysis in the high-temperature and high-pressure reaction container 5 and provide the second flash steam for supplying the conditioning container 4;

[0119] A first pressure relief valve and a second pressure relief valve are respectively provided on the top of the high-temperature and high-pressure reaction vessel 5 and the buffer container 6 to control the pressure of the high-temperature and high-pressure reaction vessel 5 and the buffer container 6;

[0120] The first pressure relief valve and the second pressure relief valve are respectively connected to the middle and lower parts of the conditioning container 4 through closed pipes;

[0121] The composting and energy recovery unit includes an anaerobic reaction container 7 and a biogas storage container 8:

[0122] The anaerobic reaction container 7 is used to perform anaerobically decomposing the sludge raw material from the buffer container 6;

[0123] The biogas storage container 8 is used to store the biogas obtained from the anaerobic reaction container 7;

[0124] The organic nutrient soil extraction unit includes an extrusion dehydration device 9, which is used to extrusion dehydrate the product obtained by anaerobic decomposition to obtain organic nutrient soil 92 in the form of fragments and a dehydrated solution 91;

[0125] The organic nutrient soil shaping unit comprises a crushing device 10 for crushing the organic nutrient soil in block form to obtain granular organic nutrient soil.

[0126] The above-mentioned urban domestic sludge refers specifically to the sludge generated during the treatment of urban domestic sewage.

[0127] Among them, the central monitoring and control unit 14 controls the corresponding equipment (unit) through the conventional settings of its human-machine interface, PLC control unit, etc. as a conventional technical means. Specifically, the corresponding equipment (unit) is provided with a sensor, and the PLC control unit is connected to each sensor for communication and / or electrical connection to control the corresponding equipment (unit), and each unit is centrally monitored and / or warned and / or adjusts the operating parameters through the human-machine interface. The central monitoring and control unit 14 controls the timing cleaning of slag and sand removal and controls the speed of the centrifuge through the human-machine interface. The conditioning container 4 is provided with a liquid level sensor and a temperature sensor. The high-temperature and high-pressure reaction container 5 is provided with a pressure sensor, a temperature sensor, and a liquid level sensor. The buffer container 6 is provided with a liquid level sensor, a pressure sensor, and a temperature sensor. The anaerobic reaction container 7 is provided with a liquid level sensor, a temperature sensor, a flow sensor, and a pH sensor. The biogas storage container 8 is provided with a height sensor to feedback the amount of gas in the biogas storage cabinet. The human-machine interface can control the material transportation of the organic nutrient soil extraction unit. The extrusion dehydration equipment 9 is provided with a pressure sensor.

[0128] Among them, the composting and energy recovery unit also includes: a steam boiler 11, which is connected to the biogas storage container 8 through a closed pipeline; the biogas in the biogas storage container 8 provides energy for the steam boiler 11, and the high-temperature saturated steam 111 obtained by the steam boiler 11 is used as a heat source for heating the material in the high-temperature and high-pressure reaction container 5, and the steam boiler 11 is connected to the high-temperature and high-pressure reaction container 5 through a closed pipeline.

[0129] The composting and energy recovery unit further includes: a power generation device 12 , which utilizes the biogas in the biogas storage container 8 to generate electrical energy 121 , and the electrical energy 121 is used for self-use 1211 of the system and / or for external power supply 1212 .

[0130] The organic nutrient soil extraction unit further includes a denitrification reaction device 13 for denitrifying the dewatered solution 91. The denitrified solution 91 after treatment may enter a sewage treatment system 131 for further treatment. The denitrification treatment step includes: converting ammonia nitrogen in the dewatered solution 91 into nitrogen gas based on an anaerobic ammonium oxidation process.

[0131] Among them, the slag and sand removal device 1 and the centrifugal concentration device 2 are connected to the pre-dehydration device through pipelines. The pre-dehydration device 3, the conditioning container 4, the high-temperature and high-pressure reaction container 5, the buffer container 6, the anaerobic reaction container 7 and the biogas storage container 8 are connected in sequence through closed pipelines. The anaerobic reaction container 7 and the extrusion dehydration device 9 are connected through a closed pipeline. The extrusion dehydration device 9 and the crushing device 10 are connected through a screw conveying device.

[0132] Among them, the slag and sand removing device specifically adopts a grid slag remover and a cyclone sand removing machine; the centrifugal concentration device 2 specifically adopts a centrifuge; the pre-dehydration device specifically adopts a centrifuge; the conditioning container specifically adopts a vertical cylindrical slurry tank; the high-temperature and high-pressure reaction container specifically adopts a vertical cylindrical high-temperature and high-pressure reactor; the buffer container specifically adopts a vertical cylindrical flash buffer tank; the anaerobic reaction container specifically adopts a cylindrical anaerobic reaction tank with mechanical stirring; the biogas storage container specifically adopts a double-membrane spherical biogas cabinet; the extrusion dehydration equipment specifically adopts a high-pressure plate and frame filter press; the crushing device specifically adopts a hammer crusher; the denitrification reaction facility specifically adopts a one-stage anaerobic ammonia oxidation reaction tank.

[0133] A method for preparing organic nutrient soil from urban domestic sludge is provided by using the above system. The sludge comes from the Gaobeidian Reclaimed Water Plant in Chaoyang District, Beijing. The method comprises:

[0134] 1) using a slag and sand removal device 1 to remove most of the impurities in the primary sludge 101 of the urban sewage treatment plant, using a centrifugal concentrator 2 to centrifugally dehydrate the excess activated sludge 201 of the urban sewage treatment plant, and then pre-dehydrating the mixture of the materials obtained by the slag and sand removal device 1 and the centrifugal concentrator 2 to obtain pre-dehydrated sludge;

[0135] 2) receiving the first flash steam and the second flash steam through the conditioning container 4 to preheat and slurry the pre-dehydrated sludge, so that the temperature of the pre-dehydrated sludge is maintained at 90°C-97°C, the solid content is maintained at 12%-14%, and the material level in the conditioning container 4 is controlled to be maintained at 60%-70% height; the initial pressure of the first flash steam is 0.6MPa-0.28MPa, and the initial pressure of the second flash steam is 0.28MPa-0.1MPa;

[0136] 3) The preheated and slurried materials are subjected to thermal hydrolysis using a high-temperature and high-pressure reaction vessel 5, and the pressure of the thermal hydrolysis is controlled to be 0.6 MPa, the temperature of the thermal hydrolysis is 160° C., and the time of the thermal hydrolysis is 30 min. After the reaction is completed, the pressure is first released through the first pressure relief valve at the top of the high-temperature and high-pressure reaction vessel 5, and the first flash steam enters the middle and lower part of the conditioning container 4 through the pipeline. When the pressure in the high-temperature and high-pressure reaction vessel 5 is less than 0.28 MPa, the central monitoring and control unit 14 controls the first pressure relief valve to automatically close, and the mud discharge valve at the bottom of the high-temperature and high-pressure reaction vessel 5 to automatically open, and the material in the high-temperature and high-pressure reaction vessel 5 is sprayed into the container from the middle and upper interface of the buffer container 6 under its own pressure;

[0137] 4) The second flash steam generated at the top of the buffer container 6 enters the container from the middle and lower interface of the conditioning container 4 through the pipeline through the second pressure relief valve, and the material in the buffer container 6 is pumped to the anaerobic reaction container 7 for anaerobic decomposition as needed. The temperature of the anaerobic decomposition process is 40±0.5°C, and the biogas obtained by the reaction is stored in the biogas storage container 8;

[0138] 5) The anaerobic decomposition product is extruded and dehydrated by an extrusion dehydration device 9, the pressure of the extrusion dehydration is controlled to be 2 MPa, and the extrusion dehydration time is 40 min, to obtain a fragmented organic nutrient soil 92 and a dehydrated solution 91; wherein, during the extrusion dehydration, an organic-inorganic composite dehydrating agent is added to assist dehydration, and the addition ratio is 6% of the dry weight of the anaerobic decomposition product, and the dehydration is performed until the moisture content is ≤60%;

[0139] 6) The organic nutrient soil 92 in a broken block form is crushed and shaped to obtain granular organic nutrient soil 101 with a particle size of ≤10 mm.

[0140] When the high-temperature and high-pressure reaction vessel 5 needs to be fed, the material is usually pumped into the upper middle portion of the high-temperature and high-pressure reaction vessel 5 from the bottom of the conditioning vessel 4 .

[0141] Among them, the high temperature and high pressure reaction vessel 5 is operated in batch mode.

[0142] Among them, in step 1), the first agent is added during the centrifugal dehydration process to assist dehydration, the agent is PAM, and the centrifugal dehydration reduces the moisture content of the remaining activated sludge to 97%-97.5%. The addition amount of the first agent is 1.5‰ of the dry weight of the remaining activated sludge.

[0143] Among them, in step 1), a second agent is added during the pre-dehydration process to assist in dehydration, the agent is PAM, and the pre-dehydration reduces the moisture content of the pretreated sludge to 83.5%. The amount of the second agent added is 4‰ of the dry weight of the sludge of the mixture of materials obtained by the slag and sand removal device 1 and the centrifugal concentrator 2.

[0144] In the anaerobic reaction container, organic matter is transformed and utilized by anaerobic microorganisms, with a residence time of 18 days, a degradation rate of 50%-60%, and a gas production rate of 350-400m 3 / t dry mud. The generated biogas is transported to the biogas cabinet. After desulfurization, the biogas first enters the steam boiler to produce 1.25MPa saturated steam to supply the high-temperature and high-pressure reaction unit. The remaining biogas enters the power generation equipment to produce electricity, which is used in the organic nutrient soil production system, and the excess electricity is supplied to the outside.

[0145] The organic nutrient soil obtained by the above system and method has been tested to have an organic matter content of ≥35%, a total nutrient content (N+P2O5+K2O) of ≥5%, and a maturity (seed germination index) of more than 70%. After dehydration, the organic nutrient soil is in a solid state, which is convenient for storage and transportation. Compared with the untreated original sludge (water content 80%), the transportation cost can be reduced by about 65%. The filtrate obtained by extrusion is transported to the denitrification reaction facility through a pipeline for denitrification treatment, and the treated filtrate is returned to the sewage treatment area without secondary pollution.

[0146] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for preparing organic nutrient soil from urban domestic sludge, characterized in that: The system utilized by this method includes: A pretreatment unit, a high temperature and high pressure reaction unit, a composting and energy recovery unit, an organic nutrient soil extraction unit, an organic nutrient soil shaping unit, and a central monitoring and control unit (14) for controlling the operation of each unit; The pretreatment unit comprises a slag and sand removal device (1), a centrifugal concentration device (2) and a pre-dehydration device (3): The slag and sand removal device (1) is used to remove most of the impurities in the primary sludge (101) of the urban domestic sewage treatment plant; The centrifugal concentrator (2) is used for centrifugally dehydrating the excess activated sludge (201) of the urban sewage treatment plant; The pre-dehydration device (3) is used to pre-dehydrate the mixture of materials obtained by the slag and sand removal device (1) and the centrifugal concentration device (2) to obtain pre-dehydrated sludge; The high temperature and high pressure reaction unit comprises a conditioning container (4), a high temperature and high pressure reaction container (5), and a buffer container (6): The conditioning container (4) is used to receive the first flash steam and the second flash steam supplied by the high-temperature and high-pressure reaction container (5) and the buffer container (6) respectively, so as to preheat and slurry the pre-dehydrated sludge; The high temperature and high pressure reaction vessel (5) is used to perform thermal hydrolysis on the material received from the conditioning vessel (4) and generate first flash steam supplied to the conditioning vessel (4); The buffer container (6) is used to receive the material after thermal hydrolysis in the high-temperature and high-pressure reaction container (5) and provide the second flash steam to supply the conditioning container (4); A first pressure relief valve and a second pressure relief valve are respectively provided on the top of the high-temperature and high-pressure reaction container (5) and the buffer container (6), for controlling the pressure of the high-temperature and high-pressure reaction container (5) and the buffer container (6); The first pressure relief valve and the second pressure relief valve are respectively connected to the middle and lower parts of the conditioning container (4) through sealed pipes; The decomposition and energy recovery unit comprises an anaerobic reaction container (7) and a biogas storage container (8): The anaerobic reaction container (7) is used to perform anaerobic decomposition on the sludge raw material from the buffer container (6); The biogas storage container (8) is used to store the biogas obtained from the anaerobic reaction container (7); The organic nutrient soil extraction unit comprises an extrusion dehydration device (9) for extruding and dehydrating the product obtained by anaerobic decomposition to obtain organic nutrient soil (92) in the form of fragments and a dehydrated solution (91); The organic nutrient soil shaping unit comprises a crushing device (10) for crushing the organic nutrient soil (92) in a broken block form to obtain granular organic nutrient soil (93); The method comprises: 1) using a slag and sand removal device (1) to remove most of the impurities in the primary sludge (101) of the urban sewage treatment plant, using a centrifugal concentrator (2) to centrifugally dehydrate the excess activated sludge (201) of the urban sewage treatment plant, and then pre-dehydrating the mixture of the materials obtained by the slag and sand removal device (1) and the centrifugal concentrator (2) to obtain pre-dehydrated sludge; 2) receiving the first flash steam and the second flash steam through the conditioning container (4) to preheat and slurry the pre-dehydrated sludge, so that the temperature of the pre-dehydrated sludge is maintained at 90° C.-97° C., the solid content is maintained at 12%-14%, and the material liquid level in the conditioning container (4) is controlled to be maintained at a height of 60%-70%; The initial pressure of the first flash steam is 0.6MPa-0.28MPa, and the initial pressure of the second flash steam is 0.28MPa-0.1MPa; 3) using a high-temperature and high-pressure reaction vessel (5) to perform thermal hydrolysis on the preheated and slurried material. After the reaction is completed, the pressure is first released through a first pressure relief valve at the top of the high-temperature and high-pressure reaction vessel (5), and the first flash steam enters the middle and lower part of the conditioning container (4) through a pipeline. When the pressure in the high-temperature and high-pressure reaction vessel (5) is less than 0.28 MPa, the central monitoring and control unit (14) controls the first pressure relief valve to automatically close, and the mud discharge valve at the bottom of the high-temperature and high-pressure reaction vessel (5) to automatically open, and the material in the high-temperature and high-pressure reaction vessel (5) is sprayed into the container through the middle and upper interface of the buffer container (6) under its own pressure; 4) The second flash steam generated at the top of the buffer container (6) enters the container through the second pressure relief valve through the pipeline from the middle and lower interface of the conditioning container (4), and the material in the buffer container (6) is pumped to the anaerobic reaction container (7) as needed for anaerobic decomposition, and the biogas obtained by the reaction is stored in the biogas storage container (8); 5) Extruding and dehydrating the anaerobic decomposition product by an extrusion dehydration device (9) to obtain organic nutrient soil (92) in the form of fragments and a dehydrated solution (91); 6) The organic nutrient soil (92) in the form of fragments is crushed and shaped to obtain granular organic nutrient soil (93).

2. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: The decomposition and energy recovery unit also includes: The steam boiler (11) is connected to the biogas storage container (8) through a sealed pipeline; the biogas in the biogas storage container (8) provides energy for the steam boiler (11), and the high-temperature saturated steam (111) obtained by the steam boiler (11) is used as a heat source for heating the material in the high-temperature and high-pressure reaction container (5). The steam boiler (11) is connected to the high-temperature and high-pressure reaction container (5) through a sealed pipeline.

3. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: The decomposition and energy recovery unit also includes: The power generation equipment (12) utilizes the biogas in the biogas storage container (8) to generate electric energy (121), and the electric energy (121) is used for self-use of the system (1211) and / or for external power supply (1212).

4. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: The organic nutrient soil extraction unit further comprises a denitrification reaction device (13) for denitrifying the dehydrated water (91). The dehydrated water (91) after treatment may optionally enter a sewage treatment system (131) for further treatment.

5. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: The slag and sand removal device (1) and the centrifugal concentration device (2) are respectively connected to the pre-dehydration device through pipelines; The pre-dehydration device (3), the conditioning container (4), the high-temperature and high-pressure reaction container (5), the buffer container (6), the anaerobic reaction container (7) and the biogas storage container (8) are connected in sequence through a sealed pipeline; The anaerobic reaction container (7) and the extrusion dehydration device (9) are connected via a sealed pipeline; The extrusion dehydration device (9) and the crushing device (10) are connected via a screw conveying device.

6. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: In step 1): During the centrifugal dehydration process, a first agent is added to assist dehydration, wherein the agent includes PAM. Centrifugal dehydration reduces the moisture content of the remaining activated sludge to 97%-97.5%, and the amount of the first agent added is 1‰-2‰ of the dry weight of the remaining activated sludge; During the pre-dehydration process, a second agent is added to assist dehydration, the agent comprising PAM. Pre-dehydration reduces the moisture content of the pre-treated sludge to 82%-86%, and the dosage of the second agent is 3‰-5‰ of the dry weight of the sludge of the mixture of materials obtained by the deslagging and desanding device (1) and the centrifugal concentrator (2); In step 3): The pressure of thermal hydrolysis is 0.6MPa-1.0MPa, the temperature of thermal hydrolysis is 160℃-180℃, and the time of thermal hydrolysis is 30min-60min; In step 4): The temperature of the anaerobic composting process is 40±0.5℃.

7. The method for preparing organic nutrient soil from urban sewage sludge according to claim 1, wherein: In step 5): The pressure of extrusion dehydration is 1.5MPa-2.5MPa, and the time of extrusion dehydration is 40min-60min; During extrusion dehydration, an organic-inorganic compound dehydrating agent is added to assist dehydration, the addition ratio is 6%-8% of the dry weight of the anaerobic decomposed product, and dehydration is performed until the moisture content is ≤60%; In step 6): The particle size of the obtained granular organic nutrient soil (93) is ≤10 mm.

8. Organic nutrient soil prepared by the method described in any one of claims 1 to 7.

9. Application of the organic nutrient soil according to claim 8 in the technical field of resource utilization and preparation of soil fertilizer.

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