Denitration total amount control method and system based on optimized ammonia injection amount feedforward

Abstract

The embodiment of the invention discloses a denitration total amount control method and system based on optimization of ammonia injection amount feedforward, in the technical scheme, the theoretical ammonia injection amount of SCR ammonia injection amount is calculated according to the NOx remaining amount design required concentration of an outlet of an SCR denitration unit, the obtained SCR denitration unit parameters and the unit actual operation condition, and the calculated theoretical ammonia injection amount is fed back to the SCR denitration unit; the ammonia spraying amount can be effectively and accurately controlled, meanwhile, the SCR denitration unit is monitored and controlled in real time through the DCS and the control server, the control server carries out calculation in real time according to parameters fed back by the SCR denitration unit, the ammonia spraying amount can be adjusted in real time when the content of NOx in flue gas at an inlet of the unit changes through the arrangement, and the ammonia spraying amount can be adjusted in real time according to the parameters fed back by the SCR denitration unit. And the ammonia spraying amount can be adjusted according to the NOx concentration required by design, the response speed of ammonia spraying amount feed-forward is increased, and the situation that NOx reduction is insufficient or ammonia spraying is wasted can be effectively avoided.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of production environmental protection technology, and in particular to a method and system for controlling the total amount of denitrification based on optimized ammonia injection amount feedforward. Background Art

[0002] In order to prevent excessive NOx from polluting the environment after coal combustion in the boiler, the coal should be denitrated. It is divided into denitration before combustion, denitration during combustion, and denitration after combustion. SCR (Selective Catalytic Reduction) is the most mature flue gas denitration technology. It is a post-furnace denitration method that uses a reducing agent (NH3, urea) to selectively react with NOx to generate N2 and H2O under the action of a metal catalyst, rather than being oxidized by O2, so it is called "selective". The popular SCR processes in the world are mainly divided into two types: ammonia SCR and urea SCR. Both methods use the reduction function of ammonia on NOx, and reduce NOx (mainly NO) to N2 and water that have little impact on the atmosphere under the action of a catalyst. The reducing agent is NH3.

[0003] This method has high denitrification efficiency and is relatively inexpensive. It is widely used in domestic and foreign projects and has become the mainstream technology for flue gas denitrification in power plants. However, in actual application, the NOx content in the flue gas generated after boiler combustion will change dynamically, and the existing SCR unit cannot adjust the amount of ammonia injection in real time according to the NOx concentration at the denitrification inlet. As a result, insufficient NOx removal or excessive ammonia injection will occur, resulting in waste of reducing agent. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] To this end, a first aspect of the present invention provides a total denitrification control method based on optimized ammonia injection amount feedforward.

[0006] The second aspect of the present invention provides a total denitration control system based on optimized ammonia injection amount feedforward.

[0007] In view of this, according to a first aspect of an embodiment of the present application, a total denitration control method based on optimized ammonia injection amount feedforward is proposed, comprising:

[0008] Monitor and control the selective catalytic reduction denitrification unit based on a distributed control system and an independent external control server;

[0009] Obtaining the parameters of the selective catalytic reduction denitrification unit and entering them into the control server as operation input parameters;

[0010] The control server divides the denitrification outlet control interval based on the standard NOx concentration at the denitrification outlet and calculates the theoretical ammonia injection amount;

[0011] The control server corrects the theoretical ammonia injection amount based on the actual operating conditions of the selective catalytic reduction denitrification unit and calculates the optimized ammonia injection amount;

[0012] The control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit.

[0013] In a feasible implementation, the monitoring and control of the selective catalytic reduction denitration unit based on the distributed control system and the independent external control server includes:

[0014] applying the control policy to the control server;

[0015] Connect the control server to the distributed control system as a remote station;

[0016] Establish a data channel for a distributed control system to transmit data from the selective catalytic reduction denitrification unit to the control server;

[0017] After the control server completes the operation of the control algorithm, the operation results are sent to the data channel of the distributed control system.

[0018] In a feasible implementation, the step of obtaining the parameters of the selective catalytic reduction denitration unit and entering the parameters into the control server as operation input parameters includes:

[0019] The load of the selective catalytic reduction denitrification unit, AGC instruction, NOx concentration at the denitrification outlet, NOx concentration at the denitrification inlet, NOx concentration at the total exhaust port, flue gas volume, oxygen volume, total air volume of the unit, primary air volume, secondary air volume, operating current of each coal mill, coal feed rate of the coal feeder, ammonia injection amount and ammonia injection valve opening are selected as input parameters for the control strategy operation.

[0020] In a feasible implementation manner, the control server divides the denitration outlet control interval based on the standard state NOx concentration at the denitration outlet, and calculates the theoretical ammonia injection amount, including:

[0021] The NOx concentration at the denitrification outlet is divided into ≤10mg / Nm3, 10-20mg / Nm3, 20-40mg / Nm3, 40-60mg / Nm3, ≥60mg / Nm3;

[0022] Calculate the theoretical ammonia injection amount, theoretical ammonia injection amount = flue gas volume * [denitrification efficiency + 5 / 22.4 / (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23)] * 10-3 * 17 (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23) * ammonia injection amount coefficient;

[0023] Wherein, NO concentration at denitration outlet = 0.92532* NOx concentration at denitration outlet;

[0024] NO2 concentration at denitration outlet = 0.07468 * NOx concentration at denitration outlet;

[0025] Denitrification efficiency = (NOx concentration at denitrification inlet - NOx concentration at denitrification outlet) / NOx concentration at denitrification inlet.

[0026] In a feasible implementation manner, the control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit, and the calculation of the optimized ammonia injection amount includes:

[0027] Determining the first ammonia injection change amount according to the load change rate;

[0028] Determine the change amount of the second ammonia injection according to the change rate of the denitration outlet;

[0029] Determine the change amount of the third ammonia injection amount according to the change rate of the denitration inlet;

[0030] The rate of change is calculated using a smoothing function: Trend(x(t))=1 / ts_A×(x(t)+x(t-1)+…+x(t-ts_A / 5)).

[0031] In a feasible implementation manner, the control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit, and further includes:

[0032] Determine the status of the coal mill;

[0033] When the coal mill is in the start / stop state, the fourth change amount is added to the theoretical ammonia injection amount.

[0034] In a feasible implementation, it also includes:

[0035] Optimize the control server interface by setting control parameters for different NOx concentration ranges at the denitration outlet in the control strategy;

[0036] The control parameters are an ammonia injection amount coefficient, an ammonia injection amount variation, a valve characteristic curve, a maximum ammonia injection amount setting value and a minimum ammonia injection amount setting value.

[0037] In a feasible implementation manner, the control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitration unit, including:

[0038] The distributed control system receives the optimized ammonia injection amount;

[0039] The distributed control system retrieves the denitrification target value;

[0040] The distributed control system retrieves the denitrification main adjustment process value;

[0041] The distributed control system inputs the optimized ammonia injection amount, denitration target value, and main adjustment process value into the PID module. The PID module calculates the change value of each valve of the selective catalytic reduction denitration unit and generates the change instruction of each valve according to the change value of each valve.

[0042] The PID module transmits the change instructions of each valve to the selective catalytic reduction denitrification unit.

[0043] In a feasible real-time manner, the control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitration unit, including:

[0044] Single-ended line test: When the single-ended line test passes, the PID module performs calculations. When the single-ended line test fails, the PID module does not perform calculations.

[0045] The single-ended line test is associated with the switching switch and the automatic manual switch in the distributed control system. The switching switch has two states, open and closed, and the automatic manual switch has two states, automatic and manual. When the switching switch is in the open state and the automatic manual switch is in the automatic state, the single-ended line test passes, otherwise, the single-ended line test fails.

[0046] According to the second aspect of the embodiment of the present application, a total denitration control system based on optimized ammonia injection amount feedforward is proposed. Any of the above-mentioned total denitration control methods can be applied to the total denitration control system, including:

[0047] Control servers;

[0048] Distributed control system, the control server is independently plugged into the distributed control system, and the control server information is connected to the distributed control system;

[0049] A selective catalytic reduction denitration unit, wherein the selective catalytic reduction denitration unit is electrically connected to the distributed control system;

[0050] The distributed control system includes a total exhaust NOx closed-loop control module and an ammonia injection amount feedforward module;

[0051] The ammonia injection amount feedforward module includes a PID module, an on-off switch and a pneumatic manual switch.

[0052] Compared with the prior art, the present invention includes at least the following beneficial effects: in actual application, the DCS system obtains various parameters of the SCR denitrification unit, and transmits the parameters of the SCR denitrification unit to the control server, the control server calculates the theoretical ammonia injection amount according to the design requirement concentration of the NOx residual at the outlet of the SCR denitrification unit and the obtained parameters of the SCR denitrification unit, the control server corrects the theoretical ammonia injection amount according to the actual operating parameters of the SCR denitrification unit, and feeds back the corrected theoretical ammonia injection amount to the DCS system, and the DCS system controls the SCR denitrification unit to inject ammonia according to the corrected theoretical ammonia injection amount, thereby realizing feedforward optimization of the ammonia injection amount.

[0053] In this technical solution, the theoretical ammonia injection amount of the SCR is calculated based on the design requirement concentration of the NOx residual at the outlet of the SCR denitrification unit, the obtained SCR denitrification unit parameters and the actual operation of the unit, and fed back to the SCR denitrification unit, which can effectively realize the precise control of the ammonia injection amount. At the same time, the SCR denitrification unit is monitored and controlled in real time through the DCS system and the control server. The control server calculates in real time according to the parameters fed back by the SCR denitrification unit. This setting can adjust the ammonia injection amount in real time when the NOx content in the flue gas at the unit inlet changes, and can adjust the ammonia injection amount according to the NOx concentration required by the design, thereby improving the response speed of the ammonia injection amount feedforward, and can effectively avoid insufficient NOx reduction or waste of ammonia injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0055] Figure 1 A schematic flowchart of the steps of a total denitration control method based on optimized ammonia injection amount feedforward according to an embodiment of the present application;

[0056] Figure 2 A control logic diagram of an ammonia injection amount feedforward module according to an embodiment of the present application;

[0057] Figure 3 A control logic diagram of a distributed control system according to an embodiment of the present application. DETAILED DESCRIPTION

[0058] In order to better understand the above-mentioned technical scheme, the technical scheme of the embodiments of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical scheme of the embodiments of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0059] like Figure 1-3 As shown, according to the first aspect of the embodiment of the present application, a total denitration control method based on optimized ammonia injection amount feedforward is proposed, comprising:

[0060] Step 100: monitoring and controlling the selective catalytic reduction denitration unit based on a distributed control system and an independent external control server;

[0061] Step 200: Obtain parameters of the selective catalytic reduction denitration unit and enter them into the control server as operation input parameters;

[0062] Step 300: The control server divides the denitration outlet control interval based on the standard state NOx concentration at the denitration outlet, and calculates the theoretical ammonia injection amount;

[0063] Step 400: The control server corrects the theoretical ammonia injection amount based on the actual operating conditions of the selective catalytic reduction denitration unit and calculates the optimized ammonia injection amount;

[0064] Step 500: The control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit.

[0065] The total denitrification control method based on optimized ammonia injection amount feedforward provided in the embodiment of the present application adds a control server outside the distributed control system (hereinafter referred to as the DCS system). The control server is independently plugged into the distributed control system and can realize remote control.

[0066] The DCS system is electrically connected to a selective catalytic reduction denitrification unit (hereinafter referred to as an SCR denitrification unit). The SCR denitrification unit is controlled by the DCS system, and the DCS system can read various parameters of the SCR denitrification unit.

[0067] In actual application, the DCS system obtains various parameters of the SCR denitrification unit and transmits the parameters of the SCR denitrification unit to the control server. The control server calculates the theoretical ammonia injection amount according to the design requirement concentration of NOx residual at the outlet of the SCR denitrification unit and the obtained SCR denitrification unit parameters. The control server corrects the theoretical ammonia injection amount according to the actual operating parameters of the SCR denitrification unit, and feeds back the corrected optimized ammonia injection amount to the DCS system. The DCS system controls the SCR denitrification unit to inject ammonia according to the corrected theoretical ammonia injection amount, thereby realizing feedforward optimization of the ammonia injection amount.

[0068] In this technical solution, the theoretical ammonia injection amount of the SCR is calculated based on the design requirement concentration of the NOx residual at the outlet of the SCR denitrification unit, the obtained SCR denitrification unit parameters and the actual operation of the unit, and fed back to the SCR denitrification unit, which can effectively realize the precise control of the ammonia injection amount. At the same time, the SCR denitrification unit is monitored and controlled in real time through the DCS system and the control server. The control server calculates in real time according to the parameters fed back by the SCR denitrification unit. This setting can adjust the ammonia injection amount in real time when the NOx content in the flue gas at the unit inlet changes, and can adjust the ammonia injection amount according to the NOx concentration required by the design, thereby improving the response speed of the ammonia injection amount feedforward, and can effectively avoid insufficient NOx reduction or waste of ammonia injection.

[0069] like Figure 1-3 As shown, the monitoring and control of the selective catalytic reduction denitration unit based on the distributed control system and the independent external control server includes:

[0070] applying the control policy to the control server;

[0071] Connect the control server to the distributed control system as a remote station;

[0072] Establish a data channel for a distributed control system to transmit data from the selective catalytic reduction denitrification unit to the control server;

[0073] After the control server completes the operation of the control algorithm, the operation results are sent to the data channel of the distributed control system.

[0074] In this technical solution, the control strategy is applied to the control server. It can be understood that the control strategy is to adjust the SCR denitrification unit through the calculated theoretical ammonia injection amount, and the control server is connected to the distributed control system as a remote station, thereby realizing remote control of the DCS system. This setting allows the staff to set up the control server without entering the denitrification site, and also makes the installation of the control server more flexible.

[0075] In actual application, after the optimization server completes the calculation of the control algorithm, it sends the calculation results to the DCS, and the DCS finally realizes the control of the SCR denitrification unit.

[0076] As shown in the figure, the method of obtaining the parameters of the selective catalytic reduction denitration unit and entering them into the control server as operation input parameters includes:

[0077] The load of the selective catalytic reduction denitrification unit, AGC instruction, NOx concentration at the denitrification outlet, NOx concentration at the denitrification inlet, NOx concentration at the total exhaust port, flue gas volume, oxygen volume, total air volume of the unit, primary air volume, secondary air volume, operating current of each coal mill, coal feed rate of the coal feeder, ammonia injection amount and ammonia injection valve opening are selected as input parameters for the control strategy operation.

[0078] In this technical solution, the SCR denitrification unit parameters obtained by DCS include SCR denitrification unit load, AGC instructions, denitrification outlet NOx concentration, denitrification inlet NOx concentration, flue gas volume, oxygen volume, unit total air volume, primary air volume, secondary air volume, operating current of each coal mill, coal feed rate, ammonia injection amount and ammonia injection valve opening. The above parameters are the parameters required to be input when the control server calculates the control strategy.

[0079] like Figure 1-3 As shown, the control server divides the denitrification outlet control interval based on the standard state NOx concentration at the denitrification outlet, and calculates the theoretical ammonia injection amount including:

[0080] The NOx concentration at the denitrification outlet is divided into ≤10mg / Nm3, 10-20mg / Nm3, 20-40mg / Nm3, 40-60mg / Nm3, ≥60mg / Nm3;

[0081] Calculate the theoretical ammonia injection amount, theoretical ammonia injection amount = flue gas volume * [denitrification efficiency + 5 / 22.4 / (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23)] * 10-3 * 17 (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23) * ammonia injection amount coefficient;

[0082] Wherein, NO concentration at denitration outlet = 0.92532* NOx concentration at denitration outlet;

[0083] NO2 concentration at denitration outlet = 0.07468 * NOx concentration at denitration outlet;

[0084] Denitrification efficiency = (NOx concentration at denitrification inlet - NOx concentration at denitrification outlet) / NOx concentration at denitrification inlet.

[0085] In this technical solution, the NO concentration at the denitrification outlet, the NO2 at the denitrification outlet and the denitrification efficiency are calculated, and the NOx concentration at the denitrification outlet is divided into ≤10mg / Nm3, 10-20mg / Nm3, 20-40mg / Nm3, 40-60mg / Nm3, ≥60mg / Nm3, and then the corresponding ammonia injection coefficient is selected according to the NOx concentration at the denitrification outlet, and then the theoretical ammonia injection amount can be obtained by calculation according to the formula.

[0086] It can be understood that the NOx concentration at the denitrification outlet is the real-time NOx concentration at the denitrification outlet of the SCR unit.

[0087] like Figure 1-3 As shown, the control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit, and the calculation of the optimized ammonia injection amount includes:

[0088] Determining the first ammonia injection change amount according to the load change rate;

[0089] Determine the change amount of the second ammonia injection according to the change rate of the denitration outlet;

[0090] Determine the change amount of the third ammonia injection amount according to the change rate of the denitration inlet;

[0091] The rate of change is calculated using a smoothing function: Trend(x(t))=1 / ts_A×(x(t)+x(t-1)+…+x(t-ts_A / 5)).

[0092] In this technical solution, in order to obtain the closest to ideal ammonia injection amount, in addition to calculating the theoretical ammonia injection amount, it is also necessary to consider the load change rate, the NOx change rate at the denitration outlet, and the NOx change rate at the denitration inlet. The above parameters will affect the ideal ammonia injection amount.

[0093] Among them, the first ammonia injection change amount is determined according to the SCR unit load change rate, the second ammonia injection change amount is determined according to the denitrification outlet change rate, and the third ammonia injection change amount is determined according to the denitrification inlet change rate.

[0094] In this technical solution, the optimized ammonia injection amount = theoretical ammonia injection amount + first ammonia injection change amount + second ammonia injection change amount + third ammonia injection change amount;

[0095] Among them, the specific method for determining the ammonia injection change amount is to determine the value of Trend(x(t)) according to the above formula, and then determine the first ammonia injection change amount, the second ammonia injection change amount, and the third ammonia injection change amount according to the value of Trend(x(t)).

[0096] For example, when calculating the load change rate, x(t) is the load value at a certain moment, and x(t-1) is the load value at an interval of five seconds. Thus, the change rate can be calculated.

[0097] like Figure 1-3 As shown, the control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit and further includes:

[0098] Determine the status of the coal mill;

[0099] When the coal mill is in the start / stop state, the fourth change amount is added to the theoretical ammonia injection amount.

[0100] In this technical solution, the influence of the coal mill state on the ammonia injection amount is introduced to make the optimized ammonia injection amount closer to the ideal value.

[0101] Among them, the start / stop of the coal mill will cause fluctuations in the amount of fuel and air, resulting in changes in the combustion state of the furnace, which will affect the NOx concentration at the furnace outlet. Before the coal mill is started, the air supply volume needs to be increased in advance, causing the coal powder in the furnace to be in an oxygen-rich combustion state. Under oxidizing atmosphere conditions, the NOx generation concentration and conversion rate will increase accordingly. When the coal mill is started, the amount of coal powder in the furnace increases, the fuel-type NOx increases, and the total amount of NOx increases. During the stop of the coal mill, the air supply volume needs to be maintained unchanged. The unchanged air volume and the reduced fuel volume will lead to an increase in the excess air coefficient, resulting in an increase in the amount of NOx generated. With the continuous enhancement of the deep peak-shaving capacity of thermal power, the start / stop frequency of the coal mill will also increase. The start / stop process of the coal mill will cause a large fluctuation in the NOx concentration at the SCR inlet. In order to ensure the denitrification efficiency while reducing the occurrence of side reactions, the ammonia injection amount should be optimized, and the ammonia injection amount of the coal mill start / stop feedforward should be increased to avoid excessive ammonia injection.

[0102] In this technical solution, the optimized ammonia injection amount = the theoretical ammonia injection amount + the first ammonia injection change amount + the second ammonia injection change amount + the third ammonia injection change amount + the fourth ammonia injection amount.

[0103] like Figure 1-3 As shown, it also includes:

[0104] Optimize the control server interface by setting control parameters for different NOx concentration ranges at the denitration outlet in the control strategy;

[0105] The control parameters are an ammonia injection amount coefficient, an ammonia injection amount variation, a valve characteristic curve, a maximum ammonia injection amount setting value and a minimum ammonia injection amount setting value.

[0106] In this technical solution, the interactive interface of the control server is optimized, and the NOx concentration range at the denitrification outlet is divided in the interactive interface. When a certain denitrification outlet NOx concentration range is selected, the interface automatically matches the corresponding ammonia injection coefficient, ammonia injection change, valve characteristic curve, maximum ammonia injection setting value and minimum ammonia injection setting value.

[0107] like Figure 1-3As shown, the control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit, including:

[0108] The distributed control system receives the optimized ammonia injection amount;

[0109] The operator sets the total outlet NOx concentration target value;

[0110] The distributed control system retrieves the denitrification main adjustment process value;

[0111] The distributed control system will optimize the ammonia injection amount, the total outlet NOx concentration target value, and the main adjustment process value through the PID module, and then issue a valve opening instruction to participate in the valve control;

[0112] The PID module transmits the change instructions of each valve to the selective catalytic reduction denitrification unit.

[0113] In this technical solution, the DCS system receives the optimized ammonia injection amount, and then sets the total outlet NOx concentration target value and the denitrification main adjustment process value. The denitrification main adjustment process value is the real-time total outlet NOx concentration of the unit.

[0114] By combining and calculating the above parameters through the PID module, the valve opening instruction can be calculated, and the valve opening instruction can be issued to participate in the valve control.

[0115] like Figure 1-3 As shown, it also includes:

[0116] Single-ended line test: When the single-ended line test passes, the PID module performs calculations. When the single-ended line test fails, the PID module does not perform calculations.

[0117] The single-ended line test is associated with the switching switch and the automatic manual switch in the distributed control system. The switching switch has two states, open and closed, and the automatic manual switch has two states, automatic and manual. When the switching switch is in the open state and the automatic manual switch is in the automatic state, the single-ended line test passes, otherwise, the single-ended line test fails.

[0118] In this technical solution, a single-ended line test is added. When the intelligent optimization control system fails or is manually cut off by the operator, the denitrification control system automatically switches to manual control mode, and the operator manually controls the ammonia injection regulating gate. When the system is in manual adjustment mode, the optimization control output is consistent with the current adjustment command, and when the system switches from manual mode to intelligent optimization control mode, disturbance-free switching can be achieved.

[0119] like Figure 1-3As shown, according to the second aspect of the embodiment of the present application, a total denitration control system based on optimized ammonia injection amount feedforward is proposed, comprising:

[0120] Control servers;

[0121] Distributed control system, the control server is independently plugged into the distributed control system, and the control server information is connected to the distributed control system;

[0122] A selective catalytic reduction denitration unit, wherein the selective catalytic reduction denitration unit is electrically connected to the distributed control system;

[0123] The distributed control system includes a total exhaust NOx closed-loop control module and an ammonia injection amount feedforward module;

[0124] The ammonia injection amount feedforward module includes a PID module and an automatic manual switching switch.

[0125] Among them, the control logic of the ammonia injection amount feedforward module is as follows: Figure 2 The overall control logic of the DCS system is as follows: Figure 3 , Figure 3 In order to introduce the calculation results of the ammonia injection amount feedforward module, the existing total denitrification DCS system and the control logic flow of the parts other than the ammonia injection amount feedforward module are very mature. Here, only the introduction position of the throttle opening instruction is illustrated, and the rest of the existing technical parts are not repeated in this technical solution.

[0126] In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0127] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0128] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0129] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A total denitrification control method based on optimized ammonia injection amount feedforward, characterized in that: include: Monitor and control the selective catalytic reduction denitrification unit based on a distributed control system and an independent external control server; Obtaining the parameters of the selective catalytic reduction denitrification unit and entering them into the control server as operation input parameters; The control server divides the denitrification outlet control interval based on the standard NOx concentration at the denitrification outlet and calculates the theoretical ammonia injection amount; The control server corrects the theoretical ammonia injection amount based on the actual operating conditions of the selective catalytic reduction denitrification unit and calculates the optimized ammonia injection amount; The control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit.

2. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 1 is characterized in that: The monitoring and control of the selective catalytic reduction denitration unit based on the distributed control system and the independent external control server includes: applying the control policy to the control server; Connect the control server to the distributed control system as a remote station; Establish a data channel for a distributed control system to transmit data from the selective catalytic reduction denitrification unit to the control server; After the control server completes the operation of the control algorithm, the operation results are sent to the data channel of the distributed control system.

3. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 1 is characterized in that: The method of obtaining the parameters of the selective catalytic reduction denitration unit and entering the parameters into the control server as operation input parameters comprises: The load of the selective catalytic reduction denitrification unit, AGC instruction, NOx concentration at the denitrification outlet, NOx concentration at the denitrification inlet, NOx concentration at the total exhaust port, flue gas volume, oxygen volume, total air volume of the unit, primary air volume, secondary air volume, operating current of each coal mill, coal feed rate of the coal feeder, ammonia injection amount and ammonia injection valve opening are selected as input parameters for the control strategy operation.

4. The total denitrification control method based on optimized ammonia injection amount feedforward according to claim 1 is characterized in that: The control server divides the denitrification outlet control interval based on the standard NOx concentration at the denitrification outlet, and calculates the theoretical ammonia injection amount, including: The NOx concentration at the denitrification outlet is divided into ≤10mg / Nm 3 10~20mg / Nm 3 20~40mg / Nm 3 40~60mg / Nm 3 , ≥60mg / Nm 3 ; Calculate the theoretical ammonia injection amount, theoretical ammonia injection amount = flue gas volume * [denitrification efficiency + 5 / 22.4 / (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23)] * 10-3 * 17 (denitrification outlet NO concentration / 30 + denitrification outlet NO2 concentration / 23) * ammonia injection amount coefficient; Wherein, NO concentration at denitration outlet = 0.92532* NOx concentration at denitration outlet; NO2 concentration at denitration outlet = 0.07468 * NOx concentration at denitration outlet; Denitrification efficiency = (NOx concentration at denitrification inlet - NOx concentration at denitrification outlet) / NOx concentration at denitrification inlet.

5. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 1 is characterized in that: The control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit, and calculates the optimized ammonia injection amount including: Determining the first ammonia injection change amount according to the load change rate; Determine the change amount of the second ammonia injection according to the change rate of the denitration outlet; Determine the change amount of the third ammonia injection amount according to the change rate of the denitration inlet; The rate of change is calculated using a smoothing function: Trend(x(t))=1 / ts_A×(x(t)+x(t-1)+…+x(t-ts_A / 5)).

6. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 5 is characterized in that: The control server corrects the theoretical ammonia injection amount in combination with the actual operating conditions of the selective catalytic reduction denitration unit, and further includes: Determine the status of the coal mill; When the coal mill is in the start / stop state, the fourth change amount is added to the theoretical ammonia injection amount.

7. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 4 is characterized in that: Also includes: Optimize the control server interface by setting control parameters for different NOx concentration ranges at the denitration outlet in the control strategy; The control parameters are an ammonia injection amount coefficient, an ammonia injection amount variation, a valve characteristic curve, a maximum ammonia injection amount setting value and a minimum ammonia injection amount setting value.

8. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 1 is characterized in that: The control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit, including: The distributed control system receives the optimized ammonia injection amount; The operator sets the total outlet NOx concentration target value; The distributed control system retrieves the denitrification main adjustment process value; The distributed control system will optimize the ammonia injection amount, the total outlet NOx concentration target value, and the main adjustment process value through the PID module, and then issue a valve opening instruction to participate in the valve control; The PID module transmits the change instructions of each valve to the selective catalytic reduction denitrification unit.

9. The total denitration control method based on optimized ammonia injection amount feedforward according to claim 8, characterized in that: The control server feeds back the optimized ammonia injection amount to the distributed control system, and the distributed control system feeds back the theoretical ammonia injection amount to the selective catalytic reduction denitrification unit, including: Single-ended line test: When the single-ended line test passes, the PID module performs calculations. When the single-ended line test fails, the PID module does not perform calculations. The single-ended line test is associated with the switching switch and the automatic manual switch in the distributed control system. The switching switch has two states, open and closed, and the automatic manual switch has two states, automatic and manual. When the switching switch is in the open state and the automatic manual switch is in the automatic state, the single-ended line test passes, otherwise, the single-ended line test fails.

10. A total denitrification control system based on optimized ammonia injection amount feedforward, characterized in that: The total denitration control method according to any one of claims 1 to 9 can be applied to a total denitration control system, comprising: Control servers; Distributed control system, the control server is independently plugged into the distributed control system, and the control server information is connected to the distributed control system; A selective catalytic reduction denitration unit, wherein the selective catalytic reduction denitration unit is electrically connected to the distributed control system; The distributed control system includes a total exhaust NOx closed-loop control module and an ammonia injection amount feedforward module; The ammonia injection amount feedforward module includes a PID module, an on-off switch and a pneumatic manual switch.

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