A segmented curing preparation process of low free acid high water-soluble phosphoric superphosphate

Abstract

This invention relates to the field of fertilizer production technology, specifically to a segmented ripening preparation process for low-free-acid, high-water-soluble superphosphate; the process includes the following steps: feeding phosphate rock powder into a ball mill for grinding to a particle size ≤120 mesh, preparing 93%±0.5% industrial sulfuric acid; adding phosphate rock powder at a molar ratio of available P2O5 to sulfuric acid of 1:1.05~1:1.07, adding 0.3%~0.5% (by weight of phosphate rock powder) of a modifying agent, and reacting at 65~70℃ for 40~50 minutes. In the later stage of the reaction, low-pressure steam of 0.2 MPa is introduced; staged maturation is carried out, first in a closed chamber at 55~60℃ for 24 hours, and then in a ventilated chamber at 45~50℃ and a wind speed of 0.8~1.0 m / s for 48 hours; granulation and screening are carried out, with the granulation drum rotating at 14~16 r / min and tilted at an angle of 3°~5°; through the above methods, the problems of high free acid, low proportion of water-soluble phosphorus and insufficient production efficiency in traditional processes are solved, and the product quality and production capacity are synergistically improved.

Description

Technical Field

[0001] This invention relates to the field of fertilizer production technology, and in particular to a segmented maturation preparation process for low-free-acid, high-water-soluble superphosphate. Background Technology

[0002] Superphosphate is a commonly used phosphate fertilizer in agricultural production. Its core quality indicators are the free acid content and the ratio of water-soluble phosphorus to available phosphorus. In traditional superphosphate production processes, a one-time curing method is usually adopted, with a curing cycle of 72 hours, and the raw material ratio depends on experience for control.

[0003] In the production process of superphosphate, the free acid content is generally between 4% and 5%, which can easily burn crop roots during fertilization and cause clumping and packaging corrosion during storage. Water-soluble phosphorus accounts for less than 80% of available phosphorus, resulting in low fertilizer utilization and failing to meet the fertilization needs of high-efficiency agriculture. The long maturation cycle leads to low production efficiency, limited capacity per unit time, and manual parameter adjustment can easily cause fluctuations in product quality, with the granulation pass rate only maintaining around 92%. Existing technologies have addressed this by extending the maturation time to reduce free acid, but this further reduces production capacity; other methods adjust acidity by adding large amounts of neutralizing agents, but this leads to the loss of water-soluble phosphorus, failing to meet the dual requirements of low free acid and high water-soluble phosphorus.

[0004] In summary, it is essential to propose a solution to address the problems of high free acid content, low water-soluble phosphorus content, and insufficient production efficiency in traditional processes, thereby achieving a synergistic improvement in product quality and production capacity. Summary of the Invention

[0005] The purpose of this invention is to provide a segmented ripening preparation process for calcium superphosphate with low free acid and high water-soluble phosphorus, which solves the problems of high free acid, low proportion of water-soluble phosphorus and insufficient production efficiency in traditional processes, and achieves synergistic improvement in product quality and production capacity.

[0006] To achieve the above objectives, the present invention employs a segmented ripening preparation process for low-free-acid, high-water-soluble superphosphate, comprising the following steps:

[0007] Phosphate rock powder is fed into a ball mill for grinding until the particle size is ≤120 mesh, and 93%±0.5% industrial sulfuric acid is prepared. The compound modifier is a mixture of diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh.

[0008] Feed the phosphate rock at a molar ratio of effective P2O5 to sulfuric acid of 1:1.05 to 1:1.07, add 0.3% to 0.5% of the phosphate rock powder as a modifier, react at 65 to 70°C for 40 to 50 minutes, and introduce 0.2 MPa low-pressure steam in the later stage of the reaction.

[0009] The curing process is carried out in stages: first, it is cured in a sealed chamber at 55~60℃ for 24 hours, and then cured in a ventilated chamber at 45~50℃ and a wind speed of 0.8~1.0m / s for 48 hours.

[0010] The granulation process involves granulation and screening, with the granulation drum rotating at 14-16 r / min and tilted at 3-5°. 1.2%-1.5% of 5% water glass binder is sprayed on the drum, and the mixture is then screened in a closed loop using three layers of screens.

[0011] In the step of feeding phosphate rock powder into a ball mill for grinding until the particle size is ≤120 mesh, preparing 93%±0.5% industrial sulfuric acid, and using a compound modifier of diatomaceous earth and bentonite mixed in a 3:2 ratio with a particle size ≤200 mesh:

[0012] The phosphate rock powder, after grinding, has a particle size <120 mesh of ≥95%, and an effective P2O5 content of 28%~30%.

[0013] In the segmented curing process, the process involves first curing in a sealed chamber at 55-60℃ for 24 hours, and then curing in a ventilated chamber at 45-50℃ with an airflow speed of 0.8-1.0 m / s for 48 hours:

[0014] The humidity in the sealed chamber is controlled at 20%~22%, while the humidity in the ventilated chamber is dynamically maintained at 18%~20% depending on the ventilation.

[0015] In the segmented curing process, the process involves first curing in a sealed chamber at 55-60℃ for 24 hours, and then curing in a ventilated chamber at 45-50℃ with an airflow speed of 0.8-1.0 m / s for 48 hours:

[0016] During the maturation process, the free acid content and water-soluble phosphorus ratio of the material are tested every 6 hours.

[0017] In the process of granulation and screening, with the granulation drum rotating at 14-16 r / min and tilted at 3-5°, and 1.2%-1.5% of 5% water glass binder being sprayed on, followed by closed-loop screening through three layers of screens:

[0018] The granulation screening uses screens with apertures of 5mm, 3mm, and 1mm. Particles with a diameter of 3-5mm are the finished product, while the remaining particles are recycled back for granulation in a closed loop.

[0019] This invention discloses a segmented ripening process for preparing low-free-acid, high-water-soluble superphosphate, comprising the following steps: phosphate rock powder is fed into a ball mill for grinding until the particle size is ≤120 mesh, preparing 93%±0.5% industrial sulfuric acid; a compound modifier is prepared by mixing diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh; phosphate rock is fed at a molar ratio of effective P2O5 to sulfuric acid of 1:1.05~1:1.07, and 0.3%~0.5% of the phosphate rock powder mass of the modifier is added; the reaction is carried out at 65~70℃ for 40~50 min; and the reaction is purged in the later stages. Low-pressure steam at 0.2 MPa is introduced; segmented maturation is carried out, first in a closed chamber at 55~60℃ for 24 hours, and then in a ventilated chamber at 45~50℃ and a wind speed of 0.8~1.0 m / s for 48 hours; granulation and screening are performed, with the granulation drum rotating at 14~16 r / min and tilted at an angle of 3°~5°, and 1.2%~1.5% of 5% water glass binder is sprayed on, followed by closed-loop screening through three layers of screens; through the above method, the problems of high free acid, low proportion of water-soluble phosphorus, and insufficient production efficiency in traditional processes are solved, and product quality and production capacity are synergistically improved. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the step-by-step preparation process of low-free-acid, high-water-soluble superphosphate calcium phosphate according to the present invention. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0025] Please see Figure 1 This invention provides a segmented ripening preparation process for low-free-acid, high-water-soluble superphosphate, comprising the following steps:

[0026] S100: Feed phosphate rock powder into a ball mill for grinding until the particle size is ≤120 mesh, and prepare 93%±0.5% industrial sulfuric acid. The compound modifier is a mixture of diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh.

[0027] S200: Feed the phosphate rock at a molar ratio of effective P2O5 to sulfuric acid of 1:1.05 to 1:1.07, add 0.3% to 0.5% of the phosphate rock powder as a modifier, react at 65 to 70°C for 40 to 50 minutes, and introduce 0.2 MPa low-pressure steam in the later stage of the reaction.

[0028] S300: Perform segmented curing, first curing in a closed chamber at 55~60℃ for 24 hours, and then curing in a ventilated chamber at 45~50℃ and 0.8~1.0m / s wind speed for 48 hours;

[0029] S400: Granulation and screening are carried out by granulation drum rotation speed of 14~16r / min and tilt angle of 3°~5°. 1.2%~1.5% of 5% water glass binder is sprayed and added, and then screened in a closed loop by three layers of screens.

[0030] Furthermore, in the step of feeding phosphate rock powder into a ball mill for grinding to a particle size ≤120 mesh, preparing 93%±0.5% industrial sulfuric acid, and using a compound modifier consisting of diatomaceous earth and bentonite mixed in a 3:2 ratio with a particle size ≤200 mesh:

[0031] The phosphate rock powder, after grinding, has a particle size <120 mesh of ≥95%, and an effective P2O5 content of 28%~30%.

[0032] Furthermore, in the step of staged maturation, first maturing in a sealed chamber at 55~60℃ for 24 hours, and then maturing in a ventilated chamber at 45~50℃ and an air velocity of 0.8~1.0m / s for 48 hours:

[0033] The humidity in the sealed chamber is controlled at 20%~22%, while the humidity in the ventilated chamber is dynamically maintained at 18%~20% depending on the ventilation.

[0034] Furthermore, in the step of staged maturation, first maturing in a sealed chamber at 55~60℃ for 24 hours, and then maturing in a ventilated chamber at 45~50℃ and an air velocity of 0.8~1.0m / s for 48 hours:

[0035] During the maturation process, the free acid content and water-soluble phosphorus ratio of the material are tested every 6 hours.

[0036] Furthermore, in the steps of granulation screening, with the granulation drum rotating at 14~16 r / min and tilted at 3°~5°, and 1.2%~1.5% of 5% water glass binder being sprayed on, followed by closed-loop screening through three layers of screens:

[0037] The granulation screening uses screens with apertures of 5mm, 3mm, and 1mm. Particles with a diameter of 3-5mm are the finished product, while the remaining particles are recycled back for granulation in a closed loop.

[0038] In this embodiment, phosphate rock with an effective P2O5 content of 29% is first selected. The phosphate rock powder is fed into a ball mill for grinding until the particle size is ≤120 mesh, preparing industrial sulfuric acid with a content of 93%±0.5%. The compound modifier is a mixture of diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh. The proportion of particles with a particle size <120 mesh after grinding is ≥95%, and the effective P2O5 content is 28%~30%. Then, the phosphate rock is fed with sulfuric acid at a molar ratio of effective P2O5 to sulfuric acid of 1:1.05~1:1.07, and 0.3%~0.5% of the phosphate rock powder mass of the modifier is added. The reaction is carried out at 65~70℃ for 40~50 min, and low-pressure steam of 0.2MPa is introduced in the later stage of the reaction. Then, staged ripening is carried out. First, it is ripened in a closed chamber at 55~60℃ for 24 h, and then at 45~ The material was cured in a ventilated chamber at 50℃ and a wind speed of 0.8~1.0m / s for 48 hours. During the curing process, the free acid content and water-soluble phosphorus ratio of the material were tested every 6 hours. The humidity in the sealed chamber was controlled at 20%~22%, while the humidity in the ventilated chamber was dynamically maintained at 18%~20% with ventilation. Finally, the material was granulated and screened. The granulation drum rotated at 14~16 r / min and tilted at 3°~5°. 1.2%~1.5% of 5% water glass binder was sprayed on and the material was screened in a closed loop through a three-layer screen. The screen apertures of the granulation screen were 5mm, 3mm, and 1mm, respectively. Particles with a diameter of 3~5mm were the finished product, and the remaining particles were recycled for granulation in a closed loop. This method solved the problems of high free acid content, low water-soluble phosphorus ratio, and insufficient production efficiency in traditional processes, and achieved a synergistic improvement in product quality and production capacity.

[0039] Example 1:

[0040] Phosphate ore with an effective P2O5 content of 29% was selected and ground to 120 mesh, of which 96% of the particles were <120 mesh; industrial sulfuric acid with a concentration of 93.2% was prepared; a compound modifier (diatomaceous earth: bentonite = 3:2) was prepared with a particle size of 200 mesh;

[0041] The feed was prepared by adding P2O5 to sulfuric acid at a molar ratio of 1:1.06, adding 0.4% of a modifying agent, and reacting at 68℃ and 90r / min for 45min. In the later stage, low-pressure steam of 0.2MPa was introduced to maintain the humidity of the system at 16%.

[0042] The material underwent segmented maturation. First, it was maturated in a sealed chamber at 58℃ and 21% humidity for 24 hours. Then, it was transferred to a ventilated chamber and maturated for 48 hours at a wind speed of 0.9 m / s and a temperature of 48℃. After maturation, the free acid content of the material was 3.2%, and the water-soluble phosphorus content was 86%.

[0043] The granulator was operated at 15 r / min and tilted at 4°. 1.3% of 5% water glass binder was sprayed on and the product was screened through three layers of sieves. The finished product had a particle size of 3~5 mm, accounting for 91% of the total, and the granulation qualification rate was 97%.

[0044] In this embodiment, phosphate rock with an effective P2O5 content of 29% is first selected and ground to 120 mesh, with 96% of the particles having a particle size <120 mesh. Industrial sulfuric acid with a concentration of 93.2% is prepared. A modifying agent (diatomaceous earth:bentonite = 3:2) with a particle size of 200 mesh is then added. The mixture is then fed at a P2O5 to sulfuric acid molar ratio of 1:1.06, with 0.4% of the modifying agent added. The reaction is carried out at 68℃ and 90 r / min for 45 min. Low-pressure steam of 0.2 MPa is introduced later to maintain the system. The humidity was 16%. Next, the material underwent segmented maturation. First, it was maturated in a sealed chamber at 58℃ and 21% humidity for 24 hours. Then, it was transferred to a ventilated chamber and maturated at 48℃ with a wind speed of 0.9 m / s for 48 hours. After maturation, the free acid content of the material was 3.2%, and the water-soluble phosphorus content was 86%. Finally, the material was granulated and screened. The granulator was set at 15 r / min and tilted at 4°. 1.3% of 5% water glass binder was sprayed on. After screening through three layers of sieves, 91% of the finished product had a particle size of 3~5 mm, and the granulation qualification rate was 97%.

[0045] Example 2:

[0046] Phosphate ore with an effective P2O5 content of 28% was selected, ground to 120 mesh, with 95% of the particles having a particle size <120 mesh, and industrial sulfuric acid with a concentration of 92.8% was prepared. The amount of compound modifier added was 0.3%.

[0047] The P2O5 to sulfuric acid molar ratio was 1:1.05, and the reaction was carried out at 65℃ and 80r / min for 40min, with a ventilation and ripening wind speed of 0.8m / s.

[0048] The test results showed that the finished product contained 3.4% free acid, 85% water-soluble phosphorus, and had a granulation qualification rate of 96.5%.

[0049] In this embodiment, phosphate rock with an effective P2O5 content of 28% is first selected and ground to 120 mesh, with 95% of the particles having a particle size <120 mesh. Industrial sulfuric acid with a concentration of 92.8% is prepared, and a compound modifier is added at a ratio of 0.3%. Then, the P2O5 to sulfuric acid is fed at a molar ratio of 1:1.05, and the reaction is carried out at 65°C and 80 r / min for 40 min, with a ventilation and maturation wind speed of 0.8 m / s. The results show that the finished product has a free acid content of 3.4%, a water-soluble phosphorus content of 85%, and a granulation qualification rate of 96.5%.

[0050] Beneficial effects: By segmented ripening and the addition of modifying agents, the free acid content of superphosphate can be stably controlled below 3.5%, and the proportion of water-soluble phosphorus to effective phosphorus can be increased to more than 85%, achieving industry-leading quality.

[0051] The total time for staged maturation remains 72 hours, but through staged temperature and humidity control, highly efficient conversion of monocalcium phosphate is achieved, increasing the unit capacity per unit time by 10% compared to traditional processes.

[0052] The closed-loop granulation system can increase the granulation qualification rate from 92% to over 96%, the product particle size uniformity (3~5mm percentage) ≥90%, and the storage agglomeration rate to below 2%.

[0053] The process requires no new large-scale equipment, can be directly adapted to existing production lines, has low modification costs, and is practical for large-scale mass production.

[0054] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0055] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A segmented ripening preparation process for low-free-acid, high-water-soluble superphosphate, characterized in that, Includes the following steps: Phosphate rock powder is fed into a ball mill for grinding until the particle size is ≤120 mesh, and 93%±0.5% industrial sulfuric acid is prepared. The compound modifier is a mixture of diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh. Feed the phosphate rock at a molar ratio of effective P2O5 to sulfuric acid of 1:1.05 to 1:1.07, add 0.3% to 0.5% of the phosphate rock powder as a modifier, react at 65 to 70°C for 40 to 50 minutes, and introduce 0.2 MPa low-pressure steam in the later stage of the reaction. The curing process is carried out in stages: first, it is cured in a sealed chamber at 55~60℃ for 24 hours, and then cured in a ventilated chamber at 45~50℃ and a wind speed of 0.8~1.0m / s for 48 hours. The granulation and screening process involves a granulation drum with a rotation speed of 14-16 r / min and an inclination angle of 3-5°. 1.2%-1.5% of 5% water glass binder is sprayed in and the mixture is then screened in a closed loop using three layers of screens.

2. The segmented ripening preparation process of low free acid and high water-soluble superphosphate as described in claim 1, characterized in that, In the process of feeding phosphate rock powder into a ball mill for grinding until the particle size is ≤120 mesh, and preparing 93%±0.5% industrial sulfuric acid, the compounding modifier is a mixture of diatomaceous earth and bentonite in a 3:2 ratio with a particle size ≤200 mesh: The phosphate rock powder, after grinding, has a particle size <120 mesh of ≥95%, and an effective P2O5 content of 28%~30%.

3. The segmented ripening preparation process of low free acid and high water-soluble superphosphate as described in claim 1, characterized in that, In the process of staged maturation, the process involves first maturing in a sealed chamber at 55-60℃ for 24 hours, and then maturing in a ventilated chamber at 45-50℃ with an airflow speed of 0.8-1.0 m / s for 48 hours: The humidity in the sealed chamber is controlled at 20%~22%, while the humidity in the ventilated chamber is dynamically maintained at 18%~20% depending on the ventilation.

4. The segmented ripening preparation process of low free acid and high water-soluble superphosphate as described in claim 3, characterized in that, In the process of staged maturation, the process involves first maturing in a sealed chamber at 55-60℃ for 24 hours, and then maturing in a ventilated chamber at 45-50℃ with an airflow speed of 0.8-1.0 m / s for 48 hours: During the maturation process, the free acid content and water-soluble phosphorus ratio of the material are tested every 6 hours.

5. The segmented ripening preparation process of low free acid and high water-soluble superphosphate as described in claim 1, characterized in that, In the granulation screening process, the granulation drum rotates at a speed of 14~16 r / min, the inclination angle is 3°~5°, 1.2%~1.5% of 5% water glass binder is sprayed in, and the granulation is carried out through a three-layer closed-loop sieve: The granulation screening screens have apertures of 5mm, 3mm, and 1mm. Particles with a diameter of 3-5mm are the finished product, while the remaining particles are recycled back for granulation in a closed loop.

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