Method for processing and humification of kitchen waste and residual sludge in cooperation

Abstract

The application discloses a method for processing and humification of kitchen waste and residual sludge, which takes kitchen waste and residual sludge as main raw materials, and carries out ultrasonic activation treatment under alkaline conditions after crushing and pulping. Then, polyphenol agricultural and forestry wastes and iron-manganese based accelerators are added into the mixed slurry, and the mixture is uniformly mixed and transferred into a hydrothermal reaction device for hydrothermal treatment under the conditions of a temperature of 180-220 DEG C and a pressure of 0.6-1.5 MPa. The reaction product is subjected to solid-liquid separation, and the obtained solid product hydrothermal carbon can be directly used for land reclamation or mine ecological restoration. The obtained liquid phase is subjected to salting-out and acidification series treatment to obtain humic acid solid. The application uses kitchen waste and residual sludge for hydrothermal treatment to obtain solid products with high humification degree, has the advantages of high reaction efficiency and high added value of products, and provides a new technical approach for low-carbon treatment and resource utilization of organic solid waste.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste treatment, disposal and resource utilization technology, specifically involving a method for the co-treatment and humification of kitchen waste and residual sludge. Background Technology

[0002] Food waste, an organic waste generated from residential life, industrial production, and agricultural activities, is mainly composed of carbohydrates, proteins, and lipids, and is characterized by high organic matter content, high water content, and easy acidification and putrefaction. Excess sludge originates from the biochemical treatment process of urban sewage, and has high levels of organic matter, water content, and pathogens. Among currently used treatment and disposal technologies, aerobic composting suffers from problems such as large land area requirements, long cycles, and difficulties in leachate treatment; while high-temperature incineration is limited by factors such as water content and calorific value, resulting in high disposal costs. Hydrothermal reaction is a process in which water acts as a solvent to drive chemical changes in substances under high temperature and high pressure conditions. It is widely used in materials synthesis, biomass energy conversion, and degradation of organic pollutants in water bodies, offering advantages such as short reaction time and high efficiency. Existing patent CN117986617A uses a high-temperature hydrothermal reaction combined with hydrothermal fluid circulation and acid-base adjustment to treat biomass waste such as traditional Chinese medicine residues. This technology requires multi-step cyclical operations, making the process complex and time-consuming. Furthermore, its adaptability to raw materials is limited; its applicability to high-moisture, complex-composition domestic wet waste is not yet reported. Existing patent CN118580517A targets lignocellulosic waste, employing acid pretreatment combined with alkaline hydrothermal oxidation to simultaneously prepare humic acid and fulvic acid. The solid product obtained from the hydrothermal carbonization of the raw material is then subjected to a hydrothermal reaction with a strong alkaline solution under oxygen. Subsequently, humic substances are collected through acid precipitation and resin extraction. This technology emphasizes oxygen pressure control to achieve synergistic production of both products. The process is energy-intensive and difficult to operate, and the separation stage relies on resin extraction and multi-stage acid-base adjustment, resulting in practical problems such as cumbersome processes, resin pollution, and high regeneration costs.

[0003] Given that organic matter such as amino acids, sugars, and polyphenols forms humic substances through a series of oxidation and polymerization reactions, this method uses organic-rich food waste and wastewater treatment plant sludge for synergistic hydrothermal treatment. During high-temperature decomposition, food waste and sludge release intermediate components such as sugars, amino acids, and proteins, which promote humic substance formation. Furthermore, humic acid precursors such as lignin in the mixed organic materials are accelerated through condensation reactions by alkali metal elements and iron-manganese promoters in the sludge. The hydrothermal co-treatment of food waste and wastewater treatment plant sludge yields biochar, a solid product that can be reused on-site or used for mine land ecological restoration. The resulting liquid mixture, after salting out and acidification, yields humic acid-based solids. This approach effectively reduces carbon emissions while increasing the added value of the products, providing a new technological pathway for the low-carbon treatment, disposal, and resource utilization of organic solid waste. Summary of the Invention

[0004] This invention provides a method for the co-treatment and humification of kitchen waste and residual sludge. Using kitchen waste and residual sludge as raw materials, the materials are crushed, mixed, and pulped. Under alkaline conditions, the mixture undergoes ultrasonic activation to partially release polysaccharide and protein intermediates. Subsequently, polyphenolic agricultural and forestry waste and iron-manganese-based promoters are added to the mixed sludge. By controlling the temperature, pressure, and time of the hydrothermal reaction, the organic matter undergoes decomposition, oxidation, and polymerization reactions, ultimately transforming into humic substances. After solid-liquid separation, the reaction products undergo salting out and acidification of the liquid phase to extract humic acid, which can be widely used in soil improvement and ecological agriculture construction. The solid-phase hydrothermal carbon also contains humic components and has a porous structure, making it suitable for on-site utilization or for ecological restoration of mine land.

[0005] The specific implementation steps of this invention are as follows: (1) After crushing the kitchen waste, mix it with the remaining sludge to make a slurry. Add alkaline substances to the resulting slurry, mix it evenly, and then perform ultrasonic activation pretreatment to release some of the polysaccharide and protein intermediate components. (2) Add polyphenolic agricultural and forestry waste and iron-manganese-based accelerator to the pretreated slurry, mix well and transfer to a reactor with a stirring paddle for hydrothermal humification treatment. (3) The hydrothermal reaction product is separated into solid and liquid phases. The obtained solid phase hydrothermal carbon is dried and then recovered. The obtained liquid phase product is subjected to a series of post-treatments such as salting out and acidification to obtain humic acid solids for recycling.

[0006] Preferably, in step (1), the dry mass ratio of kitchen waste to residual sludge is 1:4 to 1:10, and the solid content in the mixed slurry is 6% to 10%.

[0007] Preferably, the alkaline substance in step (1) is composed of potassium hydroxide and potassium oxide, with a mass ratio of 1:2 to 1:6, and the amount of alkaline substance added is 0.02‰ to 0.06‰ of the total mass of the mixed slurry.

[0008] Preferably, the ultrasonic treatment operation temperature in step (1) is 15-50 ℃, the activation time is 20-40 min, and the input power per cubic meter of mixed slurry is 5-10 kW.

[0009] Preferably, the polyphenolic agricultural and forestry waste mentioned in step (2) is the processing waste of green tea or white tea or its tea residue, pruning waste of holly trees, which must include green tea or white tea processing waste, accounting for 40%-60% of the total mass of phenolic agricultural and forestry waste, and the amount of polyphenolic agricultural and forestry waste added is 1.5‰-3.0‰ of the total mass of the pretreated slurry.

[0010] Furthermore, the polyphenolic agricultural and forestry waste is processing waste of green tea or white tea and tea residue of green tea or white tea, or the polyphenolic agricultural and forestry waste is processing waste of green tea or white tea and pruning waste of holly trees, or the polyphenolic agricultural and forestry waste is processing waste of green tea or white tea, tea residue of green tea or white tea and pruning waste of holly trees.

[0011] Preferably, the iron-manganese-based accelerator in step (2) is palygorskite and iron-manganese ore powder, with a mass ratio of 1:6 to 1:12, and its addition amount is 0.5‰ to 0.8‰ of the total mass of the pretreated slurry. The mass content of iron and manganese in the accelerator is 1.0% to 2.5%.

[0012] Preferably, in step (2), the hydrothermal treatment reaction temperature is 180-220 ℃, the operating pressure is 0.6-1.5 MPa, and the treatment time is 30-50 min.

[0013] Preferably, in step (3), the liquid phase product obtained by solid-liquid separation is sequentially added with salting-out and acidification reagents to precipitate humic acid. The acidification is to adjust the pH value of the mixture to 1.0-3.0 using 20%-30% hydrochloric acid.

[0014] Preferably, the salting-out reagent is composed of sodium chloride and sodium sulfate in a mass ratio of 1:1.2 to 1:2.5, and its dosage is 1.5‰ to 5.0‰ of the total mass of the liquid phase product.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) Using kitchen waste and residual sludge as raw materials, an endogenous reaction system is constructed under hydrothermal conditions, so that proteins, lipids and other substances are gradually decomposed and transformed into humic acid and hydrothermal carbon, thereby realizing the co-processing and resource utilization of organic solid waste.

[0016] (2) Ultrasonic treatment under alkaline conditions causes the cell walls of plants and microorganisms to be destroyed and release organic matter. Combined with the high temperature and high pressure of hydrothermal reaction, the organic matter is degraded into sugar, protein and polyphenol components to varying degrees. Then, under the action of iron and manganese-based promoters, it condenses to generate humic acid substances, which significantly reduces carbon emissions and provides a new idea for the low-carbon treatment of organic solid waste. Attached Figure Description

[0017] Figure 1 The infrared spectra of the products of Examples 1 and 2 of this invention and the humic acid standard are shown. Detailed Implementation

[0018] The following specific implementation examples further illustrate the present invention, providing detailed implementation methods and operating procedures, but the scope of protection of the present invention is not limited to the content described.

[0019] Example 1 Crushed kitchen waste and residual sludge were mixed at a mass ratio of 1:6 to obtain a mixed slurry with a solids content of 7.9%. An alkaline mixture of potassium hydroxide and potassium oxide (mass ratio 1:4) was added at 0.04‰ of the total wet-based slurry mass. After thorough mixing, the mixture was ultrasonically activated at 35 ℃ for 30 min, with an input power of 7 kW per cubic meter of slurry. Following pretreatment, polyphenolic agricultural and forestry waste (50% of the total phenolic agricultural and forestry waste) was added at 2.3‰ of the total slurry mass. Subsequently, an iron-manganese-based accelerator (1.2% iron) was added at 0.7‰ of the total wet-based slurry mass. This accelerator was prepared by mixing palygorskite and iron-manganese ore powder at a mass ratio of 1:9, with iron and manganese contents of 1.8%. The mixture was transferred to a hydrothermal reactor and subjected to high-temperature heat treatment at 200 ℃, 0.9 MPa, and 400 rpm for 40 min. After the reaction, solid-liquid separation was performed. The obtained solid-phase hydrothermal carbon was dried at 50 °C. A salting-out reagent, prepared by mixing sodium chloride and sodium sulfate at a mass ratio of 1:1.9, was added to the resulting liquid product at a concentration of 3.2‰ of the total liquid mass. Subsequently, the pH of the mixture was adjusted to 1.5 using 27% hydrochloric acid, with the upper layer of foam being scraped off promptly during the acidification process. After standing at room temperature for 12 h to precipitate, the precipitate was centrifuged, washed, and dried to obtain humic acid-based solids.

[0020] After the above process, the solid hydrothermal carbon yield was 41.2%, the liquid phase humic acid extraction rate was 4.38%, and the humic acid organic carbon content was 74.5%.

[0021] Example 2 Crushed kitchen waste and residual sludge were mixed at a mass ratio of 1:4 to obtain a mixed slurry with a solids content of 6.2%. An alkaline mixed reagent consisting of potassium hydroxide and potassium oxide in a mass ratio of 1:2 was added at 0.02‰ of the total wet-based slurry mass. After mixing, the mixture was ultrasonically activated at 17 ℃ for 25 min, with an input power of 5 kW per cubic meter of slurry. After pretreatment, polyphenolic agricultural and forestry waste was added at 1.5‰ of the total slurry mass, of which white tea processing waste accounted for 40% of the total phenolic agricultural and forestry waste. An iron-manganese-based accelerator was added at 0.5‰ of the total pretreated material mass. This accelerator was prepared by mixing palygorskite and iron-manganese ore powder in a mass ratio of 1:6, with iron and manganese contents of 1.0% and 1.6%, respectively. The mixed slurry was transferred to a reactor and heat-treated at 180 ℃ and 0.6 MPa for 45 min. After the reaction, the product was subjected to solid-liquid separation. A salting-out reagent, consisting of sodium chloride and sodium sulfate in a mass ratio of 1:1.2, was added to the resulting liquid product at a total mass of 1.5‰. The pH of the mixture was then adjusted to 1.7 with 20% hydrochloric acid, and the upper layer of foam was promptly skimmed off during the acidification process. The humic acid solids were recovered after precipitation, centrifugation, washing, and drying. The operating procedures and other conditions not mentioned were the same as in Example 1.

[0022] After the above process, the yield of solid hydrothermal char was 43.9%, the extraction rate of humic acid in the liquid phase was 4.15%, and the organic carbon content of humic acid was 72.74%. The infrared spectra of the hydrothermal char obtained here and the humic acid obtained in Examples 1 and 2 are shown in the attached figure.

[0023] Example 3 Crushed kitchen waste and residual sludge were mixed at a mass ratio of 1:10 to obtain a mixed slurry with a solids content of 9.8%. An alkaline mixture of potassium hydroxide and potassium oxide (mass ratio 1:6) was added at 0.06‰ of the total wet-based slurry mass. After mixing, the mixture was ultrasonically activated at 50 ℃ for 25 min, with an input power of 10 kW per cubic meter of slurry. After pretreatment, polyphenolic agricultural and forestry waste (60% of the total phenolic agricultural and forestry waste) was added at 3.0‰ of the total slurry mass, with holly pruning waste accounting for 60% of the total phenolic agricultural and forestry waste. An iron-manganese-based accelerator (prepared by mixing palygorskite and iron-manganese ore powder at a mass ratio of 1:12, with iron and manganese contents of 1.7% and 2.5%, respectively) was added at 0.8‰ of the total wet-based material mass. The mixed slurry was then transferred to a hydrothermal reactor and heat-treated at 220 ℃ and 1.5 MPa for 35 min. After the reaction, solid-liquid separation was performed. Add 4.8‰ of the total mass of a salting-out reagent, consisting of sodium chloride and sodium sulfate in a mass ratio of 1:2.5, to the obtained liquid product. Then adjust the pH of the mixture to 1.5 with 30% hydrochloric acid. The humic acid solids are then recovered through precipitation, centrifugation, washing, and drying. The operating procedures and other conditions not mentioned are the same as in Example 1.

[0024] After the above process, the solid hydrothermal carbon yield was 39.6%, the liquid phase humic acid extraction rate was 4.62%, and the humic acid organic carbon content was 75.28%.

Claims

1. A method for the co-treatment and humification of kitchen waste and residual sludge, characterized in that... Includes the following steps: (1) After crushing the kitchen waste, mix it with the remaining sludge, add alkaline substances to the resulting mixed slurry, mix well and then perform ultrasonic activation pretreatment; the dry basis mass ratio of kitchen waste to remaining sludge is 1:4-1:10, the solid content in the mixed slurry is 6%-10%; the alkaline substances are composed of potassium hydroxide and potassium oxide, the mass ratio of the two is 1:2-1:6, and the amount of alkaline substances added is 0.02‰-0.06‰ of the total mass of the mixed slurry; (2) Polyphenolic agricultural and forestry waste and iron-manganese-based accelerator are added to the pretreated slurry, and the mixture is transferred to a reactor with a stirring paddle for hydrothermal humification treatment; the polyphenolic agricultural and forestry waste is the processing waste of green tea or white tea or its tea residue, holly pruning waste, which must include green tea or white tea processing waste, accounting for 40%-60% of the total mass of polyphenolic agricultural and forestry waste, and the amount of polyphenolic agricultural and forestry waste added is 1.5‰-3.0‰ of the total mass of the pretreated slurry; the iron-manganese-based accelerator is palygorskite and iron-manganese ore powder, the mass ratio of the two is 1∶6-1∶12, and the amount added is 0.5‰-0.8‰ of the total mass of the pretreated slurry, and the mass content of iron and manganese in the accelerator is 1.0%-2.5%; (3) The hydrothermal reaction product is separated into solid and liquid phases. The obtained solid phase hydrothermal carbon is dried and then recovered. The obtained liquid phase product is subjected to a series of post-treatments such as salting out and acidification to obtain humic acid solids for recycling.

2. The method according to claim 1, characterized in that... The ultrasonic activation pretreatment operation temperature in step (1) is 15-50 ℃, the activation time is 20-40 min, and the input power per cubic meter of mixed slurry is 5-10 kW.

3. The method according to claim 1, characterized in that... In step (2), the hydrothermal treatment reaction temperature is 180-220 ℃, the operating pressure is 0.6-1.5 MPa, and the treatment time is 30-50 min.

4. The method according to claim 1, characterized in that... In step (3), the liquid phase product obtained from solid-liquid separation is sequentially added with salting-out and acidification reagents to precipitate humic acid. The acidification is to adjust the pH value of the mixture to 1.0-3.0 using 20%-30% hydrochloric acid.

5. The method according to claim 4, characterized in that... The salting-out reagent consists of sodium chloride and sodium sulfate in a mass ratio of 1:1.2 to 1:2.5, and its dosage is 1.5‰ to 5.0‰ of the total mass of the liquid phase product.

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