Organic waste treatment and SOFC (solid oxide fuel cell) coupled heat and power cogeneration device system and method

Abstract

The invention provides a combined heat and power device system and method for organic waste treatment and SOFC (Solid Oxide Fuel Cell) coupling, the combined heat and power device system comprises an organic waste pretreatment unit and an anaerobic digestion unit which are connected in sequence, one path of the anaerobic digestion unit is connected with a biogas purification unit and an SOFC combined heat and power unit in sequence, and the other path of the anaerobic digestion unit is connected with a biogas purification unit; the SOFC cogeneration unit comprises an SOFC device and a heat exchange device which are connected in sequence; the other path of the anaerobic digestion unit is connected to the conditioning dehydration unit, the conditioning dehydration unit is respectively connected with the biogas slurry treatment unit and the biogas residue homogenization treatment unit, and the biogas purification unit is connected with the biogas residue homogenization treatment unit. Biogas formed by organic waste treatment is purified and then is subjected to SOFC power generation, and green power is generated; the waste heat of the flue gas after power generation is utilized, so that the energy utilization rate of biogas is increased; products after power generation do not generate pollution; meanwhile, sulfur mud generated by biogas purification and biogas residues are synergistically homogenized and sold as organic fertilizer raw materials, so that the fertilizer efficiency of the biogas residues is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic waste treatment, and particularly relates to a combined heat and power device system and method for organic waste treatment and SOFC coupling. BACKGROUND

[0002] In urban life, the generated organic waste mainly includes kitchen garbage (including catering garbage, household kitchen garbage, and other kitchen garbage), municipal sludge, and urban excrement. The urban organic waste has large production amount, complex composition, high water content, low heat value, and characteristics of easy rotting and odor, and if effective harmless treatment measures are lacked, the ecological environment will be seriously threatened. However, the organic waste contains rich organic matter and has high resource utilization potential.

[0003] At present, the mainstream harmless treatment process of urban organic waste is "pretreatment + anaerobic fermentation + biogas purification and utilization". This process realizes the harmless treatment of organic waste and achieves the goal of resource utilization to some extent. However, the mainstream process still has some problems to be solved:

[0004] (1) Limited resource utilization of biogas residue: The biogas residue produced by anaerobic fermentation contains nutrients such as nitrogen, phosphorus, and potassium (organic matter content of 30%-60%), and has the potential to be used as organic fertilizer raw material. However, the biogas produced by the conventional process has low fertilizer efficiency, high water content of 80%, and problems such as high storage and transportation cost and slow release of fertilizer efficiency when directly applied, resulting in low market acceptance. At present, the biogas residue produced by most organic waste treatment projects is directly sent to the incineration plant or landfill site for harmless treatment by paying disposal fees, which significantly increases the operation cost of the project.

[0005] (2) Efficiency and pollution of biogas power generation: In terms of biogas purification and utilization, the mainstream way is to drive the biogas generator to generate electricity after the biogas produced by anaerobic fermentation is desulfurized, impurity-removed, and pressure-increased. The generated electricity is usually self-used, and the excess part is sold on the grid. However, the power generation efficiency of the biogas generator is only 38%-45%, and more than 50% of the energy is lost in the form of waste heat, which fails to realize energy cascade utilization; the biogas needs to be treated by impurity removal, pressure increase, and cold and dry dehydration before entering the generator, which requires high energy consumption; in addition, the biogas generator produces a large amount of nitrogen oxides (NOx) at high temperature, with a concentration of about 500 mg / Nm 3 (benchmark oxygen content 5%), causing secondary pollution.

[0006] For example, CN114891623A discloses a biological treatment system for organic waste, which includes: a pretreatment feeding module, an anaerobic biological treatment module, a solid-liquid separation module, an aerobic biological treatment module, and a biogas power generation module. The aerobic biological treatment module processes the biogas residue into organic fertilizer; and the biogas power generation module generates electricity from biogas to power the various modules of the system. CN119390494A discloses an integrated method for efficient simultaneous co-fermentation and cogeneration technology of organic waste, which uses biogas and urban natural gas as raw materials to drive a gas turbine to generate electricity, and directly composts the biogas residue aerobically.

[0007] However, the above-mentioned methods for treating organic waste still suffer from problems such as high energy consumption, insufficient biogas energy utilization efficiency, and insufficient resource utilization of biogas residue. Summary of the Invention

[0008] The purpose of this invention is to provide a combined heat and power system and method for organic waste treatment coupled with SOFC, thereby improving the energy efficiency of biogas utilization and the resource utilization efficiency of biogas residue in organic waste treatment.

[0009] To achieve this objective, the present invention employs the following technical solution:

[0010] In a first aspect, the present invention provides a combined heat and power (CHP) system for organic waste treatment coupled with SOFC, the CHP system comprising:

[0011] An organic waste pretreatment unit and an anaerobic digestion unit are connected in sequence. The biogas pipeline of the anaerobic digestion unit is connected in sequence to a biogas purification unit and an SOFC cogeneration unit. The SOFC cogeneration unit includes an SOFC device and a heat exchange device connected in sequence. The digestate pipeline of the anaerobic digestion unit is connected to a conditioning and dehydration unit. The conditioning and dehydration unit is connected to a biogas slurry treatment unit and a biogas residue homogenization treatment unit. The biogas purification unit and the biogas residue homogenization treatment unit are connected.

[0012] The device system provided by this invention utilizes an organic waste pretreatment unit and an anaerobic digestion unit to treat organic waste into biogas. Through hydrolysis and acidification, the large organic molecules are broken down into smaller organic molecules such as organic acids. Then, after anaerobic fermentation, the organic matter is further decomposed into components such as carbon dioxide, methane, and water, forming biogas and digestate, respectively. The biogas is then desulfurized by a biogas purification unit and used as anode fuel for SOFC (Solid Oxide Fuel Cell) to generate electricity, converting the energy of biogas into green electricity. Compared with conventional biogas generators, it has a higher energy utilization rate and improves the power generation efficiency of biogas. The flue gas produced after biogas utilization does not contain pollutants such as nitrogen oxides or sulfides and can be directly discharged without wastewater or noise pollution. The flue gas is then processed through a heat exchange device to utilize waste heat, achieving secondary heat recovery and thus improving the energy utilization rate of biogas. On the other hand, the treatment of organic waste also produces digestive liquid. After being processed by the conditioning and dehydration unit, the digestive liquid forms biogas slurry and biogas residue respectively. Biogas purification also produces biological sulfur mud. Connecting the biogas purification unit and the biogas residue homogenization unit allows the biological sulfur mud produced by desulfurization to be homogenized together with the biogas residue. The two work synergistically, so that the biogas residue can be directly used as a raw material for organic fertilizer. The biogas residue can help the sulfur mud component fix sulfur and supplement the biogas residue with sulfur elements, accurately making up for the sulfur deficiency in the soil, forming a "organic matter-sulfur-nitrogen-phosphorus-potassium" synergistic fertilizer supply system to make up for the sulfur deficiency in the soil. Compared with single chemical sulfur fertilizers (such as ammonium sulfate), the organic matter in this compound fertilizer can promote the slow release of sulfur elements, reduce leaching, and increase the utilization rate of sulfur fertilizer by 20% to 30%, greatly improving fertilizer efficiency. At the same time, sulfur mud and biogas residue organic matter can coordinate to improve the soil aggregate structure, achieving the dual effect of "fertilizer efficiency + soil improvement". Furthermore, compared to treating sulfur mud and biogas residue as solid waste, this method transforms "double waste" into "double benefit," simultaneously enhancing the resource utilization of sulfur mud and biogas residue.

[0013] Preferably, the organic waste pretreatment unit includes a waste removal device, a crushing and pulping device, a heating and oil extraction device, and a sand removal device connected in sequence.

[0014] Preferably, the anaerobic digestion unit includes a hydrolysis acidification device and an anaerobic fermentation device connected in sequence.

[0015] Preferably, in the anaerobic digestion unit, a digestive fluid storage device can be connected after the anaerobic fermentation device for storing the digestive fluid.

[0016] Preferably, the biogas purification unit includes at least a biological desulfurization device, a biogas impurity removal device, and a biogas booster device connected in sequence.

[0017] Preferably, the biogas purification unit further includes a dry desulfurization device, which is located after the biological desulfurization device along the material flow direction.

[0018] In the biogas purification unit, a biological desulfurization device is installed to remove hydrogen sulfide from the biogas, reducing its concentration to below 5 ppm. If the biological desulfurization does not achieve the target hydrogen sulfide concentration, a cold drying and dehydration device and a dry fine desulfurization device can be connected after the biological desulfurization device for further deep removal of hydrogen sulfide. The sulfur sludge produced after desulfurization can improve the fertilizer efficiency of the biogas residue. Simultaneously, the deep purification of sulfide components in the biogas facilitates the utilization of biogas as fuel in subsequent processes and reduces pollutant emissions.

[0019] Biogas impurity removal devices and biogas pressurization devices are used to remove dust from biogas and pressurize it for use as battery fuel.

[0020] Preferably, the biogas purification unit further includes a biogas temporary storage device, which is located before the biological desulfurization device along the material flow direction and is used for biogas storage.

[0021] Preferably, the biological desulfurization device in the biogas purification unit is connected to the biogas residue homogenization treatment unit.

[0022] Preferably, the conditioning and dehydration unit includes a digestion fluid conditioning device and a high-pressure diaphragm filter press connected in sequence.

[0023] The digestate produced is conditioned with a conditioning agent in the conditioning device, and then deeply dehydrated using a high-pressure diaphragm filter press. High-pressure diaphragm filter press can reduce the moisture content of the biogas residue to below 65%. Controlling the moisture content of the biogas residue can improve the homogenization effect of the biogas residue and enhance its fertilizer efficiency.

[0024] Preferably, the high-pressure diaphragm filter press is connected to the anaerobic digestion unit.

[0025] After high-pressure diaphragm filtration, biogas residue and biogas slurry are produced respectively. The biogas slurry is recycled for the hydrolysis and acidification process of organic waste. The alkalinity of the biogas slurry is used to control the pH of the hydrolysis and acidification process, thereby improving the hydrolysis rate of organic matter.

[0026] In a second aspect, the present invention provides a combined heat and power (CHP) method for organic waste treatment coupled with SOFC, wherein the CHP method uses the combined heat and power device system for organic waste treatment coupled with SOFC described in the first aspect.

[0027] Preferably, the combined heat and power method includes the following steps:

[0028] (1) Pre-treat organic waste to form a slurry;

[0029] (2) The slurry is subjected to an anaerobic digestion process to form biogas and digestate;

[0030] (3) The biogas is purified to form clean biogas and sulfur sludge is produced. The clean biogas is fed into an SOFC device as anode fuel for power generation. The flue gas generated after power generation is heat exchanged to complete the waste heat utilization.

[0031] (4) The digestive liquid is successively conditioned and dehydrated to form biogas residue and biogas slurry, respectively;

[0032] (5) The sulfur mud and biogas residue are homogenized to form organic fertilizer raw materials; the biogas slurry is treated to meet the discharge standards;

[0033] Steps (3) and (4) are not in any particular order.

[0034] Preferably, the particle size of the slurry in step (1) is ≤10mm, for example, it can be 1mm, 3mm, 5mm, 6mm, 8mm or 10mm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the total solids (TS) of the slurry in step (1) is 6%-15%, for example, it can be 6%, 8%, 10%, 12%, 13% or 15%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the oil content of the slurry in step (1) is ≤1%, for example, it can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9% or 1%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the anaerobic digestion in step (2) includes sequential hydrolysis acidification and anaerobic fermentation.

[0038] Preferably, the hydrolysis acidification temperature is 35-38°C, for example, it can be 35°C, 35.5°C, 36°C, 36.5°C, 37°C or 38°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, the pH of the hydrolysis acidification is controlled at 5-6, for example, it can be 5, 5.2, 5.4, 5.6, 5.8 or 6, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the combined heat and power method further includes: recirculating the biogas slurry for hydrolysis and acidification, and performing pH control.

[0041] In this invention, after a portion of the produced biogas slurry is recycled for pH adjustment, the remaining biogas slurry enters the downstream biogas slurry treatment process and is discharged after reaching the required standards. In the hydrolysis acidification process, the biogas slurry and sodium hydroxide (NaOH) can be added together to achieve pH adjustment.

[0042] Preferably, the hydraulic retention time of the hydrolysis acidification is ≥2.5 days, for example, it can be 2.5 days, 4 days, 5.5 days, 7 days, 8.5 days or 10 days, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the temperature of the anaerobic fermentation is 35-38℃, for example, it can be 35℃, 35.5℃, 36℃, 36.5℃, 37℃ or 38℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, in the anaerobic fermentation, the total solids content (TS) of the material is 2%-4%, for example, it can be 2%, 2.5%, 3%, 3.3%, 3.7% or 4%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, in the anaerobic fermentation, the ratio of volatile solids (VS) to total solids (TS) of the material is ≤55%, for example, it can be 30%, 35%, 40%, 45%, 50% or 55%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, in the anaerobic fermentation, the volatile fatty acid content (VFA) of the material is ≤1000ppm, for example, it can be 800ppm, 850ppm, 900ppm, 920ppm, 960ppm or 1000ppm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the hydraulic retention time of the anaerobic fermentation is ≥30 days, for example, it can be 30 days, 32 days, 34 days, 36 days, 38 days or 40 days, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, the purification in step (3) includes at least biological desulfurization, biogas impurity removal and biogas pressurization performed sequentially.

[0049] Preferably, the biological desulfurization adopts an alkaline desulfurization method.

[0050] Preferably, the temperature for biological desulfurization is 32-38°C, for example, 32°C, 33°C, 34°C, 35°C, 36°C or 38°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Preferably, the pH of the biological desulfurization is 7.8-9.0, for example, it can be 7.8, 8.0, 8.3, 8.5, 8.7 or 9.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, in the biological desulfurization, the redox potential of the reaction system is -340mV to -390mV, for example, it can be -340mV, -355mV, -370mV, -375mV, -380mV or -390mV, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, in the biological desulfurization, the conductivity of the reaction system is 45-60 mS / cm, for example, it can be 45 mS / cm, 48 mS / cm, 52 mS / cm, 55 mS / cm, 58 mS / cm or 60 mS / cm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] The reaction system refers to the sum of all materials involved in biological desulfurization.

[0055] Preferably, the purification further includes: after the biological desulfurization, performing dry fine desulfurization.

[0056] Preferably, the desulfurizing agent in the dry desulfurization process includes ferric oxide.

[0057] Preferably, the temperature of the dry desulfurization process is 15-45℃, for example, it can be 15℃, 20℃, 25℃, 30℃, 35℃, 40℃ or 45℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, the biogas space velocity in the dry desulfurization process is 1000-3000 h⁻¹. -1 For example, it could be 1000h -1 1500h -1 2000h -1 2500h -1 or 3000h -1 However, this does not apply to all values ​​listed; other unlisted values ​​within the same range also apply.

[0059] Preferably, the biogas purification process includes at least three stages of filtration.

[0060] Preferably, the accuracy of the last stage of filtration is ≤1μm.

[0061] Preferably, before being introduced into the SOFC device, the clean biogas meets the following requirements: hydrogen sulfide concentration in the clean biogas ≤ 5 ppm, solid particulate content in the clean biogas < 1 ppm, and pressure of the clean biogas ≥ 0.5 kPa.

[0062] When biogas is fed into an SOFC unit for SOFC power generation, the biogas must be purified to meet the above conditions in order to ensure the smooth operation of the SOFC unit.

[0063] The concentration of hydrogen sulfide in the clean biogas is ≤5ppm, for example, it can be 1ppm, 2ppm, 3ppm, 4ppm or 5ppm, but it is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0064] Among them, the solid particulate content in clean biogas is <1ppm, for example, it can be 0.1ppm, 0.3ppm, 0.5ppm, 0.6ppm, 0.8ppm or 0.9ppm, but it is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0065] The pressure of the clean biogas is ≥0.5 kPa, for example, it can be 0.5 kPa, 0.9 kPa, 1.3 kPa, 1.6 kPa, 1.8 kPa or 2 kPa, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0066] Preferably, the temperature of the flue gas in step (3) is 120-150°C, for example, it can be 120°C, 125°C, 130°C, 140°C, 145°C or 150°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] In step (3), after the flue gas is heated, the heat from the heat exchange can be used to heat the water to produce hot water at a temperature of 60°C or higher. The hot water can be used to heat the oil extraction process in the pretreatment of organic waste.

[0068] Preferably, the conditioning agents used in step (4) include inorganic conditioning agents and / or organic conditioning agents.

[0069] Preferably, the inorganic conditioner includes ferric chloride.

[0070] Preferably, the amount of ferric chloride used is 3%-6% of the oven-dry weight of the digestion solution, for example, it can be 3%, 4%, 5% or 6%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0071] Preferably, the concentration of the ferric chloride used is 30%-38%, for example, it can be 30%, 32%, 34%, 35%, 36% or 38%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] Preferably, the organic conditioner includes polyacrylamide (PAM).

[0073] Preferably, the amount of polyacrylamide used is 0.3%-0.6% of the oven-dry weight of the digestion solution, for example, it can be 0.3%, 0.4%, 0.5% or 0.6%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] Preferably, the concentration of the polyacrylamide used is 1‰-2‰, for example, it can be 1‰, 1.2‰, 1.4‰, 1.6‰, 1.8‰ or 2‰, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] Preferably, the dehydration in step (4) is carried out by high-pressure diaphragm filtration.

[0076] Preferably, the moisture content of the biogas residue in step (4) is ≤65%, for example, it can be 30%, 38%, 46%, 54%, 60% or 65%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] The combined heat and power (CHP) device system and method of the present invention desulfurizes biogas generated from organic waste treatment and uses it for SOFC power generation, and utilizes the waste heat of the flue gas after power generation to improve the energy utilization rate of biogas. Furthermore, the products generated by SOFC power generation do not produce pollution and can be directly discharged, and the energy consumption of biogas pretreatment is low. At the same time, the sulfur sludge produced by biogas desulfurization is synergistically homogenized with the biogas residue formed by organic waste to improve the fertilizer effect of biogas residue and improve the resource utilization efficiency of biogas residue. Attached Figure Description

[0079] Figure 1 This is a schematic diagram of the combined heat and power system of organic waste treatment and SOFC coupling in Example 1;

[0080] The system includes: 1. Pretreatment unit; 2. Hydrolysis acidification device; 3. Anaerobic fermentation device; 4. Biological desulfurization device; 5. Biogas impurity removal device; 6. Biogas pressurization device; 7. SOFC device; 8. Heat exchange device; 9. Digestive liquid conditioning device; 10. High-pressure diaphragm filter press; 11. Biogas residue homogenization treatment unit; and 12. Biogas slurry treatment unit.

[0081] Figure 2 This is a process flow diagram of the combined heat and power method for organic waste treatment coupled with SOFC in Example 1. Detailed Implementation

[0082] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0083] This invention provides a combined heat and power (CHP) system for organic waste treatment coupled with SOFC, the CHP system comprising:

[0084] The organic waste pretreatment unit and the anaerobic digestion unit are connected in sequence, and the biogas pipeline of the anaerobic digestion unit is connected in sequence to the biogas purification unit and the SOFC combined heat and power unit.

[0085] The organic waste pretreatment unit includes a purification device, a crushing and pulping device, a heating and oil extraction device, and a sand removal device connected in sequence. These devices are used to remove impurities, crush and pulp, extract oil, and remove sand from organic waste to form a slurry, which is then used in subsequent processes to produce biogas, biogas slurry, and biogas residue.

[0086] The anaerobic digestion unit comprises a hydrolysis acidification device and an anaerobic fermentation device connected in sequence. The hydrolysis acidification device hydrolyzes and acidifies the slurry. During this process, the biodegradation action of hydrolysis acidification bacteria breaks down the large organic molecules in the raw material, converting them into organic acids and other smaller organic molecules, providing the necessary conditions for subsequent efficient anaerobic fermentation to produce biogas. The hydrolysis acidification device typically uses a hydrolysis acidification tank, which is conventional equipment in the field, and its structure is not specifically limited. The anaerobic fermentation device performs anaerobic fermentation on the hydrolyzed and acidified slurry. During anaerobic fermentation, anaerobic microorganisms decompose organic matter into carbon dioxide, methane, and water, ultimately forming biogas and digestate. The anaerobic fermentation device typically uses an anaerobic fermentation tank, equipped with a vertical mixer to ensure uniform material distribution within the tank. This is also conventional equipment in the field, and its structure is not specifically limited.

[0087] The biogas purification unit comprises at least a biological desulfurization unit, a biogas impurity removal unit, and a biogas pressurization unit connected in sequence. The biological desulfurization unit removes hydrogen sulfide (H2S) from the biogas under the action of microorganisms and converts it into biological sulfur sludge containing elemental sulfur. The biological desulfurization unit can be an absorption tower and a bioreactor based on an alkaline biological scrubbing method. The biogas impurity removal unit and the biogas pressurization unit filter out solid particles from the desulfurized biogas and pressurize it, so that it can be used for subsequent SOFC power generation. The biogas impurity removal unit is equipped with at least three stages of filters, with the filtration accuracy increasing sequentially along the gas flow direction, and the accuracy of the last stage ≤1μm. After treatment by the biogas purification unit, clean biogas is finally obtained. The biological desulfurization unit, the biogas impurity removal unit, and the biogas pressurization unit use conventional equipment in the art, and their structures are not specifically limited. Preferably, if the biogas fails to reach the target hydrogen sulfide concentration after passing through the biological desulfurization device, a cold drying dewatering device and a dry fine desulfurization device are connected after the biological desulfurization device to further remove hydrogen sulfide from the biogas.

[0088] The SOFC combined heat and power unit comprises an SOFC (Solid Oxide Fuel Cell) device and a heat exchanger connected in sequence. Clean biogas is introduced into the anode fuel inlet of the SOFC device, where an electrochemical reaction occurs, converting the chemical energy of the biogas into electrical energy to generate electricity, producing green electricity. The flue gas generated after power generation then enters the heat exchanger for waste heat utilization, which can produce hot water. The SOFC device and heat exchanger use conventional equipment in the art, and their structure is not specifically limited.

[0089] The digestion liquid pipeline of the anaerobic digestion unit is connected to the conditioning and dehydration unit, and the conditioning and dehydration unit is connected to the biogas residue homogenization treatment unit and the biogas slurry treatment unit respectively.

[0090] The conditioning and dehydration unit includes a digestate conditioning device and a high-pressure diaphragm filter press connected in sequence. The digestate conditioning device is used to add conditioning agents to the digestate for conditioning, sedimentation of suspended solids, and adjustment of water quality for the next step of filtration. The high-pressure diaphragm filter press is used to filter and dehydrate the conditioned digestate to obtain biogas slurry and biogas residue; the high-pressure diaphragm filter press has an elastic diaphragm, which can effectively reduce the water content in the biogas residue, facilitating subsequent processing and utilization.

[0091] The high-pressure diaphragm filter press is connected to the hydrolysis acidification unit, and the generated biogas slurry is recycled for pH control during the hydrolysis acidification process. Using the recycled biogas slurry can effectively improve the hydrolysis acidification rate. The remaining biogas slurry is sent to the biogas slurry treatment unit, where it is treated to meet standards before being discharged.

[0092] The biogas residue homogenization unit is connected to the biological desulfurization device in the biogas purification unit. The biogas residue produced by the high-pressure diaphragm filter press is transported to the biogas residue homogenization unit, where the biosulfur sludge produced by biological desulfurization is mixed and homogenized with the biogas residue. By utilizing the interaction between the biogas residue and the sulfur sludge, the nutrients in the biogas residue are supplemented, the fertilizer efficiency of the biogas residue is improved, and organic fertilizer raw materials can be directly formed.

[0093] This invention provides a combined heat and power (CHP) method for organic waste treatment coupled with SOFC, using the aforementioned CHP system for organic waste treatment coupled with SOFC. The CHP method includes the following steps:

[0094] (1) The organic waste is pretreated in the pretreatment unit to form a slurry, and the solid content of the slurry is controlled to be 6%-15%, the oil content is ≤1%, and the particle size is ≤10mm;

[0095] (2) The slurry is transported to the hydrolysis acidification device and the anaerobic fermentation device, and hydrolysis acidification and anaerobic fermentation are carried out in sequence. In the hydrolysis acidification, the temperature is controlled at 35-38℃, the pH is 5-6, and the hydraulic retention time is ≥2.5 days. In the anaerobic fermentation, the temperature is controlled at 35-38℃, the solid content (TS) of the material is 2%-4%, VS / TS≤55%, VFA≤1000ppm, and the hydraulic retention time is ≥30 days. After the completion, biogas and digestate are obtained respectively.

[0096] (3) The biogas is subjected to biological desulfurization in a biological desulfurization device. The biological desulfurization adopts alkaline desulfurization. In the biological desulfurization, the temperature is controlled at 32-38℃, the pH is 7.8-9.0, the oxidation-reduction potential of the reaction system is -340mV to -390mV, and the conductivity of the reaction system is 45-60mS / cm, so that the hydrogen sulfide concentration in the desulfurized biogas reaches below 5ppm and sulfur sludge is obtained. The desulfurized biogas is filtered and impurities are removed at least three times until the solid particle content is <1ppm. Then it is pressurized to a pressure ≥0.5kPa to obtain clean biogas. The clean biogas is fed into the anode fuel inlet of the SOFC device to generate electricity. After generating electricity, flue gas at 120-150℃ is generated. The flue gas is transported to a heat exchange device for heat exchange and waste heat utilization. The heat exchange generates hot water at 60℃ or above. The hot water is reused for oil extraction and heating in the pretreatment of organic waste. The flue gas after heat exchange is directly discharged.

[0097] (4) The digestate is successively processed and dehydrated by a digestate conditioning device and a high-pressure diaphragm filter press. During the conditioning, a 30%-38% ferric chloride solution and a 1‰-2‰ polyacrylamide (PAM) solution are added. The amount of ferric chloride is 3%-6% of the dry weight of the digestate, and the amount of polyacrylamide is 0.3%-0.6% of the dry weight of the digestate. After conditioning and dehydration, biogas slurry and biogas residue are obtained respectively. The water content of the biogas residue is ≤65%. The biogas slurry is recycled to hydrolysis acidification for pH control. The remaining biogas slurry is discharged after being treated to meet the standards.

[0098] (5) The sulfur mud produced by biological desulfurization is mixed and homogenized with the biogas residue in the biogas residue homogenization treatment unit to form organic fertilizer raw materials.

[0099] Example 1

[0100] This embodiment provides a method such as Figure 1 The illustrated combined heat and power (CHP) system for organic waste treatment coupled with SOFC includes:

[0101] The system comprises a pretreatment unit 1, an anaerobic digestion unit, a biogas purification unit, an SOFC cogeneration unit, a conditioning and dehydration unit, a biogas residue homogenization treatment unit 11, and a biogas slurry treatment unit 12. The anaerobic digestion unit includes a hydrolysis acidification device 2 and an anaerobic fermentation device 3. The biogas purification unit includes a biological desulfurization device 4, a biogas impurity removal device 5, and a biogas pressurization device 6. The SOFC cogeneration unit includes an SOFC device 7 and a heat exchange device 8. The conditioning and dehydration unit includes a digestate conditioning device 9 and a high-pressure diaphragm filter press 10.

[0102] The pretreatment unit 1, the hydrolysis acidification unit 2, and the anaerobic fermentation unit 3 are connected in sequence. The biogas pipeline of the anaerobic fermentation unit 3 is connected in sequence to the biological desulfurization unit 4, the biogas impurity removal unit 5, the biogas pressurization unit 6, the SOFC unit 7, and the heat exchange unit 8. The digestate pipeline of the anaerobic fermentation unit 3 is connected in sequence to the digestate conditioning unit 9 and the high-pressure diaphragm filter press 10. The biogas residue pipeline of the high-pressure diaphragm filter press 10 is connected to the biogas residue homogenization treatment unit 11, and the biogas slurry pipeline of the high-pressure diaphragm filter press 10 is connected to the biogas slurry treatment unit 12. The biological desulfurization unit 4 is connected to the biogas residue homogenization treatment unit 11. The hydrolysis acidification unit 2 is connected to the high-pressure diaphragm filter press 10 through the biogas slurry pipeline.

[0103] This embodiment provides a method such as Figure 2 The illustrated cogeneration method for organic waste treatment coupled with SOFC utilizes the aforementioned cogeneration system, and the cogeneration method includes the following steps:

[0104] (1) Using kitchen waste as organic waste, the organic waste is pre-treated in the pre-treatment unit, including impurity removal, crushing and pulping, oil extraction and sand removal, to form a slurry. The solid content of the slurry is controlled to be 10%, the oil content to be 1%, and the particle size to be ≤10mm.

[0105] (2) The slurry is transported to the hydrolysis acidification device and the anaerobic fermentation device, and hydrolysis acidification and anaerobic fermentation are carried out in sequence. During the hydrolysis acidification process, the temperature is controlled in the range of 35-38℃, the pH of the material is controlled in the range of 5-6, and the hydraulic retention time is controlled in the range of 3 days. During the anaerobic fermentation process, the temperature is controlled in the range of 35-38℃, the solid content (TS) of the material is maintained in the range of 2%-4%, the VS / TS is maintained in the range of 55%, the VFA is maintained in the range of 1000ppm, and the hydraulic retention time is controlled in the range of 30 days. After the process, biogas and digestate are obtained respectively.

[0106] (3) The biogas is subjected to biological desulfurization in a biological desulfurization device. The biological desulfurization adopts alkaline desulfurization. During the biological desulfurization process, the temperature is controlled in the range of 32-38℃, the pH of the material is in the range of 7.8-9.0, the redox potential of the reaction system is in the range of -340mV to -390mV, and the conductivity of the reaction system is in the range of 45-60mS / cm. Finally, clean biogas with a hydrogen sulfide concentration ≤5ppm is obtained, and sulfur sludge is obtained. The clean biogas is subjected to at least three stages. The filtration process removes impurities, with each stage having a filtration precision of 50μm, 3μm, and 1μm, until the solid particle content is <1ppm. The gas is then pressurized to 0.5kPa and the clean biogas is fed into the anode fuel inlet of the SOFC unit for reaction and power generation. The flue gas generated after power generation is at 120-150℃. The flue gas is then transported to a heat exchanger for waste heat utilization, which can generate hot water at a temperature above 60℃. The hot water is reused to heat the oil extraction process in the pretreatment of organic waste. The flue gas after heat exchange is then directly discharged.

[0107] (4) The digestate is successively processed and dehydrated by a digestate conditioning device and a high-pressure diaphragm filter press. During the conditioning process, a 35% ferric chloride solution and a 1.5‰ polyacrylamide (PAM) solution are added. The amount of ferric chloride added is 5% of the dry weight of the digestate, and the amount of polyacrylamide added is 0.5% of the dry weight of the digestate. After conditioning and dehydration, biogas slurry and biogas residue are obtained respectively. The water content of the biogas residue is 65%. The biogas slurry is recycled to hydrolysis acidification for pH control. The remaining biogas slurry is treated in the biogas slurry treatment unit to meet the standards before being discharged.

[0108] (5) The sulfur mud produced by biological desulfurization is mixed and homogenized with the biogas residue in the biogas residue homogenization treatment unit to form organic fertilizer raw materials.

[0109] In this invention, the biogas produced contains approximately 60% methane. The biogas is used to generate electricity via SOFC (Sodium Carbonate Fuel Cell), with the SOFC achieving a power generation efficiency of approximately 60% per Nm³. 3 Biogas can generate approximately 3 kWh of electricity, improving its power generation efficiency. Testing shows that the hydrogen sulfide content in the biogas is ≤5 ppm, and the nitrogen oxide (NOx) content in the flue gas produced after power generation is below 5 ppm, indicating extremely low pollutant content. The power generation byproduct is water, all of which can be directly discharged. Furthermore, compared to conventional biogas generators, the biogas does not require cold drying and dehydration before power generation; only low-pressure pressurization is needed, significantly reducing energy consumption. After power generation, approximately 30% of the heat from the flue gas can be recovered through waste heat utilization, further improving the energy utilization rate of the biogas. The resulting biogas residue has a moisture content of less than 65%. After homogenization with sulfur mud, the composition of the biogas residue is adjusted, and sulfur elements are supplemented, forming a synergistic fertilizer supply system of "organic matter-sulfur-nitrogen-phosphorus-potassium." Organic matter promotes the slow release of sulfur elements, reducing leaching and increasing sulfur fertilizer utilization by 20%~30%, significantly improving the fertilizer efficiency of the biogas residue. The resulting organic fertilizer raw materials can also coordinately improve soil aggregate structure.

[0110] In summary, the combined heat and power (CHP) system and method of the present invention purifies the biogas generated from the treatment of organic waste and then uses it for SOFC power generation to produce green electricity; it also utilizes the waste heat of the flue gas after power generation to improve the energy utilization rate of biogas and reduce the overall energy consumption of the project; and the products after power generation do not produce pollution and can be directly discharged; at the same time, the sulfur mud and biogas residue generated from biogas purification are co-homogenized and sold as raw materials for organic fertilizer, thereby improving the fertilizer efficiency of biogas residue.

[0111] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A combined heat and power (CHP) system for organic waste treatment coupled with SOFC, characterized in that, The combined heat and power system includes: An organic waste pretreatment unit and an anaerobic digestion unit are connected in sequence. The biogas pipeline of the anaerobic digestion unit is connected in sequence to a biogas purification unit and an SOFC cogeneration unit. The SOFC cogeneration unit includes an SOFC device and a heat exchange device connected in sequence. The digestate pipeline of the anaerobic digestion unit is connected to a conditioning and dehydration unit. The conditioning and dehydration unit is connected to a biogas slurry treatment unit and a biogas residue homogenization treatment unit. The biogas purification unit and the biogas residue homogenization treatment unit are connected.

2. The combined heat and power (CHP) system according to claim 1, characterized in that, The organic waste pretreatment unit includes a waste removal device, a crushing and pulping device, a heating and oil extraction device, and a sand removal device connected in sequence.

3. The combined heat and power (CHP) system according to claim 1 or 2, characterized in that, The anaerobic digestion unit includes a hydrolysis acidification device and an anaerobic fermentation device connected in sequence.

4. The combined heat and power (CHP) system according to any one of claims 1-3, characterized in that, The biogas purification unit includes at least a biological desulfurization device, a biogas impurity removal device, and a biogas booster device connected in sequence. Preferably, the biogas purification unit further includes a dry desulfurization device.

5. The combined heat and power (CHP) system according to claim 4, characterized in that, The biogas purification unit is connected to the biogas residue homogenization treatment unit.

6. The combined heat and power (CHP) system according to any one of claims 1-5, characterized in that, The conditioning and dehydration unit includes a digestion liquid conditioning device and a high-pressure diaphragm filter press connected in sequence. Preferably, the high-pressure diaphragm filter press is connected to the anaerobic digestion unit.

7. A combined heat and power (CHP) method for organic waste treatment coupled with SOFC, characterized in that, The combined heat and power (CHP) method uses the combined heat and power (CHP) device system of organic waste treatment coupled with SOFC as described in any one of claims 1-6, and the CHP method includes the following steps: (1) Pre-treat organic waste to form a slurry; (2) The slurry is subjected to an anaerobic digestion process to form biogas and digestate; (3) The biogas is purified to form clean biogas and sulfur sludge is produced. The clean biogas is fed into an SOFC device as anode fuel for power generation. The flue gas generated after power generation is heat exchanged to complete the waste heat utilization. (4) The digestive liquid is successively conditioned and dehydrated to form biogas residue and biogas slurry; (5) The sulfur mud and biogas residue are homogenized to form organic fertilizer raw materials; the biogas slurry is treated to meet the discharge standards; Steps (3) and (4) are not in any particular order.

8. The combined heat and power method according to claim 7, characterized in that, The particle size of the slurry in step (1) is ≤10mm; Preferably, the solids content of the slurry in step (1) is 6%-15%; Preferably, the oil content of the slurry in step (1) is ≤1%; Preferably, the anaerobic digestion in step (2) includes sequential hydrolysis acidification and anaerobic fermentation; Preferably, the hydrolysis and acidification temperature is 35-38°C; Preferably, the pH of the hydrolysis acidification is controlled at 5-6; Preferably, the combined heat and power method further includes: recirculating the biogas slurry for hydrolysis and acidification, and performing pH control; Preferably, the hydraulic retention time for hydrolysis and acidification is ≥2.5 days; Preferably, the temperature for the anaerobic fermentation is 35-38℃; Preferably, in the anaerobic fermentation, the solid content of the material is 2%-4%; Preferably, in the anaerobic fermentation, the ratio of volatile solids content to total solids content is ≤55%; Preferably, in the anaerobic fermentation, the volatile fatty acid content of the material is ≤1000ppm; Preferably, the hydraulic retention time of the anaerobic fermentation is ≥30 days.

9. The combined heat and power method according to any one of claims 6-8, characterized in that, The purification process in step (3) includes at least the sequential biological desulfurization, biogas impurity removal, and biogas pressurization. Preferably, the biological desulfurization adopts an alkaline desulfurization method; Preferably, the temperature for biological desulfurization is 32-38℃; Preferably, the pH of the biological desulfurization process is 7.8-9.0; Preferably, in the biological desulfurization, the redox potential of the reaction system is -340mV to -390mV; Preferably, in the biological desulfurization, the electrical conductivity of the reaction system is 45-60 mS / cm; Preferably, the purification further includes: after the biological desulfurization, performing dry fine desulfurization; Preferably, the desulfurizing agent in the dry desulfurization process includes ferric oxide; Preferably, the temperature of the dry desulfurization process is 15-45℃; Preferably, the biogas space velocity in the dry desulfurization process is 1000-3000 h⁻¹. -1 ; Preferably, the biogas purification process includes at least three stages of filtration; Preferably, the accuracy of the last stage of filtration is ≤1μm; Preferably, before being introduced into the SOFC device, the clean biogas meets the following requirements: hydrogen sulfide concentration in the clean biogas ≤ 5 ppm, solid particulate content in the clean biogas < 1 ppm, and pressure of the clean biogas ≥ 0.5 kPa; Preferably, the temperature of the flue gas in step (3) is 120-150°C.

10. The combined heat and power method according to any one of claims 6-9, characterized in that, The conditioning agents used in step (4) include inorganic conditioning agents and / or organic conditioning agents; Preferably, the inorganic conditioner includes ferric chloride; Preferably, the amount of ferric chloride used is 3%-6% of the oven-dry weight of the digestion solution; Preferably, the concentration of the ferric chloride used is 30%-38%; Preferably, the organic conditioner includes polyacrylamide; Preferably, the amount of polyacrylamide used is 0.3%-0.6% of the oven-dry weight of the digestion solution; Preferably, the concentration of the polyacrylamide used is 1‰-2‰; Preferably, the dehydration in step (4) is performed using a high-pressure diaphragm filtration method; Preferably, the moisture content of the biogas residue in step (4) is ≤65%.

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