CN112763388A - Online monitoring system and method for concentration deviation between coal mill powder conveying pipelines - Google Patents
Online monitoring system and method for concentration deviation between coal mill powder conveying pipelines Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 281
- 239000000843 powder Substances 0.000 title claims abstract description 196
- 238000012544 monitoring process Methods 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims description 23
- 238000005070 sampling Methods 0.000 claims abstract description 162
- 238000005259 measurement Methods 0.000 claims abstract description 30
- 238000012545 processing Methods 0.000 claims abstract description 4
- 238000011010 flushing procedure Methods 0.000 claims description 12
- 238000010926 purge Methods 0.000 claims description 7
- 238000007664 blowing Methods 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 5
- 238000009434 installation Methods 0.000 claims description 4
- 238000002347 injection Methods 0.000 claims description 3
- 239000007924 injection Substances 0.000 claims description 3
- 238000005086 pumping Methods 0.000 claims description 3
- 238000000926 separation method Methods 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims 1
- 239000000523 sample Substances 0.000 description 19
- 239000002817 coal dust Substances 0.000 description 18
- 238000001514 detection method Methods 0.000 description 4
- 239000013307 optical fiber Substances 0.000 description 4
- 230000006698 induction Effects 0.000 description 3
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- 101100518501 Mus musculus Spp1 gene Proteins 0.000 description 2
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- 238000005299 abrasion Methods 0.000 description 1
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- 238000004939 coking Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
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- 239000002245 particle Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
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- 239000007790 solid phase Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000005514 two-phase flow Effects 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention provides an on-line monitoring system for concentration deviation between coal powder conveying pipelines of a coal mill, which comprises a plurality of on-line constant-speed coal powder sampling and measuring devices and a system measurement control unit, wherein the on-line constant-speed coal powder sampling and measuring devices are respectively arranged on a plurality of coal powder pipelines at the outlet of the same coal mill, the on-line constant-speed coal powder sampling and measuring devices are respectively connected with the system measurement control unit through control signal lines, and the system measurement control unit comprises an intelligent processor and a display unit and is used for carrying out logic time sequence control on the on-line constant-speed coal powder sampling and measuring devices and processing and transmitting measurement signals. According to the invention, the coal powder concentration distribution balance among the coal powder pipelines is realized by measuring the relative concentration deviation among the coal powder pipelines of the same coal mill, and the coal powder concentration balance control among different pipelines of the coal mill is simplified.
Description
Technical Field
The invention belongs to the technical field of on-line monitoring of solid-phase concentration deviation in gas-solid two-phase flow, and particularly relates to an on-line monitoring system and method for concentration deviation between powder conveying pipelines of a coal mill.
Background
A coal mill pulverizing system of a large and medium-sized coal-fired power plant grinds massive or large-particle coal into fine coal powder, the fine coal powder is carried by hot air and is conveyed into a boiler hearth through a coal powder pipeline to be combusted, 4-6 coal powder conveying pipelines are arranged at a powder outlet of a common medium-speed coal mill, and ideal boiler design assumes that the coal powder concentration and the nozzle speed of a combustor in the same layer are the same, so that the boiler is ensured to be in a safe and economic operation state. In the actual operation process of the boiler, because the coal powder pipelines have different directions and lengths, although the manual adjustable shrinkage cavity is adopted to adjust the pipeline resistance, the resistance between the coal powder pipes is basically leveled in a cold state, the pipeline resistance is changed during the operation with the coal powder, the distribution of the coal powder among the coal powder pipelines output by the same coal mill has certain deviation, the deviation of the coal powder concentration and the coal powder wind speed often exceeds 30%, the serious unbalance can cause the deflection of the flame center of a hearth, the difference of the heat load is obvious, the bad phenomena of over-temperature coking of a local water wall, larger left and right heat deviation of a superheater and a reheater and the like are caused, and the safety and the economical efficiency of the operation of the boiler are seriously influenced.
At present, the power test research institute adopts the manual sampling mode to measure the coal dust concentration, utilizes the sampling gun who inserts in the pipeline to carry out constant speed multiple spot sampling, carries out the manual weighing to the coal dust sample of collecting after the sample is ended, obtains the mass flow (or the coal dust concentration) of coal dust. The method has the disadvantages of large labor capacity, long testing and analyzing time, large data lag and incapability of continuous online monitoring.
The existing on-line detection method for the concentration of the pulverized coal comprises an optical method, a capacitance method, a charge method and the like, but the detection of the methods has different technical and engineering problems, so that the concentration of the pulverized coal cannot be practically measured at present.
An on-line measuring device for the concentration of coal dust in primary air of a boiler disclosed in patent CN201210027480.1 adopts an optical fiber correlation technique, an optical fiber and a receiver are both inserted into a coal dust pipeline, coal dust flows through between a transmitting end and a receiving end, and the concentration value of the coal dust is calculated according to the light intensity signal received by a photocell at the receiving end. The invention can only detect the concentration of the coal dust flowing through the optical path part of the optical fiber, and the data representativeness is poor because the concentration of the coal dust pipeline is not uniformly distributed on the whole pipeline section. And the problem that pulverized coal pollutes and shields the optical fiber emission light path exists, so that the practical engineering use is limited.
Patent CN201510627703.1 is an on-line measuring device and method for coal dust flow, the invention adopts two sets of multi-plate capacitive sensors respectively installed on the pipe walls at both sides of the coal dust pipe in the axial direction, calculates the coal dust concentration by measuring the dielectric constant change of the coal dust concentration, and measures the speed by correlation method. However, the method for measuring the concentration is easily affected by coal quality change, humidity change, coal powder granularity change, coal powder distribution unevenness and the like, and measurement accuracy has a lot of uncertainty.
Patent CN110631975A is an electrostatic method based primary air on-line concentration measurement algorithm, which adopts a set of inserted static inductance probes installed at the upstream and downstream of a pulverized coal pipeline, and obtains a pulverized coal concentration signal by calculating the effective voltage value of an induced charge signal. Because the influence of the charge quantity of the pulverized coal on the wind speed, the humidity of the pulverized coal, the fineness of the pulverized coal and a flow field exists, the concentration measurement accuracy has a lot of uncertainty. In addition, the induction range of the static induction probe mounting measuring point in the patent is relatively limited, and the detection representativeness of the static induction probe mounting measuring point is also problematic.
Disclosure of Invention
The invention aims to solve the technical problem of providing an on-line monitoring system for concentration deviation among powder conveying pipelines of a coal mill, which realizes the distribution balance of the concentration of pulverized coal among the pulverized coal pipelines and simplifies the control of the concentration balance of the pulverized coal among different pipelines of the coal mill by measuring the relative concentration deviation among the pulverized coal pipelines of the same coal mill.
The technical solution for realizing the purpose of the invention is as follows:
the utility model provides an on-line monitoring system of coal pulverizer powder conveying pipeline concentration deviation, including a plurality of online constant speed buggy sample measuring device and system measurement control unit, online constant speed buggy sample measuring device installs respectively on a plurality of buggy pipelines of same coal pulverizer export, and online constant speed buggy sample measuring device links to each other with system measurement control unit through control signal line respectively, system measurement control unit includes intelligent treater and display element, be used for carrying out logic time sequence control and measuring signal's processing and conveying to online constant speed buggy sample measuring device.
Furthermore, the on-line constant-speed coal powder sampling and measuring device comprises a coal powder sampling gun, a cyclone separator, an air extractor, a sampling container, a coal powder pipeline flow velocity measuring instrument, a sampling flow velocity measuring instrument and a powder amount measuring instrument, wherein the coal powder sampling gun is a hollow pipeline and is installed on the coal powder pipeline through a sealing installation seat, the coal powder sampling gun penetrates through the sealing installation seat, one end of the coal powder sampling gun extends into the coal powder pipeline, and the other end of the coal powder sampling gun is communicated with an a port of a three-way switching valve; the port b of the three-way switching valve is communicated with an inlet of the cyclone separator through an inlet pipeline of the cyclone separator, a sampling flow velocity measuring instrument is installed on the inlet pipeline of the cyclone separator, and the port c of the three-way switching valve is communicated with a compressed air source pipeline; the upper port of the cyclone separator is connected with the negative pressure port of the air extractor through an air-entraining pipe, the injection port of the air extractor is communicated with a pulverized coal pipeline, and the control port of the air extractor is communicated with a compressed air source pipeline through an electric proportional valve; the lower port of the cyclone separator is communicated with a powder falling port of the sampling container, and the bottom port of the sampling container is communicated with a compressed air source pipeline; the powder quantity measuring instrument is arranged on the sampling container; the pulverized coal pipeline flow velocity measuring instrument is arranged on the pipe wall of the pulverized coal pipeline.
Furthermore, in the on-line monitoring system for concentration deviation between the coal mill coal conveying pipelines, the coal powder sampling gun adopts a constant-speed sampling suction type coal powder sampling instrument.
Furthermore, according to the on-line monitoring system for concentration deviation between the coal mill coal conveying pipelines, the coal powder sampling gun adopts a foldable constant-section automatic coal powder sampling instrument.
Furthermore, in the on-line monitoring system for concentration deviation between the pulverized coal conveying pipelines of the coal mill, a pulverized coal return valve is arranged on a connecting pipeline between the air extractor and the pulverized coal pipelines.
Furthermore, in the on-line monitoring system for concentration deviation between the coal mill powder conveying pipelines, the powder return valve is communicated with the coal powder pipeline through the powder return pipe.
Furthermore, in the on-line monitoring system for concentration deviation between the coal mill powder conveying pipelines, a back-flushing valve is arranged on a connecting pipeline between the port c of the three-way switching valve and the compressed air source pipeline.
Furthermore, according to the on-line monitoring system for concentration deviation between the coal mill powder conveying pipelines, a purging valve is arranged on a connecting pipeline between the bottom port of the sampling container and the compressed air source pipeline.
An online monitoring method for concentration deviation among the powder conveying pipelines of the coal mill comprises the following steps:
the system measurement control unit simultaneously starts a plurality of online constant-speed coal powder sampling and measuring devices on a coal powder pipeline at the outlet of the coal mill, the online constant-speed coal powder sampling and measuring devices perform coal powder sampling in the same time period, and measure the coal powder flow rate in the coal powder pipeline in real time;
after sampling is finished, calculating the relative concentration and the average concentration of the pulverized coal of each pulverized coal pipeline according to the pulverized coal amount and the average sampling flow rate obtained by a sampling container of the on-line constant-speed pulverized coal sampling and measuring device, and calculating the concentration deviation between the pulverized coal pipelines according to the relative concentration and the average concentration of the pulverized coal;
the system measurement control unit controls the action of the adjusting mechanism of the coal mill according to the concentration deviation among the pulverized coal pipelines, and adjusts the concentration balance among different pulverized coal pipelines to be consistent.
Furthermore, the on-line monitoring method for the concentration deviation between the coal mill coal conveying pipelines of the invention comprises the following steps of:
step 1-reverse purging: opening a back-flushing valve, performing back-flushing on each coal powder sampling gun by using compressed air, and closing the back-flushing valve after a certain time;
step 2-start sampling: opening a port a and a port b of a powder return valve, an electric proportional valve and a three-way switching valve in sequence, sampling from a coal powder pipeline by a coal powder sampling gun, pumping into a cyclone separator for gas-powder separation, and dropping a coal powder sample into a sampling container;
step 3-constant sampling: the pulverized coal sampling method comprises the following steps that a pulverized coal pipe flow velocity measuring instrument measures pulverized coal flow velocity in a pulverized coal pipeline, a sampling flow velocity measuring instrument measures sampling flow velocity of a pulverized coal sampling gun, output air pressure of an electric proportional valve is controlled according to a velocity difference signal of the pulverized coal flow velocity and the sampling flow velocity, the pulverized coal flow velocity and the sampling flow velocity are adjusted to be consistent, constant-velocity sampling is achieved, and sampling average flow velocity v of the pulverized coal sampling gun in the period of sampling time is calculated;
step 4-end sampling: after the set sampling time is over, opening the port a and the port c of the three-way switching valve, closing the electric proportional valve, and finally closing the powder return valve;
step 5-powder quantity measurement: the powder quantity measuring instrument measures the quantity m of the coal powder in the sampling container;
step 6-calculate relative concentration: the relative concentration value is eta which is m/v;
step 7-emptying pulverized coal: and opening a powder return valve and a blow-down valve, blowing the pulverized coal in the sampling container into a pulverized coal pipeline by utilizing compressed air, emptying the sampling container, and closing the blow-down valve and the powder return valve in sequence after a certain time.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. the on-line monitoring system for the concentration deviation between the coal powder conveying pipelines of the coal mill does not need to actually measure the actual concentration in the coal powder pipelines, but only needs to measure the relative concentration deviation between each coal powder pipeline, so that the distribution balance of the coal powder concentration among the coal powder pipelines can be realized, and the problem of the balanced control of the coal powder concentration among different pipelines of the coal mill is simplified.
2. The on-line monitoring system for concentration deviation between the powder conveying pipelines of the coal mill has a simple structure, is convenient to use, and can be directly suitable for most of the existing coal mills.
Drawings
Fig. 1 is a schematic structural diagram of an online constant-velocity pulverized coal sampling and measuring device according to the present invention.
Fig. 2 is a schematic structural diagram of an online monitoring system for concentration deviation between coal pulverizer powder conveying pipelines in embodiment 1 of the present invention.
Fig. 3 is a flowchart of an online monitoring method for concentration deviation between powder conveying pipes of a coal mill according to embodiment 1 of the present invention.
Reference signs mean: the coal powder sampling device comprises a coal powder pipeline 1, a coal powder sampling gun 2, a sealing mounting seat 3, a three-way switching valve 4, a cyclone separator inlet pipeline 5, a cyclone separator 6, a sampling container 7, an air bleed pipe 8, an air extractor 9, a powder return valve 10, a powder return pipe 11, an electric proportional valve 12, a purge valve 13, a blowback valve 14, a powder pipe flow rate measuring instrument 15, a sampling flow rate measuring instrument 16, a powder amount measuring instrument 17, a powder amount measuring instrument 101-1, a powder pipe powder amount measuring instrument 102-2, a powder pipe powder amount measuring instrument 103-3, a powder pipe powder amount measuring instrument 104-4, a system measurement control unit 105 and a coal mill 106.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In order to solve the defects of the existing coal powder concentration detection method, the invention changes the traditional measuring thought, and does not directly measure the absolute coal powder concentration value of each pipeline but measures the relative concentration. Because the purpose of detecting the coal powder concentration is to control the adjusting mechanism to realize the concentration balance among the coal powder pipelines, if the relative concentration values of different coal powder pipelines are known, the concentration deviation among different coal powder pipelines can be calculated, and the concentration adjusting mechanism is controlled by the deviation value to realize the coal powder concentration distribution balance among the coal powder pipelines.
Therefore, the invention adopts the technical scheme that the online constant-speed coal powder sampling and measuring devices are simultaneously arranged on a plurality of coal powder pipes at the outlet of one coal mill, the obtained coal powder quantity can truly represent the mass flow of the coal powder in the pipeline, the relative concentration is obtained after the air-powder flow velocity correction calculation is carried out on the coal powder quantity obtained by sampling, and the concentration deviation among the coal powder pipes is obtained by comparing and calculating the relative concentration of each coal powder pipeline. The concentration deviation value is used for controlling an actuating mechanism to adjust the distribution of the coal powder output by the coal mill, so that the coal powder concentration balance among all coal powder pipelines can be realized.
Example 1
The utility model provides an on-line monitoring system of coal pulverizer powder conveying pipeline concentration deviation, including 4 online constant speed buggy sample measuring device and system measurement control unit, online constant speed buggy sample measuring device installs respectively on a plurality of buggy pipelines 1 of same coal pulverizer export, and online constant speed buggy sample measuring device links to each other with system measurement control unit through control signal line respectively, system measurement control unit includes intelligent treater and display element, be used for carrying out logic time sequence control and measuring signal's processing and conveying to online constant speed buggy sample measuring device. As shown in fig. 2, 4 pulverized coal pipelines, namely, a pulverized coal pipe # 1, a pulverized coal pipe # 2, a pulverized coal pipe # 3 and a pulverized coal pipe # 4 are arranged at an outlet of one coal mill 106, pulverized coal sampling and measuring devices 101 to 104 are respectively installed on the 4 pulverized coal pipelines, and the pulverized coal sampling and measuring devices 101 to 104 are respectively connected with a system measurement control unit 105 through control signal lines.
As shown in fig. 1, the on-line constant-speed coal powder sampling and measuring device includes a coal powder sampling gun 2, a cyclone separator 6, an air extractor 9, a sampling container 7, a coal powder pipeline flow velocity measuring instrument 15, a sampling flow velocity measuring instrument 16 and a powder amount measuring instrument 17. Wherein, buggy sampling gun 2 is hollow structure's pipeline, and buggy sampling gun 2 adopts the suction formula buggy sample appearance of constant speed sample, but preferred folding automatic buggy sample appearance of uniform cross-section. The foldable equal-section automatic Coal powder Sampling instrument refers to an equal-section circular rotation Sampling mode specified in the international standard of ISO9931 Coal-Sampling of sampled Coal-based controlled by gases in direct fixed Coal-based systems, and constantly monitors the Sampling flow rate and the flow rate in a Coal powder pipeline to realize constant-speed Sampling, thereby ensuring the Sampling representativeness and preventing the abrasion problem of the Coal powder Sampling gun in long-term operation.
Buggy sampling gun 2 passes through sealed mount pad 3 to be installed on buggy pipeline 1, and buggy sampling gun 2 runs through sealed mount pad 3, and in buggy sampling gun 2's one end stretched into buggy pipeline 1, the other end and tee bend switching valve 4's a port intercommunication. The port b of the three-way switching valve 4 is communicated with the inlet of the cyclone separator 6 through a cyclone separator inlet pipeline 5, a sampling flow velocity measuring instrument 16 is installed on the cyclone separator inlet pipeline 5, and the port c of the three-way switching valve 4 is communicated with a compressed air source pipeline through a back flushing valve 14. The port a of the three-way switching valve 4 is a common port, and the port a is communicated with the port c when the sampling is not performed, and the port a is communicated with the port b when the sampling is performed.
An upper port of the cyclone separator 6 is connected with a negative pressure port of the air extractor 9 through the air-entraining pipe 8, an injection port of the air extractor 9 is communicated with the pulverized coal pipeline 1 through the pulverized coal return valve 10, and the pulverized coal return valve 10 is communicated with the pulverized coal pipeline 1 through the pulverized coal return pipe 11. The control port of the air ejector 9 is communicated with a compressed air source pipeline through an electric proportional valve 12. The lower port of the cyclone separator 6 is communicated with a powder falling port of the sampling container 7, and the bottom port of the sampling container 7 is communicated with a compressed air source pipeline through a purging valve 13.
The powder amount measuring instrument 17 is mounted on the sampling container 7. The pulverized coal pipeline flow velocity measuring instrument 15 is installed on the pipe wall of the pulverized coal pipeline 1.
An on-line monitoring method for concentration deviation between powder conveying pipelines of a coal mill is shown in fig. 3 and comprises the following steps:
the system measurement control unit 105 simultaneously starts the online constant-speed coal powder sampling and measuring devices 101-104 on coal mill outlets # 1 to #4 coal powder pipelines 1, so that the 4 online constant-speed coal powder sampling and measuring devices perform coal powder sampling in the same time period and measure the coal powder flow rate in the coal powder pipelines in real time;
after sampling is finished, the coal dust relative concentration eta 1, eta 2, eta 3, eta 4 and the coal dust average concentration eta are calculated according to the coal dust amount m 1-m 4 and the sampling average flow velocity v 1-v 4 obtained by the sampling containers 7 of the 4 on-line constant-speed coal dust sampling and measuring devicesAverage，ηAverageAnd (eta 1+ eta 2+ n3+ n4)/4, calculating the concentration deviation between coal powder pipelines according to the relative concentration of the coal powder and the average concentration of the coal powder: etaDeviation of＝ηi-ηAverage；i＝1、2、3、4；
The system measurement control unit 105 measures the concentration deviation eta between the pulverized coal pipes 1Deviation ofThe adjusting mechanism of the coal mill is controlled to act, and the concentration balance among different pulverized coal pipelines is adjusted to be consistent.
It can be seen that the method does not need to actually measure the actual concentration in the pulverized coal pipes, but only needs to measure the relative concentration deviation between each pulverized coal pipe, thereby simplifying the difficulty of pulverized coal concentration balance control between different pipes of the coal mill, and fig. 3 is a flow chart of concentration deviation measurement and balance control of 4 pulverized coal pipes of the coal mill.
The sampling of the online constant-speed pulverized coal sampling and measuring device in one sampling and measuring period comprises the following steps:
step 1-reverse purging: opening a back-flushing valve 14, performing back-flushing on each coal powder sampling gun 2 by using compressed air, and closing the back-flushing valve 14 after a certain time;
step 2-start of sampling: opening a port a and a port b of a powder return valve 10, an electric proportional valve 12 and a three-way switching valve 4 in sequence, sampling from a coal powder pipeline 1 by a coal powder sampling gun 2, pumping into a cyclone separator 6 for gas-powder separation, and dropping a coal powder sample into a sampling container 7;
step 3-constant sampling: the pulverized coal flow velocity measuring instrument 15 measures the pulverized coal flow velocity in the pulverized coal pipeline 1, the sampling flow velocity measuring instrument 16 measures the sampling flow velocity of the pulverized coal sampling gun 2, the output air pressure of the electric proportional valve 12 is controlled according to the velocity difference signal of the pulverized coal flow velocity and the sampling flow velocity, the pulverized coal flow velocity and the sampling flow velocity are adjusted to be consistent, therefore, constant-velocity sampling is achieved, and the sampling average flow velocity v of the pulverized coal sampling gun 2 in the period of sampling time is calculated;
step 4-end sampling: after the set sampling time is over, opening the port a and the port c of the three-way switching valve 4, closing the electric proportional valve 12, and finally closing the powder return valve 10;
step 5-powder quantity measurement: the powder amount measuring instrument 17 measures the amount m of the pulverized coal in the sampling container 7;
step 6-calculate relative concentration: the relative concentration value is eta which is m/v;
step 7-emptying pulverized coal: and opening the powder return valve 10 and the blow-down valve 13, blowing the pulverized coal in the sampling container 7 into the pulverized coal pipeline 1 by utilizing compressed air, emptying the sampling container 7, and closing the blow-down valve 13 and the powder return valve 10 in sequence after a certain time. At this point, one sample measurement cycle is complete. And setting a full-use interval period according to a program, and carrying out the next measurement period by the system.
The foregoing is directed to embodiments of the present invention and, more particularly, to a method and apparatus for controlling a power converter in a power converter, including a power converter, a power.
Claims (10)
1. The utility model provides an on-line monitoring system of concentration deviation between coal pulverizer powder conveying pipeline, a serial communication port, including a plurality of online constant speed buggy sample measuring device and system measurement control unit, online constant speed buggy sample measuring device installs respectively on a plurality of buggy pipelines (1) of same coal pulverizer export, and online constant speed buggy sample measuring device links to each other with system measurement control unit through the control signal line respectively, system measurement control unit includes intelligent processor and display element, be used for carrying out logic time sequence control and measuring signal's processing and conveying to online constant speed buggy sample measuring device.
2. The on-line monitoring system for the concentration deviation between the coal pulverizer coal conveying pipelines according to claim 1, wherein the on-line constant-speed coal powder sampling and measuring device comprises a coal powder sampling gun (2), a cyclone separator (6), an air extractor (9), a sampling container (7), a coal powder pipeline flow velocity measuring instrument (15), a sampling flow velocity measuring instrument (16) and a powder amount measuring instrument (17), wherein the coal powder sampling gun (2) is a pipeline with a hollow structure, the coal powder sampling gun (2) is installed on the coal powder pipeline (1) through a sealing installation seat (3), the coal powder sampling gun (2) penetrates through the sealing installation seat (3), one end of the coal powder sampling gun (2) extends into the coal powder pipeline (1), and the other end of the coal powder sampling gun is communicated with an a port of a three-way switching valve (4); the port b of the three-way switching valve (4) is communicated with the inlet of the cyclone separator (6) through a cyclone separator inlet pipeline (5), a sampling flow velocity measuring instrument (16) is installed on the cyclone separator inlet pipeline (5), and the port c of the three-way switching valve (4) is communicated with a compressed air source pipeline; an upper port of the cyclone separator (6) is connected with a negative pressure port of the air extractor (9) through an air-entraining pipe (8), an injection port of the air extractor (9) is communicated with the pulverized coal pipeline (1), and a control port of the air extractor (9) is communicated with a compressed air source pipeline through an electric proportional valve (12); the lower port of the cyclone separator (6) is communicated with a powder falling port of the sampling container (7), and the bottom port of the sampling container (7) is communicated with a compressed air source pipeline; the powder amount measuring instrument (17) is arranged on the sampling container (7); the pulverized coal pipeline flow velocity measuring instrument (15) is arranged on the pipe wall of the pulverized coal pipeline (1).
3. The on-line monitoring system for concentration deviation between coal pulverizer coal conveying pipelines according to claim 2, characterized in that the coal powder sampling gun (2) adopts a constant-speed sampling suction type coal powder sampling instrument.
4. The on-line monitoring system for concentration deviation between the coal pulverizer coal conveying pipelines according to claim 2 or 3, characterized in that the coal powder sampling gun (2) adopts a foldable constant-section automatic coal powder sampling instrument.
5. The on-line monitoring system for concentration deviation between coal pulverizer powder conveying pipelines according to claim 2, characterized in that a powder return valve (10) is arranged on a connecting pipeline between the air ejector (9) and the coal pulverizer powder pipeline (1).
6. The on-line monitoring system for concentration deviation between coal pulverizer powder conveying pipelines according to claim 5, characterized in that the powder return valve (10) is communicated with the coal powder pipeline (1) through a powder return pipe (11).
7. The on-line monitoring system for concentration deviation between the coal pulverizer coal conveying pipelines according to claim 2, wherein a back-flushing valve (14) is arranged on a connecting pipeline between the c port of the three-way switching valve (4) and the compressed air source pipeline.
8. The on-line monitoring system for concentration deviation between coal pulverizer powder conveying pipelines according to claim 2, characterized in that a purge valve (13) is arranged on a connecting pipeline between a bottom port of the sampling container (7) and a compressed air source pipeline.
9. An on-line monitoring method for concentration deviation between powder conveying pipelines of a coal mill based on any one of claims 1 to 8, which is characterized by comprising the following steps:
the system measurement control unit simultaneously starts a plurality of online constant-speed coal powder sampling and measuring devices on a coal powder pipeline (1) at the outlet of the coal mill, the online constant-speed coal powder sampling and measuring devices sample coal powder in the same time period and measure the flow rate of the coal powder in the coal powder pipeline in real time;
after sampling is finished, calculating the relative concentration and the average concentration of the pulverized coal of each pulverized coal pipeline according to the pulverized coal amount and the average sampling flow rate obtained by a sampling container (7) of the on-line constant-speed pulverized coal sampling and measuring device, and calculating the concentration deviation between the pulverized coal pipelines according to the relative concentration and the average concentration of the pulverized coal;
the system measurement control unit controls the action of the adjusting mechanism of the coal mill according to the concentration deviation among the pulverized coal pipelines, and adjusts the concentration balance among different pulverized coal pipelines to be consistent.
10. The on-line monitoring method for concentration deviation between coal pulverizer coal conveying pipelines according to claim 9, wherein the sampling of the on-line constant-speed coal powder sampling and measuring device in one sampling and measuring period comprises the following steps:
step 1-reverse purging: opening a back-flushing valve (14), performing back-flushing on each coal powder sampling gun (2) by using compressed air, and closing the back-flushing valve (14) after a certain time;
step 2-start sampling: opening a port a and a port b of a powder return valve (10), an electric proportional valve (12) and a three-way switching valve (4) in sequence, sampling from a coal powder pipeline (1) by a coal powder sampling gun (2), pumping into a cyclone separator (6) for gas-powder separation, and dropping a coal powder sample into a sampling container (7);
step 3-constant sampling: a powder pipe flow velocity measuring instrument (15) measures the coal powder flow velocity in the coal powder pipeline (1), a sampling flow velocity measuring instrument (16) measures the sampling flow velocity of the coal powder sampling gun (2), the output air pressure of an electric proportional valve (12) is controlled according to the velocity difference signal of the coal powder flow velocity and the sampling flow velocity, the coal powder flow velocity and the sampling flow velocity are adjusted to be consistent, so that constant-velocity sampling is realized, and the sampling average flow velocity v of the coal powder sampling gun (2) in the period of sampling time is calculated;
step 4-end sampling: after the set sampling time is over, opening a port a and a port c of the three-way switching valve (4), closing the electric proportional valve (12), and finally closing the powder return valve (10);
step 5-powder quantity measurement: the powder amount measuring instrument (17) measures the amount m of the pulverized coal in the sampling container (7);
step 6-calculate relative concentration: the relative concentration value is eta which is m/v;
step 7-emptying pulverized coal: and opening a powder return valve (10) and a blowing valve (13), blowing the pulverized coal in the sampling container (7) into the pulverized coal pipeline (1) by utilizing compressed air, emptying the sampling container (7), and closing the blowing valve (13) and the powder return valve (10) in sequence after a certain time.
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