Air volume measuring system for over fire air inlet air duct of boiler of coal-fired generating set

Abstract

The utility model provides an air volume measuring system for a boiler over-fire air inlet air duct of a coal-fired generating set. The boiler over-fire air inlet air duct of the coal-fired generating set is communicated between a vertical over-fire air duct and a boiler; the boiler over-fire air inlet air duct comprises a first telescopic joint, a connecting air duct, a second telescopic joint and a boiler over-fire air inlet air door which are sequentially communicated in series. The air volume measuring system comprises air volume measuring sensors which are respectively arranged or integrally arranged at at least one data average air speed point position in one cross section of the connecting air duct, and an air volume flow computer connected with the air volume measuring sensors; the air flow computer measures values in real time and sends the values to a unit control system; the problem of inaccurate measurement of the air volume of the boiler over-fire air inlet air duct is solved; therefore, the running safety, flexibility, energy conservation and environmental friendliness of the unit are greatly improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of air volume measurement, and relates to an air volume measurement system for an air duct without a straight pipe section of a coal-fired generator set, and in particular to an air volume measurement system for an air duct at a burnout air inlet of a boiler of a coal-fired generator set. Background Art

[0002] The current Chinese National Metrology Verification Regulations JJG835-1993 "Velocity-area flow rate device verification regulations" page 1, the first and second paragraphs from the bottom:

[0003] "1 Appearance

[0004] 1.1 The flow device is fully equipped and well assembled.

[0005] 1.2 The length of the upstream straight pipe section of the metering section shall be at least 20 times the diameter of the circular section (or 80 times the hydraulic radius of the rectangular section), and the length of the downstream straight pipe section shall be at least 5 times the diameter of the circular section (or 20 times the hydraulic radius of the rectangular section). When the velocity is measured at a single point in the metering cross section (at the axial average velocity point or on the axis), the length of the upstream straight pipe section shall be at least the value listed in Table 1.

[0006] Table 1

[0007]

[0008] When compiling the above-mentioned national metrological verification procedures, reference was made to the international standards ISO7145:1982 "Determination of the flow velocity of a fluid in a closed conduit with circular cross-section. Method of velocity measurement at a point on the cross section", ISO7145-1982 "Determination of the flow velocity of a fluid in a closed conduit with circular cross-section. Method of velocity measurement at a point on the cross section", ISO 3966:1977 "Measurement of fluid flow in closed conduits. Velocity-area method using a pitot-static tube" and ISO3354-1988 "Measurement of clean water flow in closed conduits. Velocity-area method using a flow meter under full conduit and normal flow conditions". In these standards, it is stipulated that flow measurement can only be applied to fully developed turbulence, and it is required that there should be a straight pipe section length of 30D to 50D before the measuring section (see the first paragraph of page 210 of the "Practical Manual of Flow Measurement" published by China Electric Power Press in August 2017, the first edition). International standard ISO7194-1983 "Measurement of fluid flow in closed pipes - Velocity-area method for measuring asymmetric flow or vortex flow in circular pipes using a tachometer or pitot-static tube" uses the velocity-area method of pitot tube to measure flow when there are vortices and asymmetric flows in circular pipes. Although ISO7194 can be applied to flow measurement with asymmetric velocity distribution and vortices, it should not be considered that it can be used without restriction for all measurement sections with asymmetric velocity distribution and vortices. To achieve a certain degree of accuracy, very harsh conditions should also be met. At the same time, ISO7194 recommends the use of five types of flow conditioners, which mainly eliminate vortices, but are less effective in improving flow velocity asymmetry (see China Electric Power Press's "Practical Handbook of Flow Measurement", first edition August 2017, page 198, paragraphs 5, 6, 7, 8, 9, and 10).

[0009] like Figure 1 As shown, it is a schematic diagram of the partial side section structure of the 5th and 6th-layer boiler burnout air inlet ducts at a corner of the boiler of the No. 1 700MW coal-fired generator unit of a thermal power plant, wherein the 5th-layer boiler burnout air inlet duct 05 comprises a first telescopic joint 0501, a connecting duct 0502, a second telescopic joint 0503 and a boiler burnout air inlet damper 0504 which are sequentially connected to the vertical burnout air duct 01; the 6th-layer boiler burnout air inlet duct 06 which is connected to the vertical burnout air duct 01 is arranged directly above the 5th-layer boiler burnout air inlet duct 05. The matrix air volume measuring device 1 is arranged in the connecting air duct 0502, and the matrix air volume measuring devices are also arranged at the corresponding positions of the boiler burnout air inlet air ducts at other corners of other layers of the boiler (not shown in the figure).

[0010] Since the straight section in the duct 05 at the inlet of the burnout air of the 5th floor boiler on site is only 0.74 meters, which is far less than the requirements in the international or national standards or the "Practical Manual of Flow Measurement", the wind field in this section of the duct cannot be fully developed. Therefore, there is serious turbulence in the wind field in this section of the duct. The existing measurement technology of the prior art matrix air volume measurement device 1 set in the connecting air duct 0502 still cannot solve the problem of uneven turbulent air volume measurement, which is a common problem in the measurement of the air volume of the burnout air entering the boiler of coal-fired power generation units, resulting in the inability to meet the needs of safe production and industrial control of coal-fired power generation units. Summary of the invention

[0011] In order to solve the problem of inaccurate air volume measurement in the boiler overburnt air inlet duct of the above-mentioned coal-fired power generation unit, the utility model provides an air volume measurement system that can accurately measure the air volume of the boiler overburnt air inlet duct of the coal-fired power generation unit: the boiler overburnt air inlet duct of a coal-fired power generation unit is connected between a vertical overburnt air duct and the boiler; the overburnt air boiler inlet duct includes a first telescopic joint, a connecting air duct, a second telescopic joint and a boiler overburnt air inlet damper that are connected in series in sequence; the air volume measurement system includes: an air volume measurement sensor is respectively arranged at at least one data average wind speed point in a cross section of the connecting air duct or is arranged as a whole, and an air volume flow computer connected thereto.

[0012] Preferably, the wind volume measurement sensors respectively set up are selected from Pitot tube type wind volume measurement sensors, Venturi type wind volume measurement sensors, or unpowered fan wind volume measurement sensors; and the wind volume measurement sensors set up as a whole are selected from non-uniformly distributed Basque type wind volume measurement sensors.

[0013] Preferably, the Pitot tube type air volume measurement sensor or the Venturi type air volume measurement sensor or the non-uniformly distributed Venturi type air volume measurement sensor is provided with a back-purge device.

[0014] Preferably, the Venturi-type air volume measurement sensor is a single-throat diameter tube air volume measurement sensor, a double-throat diameter tube air volume flow sensor or a multi-throat diameter tube air volume measurement sensor.

[0015] Preferably, the unpowered fan air volume measurement sensor includes an unpowered fan and a rotation speed measurement unit for monitoring the unpowered fan; the unpowered fans may be of the same specifications or different specifications.

[0016] The utility model has an extremely short straight pipe section (connecting air duct) at the burnout air inlet duct of each corner and each layer of the boiler of the coal-fired power generation unit, and has expansion joints in front and behind with a length of only 840mm. There are dense supporting ribs at the front end of the measured straight pipe section. In this way, when there is serious turbulence in the wind field of this section of the duct, the data average wind speed point in a cross section in the straight pipe section is unexpectedly found by determining the data average wind speed value point in the cross section of the duct in the non-uniformly distributed wind field, and an air volume measurement sensor is separately or integrally arranged at the data average wind speed point, which solves the problem of inaccurate air volume measurement in the burnout air inlet duct of the boiler of the coal-fired power generation unit, and improves the accuracy of air volume measurement of the burnout air entering the boiler duct; thereby helping the coal-fired power generation unit to accurately reduce NOX generation and improve safety, flexibility, energy saving and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of a partial side section structure of a matrix air volume measurement device of the prior art installed in a corner of a boiler No. 1 700MW coal-fired generator unit in a thermal power plant, in the 5th layer of the boiler burnout air inlet duct;

[0018] Figure 2a It is a simulation Figure 1 The wind speed data of each measuring point in a cross section of the connected air duct of the fifth-layer boiler burnout air inlet air duct when the inlet air door is opened by 20% is shown;

[0019] Figure 2b It is a simulation Figure 1 The wind speed data of each measuring point in a cross section of the connected air duct of the fifth-layer boiler burnout air inlet air duct when the inlet air door is opened by 40% is shown;

[0020] Figure 2c It is a simulation Figure 1 The wind speed data of each measuring point in a cross section of the connected air duct of the fifth-layer boiler burnout air inlet air duct when the inlet air door is opened by 60% is shown;

[0021] Figure 2d It is a simulation Figure 1 The wind speed data of each measuring point in a cross section of the connected air duct of the fifth-layer boiler burnout air inlet air duct when its inlet air door is opened 80% is shown in the visual diagram;

[0022] Figure 3 Embodiment 1 provides a method based on Figure 1 The schematic diagram of the overall location of the air volume measurement sensor installed in the burnout air duct of the fifth floor of a boiler in a corner of the boiler of the No. 1 700MW coal-fired power generation unit of a thermal power plant is shown;

[0023] Figure 4 yes Figure 3The schematic diagram of the specific location of the air volume measurement sensor on the duct wall A in the cross section of the burnout air duct of the 5th floor boiler is shown;

[0024] Figure 5 yes Figure 3 The schematic diagram of the cross-sectional structure of the main body of the air volume measurement sensor is shown;

[0025] Figure 6 yes Figure 3 A schematic diagram of the structure of an air volume measurement system is shown; DETAILED DESCRIPTION

[0026] The present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods; it should be understood that the following specific implementation methods are only used to illustrate the present invention and are not used to limit the protection scope of the present invention.

[0027] Example 1

[0028] like Figure 3 , 4 , 5 and 6 are schematic diagrams of the structure of an air volume measurement system for the burnout air inlet duct of the 5th-layer boiler of a 700MW coal-fired generator set in a thermal power plant provided in this embodiment; the burnout air inlet duct 05 (rectangular duct) of the 5th-layer boiler of the coal-fired generator set is connected between the vertical burnout air duct 01 and the boiler; the boiler burnout air inlet duct 05 includes a first telescopic joint 0501, a connecting duct 0502, a second telescopic joint 0503 and a boiler burnout air inlet damper 0504 which are connected in sequence. The 6th-layer boiler burnout air inlet duct 06 connected to the vertical burnout air duct 01 is arranged directly above the 5th-layer boiler burnout air inlet duct 05. Figure 3 Only the schematic diagram of the 5th layer burnout air inlet duct structure at a corner of the boiler is shown.

[0029] The air volume measurement system comprises:

[0030] A non-uniformly distributed Ba-type air volume measurement sensor 1' is integrally arranged at at least one data average wind speed point in a certain cross section of the connecting air duct 0502 (that is, a non-uniformly distributed Ba-type air volume measurement sensor 1' (probe) is integrally arranged at two or three data average wind speed points, and the two or three data average wind speed points are all arranged at corresponding positions of the non-uniformly distributed Ba-type air volume measurement sensor 1'), and an air volume flow computer connected thereto (also called a hot air flow computer, whose air volume measurement value is calculated based on the differential pressure value measured by the non-uniformly distributed Ba-type air volume measurement sensor combined with factors such as the burnout air temperature, differential pressure and pressure).

[0031] like Figure 5As shown, it is a schematic diagram of the cross-sectional structure of the main body 1'01 of the non-uniformly distributed air volume measurement sensor 1'; its upper end pipe is a negative pressure pipe of a shuttle-shaped body, including a negative pressure chamber 1'01-3 and a negative pressure sampling hole 1'01-2 arranged on its inner rear cavity wall; its lower end pipe is a positive pressure pipe of a shuttle-shaped body that is mirror-symmetrical to the upper end pipe, including a positive pressure chamber 1'01-5 and a positive pressure sampling hole 1'01-4 arranged on its inner front cavity wall; the upper and lower end pipes are connected together by a plurality of rectifying grid pieces 1'01-1, and in the middle is a fluid flow channel consisting of a large hole for fluid inlet-a small hole in the middle-a large hole for fluid outlet. At least one data average wind speed value point is set at a position close to two adjacent rectifying grid pieces on the non-uniform air volume measurement sensor 1'; when two or three data average wind speed value points are set, it is only necessary to set the two or three data average wind speed value points at a position close to two adjacent rectifying grid pieces on the non-uniform air volume measurement sensor 1' as much as possible. A positive pressure connecting pipe 1'02 and a negative pressure connecting pipe 1'03 are respectively set at the upper end and the midpoint of the vertically arranged non-uniform air volume measurement sensor 1' main body 1'01, and are respectively led out to the air volume flow computer; in addition, an intermediate supporting connector 1'04 is set between the positive pressure connecting pipe 1'02 and the negative pressure connecting pipe 1'03, and an air duct inner wall supporting connector 1'05 is set at their lead-out ends. (Of course, when the specific setting position of the non-uniform air volume measurement sensor 1' body 1'01 in a certain cross section of the connecting air duct remains unchanged, the extraction of positive and negative pressures in the connecting air duct and the corresponding fixing structure can be changed. The principle is that the non-uniform air volume measurement sensor 1' body 1'01 is stable when working in the connecting air duct and the air volume measurement is reliable)

[0032] According to the method of determining the average wind speed value point position of the data in the cross section of the wind duct of the non-uniformly distributed wind field in Chinese patent CN2022112805951, the specific installation position of the non-uniformly distributed air volume measurement sensor 1' in the cross section of the connecting wind duct 0502 is determined (wind tunnel simulation test):

[0033] After simulation Figure 1 Wind tunnel test of the cross section of the connecting duct of the 5th layer boiler burnout air inlet duct at different opening degrees of its inlet damper, see Figure 2a-2d As shown (respectively under loads of 20% (load 1), 40% (load 2), 60% (load 3), and 80% (load 4) of the boiler burnout air inlet damper opening; the X-axis direction is the height direction of the connecting air duct, and the Y-axis direction is the width direction of the connecting air duct; the dark blue area gradually changes to the dark red area, and the wind speed in the corresponding area changes from small to large, and the blue point is the data average wind speed point with zero error; the number of measurement points in the simulated connecting air duct is set to 450).

[0034] According to the results of the wind tunnel simulation test, by analyzing the measured data, combined with the structural characteristics and installation methods of the non-uniformly distributed air volume measurement sensor, it is necessary to find a column of data in the test data that can represent the average wind speed in the entire cross-section of the connecting air duct, and it is consistent with the measurement length of the non-uniformly distributed air volume measurement sensor. By calculating and analyzing the data, the data average wind speed point is determined: under all 4 loads, it is close to the data average wind speed of the entire cross-section of the connecting air duct (within the allowable error range of industrial measurement). Combined with the non-uniformly distributed air volume measurement sensor and its air duct structural characteristics, it is planned to install a non-uniformly distributed air volume measurement sensor with a length of 900-1000mm in the direction of 3500mm in the cross-section of the connecting air duct. This can determine the specific installation position of the non-uniformly distributed air volume measurement sensor in the connecting air duct, such as Figure 3 and 4 shown.

[0035] This embodiment and the prior art (matrix air volume measurement device) provide an air volume measurement system for measuring the air volume of the burnout air inlet duct of the 5th layer of the boiler at the four corners of the boiler under the actual operation of the coal-fired power generation unit: compared with the matrix air volume measurement device of the prior art, the air volume measurement value is 60% higher; it is basically consistent with the generator power and total air volume change curve; at the same time, the changes in the four air volume measurements at the four corners are also basically consistent. The air volume measurement system using the matrix air volume measurement device of the prior art is compared with the air volume measurement system provided by this embodiment. The air volume measurement value of the matrix air volume measurement device is particularly low, and the response is not sensitive to the change of the generator power load. It even drops to zero at low load. In addition, the air volume measurements of each matrix air volume measurement device of the prior art are inconsistent with each other. Therefore, the technical solution of the air volume measurement system provided by the present invention is far superior to the technical solution of the air volume measurement system based on the matrix air volume measurement device of the prior art in terms of air volume measurement accuracy.

[0036] The selection and setting principle of the air volume measurement sensor in this embodiment is: the wind speed sampling hole of the air volume measurement sensor is at or near the data average wind speed point obtained from the wind tunnel simulation test; and these wind speed sampling holes can be all on one air volume measurement sensor (such as the unevenly distributed Ba-type air volume measurement sensor in this embodiment), or one wind speed sampling hole can correspond to one air volume measurement sensor (such as a Venturi-type or Pitot-type air volume measurement sensor). Therefore, the unevenly distributed Ba-type air volume measurement sensor described in this embodiment is replaced by a Venturi-type air volume measurement sensor, such as a single-throat tube, a double-throat tube, a multi-throat tube, etc.; it can also be replaced by a Pitot-type air volume measurement sensor.

[0037] Since the air volume measurement sensor in this embodiment is installed in a connecting air duct with a large amount of dust, a back-purge device for measuring gas pipelines in Chinese patent CN111520611A can be used to solve the problem of inaccurate air volume measurement in the air duct caused by the air volume measurement sensor being blocked by dust.

[0038] Example 2

[0039] The air volume measurement system for the burnout air inlet duct of the fifth-layer boiler of a coal-fired power generation unit provided in this embodiment is an improvement on the embodiment 1. The difference between the embodiment 1 and the embodiment 1 is as follows:

[0040] A non-powered fan air volume measurement sensor is respectively set at at least one data average wind speed point in a certain cross section of the connecting air duct 0502; and an air volume flow computer that monitors the non-powered fan air volume measurement sensor.

[0041] The unpowered fan air volume measurement sensor includes an unpowered fan and a speed measurement unit for monitoring the fan, such as the German Testo (TESTO) TESTO410-1 mini anemometer;

[0042] According to the wind speed of the average wind speed point obtained from the wind tunnel simulation test, the unpowered fans can be selected with the same specifications or different specifications. In addition, the air volume measurement system for the burnout air inlet duct of the fifth-layer boiler of the coal-fired power generation unit provided in this embodiment does not have the problem of dust clogging, so there is no need to set up a back-purge device for measuring the gas pipeline in Chinese patent CN111520611A. The rest of the parts and their working principles are basically similar to those of Example 1.

[0043] The position of the wind volume measurement sensor in the utility model is as follows: Figure 3 and 4 As shown, in principle, any cross section of the connecting air duct in the fifth-layer boiler burnout air inlet air duct can obtain at least one data average wind speed point within the allowable range of industrial air volume measurement error.

[0044] Although the above embodiment is based on the actual specific structure of the burnout air inlet duct of the 5th layer of the boiler of a specific 700MW coal-fired generator set in a thermal power plant as an example, the utility model is explained, and can be expanded to the burnout air inlet ducts at each corner and each layer of the boiler of coal-fired generator sets with different capacities; but it should be understood that the invention point of the utility model is: an air volume measurement sensor is respectively or integrally set at at least one data average wind speed point in a certain cross-section of the connected air duct, and an air volume flow computer connected thereto, and then the measurement information is sent to the DCS control system of the coal-fired generator set; its effect is: the straight pipe section of the burnout air inlet duct at each corner and each layer of the boiler of the coal-fired generator set is extremely short, and the front and rear are expansion joints with a length of 840mm, and the measured straight pipe section There are dense supporting ribs at the front end, so when there is serious turbulence in the wind field of this section of the duct, the data average wind speed point in a cross-section in the straight pipe section is unexpectedly found through wind tunnel simulation tests and the method of determining the data average wind speed value point in the cross-section of the duct in the non-uniformly distributed wind field, thereby solving the problem of inaccurate air volume measurement at the inlet duct of the boiler burnout air of the coal-fired power generation unit, and greatly improving the accuracy of the air volume measurement of the burnout air entering the boiler duct; in this way, the operating safety, flexibility, energy saving and environmental protection of the coal-fired power generation unit are greatly improved; technical personnel in this field may make changes or improvements to the present invention without departing from the essential spirit and scope of the above-mentioned inventive points of the present invention, but all should fall within the protection scope of the technical scheme of the present invention.

Claims

1. A system for measuring the air volume of a boiler burnout air inlet duct of a coal-fired power generation unit, wherein the boiler burnout air inlet duct of a coal-fired power generation unit is connected between a vertical burnout air duct and the boiler; the boiler burnout air inlet duct comprises a first telescopic joint, a connecting air duct, a second telescopic joint and a boiler burnout air inlet damper which are connected in series in sequence; characterized in that: The air volume measurement system comprises: An air volume measurement sensor and an air volume flow computer connected thereto are respectively or integrally arranged at at least one data average wind speed point in a cross section of the connected air duct.

2. The air volume measurement system according to claim 1, characterized in that: The wind volume measurement sensors respectively set up are selected from Pitot tube type wind volume measurement sensors, Venturi type wind volume measurement sensors or unpowered fan wind volume measurement sensors; the wind volume measurement sensors set up as a whole are selected from non-uniformly distributed Basque type wind volume measurement sensors.

3. The air volume measurement system according to claim 2, characterized in that: The Pitot tube type air volume measurement sensor or the Venturi type air volume measurement sensor or the non-uniform distribution type air volume measurement sensor is additionally provided with a back-purge device.

4. The air volume measurement system according to claim 3, characterized in that: The Venturi type air volume measurement sensor is a single-throat diameter tube air volume measurement sensor, a double-throat diameter tube air volume flow sensor or a multi-throat diameter tube air volume measurement sensor.

5. The air volume measurement system according to claim 2, characterized in that: The unpowered fan air volume measurement sensor comprises an unpowered fan and a rotation speed measurement unit for monitoring the unpowered fan; the unpowered fans can be of the same specification or different specifications.

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