A method for preparing magnesium sulfate round particles

Abstract

This invention provides a method for preparing magnesium sulfate spherical granules, belonging to the field of chemical fertilizer processing technology. This invention uses magnesium sulfate heptahydrate as the raw material for extrusion granulation. Magnesium sulfate heptahydrate is a crystalline substance, easily deformed under extrusion, and readily granulated. This invention granulates by adding magnesium sulfate powder. Powdered magnesium sulfate has a low water content, easily reacting with the added granulating agent's aqueous solution. In the second granulation process, the granulated magnesium sulfate and powdered magnesium sulfate roll together to form wet magnesium sulfate spherical granules. After drying, cooling, and sieving, the final product is magnesium sulfate spherical granules. This invention produces magnesium sulfate spherical granules through a two-step granulation process, filling the gap in spherical granulated magnesium sulfate fertilizers used in blended fertilizers and mechanized application. Furthermore, the preparation method provided by this invention is simple, easy to operate, and the resulting magnesium sulfate spherical granules have good water solubility and leave no residue after dissolution.

Description

Technical Field

[0001] This invention relates to the field of chemical fertilizer processing technology, and in particular to a method for preparing magnesium sulfate spherical particles. Background Technology

[0002] Micronutrient fertilizers have seen rapid development in recent years, possessing relatively high added value and experiencing a significant increase in application rates in agricultural production, particularly in the cultivation of cash crops. Micronutrients refer to the four elements calcium (Ca), magnesium (Mg), sulfur (S), and silicon (Si). Magnesium sulfate contains both sulfur (S) and magnesium (Mg), making it a high-quality micronutrient fertilizer. Magnesium sulfate can loosen the soil, enhance crop disease resistance, increase chlorophyll levels, promote flower and leaf growth, and boost crop yield without disrupting soil pH.

[0003] Most existing magnesium sulfate fertilizers are applied by foliar spraying after dissolving crystalline or powdered magnesium sulfate in water. Some are also added to compound fertilizers. A small amount of potassium sulfate extruded granules are also available. However, the irregular shape of existing magnesium sulfate extruded granules is unsuitable for mechanized application and makes them difficult to mix evenly with other round granular materials when used as blended fertilizers. Therefore, the market urgently needs a round granule magnesium sulfate fertilizer to address these inconveniences in practical application.

[0004] Chinese patent CN102020490B discloses a method for producing granular magnesium sulfate fertilizer. This method uses industrial sulfuric acid and calcined magnesium oxide as raw materials. The resulting granular magnesium sulfate is crushed, dried, and then graded to obtain the finished product. Although this production method is simple and easy to implement, the product has an irregular appearance, is easily damaged during transportation, and is not convenient for mechanized application.

[0005] Chinese patent CN1580000A discloses a method for producing granular agricultural magnesium sulfate fertilizer. The method involves adding sulfuric acid, magnesium oxide powder, and water to a mixer, mixing and reacting them thoroughly to form a thin slurry with a high liquid content. This slurry is then fed into a horizontal twin-shaft granulator to produce fine granules with a certain moisture content. Finally, the resulting granules are transferred to a belt dryer for drying, yielding the finished granules. The finished product obtained by this method has an irregular appearance and low strength, making it unsuitable for mechanized application and only suitable for water-soluble fertilizer spraying. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a method for preparing magnesium sulfate spherical particles, which can obtain magnesium sulfate spherical particles with regular shape and good water solubility.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing magnesium sulfate spherical particles, comprising the following steps:

[0009] Magnesium sulfate heptahydrate was subjected to a first extrusion granulation to obtain magnesium sulfate particles with irregular shapes;

[0010] The irregularly shaped magnesium sulfate particles, magnesium sulfate powder, and an aqueous solution of granulating agent are mixed and subjected to a second granulation to obtain wet magnesium sulfate spherical particles.

[0011] The wet magnesium sulfate spherical particles are dried, cooled, and sieved to obtain magnesium sulfate spherical particles.

[0012] Preferably, the amount of the irregularly shaped magnesium sulfate particles is 75 to 85 parts by weight;

[0013] The amount of magnesium sulfate powder used is 15 to 25 parts.

[0014] Preferably, the irregularly shaped magnesium sulfate particles have a particle size of 2.0–4.2 mm;

[0015] The magnesium sulfate powder has a fineness of 80-120 mesh.

[0016] Preferably, the magnesium sulfate in the magnesium sulfate powder is anhydrous magnesium sulfate and / or magnesium sulfate monohydrate.

[0017] Preferably, the granulating agent is one or more of gelatinized starch, polyvinyl alcohol, and polyacrylamide.

[0018] Preferably, the mass concentration of the aqueous solution of the granulating agent is 1-3%.

[0019] Preferably, the mass content of granulating agent in the magnesium sulfate spherical particles is 0.1-0.2%.

[0020] Preferably, the aqueous solution of the granulating agent is added by spraying it through an atomizer, and the spraying rate of the aqueous solution of the granulating agent is 0.3 to 0.7 m / s.

[0021] Preferably, the first extrusion granulation is performed in an extrusion granulator;

[0022] The second granulation is carried out in a disc granulator or a rotary drum granulator.

[0023] Preferably, the second granulation time is 6 to 10 minutes.

[0024] Preferably, the drying temperature is 200-500°C and the time is 30-50 minutes.

[0025] This invention provides a method for preparing magnesium sulfate spherical particles, comprising the following steps: firstly extruding and granulating magnesium sulfate heptahydrate to obtain irregularly shaped magnesium sulfate particles; mixing the irregularly shaped magnesium sulfate particles, magnesium sulfate powder, and an aqueous solution of a granulating agent, and then performing a second granulation to obtain wet magnesium sulfate spherical particles; and drying, cooling, and sieving the wet magnesium sulfate spherical particles to obtain magnesium sulfate spherical particles. This invention uses magnesium sulfate heptahydrate as the raw material for extrusion granulation. Magnesium sulfate heptahydrate is a crystal, easily deformed under extrusion, and readily forms granules through extrusion. This invention uses magnesium sulfate powder for granulation; the powdered magnesium sulfate has a low water content and readily interacts with the added aqueous solution of the granulating agent. In the second granulation process, the granulated magnesium sulfate and the powdered magnesium sulfate roll together to form wet magnesium sulfate spherical particles. In this invention, during the drying process, the wet magnesium sulfate spherical particles undergo a process where the wet "chain bonds" of agglomerated powder particles are transformed into hard "salt bridges" of solid particles. The granulating agent added during the granulation process also solidifies and hardens as the material dries. After drying, the granules undergo cooling and sieving processes to finally obtain magnesium sulfate spherical granules. This invention produces magnesium sulfate spherical granules from magnesium sulfate raw materials through a two-step granulation process, filling the gap in the field of spherical granular magnesium sulfate fertilizers for blending and mechanized application. Furthermore, the preparation method provided by this invention is simple, easy to operate, and produces magnesium sulfate spherical granules with good water solubility and no residue after dissolution.

[0026] Furthermore, the granulating agent content in the magnesium sulfate spherical particles obtained by this invention is only 0.1-0.2%, which is less than the amount of granulating agent required and is more conducive to reducing costs. Attached Figure Description

[0027] Figure 1 This is a process flow diagram for preparing magnesium sulfate spherical particles according to the present invention;

[0028] Figure 2 This is a picture of the finished product of the magnesium sulfate spherical particles obtained in Example 1;

[0029] Figure 3 This is a picture of the finished product of magnesium sulfate spherical particles obtained in Example 2;

[0030] Figure 4 This is a picture of the finished product of magnesium sulfate spherical particles obtained in Example 3. Detailed Implementation

[0031] This invention provides a method for preparing magnesium sulfate spherical particles, comprising the following steps:

[0032] Magnesium sulfate heptahydrate was subjected to a first extrusion granulation to obtain magnesium sulfate particles with irregular shapes;

[0033] The irregularly shaped magnesium sulfate particles, magnesium sulfate powder, and an aqueous solution of granulating agent are mixed and subjected to a second granulation to obtain wet magnesium sulfate spherical particles.

[0034] The wet magnesium sulfate spherical particles are dried, cooled, and sieved to obtain magnesium sulfate spherical particles.

[0035] This invention involves a first extrusion granulation of magnesium sulfate heptahydrate to obtain irregularly shaped magnesium sulfate particles. In this invention, the first extrusion granulation is performed in an extrusion granulator. The particle size of the irregularly shaped magnesium sulfate particles is preferably 2.0–4.2 mm, more preferably 3.0–4.0 mm. This invention does not have special requirements for the specific operation process of the first extrusion granulation; obtaining regularly shaped magnesium sulfate particles of the corresponding size is sufficient. This invention uses magnesium sulfate heptahydrate as the raw material for extrusion granulation. Magnesium sulfate heptahydrate is a crystalline substance that is easily deformed under extrusion and readily forms particles through extrusion.

[0036] After obtaining the irregularly shaped magnesium sulfate particles, the present invention mixes the irregularly shaped magnesium sulfate particles, magnesium sulfate powder, and an aqueous solution of a granulating agent for a second granulation to obtain wet magnesium sulfate spherical particles. In the present invention, the magnesium sulfate in the magnesium sulfate powder is preferably anhydrous magnesium sulfate and / or magnesium sulfate monohydrate, both of which have low water content and are easily mixed with the added aqueous solution of the granulating agent for granulation. In the present invention, the fineness of the magnesium sulfate powder is preferably 80-120 mesh, more preferably 100 mesh.

[0037] In this invention, the amount of the irregularly shaped magnesium sulfate particles is preferably 75 to 85 parts by weight, more preferably 80 parts; the amount of the magnesium sulfate powder is preferably 15 to 25 parts, more preferably 20 parts.

[0038] In this invention, the granulating agent is preferably one or more of gelatinized starch, polyvinyl alcohol, and polyacrylamide; the mass concentration of the aqueous solution of the granulating agent is preferably 1-3%, more preferably 2%. In this invention, based on the mass fraction of the irregularly shaped magnesium sulfate granules, the amount of the aqueous solution of the granulating agent is 6-10 parts, more preferably 7-8 parts. Using the above-mentioned granulating agent, this invention is less prone to degumming failure during the granulation process (degumming refers to the failure of the granulating agent's binding effect on the material during the granulation process, leading to granule breakage and pulverization), resulting in granules with higher final strength.

[0039] In this invention, the mass content of granulating agent in the magnesium sulfate spherical particles is preferably 0.1-0.2%, more preferably 0.12-0.18%.

[0040] In this invention, the aqueous solution of the granulating agent is preferably added by spraying it in via an atomizer, and the spraying rate of the aqueous solution of the granulating agent is 0.3 to 0.7 m / s, more preferably 0.5 m / s.

[0041] In this invention, the second granulation is preferably carried out in a disc granulator or a rotary drum granulator.

[0042] In this invention, the second granulation time is preferably 6 to 10 minutes, more preferably 7 to 8 minutes.

[0043] After obtaining the wet magnesium sulfate spherical particles, the present invention dries, cools, and sieves the wet magnesium sulfate spherical particles to obtain magnesium sulfate spherical particles. In the present invention, the drying is preferably carried out in a dryer. In the present invention, the drying temperature is preferably 200-500℃, more preferably 300-400℃; the drying time is preferably 30-50 min, more preferably 35-45 min. In the present invention, during the drying process, the wet magnesium sulfate spherical particles undergo a process in which the wet "chain bonds" of agglomerated powder particles are transformed into hard "salt bridges" of solid particles, and the granulating agent added during the granulation process also solidifies and hardens during the drying of the material.

[0044] The present invention does not have any special requirements for the cooling method; any cooling method known to those skilled in the art can be used.

[0045] In this invention, the screen aperture used for sieving is preferably 2.5mm to 4.5mm.

[0046] In this invention, the particle size of the obtained magnesium sulfate spherical particles is preferably 2.5 mm to 4.5 mm.

[0047] The process flow diagram for preparing magnesium sulfate spherical particles of the present invention is as follows: Figure 1 As shown.

[0048] The preparation method of magnesium sulfate spherical particles provided by the present invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention. All percentages in the embodiments are weight percentages.

[0049] Example 1

[0050] Take 75.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0051] Irregularly shaped magnesium sulfate granules are fed into a rotary drum granulator via a belt conveyor, followed by 25.0 parts of anhydrous magnesium sulfate powder with a fineness of 100 mesh. Simultaneously, 10.0 parts of a 1.0% (w / w) gelatinized starch solution are added via a pump through an atomizer. After the granulator runs for 8 minutes, the granules are sent to a dryer, where the drying temperature is set to 300℃ and the drying time is 50 minutes. The dried material is then cooled and sieved to obtain the finished magnesium sulfate round granules. The granule strength is measured to be 10N using a strength tester.

[0052] The actual image of the obtained magnesium sulfate spherical particles is shown below. Figure 2 As shown.

[0053] Example 2

[0054] Take 80.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0055] Irregularly shaped magnesium sulfate granules are fed into a disc granulator via a bucket elevator, followed by 20.0 parts of 100-mesh magnesium sulfate monohydrate powder. Simultaneously, 8.0 parts of a 2.0% polyvinyl alcohol solution are added via a pump and atomizer. After the granulator runs for 6 minutes, the granules are sent to a dryer, where the drying temperature is set to 500℃ and the drying time is 30 minutes. The dried material is then cooled and sieved to obtain the finished magnesium sulfate round granules. The granule strength is measured to be 15N using a strength tester.

[0056] The actual image of the obtained magnesium sulfate spherical particles is shown below. Figure 3 As shown.

[0057] Example 3

[0058] Take 85.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0059] Irregularly shaped magnesium sulfate granules are fed into a rotary drum granulator via a bucket elevator, followed by 15.0 parts of anhydrous magnesium sulfate powder with a fineness of 100 mesh. Simultaneously, 6.0 parts of a 3.0% polyacrylamide solution are added via a pump and atomizer. After the granulator runs for 10 minutes, the granules are sent to a dryer, where the drying temperature is set to 200℃ and the drying time is 40 minutes. The dried material is then cooled and sieved to obtain the finished magnesium sulfate round granules with a particle strength of 12N.

[0060] The actual image of the obtained magnesium sulfate spherical particles is shown below. Figure 4 As shown.

[0061] Comparative Example 1

[0062] Take 75.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0063] Irregularly shaped magnesium sulfate granules are fed into a rotary drum granulator via a belt conveyor. Then, 25.0 parts of 100-mesh magnesium sulfate heptahydrate crystals are added, while simultaneously, 10.0 parts of a 1.0% (w / w) gelatinized starch solution are added via a pump and atomizer. After the granulator runs for 8 minutes, the granules are sent to a dryer, where the drying temperature is set to 300℃ and the drying time is 50 minutes. The dried material is then cooled and sieved to obtain the finished product of irregularly shaped magnesium sulfate granules.

[0064] Comparative Example 2

[0065] Take 60.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0066] Irregularly shaped magnesium sulfate granules are fed into a disc granulator via a bucket elevator, followed by 40.0 parts of 100-mesh magnesium sulfate monohydrate powder. Simultaneously, 8.0 parts of a 2.0% polyvinyl alcohol solution are added via a pump and atomizer. After the granulator runs for 6 minutes, the granules are sent to a dryer, where the drying temperature is set to 500℃ and the drying time is 30 minutes. The dried material is then cooled and sieved to obtain the finished magnesium sulfate round granules. The granule strength is measured to be 15N using a strength tester. Because anhydrous magnesium sulfate is more expensive than heptahydrate magnesium sulfate, the raw material cost is correspondingly higher.

[0067] Comparative Example 3

[0068] Take 90.0 parts of magnesium sulfate heptahydrate crystals and add them to an extrusion granulator. After extrusion, irregularly shaped magnesium sulfate particles with a particle size range of 2.0 to 4.2 mm are obtained.

[0069] Irregularly shaped magnesium sulfate granules were fed into a rotary drum granulator via a bucket elevator, followed by 10.0 parts of anhydrous magnesium sulfate powder with a fineness of 100 mesh. Simultaneously, 6.0 parts of a 3.0% polyacrylamide solution were added via a pump through an atomizer. After the granulator ran for 10 minutes, the granules were sent to a dryer, where the drying temperature was set to 200°C and the drying time to 40 minutes. The dried material was then cooled and sieved to obtain the finished magnesium sulfate granules. The appearance of these granules was not as round as that of the granules in Example 3, and the granule strength was 12 N.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing magnesium sulfate spherical particles, comprising the following steps: Magnesium sulfate heptahydrate was subjected to a first extrusion granulation to obtain magnesium sulfate particles with irregular shapes; The irregularly shaped magnesium sulfate particles, magnesium sulfate powder, and an aqueous solution of granulating agent are mixed and subjected to a second granulation to obtain wet magnesium sulfate spherical particles. The wet magnesium sulfate spherical particles are dried, cooled, and sieved to obtain magnesium sulfate spherical particles; The magnesium sulfate in the magnesium sulfate powder is anhydrous magnesium sulfate and / or magnesium sulfate monohydrate. The amount of the irregularly shaped magnesium sulfate granules is 75-85 parts by weight; the amount of the magnesium sulfate powder is 15-25 parts. The irregularly shaped magnesium sulfate particles have a particle size of 2.0~4.2 mm; the magnesium sulfate powder has a fineness of 80~120 mesh. The granulating agent is one or more of gelatinized starch, polyvinyl alcohol, and polyacrylamide; the aqueous solution of the granulating agent has a mass concentration of 1-3%. The magnesium sulfate spherical granules contain 0.1-0.2% granulating agent by mass. The first extrusion granulation is carried out in an extrusion granulator; the second granulation is carried out in a disc granulator or a rotary drum granulator.

2. The production method according to claim 1, characterized by, The second granulation time is 6~10 min.

3. The preparation method according to claim 1, characterized in that, The drying temperature is 200~500℃, and the time is 30~50min.

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