Method for preparing sludge and biomass co-blended solidified fuel particles based on ultrasonic synergy

Abstract

The application discloses a sludge and biomass blending solidified fuel particle preparation method based on ultrasonic coordination, which contains 30-40wt% of dewatered sludge, 60-70wt% of biomass and 0.5-3.5wt% of composite additives; the composite additives are Ca(OH)2, sodium lignosulfonate and Fe2(SO4)3, and the mass ratio is 2:1:0.5; the process is as follows: biomass raw material pretreatment, sludge gradient drying, carbonization ultrasonic hole expansion, additive injection, ultrasonic blending modification, low-temperature pressing forming, low-temperature curing and finished product packaging; the application has the advantages of small amount of binder, high production efficiency and low cost.

Description

Technical Field

[0001] This invention relates to the field of solid waste processing technology, and in particular to a method for preparing solidified fuel pellets by blending sludge and biomass using ultrasound synergy. Background Technology

[0002] With the acceleration of the global energy transition and the rigid constraints of the "dual carbon" target, biomass boilers have become a new type of carbon reduction equipment and are being widely used.

[0003] Biomass boilers offer advantages such as higher fuel efficiency and lower carbon emissions, aligning with current low-carbon control targets. In the current energy utilization technology field, biomass boilers, as devices that utilize biomass energy for heating or power generation, typically consist of a combustion chamber, a heat exchange system, and a flue gas purification system.

[0004] However, biomass fuels (such as tree trunks and sawdust) are rich in alkali metals such as K and Na in their ash, and the dust generated during combustion has strong adhesive properties. Furthermore, sludge incineration alone suffers from poor furnace temperature stability (±40℃) due to fluctuations in sludge moisture content (45%-65%). The shift in the high-temperature zone reduces the dioxin decomposition rate to 88% (theoretically, it should be >99%). Processing 1 ton of sludge (60% moisture content) requires 0.25 tons of standard coal equivalent, while recovering only 0.18 tons of standard coal equivalent in heat energy, resulting in a negative net energy gain.

[0005] However, existing biomass processing technologies have the following problems:

[0006] 1. Individual sludge molding consumes a lot of energy (moisture content > 80%) and has low particle mechanical strength (compressive strength < 500N);

[0007] 2. Biomass as a single fuel has a limited calorific value (14-16 MJ / kg) and is prone to coking during combustion;

[0008] 3. Traditional mixed granulation requires the addition of more than 20% binder, which increases costs and generates secondary pollution.

[0009] 4. High-temperature drying (>300℃) leads to the decomposition of organic matter, resulting in a calorific value loss of ≥15%, and the NOx emissions from the combustion of the prepared particles exceed 150mg / m³. Summary of the Invention

[0010] The purpose of this invention is to provide a method for preparing solidified fuel pellets by blending sludge and biomass using ultrasound synergy. This invention has the advantages of low binder usage, high production efficiency, and low cost.

[0011] The technical solution of the present invention:

[0012] A method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasonic synergy comprises 30-40 wt% dewatered sludge, 60-70 wt% biomass, and 0.5-3.5 wt% composite additives. The dewatered sludge is prepared by dewatering sludge from at least municipal sludge, papermaking sludge, and dyeing and printing sludge, with a moisture content ≤60%. The biomass includes at least agricultural and forestry biomass from tree trunks, bark, furniture debris, and sawdust, with a particle size of 0.5-2 mm. The composite additives are Ca(OH)2, sodium lignosulfonate, and Fe2(SO4)3, with a mass ratio of Ca(OH)2:sodium lignosulfonate:Fe2(SO4)3 of 2:1:0.5.

[0013] The aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy includes the following steps:

[0014] S1. Biomass raw material pretreatment: Biomass is crushed to obtain biomass particles with a particle size of 0.5-2mm;

[0015] S2. Gradient drying of sludge: The sludge is dried in a gradient manner using a hot air circulation system, with dewatering in stages from 75℃ to 115℃ to obtain dewatered sludge; the moisture content of the dewatered sludge is ≤60%.

[0016] S3, Carbonization and Ultrasonic Pore Enlargement: Dewatered sludge is carbonized in a fluidized bed at 180℃ for 20-30 min, while 40kHz / 5kW ultrasound is applied simultaneously.

[0017] S4, Additive injection;

[0018] S5. Ultrasonic blending modification: Dewatered sludge and biomass pellets are blended by twin-screw extrusion combined with 200-400W ultrasonic vibration to obtain a blend.

[0019] S6. Low-temperature pressing molding: The blend is pressed into shape in a ring die molding machine at 70-90℃ with a pressure of 15-25MPa.

[0020] S7. Low-temperature curing: Curing in a ventilated environment at 40-50℃ for 20-28 hours to obtain finished pellets;

[0021] S8. Finished product packaging.

[0022] In the aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy, the sludge gradient drying described in S2 is as follows:

[0023] S2.1 Free water removal: The sludge enters the phase change dewatering zone to remove free water. The dewatering temperature is 75-85℃ and the dewatering time is 40-50min.

[0024] S2.2 Bound water removal: The sludge enters the bound water removal zone to remove the bound water. The dewatering temperature is 105-115℃ and the dewatering time is 15-25min.

[0025] In the aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasonic synergy, the carbonization ultrasonic pore-expanding described in step S3 is as follows:

[0026] S3.1 Low-temperature carbonization: The dewatered sludge after gradient drying is carbonized at low temperature in a fluidized bed low-temperature carbonization furnace at 180℃ for 20-30 min.

[0027] S3.2, Ultrasonic pore enlargement: Simultaneously apply 40kHz / 5kW ultrasound to construct open channels dominated by 0.5-5μm, and reshape the pore size distribution through cavitation-acoustic coupling effect;

[0028] The cavitation shock wave breaks up the wall of the large hole, the micro-jet shearing opens up the closed hole, the sonochemical oxidation generates active oxygen, and the etching of the hole surface increases the diffusion micropores.

[0029] In the aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy, the ultrasonic blending modification described in S5 is provided by a 40kHz piezoelectric transducer radially inserted and mounted on a twin-screw extruder, as detailed below:

[0030] S5.1 Conveying section: Twin screw speed 40rpm, ultrasonic power 200w;

[0031] S5.2 Melting section: Twin screw speed 45rpm, ultrasonic power 300w;

[0032] S5.3, Mixing section: Twin screw speed 50rpm, ultrasonic power 400w;

[0033] S5.4, Homogenization section: Twin screw speed 48 rpm, ultrasonic power 0 W.

[0034] In the aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasonic synergy, the power density of the ultrasonic treatment is 15-18 W / g, the penetration depth is 1.5 mm, and the blending time is ≤10 min; the ultrasonic field is applied at an angle of 30°-60° to the material flow direction; a radiator is also provided to synchronously apply a 20 MHz radio frequency field, and the insertion depth of the radiator is 1 / 3-1 / 2 of the material layer thickness.

[0035] In the aforementioned method for preparing sludge and biomass blended solid fuel pellets based on ultrasonic synergy, the low-temperature pressing molding described in S6 is as follows:

[0036] The material is pressed at 70-90℃ to form cylindrical solid particles with a length of 40mm and an aspect ratio of 4:1-6.7:1.

[0037] In the aforementioned method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy, the low-temperature curing described in S7 is as follows:

[0038] The maintenance environment should have an O2 concentration of <5%, an ambient temperature of 40-50℃, and a particle layer airflow velocity of 0.05-0.1m / s.

[0039] Compared with the prior art, this application has the following beneficial effects:

[0040] 1. Synergistic effect innovation: The addition of a composite additive composed of Ca(OH)2 + sodium lignosulfonate + Fe2(SO4)3 causes the proteins in the sludge to cross-link with the additive, forming a natural binding network, which can replace more than 70% of chemical binders, reducing the use of chemical binders to 1 / 5 compared to existing traditional processes.

[0041] 2. Breakthrough in process coupling: Through ultrasonic synergy, the ultrasonic field promotes the penetration of additives into the interior of sludge micelles, breaks down the waxy layer on the surface of biomass, and the penetration depth can reach 0.9-1.5mm. The sludge micelle breakage rate reaches more than 90%, which greatly improves the blending efficiency.

[0042] 3. Reduced production costs: The use of gradient drying, low-temperature pressing, and low-temperature curing to prepare fuel pellets reduces energy consumption and significantly lowers production costs compared to traditional preparation processes.

[0043] Therefore, the present invention has the advantages of low adhesive usage, high production efficiency and low cost. Attached Figure Description

[0044] Figure 1 This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0046] Example 1. A method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasonic synergy, comprising 30-40 wt% dewatered sludge, 60-70 wt% biomass, and 0.5-3.5 wt% composite additives; the dewatered sludge is prepared by dewatering sludge including at least municipal sludge, papermaking sludge, and dyeing sludge, and the moisture content of the dewatered sludge is ≤60%; the biomass includes at least agricultural and forestry biomass including tree trunks, bark, furniture debris, and sawdust, and the particle size of the biomass is 0.5-2 mm; the composite additives are Ca(OH)2, sodium lignosulfonate, and Fe2(SO4)3; the mass ratio of Ca(OH)2:sodium lignosulfonate:Fe2(SO4)3 is 2:1:0.5.

[0047] Preparation method of solidified fuel pellets based on ultrasonic synergy of sludge and biomass blending, such as Figure 1 As shown, the steps are as follows:

[0048] S1. Biomass raw material pretreatment: Biomass is crushed to obtain biomass particles with a particle size of 0.5-2mm;

[0049] S2. Gradual drying of sludge: The hot air circulation system performs gradient drying of sludge, dewatering in stages from 75℃ to 115℃ to obtain dewatered sludge; energy consumption is reduced by 35%, while volatile matter is retained;

[0050] S3. Carbonization and Ultrasonic Pore Enlargement: Dewatered sludge is carbonized at 180℃ for 20-30 min in a fluidized bed while simultaneously subjected to 40kHz / 5kW ultrasound; the effective pore size (0.5-5μm) ratio increases from 45% to 83%.

[0051] S4, Additive injection;

[0052] S5. Ultrasonic blending modification: Dewatered sludge and biomass pellets are blended by twin-screw extrusion combined with 200-400W ultrasonic vibration to obtain a blend; the mixing uniformity reaches 98.5%.

[0053] S6. Low-temperature pressing molding: The blend is pressed into shape in a ring die molding machine at 70-90℃ with a pressure of 15-25MPa; the resulting particle density is >1.1g / cm³.

[0054] S7. Low-temperature curing: Curing in a ventilated environment at 40-50℃ for 20-28 hours yields finished granules; compressive strength is increased to over 800N.

[0055] S8. Finished product packaging.

[0056] The sludge gradient drying described in S2 is as follows:

[0057] S2.1 Free water removal: The sludge enters the phase change dewatering zone to remove free water. The dewatering temperature is 75-85℃ and the dewatering time is 40-50min. The latent heat of vaporization is low (2300 kJ / kg).

[0058] S2.2 Bound water removal: The sludge enters the bound water removal zone to remove bound water. The dewatering temperature is 105-115℃ and the dewatering time is 15-25min. The latent heat of vaporization is relatively high (2600 kJ / kg).

[0059] In the phase change dehydration zone (low temperature section), low-energy free water (accounting for 70% of the total) is evaporated first, avoiding energy waste caused by treating free water in the bound water removal stage (high temperature section);

[0060] The bound water removal stage (high temperature stage) is only for bound water that is difficult to remove, shortening the high temperature time (reducing heat loss) and comprehensively reducing the total latent heat of vaporization.

[0061] The traditional constant temperature 120℃ process consumes 780 kWh of energy per ton of water for evaporation; while the gradient drying method used in this application consumes only 507 kWh per ton of water for evaporation (a reduction of 35.1%).

[0062] The carbonization ultrasonic pore enlargement described in S3 is carried out in the powdered semi-finished product stage (moisture content ≤8%) after gradient drying and before low-temperature molding. The specific details are as follows:

[0063] S3.1 Low-temperature carbonization: The dewatered sludge after gradient drying is carbonized at low temperature in a fluidized bed low-temperature carbonization furnace at 180℃ for 20-30 minutes.

[0064] At 180℃, hemicellulose releases bound water to generate furfural polymers (natural binders), effectively avoiding high-temperature cracking and retaining >90% of aliphatic hydrocarbon volatiles (contributing calorific value >15MJ / kg).

[0065] S3.2, Ultrasonic Pore Enlargement: Simultaneous application of 40kHz / 5kW ultrasound constructs open channels dominated by 0.5-5μm (occupying >80% of the pore volume, increasing the combustion rate). The pore size distribution is reshaped through cavitation-acoustic-fluid coupling effect, avoiding the concentration of pores in conventional particles at <0.1μm (ineffective micropores) or >50μm (weak structure), improving the rapid escape path of volatiles, and achieving a combustion efficiency of up to 92.5% (compared to only 78-85% for traditional particles).

[0066] The cavitation shock wave crushes the wall of the large pore, with a local pressure >50MPa, thereby eliminating ineffective large pores >20μm.

[0067] By using micro-jet shearing to open up closed pores, with a flow rate >100m / s, 1-5μm through-holes are generated.

[0068] Active oxygen is generated through sonochemical oxidation, and 0.5-1 μm diffusion micropores are added to the etched channel surface.

[0069] The ultrasonic blending modification described in S5 uses a 40kHz piezoelectric transducer (which converts electrical energy into mechanical vibration waves) radially inserted and mounted on a twin-screw extruder to provide ultrasound. The coupling component is a titanium alloy amplitude transformer (Φ25mm), which penetrates the barrel wall (sealing level IP68). The specific treatment details are as follows:

[0070] First, start the screw (low speed 20 rpm), feed to 30% volume, turn on the ultrasonic (start at 200W), and gradually increase the speed to the target speed (5 rpm every 5 minutes).

[0071] S5.1 Conveying section: Twin screw compressor with a speed of 40 rpm and ultrasonic power of 200 W; low-frequency cavitation breaks down sludge flocs and releases bound water;

[0072] S5.2 Melting section: Twin screw speed 45 rpm, ultrasonic power 300 W; acoustic flow effect (>10 m / s) promotes the melting of biomass lignin;

[0073] S5.3 Mixing section: Twin screw speed 50rpm, ultrasonic power 400w; sonochemical modification, generating hydroxyl radicals to degrade dye molecules in printing and dyeing sludge;

[0074] S5.4, Homogenization section: Twin screw speed 48rpm, ultrasonic power 0w; eliminates air bubbles and prevents particle micropore collapse.

[0075] The ultrasonic treatment has a power density of 15-18 W / g, a penetration depth of 1.5 mm, and a blending time of ≤10 min. The ultrasonic field is applied at an angle of 30°-60° to the material flow direction. A radiator is also provided to synchronously apply a 20 MHz radio frequency field, and the radiator is inserted to a depth of 1 / 3-1 / 2 of the material layer thickness.

[0076] S6 describes low-temperature pressing molding, which is the core technology for forming sludge biomass fuel pellets. Its core principle lies in utilizing the thermoplastic transformation of biomass and the colloidal adhesiveness of sludge, as detailed below:

[0077] The material is pressed at 70-90℃ to form cylindrical solid particles with a diameter of Φ6 / 8 / 10mm and a length of 40mm. The aspect ratio is 4:1-6.7:1, and the combustion path of volatiles is fully optimized.

[0078] The low-temperature curing described in S7 is detailed below:

[0079] The maintenance environment should have an O2 concentration of <5% (to inhibit dioxin formation; when O2 >8%, the dioxin formation reaches 0.25 ng TEQ / kg), an ambient temperature of 40-50℃, and a particle layer airflow velocity of 0.05-0.1 m / s to avoid surface cracking of the particles.

[0080] Example 2. The preparation method of the ultrasonic-assisted sludge and biomass blend solidified fuel pellet preparation method is basically the same as that of Example 1, except that:

[0081] It contains 39 wt% dewatered sludge, 60 wt% biomass and 1 wt% composite additives; the dewatered sludge is papermaking sludge; the biomass is tree trunk; the composite additives are Ca(OH)2, sodium lignosulfonate and Fe2(SO4)3, and the mass ratio of Ca(OH)2:sodium lignosulfonate:Fe2(SO4)3 is 2:1:0.5.

[0082] The biomass pellets have a diameter of Φ8mm.

[0083] The fuel pellets prepared using this application have a calorific value ≥18.5MJ / kg (210% higher than that of single sludge), and the combustion process requires no addition of any coal.

[0084] The NOx emission from combustion is ≤80mg / m³, and the heavy metal solidification rate is >97%, which greatly reduces the NOx emission concentration. If coupled with an integrated dust and nitrogen oxide equipment, NOx can be easily reduced to the national ultra-low standard (NOx≤50mg / m³).

[0085] The combustion rate reaches 0.92 mm / s (42% higher than the traditional method);

[0086] A conventional biomass boiler can easily handle this blended solid fuel pellets without any other adjustments to the boiler.

[0087] Based on an annual sludge treatment capacity of 50,000 tons, the application of this application can achieve the following value:

[0088] • Reduce landfill usage by 45 mu / year;

[0089] • It produced 32,000 tons of fuel pellets, replacing 18,000 tons of standard coal;

[0090] • Ultrasonic strengthening technology can reduce additive costs by 1.75 million yuan;

[0091] • CO2 emissions were reduced by 46,000 tons per year;

[0092] • NO emissions due to combustion X With a concentration of ≤80mg / m³, the consumption of ammonia water for denitrification can be reduced by 20 tons / year, while also reducing the frequency of catalyst replacement.

[0093] Comparative experiment

[0094] I) Comparison of Compound Additive Experiments

[0095] Comparative experimental data on the application of 0.5-3.5wt% composite additive (Ca(OH)2:sodium lignosulfonate:Fe2(SO4)3=2:1:0.5) in sludge-biomass fuel pellets (test standards: GB / T 28750 and ISO 17225-7)

[0096] I. Experimental Design and Control Group

[0097]

[0098] II. Comparison of Key Performance Data

[0099] 1. Fuel calorific value and combustion efficiency

[0100]

[0101] in conclusion:

[0102] An additive concentration of 1.0% is the optimal value, resulting in a 16.7% increase in calorific value and a 47% decrease in char residue.

[0103] Adding too much (>1.5%) will actually decrease the calorific value.

[0104] 2. Heavy metal curing effect

[0105]

[0106] Mechanism of action:

[0107] Ca(OH)2 provides an alkaline environment (pH≈11.5), which promotes the formation of insoluble hydroxides from heavy metals;

[0108] Ferrous sulfate hydrolyzes to form colloidal Fe(OH)3, which adsorbs heavy metals such as Cd / Pb in sludge to form stable co-precipitates (solidification rate ↑ 5-8%).

[0109] Sodium lignosulfonate enhances curing through phenolic hydroxyl chelation (As curing rate increases by 87%).

[0110] 3. Particle physical strength

[0111]

[0112] explain:

[0113] Sodium lignosulfonate acts as a natural binder, improving particle toughness;

[0114] Fe2(SO4)3 was dispersed by ultrasonication to maintain particle strength >800N.

[0115] Excessive Ca(OH)2 leads to increased particle brittleness (strength decreases when >1.5%).

[0116] III. Combustion Emissions Comparison (1.0% Additive vs. Control Group)

[0117]

[0118] Emission reduction mechanism:

[0119] Sulfur fixation by Ca(OH)2: CaSO4 formation rate > 95%;

[0120] Fe 3+ Catalytic decomposition of NO during combustion X (Selective non-catalytic reduction (SNCR) effect) can make NO X Emissions reduction of 15-30%;

[0121] Sodium lignosulfonate inhibits dioxins by disrupting the synthesis pathway of chlorobenzene precursors.

[0122] IV. Multivariate Comparison Experiment

[0123] 1. Additive ratio vs. total amount added (compressive strength response)

[0124]

[0125] 2. Ultrasonic power vs. total amount added (calorific value response)

[0126]

[0127] Interaction mechanism: High ultrasonic power (400W) can break down additive agglomerates → allowing for higher addition amounts (1.2-1.3%) without reducing calorific value;

[0128] Breaking with conventional wisdom: Traditional theory holds that "increased addition will inevitably lead to decreased calorific value," but ultrasound intervention breaks this limitation.

[0129] II) Experiment on the proportioning of raw materials

[0130] Verification of the proportioning properties of the raw materials themselves for blended fuel pellets of sludge and mixed biomass:

[0131] I. Setting Core Experimental Parameters

[0132]

[0133] Comparison of performance of Class II and III sludge particles (Φ8mm benchmark)

[0134] 1: Physical and mechanical properties

[0135]

[0136] Conclusion: Papermaking sludge has the best particle density and strength due to its high fiber content; dyeing and printing sludge requires additional pretreatment to reduce its moisture content.

[0137] 2: Combustion characteristics (1.0% additive)

[0138]

[0139] Explanation: Due to the presence of inorganic salt residue (approximately 18%), the calorific value of dyeing and printing sludge is reduced by 12.3%, requiring the replenishment of high-calorific-value biomass (such as tree bark chips).

[0140] III. The Influence of Particle Size on Performance (Paper Sludge System)

[0141] 3: Comparison of Φ6 / 8 / 10mm particles

[0142]

[0143] in conclusion:

[0144] The Φ8mm diameter exhibits a balanced performance in terms of energy consumption, combustion stability, and emission control, making it suitable for mainstream industrial boilers.

[0145] Although Φ6mm fuel burns quickly, it increases dust emissions by 15% (requiring enhanced dust removal).

[0146] IV. Environmental and Safety Data (Φ8mm Particles)

[0147] 4: Heavy metal leaching and discharge

[0148]

[0149] The natural anti-toxic properties of lignin in papermaking sludge result in extremely low dioxin formation.

Claims

1. A method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy, characterized in that: The product comprises 30-40 wt% dewatered sludge, 60-70 wt% biomass, and 0.5-3.5 wt% composite additives; the dewatered sludge is prepared by dewatering sludge including at least municipal sludge, papermaking sludge, and dyeing and printing sludge, and the moisture content of the dewatered sludge is ≤60%; the biomass includes at least agricultural and forestry biomass including tree trunks, bark, furniture debris, and sawdust, and the particle size of the crushed biomass is 0.5-2 mm; the composite additives are Ca(OH)2, sodium lignosulfonate, and Fe2(SO4)3; the mass ratio of Ca(OH)2:sodium lignosulfonate:Fe2(SO4)3 is 2:1:0.5; The specific steps are as follows: S1. Biomass raw material pretreatment: Biomass is crushed to obtain biomass particles with a particle size of 0.5-2mm; S2. Gradient drying of sludge: The sludge is dried in a gradient manner using a hot air circulation system, with dewatering in stages from 75℃ to 115℃ to obtain dewatered sludge; the moisture content of the dewatered sludge is ≤60%. S3, Carbonization and Ultrasonic Pore Enlargement: Dewatered sludge is carbonized in a fluidized bed at 180℃ for 20-30 min, while 40kHz / 5kW ultrasound is applied simultaneously. S4, Additive injection; S5. Ultrasonic blending modification: Dewatered sludge and biomass pellets are blended by twin-screw extrusion combined with 200-400W ultrasonic vibration to obtain a blend. S6. Low-temperature pressing molding: The blend is pressed into shape in a ring die molding machine at 70-90℃ with a pressure of 15-25MPa. S7. Low-temperature curing: Curing in a ventilated environment at 40-50℃ for 20-28 hours to obtain finished pellets; S8. Finished product packaging; The sludge gradient drying described in S2 is as follows: S2.1 Free water removal: The sludge enters the phase change dewatering zone to remove free water. The dewatering temperature is 75-85℃ and the dewatering time is 40-50min. S2.2 Bound water removal: The sludge enters the bound water removal zone to remove bound water. The dewatering temperature is 105-115℃ and the dewatering time is 15-25min. The carbonization ultrasonic pore-reaming method described in S3 is detailed below: S3.1 Low-temperature carbonization: The dewatered sludge after gradient drying is carbonized at low temperature in a fluidized bed low-temperature carbonization furnace at 180℃ for 20-30 min. S3.2, Ultrasonic pore enlargement: Simultaneously apply 40kHz / 5kW ultrasound to construct open channels dominated by 0.5-5μm, and reshape the pore size distribution through cavitation-acoustic coupling effect; The large pore walls are crushed by cavitation shock waves, the closed pores are opened by micro-jet shearing, active oxygen is generated by sonochemical oxidation, and the pore surface is etched to increase diffusion micropores. The ultrasonic blending modification described in S5 is provided by a 40kHz piezoelectric transducer radially inserted and mounted on a twin-screw extruder, as detailed below: S5.1 Conveying section: Twin screw speed 40rpm, ultrasonic power 200w; S5.2 Melting section: Twin screw speed 45rpm, ultrasonic power 300w; S5.3, Mixing section: Twin screw speed 50rpm, ultrasonic power 400w; S5.4, Homogenization section: Twin screw speed 48 rpm, ultrasonic power 0 W; The low-temperature pressing molding described in S6 is as follows: The material is pressed at 70-90℃ to form cylindrical solid particles with a length of 40mm and an aspect ratio of 4:1-6.7:

1. The low-temperature curing described in S7 is detailed below: The maintenance environment should have an O2 concentration of <5%, an ambient temperature of 40-50℃, and a particle layer airflow velocity of 0.05-0.1m / s.

2. The method for preparing solidified fuel pellets by blending sludge and biomass based on ultrasound synergy according to claim 1, characterized in that: The ultrasonic treatment has a power density of 15-18 W / g, a penetration depth of 1.5 mm, and a blending time of ≤10 min. The ultrasonic field is applied at an angle of 30°-60° to the material flow direction. A radiator is also provided to synchronously apply a 20 MHz radio frequency field, and the radiator is inserted to a depth of 1 / 3-1 / 2 of the material layer thickness.

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