Multi-point nitrogen oxide detection system

Abstract

The utility model provides a multi-point nitrogen oxide detection system which can detect a plurality of detection points simultaneously, and a control unit is electrically connected with a plurality of detection devices, so that nitrogen oxide concentration information of each detection point can be acquired in real time, and a basis can be provided for ammonia spraying adjustment more quickly; a filter and a dust detector are arranged in a flue gas collection channel of each detection device, so that dust related information can be obtained in time while part of dust is filtered, a basis is provided for system operation and maintenance, and detection errors caused by impurities in flue gas are effectively avoided; and through the purging channel, impurities such as dust in the flue gas can be effectively filtered, and the nitrogen oxide detector is purged to prevent blockage. The purging strategy of the purging channel is adjusted according to the dust concentration detected by the dust detector and the average flue gas flow velocity detected by the flue gas flow velocity meter probe, different purging frequencies are set, and the purpose of saving energy is achieved while blockage is prevented.

Description

TECHNICAL FIELD

[0001] The utility model relates to flue gas detection technical field especially is related to a multi -point type nitrogen oxide detection system. BACKGROUND

[0002] Most of coal-fired power plants in China use selective catalytic reduction (SCR) denitration technology to control NOx pollutants. The core equipment of SCR denitration technology is SCR reactor, and the process flow of SCR denitration reaction is as follows: the original flue gas from the coal economizer is mixed with diluted ammonia at the partition ammonia injection grid, the ammonia injection grid is composed of several uniformly arranged nozzles, a manual butterfly valve is installed on each ammonia injection branch to adjust the ammonia injection amount of each region, and then the mixed flue gas passes through the SCR reactor. Two or three layers of catalysts are arranged in the reactor, the mixed ammonia-containing flue gas contacts the surface of the catalyst, and NOx and NH3 on the surface of the catalyst are reduced to generate N2 and water harmless to the environment, thereby achieving the purpose of removing NOx in the flue gas. The specific chemical equation is as follows:

[0003] 4NO + 4NH3 + O2 → 4N2 + 6H2O, 4NO2 + 2NH3 + O2 → 3N2 + 6H2O;

[0004] The side effect SO3 equation is: SO2 + 1 / 2O2 → SO3, NH3 + SO3 + H2O → NH4HSO4.

[0005] From the above chemical reaction equation, the denitration reaction is real-time, and the ammonia-nitrogen molar ratio is strictly reacted. Because the nitrogen oxide flow field and concentration field distribution in each small partition of the ammonia injection grid is uneven, the total amount of nitrogen oxides contained in each partition is different. If the ammonia injection of each branch of the ammonia injection grid does not match the actual situation, it will cause local excessive ammonia injection and local insufficient ammonia injection. The ammonia-nitrogen molar ratio in the excessive ammonia injection area is large, which will inevitably increase the ammonia escape and increase the probability of forming bisulfuric acid ammonia. Due to the characteristics of bisulfuric acid ammonia, it will stick to the heat exchange fins of the air preheater when the flue gas passes through the air preheater. As a result of the accumulation of bisulfuric acid ammonia, the air preheater will be blocked, which will increase the power consumption of the induced draft fan and the forced draft fan, and even affect the safe operation of the unit. The ammonia-nitrogen molar ratio in the insufficient ammonia injection area is small, which will cause local nitrogen oxide to exceed the standard. If the emission standard is to be met, the total ammonia supply will inevitably increase, and the ammonia consumption will also increase.

[0006] Therefore, the selective catalytic reduction (SCR) denitration technology is used to treat nitrogen oxide pollutants. When the nitrogen oxide measurement adopts a multi-point measurement method, the flue gas sampling device is easily blocked due to high dust in the flue gas. In order to solve the above problems, the denitration ammonia injection grid usually needs to adjust the opening of the partition valve according to the concentration distribution of the outlet nitrogen oxide every month, so as to balance the denitration outlet nitrogen oxide concentration. At present, the single measurement point instrument has the following problems: ① it takes a lot of time to measure each partition of the ammonia injection grid; ② it cannot respond to the changes of the main machine under different working conditions; ③ it has high requirements for the sampling flow rate: 1 L / min, and the sampling cycle is long; ④ the existing instrument mostly adopts the red (purple) light analysis method or the electrochemical analysis method, which is easy to block.

[0007] Therefore, the patent application No. CN110161189A discloses a portable multi-point nitrogen oxide synchronous detection device and a detection method thereof, which realizes multi-point, distributed and simultaneous sampling and analysis of nitrogen oxide concentration, realizes simultaneous detection of multi-point data, displays the nitrogen oxide concentration value of each sampling point on the display screen in real time, and realizes real-time feedback of data by using wireless transmission. However, the problem of easy blocking of the sampling detection device during sampling has not been solved. Practical new type content

[0008] The utility model discloses a multi-point nitrogen oxide detection system, solve the problem that the device is easy to block when multi-point nitrogen oxide synchronous detection.

[0009] The utility model provides a multi-point nitrogen oxide detection system, including control unit and a plurality of detection devices, the detection device all with control unit electricity is connected, the detection device includes the device body, be equipped with the flue gas collection channel and the purging channel that intercommunication on the device body, the filter, flue gas flow speed appearance probe, dust detector and nitrogen oxide detector are equipped with gradually in the flue gas collection channel along the flue gas flow direction, the nitrogen oxide detector is installed in the flue gas collection channel and is inclined and faces away flue gas import direction.

[0010] Further, the purging channel is in communication with the end of the flue gas collection channel.

[0011] Further, the device body further comprises a drainage channel, the drainage channel is in communication with an external negative pressure device, and the drainage channel is in communication with the end of the flue gas collection channel.

[0012] Further, the device body is provided with a smoke inlet pipe in communication with the flue gas collection channel, and the smoke inlet pipe is provided with a heating pipe outside.

[0013] Further, the smoke inlet pipe is detachably mounted on the device body, and a plurality of groups of spoiler plates are arranged at intervals in the smoke inlet pipe.

[0014] Further, the heating pipe is parallel to the axis of the flue gas inlet pipe.

[0015] Further, the heating pipe is spirally wound outside the flue gas inlet pipe.

[0016] Further, the inclination angle of the nitrogen oxide detector is -45°<β<90°.

[0017] Further, the dust detector is obliquely installed in the flue gas collection channel.

[0018] Further, the outer side of the detection device is covered with a heat insulation layer.

[0019] The beneficial effects of the technical solution are: the multi-point nitrogen oxide detection system can simultaneously detect multiple detection points, the control unit is electrically connected with the multiple detection devices, the nitrogen oxide concentration information of each detection point can be obtained in real time, and the basis for adjusting ammonia injection can be provided more quickly, the real-time feedback mechanism makes the system adapt to the changes of the host under different working conditions, and the ammonia injection strategy is adjusted in time; the filter and the dust detector are arranged in the flue gas collection channel of each detection device, so that part of the dust can be filtered, dust-related information can be obtained in time, the basis for system operation and maintenance is provided, and detection errors caused by impurities in flue gas are effectively avoided; through the purging channel, dust and other impurities in flue gas can be effectively filtered, and the nitrogen oxide detector can be purged to prevent blockage. The purging strategy of the purging channel is adjusted according to the dust concentration detected by the dust detector and the average flow rate of flue gas detected by the flue gas flow rate instrument probe, different purging frequencies are set, blockage is prevented, and the purpose of energy saving is achieved. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the drawings needed in the specific embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0021] Fig. 1 It is a layout structure diagram of the present application.

[0022] Fig. 2 It is a structure diagram of the detection device in the present application.

[0023] Explanation of reference signs: 1 - multi-point nitrogen oxide detection system, 2 - control unit, 3 - device body, 4 - flue gas collection channel, 5 - purge channel, 6 - nitrogen oxide detector, 7 - dust detector, 8 - filter, 9 - diversion channel, 10 - flue gas inlet pipe, 11 - heating pipe, 12 - communication pipe. DETAILED DESCRIPTION

[0024] The technical solutions of the present application will be described below in conjunction with the embodiments, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0025] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0026] In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited. In addition, the terms "mounting", "connecting", "connection" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] Example 1

[0028] As Figs. 1-2The utility model provides a kind of multi-point nitrogen oxide detection system, which includes a control unit 2 and multiple detection devices. The multiple detection devices are electrically connected to the control unit 2. The outer side of the detection device is covered with a thermal insulation layer. This prevents the contact part of the pin wire from becoming less insulated under high temperature, causing the current output by the sensor to mix with leakage current, and resulting in a decrease in the sensitivity of the detector.

[0029] The detection device includes a device body 1 with a flue gas collection channel 4 and a purge channel 5 that are in communication with each other. The flue gas collection channel 4 has a filter 8, a dust detector 7, and a nitrogen oxide detector 6 installed in sequence along the direction of flue gas flow. To avoid the direct impact of dust mixed in the flue gas on the nitrogen oxide detector 6, the dust detector 7 and the nitrogen oxide detector 6 are both installed in the flue gas collection channel 4 at an angle and facing away from the direction of flue gas introduction. With the vertical direction as the zero-degree angle and the clockwise direction as positive, the angle of the dust detector 7 and the nitrogen oxide detector 6 is -45° < β < 90°. A flue gas flow rate instrument probe is also installed on the inner wall of the flue gas collection channel 4 to monitor the flow rate of the flue gas.

[0030] The purge channel 5 is in communication with the end of the flue gas collection channel 4 and is coaxial with it. During operation, purge gas is introduced to face the nitrogen oxide detector 6, and the purge strategy is adjusted according to the dust concentration detected by the aforementioned dust detector 7 and the average flow rate of the flue gas. The relationship between the purge frequency and the dust concentration and the average flow rate of the flue gas can be w = f(η, σ); where w is the purge frequency, η is the dust concentration, and σ is the average flow rate of the flue gas.

[0031] To ensure that the flue gas can flow smoothly into the flue gas collection channel 4, a drainage channel 9 is also provided in the device body 1. The drainage channel 9 is in communication with an external negative pressure device, and the inside of the drainage channel 9 is in communication with the end of the flue gas collection channel 4 through a communication pipe 12. The flue gas is sucked in for detection through the action of negative pressure.

[0032] The device body 1 is detachably installed with a smoke inlet pipe 10 that is in communication with the flue gas collection channel 4. The smoke inlet pipe 10 is used for sampling flue gas. The outer side of the smoke inlet pipe 10 is provided with a heating pipe 11 that is parallel to the axis of the smoke inlet pipe 10. To improve the uniformity of flue gas heating, multiple groups of spoiler plates can be installed at intervals inside the smoke inlet pipe 10.

[0033] In the multi-point nitrogen oxide detection system, when the sensitivity of a detection device is reduced due to aging, blockage and other reasons, the measured value is far from the normal value, and the error correction compensation (prediction) method is used to make the measured value reach the normal value range. The aforementioned error correction compensation (prediction) method collects a group of data within a certain time to draw a NOx detection concentration curve during normal operation, and multiple data are collected and averaged as a correction compensation (prediction) curve. When an abnormal detection occurs in a certain path, the concentration value of NOx at the abnormal node is predicted according to the correction compensation curve. At the same time, relevant personnel are notified for repair.

[0034] Embodiment 2

[0035] The difference between this embodiment and embodiment 1 is that the heating pipe 11 is spirally wound outside the smoke inlet pipe 10 in order to increase the heated area of the smoke inlet pipe 10.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-point nitrogen oxide detection system, characterized by, The device comprises a control unit and a plurality of detection devices, each of which is electrically connected to the control unit; the detection device comprises a device body, a flue gas collection channel and a purge channel are arranged in communication with each other on the device body, a filter, a flue gas flowmeter probe, a dust detector and a nitrogen oxide detector are sequentially arranged in the flue gas collection channel along the flue gas flow direction, and the nitrogen oxide detector is installed in the flue gas collection channel in a tilted manner and faces away from the flue gas introduction direction.

2. The multi-point nitrogen oxides detection system of claim 1, wherein, The purge channel is in communication with the end of the flue gas collection channel.

3. The multi-point nitrogen oxides detection system of claim 1, wherein, A drainage channel is further arranged in the device body, the drainage channel is in communication with an external negative pressure device, and the inside of the drainage channel is in communication with the end of the flue gas collection channel.

4. The multi-point nitrogen oxides detection system of claim 1, wherein, An inlet pipe in communication with the flue gas collection channel is mounted on the device body, and a heating pipe is arranged on the outside of the inlet pipe.

5. The multi-point nitrogen oxides detection system of claim 4, wherein, The inlet pipe is detachably mounted on the device body, and a plurality of groups of spoiler plates are arranged at intervals in the inside of the inlet pipe.

6. The multi-point nitrogen oxides detection system according to claim 4 or 5, characterized in that The heating pipe is parallel to the axis of the inlet pipe.

7. The multi-point nitrogen oxides detection system of claim 4 or 5, wherein, The heating pipe is spirally wound on the outside of the inlet pipe.

8. The multi-point nitrogen oxides detection system of claim 1, wherein, In a vertical direction, the angle of the nitrogen oxide detector is -45°<β<90° in a clockwise direction.

9. The multi-point nitrogen oxides detection system of claim 1, wherein, The dust detector is installed in the flue gas collection channel in a tilted manner.

10. The multi-point nitrogen oxides detection system of claim 1, wherein, The outside of the detection device is covered with a heat insulation layer.

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