Method for preparing biochar through co-pyrolysis of coal-based solid waste and biomass

Abstract

The invention relates to the field of waste resource utilization, in particular to a method for preparing biochar through co-pyrolysis of coal-based solid waste and biomass. Through co-pyrolysis of the coal-based solid waste and the biomass, the energy conversion efficiency can be effectively improved. Compared with independent pyrolysis, the interaction between the volatile components of the biomass and the semicoke of the coal in the co-pyrolysis process can promote the pyrolytic reaction, and the heat value of the pyrolysis product is increased, so that the utilization efficiency of energy is improved. According to the method disclosed by the invention, the coal-based solid waste and the biomass are subjected to co-pyrolysis, so that the environmental pollution caused by independently treating the waste is reduced. In the co-pyrolysis process, volatile components of the biomass can catalyze pyrolysis of coal, formation of coke is reduced, meanwhile, emission of pollutants such as CO2, SOx and NOx is reduced, release of chemical components is reduced, and environment friendliness is achieved.

Description

Technical Field

[0001] The invention relates to a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, belonging to the technical field of energy and environmental protection, and in particular to resource utilization of waste and preparation technology of biochar. Background Art

[0002] Coal-based solid waste refers to solid waste generated during the process of coal mining, washing, combustion and gasification, mainly including coal gangue and fly ash. The long-term stacking of these solid wastes not only occupies a large amount of land resources, but also causes serious pollution to the ecological environment such as the atmosphere, water bodies and soil. Coal-based solid waste has a low carbon content, low calorific value, and ultra-low volatile matter. It is a difficult-to-burn fuel and is difficult to burn and utilize. At the same time, the impurity composition in the ash is complex, containing toxic substances such as heavy metals. The utilization process of inorganic components is complex and energy consumption is high. These characteristics limit the large-scale utilization of coal-based solid waste.

[0003] The world is rich in biomass resources, with a huge annual net production. In particular, the large amount of waste generated in the agricultural and forestry production process, such as straw and wood waste, are potential biomass energy. These biomass resources can be pyrolyzed to obtain bio-oil, biochar and pyrolysis gas, providing a new solution for energy supply.

[0004] How to reuse coal-based solid waste and biomass resources and reuse the two raw materials is an issue that needs to be studied urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, which can effectively utilize coal-based solid waste and biomass, reduce environmental pollution, and prepare biochar products with high calorific value and low ash content. In order to achieve the above technical purpose, the technical solution provided by the present invention is as follows:

[0006] A method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, comprising the following steps:

[0007] S1: pre-treating coal-based solid waste;

[0008] S2: mixing the pretreated coal-based solid waste with biomass;

[0009] S3: Add water to the mixture and stir to mix evenly;

[0010] S4: pressing the mixture into blocks;

[0011] S5: pyrolysis under anaerobic conditions;

[0012] S6: Collect the obtained biochar product.

[0013] As an improvement, the preprocessing described in S1 includes the following steps:

[0014] S1-1: crushing coal-based solid waste;

[0015] S1-2: drying the crushed coal-based solid waste;

[0016] S1-3: Screening the dried coal-based solid waste.

[0017] As an improvement, the weight ratio of coal-based solid waste to biomass described in S2 is 1:1 to 1:4.

[0018] As an improvement, the amount of water added in S3 is 5% to 15% of the total weight of the mixture.

[0019] As an improvement, the pressure for pressing into blocks in S4 is 5 to 20 MPa.

[0020] As an improvement, the size of the block material described in S4 is 10 mm to 50 mm in diameter and 10 mm to 50 mm in height.

[0021] As an improvement, the pyrolysis temperature described in S5 is controlled at 400° C. to 800° C., and the pyrolysis time is 1 to 4 hours.

[0022] As an improvement, the biomass in step S2 includes corn straw, sorghum straw, wheat straw, rice straw, bean straw, cotton stalk and wood cellulose.

[0023] The advantages of the present invention are:

[0024] 1. The present invention can effectively improve the energy conversion efficiency by co-pyrolysis of coal-based solid waste and biomass. Compared with pyrolysis alone, the interaction between the volatile matter of biomass and the semi-coke of coal during co-pyrolysis can promote the pyrolysis reaction, increase the calorific value of the pyrolysis product, and thus improve the energy utilization efficiency.

[0025] 2. The method of the present invention reduces the environmental pollution caused by treating these wastes separately by co-pyrolyzing coal-based solid waste and biomass. During the co-pyrolysis process, the volatile matter of biomass can catalyze the pyrolysis of coal, reduce the formation of coke, and reduce pollutants such as CO 2 、SO x and NO x It reduces emissions, reduces the release of chemical components and is environmentally friendly. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with 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.

[0027] Example 1

[0028] This embodiment discloses a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, comprising the following steps:

[0029] The coal-based solid waste is crushed to a particle size of less than 10 mm, dried to a moisture content of less than 5%, and sieved to a particle size range of 0.5 mm to 5 mm. The coal-based solid waste and biomass are mixed in a weight ratio of 1:2, 10% water is added, and pressed into a block material with a diameter of 20 mm and a height of 30 mm, and pyrolyzed at 600°C for 2 hours to obtain a biochar product.

[0030] Example 2

[0031] This embodiment discloses a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, comprising the following steps:

[0032] The coal-based solid waste is crushed to a particle size of less than 10 mm, dried to a moisture content of less than 5%, and sieved to a particle size range of 0.5 mm to 5 mm. The coal-based solid waste and biomass are mixed in a weight ratio of 1:3, 8% water is added, and pressed into a block material with a diameter of 30 mm and a height of 40 mm, and pyrolyzed at 700°C for 3 hours to obtain a biochar product.

[0033] Example 3

[0034] This embodiment discloses a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, comprising the following steps:

[0035] The coal-based solid waste was crushed to a particle size of less than 10 mm, dried to a moisture content of less than 5%, and sieved to a particle size range of 0.5 mm to 5 mm. The coal-based solid waste and biomass were mixed in a weight ratio of 1:4, 12% water was added, and the mixture was pressed into a block material with a diameter of 40 mm and a height of 50 mm, and pyrolyzed at 550°C for 1.5 hours to obtain a biochar product.

[0036] Example 4

[0037] This embodiment discloses a method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, comprising the following steps:

[0038] The coal-based solid waste is crushed to a particle size of less than 10 mm, dried to a moisture content of less than 5%, and sieved to a particle size range of 0.5 mm to 5 mm. The coal-based solid waste and biomass are mixed in a weight ratio of 1:1, 15% water is added, and pressed into a block material with a diameter of 10 mm and a height of 20 mm, and pyrolyzed at 650°C for 2.5 hours to obtain a biochar product.

[0039] The products of Examples 1-4 were taken and tested for calorific value and ash content.

[0040] The test method for calorific value is as follows:

[0041] 1. Sample weighing: Weigh an appropriate amount of sample, accurate to 0.0001g.

[0042] 2. Preparation of oxygen bomb calorimeter: Select standard substances for calibrating the heat capacity of oxygen bomb calorimeter, weigh them, and then test and calculate the heat capacity of oxygen bomb calorimeter.

[0043] 3. Preparation of encapsulated capsules: Take an empty encapsulated capsule and weigh its mass; take an appropriate amount of sample and inject it into the capsule, where the volume of the sample occupies 1 / 2-3 / 4 of the volume of the capsule, weigh its mass, and calculate the sample mass.

[0044] 4. Ignition and combustion: Take the ignition wire and tightly wrap it around the outer periphery of the encapsulated capsule containing the sample, then place it in a heating container, and then place the two together in an oxygen bomb, and fill the oxygen bomb with oxygen until the pressure reaches 2-3 MPa.

[0045] 5. Calorific value determination: Place the oxygen bomb in the inner cylinder of the calorimeter, and then measure and pour an appropriate amount of water into it so that it just covers the top surface of the oxygen bomb; start the agitator and the outer cylinder to circulate, and after the temperature of the inner cylinder stabilizes, input the measured heat capacity, the mass of the empty encapsulated capsule and the mass of the sample into the calorific value test software of the oxygen bomb calorimeter, ignite and burn, and measure its calorific value.

[0046] 6. Repeat the test: Repeat steps 3 to 5 twice; the average of the three calorific value measurement results is the calorific value of the sample.

[0047] The ash content test method is as follows:

[0048] 1. Crucible pretreatment: First, burn the new ashtray until the mass is constant, and then place the ashtray in a dryer for use.

[0049] 2. Sample weighing: Weigh (1±0.1)g of the analytical coal sample, accurate to 0.0002g, and spread it evenly in an ash dish so that its mass per square centimeter does not exceed 0.15g.

[0050] 3. Ashing: Slowly push the ash pans containing coal samples into the muffle furnace preheated to 850℃, first ash the coal samples in the first row of ash pans, wait for 5 to 10 minutes until the coal samples stop smoking, and push the remaining rows of ash pans into the hot part in sequence at a speed of no more than 2cm / min. If the coal samples catch fire and explode, the test should be invalidated.

[0051] 4. Burning: Close the furnace door and leave a gap of about 15mm, and burn for 40 minutes.

[0052] 5. Cooling: Take out the ash dish, place it on a heat-resistant porcelain plate or asbestos board, cool it in the air for about 5 minutes, then move it into a dryer and cool it to room temperature (about 20 minutes).

[0053] 6. Weighing: After cooling, weigh the mass of the ash dish and residue.

[0054] 7. Inspection burning: Repeat burning until the difference between two consecutive weighings does not exceed 0.001g, whichever is the smallest.

[0055] 8. Calculation of results: The calculation formula for the mass fraction of ash (Aad) is Aad = (m1-m) / m×100%, where m1 is the mass of the residue after burning, and m is the mass of the general analytical test coal sample weighed.

[0056] The test results are shown in Table 1:

[0057] Table 1 Calorific value and ash content of each product

[0058] Example 1 Example 2 Example 3 Example 4 Calorific value (MJ / kg) 18.5 17.0 15.5 16.0 Ash content (%) 5.2 6.5 7.8 6.0

[0059] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing biochar by co-pyrolysis of coal-based solid waste and biomass, characterized in that: The following steps are involved: S1: pre-treating coal-based solid waste; S2: mixing the pretreated coal-based solid waste with biomass; S3: Add water to the mixture and stir to mix evenly; S4: pressing the mixture into blocks; S5: pyrolysis under anaerobic conditions; S6: Collect the obtained biochar product.

2. The method according to claim 1, characterized in that The preprocessing described in S1 includes the following steps: S1-1: crushing coal-based solid waste; S1-2: drying the crushed coal-based solid waste; S1-3: Screening the dried coal-based solid waste.

3. The method according to claim 1, characterized in that The weight ratio of the coal-based solid waste to the biomass described in S2 is 1:1 to 1:

4.

4. The method according to claim 1, characterized in that: The amount of water added in S3 is 5% to 15% of the total weight of the mixture.

5. The method according to claim 1, characterized in that: The pressure for pressing into blocks in S4 is 5 to 20 MPa.

6. The method according to claim 1, characterized in that The size of the block material described in S4 is 10mm to 50mm in diameter and 10mm to 50mm in height.

7. The method according to claim 1, characterized in that The pyrolysis temperature described in S5 is controlled at 400° C. to 800° C., and the pyrolysis time is 1 to 4 hours.

8. The method according to claim 1, characterized in that The biomass in step S2 includes corn straw, sorghum straw, wheat straw, rice straw, bean straw, cotton stalk and wood cellulose.