CN201311388Y - Coal dust concentration on-line monitoring system - Google Patents
Coal dust concentration on-line monitoring system Download PDFInfo
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- CN201311388Y CN201311388Y CNU2008201246511U CN200820124651U CN201311388Y CN 201311388 Y CN201311388 Y CN 201311388Y CN U2008201246511 U CNU2008201246511 U CN U2008201246511U CN 200820124651 U CN200820124651 U CN 200820124651U CN 201311388 Y CN201311388 Y CN 201311388Y
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Abstract
The utility model provides a coal dust concentration on-line monitoring system which is suitable for monitoring the coal dust concentration in a primary air duct in a directly-fired boiler. The monitoring system comprises a signal source, a microwave transmitter with a transmitting end, a receiving sensor with a receiving end and a signal processing unit, wherein the signal source is used for supplying reference microwave signals, the microwave transmitter with a transmitting end is connected with the signal source and is used for exciting the reference microwave signals, the receiving end is 300 to 700 mm far from the transmitting end and is used for receiving signals which are formed by weakening the reference microwave signals through air and coal dust in the air duct, and the signal processing unit is connected with the signal source and the receiving sensor and is used for receiving the weakened signals and the reference microwave signals and comparing the two kinds of signals so as to confirm the coal dust concentration in the primary air duct. The monitoring system can monitor the concentration of the coal dust in the boiler on line in real time, supplies real and accurate data for running and operating staff and is used as a basis for optimizing the combustion regulation.
Description
Technical field
The utility model relates to the energy and environmental protection field, particularly relates to a kind of coal powder density on-line monitoring system, and this coal powder density on-line monitoring system is applicable to the concentration of the coal dust in airduct in the monitoring direct blow boiler.
Background technology
An airduct refers to supply simultaneously the airduct of wind and coal dust, and secondary air channel refers to only supply the airduct of wind.Direct blow boiler refers to by wind coal dust directly is blown into the boiler of burner hearth.As one of ordinary skill in the known, in the power boiler burning process, the combustion conditions of boiler and burning efficiency are subjected to the direct influence of following factor: the interior speed (primary air velocity) of airduct, the ratio between the pulverized coal flow of each burner and wind and the coal dust.Be in operation, station boiler produces following phenomenon through regular meeting: unburned combustible in fly ash height, the inner coking of burner hearth; burner burns out and unstable combustion etc.; above phenomenon except with burner, outside the Pass chamber structure had, also primary air flow, the coal powder density with each burner had very big relation.Though excess air coefficient is adjusted in allowed limits in the burner hearth, for some or a plurality of burners, the proportioning of air quantity and powder amount is not necessarily in reasonable range.
If the coal powder density of certain burner and air quantity inequality or ratio depart from normal range, will cause rough burning, stove is imitated and is reduced, and can produce above problem; In addition,, very easily cause the plugging or the spontaneous combustion in an airduct road of boiler, may cause boiler extinguishment under the serious situation if the wind speed of an airduct and coal powder density control are improper.
Therefore adjust the air quantity of each burner and coal powder density and between ratio, to help perfect combustion, and can guarantee burner hearth inner air aerodynamic field balance and stable, control kindling point and flame central position well, avoid phenomenons such as local coking and tube wall local overheating, help improving boiler operating efficiency and reduce boiler operatiopn, maintenance cost.Adjust the wind speed of an airduct and the ratio between the coal powder density, at first will monitor it, therefore, it is very important monitoring the interior coal powder density of airduct of boiler in real time.
Although some coal powder density monitoring systems are provided in the prior art, as China Patent No. is ZL01107746.8, denomination of invention be " a kind of measuring method of coal powder density and measure and control device " patent disclosure a kind of monitoring pulverized-coal concentration measure and control device, this measure and control device is the energy equilibrium before and after mixing with coal dust according to defeated powder air-flow, and the parameter before and after mixing by measurement air-flow and coal dust is tried to achieve coal powder density.In fact, mainly monitor according to conservation of energy principle.
The shortcoming of this monitoring system has: 1, uncertain factor is too many, can only realize relative measurement, thereby precision is low; 2, longer hysteresis characteristic is arranged, cause hysteresis for the result of whole measurement, and sensitivity is reduced; 3, can't measure the part of calculating the heat energy that coal pulverizer self mechanical energy is converted into because of it can't use on direct blow boiler.
Coal powder density in the airduct that effective and efficient manner comes in real time, measures effectively, reliably direct blow boiler in service also is not provided in the prior art.Therefore, urgent wish that an a kind of coal powder density on-line monitoring system is arranged, the coal powder density in the airduct can be provided in the direct blow boiler one time in real time, directly, fast, for the operation personnel in time are optimized burning and adjustment provides foundation.
The utility model content
For this reason, the utility model provides a kind of coal powder density on-line monitoring system, and it is applicable to interior coal powder density of airduct in the monitoring direct blow boiler, and described coal powder density on-line monitoring system comprises: signal source, and it is used to provide the benchmark microwave signal; A microwave emitter that has transmitting terminal, it is arranged in the described airduct, is connected with described signal source, is used in the described benchmark microwave signal of a described airduct underexcitation; A receiving sensor that has receiving end, it is arranged in the described airduct, between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter at a distance of the distance of a 300mm-700mm, the described benchmark microwave signal that is used to receive described microwave emitter excitation in a described airduct wind and the signal after the coal dust decay; And signal processing unit, it is connected with described receiving sensor with described signal source, be used to receive the described benchmark microwave signal that signal after the described decay that described receiving sensor receives and described signal source provide, and signal after the described decay and described benchmark microwave signal compared, thereby determine the concentration of the coal dust in the described airduct.
Preferably, the microwave frequency source of described signal source for adopting Direct Digital compositor (DDS) and phaselocked loop (PLL) Direct Digital to synthesize, the degree of stability of the signal stabilization of this signal source, power and frequency can reach ten thousand/, control accuracy height, easy to control.
Preferably; described microwave emitter and described receiving sensor all have the outer protection pipe box; described outer protection pipe box is to be made by high temperature resistant, the high wear-resistant material that contains rare earth material; the microwave emitter and the receiving sensor that have such outer sleeve can use more than 4 years in airduct continuously, and having solved needs the often shortcoming of replacing in the prior art.
As known in the art, described microwave emitter has transmitting terminal, and described receiving sensor has receiving end, and described transmitting terminal and described receiving end are respectively the major parts that is used to the effect that transmits and receives in described microwave emitter and the described receiving sensor.
Preferably, a described airduct has straight length, and described microwave emitter and receiving sensor all are arranged in the straight length of a described airduct, and this is because even fluid distribution, the flow speed stability of straight length, and measurement data stability, consistance are higher.
Preferably, described microwave emitter is arranged on the upstream of described receiving sensor, the length of the straight length part of described microwave emitter upstream is more than or equal to five times of a described airduct straight length interior diameter, and the length of the straight length in described receiving sensor downstream part is more than or equal to three times of the straight length interior diameter of a described airduct, such installation site purpose also is at measurement zone stable fluid media (medium) to be arranged in order to guarantee, makes that data stability, the consistance measured are higher.
Preferably, the main transmit direction of described microwave emitter is parallel to the tube wall of a described airduct straight length; The main receive direction of described receiving sensor and the main transmit direction of described microwave emitter are perpendicular.Be in order to realize the optimization of measurement effect like this.
Preferably, between the described transmitting terminal of the described receiving end of described receiving sensor and described microwave emitter at a distance of the distance of a 400mm-600mm; More preferably, between the described transmitting terminal of the described receiving end of described receiving sensor and described microwave emitter at a distance of the distance of a 500mm.
Preferably, the length that is connected lead between described signal processing unit and the receiving sensor is no more than 60 meters, and more preferably, the length that is connected lead between described signal processing unit and the receiving sensor is no more than 50 meters.This is that it is very big that transmission range surpasses 60 meters microwave signal strength retrogression degree because the transmission of microwave signal has decay, is difficult to measure.
The beneficial effects of the utility model are: monitoring system of the present utility model can real-time online ground the concentration of coal dust in the monitoring boiler of power plant, can provide data really and accurately for the operation personnel, foundation as the optimized combustion adjustment, can improve boiler efficiency, energy-conservationly fall coal consumption, can improve the security of boiler operatiopn, disconnected powder warning, improve the equipment operation life-span.
Description of drawings
Fig. 1 is the synoptic diagram of an embodiment of the present utility model;
Fig. 2 is the synoptic diagram of coal powder density in-service monitoring of the present utility model system operation logic.
Embodiment
As used herein, term " rare earth material " means the alloy material that contains rare earth element.An example of described material is the wear-resisting Allen's metal alloy of rare earth (RPH).
Increasing scientific research and experimental results show that, the coal dust distribution of the coal powder density of burner and same each burner of layer is an important factor for the efficient of boiler, in service at boiler, each burner keeps best wind coal proportion, keep the pulverized coal flow balance of each burner, guaranteeing the uniform distribution of coal dust, is the effective way of optimized combustion.
From the thermal equilibrium of catching fire, the primary air ratio of coal burner is closely related with ignition process.Primary air ratio is big more, just many more for reaching the catch fire heat of required absorption of coal air mixture, it is also long more to reach the required time of kindling point, especially true when a wind-warm syndrome is low, but primary air velocity can not be too low simultaneously, in order to avoid too closely burner is burnt out because of catching fire.Combustion conditions depends on to a great extent whether the ratio of fuel and combustion air is suitable.Thereby, when the change of fuel, also need do corresponding adjusting to air (wind) amount.The whether suitable generation to boiler efficiency, NOx of coal powder density, unburned combustible in fly ash all has significant effects.
Whether surely the concentration of coal dust has direct influence to fire box temperature in the stove, be one of key factor that determines combustion.Suitably improve coal powder density, will help catching fire and steady combustion of coal dust.Chemical reaction results from the effective collision of each ingredient (activated molecule) that can react, and therefore, the number of times of effective collision just increases with the increase of concentration of reactants in unit volume, and course of reaction is also just rapid more.So under the identical situation of other conditions, in the finite concentration scope, chemical reaction velocity is directly proportional with concentration of reactants.Simultaneously, owing to the raising of coal powder density, improved the content of fugitive constituent in the unit volume, then the ignition temperature of coal dust descends, and ignition time in advance.But, be not that concentration is high more good more, in concrete coal, there is a concentration optimum value, show that from repeatedly development test ature of coal is poor more, optium concentration is high relatively more.During burning inferior coal, volatile matter is surrounded by grey branch in the coal dust, and the resistance that disengages increases, and the heat release process of volatile matter is delayed the latter stage to coal dust firing always, and the comparison difficulty of catching fire descends fire box temperature, ignition lag, and coal dust firing is incomplete, and burning efficiency is low.The height of coal powder density can compare from following several respects:
When coal powder density was too high, the coal dust plugging easily took place, can not be in stove pulverized coal conveying, also can cause coal powder natural in the pipe simultaneously, burn out duff pipe.Incomplete combustion, efficient is low, carbon monoxide increases, the high temperature corrosion of aggravation boiler furnace internal heating surface and superheater surface.Easily cause the local coking of burner hearth and superheater, have a strong impact on the safe operation of boiler.
Coal powder density is crossed when hanging down, and fire box temperature reduces, and the burner hearth fire extinguishing easily takes place, and boiler pressure reduces, and the boiler band is not gone up and loaded, and strengthens a wind (duff pipe) flow velocity in order to improve air pressure, can make in the burner hearth circle of contact skew burner hearth.
In station boiler, straight blown converter pulverized coal preparation system because of the length of its pipeline and complexity than in the storage stove more special, the deployment scenarios of pipeline is incomplete same, thereby causes the total drag coefficients of each arm unequal, will cause the inconsistent of wind powder mixture concentration in each airduct like this.Under these circumstances, may cause generation, the carbon rough burning of excessive NO x, the increase of thermal loss, boiler efficiency is descended; Boiler for corner tangential firing will certainly cause the deflection of the stove internal combustion circle of contact, the instability of combustion conditions, and issuable thus ash erosion, burning heat transfer deterioration, and even is forced to the generation of blowing out accident.Therefore, take effective method that the coal powder density of each airduct is carried out leveling, eliminate each airduct wind powder resistance to flow imbalance when actual motion, tool has very important significance.
At present, the resistance leveling in each airduct road of station boiler pulverized coal preparation system generally all is to adopt the pure air resistance leveling of cold conditions method, promptly under the cold conditions situation, when pure air flows through with airduct of one deck, on a less airduct of several resistances, add the suitable throttle of aperture, itself and an airduct of resistance maximum are wherein balanced each other.In fact, such resistance method of adjustment, can only guarantee that boiler combustion system is with resistance the balance under cold conditions of each airduct of one deck to burner outlet, and the resistance balance when flowing through coal air mixture in the pipe can not guarantee actual motion the time so just causes boiler each airduct apoplexy powder flow rate and concentration inconsistent when actual motion.
More than the analysis showed that the optimized combustion of boiler and adjusting is main means to adjust coal-air ratio all, after the boiler wind powder on-line monitoring system is installed, can adjust according to measurement data, can in time adjust the wind coal parameter of each airduct according to boiler design operating mode and unit load, make the proportioning of wind coal reach best, burner outlet gas velocity the best is adjusted excess air coefficient simultaneously in allowed limits for minimum, reaches the purpose of optimizing boiler combustion.Can also effectively prevent, reduce the accident rate of steam generator system, ensure the even running of boiler faults such as disconnected powder, pluggings.Can also improve environmental protection index in a large number in addition, purify power plant's ambient air.
Below in conjunction with the drawings and specific embodiments the utility model is described in further detail.
The utility model provides a kind of coal powder density on-line monitoring system, and it is applicable to interior coal powder density of airduct in the monitoring direct blow boiler, and described coal powder density on-line monitoring system comprises: signal source, and it is used to provide the benchmark microwave signal; A microwave emitter that has transmitting terminal, it is arranged in the described airduct, is connected with described signal source, is used in the described benchmark microwave signal of a described airduct underexcitation; A receiving sensor that has receiving end, it is arranged in the described airduct, between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter at a distance of the distance of a 300mm-700mm, the described benchmark microwave signal that is used to receive described microwave emitter excitation in a described airduct wind and the signal after the coal dust decay; And signal processing unit, it is connected with described receiving sensor with described signal source, be used to receive the described benchmark microwave signal that signal after the described decay that described receiving sensor receives and described signal source provide, and signal after the described decay and described benchmark microwave signal compared, thereby determine the concentration of the coal dust in the described airduct.
With reference to shown in Figure 1, it is the synoptic diagram of an embodiment of the present utility model.Described signal source is the microwave frequency source, it is used to provide the benchmark microwave signal, preferably, can adopt the synthetic microwave frequency source of Direct Digital compositor (DDS) and phaselocked loop (PLL) Direct Digital, the degree of stability of the signal stabilization in sort signal source, power and frequency can reach ten thousand/, control accuracy height, easy to control.Adopt the sort signal source, advantages such as the advanced person that also possesses skills, output signal frequency wide ranges.
Described microwave emitter; preferably; it is sensor with outer protection sleeve pipe; described outer protection sleeve pipe is by high temperature resistant; the high wear-resistant material that contains rare earth material is made; what flow in airduct is the high speed two-phase fluid; wear and tear very big to the sensor of generally making with metal; just be worn less than two months; and sensor of the present utility model, because the protective casing that uses special material to make can use under nominal situation minimum 4 years; and change simple and convenient; need not proofread again after the replacing, described microwave emitter is connected with described signal source, and the microwave signal that is used for described signal source is transmitted is at an airduct underexcitation.
Described receiving sensor; similar to described microwave emitter; preferably; it is sensor with outer protection sleeve pipe; described outer protection sleeve pipe is by high temperature resistant; the high wear-resistant material that contains rare earth material is made; what flow in airduct is the high speed two-phase fluid; wear and tear very big to the sensor of generally making with metal; just be worn less than two months; and sensor of the present utility model; because the protective casing that uses special material to make; can under nominal situation, use minimum 4 years; and change simple and conveniently, need not proofread again after the replacing, the described benchmark microwave signal that described receiving sensor is used to receive described microwave emitter excitation in a described airduct wind and the signal after the coal dust decay.
Described microwave emitter and described receiving sensor can be made different shape, for example, make cylindrical bar shape, horn-like etc.Known as those skilled in the art, described microwave emitter and described receiving sensor are done any shape, decide according to the operating space that will detect.In addition, in order farthest to avoid wearing and tearing, cylindrical bar shape is preferable selection.
Described receiving sensor and described microwave emitter can integrate becomes an integrated component.In one embodiment, a plurality of this kind integrated components can be set, as required each integrated component be used as receiving sensor or microwave emitter, four integrated components for example are set, two are used as receiving sensor, and two as microwave emitter.In an embodiment again, at least a portion in set this kind of integrated component can be not only as receiving sensor but also as microwave emitter, four this kind integrated components for example are set, an element is wherein arranged only as receiving sensor, one only as microwave emitter, all the other two promptly as receiving sensor, again as microwave emitter.
Described microwave emitter has transmitting terminal, and described receiving sensor has receiving end, and described transmitting terminal and described receiving end are respectively the major parts that is used to the effect that transmits and receives in described microwave emitter and the described receiving sensor.
According to an embodiment of the invention, described microwave emitter is one, described receiving sensor is one, as shown in Figure 1, in fact, the utility model can have a plurality of microwave emitters and a plurality of receiving sensor, and preferably, described microwave emitter and receiving sensor number equate and be provided with in pairs.Certainly, those skilled in the art will readily understand that the quantity of microwave emitter and receiving sensor can be unequal.
According to the utility model, described microwave emitter and described receiving sensor all are arranged in the described airduct, Fig. 1 only is the synoptic diagram of an embodiment of the present utility model, itself and not shown described microwave emitter and described receiving sensor the position specifically is set, it should be understood that to described microwave emitter and described receiving sensor and all be arranged in the described airduct, contact with the coal dust that flows in the described airduct, because the bend loss air-flow inequality of airduct causes the coal dust inequality, utilize the current-sharing effect of straight length can alleviate the degree of coal dust skewness, so, preferably, microwave emitter and receiving sensor are installed in the straight length of an airduct, equally for even fluid distribution, measurement data stability, reasons such as consistance, the length of the straight length part of described microwave emitter upstream is more than or equal to five times of a described airduct straight length interior diameter, and the length of the straight length in described receiving sensor downstream part is more than or equal to three times of the straight length interior diameter of a described airduct, for example, described microwave emitter is installed in apart from valve, elbow is the bore place more than 5 times, and described receiving sensor is installed in apart from valve, elbow is the bore place more than 3 times.
Preferably, the main transmit direction of described microwave emitter is parallel to the tube wall of a described airduct straight length, that is to say, microwave emitter makes the described benchmark microwave signal that is encouraged propagate along the tube wall direction of a parallel described airduct straight length, herein, the main transmit direction of microwave emitter is meant the direction of propagation of the described benchmark microwave signal that microwave emitter encourages; The main receive direction of described receiving sensor and the main transmit direction of described microwave emitter (being the direction of propagation of microwave) are perpendicular.Be in order to realize the optimization of measurement effect like this.
In an embodiment of the present utility model, described microwave emitter and described receiving sensor can be cylindrical bar shape, described microwave emitter and described receiving sensor all can be provided with perpendicular to a described airduct tube wall, and the angle theta between described microwave emitter and the described receiving sensor is 90 °, in fact, at this moment, θ greater than 0 degree (being that microwave emitter and receiving sensor are not overlapping), smaller or equal to 180 degree (be microwave emitter and receiving sensor offside install) can, but the optimization of measurement effect can be realized in the installation site of 90 ° of angles.
Preferably, between the described transmitting terminal of the described receiving end of described receiving sensor and described microwave emitter at a distance of the distance of a 400mm-600mm; More preferably, between the described transmitting terminal of the described receiving end of described receiving sensor and described microwave emitter at a distance of the distance of a 500mm.As known to those skilled in the art, distance between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter is a constant distance, and the medium in the distance between the two and the described airduct, for example wind is relevant with magnetic permeability with the specific inductive capacity of coal dust etc., and those skilled in the art can select in above-described scope as required.In one embodiment, between the described transmitting terminal of the described receiving end of described receiving sensor and described microwave emitter at a distance of the distance of a 500mm.Adopt microwave method to measure coal powder density, with the diameter in an airduct road and the mounting distance of sensor much relations are arranged, it is improper that distance is selected, measuring accuracy can not guarantee, even possibly can't measure, it is suitable that the diameter in an airduct road of the present utility model and the mounting distance of sensor are selected, and can measure preferably coal powder density.
When certain section pulverized coal borne air flow flows through microwave emitter and receiving sensor, can on receiving sensor, produce and the relevant signal of this section mixture state (comprising concentration, temperature, wind powder mixability etc.).At any time, the state of different pipe sections pulverized coal borne air flow is all inequality, so the signal that receiving sensor receives is a random signal, is referred to as flowing noise signal.This flowing noise signal is the characteristic signal parameter that wind powder mixture flows and produced in airduct, and it is relevant with temperature, pressure, flow velocity, concentration.
Described signal processing unit can be the Real-Time Data Handling System (RTDHS) based on digital signal processing (DSP), and this system high efficiency is succinct, satisfies the requirement of measuring and handling in real time.Described signal processing unit is connected with described receiving sensor, and preferably the two distance is no more than 60 meters, and more preferably, the length that is connected lead between described signal processing unit and the receiving sensor is no more than 50 meters.Because after the microwave signal transmission range surpasses 60 meters, the big high attenuation of microwave signal intensity, even can't measure.Described signal processing unit receives after the flowing noise signal of described receiving sensor, this flowing noise signal is converted to digital signal, principle according to the measurement concentration of the following stated compares computing then, thereby obtains the concentration of a coal dust in the airduct.
In addition, as known to those skilled in the art, the cable that can also comprise the power supply unit that is used to provide power in the described system, is used for transmission signals (for example, radio-frequency cable), be used to link up signal source and microwave emitter and link up receiving sensor and signal processing unit the signal linkage unit, be used for the input block of signal input signal processing unit, be used to interface that is connected industrial computer or Distributed Control System (DCS) (DCS) system or the like, the connected mode of these elements and purposes are that those skilled in the art are known.
Referring to Fig. 1, it is the synoptic diagram of an embodiment of the present utility model.Coal powder density on-line monitoring system as shown in Figure 1 comprises signal source; The microwave emitter that has transmitting terminal, it is installed in the straight length of an airduct; The receiving sensor that has receiving end, it is installed in the straight length of an airduct, with microwave emitter at a distance of certain distance; And signal processing unit.
When described coal powder density on-line monitoring system turns round, signal source launched microwave signal, and microwave signal is sent to microwave emitter by for example signal linkage unit, special-purpose radio-frequency cable, microwave emitter plays microwave by transmitting terminal at an airduct underexcitation, microwave is propagated along the straight length tube wall direction that is parallel to an airduct, when certain section pulverized coal borne air flow flows through emission sensor and receiving sensor, can on receiving sensor, produce and the relevant signal of this section mixture state (comprising concentration, temperature, wind powder mixability etc.).At any time, the state of different pipe sections pulverized coal borne air flow is all inequality, so the signal that receiving sensor receives is a random signal, is referred to as flowing noise signal.Flowing noise signal in the airduct that receiving sensor will measure then by for example input block sends back to signal processing unit by for example special-purpose radio-frequency cable, signal linkage unit, an example of described signal processing unit is based on the Real-Time Data Handling System (RTDHS) of DSP, in signal processing unit, this flowing noise signal is converted to digital signal, compare running, result of calculation is passed through conversion of signals, send into industry control chamber or DCS system, promptly can be observed the coal powder density in the airduct of surveying a time.
Below will introduce measurement of concetration principle of the present utility model:
Referring to Fig. 2, it is a measurement of concetration synoptic diagram of the present utility model, and by Theory of Electromagnetic Field as can be known: when playing microwave at the circular pipe underexcitation, and make microwave prolong duct orientation when propagating, the electric field intensity in the pipeline is:
E＝E
0×e
-αz×e
-jβz
α＝f
1(f，ε，μ)
β＝f
2(f，ε，μ)
In the formula: z prolongs the distance of duct orientation apart from microwave source
E prolongs the electric field intensity of duct orientation apart from microwave source z place
E
0Electric field intensity for microwave source place in the pipeline
α is an attenuation constant, and the expression per unit is apart from electric field intensity amplitude fading degree
β is a phase constant, the expression per unit phase place backward apart from electric field intensity
F is the frequency of microwave
ε is the specific inductive capacity in the pipeline
μ is the magnetic permeability in the pipeline
By the co-relation formula as can be seen: when microwave was propagated in pipeline, its amplitude was pressed the index law decay, and the rate of decay is decided by attenuation constant α.α is big more, and it is big more to decay.
Attenuation constant α is relevant with DIELECTRIC CONSTANT, magnetic permeability μ in microwave frequency f, the pipeline.ε, μ are big more, and α is big more.Select suitable frequency f, can make α maximum when identical ε, μ.
When flowing through in the pipeline when containing breeze airflow, DIELECTRIC CONSTANT and magnetic permeability μ in the pipeline change.Coal powder density η is big more, and ε, μ are big more, and α is big more, and the microwave attenuation that causes is big more.By measuring the decay of microwave on constant spacing of certain frequency, just can determine the size of α, a nearly step can be obtained ε, μ and coal powder density η.
Like this, on an airduct, prolong duct orientation two microwave remote sensors are installed, as shown in Figure 2.One is used for launched microwave, is called microwave emitter, and another is used to receive microwave signal, is called receiving sensor.Signal source is delivered to microwave emitter with microwave signal, is used in pipeline underexcitation microwave signal; Signal source is delivered to signal processing unit with microwave signal simultaneously, as E
0Receiving sensor detects the microwave signal after the decay from pipeline, as E, send into signal processing unit.The E of signal processing unit to receiving
0, E handles, and can obtain α, ε, μ and coal powder density η.Computing formula is:
ε＝k1×g(z，α)
In the formula: λ, λ
cBe two wavelength value relevant with airduct
k
1, k
2Be two computational constant of determining by experiment
Wind powder in-service monitoring of the present utility model system can be used for:
1, monitors the interior coal powder density of each airduct of boiler in real time, show with numeral, curve or rod figure;
2, to the plugging of an airduct, disconnected powder diagnosing malfunction, warning.
On above function basis, through even the mass rate adjustment that enters each burner coal dust.
1, adjust the shrinkage cavity baffle plate, can be even the mass rate adjustment that enters each burner coal dust.
2, adjust the throttle aperture, guarantee that boiler is with the hot balance of each airduct of one deck to the resistance of burner outlet.
3, adjust the coal-air ratio of burner, guarantee the optimized combustion under different load, reduce NOx, high-temperature sulfur corrosion and reduction unburned carbon in flue dust simultaneously.
Known as those skilled in the art, coal powder density on-line monitoring system of the present utility model not only is confined to the on-line monitoring of coal powder density in airduct of station boiler, for example, it also can be used for the on-line monitoring of the powder concentration in the granular material production runes such as cement, stone flour.
Online detection of primary air of the present utility model system has following characteristics:
1, realizes direct measurement of concetration.The method that in the past adopted energy conservation is to utilize the energy relationship between hot blast, coal dust and the potpourri to try to achieve, and uncertain factor is too many, can only realize relative measurement, thereby precision is low.Native system is measuring object with the mixture concentration directly, and resulting signal is directly represented concentration value, is absolute measurement, has got rid of the influence of uncertain factor, and measuring accuracy is guaranteed.
2, realize measuring fast, the speed that influences does not have hysteresis soon.Adopted the method for energy conservation need measure the temperature of wind, coal dust, hot blast potpourri in the past, and because thermopair has longer hysteresis characteristic, caused hysteresis for naturally the result of whole measurement, and make the sensitivity reduction.Native system adopts the method for directly measuring, and has improved the response speed of measuring, and has really reached real-time effect.
3, high wear-resistant sensor.The sensor that adopts special aviation high-abrasive material to make can use under nominal situation minimum 4 years, and changed simple and conveniently, need not proofread again after the replacing.
4, total digitalization is adjusted, and software carries out system debug automatically, need not manual intervention.Because adopt totally digitilized designing technique, the system that makes debugs automatically and diagnosis becomes possibility, the software systems of perfect in shape and function are finished the debugging configuration effort of system automatically, have reduced user's difficulty.
5, based on the Real-Time Data Handling System (RTDHS) of DSP, make system become efficient and succinct, satisfied the requirement of real-time measurement and processing.Interface function is perfect, possesses data-interfaces such as MODBUS, RS485, highway addressable remote transducer (HART) fieldbus, has the analog signals output function simultaneously.Possess management information system (MIS) interface, can to MIS upload data or directly with this machine as the WEB server, have the WEB module to support the visit of LAN (Local Area Network).
The beneficial effects of the utility model are: monitoring system of the present utility model can real-time online ground the concentration of coal dust in the monitoring boiler of power plant, can provide data really and accurately for the operation personnel, foundation as the optimized combustion adjustment, can improve boiler efficiency, energy-conservationly fall coal consumption, can improve the security of boiler operatiopn, can carry out plugging, disconnected powder warning in advance, improve the equipment operation life-span.
Be basic design of the present utility model as mentioned above.But, in technical field of the present utility model,, can improve other exercisable embodiment of the present utility model as long as possess the most basic knowledge.In the utility model substantive technical scheme has been proposed the patent protection request, its protection domain comprises all variation patterns with above-mentioned technical characterstic.
The above only is preferred embodiment of the present utility model, be not the utility model is done any pro forma restriction, though the utility model disclose as above with preferred embodiment, yet be not in order to limit the utility model.Those of ordinary skill in the art can utilize the technology contents of above-mentioned announcement to make amendment and change in not breaking away from the technical solutions of the utility model scope.It is pointed out that foundation technical spirit of the present utility model to any simple modification, equivalent variations and modification that above embodiment did, all still belongs in the scope of technical solutions of the utility model.Protection domain of the present utility model by and only have appended claim to limit.
Claims (10)
1. coal powder density on-line monitoring system, it is applicable in the monitoring direct blow boiler coal powder density in the airduct one time, it is characterized in that described coal powder density on-line monitoring system comprises:
Signal source, it is used to provide the benchmark microwave signal;
A microwave emitter that has transmitting terminal, it is arranged in the described airduct, is connected with described signal source, is used in the described benchmark microwave signal of a described airduct underexcitation;
A receiving sensor that has receiving end, it is arranged in the described airduct, between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter at a distance of the distance of a 300mm-700mm, the described benchmark microwave signal that is used to receive described microwave emitter excitation in a described airduct wind and the signal after the coal dust decay; And
Signal processing unit, it is connected with described receiving sensor with described signal source, be used to receive the described benchmark microwave signal that signal after the described decay that described receiving sensor receives and described signal source provide, and signal after the described decay and described benchmark microwave signal compared, thereby determine coal powder density in the described airduct.
2. coal powder density on-line monitoring system according to claim 1 is characterized in that, described signal source is for adopting the synthetic microwave frequency source of Direct Digital compositor and phaselocked loop Direct Digital.
3. coal powder density on-line monitoring system according to claim 1; it is characterized in that; described microwave emitter and described receiving sensor all have the outer protection pipe box, and described outer protection pipe box is to be made by high temperature resistant, the high wear-resistant material that contains rare earth material.
4. coal powder density on-line monitoring system according to claim 1 is characterized in that, a described airduct has straight length, and described microwave emitter and described receiving sensor are arranged in the straight length of a described airduct.
5. coal powder density on-line monitoring system according to claim 4, it is characterized in that, described microwave emitter is arranged on the upstream of described receiving sensor, the length of the straight length of described microwave emitter upstream part is more than or equal to five times of a described airduct straight length interior diameter, and the length of the straight length in described receiving sensor downstream part is more than or equal to three times of the straight length interior diameter of a described airduct.
6. coal powder density on-line monitoring system according to claim 1 is characterized in that the main transmit direction of described microwave emitter is parallel to the tube wall of a described airduct straight length.
7. coal powder density on-line monitoring system according to claim 1 is characterized in that, the main receive direction of described receiving sensor and the main transmit direction of described microwave emitter are perpendicular.
8. coal powder density on-line monitoring system according to claim 1 is characterized in that, between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter at a distance of the distance of a 400mm-600mm.
9. coal powder density on-line monitoring system according to claim 1 is characterized in that, between the described receiving end of described receiving sensor and the described transmitting terminal of described microwave emitter at a distance of the distance of a 500mm.
10. coal powder density on-line monitoring system according to claim 1 is characterized in that, the length that is connected lead between described signal processing unit and the described receiving sensor is no more than 60 meters.
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| CNU2008201246511U CN201311388Y (en) | 2008-12-16 | 2008-12-16 | Coal dust concentration on-line monitoring system |
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| CNU2008201246511U CN201311388Y (en) | 2008-12-16 | 2008-12-16 | Coal dust concentration on-line monitoring system |
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| CN201311388Y true CN201311388Y (en) | 2009-09-16 |
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