Method and device for preparing acid soil conditioner and organic fertilizer based on quicklime pretreated straw

Abstract

The invention discloses a method and device for preparing an acid soil conditioner and an organic fertilizer based on quick lime pretreated straw. The device comprises a reaction tank, an extrusion granulation device and drying equipment. The reaction tank is provided with a straw feed port, a lime feed port, an extraction opening, an exhaust port, a stirrer, a water inlet, a urea adding port and a discharge port, the discharge port is connected with the extrusion granulation device, the extrusion granulation device is connected with the drying equipment, and liquid extruded by the extrusion granulation device is collected in the storage tank. Firstly, the process that calcium oxide releases heat when encountering water is fully utilized, straw is subjected to alkaline hydrolysis under high pressure, and the decomposition rate is increased. And then, the pressure is quickly released to cause a blasting effect, so that the decomposition of the straws is further accelerated, and a porous straw structure is formed. And finally, urea is uniformly distributed in the straws by forming a negative pressure environment, so that after the urea is applied to soil, nitrogen cannot be competed with plants, and the straws can be promoted to quickly form soil organic matters under the action of microorganisms.

Description

Technical Field

[0001] The invention relates to the field of organic fertilizers, and in particular to a method and a device for preparing an acidic soil conditioner and organic fertilizer based on pre-treating straw with quicklime. Background Art

[0002] Crop straw is the main waste generated in the agricultural production process. In 2020, the global straw production reached 5.28 billion tons (FAO, 2021). Straw mainly comes from the three major grain crops of rice, corn and wheat, accounting for 84% of the total straw. These huge amounts of straw have not been fully utilized. Outdoor burning and random stacking have caused serious waste of resources, environmental pollution and soil quality degradation (Singh et al. 2021). In addition, the slow decomposition rate of straw in the soil leads to low seed germination rate, serious diseases and insect pests, and continuous straw return to the field will accelerate soil acidification (Liu et al. 2023). Therefore, promoting the efficient utilization of straw resources is of great significance to cultivating soil fertility and green agricultural development.

[0003] Traditional straw return to the field (turning, covering, crushing and mixing) mixes a large amount of straw into the surface soil, resulting in low seed germination rate, increased mineralization of soil organic matter, serious diseases and insect pests and other problems. In addition, straw, especially wheat and rice straw, has a high cellulose content and decomposes relatively slowly. Therefore, there is an urgent need to develop straw pretreatment methods with low research and development costs. In addition, most of the cultivated land in southern my country faces the problem of soil acidification. The simplest and most effective way to solve soil acidification is to apply lime. However, in recent years, due to the lack of professional lime application machinery, farmers are prone to using powdered lime, which is easily blown by the wind and unevenly applied, and farmers are not willing to apply it. Therefore, how to organically combine straw pretreatment and lime application is expected to solve the dual problems of straw utilization and soil acidification.

[0004] In the invention patent with application number CN201810251922.8, a method for improving the anaerobic digestion gas production performance of rice straw by combined pretreatment of calcium oxide and biogas slurry was published. The calcium oxide was dissolved in the biogas slurry, and after the straw was crushed, it was mixed with the pretreatment reagent and evenly stirred. The mixture was placed in a closed container and pretreated in a 5-35℃ constant temperature box for 1-4 days, and the anaerobic digestion sludge was inoculated and diluted with water for medium-temperature anaerobic fermentation. It was found that the lignin degradation rate of the pretreated straw was significantly improved, and the highest lignin degradation rate of rice straw was 62.13%. This method mainly adjusts the reaction pH by calcium oxide, and the reaction temperature is only 5-35℃, which is difficult to quickly decompose cellulose and difficult to apply on a large scale in the rapid return of straw to the field. In the patent with invention number CN201810624018.7, a method for preparing straw micro-feed by blasting, calcium oxide and probiotics is disclosed. The method crushes dry corn stalks; adds 2-5% CaO by mass and mixes to form a straw calcium oxide mixture; treats the straw calcium oxide mixture in a blasting machine at 1-2Mpa, maintains pressure for 150-280s, releases pressure instantly within 0.00875s to blast, and dries the blasted mixture; seals the lactic acid bacteria and yeast solution in the blasted mixture, and ferments at a temperature of 27-30°C for 3-5 days to obtain micro-feed. This method mainly uses the blasting reaction to destroy the straw. In a dry environment, calcium oxide is difficult to exert its own alkaline hydrolysis function and can only be used to adjust pH. In the patent with invention patent number CN202210148081.4, a preparation method and application of calcium hydroxide modified rice straw biochar is disclosed, wherein the rice straw is dried and crushed in sequence; calcium hydroxide powder is added to the rice straw, deionized water is added after mixing, the mixture of calcium hydroxide and rice straw is ultrasonically treated in water to make the mixture evenly mixed, and then dried and crushed in sequence to obtain a mixture of rice straw and calcium hydroxide; the mixture of rice straw and calcium hydroxide is pyrolyzed and crushed in sequence to obtain calcium hydroxide modified rice straw biochar. This method only simply ultrasonically mixes calcium hydroxide and straw, which fails to effectively combine, and calcium hydroxide does not release heat when it meets water, and its relative reaction intensity is lower than that of calcium oxide.

[0005] In addition, research based on the formation of soil organic matter found that organic materials such as straw are mainly absorbed and utilized by microorganisms after returning to the field, thereby forming microbial residues, which in turn form mineral-bound organic matter with soil minerals, and finally form stable soil organic matter. Therefore, improving the effectiveness of soil minerals can also improve soil carbon utilization efficiency. Therefore, combining straw with calcium can not only increase soil pH and promote the absorption and utilization of straw by microorganisms, but also increase the ratio of carbon in straw to soil organic matter. Summary of the invention

[0006] Based on the above technical drawbacks, the present invention provides a method and device for preparing acidic soil conditioner and organic fertilizer based on pre-treatment of straw with quicklime.

[0007] A device for preparing an acidic soil conditioner and an organic fertilizer based on pre-treatment of straw with quicklime comprises a reaction tank, an extrusion granulation device and a drying device. The reaction tank is provided with a straw feed port, a lime feed port, an air extraction port, an exhaust port, a stirrer, a water inlet, a urea addition port and a discharge port. The air extraction port is connected to an air extraction pump, the discharge port is connected to an extrusion granulation device, the extrusion granulation device is connected to a drying device, and the liquid extruded by the extrusion granulation device is collected in a storage tank.

[0008] The exhaust port is arranged at the top of the reaction tank. The discharge port is arranged at the bottom of the reaction tank. The air extraction port is arranged at the top of the reaction tank.

[0009] A method for preparing an acidic soil conditioner and an organic fertilizer based on pre-treatment of straw with quicklime comprises the following steps: cutting the straw into small segments of 1-5 cm and then feeding the segments into a reaction tank through a straw feed port, adding lime through a lime feed port at a mass ratio of straw to quicklime of 0.5-2:1, closing all pipeline valves, adding boiled hot water to a water inlet in the reaction tank, immediately closing the valve of the water inlet, turning on a stirrer to stir for 5-15 minutes, and then reacting for 6-48 hours; then, opening an exhaust port to quickly release the pressure, adding urea through a urea adding port, adjusting the carbon-nitrogen ratio in the reaction tank to 8-12:1 (more preferably 10:1), turning on the stirrer to stir for 5-15 minutes, and turning on a vacuum pump to nearly vacuumize; finally, opening an exhaust port to quickly restore atmospheric pressure, transferring the material to an extrusion granulation device through a discharge port, connecting the extrusion granulation device to a drying device, and collecting liquid extruded by the extrusion granulation device in a storage tank.

[0010] The mass ratio of the boiled hot water to quicklime is 1:0.3-0.7 (more preferably 1:0.5).

[0011] Turn on the vacuum pump and draw the vacuum to 0.001~0.1MPa.

[0012] This method first makes full use of the heat release process of calcium oxide in contact with water to alkaline hydrolyze the straw under high pressure to accelerate the decomposition rate. After that, by quickly releasing the pressure, a blasting effect is created, which further accelerates the decomposition of the straw and forms a porous straw structure. Finally, by forming a negative pressure environment, urea is evenly distributed inside the straw to form a suitable carbon-nitrogen ratio. After being applied to the soil, it will not compete with plants for nitrogen, but will also promote the rapid formation of soil organic matter by the straw under the action of microorganisms.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] The alkaline fertilizer prepared by the quicklime pretreatment of the present invention has the following advantages: the high temperature generated by the heat generated by calcium oxide in contact with water is utilized to accelerate the alkaline hydrolysis of straw, and the cost and energy consumption are relatively low; the small molecular substances generated are easily decomposed and utilized by microorganisms, and the generated microbial residues form a large amount of mineral-bound organic carbon under the action of a large amount of calcium, thereby improving the carbon sink capacity of the soil; the generated lime and straw mixed material can be used as an improver for improving acidic soil, which not only improves the acidified soil, but also increases the organic matter content and provides a large amount of calcium; the small molecular amino acids and sugars generated by alkaline hydrolysis can be used as water-soluble fertilizers, which can effectively stimulate beneficial microorganisms in the soil and promote soil nutrient circulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a schematic structural diagram of a device for preparing an acidic soil conditioner and an organic fertilizer based on pre-treating straw with quicklime. DETAILED DESCRIPTION

[0016] like Figure 1 As shown, a device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw comprises a reaction tank 1, an extrusion granulation device 11 and a drying device 13. The reaction tank 1 is provided with a straw feed port 2, a lime feed port 3, an air suction port 4, an exhaust port 6, a stirrer 7, a water inlet 8, a urea addition port 9 and a discharge port 10. The air suction port 4 is connected to an air pump 5, the discharge port 10 is connected to an extrusion granulation device 11, the extrusion granulation device 11 is connected to a drying device 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in a storage tank 12.

[0017] A method for preparing an acidic soil conditioner and an organic fertilizer based on pre-treating straw with quicklime comprises the following steps: chopping the straw into small segments of 1 to 5 cm and then feeding the segments into a reaction tank 1 through a straw feed port 2; adding lime through a lime feed port 3 at a mass ratio of straw to quicklime of 0.5 to 2:1; closing all pipeline valves; adding boiled hot water at a ratio of lime to water of 0.5 to 1 to a water inlet 8 in the reaction tank 1; immediately closing the valve of the water inlet 8; turning on a stirrer 7 for stirring for 5 to 15 minutes, and then reacting for 6 to 48 hours; then opening an exhaust port 6 to quickly release the pressure; adding urea through a urea adding port 9; adjusting the carbon-nitrogen ratio in the reaction tank to 10:1; turning on the stirrer 7 for stirring for 5 to 15 minutes; and turning on a vacuum pump 5 to nearly vacuumize; finally, opening an exhaust port 6 to quickly restore the atmospheric pressure; conveying the material to an extrusion granulation device 11 through a discharge port 10; the extrusion granulation device 11 is connected to a drying device 13; and the liquid extruded by the extrusion granulation device 11 is collected in a storage tank 12.

[0018] Embodiment 1:

[0019] After the straw is chopped into 5 cm small segments, it is put into the reactor 1 through the straw feed port 2, lime is added through the lime feed port 3 according to the mass ratio of straw: quicklime 0.5:1, all pipeline valves are closed, and boiled hot water with a mass ratio of lime: water 0.5:1 is added to the water inlet 8 in the reactor 1, the valve of the water inlet 8 is immediately closed, the stirrer 7 is turned on and stirred for 15 minutes, and then the reaction is carried out for 48 hours; after that, the exhaust port 6 is opened to quickly release the pressure, urea is added through the urea addition port 9, the carbon-nitrogen ratio in the reactor is adjusted to 10:1, the stirrer 7 is turned on and stirred for 15 minutes, and the vacuum pump 5 is turned on to draw a near vacuum (0.1 MPa); finally, the exhaust port 6 is opened to quickly restore the atmospheric pressure, and the material is conveyed to the extrusion granulation device 11 through the discharge port 10, the extrusion granulation device 11 is connected to the drying equipment 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in the storage tank 12.

[0020] Embodiment 2:

[0021] After the straw is chopped into 5 cm small segments, it is put into the reactor 1 through the straw feed port 2, lime is added through the lime feed port 3 according to the mass ratio of straw: quicklime 1:1, all pipeline valves are closed, and boiled hot water with a mass ratio of lime: water 0.5:1 is added to the water inlet 8 in the reactor 1, the valve of the water inlet 8 is immediately closed, the stirrer 7 is turned on and stirred for 15 minutes, and then the reaction is carried out for 48 hours; after that, the exhaust port 6 is opened to quickly release the pressure, urea is added through the urea addition port 9, the carbon-nitrogen ratio in the reactor is adjusted to 10:1, the stirrer 7 is turned on and stirred for 15 minutes, and the vacuum pump 5 is turned on to draw a near vacuum (0.1 MPa); finally, the exhaust port 6 is opened to quickly restore the atmospheric pressure, and the material is conveyed to the extrusion granulation device 11 through the discharge port 10, the extrusion granulation device 11 is connected to the drying equipment 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in the storage tank 12.

[0022] Embodiment 3:

[0023] After the straw is chopped into 5 cm small segments, it is put into the reactor 1 through the straw feed port 2, lime is added through the lime feed port 3 according to the mass ratio of straw: quicklime 2:1, all pipeline valves are closed, and boiled hot water with a mass ratio of lime: water 0.5:1 is added to the water inlet 8 in the reactor 1, the valve of the water inlet 8 is immediately closed, the stirrer 7 is turned on and stirred for 15 minutes, and then the reaction is carried out for 48 hours; after that, the exhaust port 6 is opened to quickly release the pressure, urea is added through the urea addition port 9, the carbon-nitrogen ratio in the reactor is adjusted to 10:1, the stirrer 7 is turned on and stirred for 15 minutes, and the vacuum pump 5 is turned on to draw a near vacuum (0.1 MPa); finally, the exhaust port 6 is opened to quickly restore the atmospheric pressure, and the material is conveyed to the extrusion granulation device 11 through the discharge port 10, the extrusion granulation device 11 is connected to the drying equipment 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in the storage tank 12.

[0024] Embodiment 4:

[0025] After the straw is chopped into 3 cm small segments, it is put into the reactor 1 through the straw feed port 2, lime is added through the lime feed port 3 according to the mass ratio of straw: quicklime 2:1, all pipeline valves are closed, and boiled hot water with a mass ratio of lime: water 0.5:1 is added to the water inlet 8 in the reactor 1, the valve of the water inlet 8 is immediately closed, the stirrer 7 is turned on and stirred for 15 minutes, and then the reaction is carried out for 48 hours; after that, the exhaust port 6 is opened to quickly release the pressure, urea is added through the urea addition port 9, the carbon-nitrogen ratio in the reactor is adjusted to 10:1, the stirrer 7 is turned on and stirred for 15 minutes, and the vacuum pump 5 is turned on to draw a near vacuum (0.1 MPa); finally, the exhaust port 6 is opened to quickly restore the atmospheric pressure, and the material is conveyed to the extrusion granulation device 11 through the discharge port 10, the extrusion granulation device 11 is connected to the drying equipment 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in the storage tank 12.

[0026] Embodiment 5:

[0027] After the straw is chopped into 3 cm small segments, it is put into the reactor 1 through the straw feed port 2, lime is added through the lime feed port 3 according to the mass ratio of straw: quicklime 2:1, all pipeline valves are closed, and boiled hot water with a mass ratio of lime: water 0.5:1 is added to the water inlet 8 in the reactor 1, the valve of the water inlet 8 is immediately closed, the stirrer 7 is turned on and stirred for 15 minutes, and then the reaction is carried out for 24 hours; after that, the exhaust port 6 is opened to quickly release the pressure, urea is added through the urea addition port 9, the carbon-nitrogen ratio in the reactor is adjusted to 10:1, the stirrer 7 is turned on and stirred for 15 minutes, and the vacuum pump 5 is turned on to draw a near vacuum (0.1 MPa); finally, the exhaust port 6 is opened to quickly restore the atmospheric pressure, and the material is conveyed to the extrusion granulation device 11 through the discharge port 10, the extrusion granulation device 11 is connected to the drying equipment 13, and the liquid squeezed out by the extrusion granulation device 11 is collected in the storage tank 12.

[0028] The organic fertilizer produced in Examples 1-5 was added with 10 g to 2 kg of yellow mud field soil collected from the Jinqu Basin in Zhejiang Province, and cultured for 48 hours. The effect of lime-treated straw on straw decomposition characteristics and soil pH was determined by measuring carbon dioxide emissions and soil pH. In addition, the results of calcium oxide pretreatment were compared by adding an equal amount of untreated straw. Compared with untreated straw, the carbon dioxide release of the treated soil in Examples 1-3 increased by 147%-245%, indicating that the structure of the pretreated straw was destroyed, accelerating the decomposition process of microorganisms. Among them, the carbon dioxide emission in Example 4 was the highest, indicating that the straw decomposition process can be effectively increased by reducing the straw length and increasing the reaction time. In addition, the decomposition of straw increased with the increase of the lime: straw ratio, indicating that the greater the amount of quicklime added, the better the decomposition effect. In addition, compared with the direct return of straw to the field, the modifier prepared by this method can increase the soil pH from 4.7 to 6.2-6.7, and is positively correlated with the amount of quicklime added.

Claims

1. A device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw, characterized in that: It comprises a reaction tank (1), an extrusion granulation device (11) and a drying device (13); The reaction tank (1) is provided with a straw feed port (2), a lime feed port (3), an air extraction port (4), a water inlet (8), a urea addition port (9) and a discharge port (10), and a stirrer (7) is provided inside the reaction tank (1); The discharge port (10) is connected to the extrusion granulation device (11); The extrusion granulation device (11) is connected to the drying equipment (13).

2. The device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw according to claim 1, characterized in that: The air suction port (4) is connected to an air suction pump (5).

3. The device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw according to claim 1, characterized in that: The reaction tank (1) is provided with an exhaust port (6), and the exhaust port (6) is arranged at the top of the reaction tank (1).

4. The device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw according to claim 1, characterized in that: The extrusion granulation device (11) is provided with an extrusion port, and the extrusion port is connected to a storage tank (12).

5. The device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw according to claim 1, characterized in that: The discharge port (10) is arranged at the bottom of the reaction tank (1).

6. The device for preparing acidic soil conditioner and organic fertilizer based on quicklime pretreatment of straw according to claim 1, characterized in that: The gas extraction port (4) is arranged at the top of the reaction tank (1).

7. A method for preparing an acidic soil conditioner and an organic fertilizer based on pretreatment of straw with quicklime, characterized in that: The device for preparing an acidic soil conditioner and an organic fertilizer based on pre-treatment of straw with quicklime according to any one of claims 1 to 6 comprises the following steps: The straw is chopped into small segments of 1-5 cm and then put into a reaction tank (1) through a straw feed port (2). Quicklime is added through a lime feed port (3) at a mass ratio of straw: quicklime of 0.5-2:

1. All pipeline valves are closed. Boiled hot water is added to a water inlet (8) in the reaction tank (1). The valve of the water inlet (8) is immediately closed. The stirrer (7) is turned on to stir for 5-15 minutes and then react for 6-48 hours. After that, the exhaust port (6) is opened to quickly release the pressure. Urea is added through a urea addition port (9). The carbon-nitrogen ratio in the reaction tank is adjusted. The stirrer (7) is turned on to stir. The vacuum pump (5) is turned on to draw a near vacuum. Finally, the exhaust port (6) is opened to restore atmospheric pressure. The material is transferred to an extrusion granulation device (11) through a discharge port (10). The extrusion granulation device (11) is connected to a drying device (13). The liquid squeezed out by the extrusion granulation device (11) is collected in a storage tank (12).

8. The method for preparing an acidic soil conditioner and an organic fertilizer based on quicklime pretreatment of straw according to claim 7, characterized in that: The mass ratio of the boiled hot water to quicklime is 1:0.3-0.

7.

9. The method for preparing an acidic soil conditioner and an organic fertilizer based on quicklime pretreatment of straw according to claim 7, characterized in that: Adjust the carbon-nitrogen ratio in the reaction tank to 8-12:1; Turn on the stirrer (7) and stir for 5-15 minutes.

10. The method for preparing an acidic soil conditioner and an organic fertilizer based on quicklime pretreatment of straw according to claim 7, characterized in that: Turn on the vacuum pump (5) to draw a vacuum to 0.001-0.1 MPa.

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