A three-stage quicklime continuous digestion production device based on reaction progress regulation

Abstract

This utility model discloses a three-stage continuous quicklime digestion production device based on reaction process control, comprising a pretreatment system, a digestion system, a control system, a collection system, and a drying system connected in sequence. The digestion system includes a primary digestion unit, a secondary digestion unit, and a tertiary digestion unit connected in series, corresponding to the initiation and acceleration period, the high-speed reaction period, the final reaction period, and the product stabilization period of the digestion reaction, respectively. The primary digestion unit is equipped with a quicklime inlet and a spray device with controllable water volume at the top, and is equipped with a humidity sensor, a stirring device, and a screw propeller inside, for achieving rapid mixing of quicklime and water and outputting a slurry mixture. The secondary digestion unit is a vertical tower structure with a height-to-diameter ratio greater than 3, and is equipped with a temperature sensor, a steam outlet, a stirring device, and a screw propeller inside, for extending the material residence time and promoting the agitation of the paste-like material. The tertiary digestion unit is equipped with a stirring device inside, for promoting the stable growth of calcium hydroxide crystals and converting the material from a paste state to a dry powder state. The primary, secondary, and tertiary digestion units are continuously conveyed through a screw propeller, and the control system dynamically adjusts the spray water volume, stirring rate, and material conveying speed based on feedback from the sensors of each unit.

Description

Technical Field

[0001] This utility model relates to the technical field of lime deep processing equipment, specifically to a continuous digestion system for converting quicklime (CaO) into hydrated lime (Ca(OH)2) through hydration reaction, and in particular to a three-stage series quicklime digestion production process based on the hierarchical structure and synergistic regulation of the physical state evolution of the chemical reaction process. Background Technology

[0002] The slaking process, in which quicklime (CaO) reacts with water to produce hydrated lime, is a core step in the building materials, chemical, and environmental protection industries. Currently, the industry primarily uses single-stage or multi-stage slaking equipment. Quicklime slaking is a complex, multi-stage exothermic process accompanied by significant phase changes: from an initial slurry state to a rapidly reacting paste state, and finally to a stable dry powder state. Existing single-stage or simple multi-stage slaking equipment fails to establish an effective correlation between the "reaction process - physical state - equipment structure - control strategy." It does not optimize the structure and control strategy based on the evolution of the physical states from slurry to paste to dry powder during quicklime slaking, leading to uncontrolled reaction processes, frequent local overheating, or agglomeration. This severely affects the desulfurization activity of calcium hydroxide and the continuity and stability of its industrial applications. The main problems are as follows:

[0003] Uneven reaction: The amount of water added during primary digestion is not matched with the stirring intensity, resulting in localized over-wetting and clumping or failure to start the reaction.

[0004] Uncontrolled process: The heat and steam generated during the high-speed reaction period cannot be effectively discharged, resulting in large fluctuations in pressure and temperature inside the equipment, and the reaction process becomes uncontrollable.

[0005] Low product activity: The unstable crystal growth environment at the end of the reaction leads to uneven particle size and small specific surface area of ​​calcium hydroxide crystals, resulting in poor desulfurization activity.

[0006] Obstacles to continuous operation: Material conveying between stages relies on experience, which can easily cause blockages or flow interruptions, making it impossible to achieve truly stable continuous production.

[0007] Current industry improvement solutions mostly focus on solving single technical problems, such as increasing stirring power to improve mixing efficiency and controlling water addition to prevent equipment malfunctions. However, none of them establish a correlation between the quicklime digestion state and the digestion structure design. This makes it difficult for existing production processes to simultaneously consider conversion rate, product stability, and continuous operation efficiency when processing different batches of quicklime, failing to meet the "high quality and high activity" requirements for calcium hydroxide in environmental protection, fine chemical, and other fields. Therefore, developing a digestion production device that can dynamically adjust its structure and operating parameters according to the reaction process is key to achieving the continuous production of high-quality, high-activity calcium hydroxide. Utility Model Content

[0008] The purpose of this invention is to overcome the problems of uncontrolled reaction process and unstable operation in existing equipment, and to provide a continuous digestion production process with three-level functional differentiation, dedicated structural adaptation, and process control based on state perception. This invention provides a three-level quicklime digestion system, including a quicklime pretreatment system for crushing, grading, and quantitatively conveying quicklime; a digestion system comprising a primary digestion unit, a secondary digestion unit, and a tertiary digestion unit arranged in series, corresponding to the initiation and acceleration phase, the high-speed reaction phase, the final reaction phase, and the product stabilization phase of the digestion reaction, respectively; a control system connected to each of the three digestion units for real-time adjustment of water volume, temperature, and material conveying rate according to the reaction state at each stage; a collection system and a drying system; and all systems are connected in series.

[0009] The primary digestion unit includes a primary digester (22), which has a quicklime inlet (21) and a water-controllable spray device (18) at the top. It is equipped with a humidity sensor (23), a stirring device (27) and a screw propeller (29) inside to achieve rapid mixing of quicklime and water and prevent caking, and output a slurry mixture. The spray device (18) of the primary digestion unit is connected to the control system, and the water addition rate is controlled in a closed loop according to the activity of each batch of quicklime and the temperature feedback in the primary digester.

[0010] A screw propeller (29) is provided between the primary digestion unit and the secondary digestion unit. When the proportion of particles with a diameter > 5 mm in the primary digester is ≤ 10% and the reaction temperature is stable at 70-80℃, the control system controls the screw propeller to push the slurry material to the secondary digestion unit at a set speed.

[0011] The secondary digestion unit includes a secondary digester (31), which is a vertical tower structure with a height-to-diameter ratio greater than 3. It is equipped with a temperature sensor (32) and a steam exhaust port (26) inside, as well as a stirring device and a screw propeller, which are used to extend the material residence time, enhance heat and mass transfer, and promote the turning of the paste material. The secondary digestion unit is equipped with a humidity sensor or a torque detection device to monitor the material status in real time. When the material viscosity is detected to reach a set threshold, it is determined to be in a paste state. The control system controls the screw propeller (29) inside to push the paste material to the tertiary digestion unit at a set speed.

[0012] The three-stage digestion unit includes a three-stage digester (33) with an internal stirring device to promote the stable growth of calcium hydroxide crystals, prevent caking, and use the residual heat of the reaction to change the material from a paste to a dry powder state; the stirring device of the three-stage digestion unit rotates at 5-20 rpm, which is intended to gently turn the material to avoid damage to the crystal structure, while promoting uniform evaporation of moisture.

[0013] The primary, secondary, and tertiary digestion units are connected by a screw propeller to achieve continuous material transport. The control system dynamically adjusts the spray water volume, stirring rate, and material transport speed based on feedback from sensors installed in each digestion unit.

[0014] The drying system is a tubular drum drying system (15), whose inlet is connected to the discharge port (34) of the three-stage digestion unit; when the moisture content of the material is detected to be <5%, the drying system automatically discharges the material to the sorting device (16).

[0015] The control system is an automatic control system based on PLC or DCS, which integrates temperature, humidity, torque and speed sensors to realize intelligent linkage and control of the entire process of quicklime from pretreatment to drying.

[0016] The core concept of this utility model is to deconstruct the digestion process of quicklime into three distinct stages, and to "tailor-make" the core structure and control logic for each stage, thereby achieving precise, efficient and stable control of the entire reaction process.

[0017] This invention divides the quicklime digestion process into three stages and designs a specific structure and control strategy for each stage based on its reaction characteristics: Primary digestion unit: The focus is on rapid mixing and reaction initiation, achieving "slurry" transformation through high-speed stirring and controlled spraying; Secondary digestion unit: The focus is on deep reaction and heat management, achieving "paste" transformation through a vertical tower structure and temperature monitoring; The three-stage digestion unit focuses on crystal growth and product stabilization, achieving the "dry powder" transformation through low-speed stirring and heat preservation design.

[0018] The control system of this invention acts as an intelligent brain, accurately judging the reaction progress and the physical state of the materials by real-time monitoring of key physical parameters (temperature, particle size, torque) in each digestion unit, and automatically executing corresponding operations (such as material pushing and adjusting water volume). This closed-loop control of "perception-decision-execution" ensures that the entire digestion process proceeds along the preset optimal path, thereby achieving high efficiency, high quality, and continuous stable operation.

[0019] By adopting the solution provided by this utility model, the digestion state of quicklime can be effectively correlated and regulated, thereby achieving dynamic regulation of the quicklime digestion process.

[0020] By adopting the solution provided by this utility model, the following substantial improvements can be achieved: Significantly improved conversion rate: Through three-stage deep reaction, quicklime is completely digested, and the residue rate can be reduced to below 2%.

[0021] The product exhibits excellent activity: a stable crystal growth environment allows for the production of calcium hydroxide with a high specific surface area, resulting in a desulfurization activity increase of over 30%.

[0022] Continuous and stable operation: The state-aware material conveying control effectively prevents material blockage and flow interruption, and significantly extends the continuous operation time of the system.

[0023] Reduced energy consumption: The vertical tower-type secondary digester utilizes gravity-driven natural settling to extend the residence time, while the tubular dryer utilizes waste heat from the reaction, resulting in a reduction in overall energy consumption. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0025] Figure 1 This is a flowchart illustrating the operation of a quicklime digestion process as described in this utility model; Figure 2 This is a cross-sectional view of a three-stage digester according to the present invention; Figure 3 This is a side view of a three-stage digester according to the present invention; Figure 4 This is a control logic diagram based on the reaction process of a three-stage digester as described in this utility model.

[0026] The annotations in the attached figures are explained as follows: 1. Quicklime feed hopper; 2. Ball mill; 3. High-efficiency classifier; 4. Elevator; 5. Quicklime silo; 6. Feeding fan; 7. Belt scale; 8. Sampling port; 9. Variable frequency fan; 10. Primary digestion unit; 11. Secondary digestion unit; 12. Tertiary digestion unit; 13. Elevator; 14. Dust collector; 15. Rotary drum dryer; 16. Sorting device; 17. Calcium powder silo; 18. Spraying device; 19. Water tank; 20. Fan; 21. Quicklime feed inlet; 22. Primary digester; 23. Humidity sensor; 24. Torque sensor interface; 25. Torque detection device; 26. Steam exhaust port; 27. Spiral agitator; 28. Gearbox; 29. ​​Spiral propeller; 30. Bevel gear; 31. Secondary digester; 32. Temperature sensor; 33. Tertiary digester; 34. Discharge port Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0028] Example

[0029] like Figure 1-3 As shown, this utility model provides a three-stage continuous quicklime digestion production process based on reaction process control. Figure 1 The quicklime raw material is selected from 0-50mm lumpy quicklime and stored in the raw material silo (5). The digestion water is fed into the first-stage digester (22) along with the quicklime through the spray device (18) at a set rate. The agitator in the first-stage digester is started, and the water inlet of the first-stage digester is opened at the same time to premix the fines with water into a slurry. At this time, the material is pushed into the second-stage digester (31) at a certain rate. In the second-stage digester, when the material in the second-stage digester is in the form of paste, the material is pushed into the third-stage digestion unit. The material enters the third-stage digester (33) and is stirred at low speed to promote the stable growth of calcium hydroxide crystals. The quicklime continues to release heat. At this time, the state of the material changes from paste to dry powder. The digestion is completed. The dry powder material is fed into the drum tube dryer (15) for drying. When the moisture content of the material drops to below 5%, the drying is completed. The stabilized material is sent to the finished product silo after sorting.

[0030] Working principle: In the primary digester, quicklime powder and water are added quantitatively at a set rate to ensure wetting without triggering a violent reaction, resulting in a slurry mixture as the output. In the secondary digester, during the high-speed reaction period, the deep hydration reaction of CaO particles proceeds vigorously. Unreacted CaO continues to convert to Ca(OH)2, resulting in a paste-like mixture as the output. In the tertiary digester, during the final stage of the reaction and the product stabilization period, due to the continuous exothermic reaction of quicklime, the paste-like state transforms into a dry powder. Finally, the dry powder is further dried in a drum dryer to reduce the moisture content to 5%.

[0031] Example

[0032] After pretreatment, the quicklime raw material enters the primary digester (22). The control system sets the initial water addition based on the activity of the quicklime and makes real-time fine adjustments based on the feedback from the temperature sensor to ensure the formation of a fluid slurry mixture. When the system detects that the particle size and temperature meet the following conditions: the proportion of particles with a particle size > 5 mm in the primary digester is ≤ 10%, and the reaction temperature is stable at 70-80℃, the material is pushed to the secondary digester (31).

[0033] In the secondary digester (31), the vertical tower structure and high-to-diameter ratio design provide sufficient reaction and maturation time for the paste material. The stirring device (27) and the steam exhaust port (26) ensure timely dissipation of reaction heat and steam. When the torque sensor detects that the stirring resistance (i.e., the material viscosity) reaches the set threshold, it is determined that the paste material has matured and is then pushed to the tertiary digester (33).

[0034] The low-speed stirring within the three-stage digester (33) provides a mild environment for the final growth of calcium hydroxide crystals, utilizing the residual heat of reaction to transform the material into a dry powder state. The final product is further processed by the drying system (15) to obtain high-quality hydrated lime powder with a moisture content of <5%.

[0035] Comparison of experimental data: In a pilot application at a steel plant, the production process described in this invention and the traditional single-stage digestion process were used to process the same batch of quicklime (CaO content 92%). The results are compared in Table 1: Table 1: Comparison of performance indicators between the production process of this utility model and the traditional single-stage digestion process Average digestion time 45 minutes 25 minutes shortened by approximately 44% Undigested residue rate 8% 1.5% Reduced by 81% Product BET specific surface area 15 m² / g 22 m² / g An increase of approximately 47% Continuous stable running time 48 hours >120 hours Increase by 150%

[0036] In one specific embodiment of this utility model, the spray device (18) of the primary digestion unit is connected to the control system. The control system adjusts the water addition rate of the spray device in a closed loop according to the activity of each batch of quicklime and the real-time temperature fed back by the temperature sensor (32) in the primary digester.

[0037] The screw propeller (29) between the primary digestion unit and the secondary digestion unit operates under the control of the control system. When the particle size of the material in the primary digester meets the requirement that the proportion of particles with a particle size > 5 mm is ≤ 10% and the reaction temperature is stable at 70-80℃, the control system controls the screw propeller to push the slurry material to the secondary digestion unit at a set speed.

[0038] The secondary digestion unit is equipped with a humidity sensor or torque detection device (25) to monitor the material status in real time. When the material viscosity is detected to reach the set threshold, the control system determines that the material is in a paste state and controls the internal spiral propeller to push the paste material to the tertiary digestion unit at a set speed.

[0039] The stirring device of the three-stage digestion unit is set to a speed of 5-20 rpm to gently turn the material to avoid damaging the crystal structure, while promoting uniform evaporation of moisture.

[0040] The drying system is a tubular drum drying system (15), whose inlet is connected to the discharge port (34) of the three-stage digestion unit, and is equipped with a moisture content detection device. When the moisture content of the material is detected to be <5%, the drying system automatically discharges the material to the sorting device (16).

[0041] Finally, it should be noted that the above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A three-stage continuous quicklime digestion production device based on reaction process control, characterized in that, include: Quicklime pretreatment system: used for crushing, grading and quantitative conveying of quicklime; Digestive system: includes primary digestive units, secondary digestive units and tertiary digestive units arranged in series, corresponding to the initiation and acceleration phase, high-speed reaction phase, end phase and product stabilization phase of the digestion reaction, respectively; Control system: used to dynamically adjust the spray water volume, stirring rate and material conveying speed based on feedback from sensors installed in each digestion unit; Collection system and drying system; in, The primary digestion unit includes a primary digester (22), which is equipped with a quicklime inlet (21) and a water-controllable spray device (18) at the top. It is equipped with a humidity sensor (23), a stirring device (27) and a screw propeller (29) inside, which are used to achieve rapid mixing of quicklime and water and prevent caking, and output a slurry mixture. The secondary digestion unit includes a secondary digester (31), which is a vertical tower structure with a height-to-diameter ratio greater than 3. It is equipped with a temperature sensor (32) and a steam exhaust port (26) inside, as well as a stirring device and a screw propeller, which are used to extend the material residence time, enhance heat and mass transfer and promote the turning of paste materials. The three-stage digestion unit includes a three-stage digester (33), which is equipped with a stirring device to promote the stable growth of calcium hydroxide crystals, prevent caking, and use the residual heat of the reaction to change the material from a paste to a dry powder state. The primary, secondary, and tertiary digestion units are connected by a screw propeller to achieve continuous material transport. The control system dynamically adjusts the spray water volume, stirring rate, and material transport speed based on feedback from sensors installed in each digestion unit.

2. The production apparatus according to claim 1, characterized in that: The spray device (18) of the primary digestion unit is connected to the control system, which performs closed-loop regulation of the water addition rate based on the activity of each batch of quicklime and the feedback from the temperature sensor in the primary digester.

3. The production apparatus according to claim 1, characterized in that: A screw propeller (29) is provided between the primary digestion unit and the secondary digestion unit. The screw propeller is connected to the control system. When the proportion of particles with a diameter > 5 mm in the primary digester is ≤ 10% and the reaction temperature is stable at 70-80℃, the control system controls the screw propeller to push the slurry material to the secondary digestion unit at a set speed.

4. The production apparatus according to claim 1, characterized in that: The secondary digestion unit is equipped with a humidity sensor or torque detection device (25) for real-time monitoring of the material status; the humidity sensor or torque detection device (25) is connected to the control system; when the material viscosity is detected to reach a set threshold, the control system determines that the material is in a paste state and controls the spiral propeller (29) inside the secondary digestion unit to push the paste material to the tertiary digestion unit at a set speed.

5. The production apparatus according to claim 1, characterized in that: The stirring device of the three-stage digestion unit rotates at 5-20 rpm to gently turn the material to avoid damaging the crystal structure, while promoting uniform evaporation of moisture.

6. The production apparatus according to claim 1, characterized in that: The drying system is a tubular drum drying system (15), whose inlet is connected to the discharge port (34) of the three-stage digestion unit; the drying system is equipped with a moisture content detection device, and when the moisture content of the material is detected to be <5%, the drying system automatically discharges the material to the sorting device (16).

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