A device composition and continuous process for producing biodegradable high-molecular slow / controlled-release round granular fertilizer based on a kneader

Abstract

The application belongs to the technical field of slow / controlled release fertilizer, and particularly relates to a device composition and continuous process for producing biodegradable polymer slow / controlled release round granular fertilizer by reaction extrusion based on a kneader, which sequentially comprises a reactor, a kneader, a cooling conveyor belt, a round granulator and a continuous dryer; a hydroxymethyl urea solution, a composite plastic reinforcing agent, plant essential nutrient elements and carbon-containing solids are kneaded at a certain temperature for a certain time, the obtained viscous material is continuously extruded into a strip by a die head of a screw extruder kneader and is simultaneously guided to slide into the top of the cooling conveyor belt, is conveyed to the round granulator to be granulated into wet round granules, and is solidified and dried to obtain the biodegradable polymer slow / controlled release round granular fertilizer. According to the application, the reaction extrusion is realized by using the kneader, so that the cost investment of the reaction extrusion equipment is greatly reduced; meanwhile, the molding rate and regularity of the round granules are greatly improved by using the formula composition and process control, and the final product has excellent compressive strength.

Description

Technical Field

[0001] This invention belongs to the field of slow / controlled release fertilizer technology, specifically relating to the equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on reactive extrusion using a kneader. Background Technology

[0002] To improve the nutrient utilization efficiency of traditional fertilizers, slow / controlled release fertilizers have become a research hotspot in the fertilizer field. Among them, urea-formaldehyde slow / controlled release fertilizers, as the earliest developed and first commercialized type of slow-release fertilizer, have become one of the most promising varieties, and have profound practical significance for promoting the upgrading of the nitrogen fertilizer industry and alleviating energy and environmental pressures.

[0003] Currently, the industrial production of urea-formaldehyde and its derivatives mainly employs two process routes: the dilute solution method and the concentrated solution method. The dilute solution method typically uses raw materials with a low concentration for the reaction, and the resulting suspension is then subjected to solid-liquid separation, drying, and pulverization to obtain the product. Its advantages include a more complete reaction and higher product purity, but it suffers from problems such as a long process flow, high energy consumption, and high cost, making large-scale production difficult. The concentrated solution method uses high-concentration raw materials for direct reaction, with intermediate products added to a catalyst for solidification without separation. While this process is simple and has lower production costs, the final material viscosity is extremely high, making continuous and automatic discharge from the reaction unit impossible, severely restricting its industrial scale-up and continuous production. Therefore, how to achieve smooth and continuous discharge of high-viscosity materials has become a bottleneck restricting the continuous production of urea-formaldehyde fertilizer.

[0004] Reactive extrusion technology has emerged as a novel polymer material molding technology in recent years. It integrates the polymerization and processing processes, simultaneously carrying out chemical reactions and continuous production within the processing machinery. Reactive extrusion uses the extrusion equipment as a reaction vessel, achieving mixing, conveying, plasticizing, reacting, and extrusion of raw materials from the die during screw rotation. It offers advantages such as continuous large-scale production, low investment and cost, minimal or no use of solvents harmful to humans and the environment, a wide range of choices for products and raw materials, simplified polymer volatile removal, granulation, and molding processes, high reaction efficiency, and uniform product performance, demonstrating promising development prospects.

[0005] Currently, reactive extrusion in China and abroad mainly relies on twin-screw reactive extruders. The main problems include: (1) complex equipment and high initial investment; (2) the need for professional engineering knowledge for scale-up design; and (3) relatively high maintenance costs. Screw extrusion kneaders are a high-efficiency equipment that integrates mixing, kneading and continuous extrusion functions, and are cheaper than twin-screw extruders. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides an equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer using reactive extrusion based on a kneader.

[0007] This invention is achieved through the following technical solution: an equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader via reactive extrusion, wherein the equipment composition sequentially includes a reactor, a kneader, a cooling conveyor belt, a granulator, and a continuous dryer; the kneader is a screw extrusion kneader; The continuous process includes the following steps: (1) Add formaldehyde to the reactor, then add a certain amount of urea and a certain amount of water, react at a certain temperature for a certain time to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), a certain amount of composite plasticizer, essential plant nutrients and a certain amount of carbon-containing solids to it, knead for a certain time at a certain kneading temperature to obtain a viscous material. The composite plasticizer is composed of natural polymer binder and inorganic cementitious material, accounting for 1-10% of the total mass of fertilizer; the mass ratio of natural polymer binder to inorganic cementitious material in the composite plasticizer is 1:0.5-5; The essential nutrients for plants account for 25-60% of the total mass of the fertilizer; The carbon-containing solids account for 10-40% of the total mass of the fertilizer; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30-60℃ by the cooling conveyor belt, it is transported to the pellet mill; after being granulated by the pellet mill, it becomes wet round particles. (4) The wet round particles obtained in step (3) are solidified at a certain temperature and dried for a certain time, and then cooled to room temperature to obtain the biodegradable polymer slow / controlled release round granular fertilizer.

[0008] As a further improvement to the technical solution of the present invention, in step (1), the formaldehyde is at least one of solid formaldehyde, liquid formaldehyde and gaseous formaldehyde, and urea is added according to the molar ratio of formaldehyde to urea of ​​1:1-5. The amount of water added is 0-60% of the total mass of formaldehyde and urea. The reaction temperature is 30-80°C and the reaction time is 0.5-5h.

[0009] As a further improvement to the technical solution of the present invention, in step (2), the natural polymer binder is selected from at least one of carboxymethyl cellulose, hydroxyethyl cellulose, starch derivatives, lignin sulfonate and alkali lignin; the inorganic cementing material is selected from at least one of gypsum, lime and bentonite.

[0010] As a further improvement to the technical solution of the present invention, in step (2), the essential nutrients for plants include macronutrients and micronutrients; the macronutrients are selected from at least one of nitrogen, phosphorus and potassium; the micronutrients are selected from at least one of iron, manganese, zinc, copper, boron, molybdenum, silicon and sulfur.

[0011] As a further improvement to the technical solution of the present invention, in step (2), the carbon-containing solid is selected from at least one of simple organic compounds, semi-decomposed organic matter and carbon-containing solid waste; the simple organic compounds are selected from at least one of sugars, organic acids, alcohols, aldehydes and ketones; the semi-decomposed organic matter is selected from at least one of the degradation intermediates of cellulose, hemicellulose and lignin; the carbon-containing solid waste is selected from at least one of straw, rice husks, corn cobs, bagasse, peanut shells, mushroom residue, distiller's grains, vinegar residue, sugar residue, soybean residue, fruit residue, tea residue, sawdust, bamboo powder, bark, wood shavings, garden pruning waste, kitchen waste treatment products, traditional Chinese medicine residue, fermentation industrial residue, weathered coal, lignite, peat and biochemical humic acid.

[0012] As a further improvement to the technical solution of the present invention, in step (2), the kneading temperature is 80-150℃ and the kneading time is 15-60min.

[0013] As a further improvement to the technical solution of the present invention, in step (3), the granulation time of the strip material in the pellet mill is 30-300s.

[0014] As a further improvement to the technical solution of the present invention, in step (4), the temperature for curing and drying the wet round particles is 80-130℃ and the time is 1-10h.

[0015] The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader provided by this invention have the following advantages compared with the prior art: (1) The present invention adopts an integrated continuous process of "kneading-extrusion-granulation", which completes the polycondensation reaction, mixing and plasticizing and extrusion molding of materials in sequence in the screw extrusion kneader, successfully solving the bottleneck of high viscosity urea-formaldehyde polymers being difficult to discharge automatically and continuously.

[0016] (2) This invention introduces a composite plasticizer composed of a natural polymer binder and an inorganic cementitious material. During the kneading process, the natural polymer binder can effectively increase the cohesion and plasticity of the material, enabling the high-viscosity urea-formaldehyde polymer to obtain suitable viscoelasticity and extensibility; while the inorganic cementitious material can play the role of filling the skeleton and reinforcing. The synergy of the two ensures that the strips obtained after extrusion are not prone to simple brittle fracture, but can undergo plastic deformation and become rounded through rolling and collision in the pellet mill. This not only greatly improves the forming rate and regularity of round particles, but also jointly builds a solid particle structure in the subsequent curing and drying process, so that the final product has excellent compressive strength, thereby meeting the requirements of long-distance transportation and mechanized fertilization.

[0017] (3) The present invention utilizes a kneader to achieve reactive extrusion, thereby significantly reducing the cost of reactive extrusion equipment. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This diagram illustrates the equipment composition for producing biodegradable polymer slow / controlled release granular fertilizer using reactive extrusion based on a kneader, as described in this invention. Detailed Implementation

[0021] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0022] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0023] The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on reactive extrusion using a kneader include, in sequence, a reactor, a kneader, a cooling conveyor belt, a pellet mill, and a continuous dryer; the kneader is a screw extrusion kneader. In one embodiment of the present invention, the screw extrusion kneader has a screw diameter of 10-30mm, a length-to-diameter ratio of 20-40:1, a rotational speed of 100-200r / min, a torque of 300-5000N·m, a heating power of 10-50kW, and a discharge method of extrusion through a die head orifice with a die orifice diameter of 2-4mm.

[0024] In one embodiment of the present invention, the diameter of the granulating disc of the pellet mill is 600-2500 mm, the disc edge height is 200-400 mm, and the rotation speed is 400-600 r / min.

[0025] The continuous process includes the following steps: (1) Add formaldehyde to the reactor, then add a certain amount of urea and a certain amount of water, react at a certain temperature for a certain time to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), a certain amount of composite plasticizer, essential plant nutrients and a certain amount of carbon-containing solids to it, knead for a certain time at a certain kneading temperature to obtain a viscous material. The composite plasticizer is composed of natural polymer binder and inorganic cementitious material, accounting for 1-10% of the total mass of fertilizer; the mass ratio of natural polymer binder to inorganic cementitious material in the composite plasticizer is 1:0.5-5; The essential nutrients for plants account for 25-60% of the total mass of the fertilizer; The carbon-containing solids account for 10-40% of the total mass of the fertilizer; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30-60℃ by the cooling conveyor belt, it is transported to the pellet mill; after being granulated by the pellet mill, it becomes wet round particles. (4) The wet round particles obtained in step (3) are solidified at a certain temperature and dried for a certain time, and then cooled to room temperature to obtain the biodegradable polymer slow / controlled release round granular fertilizer.

[0026] In another example provided by the present invention, in step (1), the formaldehyde is at least one of solid formaldehyde, liquid formaldehyde and gaseous formaldehyde, and urea is added according to a molar ratio of formaldehyde to urea of ​​1:1-5. The amount of water added is 0-60% of the total mass of formaldehyde and urea. The reaction temperature is 30-80℃ and the reaction time is 0.5-5h.

[0027] In one example provided by the present invention, in step (2), the natural polymer binder is selected from at least one of carboxymethyl cellulose, hydroxyethyl cellulose, starch derivatives, lignin sulfonate and alkali lignin; the inorganic cementing material is selected from at least one of gypsum, lime and bentonite.

[0028] In another example provided by the present invention, in step (2), the essential nutrients for the plant include macronutrients and micronutrients; the macronutrients are selected from at least one of nitrogen, phosphorus and potassium; the micronutrients are selected from at least one of iron, manganese, zinc, copper, boron, molybdenum, silicon and sulfur.

[0029] In one example provided by the present invention, in step (2), the carbon-containing solid is selected from at least one of simple organic compounds, semi-decomposed organic matter and carbon-containing solid waste; the simple organic compounds are selected from at least one of sugars, organic acids, alcohols, aldehydes and ketones; the semi-decomposed organic matter is selected from at least one of the degradation intermediates of cellulose, hemicellulose and lignin; the carbon-containing solid waste is selected from at least one of straw, rice husks, corn cobs, bagasse, peanut shells, mushroom residue, distiller's grains, vinegar residue, sugar residue, soybean residue, fruit residue, tea residue, sawdust, bamboo powder, bark, wood shavings, garden pruning waste, kitchen waste treatment products, traditional Chinese medicine residue, fermentation industrial residue, weathered coal, lignite, peat and biochemical humic acid.

[0030] In another example provided by the present invention, in step (2), the kneading temperature is 80-150℃ and the kneading time is 15-60min.

[0031] In one example provided by the present invention, in step (3), the granulation time of the strip material in the pellet mill is 30-300s.

[0032] In another example provided by the present invention, in step (4), the temperature for curing and drying the wet round particles is 80-130°C and the time is 1-10h.

[0033] The specific embodiments of the present invention will be described in detail below.

[0034] Example 1

[0035] A continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on reactive extrusion using a kneader is disclosed. The equipment consists of, in sequence, a reaction vessel, a screw extrusion kneader (screw diameter 15mm, length-to-diameter ratio 25, rotation speed 120r / min, torque 500N·m, heating power 20kW, discharge method is die extrusion with a die diameter of 3mm), a cooling conveyor belt, a granulator (granulation disc diameter 1000mm, disc edge height 300mm, rotation speed 444r / min), and a continuous dryer.

[0036] The continuous process includes the following steps: (1) Add 5000g of liquid formaldehyde with a mass fraction of 37% to the reactor, then add 10000g of urea, and react at 80℃ for 0.5h to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), the composite plasticizer made of 300g sulfonated lignin and 300g gypsum (accounting for 2.8% of the total fertilizer mass), 6200g potassium sulfate (accounting for 28.6% of the total fertilizer mass) and 3000g corn stalks (accounting for 13.9% of the total fertilizer mass), knead at 80°C for 60min to obtain a viscous material with strong plasticity; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30°C by the cooling conveyor belt, it is transported to the pellet mill; after being granulated in the pellet mill for 100s, it becomes wet round particles. (4) The wet round particles obtained in step (3) are solidified at 100°C and dried for 3 hours, and then cooled to room temperature to obtain the biodegradable polymer slow / controlled release round granular fertilizer.

[0037] Example 2

[0038] A continuous process for producing biodegradable polymer slow / controlled release granulated fertilizer based on reactive extrusion using a kneader is disclosed. The equipment consists of, in sequence, a reaction vessel, a screw extrusion kneader (screw diameter 30mm, length-to-diameter ratio 25, rotation speed 180r / min, torque 300N·m, heating power 25kW, discharge method is die extrusion with a die diameter of 3mm), a cooling conveyor belt, a pellet mill (granulation disc diameter 1500mm, disc edge height 400mm, rotation speed 444r / min), and a continuous dryer.

[0039] The continuous process includes the following steps: (1) Add 5000g of solid formaldehyde to the reactor, then add 20000g of urea and 5000g of water, and react at 50°C for 2h to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), the composite plasticizer made of 400g hydroxyethyl cellulose and 400g bentonite (accounting for 1.9% of the total fertilizer mass), 10740g diammonium phosphate (accounting for 25.9% of the total fertilizer mass) and 5000g lignite (accounting for 12.1% of the total fertilizer mass), knead at 150℃ for 15min to obtain a viscous material with strong plasticity; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 40°C by the cooling conveyor belt, it is transported to the pellet mill; after being granulated by the pellet mill for 30 seconds, it becomes wet round particles. (4) The wet round particles obtained in step (3) are solidified at 120°C and dried for 2 hours, and then cooled to room temperature to obtain the biodegradable polymer slow / controlled release round granular fertilizer.

[0040] Comparative Example 1 It is exactly the same as Example 1, except that no composite plasticizer is added.

[0041] Comparative Example 2 The process is exactly the same as in Example 1, except that the composite plasticizer accounts for 0.5% of the total fertilizer mass. That is, the composite plasticizer, which is composed of 52.89g of sulfonated lignin and 52.89g of gypsum, totals 105.78g.

[0042] Comparative Example 3 The process is exactly the same as in Example 1, except that the composite plasticizer accounts for 15% of the total fertilizer mass. That is, the total amount of the composite plasticizer, which is composed of 1857.35g of sulfonated lignin and 1857.35g of gypsum, is 3714.70g.

[0043] Comparative Example 4 The process is exactly the same as in Example 1, except that the mass ratio of natural polymer binder to inorganic cementitious material in the composite plasticizer is 1:0.1. That is, the total mass of the composite plasticizer, which is composed of 545.45g of sulfonated lignin and 54.55g of gypsum, is 600g (accounting for 2.8% of the total mass of fertilizer).

[0044] Comparative Example 5 The process is exactly the same as in Example 1, except that the mass ratio of natural polymer binder to inorganic cementitious material in the composite plasticizer is 1:10. That is, the total weight of the composite plasticizer, which is composed of 54.55g of sulfonated lignin and 545.45g of gypsum, is 600g (accounting for 2.8% of the total fertilizer mass).

[0045] Comparative Example 6 It is exactly the same as Example 1, except that the carbon-containing solids account for 5% of the total mass of the fertilizer. That is, the mass of corn stalks is 982g.

[0046] Comparative Example 7 It is exactly the same as Example 1, except that the carbon-containing solids account for 45% of the total mass of the fertilizer. That is, the mass of corn stalks is 15259g.

[0047] Comparative Example 8 It is exactly the same as Example 1, except that the curing and drying temperature is 70°C.

[0048] Comparative Example 9 It is exactly the same as Example 1, except that the curing and drying temperature is 140°C.

[0049] The performance test results of the biodegradable polymer slow / controlled release fertilizers prepared in Examples 1-2 and Comparative Examples 1-9 are shown in Table 1.

[0050] Table 1. Performance of Biodegradable Polymer Slow / Controlled-Release Fertilizers Produced Through Processing

[0051] A comparison of Examples 1-2 and Comparative Examples 1-9 shows that: First, composite plasticizers are key to the success of the process and the performance of the product.

[0052] (1) In Comparative Example 1, since no composite plasticizer was added, the spherical rate was only 34%, and the compressive strength of the prepared spherical fertilizer was only 2.11 MPa. This is mainly because, without plasticizer, the material has insufficient cohesion and plasticity, and cannot be effectively plastically deformed and spherical in the spherical polishing machine. At the same time, the internal structure of the particles is loose.

[0053] (2) The amount of composite plasticizer added must be appropriate: the balling rate and strength of Comparative Example 2 and Comparative Example 3 are both lower than those of Example 1. The reason is that when the amount of composite plasticizer added is insufficient, the plasticizing effect is not sufficient; while when the amount of composite plasticizer added is too high, the excess plasticizer will locally aggregate in the resin matrix, forming interface defects and hindering the full cross-linking of resin molecules. Therefore, the plasticizer needs to be added within a suitable range to form a continuous, uniform and effective plastic-strength network.

[0054] (3) The composition ratio of the plasticizer must be appropriate: When the ratio of natural polymer and inorganic material in the plasticizer added in Comparative Examples 4 and 5 was unbalanced, the performance was poor, indicating that the natural polymer binder (providing plasticity) and the inorganic cementitious material (providing strength) need to work together to avoid weakening the overall "plastic-strength" effect. In Examples 1 and 2, on the one hand, the amount of composite plasticizer added was appropriate; on the other hand, the composition ratio of the composite plasticizer was appropriate. Therefore, the sphericity rate was as high as 96% or more, and the particle strength exceeded 4.4 MPa. This is due to the bonding force and plasticity provided by the natural polymer binder in the composite plasticizer, and the skeletal reinforcement effect provided by the inorganic cementitious material. The two work together to ensure that the material can be smoothly rounded and the particles are dense and strong.

[0055] Secondly, the amount of carbon-containing solids added is also the key to determining the success of the process and the performance of the product: the performance of Comparative Example 6 and Comparative Example 7 is lower than that of Example 1. This is because when the amount of carbon-containing solids added is too small, its improvement on the rheological properties of the material is insufficient, while when the amount of carbon-containing solids added is too large, it will destroy the continuity of the resin matrix. Both situations are not conducive to particle formation and the strength of the formed particles.

[0056] Third, a suitable temperature range is conducive to the full curing of the resin: the strength of Comparative Examples 8 and 9 is lower than that of Example 1, indicating that a suitable temperature range is conducive to the full cross-linking and curing of the resin to form a strong and tough network; if the temperature is too low, the curing will be incomplete, and if it is too high, it may cause some components to degrade.

[0057] Examples 1-2 and Comparative Examples 1-9 verify that the present invention solves the key problems of difficult molding and low strength of high-viscosity materials by using composite plasticizers and their optimized formulations. Moreover, each parameter has a clear optimization window, good process stability, and has industrialization potential.

[0058] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A set of equipment and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer by reactive extrusion based on a kneader, characterized in that, The equipment consists of, in sequence, a reactor, a kneader, a cooling conveyor belt, a pellet mill, and a continuous dryer; the kneader is a screw extrusion kneader. The continuous process includes the following steps: (1) Add formaldehyde to the reactor, then add a certain amount of urea and a certain amount of water, react at a certain temperature for a certain time to obtain hydroxymethylurea solution; (2) Turn on the kneading blades of the screw extruder kneader, add the hydroxymethyl urea solution obtained in step (1), a certain amount of composite plasticizer, essential plant nutrients and a certain amount of carbon-containing solids to it, knead for a certain time at a certain kneading temperature to obtain a viscous material. The composite plasticizer is composed of natural polymer binder and inorganic cementitious material, accounting for 1-10% of the total mass of fertilizer; the mass ratio of natural polymer binder to inorganic cementitious material in the composite plasticizer is 1:0.5-5; The essential nutrients for plants account for 25-60% of the total mass of the fertilizer; The carbon-containing solids account for 10-40% of the total mass of the fertilizer; (3) Turn on the discharge screw of the screw extrusion kneader so that the viscous material obtained in step (2) is continuously extruded into strips through the die of the screw extrusion kneader and simultaneously guided to slide into the top of the cooling conveyor belt; when cooled to 30-60℃ by the cooling conveyor belt, it is transported to the pellet mill; after being granulated by the pellet mill, it becomes wet round particles. (4) The wet round particles obtained in step (3) are solidified at a certain temperature and dried for a certain time, and then cooled to room temperature to obtain the biodegradable polymer slow / controlled release round granular fertilizer.

2. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (1), the formaldehyde is at least one of solid formaldehyde, liquid formaldehyde and gaseous formaldehyde. Urea is added according to a molar ratio of formaldehyde to urea of ​​1:1-5. The amount of water added is 0-60% of the total mass of formaldehyde and urea. The reaction temperature is 30-80℃ and the reaction time is 0.5-5h.

3. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (2), the natural polymer binder is selected from at least one of carboxymethyl cellulose, hydroxyethyl cellulose, starch derivatives, lignin sulfonate and alkali lignin; the inorganic cementing material is selected from at least one of gypsum, lime and bentonite.

4. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (2), the essential nutrients for plants include macronutrients and micronutrients; the macronutrients are selected from at least one of nitrogen, phosphorus and potassium; the micronutrients are selected from at least one of iron, manganese, zinc, copper, boron, molybdenum, silicon and sulfur.

5. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (2), the carbon-containing solid is selected from at least one of simple organic compounds, semi-decomposed organic matter, and carbon-containing solid waste; the simple organic compounds are selected from at least one of sugars, organic acids, alcohols, aldehydes, and ketones; the semi-decomposed organic matter is selected from at least one of the degradation intermediates of cellulose, hemicellulose, and lignin; and the carbon-containing solid waste is selected from at least one of straw, rice husks, corn cobs, bagasse, peanut shells, mushroom residue, distiller's grains, vinegar residue, sugar residue, soybean residue, fruit residue, tea residue, sawdust, bamboo powder, bark, wood shavings, garden pruning waste, kitchen waste treatment products, traditional Chinese medicine residue, fermentation industrial residue, weathered coal, lignite, peat, and biochemical humic acid.

6. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (2), the kneading temperature is 80-150°C and the kneading time is 15-60 min.

7. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (3), the granulation time of the strip material in the pellet mill is 30-300s.

8. The equipment composition and continuous process for producing biodegradable polymer slow / controlled release granular fertilizer based on a kneader according to claim 1, characterized in that, In step (4), the temperature for curing and drying the wet round particles is 80-130℃ and the time is 1-10h.

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