Ammonia injection partition control device for denitration system

Abstract

The utility model relates to denitration ammonia spraying control device technical field, is a kind of denitration system ammonia spraying zoning control device, it includes ammonia spraying main pipe, the inlet side of ammonia spraying main pipe is connected with the mixer for ammonia gas and air mixing, along the flow direction of fluid, at least two partition pipes are fixedly connected on the ammonia spraying main pipe of mixer outlet side, partition pipe is mutually parallel, each partition pipe is fixedly connected with ammonia spraying grid by ammonia spraying branch pipe, each partition pipe is connected with switch valve and regulating valve in series. The utility model is by designing multiple partition pipes, thereby the ammonia spraying amount of each group of ammonia spraying grid is separately controlled, the actual demand of ammonia injection and denitration each region is matched, the purpose of regional ammonia spraying control is achieved. The device adopts dynamic adjustable ammonia spraying grid to adapt to flow field change, carries out regional automatic ammonia spraying control, to cope with different boiler load, flow field, coal mill operation combination mode NOx concentration field change situation.

Description

Technical Field

[0001] This utility model relates to the technical field of ammonia injection control devices for denitrification systems, and is a zoned control device for ammonia injection in a denitrification system. Background Technology

[0002] The uniformity of ammonia nitrogen distribution in flue gas is considered an important indicator for evaluating the performance of SCR denitrification. As part of the SCR denitrification system structure, the ammonia injection grid promotes thorough mixing of ammonia and flue gas before they enter the SCR reactor (i.e., the denitrification reactor). An improperly designed ammonia injection device will directly cause uneven ammonia-nitrogen mixing, thus affecting the reaction entering the catalyst bed. Only when the flue gas and ammonia have good mixing uniformity can the catalyst bed achieve optimal catalytic reaction and nitrogen removal efficiency.

[0003] In existing denitrification systems, due to variations in the size and direction (or angle) of the flue gas duct from the economizer outlet to the SCR reactor inlet, the NOx concentration field distribution at the SCR reactor inlet is uneven at any given time. This unevenness is particularly pronounced when the boiler load changes or the coal mill operating configuration changes. Because of this uneven NOx concentration distribution at the SCR reactor inlet, when using a single main control valve to control the ammonia injection rate, the constant ammonia concentration and the changing nitrogen concentration create a significant contradiction. This leads to frequent fluctuations in the ammonia-nitrogen molar ratio, inevitably resulting in excessive ammonia injection in areas with low NOx concentrations. This causes significant local ammonia escape, leading to air preheater blockage, increased resistance in the tail flue gas duct, and ultimately, reduced boiler efficiency. Summary of the Invention

[0004] This invention provides a zoned ammonia injection control device for a denitrification system, which overcomes the shortcomings of the prior art. By controlling the ammonia injection amount in zones, it effectively reduces excessive ammonia injection and lowers the ammonia escape rate, thereby enabling it to cope with the variable NOx concentration field under different boiler loads, flow fields, and coal mill operation combinations.

[0005] The technical solution of this utility model is achieved through the following measures: a denitrification system ammonia injection zone control device, including an ammonia injection main pipe, a mixer for mixing ammonia and air connected to the inlet side of the ammonia injection main pipe, at least two zone pipes fixedly connected to the ammonia injection main pipe at the outlet side of the mixer along the flow direction of the fluid, the zone pipes are connected in parallel to each other, each zone pipe is fixedly connected to an ammonia injection grid through an ammonia injection branch pipe, each zone pipe is connected in series with a switch valve and a regulating valve, and each ammonia injection branch pipe is connected in series with a switch valve.

[0006] The following are further optimizations and / or improvements to the above-mentioned utility model technical solution: The aforementioned ammonia injection main pipe is connected to four partition pipes.

[0007] The aforementioned regulating valve is an electrically operated regulating valve.

[0008] The aforementioned ammonia injection zone control device for the denitrification system also includes a controller, which is electrically connected to each electric regulating valve.

[0009] The controller described above is a PLC controller.

[0010] The ammonia injection pipe wall of the aforementioned ammonia injection grid has ammonia injection holes distributed on it.

[0011] This invention utilizes a multi-zoned pipe design to separately control the ammonia injection volume of each group of ammonia injection grids, ensuring that the injected ammonia matches the actual needs of each denitrification zone, thus achieving the goal of zoned ammonia injection control. This device implements zoned ammonia injection control for the ammonia injection grids, dividing the original single-sided ammonia injection grids into multiple automatically adjustable ammonia injection zones. It employs dynamically adjustable ammonia injection grids to adapt to changes in the flow field, enabling zoned automatic ammonia injection control to cope with varying NOx concentration fields under different boiler loads, flow fields, and coal mill operating combinations. Attached Figure Description

[0012] Appendix Figure 1 This is a schematic diagram of the process flow of this utility model.

[0013] The codes in the attached diagram are as follows: 1 is the main ammonia injection pipe, 2 is the zone pipe, 3 is the branch ammonia injection pipe, 4 is the ammonia injection grid, 5 is the on / off valve, 6 is the regulating valve, and 7 is the ammonia injection orifice. Detailed Implementation

[0014] This utility model is not limited to the following embodiments, and the specific implementation method can be determined according to the technical solution of this utility model and the actual situation.

[0015] Unless otherwise specified, all techniques or instruments used in this invention are conventional technologies or instruments used in existing SCR denitrification processes, such as obtaining the NOx concentration in the flue gas at the inlet of the SCR reactor and the conversion relationship between the NOx concentration and the ammonia injection rate.

[0016] In this utility model, for ease of description, the description of the relative positional relationships of the components is based on the appendix to the specification. Figure 1 The layout is described using a diagrammatic method, such as the positional relationships of front, back, top, bottom, left, and right, which are based on the instructions attached. Figure 1 The orientation of the layout is determined by the direction of the map.

[0017] The present invention will be further described below with reference to the embodiments and accompanying drawings: Example 1: As shown in the attached document Figure 1As shown, the ammonia injection zone control device of the denitrification system includes an ammonia injection main pipe 1. The inlet side of the ammonia injection main pipe 1 is connected to a mixer for mixing ammonia and air. Along the flow direction of the fluid, at least two zone pipes 2 are fixedly connected to the ammonia injection main pipe 1 at the outlet side of the mixer. The zone pipes 2 are connected in parallel to each other. Each zone pipe 2 is fixedly connected to an ammonia injection grid 4 through an ammonia injection branch pipe 3. Each zone pipe 2 is connected in series with a switch valve 5 and a regulating valve 6. Each ammonia injection branch pipe 3 is connected in series with a switch valve 5.

[0018] This device employs multiple zoned pipes 2 to separately control the ammonia injection rate of each group of ammonia injection grids 4, ensuring that the injected ammonia matches the actual needs of each denitrification zone, thus achieving the goal of zoned ammonia injection control. This device implements zoned ammonia injection control for the ammonia injection grids 4, dividing the original single-sided ammonia injection grids 4 into multiple automatically adjustable ammonia injection zones. The dynamically adjustable ammonia injection grids 4 adapt to changes in the flow field, enabling zoned automatic ammonia injection control to cope with varying NOx concentration fields under different boiler loads, flow fields, and coal mill operating combinations.

[0019] The ammonia injection zone control device of the above-mentioned denitrification system can be further optimized and / or improved according to actual needs: Example 2: As an optimization of the above examples, as shown in the appendix Figure 1 As shown, four partition pipes 2 are connected to the ammonia injection main pipe 1.

[0020] The four partition pipes 2 can correspond to four sets of ammonia injection grilles 4, which can control the amount of ammonia injected into the denitrification zone in four areas. This can match the injected ammonia with the actual needs of each denitrification zone. For areas with relatively low nitrogen oxide concentrations, the amount of ammonia injected in that area can be reduced to avoid excessive ammonia injection and large local ammonia escape. This effectively prevents the air preheater blockage in the denitrification system from causing increased resistance in the tail flue, and ultimately improves boiler efficiency.

[0021] The number of partition pipes 2 can be flexibly adjusted according to production needs, such as eight or ten pipes, thereby matching the number of ammonia injection grids 4 to the corresponding number of connections.

[0022] Example 3: As an optimization of the above embodiment, the regulating valve 6 may be an electric regulating valve as needed.

[0023] Example 4: As an optimization of the above embodiments, as shown in the appendix Figure 1 As shown, the ammonia injection zone control device of the denitrification system also includes a controller, which is electrically connected to each electric regulating valve.

[0024] The controller can be an existing, commonly known PLC controller or DCS controller.

[0025] The PLC controller can also be an existing PLC controller for the SCR denitrification process. In this way, the signal terminal of the electric regulating valve can be connected to the PLC controller to realize the control of the electric regulating valve.

[0026] The controller controls the electric regulating valve, thereby controlling the ammonia injection rate of the corresponding zone pipe. For example, as... Figure 1 As shown, when the leftmost ammonia injection grid 4 corresponds to a region with relatively low nitrogen oxide concentration, the opening of the electric regulating valve on the partition pipe 2 corresponding to the leftmost ammonia injection grid 4 is controlled by the PLC controller or DCS controller to reduce the amount of ammonia injected and prevent excessive ammonia injection.

[0027] Example 5: As an optimization of the above embodiments, as shown in the appendix. Figure 1 As shown, according to the conventional setup, ammonia injection holes 7 are distributed on the wall of the ammonia injection pipe of the ammonia injection grid 4.

[0028] This device forms a three-level regulation system from the physical level, consisting of a main ammonia injection valve, six ammonia injection zone regulating valves, and four ammonia injection grid branch pipes (i.e., ammonia injection branch pipes 3). It can achieve precise and appropriate ammonia injection in multiple zones, improve the full-load adaptability of the ammonia injection system, effectively reduce excessive ammonia injection, lower the ammonia escape rate, and realize precise ammonia injection control for SCR denitrification.

[0029] The above technical features constitute various embodiments of this utility model, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0030] The usage process of this utility model is as follows: After ammonia gas is mixed and diluted with air to the designed concentration in the mixer, it is delivered to the ammonia injection main pipe 1. The main valve of the ammonia injection main pipe 1 is opened (this valve... Figure 1 (Not displayed) Open the various switch valves 5 of the partition pipe 2 and the ammonia injection branch pipe 3. According to the nitrogen oxide concentration requirements of the corresponding area of ​​each group of ammonia injection grids 4, control the opening of the electric regulating valve, thereby controlling the amount of ammonia injected. The ammonia injected through the ammonia injection holes 7 of the ammonia injection grid 4 reacts with the nitrogen oxides in the flue gas. The reaction converts the nitrogen oxides into water and nitrogen, and the flue gas is purified.

Claims

1. A zoned ammonia injection control device for a denitrification system, characterized in that... It includes an ammonia injection main pipe, the inlet side of which is connected to a mixer for mixing ammonia and air. Along the flow direction of the fluid, at least two partition pipes are fixedly connected to the ammonia injection main pipe at the outlet side of the mixer. The partition pipes are connected in parallel to each other. Each partition pipe is fixedly connected to an ammonia injection grid through an ammonia injection branch pipe. Each partition pipe is connected in series with a switch valve and a regulating valve. Each ammonia injection branch pipe is connected in series with a switch valve.

2. The ammonia injection zone control device for the denitrification system according to claim 1, characterized in that... The main ammonia injection pipe is connected to four partition pipes.

3. The ammonia injection zone control device for the denitrification system according to claim 1 or 2, characterized in that... The regulating valve is an electrically operated regulating valve.

4. The ammonia injection zone control device for the denitrification system according to claim 3, characterized in that... It also includes a controller, which is electrically connected to each of the electric regulating valves.

5. The ammonia injection zone control device for the denitrification system according to claim 4, characterized in that... The controller is a PLC controller.

6. The ammonia injection zone control device for the denitrification system according to claim 1 or 2, characterized in that... The ammonia injection grid has ammonia injection holes distributed on the pipe wall of the ammonia injection pipe.

7. The ammonia injection zone control device for the denitrification system according to claim 3, characterized in that... The ammonia injection grid has ammonia injection holes distributed on the pipe wall of the ammonia injection pipe.

8. The ammonia injection zone control device for the denitrification system according to claim 4, characterized in that... The ammonia injection grid has ammonia injection holes distributed on the pipe wall of the ammonia injection pipe.

9. The ammonia injection zone control device for the denitrification system according to claim 5, characterized in that... The ammonia injection grid has ammonia injection holes distributed on the pipe wall of the ammonia injection pipe.

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