Preparation method of full-water-soluble straw-source fulvic acid granular fertilizer and product thereof

Abstract

The invention relates to a preparation method of a fully water-soluble straw-source fulvic acid granular fertilizer and a product thereof, and the preparation method comprises the following steps: rapidly mixing 75-80wt% straw-source fulvic acid concentrate with a water-soluble inorganic raw material, puffing, granulating, cooling and drying to obtain the fully water-soluble straw-source fulvic acid granular fertilizer. According to the preparation method, a straw-source fulvic acid concentrated solution with the concentration of 75-80 wt% is adopted, and rapid mixing and puffing granulation technologies are combined, so that the problem of water solubility of a compound fertilizer produced by taking straw-source fulvic acid as a raw material at present is effectively solved, and the preparation of the full-water-soluble straw-source fulvic acid granular fertilizer is realized. Meanwhile, compared with a traditional production process, the preparation method disclosed by the invention simplifies the production process, and reduces energy consumption and raw material waste in the production process, so that the production cost of a unit product is directly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer preparation, and in particular to a preparation method of a fully water-soluble straw-derived fulvic acid granular fertilizer and a product thereof. Background Art

[0002] In modern agricultural production, fertilizer plays a vital role in improving crop yield and quality. With the deepening of the concept of sustainable agriculture, people's demand for environmentally friendly, efficient and multifunctional fertilizers is growing. Fulvic acid fertilizer has become one of the hot spots in fertilizer research and development due to its unique physiological activity and beneficial effects on soil improvement, crop growth promotion and other aspects. Fulvic acid can regulate soil pH, enhance soil water and fertilizer retention capacity, promote crop root development, improve crop absorption and utilization rate of nutrients, and enhance crop resistance. It has broad application prospects in agricultural production.

[0003] Crop straw is a rich agricultural biomass resource. In recent years, converting straw into valuable products, especially fertilizer products, has become an important way to solve the problem of straw disposal and realize the resource utilization of agricultural waste. Among them, the use of straw to prepare fulvic acid fertilizer has significant economic and environmental benefits. Through specific biological or chemical processes to treat straw, fulvic acid components can be extracted from it and then processed into fulvic acid fertilizer.

[0004] At present, the production technologies of straw-derived fulvic acid granular fertilizer mainly include spray granulation, drum granulation, extrusion granulation, fluidized bed spray drying and other granulation technologies. However, these technologies have certain limitations, such as: spray granulation and drum granulation cannot produce fully water-soluble granular fertilizer using straw-derived fulvic acid, and such products are difficult to use in facility agriculture (pipe irrigation, drip irrigation); extrusion granulation has low strength, short shelf life, easy to powder and compact; fluidized bed spray drying granulation has large investment, low output and high processing cost.

[0005] Therefore, how to achieve the preparation of fully water-soluble straw-derived humic acid granular fertilizer under the premise of low cost and high production capacity has become a technical problem that needs to be urgently solved in this field. This is of great significance for promoting the large-scale application of straw-derived humic acid fertilizer and the sustainable development of agriculture. Summary of the invention

[0006] In view of the deficiencies in the prior art, the object of the present invention is to provide a method for preparing a fully water-soluble straw-derived fulvic acid granular fertilizer and a product thereof.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for preparing a fully water-soluble straw-derived fulvic acid granular fertilizer, the preparation method comprising the following steps:

[0009] The straw-derived fulvic acid concentrate with a concentration of 75-80wt% is quickly mixed with a water-soluble inorganic raw material, expanded and granulated, cooled and dried to obtain the fully water-soluble straw-derived fulvic acid granular fertilizer.

[0010] The 75-80wt% can be selected from 75wt%, 75.5wt%, 76wt%, 76.5wt%, 77wt%, 77.5wt%, 78wt%, 78.5wt%, 79wt%, 79.5wt%, 80wt%, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0011] The preparation method of the fully water-soluble straw-derived fulvic acid granular fertilizer involved in the present invention creatively adopts a straw-derived fulvic acid concentrate with a concentration of 75-80wt%, and combines rapid mixing and puffing granulation technology to effectively solve the water solubility problem of the current production of compound fertilizers using straw-derived fulvic acid as a raw material, and realizes the preparation of fully water-soluble straw-derived fulvic acid granular fertilizer. At the same time, compared with the traditional production process, the preparation method involved in the present invention simplifies the production process, reduces energy consumption and raw material waste in the production process, thereby directly reducing the production cost of the unit product.

[0012] Straw-derived fulvic acid liquid is made from crop straw (such as wheat straw, corn straw, reed, etc.) as raw materials. The upstream evaporation concentration process determines that the optimal evaporation concentration of the straw-derived fulvic acid liquid is about 50wt%. If it is higher than this value, the production cost and equipment loss will be greatly increased. The present invention creatively performs secondary concentration on the straw-derived fulvic acid liquid raw material, and concentrates the straw-derived fulvic acid liquid to 75-80wt%. The concentration of the fulvic acid liquid affects the final water content of the mixed material. Once it exceeds the critical value, it cannot be produced. The present invention can increase the amount of straw-derived fulvic acid added by concentrating the straw-derived fulvic acid liquid to 75-80wt%, thereby improving the water solubility of the straw-derived fulvic acid granular fertilizer.

[0013] Straw-derived fulvic acid has the characteristics of large molecular weight, easy moisture absorption, and more functional groups. The mixture of multiple materials will show different mixing forms over time, such as agglomeration, water precipitation, etc. Rapid mixing technology can effectively shorten the mixing time, which can not only ensure the uniformity of materials and the stability of product quality, but also ensure that the materials enter the puffing granulation in the same form.

[0014] Preferably, the water-soluble inorganic raw material includes any one of water-soluble nitrogen fertilizer, water-soluble phosphate fertilizer, water-soluble potassium fertilizer, water-soluble calcium fertilizer, water-soluble magnesium fertilizer, water-soluble sulfur fertilizer, water-soluble iron fertilizer or water-soluble zinc fertilizer, or a combination of at least two thereof.

[0015] The present invention can add different water-soluble inorganic raw materials according to product index requirements, and only a few are listed here.

[0016] Preferably, the rapid mixing is carried out in a high-speed stirring mixer.

[0017] Preferably, the stirring speed is above 1500rpm, for example 1500rpm, 1600rpm, 1700rpm, 1800rpm, 1900rpm, 2000rpm, 2100rpm, 2200rpm, 2300rpm, 2400rpm, 2500rpm, etc. Other specific point values ​​within this numerical range can be selected, which will not be described here one by one.

[0018] Preferably, the stirring time is less than 3 min, for example 3 min, 2.7 min, 2.5 min, 2.3 min, 2 min, 1.7 min, 1.5 min, 1.3 min, 1 min, 0.7 min, 0.5 min, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0019] Preferably, the stirring temperature is below 60°C, for example 60°C, 58°C, 56°C, 54°C, 52°C, 50°C, 48°C, 46°C, 44°C, 42°C, 40°C, 35°C, 30°C, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0020] Preferably, the straw-derived fulvic acid concentrate accounts for 10-30wt% of the total prepared raw materials, for example 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0021] In general puffing granulation and extrusion granulation, the amount of straw-derived fulvic acid liquid added is relatively small, basically less than 10wt%. The present invention creatively improves the adhesion of the mixed material by adding a large amount of straw-derived fulvic acid liquid, so that a large amount of heat is generated when the material passes through the puffing granulator. The organic matter in the straw-derived fulvic acid quickly expands at high temperature to form a large number of micropores, thereby increasing the water-dissolution rate of the particles.

[0022] The present invention also creatively discovered that the amount of straw-derived fulvic acid liquid added directly affects the product quality and water solubility rate of the finished straw-derived fulvic acid granular fertilizer. When the amount of straw-derived fulvic acid liquid added is too little, the material is not easy to form, and there is no puffing effect, and the water solubility and strength of the granules are greatly reduced; when the amount of straw-derived fulvic acid liquid added is too much, the material will be agglomerated, the yield rate will be reduced, the production cost will increase, and it will be unfavorable for large-scale production.

[0023] Preferably, the puffing granulation feeding temperature is 40-60°C, for example, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc. Other specific point values ​​within this numerical range can be selected, which will not be described here one by one.

[0024] Preferably, the chamber temperature of the puffing granulation is 90-100°C, for example, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, etc. Other specific point values ​​within this numerical range can be selected, which will not be described here one by one.

[0025] Preferably, the discharging time of the puffing granulation is 4-6s, for example, 4s, 4.2s, 4.4s, 4.6s, 4.8s, 5s, 5.2s, 5.4s, 5.6s, 5.8s, 6s, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0026] The present invention finds that the temperature and time in the puffing granulation process will affect the granulation effect of the production process, that is, the yield rate. When the temperature is too high, the material will be carbonized, thereby affecting the water-soluble effect of the straw-derived fulvic acid granular fertilizer.

[0027] Preferably, the cooling and drying uses a fluidized bed drying and cooling machine.

[0028] Preferably, the temperature of the drying medium in the fluidized bed drying and cooling machine is 100-110°C, for example, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0029] Preferably, the temperature of the cooling medium in the fluidized bed drying and cooling machine is 10-30°C, for example, 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0030] Preferably, the moisture content of the straw-source humic acid granular fertilizer after cooling and drying is below 3%, for example 3%, 3.7%, 3.3%, 2%, 2.7%, 2.3%, 1%, 0.7%, 0.3%, etc. Other specific point values ​​within this numerical range can be selected and will not be described here one by one.

[0031] Preferably, the temperature of the straw-derived fulvic acid granular fertilizer after cooling and drying is below 40°C, for example 40°C, 37°C, 35°C, 33°C, 30°C, 27°C, 25°C, 23°C, 20°C, etc. Other specific point values ​​within this numerical range can be selected, and they will not be described here one by one.

[0032] Preferably, the cooling and drying are followed by screening, and those that do not meet the finished product standards are put back into the mixer to be mixed with the straw-derived fulvic acid concentrate and the water-soluble inorganic raw materials for the next round of production.

[0033] Preferably, the preparation method further comprises a dust removal system, which is connected to the air outlet at the top of the air chamber of the fluidized bed dryer and cooler via a ventilation duct.

[0034] Preferably, the dust collected by the dust removal system is added back into the feeder, mixed with the straw-derived fulvic acid concentrate and the water-soluble inorganic raw materials, and enters the next round of production.

[0035] The present invention adds a dust removal system in the preparation process. On the one hand, some dust (part of the unformed powder) will be generated during the fluidized bed drying and cooling process. According to environmental protection requirements, the dust removal system must be used for treatment before it can be discharged. On the other hand, the collected dust can be reused to reduce raw material loss.

[0036] In a second aspect, the present invention provides a fully water-soluble straw-derived fulvic acid granular fertilizer prepared according to the preparation method of the fully water-soluble straw-derived fulvic acid granular fertilizer in the first aspect.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The preparation method of the fully water-soluble straw-derived fulvic acid granular fertilizer involved in the present invention creatively concentrates the straw-derived fulvic acid liquid raw material to 75-80wt%, and combines the rapid mixing and puffing granulation technology, effectively solving the water solubility problem of the current production of compound fertilizers using straw-derived fulvic acid as raw material, and realizes the preparation of fully water-soluble straw-derived fulvic acid granular fertilizer. At the same time, compared with the traditional production process, the preparation method involved in the present invention simplifies the production process, reduces the energy consumption and raw material waste in the production process, thereby directly reducing the production cost of the unit product. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to Example 1. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0041] In the following examples, unless otherwise specified, the reagents and consumables used were purchased from conventional reagent manufacturers in the field; unless otherwise specified, the experimental methods and technical means used were conventional methods and means in the field.

[0042] The straw-derived fulvic acid liquid raw material involved in the following examples was purchased from Juwei Yuanchuang (Liaocheng) Biotechnology Co., Ltd. with a concentration of 50 wt%.

[0043] Example 1

[0044] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, the preparation method of which is as follows:

[0045] (1) using a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material to 77 wt % to obtain a straw-derived fulvic acid concentrated liquid;

[0046] (2) 100 kg of urea, 650 kg of ammonium sulfate, 250 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are placed in a high-speed stirring mixer, stirred at 2000 rpm and 55° C. for 2.5 min to achieve rapid and uniform mixing; the mixture is conveyed to an extruding granulator by a conveyor belt for granulation, the feed temperature of the granulator is 50° C., the chamber temperature is 95° C., and the discharge time is 5 s; the finished product, semi-finished product, and powder from the granulator are directly placed in a fluidized bed drying and cooling machine with a drying medium of 105° C. and a cooling medium of 20° C. to reduce the moisture content to 2.5%, and at the same time reduce the product temperature to 35° C., and then placed in a screening machine to screen out the finished product particles, which are then placed in a finished product warehouse for packaging and storage;

[0047] (3) The powder collected by the dust removal system and the screened semi-finished products and powder are put back into the mixer for the next round of production.

[0048] The complete preparation process is as follows Figure 1 shown.

[0049] Example 2

[0050] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, the preparation method of which is as follows:

[0051] (1) using a single-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material to 75 wt % to obtain a straw-derived fulvic acid concentrated liquid;

[0052] (2) 100 kg of urea, 650 kg of ammonium sulfate, 300 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are placed in a high-speed stirring mixer, stirred at 2300 rpm and 60° C. for 2 min to achieve rapid and uniform mixing; transported to an extruding granulator with a conveyor belt for granulation, the feed temperature of the granulator is 40° C., the room temperature is 100° C., and the discharge time is 4 s; the finished product, semi-finished product, and powder from the granulator are directly placed in a fluidized bed drying and cooling machine with a drying medium of 100° C. and a cooling medium of 10° C. to reduce the moisture content to 2%, and the temperature is reduced to 30° C., and then placed in a screening machine to screen out finished product particles, which are then placed in a finished product warehouse for packaging and storage;

[0053] (3) The powder collected by the dust removal system and the screened semi-finished products and powder are put back into the mixer for the next round of production.

[0054] Example 3

[0055] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, the preparation method of which is as follows:

[0056] (1) using a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material to 80 wt % to obtain a straw-derived fulvic acid concentrated liquid;

[0057] (2) 100 kg of urea, 650 kg of ammonium sulfate, 220 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are placed in a high-speed stirring mixer, stirred at 1800 rpm and 50° C. for 3 min to achieve rapid and uniform mixing; the mixture is conveyed to an extruding granulator by a conveyor belt for granulation, the feed temperature of the granulator is 60° C., the chamber temperature is 90° C., and the discharge time is 6 s; the finished product, semi-finished product, and powder from the granulator are directly placed in a fluidized bed drying and cooling machine with a drying medium of 110° C. and a cooling medium of 30° C. to reduce the moisture content to 3%, and the temperature is reduced to 40° C., and then placed in a screening machine to screen out finished granules, which are then placed in a finished product warehouse for packaging and storage;

[0058] (3) The powder collected by the dust removal system and the screened semi-finished products and powder are put back into the mixer for the next round of production.

[0059] Example 4

[0060] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which differs from Embodiment 1 only in that step (1) uses a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material to 70 wt %, and other conditions remain unchanged.

[0061] Example 5

[0062] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which differs from Embodiment 1 only in that step (1) uses a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material to 90 wt %, and other conditions remain unchanged.

[0063] Example 6

[0064] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which differs from Embodiment 1 only in that in step (2), 100 kg of urea, 650 kg of ammonium sulfate, 100 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are added to a high-speed stirring mixer, and other conditions remain unchanged.

[0065] Example 7

[0066] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which differs from Embodiment 1 only in that in step (2), 100 kg of urea, 650 kg of ammonium sulfate, 600 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are added to a high-speed stirring mixer, and other conditions remain unchanged.

[0067] Example 8

[0068] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which differs from Embodiment 1 only in that the stirring speed in step (2) is 120 rpm and the stirring time is 2 min, and other conditions remain unchanged.

[0069] Example 9

[0070] This embodiment provides a fully water-soluble straw-derived fulvic acid granular fertilizer, which is different from Embodiment 1 only in that the chamber temperature of the granulator in step (2) is 120° C., and other conditions remain unchanged.

[0071] Comparative Example 1

[0072] This comparative example provides a straw-derived fulvic acid granular fertilizer, and the preparation method (spray granulation) is as follows:

[0073] (1) using a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material obtained in Preparation Example 1 to 77 wt %, to obtain a straw-derived fulvic acid concentrated liquid;

[0074] (2) 600 kg of straw-derived fulvic acid concentrate and 700 kg of humic acid are put into a mixing tank and mixed evenly. Then, the mixture is put into a spray granulation machine using a spray pump under the action of 0.4 MPa compressed air. The liquid material is evenly attached to the surface of the micro-particles in the granulator and quickly dried. This cycle is repeated until the finished product particle size is 3-5 mm. After cooling and screening, it becomes fulvic acid granular fertilizer.

[0075] Comparative Example 2

[0076] This comparative example provides a straw-derived fulvic acid granular fertilizer, and the preparation method (extrusion granulation) is as follows:

[0077] (1) using a multi-effect forced vacuum circulation evaporator to concentrate the straw-derived fulvic acid liquid raw material obtained in Preparation Example 1 to 77 wt %, to obtain a straw-derived fulvic acid concentrated liquid;

[0078] (2) 100 kg of urea, 700 kg of ammonium sulfate, 50 kg of straw-derived fulvic acid concentrate, and 100 kg of potassium sulfate are put into a high-speed stirring mixer. The mixed materials are fed into a double-roll extrusion granulator through a screw feeder. The loose materials are formed into round particles under the action of the pressing rollers, and then are sieved, dried, and packaged into finished products.

[0079] Test Example 1

[0080] This test example calculates the yield of the fully water-soluble straw-derived fulvic acid granular fertilizer prepared in Examples 1-9 and Comparative Examples 1-2. The results are shown in Table 1.

[0081] Yield rate (%) = finished particle mass / total raw material mass × 100%

[0082] Table 1

[0083]

[0084]

[0085] It can be seen from the data in Table 1 that the finished product rate of the fully water-soluble straw-derived fulvic acid granular fertilizer prepared by the preparation method provided by the present invention reaches more than 90%, which effectively improves the utilization rate of raw materials and reduces production costs.

[0086] By comparing Example 1 with Examples 4-9, it can be seen that the concentration of the straw-derived fulvic acid concentrate, the amount of the straw-derived fulvic acid concentrate added, and the stirring speed after the raw materials are mixed will affect the yield of the fully water-soluble straw-derived fulvic acid granular fertilizer, especially when the concentration of the straw-derived fulvic acid liquid is too high or the amount of the straw-derived fulvic acid liquid is too high, which will have a serious impact on the yield.

[0087] Comparing Example 1 with Comparative Examples 1-2, it can be seen that, compared with the traditional spray granulation and extrusion granulation processes, the preparation method provided by the present invention can effectively improve the yield of fully water-soluble straw-derived fulvic acid granular fertilizer and reduce production costs.

[0088] Test Example 2

[0089] This test example tests the water solubility of the finished product rate of the fully water-soluble straw-derived fulvic acid granular fertilizer prepared in Examples 1-9 and Comparative Examples 1-2.

[0090] Test method: At 25°C, 5 g of the fully water-soluble straw-derived fulvic acid granular fertilizer prepared in Examples 1-9 and Comparative Examples 1-2 were respectively dissolved in 100 mL of water, and the dissolution was observed and scored. The scoring criteria are shown in Table 2, and the results are shown in Table 3.

[0091] Table 2

[0092]

[0093]

[0094] Table 3

[0095] Group Water Solubility Example 1 9 Example 2 10 Example 3 9 Example 4 9 Example 5 10 Example 6 8 Example 7 10 Example 8 9 Example 9 7 Comparative Example 1 5 Comparative Example 2 6

[0096] It can be seen from the data in Table 3 that the fully water-soluble straw-derived fulvic acid granular fertilizer prepared by the preparation method of the present invention has excellent water solubility and can achieve the effect of being completely soluble in water.

[0097] Comparing Example 1 with Examples 4-9, it can be seen that the amount of straw-derived fulvic acid concentrate added and the temperature of puffing and granulation will affect the water solubility of the fully water-soluble straw-derived fulvic acid granular fertilizer.

[0098] By comparing Example 1 with Comparative Examples 1-2, it can be seen that compared with the traditional spray granulation and extrusion granulation processes, the preparation method provided by the present invention significantly improves the water solubility of the fully water-soluble straw-derived humic acid granular fertilizer, effectively avoids the formation of precipitated or suspended particles, and can be better combined with the irrigation water system.

[0099] Test Example 3

[0100] This test was conducted on the strength of the fully water-soluble straw-derived fulvic acid granular fertilizer prepared in Examples 1-9 and Comparative Examples 1-2. The results are shown in Table 4.

[0101] The test method is as follows: 30 grains are randomly selected from the fully water-soluble straw-derived fulvic acid granular fertilizers prepared in Examples 1-9 and Comparative Examples 1-2, and the crushing resistance of the grains is measured one by one using a grain crushing resistance tester.

[0102] Average crushing resistance of particles

[0103] Table 4

[0104]

[0105]

[0106] It can be seen from the data in Table 4 that the fully water-soluble straw-derived fulvic acid particles prepared by the preparation method provided by the present invention have an average crushing resistance of more than 21N, and can maintain the integrity of their shape during storage, transportation and use, reducing the generation of dust.

[0107] Comparing Example 1 with Examples 4-9, it can be seen that the amount of straw-derived fulvic acid concentrate added and the stirring speed after the raw materials are mixed will affect the average crushing resistance of the particles of the fully water-soluble straw-derived fulvic acid granular fertilizer.

[0108] By comparing Example 1 with Comparative Example 2, it can be seen that the strength of the straw-derived fulvic acid granular fertilizer prepared by the traditional extrusion granulation process is very low, only 12N. The preparation method provided by the present invention significantly improves the strength of the fully water-soluble straw-derived fulvic acid granular fertilizer.

[0109] The applicant declares that the present invention illustrates the technical solution of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0110] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

Claims

1. A method for preparing a fully water-soluble straw-derived fulvic acid granular fertilizer, characterized in that: The preparation method comprises the following steps: The straw-derived fulvic acid concentrate with a concentration of 75-80wt% is quickly mixed with a water-soluble inorganic raw material, expanded and granulated, cooled and dried to obtain the fully water-soluble straw-derived fulvic acid granular fertilizer.

2. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to claim 1, characterized in that: The water-soluble inorganic raw material includes any one of water-soluble nitrogen fertilizer, water-soluble phosphorus fertilizer, water-soluble potassium fertilizer, water-soluble calcium fertilizer, water-soluble magnesium fertilizer, water-soluble sulfur fertilizer, water-soluble iron fertilizer or water-soluble zinc fertilizer, or a combination of at least two thereof.

3. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to claim 1 or 2, characterized in that: The rapid mixing is carried out in a high-speed stirring mixer; Preferably, the stirring speed is above 1500 rpm; Preferably, the stirring time is less than 3 minutes; Preferably, the stirring temperature is below 60°C.

4. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to any one of claims 1 to 3, characterized in that: The straw-derived fulvic acid concentrate accounts for 10-30 wt % of the total raw materials.

5. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to any one of claims 1 to 4, characterized in that: The feeding temperature of the puffing granulation is 40-60°C; Preferably, the chamber temperature of the puffing granulation is 90-100°C; Preferably, the discharging time of the puffing granulation is 4-6s.

6. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to any one of claims 1 to 5, characterized in that: The cooling and drying uses a fluidized bed drying and cooling machine; Preferably, the temperature of the drying medium in the fluidized bed drying and cooling machine is 100-110°C; Preferably, the temperature of the cooling medium in the fluidized bed dryer is 10-30°C.

7. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to claim 1, characterized in that: The moisture content of the straw-derived fulvic acid granular fertilizer after cooling and drying is below 3%; Preferably, the temperature of the straw-derived fulvic acid granular fertilizer after cooling and drying is below 40°C.

8. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to claim 1, characterized in that: The cooling and drying are followed by screening, and those that do not meet the finished product standards are put back into the mixer to be mixed with the straw-derived fulvic acid concentrate and the water-soluble inorganic raw materials for the next round of production.

9. The method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to claim 1, characterized in that: The preparation method also includes a dust removal system, which is connected to the top air outlet of the air chamber of the fluidized bed drying and cooling machine by a ventilation duct; Preferably, the dust collected by the dust removal system is added back into the feeder, mixed with the straw-derived fulvic acid concentrate and the water-soluble inorganic raw materials, and enters the next round of production.

10. A fully water-soluble straw-derived fulvic acid granular fertilizer prepared according to the method for preparing the fully water-soluble straw-derived fulvic acid granular fertilizer according to any one of claims 1 to 9.

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