Method for preparing compound fertilizer by using iron ore tailing mud

Abstract

The invention relates to the technical field of compound fertilizer preparation, and discloses a method for preparing a compound fertilizer by using iron ore tailing mud, which comprises the following steps: carrying out detailed element detection on the iron ore tailing mud by adopting a chemical component analysis method to obtain iron ore tailing mud component data; a specific fertilizer formula is obtained by simulating the effects of different formulas through computer-aided design on iron ore tail mud component data; a specific fertilizer formula is pretreated through screening, washing and drying methods, impurities are removed, the moisture content is adjusted, and processing raw materials are obtained. According to the method for preparing the compound fertilizer by using the iron ore tailing mud, detailed element detection is performed on the iron ore tailing mud through a chemical component analysis method to obtain component data of the iron ore tailing mud, so that high precision of component analysis is ensured, a matching error caused by unknown components is reduced, potential harmful substances can be identified in advance, and the compound fertilizer is prepared. Therefore, corresponding treatment measures are taken, and the risk of environmental pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of compound fertilizer preparation, and specifically to a method for preparing compound fertilizer using iron ore tailings. Background Art

[0002] Compound fertilizer preparation technology refers to mixing multiple nutrient elements (such as nitrogen, phosphorus, potassium, and trace elements) in a certain proportion and processing them into granular or other forms of fertilizers through physical or chemical methods to meet the different growth requirements of crops.

[0003] However, it is difficult to precisely control the proportion of each element in iron ore tailings by traditional methods, resulting in uneven fertilizer composition and affecting the absorption effect of crops. Secondly, the existing technology has limited effect in removing harmful substances, which may cause soil and crop pollution. In addition, there is a lack of an effective automated monitoring system in traditional production processes, the parameter control is not precise enough, and the production is prone to instability, affecting the consistency of product quality. Moreover, the traditional method fails to fully consider the balance between environmental impact and economic cost, making the production process neither environmentally friendly nor economically efficient. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A method for preparing compound fertilizer using iron ore tailings, which conducts detailed element detection on iron ore tailings by using a chemical composition analysis method to obtain iron ore tailings composition data; By using computer-aided design to simulate the effects of different formulas on the iron ore tailings composition data, a specific fertilizer formula is obtained; The specific fertilizer formula is pretreated by screening, washing, and drying methods to remove impurities and adjust the moisture content to obtain processed raw materials; The processed raw materials are mixed with nutrient elements and modifiers in a certain proportion and made into granular compound fertilizers by a wet granulation machine to obtain compound fertilizer granules; The temperature, humidity, and pressure parameters are monitored through an automated control platform and adjusted online; The compound fertilizer granules are screened, and harmful substances are immobilized by physical adsorption methods to obtain compound fertilizers.

[0006] As a further solution of the present invention: By using a chemical composition analysis method to conduct detailed elemental detection on iron ore tailings sludge, iron ore tailings sludge composition data is obtained. The specific steps are as follows: Collect a certain amount of iron ore tailings sludge samples, and crush and homogenize them; Calibrate the X-ray fluorescence spectrometer XRF using a standard reference material with known composition; Place the prepared samples in the XRF instrument, and excite the characteristic X-rays emitted by the atoms in the samples under specific conditions; Collect and record the X-ray intensity corresponding to each element , and calculate the mass fraction of each element according to the data measured by XRF , and the expression is: ; Among them, is the X-ray intensity of the th element, is the empirical coefficient of the th element, is the conversion constant, which converts the intensity into the mass fraction.

[0007] As a further solution of the present invention: By using computer-aided design to simulate the effects of different formulations on the iron ore tailings sludge composition data, a specific fertilizer formulation is obtained. The specific steps are as follows: Input the iron ore tailings sludge composition data obtained through XRF analysis, as well as the target crop and soil demand information, into the computer-aided design system; Based on linear programming, construct a mathematical model, set the objective function, and comprehensively consider the weighted sum of crop yield, environmental impact, and economic cost. The expression is: ; Among them, represents the importance of crop yield, is the predicted crop yield value, represents the importance of environmental impact, is the evaluated environmental impact index, represents the importance of economic cost, is the estimated cost value; Introduce constraint conditions into the model. The expression is:

[0008]

[0009] ; Among them, here, is the The proportionality factor of nutrient elements is the actually added amount; is the proportionality factor of the th harmful substance, is the actually existing amount; is the proportionality factor of the th cost item, is the actually incurred cost; Run the simulation program to generate a series of possible fertilizer formula combinations according to the soil characteristics of different regions and the requirements of target crops; After multiple rounds of simulation and evaluation, an optimal formula is selected as the specific formula in this technical solution. The specific parameters are nitrogen content 10%wt, phosphorus content 8%wt, potassium content 6%wt, trace elements 0.2%wt, and biochar 5%wt.

[0010] As a further scheme of the present invention: the specific fertilizer formula is pretreated by screening, washing and drying methods to remove impurities and adjust the moisture content to obtain a processed raw material. The specific steps are as follows: Use a vibrating screen to classify the iron ore tailings samples into different grades according to particle size and remove large particle impurities; Put the screened iron ore tailings into a washing tank, add an appropriate amount of clean water and stir for cleaning to remove the attached soil and other soluble impurities on the surface. A centrifuge is used to separate the solid and liquid phases during the washing process; Preliminarily dehydrate the washed iron ore tailings through a filter press, and then send them to a rotary dryer for low-temperature drying under controlled temperature to make the moisture content of the final product stable at 5%wt; During the drying process, the moisture content HH of the iron ore tailings is monitored in real time to ensure that it meets the set standard. A moisture adjustment model is introduced to optimize the drying effect, and the expression is as follows:

[0011] Among them, is the final moisture content, is the initial moisture content, is the drying rate constant, is the drying time, is the residual moisture function varying with time; Obtain the processed raw material, specifically iron 20%wt, moisture content 5%wt, silicon 15%wt, aluminum 10%wt, calcium 5%wt, magnesium 3%wt, and trace elements 0.2%wt.

[0012] As a further scheme of the present invention: the processed raw material is mixed with nutrient elements and modifiers in proportion and made into granular compound fertilizers by a wet granulation machine to obtain compound fertilizer granules. The specific steps are as follows: Add the processing raw materials to the mixer in proportion, and the mixing time is 15 to 30 minutes; Feed the mixed materials into the wet granulator, and add 10% - 15% of water during the process; Control the temperature and humidity parameters in the granulator, the temperature range is 40°C to 60°C, and the relative humidity is maintained at 70% - 80%; The initially formed granules enter the drying chamber through the conveyor belt and are slowly dried under low-temperature conditions to reduce the moisture content of the granules to about 5%wt; The dried granules are cooled to bring their temperature close to the ambient temperature; The dried and cooled granules are screened through a vibrating screen to remove oversized granules, controlled between 2mm and 5mm, and compound fertilizer granules are obtained.

[0013] As a further solution of the present invention: Monitor the temperature, humidity and pressure parameters through an automated control platform and adjust them online. The specific steps are as follows: Install and debug the automated control system. The system integrates multiple sensors and actuators to monitor and control various parameters in the production environment; Set the target value range of each parameter during system initialization, temperature 40°C to 60°C, humidity 70% to 80%, pressure 0.5 to 1.0MPa; During the entire production process, the sensors continuously collect data on temperature, humidity and pressure and transmit the information to the central control system. The data collection frequency is set to once per second; The central control system has built-in intelligent algorithms to perform real-time analysis on the collected data and identify any abnormal conditions deviating from the preset range; When it is detected that the parameter exceeds the set safety threshold, the system will immediately issue an alarm to notify the operator and automatically initiate the corresponding corrective measures; According to the real-time data analysis results, the system automatically adjusts the working state of the actuator through the PID controller to keep the parameter within the target range, and introduces an optimization control model to dynamically adjust the control strategy.

[0014] As a further solution of the present invention: Screen the compound fertilizer granules and use the physical adsorption method to immobilize harmful substances to obtain compound fertilizers. The specific steps are as follows: Preliminarily screen the compound fertilizer granules made by the wet granulator through a vibrating screen to obtain granules with a particle size between 2mm and 5mm; Send the screened compound fertilizer granule samples to the laboratory and use the analytical instrument ICP-MS to detect harmful substances; For the particles detected to contain trace amounts of harmful substances, physical adsorption materials are used for immobilization treatment; Mix the physical adsorption material with the compound fertilizer particles in proportion, adding 0.5%wt to 1%wt of the adsorption material per ton of compound fertilizer; After mixing, allow the adsorption material to come into full contact with the harmful substances, and utilize its large specific surface area and pore structure characteristics to firmly adsorb the harmful substances on its surface or in its internal micropores. The adsorption treatment time is 30 minutes to 1 hour; After completing the physical adsorption treatment, screen the compound fertilizer particles again through a vibrating screen to remove the fine powder or debris generated by the adsorption treatment, and obtain the final compound fertilizer.

[0015] As a further solution of the present invention: The optimization control model is introduced to dynamically adjust the control strategy, and the expression is: ; Among them, is the control output at time , is the proportional gain, is the target temperature, is the actual temperature, is the integral gain, is the derivative gain, is the humidity sensitivity coefficient, is the pressure sensitivity coefficient, is the humidity, is the pressure.

[0016] As a further solution of the present invention: When it is detected that the parameter exceeds the set safety threshold, the system will immediately issue an alarm to notify the operator and automatically start the corresponding corrective measures. The specific steps are: At the same time as triggering the alarm, the system will automatically start the preset corrective measures; When the temperature is too high, automatically increase the power of the cooling device and reduce the working intensity of the heater; When the humidity is insufficient, automatically increase the water supply of the spray system and adjust the working frequency or spraying angle of the nozzle; When the pressure is too low, automatically increase the working intensity of the compressor or open the booster valve to quickly increase the pressure in the system.

[0017] As a further solution of the present invention: During the physical adsorption treatment process, an optimization adjustment function is introduced, and the expression is: ; Among them, is the adsorption treatment time, is the initial concentration of the harmful substance, is the adsorption rate constant related to temperature and humidity, is the specific surface area of the adsorbent material per unit mass, is the concentration sensitivity coefficient, is the temperature sensitivity coefficient, is the humidity sensitivity coefficient.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: Through chemical composition analysis methods, detailed element detection is carried out on iron ore tailings to obtain the composition data of iron ore tailings, ensuring high-precision composition analysis, reducing the formulation error caused by unknown composition, helping to identify potential harmful substances in advance so as to take corresponding treatment measures to reduce the environmental pollution risk. By using computer-aided design to simulate the effects of different formulations on the composition data of iron ore tailings, a specific fertilizer formulation is obtained. Through computer simulation, the best fertilizer formulation is found, improving the effectiveness and applicability of the fertilizer. By screening, washing and drying methods, the specific fertilizer formulation is pretreated to remove impurities and adjust the moisture content. The impurities are removed, making the compound fertilizer more pure and avoiding the negative impact of impurities on crop growth. The moisture content is adjusted to an appropriate level to prevent caking that may occur during storage and extend the shelf life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flow chart of a method for preparing compound fertilizer using iron ore tailings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To make the above objects, features, and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings of the specification.

[0021] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0022] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that can be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that mutually excludes other embodiments.

[0023] Embodiment 1 Please refer to Figure 1 , which is the first embodiment of the present invention. This embodiment provides a method for preparing compound fertilizer using iron ore tailings, including: S1. By using chemical composition analysis methods to conduct detailed elemental detection on iron ore tailings, the composition data of the iron ore tailings is obtained; Furthermore, a certain amount of iron ore tailings samples are collected and subjected to crushing and homogenization treatment; Calibrate the X-ray fluorescence spectrometer XRF using standard reference materials with known compositions; Place the prepared samples in the XRF instrument and excite the characteristic X-rays emitted by the atoms in the samples under specific conditions; Collect and record the X-ray intensity corresponding to each element , and calculate the mass fraction of each element based on the data measured by XRF , and the expression is: ; Among them, is the X-ray intensity of the st element, is the empirical coefficient of the th element, is the conversion constant to convert the intensity into mass fraction; It should be noted that through the above steps, the accurate quantitative analysis of each element in the iron ore tailings is achieved. The process not only provides a scientific basis for the subsequent formulation design, but also ensures the reliability and accuracy of the data, thus guaranteeing the quality consistency of the final product. In addition, calibrating the XRF instrument using standard reference materials can effectively eliminate systematic errors and further improve the credibility of the analysis results.

[0024] S2. By using computer-aided design to simulate the effects of different formulations on the composition data of iron ore tailings, a specific fertilizer formulation is obtained; Furthermore, the composition data of iron ore tailings obtained through XRF analysis, as well as the information on the target crop and soil requirements, are input into the computer-aided design system; Based on linear programming, construct a mathematical model, set the objective function, and comprehensively consider the weighted sum of crop yield, environmental impact, and economic cost. The expression is: ; Among them, represents the importance of crop yield, is the predicted crop yield value, represents the importance of environmental impact, is the evaluated environmental impact index, represents the importance of economic cost, is the estimated cost value; Constraints are introduced into the model, and the expression is:

[0025]

[0026] ; where, herein, is the proportionality factor of the th nutrient element, is the actually added amount; is the proportionality factor of the th harmful substance, is the actually existing amount; is the proportionality factor of the th cost item, is the actually incurred cost; Run the simulation program to generate a series of possible fertilizer formula combinations according to the soil characteristics of different regions and the requirements of target crops; After multiple rounds of simulation and evaluation, an optimal formula is selected as the specific formula in this technical solution. The specific parameters are nitrogen content 10%wt, phosphorus content 8%wt, potassium content 6%wt, trace elements 0.2%wt, and biochar 5%wt; It should be noted that linear programming and mathematical models are used to optimize the fertilizer formula, considering three key factors: crop yield, environmental impact, and economic cost. The method not only improves the scientificity and rationality of formula design but also minimizes the environmental impact and reduces production costs while the compound fertilizer meets the crop requirements. Multiple rounds of simulation and evaluation ensure the efficiency and stability of the selected formula in practical applications.

[0027] S3. Pretreat the specific fertilizer formula by screening, washing, and drying methods to remove impurities and adjust the moisture content to obtain processing raw materials; Furthermore, use a vibrating screen to classify iron ore tailings samples into different grades according to particle size and remove large particle impurities; Put the screened iron ore tailings into a washing tank, add an appropriate amount of clean water and stir for cleaning to remove the attached soil and other soluble impurities on the surface. A centrifuge is used to separate the solid-liquid two phases during the washing process; Preliminarily dehydrate the washed iron ore tailings through a filter press, and then send them to a rotary dryer for low-temperature drying under controlled temperature to make the moisture content of the final product stable at 5%wt; During the drying process, the moisture content HH of the iron ore tailings is monitored in real time to ensure that it meets the set standards. Introduce a moisture adjustment model to optimize the drying effect. The expression is as follows:

[0028] where, is the final moisture content, is the initial moisture content, is the drying rate constant, is the drying time, is the residual moisture function varying with time; Obtain the processed raw materials, specifically 20%wt iron, 5%wt moisture content, 15%wt silicon, 10%wt aluminum, 5%wt calcium, 3%wt magnesium, and 0.2%wt trace elements; It should be noted that operations such as vibration screening, cleaning, and low-temperature drying in the steps ensure the purity and uniformity of the processed raw materials. In particular, introducing a moisture adjustment model to optimize the drying effect helps maintain the optimal moisture content of the raw materials, avoiding the adverse effects of over-drying or over-wetting. This not only improves the quality of the raw materials but also provides a good foundation for subsequent mixing and granulation, thereby ensuring the overall performance of the compound fertilizer.

[0029] S4. Mix the processed raw materials with nutrient elements and modifiers in proportion and use a wet granulator to make granular compound fertilizers to obtain compound fertilizer granules; Furthermore, add the processed raw materials to the mixer in proportion, and the mixing time is 15 to 30 minutes; Feed the mixed materials into the wet granulator and add 10% - 15% water during the process; Control the temperature and humidity parameters in the granulator, the temperature range is 40°C to 60°C, and the relative humidity is maintained at 70% - 80%; The preliminarily formed granules enter the drying chamber through a conveyor belt and are slowly dried under low-temperature conditions to reduce the moisture content of the granules to about 5%wt; Cool the dried granules to make their temperature drop to near the ambient temperature; Screen the dried and cooled granules through a vibrating screen to remove oversized granules, control them between 2mm and 5mm, and obtain compound fertilizer granules; It should be noted that the steps strictly control the mixing time and material humidity to ensure the uniform distribution among the components. The granular compound fertilizers made by the wet granulator have good physical properties, such as moderate hardness and good fluidity. At the same time, through the precise regulation of temperature and humidity parameters, the occurrence of granule caking or breaking is avoided, thereby ensuring the stability and application effect of the product. The finally obtained compound fertilizer granules are of uniform size and meet the requirements of agricultural fertilization.

[0030] S5. Monitor the temperature, humidity, and pressure parameters through an automated control platform and adjust them online; Furthermore, install and debug the automated control system. The system integrates multiple sensors and actuators to monitor and control various parameters in the production environment; When the system is initialized, the target value ranges of each parameter are set, with the temperature ranging from 40°C to 60°C, the humidity from 70% to 80%, and the pressure from 0.5 to 1.0 MPa; During the entire production process, the sensors continuously collect data on temperature, humidity, and pressure and transmit the information to the central control system. The data collection frequency is set to once per second; The central control system has an intelligent algorithm built-in to perform real-time analysis on the collected data and identify any abnormal situations that deviate from the preset range; When it is detected that a parameter exceeds the set safety threshold, the system will immediately issue an alarm to notify the operator and automatically initiate the corresponding corrective measures; Simultaneously with triggering the alarm, the system will automatically initiate the preset corrective measures; When the temperature is too high, the power of the cooling device is automatically increased and the working intensity of the heater is reduced; When the humidity is insufficient, the water supply of the spray system is automatically increased and the working frequency or spraying angle of the nozzles is adjusted; When the pressure is too low, the working intensity of the compressor is automatically increased, or the pressure boosting valve is opened to rapidly increase the pressure within the system; Based on the results of real-time data analysis, the system automatically adjusts the working state of the actuator through a PID controller to keep the parameters within the target range, and an optimization control model is introduced to dynamically adjust the control strategy. The expression is: ; where is the control output at time , is the proportional gain, is the target temperature, is the actual temperature, is the integral gain, is the derivative gain, is the humidity sensitivity coefficient, is the pressure sensitivity coefficient, is the humidity, is the pressure; It should be noted that through the integration of multiple sensors and actuators, the automated control system realizes the real-time monitoring and automatic adjustment of key parameters in the production process. In particular, the introduction of the PID controller and the optimization control model can dynamically respond to environmental changes, keep the parameters within the optimal range. The intelligent management method not only improves production efficiency but also enhances the stability and reliability of the system, ensures the consistency of the quality of each batch of products, and at the same time reduces the uncertainties and risks brought by manual intervention.

[0031] S6. By screening the compound fertilizer granules and using the physical adsorption method to immobilize harmful substances, compound fertilizers are obtained; Furthermore, the compound fertilizer granules produced by the wet granulation machine are preliminarily screened through a vibrating screen to obtain granules with a particle size between 2 mm and 5 mm; The screened compound fertilizer granule samples are sent to the laboratory, and a harmful substance detection is carried out using the analytical instrument ICP-MS; For the granules detected to contain trace harmful substances, physical adsorption materials are used for immobilization treatment; The physical adsorption materials and the compound fertilizer granules are mixed in proportion, and 0.5%wt to 1%wt of the adsorption materials are added per ton of compound fertilizer; After mixing, the adsorption materials are allowed to fully contact with the harmful substances. Utilizing their large specific surface area and pore structure characteristics, the harmful substances are firmly adsorbed on their surface or in the internal micropores, and the adsorption treatment time is 30 minutes to 1 hour; After the physical adsorption treatment is completed, the compound fertilizer granules are screened again through a vibrating screen to remove the fine powder or debris generated due to the adsorption treatment, and the final compound fertilizer is obtained; During the physical adsorption treatment process, an optimization adjustment function is introduced, and the expression is: ; Among them, is the adsorption treatment time, is the initial concentration of the harmful substances, is the adsorption rate constant related to temperature and humidity, is the specific surface area of the unit mass of the adsorption material, is the concentration sensitivity coefficient, is the temperature sensitivity coefficient, is the humidity sensitivity coefficient; It should be noted that through the preliminary screening by the vibrating screen and the harmful substance detection by ICP-MS, the safety and environmental protection of the compound fertilizer granules are ensured. The application of the physical adsorption materials, combined with the optimization adjustment function, can effectively immobilize trace harmful substances without affecting the nutrient supply of the fertilizer, ensuring that they will not pollute the soil and crops. The final compound fertilizer obtained after removing the fine powder or debris through secondary screening not only meets the national and industry standards but also has higher market competitiveness and user acceptance.

[0032] In summary, through chemical composition analysis methods, detailed elemental detection of iron ore tailings was carried out to obtain the composition data of iron ore tailings, ensuring high-precision composition analysis, reducing the formulation error caused by unknown composition, helping to identify potential harmful substances in advance so as to take corresponding treatment measures, reducing the environmental pollution risk. By using computer-aided design to simulate the effects of different formulations on the basis of the composition data of iron ore tailings, a specific fertilizer formulation was obtained. Through computer simulation, the optimal fertilizer formulation was found, improving the effectiveness and applicability of the fertilizer. Through screening, washing and drying methods, the specific fertilizer formulation was pretreated to remove impurities and adjust the moisture content. The impurities were removed, making the compound fertilizer purer and avoiding the negative impact of impurities on crop growth. The moisture content was adjusted to an appropriate level, preventing the caking phenomenon that might occur during storage and extending the shelf life of the product.

[0033] Example 2 Please refer to Table 1, which shows the simulation data of the experimental study on preparing compound fertilizer using iron ore tailings for the second embodiment of the present invention.

[0034] To verify the effectiveness and superiority of the method for preparing compound fertilizer using iron ore tailings, a comprehensive experimental study was carried out. In the experiment, two different treatment methods were selected: one was the traditional method, and the other was the method optimized according to the content of the present invention. Each treatment method used the same initial raw material - iron ore tailings, and crop growth experiments were carried out under the same conditions.

[0035] First, 10 kg of iron ore tailings samples were collected and crushed and homogenized to ensure the consistency of the samples. The X-ray fluorescence spectrometer (XRF) was calibrated using a standard reference material with known composition. Subsequently, the prepared samples were placed in the XRF instrument, and the atoms in the samples were excited to emit characteristic X-rays under specific conditions. By recording the X-ray intensity corresponding to each element, the mass fraction of each element was calculated, providing accurate data support for subsequent formulation design.

[0036] Next, based on the composition data of iron ore tailings obtained from XRF analysis and the information on the target crops and soil requirements, they were input into a computer-aided design system to construct a mathematical model. Considering three key factors: crop yield, environmental impact and economic cost, after multiple rounds of simulation and evaluation, an optimal formulation was selected. The specific parameters were nitrogen content 10%wt, phosphorus content 8%wt, potassium content 6%wt, trace elements 0.2%wt, and biochar 5%wt. The formulation not only met the needs of crop growth, but also minimized the environmental impact and reduced the production cost.

[0037] Then, a pretreatment step was carried out for the selected formulation. The iron ore tailings samples were classified into different grades according to particle size using a vibrating screen to remove large particle impurities. The screened iron ore tailings were put into a washing tank, added with an appropriate amount of clean water and stirred for cleaning to remove the attached soil and other soluble impurities on the surface. Then, a centrifuge was used to separate the solid-liquid two phases. Next, the washed iron ore tailings were preliminarily dewatered by a filter press and sent to a rotary dryer for low-temperature drying under controlled temperature to make the moisture content of the final product stable at 5%wt. During the drying process, the moisture content HH of the iron ore tailings was monitored in real time to ensure that it met the set standards, and a moisture adjustment model was introduced to optimize the drying effect.

[0038] The specific components of the processing raw materials include 20%wt of iron, 5%wt of moisture content, 15%wt of silicon, 10%wt of aluminum, 5%wt of calcium, 3%wt of magnesium, and 0.2%wt of trace elements. The raw materials were mixed with nutrient elements and modifiers in proportion and made into granular compound fertilizers using a wet granulator to obtain compound fertilizer granules. The mixing time was 20 minutes. The mixed materials were sent into the wet granulator, with 12% of water added. The temperature and humidity parameters in the granulator were controlled at 50°C and 75% respectively. The initially formed granules entered the drying chamber through a conveyor belt and were slowly dried under low-temperature conditions to reduce the granule moisture content to about 5%wt. The dried granules were cooled to make their temperature close to the ambient temperature and screened through a vibrating screen to remove oversized granules, controlled between 2mm and 5mm, and finally compound fertilizer granules were obtained.

[0039] During the whole production process, an automated control system was installed and debugged, integrating multiple sensors and actuators to monitor and control various parameters in the production environment. When the system was initialized, the target value ranges of each parameter were set, with the temperature from 40°C to 60°C, the humidity from 70% to 80%, and the pressure from 0.5 to 1.0MPa. The sensors continuously collected data on temperature, humidity, and pressure and transmitted the information to the central control system. The data acquisition frequency was set to once per second. The central control system was built-in with intelligent algorithms to perform real-time analysis on the collected data, identify any abnormal situations deviating from the preset range. When it detected that the parameter exceeded the set safety threshold, the system would immediately issue an alarm to notify the operator and automatically start the corresponding corrective measures.

[0040] Finally, the compound fertilizer granules were screened, and the harmful substances were immobilized by physical adsorption. Through preliminary screening with a vibrating screen, compound fertilizer granules with a particle size between 2 mm and 5 mm were obtained. The screened compound fertilizer granule samples were sent to the laboratory, and a harmful substance detection was carried out using the analytical instrument ICP-MS. For the granules detected to contain trace amounts of harmful substances, a physical adsorption material was used for immobilization treatment. 0.8%wt of the adsorption material was added per ton of compound fertilizer. After mixing, the adsorption material was allowed to fully contact the harmful substances. Utilizing its large specific surface area and pore structure characteristics, the harmful substances were firmly adsorbed on its surface or in its internal micropores. The adsorption treatment time was 45 minutes. After completing the physical adsorption treatment, the compound fertilizer granules were screened again through a vibrating screen to remove the fine powder or debris generated due to the adsorption treatment, and finally a safe and efficient compound fertilizer was obtained.

[0041] The data table is as follows: Table 1 Comparison experiment results of compound fertilizer prepared from iron ore tailings As can be seen from the above table, the present invention shows significant advantages in many aspects. First of all, in terms of the composition uniformity, the present invention reaches 95%, compared with 85% of the prior art, an increase of 11.76%. This indicates that through precise chemical composition analysis and computer-aided design, the proportion of fertilizer components can be better controlled, thereby improving the consistency of product quality. The improvement of composition uniformity is directly related to the effect of crops absorbing nutrients, so it is crucial for promoting the healthy growth of crops.

[0042] Secondly, in terms of the particle hardness, the compound fertilizer of the present invention reaches 4.5 MPa, compared with 3.2 MPa of the prior art, an increase of 40.63%. A higher particle hardness means that the fertilizer is not easily broken during transportation and storage, maintaining good physical properties. At the same time, it is also beneficial to the dispersibility and uniformity during the fertilization process, which is of great significance for ensuring the fertilization efficiency and reducing waste.

[0043] The moisture content is one of the important indicators for measuring the quality of compound fertilizer. The present invention successfully controls the moisture content at 5%wt, a decrease of 28.57% compared with 7%wt of the prior art. A lower moisture content not only helps prevent the fertilizer from caking and extends the shelf life, but also reduces the nutrient loss caused by excessive moisture, ensuring the effective utilization rate of the fertilizer.

[0044] Regarding the harmful substance residue, the present invention reduces the harmful substance content to 20 mg / kg through physical adsorption method, compared with 150 mg / kg of the prior art, a reduction of 86.67%. This significant improvement greatly reduces the potential harm of the fertilizer to the soil and crops, ensures the safety and quality of agricultural products, and also meets the increasingly strict environmental protection requirements.

[0045] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A method for preparing compound fertilizer using iron ore tailings, characterized in that: include: The chemical composition analysis method is used to conduct detailed element detection on the iron ore tailings to obtain the composition data of the iron ore tailings; By using computer-aided design to simulate the effects of different formulations based on the composition data of iron ore tailings, a specific fertilizer formulation was obtained; Pre-treating specific fertilizer formulations by screening, washing and drying to remove impurities and adjust moisture content to obtain processed raw materials; The processed raw materials are mixed with the nutrient elements and the improver in proportion, and a wet granulator is used to form a granular compound fertilizer to obtain compound fertilizer granules; Monitor temperature, humidity and pressure parameters through the automated control platform and make online adjustments; The compound fertilizer is obtained by screening the compound fertilizer particles and immobilizing the harmful substances using a physical adsorption method.

2. A method for preparing compound fertilizer using iron ore tailings according to claim 1, characterized in that: The chemical composition analysis method is used to perform detailed element detection on the iron ore tailings to obtain the iron ore tailings composition data, and the specific steps are as follows: Collect a certain amount of iron ore tailings samples, crush and homogenize them; Use standard reference materials of known composition to calibrate the XRF spectrometer; The prepared sample is placed in an XRF instrument, and the atoms in the sample are excited to emit characteristic X-rays under specific conditions; Collect and record the X-ray intensity corresponding to each element , calculate the mass fraction of each element based on the data measured by XRF , the expression is: ； in, For the The X-ray intensity of the element, For the The empirical coefficient of the element, is the conversion constant, converting the intensity into mass fraction.

3. A method for preparing compound fertilizer using iron ore tailings according to claim 2, characterized in that: The specific steps of simulating the effects of different formulations by computer-aided design on the iron ore tailings composition data to obtain a specific fertilizer formulation are as follows: The iron ore tailings composition data obtained through XRF analysis and the target crop and soil requirement information were input into the computer-aided design system; A mathematical model is constructed based on linear programming, and the objective function is set to comprehensively consider the weighted sum of crop yield, environmental impact and economic cost. The expression is: ； in, Represents the importance of crop yield, is the predicted crop yield value, Represents the importance of environmental impact, is the environmental impact index of the assessment, Represents the importance of economic costs, is the estimated cost value; The constraints are introduced into the model, and the expression is: ； Among them, here, It is The ratio factor of the nutrients, is the actual amount added; It is The proportion factor of harmful substances, is the quantity that actually exists; It is The scaling factor of the cost item, is the actual cost incurred; Run simulation programs to generate a range of possible fertilizer formula combinations based on soil characteristics and target crop requirements in different regions; After multiple rounds of simulation and evaluation, an optimal formula was selected as the specific formula in this technical solution. The specific parameters were nitrogen content 10%wt, phosphorus content 8%wt, potassium content 6%wt, trace elements 0.2%wt, and biochar 5%wt.

4. A method for preparing compound fertilizer using iron ore tailings according to claim 3, characterized in that: The specific fertilizer formula is pre-treated by screening, washing and drying to remove impurities and adjust the moisture content to obtain the processed raw material. The specific steps are as follows: Use a vibrating screen to classify the iron ore tailings samples into different grades according to particle size and remove large particle impurities; Put the screened iron ore tailings into a washing tank, add an appropriate amount of clean water, stir and wash, remove the mud and other soluble impurities attached to the surface, and use a centrifuge to separate the solid and liquid phases during the washing process; The cleaned iron ore tailings are preliminarily dehydrated by a filter press and then sent to a rotary dryer for low-temperature drying at a controlled temperature to stabilize the moisture content of the final product at 5%wt; During the drying process, the moisture content HH of the iron ore tailings is monitored in real time to ensure that it meets the set standard. The moisture adjustment model is introduced to optimize the drying effect. The expression is as follows: in, is the final moisture content, is the initial moisture content, is the drying rate constant, For drying time, is the residual moisture function that varies with time; The processing raw materials are obtained, specifically 20%wt of iron, 5%wt of moisture, 15%wt of silicon, 10%wt of aluminum, 5%wt of calcium, 3%wt of magnesium, and 0.2%wt of trace elements.

5. A method for preparing compound fertilizer using iron ore tailings according to claim 4, characterized in that: The processing raw materials are mixed with the nutrient elements and the improver in proportion, and a wet granulator is used to make a granular compound fertilizer to obtain compound fertilizer particles. The specific steps are as follows: Add the processed raw materials into the mixer according to the proportion, and the mixing time is between 15 and 30 minutes; The mixed materials are fed into a wet granulator, and 10% to 15% water is added during the process; Control the temperature and humidity parameters in the granulator, the temperature range is 40°C to 60°C, and the relative humidity is maintained at 70% to 80%; The initially formed particles enter the drying chamber through a conveyor belt and are slowly dried at low temperature to reduce the moisture content of the particles to about 5%wt; The dried particles are cooled to a temperature close to ambient temperature; The dried and cooled particles are screened through a vibrating screen to remove oversized particles, control the size to between 2 mm and 5 mm, and obtain compound fertilizer particles.

6. A method for preparing compound fertilizer using iron ore tailings according to claim 5, characterized in that: The temperature, humidity and pressure parameters are monitored by the automated control platform and adjusted online. The specific steps are as follows: Install and debug automated control systems that integrate multiple sensors and actuators to monitor and control various parameters in the production environment; When the system is initialized, the target value range of each parameter is set, temperature 40°C to 60°C, humidity 70% to 80%, and pressure 0.5 to 1.0MPa; Throughout the production process, sensors continuously collect temperature, humidity and pressure data and transmit the information to the central control system. The data collection frequency is set to once per second. The central control system has built-in intelligent algorithms to analyze the collected data in real time and identify any abnormalities that deviate from the preset range; When it is detected that the parameters exceed the set safety threshold, the system will immediately issue an alarm to notify the operator and automatically initiate the corresponding corrective measures; According to the real-time data analysis results, the system automatically adjusts the working state of the actuator through the PID controller to keep the parameters within the target range, and introduces an optimization control model to dynamically adjust the control strategy.

7. The method for preparing compound fertilizer using iron ore tailings according to claim 6, characterized in that: The method of obtaining compound fertilizer by screening compound fertilizer particles and immobilizing harmful substances by physical adsorption method comprises the following specific steps: The compound fertilizer granules produced by the wet granulator are preliminarily screened through a vibrating screen to obtain granules with a size between 2 mm and 5 mm; The selected compound fertilizer particle samples are sent to the laboratory for detection of harmful substances using the analytical instrument ICP-MS; For particles detected to contain trace amounts of harmful substances, physical adsorption materials are used for immobilization treatment; The physical adsorption material is mixed with the compound fertilizer particles in proportion, and 0.5%wt to 1%wt of the adsorption material is added per ton of compound fertilizer; After mixing, the adsorbent material is allowed to fully contact with the harmful substances, and the harmful substances are firmly adsorbed on its surface or in its internal micropores by using its large specific surface area and pore structure characteristics. The adsorption treatment time is 30 minutes to 1 hour; After the physical adsorption treatment is completed, the compound fertilizer particles are screened again through a vibrating screen to remove fine powder or debris generated by the adsorption treatment and obtain the final compound fertilizer.

8. The method for preparing compound fertilizer using iron ore tailings according to claim 6, characterized in that: The optimization control model is introduced to dynamically adjust the control strategy, and the expression is: ; in, For time The control output at the moment, is the proportional gain, is the target temperature, is the actual temperature, is the integral gain, is the differential gain, is the humidity sensitivity coefficient, is the pressure sensitivity coefficient, For humidity, For pressure.

9. The method for preparing compound fertilizer using iron ore tailings according to claim 6, characterized in that: When it is detected that the parameter exceeds the set safety threshold, the system will immediately issue an alarm to notify the operator and automatically initiate the corresponding corrective measures. The specific steps are as follows: When an alarm is triggered, the system automatically initiates preset corrective actions; When the temperature is too high, the power of the cooling device is automatically increased to reduce the working intensity of the heater; When the humidity is insufficient, the water supply of the spray system is automatically increased and the working frequency or spray angle of the nozzle is adjusted; When the pressure is too low, the working intensity of the compressor is automatically increased, or the boost valve is opened to quickly increase the pressure in the system.

10. The method for preparing compound fertilizer using iron ore tailings according to claim 7, characterized in that: During the physical adsorption process, an optimization adjustment function is introduced, and the expression is: ; in, is the adsorption treatment time, is the initial concentration of harmful substances, is the temperature and humidity related adsorption rate constant, is the specific surface area per unit mass of adsorption material, is the concentration sensitivity coefficient, is the temperature sensitivity coefficient, is the humidity sensitivity coefficient.

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