SCR (Selective Catalytic Reduction) outlet flue sampling device

Abstract

An SCR outlet flue sampling device comprises a sampling mother pipe, the sampling mother pipe comprises a first mother pipe section and a second mother pipe section, the tail end of the first mother pipe section extends into a dust remover inlet flue, the head end of the first mother pipe section is communicated with the tail end of the second mother pipe section, the second mother pipe section is of a variable cross-section structure, and the cross section from the head end to the tail end of the second mother pipe section is enlarged; the upper parts of a plurality of sampling straight pipes are communicated with the second mother pipe section, and the lower parts of the sampling straight pipes extend into an inlet flue of the air pre-heater for sampling; the air cannon is communicated with the head end of the second mother pipe section; and the CEMS sampler is connected with one section of the main pipe. The second section of the main pipe adopts a variable cross-section structure, and the section of the part closer to the CEMS sampler is larger, so that the flow rate of flue gas of the whole main pipe under most operation conditions can be effectively ensured, and the sampling main pipe is prevented from being blocked due to low flow rate.

Description

Technical Field

[0001] The utility model relates to the technical field of flue gas treatment, in particular to an SCR outlet flue sampling device. Background Art

[0002] SCR denitrification technology is the most common and efficient denitrification technology for pulverized coal boilers. It has been widely used in thermal power, chemical industry, heating energy and other fields in China. As users have higher and higher control requirements for production indicators, SCR precision control technology has become the mainstream technology in the market, and precision control technology has higher and higher requirements for the accuracy and representativeness of SCR outlet NOx measurement values. The current boiler SCR denitrification technology causes uneven SCR outlet NOx due to uneven flow field, ammonia injection amount, and initial NOx in flue gas, making the measurement results of traditional single-point measurement methods distorted and unrepresentative, and there is a large difference with the desulfurization outlet NOx, making it difficult to accurately control the SCR system.

[0003] Chinese patent document CN211927423U discloses a flue gas sampling device for a SCR denitrification self-injection multi-point sampling system. By using the differential pressure between the denitrification flue and the electrostatic precipitator inlet flue, the flue gas will be collected into the flue gas main pipe (or sampling main pipe) through each sampling branch pipe and the short connecting pipe in turn, and mixed in the flue gas main pipe to achieve self-injection multi-point sampling, improve the representativeness of the sampling point, and shorten the measurement lag time. However, in actual production, since the flue gas main pipe has a certain length and the sampling branches are arranged at a certain distance on the flue gas main pipe, the flue gas flow collected in the flue gas main pipe sections at different distances from the SCR-CEMS instrument is different, resulting in different flue gas flow rates in the flue gas main pipe. For example, in the flue gas main pipe section close to the SCR-CEMS instrument, the flue gas volume is the flue gas collected by multiple sampling branch pipes, where the gas volume is large and the flow rate is fast, so it is not easy to accumulate dust in this section of the flue gas main pipe; while the flue gas main pipe section far from the SCR-CEMS instrument may only be collected by a straight pipe, where the gas volume is small and the flow rate is slow, so it is easy to accumulate dust in this section of the flue gas main pipe. In order to avoid dust accumulation, the above patent document is equipped with a branch pipe purge nozzle at each branch pipe, and is equipped with a branch pipe purge air cannon and a main pipe purge air cannon. However, since the main pipe section is prone to dust accumulation due to different flue gas flow rates, the solution of the above patent document must often open the straight pipe purge and the main pipe purge for dust removal. Therefore, these settings greatly increase the complexity of the sampling device and increase the cost of use. Utility Model Content

[0004] The embodiment of the present application provides an SCR outlet flue sampling device, which is provided with a flue gas main pipe with a variable cross-section structure, which can ensure the stability of the flue gas flow rate in the entire main pipe, reduce the probability of ash accumulation in the flue gas main pipe, and adopt the following technical solution: An SCR outlet flue sampling device, comprising:

[0005] A sampling mother pipe, the sampling mother pipe comprises a mother pipe section 1 and a mother pipe section 2, the end of the mother pipe section 1 extends into the dust collector inlet flue, the head end of the mother pipe section 1 is connected to the end of the mother pipe section 2, the mother pipe section 2 is a variable cross-section structure, and the cross-section increases from the head end to the end;

[0006] Sampling branch pipes, the upper parts of several sampling straight pipes are connected with the second section of the main pipe, and the lower parts extend into the air preheater inlet flue for sampling;

[0007] An air cannon, the air cannon being connected to the head end of the second section of the mother pipe; and

[0008] A CEMS sampler is connected to a section of the mother pipe.

[0009] Furthermore, the second section of the mother pipe includes multiple pipe sections with different cross-sections, and different pipe sections are connected with large and small heads.

[0010] Furthermore, the first section of the mother pipe is perpendicular to the horizontal plane, and the second section of the mother pipe forms an angle of 0° to 75° with the horizontal plane.

[0011] Furthermore, a plurality of sampling holes are opened on the side wall of the sampling branch pipe.

[0012] Furthermore, the opening areas of the sampling holes distributed from top to bottom on the sampling branch pipe become larger.

[0013] Furthermore, a disturbance ball is provided in the sampling branch pipe, and the disturbance ball is suspended in the sampling branch pipe through a chain.

[0014] Furthermore, the upper end of the sampling branch tube is sealed with an openable flange cover.

[0015] Furthermore, a flushing valve is also provided at the head end of the second section of the mother pipe.

[0016] Furthermore, a ash discharge pipe is connected to the middle of the sampling main pipe, and an ash discharge valve is arranged on the ash discharge pipe.

[0017] Furthermore, an isolation valve is provided on the first section of the mother pipe, and a pulse valve is provided on the second section of the mother pipe.

[0018] Beneficial effects of the present application: 1. In the embodiment of the present application, the second section of the mother pipe adopts a variable cross-section structure, and the cross-section of the part closer to the CEMS sampler is larger, which can effectively ensure that the flue gas flow velocity of the entire mother pipe is higher than 15m / s under most operating conditions, and the mother pipe will not be blocked by ash due to low flow velocity;

[0019] 2. In the embodiment of the present application, a disturbance ball suspended by a chain is provided in the sampling branch pipe, which can make the disturbance ball shake under the action of flue gas, thereby driving the chain to stir and clean the sampling branch pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present application;

[0021] Figure 2 for Figure 1 A partial enlarged view of the middle part;

[0022] Figure 3 for Figure 1 A partial enlarged view of point B in the middle;

[0023] Figure 4 for Figure 1 A partial enlarged view of point C in the middle;

[0024] Figure 5 This is a schematic diagram of the sampling branch pipe structure in the embodiment of the present application;

[0025] Figure 6 This is a schematic diagram of the self-disturbance ball and chain structure in the embodiment of the present application;

[0026] In the figure: 1 sampling branch pipe, 2 sampling main pipe, 3 reducer and reducer, 4 flange cover, 5 ash discharge valve, 6 CEMS sampler, 7 disturbance ball, 8 air cannon, 9 pulse valve, 10 air preheater inlet flue, 11 dust collector inlet flue, 12 ash discharge pipe, 13 manual valve, 14 flushing valve, 15 isolation valve, 16 thermocouple, 17 temperature patrol meter, 18 DCS control system, 19 chain, 20 sampling hole. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0028] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0029] Reference Figure 1 The present application provides an SCR outlet flue sampling device, comprising:

[0030] The sampling mother pipe 2 includes a mother pipe section 1 and a mother pipe section 2. The end of the mother pipe section 1 is connected to the dust collector inlet flue 11, and the head end of the mother pipe section 1 is connected to the end of the mother pipe section 2. The mother pipe section 2 is a variable cross-section structure, and the cross-section increases from the head end to the end end;

[0031] The upper parts of the sampling branch pipe 1 and the plurality of sampling straight pipes are connected to the second section of the main pipe, and the lower parts extend into the air preheater inlet flue 10 for sampling;

[0032] An air cannon 8, wherein the air cannon 8 is connected to the head end of the second section of the mother pipe; and

[0033] A CEMS sampler 6 is connected to a section of the mother pipe.

[0034] In the related art, the sampling mother pipe 2 mainly adopts a structure with the same cross section, which easily leads to different flue gas flow rates in the sampling mother pipe 2, thereby causing dust accumulation in part of the sampling mother pipe 2. In the present application, the second section of the mother pipe of the sampling mother pipe 2 adopts a variable cross-section structure, and the cross-section of the part closer to the CEMS sampler 6 is larger, which can effectively ensure that the flue gas flow rate of the entire mother pipe is higher than 15m / s under most operating conditions, and the sampling mother pipe 2 will not accumulate or be blocked due to low flow rate.

[0035] In the present application, the sampling main pipe 2 is connected to the sampling branch pipe 1, the front end of the sampling main pipe 2 is connected to the air cannon 8, the end of the sampling main pipe 2 is connected to the dust collector inlet flue 11, and the lower part of the sampling branch pipe 1 extends into the air preheater inlet flue 10. The negative pressure of the pipeline is used to transport part of the flue gas on the SCR outlet flue cross-section through the sampling branch pipe 1 to the dust collector inlet flue 11, thereby realizing automatic sampling.

[0036] Reference Figure 1 and 4 It is understandable that the second section of the mother pipe includes multiple sections with different cross-sections, and the different sections are connected with reducers 3. Specifically, the use of multiple sections can effectively reduce the difficulty of processing the sampling mother pipe 2, and the reducers 3 are used for connection, and the reducers 3 can be eccentric reducers. The eccentric reducers are welded and connected to multiple sections, and the bottoms of the multiple sections are ensured to be flush, which can effectively reduce the obstruction to the flue gas flow and ensure the flue gas flow rate.

[0037] Reference Figure 1It can be understood that the first section of the mother pipe is perpendicular to the horizontal plane, and the second section of the mother pipe is at an angle of 0° to 75° to the horizontal plane. Specifically, the end of the first section of the mother pipe extends into the dust collector inlet flue 11 and remains perpendicular to the horizontal plane to ensure that the first section of the mother pipe will not accumulate dust. The second section of the mother pipe is at an angle of 0° to 75° to the horizontal plane, which can effectively ensure the flow of flue gas and prevent dust accumulation and blockage.

[0038] Referring to 1 and 5, it can be understood that a plurality of sampling holes 20 are opened on the side wall of the sampling branch pipe 1 to ensure that the flue gas can smoothly enter the sampling branch pipe 1. In addition, the lower end of the sampling branch pipe 1 can adopt a structure of a reducer 3, and the sampling hole 20 can be selected as a square hole, and is opposite to the flue gas flow direction to reduce the amount of ash entering the sampling branch pipe 1.

[0039] Reference Figure 1 and 5 , the opening areas of the sampling holes 20 distributed from top to bottom on the sampling branch pipe 1 become larger. The sampling holes 20 use opening areas of different sizes to ensure that the amount of smoke taken out by each sampling hole 20 is as consistent as possible.

[0040] Reference Figure 1 and 5 It can be understood that a disturbance ball 7 is provided in the sampling branch pipe 1, and the disturbance ball 7 is suspended in the sampling branch pipe 1 by a chain 19. Specifically, any speed fluctuation of the flue gas in the flue will drive the disturbance ball 7 and its chain 19 to shake in the sampling branch pipe 1, thereby prompting the chain 19 to stir and clean the dust in the sampling branch pipe 1, thereby realizing the function of preventing dust accumulation. Compared with the method of backblowing by an air cannon 8 in the related art, the arrangement of the disturbance ball 7 and the chain 19 in the present application has a simpler structure, does not consume additional energy, and can achieve self-disturbance cleaning.

[0041] Reference Figure 1 and 4 It can be understood that the upper end of the sampling branch pipe 1 is sealed with an openable flange cover 4. In addition, the chain 19 can be suspended and connected to the flange cover 4. By providing the flange cover 4, when the sampling branch pipe 1 is seriously dusted, the flange cover 4 can be opened for manual dust removal.

[0042] Reference Figure 1 and 2 It can be understood that a flushing valve 14 is also provided at the head end of the second section of the mother pipe. Specifically, the flushing valve 14 is provided on the second section of the mother pipe between the air cannon 8 and the sampling branch pipe 1 closest to the air cannon 8. The flushing valve 14 can be connected to an external flushing device. When the system is blocked, the flushing valve 14 can be connected to an external flushing device for high-pressure water flushing. At the same time, during the maintenance of the air preheater, the device can be cleaned with high-pressure water.

[0043] Reference Figure 1 It can be understood that a dust discharge pipe 12 is also connected to the middle of the sampling main pipe 2, and a dust discharge valve 5 is provided on the dust discharge pipe 12.

[0044] Reference Figure 1 It can be understood that the first section of the main pipe is also provided with an isolation valve 15, and the second section of the main pipe is also provided with a pulse valve 9. Specifically, the isolation valve 15 is located on the first section of the main pipe between the end of the first section of the main pipe and the CEMS sampler 6; the pulse valve 9 is located on the second section of the main pipe between the flushing valve 14 and the sampling branch pipe 1.

[0045] In addition, in the embodiment of the present application, a DCS control system 18 is also included for controlling the action of each valve, receiving detection data, and controlling the start and stop of the air cannon 8. At the same time, a thermocouple 16 is arranged on the upper section (leakage flue) of each sampling branch pipe 1 to measure the temperature of the sampling branch pipe 1. The temperature measurement data is collected to the temperature patrol meter 17 arranged on site. The temperature patrol meter 17 continuously displays the temperature values ​​of each branch pipe. When the sampling branch pipe 1 is blocked by ash, its temperature will drop. The data measured by the thermocouple 16 is transmitted to the temperature patrol meter 17. The temperature patrol meter 17 can transmit the data to the DCS control system 18 to start the air cannon 8 for purging.

[0046] The control strategy of this sampling device when it is put into operation is:

[0047] 1) During the start-up and shutdown phase of the unit, when the SCR system is not in operation or has stopped operation, the isolation valve 15 and the ammonia regulating valve of the SCR system are in an interlocked state. When the opening of the ammonia regulating valve is greater than 5%, the isolation valve 15 is opened and the sampling device is put into use. When the opening of the ammonia regulating valve is ≤5%, it means that the SCR system is not in operation, the isolation valve 15 is closed, and the sampling device is withdrawn. This can effectively prevent dust accumulation in the pipeline due to insufficient negative pressure during the start-up and shutdown phase of the furnace;

[0048] 2) During normal operation, when the CEMS sampler 6 transmits a back-blowing cleaning signal to the DCS control system 18, the DCS control system 18 controls the air cannon 8 to enter the commissioning preparation stage, and after the isolation valve 15 and the ash discharge valve 5 are opened, the pulse valve 9 is opened to perform the ash blowing operation;

[0049] 3) Before opening the air cannon 8 for the second or third time, close the ash discharge valve 5 for ash blowing. After a certain number of continuous blowing, the ash blowing ends and the system continues to be put into use. At this time, the back-blowing of the CEMS sampler 6 also ends, and the SCR outlet CEMS sampler 6 continues to be put into use.

[0050] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A SCR outlet flue sampling device, characterized in that: include, A sampling mother pipe, the sampling mother pipe comprises a mother pipe section 1 and a mother pipe section 2, the end of the mother pipe section 1 extends into the dust collector inlet flue, the head end of the mother pipe section 1 is connected to the end of the mother pipe section 2, the mother pipe section 2 is a variable cross-section structure, and the cross-section increases from the head end to the end; Sampling branch pipes, the upper parts of several sampling straight pipes are connected with the second section of the main pipe, and the lower parts extend into the air preheater inlet flue for sampling; An air cannon, the air cannon being connected to the head end of the second section of the mother pipe; and A CEMS sampler is connected to a section of the mother pipe.

2. The SCR outlet flue sampling device according to claim 1, characterized in that: The second section of the mother pipe comprises a plurality of pipe sections with different cross sections, and different pipe sections are connected with large and small heads.

3. An SCR outlet flue sampling device according to claim 1 or 2, characterized in that: The first section of the mother pipe is perpendicular to the horizontal plane, and the second section of the mother pipe forms an angle of 0° to 75° with the horizontal plane.

4. The SCR outlet flue sampling device according to claim 1, characterized in that: A plurality of sampling holes are provided on the side wall of the sampling branch pipe.

5. The SCR outlet flue sampling device according to claim 4, characterized in that: The opening areas of the sampling holes distributed from top to bottom on the sampling branch pipe become larger.

6. The SCR outlet flue sampling device according to any one of claims 1, 4 or 5, characterized in that: A disturbance ball is arranged in the sampling branch pipe, and the disturbance ball is suspended in the sampling branch pipe through a chain.

7. The SCR outlet flue sampling device according to claim 6, characterized in that: The upper end of the sampling branch pipe is sealed with an openable flange cover.

8. The SCR outlet flue sampling device according to claim 1, characterized in that: A flushing valve is also provided at the head end of the second section of the mother pipe.

9. The SCR outlet flue sampling device according to claim 1, characterized in that: The middle part of the sampling main pipe is also connected with an ash discharge pipe, and an ash discharge valve is arranged on the ash discharge pipe.

10. The SCR outlet flue sampling device according to claim 1, characterized in that: The first section of the main pipe is also provided with an isolating valve, and the second section of the main pipe is also provided with a pulse valve.

Images