A high-following SCR denitration control system and method

Abstract

The present invention discloses a high-followability SCR denitrification control system and method. A matrix flue gas flowmeter, an inlet NOx rapid measuring instrument, a partitioned ammonia injection grid, a partitioned flue gas mixer and a NOx sampling point behind the ammonia injection grid are distributed in sequence along the flue gas flow direction, and the NOx sampling point behind the ammonia injection grid is connected to the inlet of a micro-denitrification reactor, and the outlet of the micro-denitrification reactor is connected to the inlet of a high-precision NOx measurement analyzer. The output end of the NOx measurement analyzer, the output end of the inlet NOx rapid measuring instrument and the output end of the matrix flue gas flowmeter are connected to the input end of the control system, the output end of the control system is connected to the control end of an ammonia regulating valve, and the outlet of the ammonia source is connected to the inlet of the ammonia injection grid via the ammonia regulating valve. The system and method can significantly improve the followability of ammonia injection control and meet the denitrification control requirements of ultra-low emissions and higher precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of denitration, and relates to a high-followability SCR denitration control system and method. Background Art

[0002] The current SCR measurement and ammonia injection control method is to measure the NOx concentration at the SCR outlet and adjust the opening of the ammonia injection regulating valve through feedback. Due to the measurement principle of the NOx concentration at the SCR outlet, the flue gas is extracted and pre-treated before entering the analyzer, and then the NOx concentration is measured. This method often has a time delay of 1 to 5 minutes. The lag in measurement makes it difficult for the SCR ammonia injection to be adjusted in time according to the actual changes in the boiler operating conditions. Therefore, the NOx concentration at the SCR outlet often fluctuates greatly. Especially after ultra-low emissions, the denitrification outlet needs to reach 50mg / m 3 When meeting emission requirements, large fluctuations in NOx concentrations force boiler operators to switch from automatic denitrification control to manual control. However, manual control often suffers from limited resources and delayed measurement at the denitrification outlet, resulting in poor control quality. This often results in excessive ammonia injection, leading to widespread blockage of ammonia bisulfate in subsequent equipment such as the air preheater and low-temperature economizers.

[0003] Even though there is currently a feedforward model that can predict the NOx concentration generated by the boiler, due to the complexity of boiler combustion, the ammonia injection follow-up performance can only be improved to a small extent and still cannot fully meet the denitrification control requirements. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a highly followable SCR denitrification control system and method, which can significantly improve the followability of ammonia injection control and meet the denitrification control requirements of ultra-low emissions and higher precision requirements.

[0005] To achieve the above-mentioned purpose, the high-followability SCR denitrification control system described in the present invention includes a control system and several adjustment components. The SCR inlet flue is divided into several sub-areas, and each area corresponds to a group of measurement and adjustment components. The measurement and adjustment components include a partitioned ammonia injection grid, a partitioned flue gas mixer, an inlet in-situ NOx meter, a matrix flue gas flow meter, a NOx sampling point after the ammonia injection grid, a micro-denitrification reactor and a NOx measurement and analyzer. Among them, the matrix flue gas flow meter, the inlet in-situ NOx meter, the ammonia injection grid, the partitioned flue gas mixer and the NOx sampling point after the ammonia injection grid are distributed in sequence along the flue gas flow direction, and the NOx sampling point after the ammonia injection grid is connected to the inlet of the micro-denitrification reactor, the outlet of the micro-denitrification reactor is connected to the inlet of the NOx measurement and analyzer, the output end of the NOx measurement and analyzer, the output end of the inlet in-situ NOx meter and the output end of the matrix flue gas flow meter are connected to the input end of the control system, the output end of the control system is connected to the control end of the ammonia regulating valve, and the outlet of the ammonia source is connected to the inlet of the ammonia injection grid via the ammonia regulating valve.

[0006] The high-followability SCR denitration control method of the present invention comprises the following steps:

[0007] Ammonia-containing flue gas is extracted through the NOx sampling point behind the ammonia injection grid and then sent to a micro-denitrification reactor for reaction. The flue gas after the denitrification reaction is then sent to a NOx measurement analyzer for NOx concentration measurement, and the measured NOx concentration is used as the NOx concentration of the flue gas after the SCR reactor in that partition. The NOx concentration in the partition before denitrification treatment is measured by an in-situ NOx meter at the inlet, and the flow rate of the flue gas in the partition is measured by a matrix flue gas flow meter. The control system calculates the total NOx content in the partition based on the measurement results of the matrix flue gas flow meter and the measurement results of the in-situ NOx meter at the inlet, calculates the required reducing agent dosage for the partition based on the total NOx content in the partition and the target value to be controlled, and then controls the opening of the ammonia regulating valve based on the required reducing agent dosage for the partition to spray ammonia in the required reducing agent amount.

[0008] The measurement result of the matrix flue gas flow meter is multiplied with the measurement result of the in-situ NOx instrument at the inlet, and the result of the multiplication is used as the total NOx content in the partition.

[0009] The present invention has the following beneficial effects:

[0010] During specific operation, the high-followability SCR denitrification control system and method described in the present invention utilizes the measurement data of the NOx measurement analyzer behind the ammonia injection grid for feedback adjustment to calculate the amount of reducing agent, which is then used to control the ammonia regulating valve, and then the amount of injected reducing agent, thereby significantly improving the followability of ammonia injection control, making the NOx concentration at the denitrification outlet stable and with small fluctuations, meeting the denitrification control requirements of ultra-low emissions and higher precision, thereby reducing the level of ammonia slip and alleviating or avoiding the blockage of subsequent equipment such as the air preheater. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a structural schematic diagram of the present invention;

[0012] Figure 2 for Figure 1 Schematic diagram of direction A.

[0013] Among them, 1 is a matrix flue gas flow meter, 2 is an in-situ NOx meter for the inlet, 3 is a partitioned ammonia injection grid, 4 is a partitioned flue gas mixer, 5 is a NOx sampling point after the ammonia injection grid, 6 is a micro-denitrification reactor, and 7 is a high-precision NOx measurement and analyzer. DETAILED DESCRIPTION

[0014] In order to enable those skilled in the art to better understand the solutions of the present invention, 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 only embodiments of a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0015] The accompanying drawings illustrate schematic diagrams of the structures of the disclosed embodiments of the present invention. These figures are not drawn to scale; for the purpose of clarity, some details are exaggerated and some details may be omitted. The shapes of the various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art may design regions / layers with different shapes, sizes, and relative positions as needed.

[0016] refer to Figure 1 and Figure 2The high-followability SCR denitrification control system of the present invention includes a control system and several regulating components. The SCR inlet flue is divided into several sub-areas, each area corresponds to a set of measurement and regulating components, and each regulating component includes a partitioned ammonia injection grid 3, a partitioned flue gas mixer 4, an inlet in-situ NOx meter 2, a matrix flue gas flow meter 1, a NOx sampling point 5 after the ammonia injection grid, a micro denitrification reactor 6 and a NOx measurement analyzer 7, wherein the matrix flue gas flow meter 1, the inlet in-situ NOx meter 2, the ammonia injection grid 3, the partitioned flue gas mixer 4 and the NOx sampling point 5 after the ammonia injection grid are distributed in sequence along the flue gas flow direction, and the NOx sampling point 5 after the ammonia injection grid is connected to the inlet of the micro-denitrification reactor 6, the outlet of the micro-denitrification reactor 6 is connected to the inlet of the NOx measurement and analyzer 7, the output end of the NOx measurement and analyzer 7, the output end of the inlet in-situ NOx instrument 2 and the output end of the matrix flue gas flowmeter 1 are connected to the input end of the control system, the output end of the control system is connected to the control end of the ammonia regulating valve, and the outlet of the ammonia source is connected to the inlet of the ammonia injection grid 3 through the ammonia regulating valve.

[0017] The high-followability SCR denitration control method of the present invention comprises the following steps:

[0018] Ammonia-containing flue gas is extracted through the NOx sampling point 5 behind the ammonia injection grid and then sent to the micro-denitrification reactor 6 for reaction. The flue gas after the denitrification reaction is then sent to the NOx measurement analyzer 7 for NOx concentration measurement, and the measured NOx concentration is used as the NOx concentration of the flue gas after the SCR reactor in the partition. The NOx concentration of the partition before denitrification treatment is measured by the in-situ NOx meter 2 at the inlet, and the flow rate of the flue gas in the partition is measured by the matrix flue gas flow meter 1. The control system multiplies the measurement result of the matrix flue gas flow meter 1 with the measurement result of the in-situ NOx meter 2 at the inlet, and uses the multiplication result as the total NOx content in the partition. The required reducing agent dosage of the partition is calculated based on the total NOx content in the partition and the target value to be controlled. Then, the opening of the ammonia regulating valve is controlled based on the required reducing agent dosage of the partition to inject the required reducing agent dosage of ammonia.

[0019] It should be noted that due to the measurement accuracy of the measuring instrument and the long-term drift of the meter, there will be a small deviation between the NOx concentration at the denitrification outlet and the target value. The present invention uses the measurement data of the NOx measurement analyzer 7 after the ammonia injection grid 3 to perform feedback adjustment so that it accurately reaches the target value, thereby leveling the NOx concentration at the denitrification outlet and greatly improving the follow-up performance of the ammonia injection.

Claims

1. A highly adaptable SCR denitrification control method, characterized in that: Based on a high-followability SCR denitrification control system, the high-followability SCR denitrification control system includes a control system and several regulating components. The SCR inlet flue is divided into several sub-areas, and each area corresponds to a group of measurement and regulating components. The measurement and regulating components include a partitioned ammonia injection grid (3), a partitioned flue gas mixer (4), an inlet in-situ NOx meter (2), a matrix flue gas flow meter (1), a NOx sampling point after the ammonia injection grid (5), a micro denitrification reactor (6) and a NOx measurement analyzer (7). The gas mixer (4) and the NOx sampling point (5) after the ammonia injection grid are sequentially distributed along the flue gas flow direction, and the NOx sampling point (5) after the ammonia injection grid is connected to the inlet of the micro-denitrification reactor (6), the outlet of the micro-denitrification reactor (6) is connected to the inlet of the high-precision NOx measurement analyzer (7), the output end of the NOx measurement analyzer (7), the output end of the inlet in-situ NOx instrument (2) and the output end of the matrix type delay-free flue gas flow meter (1) are connected to the input end of the control system, the output end of the control system is connected to the control end of the ammonia regulating valve, and the outlet of the ammonia source is connected to the inlet of the ammonia injection grid (3) through the ammonia regulating valve; The following steps are involved: The flue gas containing ammonia after the partition ammonia grid is fully mixed by the partition mixer is extracted through the NOx sampling point (5), and then sent to the micro denitrification reactor (6) for reaction. The flue gas after the denitrification reaction is then sent to the NOx measurement analyzer (7) for NOx concentration measurement, and the measured NOx concentration is used as the NOx concentration of the flue gas after the SCR reactor in the partition. The NOx concentration in the partition before denitrification is measured by the inlet in-situ NOx meter (2), and the flow rate of the flue gas in the partition is measured by the matrix flue gas flow meter (1). The control system calculates the total NOx content in the partition based on the measurement results of the matrix flue gas flow meter (1) and the measurement results of the inlet in-situ NOx meter (2), calculates the required reducing agent dosage of the partition based on the total NOx content in the partition and the target value to be controlled, and then controls the opening of the ammonia regulating valve based on the required reducing agent dosage of the partition to spray ammonia of the required reducing agent dosage; Multiplying the measurement result of the matrix flue gas flow meter (1) and the measurement result of the inlet in-situ NOx meter (2), and taking the multiplication result as the total NOx content in the partition; The NOx concentration measured by the NOx measurement analyzer (7) behind the ammonia injection grid (3) is used to feedback-regulate the ammonia injection amount, thereby leveling the NOx concentration at the denitrification outlet and significantly improving the followability of the ammonia injection.

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