Preparation method and application of bagasse biochar

Abstract

The invention discloses a bagasse biochar preparation method and application, and belongs to the technical field of biochar preparation, the preparation method comprises the following steps: drying bagasse of a sugar refinery until the water content does not exceed 28%; preheating the continuous carbonization equipment for 1.4-1.6 hours, and controlling the temperature in a main engine room to be 470-500 DEG C; the dried bagasse is fed into continuous carbonization equipment to be carbonized, the frequency of a feeding motor is controlled to range from 17.0 HZ to 1.72 HZ, the frequency of an equipment host is controlled to range from 17.3 HZ to 17.5 HZ, and the frequency of a fan is controlled to range from 19.3 HZ to 19.5 HZ. The application refers to the application in reducing the content of soil heavy metals Pb and Cd in effective states and the content of organic dyes, and the application in increasing the content of mineral binding state organic matters and condensed ring aromatic carbon in the soil. According to the preparation method, processing parameters are optimized, the bagasse biochar is produced with low oil consumption, high charcoal conversion rate and high yield, although the specific surface area of the bagasse biochar is relatively low, the average pore size and mesopore average pore size of the biochar are relatively high, and the bagasse biochar is high in aromaticity and excellent in quality. The bagasse biochar can be used for soil improvement.

Description

Technical Field

[0001] This invention belongs to the field of biochar preparation technology, specifically relating to a method for preparing bagasse biochar and its application. Background Technology

[0002] Sugarcane, as an important economic crop, produces bagasse, a byproduct that is typically used as organic fertilizer or animal feed. However, in practice, some bagasse remains unutilized due to transportation difficulties and high processing costs, resulting in on-site burning or indiscriminate dumping, thus continuing to put pressure on the environment. Although bagasse is primarily produced in sugar mills, making it convenient to collect as a biochar raw material, its high sugar content and tendency to agglomerate and coke make it difficult to stably convert in traditional horizontal continuous carbonization devices. Chinese invention patent CN109650370A discloses a method for preparing bagasse biochar using atmospheric pressure hydrothermal methods. This method employs an atmospheric pressure hydrothermal approach, utilizing a high-boiling-point co-solvent to pyrolyze bagasse in an environment surrounded by liquid water to prepare bagasse biochar with regular granules. However, this method requires the use of a high-boiling-point co-solvent, making the process complex and difficult to scale up for production. Chinese invention patent CN117361527A discloses a method for preparing nitrogen-doped porous bagasse biochar. This method involves washing the bagasse during pretreatment to remove its sugar content before further processing. Currently, there are no reports of research on the stable production of bagasse biochar directly in a traditional horizontal continuous carbonization unit without pretreatment.

[0003] Therefore, it is essential to develop a method for preparing bagasse biochar suitable for stable horizontal continuous carbonization production and its application. Summary of the Invention

[0004] To address the technical challenges of stable conversion of bagasse biochar in horizontal continuous carbonization units due to its high sugar content and tendency to agglomerate and coke, the primary objective of this invention is to provide a method for preparing bagasse biochar. Key process parameters have been optimized based on the characteristics of bagasse raw materials, resulting in a suitable carbonization solution. Developing a method for preparing bagasse biochar suitable for high-sugar biomass and its application has significant practical importance and application value, aiming to further promote the resource utilization of bagasse and alleviate pollution from agricultural and forestry waste incineration.

[0005] The second objective of this invention is to provide an application of bagasse biochar.

[0006] The first objective of this invention is achieved by the following steps: S1. Dry the sugarcane bagasse from the sugar mill to a moisture content of no more than 28%; S2. Preheat the continuous carbonization equipment for 1.4h~1.6h, and control the temperature inside the main engine compartment to 470℃~500℃; S3. The dried bagasse is fed into a continuous carbonization equipment for carbonization. The frequency of the feeding motor is controlled at 17.0HZ~1.72HZ, the frequency of the main equipment is controlled at 17.3HZ~17.5HZ, and the frequency of the blower is controlled at 19.3HZ~19.5HZ.

[0007] Among them, continuous carbonization equipment is a processing equipment known to those skilled in the art for continuous production of biochar. It includes a feeding system (equipped with a feeding motor to drive the feeding mechanism), a carbonization host (including an adjustable speed host drive motor whose frequency corresponds to the host frequency of the equipment), a temperature control system (equipped with a temperature sensor to monitor the temperature inside the host chamber), and an exhaust and atmosphere conditioning system (equipped with a fan to regulate the carbonization atmosphere and discharge volatiles). Specifically, the continuous carbonization equipment involved in the applicant's authorized utility model patent "A system for continuous carbonization of bagasse to produce biochar and recycling by-products" (patent number: ZL2023201984676) can also be used.

[0008] The temperature inside the main unit compartment refers to the average temperature inside the reaction chamber of the carbonization main unit; the feeding motor frequency refers to the operating frequency of the feeding motor of the feeding system; the main unit frequency refers to the operating frequency of the main unit drive motor that drives the carbonization main unit to rotate or propel; and the fan frequency refers to the operating frequency of the fan in the exhaust and atmosphere conditioning system.

[0009] Preferably, the moisture content in step S1 is 20% to 25%.

[0010] Preferably, the preheating in step S2 is a jacketed preheating.

[0011] Preferably, the carbonization tail gas generated in step S3 is sent to the gas storage tank after dust removal and purification, and used for combustion preheating in step S2.

[0012] Preferably, the biochar after carbonization in step S3 is cooled and transported externally.

[0013] Preferably, the feeding end of the continuous carbonization equipment is a feeding conveyor.

[0014] The second objective of this invention is achieved by pulverizing the bagasse biochar prepared by the aforementioned method through an 80-100 mesh sieve, and then applying the biochar to the soil during tillage at a rate of 50 kg / 667 m². 2 ~300kg / 667m 2 .

[0015] Compared with the prior art, the present invention has the following technical effects: 1. The preparation method of this invention controls the processing parameters, and the raw material bagasse requires no pretreatment. It can be directly used for horizontal continuous carbonization to stably produce bagasse biochar, achieving low oil consumption, high carbon conversion rate, and high yield of bagasse biochar, without any adhesion or coking. Although the biochar of this invention has particulate attachments on its surface and its structure is relatively irregular, this invention cleverly utilizes this rough surface and complex pore pattern to expose more adsorption active sites. This is one of the reasons why the biochar of this invention significantly reduces the available content of heavy metals Pb and Cd in soil. Although the bagasse biochar of this invention has a low specific surface area, its average pore size and mesopore average pore size are high. The combination of low specific surface area and large pore size indicates that the pores of bagasse biochar are mainly mesopores and macropores. These pores have low gas adsorption efficiency, but are very beneficial in adsorbing large molecular pollutants such as organic dyes or providing habitats for microorganisms in soil improvement.

[0016] 2. The bagasse biochar of this invention can be used for soil improvement, effectively increasing the content of mineral-bound organic matter and polycyclic aromatic carbon in arable soil. These two types of components are widely considered to be the most stable carbon forms in the soil carbon pool. Their accumulation not only helps improve soil structure and fertility, but also significantly enhances the long-term carbon sequestration capacity of the soil, which has important technical effects and environmental significance for improving soil quality and achieving sustainable use of arable land. Attached Figure Description

[0017] Figure 1 It is in the form of bagasse biochar; Figure 2 The results of SEM scanning of bagasse biochar; Figure 3 This is the result of infrared detection. Detailed Implementation

[0018] The present invention will be further described below with reference to the embodiments and accompanying drawings, but this does not limit the present invention in any way. Any changes or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention. Example 1

[0019] The method for preparing bagasse biochar in this embodiment includes the following steps: S1. Dry the sugarcane bagasse from the sugar mill to a moisture content of 20%; S2. Preheat the continuous carbonization equipment for 1.4 hours, controlling the temperature inside the main engine compartment to 470℃; the preheating is a jacketed preheating. S3. The dried bagasse is fed into a continuous carbonization equipment for carbonization. The frequency of the feeding motor is controlled at 17.0 Hz, the frequency of the main equipment is controlled at 17.3 Hz, and the frequency of the blower is controlled at 19.3 Hz. The carbonization tail gas generated is sent to the gas storage tank after dust removal and purification, and is used for combustion preheating in step S2. The carbonized biochar is cooled and transported to other areas. Example 2

[0020] The method for preparing bagasse biochar in this embodiment is the same as in Example 1, except that the moisture content in step S1 is 28%, the preheating time in step S2 is 1.6 h, the temperature inside the main unit is 500 °C, the frequency of the feeding motor is 1.72 Hz, the frequency of the main unit is 17.5 Hz, and the frequency of the fan is 19.5 Hz. Example 3

[0021] The method for preparing bagasse biochar in this embodiment is the same as in Example 1, except that the moisture content in step S1 is 24%, the preheating time in step S2 is 1.5 h, the temperature inside the main unit is 485 ℃, the frequency of the feeding motor is 17.1 Hz, the frequency of the main unit is 17.4 Hz, and the frequency of the fan is 19.4 Hz. Example 4

[0022] The method for preparing bagasse biochar in this embodiment is the same as in Example 1, except that the moisture content in step S1 is 25%, the preheating time in step S2 is 1.5 h, the temperature inside the main unit is 490 °C, the frequency of the feeding motor is 17 Hz, the frequency of the main unit is 17.5 Hz, and the frequency of the fan is 19.5 Hz. Example 5

[0023] The method for preparing bagasse biochar in this embodiment is the same as in Example 1, except that the moisture content in step S1 is 22.5%, the preheating time in step S2 is 1.6 h, the temperature inside the main unit is 480 ℃, the frequency of the feeding motor is 17 Hz, the frequency of the main unit is 17.5 Hz, and the frequency of the fan is 19.5 Hz. Example 6

[0024] The method for preparing bagasse biochar in this embodiment is the same as in Example 1, except that the preheating time in step S2 is 1.5 h, the temperature inside the main unit is 485 °C, the frequency of the feeding motor is 17.1 Hz, the frequency of the main unit is 17.4 Hz, and the frequency of the fan is 19.4 Hz.

[0025] Experimental Example 1 This comparative experiment designed 20 different parameters and statistically analyzed the combustion engine fuel consumption, output, and carbon conversion rate. The results are shown in Table 1.

[0026] Table 1. Statistical Table of Comparative Experiments

[0027] Serial number 5 is the technical solution of the present invention (Example 6), with a diesel consumption of 20L / h, a carbon conversion rate of 17.2%, and an output of 0.375 tons / h. It can be seen that the solution of the present invention achieves relatively low fuel consumption, high carbon conversion rate, and highest output. Based on parameter 5, four control groups (a, b, c, and d) were set up. Group a had a controlled temperature of 280℃ inside the main engine compartment, group b 330℃, group c 380℃, and group d 430℃. All other parameters were the same as in parameter 5. The biochar morphology diagrams obtained for each group are attached. Figure 1 As shown, group e (the temperature inside the main engine compartment is 470℃) is the bagasse biochar prepared by serial number 5. A comparison of SEM images of the biochar prepared in item 5 with commercially available biochar is shown in the appendix. Figure 2 As shown, the images, from top to bottom, depict the same area at different magnifications (4000x, 2000x, 1000x, 500x); (Attached) Figure 2 In the diagram, a1 and a2 are commercially available biochar, and e1 and e2 are the biochar of this invention. As can be seen from the scanning electron microscope images, the biochar of this invention has a distinct porous structure. The three biochar samples (BC1, BC3, and BC5) prepared by serial number 5 and the commercially available biochar (BC0) were subjected to BET determination. The results are shown in Table 2. Table 2. BET variation of different biochars

[0028] As shown in the table above, the specific surface area of ​​commercially available biochar is significantly higher than that of the bagasse biochar of the present invention, but the porosity is significantly lower than that of the biochar of the present invention. Combined with SEM, it can be seen that the bagasse biochar of the present invention has a larger pore size. The biochar prepared by serial number 5 was sent for elemental analysis. The results showed that the N content was 0.64%, the C content was 77.69%, the H content was 2.8%, the S content was 0%, the H / C (molar ratio) was 0.43, and the pH was 9.40, which belongs to Class I biochar. Three biochar samples (BC1, BC3, and BC5) prepared in sequence 5, as well as commercially available biochar (BC0), were subjected to infrared spectroscopy. The results are shown in the figure. Figure 3 The correspondence between wavenumber and functional group in the figure is shown in the table below; Table 3 Correspondence between wavenumber and functional group

[0029] It is evident that this biochar lacks hydroxyl groups (-OH). Figure 3 The mid-wave number is 3420 cm⁻¹ -1 The absorption peak at that point is a broad peak due to the stretching vibration of the hydroxyl group (-OH). At this wavenumber, there is essentially no absorption peak, and at a wavenumber of 2360 cm⁻¹... -1 There is a distinct absorption peak at this point, which is a C≡C stretching peak, at a wavenumber of 875 cm⁻¹. -1 The presence of absorption peaks indicates the presence of oxygen-containing functional groups, as well as monocyclic and polycyclic compounds, and indicates high aromaticity.

[0030] Experiment Example 2 The bagasse biochar prepared in Example 6 was pulverized and passed through a 100-mesh sieve. The biochar was then applied to the soil during tillage at a rate of 50 kg / 667 m². 2 The experiment was conducted in 5 groups (numbered 1 to 5); soil samples were taken after 30 days to detect mineral-bound organic carbon and polycyclic aromatic carbon in the soil samples. The results are shown in Tables 4 and 5.

[0031] Table 4. Detection results of mineral-bound organic carbon

[0032] Table 5 Detection results of polycyclic aromatic carbon

[0033] It is evident that the bagasse biochar of this invention can effectively increase the amount of bound organic carbon and polycyclic aromatic carbon in the soil.

Claims

1. A method for preparing bagasse biochar, characterized in that... Includes the following steps: S1. Dry the sugarcane bagasse from the sugar mill to a moisture content of no more than 28%; S2. Preheat the continuous carbonization equipment for 1.4h~1.6h, and control the temperature inside the main engine compartment to 470℃~500℃; S3. The dried bagasse is fed into a continuous carbonization equipment for carbonization. The frequency of the feeding motor is controlled at 17.0HZ~1.72HZ, the frequency of the main equipment is controlled at 17.3HZ~17.5HZ, and the frequency of the blower is controlled at 19.3HZ~19.5HZ.

2. The method for preparing bagasse biochar according to claim 1, characterized in that... The moisture content of step S1 is 20%–25%.

3. The method for preparing bagasse biochar according to claim 1, characterized in that... Step S2 preheating is a jacketed preheating.

4. The method for preparing bagasse biochar according to claim 1, characterized in that... The carbonization tail gas generated in step S3 is sent to the gas storage tank after dust removal and purification, and is used for combustion preheating in step S2.

5. The method for preparing bagasse biochar according to claim 1, characterized in that... After carbonization in step S3, the biochar is cooled and transported externally.

6. The method for preparing bagasse biochar according to claim 1, characterized in that... The feeding end of the continuous carbonization equipment is a feeding conveyor.

7. A bagasse biochar prepared by the method for preparing bagasse biochar according to any one of claims 1 to 6.

8. The application of bagasse biochar according to claim 7 in reducing the content of available heavy metals Pb and Cd and organic dyes in soil.

9. The application of bagasse biochar according to claim 7 in increasing the content of mineral-bound organic matter and polycyclic aromatic carbon in soil.

10. An application according to claim 8 or 9, characterized in that... The bagasse biochar is pulverized and passed through an 80-100 mesh sieve. The biochar is then applied to the soil during tilling, at a rate of 50 kg / 667 m². 2 ~300kg / 667m 2 .

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