A device and method for precise ammonia injection partition leveling of an SCR system through differential pressure

Abstract

The present application relates to a kind of by differential pressure realizes the accurate ammonia injection zoning leveling device and method of SCR system, belong to environmental protection technical field.The by differential pressure realizes the accurate ammonia injection zoning leveling device of SCR system, including SCR reactor, the inlet flue and outlet flue are equipped on the SCR reactor, the upper portion of the SCR reactor is equipped with rectifier grid, the vertical below of the rectifier grid is equipped with multiple partitions, the inlet flue is equipped with multiple ammonia injection grid, the number of the ammonia injection grid corresponds with the number of the partition one-to-one, each the partition is equipped with differential pressure measuring instrument, the outside of the SCR reactor is also equipped with the ammonia injection amount adjusting mechanism for adjusting the ammonia injection flow of each partition.Amusing effect: by differential pressure can realize the accurate ammonia injection zoning leveling of SCR system, its partition modification cost is low, instrument maintenance is convenient, and instrument measurement response time is short, ammonia injection amount and unit load change synchronism is strong.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of environmental protection, and particularly relates to a device and method for realizing precise ammonia injection partition leveling of an SCR system through differential pressure. BACKGROUND

[0002] In order to meet the environmental protection requirements, power plants have carried out denitration ultra-low emission reconstruction, but the traditional selective catalytic reduction (SCR) denitration process cannot accurately control the ammonia injection amount, so although the unit has reached the ultra-low emission control operation requirement of nitrogen oxides, the SCR denitration system has the characteristics of large flue on space, wide flow range, large delay and inertia in time, thereby causing uneven distribution of ammonia injection in space and time lag and slow response of the SCR denitration system, and finally leading to deviation of the denitration efficiency of the denitration system from the expected target. Moreover, under the influence of deep peak shaving of thermal power, the unit load fluctuates greatly, and the existing SCR ammonia injection regulation system cannot meet the demand of flexible operation of the unit, so most units can only inject excess ammonia to ensure that the denitration rate is guaranteed, but NH3 that does not participate in the reaction escapes, reacts with H2O and SO3 to generate high-viscosity NH4HSO4, which adheres to the catalyst or air preheater, not only increases the system resistance and affects the efficient operation of the system, but also corrodes the air preheater, seriously affecting the safety and economy of the unit operation.

[0003] Under this background, many power plants have carried out precise ammonia injection reconstruction, partitioned AIG, installed NOx measuring instruments in the SCR outlet flue area corresponding to the partition, replaced all manual valves with automatic valves, and finally adjusted the ammonia injection branch valve through the outlet NOx concentration value. At present, the NOx concentration measurement mainly uses the CEMS measurement system, but due to the long sampling pipeline of the CEMS system, the measurement result lags for more than 2 minutes, which leads to a certain lag of the PID in adjusting the valve, and at the same time, the CEMS system samples at a single point, so if the partition is too large, the measurement result is poor in representativeness, and if the partition is too small, multiple CEMS systems need to be installed, which increases the cost, so it is of great significance to develop a precise ammonia injection partition leveling device and method with strong sampling representativeness, rapid measurement result and low cost. SUMMARY

[0004] The present application provides a device for realizing precise ammonia injection partition leveling of an SCR system through differential pressure, which can realize precise ammonia injection partition leveling of the SCR system through differential pressure, has low partition reconstruction cost, convenient instrument maintenance, short instrument measurement response time, and strong synchronization of ammonia injection amount and unit load change.

[0005] The technical scheme for solving the above technical problems is as follows: the device for realizing precise ammonia injection zoning and leveling of an SCR system through differential pressure comprises an SCR reactor, an inlet flue and an outlet flue arranged on the SCR reactor, a rectifier grid arranged in the upper portion of the SCR reactor, a plurality of zones arranged vertically below the rectifier grid, a plurality of ammonia injection grids arranged in the inlet flue, the number of the ammonia injection grids corresponding to the number of the zones, a differential pressure measuring instrument arranged in each zone, and an ammonia injection amount adjusting mechanism arranged outside the SCR reactor and used for adjusting the ammonia injection flow of each zone.

[0006] Beneficial effects: the device can realize precise ammonia injection zoning and leveling of an SCR system through differential pressure, has low zoning transformation cost, is convenient to maintain, has short instrument measurement response time, and has strong synchronization between ammonia injection amount and unit load change.

[0007] On the basis of the above technical scheme, the device can be further improved as follows.

[0008] Further, the ammonia injection amount adjusting mechanism comprises an ammonia injection main pipe, a plurality of ammonia injection branch pipes and adjusting valves, the ammonia injection main pipe is connected with the plurality of ammonia injection branch pipes respectively, the number of the plurality of ammonia injection branch pipes corresponds to the number of the plurality of ammonia injection grids, and the adjusting valves are arranged on the plurality of ammonia injection branch pipes.

[0009] Further, the device further comprises a controller, and the controller is electrically connected with the adjusting valves.

[0010] Further, a plurality of catalyst layers are sequentially arranged in the SCR reactor from top to bottom, and the zones are arranged above the uppermost catalyst layer.

[0011] Further, the differential pressure measuring instrument is arranged above the uppermost catalyst layer and 1.5-2 m below the rectifier grid.

[0012] Further, the length-width ratio of each zone is ≤3.

[0013] The second object of the device is to provide a method for realizing precise ammonia injection zoning and leveling of an SCR system through differential pressure, and the method comprises the following steps:

[0014] S1: the total pressure and static pressure of each zone are measured by the differential pressure measuring instrument of each zone, and the total pressure and static pressure are brought into formula 1 to obtain the flue gas flow rate of each zone.

[0015] V Formula 1

[0016] wherein, P is the total pressure of the zone, V is the static pressure of the zone; V is the flue gas velocity of the zone;

[0017] S2: Substitute the flue gas velocity V obtained in step S1 into Equation 2 to obtain the flue gas volume of each zone.

[0018] Q=SV Equation 2

[0019] Where S is the area of ​​the zone; Q is the flue gas volume of the zone;

[0020] S3: The flue gas volume of each zone obtained in step S2 is used to control the ammonia injection volume adjustment mechanism to allocate the ammonia injection volume of each zone.

[0021] Preferably, the system further includes a correction system, which comprises an inlet NOx prediction system, inlet NOx concentration measurement, outlet NOx concentration measurement, total ammonia injection, total treated flue gas volume, and measured ammonia injection flow rate of the zone branch pipes. The controller performs coupled calculations on the inlet NOx concentration measurement, outlet NOx concentration measurement, ammonia injection weight, total treated flue gas volume, and measured ammonia injection flow rate of the zone branch pipes to obtain a coupled calculated value for the zone ammonia injection volume. Then, the coupled calculated value for the zone ammonia injection volume is converted into control signals for the ammonia injection volume adjustment mechanisms of each zone to correct the zone ammonia injection volume. Finally, the corrected value for the zone branch pipe ammonia injection volume is fed back to the controller for adjustment and control, thereby achieving accurate control of the zone ammonia injection volume.

[0022] Preferably, the inlet NOx prediction system performs mathematical model analysis on the processing flue gas volume, boiler load, air volume ratio, coal volume ratio, coal mill combination, oxygen distribution, and temperature distribution boundary parameters to obtain the predicted inlet NOx concentration.

[0023] Beneficial effects: The differential pressure value measured by the differential pressure measuring instrument is mainly used as the control signal for the ammonia injection branch valves of each zone, which is used to adjust the ammonia injection flow rate of each zone. At the same time, the ammonia injection amount of each zone is corrected by some other parameters. Finally, the ammonia injection valves of each zone are adjusted by the PLC intelligent control system to achieve precise ammonia injection in each zone. Attached Figure Description

[0024] Figure 1 is a schematic diagram of the structure of the present invention;

[0025] Figure 2 A schematic diagram of a differential pressure measuring instrument with multiple gas sampling points;

[0026] The attached diagram lists the components represented by each number as follows:

[0027] 1. Inlet flue; 2. Static mixer; 3. Rectifying grid; 4. Catalyst layer; 5. SCR reactor; 6. Outlet flue; 7. Ammonia injection main pipe; 8. Ammonia injection branch pipe; 9. Controller; 10. Regulating valve; 21. Ammonia injection grid; 31. Differential pressure measuring instrument. Detailed Implementation

[0028] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1

[0030] like Figures 1-2 As shown, this embodiment provides a device for precise ammonia injection zoning and leveling of an SCR system through differential pressure, comprising: an SCR reactor 5, an inlet flue 1 and an outlet flue 6 on the SCR reactor 5, a rectifier grid 3 in the upper part of the SCR reactor 5, multiple zones in the vertically lower part of the rectifier grid 3, multiple ammonia injection grids 21 in the inlet flue 1, the number of ammonia injection grids 21 corresponding one-to-one with the number of zones, a static mixer above the ammonia injection grids 21, a differential pressure measuring instrument 31 installed in each zone, and an ammonia injection flow rate adjustment mechanism for adjusting the ammonia injection flow rate of each zone on the outside of the SCR reactor 5.

[0031] It should be noted that the number of zones and ammonia injection grilles 21 is not limited and depends on the actual zone requirements.

[0032] Preferably, in this embodiment, the ammonia injection quantity regulating mechanism includes an ammonia injection main pipe 7, ammonia injection branch pipes 8, and regulating valves 10. The ammonia injection main pipe 7 is connected to a plurality of ammonia injection branch pipes 8, and the number of the plurality of ammonia injection branch pipes 8 corresponds to the number of the plurality of ammonia injection grids 21. Each of the plurality of ammonia injection branch pipes 8 is provided with the regulating valve 10. The mechanism also includes a controller 9, which is electrically connected to the regulating valves 10. The controller 9 is a PLC control system, which is existing technology and will not be described further.

[0033] Preferably, in this embodiment, the differential pressure measuring instrument 31 is installed above the uppermost catalyst layer 4 and 1.5-2m below the rectifier grid 3.

[0034] Preferably, in this embodiment, the SCR reactor 5 is generally rectangular. When dividing the area, it should be divided equally according to its length and width, meaning each area should have the same length and width. Since each area corresponds to a set of ammonia injection grilles 21-23 and their connected ammonia injection branch pipes 8, identical areas facilitate the modification of the ammonia injection grilles 21 and branch pipes 8, as well as the selection of regulating valves 10. When dividing the area, the area should not be set too large, otherwise it will cause uneven ammonia injection and poor leveling effect. Furthermore, the length-to-width ratio of each area should be ≤3; a large length-to-width ratio, resulting in a flattened area, will also affect the ammonia injection leveling effect.

[0035] like Figure 2 As shown, the differential pressure measuring instrument 31 takes gas samples from multiple points within the zone, such as points A and B. The mixed measurement results after taking gas samples from multiple points are more representative and can better represent the average flow rate of the area.

[0036] Example 2

[0037] A method for precise ammonia injection zoning and leveling of an SCR system via differential pressure, employing the aforementioned device for precise ammonia injection zoning and leveling of an SCR system via differential pressure, includes the following steps:

[0038] S1: The total pressure and static pressure of each zone are measured by the differential pressure measuring instrument 31 of each zone. Substitute these values ​​into Equation 1 to obtain the flue gas velocity of each zone.

[0039] A method for precise ammonia injection zoning and leveling of an SCR system via differential pressure, employing the aforementioned device for precise ammonia injection zoning and leveling of an SCR system via differential pressure, includes the following steps:

[0040] S1: The total pressure and static pressure of each zone are measured by the differential pressure measuring instrument 31 of each zone. Substitute these values ​​into Equation 1 to obtain the flue gas velocity of each zone.

[0041] V Formula 1

[0042] in, Full compression for partitions, V is the static pressure of the zone; V is the flue gas velocity of the zone;

[0043] S2: Substitute the flue gas velocity V obtained in step S1 into Equation 2 to obtain the flue gas volume of each zone.

[0044] Q=SV Equation 2

[0045] Where S is the area of ​​the zone; Q is the flue gas volume of the zone;

[0046] S3: The flue gas volume of each zone obtained through step S2 is used by controller 9 to control the ammonia injection volume adjustment mechanism to allocate the ammonia injection volume of each zone.

[0047] Preferably, the system further includes a correction system, which includes an inlet NOx prediction system, inlet NOx concentration measurement, outlet NOx concentration measurement, total ammonia injection, total treated flue gas volume, and measured ammonia injection flow rate of the zone branch pipes. The controller 9 performs coupled calculations on the inlet NOx concentration measurement, outlet NOx concentration measurement, ammonia injection weight, total treated flue gas volume, and measured ammonia injection flow rate of the zone branch pipes to obtain a coupled calculated value for the zone ammonia injection volume. Then, the coupled calculated value for the zone ammonia injection volume is converted into control signals for the ammonia injection volume adjustment mechanism of each zone to correct the zone ammonia injection volume. Finally, the corrected value for the zone branch pipe ammonia injection volume is fed back to the controller 9 for adjustment and control, thereby achieving accurate control of the zone ammonia injection volume.

[0048] In practical applications, the number of ammonia injection branch pipes 8 corresponds one-to-one with the number of ammonia injection branch pipe regulating valves 10, the number of groups of ammonia injection grids 21, and the number of differential pressure measuring instruments 31. The raw flue gas enters the SCR denitrification system through the inlet flue 1, mixes with the ammonia gas injected from the ammonia injection grid 21, and then is fully mixed by the static mixer 2 and rectified by the rectifier grid 3 before entering the catalyst layer 4 in the SCR reactor 5 for denitrification reaction. Finally, the denitrified flue gas flows out through the outlet flue 6 and enters the air preheater and other subsequent equipment. All control signals of the ammonia injection branch pipe regulating valves 10, data acquisition signals of the differential pressure measuring instruments 31 of each zone, as well as data acquisition signals of inlet NOx concentration, outlet NOx concentration, total ammonia injection, ammonia injection flow rate of each zone branch pipe, and total flue gas volume are connected to the PLC intelligent control system. During the precise ammonia injection zonal leveling of the SCR system, when the differential pressure of the differential pressure measuring instrument 31 changes, the PLC intelligent control system will give an opening adjustment signal for the ammonia injection branch pipe regulating valve 12 to adjust the opening of the ammonia injection branch pipe regulating valve 12, thereby adjusting the ammonia injection quantity of the ammonia injection grille 21. Then, based on the inlet NOx concentration, outlet NOx concentration, total ammonia injection, ammonia injection flow rate of each zone branch pipe, and total flue gas volume, the correction value of the ammonia injection quantity of the zone branch pipe is calculated. The correction value is then fed forward to the PLC control system to fine-tune the ammonia injection quantity of the ammonia injection grille 21, and finally complete the zonal leveling to achieve precise ammonia injection.

[0049] In the description of this invention, it should be understood that the terms "center," "length," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "inner," "outer," "circumferential," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the system or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0051] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0052] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for precise ammonia injection zoning and leveling of an SCR system via differential pressure, characterized in that, include: The SCR reactor (5) is provided with an inlet flue (1) and an outlet flue (6). A rectifier grid (3) is provided in the upper part of the SCR reactor (5). Multiple zones are provided vertically below the rectifier grid (3). Multiple ammonia injection grids (21) are provided in the inlet flue (1). The number of ammonia injection grids (21) corresponds one-to-one with the number of zones. A differential pressure measuring instrument (31) is installed in each zone. An ammonia injection flow rate regulating mechanism is also provided outside the SCR reactor (5) for adjusting the ammonia injection flow rate in each zone. The ammonia injection flow rate regulating mechanism includes a main ammonia injection pipe (7), a branch ammonia injection pipe (8), and a regulating valve (10). The main ammonia injection pipe (7) is... The reactor (5) is connected to multiple ammonia injection branch pipes (8), the number of which corresponds to the number of multiple ammonia injection grids (21), and each of the multiple ammonia injection branch pipes (8) is equipped with a regulating valve (10); it also includes a controller (9), which is electrically connected to the regulating valve (10); the SCR reactor (5) is provided with multiple catalyst layers (4) arranged from top to bottom inside, and the partition is provided above the uppermost catalyst layer (4); the controller (9) is connected to the differential pressure measuring instrument (31), and the controller (9) uses the differential pressure value measured by the differential pressure measuring instrument (31) as the control signal of the regulating valve (10) of each partition to adjust the ammonia injection flow rate of each partition.

2. The device for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 1, characterized in that, The differential pressure measuring instrument (31) is installed above the uppermost catalyst layer (4) and 1.5-2m below the rectifier grid (3).

3. The device for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 2, characterized in that, The partitions are horizontal partitions, and each partition has the same length and width dimensions.

4. The device for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 3, characterized in that, The aspect ratio of each partition is ≤3.

5. A method for precise ammonia injection zoning and leveling of an SCR system via differential pressure, comprising the device for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 4, characterized in that... Includes the following steps: S1: The total pressure and static pressure of each zone are measured by the differential pressure measuring instrument (31) of each zone. Substitute them into Equation 1 to obtain the flue gas velocity of each zone. V Formula 1 in, Full compression for partitions, V is the static pressure of the zone; V is the flue gas velocity of the zone; S2: Substitute the flue gas velocity V obtained in step S1 into Equation 2 to obtain the flue gas volume of each zone. Q=SV Equation 2 Where S is the area of ​​the zone; Q is the flue gas volume of the zone; S3: The amount of flue gas obtained in each zone through step S2 is used to control the ammonia injection amount adjustment mechanism to allocate the amount of ammonia injection to each zone using the controller (9).

6. The method for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 5, characterized in that, It also includes a correction system, which includes an inlet NOx prediction system, an inlet NOx concentration measurement value, an outlet NOx concentration measurement value, a total ammonia injection, a total amount of treated flue gas, and a measured value of ammonia injection flow rate in the zone branch pipe. The controller (9) performs coupled calculations on the inlet NOx concentration measurement value, the outlet NOx concentration measurement value, the ammonia injection weight, the total amount of treated flue gas, and the measured value of ammonia injection flow rate in the zone branch pipe to obtain the coupled calculation value of ammonia injection in the zone. Then, the coupled calculation value of ammonia injection in the zone is converted into a control signal of the ammonia injection adjustment mechanism of each zone to correct the ammonia injection in the zone. Finally, the ammonia injection correction value of the zone branch pipe is fed back to the controller (9) for adjustment and control, thereby realizing accurate control of the ammonia injection in the zone.

7. The method for precise ammonia injection zoning and leveling of an SCR system via differential pressure as described in claim 6, characterized in that, The inlet NOx prediction system uses mathematical models to analyze the boundary parameters of flue gas volume, boiler load, air volume ratio, coal volume ratio, coal mill combination, oxygen distribution, and temperature distribution to obtain the predicted inlet NOx concentration.

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