A dual PID automatic control method for desulfurization wastewater multi-effect evaporation system

Abstract

The invention discloses a dual PID automatic control method for a desulfurization wastewater multiple-effect evaporation system, wherein the liquid level of a first-effect separator with a long response time and a relatively slow adjustment is used as the main control variable, and the total temperature difference between the inlet and outlet slurries of a first-effect and a second-effect heat exchanger with a short response time and a relatively sensitive response is used as the secondary control variable. After weighted summation, the control signals output by the two finally act together on a steam inlet regulating valve, thereby stably regulating the operating output of the entire evaporation system. The dual PID automatic control method of the system realizes automatic control of the multiple-effect evaporation of desulfurization wastewater.

Description

Technical Field

[0001] The invention belongs to the field of zero discharge of desulfurization wastewater and relates to a double PID automatic control method of a desulfurization wastewater multi-effect evaporation system. Background Art

[0002] At present, negative pressure low temperature multi-effect (double) evaporation concentration process is increasingly used in the deep concentration and zero emission of desulfurization wastewater. However, due to the fluctuation of water quality and quantity, the change of steam pressure and the complexity of the system itself, its operation control mostly relies on manual adjustment and control by operators, which has problems such as large workload of monitoring and weak control stability. Therefore, it is urgent to develop corresponding automatic control methods to improve the level of system automation operation. Summary of the invention

[0003] The purpose of the present invention is to overcome the disadvantages of the prior art and provide a dual PID automatic control method for a desulfurization wastewater multi-effect evaporation system. The dual PID automatic control method of the system realizes automatic control of the desulfurization wastewater multi-effect evaporation.

[0004] To achieve the above object, the present invention discloses a desulfurization wastewater multi-effect evaporation system, comprising a water inlet pipeline, an inlet steam pipeline, a first-effect separator, a first-effect heat exchanger, a second-effect separator, a second-effect heat exchanger and a concentrated water discharge pipeline;

[0005] The water inlet pipeline is connected to the inlet of the first-effect separator through the water inlet automatic regulating valve, the inlet steam pipeline is connected to the shell side inlet of the first-effect heat exchanger through the steam regulating valve (2), the slurry outlet of the first-effect separator is divided into two paths, one of which is connected to the tube side inlet of the first-effect heat exchanger through the first-effect heat exchanger inlet slurry online thermometer, the tube side outlet of the first-effect heat exchanger is connected to the inlet of the first-effect separator through the first-effect heat exchanger outlet slurry online thermometer, and the other path is connected to the inlet of the second-effect separator through the first-effect separator to the water inlet regulating valve of the second-effect separator. The slurry outlet of the heat exchanger is divided into two routes, one of which is connected to the tube-side inlet of the second-effect heat exchanger through the second-effect heat exchanger outlet slurry online thermometer, and the other is connected to the concentrate discharge pipeline through the concentrate discharge regulating valve and the concentrate discharge online flowmeter. The tube-side outlet of the second-effect heat exchanger is connected to the inlet of the second-effect separator through the second-effect heat exchanger outlet slurry online thermometer, the steam outlet of the first-effect separator is connected to the shell-side inlet of the second-effect heat exchanger, the first-effect separator is provided with a first-effect separator online liquid level gauge, and the second-effect separator is provided with a second-effect separator online liquid level gauge.

[0006] The desulfurization wastewater multiple-effect evaporation system of the present invention is further improved in that:

[0007] Furthermore, it also includes a condensed water output pipeline, and the shell side outlet of the first-effect heat exchanger and the shell side outlet of the second-effect heat exchanger are connected to the condensed water output pipeline.

[0008] Furthermore, it also includes a condensation system, and the steam outlet at the top of the second-effect separator is connected to the condensation system.

[0009] The invention discloses a dual PID automatic control method for a desulfurization wastewater multiple-effect evaporation system, comprising:

[0010] Determine the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 ;

[0011] Determine the real-time liquid level L of the primary separator 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 ;

[0012] According to the deviation ΔT 偏差 The first PID controller generates a first control signal according to the deviation value ΔL 偏差 generating a second control signal via a second PID controller;

[0013] The first control signal and the second control signal are weightedly summed to obtain a total control signal, and the opening of the steam regulating valve is controlled according to the total control signal.

[0014] The further improvement of the dual PID automatic control method of the desulfurization wastewater multi-effect evaporation system of the present invention is:

[0015] Furthermore, the first control signal μ1 and the second control signal μ2 are respectively:

[0016]

[0017] Wherein, μ1 and μ2 are the output of the first PID controller and the output of the second PID controller respectively; K p1 , K i1 , K d1 are the proportional, integral and differential gains of the first PID controller; K p2 , K i2 , K d2 are the proportional, integral and derivative gains of the second PID controller, ΔT 偏差 =e1,ΔL 偏差 =e2.

[0018] Furthermore, the total temperature difference setting value ΔT of the heat exchanger is determined set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 The process is:

[0019] According to the inlet slurry temperature of the first-effect heat exchanger measured by the online thermometer of the inlet slurry of the first-effect heat exchanger, the inlet slurry T 进，一效 The outlet slurry T of the first-effect heat exchanger measured by the online thermometer of the outlet slurry of the first-effect heat exchanger 出，一 Calculate the inlet and outlet slurry temperature difference ΔT of a single-effect heat exchanger 一效 , ΔT 一效 =T 出，一效 -T 进，一效 ;

[0020] According to the inlet slurry temperature of the second-effect heat exchanger measured by the online thermometer of the inlet slurry of the second-effect heat exchanger, the inlet slurry T 进，二效 The outlet slurry T of the second-effect heat exchanger measured by the online thermometer of the outlet slurry of the second-effect heat exchanger 出，二效 , calculate the inlet and outlet slurry temperature difference ΔT of the two-effect heat exchanger 二效 , ΔT 二效 =T 出，二效 -T 进，二效 ;

[0021] Calculate the sum of the inlet and outlet slurry temperature differences ΔT 总 , where ΔT 总 =ΔT 一效 +ΔT 二效 ;

[0022] Determine the total temperature difference setting value ΔT of the heat exchanger according to the slurry circulation volume and evaporated water volume of the first-effect heat exchanger and the second-effect heat exchanger set , calculate the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 .

[0023] Furthermore, the real-time liquid level L of the first-effect separator is determined 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 The process is:

[0024] The real-time liquid level L of the first-effect separator is measured by the first-effect separator online level meter 一效 , set the first-effect separator liquid level control target value L 一效,set , and then calculate the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 .

[0025] Furthermore, it also includes:

[0026] The water inlet automatic regulating valve is PID-interlocked with the water inlet online flow meter, and the water inlet target flow is set to Q进 , so that the flow rate measured by the inlet online flow meter is the inlet target flow rate Q 进 .

[0027] Furthermore, it also includes:

[0028] The concentrated water discharge regulating valve is PID interlocked with the concentrated water discharge online flow meter, and the concentrated water discharge target flow rate is set to Q 浓 , so that the flow rate measured by the concentrate discharge online flow meter is the concentrate discharge target flow rate Q 浓 .

[0029] Furthermore, it also includes:

[0030] The water inlet regulating valve from the first effect separator to the second effect separator is PID-interlocked with the online liquid level gauge of the second effect separator to set the target control liquid level L of the second effect separator. 二效 , so that the liquid level measured by the online liquid level meter of the second-effect separator is the target control liquid level L of the second-effect separator 二效 .

[0031] The present invention has the following beneficial effects:

[0032] The dual PID automatic control method for the desulfurization wastewater multi-effect evaporation system described in the present invention adopts a dual PID control method during specific operation, with the liquid level of the first-effect separator having a long response time and a relatively slow adjustment as the main controlled variable, and the total temperature difference of the inlet and outlet slurries of the first and second-effect heat exchangers having a short response time and a relatively sensitive response as the secondary controlled variable, and finally act together on the steam inlet regulating valve, so that the whole evaporation system can take into account both flexible response and stable operation. It should be noted that the dual PID regulation has two regulating loops, the main loop and the secondary loop, and the secondary loop can respond to disturbances quickly, significantly improve the dynamic response characteristics of the system, and effectively reduce overshoot and oscillation in the main loop. The present invention improves the safety redundancy of the system. If one PID controller fails, the other controller can still continue to work, ensuring that some functions of the system are maintained. The overall control logic of the system of the present invention is optimized and simplified. By setting the water intake and the external discharge, the concentration ratio of the system can be flexibly and accurately adjusted and controlled, which greatly improves the adaptive adjustment ability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 It is a structural schematic diagram of the present invention;

[0035] Figure 2 The present invention is a flow chart of the method.

[0036] Among them, 1 is the water inlet automatic regulating valve, 2 is the steam regulating valve, 3 is the water inlet regulating valve from the first effect separator to the second effect separator, 4 is the concentrate discharge regulating valve, 5 is the online thermometer for the inlet slurry of the first effect heat exchanger, 6 is the online thermometer for the outlet slurry of the first effect heat exchanger, 7 is the online thermometer for the inlet slurry of the second effect heat exchanger, 8 is the online thermometer for the outlet slurry of the second effect heat exchanger, 9 is the online liquid level gauge of the first effect separator, 10 is the online liquid level gauge of the second effect separator, 11 is the water inlet online flow meter, and 12 is the concentrate discharge online flow meter. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0039] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0040] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0041] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0042] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0045] Embodiment 1

[0046] refer to Figure 1The desulfurization wastewater multi-effect evaporation system of the present invention comprises a condensate output pipeline, a water inlet pipeline, an inlet steam pipeline, a first-effect separator, a first-effect heat exchanger, a second-effect separator, a second-effect heat exchanger, a concentrated water discharge pipeline, a condensation system, an automatic water inlet regulating valve 1, a steam regulating valve 2, a water inlet regulating valve 3 from the first-effect separator to the second-effect separator, a concentrated water discharge regulating valve 4, an online thermometer for the inlet slurry of the first-effect heat exchanger 5, an online thermometer for the outlet slurry of the first-effect heat exchanger 6, an online thermometer for the inlet slurry of the second-effect heat exchanger 7, an online thermometer for the outlet slurry of the second-effect heat exchanger 8, an online liquid level meter for the first-effect separator 9, an online liquid level meter for the second-effect separator 10, an online flow meter for the inlet slurry 11 and an online flow meter for the concentrated water discharge 12;

[0047] The water inlet pipeline is connected to the inlet of the first-effect separator through the water inlet automatic regulating valve 1, the inlet steam pipeline is connected to the shell side inlet of the first-effect heat exchanger through the steam regulating valve 2, and the slurry outlet of the first-effect separator is divided into two routes, one of which is connected to the tube side inlet of the first-effect heat exchanger through the first-effect heat exchanger inlet slurry online thermometer 5, and the tube side outlet of the first-effect heat exchanger is connected to the inlet of the first-effect separator through the first-effect heat exchanger outlet slurry online thermometer 6, and the other route is connected to the second-effect separator through the first-effect separator to the water inlet regulating valve 3 is connected with the inlet of the second-effect separator, the slurry outlet of the second-effect separator is divided into two paths, one of which is connected with the tube-side inlet of the second-effect heat exchanger through the second-effect heat exchanger outlet slurry online thermometer 8, and the other is connected with the concentrate discharge pipeline through the concentrate discharge regulating valve 4 and the concentrate discharge online flowmeter 12. The tube-side outlet of the second-effect heat exchanger is connected with the inlet of the second-effect separator through the second-effect heat exchanger outlet slurry online thermometer 8, and the steam outlet of the first-effect separator is connected with the shell-side inlet of the second-effect heat exchanger.

[0048] A first-effect separator online liquid level meter 9 is provided in the first-effect separator, and a second-effect separator online liquid level meter 10 is provided in the second-effect separator.

[0049] The shell side outlet of the first effect heat exchanger and the shell side outlet of the second effect heat exchanger are connected to the condensate output pipeline, and the steam outlet at the top of the second effect separator is connected to the condensation system.

[0050] Embodiment 2

[0051] refer to Figure 2 The dual PID automatic control method of the desulfurization wastewater multi-effect evaporation system of the present invention comprises the following steps:

[0052] 1) The water inlet automatic regulating valve 1 is PID-interlocked with the water inlet online flow meter 11, and the water inlet target flow rate is set to Q 进 , so that the flow rate measured by the inlet online flow meter 11 is the inlet target flow rate Q 进 ;

[0053] 2) The concentrated water discharge regulating valve 4 is PID interlocked with the concentrated water discharge online flow meter 12, and the concentrated water discharge target flow rate is set to Q 浓 , so that the flow rate measured by the concentrated water discharge online flow meter 12 is the concentrated water discharge target flow rate Q 浓 ;

[0054] 3) The water inlet regulating valve 3 from the first effect separator to the second effect separator is PID-interlocked with the online liquid level gauge 10 of the second effect separator to set the target control liquid level L of the second effect separator. 二效 , so that the liquid level measured by the online liquid level meter 10 of the second-effect separator is the target control liquid level L of the second-effect separator 二效 ;

[0055] 4) According to the inlet slurry T of the first-effect heat exchanger measured by the inlet slurry online thermometer 5 进，一效 The outlet slurry T of the first-effect heat exchanger measured by the online thermometer 6 at the outlet of the first-effect heat exchanger 出，一效 , calculate the inlet and outlet slurry temperature difference ΔT of a single-effect heat exchanger 一效 , ΔT 一效 =T 出，一效 -T 进，一效 ;

[0056] 5) According to the inlet slurry temperature of the second-effect heat exchanger measured by the inlet slurry online thermometer 7, the inlet slurry T 进，一效 The outlet slurry T of the first effect heat exchanger measured by the online thermometer 8 of the outlet slurry of the second effect heat exchanger is 出，一效 , calculate the inlet and outlet slurry temperature difference ΔT of the two-effect heat exchanger 二效 , ΔT 二效 =T 出，二效 -T 进，二效 ;

[0057] 6) Calculate the sum of the inlet and outlet slurry temperature differences ΔT 总 , where ΔT 总 =ΔT 一效 +ΔT 二效 ;

[0058] 7) Determine the total temperature difference setting value ΔT of the heat exchanger according to the slurry circulation volume and evaporated water volume of the first-effect heat exchanger and the second-effect heat exchanger set , calculate the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 , the deviation ΔT 偏差 Marked as e1, e1 = ΔT 偏差 =ΔT set -ΔT 总 ;

[0059] 8) The real-time liquid level L of the first-effect separator is measured by the first-effect separator online liquid level meter 9 一效 , set the first-effect separator liquid level control target value L 一效,set , calculate the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 , and the deviation value ΔL 偏差 Marked as e2, e2 = ΔL 偏差 =ΔT 一效，set -ΔL 一效 ;

[0060] 9) Two separate PID controllers are set, wherein the first PID controller realizes the steam regulating valve 2 and ΔT 总 PID interlock control, as a secondary control loop, the second PID controller realizes the steam regulating valve 2 and L 一效 The PID interlocking control is used as the main control loop. The output signals of the two PID controllers are weighted and summed to obtain the final control signal for controlling the steam regulating valve 2. The weighting coefficient can be adjusted according to the actual situation to balance the control effects of the two variables of the total temperature difference of the inlet and outlet slurries of the two heat exchangers and the liquid level of the first-effect separator. Specifically, the PID control algorithm is as follows:

[0061] 91) The outputs of the first PID controller and the second PID controller are:

[0062]

[0063] Wherein, μ1 and μ2 are the output of the first PID controller and the output of the second PID controller respectively; K p1 , K i1 , K d1 are the proportional, integral and differential gains of the first PID controller; K p2 , K i2 , K d2 are the proportional, integral and derivative gains of the second PID controller.

[0064] 92) Set a weighted summation module to balance the outputs of the two PID controllers and calculate the weighted controller outputs. Set the weighting coefficient of the first PID controller to W1 and the weighting coefficient of the second PID controller to W2.

[0065] W 1,out =W1·μ1;

[0066] W 2,out =W2·μ2;

[0067] Among them, W1,out is the weighted output of the first PID controller, W 2,out is the weighted output of the second PID controller.

[0068] W1 and W2 can be flexibly adjusted according to the debugging situation to balance the control effect of total temperature difference and liquid level.

[0069] 93) Calculate the total control output and use it to control the opening of the steam regulating valve 2.

[0070] μ=W 1,out +W 2,out

[0071] Among them, μ is the total control output.

[0072] It should be noted that if more effects are connected in the future to form a three-effect, four-effect or even more-effect evaporation system, the above ΔT 总 It is the sum of the slurry temperature differences at the inlet and outlet of all heat exchangers.

[0073] Embodiment 3

[0074] A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the dual PID automatic control method of the desulfurization wastewater multi-effect evaporation system are implemented, for example, including: determining a total temperature difference setting value ΔT of a heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 ; Determine the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 ; According to the deviation ΔT 偏差 The first PID controller generates a first control signal according to the deviation value ΔL 偏差Generate a second control signal through a second PID controller; perform weighted summation of the first control signal and the second control signal to obtain a total control signal, and control the opening of the steam regulating valve 2 according to the total control signal. Wherein, the memory may include a memory, such as a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk memory, etc.; the processor, the network interface, and the memory are interconnected through an internal bus, and the internal bus may be an industrial standard architecture bus, a peripheral component interconnection standard bus, an extended industrial standard architecture bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory may include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0075] Embodiment 4

[0076] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the dual PID automatic control method of the desulfurization wastewater multi-effect evaporation system are implemented, for example, including: determining a total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 ; Determine the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效,set The deviation between 偏差 ; According to the deviation ΔT 偏差 The first PID controller generates a first control signal according to the deviation value ΔL 偏差 The second PID controller generates a second control signal; the first control signal and the second control signal are weighted and summed to obtain a total control signal, and the opening of the steam regulating valve 2 is controlled according to the total control signal. Specifically, the computer-readable storage medium includes, but is not limited to, for example, a volatile memory and / or a non-volatile memory. The volatile memory may include a random access memory (RAM) and / or a cache memory, etc. The non-volatile memory may include a read-only memory (ROM), a hard disk, a flash memory, an optical disk, a magnetic disk, etc.

[0077] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0078] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0079] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0080] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0081] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0082] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A dual PID automatic control method for a desulfurization wastewater multiple-effect evaporation system, characterized in that: include: Determine the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 ; Determine the real-time liquid level L of the primary separator 一效 The liquid level control target value L of the first-effect separator 一效，set The deviation between 偏差 ; According to the deviation ΔT 偏差 The first PID controller generates a first control signal according to the deviation value ΔL 偏差 generating a second control signal via a second PID controller; The first control signal and the second control signal are weighted and summed to obtain a total control signal, and the opening of the steam regulating valve (2) is controlled according to the total control signal.

2. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 1 is characterized in that: The desulfurization wastewater multi-effect evaporation system comprises a water inlet pipeline, a first-effect separator, a first-effect heat exchanger, a second-effect separator, a second-effect heat exchanger and a concentrated water discharge pipeline; The water inlet pipeline is connected to the inlet of the first-effect separator through the water inlet automatic regulating valve (1), the inlet steam pipeline is connected to the shell side inlet of the first-effect heat exchanger through the steam regulating valve (2), the slurry outlet of the first-effect separator is divided into two paths, one of which is connected to the tube side inlet of the first-effect heat exchanger through the first-effect heat exchanger inlet slurry online thermometer (5), the tube side outlet of the first-effect heat exchanger is connected to the inlet of the first-effect separator through the first-effect heat exchanger outlet slurry online thermometer (6), and the other path is connected to the inlet of the second-effect separator through the first-effect separator to the water inlet regulating valve (3) of the second-effect separator, and the slurry of the second-effect separator is The outlet is divided into two routes, one of which is connected to the tube-side inlet of the second-effect heat exchanger via the second-effect heat exchanger outlet slurry online thermometer (8), and the other is connected to the concentrate discharge pipeline via the concentrate discharge regulating valve (4) and the concentrate discharge online flowmeter (12). The tube-side outlet of the second-effect heat exchanger is connected to the inlet of the second-effect separator via the second-effect heat exchanger outlet slurry online thermometer (8), and the steam outlet of the first-effect separator is connected to the shell-side inlet of the second-effect heat exchanger. The first-effect separator is provided with a first-effect separator online liquid level meter (9), and the second-effect separator is provided with a second-effect separator online liquid level meter (10).

3. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 2 is characterized in that: It also includes a condensed water output pipeline, and the shell side outlet of the first-effect heat exchanger and the shell side outlet of the second-effect heat exchanger are connected to the condensed water output pipeline.

4. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 3 is characterized in that: It also includes a condensation system, and the steam outlet at the top of the second-effect separator is connected to the condensation system.

5. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4 is characterized in that: The first control signal μ1 and the second control signal μ2 are respectively: Wherein, μ1 and μ2 are the output of the first PID controller and the output of the second PID controller respectively; K p1 , K i1 , K d1 are the proportional, integral and differential gains of the first PID controller; K p2 , K i2 , K d2 are the proportional, integral and derivative gains of the second PID controller, ΔT 偏差 =e1,ΔL 偏差 =e2.

6. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4 is characterized in that: Determine the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 The process is: According to the inlet slurry temperature T of the first-effect heat exchanger measured by the inlet slurry online thermometer (5) of the first-effect heat exchanger, 进，一效 The outlet slurry T of the first-effect heat exchanger measured by the online slurry thermometer (6) at the outlet of the first-effect heat exchanger 出，一效 , calculate the inlet and outlet slurry temperature difference ΔT of a single-effect heat exchanger 一效 , ΔT 一效 =T 出，一效 -T 进，一效 ; According to the inlet slurry temperature T of the second-effect heat exchanger measured by the inlet slurry online thermometer (7) of the second-effect heat exchanger, 进，二效 The outlet slurry T of the second-effect heat exchanger measured by the online thermometer (8) of the outlet slurry of the second-effect heat exchanger 出，二效 , calculate the inlet and outlet slurry temperature difference ΔT of the two-effect heat exchanger 二效 , ΔT 二效 =T 出，二效 -T 进，二效 ; Calculate the sum of the inlet and outlet slurry temperature differences ΔT 总 , where ΔT 总 =ΔT 一效 +ΔT 二效 ; Determine the total temperature difference setting value ΔT of the heat exchanger according to the slurry circulation volume and evaporated water volume of the first-effect heat exchanger and the second-effect heat exchanger set , calculate the total temperature difference setting value ΔT of the heat exchanger set The sum of the temperature difference between the inlet and outlet slurry ΔT 总 The deviation between 偏差 .

7. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4 is characterized in that: Determine the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效，set The deviation between 偏差 The process is: The real-time liquid level L of the first-effect separator is measured by the first-effect separator online liquid level meter (9) 一效 , set the first-effect separator liquid level control target value L 一效，set , and then calculate the real-time liquid level L of the first-effect separator 一效 The liquid level control target value L of the first-effect separator 一效，set The deviation between 偏差 .

8. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4 is characterized in that: Also includes: The water inlet automatic regulating valve (1) and the water inlet online flow meter (11) are PID-interlocked, and the water inlet target flow rate is set to Q 进 , so that the flow rate measured by the inlet water online flow meter (11) is the inlet water target flow rate Q 进 .

9. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4 is characterized in that: Also includes: The concentrate discharge regulating valve (4) is PID-interlocked with the concentrate discharge online flow meter (12) to set the concentrate discharge target flow rate to Q 浓 , so that the flow rate measured by the concentrate discharge online flow meter (12) is the concentrate discharge target flow rate Q 浓 .

10. The dual PID automatic control method for the desulfurization wastewater multiple-effect evaporation system according to claim 4, characterized in that: Also includes: The water inlet regulating valve (3) from the first effect separator to the second effect separator is interlocked with the online liquid level meter (10) of the second effect separator to set the target control liquid level L of the second effect separator. 二效 , so that the liquid level measured by the online liquid level meter (10) of the second-effect separator is the target control liquid level L of the second-effect separator 二效 .

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