A system for converting urban sludge into gaseous fuel
By constructing a system for converting urban sludge into gaseous fuel and employing precisely controlled sludge treatment and biogas purification technologies, the problems of low sludge conversion efficiency and unstable product quality in existing technologies have been solved, achieving efficient and stable gaseous fuel production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SICHUAN CHANGJI ENVIRONMENTAL PROTECTION ENGINEERING CO LTD
- Filing Date
- 2025-04-03
- Publication Date
- 2026-05-26
Smart Images
Figure CN224280036U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of sludge conversion into gaseous fuel, specifically to a system for converting urban sludge into gaseous fuel. Background Technology
[0002] Urban sludge production continues to grow with urbanization and the expansion of wastewater treatment scale. Traditional disposal methods such as landfill and stockpiling not only occupy large amounts of land resources but also easily cause environmental pollution. Converting urban sludge into gaseous, liquid, and solid fuels to realize its resource utilization is of great significance, as it can alleviate environmental pressure and create economic value. With the acceleration of global urbanization, the scale of urban wastewater treatment is constantly expanding, and the amount of urban sludge generated is also increasing daily. Urban sludge is a solid or semi-solid waste generated during wastewater treatment. Its composition is complex, containing not only large amounts of organic matter and pathogens but also rich in heavy metals and other toxic and harmful substances. Improper treatment of this sludge, such as indiscriminate stockpiling or discharge, will cause serious pollution to the soil, water bodies, and atmospheric environment, threatening ecological balance and human health. Traditional urban sludge treatment methods, such as landfill and stockpiling, have many drawbacks. Landfilling not only occupies a large amount of valuable land resources, but also allows harmful substances in the sludge to seep in with rainwater, polluting groundwater. Stockpiling easily produces foul-smelling gases, causing air pollution, and may also lead to the breeding of mosquitoes and flies, spreading diseases. Furthermore, with increasingly stringent environmental standards, these traditional treatment methods are no longer sufficient to meet the requirements of sustainable development.
[0003] To achieve the harmless and resource-based treatment of urban sewage sludge, converting it into gaseous fuel is a promising technological approach. Currently, although some methods and devices exist for converting urban sewage sludge into gaseous fuel, problems remain, including technological imperfections, low processing efficiency, and unstable product quality. For example, in the sludge pretreatment stage, some existing technologies fail to adequately address dewatering, crushing, and screening, leading to excessively high moisture content and uneven particle size in the sludge entering the subsequent fermentation stage, severely impacting fermentation efficiency and gas quality. Furthermore, improper fermentation processes, such as the inability of some fermentation equipment to precisely control parameters like temperature, pH, and redox potential, hinder the full development of microbial activity, resulting in low biogas production and unstable composition. Regarding biogas purification, existing technologies are ineffective, failing to remove impurities such as hydrogen sulfide, carbon dioxide, and moisture, resulting in highly corrosive and low-calorific-value biogas that does not meet the requirements for high-quality fuel gas. Moreover, existing systems often lack comprehensive testing mechanisms for the final product, directly utilizing the output biogas without ensuring its compliance with stringent fuel gas standards. In summary, it is urgent to develop an efficient, stable, environmentally friendly system for converting urban sludge into gaseous fuel that can precisely control each stage. This patent is proposed against this background, aiming to solve the various shortcomings of existing technologies and promote the development of urban sludge resource utilization technology. Utility Model Content
[0004] Therefore, in order to overcome the above-mentioned shortcomings, this utility model provides a system for converting urban sludge into gaseous fuel, which is an efficient, stable, environmentally friendly, and feasible system for converting urban sludge into gaseous fuel with precise control over each stage.
[0005] This invention is implemented as follows: a system for converting urban sludge into gaseous fuel is constructed, characterized in that the system comprises a sludge dewatering device, a sludge crushing device, a sludge screening device, an anaerobic digester, a biogas collection box, a water washing tower, a desulfurization tower, and a biogas drying device; the sludge dewatering device is used for preliminary dewatering of urban sludge, the outlet of the sludge dewatering device is connected to the sludge crushing device, which crushes the sludge into suitable particle sizes; the outlet of the sludge crushing device is connected to the sludge screening device, which screens the sludge using a vibrating screen; the output of the sludge screening device is connected to the anaerobic digester, from which biogas is produced; the gas output of the anaerobic digester is connected to the biogas collection box; the biogas in the biogas collection box is introduced into the bottom of the water washing tower through a pipeline; the biogas treated by the water washing tower then enters the desulfurization tower containing desulfurizing agent through the top outlet; and the desulfurized biogas then enters the biogas drying device for drying.
[0006] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that: the sludge dewatering device adopts a plate and frame filter press and a centrifugal dewatering machine to perform preliminary dewatering on the urban sludge, reducing the sludge moisture content to 70%-80%; this helps to reduce energy consumption in subsequent treatment processes and improve treatment efficiency.
[0007] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that: after dewatering, the sludge is crushed into suitable particle size using a crusher, and the crushing requirement of the crushing device is to control the sludge crushing to 1-5 cm; then it is screened by a vibrating screen to remove any large impurities that may be mixed in, such as stones and plastic pieces, to ensure that the sludge has a uniform texture, which is conducive to the subsequent conversion process.
[0008] According to the present invention, a system for converting urban sewage sludge into gaseous fuel is characterized in that: an appropriate amount of anaerobic microbial agent is added to the anaerobic fermentation tank to promote the fermentation process; the temperature inside the anaerobic fermentation tank is maintained within a medium-temperature (30-38℃) or high-temperature (50-55℃) range; and the tank is periodically stirred by a stirring device to ensure sufficient contact between the sludge and microorganisms. The fermentation time is controlled within 15-30 days, during which parameters such as pH (maintained at 6.5-7.5) and oxidation-reduction potential are monitored inside the fermentation tank.
[0009] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that: biogas produced by fermentation is introduced into the bottom of a water washing tower through a pipeline. The water washing tower is filled with a large amount of regularly shaped packing material, including ceramic rings and plastic Pall rings, to increase the gas-liquid contact area. An alkaline solution (such as a dilute solution of sodium carbonate or sodium hydroxide) or water is sprayed from the top of the tower. During the ascent, the biogas comes into full contact with the sprayed liquid from above. Carbon dioxide can react chemically with the alkaline solution to form soluble carbonates, which are then absorbed into the liquid phase; some hydrogen sulfide can also be dissolved in water or react with alkaline substances to be removed. After treatment in the water washing tower, the carbon dioxide and hydrogen sulfide content in the biogas is significantly reduced, but a certain amount of hydrogen sulfide and water still remain.
[0010] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that: biogas discharged from the top of a water washing tower then enters a desulfurization tower containing a desulfurizing agent, which is iron oxide, possessing a large specific surface area and good adsorption performance. The iron oxide desulfurizing agent is generally made in granular or block form and packed inside the desulfurization tower. The biogas slowly passes through the desulfurizing agent layer inside the tower, where hydrogen sulfide reacts chemically with the iron oxide to generate iron sulfide or iron polysulfide. As the reaction proceeds, the desulfurizing agent gradually becomes saturated with sulfides, and the desulfurization efficiency decreases. At this point, air can be introduced into the desulfurization tower to oxidize and regenerate the iron sulfide under the action of oxygen, converting it back into iron oxide with desulfurization activity, thus achieving the recycling of the desulfurizing agent. After treatment by the desulfurization tower, the hydrogen sulfide content in the biogas can be reduced to meet usage standards, typically requiring a hydrogen sulfide content below 20 mg / m³.
[0011] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that the biogas drying equipment includes an adsorption drying equipment and a condensation drying equipment.
[0012] According to the present invention, a system for converting urban sludge into gaseous fuel is characterized in that it further includes a biogas detection device located at the outlet of the biogas drying equipment, used to detect the biogas collected after drying, and to detect its methane content, hydrogen sulfide content, calorific value and other indicators; the methane content is determined by gas chromatography; the hydrogen sulfide content is detected by chemical titration or electrochemical sensor; and the calorific value is measured by a calorimeter to ensure that the biogas quality meets the corresponding fuel standards.
[0013] This invention has the following advantages: Through the aforementioned treatment process of urban sludge, including pretreatment and anaerobic fermentation, urban sludge can be effectively converted into gaseous fuel. Simultaneously, this system improves the method and result of biogas purification. Therefore, in practical applications, it is necessary to strictly control the product quality testing process based on factors such as sludge characteristics, treatment scale, and market demand to ensure the safety and efficiency of the produced fuel, achieving a balance between the resource utilization of urban sludge and environmental and economic benefits. In summary, it simplifies the process of converting sludge into biogas while improving the quality of the biogas. Attached Figure Description
[0014] Figure 1 This is a diagram of the system implementation structure of this application. Detailed Implementation
[0015] The following will be combined with the appendix Figure 1This utility model will be described in detail, and the technical solutions in the embodiments of this utility model will be clearly and completely described. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.
[0016] This utility model provides a system for converting urban sewage sludge into gaseous fuel, such as Figure 1 As shown, the system can be implemented as follows: The system consists of a sludge dewatering device 1, a sludge crushing device 2, a sludge screening device 3, an anaerobic digester 4, a biogas collection box 5, a water washing tower 6, a desulfurization tower 7, and a biogas drying device 8. The sludge dewatering device 1 is used for preliminary dewatering of urban sludge. The outlet of the sludge dewatering device 1 is connected to the sludge crushing device 2, which crushes the sludge into suitable particle sizes using a crusher. The outlet of the sludge crushing device 2 is connected to the sludge screening device 3, which screens the sludge using a vibrating screen. The output of the sludge screening device 3 is connected to the anaerobic digester 4, from which biogas is produced. The gas output of the anaerobic digester 4 is connected to the biogas collection box 5. The biogas in the biogas collection box 5 is introduced into the bottom of the water washing tower 6 through a pipeline. The biogas treated by the water washing tower 6 then enters the desulfurization tower 7, which contains a desulfurizing agent, through the top outlet. The desulfurized biogas then enters the biogas drying device 8 for drying.
[0017] When this system is implemented, the sludge dewatering device 1 uses a plate and frame filter press and a centrifugal dewatering machine to perform preliminary dewatering of urban sludge, reducing the sludge moisture content to 70%-80%; this helps to reduce energy consumption in subsequent treatment processes and improve treatment efficiency.
[0018] When implementing this system, the dewatered sludge is crushed into suitable particle sizes using a crusher. The crushing requirement of crushing device 2 is to control the sludge crushing to 1-5 cm. Subsequently, it is screened by a vibrating screen to remove any large impurities that may be mixed in, such as stones and plastic pieces, to ensure that the sludge has a uniform texture, which is conducive to the subsequent conversion process.
[0019] During implementation, an appropriate amount of anaerobic microbial inoculant is added to the anaerobic fermenter 4 to promote the fermentation process. The temperature inside the anaerobic fermenter 4 is maintained within the mesophilic (30-38℃) or hyperthermic (50-55℃) range, and the sludge is stirred periodically by a stirring device to ensure sufficient contact between the sludge and microorganisms. The fermentation time is controlled within 15-30 days, during which parameters such as pH (maintained at 6.5-7.5) and oxidation-reduction potential are monitored within the fermenter.
[0020] During implementation, the biogas produced by fermentation is introduced into the bottom of a water washing tower 6 through pipes. The water washing tower 6 is filled with a large amount of regularly shaped packing material, including ceramic rings and plastic Pall rings, to increase the gas-liquid contact area. An alkaline solution (such as a dilute solution of sodium carbonate or sodium hydroxide) or water is sprayed from the top of the tower. As the biogas rises, it comes into full contact with the sprayed liquid. Carbon dioxide reacts chemically with the alkaline solution to form soluble carbonates, which are then absorbed into the liquid phase. Some hydrogen sulfide can also dissolve in water or react with alkaline substances to be removed. After treatment in the water washing tower, the carbon dioxide and hydrogen sulfide content in the biogas is significantly reduced, but a certain amount of hydrogen sulfide and moisture still remain.
[0021] In this system, biogas discharged from the top of the water washing tower then enters desulfurization tower 7, which contains a desulfurizing agent. The desulfurizing agent in tower 7 is iron oxide, which has a large specific surface area and good adsorption performance. The iron oxide desulfurizing agent is generally made in granular or block form and packed inside the tower. As the biogas slowly passes through the desulfurizing agent layer, hydrogen sulfide reacts chemically with the iron oxide to form iron sulfide or iron polysulfide. As the reaction proceeds, the desulfurizing agent gradually becomes saturated with sulfides, and the desulfurization efficiency decreases. At this point, air can be introduced into the tower to oxidize and regenerate the iron sulfide under the action of oxygen, converting it back into iron oxide with desulfurization activity, thus achieving the recycling of the desulfurizing agent. After treatment in the desulfurization tower, the hydrogen sulfide content in the biogas can be reduced to meet usage standards, typically requiring a hydrogen sulfide content below 20 mg / m³.
[0022] When implementing this system, the biogas drying equipment 8 includes adsorption drying equipment and condensation drying equipment. Although desulfurized biogas has removed most impurities, it still contains a certain amount of moisture. The presence of moisture reduces the calorific value of the biogas and easily condenses into water at low temperatures, causing pipeline corrosion and blockage. Therefore, biogas needs to be dried. Common drying methods include adsorption drying and condensation drying. Adsorption drying uses adsorbents such as silica gel and molecular sieves. Biogas passes through a drying tower filled with adsorbents, and the moisture is adsorbed by the adsorbents, thus achieving the drying purpose. Condensation drying uses refrigeration equipment to lower the biogas temperature below the dew point, causing the moisture to condense into liquid water and separate. After drying, the biogas has a significantly reduced moisture content and can be used as clean fuel, safely and efficiently applied in combustion power generation, residential cooking, and other fields, realizing the value of urban sludge resource utilization.
[0023] When this system is implemented, it also includes a biogas detection device located at the outlet of the biogas drying equipment 8, which is used to detect the biogas collected after drying, and to detect its methane content, hydrogen sulfide content, calorific value and other indicators. The methane content is determined by gas chromatography; the hydrogen sulfide content is detected by chemical titration or electrochemical sensor; and the calorific value is measured by calorimeter to ensure that the biogas quality meets the corresponding fuel standards.
[0024] The implementation of this system is described below;
[0025] (1) Sludge pretreatment:
[0026] Dewatering treatment: Mechanical dewatering equipment, such as plate and frame filter presses and centrifugal dewatering machines, is used to initially dewater urban sludge, reducing the sludge moisture content to 70%-80%. This helps reduce energy consumption in subsequent treatment processes and improves treatment efficiency. Crushing and screening: After dewatering, the sludge is crushed into suitable particle sizes, controlled at 1-5 cm, using a crusher. Then, it is screened by a vibrating screen to remove any large impurities that may be mixed in, such as stones and plastic pieces, ensuring that the sludge has a uniform texture, which is conducive to the subsequent conversion process. (2) Gas fuel conversion:
[0027] Fermentation tank preparation: The pretreated sludge is fed into the anaerobic fermentation tank, which must have good sealing and heat insulation properties. An appropriate amount of anaerobic microbial inoculant is added to the fermentation tank to promote the fermentation process.
[0028] Fermentation process control: Maintain the temperature inside the fermenter within the mesophilic (30-38℃) or hyperthermic (50-55℃) range, and agitate regularly using a stirring device to ensure sufficient contact between the sludge and microorganisms. Control the fermentation time to 15-30 days, during which time monitor parameters such as pH (maintained at 6.5-7.5) and redox potential inside the fermenter.
[0029] Biogas collection and purification: The main components of biogas produced by fermentation are methane (50%-70%) and carbon dioxide, and also contain a small amount of impurities such as hydrogen sulfide. The biogas is collected through pipelines, and first passes through a water washing tower to remove some carbon dioxide and hydrogen sulfide. Then, hydrogen sulfide is further removed by a desulfurizing agent (such as iron oxide). Finally, it is dried to obtain relatively pure biogas, which can be used as clean fuel for combustion power generation, residential cooking and other fields. (3) Biogas purification process: In the method of converting urban sludge into gaseous fuel, biogas purification is an important link to ensure the quality and safe use of biogas. The biogas produced from the anaerobic digester mainly contains methane (50%-70%) and carbon dioxide, and also contains a small amount of impurities such as hydrogen sulfide. If these impurities are not removed, they will seriously affect the combustion performance of biogas, and hydrogen sulfide is corrosive and toxic, which will harm equipment and human health. Therefore, biogas needs to be purified in multiple steps.
[0030] Water scrubbing tower purification: Biogas produced during fermentation is piped to the bottom of a water scrubbing tower. The tower is filled with a large amount of structured packing material, such as ceramic rings and plastic Pall rings, to increase the gas-liquid contact area. An alkaline solution (such as a dilute sodium carbonate or sodium hydroxide solution) or clean water is sprayed from the top of the tower. As the biogas rises, it comes into full contact with the sprayed liquid. Carbon dioxide reacts chemically with the alkaline solution to form soluble carbonates, which are then absorbed into the liquid phase; some hydrogen sulfide can also dissolve in water or react with alkaline substances to be removed. After treatment in the water scrubbing tower, the carbon dioxide and hydrogen sulfide content in the biogas is significantly reduced, but a certain amount of hydrogen sulfide and moisture still remain.
[0031] Deep desulfurization with desulfurizing agents: Biogas discharged from the top of the water washing tower then enters a desulfurization tower containing desulfurizing agents. The commonly used desulfurizing agent is iron oxide, which has a large specific surface area and good adsorption performance. Iron oxide desulfurizing agents are generally made in granular or block form and packed inside the desulfurization tower. Biogas slowly passes through the desulfurizing agent layer inside the tower, where hydrogen sulfide reacts chemically with iron oxide to form iron sulfide or iron polysulfide. As the reaction proceeds, the desulfurizing agent gradually becomes saturated with sulfides, and the desulfurization efficiency decreases. At this point, air can be introduced into the desulfurization tower to oxidize and regenerate the iron sulfide under the action of oxygen, converting it back into iron oxide with desulfurization activity, thus achieving the recycling of the desulfurizing agent. After treatment in the desulfurization tower, the hydrogen sulfide content in the biogas can be reduced to meet usage standards, typically requiring a hydrogen sulfide content below 20 mg / m³.
[0032] Drying Process: Although desulfurized biogas has removed most impurities, it still contains a certain amount of moisture. The presence of moisture lowers the calorific value of the biogas and easily condenses into water at low temperatures, causing pipeline corrosion and blockage. Therefore, biogas needs to be dried. Common drying methods include adsorption drying and condensation drying. Adsorption drying uses adsorbents such as silica gel and molecular sieves. Biogas passes through a drying tower filled with adsorbents, where the moisture is adsorbed, thus achieving the drying purpose. Condensation drying uses refrigeration equipment to lower the biogas temperature below the dew point, causing the moisture to condense into liquid water and separate. After drying, the biogas has a significantly reduced moisture content and can be used as clean fuel, safely and efficiently applied in areas such as combustion power generation and residential cooking, realizing the value of urban sludge resource utilization.
[0033] Biogas fuel testing: The collected biogas is tested for indicators such as methane content, hydrogen sulfide content, and calorific value. Methane content is determined using gas chromatography; hydrogen sulfide content is detected by chemical titration or electrochemical sensors; and calorific value is measured using a calorimeter to ensure that the biogas quality meets the relevant fuel standards.
[0034] In summary, this application, through the aforementioned pretreatment of urban sludge and subsequent anaerobic fermentation, can effectively convert urban sludge into biogas fuel. It also improves the method and outcome of biogas purification. In practical applications, factors such as sludge characteristics, treatment scale, and market demand must be considered, and strict control over product quality testing is necessary to ensure the safety and efficiency of the produced fuel, thereby achieving a balance between the resource utilization of urban sludge and environmental and economic benefits.
[0035] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A system for converting urban sewage sludge into gaseous fuel, characterized in that... ； The system consists of a sludge dewatering device (1), a sludge crushing device (2), a sludge screening device (3), an anaerobic digester (4), a biogas collection box (5), a water washing tower (6), a desulfurization tower (7), and a biogas drying device (8). The sludge dewatering device (1) is used to perform preliminary dewatering of urban sludge. The outlet end of the sludge dewatering device (1) is connected to the sludge crushing device (2), which crushes the sludge into a suitable particle size. The outlet end of the sludge crushing device (2) is connected to the sludge screening device (3), which screens the sludge through a vibrating screen. The output end of the sludge screening device (3) is connected to the anaerobic fermentation tank (4), from which biogas is produced. The gas output end of the anaerobic fermentation tank (4) is connected to the biogas collection box (5). The biogas in the biogas collection box (5) is introduced into the bottom of the water washing tower (6) through a pipeline. The biogas treated by the water washing tower (6) then enters the desulfurization tower (7) containing desulfurizing agent through the top outlet. The desulfurized biogas then enters the biogas drying equipment (8) for drying.
2. The urban sludge to gaseous fuel conversion system according to claim 1, characterized in that; The sludge dewatering device (1) uses a plate and frame filter press and a centrifugal dewatering machine to perform preliminary dewatering of urban sludge, reducing the sludge moisture content to 70%-80%.
3. The urban sludge conversion gaseous fuel system according to claim 1, characterized in that; After dewatering, the sludge is crushed into suitable particle size using a crusher. The crushing requirement of the crushing device (2) is to control the sludge crushing to 1-5 cm. Then, it is screened by a vibrating screen to remove large impurities mixed in.
4. The urban sludge to gaseous fuel conversion system according to claim 1, characterized in that; Anaerobic fermentation tank (4) is filled with anaerobic microbial agents to promote the fermentation process. The anaerobic fermentation tank (4) is equipped with a stirring device. The stirring device is used to stir the sludge regularly so that the sludge and microorganisms can come into full contact.
5. The urban sludge to gaseous fuel conversion system according to claim 1, characterized in that; The biogas collection box (5) introduces the biogas produced by fermentation into the bottom of the water washing tower (6) through a pipeline. The water washing tower (6) is filled with a large amount of regular packing material, including ceramic rings and plastic Pall rings, in order to increase the gas-liquid contact area. Alkaline solution or clean water is sprayed from the top of the tower.
6. The urban sludge conversion gaseous fuel system according to claim 1, characterized in that; The biogas discharged from the top of the water washing tower (6) then enters the desulfurization tower (7) containing desulfurizing agent. The desulfurizing agent in the desulfurization tower (7) is iron oxide, which has a large specific surface area and good adsorption performance. The iron oxide desulfurizing agent is in granular or block form and is filled in the desulfurization tower.
7. The urban sludge conversion gaseous fuel system according to claim 1, characterized in that; Biogas drying equipment (8) includes adsorption drying equipment and condensation drying equipment.
8. The urban sludge to gaseous fuel conversion system according to claim 1, characterized in that; It also includes a biogas testing device located at the outlet of the biogas drying equipment (8), which is used to test the biogas collected after drying, and to test its methane content, hydrogen sulfide content and calorific value. The methane content is determined by gas chromatography; the hydrogen sulfide content is detected by chemical titration or electrochemical sensor; and the calorific value is measured by calorimeter to ensure that the biogas quality meets the corresponding gas standards.