CN105157774A - Pulverized coal flow online measuring device and measuring method - Google Patents

Abstract

The invention discloses a pulverized coal flow online measuring device and measuring method. The device is characterized in that a measuring pipe is connected to a primary air pipeline in series and is made of a ceramic material; the two ends of the measuring pipe are each provided with two sets of capacitance sensors; the capacitance sensors are 2n electrode plates annularly and evenly distributed on the outer wall of the measuring pipe, and the 2n electrode plates are n plate capacitors oppositely arranged in pairs; capacitance of the plate capacitors serves as an output signal of the measuring device. Interval measurement of the plate capacitors is adopted, measurement errors caused due to uneven spatial distribution of pulverized coal concentration and speed are effectively reduced, and measuring precision is improved. By means of the measuring device, adjustment can be carried out in time according to data of pulverized coal flow online measuring, so that the problem that burning of the primary air pipeline, overheat of a heated face, slagging, thermal deviation and the like are caused due to pipeline pulverized coal accumulation, pulverized coal pipeline blocking and unbalance of pulverized coal distribution is avoided, and boiler combustion is optimized.

Description

A kind of pulverized coal flow on-line measurement device and measuring method

Technical field

The present invention relates to pulverized coal flow on-line measurement device and measuring method, is more particularly the device and method carrying out pulverized coal flow on-line measurement for coal-burning boiler.

Background technology

In coal-burning power plant's actual moving process, due to the difference of four First air resistances of ducting of coal pulverizer outlet, often can cause line clogging coal dust and the unequal problem of coal powder distribation.The pulverized coal flow maldistribution spraying into burner hearth directly affects the burning of boiler, cause furnace flame center deflection, thermal load difference is obvious, cause the bad phenomenon such as local water-cooling wall overtemperature coking, superheater and reheater left and right thermal deviation are larger, have a strong impact on security and the economy of boiler operatiopn.

The distribution imbalance of pulverized coal flow is boiler combustion optimization urgent problem.At present for the unbalanced problem of distribution of pulverized coal flow, main employing cold conditions First air leveling technology.Four primary air piping of coal pulverizer outlet install backing tube on-line measurement primary air velocity.The primary air velocity that gridding method demarcates backing tube on-line measurement is carried out by pibtot's tub.According to the wind speed of deviation adjusting adjustable contraction leveling four primary air piping of calibrated primary air velocity.This method demarcation is complicated, and workload is large, and the measuring accuracy of online wind speed is low, easily blocks up powder in operational process, causes measurement inaccurate.This method carries out leveling in cold conditions, and the requirement of pulverized coal flow partition equilibrium when not exclusively meeting hot operation.

The key problem in technology of dealing with problems is the flow of coal dust in Measurement accuracy primary air piping, realizes the on-line measurement of pulverized coal flow.At present, coal dust sampling mode is adopted to measure at coal-burning power plant's in-site measurement coal powder density.By sampling gun in the first-class speed sampling of First air pipeline.Ensure in sampling process that the suction velocity of sampling probe import is equal with the particle speed of surrounding.Sampling terminates weigh to sample and record sample time afterwards, obtains the mass rate of coal dust.But this mode is applicable to stable operating mode, and actual condition fluctuation is larger.In actual sampling process, be difficult to ensure constant speed, thus cause larger measuring error.Meanwhile, this method workload is large, and the reaction time is long, can not realize continuous print on-line measurement.At present, coal dust distributes and the uneven measuring error caused of speed in the duct to adopt the instrument of capacitance measurement pulverized coal flow not consider.Although capacitance chromatography imaging method can obtain the information of coal dust at the Entropy density deviation of pipeline section, cause algorithm complicated owing to being not suitable with problem and soft field effect, the problems such as resolution is lower, and measuring accuracy is not high.

Summary of the invention

The present invention is the weak point for avoiding existing for above-mentioned prior art, a kind of pulverized coal flow on-line measurement device and measuring method are provided, can adjust timely according to the data of pulverized coal flow on-line measurement to make operations staff, avoid pipeline accumulated powder, the problems such as primary air piping burns out, heating surface is overheated, slagging scorification and thermal deviation that coal dust plugging and coal powder distribation imbalance cause, optimize boiler combustion.

The present invention is that technical solution problem adopts following technical scheme:

The design feature of pulverized coal flow on-line measurement device of the present invention is:

First air pipeline is arranged in series one section of measuring tube, and described measuring tube take stupalith as material, installs two groups of capacitive transducers at the two ends of described measuring tube respectively; Described capacitive transducer is uniformly distributed 2n battery lead plate in the form of a ring on the outer wall of described measuring tube, and a described 2n battery lead plate is relatively to be formed n capacity plate antenna between two; Using the electric capacity of described capacity plate antenna as the output signal of measurement mechanism.

The design feature of pulverized coal flow on-line measurement device of the present invention is also:

The outer wall of described measuring tube 1 independently arranges each radome 3, in the radome 3 of each battery lead plate 2 autonomous closure on respective position.

Axial distance between described two groups of capacitive transducers is 200mm.

Flange is utilized to be removably connected between described measuring tube and described First air pipeline.

The feature utilizing pulverized coal flow on-line measurement device of the present invention to realize the method for pulverized coal flow on-line measurement is:

Make one group in described two groups of capacitive transducers to be first group of capacitive transducer, another group is second group of capacitive transducer;

In described first group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{1, i}(t), i=1,2 ..., n};

In described second group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{2, i}(t), i=1,2 ..., n};

Described measuring method is carried out as follows:

Calculating surveyed area corresponding to i-th capacity plate antenna in two groups of capacitive transducers is respectively m in the coal dust instantaneous concentration value of t _{1, i}(t) and m _{2, i}(t):

$m_{1,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{1,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

$m_{2,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{2,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

ρ in formula _sfor the real density of tested coal; ε _gfor dielectric constant of air; ε _sfor the specific inductive capacity of tested coal; ε ₀for permittivity of vacuum; D be in capacity plate antenna pair of electrodes distance between plates from; S is battery lead plate area;

The coal dust instantaneous concentration value obtained in t in measuring tube is calculated by formula (1) for:

$\stackrel{\‾}{m}\left(t\right)=\frac{\underset{i=1}{\overset{n}{\Σ}}{m}_{1,i}\left(t\right)+\underset{i=1}{\overset{n}{\Σ}}{m}_{2,i}\left(t\right)}{2n}---\left(1\right)$

Step 2, provide C by formula (2) _{1, i}(t) and C _{2, i}the cross correlation function R of (t) _{12, i}(τ):

$R_{12,i}\left(\mathrm{\τ}\right)=\frac{\lim }{T\→\mathrm{\∞}}\frac{1}{T}{\∫}_0^T{C}_{1,i}\left(t\right)C_{2,i}(t+\mathrm{\τ})dt---\left(2\right)$

By cross correlation function R _{12, i}(τ) to delay time T differentiate, such as formula (3):

$\frac{{\mathrm{dR}}_{12,i}\left(\mathrm{\τ}\right)}{d\mathrm{\τ}}=0---\left(3\right)$

(3) are utilized to solve R _{12, i}(τ) be delay time T corresponding during maximal value _{i, Rmax}

Order: the axial distance between two groups of capacitive transducers is D, and the pipeline section of measuring tube amasss as A, is calculated by formula (4) and obtains the average velocity that pulverized coal particle flows through measuring tube for

$\stackrel{\‾}{V}=\frac{\underset{i=1}{\overset{n}{\Σ}}\frac{D}{{\mathrm{\τ}}_{i,R_{\max }}}}{n}---\left(4\right)$

Then coal dust flows through the mass rate q (t) of measuring tube and is:

Compared with the prior art, beneficial effect of the present invention is embodied in:

1, the present invention adopts many capacity plate antennas measurement space to be divided into many little spaces, measure coal powder density and the speed of different spaces, realize drawing interval measure, and calculate the coal powder density of measuring tube and the mean value of speed thus, finally calculate the mass rate that coal dust flows through measuring tube, effectively reduce coal powder density and speed in the uneven measuring error caused of space distribution, improve measuring accuracy.Utilize the present invention can adjust timely according to the data of pulverized coal flow on-line measurement, thus avoid pipeline accumulated powder, the problems such as primary air piping burns out, heating surface is overheated, slagging scorification and thermal deviation that coal dust plugging and coal powder distribation imbalance cause, optimize boiler combustion.

2, in the present invention, measurement mechanism stream field is noiseless, has higher survey frequency, can the flow of on-line measurement coal dust, obtains the data of the coal dust real-time change of flow in the duct.

Accompanying drawing explanation

Fig. 1 is the sectional view of capacitive transducer;

Fig. 2 is the schematic diagram of condenser type pulverized coal flow measurement mechanism;

Number in the figure: 1 measuring tube, 2 battery lead plates, 3 radomes, 4 shells, 5 wires, 6 flanges.

Embodiment

See Fig. 1 and Fig. 2, in the present embodiment, the version of pulverized coal flow on-line measurement device is:

First air pipeline is arranged in series one section of measuring tube 1, and measuring tube 1 take stupalith as material, and stupalith can prevent the erosive wear of coal dust, installs two groups of capacitive transducers at the two ends of measuring tube 1 respectively; Capacitive transducer is that on the outer wall of measuring tube 1, be uniformly distributed 2n battery lead plate 2,2n battery lead plates 2 be in the form of a ring relatively to be formed n rectangular flat electric capacity between two; Using the electric capacity of capacity plate antenna as the output signal of measurement mechanism.

As depicted in figs. 1 and 2, independently arrange each radome 3 in the present embodiment on the outer wall of measuring tube 1, radome 3 is wire netting overlayer, in the radome 3 of each battery lead plate 2 autonomous closure on respective position; Axial distance between two groups of capacitive transducers is 200mm; Between measuring tube and First air pipeline, utilize flange 6 to be removably connected, shell 4 is the periphery pillars being arranged on measuring tube 1, shell 4 adopts stainless-steel tube, and by shell 4 ground connection, the wire 5 be electrically connected with capacitive transducer is drawn in shell 4, be equipped with data acquisition and control module, and utilize computing machine to carry out data processing, pulverized coal flow on-line measurement can be realized.

The method utilizing the on-line measurement of pulverized coal flow shown in Fig. 1 device to realize pulverized coal flow on-line measurement is:

Make one group in two groups of capacitive transducers to be first group of capacitive transducer, another group is second group of capacitive transducer, then have:

In first group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{1, i}(t), i=1,2 ..., n};

In second group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{2, i}(t), i=1,2 ..., n};

Measuring method is carried out as follows:

Step 1, to calculate surveyed area corresponding to i-th capacity plate antenna in two groups of capacitive transducers be respectively m in the coal dust instantaneous concentration value of t _{1, i}(t) and m _{2, i}(t):

$m_{1,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{1,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

$m_{2,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{2,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

ρ in formula _sfor the real density of tested coal; ε _gfor dielectric constant of air; ε _sfor the specific inductive capacity of tested coal; ε ₀for permittivity of vacuum; D be in capacity plate antenna pair of electrodes distance between plates from; S is battery lead plate area;

The coal dust instantaneous concentration value obtained in t in measuring tube is calculated by formula (1) for:

$\stackrel{\‾}{m}\left(t\right)=\frac{\underset{i=1}{\overset{n}{\Σ}}{m}_{1,i}\left(t\right)+\underset{i=1}{\overset{n}{\Σ}}{m}_{2,i}\left(t\right)}{2n}---\left(1\right)$

Step 2, provide C by formula (2) _{1, i}(t) and C _{2, i}the cross correlation function R of (t) _{12, i}(τ):

$R_{12,i}\left(\mathrm{\τ}\right)=\frac{\lim }{T\→\mathrm{\∞}}\frac{1}{T}{\∫}_0^T{C}_{1,i}\left(t\right)C_{2,i}(t+\mathrm{\τ})dt---\left(2\right)$

By cross correlation function R _{12, i}(τ) to delay time T differentiate, such as formula (3):

$\frac{{\mathrm{dR}}_{12,i}\left(\mathrm{\τ}\right)}{d\mathrm{\τ}}=0---\left(3\right)$

(3) are utilized to solve R _{12, i}(τ) be time delay corresponding during maximal value delay time T is that coal dust moves to the time of second group of capacitive transducer place axial location from first group of capacitive transducer place axial location.

Order: the axial distance between two groups of capacitive transducers is D, and the pipeline section of measuring tube amasss as A, is calculated by formula (4) and obtains the average velocity that pulverized coal particle flows through measuring tube for:

$\stackrel{\‾}{V}=\frac{\underset{i=1}{\overset{n}{\Σ}}\frac{D}{{\mathrm{\τ}}_{i,R_{\max }}}}{n}---\left(4\right)$

Then coal dust flows through the mass rate q (t) of measuring tube and is:

When air and coal dust two-phase mixtures flow through between battery lead plate, the change of coal powder density can change specific inductive capacity, thus change the capacitance of capacitive transducer, the present invention adopts many capacity plate antennas measurement space to be divided into many little spaces, measure coal powder density and the speed of different spaces, calculate the coal powder density of measuring tube and the mean value of speed, finally calculate the mass rate that coal dust flows through measuring tube.

In concrete enforcement, need to install pulverized coal flow on-line measurement device in the present invention respectively on every root First air pipeline, installation site straight-run of pipe section straight up after being adjustable contraction, capacitive transducer is not less than 2 times of pipe diameters from elbow distance.The segment pipe on primary air duct is substituted with measuring tube; Such as, the vertical increase in pipeline of four First air of coal pulverizer outlet installs measurement mechanism of the present invention respectively, realizes the online hot leveling of four primary air piping pulverized coal flows according to the data point reuse adjustable contraction of pulverized coal flow on-line measurement, optimize boiler combustion.

Claims (5)

1. a pulverized coal flow on-line measurement device, it is characterized in that: on First air pipeline, be arranged in series one section of measuring tube (1), described measuring tube (1) take stupalith as material, installs two groups of capacitive transducers respectively at the two ends of described measuring tube (1); Described capacitive transducer is on the outer wall of described measuring tube (1), be uniformly distributed 2n battery lead plate (2) in the form of a ring, and a described 2n battery lead plate (2) is relatively to be formed n capacity plate antenna between two; Using the electric capacity of described capacity plate antenna as the output signal of measurement mechanism.

2. pulverized coal flow on-line measurement device according to claim 1, it is characterized in that: on the outer wall of described measuring tube (1), each radome (3) is independently set, in the described radome of each battery lead plate (2) autonomous closure on respective position (3).

3. pulverized coal flow on-line measurement device according to claim 1, is characterized in that: the axial distance between described two groups of capacitive transducers is 200mm.

4. pulverized coal flow on-line measurement device according to claim 1, is characterized in that: utilize flange (6) to be removably connected between described measuring tube (1) and described First air pipeline.

5. utilize the pulverized coal flow on-line measurement device described in claim 1 to realize the method for pulverized coal flow on-line measurement, it is characterized in that:

Make one group in described two groups of capacitive transducers to be first group of capacitive transducer, another group is second group of capacitive transducer;

In described first group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{1, i}(t), i=1,2 ..., n};

In described second group of capacitive transducer, each capacity plate antenna in the temporary charge reservoir value of t is: { C _{2, i}(t), i=1,2 ..., n};

Described measuring method is carried out as follows:

Calculating surveyed area corresponding to i-th capacity plate antenna in two groups of capacitive transducers is respectively m in the coal dust instantaneous concentration value of t _{1, i}(t) and m _{2, i}(t):

$m_{1,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{1,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

$m_{2,i}\left(t\right)=\frac{\frac{{\mathrm{\ρ}}_s{C}_{2,i}\left(t\right)d}{{\mathrm{s\ϵ}}_0}-{\mathrm{\ϵ}}_g{\mathrm{\ρ}}_s}{{\mathrm{\ϵ}}_s-{\mathrm{\ϵ}}_g},i=1,2,...,n$

ρ in formula _sfor the real density of tested coal; ε _gfor dielectric constant of air; ε _sfor the specific inductive capacity of tested coal; ε ₀for permittivity of vacuum; D be in capacity plate antenna pair of electrodes distance between plates from; S is battery lead plate area;

The coal dust instantaneous concentration value obtained in t in measuring tube is calculated by formula (1) for:

$\stackrel{\‾}{m}\left(t\right)=\frac{\underset{i=1}{\overset{n}{\Σ}}{m}_{1,i}\left(t\right)+\underset{i=1}{\overset{n}{\Σ}}{m}_{2,i}\left(t\right)}{2n}---\left(1\right)$

Step 2, provide C by formula (2) _{1, i}(t) and C _{2, i}the cross correlation function R of (t) _{12, i}(τ):

$R_{12,i}\left(\mathrm{\τ}\right)=\frac{\lim }{T\→\mathrm{\∞}}\frac{1}{T}{\∫}_0^T{C}_{1,i}\left(t\right)C_{2,i}(t+\mathrm{\τ})dt---\left(2\right)$

By cross correlation function R _{12, i}(τ) to delay time T differentiate, such as formula (3):

$\frac{{\mathrm{dR}}_{12,i}\left(\mathrm{\τ}\right)}{d\mathrm{\τ}}=0---\left(3\right)$

(3) are utilized to solve R _{12, i}(τ) be time delay corresponding during maximal value

Order: the axial distance between two groups of capacitive transducers is D, and the pipeline section of measuring tube amasss as A, is calculated by formula (4) and obtains the average velocity that pulverized coal particle flows through measuring tube for:

$\stackrel{\‾}{V}=\frac{\underset{i=1}{\overset{n}{\Σ}}\frac{D}{{\mathrm{\τ}}_{i,R_{\max }}}}{n}---\left(4\right)$

Then coal dust flows through the mass rate q (t) of measuring tube and is: