Biomass fuel derived from urban septic tank sludge and its preparation method
By pre-treating urban septic tank sludge, including removing floating debris, heavy metals, fermenting for deodorization, and removing antibiotics, the problems of heavy metals and odor in the preparation of biomass fuel from urban septic tank sludge have been solved, thus improving environmental protection and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SICHUAN BAOFEI ENVIRONMENTAL PROTECTION TECH CO LTD
- Filing Date
- 2026-05-20
- Publication Date
- 2026-06-30
AI Technical Summary
The process of preparing biomass fuel from urban septic tank sludge presents problems such as heavy metal and antibiotic pollution and odor, which are difficult to effectively solve with existing technologies.
Through pretreatment steps including impurity removal, heavy metal removal, fermentation deodorization, and antibiotic removal, modified magnetic particles are used to adsorb heavy metals, microorganisms and plant extracts synergistically decompose odors, and porous adsorption materials are combined to reduce odor release during combustion.
This has reduced secondary pollution and odor emissions from biomass fuels, improving the environmental friendliness and safety of the fuels.
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of biomass fuel equipment technology, specifically to biomass fuel derived from urban septic tank sludge and its preparation method. Background Technology
[0002] Biomass fuel refers to fuel produced by burning biomass materials. It is a renewable and clean fuel, with solid biomass fuel being the most common type. The raw materials for solid biomass fuel include agricultural and forestry waste (such as sawdust, tree branches, corn stalks, rice straw, rice husks, etc.), poultry manure, and urban septic tank sludge (urban septic tank waste). For example, CN105441155B – a composite biomass fuel made from chicken manure, pig manure, yellow-brown soil, and cypress, and its preparation method – uses poultry manure and agricultural and forestry waste as raw materials to prepare biomass fuel. CN120442295A - Biomass fuel derived from urban domestic sewage sludge and its preparation method and application. This paper describes the preparation of biomass fuel using urban septic tank sludge and agricultural and forestry waste as raw materials. It describes the preparation of biomass fuel using urban domestic sewage sludge and records the hazards caused by the direct use of septic tank sludge in agriculture, such as pathogenic microorganisms, heavy metals, and drug residues (antibiotics, anti-inflammatory drugs). Therefore, this paper describes the preparation of biomass fuel by mixing urban domestic sewage sludge with biomass pellets.
[0003] However, urban septic tank sludge differs from poultry manure. It contains floating impurities such as plastics and fabrics; in addition to heavy metals and antibiotics, it has a severe odor, primarily from organic matter. This organic matter not only produces odor through fermentation within the septic tank but also during combustion, generating odors mainly composed of nitrogen oxides, sulfur dioxide, and ammonia. High-temperature combustion may cause heavy metals to volatilize, forming fly ash. Heavy metals in fly ash easily disperse with smoke and dust, polluting the air, and some may deposit in the soil, causing secondary pollution. Some antibiotics may decompose under high combustion temperatures, but incomplete combustion leaves toxic residues. Using the ash from biomass fuel combustion for agricultural purposes also presents problems. Therefore, even using urban septic tank sludge to produce biomass fuel cannot effectively solve the problems of heavy metals and antibiotics, and the odor problem remains.
[0004] Therefore, the preparation of biomass fuel from urban septic tank sludge requires pretreatment to reduce odor and secondary pollution during the combustion process. Summary of the Invention
[0005] The purpose of this invention is to provide biomass fuel derived from urban septic tank sludge and its preparation method. By pretreating urban septic tank sludge, the main focus is on deodorization and removal of heavy metals. The biomass fuel prepared from it can reduce secondary pollution and reduce odor emissions.
[0006] This invention is achieved through the following technical solution: A method for preparing biomass fuel derived from urban septic tank sludge includes the following steps: S1. Floating impurities removal: Water is added to the sludge from the municipal septic tank, stirred, and allowed to settle. The sludge settles to form a sludge layer, and a water layer is formed above the sludge layer. Floating impurities in the sludge float on the water layer. The floating impurities are removed to obtain a sludge-water system. S2. Heavy metal removal: Modified magnetic particles are added to the sludge water system. The modified magnetic particles are magnetic materials modified with heavy metal complexing groups. The mixture is stirred at intervals, and then the modified magnetic particles in the sludge water system are removed by magnetic separation. The magnetic materials include Fe3O4 nanoparticles, and the heavy metal complexing groups are derived from thiol complexing agents. S3, Deodorization: S31. Fermentation and decomposition: Add a compound deodorizing agent to the sludge water system. The compound deodorizing agent includes microorganisms, sodium chloride and plant extracts. The plant extracts include at least one of orange peel press and lemongrass extract. Anaerobic fermentation is carried out at 50-60℃ for 36-48 hours. S32, Negative pressure odor removal: Odors produced during fermentation are removed by negative pressure. The negative pressure inside the sealed fermentation tank is controlled at 10-30Pa. S4. Antibiotic removal: Add antibiotic removal agent to the fermented sludge water system; S5. Filter press to remove water and obtain fecal residue; S6. Mix the manure residue with biomass pellets to obtain biomass fuel.
[0007] The concept of this invention is as follows: By pretreating sludge from urban septic tanks, waste recycling is achieved, primarily through the use of pretreated sludge to produce biomass fuel. Pretreatment improves the environmental friendliness of biomass fuel. Although the main component of sludge from urban septic tanks is fecal residue, its composition is completely different from poultry manure. The main differences are: urban sludge contains floating impurities such as plastics and fabrics, organic matter that produces nitrogen-containing gases, sulfur dioxide, and ammonia, and heavy metals and antibiotics. Heavy metals exist in ionic form, and floating impurities can affect the combustion of biomass fuel. The combustion of organic matter produces a large amount of odorous gases (mainly nitrogen-containing gases, sulfur dioxide, hydrogen sulfide, and ammonia), while heavy metals and antibiotics make post-combustion treatment of biomass fuel difficult. If the ash is used for agricultural purposes, it can lead to farmland pollution. Therefore, this invention designs a corresponding pretreatment method to address the characteristics of harmful substances contained in urban sludge.
[0008] In step S1 of this invention, by adding water to the sludge from the urban septic tank and then stirring, it is beneficial to allow the floating impurities carried in the sludge to float and form a water layer after settling, thereby achieving the smooth removal of floating impurities. Furthermore, by diluting the sludge with water, the fluidity of the sludge can be improved, which facilitates the addition of substances to the sludge and mixing by stirring. This facilitates the pretreatment of the sludge by adding substances, such as subsequent pretreatment for heavy metal removal, deodorization, and antibiotic removal.
[0009] In step S2 of this invention, modified magnetic particles are obtained by modifying the surface of conventional magnetic materials with heavy metal complexing groups, giving them the ability to complex metal ions. Since the modified magnetic particles retain their magnetic function, they can achieve magnetic separation. That is, the modified magnetic particles prepared by this invention can effectively remove heavy metals from sludge.
[0010] In step S3 of this invention, anaerobic fermentation is carried out at 50-60℃. The volatile organic compounds that produce odors (such as those that produce ammonia, sulfur dioxide, hydrogen sulfide, etc.) can be metabolized into gases by microorganisms, while retaining the combustible organic matter (cellulose, hemicellulose, lignin, etc.) in the sludge. Microorganisms, sodium chloride, and plant extracts are added during the fermentation process. The microorganisms, such as lactic acid bacteria and acidophilic bacteria, promote the anaerobic fermentation and decomposition of volatile organic compounds. These bacteria can decompose odors such as ammonia, sulfur dioxide, and hydrogen sulfide. Sodium chloride reacts with ammonia and hydrogen sulfide in the odor, thereby reducing odor release. Orange peel extract, a natural plant extract, interacts with harmful substances in the odor during fermentation, reducing odor levels. Compared to directly adding orange peel, orange peel extract is more effective at releasing volatile components. Lemongrass extract, also a natural plant extract, works synergistically with the orange peel extract during fermentation to further enhance the deodorization effect. This invention improves the removal of odor-causing volatile organic compounds by simultaneously introducing microorganisms, sodium chloride, and plant extracts during anaerobic fermentation, through the synergistic effect of the three. Furthermore, the plant extracts and sodium chloride can also reduce odor emissions during biomass fuel combustion.
[0011] In step S4 of this invention, the antibiotic removal agent used to remove antibiotics from the sludge can be any existing technology.
[0012] In summary, this invention achieves deodorization, removal of heavy metals and antibiotics by pretreating urban septic tank sludge, and the biomass fuel prepared from it can reduce secondary pollution and reduce odor emissions.
[0013] In a preferred embodiment, in step S1, the amount of water added is measured in such a way that, after settling, the height of the water above the sludge layer is 1 / 6 to 1 / 8 of the height of the sludge layer.
[0014] The aforementioned height setting facilitates the removal of floating impurities carried in the sludge from the water layer. Specifically, floating impurities can be removed by using a filter screen. This can be done by placing the filter screen into the water layer and then moving the filter screen to remove floating impurities from the water layer. Floating impurities include plastics and fabrics.
[0015] In a preferred embodiment, step S2 involves the following preparation process for the modified magnetic particles: In an inert gas atmosphere, Fe 2+ and Fe 3+ Fe3O4 nanoparticles were prepared by mixing and co-precipitation; then the Fe3O4 nanoparticles were dispersed in an alcohol solvent, a mercaptosilane coupling agent was added to the alcohol solution, and the reaction was carried out at 40-60℃ for 4-6 hours to obtain modified magnetic particles. The amount of modified magnetic particles added is 5-8% based on the weight of sludge from urban septic tanks.
[0016] In the method for preparing modified magnetic particles described above in this invention, a co-precipitation method is employed. Co-precipitation is a common method for preparing Fe3O4 nanoparticles, and its basic principle is as follows: Fe 2+ +2Fe 3+ +8OH - →Fe3O4+4H2O.
[0017] In the preparation of modified magnetic particles using the co-precipitation method of this invention, the process is carried out under an inert gas atmosphere. Due to the decrease in oxygen partial pressure, some Fe... 3+ The oxygen is reduced to a lower valence state, thus creating oxygen vacancies. These oxygen vacancies can interact with Fe on the surface. 3+ Coordination occurs, forming Fe-O-Fe bonds, which in turn form hydroxyl groups (-OH).
[0018] The Fe3O4 nanoparticles prepared in this invention contain hydroxyl groups (-OH) on their surface. The silane groups in the mercaptosilane coupling agent react with the hydroxyl groups (-OH) on the surface of the Fe3O4 nanoparticles to form silicon-oxygen bonds (Si-O-Fe). At the same time, mercapto groups (-SH) are exposed on the surface of the Fe3O4 nanoparticles. These mercapto groups (-SH) can complex heavy metal ions in the sludge, facilitating the removal of heavy metals from the sludge.
[0019] In a preferred embodiment, during the co-precipitation method for preparing Fe3O4 nanoparticles, Fe... 2+ and Fe 3+The molar ratio is 1:2; the coprecipitant used is sodium hydroxide, the temperature is 40-50℃, and the time is 1.5-2.0h.
[0020] In a preferred embodiment, the mercaptosilane coupling agent comprises at least one of 3-mercaptopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane.
[0021] In a preferred embodiment, the preparation process of orange peel press involves washing fresh orange peels, then crushing them, heating them to 30-40°C, and pressing them to obtain orange peel press containing orange peel juice and orange peel residue. The orange peel press also contains volatile oil.
[0022] The main components of fresh orange peel are cellulose, pectin, and volatile oil (essential oil). Cellulose is relatively tough and easily rebounds, making it difficult to press. This invention adopts a method of first crushing and heating to 30-40℃ before pressing. Crushing can cut the cellulose, and heating to 30-40℃ can soften the orange peel, which helps with pressing.
[0023] Specifically, during pressing, hydraulic pressing at 5-15MPa can be used directly, or a screw press can be used at 1-3MPa.
[0024] Compared to directly pressing orange peel, crushing it and heating it to 30-40℃ before pressing it is more effective in releasing volatile substances such as volatile oils from the orange peel.
[0025] The preparation process of lemongrass extract is as follows: fresh lemongrass and water are subjected to cell wall disruption treatment at a mass ratio of 1:0.5, and then filtered under pressure. The filtrate obtained is lemongrass extract.
[0026] In a preferred embodiment, the amount of the compound deodorizer is 5-8% by weight of sludge from urban septic tanks; the mass ratio of microorganisms, sodium chloride and plant extracts is (1-2):(3-5):(12-15).
[0027] The plant extract can specifically be orange peel extract, lemongrass extract, or a combination of orange peel extract and lemongrass extract.
[0028] Under the same dosage conditions, the combination of microorganisms, sodium chloride, orange peel extract, and lemongrass extract further improves the deodorizing effect compared to the combination of microorganisms, sodium chloride, and orange peel extract alone. This may be because the different active components of orange peel extract and lemongrass extract lead to different deodorizing mechanisms, resulting in a synergistic effect by deodorizing from two different aspects.
[0029] In a preferred embodiment, the mass ratio of microorganisms, sodium chloride, orange peel press and lemongrass extract is (1-2):(3-5):(8-10):(2-5).
[0030] In the above design of the present invention, the orange peel extract and fresh lemongrass have little impact on the subsequent preparation of biomass fuel. The cellulose they contain can also be burned, and the cost of orange peel extract and fresh lemongrass is relatively low, which can realize waste utilization. Adding too much microorganism will lead to waste, and sodium chloride is an inorganic filler. Adding too much will affect the combustion efficiency of biomass fuel. The above setting of the present invention can achieve a good deodorization effect, reduce costs as much as possible, and minimize the impact of sludge pretreatment on the combustion efficiency of the prepared biomass fuel.
[0031] In a preferred embodiment, in step S4, the antibiotic removal agent comprises nano-oxides and composite bio-enzymes; the composite bio-enzymes comprise at least one of β-lactamase and chloramphenicol hydrolase; the nano-oxides comprise at least one of nano-titanium dioxide or nano-iron oxide; and the amount of nano-oxides is 1.0-2.0% and the amount of composite bio-enzymes is 2.0-2.5% based on the weight of sludge from urban septic tanks.
[0032] β-lactamases can degrade antibiotics such as penicillin and cephalosporins, and chloramphenicol hydrolase can be used to degrade chloramphenicol. That is, the composite biological enzyme of the present invention can degrade common antibiotics. Nano-oxides have a high specific surface area and can promote antibiotic degradation. That is, the composite biological enzyme and nano-oxide system of the present invention can degrade most antibiotics in sludge and reduce the antibiotic content in sludge.
[0033] In a preferred embodiment, in step S5, after dewatering by pressure filtration, a porous adsorbent material is added to the fecal residue. The porous adsorbent material includes at least one of bentonite and activated carbon. The amount of porous adsorbent material added is 2.0-5.0% by weight of the fecal residue.
[0034] The porous adsorbent material of this invention has the characteristics of high temperature resistance and can adsorb odorous gases during the combustion process of prepared biomass fuel, thereby further reducing odor leakage.
[0035] Preferably, the porous adsorbent material is sodium-modified bentonite, and the specific modification process is as follows: Take 100.00g of bentonite sample and prepare a slurry with a mass concentration of 5%. Add 4.00g of Na2CO3 solid to the slurry and stir at room temperature for 1 hour. After standing for 1 day, pour off the supernatant and centrifuge the lower layer of slurry to obtain the solid. Wash the solid with distilled water and centrifuge again. Repeat this process 3 times. After drying the obtained solid, sodium-modified bentonite is obtained.
[0036] In a preferred embodiment, in step S5, after pressure filtration to remove water, the moisture content of the fecal residue is controlled at 10-15%.
[0037] In a preferred embodiment, in step S6, the raw materials for the biomass pellets include at least one of straw, nutshells, and wood residue; the wood residue includes sawdust, etc. By incorporating straw, nutshells, and wood residue, the biomass pellets of this invention possess water absorption properties, reducing the moisture content of the manure residue, and these biomass pellets themselves also exhibit combustible properties.
[0038] Biomass fuel prepared by the above preparation method.
[0039] In a preferred embodiment, the biomass fuel is in the form of pellets or blocks.
[0040] In a preferred embodiment, the mass ratio of manure residue to biomass pellets in the biomass fuel is 1:(0.3-0.5).
[0041] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1) This invention employs pretreatment steps of floating impurity removal, heavy metal removal, fermentation deodorization, and antibiotic removal in sequence. This removes floating impurities such as plastics and fabrics from sludge sourced from urban septic tanks. Modified magnetic particles adsorb heavy metal ions in the sludge, and the magnetic properties of the modified magnetic particles achieve magnetic separation, thereby removing heavy metals from the sludge. By adding a composite deodorizing agent including microorganisms, sodium chloride, and plant extracts during fermentation, the organic matter that produces odor in the sludge can be decomposed, effectively reducing the odor during the combustion of the prepared biomass fuel and achieving a deodorization effect. Furthermore, the antibiotic removal agent removes antibiotics from the sludge, improving the environmental friendliness and safety of using the sludge to prepare biomass fuel.
[0042] 2) Through screening plant extracts, this invention found that orange peel extract, lemongrass extract, or a combination of the two can be compounded with microorganisms and sodium chloride to form a compound deodorizer, which improves the deodorization effect on fecal residue. Moreover, under the same dosage, the combined use of orange peel extract and lemongrass extract is more effective than using orange peel extract or lemongrass extract alone.
[0043] 3) This invention employs a two-step deodorization process. The first step involves adding a composite deodorizing agent composed of microorganisms, sodium chloride, and plant extracts during the anaerobic fermentation of the fecal residue. The second step involves adding porous adsorption materials to the fecal residue after pressure filtration to remove water. The first step significantly reduces the odor-producing substances in the fecal residue, while the second step utilizes the characteristics of the porous adsorption materials to adsorb the odor generated during the combustion of biomass fuel. In other words, this invention addresses both the removal of odor-producing substances and the adsorption of odors during combustion, thereby further reducing the odor generated by the combustion of biomass fuel prepared from urban fecal residue.
[0044] 4) In terms of deodorization of biomass fuels, sodium-modified bentonite can further improve the deodorization effect compared with bentonite. Detailed Implementation
[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. The embodiments described below are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.
[0046] In the following description, numerous specific details are set forth to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known structures, materials, or methods are not specifically described to avoid obscuring the invention. Unless otherwise specified, the materials, instruments, and reagents used in the following embodiments are commercially available. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art.
[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.
[0048] Example: To achieve waste utilization of urban septic tank sludge and to realize the environmental friendliness of burning biomass fuel prepared from it, this embodiment provides a method for preparing biomass fuel derived from urban septic tank sludge, including the following steps: S1. Floating Impurity Removal: Water is added to the sludge from the municipal septic tank. Specifically, the amount of water added is measured as follows: After settling, the water level above the sludge layer is 1 / 6 to 1 / 8 of the sludge layer height. Stirring is used to break up the sludge, which helps the floating impurities carried in the sludge to detach from the sludge. Then, the sludge layer and the water level above the sludge layer are formed, allowing the floating impurities that have detached from the sludge to float in the upper water level. The floating impurities, including plastic and cloth, are removed by using a filter screen to intercept them, resulting in a sludge-water system.
[0049] S2. Heavy Metal Removal: Modified magnetic particles, which are magnetic materials modified with heavy metal complexing groups, are added to the sludge-water system. The mixture is stirred intermittently, and then the modified magnetic particles are removed from the sludge-water system by magnetic separation. The magnetic material includes Fe3O4 nanoparticles, and the heavy metal complexing groups are derived from thiol complexing agents. In this embodiment, heavy metal complexing groups are modified onto the surface of the Fe3O4 nanoparticles. These complexing groups complex heavy metal ions in the sludge, and then removal is achieved through magnetic separation based on the magnetic properties of the material. The amount of modified magnetic particles added is 5-8% based on the weight of sludge from urban septic tanks.
[0050] Specifically, the preparation process of the modified magnetic particles is as follows: In an inert gas (N2) atmosphere, Fe 2+ and Fe 3+ Mixed, Fe 2+ and Fe 3+ Fe3O4 nanoparticles were prepared by coprecipitation with a molar ratio of 1:2, using sodium hydroxide as the coprecipitant at a temperature of 40-50℃ for 1.5-2.0 h. The Fe3O4 nanoparticles were then dispersed in an alcohol solvent (ethanol) at a volume ratio of 2:(3-5). A mercaptosilane coupling agent, comprising at least one of 3-mercaptopropyltrimethoxysilane and γ-mercaptopropyltrimethoxysilane, was added to the alcohol solution, and the reaction was carried out at 40-60℃ for 4-6 hours to obtain modified magnetic particles.
[0051] The amount of coprecipitant added is determined according to the following reaction formula: Fe 2+ +2Fe 3+ +8OH - →Fe3O4+4H2O.
[0052] This embodiment was carried out in an inert gas atmosphere. Due to the decrease in oxygen partial pressure, some Fe... 3+ The oxygen is reduced to a lower valence state, thus creating oxygen vacancies. These oxygen vacancies can interact with Fe on the surface. 3+Coordination forms Fe-O-Fe bonds, which in turn form hydroxyl groups (-OH). These hydroxyl groups (-OH) can then react chemically with mercaptosilane coupling agents, successfully modifying heavy metal complex groups containing mercapto groups on the Fe3O4 nano-surface.
[0053] The metal removal in this embodiment mainly considers the heavy metals Zn, Cu, Pb, and Cr, which are present in relatively large quantities in the sludge. Zn sources include: human excrement, kitchen wastewater, household products (such as detergents), and metal pipes; Cu sources include: drinking water pipes, household products, some food items, and cosmetics; Pb sources include: residual lead in drinking water pipes, certain lead-containing paints, and trace amounts of lead in food and daily necessities; Cr sources include: trace amounts of cadmium in food products, industrial wastewater, and the seepage of some plastics or batteries.
[0054] S3, Deodorization: S31. Fermentation and Decomposition: The sludge-water system is transferred to a sealed tank for fermentation. A compound deodorizing agent is added to the sludge-water system. The compound deodorizing agent includes microorganisms, sodium chloride, and plant extracts. The plant extracts include at least one of orange peel press and lemongrass extract. Anaerobic fermentation is carried out at 50-60℃ for 36-48 hours. Specifically, the amount of compound deodorizing agent used is 5-8% based on the weight of sludge from urban septic tanks. The mass ratio of microorganisms, sodium chloride, and plant extracts is (1-2):(3-5):(12-15). When the plant extract is a combination of orange peel press and lemongrass extract, the deodorizing effect is better than using orange peel press or lemongrass extract alone under the same dosage. In a preferred embodiment, the mass ratio of microorganisms, sodium chloride, orange peel press, and lemongrass extract is (1-2):(3-5):(8-10):(2-5).
[0055] The preparation process of the orange peel extract involves washing fresh orange peels, then crushing them, heating them to 30-40°C, and pressing them to obtain an orange peel extract containing orange peel juice and pulp. The microorganisms used are a mixture of lactic acid bacteria (Bifidobacterium BB536) and acidophilic bacteria (Lactobacillus acidophilus LA-10A) in a 1:1 mass ratio. Both Bifidobacterium BB536 and Lactobacillus acidophilus LA-10A used in this embodiment are commercially available products. More specifically, in this embodiment, the orange peel extract is obtained directly by hydraulic pressing at 5-15 MPa.
[0056] S32. Negative pressure odor removal: Adjust the negative pressure inside the sealed container to 10-30Pa, and use negative pressure to discharge the odor generated by fermentation through the pipe for treatment.
[0057] S4. Antibiotic Removal: An antibiotic removal agent is added to the fermented sludge water system. The antibiotic removal agent can be any existing technology. In this embodiment, the antibiotic removal agent is composed of nano-oxides and composite biological enzymes. The composite biological enzymes are a combination of β-lactamase and chloramphenicol hydrolase in a 1:1 mass ratio. The nano-oxides are a combination of nano-titanium dioxide and nano-iron oxide in a 1:1 mass ratio. Preferably, based on the weight of the sludge from urban septic tanks, the amount of nano-oxides is 1.0-2.0%, and the amount of composite biological enzymes is 2.0-2.5%.
[0058] S5. Filter press to remove water and obtain fecal residue. The moisture content of the fecal residue is controlled at 10-15%. S6. Mix manure residue with biomass pellets to obtain biomass fuel; the raw materials for biomass pellets include at least one of straw, fruit shells, and wood tailings. The prepared biomass fuel is in pellet or block form; the mass ratio of manure residue to biomass pellets in the biomass fuel is 1:(0.3-0.5).
[0059] In a preferred embodiment, a porous adsorbent material is added to the manure residue. The porous adsorbent material includes at least one of bentonite and activated carbon. The amount of porous adsorbent material added is 2.0-5.0% by weight of the manure residue. The porous adsorbent material adsorbs odors generated during the combustion of biomass fuel. Preferably, the porous adsorbent material is sodium-modified bentonite, and the specific modification process is as follows: Take 100.00g of bentonite sample and prepare a slurry with a mass concentration of 5%. Add 4.00g of Na2CO3 solid to the slurry and stir at room temperature for 1 hour. After standing for 1 day, pour off the supernatant and centrifuge the lower layer of slurry to obtain the solid. Wash the solid with distilled water and centrifuge again. Repeat this process 3 times. After drying the obtained solid, sodium-modified bentonite is obtained.
[0060] This embodiment not only removes floating impurities such as plastics and fabrics from sludge sourced from urban septic tanks, but also utilizes modified magnetic particles to adsorb heavy metal ions in the sludge and uses the magnetism of the modified magnetic particles to achieve magnetic separation, thereby removing heavy metals from the sludge. By adding a composite deodorizing agent including microorganisms, sodium chloride, and orange peel press during the fermentation process, it can decompose the organic matter in the sludge that produces odors, effectively reducing the odor during the combustion of the prepared biomass fuel, achieving a deodorization effect. Furthermore, by removing antibiotics from the sludge using an antibiotic removal agent, it improves the environmental friendliness of using sludge to prepare biomass fuel.
[0061] To better illustrate the technical effects of this embodiment, the following specific examples are used for explanation: Example 1: A method for preparing biomass fuel derived from urban septic tank sludge includes the following steps: S1. Removal of floating impurities; S2. Heavy metal removal: Modified magnetic particles are added to the sludge-water system. The amount of modified magnetic particles added is 8% by weight of the sludge from urban septic tanks. Specifically, the preparation process of the modified magnetic particles is as follows: In an inert gas (N2) atmosphere, Fe 2+ and Fe 3+ Fe3O4 nanoparticles were prepared by co-precipitation using sodium hydroxide as the coprecipitant at 40-50℃ for 1.5-2.0 h. The Fe3O4 nanoparticles were then dispersed in ethanol at a volume ratio of 2:3.5. 3-Mercaptopropyltrimethoxysilane was added to the ethanol solution, and the reaction was carried out at 50℃ for 6 hours to obtain modified magnetic particles.
[0062] S3, Deodorization: S31. Fermentation and decomposition: The sludge-water system is transferred to a sealed tank for fermentation. A compound deodorizing agent, comprising microorganisms, sodium chloride, and orange peel press, is added to the sludge-water system. Anaerobic fermentation is carried out at 55°C for 36 hours. Specifically, the amount of compound deodorizing agent is 8% based on the weight of sludge from urban septic tanks. The mass ratio of microorganisms, sodium chloride, and orange peel press is 2:5:15. The microorganisms are a mixture of lactic acid bacteria and acidophilic bacteria in a mass ratio of 1:1. The orange peel press is described in the above example. S32, negative pressure odor removal.
[0063] S4. Antibiotic Removal: An antibiotic removal agent is added to the fermented sludge-water system. The antibiotic removal agent consists of nano-oxides and composite bio-enzymes. The composite bio-enzymes are a 1:1 mass ratio of β-lactamase and chloramphenicol hydrolase. The nano-oxides are a 1:1 mass ratio of nano-titanium dioxide and nano-iron oxide. The dosage of nano-oxides is 1.5% and the dosage of composite bio-enzymes is 2.0% based on the weight of sludge from urban septic tanks.
[0064] S5. Filter press to remove water and obtain fecal residue. The moisture content of the fecal residue is controlled at 10-15%. S6. Mix manure residue with biomass pellets to obtain biomass fuel; the raw material for biomass pellets is straw powder. The mass ratio of manure residue to biomass pellets in the biomass fuel is 1:0.5. Use an extrusion pelletizing device to form fuel pellets with a particle size of 1 mm.
[0065] Example 2: This embodiment is based on Embodiment 1, and the difference between it and Embodiment 1 is as follows: In step S6, the manure residue is mixed with biomass pellets and bentonite to obtain biomass fuel; the amount of bentonite added is 3.0% by weight of the manure residue.
[0066] Example 3: This embodiment is based on Embodiment 1, and the difference between it and Embodiment 1 is as follows: In step S6, the manure residue is mixed with biomass pellets and bentonite to obtain biomass fuel; the amount of bentonite added is 5.0% by weight of the manure residue.
[0067] Example 4: This embodiment is based on Embodiment 3, and the difference between it and Embodiment 3 is as follows: Sodium-modified bentonite was used to replace bentonite; the specific modification process is described in the examples above.
[0068] Example 5: This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the compound deodorant is a mixture of microorganisms, sodium chloride, and lemongrass extract in a mass ratio of 2:5:15.
[0069] Example 6: This embodiment is based on Embodiment 1, but differs from Embodiment 1 in that the compound deodorant is a mixture of microorganisms, sodium chloride, orange peel extract and lemongrass extract in a mass ratio of 2:5:10:5.
[0070] Example 7: This embodiment is based on Embodiment 3, and the difference between it and Embodiment 3 is as follows: The compound deodorizer is a mixture of microorganisms, sodium chloride, orange peel extract, and lemongrass extract in a mass ratio of 2:5:10:5.
[0071] Comparative Example 1: This comparative example is based on Example 1, and differs from Example 1 in that: The preparation process of the modified magnetic particles is different. The magnetic material used in this comparative example is conventional Fe3O4 nanoparticles, not Fe3O4 nanoparticles prepared by co-precipitation under reduced oxygen partial pressure.
[0072] Comparative Example 2: This comparative example is based on Example 1, and differs from Example 1 in that: Step S2 is not performed.
[0073] Comparative Example 3: This comparative example is based on Example 1, and differs from Example 1 in that: The compound deodorizer is a microorganism, and its dosage is 10% based on the weight of sludge from urban septic tanks.
[0074] Comparative Example 4: This comparative example is based on Example 1, and differs from Example 1 in that: The compound deodorizer is a combination of microorganisms and sodium chloride. The amount of compound deodorizer used is 10% based on the weight of sludge from urban septic tanks; the mass ratio of microorganisms to sodium chloride is 2:5.
[0075] Comparative Example 5: This comparative example is based on Example 1, and differs from Example 1 in that: The compound deodorizer is a combination of microorganisms and orange peel extract. The amount of compound deodorizer used is 10% based on the weight of sludge from urban septic tanks. The mass ratio of microorganisms to orange peel extract is 2:15.
[0076] Comparative Example 6: This comparative example is based on Example 1, and differs from Example 1 in that: The preparation process of orange peel extract differs; in this embodiment... Preparation process of orange peel press: After washing fresh orange peel, it is crushed and pressed at the current temperature (23℃) to obtain orange peel press containing orange peel juice and orange peel residue.
[0077] Comparative Example 7: This comparative example is based on Example 1, and differs from Example 1 in that: The compound deodorizer is a combination of microorganisms and sodium chloride. The amount of compound deodorizer used is 10% based on the weight of sludge from urban septic tanks. The mass ratio of microorganisms to sodium chloride is 2:20, that is, in this comparative example, an equal amount of sodium chloride is used to replace the orange peel extract.
[0078] Control group: A method for preparing biomass fuel derived from urban septic tank sludge includes the following steps: S1. Removal of floating impurities; S2, Deodorization: S21. Fermentation and decomposition: The sludge-water system is transferred to a sealed tank for fermentation, and anaerobic fermentation is carried out at 55°C for 36 hours. S22, negative pressure exhaust of odors; S3. Filter press to remove water and obtain fecal residue. The moisture content of the fecal residue is controlled at 10-15%. S4. Mix manure residue with biomass pellets to obtain biomass fuel; the raw material for biomass pellets is straw powder. The mass ratio of manure residue to biomass pellets in the biomass fuel is 1:0.5. Use an extrusion pelletizing device to form fuel pellets with a particle size of 1 mm.
[0079] Biomass fuels prepared in Examples 1-7, Comparative Examples 1-7, and the control group were extruded and granulated to form fuel pellets with a diameter of 1 mm. 30 g of each pellet was taken out and fully combusted with oxygen. The calorific value (kcal / kg) of each sample was tested according to GB / T 30727-2014. The odor reduction rate (η1) and heavy metal reduction rate (η2) were also tested. Wherein, η1 = ((A1-A2) / A1) × 100%; A1 is the odor emission of the control group, and A2 is the odor emission of the experimental group (Examples 1-7, Comparative Examples 1-7). The odor emission is calculated as the total emission of nitrogen-containing gases, sulfur dioxide, hydrogen sulfide, and ammonia. HJ 479—2009 tests for nitrogen oxides, HJ 482—2009 tests for sulfur dioxide, HJ 1388—2024 tests for hydrogen sulfide, and HJ 533—2009 tests for ammonia. A1 and A2 are both measurements of odor during biomass fuel combustion. η2 = ((B1-B2) / B1) × 100%, B1 is the heavy metal content of the control group, and B2 is the heavy metal content of the experimental group (Examples 1-7, Comparative Examples 1-7). The heavy metal content is calculated as the total amount of Zn, Cu, Pb, and Cr, referring to GB / T GB / T 17141-1997 was used to test the Pb content in the pretreated sludge. Zn and Cu were measured according to GB / T 17138-1997, and Cr was measured according to HJ 491-2009. B1 and B2 were used to measure the heavy metal content in the fecal residue after sludge pretreatment. The results are shown in Table 1. Table 1 The data in Table 1 shows that: 1) The pretreatment method of the sludge from urban septic tanks in this invention will not reduce the calorific value of the prepared biomass fuel. Adding a certain amount of bentonite to the pretreated sludge will not have a significant impact on the calorific value of the prepared biomass fuel.
[0080] 2) The anaerobic fermentation and negative pressure exhaust of the control group can reduce odor to some extent, but the effect is poor. This invention can significantly improve the deodorization effect by adding a compound deodorizer during the anaerobic fermentation process. The combination of plant extracts, microorganisms and sodium chloride is better than the combination of microorganisms and sodium chloride alone or the combination of microorganisms and plant extracts. When only the combination of microorganisms and sodium chloride is used, even if the amount of sodium chloride is increased, it will not only reduce the odor reduction rate, but also reduce the calorific value. Furthermore, under the same dosage, the combination of lemongrass extract, orange peel extract, microorganisms and sodium chloride is the best, which is better than the combination of orange peel extract, microorganisms and sodium chloride or the combination of lemongrass extract, microorganisms and sodium chloride.
[0081] 3) This invention further improves the odor reduction rate by adding porous adsorbent material (bentonite) to the fecal residue after pressure filtration and dewatering, that is, further reduces the amount of odor emissions. The amount of porous adsorbent material used in this invention is within a certain range. As the amount of porous adsorbent material (bentonite) added increases, the odor reduction rate increases. The effect of sodium-modified bentonite is better than that of bentonite. The reason for this may be that sodium-modified bentonite improves the adsorption activity of bentonite at high temperatures.
[0082] 4) The modified magnetic particles prepared by this invention can effectively remove heavy metals from sludge. A comparison of Comparative Examples 1-2 with Example 1 shows that without using the co-precipitation method of this invention to prepare Fe3O4 nanoparticles, even with the addition of a thiol complexing agent to modify the Fe3O4 nanoparticles, the removal of heavy metals from the sludge cannot be achieved. The reason is that conventional Fe3O4 nanoparticles do not form hydroxyl groups (-OH) on their surface, and therefore cannot react with the silane groups in the thiol silane coupling agent. Even if the thiol silane coupling agent complexes heavy metal ions, they are not connected to the Fe3O4 nanoparticles, and thus cannot be removed by magnetic separation. Magnetic separation can only remove magnetic substances. Therefore, the Fe3O4 nanoparticles removed by magnetic separation in Comparative Example 1 are not thiol silane coupling agents complexed with heavy metals. The higher heavy metal reduction rate in Comparative Example 1 compared to Comparative Example 2 may be due to the physical adsorption of some of the thiol silane coupling agents complexed with heavy metals onto the Fe3O4 nanoparticles, achieving partial magnetic separation removal.
[0083] In summary, this invention, by pretreating sludge from urban septic tanks, can effectively remove heavy metals and reduce odor during combustion without reducing the quality of the biomass fuel produced.
[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing biomass fuel derived from urban septic tank sludge, characterized in that, Includes the following steps: S1. Floating impurity removal: Add water to the sludge from the municipal septic tank, stir, let it stand, remove floating impurities, and obtain a sludge-water system. S2. Heavy metal removal: Modified magnetic particles are added to the sludge-water system. The modified magnetic particles are magnetic materials modified with heavy metal complexing groups. The mixture is stirred intermittently, and then the modified magnetic particles in the sludge-water system are removed by magnetic separation. The magnetic material includes Fe3O4 nanoparticles, and the source of the heavy metal complexing groups includes thiol complexing agents. S3, Deodorization: S31. Fermentation and decomposition: Add a compound deodorizing agent to the sludge water system. The compound deodorizing agent includes microorganisms, sodium chloride and plant extracts. The plant extracts include at least one of orange peel press and lemongrass extract. Anaerobic fermentation is carried out at 50-60℃ for 36-48 hours. S32, Negative Pressure Odor Removal: Odors produced during fermentation are removed using negative pressure. S4. Antibiotic removal: Add an antibiotic removal agent to the fermented sludge water system; S5. Filter press to remove water and obtain fecal residue; S6. Mix the manure residue with biomass pellets to obtain the biomass fuel.
2. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S1, the amount of water added is measured in the following way: after settling, the height of the water above the sludge layer is 1 / 6 to 1 / 8 of the height of the sludge layer.
3. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S1, the floating impurities are removed by using a filter screen; the floating impurities include plastic and fabric.
4. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S2, the preparation process of the modified magnetic particles is as follows: In an inert gas atmosphere, Fe 2+ and Fe 3+ The Fe3O4 nanoparticles were prepared by mixing and co-precipitation. Then, the Fe3O4 nanoparticles were dispersed in an alcohol solvent, and a mercaptosilane coupling agent was added to the alcohol solution. The mixture was reacted at 40-60°C for 4-6 hours to obtain the modified magnetic particles. The amount of modified magnetic particles added is 5-8% based on the weight of sludge from urban septic tanks.
5. The method for preparing biomass fuel from urban septic tank sludge according to claim 4, characterized in that, During the preparation of Fe3O4 nanoparticles by coprecipitation, Fe 2+ and Fe 3+ The molar ratio is 1:2; the coprecipitant used is sodium hydroxide, the temperature is 40-50℃, and the time is 1.5-2.0h.
6. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, The preparation process of the orange peel press is as follows: fresh orange peel is washed, crushed, heated to 30-40℃ and then pressed to obtain the orange peel press containing orange peel juice and orange peel residue. The microorganisms include lactic acid bacteria and acidophilic bacteria.
7. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, The amount of the composite deodorizer is 5-8% based on the weight of sludge from urban septic tanks; the mass ratio of the microorganisms, the sodium chloride and the plant extract is (1-2):(3-5):(12-15).
8. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S4, the antibiotic removal agent includes nano-oxides and composite bio-enzymes; the composite bio-enzymes include at least one of β-lactamase and chloramphenicol hydrolase; the nano-oxides include at least one of nano-titanium dioxide or nano-iron oxide; the amount of nano-oxides used is 1.0-2.0% and the amount of composite bio-enzymes used is 2.0-2.5% based on the weight of sludge from urban septic tanks.
9. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S5, after dewatering by pressure filtration, a porous adsorbent material is added to the fecal residue. The porous adsorbent material includes at least one of bentonite and activated carbon. The amount of the porous adsorbent material added is 2.0-5.0% based on the weight of the fecal residue.
10. The method for preparing biomass fuel from urban septic tank sludge according to claim 1, characterized in that, In step S5, after pressure filtration to remove water, the moisture content of the fecal residue is controlled at 10-15%.
11. Biomass fuel prepared by the preparation method according to any one of claims 1-10.
12. The biomass fuel according to claim 11, characterized in that, The biomass fuel is in the form of granules or blocks.
13. The biomass fuel according to claim 11, characterized in that, In the biomass fuel, the mass ratio of manure residue to biomass pellets is 1:(0.3-0.5); the raw materials for the biomass pellets include at least one of straw, fruit shells, and wood waste.