Sludge-based nano biochar, preparation method and compost regulation and control method

Abstract

The invention discloses sludge-based nano biochar, a preparation method and a compost regulation and control method, and relates to the technical field of environmental engineering and resource recycling, and the preparation method comprises the following steps: successively carrying out dehydration treatment, drying treatment and crushing treatment on initial activated sludge to obtain crushed dry sludge; soaking the crushed dry sludge in a citric acid solution with a preset concentration, and drying after a first preset soaking time to obtain pretreated sludge; carrying out carbonization treatment on the pretreated sludge by utilizing a pyrolyzing furnace to obtain primary biochar; mechanically grinding the preliminary biochar by using a ball mill to obtain preliminary nano biochar; and soaking the primary nano-biochar in a citric acid solution for a second preset soaking time, and then treating the primary nano-biochar with a hydrogen peroxide solution to obtain the sludge-based nano-biochar. The technical problem that limitation exists in the aspects of gas emission reduction efficiency, composting efficiency and product quality improvement in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of environmental engineering and resource recycling, and in particular to a sludge-based nano biochar, a preparation method and a composting control method. Background Art

[0002] At present, aerobic composting treatment technology for residual activated sludge from urban domestic sewage treatment plants has been widely used. It mainly decomposes the organic matter in the sludge into humus or other organic fertilizers through aerobic metabolism of microorganisms, realizing the resource utilization of sludge. The existing process includes steps such as sludge dehydration, auxiliary material mixing, composting fermentation and product treatment. First, the sludge with an initial moisture content of 80% to 85% is treated by mechanical filtration or centrifugal dehydration to a moisture content of 60% to 70%, and then mixed with auxiliary materials such as straw and sawdust, and the carbon-nitrogen ratio (C / N ratio) is adjusted to an appropriate range (20:1 to 30:1). Subsequently, fermentation is carried out under aerobic conditions, and the composting temperature is controlled at 50 to 70°C for 20 to 30 days to decompose the organic matter and complete the stabilization treatment.

[0003] In the composting process, in order to reduce the emission of pollutants such as methane (CH4), nitrous oxide (N2O) and ammonia (NH3), existing technologies usually use mechanical compost turning, forced ventilation or chemical adsorption. After fermentation, the compost products are screened and blended to make organic fertilizer or soil conditioner. Although existing composting technology has achieved certain results in sludge treatment and resource utilization, it still has shortcomings in the following key aspects:

[0004] (1) Low efficiency in reducing secondary pollutant gases: Existing technologies mainly rely on ventilation and chemical adsorption to reduce the emissions of methane (CH4), nitrous oxide (N2O) and ammonia (NH3) during composting, but the reduction efficiency is low, especially for methane and nitrous oxide.

[0005] (2) Limited composting efficiency: The optimization effects of carbon-nitrogen ratio adjustment and composting conditions in traditional composting technology are limited, and the composting cycle is relatively long (20 to 30 days), which restricts the processing efficiency.

[0006] (3) The quality of compost products is unstable: the nutrient content (total nitrogen, total phosphorus, and total potassium) of existing compost products is low, the mobility of heavy metals is high, and the fertilizer efficiency and ecological safety are limited.

[0007] (4) Lack of precise control and synergistic technology: In existing composting technologies, gas emission control mostly relies on passive measures and lacks dynamic monitoring and precise control methods, making it difficult to improve the stability of the composting process. Summary of the invention

[0008] The purpose of the present invention is to provide a sludge-based nano-biochar, a preparation method and a composting control method in order to solve at least one of the above-mentioned technical problems.

[0009] In a first aspect, an embodiment of the present invention provides a method for preparing sludge-based nano-biochar, comprising: sequentially dehydrating, drying and pulverizing initial activated sludge to obtain pulverized dry sludge; soaking the pulverized dry sludge in a citric acid solution of a preset concentration, drying after a first preset immersion time, to obtain pretreated sludge; carbonizing the pretreated sludge using a pyrolysis furnace to obtain preliminary biochar; mechanically grinding the preliminary biochar using a ball mill to obtain preliminary nano-biochar; soaking the preliminary nano-biochar in the citric acid solution for a second preset immersion time, and then treating it with a hydrogen peroxide solution to obtain sludge-based nano-biochar.

[0010] Furthermore, the initial activated sludge is sequentially subjected to dehydration treatment, drying treatment and pulverization treatment, including: subjecting the initial activated sludge to mechanical filter pressing or centrifugal dehydration treatment to obtain dehydrated sludge; subjecting the dehydrated sludge to low-temperature hot air drying treatment to obtain dried sludge; and pulverizing the dried sludge to obtain the pulverized dry sludge.

[0011] Furthermore, the preset concentration includes 0.1 mol·L -1 -0.5mol·L -1 ; The first preset soaking time includes 1h-2h; the second preset soaking time includes 2h-3h.

[0012] Furthermore, the pretreated sludge is carbonized using a pyrolysis furnace, including: placing the pretreated sludge in a pyrolysis furnace and heating it under anaerobic conditions for carbonization; after the carbonization treatment has lasted for a preset pyrolysis time, cooling it to room temperature, sieving and removing uncarbonized particles, and obtaining the preliminary biochar.

[0013] Furthermore, the particle size of the preliminary nano-biochar is 20nm-100nm.

[0014] Furthermore, the hydrogen peroxide solution includes a 30% hydrogen peroxide solution; the treatment temperature of the hydrogen peroxide solution includes 50° C.-60° C., and the treatment time of the hydrogen peroxide solution includes 1 hour.

[0015] In a second aspect, an embodiment of the present invention further provides a sludge-based nano-biochar, which is obtained based on the preparation method described in the first invention.

[0016] In the third aspect, an embodiment of the present invention also provides a composting regulation method based on the sludge-based nano-biochar provided by the embodiment of the present invention, comprising: in the composting startup stage, adding a first preset quantity of the sludge-based nano-biochar in layers to the top layer, middle layer and bottom layer of the composting sludge; in the high temperature stage of composting, supplementing the middle layer and the bottom layer with a biochar suspension by a suspension spraying method; the biochar suspension is a suspension containing a preset concentration of the sludge-based nano-biochar.

[0017] Furthermore, a suspension spraying method is used to supplement the middle layer and the bottom layer with biochar suspension, including: real-time monitoring of target gas concentrations of the compost sludge; the target gas concentrations include methane concentration, nitrous oxide concentration, and ammonia concentration; when the target gas concentration exceeds a preset concentration threshold, a suspension spraying method is used to supplement the middle layer and the bottom layer with biochar suspension.

[0018] In a fourth aspect, an embodiment of the present invention also provides another composting regulation method based on the sludge-based nano-biochar provided by the embodiment of the present invention, comprising: immersing the sludge-based nano-biochar in a target bacteria culture solution to prepare microbial enhanced biochar; the target bacteria include methanotrophic bacteria and / or nitrifying bacteria; in the composting startup stage, evenly mixing and distributing a second preset amount of the microbial enhanced biochar with auxiliary materials.

[0019] The present invention provides a sludge-based nano biochar, a preparation method and a composting control method. By optimizing the preparation process of biochar and the dynamic control strategy, efficient emission reduction of secondary pollution gases during composting, significant improvement of composting efficiency and optimization of compost product quality are achieved, thereby alleviating the technical problems of limitations in the prior art in terms of gas emission reduction efficiency, composting efficiency and product quality improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 A flow chart of a method for preparing sludge-based nano-biochar provided in an embodiment of the present invention;

[0022] Figure 2 A flow chart of a composting control method based on sludge-based nano-biochar provided in an embodiment of the present invention;

[0023] Figure 3A flow chart of another composting control method based on sludge-based nano-biochar provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Embodiment 1

[0026] Figure 1 1 is a flow chart of a method for preparing sludge-based nano-biochar according to an embodiment of the present invention. Figure 1 As shown, the method specifically comprises the following steps:

[0027] Step S102, sequentially dehydrating, drying and crushing the initial activated sludge to obtain crushed dry sludge. The initial activated sludge includes excess activated sludge from a municipal sewage treatment plant. Specifically, the steps include:

[0028] Step S1021, treating the initial activated sludge by mechanical filter pressing or centrifugal dehydration to obtain dehydrated sludge;

[0029] Step S1022, subjecting the dehydrated sludge to low-temperature hot air drying to obtain dried sludge;

[0030] Step S1023, crushing the dried sludge to obtain crushed dry sludge.

[0031] Step S104, soaking the crushed dry sludge in a citric acid solution of a preset concentration, and drying it after a first preset soaking time to obtain pretreated sludge.

[0032] Optionally, the preset concentration includes 0.1 mol·L -1 -0.5mol·L -1 ; The first preset soaking time includes 1h-2h.

[0033] In an optional implementation provided by an embodiment of the present invention, the residual activated sludge with an initial moisture content of 80% to 85% is treated by mechanical filtration or centrifugal dehydration to a moisture content of 60% to 70%, and then dried by low-temperature hot air (temperature 80 to 105°C) to a moisture content of 10% to 20%, and then crushed to a particle size of 0.5 to 2 mm. The crushed dry sludge is soaked in 0.1 to 0.5 mol·L -1Citric acid solution (temperature 25-40°C, time 1-2h), after completing the passivation treatment of metal impurities, dry it for later use.

[0034] Step S106, using a pyrolysis furnace to carbonize the pretreated sludge to obtain preliminary biochar. Specifically, it includes the following steps:

[0035] Step S1061, placing the pretreated sludge in a pyrolysis furnace and heating it under anoxic conditions for carbonization treatment;

[0036] Step S1062, after the carbonization treatment has been completed for a preset pyrolysis time, the carbonized product is cooled to room temperature, and uncarbonized particles are removed by screening to obtain preliminary biochar.

[0037] In an optional embodiment provided in the embodiment of the present invention, the pretreated sludge is placed in a pyrolysis furnace and heated to 600-650°C for carbonization under anoxic or inert atmosphere (such as nitrogen or carbon dioxide), and the gas flow rate is controlled to 12 L min -1 kg -1 The pyrolysis time is 1.5 to 2 hours. After carbonization, it is cooled to room temperature, and the uncarbonized particles are removed by sieving to obtain preliminary biochar.

[0038] Step S108, using a ball mill to mechanically grind the preliminary biochar to obtain preliminary nano-biochar, wherein the particle size of the preliminary nano-biochar is 20nm-100nm.

[0039] Step S110, soaking the preliminary nano-biochar in a citric acid solution for a second preset soaking time, and then treating it with a hydrogen peroxide solution to obtain sludge-based nano-biochar.

[0040] Preferably, the second preset soaking time includes 2h-3h.

[0041] Preferably, the hydrogen peroxide solution includes a 30% hydrogen peroxide solution; the treatment temperature of the hydrogen peroxide solution includes 50° C.-60° C., and the treatment time of the hydrogen peroxide solution includes 1 hour.

[0042] In an optional implementation provided in the embodiment of the present invention, the preliminary biochar is mechanically ground using a high-energy ball mill (speed 400 r / min -1 , ball-to-material ratio 10:1, time 4h), the particle size is reduced to 20-100nm. -1 The citric acid solution (temperature 70-90°C, time 2-3h) was further treated with 30% H2O2 solution (temperature 50-60°C, time 1h) to introduce active groups such as carboxyl and hydroxyl groups to prepare sludge-based nano-biochar with high specific surface area and high active surface.

[0043] The embodiment of the present invention also provides a sludge-based nano-biochar, which is obtained based on the above-mentioned preparation method.

[0044] Embodiment 2

[0045] The method for preparing sludge-based nano-biochar provided in the embodiment of the present invention uses the residual activated sludge from the urban sewage treatment plant as raw material, and prepares nano-scale biochar with high specific surface area, rich pore structure and surface active groups through pretreatment, pyrolysis carbonization, nano-crystallization and surface active group enhancement. The specific process flow and technical parameters are as follows, and the production of 1 t of sludge-based nano-biochar is used as an example for explanation.

[0046] (1) Raw material pretreatment:

[0047] Wet sludge with an initial moisture content of about 80% is collected from the urban sewage treatment plant. First, the moisture content of the sludge is reduced to 60% to 70% by mechanical filter pressing or centrifugal dehydration. At this stage, 8 to 10 tons of wet sludge need to be processed to obtain 4 to 5 tons of dehydrated sludge. Then, low-temperature hot air drying (temperature controlled at 80 to 105°C) is used to further reduce the moisture content to 10% to 20%, and 1 to 1.2 tons of dry sludge are obtained. The dried sludge is crushed to 0.5 to 2 mm by a ball mill or a pulverizer, and finally 1 ton of crushed dry sludge is obtained as the raw material for pyrolysis carbonization.

[0048] Before pyrolysis and carbonization, the crushed dry sludge was soaked in 0.1-0.5 mol·L -1 In citric acid (C6H8O7) solution, stir evenly, maintain the temperature at 25-40°C, and soak for 1-2 hours to passivate the metal impurities in the raw material and reduce its catalytic effect during the pyrolysis process. Subsequently, the soaked sludge is filtered out and dried at 80-105°C to obtain pretreated sludge to ensure that the moisture content of the raw material is suitable for subsequent pyrolysis treatment.

[0049] (2) Pyrolysis carbonization:

[0050] 1 ton of pretreated sludge is placed in a pyrolysis furnace or rotary kiln for carbonization treatment under anoxic or inert atmosphere. During the carbonization process, nitrogen (N2) or carbon dioxide (CO2) is introduced, and the flow rate is controlled at 1-2 L / min according to the amount of raw materials. -1 kg -1 , that is, 10 to 20 m3 of water is introduced per hour 3 ·h -1 Protective gas is used to prevent oxidation of biochar. The pyrolysis temperature is controlled at 600-650°C, where 600°C can take into account both the yield and specific surface area of ​​biochar, and the pyrolysis time is 1.5-2h. After carbonization is completed, it is naturally cooled to room temperature under a protective atmosphere, the resulting product is collected, and sieved to remove uncarbonized large particles and impurities to obtain preliminary biochar.

[0051] (3) Nano-processing:

[0052] In order to increase the specific surface area and catalytic activity of biochar, the preliminary biochar was nano-processed. The biochar was mechanically ground using a high-energy ball mill, and the ball milling parameters were set at a speed of 400 r / min. -1 The ball-to-material ratio (the ratio of the weight of the ball to the weight of the biochar) was 10:1, and the ball milling time was controlled to 4 hours, so that the particle size of the biochar particles was reduced to 20-100 nm. Subsequently, the ball-milled biochar was dispersed in anhydrous ethanol or deionized water, and ultrasonic dispersion treatment was performed. The ultrasonic frequency was set to 30kHz and the treatment time was 1 hour to obtain preliminary nano-biochar, further improve the dispersibility and uniformity of the biochar, and ensure that the particle size was stable in the nanometer range.

[0053] (4) Enhancement of surface active groups:

[0054] In order to enhance the adsorption and catalytic performance of sludge-based nano-biochar, the surface chemical activation treatment of the preliminary nano-biochar was carried out to increase the content of oxygen-containing functional groups. The preliminary nano-biochar was immersed in 0.1-0.5 mol·L -1 In a citric acid (C6H8O7) solution, stir evenly, maintain a temperature of 70-90°C, and treat for 2-3 hours to remove ash and impurities on the surface of the biochar and introduce carboxyl (-COOH) and hydroxyl (-OH). Subsequently, wash with deionized water until neutral, and dry the biochar at 80-105°C for use. To further enhance the oxidative functional groups (such as hydroxyl and carboxyl), a 30% hydrogen peroxide (H2O2) solution was used for subsequent treatment. The treatment conditions were a temperature of 50-60°C and a time of 1 hour to obtain sludge-based nano-biochar with highly active surface groups.

[0055] (5) Technical indicators and product characteristics:

[0056] The sludge-based nano-biochar prepared by the above process has the following technical indicators: specific surface area of ​​300-800m 2 ·g -1 , porosity of 50% to 70%, particle size of 20 to 100nm, ash content of 10% to 15%, and surface oxygen-containing functional groups (such as carboxyl and hydroxyl) account for 5% to 15%. The prepared sludge-based nano-biochar has a high specific surface area, rich pore structure and excellent surface active functional groups, and its adsorption performance is significantly enhanced. It can be widely used in sludge composting processes, effectively reducing the emission of secondary pollutants such as methane (CH4), nitrous oxide (N2O) and ammonia (NH3), and has significant environmental benefits and resource utilization value.

[0057] Embodiment 3

[0058] The present invention also provides an application of sludge-based nano-biochar, including the synergistic application of dynamic in-situ layered addition technology and microbial enhanced biochar. Specifically, Figure 2 1 is a flow chart of a composting control method based on sludge-based nano-biochar according to an embodiment of the present invention. Figure 2 As shown, the method specifically comprises the following steps:

[0059] Step S202: During the composting start-up phase, a first preset amount of sludge-based nano-biochar is added in layers to the top layer, the middle layer and the bottom layer of the composting sludge.

[0060] Optionally, the first preset amount is 3% to 5% of the dry weight of the composting sludge.

[0061] Step S204, during the high temperature stage of composting, the middle layer and the bottom layer are supplemented with a biochar suspension by a suspension spraying method; the biochar suspension is a suspension containing sludge-based nano-biochar of a preset concentration.

[0062] Optionally, the preset concentration includes 1% to 2%.

[0063] Specifically, step S204 also includes:

[0064] Step S2041, real-time monitoring of target gas concentrations of composting sludge; the target gas concentrations include methane concentration, nitrous oxide concentration, and ammonia concentration.

[0065] In the embodiment of the present invention, the target gas concentration in the tail gas of the sludge composting process can be used as an indicator. The increase in its concentration indicates that the organic matter biomineralization process and the biological nitrification-denitrification process inside the compost are out of balance, and the removal of the target gas needs to be enhanced by supplementing nano-biochar.

[0066] Step S2042: When the target gas concentration exceeds a preset concentration threshold, a suspension spraying method is used to supplement the middle layer and the bottom layer with biochar suspension.

[0067] For example, when the methane concentration is >1% (volume ratio), or the nitrous oxide concentration is >10 ppmv (volume ratio), or the ammonia concentration is >50 ppmv (volume ratio), the biochar suspension is supplemented.

[0068] In an optional implementation provided by an embodiment of the present invention, at the initial stage of composting (i.e., the start-up stage of composting), sludge-based nano-biochar is added in layers at a ratio of 3% to 5% of the dry weight of the sludge, and optionally, 40% is used for the top layer (adsorbing ammonia and hydrogen sulfide), 40% is used for the middle layer (catalyzing methane oxidation), and 20% is used for the bottom layer (enhancing water retention and nutrient release). In the middle stage of composting (i.e., the high temperature stage of composting), by real-time monitoring of gas concentrations (CH4, N2O, NH3) and temperature and humidity parameters, the middle layer and the bottom layer are supplemented with biochar suspension (concentration 1% to 2%) by the suspension spraying method to accurately control gas emissions.

[0069] In the composting control method provided by the embodiment of the present invention, the dynamic in-situ stratification and functional gradient addition technology are implemented step by step in the early stage (start-up stage) and middle stage (high temperature stage) of composting, and the adsorption, catalysis and environmental control functions of biochar are optimized through precise stratification and dynamic supplementation. In the early stage of composting, biochar is added at a ratio of 3% to 5% of the dry weight of the sludge, of which 40% is used for the top layer to adsorb ammonia (NH3) and hydrogen sulfide (H2S), 40% is used for the middle layer to catalyze the oxidation of methane (CH4), and 20% is used for the bottom layer to enhance water retention and nutrient release. The addition method is mechanical stirring and uniform distribution. In the middle stage of composting, by real-time monitoring of the concentration of gases (CH4, N2O, NH3) and changes in temperature and humidity in the composting layer, the suspension spraying method is used to supplement the middle layer and the bottom layer with biochar suspension (concentration 1% to 2%) to dynamically control gas emissions. The present invention can significantly reduce the emission of methane and nitrous oxide (the comprehensive emission reduction efficiency reaches 60% to 70%), shorten the composting cycle by 15% to 20%, and simultaneously improve the degradation rate of organic matter.

[0070] Figure 3 FIG. 1 is a flow chart of another composting control method based on sludge-based nano-biochar according to an embodiment of the present invention. Figure 3 As shown, the method specifically comprises the following steps:

[0071] Step S302, immersing the sludge-based nano-biochar in a target bacteria culture solution to prepare microbial enhanced biochar; the target bacteria include methane oxidizing bacteria and / or nitrifying bacteria.

[0072] Step S304, in the composting start-up phase, the second preset amount of microbial enhanced biochar is evenly mixed and distributed with auxiliary materials.

[0073] In an optional embodiment provided in the present invention, the sludge-based nano-biochar is immersed in a target bacterial culture solution (e.g., methane oxidizing bacteria, nitrifying bacteria, concentration 10 8 CFU·mL -1, culturing time 24-48h) to prepare microbial enhanced biochar. In the composting startup stage, the enhanced biochar is evenly mixed and distributed with auxiliary materials at a ratio of 2% to 4% of the dry weight of the sludge. During the composting process, the microbial metabolic degradation is combined with the adsorption and catalytic functions of the biochar to effectively reduce the emission of methane (CH4) and nitrous oxide (N2O).

[0074] In the composting control method provided in the embodiment of the present invention, the synergistic application technology of microbial enhanced biochar achieves gas emission reduction and degradation efficiency improvement during composting by loading functional bacterial agents. During the preparation process, the sludge-based nano-biochar is immersed in the culture solution of target bacteria (such as methane oxidizing bacteria, nitrifying bacteria and denitrifying bacteria, with a bacterial solution concentration of 10 8 CFU·mL -1 ) for 24 to 48 hours, so that the pore structure of biochar can adsorb active microorganisms and then be dried for use. In the composting startup stage, the enhanced biochar is evenly mixed with the sludge and auxiliary materials at a ratio of 2% to 4% of the dry weight of the sludge, and uniform distribution is achieved through mechanical stirring. During the composting process, biochar significantly reduces volatile gas emissions by adsorbing ammonia (NH3) and hydrogen sulfide (H2S), while providing microbial growth sites; microbial metabolism further degrades methane (CH4) and nitrous oxide (N2O), and the synergistic effect increases the comprehensive reduction efficiency of composting gas emissions to 70% to 80%, shortens the composting cycle by 20%, and significantly improves the nutrient content and quality of the compost products.

[0075] The sludge-based nano biochar provided by the embodiment of the present invention significantly improves the physical and chemical properties and fertilizer value of the compost product through adsorption, slow release and microbial synergy during the composting process. During the composting process, methane (CH4) emissions are reduced by 60% to 70%, nitrous oxide (N2O) emissions are reduced by 50% to 65%, ammonia (NH3) volatilization is reduced by 30% to 50%, the composting cycle is shortened by 15% to 20%, and the organic matter degradation rate is increased by 20% to 30%, which significantly improves the composting efficiency. The total nitrogen (N), total phosphorus (P), and total potassium (K) nutrient content of the compost product is increased by 10% to 15%, and the water-soluble organic matter content is increased by 15% to 20%; at the same time, through the heavy metal passivation effect of the sludge-based nano biochar, the mobility of heavy metals in the compost product is reduced by 30% to 50%, ensuring the ecological safety of the product. The high water retention of biochar increases the water holding capacity of compost products by 20% and the looseness by 15% to 25%, thereby optimizing the fertilizer application effect and soil adaptability, and providing high value-added organic fertilizer for forestry greening and ecological restoration.

[0076] From the above description, it can be seen that the embodiments of the present invention provide a sludge-based nano-biochar, a preparation method and a composting control method, which have the following technical effects compared with the prior art:

[0077] 1. Comply with environmental protection policies and help achieve the "dual carbon" goals.

[0078] The present invention uses sludge-based nano-biochar as the core technology, and significantly reduces the emission of greenhouse gases such as methane (CH4) and nitrous oxide (N2O) through gas emission reduction and resource utilization during the composting process. The comprehensive emission reduction efficiency reaches 60% to 80%, and the volatilization of ammonia (NH3) is reduced by 30% to 50%.

[0079] 2. Efficient sludge resource utilization and circular economy development.

[0080] The present invention shortens the composting cycle by 15% to 20% and significantly improves the composting efficiency by optimizing the composting process and dynamic control technology. The prepared nano-biochar not only improves the treatment effect as the core functional material of composting, but also expands its application in high value-added fields such as soil remediation and water pollution control, truly realizing the resource utilization goal of sludge "turning waste into treasure". At the same time, the process design focuses on economy and industrial operability, and is suitable for large-scale application.

[0081] The quality of compost products has been significantly improved:

[0082] Improved nutrient content: The content of major nutrients such as total nitrogen, total phosphorus, and total potassium increases by 10% to 15%, and the content of water-soluble organic matter increases by 15% to 20%, significantly enhancing the value of the fertilizer.

[0083] Improved safety: The mobility of heavy metals is reduced by 30% to 50%, ensuring the ecological safety of compost products and meeting forestry and environmental protection application standards.

[0084] Optimization of physical properties: The water holding capacity of compost products is increased by 20%, and the looseness is improved by 15% to 25%, making it more suitable for forestry applications, horticultural planting and soil improvement.

[0085] Compost products can be widely used in artificial forest fertilizer, horticultural greening, ecological restoration and other fields, further broadening the scope of market application and providing high-value products for the development of resource circular economy.

[0086] 3. Significant economic benefits and broad market prospects.

[0087] The present invention has significant economic benefits and market potential:

[0088] Direct economic benefits: By shortening the composting cycle and reducing gas emissions, the cost of sludge treatment per ton is reduced by 10% to 20%, and the market price of compost products is increased by 15% to 30%, significantly increasing profits.

[0089] Industrial scale potential: my country's annual urban sludge production exceeds 50 million tons (water content 80%), and the annual average growth rate of sludge treatment and resource utilization market exceeds 10%. If this technology is promoted and applied, it can achieve market revenue of more than 5 billion yuan per year, while significantly reducing environmental governance costs.

[0090] Process maturity and industrial promotion: The technologies involved in the present invention (such as citric acid passivation, pyrolysis carbonization, nano-treatment and dynamic dosing) are all based on mature processes, with high technical integration, simple operation, and controllable operating costs. They are easy to seamlessly connect with existing sludge treatment facilities, significantly reduce transformation costs, and have the conditions for large-scale promotion.

[0091] In addition, the present invention breaks through the bottleneck of traditional sludge treatment technology and provides an efficient and economical solution for the industry. Through efficient gas emission reduction and optimal resource utilization, this technology promotes the upgrading of the sludge treatment industry towards green and standardized directions, providing strong support for enterprises to enhance their market competitiveness.

[0092] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0093] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing sludge-based nano-biochar, characterized in that: include: The initial activated sludge is sequentially subjected to dehydration treatment, drying treatment and pulverization treatment to obtain pulverized dry sludge; Soaking the crushed dry sludge in a citric acid solution of a preset concentration, drying after a first preset soaking time, to obtain pretreated sludge; Carbonizing the pretreated sludge using a pyrolysis furnace to obtain preliminary biochar; Mechanically grinding the preliminary biochar by using a ball mill to obtain preliminary nano-biochar; The preliminary nano-biochar is soaked in the citric acid solution for a second preset soaking time, and then treated with a hydrogen peroxide solution to obtain sludge-based nano-biochar.

2. The method according to claim 1, characterized in that: The initial activated sludge is sequentially subjected to dehydration, drying and pulverization, including: Processing the initial activated sludge by mechanical filtration or centrifugal dehydration to obtain dehydrated sludge; The dehydrated sludge is subjected to low-temperature hot air drying to obtain dried sludge; The dried sludge is crushed to obtain the crushed dry sludge.

3. The method according to claim 1, characterized in that: The preset concentration includes 0.1 mol·L -1 -0.5mol·L -1 ; The first preset soaking time includes 1h-2h; the second preset soaking time includes 2h-3h.

4. The method according to claim 1, characterized in that: The pretreated sludge is carbonized by using a pyrolysis furnace, comprising: placing the pretreated sludge in a pyrolysis furnace and heating it under anoxic conditions for carbonization treatment; After the carbonization treatment has been carried out for a preset pyrolysis time, the mixture is cooled to room temperature, and the uncarbonized particles are sieved to remove them, thereby obtaining the preliminary biochar.

5. The method according to claim 1, characterized in that: The particle size of the preliminary nano-biochar is 20nm-100nm.

6. The method according to claim 1, characterized in that: The hydrogen peroxide solution includes a 30% hydrogen peroxide solution; the treatment temperature of the hydrogen peroxide solution includes 50° C.-60° C., and the treatment time of the hydrogen peroxide solution includes 1 hour.

7. A sludge-based nano biochar, characterized in that: Obtained based on the preparation method according to any one of claims 1 to 6.

8. A composting control method based on the sludge-based nano-biochar according to claim 7, characterized in that: include: In the composting start-up phase, a first preset amount of the sludge-based nano-biochar is added in layers to the top layer, the middle layer and the bottom layer of the composting sludge; During the high temperature stage of composting, the middle layer and the bottom layer are supplemented with a biochar suspension by a suspension spraying method; the biochar suspension is a suspension containing the sludge-based nano-biochar at a preset concentration.

9. The method according to claim 8, characterized in that: The middle layer and the bottom layer are supplemented with a biochar suspension by a suspension spraying method, comprising: Real-time monitoring of target gas concentrations of the composting sludge; the target gas concentrations include methane concentration, nitrous oxide concentration, and ammonia concentration; When the target gas concentration exceeds a preset concentration threshold, a suspension spraying method is used to supplement the middle layer and the bottom layer with biochar suspension.

10. A composting control method based on the sludge-based nano-biochar according to claim 7, characterized in that: include: The sludge-based nano-biochar is immersed in a target bacteria culture solution to prepare microbial enhanced biochar; The target bacteria include methane oxidizing bacteria and / or nitrifying bacteria; In the composting start-up stage, the second preset amount of the microbial enhanced biochar is evenly mixed and distributed with auxiliary materials.

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