A filter press system

Abstract

The application discloses a filter pressing system to solve the technical problems of lacking full-process atmosphere protection and being unable to precisely and adaptively control the atmosphere environment in the prior filter pressing system. The filter pressing system comprises a mechanical execution unit, a protective gas supply unit, a gas monitoring unit, an exhaust control unit and a central control unit. The mechanical execution unit comprises a material pretreatment device, a material conveying device, a filter pressing device and a liquid storage device. The protective gas supply unit comprises a gas main pipe, a main pipe pressure sensor and a plurality of gas inlet branches connected to respective gas inlets of the mechanical execution unit. Each gas inlet branch is provided with a gas inlet regulating valve with adjustable opening degree. The gas monitoring unit comprises oxygen concentration sensors arranged in the material pretreatment device, the filter pressing device and the liquid storage device respectively. The exhaust control unit comprises exhaust regulating valves arranged at respective exhaust points of the mechanical execution unit.

Description

Technical Field

[0001] This invention relates to the field of pressure filtration separation technology, and in particular to a pressure filtration system that can prevent the oxidation of liquid phase components during the pressure filtration process. Background Technology

[0002] Existing filter press equipment is widely used in solid-liquid separation, such as in the processing of edible vegetable oils, natural fragrances, and medicinal plant active ingredients—processes involving oxidation-sensitive liquids. Its working principle involves applying strong mechanical pressure to the material, squeezing and separating the liquid phase components. For a long time, industry improvements to filter press equipment have mainly focused on increasing pressing efficiency, reducing energy consumption, and optimizing mechanical structure, while paying insufficient attention to the oxidation of liquid phase components during the filtration process. In fact, the filtration process generates very high frictional temperatures, typically reaching 60°C to 130°C. Under high temperature and pressure, the material comes into full contact with oxygen in the air, resulting in a thermal oxidation reaction, leading to the following problems: First, the initial quality of the separated liquid phase components is poor. The oxidation process generates peroxides and other oxidation products, deteriorating the product's chemical properties and severely affecting product quality. Second, flavor loss is severe. Natural aromatic substances are oxidized and destroyed, while unpleasant off-odor precursors are produced, reducing the product's sensory quality. Third, color darkening occurs. Oxidation causes pigments to transform, darkening the liquid phase components and placing a greater burden on subsequent refining and decolorization, increasing processing costs. Furthermore, active ingredients are damaged, and heat-sensitive and oxygen-sensitive nutrients or functional components such as vitamins, polyphenols, and unsaturated fatty acids are lost during the pressure filtration stage, reducing the nutritional value or efficacy of the product. These oxidation problems directly affect the quality of the final product, yet they have not been effectively solved in traditional pressure filtration technology. Summary of the Invention

[0003] The purpose of this invention is to provide a pressure filtration system to solve the technical problems of existing pressure filtration systems lacking full-process atmosphere protection and being unable to accurately and adaptively control the atmosphere environment.

[0004] A pressure filtration system includes: a mechanical actuator unit comprising a material pretreatment device, a material conveying device, a pressure filtration device, and a liquid storage device; a protective gas supply unit comprising a gas main pipe, a main pipe pressure sensor, and multiple air inlet branches respectively connected to each air inlet point of the mechanical actuator unit, each air inlet branch being provided with an adjustable air inlet regulating valve; a gas monitoring unit comprising oxygen concentration sensors respectively arranged inside the material pretreatment device, the pressure filtration device, and the liquid storage device; an exhaust control unit comprising exhaust regulating valves disposed at each exhaust point of the mechanical actuator unit; and a central control unit electrically connected to the mechanical actuator unit, the protective gas supply unit, the gas monitoring unit, and the exhaust control unit, and configured to execute the following control logic: 1) Detecting the pressure of the gas main pipe before the mechanical actuator unit starts; if the pressure is lower than a preset safety threshold, locking the mechanical actuator unit and forcibly closing all air inlet regulating valves; 2) When the pressure of the gas main pipe reaches the preset safety threshold, reading the feedback values ​​of each oxygen concentration sensor in real time; if any oxygen concentration sensor... If the detected value exceeds the preset high-limit alarm value, the system automatically enters the replacement mode, controlling the corresponding intake regulating valve to open to the preset large intake opening, and simultaneously controlling the corresponding exhaust regulating valve to open to the preset large exhaust opening. During this replacement mode, the mechanical actuator is prohibited from operating. 3) When the feedback values ​​from all oxygen concentration sensors are lower than the preset safety setting value and this state lasts for more than the preset stable timing threshold, the system automatically switches to the maintenance mode, controlling the opening of each intake regulating valve to decrease to the preset small intake opening, and simultaneously controlling the opening of each exhaust regulating valve to decrease to the preset small exhaust opening or close, in order to maintain the mechanical actuator. The internal pressure of the unit is slightly positive, and the mechanical actuator is unlocked. The material pretreatment device, the material conveying device, and the filter press are started and operated in sequence according to the preset process sequence; 4) During the operation of the maintenance mode, if the feedback value of the oxygen concentration sensor shows an upward trend and exceeds the preset fluctuation threshold, the corresponding intake regulating valve is controlled to automatically increase the preset compensation opening ratio based on the current opening; 5) When an emergency exhaust signal is received, regardless of the current mode of the mechanical actuator, all exhaust regulating valves are forcibly opened to the full extent, and all intake regulating valves are closed at the same time.

[0005] As an optimization and / or instantiation of the above-mentioned filter press system, further: the material pretreatment device includes a mixing tank, the material conveying device includes a closed elevator, and the filter press includes a feed buffer hopper and a vertical filter press body; the discharge port of the mixing tank is sealed and connected to the feed end of the closed elevator, the discharge end of the closed elevator is sealed and connected to the top inlet of the feed buffer hopper, the bottom outlet of the feed buffer hopper is connected to the top feed chamber of the vertical filter press body, and the drain port of the vertical filter press body is connected to the liquid storage device through a pipeline, thereby forming a material flow channel that is connected end to end and isolated from the external environment inside the mechanical execution unit; the protective gas supply unit includes: a mixing tank inlet regulating valve connected to the mixing tank, an elevator inlet regulating valve connected to the closed elevator, and a feed buffer regulating valve connected to the feed buffer hopper. The system includes: a buffer hopper inlet regulating valve, a filter press inlet regulating valve connected to the main body of the vertical filter press, and a storage device inlet regulating valve connected to the storage device; the exhaust control unit includes: a mixing tank exhaust regulating valve connected to the mixing tank, a buffer hopper exhaust regulating valve connected to the feed buffer hopper, a filter press exhaust regulating valve connected to the main body of the vertical filter press, and a storage device exhaust regulating valve connected to the storage device; the filter press exhaust regulating valve includes a main exhaust regulating valve and an auxiliary exhaust regulating valve, the main exhaust regulating valve being located at the bottom of the main body of the vertical filter press and communicating with the main liquid flow channel of the main body of the vertical filter press, and the auxiliary exhaust regulating valve being located on the side of the main body of the vertical filter press; the gas monitoring unit includes: oxygen concentration sensors respectively located in the mixing tank, the main body of the vertical filter press, and the storage device.

[0006] As an optimization and / or instantiation of the above-mentioned filter press system, further: the protective gas supplied by the protective gas supply unit is a gas with a density less than air; each inlet of the protective gas supply unit and each exhaust point of the exhaust control unit are configured such that the protective gas diffuses in the mixing tank, the feed buffer hopper, and the main body of the vertical filter press in a downward diffusion direction; each oxygen concentration sensor of the gas monitoring unit is respectively located at the bottom of the mixing tank, the main body of the vertical filter press, and the liquid storage device.

[0007] As an optimization and / or instantiation of the above-mentioned pressure filtration system, the protective gas supplied by the protective gas supply unit is specifically nitrogen.

[0008] As an optimization and / or instantiation of the above-mentioned filter press system, further: during the operation of the maintenance mode: the opening degree of the auxiliary exhaust regulating valve, the buffer hopper exhaust regulating valve, and the mixing tank exhaust regulating valve is at a preset small exhaust opening degree, and the main exhaust regulating valve and the liquid storage device exhaust regulating valve are closed.

[0009] As an optimization and / or instantiation of the above-mentioned filter press system, further: the elevator inlet regulating valve is configured to be linked to the motor operating status of the closed elevator; when the motor starts, the elevator inlet regulating valve is opened synchronously to form a dynamic nitrogen curtain at the feed inlet and discharge outlet of the closed elevator; when the motor stops, a delayed shutdown timer is triggered, and the elevator inlet regulating valve remains open for a preset delay period after the motor stops, and is closed after the delay period ends, to prevent backflow of external air caused by internal pressure fluctuations at the moment of shutdown.

[0010] As an optimization and / or instantiation of the above-mentioned filter press system, further: in the initial stage when the main body of the vertical filter press enters the pressing process, the main exhaust regulating valve is opened and the auxiliary exhaust regulating valve is closed, so as to discharge most of the gas through the liquid flow channel generated by pressing; after the pressing process has reached a preset time node, the auxiliary exhaust regulating valve is opened to discharge the residual gas pockets deep in the gap between the filter plates.

[0011] As an optimization and / or instantiation of the above-mentioned filter press system, further: the opening sequence of the buffer hopper inlet regulating valve and the buffer hopper exhaust regulating valve is related to the operating status of the closed elevator; the central control unit is configured to: open the buffer hopper inlet regulating valve after a first preset delay is detected that the closed elevator has started operation; and open the buffer hopper exhaust regulating valve after a second preset delay is detected that the buffer hopper inlet regulating valve has been opened, so as to establish a nitrogen protection environment and replace the air brought in when the material enters the buffer hopper.

[0012] As an optimization and / or instantiation of the aforementioned filter press system, further: when the central control unit executes the automatic increase of the preset compensation opening ratio, a step-by-step superposition compensation algorithm is adopted. The logic of this step-by-step superposition compensation algorithm is as follows: when the oxygen concentration exceeds the standard, the real-time opening value of the corresponding intake regulating valve is read; a preset incremental step value is superimposed on the real-time opening value to calculate a new target opening value; it is determined whether the target opening value exceeds the maximum physical stroke of the corresponding intake regulating valve. If it does not exceed the target opening value, the intake regulating valve is driven to the target opening value; if it exceeds the target opening value, the intake regulating valve is driven to the maximum physical stroke.

[0013] As an optimization and / or instantiation of the above-mentioned filter press system, further: the filter press device is a squeeze-type solid-liquid separation device; the material conveyed by the material pretreatment device and the material conveying device is a high-viscosity solid-liquid mixed slurry; the liquid phase component separated by the filter press device is an oxidation-sensitive liquid, which has the characteristic of being chemically unstable in an aerobic environment.

[0014] This invention achieves atmosphere protection for the entire process of the mechanical execution unit by setting up a protective gas supply unit, a gas monitoring unit, an exhaust control unit, and a central control unit. This ensures that the material is in a low-oxygen environment from the moment it enters the material pretreatment device until the liquid phase components are collected in the storage device. This effectively avoids thermal oxidation reactions caused by contact between the oxidation-sensitive liquid and oxygen in the air, and solves the problems of quality deterioration, flavor loss, color deepening, and destruction of active ingredients in the liquid phase components during the pressure filtration process from the source.

[0015] The central control unit detects the pressure of the gas main pipe before starting the mechanical actuator and compares it with a preset safety threshold. This ensures that the protective gas supply unit has sufficient gas supply capacity before allowing the system to operate, thus avoiding the risk of atmosphere protection failure due to insufficient gas supply.

[0016] The central control unit can automatically switch between replacement mode and maintenance mode according to the actual oxygen concentration status of each area by reading the feedback values ​​of each oxygen concentration sensor in real time. In replacement mode, it quickly replaces the air with preset large air intake opening and preset large air exhaust opening. In maintenance mode, it maintains the slight positive pressure inside the mechanical actuator with preset small air intake opening and preset small air exhaust opening, thus achieving precise adaptive control of the atmosphere environment, which not only ensures the protection effect but also saves the amount of protective gas used.

[0017] During operation in maintenance mode, the central control unit can automatically adjust the opening of the intake regulating valve to compensate for the dynamic changes in the oxygen concentration sensor feedback value. When the oxygen concentration shows an upward trend and exceeds the preset fluctuation threshold, it automatically increases the preset compensation opening ratio, realizing real-time response and dynamic control of oxygen concentration fluctuations during the pressure filtration process.

[0018] When the central control unit receives an emergency exhaust signal, it can force all exhaust regulating valves to open fully and close all intake regulating valves, providing a safety response mechanism in emergency situations and ensuring the safety of the filter press system operation.

[0019] By sealing and connecting the mixing tank, the enclosed elevator, the feed buffer hopper, the main body of the vertical filter press, and the liquid storage device, a material flow channel that is connected end to end and isolated from the external environment is formed. With the independent air intake and exhaust regulating valves of each device, the independent control and coordinated protection of each link in the entire material flow process are realized.

[0020] By employing a protective gas with a density less than air and configuring each inlet and outlet point to allow the protective gas to diffuse from top to bottom, while placing each oxygen concentration sensor at the bottom of each device, the physical properties of the protective gas are fully utilized to achieve natural stratification and replacement, thereby improving gas replacement efficiency and the accuracy of oxygen concentration monitoring.

[0021] By linking the air intake regulating valve of the elevator with the motor operation status of the closed elevator, it opens synchronously when the motor starts to form a dynamic nitrogen curtain, and closes after a delay when the motor stops to prevent external air from being sucked back in, effectively solving the problem of atmosphere protection in the material transmission process.

[0022] By setting a main exhaust regulating valve and an auxiliary exhaust regulating valve in the main body of the vertical filter press and controlling their opening at different stages of the pressing process, most of the gas can be discharged through the liquid flow channel, and residual gas pockets deep in the gaps between the filter plates can also be discharged, ensuring the complete replacement of gas inside the filter press.

[0023] A step-by-step superposition compensation algorithm is used to dynamically adjust the intake air volume. When the oxygen concentration exceeds the standard, the opening is gradually adjusted by incremental step values, which avoids drastic fluctuations in the intake air volume and achieves stable and precise atmosphere control.

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages provided by the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice. Attached Figure Description

[0025] The accompanying drawings, which form part of this specification, are used to aid in understanding the invention. The contents provided in the drawings and their related descriptions in this specification can be used to explain the invention, but do not constitute an undue limitation of the invention.

[0026] Figure 1 This is a schematic diagram of the structure of an embodiment of the filter press system of the present invention.

[0027] Figure 2 This is a ladder diagram for the gas main pressure detection and system start / stop control of the central control unit.

[0028] Figure 3 This is a ladder diagram for the automatic switching control between the replacement mode and the maintenance mode of the central control unit.

[0029] Figure 4 This is a trapezoidal diagram showing the opening control of the air inlet regulating valve and the air outlet regulating valve of the mixing tank.

[0030] Figure 5 This is a ladder diagram for the linkage control and delayed shutdown of the air intake regulating valve of a closed hoist.

[0031] Figure 6 This is a trapezoidal diagram showing the air intake and exhaust control of the feed buffer hopper and the main body of the vertical filter press.

[0032] Figure 7 This is a ladder diagram showing the control of the inlet regulating valve and the exhaust regulating valve of the liquid storage device.

[0033] Figure 8 The ladder diagram is used for monitoring oxygen concentration and controlling the step-by-step superposition compensation algorithm in the central control unit.

[0034] Figure 9 This is the ladder diagram for the emergency exhaust response control of the central control unit.

[0035] Figure 10 This is a photograph of the filter press device portion of an embodiment of the filter press system of the present invention.

[0036] The diagram is labeled as follows: Mechanical Actuation Unit 1; Protective Gas Supply Unit 2; Mixing and Stirring Box 11; Sealed Elevator 12; Feed Buffer Hopper 131; Vertical Filter Press Main Body 132; Liquid Storage Device 14; Main Pipe Pressure Sensor P-1; Mixing and Stirring Box Inlet Regulating Valve V1; Elevator Inlet Inlet Valve V2; Elevator Outlet Inlet Inlet Valve V3; Buffer Hopper Inlet Regulating Valve V4; Filter Press Inlet Regulating Valve V5; Liquid Storage Device Inlet Regulating Valve V6; Mixing and Stirring Box O2-1; Vertical Filter Press Main Body O2-2; Liquid Storage Device O2-3; Mixing and Stirring Box Pressure... Sensor P-2; Mixing tank exhaust regulating valve V8; Buffer hopper exhaust regulating valve V9; Main exhaust regulating valve V10; Auxiliary exhaust regulating valve V11; Liquid storage device exhaust regulating valve V12; Start button I0.0; Stop button I0.1; Emergency stop button I0.2; Reset button I0.3; Manual / automatic switch I0.4; Replacement mode button I0.5; Filter press tightening detection I1.0; Filter press loosening detection I1.1; Elevator operation feedback I1.2; Hopper full level detection I1.3; Liquid storage device high level detection I1.4; Mixing tank low oxygen concentration alarm signal I2.0 ; Low oxygen concentration alarm signal for the main body of the vertical filter press I2.1; Low oxygen concentration alarm signal for the liquid storage device I2.2; Low pressure alarm signal for the nitrogen main pipe I2.3; High pressure alarm signal for the mixing tank I2.4; Emergency exhaust button I2.5; Stirring motor control Q0.0; Elevator motor control Q0.1; Filter press clamping control Q0.2; Filter press loosening control Q0.3; System operation indicator Q0.4; Replacement mode indicator Q0.5; Maintenance mode indicator Q0.6; Manual mode indicator Q0.7; Mixing tank inlet regulating valve V1 control Q1.0; Elevator feed inlet inlet valve V2 Q1.1 is controlled by the following valves: Elevator discharge inlet air valve V3 controls Q1.2; Feed buffer hopper air inlet regulating valve V4 controls Q1.3; Filter press air inlet regulating valve V5 controls Q1.4; Liquid storage device air inlet regulating valve V6 controls Q1.5; Mixing and stirring box exhaust regulating valve V8 controls Q2.0; Feed buffer hopper exhaust regulating valve V9 controls Q2.1; Filter press main exhaust regulating valve V10 controls Q2.2; Filter press auxiliary exhaust regulating valve V11 controls Q2.3; Liquid storage device exhaust regulating valve V12 controls Q2.4; Buzzer controls Q2.5; Oxygen content alarm light controls Q2.6; Pressure alarm light controls Q2.7; Mixing tank oxygen concentration sensor signal AIW0; Vertical filter press main body oxygen concentration sensor signal AIW2; Liquid storage device oxygen concentration sensor signal AIW4; Nitrogen main pipe pressure sensor signal AIW6; Mixing tank pressure sensor signal AIW8; Mixing tank inlet regulating valve V1 opening control AQW0; Filter press inlet regulating valve V5 opening control AQW2; Liquid storage device inlet regulating valve V6 opening control AQW4; Mixing tank exhaust regulating valve V8 opening control AQW6; Liquid storage device exhaust regulating valve V12 opening control AQW8; System operation flag M0.0; Automatic mode flag M0.1; Manual mode flag M0.2; Low nitrogen pressure flag M1.0; Replacement mode activation flag M2.0; The following timers are used to indicate the completion and maintenance conditions of a filter press: M2.1 (condition met); M2.2 (maintenance mode); M3.0 (elevator operation feedback); M3.1 (filter press request); M3.2 (filter press tightness in place); M3.5 (mixing tank high pressure); M4.0 (storage unit oxygen concentration meets standard); M4.1 (storage unit high liquid level); M5.0 (total oxygen content alarm); M6.0 (emergency exhaust activation); T1 (displacement completion stabilization timer); T10 (elevator inlet valve delayed shutdown timer); T11 (buffer hopper inlet valve delayed opening timer); T12 (buffer hopper exhaust valve delayed opening timer); T20 (pressing time control timer); T21 (filter press auxiliary exhaust valve delayed opening timer); T30 (storage unit exhaust valve delayed closing timer). Detailed Implementation

[0037] The present invention will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0038] The technical solutions and features provided in the various sections, including the following description, can be combined with each other without conflict. Furthermore, where possible, these technical solutions, features, and related combinations can be given specific technical subject matter and protected by relevant patents.

[0039] The embodiments of the present invention described below are generally only some embodiments and not all embodiments. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of patent protection.

[0040] The term "comprising" and any variations thereof in this specification, the corresponding claims, and related sections are intended to cover a non-exclusive inclusion. Other related terms and units can be reasonably interpreted based on the relevant content provided in this specification.

[0041] I. Overall structure of the filter press system.

[0042] like Figure 1 As shown, the pressure filtration system provided by the present invention includes a mechanical actuation unit 1, a protective gas supply unit 2, a gas monitoring unit, an exhaust control unit, and a central control unit.

[0043] Mechanical execution unit 1 is the core operating part of this filter press system, responsible for completing process operations such as material pretreatment, transfer, filter press separation, and liquid phase collection. Mechanical execution unit 1 includes a material pretreatment device, a material transfer device, a filter press device, and a liquid storage device. In this embodiment, the material pretreatment device is specifically a mixing tank 11, used for pre-mixing and conditioning the material to be filtered; the material transfer device is specifically a closed-type elevator 12, used to lift and transport the pretreated material from the mixing tank 11 to the filter press device; the filter press device includes a feed buffer hopper 131 and a vertical filter press body 132. The feed buffer hopper 131 is used to temporarily store the material transported by the closed-type elevator 12 and evenly supply it to the vertical filter press body 132. The vertical filter press body 132 is a compression-type solid-liquid separation device, used to apply mechanical pressure to the material to separate the liquid phase components; the liquid storage device 14 is used to collect and store the liquid phase components separated by the filter press device.

[0044] In this embodiment, the material pretreatment device and material conveying device transport a high-viscosity solid-liquid mixture slurry. The liquid phase component separated by the filter press is an oxidation-sensitive liquid, which is chemically unstable in the presence of oxygen. Typical applications include edible vegetable oil production, natural fragrance extraction, and extraction of active ingredients from medicinal plants—processing fields involving oxidation-sensitive liquids.

[0045] The discharge port of the mixing tank 11 is sealed and connected to the feed end of the closed elevator 12. The discharge end of the closed elevator 12 is sealed and connected to the top inlet of the feed buffer hopper 131. The bottom outlet of the feed buffer hopper 131 is connected to the top feed chamber of the vertical filter press body 132. The drain port of the vertical filter press body 132 is connected to the liquid storage device 14 through a pipeline. Through the above-mentioned sealed connection method, a material flow channel that is connected end to end and isolated from the external environment is formed inside the mechanical execution unit 1. This ensures that the entire process of material entering the mixing tank 11 until the liquid phase components are collected in the liquid storage device 14 is completed in a closed environment, providing a structural basis for atmosphere protection throughout the entire process.

[0046] The protective gas supply unit 2 supplies protective gas to each component of the mechanical actuator unit 1 to replace and isolate oxygen from the air. The protective gas supply unit 2 includes a main gas pipe, a main pipe pressure sensor P-1, and multiple intake branches connected to each intake point of the mechanical actuator unit 1. Each intake branch is equipped with an adjustable intake regulating valve. The main pipe pressure sensor P-1 is located on the main gas pipe and is used to detect the pressure value within the main gas pipe in real time. In this embodiment, the protective gas supplied by the protective gas supply unit 2 is a gas with a density less than air, specifically nitrogen. Using a gas with a density less than air as the protective gas allows for natural stratification and replacement based on density differences, improving gas replacement efficiency.

[0047] Specifically, the protective gas supply unit 2 includes a mixing tank inlet regulating valve V1 connected to the mixing tank 11, elevator inlet regulating valves V2 and V3 connected to the closed elevator 12, buffer hopper inlet regulating valve V4 connected to the feed buffer hopper 131, filter press inlet regulating valve V5 connected to the vertical filter press body 132, and liquid storage device inlet regulating valve V6 connected to the liquid storage device 14. Each inlet regulating valve is an adjustable valve, and its opening can be adjusted according to the instructions of the central control unit, thereby controlling the flow rate of protective gas entering each device.

[0048] Each inlet of the protective gas supply unit 2 is configured such that the protective gas diffuses in the mixing tank 11, the feed buffer hopper 131, and the vertical filter press body 132 in a downward diffusion direction. Since nitrogen is less dense than air, the nitrogen entering from the top will naturally diffuse downward and displace the air below, and finally be discharged through the exhaust point at the bottom or lower part, achieving efficient gas replacement.

[0049] The gas monitoring unit is used to monitor the oxygen concentration in key areas of the mechanical actuator 1 in real time, providing data for the control decisions of the central control unit. This gas monitoring unit includes oxygen concentration sensors respectively arranged inside the material pretreatment device, the filter press device, and the liquid storage device 14. In this embodiment, the gas monitoring unit includes an oxygen concentration sensor O2-1 installed in the mixing tank 11, an oxygen concentration sensor O2-2 installed in the vertical filter press body 132, and an oxygen concentration sensor O2-3 installed in the liquid storage device 14. Each oxygen concentration sensor is located at the bottom of the mixing tank 11, the vertical filter press body 132, and the liquid storage device 14. The reason for placing the oxygen concentration sensors at the bottom of each device is that, since the density of the protective gas is less than that of air, air will be displaced to the bottom of the device. Therefore, the oxygen concentration at the bottom can most accurately reflect the degree of gas replacement. When the oxygen concentration at the bottom drops below the safe value, it can be considered that the atmosphere inside the entire device has met the protection requirements.

[0050] In addition, the gas monitoring unit also includes a pressure sensor P-2 installed inside the mixing tank 11, which is used to monitor the pressure status inside the mixing tank 11 in real time.

[0051] The exhaust control unit is used to control the gas discharge from each area of ​​the mechanical actuator 1, and works in conjunction with the protective gas supply unit 2 to achieve gas circulation and replacement and maintain a slight positive pressure. The exhaust control unit includes exhaust regulating valves located at each exhaust point of the mechanical actuator 1. In this embodiment, the exhaust control unit includes a mixing tank exhaust regulating valve V8 connected to the mixing tank 11, a buffer hopper exhaust regulating valve V9 connected to the feed buffer hopper 131, filter press exhaust regulating valves V10 and V11 connected to the vertical filter press body 132, and a storage device exhaust regulating valve V12 connected to the storage device 14.

[0052] The filter press exhaust regulating valves include a main exhaust regulating valve V10 and an auxiliary exhaust regulating valve V11. The main exhaust regulating valve V10 is located at the bottom of the vertical filter press body 132 and is connected to the main liquid flow channel of the vertical filter press body 132. The auxiliary exhaust regulating valve V11 is located on the side of the vertical filter press body 132. The purpose of setting two exhaust regulating valves is to adapt to the exhaust requirements of different stages of the pressing process: at the initial stage of the pressing process, the main exhaust regulating valve V10 is opened while the auxiliary exhaust regulating valve V11 is closed, and most of the gas is discharged using the liquid flow channel generated by pressing; after the pressing process reaches a preset time point, the auxiliary exhaust regulating valve V11 is opened to discharge the residual gas pockets deep in the gaps between the filter plates, ensuring the complete replacement of the gas inside the filter press.

[0053] Each exhaust point of the exhaust control unit is matched with each inlet point of the protective gas supply unit 2, and configured so that the protective gas diffuses in the mixing tank 11, the feed buffer hopper 131, and the vertical filter press body 132 in a downward diffusion direction. Specifically, the inlet points are located at the top or upper part of each device, and the exhaust points are located at the lower or lower part of each device, thereby forming a downward airflow path and making full use of the physical property that nitrogen has a lower density than air to achieve natural stratification and replacement.

[0054] The central control unit is the core of this filter press system, responsible for coordinating the working status of each unit and achieving automated atmosphere protection control. This central control unit is electrically connected to the mechanical actuator unit 1, the protective gas supply unit 2, the gas monitoring unit, and the exhaust control unit. The central control unit receives signal inputs from the main pressure sensor P-1 and the oxygen concentration sensors O2-1, O2-2, O2-3, and pressure sensor P-2, and outputs control signals to the actuators of the mechanical actuator unit 1, the intake regulating valves V1 to V6, and the exhaust regulating valves V8 to V12. In this embodiment, the central control unit is implemented using a programmable logic controller (PLC), executing various control logics through a preset control program.

[0055] II. Control Logic of the Central Control Unit.

[0056] The central control unit is configured to execute the following control logic:

[0057] First, before starting the mechanical actuator 1, the gas main pressure is checked. If the pressure is lower than a preset safety threshold, the mechanical actuator 1 is locked and all intake regulating valves V1 to V6 are forcibly closed. This control logic ensures that the protective gas supply unit 2 has sufficient gas supply capacity before allowing the system to operate, avoiding the risk of atmosphere protection failure due to insufficient gas supply. In practical applications, the preset safety threshold is determined based on the design parameters of the protective gas supply unit 2 and the volume of the mechanical actuator 1, and is usually set to a pressure value that can meet the maximum intake volume requirement in the displacement mode.

[0058] Second, when the gas main pressure reaches the preset safety threshold, the feedback values ​​of each oxygen concentration sensor (O2-1, O2-2, O2-3) are read in real time. If the detection value of any oxygen concentration sensor exceeds the preset high-limit alarm value, the system automatically enters the replacement mode, controlling the corresponding intake regulating valve to open to the preset maximum intake opening, and simultaneously controlling the corresponding exhaust regulating valve to open to the preset maximum exhaust opening. During this replacement mode, mechanical actuator 1 is prohibited from operating. The replacement mode is a rapid replacement state during the initial system startup or when the oxygen concentration is abnormal. It quickly replaces the air inside mechanical actuator 1 with protective gas by introducing a large flow of protective gas and expelling a large flow of mixed gas. The preset maximum intake and exhaust openings are determined based on the volume of each device and the desired replacement time, and are usually set to keep the intake and exhaust regulating valves at a large opening to achieve rapid replacement.

[0059] Third, when the feedback values ​​of all oxygen concentration sensors O2-1, O2-2, and O2-3 are all lower than the preset safety setpoint and this state lasts for more than the preset stability timing threshold, the system automatically switches to maintenance mode. This mode controls the opening of each intake regulating valve V1 to V6 to decrease to the preset minimum intake opening, and simultaneously controls the opening of each exhaust regulating valve V8 to V12 to decrease to the preset minimum exhaust opening or close them, in order to maintain a slight positive pressure inside the mechanical actuator 1. It also releases the lock on the mechanical actuator 1 and allows the material pretreatment device, material conveying device, and filter press device to start operating sequentially according to the preset process sequence. Maintenance mode is the steady-state protection state during normal system operation. It maintains a slight positive pressure state inside the mechanical actuator 1 relative to the external environment by continuously replenishing it with a small flow of protective gas, preventing external air infiltration. The preset stability timing threshold is used to ensure that the oxygen concentration is indeed stable within a safe range, avoiding frequent mode switching due to short-term oxygen concentration fluctuations.

[0060] During maintenance mode operation, the auxiliary exhaust regulating valve V11, the buffer hopper exhaust regulating valve V9, and the mixing tank exhaust regulating valve V8 are at their preset minimum openings, while the main exhaust regulating valve V10 and the liquid storage device exhaust regulating valve V12 are closed. This configuration ensures that in maintenance mode, the protective gas mainly enters from the mixing tank 11, the feed buffer hopper 131, and the upper part of the vertical filter press body 132, and is discharged at a low flow rate through the corresponding exhaust regulating valves, maintaining a slight positive pressure state inside each device. The main exhaust regulating valve V10 is closed in maintenance mode because it is connected to the main liquid flow channel, and keeping it closed in maintenance mode prevents the protective gas from leaking out through the liquid flow channel. The liquid storage device exhaust regulating valve V12 is closed in maintenance mode because the liquid storage device 14, as a collection container for liquid phase components, has a relatively stable internal gas space and is connected to the vertical filter press body 132 through a drain pipe. It can be indirectly protected by the atmosphere protection on the side of the vertical filter press body 132, therefore, separate exhaust is not required.

[0061] Fourth, during the maintenance mode operation, if the feedback values ​​of oxygen concentration sensors O2-1, O2-2, and O2-3 show an upward trend and exceed the preset fluctuation threshold, the corresponding air intake regulating valve will automatically increase the preset compensation opening ratio based on the current opening. This control logic realizes real-time response and dynamic regulation of oxygen concentration fluctuations during the filter press process. During the filter press process, local oxygen concentration may rise due to material entry / exit, equipment movement, etc. Dynamically increasing the air intake can compensate in a timely manner and prevent the oxygen concentration from exceeding the safe range.

[0062] When the central control unit executes the automatic increase of the preset compensation opening ratio, it adopts a step-by-step superposition compensation algorithm. The logic of this algorithm is as follows: when the oxygen concentration exceeds the standard, the real-time opening value of the corresponding intake regulating valve is read; a preset incremental step value is superimposed on the real-time opening value to calculate a new target opening value; it is then determined whether the target opening value exceeds the maximum physical stroke of the corresponding intake regulating valve. If it does not exceed the maximum physical stroke, the intake regulating valve is driven to the target opening value; if it does exceed the maximum physical stroke, the intake regulating valve is driven to the maximum physical stroke. The advantage of using the step-by-step superposition compensation algorithm is that it gradually adjusts the opening by incremental step values, avoiding drastic fluctuations in the intake volume and achieving stable and precise atmosphere control. Simultaneously, by determining whether the target opening value exceeds the maximum physical stroke, it provides upper limit protection for the valve opening, preventing control commands from exceeding the actual adjustment range of the valve.

[0063] Fifth, upon receiving an emergency exhaust signal, regardless of the current mode of mechanical actuator 1, all exhaust regulating valves V8 to V12 are forcibly opened to the fullest extent, while all intake regulating valves V1 to V6 are closed. This control logic provides a safety response mechanism in emergency situations. When an abnormal situation occurs in the system requiring emergency exhaust, the gas inside mechanical actuator 1 can be quickly discharged, ensuring the safety of system operation. The emergency exhaust signal can be manually triggered by the operator or automatically triggered by other safety protection devices.

[0064] III. Special control strategies.

[0065] In addition to the basic control logic mentioned above, the central control unit also implements specialized control strategies for specific equipment and processes.

[0066] For the air intake control of the closed-loop elevator 12, the elevator air intake regulating valves V2 and V3 are configured to be linked to the motor operation status of the closed-loop elevator 12. When the motor starts, the elevator air intake regulating valves V2 and V3 are opened synchronously to form a dynamic nitrogen air curtain at the feed inlet and discharge outlet of the closed-loop elevator 12, preventing the material from coming into contact with air during the lifting process. When the motor stops, a delayed shutdown timer is triggered. During the preset delay period after the motor stops, the elevator air intake regulating valves V2 and V3 remain open. After the delay period ends, the elevator air intake regulating valves V2 and V3 are closed. The purpose of setting the delayed shutdown is to prevent backflow of external air caused by internal pressure fluctuations during shutdown: when the motor of the closed-loop elevator 12 suddenly stops, a momentary negative pressure may be generated inside. If the air intake valve is closed immediately at this time, external air may be sucked in through the gap between the feed inlet or discharge outlet. By maintaining the air intake during the delay, a positive pressure state can be maintained during the shutdown transition, effectively preventing backflow of air.

[0067] For the air intake and exhaust control of the feed buffer hopper 131, the opening sequence of the buffer hopper air intake regulating valve V4 and the buffer hopper exhaust regulating valve V9 is related to the operating status of the closed elevator 12. The central control unit is configured to: open the buffer hopper air intake regulating valve V4 after a first preset delay since the closed elevator 12 has started operation; and open the buffer hopper exhaust regulating valve V9 after a second preset delay since the buffer hopper air intake regulating valve V4 has been open. The purpose of this timing control is to establish a nitrogen protection environment and replace the air brought in when the material enters the feed buffer hopper 131: the first preset delay ensures that nitrogen is introduced before the material is about to reach the feed buffer hopper 131; the second preset delay ensures that exhaust is opened only after a sufficient nitrogen concentration has been established in the feed buffer hopper 131, so that the air brought in with the material can be effectively replaced and discharged.

[0068] For the exhaust control of the vertical filter press body 132, in the initial stage of the pressing process, the main exhaust regulating valve V10 is opened while the auxiliary exhaust regulating valve V11 is closed, utilizing the liquid flow channel generated during pressing to discharge most of the gas. The main exhaust regulating valve V10 is connected to the main liquid flow channel. In the initial stage of pressing, the liquid phase generated after the material is compressed carries a large amount of gas and is discharged through the main liquid flow channel. Opening the main exhaust regulating valve V10 at this time can fully utilize this process to discharge the gas. After the pressing process reaches a preset time point, the auxiliary exhaust regulating valve V11 is opened to discharge the residual gas pockets deep in the filter plate gaps. As the pressing process progresses, the gas in the filter plate gaps is gradually compressed to form gas pockets. These gas pockets are difficult to discharge through the main liquid flow channel. At this time, by opening the auxiliary exhaust regulating valve V11 located on the side of the vertical filter press body 132, a discharge channel can be provided for these residual gases, ensuring complete gas replacement inside the filter press.

[0069] IV. Implementation of PLC ladder diagram program for central control unit.

[0070] The central control unit is implemented using a programmable logic controller (PLC), which executes various control logics through a ladder diagram program. The following section will discuss this further. Figures 2 to 9 Provide a detailed explanation of the specific implementation of each control program.

[0071] 4.1 I / O Address Allocation

[0072] Before explaining the ladder diagram program in detail, we will first explain the I / O address allocation of the PLC.

[0073] Digital inputs: I0.0 is the start button, I0.1 is the stop button, I0.2 is the emergency stop button, I0.3 is the reset button, I0.4 is the manual / automatic switch, and I0.5 is the replacement mode button; I1.0 is the filter press clamping position detection, I1.1 is the filter press loosening position detection, I1.2 is the elevator operation feedback, I1.3 is the hopper full position detection, and I1.4 is the liquid level high detection in the storage device; I2.0 is the low oxygen concentration alarm signal in the mixing tank, I2.1 is the low oxygen concentration alarm signal in the main body of the vertical filter press, I2.2 is the low oxygen concentration alarm signal in the storage device, I2.3 is the low pressure alarm signal in the nitrogen main pipe, I2.4 is the high pressure alarm signal in the mixing tank, and I2.5 is the emergency exhaust button.

[0074] Digital outputs: Q0.0 controls the stirring motor, Q0.1 controls the elevator motor, Q0.2 controls the filter press clamping, Q0.3 controls the filter press loosening, Q0.4 is the system operation indicator, Q0.5 is the replacement mode indicator, Q0.6 is the maintenance mode indicator, and Q0.7 is the manual mode indicator; Q1.0 controls the mixing tank air inlet regulating valve V1, Q1.1 controls the elevator inlet air valve V2, Q1.2 controls the elevator outlet air valve V3, and Q1.3 controls the feed buffer hopper air inlet regulating valve. Valve V4 controls the following valves: Q1.4 controls the filter press inlet air regulating valve V5; Q1.5 controls the liquid storage device inlet air regulating valve V6; Q2.0 controls the mixing tank exhaust regulating valve V8; Q2.1 controls the feed buffer hopper exhaust regulating valve V9; Q2.2 controls the filter press main exhaust regulating valve V10; Q2.3 controls the filter press auxiliary exhaust regulating valve V11; Q2.4 controls the liquid storage device exhaust regulating valve V12; Q2.5 controls the buzzer; Q2.6 controls the oxygen content alarm light; and Q2.7 controls the pressure alarm light.

[0075] For analog inputs: AIW0 is the oxygen concentration sensor signal for the mixing tank, AIW2 ​​is the oxygen concentration sensor signal for the vertical filter press, AIW4 is the oxygen concentration sensor signal for the liquid storage device, AIW6 is the nitrogen main pipe pressure sensor signal, and AIW8 is the mixing tank pressure sensor signal. The range of each analog input is 0 to 27648, with the oxygen concentration sensor corresponding to 0 to 25% oxygen concentration, the nitrogen main pipe pressure sensor corresponding to 0 to 1 MPa, and the mixing tank pressure sensor corresponding to 0 to 1 kPa.

[0076] For analog outputs: AQW0 controls the opening of the mixing tank inlet regulating valve V1; AQW2 controls the opening of the filter press inlet regulating valve V5; AQW4 controls the opening of the liquid storage device inlet regulating valve V6; AQW6 controls the opening of the mixing tank exhaust regulating valve V8; and AQW8 controls the opening of the liquid storage device exhaust regulating valve V12. The range of each analog output is 0 to 27648, corresponding to a valve opening of 0 to 100%.

[0077] Regarding internal flags: M0.0 is the system operation flag, M0.1 is the automatic mode flag, M0.2 is the manual mode flag; M1.0 is the low nitrogen pressure flag; M2.0 is the replacement mode activation flag, M2.1 is the replacement completion condition met flag, M2.2 is the maintenance mode flag; M3.0 is the elevator operation feedback flag, M3.1 is the filter press request flag, M3.2 is the filter press tightness complete flag, M3.5 is the mixing tank high pressure flag; M4.0 is the liquid storage device oxygen concentration standard met flag, M4.1 is the liquid storage device high liquid level flag; M5.0 is the total oxygen content alarm flag; M6.0 is the emergency exhaust activation flag.

[0078] 4.2 Gas main pipe pressure detection and system start-up and shutdown control.

[0079] like Figure 2 As shown, this ladder diagram realizes functions such as system start-stop control, operation mode selection, and gas main pressure detection.

[0080] Step 1 implements the set / reset control for system start and stop. When the start button I0.0 is pressed, the system run flag M0.0 is set, and the system enters the running state. When the stop button I0.1 or the emergency stop button I0.2 is pressed, the system run flag M0.0 is reset, and the system stops running. This design uses set / reset instructions to ensure reliable maintenance and switching of system states.

[0081] Steps 2 and 3 enable selection between automatic and manual modes. When the system operation flag M0.0 is active and the manual / automatic switch I0.4 is on, the automatic mode flag M0.1 is active; when the system operation flag M0.0 is active and the manual / automatic switch I0.4 is off, the manual mode flag M0.2 is active. Automatic and manual modes are mutually exclusive; only one mode can be active at a time.

[0082] Step 4 enables the detection of the main gas pipe pressure. A comparison command compares the value of the analog input AIW6 with a preset safety threshold of 8294, which corresponds to a pressure of 0.3 MPa. When AIW6 is less than 8294, it indicates that the nitrogen main pipe pressure is below the preset safety threshold, and the low nitrogen pressure flag M1.0 is then set.

[0083] Step 5 implements alarm and system protection functions for low nitrogen pressure. When the low nitrogen pressure indicator M1.0 is active, the hardware alarm input I2.3 is confirmed, simultaneously driving the pressure alarm light Q2.7 and buzzer Q2.5 to issue audible and visual alarms. More importantly, the low nitrogen pressure indicator M1.0 controls the system operation indicator M0.0 through a normally closed contact. When the pressure is low, the system operation indicator is forcibly reset, achieving lock protection for the mechanical actuator. This control logic ensures that when the nitrogen pressure is lower than the preset safety threshold, the mechanical actuator is locked and all intake regulating valves are forcibly closed, avoiding the risk of atmosphere protection failure due to insufficient gas supply.

[0084] Step 6 controls the indicator lights for each mode. When the system operation flag M0.0 is valid, the system operation indicator light Q0.4 is lit; when the automatic mode flag M0.1 is valid, the automatic mode indicator light is lit; when the manual mode flag M0.2 is valid, the manual mode indicator light Q0.7 is lit.

[0085] 4.3 Automatic switching control between replacement mode and maintenance mode.

[0086] like Figure 3 As shown, this ladder diagram enables automatic switching control between the replacement mode and the maintenance mode.

[0087] Step 1 enables manual forced activation of the replacement mode. When the replacement mode button I0.5 is pressed, the replacement mode activation flag M2.0 is set, and the system is forced into replacement mode.

[0088] Stage 2 implements automatic triggering of the replacement mode based on oxygen concentration. When the automatic mode flag M0.1 is valid, the system reads the feedback values ​​of each oxygen concentration sensor in real time. Through rising edge detection commands, the replacement mode activation flag M2.0 is triggered when any one of the following conditions is met: the oxygen concentration AIW0 in the mixing tank is greater than or equal to 3317 (corresponding to 3% oxygen concentration); the oxygen concentration AIW2 ​​in the vertical filter press body is greater than or equal to 3317; or the oxygen concentration AIW4 in the storage device is greater than or equal to 2211 (corresponding to 2% oxygen concentration). This design enables the system to automatically enter the replacement mode control logic when the detected value of any oxygen concentration sensor exceeds the preset high-limit alarm value. During the replacement mode, the mechanical actuator is prohibited from operation because the replacement mode activation flag M2.0 is interlocked with the start condition of the mechanical actuator.

[0089] Stage 3 determines the conditions for completion of the replacement process. When the replacement mode activation flag M2.0 is active, the system continuously monitors the feedback values ​​of each oxygen concentration sensor. Through comparison commands, when the oxygen concentration AIW0 in the mixing tank is less than 3317, the oxygen concentration AIW2 ​​in the main body of the vertical filter press is less than 3317, and the oxygen concentration AIW4 in the liquid storage device is less than 2211, the replacement completion condition fulfillment flag M2.1 is set, indicating that the feedback values ​​of all oxygen concentration sensors are lower than the preset safety setpoint.

[0090] Step 4 establishes a stable timing mechanism after oxygen replacement is completed. When the replacement completion condition is met and flag M2.1 is valid, delay timer T1 is activated to start timing, with a preset time PT of 5 minutes. This stable timing threshold ensures that the oxygen concentration remains stable within a safe range, avoiding frequent mode switching due to short-term fluctuations in oxygen concentration.

[0091] Step 5 enables automatic switching from replacement mode to sustain mode. When timer T1 completes its count, its output contact T1.Q closes, resetting the replacement mode activation flag M2.0 via a reset command, and the system exits replacement mode.

[0092] Step 6 generates the sustain mode flag. When the automatic mode flag M0.1 is valid and the replacement mode activation flag M2.0 is invalid, the sustain mode flag M2.2 is valid. The sustain mode is the steady-state protection state during normal system operation. In this mode, the opening of each intake regulating valve is reduced to the preset minimum intake opening, and the opening of each exhaust regulating valve is reduced to the preset minimum exhaust opening or closed, in order to maintain a slight positive pressure inside the mechanical actuator and release the lock on the mechanical actuator.

[0093] Step 7 controls the mode indicator lights. When the replacement mode activation flag M2.0 is valid, the replacement mode indicator light Q0.5 illuminates; when the sustain mode flag M2.2 is valid, the sustain mode indicator light Q0.6 illuminates.

[0094] 4.4 Control of the air inlet and exhaust regulating valves of the mixing tank.

[0095] like Figure 4 As shown, this trapezoidal diagram enables the intake and exhaust control of the mixing tank.

[0096] The first part controls the mixing motor. When the automatic mode flag M0.1 is active and the hopper full level detection I1.3 is active, the mixing motor Q0.0 starts running. A full hopper indicates that there is material in the mixing tank that needs to be pre-treated by mixing.

[0097] The second part controls the air intake regulating valve V1 of the mixing tank. When the automatic mode flag M0.1 is active and the low nitrogen pressure flag M1.0 is inactive, the air intake regulating valve Q1.0 of the mixing tank opens. The valve opening is automatically adjusted according to the current operating mode: when the displacement mode activation flag M2.0 is active, the value 20736 is written to the analog output AQW0 via the MOVE command, corresponding to a 75% opening, which is the preset large air intake opening; when the maintenance mode flag M2.2 is active, the value 9677 is written to the analog output AQW0 via the MOVE command, corresponding to a 35% opening, which is the preset small air intake opening.

[0098] The third part controls the exhaust regulating valve V8 of the mixing tank. When the automatic mode flag M0.1 is active and the low nitrogen pressure flag M1.0 is inactive, the exhaust regulating valve Q2.0 of the mixing tank opens. The valve opening is also automatically adjusted according to the current operating mode: when the displacement mode activation flag M2.0 is active, the value 23501 is written to the analog output AQW6 via the MOVE command, corresponding to an 85% opening, which is the preset large exhaust opening; when the maintenance mode flag M2.2 is active, the value 4147 is written to the analog output AQW6 via the MOVE command, corresponding to a 15% opening, which is the preset small exhaust opening. Keeping the exhaust regulating valve of the mixing tank slightly open in maintenance mode can maintain a slight positive pressure state inside the mixing tank and achieve slow gas renewal.

[0099] The fourth part implements pressure monitoring of the mixing tank. By detecting the rising edge triggered by the scan cycle, the mixing tank pressure AIW8 is compared with a threshold of 2765, which corresponds to a pressure value of 100 Pa. When AIW8 is greater than 2765, the high pressure indicator M3.5 of the mixing tank is set. When M3.5 is valid, the hardware alarm input I2.4 is confirmed, and the pressure alarm light Q2.7 is activated to sound an alarm.

[0100] The fifth part implements an oxygen content alarm for the mixing tank. When the maintenance mode flag M2.2 is valid, the oxygen concentration AIW8 in the mixing tank is compared with the threshold 2765. If it exceeds the threshold, the alarm output I2.4 and the oxygen content alarm light Q2.6 are triggered. Simultaneously, the oxygen concentration AIW0 in the mixing tank is compared with the threshold 2211. If it exceeds the threshold, the oxygen content alarm light Q2.6 is activated.

[0101] 4.5 Interlocking control and delayed shutdown of the air intake regulating valve of the closed-type hoist.

[0102] like Figure 5 As shown, this ladder diagram realizes the motor control of the closed hoist and the linkage control between the hoist's air intake regulating valve and the motor's operating status.

[0103] Step 1 controls the elevator motor. When the automatic mode flag M0.1 is active, the hopper full level detection I1.3 is active, the liquid storage device high level detection I1.4 is inactive, and the stirring motor Q0.0 is running, if the current elevator motor Q0.1 is not running, then elevator motor Q0.1 will be started. Simultaneously, when the elevator operation feedback I1.2 is active, the elevator operation feedback flag M3.0 is set. This control logic ensures that the elevator only starts operating when the material is ready and the liquid storage device has sufficient capacity.

[0104] Step 2 enables the linkage control of the air inlet valve V2 at the elevator feed inlet. When the automatic mode flag M0.1 is active, the low nitrogen pressure flag M1.0 is inactive, the elevator motor Q0.1 is running, and the delayed shutdown timer T10 has not completed its count, the air inlet valve Q1.1 at the elevator feed inlet opens. This design links the elevator feed inlet regulating valve with the motor operating status of the closed-loop elevator. When the motor starts, the air inlet valve opens synchronously, forming a dynamic nitrogen curtain at the feed inlet of the closed-loop elevator to prevent material from contacting air during the lifting process.

[0105] Step 3 implements a delayed shutdown timing function. When the hoist motor Q0.1 stops running, the normally closed contact of Q0.1 is used as a condition to trigger the start of the delayed timer T10, with a preset time PT of 30 seconds. During the 30 seconds after the motor stops, the normally closed contact of timer T10 remains closed, and the hoist inlet air valve Q1.1 remains open. After the 30-second delay period ends, timer T10 outputs a valid value, its normally closed contact opens, and the hoist inlet air valve Q1.1 closes. This delayed shutdown design is used to prevent backflow of external air caused by internal pressure fluctuations during shutdown: when the hoist motor suddenly stops, a momentary negative pressure may be generated inside. By maintaining the air valve open during the delay, a positive pressure state can be maintained during the shutdown transition, effectively preventing backflow of air.

[0106] Step 4 controls the air inlet valve V3 at the elevator discharge port. The air inlet valve Q1.2 at the elevator discharge port is controlled synchronously with the air inlet valve Q1.1 at the elevator feed port. When Q1.1 is opened, Q1.2 is opened synchronously, thus forming a dynamic nitrogen curtain at the discharge port of the closed elevator.

[0107] 4.6 Feed buffer hopper and air intake and exhaust control of the main body of vertical filter press.

[0108] like Figure 6 As shown, the trapezoidal diagram realizes the air intake and exhaust control of the feed buffer hopper and the main body of the vertical filter press, as well as the timing control of the filter pressing process.

[0109] Stage 1 implements delayed opening control of the feed buffer hopper air inlet regulating valve V4. When the automatic mode flag M0.1 is active, the low nitrogen pressure flag M1.0 is inactive, and the elevator motor Q0.1 is running, the delay timer T11 is activated to start timing, with a preset time PT of 5 seconds. When timer T11 completes its timeout, the feed buffer hopper air inlet regulating valve Q1.3 opens. This design achieves the control logic of opening the buffer hopper air inlet regulating valve after the first preset delay (5 seconds) has elapsed since the start-up of the sealed elevator, ensuring that nitrogen is introduced before the material reaches the buffer hopper.

[0110] Stage 2 implements delayed opening control of the feed buffer hopper exhaust regulating valve V9. When the feed buffer hopper intake regulating valve Q1.3 opens, a delay timer T12 is activated to start timing, with a preset time PT of 3 seconds. After timer T12 completes, the feed buffer hopper exhaust regulating valve Q2.1 opens. This design achieves the control logic of opening the buffer hopper exhaust regulating valve after a second preset delay (3 seconds) following the opening of the intake regulating valve, ensuring that a sufficient nitrogen concentration is established in the buffer hopper before exhaust, allowing the air brought in with the material to be effectively replaced and discharged.

[0111] Stage 3 determines the start-up conditions for filter press operation. When the automatic mode flag M0.1 is valid, the hopper full level detection I1.3 is valid, the liquid storage device high level detection I1.4 is invalid, the filter press request flag M3.1 is invalid, and the system is not currently in a filter press request state, the filter press request flag M3.1 is set, indicating that the system requests to start the filter press process.

[0112] Step 4 controls the pressing of the filter press. When the filter press request flag M3.1 is valid and the filter press release detection I1.1 is valid, the filter press pressing output Q0.2 is valid, driving the main body of the vertical filter press to perform the pressing action. When the filter press pressing completion detection I1.0 is valid, the filter press pressing completion flag M3.2 is set, indicating that the filter press has completed the pressing action and enters the pressing process.

[0113] Step 5 controls the pressing time. When the filter press is in the pressing position (marked by M3.2) is active, the delay timer T20 is activated to start timing. The preset time PT is 15 minutes, which is used to control the duration of the pressing process.

[0114] Step 6 controls the release of the filter press. When timer T20 completes and the filter press pressing position detection I1.0 is valid, the filter press release output Q0.3 is valid, driving the main body of the vertical filter press to perform the release action. When the filter press release position detection I1.1 is valid, the filter press request flag M3.1 is reset, completing one filter press cycle.

[0115] Step 7 controls the filter press inlet regulating valve V5. When the automatic mode indicator M0.1 is active, the low nitrogen pressure indicator M1.0 is inactive, and the filter press compression complete indicator M3.2 is active, the filter press inlet regulating valve Q1.4 opens. The valve opening is automatically adjusted according to the current operating mode: when the replacement mode activation indicator M2.0 is active, it corresponds to the preset large inlet opening; when the maintenance mode indicator M2.2 is active, it corresponds to the preset small inlet opening.

[0116] Step 8 controls the main exhaust regulating valve V10 of the filter press. When the filter press is in the pressed position (marked by M3.2) is active, the main exhaust regulating valve Q2.2 opens. This design achieves the control logic of opening the main exhaust regulating valve at the initial stage when the vertical filter press body enters the pressing process, utilizing the liquid flow channel generated during pressing to discharge most of the gas.

[0117] Step 8 also implements delayed opening control of the filter press auxiliary exhaust regulating valve V11. When the filter press pressing position indicator M3.2 is valid, the delay timer T21 is activated to start timing, with a preset time PT of 2 minutes. When timer T21 completes its timeout, the filter press auxiliary exhaust regulating valve Q2.3 opens. This design implements the control logic to open the auxiliary exhaust regulating valve after the pressing process reaches the preset time node (2 minutes), which is used to discharge residual gas pockets deep in the gaps between the filter plates, ensuring complete gas replacement inside the filter press.

[0118] 4.7 Control of the inlet and outlet regulating valves of the liquid storage device.

[0119] like Figure 7 As shown, this trapezoidal diagram realizes the air intake and exhaust control of the liquid storage device.

[0120] Step 1 controls the air inlet regulating valve V6 of the liquid storage device. When the automatic mode indicator M0.1 is active and the low nitrogen pressure indicator M1.0 is inactive, the air inlet regulating valve Q1.5 of the liquid storage device opens. The liquid storage device is only sealed with nitrogen from the top, utilizing the property that nitrogen is less dense than air to naturally sink and form a protective layer.

[0121] Stage 2 controls the switching of the inlet regulating valve opening of the liquid storage device. When the displacement mode activation flag M2.0 is active, the value 16589 is written to the analog output AQW4 via the MOVE command, corresponding to a 60% opening, which is the preset large inlet opening. When the maintenance mode flag M2.2 is active, the value 5530 is written to the analog output AQW4 via the MOVE command, corresponding to a 20% opening, which is the preset small inlet opening. In maintenance mode, the liquid storage device requires only a small nitrogen flow rate to maintain the top nitrogen sealing effect.

[0122] Stage 3 controls the exhaust regulating valve V12 of the liquid storage device. When the automatic mode flag M0.1 is valid, the low nitrogen pressure flag M1.0 is invalid, the replacement mode activation flag M2.0 is valid, and the stable timing timer T30 has not finished timing, the exhaust regulating valve Q2.4 of the liquid storage device opens. In replacement mode, the exhaust regulating valve of the liquid storage device opens to the preset large exhaust opening, which, in conjunction with the intake regulating valve, achieves rapid gas replacement.

[0123] Stage 4 controls the oxygen concentration compliance of the liquid storage device and the vent valve closure. A comparison command compares the oxygen concentration AIW4 of the liquid storage device with a threshold of 1106, corresponding to a 1% oxygen concentration. When AIW4 is less than 1106, the oxygen concentration compliance flag M4.0 is set. When M4.0 is active, a delay timer T30 is activated, with a preset time PT of 5 minutes. After timer T30 completes its count, the control circuit of the vent valve Q2.4 is disconnected via a normally closed contact, closing the vent valve. This design implements the control logic for closing the vent valve during maintenance mode operation, as the liquid storage device, as a collection container for liquid components, has a relatively stable internal gas space and does not require continuous venting in maintenance mode.

[0124] Step 5 enables liquid level monitoring of the storage device. When the high liquid level detection I1.4 of the storage device is valid, the buzzer Q2.5 sounds an alarm, and simultaneously disconnects the control circuit of the elevator motor Q0.1 through a normally closed contact, stopping the continued material conveying. The high liquid level indicator M4.1 of the storage device is simultaneously set for display on the human-machine interface.

[0125] 4.8 Oxygen concentration monitoring and step-by-step superposition compensation algorithm control.

[0126] like Figure 8 As shown, this trapezoidal diagram enables comprehensive monitoring of oxygen concentration at multiple points and step-by-step superimposed compensation control when oxygen concentration exceeds the standard.

[0127] Stage 1 implements multi-point oxygen concentration OR alarm logic. The low oxygen concentration alarm I2.0 of the mixing tank, the low oxygen concentration alarm I2.1 of the vertical filter press, and the low oxygen concentration alarm I2.2 of the liquid storage device are combined through OR logic. When the oxygen concentration at any point exceeds the standard, the total oxygen content alarm flag M5.0 is set.

[0128] Step 2 enables audible and visual alarms when oxygen content exceeds the standard. When the total oxygen content alarm flag M5.0 is active, it activates the oxygen content alarm light Q2.6 and the buzzer Q2.5 to emit an audible and visual alarm, alerting the operator.

[0129] The third stage implements a step-by-step superimposed compensation algorithm. When the total oxygen content alarm flag M5.0 is valid and the maintenance mode flag M2.2 is valid, the system automatically performs intake air compensation. Specifically, it reads the current value of the mixing tank intake regulating valve opening AQW0 using the ADD addition command, superimposes a preset incremental step value of 6912 (corresponding to 25% opening), calculates the new target opening value, and writes it back to AQW0. Similarly, the same superimposed compensation operation is performed on the filter press intake regulating valve opening AQW2 and the liquid storage device intake regulating valve opening AQW4. This design realizes the control logic that, during maintenance mode operation, if the feedback value of the oxygen concentration sensor shows an upward trend and exceeds the preset fluctuation threshold, the corresponding intake regulating valve is automatically increased by a preset compensation opening ratio based on the current opening.

[0130] Step 4 implements upper limit protection for valve opening. A comparison command is used to determine whether the values ​​of each analog output (AQW0, AQW2, AQW4, AQW6, AQW8) exceed the maximum value of 27648 (corresponding to 100% opening). If any analog output value exceeds 27648, a MOVE command is used to limit it to 27648. This design implements the control logic in the step-by-step superposition compensation algorithm that determines whether the target opening value exceeds the maximum physical stroke of the corresponding intake control valve: if it does not exceed, the intake control valve is driven to the target opening value; if it does exceed, the intake control valve is driven to the maximum physical stroke (100% opening). Upper limit protection prevents control commands from exceeding the actual adjustment range of the valve, ensuring the safe and stable operation of the system.

[0131] 4.9 Emergency Exhaust Response Control.

[0132] like Figure 9 As shown, this ladder diagram implements the emergency exhaust response control function.

[0133] Step 1 enables the triggering and resetting of emergency venting. When the emergency venting button I2.5 is pressed, the emergency venting activation flag M6.0 is set, and the system enters emergency venting mode. When the reset button I0.3 is pressed, the emergency venting activation flag M6.0 is reset, and the system exits emergency venting mode. The emergency venting signal can be manually triggered by the operator or automatically triggered by other safety protection devices.

[0134] Stage 2 enables all exhaust regulating valves to be forcibly fully opened during emergency exhaust. When the emergency exhaust activation flag M6.0 is active, the exhaust regulating valves Q2.0 of the mixing tank, Q2.1 of the feed buffer hopper, Q2.2 of the filter press main exhaust regulating valve, Q2.3 of the filter press auxiliary exhaust regulating valve, and Q2.4 of the liquid storage device are all forcibly opened. This design achieves the control logic of forcibly controlling all exhaust regulating valves to be fully opened when an emergency exhaust signal is received, regardless of the current mode of the mechanical actuator.

[0135] Stage 3 enables the electric regulating valve to be fully opened during emergency venting. When the emergency venting activation flag M6.0 is valid, the value 27648 (corresponding to 100% opening) is written to the opening of the mixing tank venting regulating valve AQW6 and the liquid storage device venting regulating valve AQW8 via the MOVE command, ensuring that the electric regulating valve is also fully open for venting.

[0136] It should be noted that, in emergency exhaust mode, although Figure 9 While the control circuit for closing all intake regulating valves is not explicitly shown, the emergency exhaust activation indicator M6.0 is interlocked with the control circuits of each intake regulating valve. When M6.0 is active, the system operation indicator M0.0 is reset, and the automatic mode indicator M0.1 and the maintenance mode indicator M2.2 become inactive, causing all intake regulating valves to automatically close due to unmet control conditions. Simultaneously, an audible and visual alarm is triggered by the emergency exhaust buzzer Q2.5 and the emergency exhaust alarm light Q2.6, alerting the operator that the system is in emergency exhaust mode. This design provides a safety response mechanism in emergency situations. When an abnormal situation occurs and emergency exhaust is required, the gas inside the mechanical actuator can be quickly discharged, ensuring the safety of system operation.

[0137] V. Typical Production Process Sequence.

[0138] The typical production process sequence of this filter press system is as follows:

[0139] First, the operator presses the start button I0.0, and the system automatically detects the nitrogen main pipe pressure P-1. If the pressure is greater than or equal to 0.3MPa, the system operation flag M0.0 is set, and the system enters the operating state; if the pressure is lower than 0.3MPa, the system remains locked and issues a low pressure alarm.

[0140] Secondly, the system automatically detects the oxygen concentration at each point to determine whether to enter replacement mode or maintenance mode. If any oxygen concentration sensor reading exceeds the preset high-limit alarm value, the system automatically enters replacement mode, which typically lasts 30 to 60 minutes. In replacement mode, the mixing tank inlet regulating valve V1, the filter press inlet regulating valve V5, and the liquid storage device inlet regulating valve V6 are opened at preset maximum inlet openings, while the mixing tank exhaust regulating valve V8 and the liquid storage device exhaust regulating valve V12 are opened at preset maximum exhaust openings, achieving rapid gas replacement. Once all oxygen concentration sensor readings are below the preset safety setpoint and stabilize for 5 minutes, the system automatically switches to maintenance mode.

[0141] After entering maintenance mode, the system unlocks the mechanical actuators and allows each piece of equipment to start running sequentially according to the preset process sequence. The specific process is as follows: the mixing tank's stirring motor Q0.0 starts to pre-treat the material; when the hopper full level detection I1.3 is valid and the liquid storage device high level detection I1.4 is invalid, the elevator motor Q0.1 starts, lifting the material from the mixing tank to the feed buffer hopper; after the feed buffer hopper receives the material, when the hopper is full, the filter press request flag M3.1 is set, and the filter press begins its pressing action; after pressing, the pressing process begins, lasting 15 minutes before being released, completing one filter press cycle; the separated liquid phase flows into the liquid storage device, and the liquid level is continuously monitored. The entire production process is repeated continuously.

[0142] Throughout the entire production process, all equipment operates under a slightly positive pressure nitrogen protection environment, with oxygen concentration sensors continuously monitoring the oxygen concentration in each area. If the oxygen concentration shows an upward trend and exceeds the preset fluctuation threshold during operation in maintenance mode, the system automatically performs step-by-step superimposed compensation, increasing the opening of the corresponding intake regulating valve to replenish nitrogen.

[0143] When shutting down, the operator presses the stop button I0.1. Each piece of equipment will be purged sequentially and then stop operating, but nitrogen will be maintained to prevent air from entering. In case of emergency, pressing the emergency vent button I2.5 will immediately force all vent valves to open and all intake valves to close, quickly expelling gas from the system.

[0144] like Figure 10 The image shown is a photograph of the filter press device in an embodiment of the filter press system of the present invention, illustrating the layout of the vertical filter press body and its associated air intake and exhaust pipes.

[0145] In summary, this invention, by setting up a protective gas supply unit 2, a gas monitoring unit, an exhaust control unit, and a central control unit, and by using a PLC ladder diagram program to implement various control logics, achieves atmosphere protection and precise adaptive control of the entire process of the mechanical execution unit, effectively solving the technical problems of existing pressure filter systems lacking full-process atmosphere protection and being unable to perform precise adaptive control of the atmosphere environment.

[0146] The foregoing has described the relevant content of the present invention. Those skilled in the art will be able to implement the present invention based on these descriptions. All other embodiments obtained by those skilled in the art based on the foregoing content of this specification without inventive effort should fall within the scope of the present invention.

Claims

1. A filter press system, characterized in that: include: The mechanical execution unit includes a material pretreatment device, a material conveying device, a filter press device, and a liquid storage device; A protective gas supply unit includes a gas main pipe, a main pipe pressure sensor, and multiple air intake branches connected to each air intake point of the mechanical actuator. Each air intake branch is equipped with an air intake regulating valve with an adjustable opening. A gas monitoring unit, comprising oxygen concentration sensors respectively arranged inside the material pretreatment device, the filter press and the liquid storage device; An exhaust control unit, comprising exhaust regulating valves disposed at each exhaust point of the mechanical actuator; A central control unit, which is electrically connected to the mechanical actuator, the protective gas supply unit, the gas monitoring unit, and the exhaust control unit, is configured to execute the following control logic: 1) Before the mechanical actuator is started, the pressure of the gas main pipe is detected. If the pressure is lower than the preset safety threshold, the mechanical actuator is locked and all intake regulating valves are forcibly closed. 2) When the gas main pressure reaches the preset safety threshold, the feedback values ​​of each oxygen concentration sensor are read in real time. If the detection value of any oxygen concentration sensor is higher than the preset high limit alarm value, the replacement mode is automatically entered. The corresponding intake regulating valve is controlled to open at the preset large intake opening, and the corresponding exhaust regulating valve is controlled to open at the preset large exhaust opening. During this replacement mode, the mechanical actuator is prohibited from operating. 3) When the feedback values ​​of all oxygen concentration sensors are lower than the preset safety setting value and the duration of this state exceeds the preset stable timing threshold, the system automatically switches to the maintenance mode, controls the opening of each intake regulating valve to decrease to the preset small intake opening, and simultaneously controls the opening of each exhaust regulating valve to decrease to the preset small exhaust opening or closes it, so as to maintain a slight positive pressure inside the mechanical actuator, and releases the lock on the mechanical actuator, allowing the material pretreatment device, the material conveying device, and the filter press to start operation in sequence according to the preset process timing. 4) During the operation of the maintenance mode, if the feedback value of the oxygen concentration sensor shows an upward trend and exceeds the preset fluctuation threshold, the corresponding intake regulating valve is controlled to automatically increase the preset compensation opening ratio based on the current opening. When the central control unit executes the automatic increase of the preset compensation opening ratio, a step-by-step superimposed compensation algorithm is adopted. The logic of the step-by-step superimposed compensation algorithm is as follows: when the oxygen concentration is detected to exceed the standard, the real-time opening value of the corresponding intake regulating valve at the current moment is read. A preset incremental step value is superimposed on the real-time opening value to calculate a new target opening value; Determine whether the target opening value exceeds the maximum physical stroke of the corresponding intake regulating valve. If it does not exceed the target opening value, drive the intake regulating valve to the target opening value. If the limit is exceeded, the intake regulating valve will be driven to its maximum physical stroke. 5) When an emergency exhaust signal is received, regardless of the current mode of the mechanical actuator, all exhaust regulating valves are forcibly opened, and all intake regulating valves are closed at the same time. The material pretreatment device includes a mixing tank, the material conveying device includes a closed elevator, and the filter press includes a feed buffer hopper and a vertical filter press body. The discharge port of the mixing tank is sealed and connected to the feed end of the closed elevator, the discharge end of the closed elevator is sealed and connected to the top inlet of the feed buffer hopper, the bottom outlet of the feed buffer hopper is connected to the top feed chamber of the vertical filter press body, and the drain port of the vertical filter press body is connected to the liquid storage device through a pipeline, thereby forming a material flow channel that is connected end to end and isolated from the external environment inside the mechanical execution unit. The protective gas supply unit includes: a mixing tank inlet regulating valve connected to the mixing tank, an elevator inlet regulating valve connected to the closed elevator, a buffer hopper inlet regulating valve connected to the feed buffer hopper, a filter press inlet regulating valve connected to the main body of the vertical filter press, and a storage device inlet regulating valve connected to the storage device. The exhaust control unit includes: a mixing tank exhaust regulating valve connected to the mixing tank, a buffer hopper exhaust regulating valve connected to the feed buffer hopper, a filter press exhaust regulating valve connected to the vertical filter press body, and a storage device exhaust regulating valve connected to the storage device; the filter press exhaust regulating valve includes a main exhaust regulating valve and an auxiliary exhaust regulating valve, the main exhaust regulating valve is located at the bottom of the vertical filter press body and is connected to the main liquid flow channel of the vertical filter press body, and the auxiliary exhaust regulating valve is located on the side of the vertical filter press body; The gas monitoring unit includes: oxygen concentration sensors respectively installed in the mixing tank, the vertical filter press body, and the liquid storage device; The elevator inlet regulating valve is configured to be linked to the motor operation status of the closed elevator; when the motor starts, the elevator inlet regulating valve is opened synchronously to form a dynamic nitrogen curtain at the feed inlet and discharge outlet of the closed elevator; when the motor stops, a delayed shutdown timer is triggered, and the elevator inlet regulating valve remains open for a preset delay period after the motor stops, and is closed after the delay period ends, to prevent external air backflow caused by internal pressure fluctuations at the moment of shutdown; The opening sequence of the buffer hopper air inlet regulating valve and the buffer hopper exhaust regulating valve is related to the operating status of the closed elevator; the central control unit is configured to: open the buffer hopper air inlet regulating valve after a first preset delay is detected that the closed elevator has started operation; and open the buffer hopper exhaust regulating valve after a second preset delay is detected that the buffer hopper air inlet regulating valve has been opened, so as to establish a nitrogen protection environment and replace the air brought in when the material enters the buffer hopper; During the operation of the maintenance mode: the opening degree of the auxiliary exhaust regulating valve, the buffer hopper exhaust regulating valve, and the mixing tank exhaust regulating valve is at the preset small exhaust opening degree, while the main exhaust regulating valve and the liquid storage device exhaust regulating valve are closed; In the initial stage of the pressing process, the main exhaust regulating valve is opened and the auxiliary exhaust regulating valve is closed, and most of the gas is discharged through the liquid flow channel generated by pressing. After the pressing process reaches a preset time point, the auxiliary exhaust regulating valve is opened to discharge the residual gas pockets deep in the gaps between the filter plates. The filter press is a compression-type solid-liquid separation device; the material pretreatment device and the material conveying device transport a high-viscosity solid-liquid mixture slurry; the liquid phase component separated by the filter press is an oxidation-sensitive liquid, which has the characteristic of being chemically unstable in an aerobic environment.

2. The filter press system as described in claim 1, characterized in that: The protective gas supplied by the protective gas supply unit is a gas with a density less than air; the air inlet of the protective gas supply unit and the exhaust outlet of the exhaust control unit are configured such that the protective gas diffuses in the mixing tank, the feed buffer hopper, and the main body of the vertical filter press in a downward diffusion direction; the oxygen concentration sensors of the gas monitoring unit are respectively located at the bottom of the mixing tank, the main body of the vertical filter press, and the liquid storage device.

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