Process pressure and pressing pressure segmented stepped linkage control method and system

Abstract

The invention provides a process pressure and pressing pressure segmented stepped linkage control method and system, and the method comprises the steps: dividing the process pressure and the pressing pressure into N stages in advance, and enabling the process pressure of each stage to correspond to the pressing pressure of the stage; the PLC controls a power source of the process treatment system to operate in a variable frequency manner according to the division of the process pressure, and controls the pressing pressure of the pressing oil cylinder in a linkage manner; the PLC detects the current process pressure and the pressing pressure in real time, when the pressing pressure exceeds the pressure value of the current stage, the PLC controls the hydraulic proportional valve to act in a linkage mode, the pressing oil cylinder relieves the pressure to be within the range of the current stage of the pressing pressure, the situation that the functional filter plate is damaged due to the fact that the pressing pressure is too large is avoided, and the service life of the functional filter plate is prolonged. The utilization rate and the filtering efficiency of equipment are ensured to the greatest extent; when the pressing pressure is smaller than the pressure value of the current stage, the PLC controls the hydraulic station and the hydraulic proportional valve in a linkage mode, so that the pressing pressure is kept within the range of the current stage, and material spraying caused by insufficient pressing pressure is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of filter presses, and in particular to a stepwise linkage control method for process pressure and compaction pressure, and a stepwise linkage control system for process pressure and compaction pressure. Background Art

[0002] In the sludge vacuum low-temperature drying treatment system, the drying host is one of the core equipment. Usually, the drying host is composed of several heating filter plates and diaphragm filter plates arranged at intervals to form multiple filter chambers. Feed holes and liquid outlet holes are provided in the middle of the heating filter plates and the diaphragm filter plates. After the heating filter plates and the diaphragm filter plates are assembled, several feed holes are connected to form a complete feed channel, and several liquid outlet holes are connected to form a complete liquid outlet channel. Both the feed channel and the liquid outlet channel are connected to each filter chamber. At the same time, the feed channel is also used to connect with the feed system, vacuum system and purge system, and the diaphragm chamber of the diaphragm filter plate is connected to the pressing system. In this way, the needs of sludge dehydration and drying are met through process steps such as feed filtration, diaphragm drum pressing, vacuum low-temperature drying, and gas purge.

[0003] At present, both sides of the heating filter plate and the membrane filter plate are provided with handles, through which each filter plate can be movably supported on the system beam, and the plate pulling manipulator pulls the handle to drive each filter plate to move along the beam to realize automatic plate pulling. In addition, a clamping cylinder and a clamping plate are also configured, and the piston rod of the clamping cylinder is connected to the clamping plate; when the piston rod of the clamping cylinder extends and pushes the clamping plate to move, several heating filter plates and membrane filter plates are clamped, so that several heating filter plates and membrane filter plates are sealed.

[0004] When the sludge vacuum low-temperature drying treatment system is in operation, during the feeding stage, squeezing stage, vacuum low-temperature drying stage and purging stage, the process pressures such as the feeding pressure, squeezing pressure, vacuum pressure and purging pressure will fluctuate gradually or instantly, which can easily lead to an increase in the clamping pressure of the clamping cylinder, thereby causing the filter plates to rupture. Take feeding as an example: in the feeding stage, the feeding system sends the material liquid to be filtered to each filter chamber through the pipeline and the feeding channel, separates the solid and liquid through the filter cloth, and forms filter residue on the filter cloth until the filter residue fills the filter chamber to form a filter cake, and the filtrate passes through the filter cloth and flows along the grooves in the filter plate to the liquid outlet hole on the filter plate, and is discharged through the liquid outlet channel. During the feeding process, the sludge enters the drying host and gradually fills each filter chamber, causing the feeding pressure to gradually increase. The reaction force of the feed pressure on the clamping cylinder increases, which in turn increases the pressure on the sealing surface of each filter plate chamber. When the pressure exceeds the pressure bearing capacity of the sealing surface of the filter plate chamber, the filter plate will rupture and the equipment will be damaged. Therefore, it is necessary to control the clamping pressure of the clamping cylinder.

[0005] In the prior art, the conventional method for controlling the clamping pressure of the clamping cylinder is: setting the upper and lower limits of the electric contact pressure gauge to maintain the clamping pressure. This control method is relatively simple and extensive, with low control accuracy and inability to adjust the clamping pressure in different process stages; and, when the electric contact pressure is set too low, it is easy for the chamber sealing surfaces of each filter plate to fail to be completely sealed, resulting in leakage and spraying of the material; when the electric contact pressure is set too high, due to the effect of the process pressure (including feed pressure, squeezing pressure, vacuum pressure and purge pressure, etc.), the greater the reaction force on the clamping cylinder, the greater the clamping pressure, which is more likely to cause the pressure on the sealing surface of the filter plate chamber to increase, causing the filter plate to rupture, which is also the main reason why the filter plate of the sludge drying main unit is easily damaged.

[0006] In order to overcome the shortcomings of the above technologies, the pressure level of the filter plate can be increased. However, after the pressure level of the filter plate is increased, the pressure level of the main frame and feed system (including feed pump and feed pipeline) of the filter press system also needs to be increased synchronously. Therefore, the increase in the pressure level of the filter plate is a systematic upgrade issue, which affects the entire system and is costly. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a segmented step-by-step linkage control method for process pressure and clamping pressure, which can effectively control the clamping pressure of the clamping cylinder, achieve synchronization and coordination between equipment and process, and protect the equipment.

[0008] To achieve the above object, the present invention provides a stepwise linkage control method for process pressure and compaction pressure, comprising the following steps:

[0009] S1. Establish a staged and stepped linkage control system for process pressure and clamping pressure, wherein the staged and stepped linkage control system for process pressure and clamping pressure includes a drying main machine, a process treatment system connected to the drying main machine, a human-machine interface, a PLC controller, and a hydraulic station; the drying main machine includes a frame, several functional filter plates movably supported on the frame, a filter chamber formed between two adjacent functional filter plates, and a clamping cylinder for driving the functional filter plates to be clamped, wherein after the functional filter plates are clamped, a feed channel and a liquid outlet channel are formed which are both connected to the filter chamber, the hydraulic station is connected to the clamping cylinder, and a cylinder pressure transmitter is provided on the connecting pipeline between the two, a hydraulic proportional valve is configured in the hydraulic station, and a process pressure transmitter is provided on the pipeline of the process treatment system; the power source and process pressure transmitter, the human-machine interface, the hydraulic station, the hydraulic proportional valve and the cylinder pressure transmitter in the process treatment system are all communicatively connected to the PLC controller;

[0010] S2. When the process treatment system is running, the process treatment system applies process pressure to the functional filter plate, and the process pressure transmitter feeds back the process pressure to the PLC controller;

[0011] When the hydraulic station drives the clamping oil cylinder to move, the clamping oil cylinder drives several functional filter plates to be clamped, the clamping oil cylinder applies a clamping pressure to the functional filter plates, and the oil cylinder pressure transmitter feeds back the clamping pressure to the PLC controller;

[0012] S3, pre-dividing the process pressure and the compaction pressure into N stages through the human-machine interface, and the process pressure of each stage corresponds to the compaction pressure of the stage;

[0013] S4, the PLC controller first controls the hydraulic station to drive the clamping cylinder to move, and then controls the operation of the process treatment system;

[0014] The PLC controller controls the variable frequency operation of the power source of the process treatment system according to the division of the process pressure, and controls whether the process pressure enters the next stage from the current stage according to the current operating parameters of the process treatment system;

[0015] The PLC controller controls the clamping pressure of the clamping cylinder in a linkage manner according to the stage of the process pressure, so that the clamping pressure is in a stage corresponding to the current stage of the process pressure;

[0016] S5, the PLC controller detects the process pressure in real time according to the feedback of the process pressure transmitter, and detects the compaction pressure in real time according to the feedback of the oil cylinder pressure transmitter;

[0017] When the clamping pressure exceeds the pressure value of the current stage, the PLC controller controls the hydraulic proportional valve to release the pressure of the clamping cylinder until the real-time clamping pressure fed back by the cylinder pressure transmitter is within the preset current stage range;

[0018] When the clamping pressure is less than the pressure value of the current stage, the PLC controller controls the hydraulic station and the hydraulic proportional valve to increase the pressure of the clamping cylinder until the real-time clamping pressure fed back by the cylinder pressure transmitter remains within the preset current stage range.

[0019] Furthermore, a flow meter is provided on the pipeline of the process treatment system, and the flow meter is communicatively connected with the PLC controller to feed back the flow rate to the PLC controller;

[0020] In the step S4, the current operating parameters of the process treatment system include the current process pressure fed back by the process pressure transmitter and the current flow fed back by the flow meter.

[0021] Furthermore, the process pressure and compaction pressure segmented step-by-step linkage control system further includes a PID algorithm module connected to the PLC controller; in the step S4, the PID algorithm module calculates the actual output value of the power source in the process treatment system corresponding to the process pressure at the current stage, and the PLC controller controls the output of the power source in the process treatment system according to the feedback of the PID algorithm module;

[0022] The PID algorithm module calculates the actual output value U(n) of the power source in the process treatment system corresponding to the process pressure at the current stage as: U(n)=Kp{e(n)+T / Ti*e(n)+Td / T*[e(n)-e(n-1)]}+U(n-1);

[0023] In the above formula: U(n-1) is the actual output value of the power source in the process treatment system in the previous sampling period;

[0024] e(n) is the error between the actual output value and the set value of the power source in the process treatment system in the current sampling period;

[0025] e(n-1) is the error between the actual output value and the set value of the power source in the process treatment system in the previous sampling period;

[0026] Kp is the proportional coefficient; T is the sampling period; Ti is the integral time constant; Td is the differential time constant.

[0027] Furthermore, the functional filter plates in the drying host include heating filter plates and membrane filter plates arranged at intervals;

[0028] The process treatment system comprises a feed system, and the feed system applies a process pressure to the functional filter plate as a feed pressure;

[0029] The feed system includes a feed pipeline connected to the feed channel, and a variable frequency feed pump installed on the feed pipeline, the variable frequency feed pump is the power source of the feed system, and the process pressure transmitter includes a feed pressure transmitter installed on the feed pipeline, and the feed pressure transmitter is used to feed back the feed pressure to the PLC controller.

[0030] Furthermore, the functional filter plates in the drying host include heating filter plates and membrane filter plates arranged at intervals, and the membrane filter plates are provided with a membrane inner cavity on the side of the membrane facing away from the filter chamber;

[0031] The process treatment system comprises a pressing system, and the pressing system applies a process pressure to the functional filter plate as a pressing pressure;

[0032] The pressing system includes a pressing pipe connected to the inner cavity of the diaphragm, and a variable frequency pressing pump installed on the pressing pipe. The variable frequency pressing pump is the power source of the pressing system. The process pressure transmitter includes a pressing pressure transmitter installed on the pressing pipe, and the pressing pressure transmitter is used to feed back the pressing pressure to the PLC controller.

[0033] Furthermore, the human-machine interface is a touch screen.

[0034] The present invention also provides a process pressure and clamping pressure segmented step-by-step linkage control system, including a drying main machine and a process treatment system connected to the drying main machine, the drying main machine including a frame, several functional filter plates movably supported on the frame, a filter chamber formed between two adjacent functional filter plates, and a clamping cylinder for driving the several functional filter plates to be clamped, after the several functional filter plates are clamped, a feed channel and a liquid outlet channel are formed which are both connected to the filter chamber; the process pressure and clamping pressure segmented step-by-step linkage control system also includes a human-machine interface, a PLC controller, and a hydraulic station, the hydraulic station is connected to the clamping cylinder, and a cylinder pressure transmitter is provided on the connecting pipeline between the two, a hydraulic proportional valve is configured in the hydraulic station, and a process pressure transmitter is provided on the pipeline of the process treatment system; the power source and process pressure transmitter, the human-machine interface, the hydraulic station, the hydraulic proportional valve and the cylinder pressure transmitter in the process treatment system are all communicatively connected to the PLC controller.

[0035] As described above, the process pressure and compaction pressure segmented step-by-step linkage control method and system according to the present invention have the following beneficial effects:

[0036] The present application realizes precise regulation of process pressure and clamping pressure through phased and linkage control, ensures that the clamping pressure and process pressure operate stably in each stage, satisfies the sealing pressure required by the process pressure, achieves synchronization and coordination between equipment and process, avoids material spraying due to too low clamping pressure, and optimizes the filtration effect; at the same time, when it is judged that the real-time clamping pressure exceeds the pressure value of this stage, the pressure is relieved in time to avoid damage to the functional filter plate due to excessive clamping pressure, protects the equipment, and maximizes the utilization rate and filtration efficiency of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a block diagram of the composition of the segmented and stepped linkage control system for process pressure and compaction pressure in this application.

[0038] Figure 2 This is a schematic diagram of the forces acting on the functional filter plate in the feeding stage in this application.

[0039] Figure 3 for Figure 2 Block diagram of closed-loop control of feed pressure.

[0040] Figure 4 for Figure 2 Block diagram of closed-loop control of the clamping pressure.

[0041] Figure 5 It is a pressure curve diagram of the segmented step-by-step linkage control of the feed pressure and the compaction pressure in the feed stage.

[0042] Component number description

[0043] 10 Drying host

[0044] 101 Heating filter plate

[0045] 102 Membrane filter plate

[0046] 20 Human Machine Interface

[0047] 30 PLC controller

[0048] 40 Hydraulic station

[0049] 51 Clamping cylinder

[0050] 52 Cylinder Pressure Transmitter

[0051] 60 Flow Meter

[0052] 70 Feeding system

[0053] 71 Feed pipe

[0054] 72 variable frequency feed pump

[0055] 73 Feed pressure transmitter

[0056] 80 Pressing system

[0057] 81 Pressing Pipe

[0058] 82 variable frequency squeeze pump

[0059] 83 Pressing pressure transmitter

[0060] 90 Vacuum system

[0061] 91 Vacuum pipe

[0062] 92 Vacuum Pump

[0063] 93 Vacuum pressure transmitter DETAILED DESCRIPTION

[0064] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0065] It should be noted that the structures, proportions, sizes, etc. drawn in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0066] It should also be noted that when an element is referred to as being "fixed on" or "disposed on" another element, it may be directly on the other element or there may be an intermediate element at the same time. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or may be indirectly connected to the other element through an intermediate element.

[0067] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0068] The present invention provides a process pressure and compacting pressure segmented step linkage control system and a process pressure and compacting pressure segmented step linkage control method using the process pressure and compacting pressure segmented step linkage control system. The process pressure and compacting pressure segmented step linkage control method of the present invention comprises the following steps.

[0069] Step S1, establish a step-by-step linkage control system for process pressure and compaction pressure: Figure 1As shown, the process pressure and compaction pressure segmented step linkage control system involved in the present application includes a drying host 10, a process treatment system connected to the drying host 10, a human-machine interface 20, a PLC controller 30, and a hydraulic station 40. Among them, the drying host 10 includes a frame, several functional filter plates movably supported on the frame, a filter chamber formed between two adjacent functional filter plates, and a compaction cylinder 51 for driving several functional filter plates to be compacted; the functional filter plates are square plates, and each functional filter plate is provided with a concave cavity for forming a filter chamber on both sides of its thickness, and a compaction sealing cover is provided on the outer peripheral side of the concave cavity, a feed hole that passes through left and right is opened in the middle of each functional filter plate, and left and right through holes are opened at the four corners of each functional filter plate. In this way, after several functional filter plates are pressed, the pressed surfaces of two adjacent functional filter plates are in contact and matched, the concave cavities of two adjacent functional filter plates are connected and form a filter chamber, the feed holes of several functional filter plates are connected and form a feed channel, the liquid outlet holes of several functional filter plates are connected and form a liquid outlet channel, and the feed channel and the liquid outlet channel filter chamber are connected; the hydraulic station 40 is connected to the pressing cylinder 51, and a cylinder pressure transmitter 52 is provided on the connecting pipeline between the two, and a hydraulic proportional valve is configured in the hydraulic station 40. A process pressure transmitter is provided on the pipeline of the process treatment system. The power source and process pressure transmitter, the human-machine interface 20, the hydraulic station 40, the hydraulic proportional valve and the cylinder pressure transmitter 52 in the process treatment system are all connected to the PLC controller 30 through cable communication to form a linkage control system.

[0070] Step S2, when the process treatment system is running, the process treatment system applies process pressure to the functional filter plate, and the process pressure transmitter feeds back the real-time process pressure to the PLC controller 30; when the hydraulic station 40 drives the clamping cylinder 51 to operate, the clamping cylinder 51 drives several functional filter plates to be clamped, and the clamping cylinder 51 applies clamping pressure to the functional filter plate, and the cylinder pressure transmitter 52 feeds back the real-time clamping pressure to the PLC controller 30.

[0071] Step S3, as shown in Table 1 below, the process pressure and the clamping pressure are pre-divided into N stages (or N pressure stages) through the human-machine interface 20, and the process pressure in each stage corresponds to the clamping pressure in that stage. In Table 1 below, the process pressure in each stage is Pai, and the clamping pressure in each stage is Pbi; the process pressure Pai and the clamping pressure Pbi in each stage can be specific values ​​or value ranges; the process pressure Pai in each stage is different, and the clamping pressure Pbi in each stage is also different; the process pressure Pai and the clamping pressure Pbi in each stage correspond to each other, that is: the process pressure Pa1 in stage 1 corresponds to the clamping pressure Pb1 in stage 1, the process pressure Pa2 in stage 2 corresponds to the clamping pressure Pb2 in stage 2, and the process pressure Pai in stage i corresponds to the clamping pressure Pbi in stage i, i=1,2,3,4…N. The larger the value of N, the finer the division and the more precise the control.

[0072] Table 1 Division of process pressure and compaction pressure

[0073] stage Process pressure Compressing pressure Stage 1 Pa1 Pb1 Stage 2 Pa2 Pb2 Stage 3 Pa3 Pb3 Stage 4 Pa4 Pb4 … … … Phase i Pai Pb … … … N-stage Pn PbN

[0074] Step S4, the PLC controller 30 first controls the hydraulic station 40 to drive the pressing cylinder 51 to operate, so that several functional filter plates are pressed; then, the PLC controller 30 controls the operation of the process treatment system according to the stage requirements;

[0075] When the process treatment system is running, the PLC controller 30 controls the power source of the process treatment system to operate at a variable frequency according to the division of the process pressure, that is, the PLC controller 30 adjusts the process pressure according to the logic and the PID algorithm of the following PID algorithm module, so that the process pressure operates stably according to the divided stages, and the process pressure is first the process pressure Pa1 of stage 1; at the same time, the PLC controller 30 controls whether the process pressure enters the next stage from the current stage according to the current operating parameters of the process treatment system;

[0076] At the same time, the PLC controller 30 controls the hydraulic station 40 in linkage according to the stage of the process pressure, and also controls the clamping pressure of the clamping cylinder 51 in linkage, so that the clamping pressure applied by the clamping cylinder 51 is within the pressure value specified by the pressure stage corresponding to the current stage of the process pressure, and the clamping pressure is first the clamping pressure Pb1 of stage 1; if the process pressure enters the next stage, the PLC controller 30 controls the clamping pressure to enter the next stage accordingly. In this way, the precise adjustment of the process pressure and the clamping pressure is achieved through staged and linkage control to meet the sealing pressure required by the process pressure. The sealing pressure is the difference between the clamping pressure and the process pressure, so that the equipment and the process are synchronized and coordinated. At the same time, the process pressure increases slowly step by step, and the clamping pressure is linked to the process pressure, so that the pressure of each process stage is stable to avoid pressure instability caused by shock.

[0077] Step S5 , during the operation of the process treatment system, the PLC controller detects the process pressure in real time according to the feedback from the process pressure transmitter, and the PLC controller detects the compaction pressure in real time according to the feedback from the cylinder pressure transmitter 52 . When the PLC controller 30 determines that the real-time clamping pressure exceeds the pressure value of the current stage of the clamping pressure, the PLC controller 30 controls the hydraulic proportional valve to operate, increases the hydraulic proportional valve, relieves the pressure of the clamping cylinder 51, automatically relieves part of the reaction force, and reduces the clamping pressure until the real-time clamping pressure fed back by the cylinder pressure transmitter 52 is within its preset current stage; conversely, when the PLC controller 30 determines that the real-time clamping pressure is insufficient, that is, the real-time clamping pressure is less than the pressure value of the current stage of the clamping pressure, the PLC controller 30 controls the hydraulic station 40 and the hydraulic proportional valve to operate, decreases the hydraulic proportional valve, pressurizes the clamping cylinder 51, and increases the clamping pressure until the real-time clamping pressure fed back by the cylinder pressure transmitter 52 is within the preset current stage of the clamping pressure, thereby ensuring that the clamping pressure and the process pressure operate stably in each stage, that is, keeping the sealing pressure within a constant range. In this way, not only can the sealing pressure required by the process pressure be met, the material spraying due to too low pressing pressure can be avoided, and the solid-liquid separation effect can be improved, but also the damage to the functional filter plate due to excessive pressing pressure can be avoided, thus protecting the equipment and maximizing the equipment utilization rate and filtration efficiency.

[0078] Furthermore, a flow meter 60 is provided on the pipeline of the process treatment system, and the flow meter 60 is connected to the PLC controller 30 for feeding back the flow rate to the PLC controller 30; in step S4, the current operating parameters of the process treatment system include the current process pressure fed back by the process pressure transmitter, and the current flow fed back by the flow meter 60. Specifically, when the PLC controller 30 determines that the process pressure of each stage reaches the set value and is maintained for a certain period of time, and the current flow fed back by the flow meter 60 meets the flow set value of the current stage, the PLC controller 30 controls the process pressure to enter the next stage.

[0079] Furthermore, if Figure 3 As shown, the process pressure and compaction pressure segmented step linkage control system also includes a PID algorithm module connected to the PLC controller 30; in step S4, the PID algorithm module calculates the actual output value of the power source in the process treatment system corresponding to the process pressure at the current stage, and the PLC controller 30 controls the output of the power source in the process treatment system according to the feedback of the PID algorithm module. In particular, the PID algorithm module calculates the actual output value U(n) of the power source in the process treatment system corresponding to the process pressure at the current stage as: U(n)=Kp{e(n)+T / Ti*e(n)+Td / T*[e(n)-e(n-1)]}+U(n-1).

[0080] In the above formula: U(n-1) is the actual output value of the power source in the process treatment system in the previous sampling period; e(n) is the error between the actual output value and the set value of the power source in the process treatment system in the current sampling period; e(n-1) is the error between the actual output value and the set value of the power source in the process treatment system in the previous sampling period; Kp is the proportional coefficient; T is the sampling period; Ti is the integral time constant; Td is the differential time constant. Among them, the set value of the power source in the process treatment system is the target value, which is set through the human-machine interface 20. Preferably, the human-machine interface 20 is a touch screen.

[0081] The following is an example of the process pressure and compaction pressure segmented step-by-step linkage control system and method involved in this application for sludge vacuum low-temperature drying treatment. In this embodiment, the several functional filter plates in the drying host 10 include a heating filter plate 101 and a diaphragm filter plate 102 arranged at intervals, and the diaphragm filter plate 102 is provided with a diaphragm inner cavity on the side of the diaphragm facing away from the filter chamber; the structures of the heating filter plate 101 and the diaphragm filter plate 102 are both prior art and will not be described in detail here. The sludge vacuum low-temperature drying process mainly includes a feeding process, a pressing process, a low-temperature vacuuming process and a purging process, and the process treatment system includes a feeding system 70 for the feeding process, a pressing system 80 for the pressing process, a vacuum system 90 for the low-temperature vacuuming process, and a purging system for the purging process. During the sludge vacuum low-temperature drying process, the process pressure includes the feed pressure applied by the feed system 70 on the functional filter plate, the pressing pressure applied by the pressing system 80 on the functional filter plate, the vacuum pressure applied by the vacuum system 90 on the functional filter plate, and the purge pressure applied by the purge system on the functional filter plate. The pressure value of each process stage is different, that is, the feed pressure, pressing pressure, vacuum pressure and purge pressure are different, and their reaction forces on the compacting pressure are also different, which meets the different requirements for process pressure and compacting pressure of the drying main unit 10 in different process stages during the sludge vacuum low-temperature drying process.

[0082] like Figure 1As shown, the feeding system 70 includes a feeding pipeline 71 connected to the feeding channel, and a variable frequency feeding pump 72, a valve, a pressure sensor and a flow meter 60 installed on the feeding pipeline 71. The variable frequency feeding pump 72 is the power source of the feeding system 70. The process pressure transmitter includes a feeding pressure transmitter 73 installed on the feeding pipeline 71. The feeding pressure transmitter 73 is used to feed back the feeding pressure to the PLC controller 30. The squeezing system 80 includes a squeezing pipeline 81 connected to the diaphragm inner cavity of the diaphragm filter plate 102, and a variable frequency squeezing pump 82, a valve and a flow meter installed on the squeezing pipeline 81. The variable frequency squeezing pump 82 is the power source of the squeezing system 80. The process pressure transmitter includes a squeezing pressure transmitter 83 installed on the squeezing pipeline 81. The squeezing pressure transmitter 83 is used to feed back the squeezing pressure to the PLC controller 30. The vacuum system 90 includes a vacuum pipe 91 connected to the feed channel, and a vacuum pump 92, a valve and a flow meter installed on the vacuum pipe 91. The vacuum pump 92 is the power source of the vacuum system 90. The process pressure transmitter includes a vacuum pressure transmitter 93 installed on the vacuum pipe 91. The vacuum pressure transmitter 93 is used to feed back the vacuum pressure to the PLC controller 30. The purge system includes a purge pipe connected to the feed channel, and a fan, a valve and a flow meter installed on the purge pipe. The fan is the power source of the purge system. The process pressure transmitter includes a purge pressure transmitter installed on the purge pipe. The purge pressure transmitter is used to feed back the purge pressure to the PLC controller 30.

[0083] During the sludge vacuum low-temperature drying process, the feed pressure and the compacting pressure in the feeding stage are controlled by segmented step linkage, and the pressing pressure and the compacting pressure in the pressing stage are also controlled by segmented step linkage. Therefore, the segmented step linkage control method of the feed pressure and the compacting pressure involved in the sludge vacuum low-temperature drying process is mainly used for the feed pressure and the pressing pressure involved in the sludge vacuum low-temperature drying process, while the vacuum pressure and the purge pressure are not controlled by segmented step, but only by linkage control. The following takes the feeding stage as an example to illustrate the segmented step linkage control of the feed pressure and the compacting pressure.

[0084] Before feeding, the pressing oil cylinder 51 first applies a relatively small pressing pressure to the drying main unit 10 to pre-press the drying main unit 10, so that the heating filter plate 101 and the diaphragm filter plate 102 in the drying main unit 10 are closed and sealed to form a filter chamber; when feeding, the sludge enters the feeding channel of the drying main unit 10 through the feeding pipe 71 of the feeding system 70, and gradually fills each filter chamber. For the convenience of description, the pressing pressure applied by the pressing oil cylinder 51 during the feeding process is defined as the feeding pressing pressure. During the feeding process, if Figure 2 As shown, the heating filter plate 101 and the membrane filter plate 102 are subjected to a positive feed pressing pressure Pbj and a reverse feed pressure Paj.

[0085] First, as shown in Table 2 below, the feed pressure Paj and the feed compaction pressure Pbj are pre-divided into N stages through the human-machine interface 20, and the feed pressure Paji and the feed compaction pressure Pbji in each stage correspond to each other.

[0086] Table 2 Division of feed pressure Paj and feed compaction pressure Pbj

[0087] stage Feed pressure Feed pressing pressure Stage 1 Paj1 Pbj Stage 2 Paj2 Pbj Stage 3 Paj3 PbJ Stage 4 Paj4 Pj … … … Phase i Paji PcqI … … … N-stage Pj PcqI

[0088] Second, the PLC controller 30 controls the action of the clamping cylinder 51 and the variable frequency feed pump 72 in sequence, so that the feed pressure operates under the corresponding parameters, and controls the feed clamping pressure in linkage, then the feed pressures are Paj1, Paj2, ..., PajN in sequence, and correspondingly, the feed clamping pressures are Pbj1, Pbj2, ..., PbjN in sequence, such as Figure 5 As shown in the figure, the difference between the feed compaction pressure and the feed pressure is the sealing pressure Pe in the feed stage. Figure 3 As shown, the feed pressure is controlled by PID closed loop, and the PLC controller 30 controls the output of the variable frequency feed pump 72 through the feedback of the PID algorithm module, and the real-time feed pressure is fed back to the PLC controller 30 by the feed pressure transmitter 73 in a closed loop. When the PLC controller 30 determines that the process pressure of each stage reaches the set value and is maintained for a certain period of time, and the current flow rate fed back by the flow meter 60 meets the flow rate setting value of the current stage, the PLC controller 30 controls the feed pressure to enter the next stage, and controls the feed pressing pressure to enter the next stage in a linked manner; and so on, until the feeding is completed. The formula for calculating the actual output value of the variable frequency feed pump 72 at each stage by the PID algorithm module is: U(n)=Kp{e(n)+T / Ti*e(n)+Td / T*[e(n)-e(n-1)]}+U(n-1).

[0089] Third, during the feeding process, the PLC controller detects the real-time feeding pressure and the clamping pressure. When the PLC controller 30 determines that the real-time feeding and clamping pressure exceeds the pressure value of the current stage according to the feedback of the oil cylinder pressure transmitter 52, such as Figure 4 As shown, the PLC controller 30 automatically adjusts the hydraulic proportional valve through the PID algorithm module to relieve the pressure of the clamping cylinder 51, automatically relieve part of the reaction force, and reduce the feed clamping pressure until the real-time feed clamping pressure fed back by the cylinder pressure transmitter 52 is within the preset feed clamping pressure current stage, thereby avoiding damage to the functional filter plate due to excessive clamping pressure and maximizing the utilization rate and filtration efficiency of the equipment. When the PLC controller 30 determines that the real-time feed clamping pressure is less than the pressure value of the current stage according to the feedback of the cylinder pressure transmitter 52, as shown in FIG. Figure 4As shown, the PLC controller 30 automatically adjusts the hydraulic station 40 and the hydraulic proportional valve through the PID algorithm module to increase the pressure of the clamping cylinder 51 and the feed clamping pressure until the real-time feed clamping pressure fed back by the cylinder pressure transmitter 52 is within the preset feed clamping pressure current stage, thereby avoiding material spraying due to insufficient clamping pressure. In this way, the sealing pressure Pe is always kept within a constant range, realizing segmented step-by-step linkage control.

[0090] From the perspective of filtering principles, filter cloth plays an important role in the initial stage of feed filtration. After the material fills the filter chamber, the material in the filter chamber is stacked layer by layer to form a new filter layer, just like sand filtering water. Therefore, this application adopts segmented step-type PID control, which can not only realize the linkage adjustment of process pressure and compression pressure, protect each functional filter plate, and increase the service life of the functional filter plate, but also improve the filtering effect. Through verification and comparison of multiple projects, the thickness and uniformity of the filter cake increased significantly after adopting segmented step-type PID control.

[0091] The principle of the segmented step-by-step linkage control between the pressing pressure and the compacting pressure in the pressing stage of the sludge vacuum low-temperature drying treatment is the same as the segmented step-by-step linkage control between the feed pressure and the feed compacting pressure mentioned above, and will not be repeated.

[0092] In addition, for the vacuum pressure and the clamping pressure in the vacuum stage: the two are not segmented but linked and controlled. When the vacuum pump is evacuating, the variable frequency squeezing pump also runs, applying a small but constant squeezing pressure. Then the process pressure composed of the vacuum pressure and the squeezing pressure is a constant pressure. The PLC controller 30 controls the hydraulic station 40 and the hydraulic proportional valve in linkage according to the constant pressure, thereby linking and controlling the clamping pressure applied by the clamping cylinder 51 in the vacuum stage. Similarly, the purge pressure is also a constant pressure value. The PLC controller 30 controls the hydraulic station 40 and the hydraulic proportional valve in linkage according to the constant pressure, thereby linking and controlling the clamping pressure applied by the clamping cylinder 51 in the purge stage.

[0093] In summary, the present application performs segmented and stepped linkage control on the process pressure and the clamping pressure of each process stage to achieve more refined and accurate control. While using the PID algorithm to quickly and accurately adjust each process pressure, it also links and controls the corresponding clamping pressure to meet the sealing pressure required by the process pressure, ensuring that the drying host 10 has sufficient sealing performance, while avoiding damage to the functional filter plate caused by excessive clamping pressure, improving the solid-liquid separation effect, and maximizing the utilization rate and filtration efficiency of the equipment. In particular, the present application has low implementation cost, reasonable structural design, fast control response, high control accuracy, good stability, and is simple and easy to implement; it has the advantages of parameter formulation, flexibility, convenience, and simple operation.

[0094] In summary, the present invention effectively overcomes various shortcomings of the prior art and has high industrial utilization value.

[0095] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A step-by-step linkage control method for process pressure and compaction pressure, characterized in that: The following steps are involved: S1. Establish a staged and stepped linkage control system for process pressure and clamping pressure, wherein the staged and stepped linkage control system for process pressure and clamping pressure includes a drying main machine, a process treatment system connected to the drying main machine, a human-machine interface, a PLC controller, and a hydraulic station; the drying main machine includes a frame, several functional filter plates movably supported on the frame, a filter chamber formed between two adjacent functional filter plates, and a clamping cylinder for driving the functional filter plates to be clamped, wherein after the functional filter plates are clamped, a feed channel and a liquid outlet channel are formed which are both connected to the filter chamber, the hydraulic station is connected to the clamping cylinder, and a cylinder pressure transmitter is provided on the connecting pipeline between the two, a hydraulic proportional valve is configured in the hydraulic station, and a process pressure transmitter is provided on the pipeline of the process treatment system; the power source and process pressure transmitter, the human-machine interface, the hydraulic station, the hydraulic proportional valve and the cylinder pressure transmitter in the process treatment system are all communicatively connected to the PLC controller; S2. When the process treatment system is running, the process treatment system applies process pressure to the functional filter plate, and the process pressure transmitter feeds back the process pressure to the PLC controller; When the hydraulic station drives the clamping oil cylinder to move, the clamping oil cylinder drives several functional filter plates to be clamped, the clamping oil cylinder applies a clamping pressure to the functional filter plates, and the oil cylinder pressure transmitter feeds back the clamping pressure to the PLC controller; S3, pre-dividing the process pressure and the compaction pressure into N stages through the human-machine interface, and the process pressure of each stage corresponds to the compaction pressure of the stage; S4, the PLC controller first controls the hydraulic station to drive the clamping cylinder to move, and then controls the operation of the process treatment system; the PLC controller controls the power source of the process treatment system to operate at a variable frequency according to the division of the process pressure, and controls whether the process pressure enters the next stage from the current stage according to the current operating parameters of the process treatment system; The PLC controller controls the clamping pressure of the clamping cylinder in a linkage manner according to the stage of the process pressure, so that the clamping pressure is in a stage corresponding to the current stage of the process pressure; S5, the PLC controller detects the process pressure in real time according to the feedback of the process pressure transmitter, and detects the compaction pressure in real time according to the feedback of the oil cylinder pressure transmitter; When the clamping pressure exceeds the pressure value of the current stage, the PLC controller controls the hydraulic proportional valve to release the pressure of the clamping cylinder until the real-time clamping pressure fed back by the cylinder pressure transmitter is within the preset current stage range; When the clamping pressure is less than the pressure value of the current stage, the PLC controller controls the hydraulic station and the hydraulic proportional valve to increase the pressure of the clamping cylinder until the real-time clamping pressure fed back by the cylinder pressure transmitter remains within the preset current stage range.

2. The stepwise stepwise linkage control method for process pressure and compaction pressure according to claim 1 is characterized in that: A flow meter is also provided on the pipeline of the process treatment system, and the flow meter is communicatively connected with the PLC controller to feed back the flow rate to the PLC controller; In the step S4, the current operating parameters of the process treatment system include the current process pressure fed back by the process pressure transmitter and the current flow fed back by the flow meter.

3. The stepwise stepwise linkage control method for process pressure and compaction pressure according to claim 1 is characterized in that: The process pressure and compaction pressure segmented step-by-step linkage control system further includes a PID algorithm module connected to the PLC controller; in step S4, the PID algorithm module calculates the actual output value of the power source in the process treatment system corresponding to the process pressure at the current stage, and the PLC controller controls the output of the power source in the process treatment system according to the feedback of the PID algorithm module; The PID algorithm module calculates the actual output value U(n) of the power source in the process treatment system corresponding to the process pressure at the current stage as: U(n)=Kp{e(n)+T / Ti*e(n)+Td / T*[e(n)-e(n-1)]}+U(n-1); In the above formula: U(n-1) is the actual output value of the power source in the process treatment system in the previous sampling period; e(n) is the error between the actual output value and the set value of the power source in the process treatment system in the current sampling period; e(n-1) is the error between the actual output value and the set value of the power source in the process treatment system in the previous sampling period; Kp is the proportional coefficient; T is the sampling period; Ti is the integral time constant; Td is the differential time constant.

4. The stepwise stepwise linkage control method for process pressure and compaction pressure according to claim 1 is characterized in that: The functional filter plates in the drying host include heating filter plates and membrane filter plates arranged at intervals; The process treatment system comprises a feed system, and the feed system applies a process pressure to the functional filter plate as a feed pressure; The feed system includes a feed pipeline connected to the feed channel, and a variable frequency feed pump installed on the feed pipeline, the variable frequency feed pump is the power source of the feed system, and the process pressure transmitter includes a feed pressure transmitter installed on the feed pipeline, and the feed pressure transmitter is used to feed back the feed pressure to the PLC controller.

5. The stepwise stepwise linkage control method for process pressure and compaction pressure according to claim 1 is characterized in that: The functional filter plates in the drying host include a heating filter plate and a membrane filter plate arranged at intervals, and the membrane filter plate is provided with a membrane inner cavity on the side of the membrane facing away from the filter chamber; The process treatment system comprises a pressing system, and the pressing system applies a process pressure to the functional filter plate as a pressing pressure; The pressing system includes a pressing pipe connected to the inner cavity of the diaphragm, and a variable frequency pressing pump installed on the pressing pipe. The variable frequency pressing pump is the power source of the pressing system. The process pressure transmitter includes a pressing pressure transmitter installed on the pressing pipe, and the pressing pressure transmitter is used to feed back the pressing pressure to the PLC controller.

6. The stepwise stepwise linkage control method for process pressure and compaction pressure according to claim 1 is characterized in that: The human-machine interface is a touch screen.

7. A process pressure and compaction pressure segmented step linkage control system, comprising a drying main machine and a process treatment system connected to the drying main machine, wherein the drying main machine comprises a frame, several functional filter plates movably supported on the frame, a filter chamber formed between two adjacent functional filter plates, and a compaction oil cylinder for driving the several functional filter plates to compact, wherein after the several functional filter plates are compacted, a feed channel and a liquid outlet channel are formed which are connected to the filter chamber, and the characteristics are as follows: It also includes a human-machine interface, a PLC controller, and a hydraulic station. The hydraulic station is connected to the clamping cylinder, and a cylinder pressure transmitter is provided on the connecting pipeline between the two. A hydraulic proportional valve is configured in the hydraulic station, and a process pressure transmitter is provided on the pipeline of the process treatment system; the power source and process pressure transmitter, the human-machine interface, the hydraulic station, the hydraulic proportional valve and the cylinder pressure transmitter in the process treatment system are all communicatively connected with the PLC controller.

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