Apparatus for preparing gypsum using chemical by-product and control method thereof

Abstract

This invention discloses an apparatus and its control method for preparing gypsum using chemical byproducts, belonging to the field of industrial waste resource utilization technology. The apparatus includes a raw material pretreatment unit, a raw material buffer and reaction unit, a product post-processing unit, and a control unit. The raw material pretreatment unit is equipped with a coarse filtration module and a fine filtration module. The fine filtration module includes at least two sets of switchable filter components, each with a pressure detection element before it. The control unit incorporates inter-group switching control logic based on pressure thresholds. When the pressure reaches the switching preparation threshold, the standby group is pre-pressurized and ready to switch; when the pressure reaches the switching execution threshold, an uninterrupted switching is performed. The control unit also incorporates a master-slave dynamic ratio control algorithm and includes a fault diagnosis self-protection module and a human-machine interface. This invention achieves continuous and stable operation, high product purity, and a high degree of automation, effectively solving the problems of easy clogging of filter devices and inaccurate feeding control in existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of industrial waste resource utilization technology, specifically relating to an apparatus and control method for preparing gypsum using calcium solution, a byproduct of soda ash production, and sodium sulfate, a byproduct of chemical fiber production. Background Technology

[0002] The soda ash and chemical fiber industries are important basic raw material industries for my country's chemical and chemical fiber industries. During soda ash production, the ammonia distillation wastewater produced in the distillation process contains a large amount of calcium chloride; this wastewater is known as calcium chloride wastewater (or simply "calcium solution"). In chemical fiber production, the viscose fiber spinning process generates a large amount of sodium sulfate-containing wastewater (or simply "miracle salt") during fiber forming. Direct discharge of these two byproducts would not only occupy a large amount of land resources but also cause serious pollution to soil and water bodies; therefore, it is necessary to find effective ways to utilize them.

[0003] The double decomposition reaction between calcium chloride in calcium solution and sodium sulfate in Glauber's salt produces calcium sulfate (gypsum) and sodium chloride. The main reaction equation is as follows: This reaction process enables the synergistic treatment of two industrial byproducts, turning waste into treasure. The gypsum produced by the reaction can be widely used in building materials and other fields, yielding significant economic and environmental benefits. Therefore, the technical route for preparing gypsum using calcium solution and sodium sulfate has attracted widespread attention.

[0004] However, the existing technology has the following problems in implementing the above reaction:

[0005] Firstly, both calcium hydroxide solution and sodium sulfate are industrial byproducts containing a large number of suspended particulate impurities. These impurities not only affect the completeness of the reaction but also mix into the final product, resulting in low purity of the gypsum product, making it difficult to meet the requirements for use as a building material.

[0006] Secondly, due to the high impurity content in the raw materials, the filtration device is prone to clogging during the pretreatment filtration stage. Current technologies typically use a single filtration unit; once clogging occurs, the machine needs to be shut down for cleaning or filter replacement, causing production line interruptions and severely impacting production efficiency. Even with a backup filtration unit, current switching methods rely heavily on manual judgment of switching time and manual operation, which can easily lead to problems such as material interruption and pressure fluctuations, making continuous and stable operation difficult.

[0007] Third, there is a lack of precise process control. To ensure the reaction proceeds fully, calcium solution and sodium sulfate need to be added precisely according to the stoichiometric ratio. However, the existing technology lacks precise process control methods, making it difficult to maintain the actual addition ratio stably near the theoretical value, resulting in incomplete reaction, low product yield, and unstable product quality.

[0008] Due to the combined effects of raw material impurities, clogging of filtration devices, and inaccurate feeding control, the prepared gypsum products exhibit significant fluctuations in key indicators such as purity, particle size, and moisture content. This makes it difficult to guarantee product quality and meet the downstream market's requirements for stable gypsum product quality, severely hindering the industrial promotion and application of this technology. Summary of the Invention

[0009] The present invention aims to overcome the shortcomings of the prior art and provides an apparatus and control method for preparing gypsum using chemical by-products, so as to solve the technical problems in the prior art, such as low product purity due to impurities in raw materials, easy clogging of filtration devices leading to production line interruption, and inaccurate feeding ratio and unstable product quality due to lack of precise process control.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an apparatus for preparing gypsum using chemical by-products, comprising:

[0011] The raw material pretreatment unit includes a calcium solution treatment branch and a sodium sulfate treatment branch; both the calcium solution treatment branch and the sodium sulfate treatment branch include a coarse filtration module and a fine filtration module connected sequentially along the material flow direction; the fine filtration module includes at least two sets of switchable filter components, each set of filter components is equipped with an on / off control valve, and a pressure detection element is provided on the main material pipeline before each set of filter components;

[0012] The raw material buffer and reaction unit includes a calcium solution buffer tank, a sodium sulfate buffer tank, and a reactor. The inlets of the calcium solution buffer tank and the sodium sulfate buffer tank are respectively connected to the outlets of the fine filtration modules of the corresponding pretreatment branches. The outlets are respectively connected to the inlet of the reactor through conveying pipelines and metering pumps installed thereon. The calcium solution buffer tank and the sodium sulfate buffer tank are equipped with parameter detection units for detecting liquid level and density, and the conveying pipelines are equipped with parameter detection units for detecting flow rate.

[0013] The product post-processing unit includes a post-reaction buffer tank connected to the reactor outlet, and a solid-liquid separation device, a drying device, a grinding and air-classifying device, and a finished product silo connected in sequence.

[0014] The control unit is electrically connected to the pressure detection element, each of the parameter detection units, each of the on / off control valves, and the metering pump; the control unit has built-in inter-group switching control logic based on pressure thresholds, configured as follows:

[0015] The filtration status of the current working group is determined based on the pressure value collected by the pressure detection element;

[0016] When the pressure value reaches the preset switching preparation threshold, the control standby group enters the pre-pressurization standby state.

[0017] When the pressure value reaches the preset switching execution threshold, the switching between execution groups is uninterrupted, and the material flow is switched from the current work group to the standby group.

[0018] As a limitation of the present invention, the filtration assembly is a bag filter canister, and the filter bag has a precision of 5-20 μm; each bag filter canister adopts a bottom-inlet and top-outlet structure, and each bag filter canister is independently equipped with an inlet valve and an outlet valve as the on / off control valve;

[0019] The coarse filtration module includes at least two sand filter tanks connected in series. The sand filter tanks adopt a top-inlet and bottom-outlet structure, and the filter media is quartz sand with a particle size range of 0.8 to 2.0 mm.

[0020] As a further limitation of the present invention, each of the bag filter tanks is also connected to a backwash water injection pipeline and a compressed air purging pipeline; a water injection valve is provided on the water injection pipeline, and a purging valve is provided on the purging pipeline; a drain valve is provided at the bottom drain port of each of the bag filter tanks.

[0021] The water injection valve, the purge valve, and the drain valve are all electrically connected to the control unit.

[0022] As a further limitation of the present invention, the control unit is a DCS control system; the metering pump is a diaphragm metering pump with a control accuracy of ±1%; the parameter detection unit for detecting liquid level is a radar level gauge with a detection accuracy of ±5mm; the parameter detection unit for detecting density is an online density meter with a detection accuracy of ±0.001g / cm³; and the parameter detection unit for detecting flow rate is an electromagnetic flow meter.

[0023] As another limitation of the present invention, the control unit also has a built-in fault diagnosis self-protection module, which is configured as follows:

[0024] Real-time acquisition of operating status signals, with a fault diagnosis response time of ≤1 second;

[0025] When the parameter detection unit experiences signal interruption, value jump, or over-range fault, it is determined to be an instrument fault. The fault location and fault type are displayed on the human-machine interface, and a local interlock is triggered.

[0026] When the on / off control valve, the metering pump, or the stirring motor of the reactor experiences no feedback, timeout, or abnormal operating parameters, it is determined to be an actuator failure. The upstream and downstream pipeline valves corresponding to the faulty equipment are interlocked and closed, and the name of the faulty equipment and the cause of the failure are displayed on the human-machine interface.

[0027] The control unit also has a redundancy protection function. When the primary module fails, the backup module will switch seamlessly with a switching time of ≤0.1s.

[0028] As a further limitation of the present invention, the human-machine interface of the control unit is divided into a process flow diagram main interface, a parameter monitoring interface, a control operation interface, a fault alarm interface, and a historical data interface; the operation permissions are divided into operator level, engineer level, and administrator level.

[0029] The present invention also discloses a control method for preparing gypsum using the apparatus described above, comprising the following steps:

[0030] S1. Raw material pretreatment: Calcium solution and Glauber's salt are filtered through their respective pretreatment branches to remove impurities;

[0031] S2. Intelligent switching of fine filtration modules: The control unit collects the pressure value at the inlet side of the fine filtration module in each pretreatment branch in real time and divides the pressure into normal zone, warning zone and blockage zone; when the pressure enters the warning zone, the standby group pre-pressurization logic is triggered: the on / off control valve of the standby group is controlled to fill the standby group pipeline with liquid and purge the gas, and enter the pre-pressurization standby state; when the pressure enters the blockage zone, automatic switching is executed: the on / off control valve is controlled to switch the material flow from the current working group to the standby group to maintain the continuous operation of the production line;

[0032] S3. Precise Proportional Feeding: Calcium solution is used as the main material and Glauber's salt as the secondary material. The reaction ratio coefficient K is preset in the control unit. The delivery rate of the calcium solution metering pump is adjusted based on the liquid level measurement value of the calcium solution buffer tank. The volumetric flow rate and density of the calcium solution are collected in real time, and the real-time mass flow rate of the calcium solution is calculated. The target flow rate setting value of Glauber's salt is dynamically calculated through ratio calculation. Based on the target flow rate setting value, the delivery rate of the Glauber's salt metering pump is adjusted in real time so that the two materials enter the reactor in a preset ratio.

[0033] S4. Post-processing of products: The mixture after reaction is subjected to solid-liquid separation, drying, grinding and air classification to obtain the finished gypsum product.

[0034] As a limitation of the present invention, in step S2, the blocked group that has been switched off is automatically cleaned by the control unit according to the sequential control logic. The cleaning process includes: depressurization and drainage, backwashing, sewage discharge, and purging in sequence; wherein, backwashing uses clean water at 0.2 to 0.4 MPa, and purging uses dry compressed air at 0.5 to 0.7 MPa.

[0035] As a further limitation of the present invention, in step S2, the specific process of automatic switching is as follows: first, open the on / off control valve on the outlet side of the standby group, and then open the on / off control valve on the inlet side; after the pipeline pressure stabilizes, close the on / off control valve on the inlet side of the original working group, and then close the on / off control valve on the outlet side.

[0036] As another limitation of the present invention, in step S3, the real-time mass flow rate of the calcium solution is determined by the formula... calculate;

[0037] The target flow rate setpoint for Glauber's salt is determined by the formula. Calculate; to As the input setpoint of the loop flow PID controller in the control unit, the real-time mass flow rate of Glauber's salt is determined by the formula... Calculations are made by the PID controller for loop flow based on flow deviation. The speed of the sodium sulfate metering pump is adjusted in real time so that the real-time mass flow rate of sodium sulfate tracks the real-time mass flow rate of calcium solution.

[0038] in, This refers to the real-time mass flow rate of the calcium solution. This is the measured density of the calcium solution; This is the measured value of the calcium liquid volumetric flow rate; Set the target flow rate for Glauber's salt; This refers to the real-time mass flow rate of Glauber's salt. This is the measured density of Glauber's salt; This is the measured value of the volumetric flow rate of Glauber's salt; This is for flow rate deviation.

[0039] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0040] (1) By setting up a coarse filter module and a fine filter module, the present invention forms a two-stage filtration structure, which can effectively remove impurities such as suspended particles in the raw materials. The removal rate of solid impurities with a particle size ≥5μm is ≥99%, ensuring the purity of the raw materials for subsequent reactions. The purity of the resulting gypsum product is ≥95%, which greatly improves the quality of the gypsum product and meets the requirements for use in building materials.

[0041] (2) The fine filtration module of the present invention includes at least two sets of switchable filter components, a pressure detection element on the main material pipeline before the filter components, and a pressure threshold-based inter-group switching control logic built into the control unit. When the pressure value reaches the preset switching preparation threshold, the standby group is controlled to enter the pre-pressurization standby state; when the pressure value reaches the preset switching execution threshold, the inter-group switching is performed without interruption, and the material is switched from the current working group to the standby group. This process does not require manual intervention, and there is no interruption of material or pressure fluctuation during the switching process, which effectively solves the problem of production line shutdown caused by filter blockage, realizes continuous and stable operation of the device, and greatly improves production efficiency. At the same time, the blocked group that is switched off can be automatically cleaned by the control unit, further reducing labor intensity.

[0042] (3) This invention achieves master-slave dynamic ratio control through a control unit: using calcium solution as the main material, the calcium solution metering pump delivery rate is adjusted based on the liquid level measurement value; the volumetric flow rate and density of the calcium solution are collected in real time, and the real-time mass flow rate of the calcium solution is calculated; the target flow rate set value of sodium sulfate is dynamically calculated, and the delivery rate of the sodium sulfate metering pump is adjusted in real time, so that the two materials are precisely fed into the reactor according to the preset stoichiometric ratio. This control method eliminates the influence of raw material density fluctuations on the feeding accuracy, and the feeding control accuracy can reach ±1%, thereby significantly optimizing the reaction efficiency and the yield of the target product.

[0043] (4) This invention achieves full-process status monitoring, fault self-diagnosis, and interlock protection, with a high degree of automation. Specifically, the control unit of this invention has a built-in fault diagnosis and self-protection module, which can collect the operating status signals of each detection element and actuator in real time. When signal interruption, value jump, over-range, no feedback of action, action timeout, or abnormal operating parameters occur, the fault type is automatically determined and displayed on the human-machine interface. At the same time, local interlocking or closing of upstream and downstream valves is triggered to ensure production safety. The control unit also has a redundancy protection function. When the main module fails, the backup module switches seamlessly with a switching time of ≤0.1s, ensuring continuous operation of the control system. The human-machine interface is modularly designed with hierarchical operation permissions, which facilitates operation and management by personnel at different levels.

[0044] (5) This invention utilizes calcium solution, a byproduct of soda ash production, and sodium sulfate, a byproduct of chemical fiber production, to prepare gypsum. This achieves the synergistic treatment and resource utilization of the two industrial waste liquids, which not only solves the environmental pollution problem but also produces high-purity building gypsum, resulting in significant economic and social benefits. Attached Figure Description

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0046] Figure 1 This is a diagram illustrating the device structure and process flow of an embodiment of the present invention;

[0047] Figure 2 This is a flowchart illustrating the switching logic of the fine filtration module in an embodiment of the present invention.

[0048] In the diagram: 1. Calcium solution inlet; 2. Glauber's salt inlet; 3. Sand filter tank; 4. Bag filter tank; 5. Inlet valve; 6. Outlet valve; 7. Calcium solution pipeline pressure transmitter; 8. Glauber's salt pipeline pressure transmitter; 9. Group A; 10. Group B; 11. Calcium solution buffer tank; 12. Glauber's salt buffer tank; 13. Reactor; 14. Radar level gauge; 15. Online density meter; 16. Electromagnetic flow meter; 17. Metering pump; 18. Stirring motor; 19. Slurry stirring motor; 20. Post-reaction buffer tank; 21. Slurry pump; 22. Belt filter; 23. Drying oven; 24. Grinding and air separation equipment; 25. Finished product silo. Detailed Implementation

[0049] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustrative and understanding purposes only and are not intended to limit the scope of the invention.

[0050] This embodiment discloses an apparatus for preparing gypsum using chemical byproducts, such as... Figure 1 As shown, the device includes a raw material pretreatment unit, a raw material buffer and reaction unit, a product post-processing unit, and a control unit.

[0051] I. Raw Material Pretreatment Unit

[0052] The raw material pretreatment unit includes a calcium solution treatment branch and a sodium sulfate treatment branch. The two branches have the same structure, both including a coarse filter module and a fine filter module connected sequentially along the material flow direction.

[0053] Taking the calcium solution treatment branch as an example: the calcium solution enters from the calcium solution inlet 1, first passing through the coarse filtration module, and then the coarsely filtered calcium solution enters the fine filtration module. The coarse filtration module includes at least two sand filter tanks 3 connected in series. The sand filter tanks 3 adopt a top-in, bottom-out structure, and the filter media is quartz sand with a particle size range of 0.8–2.0 mm (preferably 1.0–1.8 mm in this embodiment). The fine filtration module includes at least two sets of switchable filter components (Group A 9 and Group B 10), each set of filter components is equipped with an on / off control valve. In this embodiment, the filter components are bag filter tanks 4, and each set (Group A 9 and Group B 10) includes two parallel bag filter tanks 4, with a filter bag precision of 5–20 μm (preferably 10 μm in this embodiment). Each bag filter tank 4 adopts a bottom-in, top-out structure, and each bag filter tank 4 is independently equipped with an inlet valve 5 and an outlet valve 6 as on / off control valves. A pressure detection element (calcium solution pipeline pressure transmitter 7) is installed on the main material pipeline before each set of filter components to monitor the inlet side pressure in real time.

[0054] Each bag filter tank 4 is also connected to a backwash water injection line and a compressed air purging line. The water injection line is equipped with a water injection valve, and the purging line is equipped with a purging valve. Each bag filter tank 4 has a drain valve at its bottom drain port. The aforementioned water injection valve, purging valve, and drain valve are all electrically connected to the control unit for subsequent automatic cleaning.

[0055] The structure of the sodium sulfate treatment branch is the same as above. The sodium sulfate enters from the sodium sulfate inlet 2 and passes through the sodium sulfate sand filter tank 3, the sodium sulfate pipeline pressure transmitter 8, the sodium sulfate A group 9 bag filter tank 4 or the sodium sulfate B group 10 bag filter tank 4, as well as the corresponding inlet valve 5 and outlet valve 6.

[0056] II. Raw Material Buffer and Reaction Unit

[0057] The raw material buffer and reaction unit includes a calcium solution buffer tank 11, a sodium sulfate buffer tank 12, and a reactor 13.

[0058] The inlet of the calcium solution buffer tank 11 is connected to the outlet of the fine filtration module in the calcium solution treatment branch, and the inlet of the sodium sulfate buffer tank 12 is connected to the outlet of the fine filtration module in the sodium sulfate treatment branch. Both the calcium solution buffer tank 11 and the sodium sulfate buffer tank 12 are equipped with parameter detection units for detecting liquid level and density. In this embodiment, the parameter detection unit for detecting liquid level is a radar level gauge 14 with a detection accuracy of ±5mm; the parameter detection unit for detecting density is an online density meter 15 with a detection accuracy of ±0.001g / cm³.

[0059] The outlets of the calcium solution buffer tank 11 and the sodium sulfate buffer tank 12 are connected to the inlet of the reactor 13 via delivery pipelines and metering pumps 17 mounted on them. The metering pumps 17 are diaphragm metering pumps with a control accuracy of ±1%. A parameter detection unit for detecting flow rate is provided on the delivery pipeline; in this embodiment, an electromagnetic flow meter 16 is used.

[0060] Reactor 13 is an existing structure, which is equipped with a stirring motor 18 and stirring blades inside, for fully mixing and reacting calcium solution and sodium sulfate.

[0061] III. Product Post-processing Unit

[0062] The product post-processing unit includes a post-reaction buffer tank 20 connected to the outlet of reactor 13, and a solid-liquid separation device, a drying device, a grinding and air-classifying device 24 and a finished product silo 25 connected in sequence.

[0063] The post-reaction buffer tank 20 is equipped with a slurry stirring motor 19 to prevent slurry sedimentation. The outlet of the post-reaction buffer tank 20 delivers the slurry to a solid-liquid separation device via a slurry pump 21. In this embodiment, the solid-liquid separation device is a belt filter 22, which is equipped with a vacuum filter box and a vacuum pump. Under vacuum, the gypsum slurry is dehydrated, and a water spray wash is installed above the filter cake to remove soluble salts. The belt filter 22 is driven by a variable frequency motor with adjustable speed.

[0064] The dehydrated gypsum filter cake is conveyed to the drying equipment via a conveyor belt. In this embodiment, the drying equipment is a drying furnace 23, and the drying temperature is controlled at 120-180℃ (preferably 150℃ in this embodiment). The moisture content of the dried gypsum is ≤5% (≤3% in this embodiment). The dried gypsum enters the grinding and air classification equipment 24 to obtain gypsum powder, which is finally stored in the finished product silo 25. The outlet can be connected to a packaging device for finished product packaging.

[0065] IV. Control Unit

[0066] The control unit is electrically connected to pressure detection elements, various parameter detection units (radar level gauge 14, online density meter 15, electromagnetic flowmeter 16), various on / off control valves, and metering pump 17. Furthermore, the control unit is also electrically connected to actuators such as the reactor 13 stirring motor 18, slurry stirring motor 19, slurry pump 21, belt filter 22 drive motor, and drying oven 23 temperature controller, achieving centralized control of the entire process. The actuator response time is ≤0.5s. In this embodiment, the control unit adopts a DCS (Distributed Control System), and all field instruments are intrinsically safe, adapting to the explosion-proof requirements of chemical production. All detection signals are processed by safety barriers before being input to the DCS to avoid signal interference.

[0067] The control unit incorporates pressure threshold-based inter-group switching control logic, master-slave dynamic ratio control algorithm, sequential control logic (SFC), and a fault diagnosis and self-protection module. The control unit receives signals from field instruments such as pressure sensors, level gauges, density meters, and flow meters, and controls the start / stop and operating status of actuators such as on / off control valves, metering pump 17, stirring motor 18, slurry pump 21, and belt filter 22 drive motor according to preset logic. This enables intelligent switching and automatic cleaning of the fine filtration module, precise feeding of raw materials at equivalent reaction amounts, and status monitoring and fault interlocking of the entire process equipment.

[0068] Specifically, the functions of the control unit include at least the following aspects:

[0069] (a) Inter-group switching control logic

[0070] The control unit has a built-in inter-group switching control logic based on pressure thresholds, configured as follows: determine the filtering status of the current working group (referring to Group A 9 or Group B 10) based on the pressure value collected by the pressure detection element; when the pressure value reaches the preset switching preparation threshold, control the standby group (referring to Group B 10 or Group A 9) to enter the pre-pressurization standby state; when the pressure value reaches the preset switching execution threshold, perform uninterrupted inter-group switching, switching the material from the current working group to the standby group.

[0071] (ii) Sequential Control Logic (SFC) for Automatic Cleaning

[0072] The control unit has built-in sequential control logic for fully automatic cleaning of the switched-off blockage groups. The cleaning process executes steps such as pressure relief and drainage, backwashing, sewage discharge, and purging in a preset order. The number of cleaning cycles and the cycle time can be set on the human-machine interface.

[0073] (III) Master-slave dynamic ratio control algorithm for precise feeding

[0074] The control unit incorporates a master-slave dynamic ratio control algorithm to achieve precise feeding of calcium solution and sodium sulfate at the same reaction equivalence. This algorithm uses calcium solution as the master material and sodium sulfate as the slave material. It calculates the real-time mass flow rate of the calcium solution by collecting its volumetric flow rate and density data, dynamically calculates the target flow rate setpoint for sodium sulfate, and adjusts the speed of the sodium sulfate metering pump 17 via a PID controller, ensuring that both materials enter the reactor 13 precisely according to the preset stoichiometric ratio.

[0075] (iv) Fault diagnosis and self-protection module

[0076] The control unit has a built-in fault diagnosis and self-protection module with a fault diagnosis response time of ≤1s. This module acquires real-time operating status signals from various detection elements (pressure transmitter, radar level gauge 14, online density meter 15, electromagnetic flowmeter 16) and actuators (on / off control valve, metering pump 17, reactor 13 stirring motor 18, slurry stirring motor 19, slurry pump 21, belt filter 22 drive motor, drying oven 23 heating element, etc.) to achieve the following functions:

[0077] a. Instrument fault diagnosis: When the parameter detection unit or pressure detection element experiences signal interruption, value jump or over-range fault, the control unit immediately determines it as an instrument fault, displays the fault location and fault type on the human-machine interface, and triggers local interlock (such as suspending the feed of that branch).

[0078] b. Actuator fault diagnosis: When actuators such as on / off control valve, metering pump 17, stirring motor 18, slurry pump 21, belt filter 22 drive motor have no feedback, timeout, or abnormal operating parameters (such as speed deviating from the set value, motor overload), the control unit determines that the actuator is faulty, interlocks and closes the upstream and downstream pipeline valves corresponding to the faulty equipment, and displays the name of the faulty equipment and the cause of the fault on the human-machine interface.

[0079] c. System redundancy protection: The primary and backup modules of the control unit are redundantly configured. When the primary module fails, the backup module will seamlessly switch over within ≤0.1s to ensure continuous operation of the control system without the risk of control interruption.

[0080] (v) Human-computer interface

[0081] The control unit is also equipped with a human-machine interface (HMI). This HMI adopts a modular layout, with operation permissions divided into operator, engineer, and administrator levels. Different permissions correspond to different operation functions to prevent accidental operation. The interface is divided into the following five core modules:

[0082] a. Process flow diagram main interface: 1:1 reproduction of the actual process layout of the device, real-time display of material flow direction, operating status of all equipment, real-time values ​​of key process parameters, and automatic flashing when parameters exceed limits;

[0083] b. Parameter monitoring interface: Displays the real-time and historical changes of each key process parameter in the form of trend curves. The curves support zooming in, zooming out, and panning operations. Upper and lower limits and alarm thresholds of parameters can be set. Modification of thresholds requires engineer level or above permissions.

[0084] c. Control operation interface: Enables manual / automatic mode switching for each device. It allows for individual setting of parameters such as cleaning parameters of bag filter tank 4, feeding ratio of calcium solution and sodium sulfate, speed of metering pump 17, speed of stirring motor 18, and running speed of belt filter 22. All parameters are automatically saved after modification.

[0085] d. Fault alarm interface: Real-time display of fault location, fault type, occurrence time, and fault level; supports fault mute, confirmation, and clearing operations; historical fault information can be filtered and queried by time, fault type, and equipment name.

[0086] e. Historical data interface: Supports data query, curve playback, and Excel format export of key process parameters, fault information, and control action records. The query time range (hour / day / month / year) can be set to meet the traceability requirements of industrial production.

[0087] This embodiment also discloses a control method for preparing gypsum using the above-described apparatus, comprising the following steps:

[0088] Step S1: Raw material pretreatment

[0089] Calcium solution and Glauber's salt enter their respective pretreatment branches. Taking calcium solution as an example: the calcium solution first undergoes coarse filtration in sand filter tank 3 to remove large particulate impurities with a particle size ≥20μm; after coarse filtration, the calcium solution enters the fine filtration module, and after filtration in bag filter tank 4, the removal rate of solid impurities with a particle size ≥5μm in the solution is ≥99%. The Glauber's salt treatment branch is similar.

[0090] Step S2: Intelligent switching of the fine filtration module

[0091] like Figure 2 As shown, the control unit collects the pressure values ​​of the pressure detection elements in front of each filter assembly in real time and divides the pressure into normal zone, warning zone, and blockage zone. The threshold values ​​for each zone can be modified on the human-machine interface according to the impurity content of the raw materials; the threshold value of the warning zone ensures that sufficient switching time is reserved before blockage occurs, avoiding production interruption.

[0092] When the pressure value is within the normal range, the current working group operates normally, while the standby group is in standby mode. The human-machine interface displays the real-time pressure value and the "normal operation" status.

[0093] When the pressure value enters the warning zone (e.g., the pressure reaches 80% of the preset threshold), the control unit determines that the current working group is in a critical blockage state and immediately triggers the standby group pre-pressurization logic: automatically opening the outlet valve 6 of the standby group bag filter tank 4 (keeping the inlet valve 5 closed), and using the system pipeline pressure to inject slurry into the standby group pipeline until the gas in the pipeline is purged and the pressure is balanced, at which point the standby group enters the "full liquid standby" state. At the same time, a yellow warning prompt pops up on the human-machine interface, indicating to the operator that the current switchover preparation period is underway.

[0094] When the pressure value enters the blockage zone (e.g., the pressure reaches 100% of the preset threshold), the control unit determines that the current working group is blocked and immediately executes the automatic switching logic: first, it opens the outlet valve 6 of the standby bag filter tank 4, and then opens its inlet valve 5; after the pressure in the standby group pipeline stabilizes, it first closes the inlet valve 5 of the original working group, and then closes its outlet valve 6. This process ensures continuous operation of the production line without material interruption. If the pressure difference of the standby group is also in the blockage zone, it indicates that the overall impurity load of the system is too high. The control unit immediately triggers the full-line interlock shutdown, stops the feeding, and keeps the stirring motor 18 of reactor 13 running to prevent material deposition in reactor 13; and pops up an "Emergency alarm for dual filter blockage" on the human-machine interface, prompting the operator to check the fine filtration module.

[0095] The removed blockage group is automatically cleaned by the control unit according to sequential control logic. The cleaning process is divided into four consecutive steps: pressure relief and drainage → backwashing → sewage discharge → purging. The total time, number of cleaning cycles, water injection time, and purging time for a single cleaning cycle can be set on the human-machine interface. The cleaning process specifically includes:

[0096] a. Pressure relief and liquid discharge: Open the drain valve of the clogged bag filter tank 4 to relieve pressure, and collect the pressure signal in the bag filter tank 4 in real time. When the pressure is ≤0.05MPa, it is determined that the residual liquid has been discharged and the drain valve is automatically closed; if the pressure does not drop below 0.05MPa within 10 seconds, the "liquid discharge failure" alarm is triggered.

[0097] b. Backwashing: Open the water injection valve and introduce clean water at 0.2-0.4 MPa for backwashing. After backwashing, close the water injection valve.

[0098] c. Sewage discharge: Open the sewage discharge valve to discharge sewage. The sewage discharge time can be adjusted according to the actual situation.

[0099] d. Purging: Open the purging valve and introduce dry compressed air at 0.5-0.7 MPa for purging. After purging is completed, close the drain valve and the purging valve.

[0100] Step S3: Precise proportion of material feeding

[0101] The control unit uses calcium solution as the master material and sodium sulfate as the slave material, and presets the reaction ratio coefficient K (based on the chemical reaction equation). The mass ratio of calcium solution to sodium sulfate should be such that the molar ratio of calcium chloride to sodium sulfate is 1:1. The specific K value is calculated based on the concentration of the raw materials.

[0102] Main circuit: A liquid level PID control circuit is constructed based on the liquid level measurement value of the calcium solution buffer tank 11. The output signal adjusts the speed of the calcium solution metering pump 17, so that the liquid level of the calcium solution buffer tank 11 is stabilized within the preset safe range, ensuring production continuity and preventing the risk of overflow or cavitation.

[0103] Simultaneously, the volumetric flow rate and density of the calcium solution pipeline are collected in real time, using the formula... Calculate the real-time mass flow rate of the calcium solution. Where, This refers to the real-time mass flow rate of the calcium solution. This is the measured density of the calcium solution; This is the measured value of the calcium liquid volumetric flow rate;

[0104] The target flow rate setpoint for sodium sulfate is dynamically calculated using the ratio calculator built into the control unit. In the formula, Set the target flow rate for Glauber's salt; This refers to the real-time mass flow rate of the calcium solution.

[0105] From the loop: Set the target flow rate of sodium sulfate. As the input setpoint of the loop flow PID controller, the volumetric flow rate and density of the sodium sulfate pipeline are collected in real time, according to the formula... Calculate the real-time mass flow rate of Glauber's salt. Where, This refers to the real-time mass flow rate of Glauber's salt. This is the measured density of Glauber's salt; This is the measured value of the volumetric flow rate of Glauber's salt;

[0106] The PID controller for loop flow is based on flow deviation. The speed of the sodium sulfate metering pump 17 is adjusted in real time to ensure that the real-time mass flow rate of sodium sulfate accurately tracks the real-time mass flow rate changes of the calcium solution, thus ensuring that both materials enter reactor 13 in a preset ratio K. This is for flow rate deviation.

[0107] In this embodiment, when the flow rate of the main material changes due to fluctuations in liquid level or upstream disturbances, the slave loop updates the set value in real time through ratio calculation, achieving millisecond-level proportional following and a feeding control accuracy of ±1%.

[0108] Ensure that level control and proportional control are optimized independently to effectively suppress interference from changes in pipeline pressure and pump characteristics, thereby improving the overall system's anti-interference capability.

[0109] Step S4: Product post-processing

[0110] The reacted mixture flows from the bottom of reactor 13 into post-reaction buffer tank 20, and is then pumped by slurry pump 21 to belt filter 22. On belt filter 22, the gypsum slurry is filtered through filter cloth to form a filter cake, which is further dehydrated under the suction of a vacuum filter box. Simultaneously, water is sprayed onto the filter cake for washing to remove entrained soluble salts such as sodium chloride. The dehydrated and washed gypsum filter cake is conveyed by belt conveyor to drying oven 23, where it is dried at 150℃ until the moisture content is ≤3%. The dried gypsum then enters grinding and air-classifying equipment 24 to obtain gypsum powder with a purity ≥96%, which is finally stored in finished product silo 25 and packaged.

[0111] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical solutions described in the above 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 invention should be included within the protection scope of the present invention.

Claims

1. An apparatus for preparing gypsum using chemical byproducts, characterized in that, include: The raw material pretreatment unit includes a calcium solution treatment branch and a sodium sulfate treatment branch; both the calcium solution treatment branch and the sodium sulfate treatment branch include a coarse filtration module and a fine filtration module connected sequentially along the material flow direction; the fine filtration module includes at least two sets of switchable filter components, each set of filter components is equipped with an on / off control valve, and a pressure detection element is provided on the main material pipeline before each set of filter components; The raw material buffer and reaction unit includes a calcium solution buffer tank, a sodium sulfate buffer tank, and a reactor. The inlets of the calcium solution buffer tank and the sodium sulfate buffer tank are respectively connected to the outlets of the fine filtration modules of the corresponding pretreatment branches. The outlets are respectively connected to the inlet of the reactor through conveying pipelines and metering pumps installed thereon. The calcium solution buffer tank and the sodium sulfate buffer tank are equipped with parameter detection units for detecting liquid level and density, and the conveying pipelines are equipped with parameter detection units for detecting flow rate. The product post-processing unit includes a post-reaction buffer tank connected to the reactor outlet, and a solid-liquid separation device, a drying device, a grinding and air-classifying device, and a finished product silo connected in sequence. The control unit is electrically connected to the pressure detection element, each of the parameter detection units, each of the on / off control valves, and the metering pump; the control unit has built-in inter-group switching control logic based on pressure thresholds, configured as follows: The filtration status of the current working group is determined based on the pressure value collected by the pressure detection element; When the pressure value reaches the preset switching preparation threshold, the control standby group enters the pre-pressurization standby state. When the pressure value reaches the preset switching execution threshold, the switching between execution groups is uninterrupted, and the material flow is switched from the current work group to the standby group.

2. The device for preparing gypsum using chemical by-products according to claim 1, characterized in that, The filtration assembly is a bag filter canister with a filter bag precision of 5-20μm; each bag filter canister adopts a bottom-inlet and top-outlet structure, and each bag filter canister is independently equipped with an inlet valve and an outlet valve as the on / off control valve; The coarse filtration module includes at least two sand filter tanks connected in series. The sand filter tanks adopt a top-inlet and bottom-outlet structure, and the filter media is quartz sand with a particle size range of 0.8 to 2.0 mm.

3. The apparatus for preparing gypsum using chemical by-products according to claim 2, wherein, Each of the bag filter tanks is also connected to a backwash water injection pipeline and a compressed air purging pipeline; the water injection pipeline is equipped with a water injection valve, and the purging pipeline is equipped with a purging valve; each of the bag filter tanks is equipped with a drain valve at the bottom drain port; The water injection valve, the purge valve, and the drain valve are all electrically connected to the control unit.

4. The apparatus for preparing gypsum using chemical by-products according to claim 3, wherein, The control unit is a DCS control system; the metering pump is a diaphragm metering pump with a control accuracy of ±1%; the parameter detection unit for detecting liquid level is a radar level gauge with a detection accuracy of ±5mm; the parameter detection unit for detecting density is an online density meter with a detection accuracy of ±0.001g / cm³; and the parameter detection unit for detecting flow rate is an electromagnetic flow meter.

5. The apparatus for preparing gypsum using chemical by-products according to any one of claims 1 to 4, wherein The control unit also has a built-in fault diagnosis and self-protection module, which is configured as follows: Real-time acquisition of operating status signals, with a fault diagnosis response time of ≤1 second; When the parameter detection unit experiences signal interruption, value jump, or over-range fault, it is determined to be an instrument fault. The fault location and fault type are displayed on the human-machine interface, and a local interlock is triggered. When the on / off control valve, the metering pump, or the stirring motor of the reactor experiences no feedback, timeout, or abnormal operating parameters, it is determined to be an actuator failure. The upstream and downstream pipeline valves corresponding to the faulty equipment are interlocked and closed, and the name of the faulty equipment and the cause of the failure are displayed on the human-machine interface. The control unit also has a redundancy protection function. When the primary module fails, the backup module will switch seamlessly with a switching time of ≤0.1s.

6. The apparatus for preparing gypsum using chemical by-products according to claim 5, wherein, The human-machine interface of the control unit is divided into a process flow diagram main interface, a parameter monitoring interface, a control operation interface, a fault alarm interface, and a historical data interface; the operation permissions are divided into operator level, engineer level, and administrator level.

7. A control method for the production of gypsum using the apparatus according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Raw material pretreatment: Calcium solution and Glauber's salt are filtered through their respective pretreatment branches to remove impurities; S2. Intelligent switching of fine filtration modules: The control unit collects the pressure value at the inlet side of the fine filtration module in each pretreatment branch in real time and divides the pressure into normal zone, warning zone and blockage zone; when the pressure enters the warning zone, the standby group pre-pressurization logic is triggered: the on / off control valve of the standby group is controlled to fill the standby group pipeline with liquid and purge the gas, and enter the pre-pressurization standby state; when the pressure enters the blockage zone, automatic switching is executed: the on / off control valve is controlled to switch the material flow from the current working group to the standby group to maintain the continuous operation of the production line; S3. Precise Proportional Feeding: Calcium solution is used as the main material and Glauber's salt as the secondary material. The reaction ratio coefficient K is preset in the control unit. The delivery rate of the calcium solution metering pump is adjusted based on the liquid level measurement value of the calcium solution buffer tank. Real-time volumetric flow rate and density of calcium solution are collected, and real-time mass flow rate of calcium solution is calculated; The target flow rate setting value of Glauber's salt is dynamically calculated by ratio calculation; based on this target flow rate setting value, the delivery volume of Glauber's salt metering pump is adjusted in real time so that the two materials enter the reactor in a preset ratio. S4. Post-processing of products: The mixture after reaction is subjected to solid-liquid separation, drying, grinding and air classification to obtain the finished gypsum product.

8. The control method according to claim 7, characterized by, In step S2, the switched-off blockage group is automatically cleaned by the control unit according to the sequential control logic. The cleaning process includes: depressurization and drainage, backwashing, sewage discharge, and purging. The backwashing uses clean water at 0.2 to 0.4 MPa, and the purging uses dry compressed air at 0.5 to 0.7 MPa.

9. The control method according to claim 8, characterized by, In step S2, the specific process of automatic switching is as follows: first, open the on / off control valve on the outlet side of the standby group, and then open the on / off control valve on the inlet side; after the pipeline pressure stabilizes, close the on / off control valve on the inlet side of the original working group, and then close the on / off control valve on the outlet side.

10. The control method according to any one of claims 7-9, characterized by, In step S3, the real-time mass flow of the calcium liquid is calculated by the formula calculation; The mirabilite target flow set value is calculated by the formula ; the mirabilite real-time mass flow is calculated by the formula as the input set value of the loop flow PID controller in the control unit, the mirabilite real-time mass flow is calculated by the formula based on the flow deviation The mirabilite metering pump speed is adjusted in real time, so that the mirabilite real-time mass flow tracks the calcium liquid real-time mass flow variation; Wherein, is the calcium liquid real-time mass flow rate; is the calcium liquid density measured value; is the calcium liquid volume flow rate measured value; is the mirabilite target flow rate set value; is the mirabilite real-time mass flow rate; is the mirabilite density measured value; is the mirabilite volume flow rate measured value; is the flow rate deviation.

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