CN101344473A - Microwave measurement system for breeze concentration of power station boiler - Google Patents
Microwave measurement system for breeze concentration of power station boiler Download PDFInfo
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- CN101344473A CN101344473A CNA2007100250187A CN200710025018A CN101344473A CN 101344473 A CN101344473 A CN 101344473A CN A2007100250187 A CNA2007100250187 A CN A2007100250187A CN 200710025018 A CN200710025018 A CN 200710025018A CN 101344473 A CN101344473 A CN 101344473A
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Abstract
The invention discloses a microwave measuring system of pulverized coal concentration of an electric station boiler, which comprises a coal transmission pipe and an emitter and a receiver that are arranged at two sides of the coal transmission pipe and positioned along the radial direction in a staggered way, thus leading the transmission direction of a microwave signal emitted by the emitter and the flowing direction of pulverized coals in the coal transmission pipe to form an offset angle; according to the one-to-one correspondence between voltage difference and the pulverized coal concentration in the coal transmission pipe, the emitter and the receiver determine the pulverized coal concentration value corresponding to the pressure difference. The microwave measuring system of the pulverized coal concentration of the electric station boiler leads the emitting and receiving devices to be obliquely arranged at two sides of the coal transmission pipe, and the microwave signal is received by a certain offset angle with the flowing direction of the pulverized coals in the pipe, thus adding a measuring travel, enlarging the absorptive attenuating action of the pulverized coals to the microwave, increasing the measured voltage difference, avoiding the problems of the reflection measurement, and accurately measuring the pulverized coal concentration value; through the method that measures a voltage difference signal, the microwave measuring system of the pulverized coal concentration of the electric station boiler effectively solves the problem of inconsistent measured results and can accurately measure the pulverized coal concentration value.
Description
One technical field
The invention belongs to the microwave measurement system of multiphase flow measurement technology, particularly power boiler breeze concentration.
Two background technologies
In the operational process of boiler of power plant, the homogeneity of wind of coal burner and coal dust amount (being coal powder density) plays an important role to the safety and economic operation of boiler.Keeping suitable coal powder density is to set up the good furnace air power regime and the necessary condition of smooth combustion, many scholars both domestic and external were doing a large amount of research aspect the measurement of coal powder density, current measuring methods mainly is divided into direct method and indirect method, and indirect method comprises: resistance pressure differential method, energy method, temperature method, heat balance method of; Direct method comprises: optics fluctuation method, laser method, capacitance method and supercritical ultrasonics technology.These measuring methods have than big-difference on measuring principle, applicability, reliability, reaction velocity, system complex degree.
A topmost measurement defective of indirect measurement method be exactly its measured parameter be not coal powder density, but by measure other parameter such as temperature, pressure waits and reflects concentration indirectly, thereby also just cause these methods to be subjected to the influence of other factors a lot, as: the layout of the burner of boiler, burner hearth inner structure, on every side environment temperature etc., so the unusual difficulty of the accurate measurement that wants to realize coal powder density by indirect measurement method.
Though there is not the intrinsic shortcoming of the indirect method of measurement in the direct method of measurement, also there is serious defective separately in the above-mentioned direct method of measurement, and application prospect is not very extensive.Imbody is as follows:
The measuring accuracy of optics fluctuation method is influenced by the diameter of the structure of fibre-optical probe, measured particulate, the height of coal powder density mainly, whether probe the contaminated accuracy that also directly has influence on measurement, instrument exists the price height, checks difficult, the difficult problem of Operation and Maintenance simultaneously, and therefore promoting in factory uses has bigger difficulty; The checkout area of capacitance method belongs to " soft ", its intrinsic sensitivity profile non-uniformity problem is arranged, make measurement result not only relevant with coal powder density, and be subjected to the influence of coal dust distribution and variations in flow patterns very big, measuring error is bigger, this is very limited capacitance method in the pipeline powder coal measurement of concetration, can only be used to measure the pulverized coal flow of low concentration; So the probe of laser method is subjected to coal dust to pollute this method because of used by the rare power plant of factor affecting such as working environment and equipment manufacturing cost easily.
And microwave measuring method belongs to direct method of measurement category as a kind of novel coal powder density mensuration, does not have the defective of the indirect method of measurement, and it is also influenced by many extra factors unlike other several direct measuring method in addition.For microwave measurement system, using maximum at present is to adopt probe to receive and emitter as signal, also has to adopt electromagnetic horn as R-T unit.But the measuring system of these two kinds of R-T units all has certain limitation, can accurately not measure the coal powder density value.
When adopting probe as sender unit, probe need be inserted in the coal chute, this can cause measurement and have a strong impact on, can accurately not record the coal powder density value, the probe because the pulverized coal flow in the one side coal chute can wear and tear influences measurement result, also can cause probe to change frequently simultaneously; Pulverized coal flow in the opposing party's facial canal can form the periptery in probe tip, produces than great fluctuation process when causing the microwave signal transmission by coal chute, also can affect greatly measuring.Adopt the microwave system of electromagnetic horn, in the design of system, have bigger difference as R-T unit; And to neither be quite reasonable in the processing of microwave signal, bigger variation also can take place in its measurement result under same measuring condition even cause, and can not effectively measure the coal powder density value.
At present, the microwave measurement system of power boiler breeze concentration generally adopts electromagnetic horn (or probe) to transmit and receive device as signal, and its different modes of emplacement can make the measurement result of microwave system differ greatly.The probe commonly used at present and the modes of emplacement of electromagnetic horn have two kinds: place in coal chute both sides equity (1), and microwave signal is received perpendicular to the direction that coal dust in the pipe flows; (2) place at the coal chute homonymy, microwave signal is received after tube wall reflection several times.The microwave system of these two kinds of modes of emplacements all has certain problem when carrying out the coal powder density on-line measurement, can't implement accurately to measure.
A kind of microwave system of modes of emplacement before adopting, because its measurement is shorter along journey, the coal dust amount in the measuring section is less, thus also less to the attenuation by absorption of microwave signal, make that the magnitude of voltage before and after the decay changes less.This less voltage difference sometimes can't be measured, therefore also just can't determine the coal powder density value.
Adopt the microwave system of a kind of modes of emplacement in back, because microwave signal has a reflection process on tube wall, measurement is longer along journey, coal dust amount in the measuring section is bigger, so the attenuation by absorption to microwave is also bigger, make the magnitude of voltage before and after the decay change greatly, voltage difference in this case is more measured.But because coal chute is a pipe, when microwave reflex time on tube wall, having greatly microwave signal is reflected to and can't be received device on other directions and receives, magnitude of voltage before and after this also can cause decaying changes, so the voltage difference that this system records is not only to be caused by the attenuation by absorption of coal dust in the pipe to microwave, also comprise because of a part of microwave signal is reflected causing, therefore can not determine the coal powder density value with its voltage difference that records.
In addition, microwave transmits and receives device and generally all realizes by electromagnetic horn or probe, and it is outer that electromagnetic horn is placed on coal chute, and probe is placed in the pipe.What flow in the coal chute is coal dust and AIR MIXTURES, and coal dust is the structure of a kind of many porosities of surface grain, has stronger clinging power, is easier to be attached to the inside pipe wall face.And the primary air velocity in the pipe is higher, generally more than 15m/s, this higher wind speed is the continuous scavenging duct internal face of meeting in the process of pulverized coal conveying, make the coal dust that is attached on the wall be unlikely to too much, but be attached on coal dust on the tube wall face owing to can not purge all fully, remaining in this a part of coal dust of tube wall can exert an influence to microwave measurement, can increase measuring error.
Three summary of the invention
The object of the present invention is to provide a kind of microwave measurement system of power boiler breeze concentration, this system can improve the measuring voltage difference, reduces measuring error, has effectively eliminated the influence of the sticking coal dust of tube wall simultaneously, improve measuring accuracy, realize the accurate measurement of coal powder density.
Realize that the object of the invention technical solution is: a kind of microwave measurement system of power boiler breeze concentration, comprise coal chute, transmitter and receiver are arranged on the coal chute both sides, and radially arranged in dislocation so that the interior coal dust flow direction of the microwave signal transmission direction of transmitter emission and coal chute becomes the drift angle.
The microwave signal transmission direction and the bias angle theta between the coal dust flow direction of the transmitter emission of the microwave measurement system of power boiler breeze concentration of the present invention are 30 °～60 °.
The microwave oscillator of the microwave measurement system of power boiler breeze concentration of the present invention, merit divide meter and transmitter to constitute emitter, and receiving trap comprises measuring-signal receiving trap and reference signal receiving trap, the measuring-signal receiving trap comprises receiver, first detector, first dc amplification circuit and first low-pass filter, and the reference signal receiving trap comprises second detector, second dc amplification circuit, second low-pass filter and difference discharge road; Described coal chute both sides are provided with transmitter and receiver, the microwave signal that microwave oscillator produces is input to merit and divides meter behind isolator filtering noise signal, this microwave signal is divided into the identical signal of two bundles, and a branch of conduct is with reference to signal, another Shu Zuowei measuring-signal; This measuring-signal is transmitted into coal chute by transmitter, be received by the receiver after coal dust in the pipe absorption generation decay, and be transferred on the first detector microwave attenuation signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming by first dc amplification circuit amplifies, and is transferred in the difference channel behind the first low pass filter filters out low frequency signal again; Described reference signal directly is transferred on the second detector microwave signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming through second dc amplification circuit amplifies, behind the second low pass filter filters out low frequency signal, be transferred in the difference channel again; Reference signal and measuring-signal produce voltage difference in difference channel, have one-to-one relationship between the coal powder density in this voltage difference and the coal chute, and measure in the voltage measurement end, thereby determine and the corresponding coal powder density value of voltage difference.
The transmitter of the microwave measurement system of power boiler breeze concentration of the present invention and receiver radially shift to install in coal chute both sides formation measured zone, near perforate on the coal chute of this measured zone spout is being set, pressurized air purges the coal chute tube wall of measured zone by this spout, and the mobile direction of compressed-air actuated purging direction and the coal dust in the coal chute is identical.
The present invention compared with prior art, its remarkable advantage is: (1) changes the arrangement of traditional microwave signal receiving/transmission device, R-T unit is in tilted layout in the coal chute both sides, microwave signal becomes certain drift angle to be received with the interior coal dust flow direction of pipe, thereby increased measurement along journey, made full use of the dobla effect, increased the attenuation by absorption effect of coal dust to microwave, thereby increased the voltage difference of measuring, and the problem that occurs when having avoided adopting reflection measurement, the coal powder density value can accurately be measured, the on-line measurement of power boiler breeze concentration can be effectively be used for.(2) utilize the absorption of coal dust to microwave, select for use electromagnetic horn as the microwave signal R-T unit, in conjunction with microwave launcher and receiving trap, the microwave attenuation signal is converted into the voltage difference signal, determine the coal powder density value by the measuring voltage difference, the problem that has existed when having avoided adopting probe measurement; By the method for measuring voltage difference signal, effectively solved the inconsistent problem of measurement result, can measure the coal powder density value accurately.(3) on coal chute, open two holes spout is installed, in pipe, add the compression air by spout, the coal dust that the scavenging duct wall sticks, compressed-air actuated purging direction is identical with the coal dust flow direction, velocity of compressed air is greater than primary air velocity, thereby eliminate the influence that tube wall glues coal dust, improved the precision of microwave measurement.(4) simple in structure, have easy for installation, measure smart high, real-time is good, can effectively be used for the on-line measurement of coal powder density.
Below in conjunction with accompanying drawing the present invention is described in further detail.
Four description of drawings
Fig. 1 is the structural representation of the microwave measurement system of power boiler breeze concentration of the present invention.
Fig. 2 is that the difference voltage of microwave measurement system of power boiler breeze concentration of the present invention is with the change curve of coal powder density.
Five embodiments
In conjunction with Fig. 1, the microwave measurement system of power boiler breeze concentration of the present invention, comprise coal chute 14, transmitter 4 and receiver 5 are arranged on coal chute 14 both sides, and radially arranged in dislocation is so that the microwave signal transmission direction of transmitter 4 emission and coal chute 14 interior coal dust 17 flow directions become bias angle theta, and this bias angle theta is preferably 30 °～60 ° most.Transmitter 4 and receiver 5 can be probe or electromagnetic horn, if transmitter 4 and receiver 5 are arranged on the inboard of coal chute 14 during for probe, if transmitter 4 and receiver 5 are arranged on the outside of coal chute 14 during for electromagnetic horn.When transmitter 4 and receiver 5 are electromagnetic horn, in order to eliminate the absorption of tube wall, be arranged at transmitter 4 and receiver 5 that perforate is provided with two teflon flat boards on the tube wall of coal chute 14 both sides to microwave signal.
The present invention utilizes the absorption of coal dust to microwave, and design microwave launcher and receiving trap are converted into the voltage difference signal with the microwave attenuation signal, determine the coal powder density value by the measuring voltage difference.Be that microwave oscillator 1, merit divide meter 3 and transmitter 4 to constitute emitter, and receiving trap comprises measuring-signal receiving trap and reference signal receiving trap, the measuring-signal receiving trap comprises receiver 5, first detector 6, first dc amplification circuit 7 and first low-pass filter 8, and the reference signal receiving trap comprises second detector 11, second dc amplification circuit 12, second low-pass filter 13 and difference discharge road 9; Described coal chute 14 both sides are provided with transmitter 4 and receiver 5, the microwave signal that microwave oscillator 1 produces is input to merit and divides meter 3 behind isolator 2 filtering noise signals, this microwave signal is divided into the identical signal of two bundles, and a branch of conduct is with reference to signal, another Shu Zuowei measuring-signal; This measuring-signal is transmitted into coal chute 14 by transmitter 4, being received device 5 after coal dust in the pipe absorption generation decay receives, and be transferred on the first detector 6 the microwave attenuation signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming by first dc amplification circuit 7 amplifies, and is transferred in the difference channel 9 behind first low-pass filter, 8 filtering low frequency signals again; Described reference signal directly is transferred on the second detector 11 microwave signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming through second dc amplification circuit 12 amplifies, behind second low-pass filter, 13 filtering low frequency signals, be transferred in the difference channel 9 again; Reference signal and measuring-signal produce voltage difference in difference channel 9, have one-to-one relationship between the coal powder density in this voltage difference and the coal chute, and measure in voltage measurement end 10, thereby determine and the corresponding coal powder density value of voltage difference.Therefore, when carrying out breeze concentration microwave measurement, calibrate the change curve of voltage difference in advance, and set up a database for this curve with coal powder density at the boiler scene.In the measuring process afterwards, the voltage difference that records is input in the database automatically, can finds out coal powder density value corresponding under this difference, finish total measuring process.
In order to eliminate the influence of the sticking coal dust 17 of tube wall, transmitter 4 and receiver 5 radially shift to install in coal chute 14 both sides formation measured zone 15, near perforate on the coal chute 14 of this measured zone 15 spout 16 is being set, pressurized air 18 purges the coal chute tube wall of measured zone 15 by this spout 16, and the mobile direction of coal dust in the purging direction of pressurized air 18 and the coal chute 14 17 is identical.In the measuring process of the coal dust 17 in coal chute 14, pass through a side measured zone 15 by the microwave signal transmission of transmitter 4 emissions, absorbed by coal dust 17, the measured zone of passing opposite side again is received.Pressurized air 18 is to add by the spout 16 that is installed on the coal chute 14, and purges the measurement zone tube wall, and the direction that coal dust 17 flowed in it purged direction and manages is identical, prevents that the coal dust 17 that flows from stopping up spout.The size of spout 16 is decided according to the width of measured zone, and basic demand is the inner tubal wall that can purge measured zone 15 from the pressurized air 18 of spout 16 spirts fully, and the flow velocity of pressurized air 18 is greater than primary air velocity.
In a word, the microwave measurement system of power boiler breeze concentration of the present invention is to utilize coal dust that the absorption of microwave is developed.Microwave signal is divided into the identical signal (measuring-signal and reference signal) of two bundles.Measuring-signal absorbs the back through coal dust and produces decay.Reference signal is not absorbed by coal dust 17, and the measuring-signal preceding with decay has identical magnitude of voltage.Then the voltage difference between reference signal and the measuring-signal promptly is the voltage change before and after measuring-signal is absorbed by coal dust, has one-to-one relationship between this changing value and the coal dust matchmaker powder concentration, promptly can be used to determine the coal powder density value by the measuring voltage difference.Adopting transmitter 4 and receiver 5 dislocation to place, is in order to increase measurement along journey, to produce the dobla effect, increase the measuring voltage value, improving measuring accuracy.It is in order to eliminate the influence of the sticking coal dust of tube wall, to reduce the error of microwave measurement that perforate is provided with spout 16.
In conjunction with Fig. 2, the voltage difference that utilizes four kinds of different coal dusts that the microwave measurement system of power boiler breeze concentration of the present invention records is with the coal powder density change curve, and the coal powder density among the figure changes between 0～0.8kg/kg, and is consistent with on-the-spot coal powder density scope.As seen from the figure, there is a kind of monotonous curve relation between voltage difference that microwave measurement system by power boiler breeze concentration of the present invention records and the coal powder density, when measuring at the scene, as long as with voltage difference and the contrast of this curve that records, can determine the coal powder density value, the coal powder density that therefore can effectively be used for the boiler scene is measured.
Claims (8)
1, a kind of microwave measurement system of power boiler breeze concentration, comprise coal chute [14], it is characterized in that: transmitter [4] and receiver [5] are arranged on coal chute [14] both sides, and radially arranged in dislocation so that interior coal dust [17] flow direction of the microwave signal transmission direction of transmitter [4] emission and coal chute [14] becomes the drift angle.
2, the microwave measurement system of power boiler breeze concentration according to claim 1 is characterized in that: the microwave signal transmission direction of transmitter [4] emission and the bias angle theta between coal dust [17] flow direction are 30 °～60 °.
3, the microwave measurement system of power boiler breeze concentration according to claim 1, it is characterized in that: microwave oscillator [1], merit divide meter [3] and transmitter [4] to constitute emitter, and receiving trap comprises measuring-signal receiving trap and reference signal receiving trap, the measuring-signal receiving trap comprises receiver [5], first detector [6], first dc amplification circuit [7] and first low-pass filter [8], and the reference signal receiving trap comprises second detector [11], second dc amplification circuit [12], second low-pass filter [13] and difference discharge road [9]; Described coal chute [14] both sides are provided with transmitter [4] and receiver [5], the microwave signal that microwave oscillator [1] produces is input to merit and divides meter [3] behind isolator [2] filtering noise signal, this microwave signal is divided into the identical signal of two bundles, a branch of conduct is with reference to signal, another Shu Zuowei measuring-signal; This measuring-signal is transmitted into coal chute [14] by transmitter [4], being received device [5] after coal dust in the pipe absorption generation decay receives, and be transferred to first detector [6] and go up the microwave attenuation signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming by first dc amplification circuit [7] amplifies, and is transferred in the difference channel [9] behind first low-pass filter [8] filtering low frequency signal again; Described reference signal directly is transferred to second detector [11] and upward microwave signal is converted into d. c. voltage signal, and the d. c. voltage signal after will transforming through second dc amplification circuit [12] amplifies, behind second low-pass filter [13] filtering low frequency signal, be transferred in the difference channel [9] again; Reference signal and measuring-signal produce voltage difference in difference channel [9], there is one-to-one relationship between the coal powder density in this voltage difference and the coal chute, and in voltage measurement end [10], measure, thereby determine and the corresponding coal powder density value of voltage difference.
4, according to the microwave measurement system of claim 1,2 or 3 described power boiler breeze concentrations, it is characterized in that: transmitter [4] and receiver [5] radially shift to install in coal chute [14] both sides formation measured zone [15], go up perforate at the coal chute [14] of close this measured zone [15] spout [16] is set, pressurized air [18] purges the coal chute tube wall of measured zone [15] by this spout [16], and the mobile direction of the purging direction of pressurized air [18] and the coal dust [17] in the coal chute [14] is identical.
The microwave measurement system of power boiler breeze concentration according to claim 7 is characterized in that: during for electromagnetic horn, perforate is provided with two teflon flat boards on the tube wall of coal chute [14] at transmitter [4] and receiver [5].
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| Application Number | Priority Date | Filing Date | Title |
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| CNA2007100250187A CN101344473A (en) | 2007-07-10 | 2007-07-10 | Microwave measurement system for breeze concentration of power station boiler |
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| CNA2007100250187A CN101344473A (en) | 2007-07-10 | 2007-07-10 | Microwave measurement system for breeze concentration of power station boiler |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102680370A (en) * | 2012-05-21 | 2012-09-19 | 常州市新港热电有限公司 | Pulverized coal concentration online monitoring system |
| CN105136609A (en) * | 2015-08-05 | 2015-12-09 | 中国石油天然气股份有限公司 | Method and apparatus for measuring coal bed gas well produced fluid coal powder mass percentage concentration |
-
2007
- 2007-07-10 CN CNA2007100250187A patent/CN101344473A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102680370A (en) * | 2012-05-21 | 2012-09-19 | 常州市新港热电有限公司 | Pulverized coal concentration online monitoring system |
| CN105136609A (en) * | 2015-08-05 | 2015-12-09 | 中国石油天然气股份有限公司 | Method and apparatus for measuring coal bed gas well produced fluid coal powder mass percentage concentration |
| CN105136609B (en) * | 2015-08-05 | 2018-02-02 | 中国石油天然气股份有限公司 | Measure the method and device of output liquid of coal bed methane well quality of pc percent concentration |
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Open date: 20090114 |