A method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and restaurant waste filtrate.

Abstract

This invention discloses a method for preparing artificial coal through synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate. First, straw is treated under a certain steam pressure for a period of time to obtain steam-exploded straw. Second, catering waste is centrifuged to obtain catering waste filtrate, which is then allowed to stand for a period of time to obtain upper and lower layers of catering waste filtrate. Finally, the steam-exploded straw and the upper or lower layer of catering waste filtrate are subjected to a hydrothermal carbonization reaction. The hydrothermal carbonization product is then separated into solid and liquid components, and the resulting solid product is the artificial coal. The steam explosion technology can initially remove easily hydrolyzed and difficult-to-carbonize cellulose and hemicellulose, increasing lignin content and enhancing the carbonizability of straw. The Maillard reaction between the reducing polysaccharides produced by straw hydrolysis and the amino acids produced by catering waste protein hydrolysis converts the organic matter in the raw materials into artificial coal, maximizing the utilization of the organic matter in the raw materials.

Description

Technical Field

[0001] This invention belongs to the field of organic solid and liquid waste resource utilization technology, specifically relating to a method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate. Background Technology

[0002] Coal is a product of crustal movement. Over 300 million years ago in the Paleozoic Era, over 100 million years ago in the Mesozoic Era, and tens of millions of years ago in the Cenozoic Era, large quantities of plant remains were transformed into coal through complex biochemical, geochemical, and physicochemical processes. The process of transforming plant remains into coal is extremely lengthy, involving a wide variety of chemical reactions, including dehydration, decarboxylation, demethanization, deoxygenation, and condensation. Coal is a fossil fuel, a non-renewable energy source. The production of fossil coal requires three conditions: time, pressure, and heat. Hydrothermal carbonization technology precisely meets these three conditions. Hydrothermal carbonization uses biomass or its components as raw materials, water as a solvent and reaction medium, and operates at 150℃-375℃ and autogenous pressure to produce a black solid product, primarily composed of carbon and rich in oxygen-containing functional groups. This black solid substance is called artificial coal. Due to its economic and environmentally friendly nature, hydrothermal carbonization technology has attracted increasing attention for the efficient conversion and application of organic solid waste resources. Due to the involvement of subcritical water media, artificial coal obtained through hydrothermal carbonization has many inherent advantages, such as uniform size, regular morphology, good physicochemical stability, and a surface rich in oxygen-containing functional groups. In terms of energy density, artificial coal is close to bituminous coal and can be directly burned as a solid fuel.

[0003] Currently, the utilization rate of crop straw is relatively low. Only about 25% of the total straw is used as feed for herbivores each year, while over 70% is piled up or directly burned. This not only wastes resources but also causes significant air pollution from the smoke and dust produced. Therefore, the comprehensive utilization of straw is closely related to agriculture, energy, and environmental protection. Crop straw is composed of a large amount of organic matter and a small amount of inorganic matter and water. Its main organic component is cellulose carbohydrates, along with small amounts of crude protein and crude fat. Therefore, its application in artificial coal production has great potential. Furthermore, crop straw is abundant, easy to collect, and inexpensive. Deep processing of crop straw can increase farmers' income and protect the ecological environment. At the same time, it will significantly reduce the economic cost of artificial coal, further enhancing its competitiveness with traditional fossil fuels.

[0004] Steam explosion is widely considered one of the most promising technologies for biomass treatment and disposal. Steam explosion involves treating biomass with hot steam (180-240°C) at a certain pressure (1-3.5 MPa), then rapidly reducing the pressure to atmospheric pressure. This causes the rigid structure of the biomass fibers to break down, disrupting the microstructure of the biomass. The shear force generated by the sudden pressure release can hydrolyze the biomass components. Steam explosion of straw can reduce the content of cellulose and hemicellulose, which are difficult to carbonize, and increase the content of lignin, which is easy to carbonize. However, during the hydrothermal carbonization of straw, some polysaccharides formed from the hydrolysis of cellulose and hemicellulose dissolve in water and cannot be carbonized. But if proteins and hydrolysis products (amino acids) are present during the hydrothermal carbonization of straw, the polysaccharides obtained from the hydrolysis of crude fibers in the straw can undergo a Maillard reaction with the amino acids obtained from the hydrolysis of proteins to form carbon, significantly increasing the carbonization rate of organic matter.

[0005] Food waste has become a complex issue affecting the economy, environment, and society. Its high organic matter and moisture content makes it highly susceptible to bacterial growth, leading to rapid decomposition, spoilage, and foul odors. If not treated promptly, it will cause serious soil and air pollution. Food waste contains abundant organic matter, such as protein, fiber, fat, and starch, all crucial energy sources. The dry basis content of Chinese food waste is approximately 35%, with crude fat accounting for about 12% and protein exceeding 20%. Therefore, developing an efficient and harmless method to rationally utilize the energy in food waste will yield significant energy benefits. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate. This method can effectively solve the technical problem that cellulose and hemicellulose hydrolysis is easy to remain in the aqueous phase and difficult to form carbon during the direct hydrothermal carbonization of straw, while effectively treating catering waste and straw.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] This invention discloses a method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and restaurant waste filtrate, comprising the following steps:

[0009] 1) Pretreatment of straw by steam explosion

[0010] Under high pressure steam, the crushed straw is subjected to a steam explosion reaction, and then the pressure is quickly released to obtain pretreated straw slurry. The pretreated straw slurry is then centrifuged to obtain steam-exploded straw.

[0011] 2) Preparation of leachate from catering waste

[0012] The collected food waste was centrifuged to separate solids and liquids, and the filtrate was collected and allowed to stand for 12 hours to obtain the upper filtrate and the lower filtrate of the food waste.

[0013] 3) Preparation of artificial coal

[0014] After mixing steam-exploded straw with the upper or lower filtrate of catering waste, a hydrothermal reaction is carried out to obtain hydrothermal carbonized slurry. The hydrothermal carbonized slurry is then centrifuged to separate the solids, thus producing artificial coal.

[0015] Preferably, in step 1), the steam explosion reaction is carried out at a steam pressure of 1.8 to 2.4 MPa, a steam temperature of 200 to 240°C, a pressure holding time of 10 to 25 min, and a rapid pressure relief requirement that the pressure relief be completed within 0.01 s.

[0016] Preferably, the steam-exploded straw obtained in step 1) contains, by mass percentage, 2% to 6% ash, 70% to 80% volatile matter, 15% to 25% fixed carbon, and 40% to 45% lignin; the calorific value of the steam-exploded straw is 18 to 22 MJ / kg.

[0017] Preferably, in step 2), the organic matter content in the upper layer filtrate of the catering waste is 8-12 wt% and the pH value is 3.0; the organic matter content in the lower layer filtrate of the catering waste is 2-5 wt% and the pH value is 3.5.

[0018] Preferably, in step 3), the mass ratio of the steam-exploded straw to the upper or lower layer filtrate of the catering waste is (1-3):8.

[0019] Preferably, in step 3), the hydrothermal carbonization reaction temperature is 250–350°C, and the reaction time is 30–120 minutes.

[0020] Preferably, the straw used is one or more of the following: wheat straw, corn straw, rice straw, soybean straw, potato straw, cotton straw, tomato straw, sugarcane straw, and sunflower straw. The moisture content of the straw is not limited, and the particle size is 5 to 50 mesh.

[0021] Preferably, the food waste used is leftover food from the catering industry, and there are no restrictions on its moisture content.

[0022] Preferably, the synthesized coal contains: 74.2-78.8 wt% carbon, 5.7-7.2 wt% hydrogen, 10.2-16.3 wt% oxygen, 2.1-2.8 wt% nitrogen, and 0.1-0.3 wt% sulfur; the yield of the synthesized coal is 35-45 wt.%, and the calorific value is 30-34 MJ / kg.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention discloses a method for preparing artificial coal through the synergistic hydrothermal carbonization of steam-exploded straw and restaurant waste filtrate. This method fully utilizes waste resources, making efficient use of both straw and restaurant waste filtrate. The steam explosion technology initially removes easily hydrolyzed and difficult-to-carbonize cellulose and hemicellulose from the straw, increasing lignin content and enabling partial carbonization, thus enhancing the carbonizability of the straw. The method utilizes the Maillard reaction between reducing polysaccharides produced by straw hydrolysis and amino acids produced by restaurant waste protein hydrolysis to convert the organic matter in the raw materials into artificial coal, maximizing the utilization of organic matter. It shortens the coal formation time from hundreds of millions of years to less than an hour, significantly improving conversion efficiency. The method is low-cost, low-energy, and pollution-free, with a processing cost of 40-50 yuan per ton. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] The present invention will be further described in detail below with reference to embodiments:

[0028] The raw materials used in the following embodiments of the present invention are: ① Straw is one or any two or more of the crop straws such as wheat, corn, rice, soybean, potato, cotton, tomato, sugarcane, and sunflower, with no limit on the moisture content of the straw and a particle size of 5-50 mesh; ② Catering waste filtrate is the upper and lower liquids after the catering waste filtrate has been allowed to stand and separate.

[0029] Preparation of steam-exploded straw:

[0030] Taking wheat straw as an example, 120g of dried, pre-crushed wheat straw is placed into a cylinder. After tightening the cylinder, 2.4MPa steam is introduced to pressurize the raw material, and the cylinder pressure is maintained at 2.3±0.05MPa for 20 minutes. Then, the pressure is released instantly, and the straw explodes into the material collection bin. The mud-like product obtained after steam explosion is collected and filtered using a circulating water vacuum pump until the product no longer drips water. The product is then placed in a 105℃ oven to dry for at least 12 hours to obtain steam-exploded wheat straw.

[0031] Other straws are treated in the same way as wheat straw.

[0032] Preparation of food waste filtrate:

[0033] 20 kg of food waste was collected from a university cafeteria and centrifuged at 1500 rpm. The resulting liquid was left to stand in a separatory funnel for 12 hours to obtain the upper and lower filtrates.

[0034] Aging of the reactor:

[0035] Hydrothermal carbonization experiments were conducted using a custom-designed stainless steel ultrasonic high-temperature and high-pressure reactor. The reactor had a volume of 100 mL, a rated temperature of 350℃, and a rated pressure of 25 MPa. It was equipped with a magnetic stirrer, an ultrasonic frequency of 28 kHz, and a power of 1200 W. Before the formal experiment, 60 mL of deionized water was added to the reactor, and the reaction was carried out at 350℃ for 1 hour to remove any residues inside the reactor and to mitigate any potential influences from the reactor's internal environment on the reaction.

[0036] Example 1: Hydrothermal carbonization of steam-exploded wheat straw and restaurant waste filtrate

[0037] Take 5g of dried, steam-exploded wheat straw and place it in a beaker. Add 40mL of the supernatant from food waste and mix it with the beaker. Then add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 250℃, the reaction time to 120min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, remove all the products from the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid product with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 35 wt.%, with carbon 68.3 wt%, hydrogen 4.6 wt%, oxygen 16.4 wt%, nitrogen 1.8 wt%, sulfur 0.1 wt%, and a calorific value of 28 MJ / kg.

[0038] Example 2: Hydrothermal carbonization of steam-exploded corn stalks and restaurant waste filtrate

[0039] Take 10g of dried, steam-exploded corn stalks and place them in a beaker. Add 40mL of the supernatant from food waste and mix them together. Then add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 270℃, the reaction time to 60min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, remove all the products from the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid product with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 38 wt.%, with carbon 69.3 wt%, hydrogen 4.8 wt%, oxygen 17.2 wt%, nitrogen 2.2 wt%, sulfur 0.2 wt%, and a calorific value of 30 MJ / kg.

[0040] Example 3: Hydrothermal carbonization of steam-exploded rice straw and restaurant waste filtrate

[0041] Take 10g of dried, steam-exploded rice straw and put it into a beaker. Then, take 40mL of the supernatant from food waste and mix it with the beaker. Then, add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 300℃, the reaction time to 50min, and the stirring speed to 200r / min. After the reaction is completed, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, take out all the products in the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, filter them using a Buchner funnel to separate the solid and liquid products, and wash the solid products with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 40 wt.%, with carbon 75.4 wt%, hydrogen 5.8 wt%, oxygen 16.2 wt%, nitrogen 2.8 wt%, sulfur 0.3 wt%, and calorific value of 31 MJ / kg.

[0042] Example 4: Hydrothermal carbonization of steam-exploded soybean straw and restaurant waste filtrate

[0043] Take 15g of dried, steam-exploded soybean straw and place it in a beaker. Add 40mL of the supernatant from food waste and mix it with the beaker. Then add the mixture to a 100mL reactor and seal it. Replace the air in the reactor with helium and pressurize it to 0.1MPa. Set the reaction temperature to 330℃, the reaction time to 40min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reactor in cold water to terminate the reaction. After the reactor cools to room temperature, remove it. Open the reactor, remove all the products from the reactor, and wash the inner wall of the reactor with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid products with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 37 wt.%, with carbon 74.2 wt%, hydrogen 5.7 wt%, oxygen 16.3 wt%, nitrogen 2.5 wt%, sulfur 0.2 wt%, and a calorific value of 30 MJ / kg.

[0044] Example 5: Hydrothermal carbonization of steam-exploded potato straw and restaurant waste filtrate

[0045] Take 15g of dried, steam-exploded potato straw and put it into a beaker. Then, take 40mL of the supernatant from food waste and mix it with the beaker. Then, add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 350℃, the reaction time to 30min, and the stirring speed to 200r / min. After the reaction is completed, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, take out all the products in the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, filter them using a Buchner funnel to separate the solid and liquid products, and wash the solid products with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 43 wt.%, with carbon 78.4 wt%, hydrogen 5.8 wt%, oxygen 12.2 wt%, nitrogen 2.8 wt%, sulfur 0.1 wt%, and a calorific value of 33 MJ / kg.

[0046] Example 6: Hydrothermal carbonization of steam-exploded cotton stalks and restaurant waste filtrate

[0047] Take 15g of dried, vaporized cotton stalks and place them in a beaker. Add 40mL of the supernatant from food waste and mix with the beaker. Then add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 350℃, the reaction time to 30min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, remove all the products from the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid product with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 45 wt.%, with carbon 78.5 wt%, hydrogen 6.8 wt%, oxygen 10.2 wt%, nitrogen 2.8 wt%, sulfur 0.3 wt%, and a calorific value of 34 MJ / kg.

[0048] Example 7: Hydrothermal carbonization of steam-exploded tomato straw and restaurant waste filtrate

[0049] Take 15g of dried, steam-exploded tomato straw and place it in a beaker. Add 40mL of the supernatant from food waste and mix it with the beaker. Then add the mixture to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 350℃, the reaction time to 30min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reaction vessel in cold water to terminate the reaction. After the reaction vessel cools to room temperature, remove it. Open the reaction vessel, remove all the products from the reaction vessel, and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid product with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 44 wt.%, with carbon 78.8 wt%, hydrogen 7.2 wt%, oxygen 10.3 wt%, nitrogen 2.2 wt%, sulfur 0.2 wt%, and a calorific value of 35 MJ / kg.

[0050] Example 8: Hydrothermal carbonization of steam-exploded sugarcane straw and restaurant waste filtrate

[0051] Take 15g of dried, steam-exploded sugarcane straw and place it in a beaker. Add 40mL of the supernatant from food waste and mix it with the beaker. Then add the mixture to a 100mL reactor and seal it. Replace the air in the reactor with helium and pressurize it to 0.1MPa. Set the reaction temperature to 350℃, the reaction time to 30min, and the stirring speed to 200r / min. After the reaction is complete, immediately place the reactor in cold water to terminate the reaction. After the reactor cools to room temperature, remove it. Open the reactor, remove all the products from the reactor, and wash the inner wall of the reactor with dichloromethane. Collect all the extracts together, separate the solid and liquid products by filtration using a Buchner funnel, and wash the solid products with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 42 wt.%, with carbon 77.8 wt%, hydrogen 6.4 wt%, oxygen 11.8 wt%, nitrogen 2.4 wt%, sulfur 0.3 wt%, and a calorific value of 33 MJ / kg.

[0052] Example 9: Hydrothermal carbonization of steam-exploded (wheat and corn) straw and restaurant waste filtrate

[0053] Take 15g of dried steam-exploded wheat and corn (mass ratio 1:1) straw and put it into a beaker. Then take 40mL of the upper liquid of catering waste and mix it with the beaker. Then add it to a 100mL reaction vessel and seal it. Replace the air in the vessel with helium and pressurize it to 0.1MPa. Set the reaction temperature to 350℃, the reaction time to 30min, and the stirring speed to 200r / min. After the reaction is completed, immediately put the reaction vessel into cold water to terminate the reaction. After the reaction vessel cools to room temperature, take it out. Open the reaction vessel, take out all the products in the reaction vessel and wash the inner wall of the reaction vessel with dichloromethane. Collect all the extracts together, filter them with a Buchner funnel to separate the solid and liquid products, and wash the solid products with dichloromethane until the dichloromethane is pale yellow or colorless. The solid obtained after filtration was dried in an oven at 105℃ until its weight no longer changed, and a solid product was obtained, which is artificial coal. The yield of the artificial coal was 44 wt.%, with carbon 78.8 wt%, hydrogen 6.6 wt%, oxygen 1.2 wt%, nitrogen 2.1 wt%, sulfur 0.3 wt%, and a calorific value of 33 MJ / kg.

[0054] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and restaurant waste filtrate, characterized in that, Includes the following steps: 1) Pretreatment of straw by steam explosion Under high pressure steam, the crushed straw is subjected to a steam explosion reaction, and then the pressure is quickly released to obtain pretreated straw slurry. The pretreated straw slurry is then centrifuged to obtain steam-exploded straw. The steam explosion reaction is carried out at a steam pressure of 1.8~2.4 MPa, a steam temperature of 200~240 ℃, a pressure holding time of 10~25 min, and a rapid pressure release requirement of completing the pressure release within 0.01 s. The resulting steam-exploded straw contains, by mass percentage, 2%~6% ash, 70%~80% volatile matter, 15%~25% fixed carbon, and 40%~45% lignin. The calorific value of the steam-exploded straw is 18~22 MJ / kg. 2) Preparation of leachate from food waste The collected food waste was centrifuged to separate solids and liquids, and the filtrate was collected and allowed to stand for 12 hours to obtain upper and lower layers of food waste filtrate. The upper layer of food waste filtrate had an organic matter content of 8-12 wt% and a pH of 3.0, while the lower layer of food waste filtrate had an organic matter content of 2-5 wt% and a pH of 3.

5. 3) Preparation of artificial coal After mixing steam-exploded straw with the upper or lower filtrate of catering waste, a hydrothermal reaction is carried out to obtain hydrothermal carbonized slurry. The hydrothermal carbonized slurry is then centrifuged to separate the solids, thus producing artificial coal.

2. The method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate according to claim 1, characterized in that, In step 3), the mass ratio of the steam-exploded straw to the upper or lower layer filtrate of the catering waste is (1~3):

8.

3. The method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate according to claim 1, characterized in that, In step 3), the hydrothermal carbonization reaction temperature is 250~350 ℃, and the reaction time is 30~120 minutes.

4. The method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate according to any one of claims 1 to 3, characterized in that, The straw used is one or more of the following: wheat straw, corn straw, rice straw, soybean straw, potato straw, cotton straw, tomato straw, sugarcane straw, and sunflower straw. The moisture content of the straw is not limited, and the particle size is 5-50 mesh.

5. The method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate according to any one of claims 1 to 3, characterized in that, The food waste used in the catering industry consists of leftover food, and there are no restrictions on the moisture content.

6. The method for preparing artificial coal by synergistic hydrothermal carbonization of steam-exploded straw and catering waste filtrate according to any one of claims 1 to 3, characterized in that, The synthesized coal contains: 74.2~78.8 wt% carbon, 5.7~7.2 wt% hydrogen, 10.2~16.3 wt% oxygen, 2.1~2.8 wt% nitrogen, and 0.1~0.3 wt% sulfur; the yield of synthesized coal is 35~45 wt.%, and the calorific value is 30~34 MJ / kg.