Method for denitrification of sludge and simultaneous hydrothermal carbon upgrading in hydrothermal treatment of municipal sludge

Abstract

This invention discloses a method for synergistic hydrothermal carbonization of urban sludge in hydrothermal treatment, a green method for treating urban sludge through hydrothermal carbonization, achieving synergistic improvement in sludge denitrification efficiency and upgrading of hydrothermal carbon fuel quality. Urban sludge with a moisture content of 60.05–82.24% is loaded into a reactor, and deionized water, organic acid, and 30% hydrogen peroxide solution are added for hydrothermal reaction at a temperature of 180–270°C, a pressure of 2–15 MPa, and a time of 15–120 min. After the reaction, the reactor is cooled to room temperature; the reactor is opened, and the solid products are separated by vacuum filtration; the solid products are then dried at 105°C for 24 h to obtain hydrothermal carbon solid fuel. Compared to untreated urban sludge, the treated hydrothermal carbon solid fuel exhibits a 44.60%–67.68% increase in denitrification efficiency, a 51.73%–32.49% increase in N / C reduction efficiency, and a calorific value of 2.06–5.29 MJ / Kg. The present invention has a simple process and is easy to operate, which significantly improves the quality of sludge-derived solid fuel. It is suitable for large-scale industrial production and is conducive to the harmless disposal and resource utilization of urban sludge with high water content.

Description

Technical Field

[0001] This invention belongs to the field of organic solid waste reduction and resource utilization treatment, specifically involving a method for sludge denitrification and hydrothermal carbon upgrading in urban sludge hydrothermal treatment. Background Technology

[0002] Currently, the conversion of urban sewage sludge into solid fuel through hydrothermal carbonization technology has garnered widespread attention from researchers. While hydrothermal carbonization can achieve high nitrogen removal efficiency, further deep denitrification is still needed to meet the requirements of high-quality clean solid fuel. Hydrothermal oxidation of sludge can achieve volume reduction and harmless disposal with minimal pollutant emissions. When H2O2 acts as an oxidant, it causes the evolution of oxygen-containing functional groups on the outer surface of sludge particles, disrupting the sludge floc structure. Simultaneously, the free radicals generated by H2O2 decomposition lower the activation energy required for the reaction of nitrogen-containing components such as proteins, promoting their hydrolysis and improving sludge denitrification efficiency.

[0003] Previously published patents indicate that after hydrothermal oxidation treatment of sludge, the quality of hydrothermal carbon fuel significantly decreases due to the large-scale oxidation and decomposition of organic matter (Publication No.: CN116004259A). The introduction of catalysts can significantly improve sludge denitrification efficiency, but the production process is complex and costly, making it difficult to effectively meet the needs of large-scale sludge treatment. Furthermore, because catalysts cannot be effectively separated, they can lead to an increase in pollutants or harmful components during solid fuel combustion, reducing solid fuel quality and adversely affecting combustion equipment (Publication Nos.: CN110577346A; CN110577346A). In summary, how to achieve efficient sludge denitrification with simple procedures, economic feasibility, and industrial-scale implementation prospects, while simultaneously improving the quality of hydrothermal carbon fuel, is a problem worthy of further research. During the hydrothermal treatment of sludge, the hydrothermal carbonization liquid contains a large amount of short-chain carboxylic acids. These short-chain carboxylic acids can participate in the carbonization process of organic matter as reaction substrates. Simultaneously, organic acids can catalyze the hydrolysis of nitrogen-containing organic matter in the sludge, enhancing the degree of carbonization. Therefore, coupling hydrothermal oxidation with organic acid treatment has the potential to improve sludge denitrification efficiency and upgrade the quality of hydrothermal carbon fuel. In summary, strengthening the coupling effect of organic acids and hydrothermal oxidation in the hydrothermal carbonization of urban sludge to prepare solid fuel is of great significance for achieving the preparation of high-quality solid fuel. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by providing a method for sludge denitrification and hydrothermal carbon upgrading in the hydrothermal treatment of urban sludge. This method effectively solves the technical problem of the common conflict between sludge denitrification and hydrothermal carbon fuel quality upgrading during the hydrothermal carbonization process of urban sludge.

[0005] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0006] A method for sludge denitrification and hydrothermal carbon upgrading in the hydrothermal treatment of urban sludge, comprising the following steps:

[0007] Urban sewage sludge with a certain moisture content was added to a reactor, followed by deionized water, organic acid, and a 30% hydrogen peroxide solution. The reactor was then sealed. The reactor was placed in a heating device and reacted at a specific temperature for a specific time. After the reaction was complete, the reactor was cooled to room temperature, the pressure was reduced, and the reactor was opened. The product underwent solid-liquid separation, drying, and dehydration to obtain hydrothermal carbon. The nitrogen content of the hydrothermal carbon was reduced by at least 44.60% compared to the raw material.

[0008] The selected municipal sludge is activated sludge, which comes from the secondary sedimentation tank of a wastewater treatment plant; the selected organic acid is one of formic acid, acetic acid, propionic acid and butyric acid.

[0009] The deionized water, organic acid, and 30% hydrogen peroxide solution are used as the reaction medium.

[0010] The mass ratio of activated sludge to reaction medium in the reactor is 1:0.78-3, and the volume of the added material occupies 80% of the reactor volume; the hydrothermal carbonization reaction temperature is 180-270℃, the pressure is 2-15MPa, and the reaction time is 15-120min.

[0011] Within the reaction system, the amount of organic acid added is 3.55-7.99% of the mass of activated sludge; the ratio of the amount of 30% hydrogen peroxide solution added to the mass of activated sludge is 0.56-2.25:1.

[0012] Hydrothermal carbonization treatment improved the denitrification efficiency by 44.60% to 67.68%, and the N / C ratio reduction efficiency by -51.73% to 32.49%.

[0013] This invention has at least one, more, or all of the following advantages:

[0014] Raw material advantages: Urban sewage sludge is an important byproduct of urban wastewater treatment. It is a wet biomass rich in organic matter with high energy recovery value; however, it also contains a large amount of organic and inorganic pollutants. Statistics show that approximately 60 million tons of urban sewage sludge are generated annually, of which about 30 million tons are not properly disposed of. The ever-accumulating urban sewage sludge poses a significant threat to the ecological environment and also results in a large waste of potential biomass resources. Converting urban sewage sludge into solid fuel can effectively achieve its harmless disposal and resource utilization.

[0015] Technical advantages: 1) It achieves efficient denitrification of sludge under hydrothermal oxidation conditions, with a green reaction medium, avoiding environmental problems and additional costs caused by the use of catalysts; 2) While reducing the hydrothermal carbon and nitrogen content, it avoids the problem of significant decline in the quality of hydrothermal carbon fuel due to excessive loss of organic matter. Detailed Implementation

[0016] The present invention will be described in detail below with reference to the embodiments.

[0017] This invention relates to a method for sludge denitrification and hydrothermal carbon upgrading in the hydrothermal treatment of urban sludge, comprising the following steps:

[0018] First, weigh a certain amount of fresh wet sludge, deionized water, 30% hydrogen peroxide solution, and organic acids (formic acid, acetic acid, propionic acid, and butyric acid) and place them in a batch reactor, then seal the flange. Second, place the reactor in a matching electric heating device and react at a certain temperature for a period of time. After the reaction is complete, place the reactor in an ice bath to cool it rapidly to room temperature, reduce the pressure, and open the reactor. Transfer the product from the reactor and filter it to remove moisture. Then, dry the solid product at 105°C for 24 hours to obtain solid fuel.

[0019] In a preferred embodiment of the present invention, the activated sludge has a water content of 60.05–82.24 wt.% and a dry sludge addition amount of 4 g.

[0020] In a preferred embodiment of the present invention, the mass ratio of activated sludge to reaction medium in the reactor is 1:0.78 to 3, depending on the moisture content of the sludge.

[0021] In a preferred embodiment of the present invention, the reaction medium comprises water, a 30% hydrogen peroxide solution, and an organic acid, and the mass ratio of water (including the water contained in the sludge itself and added deionized water), hydrogen peroxide, and organic acid in the reactor is 26.2:9:0.8.

[0022] In a preferred embodiment of the present invention, the selected organic acid is butyric acid.

[0023] In a preferred embodiment of the present invention, the reaction temperature is 210°C and the reaction time is 60 min.

[0024] In a preferred embodiment of the present invention, compared with the original sludge (dry basis), the denitrification efficiency of the obtained hydrothermal carbon solid fuel is increased by 44.60%-67.68%, and the N / C value reduction efficiency is increased by -51.73%-32.49%.

[0025] Comparative Example 1

[0026] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water) and 17.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 240℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0027] Comparative Example 2

[0028] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 2.25 g of 30% hydrogen peroxide solution, and 15.23 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 240℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0029] Comparative Example 3

[0030] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 4.5 g of 30% hydrogen peroxide solution, and 12.98 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 240℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0031] Comparative Example 4

[0032] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 240℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0033] Based on Comparative Examples 1-4, the characterizations of different hydrothermal carbon solid fuels are shown in Table 1:

[0034] Table 1. Hydrothermal carbon element analysis, calorific value, and yield results under different oxidant addition amounts.

[0035]

[0036] Comparative Example 5

[0037] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 180℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0038] Comparative Example 6

[0039] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0040] Comparative Example 7

[0041] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 270℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0042] Based on Comparative Examples 5-7, the characterizations of different hydrothermal carbon solid fuels are shown in Table 2:

[0043] Table 2. Hydrothermal carbon elemental analysis, calorific value, and yield results at different reaction temperatures.

[0044]

[0045] Comparative Example 8

[0046] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 15 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0047] Comparative Example 9

[0048] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 30 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0049] Comparative Example 10

[0050] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 120 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0051] Based on Comparative Examples 8-10, the characterizations of different hydrothermal carbon solid fuels are shown in Table 3:

[0052] Table 3. Hydrothermal carbon element analysis, calorific value, and yield results at different reaction times.

[0053]

[0054] Example 1

[0055] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, 0.8 g of formic acid, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0056] Example 2

[0057] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, 0.8 g of acetic acid, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0058] Example 3

[0059] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, 0.8 g of propionic acid, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0060] Example 4

[0061] 22.52 g of wet sludge (82.24 wt.% moisture content, 4 g dry sludge, 18.52 g water), 9 g of 30% hydrogen peroxide solution, 0.8 g of butyric acid, and 8.48 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0062] Based on Examples 1-4, the characterization of different hydrothermal carbon solid fuels is shown in Table 4:

[0063] Table 4. Hydrothermal carbon element analysis, calorific value, and yield results under the action of different organic acids.

[0064]

[0065] Example 5

[0066] 16.31 g of wet sludge (75.48 wt.% moisture content, 4 g dry sludge, 12.31 g water), 9 g of 30% hydrogen peroxide solution, 0.8 g of butyric acid, and 13.89 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The resulting solid product is the hydrothermal carbon solid fuel.

[0067] Example 6

[0068] 12.59 g of wet sludge (moisture content 68.22 wt.%, dry sludge mass 4 g, water 8.59 g), 9 g of 30% hydrogen peroxide solution, 0.8 g of butyric acid, and 17.61 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The obtained solid product is the hydrothermal carbon solid fuel.

[0069] Example 7

[0070] 10.01 g of wet sludge (moisture content 60.05 wt.%, dry sludge mass 4 g, water 6.01 g), 9 g of 30% hydrogen peroxide solution, 0.8 g of butyric acid, and 20.19 g of deionized water were mixed in a reactor, and the flange was sealed. The reactor containing the materials was purged with nitrogen to remove the influence of air, then sealed, and heated under the set reaction conditions (reaction temperature 210℃, reaction time 60 min). After the reaction was completed and cooled to room temperature, the gas valve was opened to release the gas. The mixture in the reactor was transferred to a sintered sand funnel, and the solid and liquid products were separated by vacuum filtration. The solid product was washed with deionized water until the filtrate was colorless, and then dried at 105℃ for 24 h. The obtained solid product is the hydrothermal carbon solid fuel.

[0071] Based on Examples 5-7, the characterization of different hydrothermal carbon solid fuels is shown in Table 5:

[0072] Table 5. Analysis of calorific value and yield of sludge wastewater with different moisture contents (calorific value, carbon content, and yield)

[0073]

[0074] At 210℃, with an H2O2 solution concentration of 135 g / L and the addition of 0.8 g butyric acid, and using activated sludge with a water content of 60.05 wt.%, the sludge denitrification efficiency was 65.37%; the hydrothermal carbon N / C ratio reduction efficiency was 32.49%; the resulting hydrothermal carbon yield was 73.36 wt.%, with carbon 9.98 wt%, hydrogen 1.77 wt%, oxygen 13.97 wt%, nitrogen 1.25 wt%, sulfur 0.27 wt%, and a calorific value of 3.53 MJ / kg.

[0075] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for synergistic hydrothermal carbon upgrading of sludge denitrification in the hydrothermal treatment of urban sludge, characterized in that, Includes the following steps: Urban sewage sludge was added to a reactor, followed by deionized water, organic acid, and a 30% hydrogen peroxide solution. The reactor was then sealed. The reactor was placed in a heating device for hydrothermal carbonization. After the reaction, the mixture was cooled to room temperature, the pressure was reduced, and the reactor was opened. The product underwent solid-liquid separation, drying, and dehydration to obtain hydrothermal carbon. The nitrogen content of the hydrothermal carbon was reduced by at least 44.60% compared to the raw material. The selected municipal sludge is activated sludge, which comes from the secondary sedimentation tank of a wastewater treatment plant; the selected organic acid is one of formic acid, acetic acid, propionic acid and butyric acid. The deionized water, organic acid, and 30% hydrogen peroxide solution constitute the reaction medium. The mass ratio of activated sludge to reaction medium in the reactor is 1:0.78~3, and the volume of the added material occupies 80% of the reactor volume; the hydrothermal carbonization reaction temperature is 180~270℃, the pressure is 2~15MPa, and the reaction time is 15~120min. Within the reaction system, the amount of organic acid added is 3.55-7.99% of the mass of activated sludge; the ratio of the amount of 30% hydrogen peroxide solution added to the mass of activated sludge is 0.56-2.25:

1.

2. The method for sludge denitrification and hydrothermal carbon upgrading in the hydrothermal treatment of urban sludge according to claim 1, characterized in that, The hydrothermal carbonization process improved the denitrification efficiency by 44.60% to 67.68% and the N / C ratio reduction efficiency by -51.73% to 32.49%.

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