Method and system for producing organic fertilizer by recycling sulfur based on methane complex iron desulfurization

Abstract

The invention discloses a method and a system for producing an organic fertilizer by recycling sulfur based on methane complex iron desulfurization. The method comprises the following steps: S1, carrying out mechanical filter pressing dehydration on a wet sulfur-containing cake generated by methane complex iron desulfurization; s2, placing the obtained purified sulfur cake in a high-temperature aerobic fermentation area; s3, in the high-temperature aerobic fermentation process, adding a composite microbial agent in a specific proportion; s4, in the high-temperature aerobic fermentation process, maintaining and adjusting the pH value of the system by utilizing the organic acid secreted by the compound microbial agent and combining with an externally added acidic regulator; s5, under the synergistic effect of the compound microbial agent and the dynamic regulation and control of the pH value, the elemental sulfur element in the sulfur cake is subjected to an oxidation process and is combined with a nitrogen source in the system, and the ammonium sulfate-containing organic fertilizer is formed through conversion. Based on the synergistic effect of the sulfur oxidizing bacteria-organic sulfur degrading bacteria-thermophilic actinomycetes complex microbial inoculants, the biochemical conversion rate of sulfur to plant absorbable ammonium sulfate is remarkably increased.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology, and more specifically, relates to a method for the resource-based production of organic fertilizer from sulfur using biogas-based iron complexation desulfurization. This invention also relates to a system for the resource-based production of organic fertilizer from sulfur using biogas-based iron complexation desulfurization. Background Technology

[0002] Biogas often contains hydrogen sulfide impurities during production, requiring desulfurization. Common biogas desulfurization methods include the complexation iron process to produce elemental sulfur (sulfur cake), but these traditional methods pose a risk of secondary pollution. Composting is a natural biological process driven by microorganisms to degrade organic matter, and sulfur powder is widely used as an additive in composting to adjust pH and fix ammonia nitrogen. This invention belongs to the field of biogas purification and resource utilization, specifically relating to a method for sulfur purification and high-temperature aerobic fermentation to prepare ammonium sulfate fertilizer based on the complexation iron desulfurization process. This method is suitable for the deep treatment of sulfur-containing biogas and the high-value utilization of by-products.

[0003] Existing sulfur conversion systems have three shortcomings: crude temperature control during the oxidation stage leads to the inactivation of thermophilic sulfur bacteria; pH adjustment relies on purchased concentrated sulfuric acid, neglecting the acidic wastewater resources of the biogas purification stage's washing tower; and forced discharge of waste residue results in secondary pollution of sulfur resources due to the lack of screening and reuse technology for unconverted sulfur residue. Therefore, we propose a method and system for the resource-based production of organic fertilizer from sulfur based on biogas-complexed iron desulfurization. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method and system for the production of organic fertilizer from sulfur resources based on biogas-based desulfurization of iron complexes. Based on the synergistic effect of a compound microbial agent consisting of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria, and thermophilic actinomycetes, the biochemical conversion rate of sulfur to plant-absorbable ammonium sulfate is significantly improved in the oxygen-rich microenvironment created by a multi-axis turning machine.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The method for producing organic fertilizer from sulfur resources based on biogas-based iron complexation desulfurization includes the following steps:

[0007] S1. The wet sulfur cake produced by biogas complex iron desulfurization is mechanically dehydrated by pressure filtration to reduce its moisture content to below 40% and make the sulfur purity of the oven-dried sulfur cake reach ≥96%.

[0008] S2. Place the obtained purified sulfur cake in a high-temperature aerobic fermentation zone, control the fermentation environment to be aerobic with an oxygen concentration ≥10%, and regulate the temperature.

[0009] S3. During the high-temperature aerobic fermentation process, a specific proportion of compound microbial inoculant is added; the compound microbial inoculant contains sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes, which work synergistically.

[0010] S4. During the high-temperature aerobic fermentation process, the organic acids secreted by the compound microbial agent, combined with an externally added acidic regulator, are used to maintain and adjust the pH value of the system; the acidic regulator includes waste liquid generated from the biogas washing tower.

[0011] S5. Under the synergistic effect of the compound microbial agent and dynamic pH control, the elemental sulfur in the sulfur cake undergoes an oxidation process and combines with the nitrogen source in the system to form an organic fertilizer containing ammonium sulfate.

[0012] Preferably, the sulfur cake purification step further includes:

[0013] A diaphragm filter press is used for mechanical filtration and dehydration. By continuously applying pressure, the wet sulfur cake produced by biogas complex iron desulfurization is compressed and filtered to effectively reduce the overall moisture content of the sulfur cake to meet the required moisture content.

[0014] This step also involves sulfur cake crushing and screening, breaking the filtered sulfur cake into smaller particle sizes to ensure uniform distribution of sulfur and reaction efficiency in subsequent processing.

[0015] The crushing process is carried out in a closed environment to prevent sulfur dust from escaping. The crushing equipment is made of a specific wear-resistant material to prevent sulfur contamination, and finally, sulfur cake with the required purity is obtained.

[0016] Preferably, the high-temperature aerobic fermentation zone is equipped with a continuous oxygen supply system to ensure that the oxygen concentration in the fermentation environment is maintained above the required level. This oxygen supply system maintains good gas diffusion through forced ventilation devices such as fans or compressed air injection equipment, combined with the structural design of the fermentation material, and is dynamically adjusted based on oxygen concentration monitoring feedback.

[0017] Preferably, the process for adding the specific proportion of compound microbial agent is as follows:

[0018] 1) Before adding, sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes are cultured and propagated separately to achieve peak activity in a suitable nutrient medium.

[0019] 2) Then, the various strains are mixed and compounded in a specific ratio to form a compound bacterial agent suspension, and it is ensured that the three have a synergistic effect to improve the efficiency of sulfur dissolution and oxidation.

[0020] 3) The addition method includes spraying the compound microbial agent evenly on the surface of the high-purity sulfur cake at the beginning of fermentation, and supplementing the spray in the middle to maintain the balance of microbial numbers.

[0021] 4) The amount of compound microbial agent added should be sufficient to cover the surface of the sulfur cake and penetrate into the internal particles, thereby initiating the secretion process of sulfur oxidase system and biosurfactant.

[0022] Preferably, the pH dynamic control step further supplements the use of dilute sulfuric acid as an external acidic regulator, which is automatically switched by the acid adjustment system when the supply of waste liquid from the biogas washing tower is insufficient; the dilute sulfuric acid is selected and prepared within a suitable concentration range in combination with its acidification characteristics and safety considerations, so as to assist the pH of the fermentation system to decrease and lock in quickly.

[0023] Preferably, the sulfur conversion efficiency during the high-temperature aerobic fermentation process is defined by the following formula:

[0024] ηs=α ox ×β AS Where ηs is the sulfur resource utilization rate, referring to the baseline value of the efficiency of converting elemental sulfur into ammonium sulfate; α ox The sulfur oxidation rate refers to the ratio of elemental sulfur in the sulfur cake to sulfate ions, and its range β is defined by material experimental data. AS Ammonium sulfate conversion rate refers to the ratio of sulfate ions generated by oxidation to ammoniacal nitrogen to form ammonium sulfate; the above formula quantifies the overall conversion path efficiency of sulfur element from elemental sulfur to the target fertilizer product, providing a core evaluation indicator for process optimization.

[0025] Preferably, the temperature control process needs to satisfy a compensation relationship, expressed as:

[0026] L T = k·(ΔT) 2 , where L T is the temperature deviation loss coefficient, reflecting the efficiency decay caused by the actual temperature deviating from the optimal value; k is the process sensitivity constant, determined by the temperature dependence of microbial activity; ΔT is the absolute value of the difference between the actual fermentation temperature Treal and the optimal fermentation temperature Topt, where Topt is set based on the highest efficiency point limited by the material.

[0027] A system for the production of organic fertilizer from sulfur resources based on biogas-based iron complexation desulfurization, the system being used to implement the above-mentioned method, including:

[0028] The desulfurization sulfur pretreatment module is used to receive the wet sulfur slurry produced in the biogas complex iron desulfurization process, and dehydrate it by pressure filtration to generate an absolutely dry sulfur cake with a moisture content of ≤40% and a sulfur purity of ≥96%. It can also crush and screen the sulfur cake to a suitable particle size to ensure the uniformity of subsequent fermentation reactions.

[0029] The high-temperature aerobic fermentation conversion module is used for crushing sulfur cake. It maintains an oxygen concentration of ≥10% through forced ventilation, integrates a heating device and sensor for temperature control, and is equipped with a multi-axis agitator to periodically reorganize the material structure, thereby enhancing oxygen penetration and heat distribution.

[0030] The microbial regulation central module is used to add a compound bacterial agent of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes in a specific ratio. It can also monitor the pH of the fermentation system in real time, automatically switch between biogas water washing tower waste liquid or dilute sulfuric acid to adjust the pH to the range of 6.8±0.2, and at the same time link the turning machine to achieve uniform mixing of acid regulators and inhibit the reverse decomposition of ammonium sulfate.

[0031] The fertilizer forming and quality control module is used for cooling and maturing after fermentation, adding calcium and magnesium oxides to enhance particle strength, sieving out unconverted sulfur residue, hot air drying to a suitable moisture content, testing ammonium sulfate content, and packaging and storing to prevent moisture degradation.

[0032] Preferably, the desulfurization sulfur pretreatment module includes a diaphragm filter press dewatering unit, a closed crushing and screening unit, and a waste liquid recovery unit; wherein the diaphragm filter press is configured to dewater the wet sulfur slurry produced by biogas complex iron desulfurization to an absolutely dry sulfur cake with a moisture content of ≤40% by continuous pressurization; the closed crushing and screening unit uses wear-resistant equipment to avoid sulfur contamination and crushes the sulfur cake to a suitable particle size to ensure fermentation uniformity; the waste liquid recovery unit transports the waste liquid produced by the filter press to a central treatment tank for sedimentation, and the supernatant after sedimentation is reused for humidity control in the high-temperature aerobic fermentation conversion module;

[0033] The high-temperature aerobic fermentation conversion module integrates an interactive environmental control chain: the temperature sensor embedded in the insulated fermentation tank and the external heating device work together to maintain a fermentation range of 50–65℃; the forced ventilation oxygen supply system injects air through a fan to ensure an oxygen concentration of ≥10%; the multi-axis agitator turns the material layer according to a preset frequency to enhance gas diffusion in conjunction with the oxygen supply system; this module transmits temperature and oxygen data to the microbial-control center module in real time to drive the dynamic addition of compound bacterial agents and acid regulators.

[0034] The technical effects and advantages of this invention are as follows: Compared with the prior art, the method and system for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization provided by this invention, based on the synergistic effect of a compound microbial agent of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria, and thermophilic actinomycetes, significantly improves the biochemical conversion rate of sulfur to plant-absorbable ammonium sulfate in the oxygen-rich microenvironment created by the multi-axis turning machine; the linkage mechanism of temperature sensor, oxygen supply fan and acid adjustment pump maintains the optimal fermentation conditions in real time, breaking through the bottleneck of microbial activity inhibition caused by temperature / oxygen / pH fluctuations in traditional composting.

[0035] Secondly, the three-stage internal circulation of filter press waste liquid as a humidity control carrier, screening residue as a supplementary carbon source, and water washing tower waste liquid as an acid regulator enables 100% resource utilization of desulfurization by-products; the closed crushing and screening equipment and atomized spraying acid agent design effectively avoid the risk of sulfur dust explosion and strong acid contact hazards, and inhibit the high-temperature decomposition side reaction of ammonium sulfate.

[0036] Finally, through a closed-loop design of filter press dehydration purification - fermentation conversion - screening and return, all elemental sulfur in the wet sulfur slurry is converted into organic fertilizer components, eliminating soil acidification and groundwater pollution caused by open-air sulfur slag dumping; the filter press waste liquid is reused for fermentation humidity regulation after sedimentation treatment, and the biogas washing tower waste liquid is used as a natural acid source to replace purchased chemicals, eradicating the cumulative toxicity of complexing agents and strong acids to the surrounding ecosystem. Attached Figure Description

[0037] Figure 1 This is a flowchart of the method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to the present invention.

[0038] Figure 2 This is a mind map of the system architecture for the production of organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization, as described in this invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0040] This invention provides, for example Figure 1 The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization includes the following steps:

[0041] (1) Sulfur cake purification treatment: The wet sulfur cake produced by biogas complex iron desulfurization is mechanically dehydrated by pressure filtration to reduce its moisture content to below 40% and to achieve a sulfur purity of ≥96% in the oven-dried sulfur cake. The sulfur cake purification treatment step further includes mechanical pressure filtration dehydration using a diaphragm filter press. By continuously applying pressure, the wet sulfur cake produced by biogas complex iron desulfurization is compressed and filtered to effectively reduce the overall moisture content of the sulfur cake to meet the moisture content requirements.

[0042] This step also involves sulfur cake crushing and screening, breaking the filtered sulfur cake into smaller particles to ensure uniform sulfur distribution and reaction efficiency in subsequent processing. This crushing process is conducted in a closed environment to prevent sulfur dust from escaping, and the crushing equipment uses specific wear-resistant materials to prevent sulfur contamination, ultimately obtaining oven-dried sulfur cake with the required sulfur purity. Simultaneously, this dewatering operation includes the recycling of filtration waste liquid to reduce overall resource consumption and environmental burden.

[0043] (2) High-temperature aerobic fermentation reaction: The purified sulfur cake obtained in step (1) is placed in a high-temperature aerobic fermentation zone, and the fermentation environment is controlled to be aerobic with an oxygen concentration of ≥10%, and the temperature is regulated; the high-temperature aerobic fermentation reaction step further includes setting up a continuous oxygen supply system in the high-temperature aerobic fermentation zone to ensure that the oxygen in the fermentation environment is maintained at the required concentration level.

[0044] The oxygen supply system maintains good gas diffusion through forced ventilation devices such as fans or compressed air injection equipment, combined with the structural design of the fermentation material, and is dynamically adjusted based on oxygen concentration monitoring feedback; in addition, the temperature control steps involve the integrated application of temperature sensors and heating devices to maintain a suitable temperature environment in the fermentation zone through external heat sources to promote microbial activity.

[0045] The fermentation zone also needs to be equipped with a heat insulation layer to prevent heat loss, and a multi-stage turning device should be set up to turn the material layer regularly during the fermentation process to enhance oxygen penetration and distribute heat and humidity evenly, so as to ensure that the entire reaction area reaches stable high temperature and aerobic conditions.

[0046] The process includes a pre-conditioning step before the high-temperature aerobic fermentation reaction to ensure a balanced nitrogen supply to the system. This pre-conditioning step involves adding appropriate proportions of carbon and nitrogen sources to the purified sulfur cake, with the nitrogen source derived from organic waste or byproducts. The mixture is then uniformly mixed using a mixing device to create a carbon-nitrogen nutrient environment to support fermentation initiation. This step involves temperature pre-conditioning and humidity control in specific equipment to prevent localized over-acidification. Simultaneously, the conditioning process also requires monitoring microbial activity prediction tests to verify nitrogen sufficiency, thereby creating optimal conditions for the subsequent oxidation of elemental sulfur in the sulfur cake and its combination with the nitrogen source. This pre-conditioning operation improves overall conversion efficiency and reduces wasted fermentation time.

[0047] (3) Addition of compound microbial agents: During the high-temperature aerobic fermentation process, a specific proportion of compound microbial agents is added; the compound microbial agents include sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes, which work synergistically; the compound microbial agent addition step further involves the preparation and activation process of a specific proportion of compound microbial agents;

[0048] The process involves separately culturing and propagating sulfur-oxidizing bacteria, organic sulfur-degrading bacteria, and thermophilic actinomycetes before addition, allowing them to reach peak activity in a suitable nutrient medium; then, mixing and compounding each strain in a specific ratio to form a compound microbial agent suspension, ensuring a synergistic effect among the three to improve sulfur dissolution and oxidation efficiency; the addition method includes uniformly spraying the compound microbial agent onto the surface of the high-purity sulfur cake at the beginning of fermentation, and supplementing spraying during the process to maintain the balance of microbial numbers; the amount of compound microbial agent added must be sufficient to cover the surface of the sulfur cake and penetrate into the internal particles, thereby initiating the secretion process of sulfur oxidizing enzyme system and biosurfactants;

[0049] The sulfur conversion efficiency during high-temperature aerobic fermentation is defined by the following formula:

[0050] ηs=α ox ×β AS Where ηs is the sulfur resource utilization rate, referring to the baseline value of the efficiency of converting elemental sulfur into ammonium sulfate; α ox The sulfur oxidation rate refers to the ratio of elemental sulfur in the sulfur cake to sulfate ions, and its range β is defined by material experimental data. AS Ammonium sulfate conversion rate refers to the ratio of sulfate ions generated by oxidation to ammoniacal nitrogen to form ammonium sulfate; the above formula quantifies the overall conversion efficiency of sulfur element from elemental sulfur to the target fertilizer product, providing a core evaluation indicator for process optimization.

[0051] The temperature control process must satisfy a compensation relationship, expressed as:

[0052] L T = k·(ΔT) 2 , where L T is the temperature deviation loss coefficient, reflecting the efficiency decay caused by the actual temperature deviating from the optimal value; k is the process sensitivity constant, determined by the temperature dependence of microbial activity; ΔT is the absolute value of the difference between the actual fermentation temperature Treal and the optimal fermentation temperature Topt, where Topt is set based on the highest efficiency point limited by the material.

[0053] (4) Dynamic pH control: During the high-temperature aerobic fermentation process, the organic acid secreted by the compound microbial agent is combined with the externally added acid regulator to maintain and adjust the pH value of the system; the acid regulator includes the waste liquid generated by the biogas washing tower; the dynamic pH control step further includes the establishment of an automated control system, which integrates an online pH sensor to monitor the acid-base fluctuations of the fermentation system in real time, and connects the acid adjustment pump and the waste liquid storage tank for precise adjustment;

[0054] When the sensor detects that the pH deviates from the set range, the acid adjustment pump automatically sprays the waste liquid produced by the biogas washing tower as an external acid regulator into the fermentation material. This spraying process, together with the turning and turning system, ensures that the acid regulator is evenly mixed. The use of the waste liquid from the biogas washing tower also plays a role in resource recycling and reduces the consumption of additional chemicals. At the same time, the organic acids secreted by the compound microbial agent are used as an internal buffer mechanism to form a dual compound pH control strategy to stabilize the pH within a specific range that inhibits ammonia volatilization and prevents reverse decomposition reactions from occurring.

[0055] In addition, the dynamic pH control step further supplements the use of dilute sulfuric acid as an external acidic regulator. When the supply of waste liquid from the biogas washing tower is insufficient, the acid adjustment system automatically switches to a different concentration. The dilute sulfuric acid is selected and prepared within a suitable concentration range, taking into account its acidification characteristics and safety considerations, to assist in the pH reduction and rapid locking of the fermentation system. During the addition of dilute sulfuric acid, it is necessary to ensure spray atomization and slow infiltration to avoid local over-acidity that could affect the survival of microorganisms. This step includes regular cleaning and corrosion protection measures for the sulfuric acid storage tank to maintain the equipment's lifespan and to ensure that the fermentation material remains in a uniformly acidified state after pH adjustment, which is conducive to the continuous and uninterrupted subsequent sulfur oxidation reaction.

[0056] It should be noted that the pH dynamic control system needs to maintain the following relationship:

[0057] Among them, K pH The pH control factor, with a value range of (0,1], characterizes the effect of pH control precision on nitrogen retention; pH real pH values ​​are acquired by an online sensor for real-time monitoring; pH set The pH reference value is determined based on the critical decomposition point of the material; λ is the buffer capacity constant, which is determined by the acid-base buffering capacity of the system.

[0058] (5) Generation of organic fertilizer: Under the synergistic effect of compound microbial agents and dynamic pH control, the elemental sulfur in the sulfur cake undergoes an oxidation process and combines with the nitrogen source in the system to form organic fertilizer containing ammonium sulfate; the synergistic effect of compound microbial agents is further manifested in the high-temperature aerobic fermentation as a three-stage conversion mechanism, namely the gradual action of dissolution, oxidation and chelation; in the dissolution stage, the organic sulfur-degrading bacteria secrete biosurfactants to reduce the surface tension of sulfur particles and release organic acids to chelate metal ions to enhance sulfur release; in the oxidation stage, the sulfur oxidizing bacteria drive the sulfur oxidase system to carry out the gradual oxidation process of elemental sulfur to produce sulfate ions;

[0059] During the chelation stage, thermophilic actinomycetes secrete siderophores to capture metal ions from sulfides to promote the release of oxidizable sulfur. This mechanism ensures that the collaborative division of labor among microorganisms improves the overall conversion efficiency and bioavailability of sulfur. At the same time, the turning of fermentation materials promotes uniform distribution of microorganisms and conversion of intermediate products.

[0060] In addition, the organic fertilizer production process further includes a stabilization treatment stage after the synergistic effect of compound microbial agents. This stage involves cooling and maturation operations after the high-temperature fermentation ends, i.e., stopping oxygen supply and heating and allowing the material to cool naturally to ambient temperature. During this process, regular ventilation is carried out to remove excess moisture and fix ammonium sulfate crystals. The maturation stage also includes adding trace elements such as calcium and magnesium oxides to improve the strength of fertilizer particles, while removing large particles of sulfur residue that have not been converted through screening equipment. The generated organic fertilizer also needs to be packaged and stored to keep it dry and prevent moisture absorption and degradation. This step finally yields a powdered or granular organic fertilizer product containing ammonium sulfate that can be applied directly.

[0061] In addition, this implementation also proposes, such as Figure 2 The system shown is for the production of organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization. The system is used to implement the above method and includes:

[0062] The desulfurization sulfur pretreatment module includes a diaphragm filter press, a sulfur cake crusher, and screening equipment. It receives the moist sulfur slurry produced during the biogas complex iron desulfurization process, dehydrates it via filter press to produce an oven-dry sulfur cake with a moisture content ≤40% and a sulfur purity ≥96%, and then crushes and screens the sulfur cake to a suitable particle size to ensure uniformity in subsequent fermentation reactions. Byproduct treatment: the filter press waste liquid is recycled to a central treatment tank, and after sedimentation, it is reused for humidity control during fermentation.

[0063] The high-temperature aerobic fermentation conversion module includes an insulated fermentation tank, a forced ventilation oxygen supply system, a turning machine, and a temperature control device. It is used to receive broken sulfur cake and maintain an oxygen concentration of ≥10% through forced ventilation. It integrates a heating device and a sensor for temperature control (50–65℃ range). It is equipped with a multi-shaft agitator turning machine to periodically restructure the material, enhancing oxygen penetration and heat distribution.

[0064] The microbial regulation central module includes a compound microbial agent dosing device, an online pH monitor, an acid adjustment pump, and a dual-source storage tank for waste liquid / dilute sulfuric acid. It is used to add a compound microbial agent of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria, and thermophilic actinomycetes in a specific ratio; monitor the pH of the fermentation system in real time; and automatically switch between biogas washing tower waste liquid or dilute sulfuric acid to adjust the pH to the 6.8±0.2 range. A linked turning machine ensures uniform mixing of the acidic regulator and inhibits the reverse decomposition of ammonium sulfate.

[0065] The fertilizer forming and quality control module includes a maturation chamber, a drying tower, a screening machine, and a packaging line. It is used for cooling and maturation after fermentation, adding calcium and magnesium oxides to enhance particle strength, screening out unconverted sulfur residue, drying with hot air to a suitable moisture content, testing the ammonium sulfate content, and packaging and storing the fertilizer to prevent moisture absorption and degradation.

[0066] The interaction relationships between the above modules are as follows: Figure 2 As shown, specifically:

[0067] Material flow: The pretreatment module outputs purified sulfur cake to the fermentation module; the fermentation module outputs ammonium sulfate crude fertilizer to the molding module; the molding module screens the residue and returns it to the fermentation module to replenish the carbon source;

[0068] Data flow: The temperature / oxygen sensor in the fermentation module transmits real-time data to the control center; the pH sensor in the control center triggers an acid adjustment command, which in turn activates the waste liquid storage tank and the turning machine.

[0069] Resource recycling flow: Pretreatment filter press waste liquid - humidity regulation in fermentation module; acidic waste liquid from biogas washing tower - pH regulator in central control; unconverted sulfur slag from screening - carbon source reuse in fermentation module.

[0070] In summary, this invention, based on the synergistic effect of a compound microbial agent consisting of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria, and thermophilic actinomycetes, significantly enhances the biochemical conversion rate of sulfur to plant-absorbable ammonium sulfate in the oxygen-rich microenvironment created by a multi-axis compost turner. The linkage mechanism of temperature sensor, oxygen supply fan, and acid adjustment pump maintains optimal fermentation conditions in real time, breaking through the bottleneck of microbial activity inhibition caused by temperature / oxygen / pH fluctuations in traditional composting.

[0071] Secondly, the three-stage internal circulation of filter press waste liquid as a humidity control carrier, screening residue as a supplementary carbon source, and water washing tower waste liquid as an acid regulator enables 100% resource utilization of desulfurization by-products; the closed crushing and screening equipment and atomized spraying acid agent design effectively avoid the risk of sulfur dust explosion and strong acid contact hazards, and inhibit the high-temperature decomposition side reaction of ammonium sulfate.

[0072] Finally, through a closed-loop design of filter press dehydration purification - fermentation conversion - screening and return, all elemental sulfur in the wet sulfur slurry is converted into organic fertilizer components, eliminating soil acidification and groundwater pollution caused by open-air sulfur slag dumping; the filter press waste liquid is reused for fermentation humidity regulation after sedimentation treatment, and the biogas washing tower waste liquid is used as a natural acid source to replace purchased chemicals, eradicating the cumulative toxicity of complexing agents and strong acids to the surrounding ecosystem.

[0073] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing organic fertilizer from sulfur resources based on biogas-based iron complexation desulfurization, comprising the following steps: S1. The wet sulfur cake produced by biogas complex iron desulfurization is mechanically dehydrated by pressure filtration to reduce its moisture content to below 40% and make the sulfur purity of the oven-dried sulfur cake reach ≥96%. S2. Place the obtained purified sulfur cake in a high-temperature aerobic fermentation zone, control the fermentation environment to be aerobic with an oxygen concentration ≥10%, and regulate the temperature. S3. During the high-temperature aerobic fermentation process, a specific proportion of compound microbial inoculant is added; the compound microbial inoculant contains sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes, which work synergistically. S4. During the high-temperature aerobic fermentation process, the organic acids secreted by the compound microbial agent, combined with an externally added acidic regulator, are used to maintain and adjust the pH value of the system; the acidic regulator includes waste liquid generated from the biogas washing tower. S5. Under the synergistic effect of the compound microbial agent and dynamic pH control, the elemental sulfur in the sulfur cake undergoes an oxidation process and combines with the nitrogen source in the system to form an organic fertilizer containing ammonium sulfate.

2. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 1, characterized in that, The sulfur cake purification process further includes: A diaphragm filter press is used for mechanical filtration and dehydration. By continuously applying pressure, the wet sulfur cake produced by biogas complex iron desulfurization is compressed and filtered to effectively reduce the overall moisture content of the sulfur cake to meet the required moisture content. This step also involves sulfur cake crushing and screening, breaking the filtered sulfur cake into smaller particle sizes to ensure uniform distribution of sulfur and reaction efficiency in subsequent processing. The crushing process is carried out in a closed environment to prevent sulfur dust from escaping. The crushing equipment is made of a specific wear-resistant material to prevent sulfur contamination, and finally, sulfur cake with the required purity is obtained.

3. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 1, characterized in that, The high-temperature aerobic fermentation zone is equipped with a continuous oxygen supply system to ensure that the oxygen concentration in the fermentation environment is maintained above the required level. This oxygen supply system maintains good gas diffusion through forced ventilation devices such as fans or compressed air injection equipment, combined with the structural design of the fermentation materials, and is dynamically adjusted based on oxygen concentration monitoring feedback.

4. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 1, characterized in that, The specific ratio of compound microbial agent addition process is as follows: 1) Before adding, sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes are cultured and propagated separately to achieve peak activity in a suitable nutrient medium. 2) Then, the various strains are mixed and compounded in a specific ratio to form a compound bacterial agent suspension, and it is ensured that the three have a synergistic effect to improve the efficiency of sulfur dissolution and oxidation. 3) The addition method includes spraying the compound microbial agent evenly on the surface of the high-purity sulfur cake at the beginning of fermentation, and supplementing the spray in the middle to maintain the balance of microbial numbers. 4) The amount of compound microbial agent added should be sufficient to cover the surface of the sulfur cake and penetrate into the internal particles, thereby initiating the secretion process of sulfur oxidase system and biosurfactant.

5. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 1, characterized in that, The pH dynamic control step further supplements the use of dilute sulfuric acid as an external acidic regulator. When the supply of waste liquid from the biogas washing tower is insufficient, the acid adjustment system automatically switches to a different concentration. The dilute sulfuric acid is selected and prepared within a suitable concentration range, taking into account its acidification characteristics and safety considerations, to assist in the pH decrease and rapid locking of the fermentation system.

6. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 3, characterized in that, The sulfur conversion efficiency during the high-temperature aerobic fermentation process is defined by the following formula: ηs=α ox ×β AS Where ηs is the sulfur resource utilization rate, referring to the baseline value of the efficiency of converting elemental sulfur into ammonium sulfate; α ox The sulfur oxidation rate refers to the ratio of elemental sulfur in the sulfur cake to sulfate ions, and its range β is defined by material experimental data. AS Ammonium sulfate conversion rate refers to the ratio of sulfate ions generated by oxidation to ammoniacal nitrogen to form ammonium sulfate; the above formula quantifies the overall conversion path efficiency of sulfur element from elemental sulfur to the target fertilizer product, providing a core evaluation indicator for process optimization.

7. The method for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 3, characterized in that, The temperature control process must satisfy a compensation relationship, expressed as follows: L T = k·(ΔT) 2 , where L T is the temperature deviation loss coefficient, reflecting the efficiency decay caused by the actual temperature deviating from the optimal value; k is the process sensitivity constant, determined by the temperature dependence of microbial activity; ΔT is the absolute value of the difference between the actual fermentation temperature Treal and the optimal fermentation temperature Topt, where Topt is set based on the highest efficiency point limited by the material.

8. The system for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 1, wherein the system is used to implement the method described in any one of claims 1-7, characterized in that, include: The desulfurization sulfur pretreatment module is used to receive the wet sulfur slurry produced in the biogas complex iron desulfurization process, and dehydrate it by pressure filtration to generate an absolutely dry sulfur cake with a moisture content of ≤40% and a sulfur purity of ≥96%. It can also crush and screen the sulfur cake to a suitable particle size to ensure the uniformity of subsequent fermentation reactions. The high-temperature aerobic fermentation conversion module is used for crushing sulfur cake. It maintains an oxygen concentration of ≥10% through forced ventilation, integrates a heating device and sensor for temperature control, and is equipped with a multi-axis agitator to periodically reorganize the material structure, thereby enhancing oxygen penetration and heat distribution. The microbial regulation central module is used to add a compound bacterial agent of sulfur-oxidizing bacteria, organic sulfur-degrading bacteria and thermophilic actinomycetes in a specific ratio. It can also monitor the pH of the fermentation system in real time, automatically switch between biogas water washing tower waste liquid or dilute sulfuric acid to adjust the pH to the range of 6.8±0.2, and at the same time link the turning machine to achieve uniform mixing of acid regulators and inhibit the reverse decomposition of ammonium sulfate. The fertilizer forming and quality control module is used for cooling and maturing after fermentation, adding calcium and magnesium oxides to enhance particle strength, sieving out unconverted sulfur residue, hot air drying to a suitable moisture content, testing ammonium sulfate content, and packaging and storing to prevent moisture degradation.

9. The system for producing organic fertilizer from sulfur resources based on biogas-complexed iron desulfurization according to claim 8, characterized in that, The desulfurization pretreatment module includes a diaphragm filter press dewatering unit, a closed crushing and screening unit, and a waste liquid recovery unit. The diaphragm filter press is configured to continuously pressurize and dewater the wet sulfur slurry produced by biogas complex iron desulfurization to an oven-dry sulfur cake with a moisture content of ≤40%. The closed crushing and screening unit uses wear-resistant materials to avoid sulfur contamination and crushes the sulfur cake to a suitable particle size to ensure uniform fermentation. The waste liquid recovery unit transports the waste liquid produced by the filter press to a central treatment tank for sedimentation. The supernatant after sedimentation is reused for humidity control in the high-temperature aerobic fermentation conversion module. The high-temperature aerobic fermentation conversion module integrates an interactive environmental control chain: the temperature sensor embedded in the insulated fermentation tank and the external heating device work together to maintain a fermentation range of 50–65℃; the forced ventilation oxygen supply system injects air through a fan to ensure an oxygen concentration of ≥10%; the multi-axis agitator turns the material layer according to a preset frequency to enhance gas diffusion in conjunction with the oxygen supply system; this module transmits temperature and oxygen data to the microbial-control center module in real time to drive the dynamic addition of compound bacterial agents and acid regulators.

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