A granulation method for a difficult-to-bond iron-based inorganic powder material

Abstract

The present invention discloses a granulation method for a difficult-to-bond iron-based inorganic powder material, comprising the following steps: 1) determining the chemical composition and zeta potential of the iron-based active component, particle size, and auxiliary materials of the powder raw material; 2) mixing the iron-based active component with the auxiliary materials according to the absolute value of the zeta potential and the properties of the powder raw material to obtain a mixed powder; 3) then bonding the mixed powder to a carrier under the action of capillary water to form a material core with the carrier as the core; 4) granulating the material core to obtain iron-based slow-release particles. The iron-based slow-release particles obtained by the method of the present invention have high strength, low cost, less waste, are easy to produce, are not easy to pulverize and agglomerate, are resistant to transportation and storage, and have a good slow-release effect. They can be applied to various fields such as fertilizer production, chemical engineering, groundwater and soil remediation.

Description

Technical Field

[0001] The invention belongs to the field of powder material processing, and in particular relates to a granulation method for difficult-to-bond iron-based inorganic powder materials. Background Art

[0002] Currently, inorganic powder materials are widely used in industries such as chemical engineering, agricultural fertilizers, and environmental soil and groundwater remediation. However, due to drawbacks such as fly ash generation, rapid release rates, and the risk of loss of active ingredients, powder materials are prone to resource waste and secondary pollution. It is reported that over 10 million tons of fertilizer are lost in my country annually, with the highest seasonal fertilizer utilization rate for the three major grains being only 33%, which remains a relatively low level. Furthermore, studies have shown that fine powder materials, such as biochar, can easily enter the human body through exposure routes such as inhalation and skin contact during production and transportation, causing harm. The loss of powders not only wastes resources and exacerbates environmental pollution, but also requires multiple additions to improve the effectiveness of powder application, increasing the cost of environmental remediation and creating a vicious cycle. Currently, granulation is a key solution for the large-scale industrial application of powder materials. It facilitates storage and transportation, while also allowing for the slow release of active ingredients in granules, improving material utilization and reducing costs. Common granulation methods include dry and wet methods. The dry method has high requirements for material compressibility, moisture content, viscosity, and equipment parameters. It also has problems such as low strength, high fine powder content, dust flying during the granulation process, and secondary pollution. Wet granulation, on the other hand, first wets the surface of the drug powder particles with the liquid in the binder, creating adhesion between the particles. Then, under the action of liquid bridging and external mechanical force, particles of a certain shape and size are formed. This method has the advantages of high product strength, low fine powder content, and low pollution, making it suitable for large-scale production. However, this method is less effective for granulating powders that are unstable under certain humid and hot conditions, and requires the use of exogenous substances such as wetting agents and binders to assist in forming. Iron-based powder materials combine adsorption, reduction, precipitation, and electron transfer properties. At the same time, they are low-cost, environmentally friendly, and have no risk of secondary pollution. They have broad application prospects in agricultural fertilizers, chemical engineering, environmental remediation, and other fields. However, some iron-based powders are sensitive to moisture, easily hydrolyzed, and difficult to bond. It is difficult to form stable granular materials through conventional dry and wet granulation. To address the above problems, we urgently need to carry out research on granulation methods for difficult-to-bond iron-based inorganic powder materials. Summary of the Invention

[0003] Based on the problems existing in the prior art, the purpose of the present invention is to provide a granulation method for difficult-to-bond iron-based inorganic powder materials. This method not only has an extremely high molding rate, but also the iron-based active components in the particles can be slowly released in water, so as to solve the technical problems of fast release rate, low utilization rate and easy failure of iron-based active components. The developed iron-based slow-release particles have broad application prospects in the fields of agricultural fertilizers, chemical industry, environmental remediation, etc.

[0004] The present invention provides a granulation method for difficult-to-bond iron-based inorganic powder materials. The method performs granulation by optimizing the surface interface parameters of the powder materials, regulating the ratio of the iron-based active components to the carrier and auxiliary materials, and adjusting parameters such as the granulation process flow. The obtained iron-based slow-release particles have a stable mechanical structure, are round and full, and are not broken. They have the advantages of high granulation rate, low rework rate, low production cost, and good slow-release effect.

[0005] The granulation method of the difficult-to-bond iron-based inorganic powder material provided by the present invention comprises the following steps:

[0006] 1) Mixing: Mix the powdered iron-based active component and auxiliary materials in proportion, then grind them, dry them, and finally sieve them to obtain a mixed powder;

[0007] 2) Preparing a core: Obtain a carrier, spray water mist on its surface to evenly wet it, then add part of the mixed powder obtained in step 1), mix thoroughly, and allow the mixed powder to adhere to the carrier to form a core with the carrier as the core;

[0008] 3) Particle growth and granulation: Add the core material from step 2) into the granulator, adjust the speed, control the temperature, and observe while rotating. If the surface of the core material is dry and there is flying powder in the granulator, spray water to make the surface of the core material slightly moist, and no flying powder appears in the granulator. If the core material is moist and adheres to the inner wall of the granulator, sprinkle the core material with the remaining mixed powder to separate the core material from the inner wall of the granulator. Repeat this process until the powder material is added and the formed granules are round and plump. Then, the granulator is kept rotating for 10 to 60 minutes.

[0009] 4) Screening: Screening is performed using sieves of different apertures to separate qualified particles from powder and bulk powder to obtain iron-based sustained-release particles;

[0010] 5) Drying and packaging: Dry the iron-based slow-release particles and then package them according to actual application needs.

[0011] In some embodiments, in step 1), the iron-based active component is at least one of ferric oxyhydroxide, polyferric sulfate, and iron oxide; and the auxiliary material is at least one of cement, attapulgite, lime, biochar, and bamboo charcoal.

[0012] In some embodiments, in step 1), based on the total mass of the mixed powder being 100 wt%, the content of the iron-based active component is 25-75 wt%, and the content of the auxiliary material is 75-25 wt%.

[0013] In some embodiments, in step 2), the carrier is guami stone; the particle size of the carrier is one of 1-2 mm, 2-4 mm, or 4-6 mm.

[0014] In some embodiments, the ratio of the mass of the carrier to the total mass of the mixed powder is (25-50):100.

[0015] In some embodiments, in step 3), the granulator is one of a drum disc granulator, a rotary drum granulator, a stainless steel sugar coating machine or a double-shaft granulator; the speed adjustment is specifically: the speed is 35-40 r / min within the initial 10 minutes, and then 50-60 r / min until the granulation is completed; the temperature is controlled within the range of 25±5°C.

[0016] In some embodiments, in step 4), the absolute value of the zeta potential of the iron-based sustained-release particles is determined to be ≤5.

[0017] In some embodiments, in step 4), the pore size of the sieve includes at least one of 2.5 mm, 5 mm, and 10 mm.

[0018] In some embodiments, in step 5), the drying temperature is 30-80°C.

[0019] It should be noted that before performing the step 1), the chemical composition and zeta potential of the iron-based active component and auxiliary materials of the powder raw material are first determined. According to the properties of the powder, the powder ratio of each component is adjusted to increase the viscosity of the slurry. The absolute value of the zeta potential and the charge carried by each component determine whether agglomeration and granulation can be performed; the purpose of screening the powder raw materials is to strive to meet the special needs under different application scenarios. The whole process of screening the powder raw materials includes determining the content of the iron-based active component in the powder raw material, the particle size and Zeta potential of the powder material. The iron-based active component content is required to be greater than 80%, the particle size of the powder material is less than 0.25mm, and the zeta potential is between 0 and 5 under the respective pH conditions of the application scenario. At this time, the colloid can quickly condense or agglomerate and carry an opposite charge with the auxiliary material; the powder raw materials and auxiliary materials initially screened are granulated according to different combinations and different ratio ranges, and the ratio and mixing components are determined by measuring the molding rate and failure rate.

[0020] Mechanism analysis of the present invention:

[0021] The present invention uses melonite as a core and performs granulation by adding iron-based active components and auxiliary inorganic powders. The main principles involved are: (1) in the wetting and nucleation stage, the irregular carrier melonite provides a large specific surface area, and sprays mist water evenly, forming multiple capillary water between the powder material and the melonite at different positions. Under the action of the capillary water, the powder material adheres to the melonite. Subsequently, under the combined action of gravity and centrifugal force, the powder material can effectively contact and squeeze each other, thereby forming larger particles. At the same time, the amount of powder material that the particles can adsorb is certain. Therefore, in the whole process, it is necessary to continuously adjust the absolute value of the zeta potential and the charge carried by the iron-based active components and auxiliary materials by controlling the three phases of liquid, solid and gas. The lower the absolute value, the more corresponding the positive and negative charges are, and the more inclined to condense or agglomerate to form granules; (2) in the growth and collision stage, the larger particles, i.e., microparticles, continue to squeeze and contact under the combined action of gravity, inner wall friction and centrifugal force, and the microparticles gradually grow.

[0022] The present invention has the following beneficial effects:

[0023] 1) The present invention uses a guami stone carrier as the core, which saves the wetting nucleation stage of particle forming, greatly improves the granulation rate during initial production, enables the particle surface skeleton to form rapidly, reduces the powder sticking loss rate, and is suitable for a variety of granulation methods, such as a rotary drum granulator, a stainless steel sugar coating machine, or a double-shaft granulator.

[0024] 2) The present invention does not require the addition of other adhesives, does not require blast heating, has low cost, less waste, is easy to produce, and is suitable for mass production.

[0025] 3) The final product particles of the present invention have high strength, are not easy to pulverize, coke or agglomerate, are resistant to transportation and storage, and have good sustained-release effect.

[0026] The present invention provides a granulation method for difficult-to-bond iron-based inorganic powder materials, which can be applied to fertilizer production, fly ash sintering, groundwater and soil remediation and other fields. It solves the problems of fast active ingredient release rate, low utilization rate, active component loss, and secondary pollution risk caused by the direct use of instant iron-based powder materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The zeta potential diagrams of three materials: iron oxyhydroxide, polyferric sulfate, and iron oxide;

[0028] Figure 2 Figure 1 is a diagram of the iron-based sustained-release granules prepared in Examples 1 to 4, 6 to 9;

[0029] Figure 3 Graph showing the compressive strength analysis results of the sustained-release granules prepared in Examples 2 to 4;

[0030] Figure 4 The figure shows the results of the sustained-release kinetic analysis of the sustained-release granules prepared in Examples 2 to 4. The specific method is as follows: 20 g of the finished products prepared in Examples 2 to 4 were respectively placed in a wide-mouth beaker, and samples were taken in a set time gradient sequence, and the iron ion concentration was determined by the ICP method. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below by way of specific embodiments, which are intended to further illustrate the present invention rather than to limit the present invention.

[0032] The zeta potential diagrams of the three materials of ferric oxyhydroxide, polyferric sulfate and ferric oxide used in the following examples are shown in Figure 1 As shown. Figure 1 It can be seen that the zeta potential of ferric oxyhydroxide and ferric oxide varies with pH, ranging from positive, negative, or neutral. This indicates that these two materials initially acquire a positive charge, then pass through an isoelectric point, and then acquire a negative charge as the pH increases. The absolute values of the zeta potential of ferric oxyhydroxide and ferric oxide range from 3.77 to 10.5 and 2.97 to 17.4, respectively. In the broadest applicable pH range (7 to 9), the absolute value of the zeta potential of ferric oxyhydroxide is approximately 3 to 4, less than 5, indicating an unstable system and a tendency to aggregate and granulate more easily than the other two materials. The zeta potential of polyferric sulfate remains negative throughout the entire pH range, indicating that it carries a negative charge. This result indicates that the charge-carrying properties of the auxiliary material are highly demanding during the polyferric sulfate granulation process. The zeta potential of the auxiliary material varies with pH, and the charge-carrying properties cannot change significantly with it. The absolute value of the zeta potential of polyferric sulfate ranges from 7.86 to 9.33.

[0033] Example 1

[0034] 1) Mix ferric oxyhydroxide and cement in a mass ratio of 3:1, grind them in a grinder, dry them in a drying oven at 60° C., and pass them through a 0.25 mm sieve to obtain a mixed powder for later use;

[0035] 2) Weighing a guami stone (with a particle size of 1 to 2 mm), ensuring that the mass ratio of the mixed powder to the guami stone in step 1 is 100:50, then spraying a water mist to moisten the surface of the guami stone, wherein the mass of the water mist is 0.5 to 5 wt % of the mass of the guami stone, then adding 10 wt % of the mixed powder, rotating at a speed of 8 rpm to mix, to obtain a core;

[0036] 3) Add the prepared cores to a stainless steel sugar coating machine and adjust the speed to 35-40 r / min;

[0037] 4) Then, spray the cores in the stainless steel sugar coating machine with a water mist of 0.5-5 wt% of the total mass of the guami stone and the mixed powder to make the surface slightly moist and no flying powder appears;

[0038] 5) Then add 20wt% of the mixed powder and adjust the speed to 50-60r / min;

[0039] 6) Repeat steps 4) and 5) until all the powder has been added and the granules are round and plump. Keep the stainless steel sugar coating machine rotating for 10-60 minutes.

[0040] 7) Passing the granules prepared in step 6) through 5 mm and 10 mm sieves respectively;

[0041] 8) drying the granules screened in step 7) at 30-80° C. for 12 hours;

[0042] 9) Packaging: Pack the dried particles.

[0043] Table 1 Properties of the particles produced in Example 1

[0044] Molding speed Forming rate Crushing rate Example 1 18min 93％ 5％

[0045] The molding speed in Table 1 is 18 min, which means that the powder material is granulated and molded in 18 min.

[0046] Example 2

[0047] The difference between this embodiment and embodiment 1 is that the mass ratio of ferric oxyhydroxide to cement is 1:1, and the remaining steps are the same. The properties of the produced particles are shown in Table 2.

[0048] Table 2 Characteristics of the particles produced in Example 2

[0049] Molding speed Forming rate Crushing rate Example 2 20min 95％ 4％

[0050] Example 3

[0051] The difference between this embodiment and embodiment 2 is that the particle size of the guami stone is 2-4 mm, and the drying temperature in step 8) is 50-60° C. The other steps are the same. The properties of the produced particles are shown in Table 3.

[0052] Table 3 shows the properties of the particles produced in Example 3

[0053] Molding speed Forming rate Failure rate Example 3 12min 97％ 4％

[0054] Example 4

[0055] The difference between this embodiment and embodiment 3 is that the particle size of the guami stone is 4 to 6 mm, and the remaining steps are the same. The properties of the produced particles are shown in Table 4.

[0056] Table 4 Properties of the particles produced in Example 4

[0057] Molding speed Forming rate Failure rate Example 4 10min 98％ 6％

[0058] Example 5

[0059] The difference between this embodiment and embodiment 1 is that the mass ratio of ferric oxyhydroxide to cement is 1:3, the particle size of the guami stone is 2-4 mm, and the remaining steps are the same. The properties of the produced particles are shown in Table 5.

[0060] Table 5 Properties of the particles produced in Example 5

[0061] Molding speed Forming rate Failure rate Example 5 30min 40％ 60％

[0062] Example 6

[0063] The difference between this embodiment and embodiment 1 is that the auxiliary material is lime, and the mass ratio of ferric oxyhydroxide to lime is 1:1. The remaining steps are the same. The properties of the produced particles are shown in Table 6.

[0064] Table 6 Properties of the particles produced in Example 6

[0065]

[0066]

[0067] Example 7

[0068] The difference between this embodiment and embodiment 1 is that the auxiliary material is attapulgite, the mass ratio of ferric oxyhydroxide to attapulgite is 1:1, and the remaining steps are the same. The properties of the produced particles are shown in Table 7.

[0069] Table 7 Properties of the particles produced in Example 7

[0070] Molding speed Forming rate Failure rate Example 7 10min 98％ 6％

[0071] Example 8

[0072] This embodiment differs from embodiment 1 in that the iron-based active component is iron oxide, and the mass ratio of iron oxide to cement is 1:1. The remaining steps are the same. The properties of the produced particles are shown in Table 8.

[0073] Table 8 Properties of the particles produced in Example 8

[0074] Molding speed Forming rate Failure rate Example 8 20min 85％ 21％

[0075] Example 9

[0076] The difference between this embodiment and embodiment 3 is that the iron-based active component is polyferric sulfate, the mass ratio of polyferric sulfate to cement is 1:1, and the remaining steps are the same. The properties of the produced particles are shown in Table 9.

[0077] Table 9 Properties of the particles produced in Example 9

[0078] Molding speed Forming rate Failure rate Example 9 22min 79％ 28％

[0079] The granules prepared in Examples 2 to 4 were subjected to compressive strength test and sustained release kinetics analysis. The results are shown in Table 10 and Table 11, respectively. Figure 4 shown.

[0080] Table 10 Compressive strength properties of the particles produced in Examples 2 to 4

[0081]

[0082] Table 10 shows the compressive strength characteristics of Examples 2, 3, and 4, including four parameters: compressive strength, compressive yield strain, compressive yield stress, and compression modulus (E). Example 2 has the best compressive strength because the carrier particle size is 1-2 mm during granulation, resulting in a compact and dense powder granulation process, resulting in a strong compressive strength. In Examples 3 and 4, the carrier particle sizes are 2-4 mm and 4-6 mm, respectively. During particle growth, the powder granules are less compacted, resulting in weaker compressive strength than Example 2.

[0083] Figure 4 The sustained release rates of the three examples are shown. The change patterns of the sustained release rates of the three examples are similar in the first 500 minutes. After 500 minutes, the sustained release rate of Example 2 is very stable. The changes in the sustained release of Examples 3 and 4 are greater than that of Example 2.

[0084] The above is only a preferred embodiment of the present invention, and the scope of protection of the present invention is not limited to the above embodiment. For those skilled in the art, improvements and modifications obtained without departing from the technical concept of the present invention should also be considered as the scope of protection of the present invention.

Claims

1. A method for granulating a difficult-to-bond iron-based inorganic powder material, comprising the following steps: 1) Mixing: Mix the powder raw material iron-based active component and auxiliary materials in proportion, then grind, dry and sieve to obtain mixed powder; 2) Preparing the core: Obtain a carrier and spray water mist on its surface to evenly wet it. Then, add part of the mixed powder obtained in step 1) and mix thoroughly to allow the mixed powder to adhere to the carrier, forming a core with the carrier as the core. 3) Particle growth and granulation: Add the core material from step 2) into the granulator, adjust the speed, control the temperature, and observe while rotating. If the surface of the core material is dry and there is flying powder in the granulator, spray water to make the surface of the core material slightly moist, and no flying powder will appear in the granulator. If the core material is moist and adheres to the inner wall of the granulator, use the remaining mixed powder to dust the core material and add powder to make the core material separate from the inner wall of the granulator. Repeat this process until the powder material is added and the formed granules are round and plump. Then, keep the granulator rotating for 10-60 minutes. 4) Screening: Use sieves of different apertures to separate qualified granules from powder and bulk powder to obtain iron-based sustained-release granules; 5) Drying and packaging: Dry the iron-based slow-release granules and then package them according to actual application needs; In step 1), the iron-based active component is at least one of ferric oxyhydroxide, polyferric sulfate, and ferric oxide; based on the total mass of the mixed powder as 100wt%, the content of the iron-based active component is 25-75wt%, and the content of the auxiliary material is 75-25wt%; In step 2), the carrier is guami stone; the particle size of the carrier is one of 1-2 mm, 2-4 mm or 4-6 mm.

2. The granulation method according to claim 1, characterized in that In step 1), the auxiliary material is at least one of cement, attapulgite, lime, biochar and bamboo charcoal.

3. The granulation method according to claim 1, characterized in that The ratio of the mass of the carrier to the total mass of the mixed powder is (25-50):

100.

4. The granulation method according to claim 1, characterized in that In step 3), the granulator is a drum disc granulator, a rotary drum granulator or a biaxial granulator; the speed is adjusted as follows: the speed is 35-40 r / min in the initial 10 minutes, and then 50-60 r / min until the granulation is completed; the temperature is within the range of 25±5°C.

5. The granulation method according to claim 1, characterized in that In the step 4), the absolute value of the zeta potential of the iron-based sustained-release particles is measured to be ≤5.

6. The granulation method according to claim 1, characterized in that In step 4), the pore size of the sieve is at least one of 2.5 mm, 5 mm, and 10 mm.

7. The granulation method according to claim 1, characterized in that In step 5), the drying temperature is 30-80°C.

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