CN104614024A - Method and device for representing electrostatic measurement of coal powder flows of milling and conveying system of power plant - Google Patents

Abstract

The invention provides a method and a device for representing the electrostatic measurement of coal powder flows of a milling and conveying system of a power plant. The representing method comprises the following steps: using ring-shaped electrodes with different widths, utilizing a relation between effective values of two static electricity signals, calculating the effective values of output electrical signals of wide and narrow ring-shaped static electricity sensors and the flow rate of coal powder, further calculating the ratio of the effective values, combining the particle speed of the coal powder to be used for representing the flow of the coal powder in a transmission pipeline, and on the basis, representing the distributing uniformity of the coal powder supplied by the same coal mill to each burner. Through the adoption of the method and device, disclosed by the invention, the stability and the accuracy of an electrostatic measurement signal of the coal powder can be improved, the cost of a measurement device is reduced, and accurate basic data can be provided for the balanced distribution control of the coal powder of the milling and conveying system of the power plant.

Description

A kind of power station powder process induction system pulverized coal flow electrostatic measurement characterizing method and device

Technical field

The invention belongs to powder flowing field of measuring technique, be specifically related to a kind of power station powder process induction system pulverized coal flow electrostatic measurement characterizing method and device.

Background technology

In the outer large-scale thermal power machine group of Present Domestic, generally all adopt unit pulverized-coal system.During unit operation, hot blast carries the primary wind and powder that in coal pulverizer, coal dust is formed and leaves coal pulverizer, enters different conveyance conduits, and enters corresponding burner by these pipelines.Enter degree of uniformity that the wind speed of the First air of burner hearth, coal powder density and flow and each burner wind powder distribute all by the burning efficiency of the stability and boiler that directly affect stove combustion operating mode.The wind powder of each burner distributes inequality and can produce furnace flame deflection, local heat load is too high, in stove, reducing atmosphere is caused because coal powder density is too high in some region, exacerbate slagging scorification and high temperature corrosion process, and some burner can produce the even flame-out phenomenon of combustion pulsation and causes fluctuating widely of negative pressure in stove.In addition, between each burner, wind powder deviation strengthens, and causes the problem that unburned carbon loss increases, makes burner off-target working condition.With the increase of boiler capacity, number of burners increases, and the wind powder in powder process and combustion system distributes uneven problem can be more outstanding.Therefore measure power station powder process induction system coal powder density, mass rate is significant to the adjustment of wind powder ratio in the equilibrium assignment of each burner internal coal dust and burner.

Usually, in duff pipe, the mass concentration of coal dust is 300-500g/m ³, wind powder mass ratio is 1.5-3:1, and volume ratio is only in the order of magnitude (when 100 DEG C) of 0.05%, and powder content low like this makes the coal dust such as radiation, electric capacity measuring method seem helpless.In the middle of power station, warehouse formula coal-fired boiler combustion device entrance coal powder density is measured and is often adopted heat balance method of, but for pulverized coal preparation system that is direct-firing or employing transporting pulverized coal with exhaust gas, there is not larger temperature difference owing to carrying gas and being transferred between powder, therefore heat balance method of also cannot be applied.

The electrostatic sensing technique grown up in recent years is based on gas-solid rolling particles charged detection particle flow parameter, has that system architecture is simple, noncontact, highly sensitive, cheap, safe and be suitable for the advantages such as severe industrial Geldart-D particle site environment.Although electrostatic transducer cannot provide granule density and the isoparametric absolute measured value of mass rate, from control and balanced angle, the relative measurement of concentration and flow is enough.This is that the factor such as composition, particle size, shape, water capacity as solid has similarity, and therefore in each pipeline, the output of electrostatic transducer has comparability because same coal pulverizer coal dust out has similar charging characteristic.At present, for the powder granule of given moist ingredients and particle size distribution, under dilute phase conditions, think that the effective value (RMS) that electrostatic transducer outputs signal is directly proportional to grain flux.But in fact, coal powder two-phase flow in pipeline due to piping arrangement, service condition etc., cause the distributing position of coal dust solid particle in pipeline different, the effective value (RMS) of the output signal that annulus electrostatic transducer detects also can be different, this produces comparatively big error by causing the characterization value of pulverized coal flow, and the coal dust Balance route of therefore powder process induction system can produce larger deviation.

Summary of the invention

In order to overcome the deficiency of existing power station powder process induction system pulverized coal flow electrostatic measurement method, the present invention proposes a kind of multiple round annular electrode pulverized coal flow electrostatic measurement characterizing method and device, adopt the circular ring electrode that width is different, the contact of both utilizations electrostatic signal effective value, wide by calculating, the effective value of the output electric signal of narrow circular electrostatic transducer and coal dust flowing velocity, and a step calculates the ratio of effective value, in conjunction with pulverized coal particle speed, for characterizing the flow of coal dust in conveyance conduit, the homogeneity that the coal powder distribation of each burner supplied by same coal pulverizer can be characterized on this basis.The method and device can improve stability and the accuracy of coal dust electrostatic measurement signal, and reduce the cost of measurement mechanism, and the equilibrium assignment that can be power station powder process induction system coal dust controls to provide basic data accurately.

The present invention adopts following technical scheme:

A kind of for power station powder process induction system pulverized coal flow electrostatic measurement characterizing method, it is characterized in that, step is as follows:

Step one, prolong the pipeline axial of pulverized coal flow warp, pipeline outer wall arranges three groups of circular array electrostatic transducers, the width wherein occuping two groups of both sides is identical and be less than the width of middle a group, and three groups of electrostatic signal data detected by three groups of circular array electrostatic transducers, the electrode electrostatic signal wherein occuping two groups of circular array electrostatic transducers of both sides is respectively { x (i), i=1, 2 ... N} and { y (i), i=1, 2 ... N}, the electrode electrostatic signal of middle one group of circular array electrostatic transducer is { z (i), i=1, 2 ... N}, calculate the effective value X of three groups of circular electrostatic transducer output signals respectively, Y, Z:

$X=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{x}^2\left(i\right)}$

$Y=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{y}^2\left(i\right)}$

$Z=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{z}^2\left(i\right)}$

Wherein, N is the number of electrostatic signal data acquisition sampling point;

Step 2, utilization calculate effective value X, Y, Z of three groups of circular electrostatic transducers output signals, calculate the ratio C of circular electrostatic transducer and the middle circular electrostatic transducer output signal effective value obtaining both sides, the characterization value as coal powder density in pipeline:

$C=\frac{2Z}{(X+Y)}$

Step 3, the electrostatic signal { x (i) utilizing the circular electrostatic transducer in two groups, both sides to export, i=1,2 ... N} and { y (i), i=1,2 ... N}, in conjunction with cross-correlation method, calculates the delay time T of pulverized coal flow through the two groups of round loop electrode sensors in both sides, and by the spacing L between the circular electrostatic transducer in two groups, both sides, calculate pulverized coal particle Flow Velocity ν in pipeline:

$v=\frac{L}{\mathrm{\τ}}---\left(7\right)$

Step 4, calculating flow through the pulverized coal flow characterization value of three groups of circular array electrostatic transducers:

Q＝C·v

Wherein, Q is pulverized coal flow characterization value.

Delay time T is:

τ＝m·Δt

Wherein, Δ t is electrostatic signal sampling time interval, and m is that the delay that R (n) has a maximal value place is counted, and R (n) is electrostatic signal { x (i), i=1,2 ... N} and { y (i), i=1,2 ... the cross correlation function of N},

$R\left(n\right)=\frac{1}{N}\mathrm{\Σ}[x\left(i\right)y(i+n)$

Wherein, n is counting of delay.

A kind of for power station powder process induction system pulverized coal flow electrostatic measurement characterization apparatus, the data processing equipment comprising data collector and be connected with described data collector, it is characterized in that, described data collector is circular array electrostatic transducer measuring head, this circular array electrostatic transducer measuring head comprises insulation tube and is arranged on the narrow circular electrostatic transducer of two of insulation tube outside surface and a wide circular electrostatic transducer, and wherein wide circular electrostatic transducer is arranged between two narrow circular electrostatic transducers between two parties.

Described data processing equipment comprises signal conditioning circuit, data collecting card and computing machine, described circular array electrostatic transducer measuring head is connected with the signal input part of described signal conditioning circuit, connects described data collecting card and computing machine successively at the signal output part of signal conditioning circuit.

Described circular array electrostatic transducer measuring head also comprises radome, insulation course and for by circular array electrostatic transducer measuring head and conveyance conduit joint flange, described insulation course is arranged on the outside of described circular electrostatic transducer, at the radome described in the arranged outside of insulation course.

Compared with prior art, tool of the present invention has the following advantages:

1, compared to existing Dual-Phrase Distribution of Gas olid electrostatic measurement method, the present invention utilizes the ratio of the circular electrostatic transducer output signal effective value of different in width electrode, decrease due to the Dual-Phrase Distribution of Gas olid solid particle uneven electrostatic signal characterization value measuring error caused spatially, power station pulverized coal preparation system coal dust Balance route can be directly used in;

2, annulus electrostatic transducer is arranged in pipeline outer wall, belong to contactless or non-intervention type measurement, therefore, the flow condition interference of convection cell is little, and electrostatic transducer measuring system can not affect the flow field of detected fluid, the extra loss of manifold pressure also can not be caused.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of power station powder process induction system pulverized coal flow electrostatic measuring device;

Fig. 2 is the schematic diagram of circular array electrostatic transducer measuring head;

Wherein, 1-isolated pipe; The circular electrostatic transducer that 2-is narrow; The circular electrostatic transducer that 3-is wide; 4-radome; 5-insulation course; 6-joint flange; 7-signal conditioning circuit; 8-data collecting card; 9-computing machine, L is the distance between two narrow circular electrostatic transducers, and L1 is the distance between narrow circular electrostatic transducer and wide circular electrostatic transducer.

Embodiment

Embodiment

Power station powder process induction system pulverized coal flow electrostatic measurement characterizing method, get one section of isolated pipe, the outer wall of isolated pipe is arranged the circular electrostatic transducer that electrode width is different, and wherein the narrow circular electrostatic transducer spacing at two ends is L, circular electrostatic transducer is along the axial distribution of isolated pipe, the electrostatic signal detected by circular electrostatic transducer is through amplifying, after being gathered by data collecting card, utilize correlation method to carry out speed that computing draws pulverized coal particle, and by calculating the ratio C of wide circular electrostatic transducer and narrow circular electrostatic transducer electrostatic signal effective value, the concentration of pulverized coal particle in pipeline is characterized, pulverized coal particle flowmeter value indicative Q is calculated by C and solid particle speed v.When Dual-Phrase Distribution of Gas olid electrostatic signal is more weak, wide circular electrostatic transducer can normally work, but narrow circular electrostatic transducer Received signal strength is too weak, survey data accuracy and stability cannot be protected, in addition, the deviation that the space distribution of pulverized coal particle also will cause electrostatic transducer to output signal, now utilize the ratio of two of width Different electrodes circular electrostatic transducer electrostatic signal effective values, effectively improve the Stability and veracity of flowmeter value indicative, power station pulverized coal preparation system coal dust Balance route can be directly used in.

With reference to the accompanying drawings 1 and Fig. 2, explanation is specifically made to specific embodiment of the invention scheme:

1) three circular electrostatic transducers are arranged on isolated pipe 1 outer wall vertically, the electrode axial length of wherein wide circular electrostatic transducer is 5cm, the electrode axial length of narrow circular electrostatic transducer is 1cm, and two electrode circle ring-types are all be made up of the copper sheet that 0.2mm is thick.Electrode covers an insulation course 3 outward, and is the radome 4 be made up of the latten(-tin) that 1mm is thick outside insulation course, for shielding external electromagnetic interference.Spacing between two narrow electrodes is L=10cm.Because the charged signals of pulverized coal particle is relatively weak, cause the input signal of the induced signal on electrostatic attraction electrode and prime amplifier less, so by radome reliably ground connection, to ensure its shield effectiveness.Then by signal conditioning circuit 7, electrostatic induction signal is changed into the signal that can be gathered by data collecting card 8, and send into computing machine 9 by data collecting card.

2) in computing machine, to the three groups of electrostatic signal data collected, comprise 2 groups narrow electrode electrostatic signal and be respectively { x (i), i=1,2 ... N}, { y (i), i=1,2 ... N} and 1 group wide electrode output signal is { z (i), i=1,2 ... N}, calculates effective value X, Y, the Z in circular electrostatic transducer output signal collection period T respectively.

$X=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{x}^2\left(i\right)}---\left(1\right)$

$Y=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{y}^2\left(i\right)}---\left(2\right)$

$Z=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{z}^2\left(i\right)}---\left(3\right)$

Wherein, N is in cycle T, the number of the electrostatic signal data point of collection.

3) ratio C of the electrostatic signal effective value that the circular electrostatic transducer that molded breadth is different is surveyed.Utilize electrostatic signal effective value ratio C, the concentration of pulverized coal particle in the pipeline in pipeline is characterized, to improve the Stability and veracity of measurement data.

$C=\frac{2Z}{(X+Y)}---\left(4\right)$

4) suppose according to " solidifying " pattern of fluid, utilize the electrostatic signal { x (i) that two narrow circular electrostatic transducers export, i=1,2 ... N}, { y (i), i=1,2 ... N}, in conjunction with cross-correlation method, calculates the delay time T of pulverized coal flow through two narrow annulus electrostatic transducers:

$R\left(n\right)=\frac{1}{N}\mathrm{\Σ}[x\left(i\right)y(i+n)---\left(5\right)$

Wherein, R (n) is electrostatic signal { x (i), i=1,2 ... N} and { y (i), i=1,2 ... the cross correlation function of N}, n is counting of delay.

If R (n) has maximal value at n=m place, so delay time T:

τ＝m·Δt (6)

Wherein, Δ t is electrostatic signal sampling time interval, and m is that the delay that R (n) has a maximal value place is counted.

5) by the spacing L between known two narrow circular ring electrodes, pulverized coal particle Flow Velocity ν in pipeline is calculated:

$v=\frac{L}{\mathrm{\τ}}---\left(7\right)$

6) the pulverized coal flow characterization value Q flowing through electrostatic transducer measuring head is calculated:

Q＝C·v (8)

Shown in seeing figures.1.and.2, for power station powder process induction system pulverized coal flow electrostatic measurement characterization apparatus, comprise circular array electrostatic transducer measuring head, signal conditioning circuit, data collecting card and computing machine.Circular array electrostatic transducer measuring head comprises radome, isolated pipe, insulation course, two narrow circular ring electrodes with, a wide circular ring electrode and two joint flanges.

Principle of the present invention is as follows:

The course of work of instrument is: first for pulverized coal particle in pipeline space and velocity distribution uneven, the present invention utilizes wide circular electrostatic transducer and narrow circular electrostatic transducer electrostatic signal effective value ratio C, characterizes pulverized coal particle concentration in pipeline.Then the electrostatic signal that the circular electrostatic transducer utilizing correlation method process two narrow detects, calculate the delay time T between two groups of signals, at two narrow circular electrostatic transducer distance L, when known, the speed v of solid particle in Dual-Phrase Distribution of Gas olid can be calculated, then the characterization value Q of pulverized coal flow in pipeline can be calculated, improve stability and the accuracy of measurement data, described device have cost low, to advantages such as powder flowing undisturbeds, power station pulverized coal preparation system coal dust Balance route can be directly used in.

Claims (5)

1., for a power station powder process induction system pulverized coal flow electrostatic measurement characterizing method, it is characterized in that, step is as follows:

Step one, along the pipeline axial of pulverized coal flow warp, pipeline outer wall arranges three groups of circular array electrostatic transducers, the width wherein occuping two groups of both sides is identical and be less than the width of middle a group, and three groups of electrostatic signal data detected by three groups of circular array electrostatic transducers, the electrode electrostatic signal wherein occuping two groups of circular array electrostatic transducers of both sides is respectively { x (i), i=1, 2 ... N} and { y (i), i=1, 2 ... N}, the electrode electrostatic signal of middle one group of circular array electrostatic transducer is { z (i), i=1, 2 ... N}, calculate the effective value X of three groups of circular electrostatic transducer output signals respectively, Y, Z:

$X=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{x}^2\left(i\right)}$

$Y=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{y}^2\left(i\right)}$

$Z=\sqrt{\frac{1}{N-1}\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{z}^2\left(i\right)}$

Wherein, N is the number of electrostatic signal data acquisition sampling point;

Step 2, utilization calculate effective value X, Y, Z of three groups of circular electrostatic transducers output signals, calculate the ratio C of circular electrostatic transducer and the middle circular electrostatic transducer output signal effective value obtaining both sides, the characterization value as coal powder density in pipeline:

$C=\frac{2Z}{(X+Y)}$

Step 3, the electrostatic signal { x (i) utilizing the circular electrostatic transducer in two groups, both sides to export, i=1,2 ... N} and { y (i), i=1,2 ... N}, in conjunction with cross-correlation method, calculates the delay time T of pulverized coal flow through the two groups of round loop electrode sensors in both sides, and by the spacing L between the circular electrostatic transducer in two groups, both sides, calculate pulverized coal particle Flow Velocity ν in pipeline:

$v=\frac{L}{\mathrm{\τ}}$

Step 4, calculating flow through the pulverized coal flow characterization value of three groups of circular array electrostatic transducers:

Q＝C·v

Wherein, Q is pulverized coal flow characterization value.

2. according to claim 1 for power station powder process induction system pulverized coal flow electrostatic measurement characterizing method, it is characterized in that, delay time T is:

τ＝m·Δt

Wherein, Δ t is electrostatic signal sampling time interval, and m is that the delay that R (n) has a maximal value place is counted, and R (n) is electrostatic signal { x (i), i=1,2 ... N} and { y (i), i=1,2 ... the cross correlation function of N},

$R\left(n\right)=\frac{1}{N}\mathrm{\Σ}\left[x\left(i\right)y(i+n)\right]$

Wherein, n is counting of delay.

3. one kind for power station powder process induction system pulverized coal flow electrostatic measurement characterization apparatus, the data processing equipment comprising data collector and be connected with described data collector, it is characterized in that, described data collector is circular array electrostatic transducer measuring head, this circular array electrostatic transducer measuring head comprises insulation tube and is arranged on the narrow circular electrostatic transducer of two of insulation tube outside surface and a wide circular electrostatic transducer, and wherein wide circular electrostatic transducer is arranged between two narrow circular electrostatic transducers between two parties.

4. according to claim 3 for power station powder process induction system pulverized coal flow electrostatic measurement characterization apparatus, it is characterized in that: described data processing equipment comprises signal conditioning circuit, data collecting card and computing machine, described circular array electrostatic transducer measuring head is connected with the signal input part of described signal conditioning circuit, connects described data collecting card and computing machine successively at the signal output part of signal conditioning circuit.

5. according to claim 4 for power station powder process induction system pulverized coal flow electrostatic measurement characterization apparatus, it is characterized in that: described circular array electrostatic transducer measuring head also comprises radome, insulation course and for by circular array electrostatic transducer measuring head and conveyance conduit joint flange, described insulation course is arranged on the outside of described circular electrostatic transducer, at the radome described in the arranged outside of insulation course.