A biochar, its preparation method and application

Abstract

The present invention belongs to the technical field of biochar preparation, and discloses a biochar, a preparation method thereof and an application. The preparation method of the biochar comprises the following steps: crushing biomass, and then successively performing low-temperature carbonization and high-temperature carbonization on the crushed biomass to obtain an intermediate biochar; the temperature of the low-temperature carbonization is 300-450 °C, and the time of the low-temperature carbonization is 2-4 h; the temperature of the high-temperature carbonization is 600-800 °C, and the time of the high-temperature carbonization is 4-5 h; mixing the intermediate biochar with water and performing a hydrothermal reaction to obtain the biochar. The preparation method of the biochar provided by the present invention, by adopting pyrolytic carbonization and hydrothermal carbonization methods and further regulating the parameters of the hydrothermal carbonization and pyrolytic carbonization processes, can prepare high-quality biochar with the characteristics of low ash content and high fixed carbon content, combining the advantages of pyrolytic carbonization and hydrothermal carbonization.

Description

Technical Field

[0001] The present invention relates to the technical field of biochar preparation, and in particular to a biochar, a preparation method thereof, and an application thereof. Background Art

[0002] Biomass generally refers to any renewable or recyclable organic matter, including all animals, plants, microorganisms, and all organic matter generated by their life activities. Due to the current shortage of energy and the severe situation of environmental pollution, the efficient, circular, and reasonable utilization of biomass has become the preferred way for countries around the world to build a low-carbon economy and social system. Biomass carbonization technology is an emerging technology for the resource utilization of biomass. It mainly carbonizes biomass and fixes it in the form of stable carbon, thereby forming a new type of biochar product.

[0003] The preparation methods of biochar are mainly divided into dry pyrolysis carbonization method and hydrothermal carbonization method. Among them, the hydrothermal carbonization method is a process in which biomass in a closed high-pressure reactor is converted into hydrothermal carbon (carbon spheres) with water as the reaction medium at a certain temperature and pressure. However, generally, the fixed carbon content of hydrothermal carbon is low, the ash content is low, and the volatile matter content is high, which leads to a low fuel ratio of the prepared biochar. The dry pyrolysis carbonization method is the most widely used method at present. However, the biochar prepared by the dry pyrolysis carbonization method has a high ash content, and at the same time, the biochar material obtained by the dry pyrolysis carbonization method requires high energy consumption and economic cost.

[0004] Therefore, providing a biochar with a low ash content and a high fixed carbon content while reducing the energy consumption in the reaction process is an urgent problem to be solved at present. Summary of the Invention

[0005] The purpose of the present invention is to provide a biochar, a preparation method thereof, and an application thereof, so as to solve the problems of high ash content, low fixed carbon content of the existing prepared biochar, and high energy consumption in the preparation process.

[0006] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a preparation method of biochar, comprising the following steps:

[0008] (1) Crushing biomass, and then sequentially performing low-temperature carbonization and high-temperature carbonization on the crushed biomass to obtain an intermediate biochar;

[0009] The temperature of the low-temperature carbonization is 300-450°C, and the time of the low-temperature carbonization is 2-4 h;

[0010] The temperature of the high-temperature carbonization is 600-800°C, and the time of the high-temperature carbonization is 4-5 h;

[0011] (2) Mix the intermediate biochar with water and conduct hydrothermal reaction to obtain biochar.

[0012] Preferably, in the above-mentioned method for preparing a kind of biochar, in step (1), the biomass is one or more of walnut shell, pine nut shell, coconut shell, peanut shell, rice husk, sunflower seed shell, corn cob, and crop straw.

[0013] Preferably, in the above-mentioned method for preparing a kind of biochar, in step (1), the atmospheres of the low-temperature carbonization and the high-temperature carbonization are independently nitrogen atmospheres.

[0014] Preferably, in the above-mentioned method for preparing a kind of biochar, in step (1), the particle size of the crushed biomass is 0.2 - 5 cm.

[0015] Preferably, in the above-mentioned method for preparing a kind of biochar, in step (1), the mass ratio of the biomass to the water in step (2) is 1:2 - 5.

[0016] Preferably, in the above-mentioned method for preparing a kind of biochar, in step (2), the temperature of the hydrothermal reaction is 150 - 220 °C, and the time of the hydrothermal reaction is 60 - 120 min.

[0017] The present invention also provides a biochar prepared by the method for preparing a kind of biochar.

[0018] The present invention also provides an application of the biochar in steel smelting.

[0019] From the above technical solutions, it can be seen that compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The method for preparing biochar provided by the present invention, by adopting pyrolytic carbonization and hydrothermal carbonization methods and further regulating the parameters of the hydrothermal carbonization and pyrolytic carbonization processes, can prepare high-quality biochar with the characteristics of low ash content and high fixed carbon content, effectively improving the combustion performance of biochar and at the same time improving the activity of biochar in steel smelting; combining the advantages of pyrolytic carbonization and hydrothermal carbonization, reducing the reaction energy consumption.

[0021] (2) In the present invention, the crushed biomass is first subjected to low-temperature carbonization and then high-temperature carbonization under a protective atmosphere. During the low-temperature carbonization process, the organic compounds in the raw materials decompose into carbon and various gases under anaerobic and high-temperature conditions. When the gases are generated, a large number of pores can be formed in the carbon matrix and maintained for a long time at this temperature, which is beneficial to increasing the specific surface area of the carbon. During the high-temperature carbonization process, the carbon source continues to heat up and then generates carbon with stronger rigidity. At this time, the generated high-temperature vapor can form micropores with smaller sizes on the carbon matrix, further increasing the specific surface area of the carbon. Detailed implementation manners

[0022] The present invention provides a method for preparing biochar, comprising the following steps:

[0023] (1) Crush the biomass, and then subject the crushed biomass to low-temperature carbonization and high-temperature carbonization in sequence to obtain intermediate biochar;

[0024] The temperature of the low-temperature carbonization is preferably 300-450 °C, more preferably 320-420 °C, and still more preferably 350-400 °C; the time of the low-temperature carbonization is preferably 2-4 h, more preferably 2.5-3.5 h, and still more preferably 3 h;

[0025] The temperature of the high-temperature carbonization is preferably 600-800 °C, more preferably 650-750 °C, and still more preferably 680-720 °C; the time of the high-temperature carbonization is preferably 4-5 h, more preferably 4.2-4.75 h, and still more preferably 4.5 h;

[0026] (2) Mix the intermediate biochar with water and carry out a hydrothermal reaction to obtain biochar.

[0027] In the present invention, the biomass in step (1) is preferably one or more of walnut shells, pine nut shells, coconut shells, peanut shells, rice husks, sunflower seed husks, corn cobs, and crop straws, more preferably one or more of walnut shells, coconut shells, sunflower seed husks, and crop straws, and still more preferably one or more of walnut shells, coconut shells, and sunflower seed husks.

[0028] In the present invention, the atmosphere of the low-temperature carbonization and the high-temperature carbonization in step (1) is preferably an independent nitrogen atmosphere.

[0029] In the present invention, the heating rate of the low-temperature carbonization and the high-temperature carbonization in step (1) is preferably 8-12 °C / min, more preferably 9-11 °C / min, and still more preferably 10 °C / min.

[0030] In the present invention, the particle size of the crushed biomass in step (1) is preferably 0.2-5 cm, more preferably 2-4 cm, and still more preferably 3 cm.

[0031] In the present invention, the mass ratio of the biomass in step (1) to the water in step (2) is preferably 1:2-5, more preferably 1:2.5-4.5, and still more preferably 1:3-4.

[0032] In the present invention, the temperature of the hydrothermal reaction in step (2) is preferably 150-220°C, more preferably 160-210°C, and even more preferably 170-200°C; the time of the hydrothermal reaction is preferably 60-120 min, more preferably 70-100 min, and even more preferably 80-90 min.

[0033] The present invention also provides a biochar prepared by the method for preparing biochar.

[0034] The present invention also provides an application of the biochar in steel smelting.

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0036] Example 1

[0037] A method for preparing biochar includes the following steps:

[0038] Crush 200 g of walnut shells to a particle size of 0.2-5 cm, and then, under a nitrogen atmosphere, heat the crushed walnut shells to 400°C at a heating rate of 10°C / min for low-temperature carbonization for 3 h. After the low-temperature carbonization is completed, heat the obtained product to 700°C at a heating rate of 10°C / min for high-temperature carbonization for 4 h to obtain an intermediate biochar;

[0039] Mix the intermediate biochar with 500 mL of water and carry out a hydrothermal reaction at 200°C for 100 min to obtain biochar.

[0040] The specific surface area of the biochar prepared above is detected to be 2452 m 2 / g, the ash content is less than or equal to 7 wt%, and the fixed carbon content is greater than or equal to 85 wt%.

[0041] Example 2

[0042] A method for preparing biochar includes the following steps:

[0043] Crush 50 g of walnut shells and 100 g of corn cobs to a particle size of 0.2-5 cm and mix them. Then, under a nitrogen atmosphere, heat the crushed walnut shells and corn cobs to 300°C at a heating rate of 8°C / min for low-temperature carbonization for 2 h. After the low-temperature carbonization is completed, heat the obtained product to 600°C at a heating rate of 10°C / min for high-temperature carbonization for 4.5 h to obtain an intermediate biochar;

[0044] Mix the intermediate biochar with 300 mL of water and carry out a hydrothermal reaction at 180 °C for 100 min to obtain biochar.

[0045] The specific surface area of the biochar prepared above was detected to be 2508 m 2 / g, the ash content is less than or equal to 5.6 wt%, and the fixed carbon content is greater than or equal to 82 wt%.

[0046] Example 3

[0047] A method for preparing biochar, comprising the following steps:

[0048] Crush 100 g of coconut shells and 100 g of peanut shells to a particle size of 0.2 - 5 cm and mix them. Then, in an N2 atmosphere, heat the crushed coconut shells and peanut shells to 450 °C at a heating rate of 12 °C / min for low-temperature carbonization for 3 h. After the low-temperature carbonization is completed, heat the obtained product to 700 °C at a heating rate of 8 °C / min for high-temperature carbonization for 4 h to obtain intermediate biochar;

[0049] Mix the intermediate biochar with 400 mL of water and carry out a hydrothermal reaction at 200 °C for 80 min to obtain biochar.

[0050] The specific surface area of the biochar prepared above was detected to be 2499 m 2 / g, the ash content is less than or equal to 7 wt%, and the fixed carbon content is greater than or equal to 86 wt%.

[0051] Example 4

[0052] A method for preparing biochar, comprising the following steps:

[0053] Crush 200 g of crop straw to a particle size of 0.2 - 5 cm. Then, in an N2 atmosphere, heat the crushed crop straw to 400 °C at a heating rate of 8 °C / min for low-temperature carbonization for 3 h. After the low-temperature carbonization is completed, heat the obtained product to 800 °C at a heating rate of 8 °C / min for high-temperature carbonization for 4 h to obtain intermediate biochar;

[0054] Mix the intermediate biochar with 450 mL of water and carry out a hydrothermal reaction at 220 °C for 80 min to obtain biochar.

[0055] The specific surface area of the biochar prepared above was detected to be 2465 m 2 / g, the ash content is less than or equal to 6 wt%, and the fixed carbon content is greater than or equal to 83 wt%.

[0056] Comparative Example 1

[0057] A method for preparing biochar, comprising the following steps:

[0058] Crush 200 g of walnut shells to a particle size of 0.2 - 5 cm, and then under a N₂ atmosphere, heat the crushed walnut shells to 400 °C at a heating rate of 10 °C / min for low-temperature carbonization for 3 h. After the low-temperature carbonization is completed, heat the resulting product to 700 °C at a heating rate of 10 °C / min for high-temperature carbonization for 4 h to obtain biochar.

[0059] The specific surface area of the biochar prepared above was detected to be 2242 m 2 / g, the ash content is less than or equal to 12 wt%, and the fixed carbon content is greater than or equal to 80 wt%.

[0060] Comparative Example 2

[0061] A method for preparing biochar, comprising the following steps:

[0062] Crush 200 g of walnut shells to a particle size of 2 - 5 cm, mix the crushed walnut shells with 500 mL of water, and carry out a hydrothermal reaction at 200 °C for 100 min to obtain biochar.

[0063] The specific surface area of the biochar prepared above was detected to be 1853 m 2 / g, the ash content is less than or equal to 5 wt%, and the fixed carbon content is greater than or equal to 60 wt%.

[0064] Comparative Example 3

[0065] A method for preparing biochar, comprising the following steps:

[0066] Crush 200 g of walnut shells to a particle size of 0.2 - 5 cm, and then under a N₂ atmosphere, heat the crushed walnut shells to 400 °C at a heating rate of 10 °C / min for low-temperature carbonization for 3 h to obtain intermediate biochar;

[0067] Mix the intermediate biochar with 500 mL of water, and carry out a hydrothermal reaction at 200 °C for 100 min to obtain biochar.

[0068] The specific surface area of the biochar prepared above was detected to be 1908 m 2 / g, the ash content is less than or equal to 8 wt%, and the fixed carbon content is greater than or equal to 75 wt%.

[0069] Comparative Example 4

[0070] A method for preparing biochar, comprising the following steps:

[0071] Crush 200 g of walnut shells to a particle size of 0.2 - 5 cm, and then under a N₂ atmosphere, heat to 700 °C at a heating rate of 10 °C / min for high-temperature carbonization for 4 h to obtain intermediate biochar;

[0072] Mix the intermediate biochar with 500 mL of water and carry out a hydrothermal reaction at 200 °C for 100 min to obtain biochar.

[0073] The specific surface area of the biochar prepared above was detected to be 1802 m 2 / g, the ash content is less than or equal to 10 wt%, and the fixed carbon content is greater than or equal to 78 wt%.

[0074] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing biochar, characterized in that, It includes the following steps: (1) Crush the biomass, and then subject the crushed biomass to low-temperature carbonization and high-temperature carbonization in sequence to obtain an intermediate biochar; The temperature of the low-temperature carbonization is 300-450 °C, and the time of the low-temperature carbonization is 2-4 h; The temperature of the high-temperature carbonization is 600-800 °C, and the time of the high-temperature carbonization is 4-5 h; (2) Mix the intermediate biochar with water and conduct a hydrothermal reaction to obtain biochar; The atmosphere of the low-temperature carbonization and the high-temperature carbonization in step (1) is independently a nitrogen atmosphere; The heating rate of the low-temperature carbonization and the high-temperature carbonization in step (1) is independently 8-12 °C / min; The mass ratio of the biomass in step (1) to the water in step (2) is 1:2-5; The biomass in step (1) is one or more of walnut shells, pine nut shells, coconut shells, peanut shells, rice husks, sunflower seed husks, corncobs, and crop straws; The temperature of the hydrothermal reaction in step (2) is 150-220 °C, and the time of the hydrothermal reaction is 60-120 min.

2. The preparation method of the biochar according to claim 1, characterized in that, The particle size of the crushed biomass in step (1) is 0.2-5 cm.

3. The biochar prepared by the method for preparing biochar according to any one of claims 1-2.

4. The application of the biochar according to claim 3 in steel smelting.