A method for preparing clean energy by using sludge ash to catalyze sludge denitrification and desulfurization

Abstract

The application discloses a method for preparing clean energy by catalyzing sludge denitrification and desulfurization by using sludge ash, which comprises the following steps: S1, drying the first sludge and then placing it in a muffle furnace for combustion to obtain sludge ash; S2, adding the second sludge, the sludge ash and water into a reaction kettle in proportion to perform hydrothermal carbonization, collecting a solid product and obtaining hydrothermal carbon after drying. The application realizes efficient sludge denitrification and desulfurization by using sludge combustion waste, sludge ash to catalyze sludge hydrothermal carbonization. The hydrothermal carbon after denitrification and desulfurization is used as fuel or auxiliary fuel, which can relatively reduce the emission of nitrogen and sulfur compounds. Meanwhile, the waste reuse of sludge ash is realized by using the sludge ash as a catalyst. Compared with metal and metal compounds, molecular sieves, acids and other catalysts, the sludge ash has a wide source of raw materials and low cost.

Description

Technical Field

[0001] This invention relates to the field of sludge hydrothermal carbonization technology, specifically to a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash. Background Technology

[0002] The world generates billions of tons of wastewater annually, including domestic and industrial wastewater, and this volume is expected to continue increasing with population growth and rising living standards. Sludge is a complex multiphase composite material produced during wastewater treatment, containing various toxic substances such as heavy metals, sulfur- and chlorine-containing inorganic pollutants, organic pollutants, and pathogens. Due to its high water content and complex composition, sludge has long been a difficult biomass waste to treat.

[0003] Converting sludge into high-value-added products or biofuels through hydrothermal carbonization has always been a research focus in sludge resource utilization. Hydrothermal carbonization is an important thermochemical conversion process that can improve the dewatering capacity of sludge and convert it into high-value-added products such as fuels, organic fertilizers, and precursors for functional materials. Among these, preparing primary or auxiliary fuels from sludge through hydrothermal carbonization is an attractive technology; however, the nitrogen, sulfur oxides, and combustion ash produced during sludge hydrothermal carbonization are unavoidable challenges in subsequent disposal processes.

[0004] The addition of catalysts can further improve the hydrothermal carbonization effect of sludge, reduce pyrolysis temperature, reduce energy consumption, and increase the yield of target products. Finding suitable and efficient catalysts has become a hot topic in this field of research and application. However, the catalysts currently being studied for hydrothermal carbonization of sludge, such as metals and metal compounds, molecular sieves, and acids, will additionally increase the cost of the hydrothermal carbonization process. Summary of the Invention

[0005] To address the technical problems described in the background section, the purpose of this application is to propose a method for producing clean energy by catalyzing the denitrification and desulfurization of sludge using sludge ash. By using sludge ash as a catalyst for hydrothermal carbonization of sludge, efficient desulfurization and denitrification of sludge are achieved, which can reduce the emissions of nitrogen and sulfur compounds when hydrothermal carbon is burned as fuel or auxiliary fuel. At the same time, the waste reuse of sludge ash is also realized.

[0006] To achieve the above objectives, this application discloses a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, comprising the following steps:

[0007] S1. After drying the first sludge, it is burned in a muffle furnace to obtain sludge ash;

[0008] S2. Add the second sludge, the sludge ash and water to the reactor in proportion for hydrothermal carbonization, collect the solid product, and dry it to obtain hydrothermal carbon.

[0009] In a preferred implementation of a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, in S2, the mass ratio of the second sludge to the sludge ash ranges from 1:10 to 1:1.

[0010] As a preferred implementation of a method for catalytic denitrification and desulfurization of sludge to produce clean energy using sludge ash, the reaction temperature range of hydrothermal carbonization in S2 is 180-260℃.

[0011] As a preferred implementation of a method for catalytic denitrification and desulfurization of sludge to produce clean energy using sludge ash, the reaction time of hydrothermal carbonization in S2 is 0.5-5h.

[0012] In a preferred implementation of a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, in S1, the combustion temperature range of the first sludge in the muffle furnace is 500-850℃.

[0013] In a preferred implementation of a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, in S1, the combustion time of the first sludge in the muffle furnace is at least 1 hour.

[0014] In a preferred implementation of a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, in S1, the drying temperature of the first sludge is not lower than 100°C.

[0015] In a preferred implementation of a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, in S1, the drying time of the first sludge is at least 2 hours.

[0016] In a preferred implementation of a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, the first sludge and / or the second sludge includes one or more of water supply sludge, domestic sludge, and industrial wastewater sludge.

[0017] In a preferred embodiment of a method for producing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash, the nitrogen content of the hydrothermal carbon ranges from 0.24% to 0.6%, and the sulfur content of the hydrothermal carbon ranges from 0.16% to 0.23%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention utilizes sludge combustion waste, namely sludge ash, to catalyze hydrothermal carbonization of sludge, achieving efficient denitrification and desulfurization of sludge. The hydrothermal carbon after denitrification and desulfurization can be used as fuel or auxiliary fuel, which can relatively reduce the emission of nitrogen and sulfur compounds. At the same time, sludge ash can also be reused as a catalyst. Compared with catalysts such as metals and metal compounds, molecular sieves, and acids, sludge ash raw materials are widely available and inexpensive. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a schematic flowchart illustrating a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash.

[0022] Figure 2 This is a schematic flowchart illustrating a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash.

[0023] Figure 3 This is a table showing the nitrogen and sulfur content of hydrothermal carbon generated when sludge ash at different ashing temperatures is added in an illustrative embodiment of a method for catalytic denitrification and desulfurization of sludge to produce clean energy.

[0024] Figure 4 This is a table showing the nitrogen and sulfur content of hydrothermal carbon generated when sludge ash is added at different hydrothermal carbonization temperatures in an illustrative embodiment of a method for catalytic denitrification and desulfurization of sludge to produce clean energy using sludge ash. Detailed Implementation

[0025] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate components with the same or similar structures but the same function.

[0026] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0027] Currently, the main method for sludge treatment is drying and incineration. After incineration, a large amount of sludge ash remains. This specific embodiment provides a method for catalytic denitrification and desulfurization of sludge using sludge ash to produce clean energy. This method utilizes the catalytic effect of metal oxides in the sludge ash after incineration to promote hydrothermal carbon denitrification, deoxygenation, and desulfurization of the sludge. The method includes the following steps:

[0028] S1. After drying the first sludge, it is burned in a muffle furnace to obtain sludge ash;

[0029] S2. Add the second sludge, sludge ash and water to the reactor in proportion for hydrothermal carbonization, collect the solid product, dry it and grind it to obtain hydrothermal carbon.

[0030] In this specific embodiment, the sludge ash mainly contains non-combustible inorganic components, including alkali metal and alkaline earth metal oxides, sulfates, chlorides, phosphates, silicates, and some heavy metal waste. Specifically, the main components of the sludge ash are 18.2% iron oxide (Fe2O3), 13.1% aluminum oxide (Al2O3), 28.5% silicon dioxide (SiO2), 36.5% calcium oxide (CaO), and 2.7% magnesium oxide (MgO).

[0031] Therefore, this specific embodiment utilizes the waste from sludge drying and incineration, namely sludge ash, to catalyze the hydrothermal carbonization of sludge. On the one hand, it achieves efficient denitrification and desulfurization of sludge. The hydrothermal carbon after denitrification and desulfurization can be used as fuel or auxiliary fuel, which can relatively reduce the emission of nitrogen and sulfur compounds. On the other hand, using sludge ash as a catalyst also realizes the waste reuse of sludge ash. Compared with catalysts such as metals and metal compounds, molecular sieves, and acids, sludge ash raw materials are widely available and inexpensive.

[0032] In this specific embodiment, in S2, the mass ratio of the second sludge to the sludge ash ranges from 1:10 to 1:1. Specifically, it can be 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, etc.

[0033] In this specific embodiment, the reaction temperature range for hydrothermal carbonization in S2 is 180-260℃. Specifically, it can be 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, etc.

[0034] In this specific embodiment, the hydrothermal carbonization reaction time in S2 is 0.5-5 hours. Specifically, it can be 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, etc.

[0035] In this specific embodiment, in S1, the combustion temperature range of the first sludge in the muffle furnace is 500-850℃. Specifically, it can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, etc.

[0036] In this specific embodiment, in S1, the combustion time of the first sludge in the muffle furnace is at least 1 hour.

[0037] In this specific embodiment, in S1, the drying temperature of the first sludge is not lower than 100°C.

[0038] In this specific embodiment, in S1, the drying time of the first sludge is at least 2 hours.

[0039] In this specific embodiment, the first sludge and / or the second sludge includes one or more of water supply sludge, domestic sludge, and industrial wastewater sludge.

[0040] In this specific embodiment, the nitrogen content of the hydrothermal carbon ranges from 0.2% to 0.6%, and the sulfur content of the hydrothermal carbon ranges from 0.16% to 0.23%.

[0041] The following specific examples further illustrate a method for preparing clean energy by catalytic denitrification and desulfurization of sludge using sludge ash.

[0042] Example 1

[0043] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 500℃ for 4 hours, then removed and cooled. The cooled sludge ash was ground into powder for later use. 0.500g of sludge ash, 2.0000g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 220℃, and the reaction time was 1 hour. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon, which had a nitrogen content of 0.60% and a sulfur content of 0.201%.

[0044] Example 2

[0045] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 500℃ for 4.5 hours, then removed and cooled. The cooled sludge ash was ground into powder. 0.200g of sludge ash, 1.500g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 180℃, and the reaction time was 1.5 hours. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon, with a nitrogen content of 0.37% and a sulfur content of 0.179%.

[0046] Example 3

[0047] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 600℃ for 5 hours, then removed and cooled. The cooled sludge ash was ground into powder. 0.200g of sludge ash, 1.500g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 200℃, and the reaction time was 2 hours. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon, with a nitrogen content of 0.59% and a sulfur content of 0.197%.

[0048] Example 4

[0049] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 700℃ for 5.5 hours, then removed and cooled. The cooled sludge ash was ground into powder. 0.500g of sludge ash, 2.000g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 220℃, and the reaction time was 1.5 hours. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon, with a nitrogen content of 0.57% and a sulfur content of 0.188%.

[0050] Example 5

[0051] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 800℃ for 5 hours, then removed and cooled. The cooled sludge ash was ground into powder. 0.200g of sludge ash, 1.500g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 240℃, and the reaction time was 2 hours. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon, with a nitrogen content of 0.24% and a sulfur content of 0.178%.

[0052] Example 6

[0053] The first sludge, dried for 24 hours, was placed in a muffle furnace and burned at 800℃ for 5.5 hours, then removed and cooled. The cooled sludge ash was ground into powder. 0.200g of sludge ash, 2.000g of the second sludge, and 40ml of water were added to a 100ml reactor. The reaction temperature was set at 220℃, and the reaction time was 1 hour. After the reaction, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon. The nitrogen content of the solid product was 0.28%, and the sulfur content was 0.174%.

[0054] Comparative Example

[0055] 2.000g of the second sludge and 40ml of water were added to a 100ml reactor. The reaction temperature was set to 220℃ and the reaction time was 1h. After the reaction was completed, the mixture was filtered, and the solid and liquid products were collected separately. The solid product was dried to obtain hydrothermal carbon. The nitrogen content of the solid product was 0.82%, and the sulfur content was 0.269%.

[0056] Comparing Examples 1-6 with the comparative examples yields the following results:

[0057] Compared with the nitrogen content of approximately 0.8% in hydrothermal carbonization solid products without added ash, the nitrogen content of hydrothermal carbonization solid products catalyzed by sludge ash is 0.26-0.6%, a year-on-year decrease of 25-67.5%. Compared with the sulfur content of approximately 0.27% in hydrothermal carbonization solid products without added ash, the sulfur content of hydrothermal carbonization solid products catalyzed by sludge ash is approximately 0.17-0.197%, a year-on-year decrease of 27-37%.

[0058] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0059] The above are merely embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A method for preparing clean energy by catalyzing denitrification and desulfurization of sludge using sludge ash, characterized by, Includes the following steps: S1. After drying the first sludge, it is burned in a muffle furnace to obtain sludge ash; S2. Add the second sludge, the sludge ash and water to the reactor in proportion for hydrothermal carbonization, collect the solid product, and dry it to obtain hydrothermal carbon.

2. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 1, characterized in that, In S2, the mass ratio of the second sludge to the sludge ash is in the range of 1:10-1:

1.

3. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 1, characterized in that, In S2, the reaction temperature range for hydrothermal carbonization is 180-260℃.

4. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 3, characterized in that, In S2, the reaction time for hydrothermal carbonization is 0.5-5 hours.

5. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 1, characterized in that, In S1, the combustion temperature range of the first sludge in the muffle furnace is 500-850℃.

6. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 5, characterized in that, In S1, the combustion time of the first sludge in the muffle furnace is at least 1 hour.

7. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 1, characterized in that, In S1, the drying temperature of the first sludge is not lower than 100℃.

8. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 7, characterized in that, In S1, the drying time of the first sludge is at least 2 hours.

9. The method for preparing clean energy by catalyzing sludge denitrification and desulfurization using sludge ash according to claim 1, characterized in that, The first sludge and / or the second sludge includes one or more of water supply sludge, domestic sludge and industrial wastewater sludge.

10. The method for preparing clean energy by catalyzing denitrification and desulfurization of sludge using sludge ash according to claim 1, characterized in that, The nitrogen content of the hydrothermal carbon ranges from 0.2% to 0.6%; the sulfur content of the hydrothermal carbon ranges from 0.16% to 0.23%.

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