Method for preparing biochar by taking garden waste as raw material

Abstract

The invention discloses a method for preparing biochar by taking garden waste as a raw material, and belongs to the technical field of solid waste resource utilization, and the method comprises the following steps: S1, drying the garden waste; s2, putting the treated raw materials into a sealed pyrolyzing furnace, introducing protective gas, and then carrying out heating carbonization treatment; and S3, cooling the carbonized biomass raw material to room temperature, and sequentially grinding and sieving to obtain the biochar. According to the invention, the garden waste is used as the raw material to prepare the biochar, so that resource utilization of the waste is realized; in the preparation process, firstly, the amine-containing solution is used for treating the waste crushed aggregates, so that the subsequent carbonization treatment is facilitated; in the carbonization process, a front heat treatment process and a rear heat treatment process are adopted, the progressive effect is achieved, the porosity of the raw material structure can be further improved, the pyrolysis effect is improved, and the finally obtained biochar is developed in pore structure, high in yield, large in surface area and excellent in adsorption performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource utilization, and specifically relates to a method for preparing biochar using garden waste as raw materials. Background Art

[0002] Biochar is a carbon-rich, fine-grained, porous material produced by high-temperature thermal decomposition of biomass under oxygen-limited conditions. It has a surface adsorption effect and plays a certain role in increasing the adsorption of nutrients by the soil, reducing emissions to the atmosphere and water bodies, reducing environmental pollution, and improving nutrient utilization. In addition, due to its low price and environmental protection, biochar has received more and more attention in dealing with soil nutrients, acidification, heavy metals and other issues. In addition, the organic combination of biochar and ordinary organic fertilizer has the advantages of improving soil nutrients, increasing fertilizer utilization, stabilizing production, and reducing environmental pollution. It has high research value and good development prospects.

[0003] Garden waste mainly refers to dead branches, fallen leaves, grass clippings, withered flowers, tree and shrub prunings and other plant residues produced by natural withering or artificial pruning of garden plants. It is a potential underutilized renewable biomass raw material. Garden waste has high lignin and cellulose content and is a good raw material for preparing biochar. However, there are technical bottlenecks such as low carbon conversion efficiency and specific surface area, which limit its application in environmental aspects. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing biochar using garden waste as raw material. Using garden waste as raw material, biochar is prepared through a special process, which not only realizes the resource utilization of waste, but also the prepared biochar has excellent adsorption performance.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0007] S1. Drying the garden waste;

[0008] S2. The treated raw material is placed in a sealed pyrolysis furnace, and a protective gas is introduced, and then the temperature is increased for carbonization treatment;

[0009] S3. The biomass raw material after carbonization is cooled to room temperature, and then ground and sieved in sequence to obtain biochar.

[0010] Furthermore, the garden waste includes branches, leaves, plant and flower residues, dead grass, etc., preferably branches pruned from trees and shrubs.

[0011] Furthermore, the specific operations of step S1 are:

[0012] The garden waste is naturally air-dried, crushed, and then mixed with an amine solution, heated to 55-65°C and stirred thoroughly, naturally cooled to room temperature, filtered, and the filter residue is dried in an oven to complete the treatment process.

[0013] Furthermore, the particle size of the crushed garden waste is 2-6 mm.

[0014] Furthermore, the amine-containing solution is aqueous ammonia or ammonium chloride solution with a concentration of 12-15 g / L.

[0015] Furthermore, the solid-liquid ratio of the crushed garden waste to the amine-containing solution is 1 g:3-5 mL.

[0016] Furthermore, the oven drying parameters are: drying at 70-80°C for 15-24h.

[0017] The crushed garden waste is first treated with an amine solution, which can initially destroy the chemical bonds between lignin and polysaccharides in the waste, converting insoluble lignin into more soluble hydroxyl lignin, and crystalline cellulose into amorphous cellulose, causing cell expansion, making the raw material structure loose, and facilitating subsequent carbonization treatment.

[0018] Furthermore, in step S2, the protective gas is nitrogen or argon, the flow rate of the protective gas is 2-3 L / min, and the introduction time is 30 min.

[0019] Furthermore, the temperature carbonization treatment includes two processes:

[0020] 1) Heating from room temperature to 200-300°C at a heating rate of 10°C / min and holding time of 30-60min;

[0021] 2) Continue to raise the temperature from the final temperature of the first stage to 500-700°C, the heating rate is 5°C / min, and the pyrolysis time is 2-3h.

[0022] Through the two heat treatment processes, the former process is a pre-treatment at a lower temperature (200-300°C), and the latter process is a pyrolysis treatment at a higher temperature (500-700°C). It not only has a gradual effect to prevent incomplete pyrolysis of the raw materials, but also the heat preservation process of the pre-treatment can further improve the looseness of the raw material structure and further improve the subsequent pyrolysis effect.

[0023] Furthermore, the screening process in step S2 is through a 10-20 mesh sieve.

[0024] Beneficial effects of the present invention:

[0025] 1) The present invention uses garden waste as raw materials to prepare biochar, realizes the resource utilization of waste, and has environmental and commercial value;

[0026] 2) In the process of preparing biochar, the present invention first uses an amine-containing solution to treat the garden waste fragments, which can preliminarily destroy the chemical bonds between lignin and polysaccharides in the waste, convert insoluble lignin into more soluble hydroxyl lignin, and convert crystalline cellulose into amorphous cellulose, causing cell expansion, making the raw material structure loose, which is convenient for subsequent carbonization treatment; in the carbonization process, two front and back heat treatment processes are used, the front process is a pre-treatment at a lower temperature, and the rear process is a pyrolysis treatment at a higher temperature, which not only has a gradual effect and prevents incomplete pyrolysis of the raw material, but also the heat preservation process of the pre-treatment can further improve the looseness of the raw material structure and further improve the subsequent pyrolysis effect, so that the final biochar has a developed pore structure, high yield, large surface area, and excellent adsorption performance. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Example 1

[0029] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0030] S1. After the garden waste is naturally air-dried, it is crushed to control the particle size to 2-6 mm, and then mixed with ammonia water or ammonium chloride solution with a concentration of 12 g / L according to a solid-liquid ratio of 1 g: 5 mL, the temperature is raised to 55 ° C and stirred thoroughly, and the residue is naturally cooled to room temperature and filtered. After the filter residue is dried in an oven at 70 ° C for 24 hours, the treatment process is completed;

[0031] S2. The treated raw material is placed in a sealed pyrolysis furnace and nitrogen or argon is introduced at a flow rate of 2L / min for 30min, and then the temperature is increased to carbonize: 1) the temperature is increased from room temperature to 200°C at a heating rate of 10°C / min for 30min; 2) the temperature is continued to be increased from the final temperature of the first stage to 500°C at a heating rate of 5°C / min for 2h;

[0032] S3. The biomass raw material after carbonization treatment is cooled to room temperature, and then ground and passed through a 10-mesh sieve to obtain biochar.

[0033] Example 2

[0034] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0035] S1. After the garden waste is naturally air-dried, it is crushed to control the particle size to 2-6 mm, and then mixed with ammonia water or ammonium chloride solution with a concentration of 14g / L according to a solid-liquid ratio of 1g:4mL, the temperature is raised to 60°C and stirred thoroughly, and the mixture is naturally cooled to room temperature, filtered, and the residue is dried in an oven at 75°C for 20h to complete the treatment process;

[0036] S2. The treated raw material is placed in a sealed pyrolysis furnace and nitrogen or argon is introduced at a flow rate of 2.5 L / min for 30 min, and then the temperature is increased to carbonize: 1) the temperature is increased from room temperature to 250 ° C, the heating rate is 10 ° C / min, and the holding time is 45 min; 2) the temperature is continued to be increased from the final temperature of the first stage to 600 ° C, the heating rate is 5 ° C / min, and the pyrolysis time is 2.5 h;

[0037] S3. The biomass raw material after carbonization treatment is cooled to room temperature, and then ground and passed through a 15-mesh sieve to obtain biochar.

[0038] Example 3

[0039] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0040] S1. After the garden waste is naturally air-dried, it is crushed to control the particle size to 2-6 mm, and then mixed with ammonia water or ammonium chloride solution with a concentration of 15g / L according to a solid-liquid ratio of 1g:3mL, the temperature is raised to 65°C and stirred thoroughly, and the residue is naturally cooled to room temperature and filtered. After the residue is dried in an oven at 80°C for 15h, the treatment process is completed;

[0041] S2. The treated raw material is placed in a sealed pyrolysis furnace and nitrogen or argon is introduced at a flow rate of 3L / min for 30min, and then the temperature is increased for carbonization: 1) the temperature is increased from room temperature to 300°C at a heating rate of 10°C / min for 60min; 2) the temperature is continued to be increased from the final temperature of the first stage to 700°C at a heating rate of 5°C / min for 3h;

[0042] S3. The biomass raw material after carbonization treatment is cooled to room temperature, and then ground and passed through a 20-mesh sieve to obtain biochar.

[0043] Comparative Example 1

[0044] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0045] S1. After the garden waste is naturally air-dried, it is crushed to control the particle size to 2-6 mm, and dried to complete the treatment process;

[0046] S2. The treated raw material is placed in a sealed pyrolysis furnace and nitrogen or argon is introduced at a flow rate of 2L / min for 30min, and then the temperature is increased to carbonize: 1) the temperature is increased from room temperature to 200°C at a heating rate of 10°C / min for 30min; 2) the temperature is continued to be increased from the final temperature of the first stage to 500°C at a heating rate of 5°C / min for 2h;

[0047] S3. The biomass raw material after carbonization treatment is cooled to room temperature, and then ground and passed through a 10-mesh sieve to obtain biochar.

[0048] Comparative Example 2

[0049] A method for preparing biochar using garden waste as raw material comprises the following steps:

[0050] S1. After the garden waste is naturally air-dried, it is crushed to control the particle size to 2-6 mm, and then mixed with ammonia water or ammonium chloride solution with a concentration of 12 g / L according to a solid-liquid ratio of 1 g: 5 mL, the temperature is raised to 55 ° C and stirred thoroughly, and the residue is naturally cooled to room temperature and filtered. After the filter residue is dried in an oven at 70 ° C for 24 hours, the treatment process is completed;

[0051] S2. The treated raw material is placed in a sealed pyrolysis furnace and nitrogen or argon is introduced at a flow rate of 2 L / min for 30 min, and then the temperature is raised to 500 ° C at a heating rate of 8 ° C / min for 2.5 h of pyrolysis treatment;

[0052] S3. The biomass raw material after carbonization treatment is cooled to room temperature, and then ground and passed through a 10-mesh sieve to obtain biochar.

[0053] The performance parameters of the biochar obtained in Examples 1-3 and Comparative Examples 1-2 were measured, and the results are shown in the following table:

[0054] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 pH 8.10 7.95 8.15 7.86 7.82 Yield / % 40.8 41.2 41.5 34.2 36.7 <![CDATA[Specific surface area / m 2 ·g -1 > 82.35 83.27 83.33 66.79 68.92 <![CDATA[Pore volume / cm 3 ·g -1 > 0.07 0.06 0.06 0.04 0.05 Average pore size / nm 22.6 21.8 21.9 19.9 20.4

[0055] From the above, it can be seen that the biochar obtained by the present invention has a well-developed pore structure, high yield, large surface area, and excellent adsorption performance; combined with the data of the comparative example, it can be seen that the performance parameters of the finished product can be improved to a certain extent by controlling the amine-containing solution and the carbonization process.

[0056] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing biochar using garden waste as raw materials, characterized in that: The following steps are involved: S1. Drying the garden waste; S2. The treated raw material is placed in a sealed pyrolysis furnace, and a protective gas is introduced, and then the temperature is increased for carbonization treatment; S3. The biomass raw material after carbonization is cooled to room temperature, and then ground and sieved in sequence to obtain biochar.

2. The method for preparing biochar using garden waste as raw materials according to claim 1, characterized in that: The specific operations of step S1 are: The garden waste is naturally air-dried, crushed, and then mixed with an amine solution, heated to 55-65°C and stirred thoroughly, naturally cooled to room temperature, filtered, and the filter residue is dried in an oven to complete the treatment process.

3. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: The particle size of the crushed garden waste is 2-6 mm.

4. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: The amine-containing solution is aqueous ammonia or ammonium chloride solution with a concentration of 12-15 g / L.

5. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: The solid-liquid ratio of the crushed garden waste to the amine-containing solution is 1g:3-5mL.

6. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: Oven drying parameters are: drying at 70-80°C for 15-24h.

7. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: In step S2, the protective gas is nitrogen or argon, the flow rate of the protective gas is 2-3 L / min, and the introduction time is 30 min.

8. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: The heating carbonization process includes two steps: 1) Heating from room temperature to 200-300°C at a heating rate of 10°C / min and holding time of 30-60min; 2) Continue to raise the temperature from the final temperature of the first stage to 500-700°C, the heating rate is 5°C / min, and the pyrolysis time is 2-3h.

9. The method for preparing biochar using garden waste as raw materials according to claim 2, characterized in that: The screening process in step S2 is through a 10-20 mesh sieve.