Biological dewatering and drying method of sludge, obtained dried sludge and application of dried sludge

Abstract

The invention belongs to the technical field of sludge treatment, and particularly relates to a biological dewatering and drying method of sludge, obtained dried sludge and application of the dried sludge. The method comprises the following steps: mixing sludge and a conditioner, and carrying out biological fermentation to obtain a fermentation system; and dehydrating the fermentation system to obtain the dried sludge. The sludge and the conditioner are combined for treatment, so that the biochemical performance of the material can be improved, biological fermentation dehydration is promoted, and the heat value of the mixed material is improved; in the biological fermentation process, heat is generated through the metabolic activity of microorganisms, natural dehydration of materials can be achieved, and meanwhile the property of the sludge is improved. According to the biological dehydration drying method provided by the invention, the ash content in the sludge is reduced, the proportion of combustible materials is increased, low-carbon dehydration is realized, and the calorific value per unit volume is increased. According to the method provided by the invention, the water content of the sludge can be effectively reduced, so that the energy consumption in the traditional mechanical dehydration process is reduced, and the land resource occupation caused by solid waste landfill treatment is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to a biological dehydration and drying method for sludge, the obtained dried sludge and application thereof. Background Art

[0002] With the acceleration of urbanization, the output of municipal sludge continues to grow, and its treatment and disposal has become an environmental problem that needs to be solved urgently. Traditional sludge treatment methods such as landfill and incineration not only occupy a large amount of land resources, but may also cause secondary pollution. At the same time, the high moisture content and low calorific value of sludge limit its direct energy utilization. On the other hand, although biomass resources such as straw, garden waste, wood chips, and feces have high calorific value, a large amount of resources have not been effectively utilized due to the difficulties in collection, storage, and transportation. Therefore, it is of great significance to develop a technology that can synergistically treat sludge with other biomass and convert it into clean fuel. At present, conventional sludge dehydration mainly relies on mechanical dehydration, which not only has high energy consumption, but also has limited dehydration effect. Summary of the invention

[0003] The purpose of the present invention is to provide a biological dehydration and drying method for sludge, the obtained dried sludge and application thereof.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a biological dehydration and drying method for sludge, comprising the following steps:

[0006] The sludge and the conditioning agent are mixed and subjected to biological fermentation to obtain a fermentation system;

[0007] The fermentation system is dehydrated to obtain dried sludge.

[0008] Preferably, the mass percentage of inorganic matter in the sludge is ≤25%.

[0009] Preferably, the conditioning agent comprises carbonaceous waste, and the carbonaceous waste comprises at least one of straw, yard waste, wood chips and feces;

[0010] The mass of the conditioning agent is 10-60% of the mass of the sludge.

[0011] Preferably, the biological fermentation process further includes adding a biological enhancement agent;

[0012] The biological strengthening agent includes bacillus and yeast, and the mass ratio of the bacillus to the yeast is 1:1;

[0013] The inoculation amount of the biological enhancement bacterial agent is 2-20%.

[0014] Preferably, the biological fermentation includes anaerobic fermentation, anoxic fermentation, and aerobic fermentation in sequence;

[0015] The conditions for the anaerobic fermentation include: the temperature is 35 - 45°C, the time is 7 - 9 days, the oxygen concentration is less than 0.5%, and the stirring frequency is intermittent stirring 1 - 2 times every 24 hours, each time for 10 - 20 minutes;

[0016] The conditions for the anoxic fermentation include: the temperature is 45 - 55°C, the time is 1 - 3 days, the oxygen concentration is 0.5 - 5%, and oxygen supply is carried out alternately by intermittent air blowing and static stacking. The blower is turned on for 15 - 30 minutes every 24 hours to ensure that the oxygen concentration always ranges from 0.5 - 5%. After the oxygen concentration reaches 4.5 - 5%, the blower is turned off;

[0017] The conditions for the aerobic fermentation include: the temperature is 55 - 65°C, the time is 10 - 15 days, the oxygen concentration is greater than 10%, and the compost is turned over 1 - 2 times a day.

[0018] Preferably, the water content of the dried sludge is 25 - 50%.

[0019] The present invention also provides the dried sludge obtained by the biological dehydration and drying method of the above technical solution.

[0020] The present invention also provides the application of the dried sludge of the above technical solution in being used as a biofuel, preparing biochar, and preparing syngas;

[0021] Before the application, it further includes granulating the dried sludge to obtain sludge particles.

[0022] Preferably, when the application is for preparing biochar, the method for preparing biochar includes:

[0023] Subjecting the sludge particles to low-temperature pyrolysis and high-temperature carbonization in sequence;

[0024] The temperature of the low-temperature pyrolysis is 300 - 400°C, the heating rate is 20 - 35°C / min, and the heat preservation time is 30 - 50 min;

[0025] The temperature of the high-temperature carbonization is 500 - 600°C, the heating rate is 5 - 15°C / min, and the heat preservation time is 60 - 90 min.

[0026] Preferably, when the application is for preparing syngas, the method for preparing syngas includes:

[0027] Subjecting the sludge particles to pyrolysis gasification;

[0028] The temperature of the pyrolysis gasification is 800 - 1200°C, the heating rate is 60 - 120°C / min, and the heat preservation time is 30 - 60 min.

[0029] The present invention provides a method for biological dehydration and drying of sludge, comprising the following steps: mixing sludge and a conditioner, and performing biological fermentation to obtain a fermentation system; dehydrating the fermentation system to obtain dried sludge.

[0030] The present invention combines the treatment of sludge with a conditioner, which can improve the biochemical properties of the material, promote biological fermentation and dehydration, thereby contributing to the increase of the calorific value of the mixed material; during the biological fermentation process, heat is generated through the metabolic activities of microorganisms, which can achieve natural dehydration of the material and simultaneously improve the properties of the sludge.

[0031] The biological dehydration and drying method provided by the present invention reduces the ash content in the sludge, increases the proportion of combustibles, achieves low-carbon dehydration, and increases the calorific value per unit volume. The method provided by the present invention can effectively reduce the moisture content of the sludge, thereby reducing the energy consumption in the traditional mechanical dehydration process and avoiding the occupation of land resources by landfill disposal of solid waste.

[0032] This technology reverses the situation of high energy consumption and low efficiency caused by the passive treatment of sludge, provides a new and sustainable solution for sludge treatment, and belongs to the field of solid waste treatment and bioenergy. By developing clean and efficient sludge treatment technologies, it not only avoids the occupation of land resources by landfill disposal but also reduces the dependence on fossil energy. Adopting the method of co-processing multiple wastes not only realizes the resource utilization of sludge but also establishes a unified treatment route for multiple wastes, significantly reducing the negative impact on the environment. This technological innovation provides strong support for building a green and low-carbon circular economy system and reflects the response of the sludge treatment field to the national sustainable development strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic flow chart of the biological dehydration and drying method provided by the present invention and subsequent applications. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The following discusses the drying method provided by the present invention and subsequent application processes in combination with the principles of bionics.

[0035] The present invention provides a method for biological dehydration and drying of sludge, comprising the following steps:

[0036] Mixing sludge and a conditioner, and performing biological fermentation to obtain a fermentation system;

[0037] Dehydrating the fermentation system to obtain dried sludge.

[0038] The present invention mixes sludge and a conditioner and performs biological fermentation to obtain a fermentation system.

[0039] The present invention does not impose special limitations on the source of the sludge, and those well-known to those skilled in the art can be adopted. In a specific embodiment of the present invention, the sludge is preferably obtained by subjecting municipal sludge to sand and gravel screening treatment. In the present invention, the screening treatment includes coarse screening and fine screening in sequence. The aperture of the screen used for coarse screening is preferably 3-5 mm, and the aperture of the screen used for fine screening is preferably 1-2 mm. In the present invention, by subjecting municipal sludge to sand and gravel screening treatment, incombustibles such as sand and gravel therein can be removed. In the present invention, the mass percentage content of inorganic substances in the sludge is preferably ≤25%.

[0040] In the present invention, subjecting municipal sludge to sand and gravel screening treatment is similar to the chewing organ of cattle in animal bionics, separating large particulate incombustibles (such as sand and gravel) in the municipal sludge to ensure that the materials entering the subsequent treatment stage have high biodegradability, similar to cattle making food more easily digestible by chewing. In the present invention, the sand and gravel screening treatment is carried out by a multi-stage composite screening process. The grille removes large particulate impurities and initially reduces the content of inorganic substances in the sludge. Then, a hydrocyclone is used to separate materials with different densities by centrifugal force. The heavier particles are thrown to the outside, and the lighter organic substances remain in the central area. Finally, through gravity sedimentation, the heavier particles naturally settle to the bottom of the pool to form mud residue, and the lighter organic substances float on the upper layer. This multi-stage composite screening process reduces the incombustible components in the sludge, improves the biological dewatering performance, and further helps to improve the calorific value property of the sludge-based biofuel.

[0041] In the present invention, the conditioner preferably includes carbon-containing waste, and the carbon-containing waste preferably includes at least one of straw, yard waste, wood chips, and feces. The feces preferably include sheep manure or cow manure; the mass of the conditioner is preferably 10-60% of the mass of the sludge, and specifically can be 10%, 20%, 30%, 40%, 50%, 60%. In the present invention, the purpose of adding the conditioner is as follows: (1) reducing the moisture content of the material. These conditioners can absorb part of the water, helping to reduce the moisture content of the sludge and making it easier to carry out subsequent treatment; (2) the conditioner can improve the material structure, form a loose and porous network structure, increase the specific surface area of water evaporation, reduce the binding force between water and sludge particles, and effectively promote the conversion of bound water to free water; (3) increasing the co-treatment effect. The organic substances in the conditioner can provide additional carbon sources and nutrients for microorganisms. Secondly, it improves the air permeability of the material, provides a support framework, and optimizes the stack structure; (4) increasing the calorific value of the material. The high-carbon substances in the conditioner directly increase the calorific value of the mixture, and finally further improve the energy density through biological fermentation. The finally prepared product is more suitable for combustion in coal-fired boilers, pyrolytic carbonization, or gasification.

[0042] In the present invention, during the biological fermentation process, it is further preferably to include adding a bio-enhanced bacterial agent; the bio-enhanced bacterial agent preferably includes Bacillus and yeast, and the mass ratio of Bacillus to yeast is preferably 1:1; the inoculation amount of the bio-enhanced bacterial agent is preferably 2-20%, specifically it can be 2%, 5%, 10%, 12%, 15%, 18%, 20%.

[0043] In the present invention, the biological fermentation preferably includes anaerobic fermentation, facultative anaerobic fermentation and aerobic fermentation in sequence.

[0044] In the present invention, the conditions for anaerobic fermentation preferably include: the temperature is 35-45°C, the time is 7-9 days, the oxygen concentration is less than 0.5%, and the stirring frequency is intermittent stirring 1-2 times every 24 hours, each time for 10-20 minutes. In the present invention, during the anaerobic fermentation process, it can promote the preliminary degradation of organic matter, increase the bioavailability of the material, and achieve the reduction of the high water content of the material.

[0045] In the present invention, the conditions for facultative anaerobic fermentation preferably include: the temperature is 45-55°C, the time is 1-3 days, the oxygen concentration is 0.5-5%, and oxygen supply is carried out by alternating intermittent air blowing and static stacking. The fan is turned on for 15-30 minutes every 24 hours to ensure that the oxygen concentration is always between 0.5-5%, and the fan is turned off after the oxygen concentration reaches 4.5-5%. In the present invention, during the facultative anaerobic fermentation process, it can play a role of transition buffer, enabling the system to smoothly transition to an aerobic environment, avoiding the impact of drastic environmental changes on microorganisms, and at the same time, part of the organic matter is degraded to produce a small amount of nitrates and nitrites, providing basic conditions for subsequent aerobic fermentation.

[0046] In the present invention, the conditions for aerobic fermentation preferably include: the temperature is 55-65°C, the time is 10-15 days, the oxygen concentration is greater than 10%, and the pile is turned over 1-2 times a day. In the present invention, during the aerobic fermentation process, it can accelerate water evaporation, further reduce the water content, and improve the stability of the fermentation product.

[0047] In the present invention, during the biological fermentation process, it is further preferably to include using an on-line monitoring system to monitor the fermentation process, realizing automatic adjustment of process parameters, and solving the problems of difficult degradation of complex organic matter, low dehydration efficiency and unstable fermentation process.

[0048] After obtaining the fermentation system, the present invention dehydrates the fermentation system to obtain dried sludge. In the present invention,

[0049] In the present invention, the water content of the dried sludge is preferably 25-50%. In the present invention, when the dried sludge has a suitable water content, the material is convenient for storage and transportation, not prone to mildew, and can effectively reduce the combustion energy consumption, with relatively high economy. In the present invention, the dehydration process preferably includes transpiration and leachate backflow carried out in sequence. The present invention has no special limitation on the processes of transpiration and leachate backflow, and those well-known to those skilled in the art can be adopted.

[0050] In the present invention, the processes of biological fermentation and dehydration are similar to the digestive organs of cattle in animal bionics. At this stage, the complex organic substances in the sludge are gradually decomposed and the water content is reduced, improving the stability and safety of the sludge, similar to how cattle digest food through the digestive system.

[0051] The present invention also provides the dried sludge obtained by the biological dehydration and drying method described in the above technical solution.

[0052] The present invention also provides the application of the dried sludge described in the above technical solution in being used as a biofuel, preparing biochar, and preparing syngas;

[0053] Before the above application, it also includes granulating the dried sludge to obtain sludge particles.

[0054] In a specific application, granulating the dried sludge to obtain sludge particles is similar to the intestine of cattle in animal bionics. The dehydrated sludge after fermentation treatment forms sludge particles that are convenient for storage and transportation through granulation. This process is similar to the intestinal system of cattle, which compresses and shapes the treated material into a form convenient for storage and transportation and finally excretes it out of the body.

[0055] In the present invention, when the application is to prepare biochar, the method for preparing biochar preferably includes: subjecting the sludge particles to low-temperature pyrolysis and high-temperature carbonization in sequence; the temperature of the low-temperature pyrolysis is preferably 300-400°C, the heating rate is preferably 20-35°C / min, and the heat preservation time is preferably 30-50 min; the temperature of the high-temperature carbonization is preferably 500-600°C, the heating rate is preferably 5-15°C / min, and the heat preservation time is preferably 60-90 min. The dried sludge provided by the present invention can achieve the efficient and clean production of biochar through two-stage processes of low-temperature rapid pyrolysis - high-temperature deep carbonization. In the low-temperature rapid pyrolysis stage, a large amount of volatile components are released, and nitrogen-containing substances (such as proteins) begin to crack, releasing nitrogen-containing gases such as NH3. High-temperature deep carbonization can further remove the residual heavy tar, improve the purity of the carbon product, improve the pore structure, increase the specific surface area, break through the technical bottlenecks of tar formation, poor biochar performance, and high energy consumption, and effectively solve the problems of unstable product quality and serious environmental pollution existing in the traditional carbonization process.

[0056] In the present invention, when the application is for preparing syngas, the method for preparing syngas preferably includes: pyrolyzing and gasifying the sludge particles; the temperature of the pyrolysis gasification is preferably 800 - 1200 °C, the heating rate is preferably 60 - 120 °C / min, and the heat preservation time is preferably 30 - 60 min. Using the dried sludge provided by the present invention to prepare syngas solves the problem that traditional incineration methods will produce a large amount of greenhouse gases and other pollutants (such as dioxins, furans, etc.) that are harmful to the environment and human health.

[0057] In the present invention, the specific application process is similar to the muscle and energy utilization of cows in animal bionics. The sludge particles can be incorporated into the combustion of coal-fired boilers, or biochar can be prepared by pyrolytic carbonization, or syngas can be prepared by pyrolysis gasification. This process is similar to a cow consuming energy through muscle movement to maintain life activities. The sludge particles convert chemical energy into heat energy or syngas through combustion or pyrolysis, achieving the maximum utilization of resources.

[0058] The present invention collaboratively processes municipal sludge with various wastes such as straw, household garbage, and wood chips, establishing a complete resource utilization chain of "waste - biofuel - energy products"; at the same time, diversified product development expands the resource utilization pathways. Among them, biochar products can also be used for soil improvement to form a carbon sink, further strengthening the carbon neutralization effect. This whole-process resource treatment mode not only avoids the occupation of land resources and greenhouse gas emissions caused by landfilling, but also provides technical support for building a circular economy system.

[0059] The flow schematic diagram of the biological dehydration and drying method and subsequent applications provided by the present invention is as Figure 1 shown.

[0060] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0061] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0062] Example 1

[0063] The municipal sludge is subjected to sand and gravel screening treatment (coarse sieve aperture 4 mm, fine sieve aperture 1.5 mm) to obtain sludge, with the inorganic matter content being 25%;

[0064] Mix the sludge and rice straw, with the addition amount of the conditioner being 40% of the sludge mass. Ferment the obtained mixture, where the fermentation includes anaerobic fermentation (temperature is 45°C, time is 7 days, oxygen concentration is 0.3%, stirring frequency is intermittent stirring once every 24 hours, 15 minutes each time), facultative anaerobic fermentation (temperature is 50°C, time is 2 days, oxygen concentration is 4.5%, oxygen supply is carried out alternately by intermittent air blowing and static stacking, the blower is turned on for 20 minutes every 24 hours), and aerobic fermentation (temperature is 60°C, time is 12 days, oxygen concentration is 15%, turning the pile once a day). Monitor the fermentation process using an online monitoring system. After fermentation is completed, obtain dewatered sludge through transpiration and leachate backflow (backflow once every 6 hours), where the water content is 38%;

[0065] Granulate the obtained dewatered sludge to obtain dried sludge.

[0066] Example 2

[0067] Prepare dried sludge in the same way as in Example 1, except that during the fermentation process, inoculate a bioaugmentation agent in the mixture (specifically composed of Bacillus and Saccharomyces cerevisiae in equal mass, inoculation amount is 10%). The fermentation includes anaerobic fermentation (temperature is 40°C, time is 7 days, oxygen concentration is 0.3%, stirring frequency is intermittent stirring once every 24 hours, 15 minutes each time), facultative anaerobic fermentation (temperature is 55°C, time is 2 days, oxygen concentration is 5%, oxygen supply is carried out alternately by intermittent air blowing and static stacking, the blower is turned on for 30 minutes every 24 hours), and aerobic fermentation (temperature is 65°C, time is 10 days, oxygen concentration is 15%, turning the pile once a day).

[0068] The water content of the obtained dewatered sludge is 35%.

[0069] Example 3

[0070] Prepare dried sludge in the same way as in Example 1, except that mix the sludge and cow dung, with the addition amount of the conditioner being 50% of the sludge mass. Ferment the obtained mixture, and during the fermentation process, inoculate a bioaugmentation agent in the mixture (specifically composed of Bacillus and Saccharomyces cerevisiae in equal mass, inoculation amount is 15%). The fermentation includes anaerobic fermentation (temperature is 40°C, time is 8 days, oxygen concentration is 0.3%, stirring frequency is intermittent stirring once every 24 hours, 15 minutes each time), facultative anaerobic fermentation (temperature is 55°C, time is 3 days, oxygen concentration is 5%, oxygen supply is carried out alternately by intermittent air blowing and static stacking, the blower is turned on for 30 minutes every 24 hours), and aerobic fermentation (temperature is 65°C, time is 10 days, oxygen concentration is 15%, turning the pile once a day).

[0071] The water content of the obtained dewatered sludge is 38%.

[0072] Example 4

[0073] The dried sludge was prepared in the same manner as in Example 1, except that the sludge was mixed with yard waste, and the addition amount of the conditioner was 50% of the mass of the sludge. The obtained mixture was fermented. During the fermentation process, a bioaugmentation agent was inoculated into the mixture (specifically, composed of equal masses of Bacillus and Saccharomyces cerevisiae, and the inoculation amount was 10%). The fermentation included anaerobic fermentation (temperature 40°C, time 7 d, oxygen concentration 0.3%, stirring frequency intermittent stirring once every 24 hours, 15 minutes each time), facultative anaerobic fermentation (temperature 55°C, time 3 d, oxygen concentration 5%, oxygen supply was carried out alternately by intermittent blowing and static stacking, the blower was turned on for 30 minutes every 24 hours), and aerobic fermentation (temperature 65°C, time 12 d, oxygen concentration 15%, turning the pile once a day).

[0074] The water content of the obtained dehydrated sludge was 33%.

[0075] Example 5

[0076] The dried sludge was prepared in the same manner as in Example 1, except that the sludge was mixed with yard waste, and the addition amount of the conditioner was 60% of the mass of the sludge. During the fermentation process, a bioaugmentation agent was inoculated into the mixture (specifically, composed of equal masses of Bacillus and Saccharomyces cerevisiae, and the inoculation amount was 10%). The fermentation included anaerobic fermentation (temperature 40°C, time 9 d, oxygen concentration 0.3%, stirring frequency intermittent stirring once every 24 hours, 15 minutes each time), facultative anaerobic fermentation (temperature 55°C, time 3 d, oxygen concentration 5%, oxygen supply was carried out alternately by intermittent blowing and static stacking, the blower was turned on for 30 minutes every 24 hours), and aerobic fermentation (temperature 65°C, time 15 d, oxygen concentration 15%, turning the pile once a day).

[0077] The water content of the obtained dehydrated sludge was 33%.

[0078] Performance test

[0079] Test Example 1

[0080] The dried sludge obtained in the example was granulated to obtain sludge particles;

[0081] The obtained sludge particles were used as biofuels for testing, and the test results obtained are shown in Table 1;

[0082] Taking existing biofuels (charcoal as an example) as a comparison;

[0083] Table 1 Performance test results of sludge particles obtained in the example

[0084]

[0085] As can be seen from Table 1, the biofuel obtained from the sludge as the raw material of the present invention can obtain calorific value, volatile matter and ash similar to those of the existing biofuels.

[0086] Test Example 2

[0087] The dried sludge obtained in the embodiment is granulated to obtain sludge particles;

[0088] The obtained sludge particles are pyrolyzed and gasified, wherein the temperature is 800 °C, the heating rate is 60 °C / min, and the heat preservation time is 60 min to obtain syngas;

[0089] Detect the composition and calorific value of the obtained syngas;

[0090] The sludge obtained in Example 1 is mechanically dehydrated, dried and granulated, and the obtained sludge particles are used as a control;

[0091] The obtained test results are shown in Table 2;

[0092] Table 2 Performance test results of sludge particles obtained in the embodiment

[0093] Example 1 Example 2 Example 3 Example 4 Example 5 Control <![CDATA[H2 content (%)]]> 31.9 33.1 29.4 33.9 34.7 24.4 CO content (%) 29.5 28.7 24.6 34.4 34.5 22.9 <![CDATA[Calorific value (MJ / m 3 )]]> 20.2 21.2 18.2 24.1 24.8 17.4

[0094] As can be seen from Table 2, the sludge dry material obtained by the biological dehydration and drying method of the present invention, after pyrolysis, has higher contents of hydrogen and carbon monoxide in the obtained syngas compared with direct drying of the sludge, thereby making the calorific value of the syngas higher.

[0095] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. Other embodiments can be obtained according to this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A biological dehydration and drying method for sludge, characterized in that, It includes the following steps: Mix the sludge and the conditioner and carry out biological fermentation to obtain a fermentation system; Dehydrate the fermentation system to obtain dried sludge.

2. The biological dehydration and drying method according to claim 1, wherein The mass percentage of inorganic substances in the sludge is ≤ 25%.

3. The biological dehydration and drying method according to claim 1, characterized in that, The conditioner includes carbon-containing waste, and the carbon-containing waste includes at least one of straw, yard waste, wood chips, and feces; The mass of the conditioner is 10 - 60% of the mass of the sludge.

4. The biological dehydration and drying method according to claim 1, characterized in that, During the biological fermentation process, a bioaugmentation agent is also added; The bioaugmentation agent includes Bacillus and Saccharomyces cerevisiae, and the mass ratio of Bacillus to Saccharomyces cerevisiae is 1:1; The inoculation amount of the bioaugmentation agent is 2 - 20%.

5. The biological dehydration and drying method according to claim 1 or 4, characterized in that, The biological fermentation includes anaerobic fermentation, facultative anaerobic fermentation, and aerobic fermentation in sequence; The conditions for the anaerobic fermentation include: the temperature is 35 - 45 °C, the time is 7 - 9 days, the oxygen concentration is lower than 0.5%, and the stirring frequency is intermittent stirring 1 - 2 times every 24 hours, each time for 10 - 20 minutes; The conditions for the facultative anaerobic fermentation include: the temperature is 45 - 55 °C, the time is 1 - 3 days, the oxygen concentration is 0.5 - 5%, and oxygen supply is carried out alternately by intermittent air blowing and static stacking. The blower is turned on for 15 - 30 minutes every 24 hours to ensure that the oxygen concentration is always between 0.5 - 5%, and the blower is turned off after the oxygen concentration reaches 4.5 - 5%; The conditions for the aerobic fermentation include: the temperature is 55 - 65 °C, the time is 10 - 15 days, the oxygen concentration is greater than 10%, and the pile is turned over 1 - 2 times a day.

6. The biological dehydration and drying method according to claim 1, characterized in that, The water content of the dried sludge is 25 - 50%.

7. The dried sludge obtained by the biological dehydration and drying method according to any one of claims 1 - 6.

8. The application of the dried sludge according to claim 7 in being used as a biofuel, preparing biochar, and preparing syngas; Before the application, it also includes granulating the dried sludge to obtain sludge particles.

9. The application according to claim 8, wherein When the application is for preparing biochar, the method for preparing biochar includes: Subjecting the sludge particles to low-temperature pyrolysis and high-temperature carbonization in sequence; The temperature of the low-temperature pyrolysis is 300 - 400 °C, the heating rate is 20 - 35 °C / min, and the heat preservation time is 30 - 50 min; The temperature of the high-temperature carbonization is 500 - 600 °C, the heating rate is 5 - 15 °C / min, and the heat preservation time is 60 - 90 min.

10. The application according to claim 8, wherein When the application is for preparing syngas, the method for preparing syngas includes: Subjecting the sludge particles to pyrolysis gasification; The temperature of the pyrolysis gasification is 800 - 1200 °C, the heating rate is 60 - 120 °C / min, and the heat preservation time is 30 - 60 min.

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