CN105929260A - Method for on-line measuring charge-to-mass ratio of particles in fluidized bed - Google Patents

Abstract

The invention discloses a method for on-line measuring charge-to-mass ratio of particles in a fluidized bed. The method comprises the steps of acquiring induction electrostatic current signals generated during a granule fluidization process through an annular induction electrode and pressure pulsation and differential pressure signals on two sides of the annular induction electrode, and obtaining the charge-to-mass ratio through the quantitative correlations between the electrostatic current and differential pressure signals. The detection result is accurate, and the detection apparatus is simple in structure, low in cost and wide in application scope. The method is applicable to real-time on-line detection of charge-mass ratio of particles in the fluidized bed.

Description

A kind of On-line Measuring Method of Granules in Fluidized Bed charge-mass ratio

Technical field

The present invention relates to the detection method of electrostatic level in a kind of gas-solid system, particularly relate to a kind of Granules in Fluidized Bed lotus The real-time online measuring method of matter ratio.

Technical background

Gas-particle two-phase system is widely present in the industrial process such as Coal Chemical Industry, petrochemical industry, pharmacy industry, Metallurgy Industry.Electrostatic Being the phenomenon generally existed in gas-particle two-phase system, the frictional impact between granule, between granule and wall result in electrostatic charge Generation and accumulation.Particularly in olefinic polymerization fluidized-bed reactor, the strenuous exercise of high-insulativity granule and extremely low ring Border humidity makes the generation of electrostatic charge and accumulation be particularly acute.The existence of electrostatic can affect the hydrodynamics behavior in reactor, The accumulation of excessive static electricity lotus may cause the generation of the phenomenons such as viscous wall, caking, even causes stopping in emergency of reactor, for peace Full steady production brings hidden danger.In industry gas-solid fluidized bed reactor, it is often desirable that reduce the harm that electrostatic brings as far as possible, By Electrostatic Control at reduced levels.The either exploration to electrostatic mechanism of production, or the exploitation to electrostatic regulation and control method, accurately Electrostatic detection means essential.

Electrostatic detection methods conventional in fluid bed includes electrostatic probe method and Faraday cup method.The measurement of electrostatic probe method During, probe stretches to inside fluid bed, is reflected by the electrostatic potential in measure loop, electrostatic current or electrostatic charges accumulated situation Change in electrical charge at probe.He etc. (Powder Technology.2016,290:11-20) propose " bi-material layers probe " and " bipolar electrode probe ", by measuring transfer current when colliding of popping one's head in of electrically charged particle and different materials, combination model calculating The average charge-mass ratio of grain.This method has some limitations: for different fluidisation systems, before detecting, and needs Model parameter is re-scaled, so reducing the universality of the method；Probe contacts with granule direct collision, can shadow Ring fluid bed local flow field.Faraday cup method is the overall carrying capacity of granule by measuring certain mass, can directly obtain The average charge-mass ratio of grain.For the detection of gas-solid fluidized bed middle granule charge-mass ratio, generally granule sampling is set at fluid bed wall Mouthful, make electrically charged particle be directly entered in Faraday cup, obtain the carrying capacity of granule.The method has some limitations: by lotus During electricity granule is transferred to Faraday cup, charging particle amount can be affected by sampling process；Cannot realize fluid bed The on-line checking of middle local granule carrying capacity.Therefore, develop the granule charge-mass ratio on-line measurement means of a kind of simple in construction, be quiet Electro-detection field problem demanding prompt solution.

It is the main cause that electrostatic current produces that electrically charged particle constantly enters and leaves toroidal inductive electrode detection region, and its The change of middle electrically charged particle quantity also will necessarily cause the change of induction electrode both sides pressure reduction, thus causes the similar of the two Property.When assuming that induction electrode detection region endoparticle size is identical, charged uniform and when stablize, electrostatic current and differential pressure versus time First derivative is directly proportional, and proportionality coefficient is relevant with granule charge-mass ratio and fluid bed size.According to electrostatic current and pressure difference signal, permissible Calculate the average charge-mass ratio of the Granules in Fluidized Bed of certain size.Granule charge-mass ratio measuring method based on toroidal inductive electrode can To realize the on-line monitoring of charging particle amount change procedure.

Summary of the invention

The technical problem to be solved is that existing electrostatic detection technology cannot the asking of on-line measurement granule charge-mass ratio Topic, it is provided that a kind of fluid bed granulate charge-mass ratio On-line Measuring Method based on electrostatic current and pressure difference signal.

The On-line Measuring Method of fluid bed granulate charge-mass ratio based on electrostatic current and pressure difference signal comprises the steps of

1) use the sensing electrostatic current produced in toroidal inductive electrode detection electrically charged particle fluid mapper process, use pressure simultaneously The pressure reduction pulsation of pulsation probe detection toroidal inductive electrode both sides；

2) criterion of particle charge polarity: will sensing electrostatic current I (i) and pressure reduction pulsation first derivative DP (i) to the time NI (i) and NDP (i), defined parameters is respectively obtained after normalizationN is data point sum, Experiment with computing value Y_exp；Keep DP (i) invariant position in time domain, by I (i) in time domain often to one unit of right translation, weight Calculated all Y values are compared, obtain Y by Y value of new calculating_maxAnd Y_min；Defined parametersWhen α value of calculation is 1, granule entirety shows positive electricity, and when α value of calculation is 0, granule entirety shows negative electricity；

3) axial height of toroidal inductive electrode is designated as W, and electrode diameter is designated as D, and the radial position at electrically charged particle place is X, defines dimensionless group θ is the polar angle of different radial position, and the space obtaining toroidal inductive electrode is sensitive Degree is:

$S_s\left(r\right)=\frac{k}{4\mathrm{\π}}{\∫}_0^{\mathrm{\π}}\frac{0.5-rcos\mathrm{\θ}}{\left\{(0.25+r^2-rcos\mathrm{\θ}){(0.25k^2+0.25+r^2-rcos\mathrm{\θ})}^{1/2}\right\}}d\mathrm{\θ},$

In conjunction with spatial sensitivity value S of different radially positions, ask for mean space sensitivity S_ave；

4) utilizing the granule charge-mass ratio computing formula in fluid bed to calculate charge-mass ratio, the computing formula of granule charge-mass ratio is:Wherein L is the measured zone height of pressure fluctuation, and A is fluid bed cross-sectional area, and W is electrode Axial height, I_indFor sensing electrostatic current, d Δ P/dt is the first derivative of differential pressure versus time.

The measurement object of fluid bed granulate charge-mass ratio measuring method based on electrostatic current and pressure difference signal is gas-solid fluidized bed Device.

The structural parameters W/D of the toroidal inductive electrode used in the range of 1/50-1/5, toroidal inductive thickness of electrode is 1-5mm。

Synchronous detecting sensing electrostatic current and the pressure reduction fluctuating signal of toroidal inductive electrode both sides, frequency reception signal scope is 0-20kHz。

Compared with prior art, the present invention is had the beneficial effect that

1) present invention is by carrying out synchronous detecting to the pressure reduction fluctuating signal of sensing electrostatic current and toroidal inductive electrode both sides, And connect signal reception and processing system, the real-time online detection of granule charge-mass ratio can be realized；2) measurement result accuracy is higher； 3) suitability is extensive, it is adaptable to different size, different types of fluidized bed plant；4) measurement apparatus is installed simple, only need to be at stream Fluidized bed reactor sidewall installs toroidal inductive electrode additional and pressure fluctuation is popped one's head in.

Accompanying drawing explanation

Fig. 1 is lucite fluid bed cold work die device；

Fig. 2 is the electrostatic current under superficial gas velocity 0.5m/s at grain fluidized bed middle distance distribution grid 100mm and 240mm of B class Scheme over time with pressure reduction derivative；

Fig. 3 is the spatial sensitivity profile of toroidal inductive electrode；

Fig. 4 is to be calculated by direct computing method at the grain fluidized bed middle distance distribution grid 100mm of B class under superficial gas velocity 5m/s The granule average charge-mass ratio numerical value arrived；

Fig. 5 is calculated by direct computing method and the axially different position B class that records of Faraday cup sampling method The grain average charge-mass ratio of granule under different superficial gas velocities；

Fig. 6 is fluidization number u/u_mfCalculated by area-method at the grain fluidized bed middle distance distribution grid 100mm of B class when=2.5 The granule average charge-mass ratio numerical value arrived；

Fig. 7 is calculated by area-method and the axially different position B class granule that records of Faraday cup sampling method exists The average charge-mass ratio of granule under different LAA content；

Fig. 8 is fluidization number u/u_mfWhen=2.5 D class grain fluidized bed middle distance distribution grid 100mm place sensing electrostatic current with The envelope up and down of pressure reduction derivative；

Fig. 9 be envelope method is calculated and Faraday cup sampling method records D class granule under different LAA content The average charge-mass ratio of grain；

Detailed description of the invention

1) use the sensing electrostatic current produced in toroidal inductive electrode detection electrically charged particle fluid mapper process, use pressure simultaneously The pressure reduction pulsation of pulsation probe detection toroidal inductive electrode both sides；

2) criterion of particle charge polarity: will sensing electrostatic current I (i) and pressure reduction pulsation first derivative DP (i) to the time NI (i) and NDP (i), defined parameters is respectively obtained after normalizationN is data point sum, Experiment with computing value Y_exp；Keep DP (i) invariant position in time domain, by I (i) in time domain often to one unit of right translation, weight Calculated all Y values are compared, obtain Y by Y value of new calculating_maxAnd Y_min；Defined parametersWhen α value of calculation is 1, granule entirety shows positive electricity, and when α value of calculation is 0, granule entirety shows negative electricity；

3) axial height of toroidal inductive electrode is designated as W, and electrode diameter is designated as D, and the radial position at electrically charged particle place is X, defines dimensionless group θ is the polar angle of different radial position, and the space obtaining toroidal inductive electrode is sensitive Degree is:

$S_s\left(r\right)=\frac{k}{4\mathrm{\π}}{\∫}_0^{\mathrm{\π}}\frac{0.5-rcos\mathrm{\θ}}{\left\{(0.25+r^2-rcos\mathrm{\θ}){(0.25k^2+0.25+r^2-rcos\mathrm{\θ})}^{1/2}\right\}}d\mathrm{\θ},$

In conjunction with spatial sensitivity value S of different radially positions, ask for mean space sensitivity S_ave；

4) calculating granule charge-mass ratio, the computing formula of granule charge-mass ratio is:Wherein L is pressure The measured zone height of power pulsation, A is fluid bed cross-sectional area, and W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt is the first derivative of differential pressure versus time.

The measurement object of the On-line Measuring Method of fluid bed granulate charge-mass ratio based on electrostatic current and pressure difference signal is gas-solid Fluidized bed plant.The structural parameters W/D of described toroidal inductive electrode in the range of 1/50-1/5, toroidal inductive thickness of electrode is 1-5mm.Synchronous detecting sensing electrostatic current and the pressure reduction fluctuating signal of toroidal inductive electrode both sides, frequency reception signal scope is 0- 20kHz。

Embodiment 1

Fig. 1 is shown in by experimental provision, uses lucite fluid bed cold work die device, and device internal diameter is 300mm, fluidisation be System and detecting system form, and black heavy line represents fluidisation gas circuit, and dotted line representation signal gathers circuit.Detecting system is felt by annular Answer electrode, pressure fluctuation probe and Faraday cup composition.Toroidal inductive electrode is used for detecting electrically charged particle in fluid mapper process to be passed through The sensing electrostatic current produced during electrode sensitive district, the width W of toroidal inductive electrode is 20mm, remains toroidal inductive during installation Electrode base Edge Distance distribution grid 100mm and 240mm position.Pressure fluctuation probe is used for detecting toroidal inductive electrode both sides Pressure reduction, differential pressure measurement height is 30mm.Faraday cup off-line sample tap is arranged at range distribution plate 90mm and 230mm, uses In the average charge-mass ratio of granule of detection toroidal inductive electrode installed position, average to verify granule based on toroidal inductive electrode The accuracy of charge-mass ratio measurement result.The sample frequency of sensing electrostatic current and pressure fluctuation is 400Hz, and the sampling time is 240s.

Use fluidized particles be linear low density polyethylene (Linear Low Density Polyethylene, LLDPE) granule, physical parameter is as shown in table 1, belongs to Geldart B class granule, and it is initial that the classical pressure decline method measurement of utilization obtains Fluidizing velocity is 0.2m/s.Fluidizing gas is dry air, and relative humidity is 8-15%, and experiment is at room temperature carried out.

Table 1 linear low density polyethylene physical parameter

Use dry air that lucite fluid bed is purged 10min, be subsequently added the LLDPE that 1.5kg was pre-dried Granule, the quiet height of bed is 265mm.The superficial gas velocity used is respectively 0.4, and 0.5,0.6 and 0.7m/s.At the apparent gas that experiment relates to In the range of speed, in fluid bed, remain bubbling fluidization state.

By grain fluidized 30min under certain superficial gas velocity, to ensure that granule is the most charged, reach saturated.Survey simultaneously Sensing electrostatic current and electrode both sides pressure reduction on amount toroidal inductive electrode are pulsed over time.Under superficial gas velocity 0.5m/s, Electrostatic current at range distribution plate H=100mm and H=240mm and pressure reduction derivative are the most as shown in Figure 2.

Sensing electrostatic current I (i) and pressure reduction pulsation are obtained NI (i) and DP to first derivative DP (i) normalization of time (i), defined parametersExperiment with computing value Y_exp；Keep pressure reduction derivative position in time domain Constant, electrostatic current signal is moved right one by one, often moves a data point, recalculate a Y value, by calculated institute There is Y value to compare, obtain Y_maxAnd Y_min；Defined parametersWhen α value of calculation is 1, granule entirety is aobvious just Electricity, when α value of calculation is 0, granule entirety shows negative electricity.Under this experiment condition, be calculated α value and be always 0, i.e. granule is main Electronegative.

The calculating formula of the spatial sensitivity of electrostatic transducer is

Wherein dimensionless groupW is the axial height of toroidal inductive electrode, and D is electrode diameter, definitionX is The radial position at electrically charged particle place.The spatial sensitivity profile of toroidal inductive electrode as shown in Figure 3 calculates and understands, and width is The mean space sensitivity S of 20mm electrode_aveIt is 27%.

The computing formula of granule charge-mass ratio is:Wherein L is the height in differential pressure measurement region, A For fluid bed cross-sectional area, W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt is the single order of differential pressure versus time Derivative.

During measuring due to reality, pressure reduction derivative and electrostatic current are the discrete point in zero crossings fluctuation, if by two The discrete point of person is directly divided by, then can produce the great null result of some numerical value.In order to reject invalid data, improve and calculate knot The Stability and veracity of fruit, by the theoretical maximum charge-mass ratio of following formula calculating Granules in Fluidized Bed as threshold value, carries out data Screening.

$|\frac{Q}{m}{|}_{max}=\frac{{\mathrm{\ϵ}}_0{E}_d{\mathrm{\πD}}_{in}{H}_f}{m}$

Wherein ε₀For permittivity of vacuum, numerical value is 8.854 × 10^-12F/m, E_dFor the disruptive field intensity of fluidizing gas, for Air is 3.0 × 10⁶V/m, D_in、H_fBeing respectively fluid bed internal diameter and fluid height, m is the granular mass in fluid bed.Calculate Obtaining the theoretical maximum of fluidized particles charge-mass ratio absolute value in this experimental system is 6.23 μ C/kg, therefore, utilizes and directly calculates Method calculated sensing electrostatic current is with the ratio of the amplitude of pressure reduction derivative, and absolute value will be considered more than the result of calculation of this value It is invalid value and rejects.

With superficial gas velocity 0.5m/s, as a example by sensing electrostatic current and pressure reduction derivative data at range distribution plate 100mm, by electrostatic Stream is directly divided by with pressure reduction derivative amplitude, and the computing formula substituting into granule charge-mass ratio obtains a series of charge-mass ratio data；In conjunction with After fluidized particles charge-mass ratio theoretical maximum rejects invalid data, obtain a series of granules average charge-mass ratio number as shown in Figure 4 Value, in the meansigma methods of these numerical value being measured as this, the measurement result of the average charge-mass ratio of granule, utilizes three survey calculation The meansigma methods of result is as final granule average charge-mass ratio result.

In conjunction with the judged result of charging particle polarity, utilize direct method calculated axially different position granule average Charge-mass ratio with superficial gas velocity change as shown in Figure 5.Visible, the average charge-mass ratio of axially different position fluidized particles is all with table See the increase of gas speed and increase, with the average charge-mass ratio of granule that records by Faraday cup sampling method in Fig. 5 with the change of superficial gas velocity Change trend is consistent.

Embodiment 2

Fig. 1 is shown in by experimental provision, uses lucite fluid bed cold work die device, and device internal diameter is 300mm, fluidisation be System and detecting system form, and black heavy line represents fluidisation gas circuit, and dotted line representation signal gathers circuit.Detecting system is felt by annular Answer electrode, pressure fluctuation probe and Faraday cup composition.Toroidal inductive electrode is used for detecting electrically charged particle in fluid mapper process to be passed through The sensing electrostatic current produced during electrode sensitive district, the width W of toroidal inductive electrode is 40mm, remains toroidal inductive during installation Electrode base Edge Distance distribution grid 100mm and 240mm position.Pressure fluctuation probe is used for detecting toroidal inductive electrode both sides Pressure reduction, differential pressure measurement height is that 60mm Faraday cup off-line sample tap is arranged at range distribution plate 90mm and 230mm, is used for The average charge-mass ratio of granule of detection toroidal inductive electrode installed position, to verify the average lotus of granule based on toroidal inductive electrode Matter is than the accuracy of measurement result.The injection position of liquid antistatic additive is arranged at above nearly distribution grid, to ensure antistatic additive Obtain under the effect of high velocity air quick, sufficiently disperse, it is to avoid it concentrates in fluid bed regional area.Sensing electrostatic current Being 800Hz with the sample frequency of pressure fluctuation, the sampling time is 240s.

Use fluidized particles be linear low density polyethylene (Linear Low Density Polyethylene, LLDPE) granule, physical parameter is as shown in table 1, belongs to Geldart B class granule, and it is initial that the classical pressure decline method measurement of utilization obtains Fluidizing velocity is 0.2m/s.Fluidizing gas is dry air, and relative humidity is 8-15%, and experiment is at room temperature carried out.

Use dry air that lucite fluid bed is purged 10min, be subsequently added the LLDPE that 1.5kg was pre-dried Granule, the quiet height of bed is 265mm.Fluidization number (the u/u used_mf) it is 2.5, remain bubbling fluidization state in fluid bed.General Grain fluidisation 30min, to ensure that granule is the most charged, reaches saturated.Sense electrostatic current and electricity on measure annular induction electrode simultaneously The pressure reduction of both sides, pole is pulsed over time.Utilize off-line Faraday cup Measurement with Sampling Method span from distribution grid 90mm and 230mm Place granule average charge-mass ratio, using continuous three times measure meansigma methods as final measurement.Charge-mass ratio will after being measured Sampling particles rejoins fluid bed, to ensure that the granule gross mass of whole bed does not changes.

Keep fluidization number u/u_mf=2.5, after fluidisation 30min, in fluid bed, inject the LAA of certain content, inject body Long-pending and corresponding mass fraction is shown in Table 2, senses electrostatic current in record LAA diffusion process at distance distribution grid 100mm and 240mm Change.After LAA injects 20min, measure sensing electrostatic current and the pressure reduction of toroidal inductive electrode both sides simultaneously, and use off-line farad Method measures the average charge-mass ratio of granule at range distribution plate 90mm and 230mm.

Table 2 liquid antistatic additive injection rate

Sensing electrostatic current I (i) and pressure reduction pulsation are obtained NI (i) and DP to first derivative DP (i) normalization of time (i), defined parametersExperiment with computing value Y_exp；Keep pressure reduction derivative position in time domain Constant, electrostatic current signal is moved right one by one, often moves a data point, recalculate a Y value, by calculated institute There is Y value to compare, obtain Y_maxAnd Y_min；Defined parametersWhen α value of calculation is 1, granule entirety is aobvious just Electricity, when α value of calculation is 0, granule entirety shows negative electricity.Under this experiment condition, be calculated α value and be always 0, i.e. granule is main Electronegative.

The calculating formula of the spatial sensitivity of electrostatic transducer is

Wherein dimensionless groupW is the axial height of toroidal inductive electrode, and D is electrode diameter, definitionX is The radial position at electrically charged particle place.The spatial sensitivity profile of toroidal inductive electrode as shown in Figure 3 calculates and understands, and width is The mean space sensitivity S of 40 mm electrodes_aveIt is 41%.

The computing formula of granule charge-mass ratio is:Wherein L is differential pressure measurement region Highly, A is fluid bed cross-sectional area, and W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt is differential pressure versus time First derivative.

WillCertain period of time is integrated by the right and left, then the average charge-mass ratio of granule Expression formula be rewritten asThis formula is utilized to carry out the calculating of the average charge-mass ratio of granule, referred to as face Area method.With fluidization number u/u_mf=2.5, as a example by sensing electrostatic current and pressure reduction derivative data at range distribution plate 100mm, every 10s pair Electrostatic current and pressure reduction derivative curve carry out an integral and calculating, and the absolute area value taking integration calculates as integral result, substitution Obtain the average charge-mass ratio of granule, as shown in Figure 6.Using the meansigma methods of charge-mass ratio value of calculation in figure as the average charge-mass ratio of final granule Measurement result, calculated and Faraday cup sampling method records under different LAA content the change of the average charge-mass ratio of granule such as Shown in Fig. 7, both variation tendencies are consistent.

Embodiment 3

Fig. 1 is shown in by experimental provision, uses lucite fluid bed cold work die device, and device internal diameter is 300mm, fluidisation be System and detecting system form, and black heavy line represents fluidisation gas circuit, and dotted line representation signal gathers circuit.Detecting system is felt by annular Answer electrode, pressure fluctuation probe and Faraday cup composition.Toroidal inductive electrode is used for detecting electrically charged particle in fluid mapper process to be passed through The sensing electrostatic current produced during electrode sensitive district, the width W of toroidal inductive electrode is 40mm, remains toroidal inductive during installation Electrode base Edge Distance distribution grid 100mm position.Pressure fluctuation probe is used for detecting the pressure reduction of toroidal inductive electrode both sides, Differential pressure measurement height is that 60mm Faraday cup off-line sample tap is arranged at range distribution plate 90mm, is used for detecting toroidal inductive electricity The average charge-mass ratio of granule of pole installed position, with the checking average charge-mass ratio measurement result of granule based on toroidal inductive electrode Accuracy.The sample frequency of sensing electrostatic current and pressure fluctuation is 400Hz, and the sampling time is 240s.

The fluidized particles used is polypropylene (Polypropylene, PP) granule, and physical parameter is as shown in table 3, belongs to Geldart D class granule, the minimum fluidizing velocity utilizing classical pressure decline method measurement to obtain is 0.55m/s.Fluidizing gas is dry Air, relative humidity is 8-15%, and experiment is at room temperature carried out.

Table 3 PP GRANULES physical parameter

Use dry air that lucite fluid bed is purged 10min, be subsequently added the PP granule that 5kg was pre-dried, The quiet height of bed is 300mm.Fluidization number (the u/u used_mf) it is 2.5, remain bubbling fluidization state in fluid bed.By grain fluidized 30min, to ensure that granule is the most charged, reaches saturated.Sense electrostatic current and electrode both sides on measure annular induction electrode simultaneously Pressure reduction pulse over time.Utilize off-line Faraday cup Measurement with Sampling Method span average lotus of granule away from distribution grid 90mm Matter ratio, using continuous three times measure meansigma methods as final measurement.Sampling particles is added after being measured by charge-mass ratio again Fluidized bed, to ensure that the granule gross mass of whole bed does not changes.

Keep fluidization number u/u_mf=2.5, after fluidisation 30min, in fluid bed, inject the LAA of certain content, inject body Long-pending and corresponding mass fraction is shown in Table 2, senses the change of electrostatic current in record LAA diffusion process at distance distribution grid 100mm.Treat After LAA injects 20min, measure sensing electrostatic current and the pressure reduction of toroidal inductive electrode both sides simultaneously, and survey by off-line faraday's method Span is the average charge-mass ratio of granule away from distribution grid 90mm.

Sensing electrostatic current I (i) and pressure reduction pulsation are obtained NI (i) and DP to first derivative DP (i) normalization of time (i), defined parametersExperiment with computing value Y_exp；Keep pressure reduction derivative position in time domain Constant, electrostatic current signal is moved right one by one, often moves a data point, recalculate a Y value, by calculated institute There is Y value to compare, obtain Y_maxAnd Y_min；Defined parametersWhen α value of calculation is 1, granule entirety is aobvious just Electricity, when α value of calculation is 0, granule entirety shows negative electricity.Under this experiment condition, be calculated α value and be always 0, i.e. granule is main Electronegative.

The calculating formula of the spatial sensitivity of electrostatic transducer is

Wherein dimensionless groupW is the axial height of toroidal inductive electrode, and D is electrode diameter, definitionX is The radial position at electrically charged particle place.The spatial sensitivity profile of toroidal inductive electrode as shown in Figure 3 calculates and understands, and width is The mean space sensitivity S of 40mm electrode_aveIt is 41%.

The computing formula of granule charge-mass ratio is:Wherein L is differential pressure measurement region Highly, A is fluid bed cross-sectional area, and W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt is differential pressure versus time First derivative.

The computing formula of granule charge-mass ratio is:Wherein L is the height in differential pressure measurement region, A For fluid bed cross-sectional area, W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt is the single order of differential pressure versus time Derivative.

The meansigma methods using electrostatic current and pressure reduction derivative fluctuating margin is divided by and is calculated the average charge-mass ratio of granule.By a period of time The peak point line of the signal of length, it is possible to obtain top (positive) line and lower section (negative) line, be referred to as wrapping Winding thread.Envelope can reflect the fluctuating margin change of signal, use following formula calculating electrostatic current and the ratio of the amplitude of pressure reduction derivative:

${\left(\frac{I_{ind}}{d\mathrm{\Δ}P/dt}\right)}_{mean}=\frac{E_{max}-E_{\min }}{{\mathrm{DP}}_{\max }-{\mathrm{DP}}_{\min }}$

Wherein E_max、E_min、DP_max、DP_minIt is respectively the average of the coenvelope that fluctuates with pressure reduction derivative of electrostatic current and lower envelope Value.With fluidization number u/u_mf=2.5, as a example by range distribution plate height is the sensing electrostatic current at 100mm and pressure reduction derivative, the two Envelope is as shown in Figure 8 up and down.The ratio of calculated electrostatic current with the amplitude of pressure reduction derivative is substituted intoThe middle average charge-mass ratio of calculating granule, takes final as charge-mass ratio of the meansigma methods of three measurement results Result of calculation.Envelope method is calculated and Faraday cup sampling method records D class granule average lotus of granule under different LAA content The change of matter ratio is as it is shown in figure 9, both variation tendencies are consistent.

Claims (4)

1. the On-line Measuring Method of a Granules in Fluidized Bed charge-mass ratio, it is characterised in that said method comprising the steps of:

1) use the sensing electrostatic current produced in toroidal inductive electrode detection electrically charged particle fluid mapper process, use pressure fluctuation simultaneously The pressure reduction pulsation of probe detection toroidal inductive electrode both sides；

2) criterion of particle charge polarity: will sensing electrostatic current I (i) and pressure reduction pulsation first derivative DP (i) normalizing to the time NI (i) and NDP (i), defined parameters is respectively obtained after changeN is data point sum, calculates Experiment value Y_exp；Keep DP (i) invariant position in time domain, by I (i) in time domain often to one unit of right translation, again count Calculate a Y value, calculated all Y values are compared, obtains Y_maxAnd Y_min；Defined parametersWork as α When value of calculation is 1, granule entirety shows positive electricity, and when α value of calculation is 0, granule entirety shows negative electricity；

3) axial height of toroidal inductive electrode is designated as W, and electrode diameter is designated as D, and the radial position at electrically charged particle place is x, fixed Justice dimensionless groupθ is the polar angle of different radial position, obtains the spatial sensitivity of toroidal inductive electrode For:

$S_s\left(r\right)=\frac{k}{4\mathrm{\π}}{\∫}_0^{\mathrm{\π}}\frac{0.5-rcos\mathrm{\θ}}{\left\{(0.25+r^2-rcos\mathrm{\θ}){(0.25k^2+0.25+r^2-rcos\mathrm{\θ})}^{1/2}\right\}}d\mathrm{\θ},$

In conjunction with spatial sensitivity value S of different radially positions, ask for mean space sensitivity S_ave；

4) calculating granule charge-mass ratio, the computing formula of granule charge-mass ratio is:Wherein L is pressure arteries and veins Dynamic measured zone height, A is fluid bed cross-sectional area, and W is the axial height of electrode, I_indFor sensing electrostatic current, d Δ P/dt First derivative for differential pressure versus time.

2. according to the measuring method of the granule charge-mass ratio described in claim 1, it is characterised in that the survey of described measuring method Amount object is gas-solid fluidized bed apparatus.

3. according to the measuring method of the granule charge-mass ratio described in claim 1, it is characterised in that described toroidal inductive electrode Structural parameters W/D in the range of 1/50-1/5, toroidal inductive thickness of electrode is 1-5mm.

4. according to the measuring method of the granule charge-mass ratio described in claim 1, it is characterised in that described sensing electrostatic current and The pressure reduction fluctuating signal synchronous detecting of toroidal inductive electrode both sides, frequency reception signal scope is 0-20kHz.