Preparation method and control system of high-activity calcium hydroxide

Abstract

The invention discloses a high-activity calcium hydroxide preparation method and a control system, and relates to the technical field of chemical building material production. The method is applied to a vertical premixer with independent double-shaft stirring and dynamic weighing functions, and the charging quality and the exhaust temperature in a mixing barrel are collected in real time by a control unit. And the control unit establishes a nonlinear relation between the stirring rotation speed and the loading mass based on a preset shear rheological coupling model, and adaptively adjusts the rotation speed of the double shafts according to the nonlinear relation so as to stabilize the shear energy input of unit materials. And meanwhile, through cascade adjustment of the temperature and the loading quality, the material retention time is corrected by utilizing the change of the unloading opening degree, and rotation speed compensation is linked, so that stable control of the premixing process is realized. According to the invention, the stability of the preparation process and the product quality consistency can be improved.

Description

Technical Field

[0001] This invention relates to the field of chemical building materials production technology, specifically to a method and control system for preparing highly active calcium hydroxide. Background Technology

[0002] Calcium hydroxide is a commonly used desulfurizing agent, and its reactivity directly affects desulfurization efficiency. Generally, highly active calcium hydroxide requires a high specific surface area (BET ≥ 40 m²). 2 (g), porous structure, and good dispersibility. Currently, the digestion process of quicklime is mainly divided into wet digestion and dry digestion, among which dry digestion has become the mainstream choice due to its relatively simple system and low energy consumption.

[0003] In existing dry digestion production processes, although vertical premixing devices with stirring functions have begun to be used for preliminary mixing of quicklime, water, and additives, the control methods are relatively crude. Most existing equipment operates with a fixed stirring speed and a fixed material residence time, and cannot be dynamically adjusted according to the density fluctuations, activity changes, and real-time disturbances in the feed rate of the raw quicklime.

[0004] This open-loop or simple single-variable control method has the following problems: when the feed rate increases instantaneously, the mechanical shear energy distributed per unit mass of material is insufficient, leading to uneven mixing (under-mixing) or clumping; when the feed rate decreases or the reaction is too exothermic, the material stays in the machine for too long and is excessively sheared, resulting in localized overheating (overheating), severely damaging the microporous structure of calcium hydroxide and causing a decrease in the specific surface area of ​​the product. Therefore, how to achieve adaptive control of the premixing process, ensuring mixing uniformity while preventing overheating, is a technical problem that urgently needs to be solved in the preparation of highly active calcium hydroxide. Summary of the Invention

[0005] The purpose of this invention is to provide a method and control system for preparing highly active calcium hydroxide, which aims to solve the problems in the prior art where the use of fixed process parameters cannot adapt to fluctuations in raw materials and operating conditions, resulting in unstable product specific surface area and poor mixing effect.

[0006] To achieve the above objectives, the present invention provides a method for preparing highly active calcium hydroxide, applicable to a preparation system including a vertical premixer. The vertical premixer is equipped with independently driven first and second stirring tools, and a discharge device with an adjustable opening at the bottom. The method is executed by a central control unit and includes the following steps: S1, Parameter Initialization: Receives preset homogenization control parameters σ and target exhaust temperature range [T]. min ,T max And the standard charge quantity M0; S2. Dynamic monitoring: Real-time acquisition of the instantaneous loading mass M(t) in the mixing drum and the real-time temperature T(t) at the exhaust port; S3. Rotation speed calculation based on constant shear energy consumption: When a deviation is detected between the instantaneous loading mass M(t) and the reference loading mass M0, or when the loading state changes due to the adjustment in step S4, the control unit is triggered to update the first rotation speed n1 of the first stirring tool and the second rotation speed n2 of the second stirring tool according to the current M(t) through a preset shear rheological coupling model. The shear rheological coupling model is configured to establish a nonlinear mapping relationship between the rotation speed and the instantaneous loading mass, so that the rotation speed increases nonlinearly with the increase of the instantaneous loading mass according to a predetermined rheological index, so as to maintain a constant shear power density obtained per unit mass of material. S4, Temperature-Mass-Speed ​​Cascade Regulation: When the real-time temperature T(t) exceeds the target range [T min ,T max When the temperature deviation value ΔT is reached, the cascade control action is executed: First, the corrected opening degree α' of the unloading device is calculated based on the temperature deviation value ΔT and the action is executed. The change in the physical unloading rate forces the instantaneous loading mass M(t) in the cylinder to drift. Then, the updated M(t) is substituted into the model described in step S3 as the only mass input variable, and new speed commands n1 and n2 are automatically generated and driven to execute the motor. The cascade adjustment forms a closed loop until T(t) returns to the target range and M(t) reaches dynamic equilibrium.

[0007] Furthermore, the specific mathematical expression of the pre-set shear rheological coupling model in step S3 is as follows:

[0008]

[0009] Where: n1 and n2 are the rotational speeds of the first and second stirring tools, respectively; M(t) is the instantaneous loading mass in the mixing drum; r1 and r2 are the rotational radii of the two sets of stirring tools, respectively; ρ is the material density; A1 and A2 are constant factors determined based on the geometric characteristics of the equipment; k1 and g1 are material rheological indices; Φ1 and Φ2 are the basic rotational speed compensation terms.

[0010] Furthermore, the material rheological index k1 corresponding to the first stirring tool and the material rheological index g1 corresponding to the second stirring tool have different values, and k1>g1; the model configures different rheological indices so that the first stirring tool is more sensitive to the rotational speed response of the change in the amount of material than the second stirring tool, thereby prioritizing the shearing and dispersing ability of the first stirring tool when the load fluctuates.

[0011] Furthermore, the specific cascaded adjustment logic in step S4 is as follows: when T(t) > T maxIf the reaction is deemed too vigorous or the residence time too long, the control system increases the correction opening α' of the unloading device, resulting in a decrease in the instantaneous loading mass M(t). The rotational speeds n1 and n2, calculated based on the model, subsequently decrease to reduce the mechanical heat input per unit time. When T(t)... <T min When the reaction is delayed, the control system reduces the correction opening α' of the unloading device, which causes the instantaneous loading mass M(t) to increase. The rotational speeds n1 and n2 calculated according to the model are then increased to enhance shearing and replenish mechanical heat energy.

[0012] Furthermore, it also includes a process water addition control step: the preparation system is equipped with a liquid inlet pipe for dripping liquid into the mixing cylinder; the control unit calculates the instantaneous change rate of the feeding mass dM(t) / dt in real time, and adjusts the flow rate of the liquid inlet pipe proportionally according to the change rate to ensure that the water-cement ratio remains constant during dynamic feeding.

[0013] Furthermore, the basic speed compensation terms Φ1 and Φ2 are dynamic variables, and their values ​​are related to the revolution speed N of the mixing drum. drum There is a negative correlation; when the revolution speed N of the mixing drum is... drum When changes occur, the control unit automatically adjusts Φ1 and Φ2 to maintain a constant absolute linear velocity of the mixing tool relative to the material.

[0014] This invention also provides a control system for the preparation of highly active calcium hydroxide. The system includes: a premixing execution unit comprising a vertical premixer body, a first variable frequency motor independently driving a first stirring tool, a second variable frequency motor independently driving a second stirring tool, and an electric actuator for driving the opening and closing of a bottom unloading device; a data acquisition unit comprising a weighing sensor located at the bottom of the vertical premixer for acquiring the instantaneous loading mass M(t); and a temperature sensor located at the exhaust port for acquiring the real-time temperature T(t); and a central control unit electrically connected to the premixing execution unit and the data acquisition unit; the central control unit has a built-in memory and a processor, the memory storing a computer program, and the processor executing the computer program to implement the above-described method steps.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention achieves quantitative control of premixed energy input by establishing a speed control mechanism based on a shear rheology coupling model. The system can nonlinearly adjust the stirring speed according to a predetermined rheological index based on the instantaneous change in the feed mass M(t), thereby maintaining the shear power density (P) per unit mass of material under fluctuating load conditions. density The shearing is constant. This control method effectively avoids excessive shearing at low loads (leading to overheating) and insufficient shearing at high loads (leading to uneven mixing), providing a stable kinetic basis for the product to obtain a high specific surface area.

[0016] 2. This invention achieves effective decoupling of thermodynamic and kinetic control by employing a cascaded adjustment strategy of temperature-mass-speed. When the exhaust temperature T(t) is abnormal, the system does not directly adjust the speed, but instead prioritizes adjusting the discharge opening to change the material residence time. The resulting physical drift in the charge mass M(t) then triggers adaptive speed adjustment. This indirect control logic avoids system oscillations that may be caused by single-variable adjustment. While ensuring controlled reaction temperature, it automatically matches the optimal stirring intensity required for the current material quantity, improving the system's response speed and stability.

[0017] 3. This invention achieves differentiated mixing functional zones by configuring different material rheological indices (k1>g1) for the first and second mixing tools. When the charge amount changes by the same magnitude, the rotational speed of the first mixing tool is more sensitive, prioritizing rapid shearing and dispersion of the newly added material; while the rotational speed of the second mixing tool changes relatively gradually, focusing on homogenizing the overall flow field. This differentiated control strategy optimizes energy distribution and improves overall mixing efficiency.

[0018] 4. This invention achieves predictive compensation for feed fluctuations by introducing water control logic based on the instantaneous feed mass change rate (dM(t) / dt). Compared to water distribution based solely on static weight, this method can sensitively capture transient changes in feed rate and synchronously adjust the water injection volume, ensuring that the water-cement ratio remains constant throughout the dynamic process in the initial stage of the reaction, thereby reducing clumping caused by localized water shortages or excesses from the source. Attached Figure Description

[0019] Figure 1 This is a block diagram illustrating the overall structural principle of the adaptive control system for the preparation of highly active calcium hydroxide provided in this embodiment of the invention. Figure 2 This is the main flowchart of the adaptive control method for preparing highly active calcium hydroxide provided in the embodiments of the present invention; Figure 3 This is a schematic diagram of the temperature-mass-speed cascade control logic and thermo-mechanical decoupling principle described in step S4 of this embodiment of the invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] This embodiment provides a method and control system for preparing highly active calcium hydroxide. The system's physical architecture includes a premixing execution unit, a data acquisition unit, and a central control unit.

[0022] The main body of the premixing execution unit is a vertical premixer, such as... Figure 1 The hardware system of the premixer is shown in the figure. This vertical premixer uses a mixing drum as its core container, with an inlet at the top for connecting to external material conveying equipment (for adding quicklime, water, and additives). Inside the mixing drum, two independently driven stirring shafts are eccentrically mounted and rotate. Figure 1 The first and second mixing tools are shown. These two sets of mixing tools are symmetrically arranged, and each has multiple sets of hammer blades spaced axially on its shaft. The hammer blades have a trapezoidal rod-like structure, and one of their length sides is designed as an inclined surface to reduce resistance when cutting into the material and enhance the turning effect.

[0023] In terms of the power system, the first and second stirring tools are driven by independent first and second variable frequency motors, respectively, capable of rotating in opposite directions at high speeds of 200-500 r / min. Simultaneously, the mixing drum itself is driven by an independent drive mechanism, capable of revolving at a low speed of 6-10 r / min, thus forming a complex mixing flow field with superimposed revolution and rotation between the two sets of stirring tools. The bottom of the mixing drum is equipped with a discharge device for discharging materials (such as...). Figure 1 As shown, the unloading device adopts an adjustable electric valve structure, and its opening α is linearly driven by an electric actuator to precisely control the outflow cross-sectional area of ​​the material.

[0024] The data acquisition unit mainly includes load cells and temperature sensors (such as...). Figure 1 (As shown). The weighing sensor is located on the support of the vertical premixer to collect the overall weight of the equipment in real time, and the instantaneous charge mass M(t) in the mixing drum is calculated by tare. The temperature sensor is located at the exhaust port of the premixer to monitor the temperature T(t) of the steam generated during the reaction process in real time. All the above sensors and the actuator motor are electrically connected to the central control unit (MCU).

[0025] Based on the above system, the specific process of the high-activity calcium hydroxide preparation method in this embodiment is as follows (see Figure 2 ): First, parameter initialization is performed (step S1). The operator or host computer system inputs the preset process values ​​to the central control unit: The homogenization control parameter σ is set to 1.0, reflecting the activity level of the current quicklime raw material and the required mixing intensity; the baseline loading amount M0 is set to 800 kg, which is the ideal material holding capacity for maintaining the optimal gas-solid contact ratio under full-load conditions for this type of premixer; the target exhaust temperature range is set to [85℃, 95℃] (i.e., [T...). min ,T max This temperature range corresponds to the optimal thermodynamic window for the quicklime digestion reaction to produce calcium hydroxide with a high specific surface area.

[0026] After system startup, the system enters the dynamic monitoring and feed control stage (step S2). Quicklime raw materials are continuously fed into the mixing drum via a conveyor belt and feed inlet. The central control unit reads data from the weighing sensor at a sampling period of 10-50ms to obtain the instantaneous feed mass M(t), and simultaneously calculates the rate of change of the feed mass over time, dM(t) / dt, using a differential algorithm. When the feed is detected to cause dM(t) / dt to become positive and increase, the control unit sends a command to the liquid pump connected to the inlet pipe to proportionally increase the injection flow rate of the digesting water or additives; conversely, it decreases the flow rate. This dynamic follow-up water distribution mechanism based on the rate of change of mass eliminates the time lag of traditional static batching, ensuring that each batch of quicklime receives an accurate stoichiometric water ratio instantly, maintaining a constant water-cement ratio.

[0027] During the material mixing and digestion reaction, the central control unit continuously performs rotational speed calculations based on constant shear energy consumption (step S3). The system has a pre-set shear rheological coupling model, which establishes a nonlinear mapping relationship between the stirring speed and the instantaneous loading mass M(t). Specifically, the rotational speed n1 of the first variable frequency motor driving the first stirring tool, and the rotational speed n2 of the second variable frequency motor driving the second stirring tool, are updated in real time according to the following logic: n1∝M(t)^k1 n2∝M(t)^g1 In this embodiment, the material rheological index k1 corresponding to the first stirring tool is set to 0.7, and the material rheological index g1 corresponding to the second stirring tool is set to 0.4. Since k1 > g1, when the instantaneous charge mass M(t) fluctuates, the rotational speed response sensitivity of the first stirring tool is significantly higher than that of the second stirring tool. For example, when the charge amount increases, the first stirring tool rapidly accelerates, using high-speed rotating hammer blades to forcefully crush and shear the incremental material; while the second stirring tool accelerates gently, mainly responsible for the overall material circulation and homogenization. Furthermore, the model also includes the revolution speed N relative to the mixing drum. drum Related compensation items. When the revolution speed of the mixing drum is adjusted, the control unit automatically corrects the base values ​​of n1 and n2 to maintain a constant absolute linear velocity of the hammer blades relative to the material, thereby maintaining the shear power density (P) obtained per unit mass of material. density The mixing should be constant to prevent over- or under-mixing due to load changes.

[0028] Throughout the entire operating cycle, the system executes a cascaded regulation strategy of temperature-mass-speed in parallel (step S4 and...). Figure 3 To cope with fluctuations in reaction heat.

[0029] When the exhaust temperature T(t) is monitored to exceed 95℃ (T maxWhen the reaction is too vigorous or the material stays in the machine for too long, leading to heat accumulation, it may cause the product to overheat. At this time, the central control unit executes the first-level adjustment: instructing the unloading device to increase the opening, and correcting the opening α' to increase. The increased flow area of ​​the unloading port makes the material outflow rate faster, causing the instantaneous loading mass M(t) in the mixing drum to begin to decrease (i.e., mass drift occurs, for example, from 800kg to 750kg). Immediately afterwards, the system executes the second-level response: the updated M(t) (750kg) is substituted as the sole variable into the shear rheological coupling model in step S3. As the input variable M(t) decreases, the rotational speeds n1 and n2 calculated by the model automatically decrease nonlinearly. The decrease in rotational speed directly reduces the input of mechanical frictional heat, and the smaller material layer thickness also facilitates heat dissipation, thereby causing the temperature T(t) to fall back to the target range.

[0030] Conversely, when the exhaust temperature T(t) is monitored to be below 85℃ (T min When the reaction temperature is sluggish or insufficient heat generation, the central control unit performs a reverse cascade operation: reducing the opening α' of the unloading device. The obstruction of material outflow leads to a prolonged residence time in the mixing drum, causing the instantaneous loading mass M(t) to gradually increase (e.g., from 800 kg to 850 kg). Substituting the increased M(t) into the model triggers the control unit to calculate higher rotational speeds n1 and n2. The increased speed enhances the stripping effect of the hammer blades on the quicklime, exposing new reaction interfaces and replenishing more mechanical shear heat, thereby causing the reaction temperature T(t) to rise again.

[0031] Through the above embodiments, the present invention utilizes the charge mass M(t) as a physical bridge connecting the thermodynamic process and the kinetic process, and realizes adaptive closed-loop control of the digestion reaction environment without directly relying on temperature to adjust the rotation speed, and finally prepares a calcium hydroxide product with stable specific surface area and uniform activity.

[0032] This specific embodiment is merely an explanation of the present invention and is not intended to limit the invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for producing a highly active calcium hydroxide, characterized by, The application is applied to a preparation system comprising a vertical premixer, wherein a first stirring tool and a second stirring tool are independently driven, and a discharge device with adjustable opening degree is arranged at the bottom; the method is executed by a central control unit, and comprises the following steps: S1, parameter initialization: receiving preset homogenization control parameter σ, target exhaust temperature range [T min ,T max and reference charge amount M0; S2, dynamic monitoring: real-time acquisition of the instantaneous charging mass M(t) in the mixing cylinder and the real-time temperature T(t) of the exhaust port; S3, rotational speed calculation based on constant shear energy consumption: when it is monitored that the instantaneous charging mass M(t) deviates from the reference charging mass M0, or the charging state changes due to the adjustment of step S4, the control unit triggers to update the first rotational speed n1 of the first stirring tool and the second rotational speed n2 of the second stirring tool according to the current M(t) through a preset shear rheological coupling model; the shear rheological coupling model is configured to establish a nonlinear mapping relationship between the rotational speed and the instantaneous charging mass, so that the rotational speed is nonlinearly increased according to a predetermined rheological index with the increase of the instantaneous charging mass, so as to maintain the shear power density obtained by unit mass material constant; S4, Temperature-Mass-Speed Cascade Regulation: When the real-time temperature T(t) exceeds the target interval [T min ,T max ], the cascade control action is executed: first, the modified opening degree a' of the discharge device is calculated according to the temperature deviation ΔT, and the action is executed, and the instantaneous charge mass M(t) in the cylinder is forced to drift by changing the physical discharge rate; then the updated M(t) is substituted into the model described in step S3 as the only mass input variable, and the new speed instructions n1, n2 are automatically generated and drive the motor to execute; the cascade regulation constitutes a closed loop until T(t) returns to the target interval and M(t) reaches dynamic equilibrium.

2. The method for preparing highly active calcium hydroxide according to claim 1, characterized in that, The specific mathematical expression of the preset shear rheological coupling model in the step S3 is: ； ； Wherein: n1 and n2 are the rotational speeds of the first and second stirring tools respectively; M(t) is the instantaneous charging mass in the mixing cylinder; r1 and r2 are the rotational radii of the two groups of stirring tools respectively; p is the material density; A1 and A2 are constant factors determined based on the geometric characteristics of the equipment; k1 and g1 are the material rheological indexes; and Φ1 and Φ2 are the basic rotational speed compensation terms.

3. The method for preparing highly active calcium hydroxide according to claim 2, characterized in that, The material rheological index k1 corresponding to the first stirring tool and the material rheological index g1 corresponding to the second stirring tool have different values, and k1>g1; the model is configured by different rheological indexes, so that the rotational speed response sensitivity of the first stirring tool to the charging amount change is higher than that of the second stirring tool, thereby preferentially ensuring the shear dispersion capacity of the first stirring tool when the load fluctuates.

4. The method for preparing highly active calcium hydroxide according to claim 1, characterized in that, The specific cascade regulation logic in step S4 is: when T(t) > T max , it is determined that the reaction is too violent or the residence time is too long, the control system increases the correction opening α' of the discharge device, which leads to the decrease of the instantaneous charging mass M(t), and the rotational speed n1, n2 calculated according to the model is reduced, so as to reduce the mechanical heat input per unit time; when T(t) < T min , it is determined that the reaction is lagging, the control system reduces the correction opening α' of the discharge device, which leads to the increase of the instantaneous charging mass M(t), and the rotational speed n1, n2 calculated according to the model is increased, so as to strengthen the shear and supplement the mechanical heat energy.

5. The method for preparing highly active calcium hydroxide according to claim 1, characterized in that, Further comprising a process water addition control step: the preparation system is provided with a liquid inlet pipe for adding liquid into the mixing cylinder; the control unit calculates the change rate dM(t) / dt of the instantaneous charging mass in real time, and adjusts the flow rate of the liquid inlet pipe in direct proportion according to the change rate, so as to ensure that the water-cement ratio is maintained constant during the dynamic feeding process.

6. The method for preparing highly active calcium hydroxide according to claim 2, characterized in that, The base rotation speed compensation terms Φ1, Φ2 are dynamic variables, whose values are related to the revolution rotation speed N of the mixing drum drum of the mixing drum, the control unit automatically adjusts Φ1, Φ2 to keep the absolute linear speed of the stirring tool relative to the material constant. drum of the mixing drum, the control unit automatically adjusts Φ1, Φ2 to keep the absolute linear speed of the stirring tool relative to the material constant.

7. A high-activity calcium hydroxide production control system, characterized by, It comprises: a premixing execution unit, which comprises a vertical premixer body, a first variable frequency motor for independently driving a first stirring tool, a second variable frequency motor for independently driving a second stirring tool, and an electric actuating mechanism for driving the opening and closing of the discharge device at the bottom; a data acquisition unit, which comprises a weighing sensor arranged at the bottom of the vertical premixer and used for acquiring the instantaneous charging mass M(t); and a temperature sensor arranged at the exhaust port and used for acquiring the real-time temperature T(t); a central control unit, which is electrically connected with the premixing execution unit and the data acquisition unit; the central control unit is internally provided with a memory and a processor, the memory stores a computer program, and the processor realizes the method steps of any one of claims 1 to 6 when executing the computer program.

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