A method and system for soil improvement based on indirect carbonization of straw

Abstract

A straw indirect carbonization-based soil improvement method and system, the method comprising the following steps: (A) collecting straw, cutting the straw into straw particles; (B) extruding and destroying the surface of the straw particles; (C) using microwave heating to extrude the straw particles, obtaining puffed straw particles; (D) carbonizing the surface of the puffed straw particles, obtaining carbonized particles for discharge into soil. The indirect carbonization method of first breaking the wall and then puffing and carbonizing the surface can significantly reduce the energy consumed during carbonization and shorten the processing time of the straw, which is conducive to the straw carbonization and field application treatment of a large area of soil. At the same time, the surface-carbonized carbonized particles can provide sufficient biomass carbon for the soil, and it is not necessary to remove part of the carbonized particles from the field due to the excessive biomass carbon of the soil. In addition, the carbonized particles also well retain the nutrients in the straw.

Description

Technical Field

[0001] This invention relates to the field of agricultural equipment technology, specifically to a soil improvement method and system based on indirect carbonization of straw. Background Technology

[0002] Straw is an important source of soil organic matter, and straw char contains over 65% carbon, playing a significant role in carbon sequestration and emission reduction. Returning straw to the field effectively improves soil properties, optimizes soil function, and enhances arable land quality. The scientific implementation of crop straw recycling is of great significance for stabilizing agricultural ecological balance, improving the ecological environment, and alleviating resource constraints.

[0003] Currently, there are two main ways to return straw to the field. One is to collect the straw, remove it from the field for processing, and then add the processed material back into the soil. For example, the straw can be removed from the field and allowed to ferment before being returned to the field. Another example is to carbonize the straw into biochar before adding it to the soil. However, this method of removing the straw from the field inevitably consumes more manpower and resources and is more costly, making it unsuitable for large-scale straw processing. Another approach involves processing straw while collecting it in the field, achieving in-situ return of straw to the field. In recent years, the direct return of straw to the field after carbonizing it into biochar has become a focus of attention. For example, patent CN102640617B discloses an integrated device for rice and wheat harvesting and straw carbonization and return to the field, which can simultaneously complete rice and wheat harvesting and straw carbonization and return to the field, saving transportation costs. Patent CN112063401B discloses a mobile straw baking and carbonization treatment in-situ return method that integrates straw collection, crushing, baking, carbonization and return to the field, realizing in-situ return of straw baking and carbonization to the field.

[0004] However, due to the high moisture content of straw, direct carbonization typically consumes a large amount of energy. Therefore, while it saves on transportation costs, the carbonization time and energy consumption are not significantly reduced, and it still faces the problems of high energy consumption and low efficiency when applied to large-scale soil carbonization and returning to the field. Furthermore, direct carbonization also consumes nutrients in the straw, resulting in low nutrient utilization and hindering soil improvement. Moreover, if all collected straw is carbonized into biochar and returned to the field, exceeding the soil's carrying capacity, it can have adverse effects. Therefore, existing in-situ carbonization and returning to the field usually requires removing some of the biochar. Summary of the Invention

[0005] One objective of this invention is to provide a soil improvement method based on indirect carbonization of straw. This method involves extruding and microwaving collected straw to obtain expanded straw particles, followed by carbonization of the surface of these particles. The resulting carbonized particles retain the main nutrients of the straw within their interior, while possessing certain carbonaceous properties and mechanical strength on their surface. This approach not only meets the soil's need for biochar but also better provides nutrients to the soil, thereby effectively improving soil improvement.

[0006] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0007] A soil improvement method based on indirect carbonization of straw includes the following steps:

[0008] (A) Collect straw and cut the straw into straw pellets;

[0009] (B) Squeeze and break the outer skin of the straw particles;

[0010] (C) Extruded straw pellets are obtained by heating and pressing the extruded straw pellets with microwaves;

[0011] (D) Carbonize the surface of the puffed straw pellets to obtain carbonized pellets for discharge into the soil.

[0012] In this technical solution, straw collected from the field is directly processed into carbonized particles with surface carbonization and internal nutrient retention, and then the carbonized particles are discharged into the soil to achieve the purpose of soil improvement.

[0013] Specifically, in step (A), after picking up and collecting straw in the field, the straw is crushed and cut to obtain a number of straw pellets. In one or more embodiments, the collection and cutting of straw can be accomplished using an existing integrated carbonization and returning-to-field device.

[0014] In step (B), the outer skin of the straw pellets is squeezed, for example by using a screw extruder, so that the straw pellets are continuously squeezed together and between the straw pellets and the screw or the inner wall of the extruder, thereby destroying the complete structure of the outer skin of the straw pellets.

[0015] In step (C), microwaves are used to heat the straw pellets with damaged outer skins, causing the surface and interior moisture of the straw pellets to continuously turn into water vapor. Because the surface moisture evaporates faster, the interior moisture continuously accumulates. When the pressure difference between the inside and outside of the outer skin reaches a certain level, the steam causes the outer skin of the straw pellets to break down and expand, resulting in expanded straw pellets with damaged outer skins and a porous mesh structure inside. Simultaneously, during the expansion process, nutrients such as sugars, proteins, and minerals inside the straw pellets are gradually released, the solubility of soluble proteins and dietary fiber increases, while the activity of harmful microorganisms decreases.

[0016] In step (D), the surface of the puffed straw pellets is carbonized. The surface of the carbonized pellets forms a carbonaceous structure with high ash content under the carbonization process, which obtains certain carbonaceous properties while retaining the original characteristics of the straw. At the same time, the interior of the carbonized pellets is not carbonized and still maintains a loose porous network structure, so the nutrients are not affected by carbonization.

[0017] Compared to existing direct carbonization methods that involve crushing and carbonizing all the straw, this indirect carbonization method, which first breaks down the straw walls and then carbonizes the surface, significantly reduces the energy consumed during carbonization and shortens the straw processing time. This is beneficial for large-scale straw carbonization and return to the field. Furthermore, the carbonized particles on the surface provide sufficient biochar to the soil, preventing the removal of some particles from the field due to excess biochar. Additionally, the carbonized particles effectively retain the nutrients in the straw, and the porous internal structure formed by the expansion process facilitates microbial decomposition, thus improving straw utilization and accelerating its decomposition in the field.

[0018] Furthermore, in step (B), the cut straw particles are first humidified at a temperature of 40–80°C before being squeezed and their outer skin broken. In this technical solution, the straw particles are heated and humidified before being squeezed and broken down. Heating the straw particles makes them easier to break down during the squeezing and breaking process, and the initial temperature already present during microwave breaking down effectively improves the processing efficiency and reduces energy consumption. Humidifying the straw particles further increases the moisture content on the surface and inside of the particles, for example, to over 40%. The outer skin of the straw particles with higher moisture content is more easily broken down in the subsequent squeezing and breaking process, which is beneficial for the puffing of the straw particles in the microwave breaking process. At the same time, the increased moisture inside the straw particles effectively enhances the pumping effect inside and outside the straw particles in the microwave breaking process, making the straw particles easier to puff up and further improving the processing efficiency of puffed straw particles.

[0019] Further, in step (C), the temperature of the microwave-heated straw pellets is 90–160°C, and the heating time is 3–10 minutes. In this technical solution, the microwave heating temperature should not be too low; otherwise, it will not only fail to effectively affect the activity of harmful microorganisms in the straw, but the moisture in the straw itself or the moisture added in the pretreatment step will also be detrimental to the subsequent carbonization of the expanded straw pellets. Simultaneously, the microwave heating temperature should not be too high; otherwise, the nutrients in the straw will easily be lost with the water vapor or react and lose their nutritional value at high temperatures. Therefore, in this technical solution, preferably, the temperature of the microwave-heated straw pellets is controlled at 90–160°C. This achieves better expansion of the straw pellets, and the discharged gas also has a certain temperature, which can be reused in the pretreatment device to heat the collected straw pellets, reducing the overall energy consumption of the processing process.

[0020] Further, in step (D), the puffed straw pellets roll past a flame, which scorches the surface of the puffed straw pellets, causing the surface of the puffed straw pellets to be uniformly carbonized. In this technical solution, the puffed straw pellets roll past the flame so that the flame can quickly scorch all parts of the surface of the puffed straw pellets, while avoiding scorching the interior of the puffed straw pellets, thereby making the surface of the puffed straw pellets quickly and uniformly carbonized. In some preferred embodiments, the scorching time of the flame on the surface of the puffed straw pellets is no more than 5 seconds. In one or more embodiments, a ceramic microporous plate is used as a platform for the puffed straw pellets to roll, and a flame is placed below the ceramic microporous plate. The flame passes through the micropores on the ceramic microporous plate to uniformly scorch the rolling puffed straw pellets, causing their surface to carbonize.

[0021] Furthermore, in step (D), before carbonizing the surface of the puffed straw particles, the puffed straw particles are swept away using airflow. In this technical solution, after the puffed straw particles are broken down by microwave, airflow is used to sweep away the puffed straw particles to remove residues. More importantly, the airflow can further reduce the moisture content of the puffed straw particles, especially the moisture on the surface of the puffed straw particles, thereby making the surface of the puffed straw particles easier to carbonize during the subsequent flame carbonization process, resulting in lower carbonization energy consumption. Moreover, the airflow can recycle some of the moisture back to the pretreatment device to humidify the collected straw particles, reducing the overall energy consumption of the processing process.

[0022] Further, in step (D), the obtained carbonized particles are cooled, and a bacterial agent is sprayed onto the cooled carbonized particles. The surface temperature of the carbonized particles is high after burning; therefore, in order to spray the bacterial agent onto them, the carbonized particles first need to be cooled. There are various ways to cool the carbonized particles, such as using airflow or water flow to lower their temperature. In some preferred embodiments, water is sprayed onto the carbonized particles to lower their temperature and increase their humidity, which is beneficial for the survival of the bacterial agent. Afterwards, the bacterial agent is sprayed onto the cooled carbonized particles. The porous structure of the carbonized surface and the expanded porous network structure inside the carbonized particles provide a shelter for the growth and reproduction of the microbial community, which is conducive to the immobilization of the microbial community. This allows the microbial community to exert its advantages after the carbonized particles are discharged into the soil, improving the soil amendment effect.

[0023] Another objective of this invention is to provide a soil improvement system that utilizes an extrusion cell wall breaking device, a microwave cell wall breaking device, and an indirect carbonization device to process collected straw in situ, thereby obtaining indirect carbonized particles with surface carbonization and an internal porous network structure. This system can not only meet the soil's demand for biochar but also provide the soil with more nutrients from the straw, thus improving the soil structure.

[0024] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0025] A soil improvement system based on indirect carbonization of straw includes a frame, on which a walking device is mounted, and the frame is further equipped with:

[0026] A collecting and cutting device for collecting straw and cutting the straw into straw pellets;

[0027] The pretreatment device is connected to the collecting and cutting device via the first conveying device. The pretreatment device is used to heat and humidify the straw particles.

[0028] An extrusion and cell-wall breaking device is connected to the pretreatment device. The extrusion and cell-wall breaking device is used to extrude the straw particles and break the outer skin of the straw particles.

[0029] One or more microwave cell-wall breaking devices are connected to the extrusion cell-wall breaking device, wherein the microwave cell-wall breaking device is used to microwave heat the extruded straw pellets to obtain puffed straw pellets.

[0030] An indirect carbonization device is connected to the microwave cell-breaking device via a second conveying device. The indirect carbonization device is used to carbonize the surface of the expanded straw particles to obtain carbonized particles for discharge into the soil.

[0031] Similar to existing straw carbonization devices, the soil improvement system provided in this technical solution also includes a frame and a walking device to enable movement in the field, collection, and in-situ carbonization of straw.

[0032] Unlike existing straw carbonization devices, the soil improvement system in this technical solution uses a collection and cutting device, a pretreatment device, an extrusion and cell wall breaking device, a microwave cell wall breaking device, and an indirect carbonization device to process the collected straw into carbonized particles with surface carbonization and a porous mesh structure inside.

[0033] Specifically, in this technical solution, after collecting the straw, the collecting and cutting device crushes and cuts the straw into segments of straw particles. The output end of the collecting and cutting device is connected to the input end of the first conveying device, and the output end of the first conveying device is connected to the pre-treatment device. Therefore, the cut straw particles are transferred to the pre-treatment device via the first conveying device for pre-treatment.

[0034] In this technical solution, the pretreatment device is used to heat and humidify the straw pellets. The increased temperature and humidity of the pretreated straw pellets facilitate subsequent processing by the extrusion and microwave crushing devices, enhancing the surface damage of the straw pellets and improving the puffing effect of microwave heating. In some preferred embodiments, the pretreatment device is equipped with a stirring mechanism, a heating mechanism, and a humidifying mechanism. After the straw pellets enter the pretreatment device, moisture is introduced into the straw pellets through the humidifying mechanism, the heating mechanism raises the temperature of the straw pellets, and the stirring mechanism ensures that the straw pellets are fully heated and humidified. Finally, the pellets are discharged through the discharge port and enter the extrusion and crushing device.

[0035] In this technical solution, the extrusion crushing device preferably adopts the structure of a screw extruder, utilizing the rotation of the screw to drive the straw particles from the feed inlet to the discharge outlet. During this movement, continuous compression occurs between the straw particles, between the straw particles and the screw, and between the straw particles and the inner wall of the extruder, disrupting the integrity of the straw particle surface. In one or more preferred embodiments, the extrusion crushing device employs a screw extruder with a gradually decreasing screw pitch, where the screw pitch gradually decreases from the feed inlet to the discharge outlet, thereby reducing the space between adjacent helical blades, strengthening the compression of the straw particles, and increasing the degree of damage to the straw particle surface.

[0036] In this technical solution, the discharge port of the extrusion crushing device is connected to the inlet of one or more microwave crushing devices. In some embodiments, the microwave crushing device can also adopt the structure of a screw extruder. Meanwhile, several magnetrons are provided on the outer wall of the screw extruder housing. The microwaves generated by the magnetrons enter the microwave crushing device through the through holes provided on the outer wall and the mica sheets located in the through holes, heating the straw particles whose skin has been damaged, and obtaining puffed straw particles with a porous mesh structure inside.

[0037] In this technical solution, the discharge port of one or more microwave cell-breaking devices is connected to the input end of a second conveying device, and the output end of the second conveying device is connected to an indirect carbonization device. The indirect carbonization device carbonizes the surface of the expanded straw particles, resulting in a carbonaceous structure with high ash content on the surface of the carbonized particles. While retaining the original characteristics of the straw, the particles acquire certain carbonaceous properties. Furthermore, the interior of the carbonized particles is not carbonized and retains a loose, porous network structure, so the nutrients are not affected by carbonization.

[0038] Furthermore, the indirect carbonization device contains, from top to bottom, a carbonization mechanism, a cooling mechanism, and a microbial agent addition mechanism. The carbonization mechanism is used to burn the surface of the puffed straw pellets, the cooling mechanism is used to spray cooling liquid onto the carbonized pellets, and the microbial agent addition mechanism is used to spray microbial agent onto the cooled carbonized pellets. In this technical solution, the carbonization mechanism, cooling mechanism, and microbial agent addition mechanism are arranged inclined from top to bottom within the indirect carbonization device. In some preferred embodiments, the carbonization mechanism includes a carbonization plate, such as a ceramic microporous plate, with the upper part of the carbonization plate for rolling the puffed straw particles, and a flame head disposed below the carbonization plate to spray flames to scorch the surface of the rolling puffed straw particles; the cooling mechanism includes a first guide plate, which is also provided with several through holes so that when the carbonized particles roll on the first guide plate, the spray head below the first guide plate can spray coolant to reduce the temperature of the carbonized particles; the microbial agent addition mechanism includes a second guide plate, which has a similar structure to the first guide plate. When the cooled carbonized particles roll on the second guide plate, the microbial agent spray head below the second guide plate sprays microbial agent onto the cooled carbonized particles, ultimately obtaining carbonized particles loaded with microbial agent.

[0039] Furthermore, a return pipe connects the indirect carbonization device and the pretreatment device. After the straw pellets are processed by the extrusion and microwave crushing devices, the high-temperature gas generated during the processing carries a certain amount of moisture and eventually enters the carbonization device. In this technical solution, a return pipe is set between the indirect carbonization device and the pretreatment device. A blower can be used to reintroduce some of the high-temperature gas from the indirect carbonization device into the pretreatment device through the return pipe to heat and humidify the straw pellets in the pretreatment device, thereby improving the utilization efficiency of heat and moisture and effectively reducing the energy consumption of the system.

[0040] Furthermore, the system also includes a blower used to deliver airflow into the second conveying device. In this technical solution, the blower delivers airflow into the second conveying device through a pipe connected to its interior. This airflow sweeps away the puffed straw particles moving within the second conveying device, reducing moisture and residue on the surface of the particles. This prevents excess moisture from increasing carbonization energy consumption and prolonging carbonization time, thus improving the subsequent carbonization effect of the puffed straw particles. Simultaneously, this moisture can be returned to the pretreatment device via a return pipe to further reduce system energy consumption.

[0041] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0042] 1. The present invention adopts an indirect carbonization method of first breaking the cell wall and then carbonizing the surface, which can significantly reduce the energy consumed during carbonization and shorten the processing time of straw, which is beneficial for the large-scale carbonization and return of straw to the field.

[0043] 2. The carbonized particles obtained by indirect carbonization in this invention are only carbonized on the surface, so they can provide enough biochar for the soil without having to transport some carbonized particles out of the field because the biochar exceeds the soil's carrying capacity. At the same time, the carbonized particles also retain the nutrients in the straw well, and the internal porous structure formed by expansion is also conducive to microbial decomposition, creating conditions for improving the utilization rate of straw and accelerating the decomposition of straw in the field.

[0044] 3. This invention, by heating the straw particles, makes them easier to break down during the extrusion and cell-wall breaking process, and reduces the energy consumption of microwave cell-wall breaking. By humidifying the straw particles, the outer skin of the straw particles is more easily broken down in the subsequent extrusion and cell-wall breaking process, promoting the expansion of the straw particles in the microwave cell-wall breaking process. At the same time, the increased moisture inside the straw particles will effectively enhance the pumping effect inside and outside the straw particles in the microwave cell-wall breaking process, making the straw particles easier to expand and further improving the processing efficiency of expanded straw particles.

[0045] 4. In this invention, the puffed straw particles are swept by airflow before carbonization, which can further reduce the moisture and residue of the puffed straw particles, especially the moisture on the surface of the puffed straw particles. This makes it easier for the surface of the puffed straw particles to be carbonized in the subsequent flame carbonization process, and the energy consumption of carbonization is lower.

[0046] 5. This invention provides a soil improvement system that utilizes an extrusion cell wall breaking device, a microwave cell wall breaking device, and an indirect carbonization device to process collected straw in situ, thereby obtaining indirect carbonized particles with surface carbonization and an internal porous network structure. This not only meets the soil's demand for biochar but also provides the soil with more nutrients from the straw, thus improving the soil structure. Attached Figure Description

[0047] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0048] Figure 1 This is a flowchart of a soil improvement method in a specific embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of the soil improvement system in a specific embodiment of the present invention;

[0050] Figure 3 This is a schematic diagram of the microwave cell-wall breaking device in a specific embodiment of the present invention;

[0051] Figure 4 This is a schematic diagram of the extrusion and cell wall breaking device in a specific embodiment of the present invention;

[0052] Figure 5 This is a schematic diagram of the pretreatment device in a specific embodiment of the present invention;

[0053] Figure 6 This is a schematic diagram of the indirect carbonization device in a specific embodiment of the present invention;

[0054] Figure 7 This is a schematic diagram of the adjustable mechanism of the carbonization plate in the indirect carbonization device according to a specific embodiment of the present invention.

[0055] The attached diagram shows the markings and corresponding component names:

[0056] 1-Collecting and cutting device, 2-Extrusion and cell-wall breaking device, 21-Second housing, 22-Second screw, 23-Second motor, 24-Second feed inlet, 25-Second discharge outlet, 3-Microwave cell-wall breaking device, 31-First housing, 32-First screw, 33-Magnetron, 34-Through hole, 35-First motor, 36-First feed inlet, 37-First discharge outlet, 4-Indirect carbonization device, 41-Fourth housing, 42-Fourth feed inlet, 43-Exhaust port, 44-Fourth discharge outlet, 45-Carbonization plate, 46-Burning head, 47-Airflow regulating valve, 48-First guide plate, 49-The Two water tanks, 410-Second spray head, 411-Agent tank, 412-Second guide plate, 413-Agent spray head, 414-Hydraulic cylinder, 415-Bearing, 416-Slider, 417-Groove, 5-Pretreatment device, 51-Third housing, 52-Third motor, 53-Agitator, 54-Baffle plate, 55-Third feed inlet, 56-Third discharge outlet, 57-First water tank, 58-First spray head, 6-First conveying device, 7-Second conveying device, 71-Air jet pipe, 8-Blower, 9-Return pipe, 10-Walking device, 11-Plowing device, 12-Frame. Detailed Implementation

[0057] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0058] In the description of this invention, it should be understood that the terms "front", "rear", "left", "right", "up", "down", "vertical", "horizontal", "high", "low", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this invention.

[0059] Example 1:

[0060] like Figure 1 The method for soil improvement based on indirect carbonization of straw, as shown, includes the following steps:

[0061] (A) Collect straw and cut the straw into straw pellets;

[0062] (B) Squeeze and break the outer skin of the straw particles;

[0063] (C) Extruded straw pellets are obtained by heating and pressing the extruded straw pellets with microwaves;

[0064] (D) Carbonize the surface of the puffed straw pellets to obtain carbonized pellets for discharge into the soil.

[0065] Compared to the direct carbonization method in the existing technology that involves crushing and carbonizing all the straw, the indirect carbonization method in this embodiment, which involves first breaking down the straw walls and then carbonizing the surface, can significantly reduce the energy consumed during carbonization and shorten the straw processing time, which is beneficial for the large-scale application of straw carbonization in soil.

[0066] In some preferred embodiments, in step (B), the cut straw particles are first moistened at a temperature of 40–80°C before being compressed to break down the outer skin of the straw particles. In one or more embodiments, a pretreatment device can be set up before the compression and cell-wall breaking process to stir, heat, and moisten the collected straw particles. The compression and cell-wall breaking process is then carried out after the straw particles reach the required humidity and temperature. In one or more embodiments, the pressure of the compression and cell-wall breaking process can be adjusted to gradually increase from the inlet to the outlet to further improve the effect of breaking down the outer skin of the straw particles.

[0067] In some preferred embodiments, in step (C), the temperature of the microwave-heated straw pellets is 90–160°C, and the heating time is 3–10 minutes.

[0068] In some preferred embodiments, in step (D), the puffed straw pellets roll past a flame, which scorches the surface of the puffed straw pellets, causing the surface of the puffed straw pellets to be uniformly carbonized. In some embodiments, the scorching time of the flame on the surface of the puffed straw pellets is no more than 5 seconds.

[0069] In some preferred embodiments, in step (D), before carbonizing the surface of the puffed straw pellets, the puffed straw pellets are purged with an airflow. In one or more embodiments, the temperature of the purging airflow is preferably 20–30°C to reduce the loss of volatile nutrients in the puffed straw pellets, and to cool the puffed straw pellets as a whole, especially inside, which is beneficial for subsequent spraying of active microbial agents onto the carbonized pellets.

[0070] In some preferred embodiments, in step (D), the obtained carbonized particles are cooled, and a bacterial agent is sprayed onto the cooled carbonized particles. The porous structure of the carbonized surface and the expanded porous network structure inside the carbonized particles can provide a shelter for the growth and reproduction of the microbial community, which is conducive to the immobilization of the microbial community. In this way, the microbial community can exert its advantages after the carbonized particles are discharged into the soil, thereby improving the soil improvement effect.

[0071] Example 2:

[0072] like Figure 2 The soil improvement system based on indirect carbonization of straw shown includes a frame 12, on which a walking device 10 is installed, and the frame 12 is also equipped with:

[0073] The collecting and cutting device 1 is used to collect straw and cut the straw into straw pellets;

[0074] The pretreatment device 5 is connected to the collecting and cutting device 1 via the first conveying device 6. The pretreatment device 5 is used to heat and humidify the straw particles.

[0075] The extrusion and cell wall breaking device 2 is connected to the pretreatment device 5. The extrusion and cell wall breaking device 2 is used to extrude the straw particles and break the outer skin of the straw particles.

[0076] One or more microwave cell-wall breaking devices 3 are connected to the extrusion cell-wall breaking device 2. The microwave cell-wall breaking device 3 is used to microwave heat the extruded straw particles to obtain puffed straw particles.

[0077] The indirect carbonization device 4 is connected to the microwave cell-wall breaking device 3 via the second conveying device 7. The indirect carbonization device 4 is used to carbonize the surface of the expanded straw particles to obtain carbonized particles for discharge into the soil.

[0078] During operation, the collecting and cutting device crushes and cuts the collected straw into segments of straw pellets. The collected straw pellets are then conveyed to a pre-treatment device, where they are heated and humidified. This increased temperature and humidity facilitates subsequent processing by the extrusion and microwave breaking devices, enhancing the surface damage and puffing effect of the microwave heating. Next, during the conveying process, the extrusion breaking device disrupts the surface integrity of the straw pellets. The microwave breaking device then radiates microwaves into the internal straw pellets, heating the damaged surface and resulting in puffed straw pellets with a porous mesh structure. Finally, the puffed straw pellets enter an indirect carbonization device, which carbonizes the surface of the pellets without affecting their internal porous mesh structure. The resulting carbonized particles, with their surface carbonization, can provide sufficient biochar to the soil, preventing the removal of some carbonized particles from the field due to biochar exceeding the soil's carrying capacity. Furthermore, the carbonized particles effectively retain the nutrients in the straw, and the porous internal structure formed by the expansion process facilitates microbial decomposition, thus creating conditions for improving straw utilization and accelerating straw decomposition in the field.

[0079] In one or more embodiments, the first and second conveying devices are screw conveyors.

[0080] In some embodiments, such as Figure 2 As shown, a return pipe 9 connects the indirect carbonization device 4 and the pretreatment device 5. A blower can be used to reintroduce some of the high-temperature gas from the indirect carbonization device into the pretreatment device through the return pipe to heat and humidify the straw particles in the pretreatment device, thereby improving the utilization efficiency of heat and moisture and effectively reducing the energy consumption of the system.

[0081] In some embodiments, a blower 8 is also included, which is used to deliver airflow into the second conveying device 7. In one or more embodiments, the temperature of the airflow is preferably 20–30°C.

[0082] Example 3:

[0083] Based on the above embodiments, the indirect carbonization device 4 is provided with a carbonization mechanism, a cooling mechanism and a microbial agent addition mechanism from top to bottom. The carbonization mechanism is used to burn the surface of the puffed straw particles, the cooling mechanism is used to spray cooling liquid onto the carbonized particles, and the microbial agent addition mechanism is used to spray microbial agent onto the cooled carbonized particles.

[0084] In some preferred embodiments, such as Figure 6 As shown, the indirect carbonization device 4 includes a fourth housing 41, which is provided with a fourth inlet 42 for connecting to the output end of the second conveying device, a fourth outlet 44 for discharging carbonized particles containing bacterial agent, and an exhaust port 43 connected to the return pipe.

[0085] The indirect carbonization device 4 includes, from top to bottom, a carbonization mechanism, a cooling mechanism, and a microbial agent addition mechanism. The carbonization mechanism includes a carbonization plate 45, such as a ceramic microporous plate, inclined towards the center of the fourth housing. A burner head 46 is positioned below the carbonization plate 45, spraying flames onto it. The flames pass through the micropores on the carbonization plate 45, burning the expanded straw particles rolling on it. In one or more embodiments, an airflow regulating valve is provided between the burner head 46 and the air source to adjust the size of the flame, thereby adjusting the carbonization effect. The cooling mechanism includes a first guide plate 48 inclined towards the center of the fourth housing. The first guide plate 48 has a first through hole. A second spray head 410 is positioned below the first guide plate 48, communicating with a second water tank 49. This allows cooling water from the second water tank 49 to be pressurized to the second spray head 410 and sprayed onto the carbonized particles to lower their temperature. The microbial agent addition mechanism includes a second guide plate 412 inclined toward the center of the fourth housing. The second guide plate 412 is provided with a second through hole. A microbial agent nozzle 413 is provided below the second guide plate 412. The microbial agent nozzle 413 is connected to the microbial agent tank 411 to press the microbial agent in the microbial agent tank to the microbial agent nozzle 413 and spray it onto the cooled carbonized particles. Finally, the carbonized particles carrying the microbial agent are discharged into the soil through the fourth discharge port 44.

[0086] In one or more embodiments, the length and quantity of the carbonization mechanism, cooling mechanism, and microbial agent addition mechanism can be set according to actual needs to ensure that the surface of the puffed straw pellets is fully carbonized, the carbonized pellets are fully cooled, and carry the expected amount of microbial agent.

[0087] In some embodiments, the tilt angle of the carbonized plate is adjustable. For example... Figure 7As shown, a hydraulic cylinder 414 is provided on the fourth housing 41. A bearing 415 is provided on the output end of the hydraulic cylinder and is hinged to the first end of the carbonization plate 45. The hydraulic cylinder can push the first end of the carbonization plate 415 to move toward or away from the center of the first housing 41. A slider 416 is connected to the second end of the carbonization plate 45. The slider 416 can move vertically up and down along the sliding groove 417 provided on the inner wall of the fourth housing 41. Through the reciprocating movement of the hydraulic cylinder 414, the first end of the carbonization plate 415 can be driven to move, thereby making the tilt angle of the carbonization plate adjustable, and thus changing the carbonization time.

[0088] Example 4:

[0089] Based on the above embodiments, the pretreatment device 5 includes a third housing 51, inside which is a baffle plate 54 that can be opened or closed. A third motor 52 is disposed outside the third housing 51, and the output end of the third motor 52 is connected to a stirring paddle 53 located inside the third housing 51, the stirring paddle 53 being positioned above the baffle plate 54. The third housing 51 is also connected to an indirect carbonization device 4 via a return pipe 9.

[0090] During operation, the baffle plate is closed to collect a sufficient number of straw pellets. High-temperature gas containing moisture enters above the baffle plate 54 through the return pipe 9 and comes into contact with the straw pellets. The stirring paddle drives the straw pellets to rotate so that they are fully heated and humidified. Then the baffle plate is opened and the straw pellets are discharged through the third discharge port 56 to the extrusion and crushing device 2.

[0091] In one or more embodiments, a first water tank 57 is also provided on the third housing 51. The first water tank 57 is connected to a first spray head 58 located inside the third housing 51, so that when the moisture carried in the high-temperature gas is insufficient, the liquid stored therein is sprayed onto the straw pellets through the first spray head to help increase the moisture content of the straw pellets.

[0092] Example 5:

[0093] Based on the above embodiments, such as Figure 3 As shown, the microwave cell-wall breaking device 3 includes a first housing 31, on which a first feed inlet 36 and a first discharge outlet 37 are provided. A first screw 32 is provided inside the first housing 31. The first screw 32 rotates under the drive of a first motor 35, causing the straw particles inside to move from the feed inlet to the discharge outlet.

[0094] A magnetron 33 is installed on the outer wall of the first housing 31. The microwave emitting end of the magnetron 33 is connected to the first housing 31 through a through hole 34, and a mica sheet is installed inside the through hole 34. During the movement of the straw particles, the microwaves generated by the magnetron 33 enter the interior of the first housing 31 through the through hole and radiate to heat the straw particles.

[0095] Example 6:

[0096] Based on the above embodiments, such as Figure 4 As shown, the extrusion and cell wall breaking device 2 includes a second housing 21, on which a second feed inlet 24 and a second feed outlet 25 are provided. A second screw 22 is provided inside the second housing 21. The second screw 22 rotates under the drive of a second motor 23, which drives the straw particles inside to move from the feed inlet to the discharge outlet. During the movement, the straw particles are continuously squeezed against each other, against the screw, and against the inner wall of the housing, thus breaking the skin of the straw particles.

[0097] In some preferred embodiments, the pitch of the second screw gradually decreases along the second feed inlet 24 to the second discharge outlet 25, so that the compressive force on the straw particles continuously increases during the movement.

[0098] The terms "first," "second," "third," "fourth," etc., used in this invention (e.g., first discharge port, second discharge port, third discharge port, fourth discharge port, first water tank, second water tank, etc.) are merely for clarity of description and are not intended to limit any order or emphasize importance. Furthermore, the term "connection" used in this invention, unless otherwise specified, can refer to a direct connection or an indirect connection via other components.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A soil improvement method based on indirect carbonization of straw, characterized in that, Includes the following steps: (A) Collect straw and cut the straw into straw pellets; (B) Squeezing and damaging the outer skin of the straw particles; (C) Extruded straw pellets are obtained by heating and pressing the extruded straw pellets with microwaves; (D) Carbonize the surface of the puffed straw pellets to obtain carbonized pellets for discharge into the soil. The puffed straw pellets roll through a flame, which scorches the surface of the puffed straw pellets to uniformly carbonize the surface of the puffed straw pellets. The scorching time of the flame on the surface of the puffed straw pellets is no more than 5 seconds. Before carbonizing the surface of the puffed straw pellets, the puffed straw pellets are swept away by an airflow.

2. The soil improvement method based on indirect carbonization of straw according to claim 1, characterized in that, In step (B), the cut straw particles are first moistened at a temperature of 40-80°C, and then squeezed to break the outer skin of the straw particles.

3. The soil improvement method based on indirect carbonization of straw according to claim 1, characterized in that, In step (C), the temperature of the microwave-heated straw particles is 90~160°C, and the heating time is 3~10 minutes.

4. A soil improvement method based on indirect carbonization of straw according to claim 1, characterized in that, In step (D), the obtained carbonized particles are cooled and then sprayed with a bacterial agent.

5. A soil improvement system based on indirect carbonization of straw, comprising a frame (12) on which a walking device (10) is provided, characterized in that, The frame (12) is also equipped with: A collecting and cutting device (1) is used to collect straw and cut the straw into straw pellets; The pretreatment device (5) is connected to the collection and cutting device (1) via the first conveying device (6). The pretreatment device (5) is used to heat and humidify the straw particles. The extrusion and cell wall breaking device (2) is connected to the pretreatment device (5). The extrusion and cell wall breaking device (2) is used to extrude the straw particles and break the outer skin of the straw particles. One or more microwave cell-wall breaking devices (3) are connected to the extrusion cell-wall breaking device (2). The microwave cell-wall breaking device (3) is used to microwave heat the extruded straw pellets to obtain puffed straw pellets. An indirect carbonization device (4) is connected to the microwave cell-breaking device (3) via a second conveying device (7). The indirect carbonization device (4) is used to carbonize the surface of the puffed straw particles to obtain carbonized particles for discharge into the soil. The interior of the indirect carbonization device (4) is provided with a carbonization mechanism, a cooling mechanism, and a microbial agent addition mechanism from top to bottom. The carbonization mechanism is used to burn the surface of the puffed straw particles, the cooling mechanism is used to spray cooling liquid onto the carbonized particles, and the microbial agent addition mechanism is used to spray microbial agent onto the cooled carbonized particles. The carbonization mechanism includes a carbonization plate (45) inclined toward the center of the fourth shell. A flame nozzle (46) is provided below the carbonization plate (45). The flame nozzle (46) is used to spray flames onto the carbonization plate (45). The flames burn the puffed straw particles rolling on the carbonization plate (45) through the micropores on the carbonization plate (45).

6. The soil improvement system based on indirect carbonization of straw according to claim 5, characterized in that, A reflux pipe (9) is connected between the indirect carbonization device (4) and the pretreatment device (5).

7. A soil improvement system based on indirect carbonization of straw according to claim 5, characterized in that, It also includes a blower (8) for delivering airflow into the second conveying device (7).

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