Preparation method of microporous needle-like fertilizer

Abstract

The invention relates to a preparation method of a microporous needle-shaped fertilizer, which comprises the following steps: feeding a to-be-granulated fertilizer premix into a feed port of a press machine, and carrying out extrusion and first shearing on the fertilizer premix and gas entrained by the fertilizer premix by using double screws, and carrying out second shearing and kneading on the extruded and primarily sheared material by using a stirring paddle to obtain a microbubble-containing pasty material, and extruding the microbubble-containing pasty material through a pore plate. The microporous needle-shaped fertilizer prepared by the press is higher in dissolution speed, and the dissolved solution is low in viscosity and turbidity and can be better suitable for a large-area drip irrigation system.

Description

[0001] Related applications This application is a divisional case of the Chinese invention patent application filed on October 17, 2024, with application number 202411450396.X and invention name “A press for preparing microporous needle-shaped fertilizers”. Technical Field

[0002] The present invention relates to the technical field of fertilizer production, and in particular to a method for preparing microporous needle-shaped fertilizer. Background Art

[0003] CN110526761A discloses a dry production process for granular fertilizer, which includes the following steps: crushing, mixing and stirring raw materials of granular fertilizer containing starch or polyethylene glycol to obtain a dry powder material with a water content of 1.5% to 3%; introducing the dry powder material into a twin-screw extruder, and extruding the dry powder material under an environment of 65 to 70°C to extrude a continuous long fertilizer strip with a water content of less than 2%; drying, cooling and pelletizing the continuous long fertilizer strip to obtain granular fertilizer.

[0004] However, the granular fertilizers prepared by the existing methods still have the problem of slow dissolution rate. Summary of the Invention

[0005] The object of the present invention is to overcome the above-mentioned defects of the existing granular fertilizers and provide a press for preparing microporous needle-shaped fertilizers with a faster dissolution rate.

[0006] To achieve the above objectives, the present invention provides a press for preparing microporous needle-shaped fertilizers, comprising a barrel 1 and a twin screw disposed within the barrel 1. The barrel 1 has a feed port 5 on its side and a perforated plate 6 on its bottom. The twin screws include a first screw 21 and a second screw 22 arranged side by side and rotating in opposite directions. The threads of the first screw 21 and the threads of the second screw 22 engage with each other. A drive mechanism is connected to one end of the twin screws near the feed port 5. Two to six stirring paddles 9 are respectively installed at the ends of the first screw 21 and the second screw 22 near the perforated plate 6. The driving mechanism includes a driving motor 4 connected to the first screw 21 and a gear set 12 connected between the first screw 21 and the second screw 22; the gear set 12 includes a first gear 121 and a second gear 122, the first gear 121 is fixed on the first screw 21, and the second gear 122 is fixed on the second screw 22, and the first gear 121 and the second gear 122 are engaged with each other; the driving motor 4 forms a driving connection with the first screw 21 through a reducer 41; the first screw 21 and the second screw 22 can rotate in opposite directions at the same speed.

[0007] Optionally, the diameters of the first screw 21 and the second screw 22 are 20-50 cm, and the lengths are 40-100 cm, respectively; and the center distance between the first screw 21 and the second screw 22 is 20-50 cm.

[0008] Optionally, the first screw 21 and the second screw 22 have a screw groove depth of 5-10 cm, a screw flight width of 1-5 cm, and a thread lead angle of 2-10°.

[0009] Optionally, the length of the stirring paddle 9 is 5-22 cm, the width is 1-5 cm, and the thickness is 0.5-3 cm. The inner ends of multiple stirring paddles 9 are surrounded to form a gap area 10, the diameter of the gap area 10 is 2-10 cm, and the distance between the inner ends of two adjacent stirring paddles 9 is 2-10 cm; the stirring paddle 9 includes a first stirring paddle 91 and a second stirring paddle 92, the first stirring paddle 91 and the second stirring paddle 92 can rotate on the same plane, and the outer end of the first stirring paddle 91 extends into between the two adjacent second stirring paddles 92.

[0010] Optionally, the thickness of the cylinder 1 is 1-5 cm; the inner wall of the cylinder 1 is further provided with an internal thread 11, the depth of the internal thread 11 is 1-8 mm, the width is 1-5 mm, and the thread lead angle is 1-15°.

[0011] Optionally, the distances between the screw ridges of the first screw 21 and the second screw 22 and the inner surface of the barrel 1 are 0.1-5 mm respectively.

[0012] Optionally, the thickness of the orifice plate 6 is 0.5-2 cm, and holes 61 are provided on the orifice plate 6 . The hole diameter of the holes 61 is 1-3 mm, and the hole spacing is 2-10 mm.

[0013] Optionally, the distance between the stirring paddle 9 and the orifice plate 6 is 1-5 mm.

[0014] Optionally, a non-porous belt 62 is provided in the middle of the orifice plate 6, and the non-porous belt 62 includes a first zone 63, a second zone 64 and a third zone 65 connected in sequence, and the first zone 63 and the third zone 65 are respectively rectangular, 4-14 cm long and 1-4 cm wide; the second zone 64 is circular, with a diameter of 2-5 cm.

[0015] Optionally, a cooling jacket 7 is provided at the tail of the cylinder 1 corresponding to the stirring paddle 9 , and the cooling jacket 7 is connected to a cooling water pipe 8 .

[0016] Through the above technical solution, the microporous needle-shaped fertilizer prepared by the press of the present invention dissolves faster and can be better applied to large-area drip irrigation systems.

[0017] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings: Figure 1 It is a structural schematic diagram of the press of the present invention; Figure 2 It is a partial structural diagram of the twin-screw and gear set of the present invention; Figure 3 Schematic diagram of the structure of the upper part of the twin-screw extruder of the present invention; Figure 4 It is a partial structural schematic diagram of the cylinder of the present invention; Figure 5 It is a partial structural schematic diagram of the orifice plate of the present invention.

[0019] Description of Reference Numerals 1-barrel; 11-internal thread; 12-gear set; 121-first gear; 122-second gear; 123-gear box; 2-drive rod; 21-first screw; 22-second screw; 4-drive motor; 41-reducer; 5-feed port; 6-orifice plate; 61-hole; 62-non-porous belt; 63-first zone; 64-second zone; 65-third zone; 7-cooling jacket; 8-cooling water pipe; 9-stirring paddle; 91-first stirring paddle; 92-second stirring paddle; 10-gap area. DETAILED DESCRIPTION

[0020] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0021] The present invention unexpectedly discovered that, under appropriate pressure, shear, and kneading conditions, a powdered fertilizer premix without a binder and / or filler can be converted into a slurry of suitable viscosity, and that gas entrained in the fertilizer premix can be evenly dispersed into the slurry of suitable viscosity to form microbubbles. These microbubbles can then be further subjected to microporous pore formation after extrusion, thereby producing a microporous needle-shaped fertilizer, and thus the present invention. The microporous needle-shaped fertilizer of the present invention can be prepared by extrusion granulation without a binder and / or filler, thereby avoiding the adverse effects of binders and / or fillers on dissolution rate and turbidity after dissolution. Furthermore, the microporous needle-shaped fertilizer of the present invention, due to its micropores, can further significantly increase its dissolution rate, enabling instantaneous dissolution.

[0022] The present invention provides a press for preparing microporous needle-shaped fertilizers, Figure 1-3 The press includes a barrel 1 and a twin screw arranged in the barrel 1, a feed port 5 is provided on the side of the barrel 1, and a perforated plate 6 is provided on the bottom; the twin screw includes a first screw 21 and a second screw 22 arranged side by side and rotating in opposite directions, the thread of the first screw 21 and the thread of the second screw 22 are engaged with each other, and the end of the twin screw close to the feed port 5 is connected to a driving mechanism, which is located at the upper end of the barrel 1; the ends of the first screw 21 and the second screw 22 close to the perforated plate 6 are respectively equipped with 2-6 stirring paddles 9; the drive motor 4 is driven and connected to the first screw 21 through a reducer 41; the first screw 21 and the second screw 22 can rotate in opposite directions at the same speed.

[0023] In the press of the present invention, the first screw 21 and the second screw 22 are arranged side by side and rotate in opposite directions. The threads of the first screw 21 and the second screw 22 are meshed with each other, and the first screw 21 and the second screw 22 can squeeze and shear the fertilizer premix and the air entrained in the fertilizer premix, so that the material begins to soften and melt into a slurry material under the action of mechanical forces such as extrusion and shearing. The stirring paddle 9 in the press of the present invention can perform a second shear and kneading on the material after extrusion and the first shear, further increasing the shear force, so that the material is fully mixed and uniformly obtained to obtain a slurry material containing microbubbles. More specifically, the present invention greatly increases the shear force by adding a stirring paddle 9 to the end of the twin screw. On the one hand, the raw material is converted into a slurry material, and on the other hand, the entrained gas is evenly mixed into the slurry material in the form of microbubbles. The slurry material containing microbubbles forms lines after passing through the orifice plate 6. During the hardening process, the microbubbles expand and form holes, and the lines are segmented to obtain microporous needle-shaped fertilizers. In the present invention, due to the presence of micropores, the dissolution rate of the microporous needle-shaped fertilizer is greatly improved; and raw materials without adding binders or fillers can be prepared into microporous needle-shaped fertilizer, so that the viscosity and turbidity of the microporous needle-shaped fertilizer are significantly reduced after dissolution.

[0024] According to the present invention, optionally, the driving mechanism includes a driving motor 4 connected to the first screw 21 and a gear set 12 connected between the first screw 21 and the second screw 22. The gear set 12 includes a first gear 121 and a second gear 122. Figure 2 The first gear 121 of the two gears is fixed on the first screw 21 and can rotate coaxially with the first screw 21. Figure 2Of the two gears, the second gear 122 is fixed to the second screw 22 and can rotate coaxially with the second screw 22. The first gear 121 and the second gear 122 are meshed with each other. The drive motor 4 can be driven by the first screw 21 via an appropriate reducer 41. The first screw 21 and the second screw 22 can rotate in opposite directions at the same speed. The reducer 41 can be connected to the upper end of the first screw 21 via a drive rod 2. The gear set 12 can be housed in a gear box 123.

[0025] According to the present invention, optionally, the threads of the first screw 21 and the second screw 22 are staggered, and the threads are alternately arranged and meshed with each other.

[0026] According to the present invention, as a preferred embodiment, the diameters of the first screw 21 and the second screw 22 are 20-50 cm and 40-100 cm, respectively. The center-to-center distance between the first screw 21 and the second screw 22 is 20-50 cm. In this preferred embodiment, the first screw 21 and the second screw 22 can provide sufficient and appropriate pressure and shear forces. The length direction of the first screw 21 and the second screw 22 refers to the direction of their rotational axis.

[0027] According to the present invention, as a preferred embodiment, the first screw 21 and the second screw 22 have a screw groove depth of 5-10 cm, a screw flight width of 1-5 cm, and a thread lead angle of 2-10°. The screw flights are inclined downward from the outside to the inside of the barrel 1. In this preferred embodiment, the energy consumption and wear rate of the press can be reduced.

[0028] According to the present invention, the number of the plurality of stirring paddles 9 can be 2, 3, 4, 5 or 6, and the plurality of stirring paddles 9 can be evenly and symmetrically arranged at the ends of the first screw 21 and the second screw 22 close to the orifice plate 6; optionally, the length of the stirring paddle 9 is 5-22 cm, the width is 1-5 cm, and the thickness is 0.5-3 cm. The inner ends of the plurality of stirring paddles 9 are surrounded to form a gap area 10, the diameter of the gap area 10 is 2-10 cm, and the distance between the inner ends of two adjacent stirring paddles 9 is 2-10 cm; the stirring paddle 9 includes a first stirring paddle 91 and a second stirring paddle 92, the first stirring paddle 91 and the second stirring paddle 92 can rotate on the same plane, and the outer end of the first stirring paddle 91 extends into between the two adjacent second stirring paddles 92. The gap area 10 allows the material to flow, which is conducive to enhancing the shearing and kneading effect. The length direction of the stirring paddle 9 refers to the radial direction of the screw.

[0029] According to the present invention, optionally, Figure 4 As shown, the thickness of the barrel 1 is 1-5 cm. The inner wall of the barrel 1 is also provided with an internal thread 11. The internal thread 11 has a depth of 1-8 mm, a width of 1-5 mm, and a thread lead angle of 1-15°. The internal thread 11 on the inner wall of the barrel of the present invention can further enhance shearing and kneading of the material, thereby achieving eutectic melting of the material.

[0030] According to the present invention, optionally, the distance between the screw flights of the first screw 21 and the second screw 22 and the inner surface of the barrel 1 is 0.1-5 mm. This embodiment facilitates heat conduction of the mechanical heat generated by the first screw 21 and the second screw 22 and increases shear force, thereby obtaining a slurry material, while reducing the amount of slurry material backflow.

[0031] According to the present invention, optionally, Figure 5 As shown, the thickness of the orifice plate 6 is 0.5-2 cm, and the orifice plate 6 is provided with holes 61. The hole diameter of the holes 61 is 1-3 mm, and the hole spacing is 2-10 mm. The above embodiment facilitates the extrusion of the slurry containing microbubbles through the orifice plate 6. The slurry containing microbubbles after extrusion through the orifice plate 6 can be cut and granulated to form microporous needle-shaped fertilizer.

[0032] According to the present invention, optionally, the distance between the stirring paddle 9 and the orifice plate 6 is 1-5mm; a non-porous belt 62 is provided in the middle of the orifice plate 6, and the non-porous belt 62 includes a first area 63, a second area 64 and a third area 65 connected in sequence, the first area 63 and the third area 65 are respectively rectangular, 4-14cm long and 1-4cm wide; the second area 64 is circular, with a diameter of 2-5cm. There is a certain distance between the stirring paddle 9 and the orifice plate 6 of the present invention, forming a space. This spatial distance is conducive to the non-porous belt 62 of the orifice plate 6 cooperating with the stirring paddle 9, so that the density of the extruded slurry material containing microbubbles produces periodic fluctuations, so that the extruded slurry material containing microbubbles can be naturally and evenly broken and hardened into microporous needle-shaped fertilizers, and cutting granulation can no longer be used.

[0033] According to the present invention, a cooling jacket 7 is optionally provided at the rear of the portion of the barrel 1 corresponding to the stirring paddle 9, and the cooling jacket 7 is connected to a cooling water pipe 8. The present invention can control the material temperature during the second shearing and kneading process through the cooling jacket 7, thereby preventing partial decomposition of the material due to high temperature and facilitating the stable distribution of microbubbles in the slurry material.

[0034] In a preferred embodiment of the present invention, the diameters of the first screw 21 and the second screw 22 are preferably 25-40 cm, more preferably 30 cm, and the lengths are preferably 45-90 cm, more preferably 50 cm. The center-to-center distance between the first screw 21 and the second screw 22 is preferably 25-40 cm, more preferably 30 cm. The screw groove depths of the first screw 21 and the second screw 22 are preferably 6-8 cm, more preferably 7 cm, and the flight widths of the first screw 21 and the second screw 22 are preferably 2-5 cm, more preferably 3 cm. The lead angles of the first screw 21 and the second screw 22 are preferably 3-9°, more preferably 5°.

[0035] In a preferred embodiment of the present invention, the length of the stirring paddle 9 is preferably 8-15 cm, more preferably 10 cm, the width is preferably 2-4 cm, more preferably 3 cm, the thickness is preferably 1-2 cm, more preferably 1.5 cm, and the diameter of the gap area 10 is preferably 3-9 cm; more preferably 5 cm.

[0036] In a preferred embodiment of the present invention, the thickness of the barrel 1 is preferably 2-4 cm, more preferably 3 cm; the depth of the internal thread 11 provided on the inner wall of the barrel 1 is preferably 2-7 mm, more preferably 5 mm, the width is preferably 2-4 mm, more preferably 3 mm, the thread lead angle is preferably 2-12°, more preferably 5°, and the distances between the screw ridges of the first screw 21 and the second screw 22 and the inner surface of the barrel 1 are preferably 0.2-4 mm, more preferably 0.3 mm.

[0037] In a preferred embodiment of the present invention, the thickness of the orifice plate 6 is preferably 0.8-1.5 cm, more preferably 1 cm, the aperture of the holes 61 provided on the orifice plate 6 is preferably 1.5-2.5 mm, more preferably 2 mm, the hole spacing is preferably 5-8 mm, more preferably 6 mm, the distance between the stirring paddle 9 and the orifice plate 6 is preferably 2-4 mm, more preferably 3 mm, the rectangular length of the non-porous belt 62 provided in the middle of the orifice plate 6 is preferably 6-10 cm, more preferably 8 cm, the width is preferably 1-3 cm, more preferably 2 cm, and the circular diameter is preferably 2.5-4 cm, more preferably 3 cm.

[0038] The press of the present invention is suitable for a method for preparing microporous needle-shaped fertilizers. This method can use a suitable press to granulate the fertilizer. Preferably, the method uses the press provided by the present invention to granulate the fertilizer. The method comprises: feeding a fertilizer premix to be granulated into a feed port 5 of the press; using a twin-screw extruder to extrude and perform a primary shearing operation on the fertilizer premix and gas entrained therein; and using a stirring paddle 9 to perform a secondary shearing operation and kneading on the extruded and primary sheared material to obtain a slurry containing microbubbles; and then extruding the slurry containing microbubbles through a perforated plate 6.

[0039] Through extrusion and a first shearing step, a powdered fertilizer premix can be converted into a slurry of suitable viscosity. Furthermore, through a second shearing step and kneading step, gas entrained in the fertilizer premix can be evenly dispersed into the slurry of suitable viscosity, forming microbubbles. These microbubbles can then be further extruded to form micropores, thereby producing a microporous needle-shaped fertilizer, and thus the present invention. Due to the micropores, the microporous needle-shaped fertilizer of the present invention can significantly increase its dissolution rate, enabling instantaneous dissolution.

[0040] The powdered fertilizer premix may or may not contain a binder and / or filler. Particularly preferably, the powdered fertilizer premix does not contain a binder and / or filler. This can avoid the adverse effects of the binder and / or filler on the dissolution rate and turbidity after dissolution, while also increasing the content of effective nutrients in the fertilizer product after extrusion granulation and reducing the cost of purchasing raw materials, transportation, and storage.

[0041] The present invention uses a twin-screw extruder to extrude and perform a first shear on the fertilizer premix and the gas entrained in the fertilizer premix, and uses a stirring paddle 9 to perform a second shear and kneading on the material after extrusion and the first shearing, which can increase the shear force, reduce the viscosity of the premix, and convert the gas entrained in the premix into pressurized microbubbles that mix into the slurry premix to obtain a slurry material containing microbubbles. The slurry material containing microbubbles after extrusion through the orifice plate 6 is naturally cooled, the microbubbles therein expand, and micropores are naturally formed. The extruded line-like slurry naturally breaks and hardens to form microporous needle-shaped fertilizer.

[0042] According to the present invention, optionally, the extrusion pressure is 5-50 MPa, the shear forces of the first shear and the second shear are each 30-300 kN, and the weight of the slurry containing microbubbles extruded through the orifice plate 6 per minute is 5-20 kg. In the present invention, the pressure and shear force are both maximum values ​​within the press and can be achieved by adjusting the structure and operating parameters of the press. In the present invention, the pressure can be measured by a pressure probe, and the shear force can be calculated based on the motor power and shear linear velocity.

[0043] According to the present invention, optionally, the rotation speed of the twin screw is 10-100 rpm, preferably 40-80 rpm, more preferably 50-70 rpm.

[0044] According to the present invention, optionally, the temperature of the material after extrusion and first shearing is 70°C-150°C, and the temperature of the slurry material containing microbubbles is 50°C-120°C.

[0045] According to the present invention, to further facilitate micropore formation, as a preferred embodiment, the fertilizer premix has a moisture content of 0.5-3% by weight and a bulk density of 0.8-1.5 g / cm³. In this preferred embodiment, the entrained gas in the fertilizer premix is ​​within a suitable range, which facilitates both micropore formation and the fracture formation of microporous needle-shaped fertilizers.

[0046] According to the present invention, there are no special requirements for the composition of the fertilizer premix. It can be an existing composition or a mature composition, or it can be a new composition that will appear in the future. Optionally, the fertilizer premix includes at least one of nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, calcium fertilizer, magnesium fertilizer, sulfur fertilizer, boron fertilizer, manganese fertilizer, iron fertilizer, zinc fertilizer, copper fertilizer, molybdenum fertilizer and chlorine fertilizer.

[0047] Preferably, the fertilizer premix is ​​a nitrogen, phosphorus and potassium compound fertilizer premix, and relative to 20-80 parts by weight of the nitrogen fertilizer, the content of the phosphorus fertilizer is 5-65 parts by weight, and the content of the potassium fertilizer is 10-50 parts by weight.

[0048] According to the present invention, the raw materials are optionally crushed, and after crushing, they are optionally sieved through a sieve with an aperture of 0.5-1.5 mm, and then sent to a mixer for stirring and mixing to obtain a fertilizer premix.

[0049] According to the present invention, optionally, the nitrogen fertilizer includes one or more of ammonium nitrate, ammonium nitrate phosphate, urea, ammonium chloride, ammonium sulfate, ammonium bicarbonate, monoammonium phosphate, diammonium phosphate, and ammonium polyphosphate.

[0050] According to the present invention, optionally, the phosphate fertilizer includes one or more of ammonium nitrate phosphate, monoammonium phosphate, diammonium phosphate, nitrophosphate, superphosphate, triple superphosphate, calcium magnesium phosphate, and ammonium polyphosphate.

[0051] According to the present invention, optionally, the potash fertilizer includes one or more of potassium chloride, potassium sulfate, potassium magnesium sulfate fertilizer, and potassium nitrate.

[0052] The invention obtains a microporous needle-shaped fertilizer. The diameter of the microporous needle-shaped fertilizer is 1.2-3 mm, and the length is 2-15 mm. The pore size of the micropores is 0.1-50 μm, and the porosity is 7-25%.

[0053] According to the present invention, optionally, the microporous needle-shaped fertilizer has a water content of 0.1-1% by weight and a bulk density of 0.6-1.1 g / cm3.

[0054] According to the present invention, optionally, a 10 wt % aqueous solution of the dissolved microporous needle-shaped fertilizer has a viscosity of 1-10 centipoise and a turbidity of 2-100 NTU.

[0055] The microporous needle-shaped fertilizer may contain at least one of nitrogen fertilizer, phosphorus fertilizer, potassium fertilizer, calcium fertilizer, magnesium fertilizer, sulfur fertilizer, boron fertilizer, manganese fertilizer, iron fertilizer, zinc fertilizer, copper fertilizer, molybdenum fertilizer and chlorine fertilizer.

[0056] Preferably, the microporous needle-shaped fertilizer is a nitrogen, phosphorus and potassium composite microporous needle-shaped fertilizer, wherein, relative to 20-80 parts by weight of the nitrogen fertilizer, the content of the phosphorus fertilizer is 5-65 parts by weight, and the content of the potassium fertilizer is 10-50 parts by weight.

[0057] Preferably, the microporous needle-shaped fertilizer is prepared by the above method.

[0058] The microporous needle-shaped fertilizer of the present invention has a faster dissolution speed, and the solution after dissolution has low viscosity and low turbidity, and can be better applied to large-area drip irrigation systems.

[0059] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0060] The diameters of the first screw 21 and the second screw 22 of the press used in the embodiment of the present invention are 30 cm and 50 cm respectively; the center distance between the first screw 21 and the second screw 22 is 30 cm. The screw groove depths of the first screw 21 and the second screw 22 are 3 cm, the screw ridge widths are 4 cm, and the thread lead angles are 5°. The length of the first stirring paddle 91 and the second stirring paddle 92 are 10 cm, the width and thickness are 3 cm and 1.5 cm respectively, and the diameter of the gap area 10 is 5 cm. The thickness of the barrel 1 is 3 cm, and the distances between the screw ridges of the first screw 21 and the second screw 22 and the inner surface of the barrel 1 are 0.3 mm respectively. The thickness of the orifice plate 6 is 1 cm, the aperture of the hole 61 is 1.1 mm, and the hole spacing is 6 mm.

[0061] Example 1 This embodiment prepares a microporous needle-shaped fertilizer, and the specific method includes: The fertilizer premix includes, by mass percentage, 15.6% urea, 36.5% monoammonium phosphate, 20.8% ammonium chloride, and 27.1% potassium chloride.

[0062] The fertilizer premix to be granulated is fed into the feed port 5 of the press, and the drive motor 4 drives the first screw 21 and drives the second screw 22 to rotate in the opposite direction in the barrel 1, so as to extrude and shear the fertilizer premix and the air entrained by the fertilizer premix, and use the first stirring paddle 91 and the second stirring paddle 92 to perform the second shear and kneading on the material after extrusion and the first shearing. At the same time, the material temperature is controlled by the cooling jacket 7 to obtain a slurry material containing microbubbles, and then the slurry material containing microbubbles is extruded through the holes 61 on the orifice plate 6. The extruded slurry material containing microbubbles is naturally cooled, and the microbubbles therein expand to naturally form micropores. The extruded line-like slurry naturally breaks and hardens to form microporous needle-shaped fertilizer.

[0063] Among them, the extrusion pressure is 40MPa, the shear force of the first shear and the second shear is 200kN each, the weight of the slurry material containing microbubbles extruded through the orifice plate per minute is 18kg, the speed of the first screw and the second screw is 60rpm, the temperature of the material after extrusion and the first shear is 90°C, and the temperature of the slurry material containing microbubbles is 80°C.

[0064] The microporous needle-shaped fertilizer obtained in this embodiment has a diameter of 1.4-1.6 mm and a length of 8-12 mm.

[0065] Example 2 This embodiment prepares a microporous needle-shaped fertilizer, and the specific method includes: The fertilizer premix includes, by mass percentage, urea 62.0%, monoammonium phosphate 15.0%, and potassium chloride 23.0%.

[0066] The fertilizer premix to be granulated is fed into the feed port 5 of the press, and the drive motor 4 drives the first screw 21 and drives the second screw 22 to rotate in the opposite direction in the barrel 1, so as to extrude and shear the fertilizer premix and the air entrained by the fertilizer premix, and use the first stirring paddle 91 and the second stirring paddle 92 to perform the second shear and kneading on the material after extrusion and the first shearing. At the same time, the material temperature is controlled by the cooling jacket 7 to obtain a slurry material containing microbubbles, and then the slurry material containing microbubbles is extruded through the holes 61 on the orifice plate 6. The extruded slurry material containing microbubbles is naturally cooled, and the microbubbles therein expand to naturally form micropores. The extruded line-like slurry naturally breaks and hardens to form microporous needle-shaped fertilizer.

[0067] Among them, the extrusion pressure is 30MPa, the shear force of the first shear and the second shear is 150 kN each, the weight of the slurry material containing microbubbles extruded through the orifice plate per minute is 15kg, the speed of the first screw and the second screw is 50rpm, the temperature of the material after extrusion and the first shear is 80°C, and the temperature of the slurry material containing microbubbles is 70°C.

[0068] The microporous needle-shaped fertilizer obtained in this embodiment has a diameter of 1.2-1.4 mm and a length of 10-15 mm.

[0069] Example 3 This embodiment prepares a microporous needle-shaped fertilizer, and the specific method includes: The fertilizer premix includes, by mass percentage, 22.4% ammonium nitrate phosphate, 32.2% monoammonium phosphate, 2.0% ammonium sulfate, and 43.4% potassium sulfate.

[0070] The fertilizer premix to be granulated is fed into the feed port 5 of the press, and the drive motor 4 drives the first screw 21 and the second screw 22 to rotate in the opposite direction in the barrel 1, thereby extruding and shearing the fertilizer premix and the air entrained in the fertilizer premix. The first stirring paddle 91 and the second stirring paddle 92 are used to perform a second shearing and kneading on the material after extrusion and the first shearing. At the same time, the material temperature is controlled by the cooling jacket 7 to obtain a slurry material containing microbubbles. The slurry material containing microbubbles is then extruded through the holes 61 (aperture 2 mm) on the orifice plate 6. The extruded slurry material containing microbubbles is naturally cooled, and the microbubbles therein expand to naturally form micropores. The extruded line-like slurry naturally breaks and hardens to form microporous needle-shaped fertilizer.

[0071] Among them, the extrusion pressure is 50 MPa, the shear force of the first shear and the second shear is 300 kN each, the weight of the slurry material containing microbubbles extruded through the orifice plate per minute is 20 kg, the speed of the first screw and the second screw is 100 rpm, the temperature of the material after extrusion and the first shear is 130 ° C, and the temperature of the slurry material containing microbubbles is 100 ° C.

[0072] The microporous needle-shaped fertilizer obtained in this embodiment has a diameter of 2.3-2.5 mm and a length of 6-10 mm.

[0073] Example 4 This embodiment prepares a microporous needle-shaped fertilizer, and the specific method includes: The fertilizer premix includes, by mass percentage, 44.1% urea, 10.2% potassium sulfate, 38.9% ammonium sulfate, 6.7% potassium chloride, and 0.1% ammonium bicarbonate.

[0074] The fertilizer premix to be granulated is fed into the feed port 5 of the press, and the drive motor 4 drives the first screw 21 and drives the second screw 22 to rotate in the opposite direction in the barrel 1, so as to extrude and shear the fertilizer premix and the air entrained in the fertilizer premix, and use the first stirring paddle 91 and the second stirring paddle 92 to perform the second shear and kneading on the material after extrusion and the first shearing, and at the same time control the material temperature by the cooling jacket 7 to obtain a slurry material containing microbubbles, and then extrude the slurry material containing microbubbles through the holes 61 on the orifice plate 6. The extruded slurry material containing microbubbles is naturally cooled, and the microbubbles therein expand to naturally form micropores. The extruded line-like slurry naturally breaks and hardens to form microporous needle-shaped fertilizer material.

[0075] Among them, the extrusion pressure is 30MPa, the shear force of the first shear and the second shear is 150 kN each, the weight of the slurry material containing microbubbles extruded through the orifice plate per minute is 10kg, the speed of the first screw and the second screw is 40rpm, the temperature of the material after extrusion and the first shear is 70°C, and the temperature of the slurry material containing microbubbles is 60°C.

[0076] The microporous needle-shaped fertilizer obtained in this embodiment has a diameter of 1.2-1.3 mm and a length of 5-12 mm.

[0077] Comparative Example 1 Fertilizer was prepared according to the method of Example 1, except that the stirring paddles 9 on the first screw 21 and the second screw 22 of the press were all removed; after the press was turned on and the premix was added, the orifice plate 6 of the press was squeezed and deformed, and the fertilizer could not be extruded and granulated.

[0078] Comparative Example 2 Fertilizer was prepared according to the method of Example 1, except that the stirring paddles 9 on the first screw 21 and the second screw 22 of the press were all removed, and 2 weight% starch was added to the premix. After the press was turned on and the premix was added, continuous long strips of fertilizer could be squeezed out of the orifice plate 6 of the press, but they did not have micropores and could not be broken naturally, and required additional pelletizing.

[0079] Test Example 1 The fertilizers prepared in Examples 1-4 and Comparative Example 2 were tested for dissolution rate, turbidity, viscosity, oil absorption, pore size and porosity. The results are shown in Table 1.

[0080] Dissolution rate: The dissolution time of 10g fertilizer in 100mL water.

[0081] Turbidity: measured using a turbidimeter.

[0082] Viscosity: The viscosity of a solution containing 10g of fertilizer dissolved in 100mL of water. This test is based on the method for determining liquid viscosity in GB / T 22235-2008.

[0083] Oil absorption rate: The porosity of the particles is reflected by the oil absorption rate index, which is tested in accordance with "4.4 Oil Absorption Gravimetric Method" in "HG / T 3280-2011 Porous Granular Ammonium Nitrate".

[0084] Pore ​​diameter and porosity: measured by mercury pressure method according to GB / T 21650.1-2008.

[0085] Table 1.

[0086]

[0087] As can be seen from Table 1, the microporous needle-shaped fertilizer of the present invention has a faster dissolution speed, low solution viscosity, low turbidity, and a higher oil absorption rate, and is better suitable for large-area drip irrigation systems.

[0088] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0090] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing microporous needle-shaped fertilizer, characterized in that: The method includes: The fertilizer premix to be granulated is fed into the feed port (5) of the press, the fertilizer premix and the gas entrained in the fertilizer premix are extruded and first sheared using a twin screw, and the material after the extrusion and first shearing is secondarily sheared and kneaded using a stirring paddle (9) to obtain a slurry material containing microbubbles, and the slurry material containing microbubbles is then extruded through a perforated plate (6); The press comprises a barrel (1) and a twin screw arranged in the barrel (1); a feed port (5) is provided on the side of the barrel (1), and a perforated plate (6) is provided on the bottom; the twin screw comprises a first screw (21) and a second screw (22) arranged side by side and rotating in opposite directions, the threads of the first screw (21) and the threads of the second screw (22) are meshed with each other, one end of the twin screw near the feed port (5) is connected to a driving mechanism, and the ends of the first screw (21) and the second screw (22) near the perforated plate (6) are respectively equipped with 2-6 stirring paddles (9); The stirring paddle (9) has a length of 5-22 cm, a width of 1-5 cm, and a thickness of 0.5-3 cm. The inner ends of the plurality of stirring paddles (9) are surrounded to form a gap area (10). The diameter of the gap area (10) is 2-10 cm, and the distance between the inner ends of two adjacent stirring paddles (9) is 2-10 cm. The stirring paddle (9) comprises a first stirring paddle (91) and a second stirring paddle (92), wherein the first stirring paddle (91) and the second stirring paddle (92) are capable of rotating on the same plane, and an outer end of the first stirring paddle (91) extends into between two adjacent second stirring paddles (92); The thickness of the orifice plate (6) is 0.5-2 cm, and holes (61) are provided on the orifice plate (6). The hole diameter of the holes (61) is 1-3 mm, and the hole spacing is 2-10 mm. The distance between the stirring paddle (9) and the orifice plate (6) is 1-5 mm; A non-porous belt (62) is provided in the middle of the orifice plate (6), and the non-porous belt (62) includes a first area (63), a second area (64) and a third area (65) connected in sequence, wherein the first area (63) and the third area (65) are respectively rectangular, with a length of 4-14 cm and a width of 1-4 cm; the second area (64) is circular, with a diameter of 2-5 cm; The driving mechanism comprises a driving motor (4) connected to the first screw (21) and a gear set (12) connected between the first screw (21) and the second screw (22); the gear set (12) comprises a first gear (121) and a second gear (122), the first gear (121) being fixed on the first screw (21), the second gear (122) being fixed on the second screw (22), and the first gear (121) and the second gear (122) being meshed with each other; The driving motor (4) is connected to the first screw (21) through a speed reducer (41); the first screw (21) and the second screw (22) can rotate in opposite directions at the same speed; The inner wall of the cylinder (1) is further provided with an internal thread (11), the internal thread (11) has a depth of 1-8 mm, a width of 1-5 mm, and a thread lead angle of 1-15°; The distances between the screw ridges of the first screw (21) and the second screw (22) and the inner surface of the barrel (1) are respectively 0.1-5 mm.

2. The method according to claim 1, wherein The extrusion pressure is 5-50 MPa, and the shearing forces of the first shearing and the second shearing are respectively 30-300 kN.

3. The method according to claim 1, wherein The weight of the slurry material containing microbubbles extruded through the orifice plate per minute is 5-20 kg.

4. The method according to claim 1, wherein The rotation speed of the twin screw is 10-100 rpm, preferably 40-80 rpm, more preferably 50-70 rpm.

5. The method according to claim 3, wherein: The temperature of the material after the extrusion and the first shearing is 70°C-150°C.

6. The method according to claim 5, wherein: The temperature of the slurry material containing microbubbles is 50°C-120°C.

7. The method according to claim 1, wherein The fertilizer premix has a water content of 0.5-3% by weight and a bulk density of 0.8-1.5 g / cm3.

8. The method according to claim 7, wherein: The fertilizer premix includes at least one of nitrogen fertilizer, phosphorus fertilizer, potash fertilizer, calcium fertilizer, magnesium fertilizer, sulfur fertilizer, boron fertilizer, manganese fertilizer, iron fertilizer, zinc fertilizer, copper fertilizer, molybdenum fertilizer and chlorine fertilizer.

9. The method according to claim 8, wherein Relative to 20-80 parts by weight of the nitrogen fertilizer, the content of the phosphate fertilizer is 5-65 parts by weight, and the content of the potash fertilizer is 10-50 parts by weight.

10. The method according to claim 9, wherein: The nitrogen fertilizer includes one or more of ammonium nitrate, ammonium nitrate phosphate, urea, ammonium chloride, ammonium sulfate, ammonium bicarbonate, monoammonium phosphate, diammonium phosphate and ammonium polyphosphate; The phosphate fertilizer includes one or more of ammonium nitrate phosphate, monoammonium phosphate, diammonium phosphate, nitrophosphate, superphosphate, triple superphosphate, calcium magnesium phosphate and ammonium polyphosphate; The potash fertilizer includes one or more of potassium chloride, potassium sulfate, potassium magnesium sulfate fertilizer and potassium nitrate.

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