Drying-free compound fertilizer granulation automatic control system and method based on electromagnetic heating

Abstract

The invention relates to the technical field of compound fertilizer production, in particular to a drying-free compound fertilizer granulation automatic control system and method based on electromagnetic heating, raw materials are weighed and proportioned according to a formula, and feeding is controlled by a PID controller; performing electromagnetic heating and drying on the raw materials, and adjusting the heating power by constructing an electromagnetic heating model and a PID (Proportion Integration Differentiation) controller to enable the raw materials to reach the target water content; the dried raw materials are put into a roller granulator, a granulation adhesive is added at the same time, and roller granulation parameters are optimized according to the constructed compound fertilizer particle size model and compound fertilizer particle strength model; cooling the granulated hot particles in a fluidized bed, and realizing cooling and inert protection by adjusting the air volume and controlling the oxygen concentration; and screening finished product particles, detecting particle size distribution by using a laser particle size analyzer, and feeding back a deviation signal to a granulation stage to realize closed-loop optimization control of product quality. According to the method, accurate control and intelligent optimization of the whole production process of the compound fertilizer are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of compound fertilizer production, specifically to an automatic control system and method for compound fertilizer granulation without drying based on electromagnetic heating. Background Art

[0002] Traditional compound fertilizer production processes usually include links such as raw material mixing, granulation, drying, cooling, screening, etc. Precise control of process parameters is required in each link to ensure the stable quality of compound fertilizer products.

[0003] At present, the level of automatic control in the compound fertilizer production process is relatively low, and there are a series of problems to be solved urgently. First, there are many types of compound fertilizer raw materials, and the physical and chemical properties of different raw materials vary greatly. Deviations are likely to occur in traditional manual batching, and it is difficult to accurately control the raw material feeding amount, resulting in fluctuations in the nutrient content of compound fertilizers and unstable product quality. Second, traditional drying processes use high-temperature hot air to directly contact the materials, with low thermal efficiency, high energy consumption, uneven drying, and easy local overheating, causing nutrient loss. Third, the granulation link involves many process parameters, such as drum rotation speed, inclination angle, liquid-solid ratio, granulation time, etc. The influence of each parameter on the particle forming quality is complex. At present, there is a lack of in-depth research on the particle formation mechanism, and granulation process control mainly relies on experience, resulting in problems such as uneven particle size and insufficient strength. In addition, hot-state granulated fertilizers need to be cooled as soon as possible to prevent caking. However, during the cooling process, if the oxygen concentration is too high, it is easy to cause nutrient oxidation and decomposition. At present, there is a lack of effective inert gas protection measures. Finally, the existing process usually conducts screening tests before the finished product is warehoused, with a lag in feedback, which is not conducive to timely adjustment of granulation parameters. There is a lack of on-line particle size monitoring means, and it is difficult to achieve real-time closed-loop optimization control of product quality.

[0004] In view of the above problems, it is urgent to develop a new automatic control method for compound fertilizer production lines. From raw material ratio, drying, granulation, cooling to product detection, deepen the research on process mechanisms, innovate the process parameter optimization control model, construct an on-line product quality detection and feedback control system, realize precise control of the entire compound fertilizer production process, improve the stability of product quality, reduce energy consumption, and improve production efficiency. This is of great significance for promoting the intelligent manufacturing development of the compound fertilizer industry.

[0005] In view of this, the present invention proposes an automatic control system and method for compound fertilizer granulation without drying based on electromagnetic heating. Summary of the Invention

[0006] To achieve the above object, the present invention provides an automatic control method for compound fertilizer granulation without drying based on electromagnetic heating. The specific technical solution is as follows: including:

[0007] Weigh and proportion various raw materials according to the compound fertilizer formula, weigh and proportion the raw materials for compound fertilizer granulation, and construct a PID feeding controller to control the feeding of the raw materials for compound fertilizer granulation;

[0008] Carry out electromagnetic heating and drying on the raw materials for compound fertilizer granulation, construct an electromagnetic heating model, reduce the moisture content of the raw materials for compound fertilizer granulation to the target moisture content, and design a PID heating controller to adjust the power of the electromagnetic heater in real time;

[0009] Discharge the raw materials for compound fertilizer granulation after electromagnetic heating and put them into a drum granulator. At the same time, add a granulation binder, construct a compound fertilizer particle size model and a compound fertilizer particle strength model, calculate the drum granulation parameters in combination with the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjust the compound fertilizer drum granulation process;

[0010] Automatically adjust the fluidized bed cooling air volume according to the temperature of the compound fertilizer particles, control the oxygen concentration during the cooling process and provide inert gas protection to obtain cooled finished compound fertilizer particles;

[0011] Screen the finished compound fertilizer particles, screen out compound fertilizer particles of different particle sizes, monitor the particle size distribution through a laser particle size analyzer, and perform feedback adjustment on the compound fertilizer drum granulation process.

[0012] Preferably, weigh and proportion various raw materials according to the compound fertilizer formula, weigh and proportion the raw materials for compound fertilizer granulation, and construct a PID feeding controller to control the feeding of the raw materials for compound fertilizer granulation; the weighing and feeding mathematical model is: Among them, G(s) is the feeding amount of the compound fertilizer raw materials, K c is the feeding gain coefficient, η is the feeding delay time, T c is the feeding time constant, and s is the Laplace operator;

[0013] The control law of the PID feeding controller is: In the formula, u(t) is the feeding amount of the compound fertilizer material, e(t) is the deviation signal, K pu is the feeding proportionality coefficient, T i is the integral time constant, and T d is the differential time constant.

[0014] Preferably, according to the initial moisture content w0 and the target moisture content w of the raw materials for compound fertilizer granulation, combined with the drying kinetics, construct an electromagnetic heating model to estimate the total heating energy Q required for drying t :

[0015] Q t = m×c p ×(T - T0)+ m×(w0 - w)×r w

[0016] Among them, m is the mass flow rate of the compound fertilizer granulation raw materials, c p is the specific heat capacity of the compound fertilizer granulation raw materials, T0 and T are the initial temperature and the target temperature of the compound fertilizer granulation raw materials respectively, r w is the latent heat of vaporization of water;

[0017] According to the total heating energy and the average residence time τ of the compound fertilizer granulation raw materials in the heating zone, the total power P0 of the electromagnetic heater is set: P0 = Q t / τ;

[0018] The total power P0 is distributed to each induction coil according to a fixed ratio to form a power distribution curve;

[0019] Continuously measure the real-time moisture content w of the compound fertilizer granulation raw materials at the outlet of the silo r , compare the real-time moisture content w r with the target moisture content w, and calculate the moisture content deviation E w : E w = w - w r ; According to the moisture content deviation E w , design a PID heating controller to adjust the total power P of the electromagnetic heater in real time t :

[0020]

[0021] Among them, K pw , K iw , K dw are the heating control proportional coefficient, integral coefficient, and differential coefficient of the PID heating controller respectively;

[0022] Arrange multi-point infrared thermometers in the silo to monitor the temperature distribution of the compound fertilizer granulation raw materials in real time, and set the safety upper limit T S of the temperature of the compound fertilizer granulation raw materials. When the measured temperature T m exceeds the safety upper limit T S , immediately reduce the power of the electromagnetic heater, stop heating and give an alarm.

[0023] Preferably, the compound fertilizer granulation raw materials after electromagnetic heating and drying are transported to a drum granulator, and the target particle size of the compound fertilizer particles is adjusted by controlling the rotation speed n, inclination angle θ, and granulation time t of the drum granulator Establish a compound fertilizer particle size model:

[0024]

[0025] Among them, d0 is the initial particle size of the compound fertilizer granulation raw materials, k1 is the granulation rate coefficient, a is the influence index of the rotation speed and inclination angle on the particle size, D is the drum diameter, D0 is the standard drum diameter, and b is the influence index of the drum diameter on the particle size;

[0026] During the drum granulation process, the granulation binder solution is sprayed into the drum through the spray system, the concentration C and the spray volume Q of the granulation binder are adjusted, the formation process of the compound fertilizer particle strength σ is controlled, and the compound fertilizer particle strength model is constructed:

[0027]

[0028] Among them, σ0 is the initial granule strength without adding binder, k2 is the bonding coefficient of the granulation binder, α is the amount of granulation binder added, and ψ is the influence index of rotation speed and inclination angle on strength;

[0029] Based on the performance parameters of the selected granulation binder and the target compound fertilizer quality requirements, including the bonding coefficient k2 of the granulation binder, the concentration C of the granulation binder, the addition amount of the granulation binder α, and the target particle size of the compound fertilizer As well as the compound fertilizer particle strength σ, the particle size model and strength model established by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, the process parameter optimization model of the compound fertilizer granulation process is obtained:

[0030]

[0031]

[0032] Where f is the objective function, which represents the sum of squares of the deviations of particle size and intensity from the target values. is the optimal compound fertilizer particle size, σ * is the optimal compound fertilizer intensity, β is the weight coefficient of intensity deviation; n , θ , t , Q , C , They are the minimum value of the drum speed, the maximum value of the speed, the minimum value of the inclination angle, the maximum value of the inclination angle, the minimum value of the granulation time, the maximum value of the granulation time, the minimum value of the spray amount of the adhesive, the maximum value of the spray amount of the adhesive, the minimum value of the concentration of the adhesive and the maximum value of the concentration of the adhesive;

[0033] Solve the process parameter optimization model of compound fertilizer granulation process and obtain the drum control parameters of compound fertilizer in the drum granulation process.

[0034] Preferably, after the drum granulation of the compound fertilizer is completed, a fluidized bed cooler is used to cool the hot compound fertilizer particles after the drum granulation, and the compound fertilizer particles are fully in contact with the cooling air in the fluidized bed for heat transfer and are finally cooled to the desired temperature;

[0035] The heat transfer mathematical model of the cooling process is as follows:

[0036] where ρ p is the particle density, V p is the particle volume, is the average specific heat capacity of the particles, T p is the particle temperature, h p is the convective heat transfer coefficient, A p is the heat transfer area, T f is the fluidized air temperature;

[0037] According to the deviation between the particle temperature and the target temperature, a PID cooling controller is constructed to adjust the cooling air volume F(t):

[0038]

[0039] In the formula, K pf , T if , T df are respectively the proportional coefficient, integral coefficient, and differential coefficient of the cooling air volume control of the PID cooling controller, and E T (t) is the deviation between the particle temperature and the target temperature.

[0040] Preferably, when cooling hot compound fertilizer particles, additional nitrogen is introduced during the cooling process to control the inlet air oxygen concentration;

[0041] The oxygen concentration control adopts a feedforward-feedback composite control strategy. The feedforward control calculates the nitrogen supplement amount according to the cooling air volume F(t) where represents the total inlet air volume required to reach the target oxygen concentration ;

[0042] The feedback control adjusts the nitrogen flow rate according to the oxygen concentration deviation

[0043]

[0044] where K pN is the proportional coefficient of the nitrogen flow rate, T iN is the integral time constant, and E C (t) is the oxygen concentration deviation.

[0045] Preferably, the cooled compound fertilizer particles are sieved and classified, and the particle size distribution is detected by the laser diffraction method;

[0046] The cooled compound fertilizer particles are subjected to multi-layer vibration screening to classify the compound fertilizer particles. The screen apertures decrease successively from top to bottom. Under the vibration and inclination of the screen, the compound fertilizer particles pass through the screens with sizes equivalent to the screen apertures layer by layer, separating compound fertilizer particles with different particle sizes.

[0047] For the classified compound fertilizer particles at each level after screening, laser diffraction method is used for particle size analysis. The particle samples are dispersed in a liquid medium to form a stable particle suspension; then the particle suspension is irradiated with a collimated laser beam, and the particles produce diffraction and scattering of the incident light; by measuring the angular distribution and intensity distribution of the scattered light, according to the scattering theory and diffraction theory, the compound fertilizer particle size distribution data is calculated; based on the measured compound fertilizer particle size, the compound fertilizer particle error is calculated, and the process parameter optimization model of the compound fertilizer granulation process is modified according to the compound fertilizer particle error to obtain the improved compound fertilizer granulation process parameters.

[0048] The automatic control system for electromagnetic heating-based non-drying compound fertilizer granulation, which is used to implement the above-mentioned automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation, includes: a feeding control module, an electromagnetic heating module, a granulation module, a cooling module, and a detection module;

[0049] The feeding control module proportions various raw materials according to the compound fertilizer formula, weighs and proportions the compound fertilizer granulation raw materials, and constructs a PID feeding controller to control the feeding of the compound fertilizer granulation raw materials;

[0050] The electromagnetic heating module conducts electromagnetic heating and drying on the compound fertilizer granulation raw materials, constructs an electromagnetic heating model, reduces the moisture content of the compound fertilizer granulation raw materials to the target moisture content, and designs a PID heating controller to adjust the power of the electromagnetic heater in real time;

[0051] The granulation module discharges the electromagnetic-heated compound fertilizer granulation raw materials and feeds them into a drum granulator, and at the same time adds a granulation binder, constructs a compound fertilizer particle size model and a compound fertilizer particle strength model, calculates the drum granulation parameters by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjusts the compound fertilizer drum granulation process;

[0052] The cooling module automatically adjusts the fluidized bed cooling air volume according to the temperature of the compound fertilizer particles, controls the oxygen concentration during the cooling process, and provides inert gas protection to obtain cooled finished compound fertilizer particles;

[0053] The detection module screens the finished compound fertilizer particles, screens out compound fertilizer particles of different particle sizes, monitors the particle size distribution through a laser particle size analyzer, and conducts feedback regulation on the compound fertilizer drum granulation process.

[0054] An electronic device includes: a processor and a memory, wherein a computer program that can be called by the processor is stored in the memory; the processor executes the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation by calling the computer program stored in the memory.

[0055] A computer-readable storage medium stores instructions, which when run on a computer, cause the computer to execute the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation.

[0056] Advantages of the present invention: By constructing a PID controller, the present invention accurately controls the raw material ratio and feeding rate, ensures that the compound fertilizer raw material input meets the formula requirements, improves the stability and consistency of the compound fertilizer product quality, and realizes the automation and intelligence of raw material management.

[0057] The present invention uses electromagnetic heating technology to quickly and uniformly dry the granulation raw materials. By constructing an electromagnetic heating model and a PID controller to optimize the drying process, it ensures that the granulation raw materials reach the optimal moisture content, lays a good foundation for the subsequent granulation process, and improves production efficiency and energy utilization rate.

[0058] The present invention combines the compound fertilizer particle size model and the compound fertilizer particle strength model, accurately predicts the influence of granulation process parameters on particle characteristics, optimizes the control parameters of the drum granulation process, produces high-quality compound fertilizer particles with uniform particle size distribution and meeting strength requirements, and enhances the product competitiveness.

[0059] The present invention automatically and accurately controls the fluidized bed cooling air volume according to the compound fertilizer particle temperature. At the same time, by controlling the oxygen concentration, it provides inert gas protection to prevent the oxidation loss of compound fertilizer nutrients during the cooling process, ensures the stable quality of the compound fertilizer finished product, and reduces energy consumption and nitrogen consumption.

[0060] The present invention uses vibration screening to efficiently classify the compound fertilizer finished product particles, uses a laser particle size analyzer to monitor the particle size distribution in real time, and performs feedback adjustment on the drum granulation process to form a closed-loop control of product quality, continuously improving the compound fertilizer production process and product performance. Description of the Drawings

[0061] Figure 1 It is a flowchart of the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation provided by the present invention;

[0062] Figure 2 It is a structure diagram of the automatic control system for electromagnetic heating-based non-drying compound fertilizer granulation provided by the present invention. Detailed Embodiments

[0063] To better understand the present invention, various aspects of the present invention will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are only descriptions of exemplary embodiments of the present invention and do not limit the scope of the present invention in any way. Throughout the specification, the same reference numerals refer to the same elements. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0064] In the accompanying drawings, for ease of illustration, the size, dimensions, and shape of the elements have been slightly adjusted. The drawings are for example only and are not drawn to an exact scale. As used herein, terms such as "substantially", "about", and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by a person of ordinary skill in the art. Additionally, in the present invention, the order of description of the various steps does not necessarily represent the order in which these processes occur in actual operation, unless otherwise clearly specified or derivable from the context.

[0065] It should also be understood that expressions such as "comprising", "including", "having", "containing", and / or "including having" are open-ended rather than closed-ended expressions in this specification, which mean the presence of the stated features, elements, and / or components, but do not exclude the presence of one or more other features, elements, components, and / or combinations thereof. Further, when an expression such as "at least one of..." appears after a list of listed features, it modifies the entire list of features rather than just individual elements in the list. Additionally, when describing embodiments of the present invention, the use of "may" means "one or more embodiments of the present invention". And the term "exemplary" is intended to refer to an example or illustration.

[0066] Unless otherwise defined, all terms used herein (including engineering terms and scientific and technical terms) have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. It should also be understood that, unless clearly stated in the present invention, words defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense.

[0067] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0068] Example 1

[0069] Referring to Figure 1 , for the first embodiment of the present invention, an automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation is provided.

[0070] S1: According to the compound fertilizer formula, various raw materials are proportioned, the raw materials for compound fertilizer granulation are weighed and proportioned, and a PID feeding controller is constructed to control the feeding of compound fertilizer granulation raw materials.

[0071] According to the compound fertilizer formula, various raw materials are proportioned, the raw materials for compound fertilizer granulation are weighed and proportioned, and a PID feeding controller is constructed to control the feeding of compound fertilizer granulation raw materials; the weighing and feeding mathematical model is: where G(s) is the feeding amount of compound fertilizer raw materials, K c is the feeding gain coefficient, η is the feeding delay time, T c is the feeding time constant, and s is the Laplace operator.

[0072] The control law of the PID feeding controller is: In the formula, u(t) is the feeding amount of compound fertilizer materials, e(t) is the deviation signal, K pu is the feeding proportionality coefficient, T i is the integral time constant, T d is the differential time constant.

[0073] By precisely proportioning the compound fertilizer raw materials, not only the formula requirements are met, but also the stability and consistency of the compound fertilizer quality are improved; further, through the PID control strategy, the raw material feeding rate can be adjusted in real time, quickly respond to the changes in working conditions, reduce the error of the raw material feeding amount, and improve the automation control level; constructing the feeding mathematical model can predict and optimize the feeding process and realize the intelligent management of the raw material feeding process.

[0074] S2: Electromagnetic heating drying is carried out on the raw materials for compound fertilizer granulation, an electromagnetic heating model is constructed, the moisture content of the raw materials for compound fertilizer granulation is reduced to the target moisture content, and a PID heating controller is designed to adjust the power of the electromagnetic heater in real time.

[0075] According to the initial moisture content w0 and the target moisture content w of the raw materials for compound fertilizer granulation, combined with drying kinetics, an electromagnetic heating model is constructed to estimate the total heating energy Q required for drying t :

[0076] Q t = m×c p ×(T - T0) + m×(w0 - w)×r w

[0077] where m is the mass flow rate of the raw materials for compound fertilizer granulation, c p is the specific heat capacity of the raw materials for compound fertilizer granulation, T0 and T are the initial temperature and the target temperature of the raw materials for compound fertilizer granulation respectively, and r w is the latent heat of vaporization of water.

[0078] According to the total heating energy and the average residence time τ of the compound fertilizer granulation raw materials in the heating zone, set the total power P0 of the electromagnetic heater: P0 = Q t / τ.

[0079] Distribute the total power P0 to each induction coil according to a fixed ratio to form a power distribution curve.

[0080] Continuously measure the real-time moisture content w of the compound fertilizer granulation raw materials at the outlet of the silo r , and compare the real-time moisture content w r with the target moisture content w to calculate the moisture content deviation E w : E w = w - w r ; According to the moisture content deviation E w , design a PID heating controller to adjust the total power P of the electromagnetic heater in real time t :

[0081]

[0082] Among them, K pw , K iw , K dw are the heating control proportional coefficient, integral coefficient, and differential coefficient of the PID heating controller respectively; they need to be optimized through on-site debugging.

[0083] Arrange multi-point infrared thermometers in the silo to monitor the temperature distribution of the compound fertilizer granulation raw materials in real time, especially local high-temperature points; set the safety upper limit T of the temperature of the compound fertilizer granulation raw materials S , when the measured highest temperature T m exceeds the safety upper limit T S , immediately reduce the power of the electromagnetic heater, stop heating and alarm.

[0084] Electromagnetic heating has the advantages of fast heating rate, high thermal efficiency, and good temperature control accuracy, and can realize the rapid drying of compound fertilizer granulation raw materials in a short time, improving the production efficiency of compound fertilizers; through the PID control strategy, the heating power can be accurately adjusted, quickly tracking the change of moisture content, realizing intelligent drying control, ensuring that the compound fertilizer granulation raw materials are always at the best moisture content, laying a good foundation for the subsequent granulation process; arranging multi-point infrared thermometers to monitor the temperature and setting high-temperature alarms can prevent safety accidents caused by local overheating and provide safety guarantees for compound fertilizer production.

[0085] S3: Discharge the compound fertilizer granulation raw materials after electromagnetic heating and put them into a drum granulator. At the same time, add a granulation binder, construct a compound fertilizer particle size model and a compound fertilizer particle strength model, calculate the drum granulation parameters in combination with the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjust the compound fertilizer drum granulation process.

[0086] The compound fertilizer granulation raw materials after electromagnetic heating drying are transported to the drum granulator. Under the rotation and tilt of the drum, the raw material particles are constantly aggregated, gradually grow and form spherical particles. The target particle size of the compound fertilizer particles can be adjusted by controlling the speed n, tilt angle θ and granulation time t of the drum granulator. Establishing compound fertilizer particle size model:

[0087]

[0088] Among them, d0 is the initial particle size of the compound fertilizer granulation raw material, k1 is the granulation rate coefficient, a is the influence index of rotation speed and inclination angle on particle size, D is the roller diameter, D0 is the standard roller diameter, and b is the influence index of roller diameter on particle size.

[0089] During the drum granulation process, the granulation binder solution is sprayed into the drum through the spray system, and the bonding effect of the binder is used to improve the strength and durability of the particles. By selecting different types of binders (such as molasses, starch, bentonite, etc.), adjusting the concentration C and spray volume Q of the granulation binder, and controlling the formation process of the compound fertilizer particle strength σ, the compound fertilizer particle strength model is constructed:

[0090]

[0091] Among them, σ0 is the initial granule strength without adding binder, k2 is the bonding coefficient of the granulation binder, α is the amount of granulation binder added, and ψ is the influence index of rotation speed and inclination angle on strength.

[0092] Based on the performance parameters of the selected granulation binder and the target compound fertilizer quality requirements, including the bonding coefficient k2 of the granulation binder, the concentration C of the granulation binder, the addition amount of the granulation binder α, and the target particle size of the compound fertilizer As well as the compound fertilizer particle strength σ, the particle size model and strength model established by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, the process parameter optimization model of the compound fertilizer granulation process is obtained:

[0093]

[0094] Where f is the objective function, which represents the sum of squares of the deviations of particle size and intensity from the target values. is the optimal compound fertilizer particle size, σ * is the optimal compound fertilizer intensity, β is the weight coefficient of intensity deviation; n , θ , t , Q , C , They are respectively the minimum value of the drum rotation speed, the maximum value of the rotation speed, the minimum value of the inclination angle, the maximum value of the inclination angle, the minimum value of the granulation time, the maximum value of the granulation time, the minimum value of the spraying amount of the binder, the maximum value of the spraying amount of the binder, the minimum value of the concentration of the binder, and the maximum value of the concentration of the binder.

[0095] Solve the optimization model of the process parameters for compound fertilizer granulation to obtain the drum control parameters during the drum granulation process of compound fertilizer.

[0096] By adjusting the drum control parameters, the granulation binder solution, and the spraying parameters, compound fertilizer particles with uniform particle size distribution and appropriate strength are obtained.

[0097] By conducting a mechanism modeling of the kinetic process of particle formation, the influence of granulation process parameters on particle size and strength can be accurately predicted, realizing theoretical guidance for parameter selection; by solving the optimization model of the process parameters for granulation, while meeting the target quality of compound fertilizer, the granulation process can be optimized, energy consumption can be reduced, and production efficiency and product quality can be improved; by adjusting the drum parameters and binder parameters, the particle size distribution and strength level of compound fertilizer particles can be flexibly controlled to meet different application requirements.

[0098] S4: Automatically adjust the fluidized bed cooling air volume according to the temperature of compound fertilizer particles, control the oxygen concentration during the cooling process, and provide inert gas protection to obtain cooled finished compound fertilizer particles.

[0099] After the compound fertilizer completes drum granulation, a fluidized bed cooler is used to cool the hot compound fertilizer particles after drum granulation. The compound fertilizer particles are in full contact with the cooling air in the fluidized bed for heat transfer and are finally cooled to the required temperature.

[0100] The heat transfer mathematical model for the cooling process is:

[0101] Among them, ρ p is the particle density, V p is the particle volume, is the average specific heat capacity of the particles, T p is the particle temperature, h p is the convective heat transfer coefficient, A p is the heat transfer area, T f is the temperature of the fluidizing air.

[0102] Based on the deviation between the particle temperature and the target temperature, construct a PID cooling controller to adjust the cooling air volume F(t):

[0103]

[0104] In the formula, K pf , T if , Tdf are the proportional coefficient, integral coefficient, and differential coefficient for the cooling air volume control of the PID cooling controller, respectively, and E T (t) is the deviation between the particle temperature and the target temperature.

[0105] When cooling the compound fertilizer produced by hot-state drum granulation, additional nitrogen is introduced during the cooling process to control the oxygen concentration in the incoming air, provide inert protection, and prevent the compound fertilizer particles from contacting excessive oxygen during the cooling process and thus oxidizing and deteriorating.

[0106] The oxygen concentration control adopts a feedforward-feedback composite control strategy. The feedforward control calculates the nitrogen supplement amount based on the cooling air volume F(t) where represents the total incoming air volume required to reach the target oxygen concentration

[0107] The feedback control adjusts the nitrogen flow rate according to the oxygen concentration deviation

[0108]

[0109] where K pN is the proportional coefficient of the nitrogen flow rate, T iN is the integral time constant, and E C (t) is the oxygen concentration deviation.

[0110] Using a PID controller to automatically adjust the cooling air volume can accurately control the cooling rate and the final temperature according to the real-time temperature of the compound fertilizer particles, ensuring uniform and thorough cooling of the particles; introducing nitrogen during the cooling process to form an inert atmosphere can prevent the compound fertilizer particles from oxidizing and deteriorating, avoid nutrient loss, and ensure the quality of the compound fertilizer product. The oxygen concentration adopts a composite control scheme, which can minimize the nitrogen consumption while meeting the requirements of inert protection and save production costs.

[0111] S5: Screen the finished compound fertilizer particles, screen out compound fertilizer particles of different particle sizes, and monitor the particle size distribution through a laser particle size analyzer to perform feedback adjustment on the compound fertilizer drum granulation process.

[0112] The cooled compound fertilizer particles are sieved and classified, and the particle size distribution of the particles is detected by the laser diffraction method.

[0113] The cooled compound fertilizer particles are subjected to multi-layer vibrating screening to classify the compound fertilizer particles. The screen hole diameters decrease from top to bottom. Under the action of the vibration and inclination of the screen, the compound fertilizer particles pass through the screen with a size equivalent to the screen hole layer by layer, separating compound fertilizer particles with different particle sizes.

[0114] ​For the compound fertilizer particles at each level after screening, laser diffraction method is used for particle size analysis. The particle samples are dispersed in a liquid medium to form a stable particle suspension. Then, the particle suspension is irradiated with a collimated laser beam, and the particles produce diffraction and scattering on the incident light. By measuring the angular distribution and intensity distribution of the scattered light, according to the scattering theory and diffraction theory, the particle size distribution data of the compound fertilizer is calculated. Based on the measured particle size of the compound fertilizer particles, the error of the compound fertilizer particles is calculated, and the process parameter optimization model of the compound fertilizer granulation process is modified according to the error of the compound fertilizer particles to obtain the improved process parameters of the compound fertilizer granulation.

[0115] Through vibration screening, compound fertilizer particles with different particle sizes can be efficiently separated, the compound fertilizer product can be purified, and the application requirements of different users can be met. By using the laser particle size analysis technology, the particle size distribution characteristics of the compound fertilizer product can be measured quickly and accurately, providing data support for product quality evaluation and process optimization.

[0116] Using the detection results of the particle size distribution to correct the process parameters of the drum granulation process to form a quality feedback closed-loop control can continuously improve the granulation effect and stabilize the quality of the compound fertilizer product.

[0117] Example 2

[0118] Refer to Figure 2 , the second embodiment of the present invention provides an automatic control system for electromagnetic heating-based compound fertilizer granulation without drying.

[0119] The system includes: a feeding control module, an electromagnetic heating module, a granulation module, a cooling module and a detection module.

[0120] The feeding control module proportions various raw materials according to the compound fertilizer formula, weighs and proportions the raw materials for compound fertilizer granulation, and constructs a PID feeding controller to control the feeding of the raw materials for compound fertilizer granulation.

[0121] The electromagnetic heating module conducts electromagnetic heating and drying on the raw materials for compound fertilizer granulation, constructs an electromagnetic heating model, reduces the moisture content of the raw materials for compound fertilizer granulation to the target moisture content, and designs a PID heating controller to adjust the power of the electromagnetic heater in real time.

[0122] The granulation module discharges the raw materials for compound fertilizer granulation after electromagnetic heating and feeds them into a drum granulator, and at the same time adds a granulation binder, constructs a compound fertilizer particle size model and a compound fertilizer particle strength model, calculates the drum granulation parameters by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjusts the compound fertilizer drum granulation process.

[0123] The cooling module automatically adjusts the fluidized bed cooling air volume according to the temperature of the compound fertilizer particles, controls the oxygen concentration during the cooling process and provides inert gas protection to obtain cooled finished compound fertilizer particles.

[0124] The detection module screens the finished compound fertilizer particles, screens out compound fertilizer particles of different particle sizes, monitors the particle size distribution through a laser particle size analyzer, and performs feedback adjustment on the compound fertilizer drum granulation process.

[0125] Example 3

[0126] The present invention also provides an electronic device. The electronic device may include one or more processors and one or more memories. Among them, computer-readable code is stored in the memory, and when the computer-readable code is run by one or more processors, it can execute the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation as described above.

[0127] The method or system according to the embodiment of the present invention can also be implemented by means of the architecture of the electronic device of the present invention.

[0128] The electronic device may include a bus, one or more CPUs, a read-only memory (ROM), a random access memory (RAM), a communication port connected to a network, input / output components, a hard disk, etc.

[0129] The storage device in the electronic device, such as ROM or a hard disk, can store the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation provided by the present invention.

[0130] The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation includes: proportioning various raw materials according to the compound fertilizer formula, weighing and proportioning the compound fertilizer granulation raw materials, and constructing a PID feeding controller to control the feeding of the compound fertilizer granulation raw materials; performing electromagnetic heating and drying on the compound fertilizer granulation raw materials, constructing an electromagnetic heating model, reducing the moisture content of the compound fertilizer granulation raw materials to the target moisture content, and designing a PID heating controller to adjust the power of the electromagnetic heater in real time; discharging the electromagnetic heated compound fertilizer granulation raw materials and feeding them into a drum granulator, and adding a granulation binder at the same time, constructing a compound fertilizer particle size model and a compound fertilizer particle strength model, calculating the drum granulation parameters by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjusting the compound fertilizer drum granulation process; automatically adjusting the fluidized bed cooling air volume according to the compound fertilizer particle temperature, controlling the oxygen concentration during the cooling process and providing inert gas protection to obtain cooled finished compound fertilizer particles; screening the finished compound fertilizer particles, screening out compound fertilizer particles of different particle sizes, and monitoring the particle size distribution through a laser particle size analyzer to perform feedback adjustment on the compound fertilizer drum granulation process.

[0131] Furthermore, the electronic device may further include a user interface. Of course, the architecture of the present invention is only exemplary, and when implementing different devices, one or more components of the electronic device disclosed in the present invention can be omitted according to actual needs.

[0132] Example 4

[0133] The present invention also discloses a computer-readable storage medium.

[0134] The computer-readable storage medium stores computer-readable instructions.

[0135] When the computer-readable instructions are run by a processor, the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to the embodiments of the present invention described with reference to the above drawings can be executed.

[0136] The storage medium includes but is not limited to, for example, volatile memory and / or non-volatile memory. Volatile memory may include, for example, random access memory (RAM) and cache memory, etc. Non-volatile memory may include, for example, read-only memory (ROM), hard disk, flash memory, etc. Additionally, according to the embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs.

[0137] For example, the present invention provides a non-transitory machine-readable storage medium, the non-transitory machine-readable storage medium stores machine-readable instructions, and the machine-readable instructions can be run by a processor to execute instructions corresponding to the method steps provided by the present invention, such as: proportioning various raw materials according to the compound fertilizer formula, weighing and proportioning the compound fertilizer granulation raw materials, and constructing a PID dosing controller to control the feeding of the compound fertilizer granulation raw materials; drying the compound fertilizer granulation raw materials by electromagnetic heating, constructing an electromagnetic heating model, reducing the moisture content of the compound fertilizer granulation raw materials to the target moisture content, and designing a PID heating controller to adjust the power of the electromagnetic heater in real time; discharging the electromagnetic-heated compound fertilizer granulation raw materials and feeding them into a drum granulator, adding a granulation binder at the same time, constructing a compound fertilizer particle size model and a compound fertilizer particle strength model, calculating the drum granulation parameters by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjusting the compound fertilizer drum granulation process; automatically adjusting the fluidized bed cooling air volume according to the compound fertilizer particle temperature, controlling the oxygen concentration during the cooling process and providing inert gas protection to obtain cooled finished compound fertilizer particles; screening the finished compound fertilizer particles, screening out compound fertilizer particles of different particle sizes, monitoring the particle size distribution through a laser particle size analyzer, and performing feedback adjustment on the compound fertilizer drum granulation process.

[0138] When the computer program is executed by a central processing unit (CPU), the above functions defined in the method of the present invention are executed. The method, device, and equipment of the present invention can be implemented in many ways. For example, the method, device, and equipment of the present invention can be implemented through software, hardware, firmware, or any combination of software, hardware, and firmware.

[0139] The above order of steps for the method is for illustrative purposes only. The steps of the method of the present invention are not limited to the order specifically described above, unless otherwise specifically stated.

[0140] In addition, in some embodiments, the present invention can also be implemented as a program recorded in a recording medium, and these programs include machine-readable instructions for implementing the method according to the present invention. Therefore, the present invention also covers a recording medium storing a program for executing the method according to the present invention.

[0141] Furthermore, parts of the above technical solutions provided in the embodiments of the present invention that are consistent with the corresponding technical solutions in the prior art in terms of implementation principles are not described in detail to avoid excessive elaboration.

[0142] As described above, the specific embodiments further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An automatic control method for electromagnetic heating-based drying-free compound fertilizer granulation, characterized in that, Including: According to the compound fertilizer formula, various raw materials are proportioned, the raw materials for compound fertilizer granulation are weighed and proportioned, and a PID feeding controller is constructed to control the feeding of the raw materials for compound fertilizer granulation; The raw materials for compound fertilizer granulation are dried by electromagnetic heating. An electromagnetic heating model is constructed to reduce the moisture content of the raw materials for compound fertilizer granulation to the target moisture content, and a PID heating controller is designed to adjust the power of the electromagnetic heater in real time; The raw materials for compound fertilizer granulation after electromagnetic heating are discharged and fed into a drum granulator. Meanwhile, a granulation binder is added. A compound fertilizer particle size model and a compound fertilizer particle strength model are constructed, and the drum granulation parameters are calculated by combining the compound fertilizer particle size model and the compound fertilizer particle strength model to adjust the compound fertilizer drum granulation process; The fluidized bed cooling air volume is automatically adjusted according to the temperature of the compound fertilizer particles, the oxygen concentration in the cooling process is controlled, and an inert gas protection is provided to obtain cooled finished compound fertilizer particles; The finished compound fertilizer particles are screened to screen out compound fertilizer particles of different particle sizes, and the particle size distribution is monitored by a laser particle size analyzer to perform feedback adjustment on the compound fertilizer drum granulation process; 2. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 1, wherein, Weigh various raw materials according to the compound fertilizer formula, weigh and proportion the raw materials for compound fertilizer granulation, and construct a PID dosing controller to control the feeding of compound fertilizer granulation raw materials. The weighing and feeding mathematical model is as follows: Among them, G(s) is the feeding amount of compound fertilizer raw materials, and K c is the feeding gain coefficient, η is the feeding delay time, and T c is the feeding time constant, and s is the Laplace operator; The control law of the PID dosing controller is as follows: In the formula, u(t) is the dosing amount of the compound fertilizer material, e(t) is the deviation signal, and K pu is the dosing ratio coefficient, T i is the integral time constant, and T d is the differential time constant.

3. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 2, wherein, According to the initial moisture content w0 and the target moisture content w of the compound fertilizer granulation raw materials, combined with the drying kinetics, an electromagnetic heating model is constructed to estimate the total heating energy Q required for drying t : Q t = m × c p × (T - T0) + m × (w0 - w) × r w where m is the mass flow rate of the compound fertilizer granulation raw materials, c p is the specific heat capacity of the compound fertilizer granulation raw materials, T0 and T are the initial temperature and the target temperature of the compound fertilizer granulation raw materials respectively, r w is the latent heat of vaporization of water; According to the total heating energy and the average residence time τ of the compound fertilizer granulation raw materials in the heating zone, set the total power P0 of the electromagnetic heater: P0 = Q t / τ; The total power P0 is distributed to each induction coil according to a fixed ratio to form a power distribution curve; Continuously measure the real-time moisture content w of the raw materials for compound fertilizer granulation at the bin outlet r , and compare the real-time moisture content w r with the target moisture content w to calculate the moisture content deviation E w : E w = w - w r ; According to the moisture content deviation E w , design a PID heating controller to adjust the total power P of the electromagnetic heater in real time t : Among them, K pw , K iw , K dw are respectively the heating control proportional coefficient, integral coefficient, and differential coefficient of the PID heating controller; Arrange multi-point infrared thermometers in the silo to monitor the temperature distribution of compound fertilizer granulation raw materials in real time, and set the safety upper limit T of the temperature of compound fertilizer granulation raw materials S , when the measured temperature T m exceeds the safety upper limit T S , immediately reduce the power of the electromagnetic heater, stop heating and give an alarm.

4. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 3, characterized in that, The compound fertilizer granulation raw materials after electromagnetic heating drying are transported to a drum granulator, and the target particle size of the compound fertilizer particles is adjusted by controlling the rotation speed n, inclination angle θ, and granulation time t of the drum granulator. Establish a compound fertilizer particle size model: Among them, d0 is the initial particle size of the raw materials for compound fertilizer granulation, k1 is the granulation rate coefficient, a is the influence index of rotation speed and inclination angle on the particle size, D is the drum diameter, D0 is the standard drum diameter, and b is the influence index of the drum diameter on the particle size; During the drum granulation process, a granulation binder solution is sprayed into the drum through a spray system. The concentration C and the spray amount Q of the granulation binder are adjusted to control the formation process of the compound fertilizer particle strength σ, and a compound fertilizer particle strength model is constructed: Among them, σ0 is the initial particle strength without adding a binder, k2 is the adhesion coefficient of the granulation binder, α is the addition amount of the granulation binder, and ψ is the influence index of rotation speed and inclination angle on the strength; Based on the performance parameters of the selected granulation binder and the target compound fertilizer quality requirements, including the bonding coefficient k2 of the granulation binder, the concentration C of the granulation binder, the addition amount of the granulation binder α, and the target particle size of the compound fertilizer As well as the compound fertilizer particle strength σ, the particle size model and strength model established by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, the process parameter optimization model of the compound fertilizer granulation process is obtained: Among them, f is the objective function, representing the sum of the squared deviations of the particle size and strength from the target values. is the optimal compound fertilizer particle size, and σ * is the optimal compound fertilizer strength, and β is the weight coefficient of the strength deviation; are respectively the minimum value of the roller speed, the maximum value of the speed, the minimum value of the inclination angle, the maximum value of the inclination angle, the minimum value of the granulation time, the maximum value of the granulation time, the minimum value of the spraying amount of the binder, the maximum value of the spraying amount of the binder, the minimum value of the concentration of the binder, and the maximum value of the concentration of the binder; Solve the process parameter optimization model of the compound fertilizer granulation process to obtain the drum control parameters of the compound fertilizer during the drum granulation process; 5. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 4, characterized in that, After the compound fertilizer completes drum granulation, a fluidized bed cooler is used to cool the hot compound fertilizer particles after drum granulation. The compound fertilizer particles are in full contact with the cooling air in the fluidized bed for heat transfer and are finally cooled to the required temperature; The heat transfer mathematical model of the cooling process is as follows: Among them, ρ p is the particle density, V p is the particle volume, is the average specific heat capacity of the particles, T p is the particle temperature, h p is the convective heat transfer coefficient, A p is the heat transfer area, T f is the fluidized air temperature; According to the deviation between the particle temperature and the target temperature, a PID cooling controller is constructed to adjust the cooling air volume F(t); Where K pf , T if , T df are the proportional coefficient, integral coefficient, and differential coefficient of the cooling air volume control of the PID cooling controller respectively, and E T (t) is the deviation between the particle temperature and the target temperature.

6. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 5, wherein When cooling the hot compound fertilizer particles, extra nitrogen is introduced during the cooling process to control the inlet air oxygen concentration; The oxygen concentration control adopts a feedforward-feedback composite control strategy. The feedforward control calculates the nitrogen supplement amount according to the cooling air volume F(t). Among them, represents the total incoming air volume required to reach the target oxygen concentration; the total incoming air volume required The feedback control adjusts the nitrogen flow rate according to the oxygen concentration deviation Among them, K pN is the proportionality coefficient of the nitrogen flow rate, T iN is the integral time constant, and E C (t) is the oxygen concentration deviation.

7. The automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to claim 6, characterized in that, The cooled compound fertilizer particles are sieved and classified, and the particle size distribution is detected by the laser diffraction method; The cooled compound fertilizer particles are subjected to multi-layer vibrating screening to classify the compound fertilizer particles. The screen apertures decrease from top to bottom. Under the vibration and inclination of the screen, the compound fertilizer particles pass through the screen with a size equivalent to the screen hole layer by layer to separate compound fertilizer particles of different particle sizes; For the compound fertilizer granules at each level after screening, laser diffraction method is used for particle size analysis. The particle samples are dispersed in a liquid medium to form a stable particle suspension; then the particle suspension is irradiated with a collimated laser beam, and the particles produce diffraction and scattering on the incident light; by measuring the angular distribution and intensity distribution of the scattered light, according to the scattering theory and diffraction theory, the particle size distribution data of the compound fertilizer are calculated; Based on the measured particle size of the compound fertilizer granules, the error of the compound fertilizer granules is calculated, and the process parameter optimization model of the compound fertilizer granulation process is modified according to the error of the compound fertilizer granules to obtain the improved process parameters of the compound fertilizer granulation.

8. An automatic control system for electromagnetic heating-based non-drying compound fertilizer granulation, which is used to implement the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to any one of claims 1 to 7, characterized in that, Including: A feeding control module, an electromagnetic heating module, a granulation module, a cooling module and a detection module; The feeding control module proportionally weighs various raw materials according to the compound fertilizer formula, weighs and mixes the compound fertilizer granulation raw materials, and constructs a PID feeding controller to control the feeding of the compound fertilizer granulation raw materials; The electromagnetic heating module conducts electromagnetic heating and drying on the compound fertilizer granulation raw materials, constructs an electromagnetic heating model, reduces the moisture content of the compound fertilizer granulation raw materials to the target moisture content, and designs a PID heating controller to adjust the power of the electromagnetic heater in real time; The granulation module discharges the compound fertilizer granulation raw materials after electromagnetic heating and feeds them into a drum granulator, and at the same time adds a granulation binder, constructs a compound fertilizer particle size model and a compound fertilizer particle strength model, calculates the drum granulation parameters by combining the compound fertilizer particle size model and the compound fertilizer particle strength model, and adjusts the compound fertilizer drum granulation process; The cooling module automatically adjusts the fluidized bed cooling air volume according to the temperature of the compound fertilizer granules, controls the oxygen concentration during the cooling process and provides inert gas protection to obtain the cooled finished compound fertilizer granules; The detection module screens the finished compound fertilizer granules, screens out the compound fertilizer granules of different particle sizes, monitors the particle size distribution through a laser particle size analyzer, and performs feedback adjustment on the compound fertilizer drum granulation process.

9. An electronic device, characterized in that, Including: A processor and a memory, wherein the memory stores a computer program that can be called by the processor; the processor executes the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to any one of claims 1 to 7 by calling the computer program stored in the memory.

10. A computer-readable storage medium, characterized in that: Stores instructions, when the instructions run on a computer, the computer is caused to execute the automatic control method for electromagnetic heating-based non-drying compound fertilizer granulation according to any one of claims 1 to 7.

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