Ammonia water flow automatic control method for denitration, medium and system

Abstract

The invention discloses an ammonia water flow automatic control method, medium and system for denitration, and the method comprises the steps: presetting a NOX target value, and generating a main ammonia water amount according to the NOX target value; the actual secondary air volume is obtained, and the secondary ammonia water amount is obtained according to the actual secondary air volume; and correcting the main ammonia water amount according to the secondary ammonia water amount to obtain the final ammonia water amount. Research finds that the actual secondary air volume can influence the corresponding NOx content, so that the corresponding secondary ammonia water amount is generated according to the corresponding function relational expression to serve as the feedforward signal, the problem that the ammonia water flow is not adjusted in time due to large delay and large inertia of a denitration control system is effectively solved, the stability of the system is improved, and the control accuracy of the denitration control system is improved. The great fluctuation of the ammonia water control valve is slowed down, the ammonia water consumption is reduced, and the ammonia escape is reduced; and in-furnace denitration is carried out by giving more accurate ammonia water amount, so that the reaction efficiency of SNCR is improved.

Description

TECHNICAL FIELD

[0001] The present application mainly relates to the technical field of denitration, and particularly relates to an ammonia water flow automatic control method, medium and system for denitration. BACKGROUND

[0002] SNCR denitration technology, i.e. selective non-catalytic reduction technology, is a clean denitration technology that uses a catalyst to spray a reducing agent (such as ammonia water, urea solution, etc.) containing an amino group into a furnace at a temperature range of 850-1100°C to reduce and remove NOx in flue gas, and generate nitrogen and water.

[0003] Currently, the automatic control of SNCR ammonia water flow is adjusted according to the content of NOx in clean flue gas. The PID of NOx automatically calculates a value A (a value between 0 and 1) according to the feedback of NOx. When NOx is higher than the set value, the output of the PID of NOx increases; when NOx is lower than the set value, the output of the PID of NOx decreases (the feedback value of NOx, which takes the moving 30-second average of the content of NOx in clean flue gas as the feedback value, is used for adjustment).

[0004] Due to the characteristics of large delay and large inertia of the denitration control system, the feedback value of NOx cannot timely reflect the running state of the denitration in the furnace, resulting in poor stability of the denitration control system. X The feedback value cannot timely reflect the running state of the denitration in the furnace, resulting in poor stability of the denitration control system. SUMMARY

[0005] In view of the technical problems in the prior art, the present application provides an ammonia water flow automatic control method for denitration, which has good real-time performance.

[0006] To solve the above technical problems, the technical solution provided by the present application is as follows: An ammonia water flow automatic control method for denitration, comprising the following steps: pre-setting a NOx target value, and generating a main ammonia water amount according to the NOx target value; X acquiring an actual secondary air amount, and obtaining a secondary ammonia water amount according to the actual secondary air amount; X correcting the main ammonia water amount according to the secondary ammonia water amount to obtain a final ammonia water amount.

[0007] Preferably, the specific process of acquiring the actual secondary air amount and obtaining the secondary ammonia water amount according to the actual secondary air amount is as follows: After acquiring the actual secondary air amount during system operation, the corresponding output NOx value is obtained according to the functional relationship between the content of NOx and the secondary air amount, and then the corresponding secondary ammonia water amount is obtained according to the output NOx value and the NOx target value. X X X X ​​​​​​

[0008] Preferably, NO X The function relation of the content and the secondary air quantity is: y=3.4027x+106.87 Wherein y is the NOx content, and x is the secondary air quantity.

[0009] Preferably, the output NO X value and the NO X target value are used to obtain a calculation formula of the corresponding hydrazine amount: Hydrazine amount=(output NO X value-NO X target value) / proportion coefficient a. Wherein the proportion coefficient a is obtained through long-time operation data.

[0010] Preferably, the main hydrazine amount is corrected according to the hydrazine amount to obtain the specific process of the final hydrazine amount: The main hydrazine amount is comprehensively compared with the hydrazine amount; when the hydrazine amount is less than the main hydrazine amount, the final hydrazine amount will be reduced; when the hydrazine amount is greater than the main hydrazine amount, the final hydrazine amount will be increased.

[0011] The application further discloses a computer program product, comprising a computer program, which executes the steps of the method when run by a processor.

[0012] The application further discloses a computer readable storage medium, which stores a computer program, which executes the steps of the method when run by a processor.

[0013] The application further discloses an ammonia water flow automatic control system for denitration, comprising a memory and a processor connected with each other, wherein the memory stores a computer program, and the computer program executes the steps of the method when run by the processor.

[0014] Compared with the prior art, the application has the following advantages: The ammonia water flow automatic control method for denitration of the application effectively reduces the problem of untimely ammonia water flow adjustment caused by large delay and large inertia of the denitration control system, improves the stability of the system, slows down the large fluctuation of the ammonia water regulating valve, reduces the ammonia water consumption, and reduces ammonia escape, by generating the corresponding hydrazine amount as a feedforward signal according to the corresponding function relation of the actual secondary air quantity and the corresponding NOx content. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1The flowchart is shown in an embodiment of the automatic ammonia flow control method of the present invention.

[0016] Figure 2 This is a fitted curve of secondary air volume and NOx in this invention.

[0017] Figure 3 This is a graph showing the changes in indicators before and after optimization in this invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0019] The patent applicant, through relevant research, discovered that secondary air volume affects NO. X This leads to conclusions with significant implications. Specifically, regarding NO in incinerators... X The generation of NOx is closely related to the excess air coefficient, which is controlled in the ACC control system by the secondary air volume output from the secondary fan. Based on this, an experiment was conducted: with no ammonia added to the boiler's SNCR system, data on its secondary air volume and NOx were retrieved and linearly fitted. The results are as follows... Figure 2 As shown, NO is obtained. X The functional relationship between content and secondary air volume: y = 3.4027x + 106.87; Where y is the NOx content and x is the secondary air volume.

[0020] like Figure 2 As shown, when the secondary air volume is between 15-25 kNm 3 When the / h interval is reached, NO X The generation of [something] tends to increase with the increase of secondary air volume.

[0021] Therefore, the output NO can be simulated by using the actual secondary air volume. X value.

[0022] like Figure 1 As shown in the figure, the automatic control method for ammonia water flow rate for denitrification provided in this embodiment of the invention includes the following steps: S1, Preset NO X Target value, and based on NO X The target value generates the main ammonia volume, which serves as the main signal; NO X The target value is set according to national flue gas emission standards. Currently, the standard for Hunan Province is NO. X Hourly average not exceeding 300 mg / Nm 3 The 24-hour average value does not exceed 250 mg / Nm³. 3 Our factory currently has NO. X The target value is set at 170 mg / Nm3 .

[0023] According to NO X The target value of the ammonia water flow is calculated by the PID system, and in fact, it is realized by adjusting the valve opening. The value is not a fixed value, but after changing the valve opening, the change of the ammonia water flow causes the change of the NO X x, and the adjustment is carried out after the change.

[0024] S2, the actual secondary air flow is obtained, and the secondary ammonia water flow is obtained according to the actual secondary air flow; Specifically, after obtaining the actual secondary air flow during the operation of the system, the corresponding output NO X x value is obtained according to the functional relationship (y=3.4027x+106.87) between the NO X x content and the secondary air flow; and the corresponding secondary ammonia water flow is obtained according to the following formula: Secondary ammonia water flow=(output NO X x value-NO X target value) / proportion coefficient a; Wherein, the proportion coefficient a can be obtained by long-time running data, and can be adjusted according to the actual situation of different boilers.

[0025] S3, the primary ammonia water flow is corrected according to the secondary ammonia water flow to obtain the final ammonia water flow.

[0026] Specifically, the primary ammonia water flow and the secondary ammonia water flow are compared; when the secondary ammonia water flow is less than the primary ammonia water flow, the final ammonia water flow will be reduced; when the secondary ammonia water flow is greater than the primary ammonia water flow, the final ammonia water flow will be increased. Specifically, the difference between the primary ammonia water flow and the secondary ammonia water flow is taken as the input quantity of the PID controller of the denitration control system, the control instruction of the PID controller is output to control the opening of the ammonia water regulating valve, and then the adjustment of the ammonia water flow is realized.

[0027] The ammonia water flow automatic control method for denitration of the application, through research, it is found that the actual secondary air flow will affect the corresponding NOx content, so according to the corresponding function relationship, the corresponding secondary ammonia water flow is generated as a feedforward signal, which effectively reduces the problem of not timely ammonia water flow adjustment caused by large delay and large inertia of the denitration control system, improves the stability of the system, slows down the large fluctuation of the ammonia water regulating valve, reduces the ammonia water consumption, and reduces the ammonia escape; by giving more accurate ammonia water flow for in-furnace denitration, the reaction efficiency of SNCR is improved.

[0028] Experimental verification: as Figure 3As shown, by comparing the average ammonia water flow (L / h), ammonia escape (mg / Nm3) and monthly ammonia water consumption (t) of the four furnaces before and after the logic optimization. After adjustment, compared with before adjustment, the ammonia water flow is reduced by 21.05%, the ammonia escape is reduced by 21.09%, and the monthly ammonia water consumption is reduced by 21.68%. In view of the above, in the case that the average content of chimney NOx is 170mg / Nm 3 before and after adjustment, the ammonia water consumption after adjustment can be reduced by 16.8% compared with before adjustment.

[0029] In addition, the average content of chimney NOx before adjustment is 161mg / Nm3, and the average content of chimney NOx after adjustment is 171mg / Nm3, and the NO X x average content increases by 6.21%, which is closer to the NOx target value 170mg / Nm 3 . In the case that the NO X x target value is 170mg / Nm3, the actual value after logic optimization is obviously closer to the target value, and the stability of the denitration system is improved.

[0030] The application also discloses a computer program product, comprising a computer program, which executes the steps of the method when run by a processor. The application further discloses a computer readable storage medium, which stores a computer program, which executes the steps of the method when run by a processor. The application also discloses an ammonia water flow automatic control system for denitration, comprising a memory and a processor connected to each other, wherein the memory stores a computer program, which executes the steps of the method when run by the processor.

[0031] The present application can realize all or part of the processes in the above-mentioned embodiment methods, and can also be completed by computer program instruction related hardware. The computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned method embodiment can be realized. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms, etc. The computer readable storage medium includes any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium, etc. The memory is used to store computer programs and / or modules. The processor realizes various functions by running or executing the computer programs and / or modules stored in the memory, and calling the data stored in the memory. The memory can include high-speed random access memory, and can also include non-volatile memory, such as hard disk, memory, plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, at least one magnetic disk storage device, flash memory device, or other volatile solid-state storage device, etc.

[0032] The above is only the preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned embodiment. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principle of the present application shall be considered as the protection scope of the present application.

Claims

1. An automatic control method for the flow of ammonia water for denitration, characterized by, The method comprises the steps of: Pre-set NO X Target value, and according to NO X Target value to generate the main ammonia water quantity; acquiring the actual secondary air quantity and obtaining the secondary ammonia water quantity according to the actual secondary air quantity; correcting the main ammonia water quantity according to the secondary ammonia water quantity to obtain the final ammonia water quantity.

2. The method for automatic control of ammonia water flow for denitration according to claim 1, characterized by, The specific process of acquiring the actual secondary air quantity and obtaining the secondary ammonia water quantity according to the actual secondary air quantity is as follows: After the actual air amount of secondary air is obtained when the system is running, the function relation between the content of NO X and the air amount of secondary air is obtained, the corresponding output NO X value is obtained, and then the corresponding amount of hydrazine solution is obtained according to the output NO X value and the target value of NO X .

3. The ammonia water flow automatic control method for denitration according to claim 2, characterized by, NO X The function of the content and the secondary air quantity is: y=3.4027x+106.87 wherein y is the NOx content and x is the secondary air quantity.

4. The method for automatic control of the flow of ammonia water for denitration according to claim 2 or 3, characterized by, According to the output NO X value and the NO X The calculation formula of the corresponding hydrazine amount is obtained according to the target value. Amount of hydrazine = (Output NOx - Target value) / Proportionality coefficient a X Value - NOx X Target value) / Proportionality coefficient a; The proportional coefficient a is obtained through long-time operation data.

5. The automatic control method for ammonia water flow for denitration according to claim 1 or 2 or 3, characterized by, The specific process of correcting the main ammonia water quantity according to the secondary ammonia water quantity to obtain the final ammonia water quantity is as follows: comprehensively comparing the secondary ammonia water quantity with the main ammonia water quantity; when the secondary ammonia water quantity is less than the main ammonia water quantity, the final ammonia water quantity will be reduced; when the secondary ammonia water quantity is greater than the main ammonia water quantity, the final ammonia water quantity will be increased.

6. A computer program product comprising a computer program, characterized in that, The computer program, when executed by a processor, performs the steps of the method according to any one of claims 1-5.

7. A computer-readable storage medium having stored thereon a computer program, characterized in that The computer program, when executed by a processor, performs the steps of the method according to any one of claims 1-5.

8. An ammonia water flow automatic control system for denitration, comprising a memory and a processor connected to each other, and a computer program is stored on the memory, characterized in that, The computer program, when executed by a processor, performs the steps of the method according to any one of claims 1-5.

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