Acidic water-soluble fertilizer optimization method based on online monitoring of raffinate acid components

Abstract

The invention discloses an acidic water-soluble fertilizer optimization method based on online monitoring of raffinate acid components, and relates to the technical field of acidic water-soluble fertilizer preparation, and the method comprises the following steps: filtering a raffinate acid solution to remove impurities, and mixing with process water for dilution; introducing liquid ammonia into the diluted solution, and regulating and controlling a neutralization reaction through online monitoring to generate monoammonium phosphate and retain part of unreacted raffinate acid; cooling the solution after the neutralization reaction to below 50 DEG C, and monitoring the viscosity in the cooling process; adding urea, polypeptide chelated potassium and a high polymer material into the cooled solution, and uniformly stirring and mixing; the mixed slurry is ground, and the fineness of insoluble substances reaches 300 meshes or above; and temporarily storing the ground finished product solution, monitoring the specific gravity, and filling and packaging after the standard is reached, so that the problems of high production cost, resource waste and poor product stability caused by dependence on high-cost wet-process phosphoric acid, complex working procedures and incapability of efficiently utilizing raffinate acid with complex components in the existing acidic water-soluble fertilizer production are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acid water-soluble fertilizer preparation, in particular to an acid water-soluble fertilizer optimization method based on online monitoring of raffinate acid components. BACKGROUND

[0002] As an important category of water-soluble fertilizers, acid water-soluble fertilizer is widely used in modern agriculture, especially in facility agriculture, due to its high nutrient content, rapid dissolution, and high absorption efficiency. It can be combined with drip irrigation and sprinkler irrigation systems to achieve water and fertilizer integration, significantly improving fertilizer utilization and reducing water waste. It is a key fertilizer type for addressing the needs of sustainable agricultural development. Its core advantage is that it can accurately meet the nutritional needs of crops at different growth stages, especially for large-scale planting of high-value economic crops, and has outstanding effects in water and fertilizer saving and quality improvement.

[0003] However, the current production raw materials of acid water-soluble fertilizer mainly rely on high-purity wet-process phosphoric acid, which not only has high raw material cost, but also requires multiple complex processes such as neutralization, filtration, flash concentration, and spray drying in the production process, resulting in high equipment investment and high energy consumption. The high overall cost of the product limits its popularity in ordinary crop planting. At the same time, the existing process has strict requirements on the purity of raw materials, making it difficult to directly use industrial by-products such as raffinate acid from the phosphorus chemical industry, which not only wastes resources but also increases the pressure of industrial waste treatment, which is contrary to the concept of circular economy.

[0004] Raffinate acid, as a by-product of the production process of wet-process phosphoric acid, contains a certain amount of phosphoric acid and phosphorus components, and has the potential to be converted into water-soluble fertilizer raw materials. However, due to its complex composition, containing insoluble impurities such as phosphogypsum, and large fluctuations in acidity, direct use in production can easily lead to poor product stability, excessive impurities, and other problems. The existing technology lacks precise control schemes for the characteristics of raffinate acid, making it difficult to achieve efficient resource utilization. Therefore, developing an acid water-soluble fertilizer optimization method based on online monitoring of raffinate acid components is of great significance for reducing production costs and promoting the resource utilization of industrial by-products. SUMMARY

[0005] Therefore, in view of the above problems, the present application provides an acid water-soluble fertilizer optimization method based on online monitoring of raffinate acid components, which solves the problems of high production cost, resource waste, and poor product stability caused by the current acid water-soluble fertilizer production relying on high-cost wet-process phosphoric acid, complex processes, and the inability to efficiently utilize complex raffinate acid components.

[0006] The technical scheme of the present application is as follows: An acid water-soluble fertilizer optimization method based on online monitoring of raffinate acid components, comprising the following steps: S1: After filtering and removing impurities from the raffinate acid solution, mix and dilute it with process water; S2: Ammonia gas is introduced into the diluted solution, and the neutralization reaction is monitored online to generate monoammonium phosphate and retain part of the unreacted raffinate acid; S3: The solution after the neutralization reaction is cooled to below 50°C, and the viscosity is monitored during the cooling process; S4: Urea, poly-peptide chelated potassium, and high molecular materials are added to the cooled solution, and the mixture is stirred until uniform; S5: The mixed slurry is ground to a fineness of more than 300 mesh; S6: The ground finished product solution is temporarily stored and the specific gravity is monitored. After meeting the standard, it is filled and packaged.

[0007] Preferably, the P2O5 concentration of the raffinate acid solution in step S1 is 44%-48%, a detachable filter is used for filtration to remove impurities with a particle size greater than 1mm, and the mixture is mixed with process water at a mass ratio of 1:0.1-0.3 to control the specific gravity of the diluted solution to 1.6-1.7g / cm³.

[0008] Preferably, the filter hole size of the detachable filter in step S1 is 0.8-1mm, and the filtration pressure is controlled at 0.2-0.3MPa.

[0009] Preferably, in step S2, the solution neutralization degree is monitored by an online pH meter, and the specific gravity is monitored by an online density meter. The solution neutralization degree is controlled to be 0.7-0.8, and the specific gravity is controlled to be 1.5-1.6g / cm³. The ammonia gas is introduced into the pipeline in a dispersed manner, and a spray head is provided on the pipeline.

[0010] Preferably, in step S2, the online monitoring and control of the neutralization reaction uses a linkage adjustment algorithm of the solution neutralization degree and the ammonia gas introduction rate. The specific adjustment rules are as follows: When the online pH meter measures the solution neutralization degree to be less than 0.7, introduce ammonia gas at a rate of 0.5-1L / min; When the measured solution neutralization degree is greater than or equal to 0.7 and less than the preset solution neutralization degree, introduce ammonia gas at a rate of 0.2-0.3L / min, and the preset solution neutralization degree is between 0.7 and 0.8; When the measured solution neutralization degree is greater than or equal to the preset solution neutralization degree and less than or equal to 0.8, introduce ammonia gas at a rate of 0.1-0.2L / min; When the measured solution neutralization degree is greater than 0.8, stop introducing ammonia gas. When the measured solution neutralization degree falls back to greater than or equal to 0.7 and less than or equal to the preset solution neutralization degree interval, introduce ammonia gas at a rate of 0.2-0.3L / min.

[0011] Preferably, ice machine cooling is adopted in step S3, and the cooling medium is a 30%-40% mass concentration glycol aqueous solution; the normal cooling stage rate is controlled at 5-6 DEG C / h, sampling is performed at a period of 1 h / time, the solution viscosity is determined by using a rotary viscometer, and the viscosity is controlled at 500-800 mPa s; when the viscosity exceeds 800 mPa s, the accelerated cooling stage is switched to, and the rate is increased to 7-8 DEG C / h.

[0012] Preferably, in step S4, the urea is agricultural grade and has a purity of greater than or equal to 99.5%, and the mass ratio of the urea to the solution after cooling in step S3 is 1:0.6-0.7; the mass ratio of the poly-peptide chelated potassium to the solution after cooling in step S3 is 1:0.005-0.01; the high molecular material is agricultural grade poly-aspartic acid potassium, has a number average molecular weight of 3000-6000 Da, and has a purity of greater than or equal to 98%, and the mass ratio of the high molecular material to the solution after cooling in step S3 is 1:0.003-0.005; stirring is performed by using an emulsifying shearing stirrer, the rotating speed is 1200-1500 r / min, the shearing gap is 0.1-0.2 mm, and the stirring time is 15-30 min.

[0013] Preferably, in step S5, the grinding object includes phosphogypsum brought by the residual acid and urea not sufficiently dissolved, and the grinding is performed by using a precision grinder, the grinding medium is zirconia beads with a particle size of 0.8-1.2 mm, the grinding time is 20-30 min, and the fineness is monitored by using an online particle size analyzer.

[0014] Preferably, in step S6, temporary storage is performed by using a product buffer tank, the temporary storage time is 1-2 h, the product buffer tank stirring device is kept open, the rotating speed of the stirring device is 300-500 r / min, the specific gravity is maintained at 1.5-1.6 g / cm3 by using an online specific gravity meter, the filling speed is 10-15 L / min, and the packaging barrel is sterilized by ultraviolet light for 15-20 s before filling.

[0015] Preferably, in the whole process of steps S1-S6, online monitoring data are recorded every 1-2 min to form monitoring records, so that the data in the production process can be conveniently traced.

[0016] Compared with the prior art, the present application has the following beneficial effects: The application generates monoammonium phosphate and retains part of the raffinate acid by filtering impurities, diluting, monitoring and controlling the ammonia neutralization reaction in line, cooling and monitoring the viscosity, adding auxiliary materials, stirring and mixing, grinding to a fineness of insoluble matter of 300 meshes or more, and finally storing and monitoring the specific gravity to meet the standard before filling to form a closed-loop process with full-process online monitoring. The beneficial effects are that the low-cost raffinate acid is used to replace high-purity wet-process phosphoric acid, the production process is simplified, the production cost is greatly reduced, the resource utilization of industrial by-products is realized, the product stability is ensured by precise control of parameters, the drip irrigation blockage is avoided, the process controllability is improved, it is suitable for large-scale production, and the problems of high production cost, resource waste and poor product stability caused by the dependence on high-cost wet-process phosphoric acid, complex process and the inability to efficiently utilize complex raffinate acid in the production of acid aqueous fertilizer are solved. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as limiting the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0018] Figure 1 is a flowchart of an acid aqueous fertilizer optimization method based on online monitoring of raffinate acid components in the embodiments of the present application; Figure 2 is a schematic diagram of the framework structure of the acid aqueous production system in the embodiments of the present application. DETAILED DESCRIPTION

[0019] In the following, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the embodiments of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0020] In the description of the embodiments of the present application, it should be understood that the orientations or positional relationships indicated by the terms "length", "vertical", "horizontal", "top", "bottom" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the embodiments of the present application.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0023] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0025] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] Example: like Figure 1 As shown in the figure, this embodiment discloses an optimization method for acidic water-soluble fertilizers based on online monitoring of residual acid components, including the following steps: S1: After filtering out impurities, the residual acid solution is mixed and diluted with process water; S2: Liquid ammonia is introduced into the diluted solution, and the neutralization reaction is controlled by online monitoring to generate monoammonium phosphate while retaining some unreacted residual acid; S3: Cool the solution after the neutralization reaction to below 50°C, and monitor the viscosity during the cooling process; S4: Add urea, potassium polypeptide chelate and polymer materials to the cooled solution and stir to mix evenly; S5: Grind the mixed slurry to make the fineness of the insoluble matter reach 300 mesh or more; S6: Temporarily store the ground finished solution and monitor its specific gravity. Once it meets the standard, fill and package it.

[0027] Preferably, the P2O concentration of the residual acid solution in step S1 is 44%-48%, the filtration uses a detachable filter to remove impurities with a particle size greater than 1 mm, and it is mixed with process water at a mass ratio of 1:0.1-0.3 so that the specific gravity of the diluted solution is controlled at 1.6-1.7 g / cm³.

[0028] Preferably, the pore size of the removable filter in step S1 is 0.8-1 mm, and the filtration pressure is controlled at 0.2-0.3 MPa.

[0029] Preferably, in step S2, the neutralization degree of the solution is monitored by an online pH meter and the specific gravity is monitored by an online density meter to control the neutralization degree of the solution to be 0.7-0.8 and the specific gravity to be 1.5-1.6 g / cm³. The liquid ammonia is introduced by a decentralized pipeline with a nozzle on the pipeline.

[0030] Preferably, in step S2, the online monitoring and control of the neutralization reaction adopts a linkage adjustment algorithm between the degree of solution neutralization and the liquid ammonia introduction rate, and the specific adjustment rules are as follows: When the neutrality of the solution measured by the online pH meter is less than 0.7, liquid ammonia is introduced at a rate of 0.5-1 L / min; the liquid ammonia introduction rate decreases as the neutrality of the measured solution increases. When the measured solution neutralization degree is greater than or equal to 0.7 and less than the preset solution neutralization degree, liquid ammonia is introduced at a rate of 0.2-0.3 L / min, and the preset solution neutralization degree is between 0.7 and 0.8. When the measured solution neutralization degree is greater than or equal to the preset solution neutralization degree and less than or equal to 0.8, liquid ammonia is introduced at a rate of 0.1-0.2 L / min. When the measured neutrality of the solution is greater than 0.8, the liquid ammonia input is suspended. When the measured neutrality of the solution drops back to a value greater than or equal to 0.7 and less than or equal to the preset neutrality range, liquid ammonia is introduced again at a rate of 0.2-0.3 L / min.

[0031] To achieve precise dynamic control of the neutralization reaction in step S2, a dual-core and three-auxiliary multi-dimensional linkage control strategy was established, with neutralization degree (pH conversion) and specific gravity as core control indicators, and phosphate ion concentration, ammonia nitrogen concentration, and reaction temperature as auxiliary verification indicators. The monitoring data of each indicator are deeply bound to preset value requirements. Through a closed-loop process of real-time monitoring, data comparison, logical judgment, and parameter adjustment, the reaction process is ensured to remain within a controllable range. More specifically: Based on the neutralization reaction process, the system is divided into stages with the degree of neutralization as the core. By combining real-time monitoring data of various indicators, the liquid ammonia injection rate is adjusted in stages to achieve rapid reaction without overshoot and precise control to achieve the target.

[0032] Phase 1: Initial rapid neutralization phase (i.e., neutralization degree < 0.65, not reaching the warning range) Core objective: To rapidly increase the degree of neutralization to near the target range while ensuring a stable reaction, thereby shortening the reaction cycle.

[0033] Liquid ammonia rate setting: Use the initial rate setting (0.5-1L / min). The specific initial value can be fine-tuned according to the reaction temperature. If the initial temperature is <40℃ (close to the lower warning limit), select a higher rate (0.8-1L / min) to increase the temperature by utilizing the exothermic neutralization reaction. If the initial temperature is >55℃ (close to the upper target limit), select a lower rate (0.5-0.7L / min) to avoid the temperature rising too quickly to the warning range.

[0034] Multi-indicator collaborative monitoring and judgment: Temperature linkage: If the temperature is detected to rise to 60℃ (the upper limit of the warning), immediately reduce the rate to 0.3-0.5L / min (below the initial setting) and continue to monitor the temperature. Once the temperature drops below 55℃, restore the rate to 0.5-0.7L / min. If the temperature is <35℃ (set as the emergency zone), pause the rate adjustment and resume the response once the temperature rises above 40℃.

[0035] Specific gravity prediction: If the specific gravity reaches 1.45 g / cm³ (lower warning limit) in advance at this stage, even if the degree of neutralization does not reach 0.65, the rate should be reduced to 0.4-0.5 L / min to avoid the specific gravity exceeding the standard in the future. Since the specific gravity reflects the total solid content, an increase in the specific gravity in advance may mean that the impurity content is too high or the initial dilution ratio is deviated. The reaction rate should be slowed down for observation.

[0036] Phosphate and ammonia nitrogen verification: During this stage, the concentrations of both should increase synchronously with the degree of neutralization (e.g., when the degree of neutralization increases from 0.4 to 0.6, the phosphate concentration increases from 120 g / L to 170 g / L, and the ammonia nitrogen concentration increases from 15 g / L to 25 g / L). If the degree of neutralization increases but the phosphate concentration decreases (possibly due to impurity adsorption), the reaction should be paused, and the impurity removal effect of S1 filtration should be checked. If the degree of neutralization increases but the ammonia nitrogen concentration increases sharply (possibly due to local excess of liquid ammonia that has not reacted), the reaction rate should be reduced and stirring should be intensified.

[0037] Phase 2: Fine-grained approach to the target phase (neutrality 0.65-0.7, entering the warning zone) Core objective: to adjust slowly to avoid the neutralization degree from rapidly exceeding the target lower limit (0.7), while ensuring that indicators such as specific gravity and ammonia nitrogen move towards the target range in a synchronous manner.

[0038] Liquid ammonia rate switching: When the neutralization degree is detected to reach 0.65 (lower warning limit) online, the rate is immediately reduced from the initial setting to the transition setting (0.3-0.4 L / min) - between the initial setting and the fine setting, to achieve deceleration and buffer, and avoid reaction stagnation caused by directly switching to the fine setting.

[0039] Multi-indicator fine-tuning: Neutralization degree and ammonia nitrogen synergy: If the neutralization degree rises to 0.68 (close to the target lower limit of 0.7), but the ammonia nitrogen concentration has reached 45 g / L (close to the target upper limit of 50 g / L), it indicates that the utilization rate of liquid ammonia has decreased (some unreacted). The rate should be reduced to the fine setting (0.2-0.3 L / min) in advance to avoid ammonia nitrogen exceeding the standard.

[0040] Specific gravity and phosphate synergy: If the degree of neutralization rises to 0.68, but the specific gravity is only 1.42 g / cm³ (below the warning lower limit of 1.45), and the phosphate concentration is 15% lower than the matching value (e.g., only 150 g / L, the matching value should be 175 g / L), it indicates that the available phosphorus content in the residual acid is too low. The rate needs to be appropriately increased to 0.35-0.4 L / min to accelerate the neutralization reaction and increase the total solid content. At the same time, the phosphate concentration should be closely monitored to ensure that its growth trend is normal.

[0041] Phase 3: Precise and stable target phase (neutralization degree 0.7-0.8, within the target range) Core objective: To maintain the stability of all indicators within the target range, avoid fluctuations that could cause the reaction to deviate, and ensure that the product state meets the requirements.

[0042] Liquid ammonia rate setting: Uses a fine adjustment setting (0.2-0.3L / min), and makes small-amplitude and high-frequency fine adjustments based on the real-time fluctuations of multiple indicators.

[0043] Multi-indicator closed-loop control logic: Neutralization degree priority control: If the neutralization degree drops to 0.72 (lower than the target range) and the ammonia nitrogen concentration is 32 g / L (lower limit of the target range 30 g / L), appropriately increase the rate to 0.3-0.35 L / min (slightly higher than the upper limit of the fine setting). After purging for 1-2 minutes, monitor whether the neutralization degree rises back to around 0.75, and at the same time observe whether the ammonia nitrogen concentration exceeds 35 g / L (avoid overdose).

[0044] If the degree of neutralization rises to 0.78 (higher than the target range) and the specific gravity is 1.58 g / cm³ (upper limit of the target range 1.6 g / cm³), immediately reduce the flow rate to 0.15-0.2 L / min (slightly below the lower limit of the fine setting), or pause the flow for 1 minute, stir evenly, and then monitor. If the degree of neutralization stabilizes at 0.76-0.78 and the specific gravity stabilizes at 1.56-1.58, this rate can be maintained. If the degree of neutralization continues to rise to 0.82 (warning range), pause the flow until the degree of neutralization falls back below 0.8 (because the neutralization reaction has a lag, the reaction will continue for a period of time after pausing).

[0045] Temperature and ammonia nitrogen linkage temperature control: If the reaction temperature rises to 62℃ (warning range) and the ammonia nitrogen concentration is 48g / L (close to the target upper limit of 50g / L), it indicates an increased risk of ammonia volatilization. The reaction rate should be reduced to 0.15-0.2L / min, and the cooling water in the reactor jacket should be turned on to lower the temperature to below 58℃. At the same time, the ammonia nitrogen concentration should be monitored to prevent it from dropping below 35g / L (the lower limit of the target range of 30g / L) due to ammonia volatilization.

[0046] Phosphate and specific gravity verification of product validity: If the degree of neutralization is stable at 0.75 and the specific gravity is 1.55 g / cm³ (within the target range), but the phosphate concentration is only 170 g / L (lower than the matching value of 180 g / L), it indicates that some phosphorus may exist in the form of insoluble impurities (such as incompletely filtered phosphogypsum). It is necessary to combine the viscosity monitoring data of step S3 (if the viscosity is high in the subsequent steps, it can be inferred that the phosphorus utilization rate is low here). The filtration process of step S1 can be optimized for subsequent batches (such as replacing the filter with one with a finer pore size). Since other indicators meet the standards, this batch can continue to complete the reaction, but the data needs to be recorded for process optimization.

[0047] Phase 4: Determination of the reaction endpoint and stabilization phase Endpoint determination criteria: All of the following conditions must be met, and there must be no significant fluctuations (fluctuation range ≤ ±2%) in three consecutive data collections (30-second intervals): The neutrality remained stable at 0.7-0.8; Its specific gravity remains stable at 1.5-1.6 g / cm³; Phosphate concentration is within the target matching range (e.g., 180-200 g / L). The ammonia nitrogen concentration is within the target matching range (e.g., 30-50 g / L). The reaction temperature is stable at 40-60℃.

[0048] Subsequent operations: When the endpoint conditions are met, stop the flow of liquid ammonia and continue stirring for 1-2 minutes (to ensure uniform reaction). Then proceed to step S3 (cooling stage). At the same time, store all monitoring data of this batch (curves of changes in various indicators, rate adjustment records) into the database for subsequent optimization of process parameters (such as the adaptation of the initial rate of different batches of residual acid).

[0049] Emergency response mechanism for abnormal situations: When a certain indicator enters the emergency adjustment range, emergency control measures need to be initiated to prevent the reaction from getting out of control or the product from being scrapped, as shown in Table 1: Table 1 By employing the aforementioned phased, multi-index-linked dynamic control strategy, the core control functions of pH (neutralization degree) and specific gravity are fully combined with the auxiliary verification functions of phosphate concentration, ammonia nitrogen concentration, and reaction temperature. This approach not only strictly adheres to the preset numerical index requirements but also addresses various fluctuations during the reaction process. Ultimately, it achieves precise control over the amount of liquid ammonia introduced and the reaction progress, ensuring the generation of qualified monoammonium phosphate product while maximizing the utilization of available phosphorus in the residual acid.

[0050] Preferably, in step S3, an ice machine is used for cooling, and the cooling medium is an aqueous solution of ethylene glycol with a mass concentration of 30%-40%. During the normal cooling stage, the cooling rate is controlled at 5-6℃ / h, and samples are taken at a cycle of 1h / time. The viscosity of the solution is measured using a rotational viscometer and controlled at 500-800mPa·s. When the viscosity exceeds 800mPa·s, the process is switched to the accelerated cooling stage, and the rate is increased to 7-8℃ / h.

[0051] Preferably, the urea in step S4 is agricultural grade with a purity ≥99.5%, and its mass ratio to the solution after cooling in step S3 is 1:0.6-0.7; the mass ratio of the polypeptide chelated potassium to the solution after cooling in step S3 is 1:0.005-0.01; the polymer material is agricultural grade polyaspartic acid potassium with a number average molecular weight of 3000-6000 Da and a purity ≥98%, and its mass ratio to the solution after cooling in step S3 is 1:0.003-0.005; the stirring is carried out using an emulsifying shear mixer with a speed of 1200-1500 r / min, a shear gap of 0.1-0.2 mm, and a stirring time of 15-30 min.

[0052] Preferably, the grinding objects in step S5 include phosphogypsum brought in by residual acid and undissolved urea. A fine grinding mill is used for grinding, the grinding media is zirconia beads with a particle size of 0.8-1.2 mm, the grinding time is 20-30 min, and the fineness is monitored by an online particle size analyzer.

[0053] Preferably, in step S6, a product buffer tank is used for temporary storage, with a storage time of 1-2 hours. The stirring device in the product buffer tank is kept on, with a stirring speed of 300-500 r / min. The specific gravity is maintained at 1.5-1.6 g / cm³ by monitoring with an online density meter. The filling speed is 10-15 L / min, and the packaging barrel is disinfected with ultraviolet light for 15-20 seconds before filling.

[0054] Preferably, during the entire process of steps S1-S6, online monitoring data is recorded every 1-2 minutes to form a monitoring record, which facilitates the traceability of data during the production process.

[0055] Preferably, the monitoring records are stored in the database of the PLC control cabinet for a period of not less than 3 years; when the online data exceeds the set range twice in a row, the system will automatically trigger an alarm and suspend the corresponding process, and manual confirmation of parameter adjustment is required before restarting.

[0056] This invention utilizes residual raffinate as a raw material. After filtration to remove impurities and dilution, the process involves online monitoring and control of ammonia neutralization to generate monoammonium phosphate while retaining some residual raffinate. The mixture is then cooled and its viscosity monitored. Additives are added, stirred, and ground until the insoluble matter reaches a fineness of 300 mesh or higher. Finally, the mixture is temporarily stored, and after monitoring the specific gravity to ensure it meets standards, it is bottled. This forms a closed-loop process with online monitoring throughout the entire process. Its advantages include using low-cost residual raffinate to replace high-purity wet-process phosphoric acid, simplifying production procedures, significantly reducing production costs, and realizing the resource utilization of industrial by-products. Simultaneously, precise parameter control ensures product stability, avoids drip irrigation blockage, and improves process controllability. It is suitable for large-scale production and solves the problems of high production costs, resource waste, and poor product stability currently associated with the production of acidic water-soluble fertilizers, which relies on high-cost wet-process phosphoric acid, involves complex processes, and cannot efficiently utilize the complex components of residual raffinate.

[0057] The present invention discloses an optimization method for acidic water-soluble fertilizers based on online monitoring of residual acid components, which is applied to the following acidic water-soluble fertilizer production systems: like Figure 2 As shown, the acidic water-soluble production system includes: Pretreatment Unit: The pretreatment unit includes a residual acid storage tank, a removable filter, a process water storage tank, and a static mixer. The inlet of the removable filter is connected to the outlet of the residual acid storage tank via a pipeline. A transfer pump and a solenoid valve are installed on the pipeline between the residual acid storage tank and the removable filter. The outlet of the removable filter is connected to the inlet of the static mixer via a pipeline. The outlet of the process water storage tank is connected to the inlet of the static mixer via a pipeline. A transfer pump and a solenoid valve are installed on the pipeline between the process water storage tank and the static mixer. An online density meter is installed at the outlet of the static mixer to complete the filtration and dilution in step S1. Neutralization reaction unit: The neutralization reaction unit includes a reaction vessel. The outlet of the static mixer is connected to the inlet of the reaction vessel through a pipeline. The pipeline is equipped with a delivery pump and a solenoid valve. The reaction vessel is equipped with a stirring device. The reaction vessel body is equipped with an online pH meter. The online pH meter probe is inserted into the reaction vessel to 1 / 2 below the liquid level. An online density meter is installed at the bottom outlet of the reaction vessel. A liquid ammonia inlet pipe is installed at the top. The end of the liquid ammonia inlet pipe is placed at the bottom of the reaction vessel and is connected to a nozzle for controlling the neutralization reaction in step S2. Cooling Unit: The cooling unit includes a jacketed cooling tank. The bottom outlet of the reactor is connected to the inlet of the jacketed cooling tank via a pipeline. The pipeline is equipped with a delivery pump and a solenoid valve. Ethylene glycol aqueous solution is introduced into the jacket of the jacketed cooling tank. The jacket of the jacketed cooling tank is connected to an ice machine via a pipeline for circulating the ethylene glycol aqueous solution. An online temperature sensor is installed inside the jacketed cooling tank. A sampling port is provided at the lower end of the jacketed cooling tank for cooling and viscosity monitoring in step S3. Mixing Unit: The mixing unit includes an emulsifying shear mixer, which has four feeding ports. One feeding port is connected to the outlet of the jacketed cooling tank through a pipeline. The pipeline is equipped with a delivery pump and a solenoid valve. The other three feeding ports are respectively connected to urea, polymer materials and chelated potassium for the mixing of auxiliary materials in step S4. Grinding Unit: The grinding unit includes a fine grinding mill with built-in zirconia bead grinding media. The feed inlet of the fine grinding mill is connected to the discharge outlet of the emulsifying shear mixer. An online particle size analyzer is installed at the discharge outlet of the fine grinding mill for refining insoluble matter in step S5.

[0058] Finished product processing unit: The finished product processing unit includes a product buffer tank and a filling machine. The product buffer tank is equipped with a stirring device and an online density meter. The discharge port of the fine grinding mill is connected to the inlet of the product buffer tank through a pipeline. The pipeline is equipped with a conveying pump and a solenoid valve. The discharge port of the product buffer tank is connected to the inlet of the filling machine through a pipeline. The pipeline is equipped with a conveying pump and a solenoid valve. The packaging barrel conveyor line is equipped with an ultraviolet disinfection device for temporary storage and filling in step S6.

[0059] Control system: The control system includes a PLC control cabinet, which is electrically connected to all the above-mentioned online monitoring devices (online pH meter, online density meter, online temperature sensor) and execution devices (transfer pump, solenoid valve, motor in the stirring device), to collect data in real time and dynamically adjust parameters, such as liquid ammonia inlet rate and cooling medium flow rate.

[0060] In operation, residual raffinate is pumped from the raffinate storage tank into a removable filter to remove large particulate impurities before entering a static mixer to be mixed and diluted with process water at a set ratio. The diluted solution then enters the reactor, where liquid ammonia is introduced through a nozzle. The PLC control cabinet automatically adjusts the liquid ammonia valve opening (i.e., the liquid ammonia input rate) based on data from the online pH meter and online density meter to control the solution's neutralization degree and specific gravity. After neutralization, the solution enters a jacketed cooling tank, where an ethylene glycol aqueous solution is circulated through the jacket of the cooling tank via an ice machine for cooling. The solution is cooled every hour by pumping water through the cooling tank. The sample is collected at the sampling port to determine its viscosity. The PLC control cabinet automatically adjusts the cooling rate based on the viscosity value. After cooling, the solution enters the emulsifying shear mixer, where urea, potassium polypeptide chelate, and polymer materials are added in proportion and stirred until homogeneous at a set speed. The mixed slurry enters the fine grinding mill and is ground until the fineness of insoluble matter is ≥300 mesh as shown by the online particle size analyzer. Then, it is sent to the product buffer tank. The stirring device in the product buffer tank is kept running. After the specific gravity is confirmed to be qualified by the online density meter, the slurry is pumped into the filling machine. The packaging barrels are sterilized by ultraviolet light and then filled.

[0061] The following is an example generated based on the midpoint value of the parameter range for each step: Step S1: The residual acid P2O concentration is 46%. It is passed through a detachable filter with a pore size of 0.9 mm and a filtration pressure of 0.25 MPa to remove impurities >1 mm. It is then mixed with process water at a mass ratio of 1:0.2. The specific gravity of the diluted solution is 1.65 g / cm³. Step S2: The preset solution neutralization degree is set to 0.75. The initial measured solution neutralization degree is monitored to be 0.6 by an online pH meter. Liquid ammonia is introduced into the diluted solution through a nozzle at an initial rate of 1 L / min. The liquid ammonia introduction rate gradually decreases to 0.5 L / min as the measured solution neutralization degree increases. When the solution neutralization degree reaches 0.7 by the online pH meter, the rate is reduced to 0.3 L / min. The liquid ammonia introduction rate gradually decreases to 0.2 L / min as the measured solution neutralization degree increases. When the solution neutralization degree reaches 0.75 by the online pH meter, the rate is reduced to below 0.2 L / min. Finally, the measured solution neutralization degree is controlled to be maintained at 0.75 and the specific gravity at 1.55 g / cm³. When the measured solution neutralization degree rises to greater than 0.8, the liquid ammonia input is stopped. When the measured solution neutralization degree falls back to greater than or equal to 0.7 and less than or equal to the preset solution neutralization degree range, liquid ammonia is reintroduced at a rate of 0.2-0.3 L / min. Step S3: Use 35% ethylene glycol aqueous solution as cooling medium and cool at a rate of 5.5℃ / h; take 50ml samples every 1h and measure the viscosity with an NDJ-1 type rotational viscometer. The viscosity is stable at 650mPa・s, which does not exceed the standard. Finally, cool down to 45℃.

[0062] Step S4: Add agricultural-grade urea (mass ratio 1:0.65), potassium polypeptide chelate (mass ratio 1:0.0075), and agricultural-grade potassium polyaspartate (mass ratio 1:0.004) to the cooled solution. The polymer material is agricultural-grade potassium polyaspartate with a number average molecular weight of 4500 Da and a purity ≥98%, and its mass ratio to the cooled solution from Step S3 is 1:0.004. Use an emulsifying shear mixer at a speed of 1350 r / min and a shear gap of 0.15 mm to stir for 22 min until homogeneous. Step S5: Grind the slurry using a fine grinding mill with 1.0mm zirconia beads as the grinding medium for 25 minutes. Detect the particle size using an online particle size analyzer to ensure that the fineness of the insoluble matter reaches 320 mesh, which is better than the 300 mesh standard. Step S6: The finished solution is temporarily stored in the product buffer tank for 1.5 hours with a stirring speed of 400 r / min and the specific gravity is monitored by an online density meter to be 1.55 g / cm³; it is then filled at a rate of 12.5 L / min, and the packaging barrels are sterilized by ultraviolet light for 17 seconds to complete the packaging.

[0063] The polymer material used in the above embodiments is agricultural-grade potassium polyaspartate, with a number-average molecular weight of 3000-6000 Da and a purity of ≥98%, meeting the standard for "Polyaspartic Acid as a Fertilizer Enhancer," and free of heavy metals and industrial residues. Alternatively, the above polymer material can be replaced with a peptide-chelated potassium polymer derivative.

[0064] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components, characterized in that, Includes the following steps: S1: After filtering out impurities, the residual acid solution is mixed and diluted with process water; S2: Liquid ammonia is introduced into the diluted solution, and the neutralization reaction is controlled by online monitoring to generate monoammonium phosphate while retaining some unreacted residual acid; S3: Cool the solution after the neutralization reaction to below 50°C, and monitor the viscosity during the cooling process; S4: Add urea, potassium polypeptide chelate and polymer materials to the cooled solution and stir to mix evenly; S5: Grind the mixed slurry to make the fineness of the insoluble matter reach 300 mesh or more; S6: Temporarily store the ground finished solution and monitor its specific gravity. Once it meets the standard, fill and package it.

2. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 1, characterized in that, The P2O concentration of the residual acid solution in step S1 is 44%-48%. A detachable filter is used for filtration to remove impurities with a particle size greater than 1 mm. The solution is mixed with process water at a mass ratio of 1:0.1-0.3 to control the specific gravity of the diluted solution at 1.6-1.7 g / cm³.

3. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 2, characterized in that, The detachable filter described in step S1 has a pore size of 0.8-1mm and a filtration pressure controlled at 0.2-0.3MPa.

4. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 3, characterized in that, In step S2, the neutralization degree of the solution is monitored by an online pH meter and the specific gravity is monitored by an online density meter. The neutralization degree of the solution is controlled to be 0.7-0.8 and the specific gravity is 1.5-1.6 g / cm³. The liquid ammonia is introduced by a decentralized pipeline with nozzles installed on the pipeline.

5. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 4, characterized in that, In step S2, the online monitoring and control of the neutralization reaction adopts a linkage adjustment algorithm between the degree of solution neutralization and the liquid ammonia introduction rate. The specific adjustment rules are as follows: When the neutrality of the solution measured by the online pH meter is less than 0.7, liquid ammonia is introduced at a rate of 0.5-1 L / min. When the measured solution neutralization degree is greater than or equal to 0.7 and less than the preset solution neutralization degree, liquid ammonia is introduced at a rate of 0.2-0.3 L / min, and the preset solution neutralization degree is between 0.7 and 0.

8. When the measured solution neutralization degree is greater than or equal to the preset solution neutralization degree and less than or equal to 0.8, liquid ammonia is introduced at a rate of 0.1-0.2 L / min. When the measured neutrality of the solution is greater than 0.8, the liquid ammonia input is suspended. When the measured neutrality of the solution drops back to a value greater than or equal to 0.7 and less than or equal to the preset neutrality range, liquid ammonia is introduced again at a rate of 0.2-0.3 L / min.

6. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 5, characterized in that, In step S3, an ice machine is used for cooling, and the cooling medium is an ethylene glycol aqueous solution with a mass concentration of 30%-40%. During the normal cooling stage, the cooling rate is controlled at 5-6℃ / h, and samples are taken at a cycle of 1h / time. The viscosity of the solution is measured using a rotational viscometer and controlled at 500-800mPa・s. When the viscosity exceeds 800 mPa·s, switch to the accelerated cooling stage, and increase the rate to 7-8 °C / h.

7. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 6, characterized in that, The urea mentioned in step S4 is agricultural grade with a purity ≥99.5%, and its mass ratio with the solution after cooling in step S3 is 1:0.6-0.7; the mass ratio of the polypeptide chelated potassium with the solution after cooling in step S3 is 1:0.005-0.01; the polymer material is agricultural grade polyaspartic acid potassium, with a number average molecular weight of 3000-6000 Da and a purity ≥98%, and its mass ratio with the solution after cooling in step S3 is 1:0.003-0.005; the stirring is carried out using an emulsifying shear mixer with a speed of 1200-1500 r / min, a shear gap of 0.1-0.2 mm, and a stirring time of 15-30 min.

8. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 7, characterized in that, In step S5, the grinding objects include phosphogypsum brought in by residual acid and undissolved urea. A fine grinding mill is used for grinding, and the grinding media is zirconia beads with a particle size of 0.8-1.2 mm. The grinding time is 20-30 min, and the fineness is detected by an online particle size analyzer.

9. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 8, characterized in that, In step S6, a product buffer tank is used for temporary storage for 1-2 hours. The stirring device in the product buffer tank is kept on and the stirring speed is 300-500 r / min. The specific gravity is maintained at 1.5-1.6 g / cm³ by monitoring with an online density meter. The filling speed is 10-15 L / min. The packaging barrel is disinfected with ultraviolet light for 15-20 seconds before filling.

10. The method for optimizing acidic water-soluble fertilizers based on online monitoring of residual acid components according to claim 9, characterized in that, Throughout steps S1-S6, online monitoring data is recorded every 1-2 minutes to form a monitoring record, facilitating data traceability during the production process.

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