SCR (Selective Catalytic Reduction) denitration system for bypass sampling and uniform ammonia spraying of thermal power plant

Abstract

The utility model provides an SCR denitration system for bypass sampling and uniform ammonia spraying of a thermal power plant, the SCR denitration system comprises an SCR control system and an electrical control cabinet, the SCR control system comprises 9 subareas, each subarea comprises 9 DN100 sampling branch pipes and 9 electric control valves, the upper ends of the 9 DN100 sampling branch pipes converge to a DN150 sampling mother pipe, branch pipe valves are arranged between the DN100 sampling branch pipes and the DN150 sampling mother pipe, and the electric control valves are connected with the DN150 sampling mother pipe. The output end of the DN150 sampling main pipe is provided with a CEMS sampling probe, the outer end of the DN150 sampling main pipe is provided with a purging pipeline and a purging valve, the outer end of each electric control valve is provided with an ammonia spraying control valve and an ammonia spraying pipeline, and the nine DN100 sampling branch pipes and the DN150 sampling main pipe converge and are uniformly mixed and then reach the CEMS sampling probe for measurement. According to the invention, the problem that the ammonia spraying efficiency and uniformity cannot be automatically controlled in the design of CEMS sampling of a thermal power plant is solved.

Description

Technical Field

[0001] This utility model relates to the field of CEMS sampling technology in thermal power plants, and more specifically, to an SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants. Background Technology

[0002] In selective catalytic reduction (SCR) denitrification systems in thermal power plants, ammonia injection optimization and bypass sampling are crucial for ensuring denitrification efficiency and reducing ammonia slip. Ammonia injection optimization involves adjusting the injection rate and distribution to achieve efficient reaction between ammonia and nitrogen oxides (NOx), while bypass sampling refers to setting up bypass pipelines in the SCR denitrification system to collect flue gas samples for analysis and monitoring.

[0003] The purpose of ammonia injection optimization is to improve the mixing uniformity of ammonia and NOx within the SCR reactor, reduce ammonia slip, and increase denitrification efficiency. Optimization measures include adjusting the ammonia injection branch pipe valves, using CFD flow field simulation software, and installing zone leveling valves. For example, a power plant improved the uniformity of NOx and ammonia mixing and eliminated NOx concentration deviations by increasing the ammonia injection rate and optimizing the ammonia injection branch pipe valves. Furthermore, patented technologies provide a precise ammonia injection device and method for denitrification SCR reactors in thermal power plants, achieving accurate control and monitoring of the ammonia injection rate through the use of zone leveling valves and ammonia flow meters.

[0004] The design of a bypass sampling system helps improve the representativeness and accuracy of flue gas sampling. By installing a bypass pipe at the SCR reactor outlet, flue gas samples can be collected without affecting the operation of the main flue. This design can reduce potential problems in flue gas cooling and dehydration steps, such as ammonium salt blockage, and allows for faster and more accurate measurements of NOx and ammonia slip.

[0005] When implementing ammonia injection optimization and bypass sampling, it is necessary to consider the characteristics of the flue gas flow field, the activity and distribution of the catalyst, and the overall design of the SCR system. By comprehensively utilizing modern sensor technology, control systems, and fluid dynamics simulation tools, efficient operation of the SCR denitrification system and strict control of pollutant emissions can be achieved.

[0006] SCR, or Selective Catalytic Reduction, has seen rapid development in recent years and is widely used in Western Europe and Japan. Currently, ammonia catalytic reduction is the most widely applied technology. It has advantages such as no byproducts, no secondary pollution, simple device structure, high removal efficiency (over 90%), reliable operation, and easy maintenance. CEMS systems use a basic sampling bypass. Currently, two common methods are used: one involves three branch pipes converging to a main pipe, with three main pipes on each side, and then sampling via probes installed on the main pipes. This method requires three probes and three CEMS meters per side per unit, totaling six probes and six CEMS meters per unit; the other method involves sampling with three probes on each side, mixing the samples in a mixing bottle within the CEMS cabinet, and then measuring with a single meter. The former requires more CEMS systems, resulting in higher investment and maintenance costs, and this method may not necessarily obtain sample gases with stable pressure, sensitive reflection of true component changes, or representative analytical samples. While the latter method reduces the number of CEMS systems by two and lowers costs significantly, it is still difficult to measure the correct flue gas composition, and in practice, it usually only involves one sampling probe.

[0007] In existing technologies, the uniformity of ammonia injection by SCR cannot be improved during the use of CEMS sampling in thermal power plants, and most of the maintenance work of CEMS systems is probe maintenance, which cannot reduce the maintenance workload. Therefore, we have made improvements and proposed an SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants. Utility Model Content

[0008] The purpose of this invention is to address the current design of CEMS sampling in thermal power plants, which cannot improve the uniformity of SCR ammonia injection, and the fact that most CEMS system maintenance work involves probe maintenance, which does not reduce the workload.

[0009] To achieve the above-mentioned objectives, this utility model provides the following technical solution:

[0010] An SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants is proposed to improve the aforementioned problems.

[0011] The application is as follows:

[0012] An SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants includes an SCR control system and an electrical control cabinet. The SCR control system includes nine zones, each zone including nine DN100 sampling branches and nine electric regulating valves. The upper ends of the nine DN100 sampling branches converge to a DN150 sampling main pipe. Branch valves are provided between the DN100 sampling branches and the DN150 sampling main pipe. A CEMS sampling probe is provided at the output end of the DN150 sampling main pipe. A purge pipeline and a purge valve are provided at the outer end of the DN150 sampling main pipe. An ammonia injection regulating valve and an ammonia injection pipeline are provided at the outer end of each electric regulating valve.

[0013] As a preferred technical solution of this application, the nine DN100 sampling branch pipes and the DN150 sampling main pipe are mixed evenly before being fed to the CEMS sampling probe for measurement.

[0014] As a preferred technical solution of this application, the flow velocity in the opening distribution area of ​​the nine electric regulating valves is determined manually.

[0015] As a preferred technical solution of this application, the purging time and cycle of the purging pipeline and purging valve are set by the SCR control system.

[0016] A method for measuring ammonia injection in an SCR denitrification system used for bypass sampling and uniform ammonia injection in thermal power plants:

[0017] S1. Withdraw the automatic ammonia injection system and close the 9 electric regulating valves;

[0018] S2. Open the DN150 sampling header and purge for 30 seconds;

[0019] S3. Open all 9 electric regulating valves in sequence until they are fully open;

[0020] S4. Wait for the data changes from the CEMS sampling probe. The O2 of the CEMS sampling probe will rise and then fall until the data stabilizes. Then you can know the NOx situation of the partition.

[0021] S5. Adjust the valve size of the ammonia injection regulating valve corresponding to the zone, and make step-by-step switching adjustments according to the NOx situation of the zone and the total NOx situation.

[0022] As a preferred technical solution of this application, in step S5, the DN100 sampling branch pipe of the partition has the same diameter as the DN150 sampling main pipe.

[0023] As a preferred technical solution of this application, in step S5, the DN100 sampling branch pipe and the DN150 sampling main pipe of the partition are installed vertically.

[0024] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0025] In the scheme of this application:

[0026] 1. When dust blockage occurs in the pipeline, it can be purged automatically by adjusting the purging pipeline and purging valve. The purging time and cycle are adjustable.

[0027] 2. The added ammonia injection regulating valve can adjust the ammonia injection amount to achieve uniform ammonia injection;

[0028] 3. The DN100 sampling branch pipe is arranged vertically to reduce the chance of dust blockage inside the DN100 sampling branch pipe and reduce the sampling failure rate.

[0029] 4. The reasonable length of the DN150 sampling header and the reasonable installation position of the CEMS sampling probe ensure stable sampling pressure, sensitive reflection of changes in the true composition, and acquisition of the location of representative analytical samples. Attached Figure Description

[0030] Figure 1 This application provides a schematic diagram of an SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants.

[0031] The image shows:

[0032] 1. Electric regulating valve; 3. DN100 sampling branch pipe; 4. Branch pipe valve; 5. DN150 sampling main pipe; 6. Purge pipeline; 7. Purge valve; 8. Ammonia injection regulating valve; 9. Ammonia injection pipeline; 10. CEMS sampling probe. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model.

[0034] Therefore, the following detailed description of the embodiments of this utility model is not intended to limit the scope of the claimed utility model, but merely illustrates some embodiments of the utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without inventive effort are within the scope of protection of this utility model. It should be noted that, unless otherwise specified, the embodiments, features, and technical solutions in the embodiments of this utility model can be combined with each other.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] like Figure 1As shown, this embodiment proposes an SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants, including an SCR control system and an electrical control cabinet. The SCR control system includes 9 zones, each zone including 9 DN100 sampling branch pipes 3 and 9 electric regulating valves 1. The upper ends of the 9 DN100 sampling branch pipes 3 are connected to a DN150 sampling main pipe 5. A branch pipe valve 4 is provided between the DN100 sampling branch pipes 3 and the DN150 sampling main pipe 5. A CEMS sampling probe 10 is provided at the output end of the DN150 sampling main pipe 5. A purge pipeline 6 and a purge valve 7 are provided at the outer end of the DN150 sampling main pipe 5. An ammonia injection regulating valve 8 and an ammonia injection pipeline 9 are provided at the outer end of each electric regulating valve 1.

[0037] Nine DN100 sampling branch pipes 3 and DN150 sampling main pipe 5 are combined and mixed evenly before being fed into the CEMS sampling probe 10 for measurement.

[0038] Nine electrically operated regulating valves are used to manually determine the flow velocity in the distribution area of ​​the opening.

[0039] The purging time and cycle of the purging pipeline 6 and purging valve 7 are set by the SCR control system.

[0040] The components of this utility model can adopt the following hardware:

[0041] The control system samples a Siemens S7200 PLC or is directly connected to the host DCS system.

[0042] Branch valves 4FF1~FF9, 220VAC, butterfly valves, with 4-20mA position feedback.

[0043] Ammonia injection regulating valve 8 (AF).

[0044] Purge line 6 (CG).

[0045] Purge electric valves FC0~FC9.

[0046] CEMS sampling probe 10 (T) is installed at 5 locations on the DN150 sampling header after the flue gas is fully mixed.

[0047] A method for measuring ammonia injection in an SCR denitrification system used for bypass sampling and uniform ammonia injection in thermal power plants:

[0048] S1. Withdraw the automatic ammonia injection system and close the 9 electric regulating valves 1;

[0049] S2. Open the DN150 sampling header tube 5 and purge for 30 seconds;

[0050] S3. Open the 9 electric regulating valves 1 to full opening in sequence;

[0051] S4. Wait for the data change of CEMS sampling probe 10. The O2 of CEMS sampling probe 10 will rise and then drop until the data stabilizes. Then you can know the NOx situation of the partition.

[0052] S5. The valve size of the ammonia injection regulating valve 8 corresponding to the zone is adjusted by step-by-step switching according to the NOx situation of the zone and the total NOx situation.

[0053] In step S5, the DN100 sampling branch pipe 3 and the DN150 sampling main pipe 5 of the partition have the same pipe diameter.

[0054] In step S5, the DN100 sampling branch pipe 3 and the DN150 sampling main pipe 5 of the partition are installed vertically.

[0055] The CEMS sampling probe 10 should not be positioned too far forward, as this will result in uneven mixing; if it is positioned too far back, the time required for step S4 will be very long.

[0056] During normal operation, each of the nine electric regulating valves 1 has an opening of 30% to 40%, and the flue gas is mixed and then supplied to the CEMS sampling probe 10 for sampling.

[0057] When this application is in use: when ash blockage occurs in the bypass, it can be purged automatically through the purging pipeline 6 and purging valve 7, and the purging time and cycle can be adjusted; the added ammonia injection regulating valve 8 can adjust the ammonia injection amount to achieve uniform ammonia injection; the DN100 sampling branch pipe 3 is arranged vertically to reduce the probability of ash blockage inside the DN100 sampling branch pipe 3 and reduce the sampling failure rate; the reasonable length of the DN150 sampling main pipe 5 and the reasonable installation position of the CEMS sampling probe 10 ensure stable sampling pressure, can sensitively reflect changes in the true composition, and obtain the location of representative analytical samples;

[0058] This application significantly reduces the maintenance workload and investment cost of the CEMS system. By utilizing the CEMS equipment used in the denitrification process control, the uniformity of SCR ammonia injection is improved without adding CEMS equipment.

[0059] The above embodiments are only used to illustrate the present utility model and are not intended to limit the technical solutions described in the present utility model. Although the present utility model has been described in detail with reference to the above embodiments, the present utility model is not limited to the specific embodiments described above. Therefore, any modifications or equivalent substitutions to the present utility model, and all technical solutions and improvements that do not depart from the spirit and scope of the utility model, are covered within the scope of the claims of the present utility model.

Claims

1. An SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants, comprising an SCR control system and an electrical control cabinet, characterized in that, The SCR control system includes 9 zones, each zone including 9 DN100 sampling branch pipes (3) and 9 electric regulating valves (1). The upper ends of the 9 DN100 sampling branch pipes (3) are connected to a DN150 sampling main pipe (5). A branch pipe valve (4) is provided between the DN100 sampling branch pipes (3) and the DN150 sampling main pipe (5). The output end of the DN150 sampling main pipe (5) is provided with a CEMS sampling probe (10). The outer end of the DN150 sampling main pipe (5) is provided with a purge pipeline (6) and a purge valve (7). The outer end of each electric regulating valve (1) is provided with an ammonia injection regulating valve (8) and an ammonia injection pipeline (9).

2. The SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants according to claim 1, characterized in that, After the nine DN100 sampling branch pipes (3) and the DN150 sampling main pipe (5) are mixed evenly, the mixture is then sent to the CEMS sampling probe (10) for measurement.

3. The SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants according to claim 2, characterized in that, The flow velocity in the opening distribution area of ​​the nine electric regulating valves (1) is determined manually.

4. The SCR denitrification system for bypass sampling and uniform ammonia injection in thermal power plants according to claim 3, characterized in that, The purging time and cycle of the purging pipeline (6) and purging valve (7) are set by the SCR control system.

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