Preparation method and application of potassium-rich biochar and hydrogen-rich gas based on banana peel

Abstract

The invention discloses a preparation method and application of banana peel-based potassium-rich biochar and hydrogen-rich gas, the preparation method comprises the following steps: mixing banana peel and water according to a mass ratio of 4: 1-1: 4, carrying out in-situ gasification on the obtained mixed raw material at a high temperature of 800-900 DEG C to prepare the potassium-rich biochar, and obtaining a large amount of hydrogen-rich gas in the reaction process. The preparation method is simple, the potassium content in the biochar is greatly increased, the thought of biochar organic fertilizer utilization and banana peel utilization is expected to be developed, and waste resource utilization and agricultural sustainable development are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of biomass resource utilization, and in particular to a preparation method and application of potassium-rich biochar and hydrogen-rich gas based on banana peel. Background Art

[0002] The lack of potassium in the soil is one of the key factors affecting the sustainable development of agriculture in my country. With the increasing cost of imported potash fertilizers, the development of alternative potassium sources has become a top priority. As a byproduct of banana processing, the utilization technology of banana peels has attracted widespread attention because it not only helps reduce waste but also brings potential economic benefits to related industries. Banana peels are particularly rich in potassium. Recycling and enriching potassium in them not only helps to recycle waste, but also alleviates the shortage of land potassium resources, which has far-reaching significance for the sustainable development of agriculture.

[0003] Through gasification technology, banana peels can be converted into biochar, which not only realizes the effective recovery of potassium and the production of hydrogen-rich gas, but also helps to improve soil and reduce carbon emissions. Biochar is rich in nutrients, and applying it to fields can increase the nutrient content of soil. The development of high-potassium biochar is necessary. It has a potassium content equivalent to that of chemical fertilizer potassium and has obvious advantages as a substitute for chemical fertilizers, which is conducive to the development and utilization of biochar-based fertilizers. In this way, a new type of potassium-rich biochar can be developed, which can not only replace potassium fertilizers, but also improve the utilization rate of potassium. Prior art CN 111440013 A discloses a potassium-rich slow-release biochar and its preparation method and application. The preparation method comprises mixing sludge and biomass direct combustion bottom ash in a mass ratio of 9:1 to 4:1, and subjecting the obtained mixed raw materials to closed pyrolysis to obtain the potassium-rich slow-release biochar. CN 116655426 A discloses a method for preparing biochar potassium slow-release fertilizer using potassium-rich straw, the method comprising: preparing canna powder, mixing canna powder with minerals in proportion to obtain a granular composite raw material; pyrolyzing the granular composite raw material, cooling naturally to room temperature after the pyrolysis, taking out the solid product, obtaining a granular composite biochar, and obtaining a biochar potassium slow-release fertilizer. The biochar potassium slow-release fertilizer prepared by the above technology uses biogas residue and canna, and the method used is a medium-temperature carbonization method. The highest total potassium content in the carbon fertilizer prepared using biogas residue is 2.82wt%. Potassium is an important quality element and has many effects on improving crop quality. Potassium can improve crop resistance, promote the development of crop epidermal tissue and vascular tissue, strengthen cell water holding capacity, reduce plant transpiration, and thus enhance crop drought resistance; potassium can increase sugar reserves in crops, increase cell osmotic pressure, and enhance crop cold resistance. China is a large agricultural country, consuming about 30% of the world's potash fertilizers each year, and most of it is imported. Using high-potassium biomass waste as raw material for preparing potash fertilizers can, on the one hand, achieve the circulation of potassium elements, and on the other hand, reduce environmental pollution caused by waste biomass. Summary of the invention

[0004] Purpose of the invention: In view of the current increase in demand for potash fertilizers and the low potassium content in biochar potash fertilizers prepared by the prior art, the present invention provides a method for preparing potassium-rich biochar and hydrogen-rich gas based on banana peels, using banana peels as raw materials to enrich potassium in banana peel charcoal to achieve potassium element circulation. The potassium-rich biochar prepared by the present invention solves the problem of low potassium content in conventional biochar, and the biochar has the function of improving soil, and a large amount of hydrogen-rich gas can be obtained during the reaction process for energy supply.

[0005] Technical solution: In order to achieve the above-mentioned purpose, the method for preparing potassium-rich biochar and hydrogen-rich gas based on banana peel described in the present invention comprises the following steps: mixing banana peel powder and water in a mass ratio of 1:4-4:1, subjecting the obtained mixed raw material to high-temperature in-situ gasification to obtain the potassium-rich biochar, and at the same time obtaining hydrogen-rich gas.

[0006] The banana peel is a banana peel that has been cleaned and decontaminated.

[0007] Wherein, the total potassium content of the banana peel is not less than 69000 mg / kg.

[0008] The banana peel is cleaned and impurity-free banana peel, dried at a constant temperature of 100-105° C., and then crushed and sieved to obtain banana peel powder.

[0009] Wherein, the particle size of the banana peel is 20 meshes to 80 meshes.

[0010] The mass ratio of the banana peel to water is 4:1-1:4, that is, the water content of the banana peel ranges from 20% to 80%.

[0011] Among them, high-temperature in-situ gasification is carried out in a tubular furnace. The porcelain boat containing the raw materials is pushed into the constant temperature zone of the tubular furnace, and the reactor is purged with nitrogen to remove the air in the reactor. The heating program is set to heat the tube furnace to 800℃-900℃ at a heating rate of 10±1℃ / min and then maintain it for 30-40min, and the generated gas is collected. After the reaction is completed, the reactor is purged with nitrogen to cool down to room temperature, the porcelain boat is taken out and weighed, and the gasification residue is collected and stored.

[0012] Preferably, the mass ratio of the banana peel to water is 1:4-2:3, and the reaction temperature is 800° C.-900° C. and maintained for 30-40 minutes.

[0013] Preferably, the mass ratio of the banana peel to water is 1:4, 2:3, 3:2, 4:1, that is, the water content of the banana peel is 80%, 60%, 40% and 20% respectively.

[0014] The hydrogen-rich gas is collected by the water displacement method, and the volume percentage of hydrogen in the gas is determined by a gas chromatograph (GC).

[0015] Potassium-rich biochar prepared by the preparation method of the present invention.

[0016] The potassium-rich biochar of the present invention is used as a soil conditioner to improve soil and increase the effective potassium pool in the soil.

[0017] The potassium-rich biochar of the present invention is used as a gasification catalyst or a raw material for preparing potassium fertilizer.

[0018] The potassium-rich biochar described in the present invention is mainly used as a raw material for preparing potassium fertilizer, or as a soil conditioner to improve soil.

[0019] The composition of banana peel in the present invention is different from that of lignocellulosic biomass, and the main components of lignocellulosic biomass are cellulose, hemicellulose and lignin. As a peel waste, banana peel mainly consists of carbohydrates, cellulose, hemicellulose, lignin, water, minerals and a small amount of protein and fat. In order to meet the demand for banana peel to be rationally utilized, based on the consideration that alkali metal potassium in banana peel can catalyze biomass gasification and change the nutrient characteristics of biochar, the present invention utilizes banana peel in-situ gasification to prepare potassium-rich biochar, and suppresses the release of potassium in banana peel during gasification with water, thereby obtaining potassium-rich biochar, which can overcome the weakness of low potassium content of traditional biochar, has the characteristics of high potassium content, and has huge advantages as potash fertilizer directly.

[0020] Specifically, the present invention provides a method for preparing potassium-rich biochar, comprising the following steps: mixing banana peel powder and water in a mass ratio of 1:4, 2:3, 3:2, 4:1, and subjecting the obtained mixed raw material to high-temperature in-situ gasification to obtain the potassium-rich biochar. In the present invention, the release of potassium is regulated by changing the temperature and moisture content, thereby obtaining potassium-rich biochar. Among them, the total potassium content of banana peel is not less than 69000 mg / kg. If the total potassium content is too low, it will affect the potassium content in the obtained potassium-rich biochar; the particle size of banana peel is 20 mesh to 80 mesh, ensuring that it can be mixed evenly with water later, ensuring sufficient gasification reaction and biochar quality. Among them, banana peel and water are mixed in a mass ratio of 1:4, 2:3, 3:2, 4:1. If the water content is too low, it is not conducive to increasing the potassium content in biochar. If the water content is too high, it will increase energy consumption. The present invention is based on the experiment of preparing hydrogen-rich gas by high-temperature in-situ gasification. It is found that the potassium content in the residual carbon varies greatly through in-situ gasification with different moisture contents, and the total potassium content is much higher than the potassium content in the current biochar.

[0021] The present invention has been found through experiments that in the method of the present invention, the mass ratio of banana peel to water and the high-temperature in-situ gasification temperature are very important in the reaction, and significantly affect the potassium content of the prepared biochar and the yield of hydrogen-rich gas. Potassium-rich biochar is obtained by in-situ gasification at a specific banana peel to water mass ratio of 1:4 and a high temperature of 800°C for 30 minutes at a specific temperature. The total potassium content TK in the potassium-rich biochar is 358096 mg / kg, which is converted into the total potassium content of the biochar (K 2 O) is about 43.15wt.%, and the potassium nutrient is much higher than the total nutrient content (≥4%) specified in the organic fertilizer standard NY525-2021, and is also significantly higher than other banana peel and water mass ratios and reaction conditions.

[0022] The potassium-rich biochar prepared by the preparation method of the present invention can be close to the potassium content standard in chemical fertilizers and far higher than the potassium content standard in organic fertilizers. The biochar is easy to obtain and has a simple production process. It is expected to develop the utilization of biochar as an organic fertilizer, avoid environmental pollution caused by the irrational application of chemical fertilizers and the low fertilizer efficiency of traditional organic fertilizers, and realize the resource utilization of waste and sustainable agricultural development.

[0023] The present invention adopts a specific high-temperature in-situ gasification method to enrich potassium in the raw material into a solid product. If the raw material is directly gasified at high temperature, the potassium in the raw material will be released into the gas or liquid in the form of gas KCl or gaseous potassium under high temperature conditions. The present invention provides a method using in-situ gasification to enrich potassium in potassium-rich biomass, which is beneficial to the circulation of potassium elements and realizes the sustainable utilization of potassium. In addition, the method of the present invention only uses water and does not require the addition of other chemical reagents. The entire experiment is simple and efficient.

[0024] The present invention utilizes banana peels for high-temperature in-situ gasification, and the total potassium content in the potash fertilizer finally prepared is significantly higher than that of existing materials, and hydrogen-rich gas can be obtained. The hydrogen-rich gas can be directly burned to provide heat, or used in other applications such as fuel cells and chemical product production. The present invention enriches potassium in potassium-containing biomass to prepare potash fertilizer, which is beneficial to the sustainable development of the environment and energy. The present invention provides a high-temperature in-situ gasification method to enrich potassium in banana peels into gasification residues, and simultaneously obtain hydrogen-rich gas.

[0025] Beneficial effects: Compared with the prior art, it has the following advantages:

[0026] The charcoal-making raw material of the present invention has high potassium content and autocatalytic potential, and the quality of the biochar fertilizer produced is improved. The total potassium content of the biochar prepared by the present invention is significantly improved compared with biochar prepared from other biomass. The present invention not only provides a method for enriching potassium in potassium-containing biomass raw materials, but also provides a method for obtaining potassium-rich charcoal fertilizer and hydrogen-rich gas.

[0027] The preparation method of the invention is simple, the raw materials are easily available, the high-value performance of the effective components in the raw materials is fully considered, the disposal problem of by-products of biomass energy utilization technology is solved, and good economic and ecological benefits are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart for preparing potassium-rich biochar according to Examples 1-4 of the present invention;

[0029] Figure 2 This is a flow chart for preparing potassium-rich biochar according to Comparative Example 1-2 of the present invention;

[0030] Figure 3 is the total potassium content in the potassium-rich biochar and the raw materials in Examples 1-4 and Comparative Examples 1-2;

[0031] Figure 4 is the hydrogen yield in Examples 1-4 and Comparative Examples 1-2;

[0032] Figure 5 It is the volume percentage of hydrogen in Examples 1-4 and Comparative Examples 1-2. DETAILED DESCRIPTION

[0033] The present invention will be further described below by way of examples.

[0034] Unless otherwise specified, the materials and reagents used in the examples of the present invention can be obtained from commercial sources. Experimental methods without specific conditions in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0035] The banana peel in the embodiment of the present invention is the banana peel of common bananas available on the market, and the total potassium content of the banana peel is about 69649 mg / kg.

[0036] Example 1

[0037] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 1 As shown, the specific steps include:

[0038] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0039] 2. According to the mass ratio of 1:4, weigh 2g banana peel powder and 8g water respectively, place them in a 20mL corundum crucible, and shake with a glass rod to mix well.

[0040] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 800℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0041] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0042] After testing, the total potassium content TK in the potassium-rich biochar obtained in this example is 358096 mg / kg, which is converted into the total potassium content of biochar (K 2 O) is about 43.15wt.%, such as Figure 3 As shown in the figure, the potassium nutrient is much higher than the total nutrient content (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, the hydrogen yield in this embodiment is 578.24 mL / g, and the hydrogen volume percentage content is 55.78%.

[0043] Example 2

[0044] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 1 As shown, the specific steps include:

[0045] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0046] 2. According to the mass ratio of 1:4, weigh 2g banana peel and 8g water respectively, place them in a 20mL corundum crucible, and shake with a glass rod to mix well.

[0047] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 900℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0048] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0049] After testing, the total potassium content TK in the potassium-rich biochar obtained in this example is 286032 mg / kg, which is converted into the total potassium content of biochar (K 2 O) is about 34.47wt.%, such as Figure 3 As shown in the figure, potassium nutrient is much higher than the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, the hydrogen yield in this embodiment is 658.2 mL / g, and the hydrogen volume percentage content is 56.19%.

[0050] Example 3

[0051] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 1 As shown, the specific steps include:

[0052] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0053] 2. According to the mass ratio of 2:3, weigh 4g banana peel and 6g water respectively, place them in a 20mL corundum crucible, and shake with a glass rod to mix well.

[0054] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 900℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0055] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0056] After testing, the total potassium content TK in the potassium-rich biochar obtained in this example is 193690 mg / kg, which is converted into the total potassium content of the biochar (K 2 O) is about 23.34wt.%, such as Figure 3 As shown in the figure, potassium nutrient is much higher than the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, in this embodiment, the hydrogen yield is 495.57 mL / g, and the hydrogen volume percentage content is 44.06%.

[0057] Example 4

[0058] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 1 As shown, the specific steps include:

[0059] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0060] 2. According to the mass ratio of 3:2, weigh 6g of banana peel and 4g of water respectively, place them in a 20mL corundum crucible, and shake with a glass rod to mix well.

[0061] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 900℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0062] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0063] After testing, the total potassium content TK of the potassium-rich biochar obtained in this example is 117266 mg / kg, which is converted into the total potassium content of the biochar (K 2 O) is about 14.13wt.%, such as Figure 3 As shown in the figure, potassium nutrient is higher than the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, in this embodiment, the hydrogen yield is 360.96 mL / g, and the hydrogen volume percentage content is 44.51%.

[0064] Example 5

[0065] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 1 As shown, the specific steps include:

[0066] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0067] 2. According to the mass ratio of 4:1, weigh 8g banana peel and 2g water respectively, place them in a 20mL corundum crucible, and shake with a glass rod to mix well.

[0068] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 900℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0069] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0070] After testing, the total potassium content TK of the potassium-rich biochar obtained in this example is 36914 mg / kg, which is converted into the total potassium content of the biochar (K 2 O) is about 4.45wt.%, such as Figure 3 As shown in the figure, potassium nutrient is close to the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, the hydrogen yield in this embodiment is 221.3 mL / g, and the hydrogen volume percentage content is 36.35%.

[0071] Comparative Example 1

[0072] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 2 As shown, the specific steps include:

[0073] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0074] 2. According to the standard of mass ratio of 4:0, 8g of banana peel was weighed without adding water and placed in a 20mL corundum crucible, that is, the banana peel was directly used for pyrolysis and gasification to prepare biochar.

[0075] 3. Place the corundum crucible containing the mixed raw materials into the constant temperature zone of the tube furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the heating rate of the tube furnace to 10℃ / min, the end temperature to 900℃, and maintain the temperature for 30 minutes. After the gasification is completed, purge the reactor with nitrogen until the tube furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0076] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0077] After testing, the total potassium content TK of the potassium-rich biochar obtained in this example is 85508 mg / kg, which is converted into the total potassium content of the biochar (K 2 O) is about 10.26wt.%, such as Figure 3 As shown in the figure, potassium nutrient is higher than the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, in this embodiment, the hydrogen yield is 301.75 mL / g, and the hydrogen volume percentage content is 41.88%.

[0078] Comparative Example 2

[0079] The process flow of preparing potassium-rich biochar in this embodiment is as follows Figure 2 As shown, the specific steps include:

[0080] 1. Place the cleaned banana peel in a constant temperature drying oven at 105°C and dry it naturally. Crush it with a grinder, pass it through a 20-mesh and 80-mesh sieves, and take the part between the two sieves to obtain the raw material powder.

[0081] 2. According to the standard of mass ratio of 4:0, that is, the preparation of conventional biochar (using direct pyrolysis and carbonization of dry materials), weigh 8g of banana peel, put it in a 20mL corundum crucible, and shake it with a glass rod to mix it.

[0082] 3. Place the corundum crucible containing the raw materials into the constant temperature zone of the tubular furnace. Use 200ml / min of high-purity nitrogen (nitrogen purity 99.99%) to purge the reactor for 30 minutes to exhaust the air in the reactor. Set the tubular furnace to a heating rate of 10°C / min, an end temperature of 600°C, and maintain the temperature for 30 minutes. After carbonization is completed, purge the reactor with nitrogen until the tubular furnace cools to room temperature, take out the sample and place it in a drying dish for standby. Crush the sample evenly to obtain potassium-rich biochar.

[0083] 4. The prepared biochar was first microwave digested, and then the potassium content in the biochar was tested by inductively coupled plasma optical emission spectrometry (ICP-OES). During the reaction (from the beginning to the end of the reaction), the gas was collected by drainage method and the volume percentage of hydrogen in the gas was tested by gas chromatograph (GC); the hydrogen yield was obtained by multiplying the total gas output by the volume percentage of hydrogen divided by the mass of the raw material.

[0084] After testing, the total potassium content TK in the potassium-rich biochar obtained in this example is 67618 mg / kg, which is converted into total potassium content (K 2 O) 8.11wt.% Figure 3 As shown in the figure, potassium nutrient is higher than the total nutrient content index (≥4%) specified in the organic fertilizer standard NY525-2021. Figure 4 and 5 As shown, in this embodiment, the hydrogen yield is 118.28 mL / g, and the hydrogen volume percentage content is 11.97%.

[0085] By comparing Examples 1-5 with Comparative Examples 1 and 2, it can be seen that ( Figure 3 ), the total potassium content in Examples 1-4 is significantly higher than that in Comparative Examples 1 and 2. Among them, the potassium content in the biochar prepared in Example 1 is the largest, reaching 358096 mg / kg, which is converted into the total potassium content of biochar (K 2 O) is about 43.15wt.%, and the TK in the biochar prepared in Comparative Example 1 is 85508mg / kg, which is converted into the total potassium content of biochar (K 2O) is about 10.26wt.%. The total potassium content in Example 1 is 4.19 times that in Comparative Example 1. This is because temperature affects the carbonization and gasification of banana peels, affecting the release rate of K in the raw material. At the same time, after adding water, the water evaporates during the gasification process to produce water vapor, which can react with solids, volatiles, etc. as a gasifying agent to produce hydrogen-rich gas, and inhibit the release of potassium in the form of gas. The present invention can inhibit the release rate of potassium under high temperature conditions at a specific temperature and moisture content, so that potassium is efficiently enriched in solid carbon, and a large amount of hydrogen-rich gas is obtained for energy supply.

[0086] Comparative Example 3

[0087] The biochar prepared in Example 1 of the present invention was compared with other biochars in the prior art, and the potassium content of different biochars was determined and converted into the total potassium content of biochar (K 2 O), and the results are shown in Table 1. The potassium content of the biochar prepared by the present invention significantly exceeds that of other existing biochars.

[0088] Table 1. Comparison of potassium-rich biochar based on banana peel and other biochars

[0089]

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Claims

1. A method for preparing potassium-rich biochar and hydrogen-rich gas based on banana peel, characterized in that: The steps include: Banana peel powder and water are mixed in a mass ratio of 4:1-1:4, and the obtained mixed raw material is subjected to high-temperature in-situ gasification to obtain the potassium-rich biochar and simultaneously obtain hydrogen-rich gas.

2. The preparation method according to claim 1, characterized in that: The banana peel is a banana peel that has been cleaned and decontaminated.

3. The preparation method according to claim 1, characterized in that: The total potassium content of the banana peel is not less than 69000 mg / kg.

4. The preparation method according to claim 1, characterized in that: The banana peel powder is dried at a constant temperature of 100-105° C., and then crushed through a 20-mesh to 80-mesh sieve to obtain dry banana peel powder.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the banana peel powder to water is 1:4-4:

1.

6. The preparation method according to claim 1, characterized in that: The mass ratio of the banana peel powder to water is preferably 1:4, 2:3, 3:2 or 4:

1.

7. The preparation method according to claim 1, characterized in that: The in-situ gasification conditions of the raw materials are: heating to 800°C-900°C at a heating rate of 10±1°C / min in a tubular furnace and then maintaining the temperature for 30-40 minutes.

8. Potassium-rich biochar and hydrogen-rich gas prepared by the preparation method according to claim 1.

9. Use of the potassium-rich biochar according to claim 8 as a soil conditioner to improve soil and increase the effective potassium pool in soil.

10. Use of the potassium-rich biochar according to claim 8 as a gasification catalyst or a raw material for preparing potassium fertilizer.

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