DD285533A7 - MEASURING ARRANGEMENT AND METHOD FOR MEASURING THE SOLID SOLID STREAM OF STERLING GAS SOLID MIXTURES - Google Patents

Abstract

The invention relates to a method and a Meszanordnung for measuring the mass flow of solids flowing into technological Reaktionsraeume gas-solid mixtures. The aim of the invention is that regardless of the flow form of the gas-solid mixture, the mass flow is determined in order to ensure a process procedure adapted to accurate control and safe monitoring of the mass flow. The object of the invention is to eliminate the Meszprobleme resulting from the Entmischungsvorgaengen in the mass flow measurement of the solid phase of gas-solid streams. According to the invention, the object is achieved by using the results of demixing investigations, the sensors and detectors are arranged on the conveyor tube, as necessary due to the demixing and so that thus significant density, Geschwindigkeitsmeszwerte and Stroemungsquerschnitte for the calculation of the mass flow are obtained. According to the invention, the density and concentration measurements are determined at much smaller time intervals than the transit time of a closed solid plug of a plug flow past a sensor. Figure {gas-solid Rohrstroemung; Grain layer; Solids mass flow; segregation; fine-grained Schuettgut; Density; Speed; Density measurement; Concentration measurement; Speed measurement; capacitive sensor; radiometric detector}

Description

Grain layer is thereby loosened up due to the relaxation effect of Gap end is well flowable. The loosening is limited but analogous to a fluidized bed. When the average density decreases (p ₍ = s 0.6 a _m )) , the flow velocity of the gaseous liqueur decreases and the gaseous residue flow separates, forming a segregated, flowing grain layer with a high density D ₁₀ and dynamic viscosity The degree of turbulence of the segregated grain layer increases with increasing mass flow, because the required gas pressure increase increases the gap gas velocity due to the gas relaxation effect. ₀ decreases, but does not reach the density, as it exists in a quasi-homogeneous flow promotion.The loosening effect with a segregated grain layer is smaller by orders of magnitude than with a qualihomogeneous flow promotion, because the relaxing gap gas in the shortest path radially into the adjacent gas flow h In the flow promotion, the relaxing gaseous gas flows in the axial direction in the grain layer. The density range of the segregated grain layer p ₍₀ extends maximally from p, "to pf and in the usual range of dense phase conveying from p _fD to p _{) L.} Here, p _{(D represents} the maximum possible density of the loosened grain layer, which is a fixed point of a solid fluidized bed, PfL is the density at the conventional loosening point and pf is the density at the point of free flow of the loosened grain layer, densities below ρT occur in a fluidized bed and thus A density p ₍₀ <Pi leads again to a quasi-homogeneous flow, ie finally to a fly-off, it occurs when the gas velocity u, the separated gas flow exceeds approximately the following size:

Pg

From this one can see the pressure dependence of the necessary gas velocity of a gas-solid flow. With increase

the pressure level increases the conveying continuity.

Investigations have shown that a gas-solid flow depending on the flowability of a Bulk material can separate radially and axially. In the case of radial segregation, the segmental shape occurs in the case of horizontal conveyance

and when conveyed vertically, the annularly flowing grain layers. With axial segregation arises the

Plug flow. The prediction of the incoming flow shape, which is used to determine the significant flow cross section A _{5 of} the

Demixing, flowing grain layer is needed would require extensive fluid bed investigations with the bulk material. Because of the knowledge about the demixing can and because of the flow dependent dependence of the density ςιο, the speed u, as well as the flow cross section As, the significant sizes of

Solid mass flow determination can be measured directly in the segregated grain layer. Herein lies the surprising,

inventive way of solving the problem to solve the problems of speed and density inequalities

To eliminate delivery pipe and the variable sensitivity of the sensors along the measuring path. The distinction of the shape of the segregated gas-solid flow can by means of the measured concentrations Kr, K _ra

or densities Pr, pro are made as follows:

- Kf <Kfo or pt <Pto mean a segment flow for horizontal conveyance and a circular flow for vertical conveyance

- Kt »Kf ₀ means plug flow if p ₍ 0,6 0.6 · p < ₀₎ or demixing-free flow promotion if p> 0.6 · pro For the solid mass flow determination, the following equation with the significant measurands p _ra , u "A" where A, generally represents the flow cross-section of the segregated grain layer, requires:

According to the invention in the method for measuring the solid mass flow m, a segregated gas-solid mixture in a conveying tube for fine-grained bulk materials by known methods for speed, density and concentration measurement taking into account the demixing effect of flowing media with the measured values of concentrations K _(of the gas -Feststoff-Gemisch and Kf ₀ the segregated grain layer, the densities p, the gas-solid mixture and pto the segregated grain layer according to the following relationships the shape of the segregated gas-solid flow as Grundlago for the calculation of the flow cross-section A ₁ , Ar or the plug length Ip

- Pt <Pra or Kr <Kfo in the horizontal conveying segment flow of the grain layer with the segment height h, and in the vertical promotion a ring flow of the grain layer with the ring inner diameter d | as well as outside diameter d

- K ₁ w Kro means plug conveying, if p ₍ <0.6 · p _ro , or demixing-free flow promotion, if p ₍ > 0.6 · p _(D , where pio the characteristic, occurring during fluidization of a bulk material, maximum density of a gas Represents solid mixture,

determined.

The significant values A ₅ , Ar and I _P are determined by means of the proportions

h » _ Pt . _ _d ^ _ Pt Jp ^ _ pt d ρ «d per I pto

A Kro A Kfo I Kfo calculated as follows.

It turns out for

- the flow cross section

ace

360

α - = arc cos

/, 2h, \

\ ¹ --y

the density p _ro using the radiometrically measured mean density Pf at the

Segment flow: P ₁₀ = - ---

h / d

_D. ... p, - (dj / d) p _g

Ring current: Pro

1 - dj / d plug flow: p «= Pt = * Pro

¹ p

- The flow velocity u, as an immediate reading.

The solid mass flow rh, according to the known continuity equation with m, = u, · p _ro · A, for the segment and Ring flow and rh, = u, · p _ra · A · l _p / l = u, · p, · A calculated for the plug flow. To carry out the method, a measuring arrangement is used, which consists of a combination of capacitive and

radiometric measuring devices, which are located in a narrow axial flow area with constant property characteristics and wherein the radiation source and the detector of the radiometric measuring device is arranged diametrically on the outer wall of the conveying tube.

The collimated Sirahlenbündel is parallel with radial separation and perpendicular to the axial demixing Entmischungsrichtung. According to the invention, the two capacitive electrode pairs for the measurement of the grain layer velocity u, and

capacitive electrode pair 5 for the measurement of the concentration Kf ₀ or the density p _{m of} the segregated grain layer 2 on the

Inside the tube wall 1 with contact to the grain layer at an angle <180 °. The radiation source 8 and the Detector 9 are arranged at the conveyor tube circumference at an angle <180 ° and the StrahlerVDetektorachse forms a secant

of the delivery pipe cross-section.

embodiments

1st embodiment according to FIG. 1

The A-Jsführungsform the measuring method and the measuring arrangement of Figure 1 is described for a horizontal conveyor pipe 1 with the nominal diameter DN40mm, is promoted in the fine-grained PVC with a narrow particle size distribution. PVC has an easy flow-through capability, which means that during conveyance under the condition p, s 0.6 p _ID an axial segregation occurs and thus plug propagation occurs. The maximum possible density pm when loosening the PVC is 588 kgm- ³ .

For the measurement and calculation of the solid mass flow m, in the conveyor line 1 successively a radiometric measuring device with the radiation source 8 and the detector 9 for measuring the average density Pi of the gas-solid flow, a capacitive electrode pair 4 for measuring the average concentration Kf Gas-solid flow, a capacitive electrode pair 5 for measuring the concentration Κκ> of the segregated grain layer 2 and two capacitive electrode pairs 6; 7 for the measurement of the film layer speed u. Radiation source 8 and detector 9 and the electrodes of the electrode pair 4 are diametrically opposed to the tube circumference, with their connecting lines are vertical. The electrodes of the electrode pairs 5; 6; 7 are arranged at an angle of 45 °. The measured values of the concentrations Ki, K (o and the density pi are detected in time intervals of 50 ms.

When carrying out the measurements, Kf = »K ₁₀ results for the concentrations determined at short time intervals . The density p, averaged over short-term readings, is 200 kgm " ³ , which is less than 0.6 p, _D = 353 kgm"" ^3. This confirms the existence of a plug flow from the average concentration Kf and the high short-term measured values Kf ₀ results in the plug length ratio I _P / I ~ K ₍ / K _w = 0.34 With the pairs of electrodes 6, 7 the velocity u, the plug is measured to 2.1 ms " ^1. Either dire'.t with p / = 200kgm " ³ or with p" = p »· l / l _p = 588kgm" ³ results in the solid mass flow m, too

m, = u. · Ρ »· A · lp / l · 3600 = u, · ρ, · A · 360 = 1905kgh

The average length of a solid plug is 0.53m, the gauge length at the electrode pairs 6; 7 of the speed measurement 20mm and the entire measuring arrangement is housed on a 400 mm pipe section.

2nd embodiment according to FIG. 2

The embodiment of the measuring method and the measuring arrangement of Figure 2 is for a vertical conveyor pipe 1 with the Nominal diameter DN 65mm explained. It is very fine-grained, dried hard coal with a broad particle size distribution

metered into a reactor. The maximum possible density pm of the bulk material during loosening is about 680 kgm ^-3 . Due to the high specific flow resistance of the bulk material occurs at p <S 0.6 pm a radial segregation and thus in the vertical conveying pipe a ring flow.

In the vertical conveyor pipe 1 downstream of a radiometric measuring device with the radiation source. 8

and the detector 9 for measuring the mean density p, the gas-solid flow, two capacitive pairs of electrodes 6; 7 to

Velocity measurement u, the segregated grain layer 2 and a radiometric MesseinrichUng with the Radiation source 10 and the detector 11 for measuring the density p _{ro of} the segregated grain layer 2 installed. Radiation source 8

and detector 9 are diametrically opposite and arranged on the pipe circumference. The electrode pairs 6; 7 as well as the

Radiation source 10 and the detector 11 are each at an angle of 60 ° to each other, wherein the axis of the radiation source 10 and

of Detektros 11 lie on a secant of the conveyor tube cross-section. Silk density measuring devices have a possibility of measured value acquisition in short-term intervals of 35 ms. The measuring length of the electrode pairs 6; 7 for the

Speed measurement is 20mm. In the present dosing case, the measured value recording shows a density averaged from short-term measured values of = = 330 kgm ^-3 and

a density O ₁₀ = 630 kgm ^-3 of short-term values, it is confirmed that a ring flow form with p ₍ <p _ro and

Pf / Pro = 0.48 <0.6. This control of the measuring device is always needed to determine the flow shape. The Density ρ »of the segregated grain layer does not need to be calculated first because of the direct measurement with the detector 11

become.

The significant flow cross-section A, = Followed by - (d | / d) = pf / pn = 0.52 to 25.5 cm ² when the conveyor tube diameter

65mm. From this we calculate the mass flow m, mitu, = 4.4ms " ¹ , ρ") = 630kgm " ³ , A _H = 25.5cm ² as follows:

m, = u, · Pf ₀ · Ar · 3600 = 25500kgh ~ '

 The measuring arrangement is arranged within a conveying pipe section of 450 mm.

3rd embodiment according to FIG. 3

The embodiment of the measuring method and the measuring arrangement of Figure 3 is for a horizontal conveyor pipe 1 with the Nominal diameter DN 50mm, in which a mineral bulk material with high fine grain size and narrow particle size distribution

is conveyed to a mixer described.

The bulk material to be conveyed has a high specific flow resistance, so that when conveying in the density range Pi S 0.6 · Pf ₀ a radial segregation in the form of a segment flow occurs. The maximum possible density when loosening

Pid = 855kgm ~ ³ .

For the measurement and calculation of the solid mass flow m, one after the other in the conveying pipe 1 upstream

radiometric measuring device with the radiation source 10 and the detector 11 for measuring the density ρκ> the demixed

Grain layer, two capacitive electrode pairs 6; 7 for the measurement of the grain layer velocity, a capacitive Electrode pair 5 for the measurement of the concentration Kro of the segregated grain layer and a pair of capacitive electrodes 4 for

the measurement of the average concentration K _{f of} the gas-solid mixture is incorporated. Radiation source 10 and detector 11 and the electrodes of the electrode pairs 5; 6; 7 are arranged at an angle of 60 "at the circumference of the tube so that they lie symmetrically to the deepest tube longitudinal line on the tube circumference .The electrodes of the electrode pair 4 are diametrically opposite each other on the tube circumference The middle field lines point in the vertical direction. 5 and the radiometric measuring device 10, 11 are detected at time intervals of 35 ms.

The control measurements for determining the flow shape by means of the capacitive measuring devices 4; 5 show that K | / Kfo = 0.51 and because of Pi <0.6 · p _{m is} a radially segregated flow form. p ₍₀ comes with 820kgm ~ ³

measured.

As is calculated by Kf / K ₍₀ and A with the following relationship:

A ₈ = A · Kf / Kfo = 19.6 · 0.51 = 10.0cm ² Using the equations

As = · - ^{(d / 2} - "·> ^{d / 2} " ^{8ina / 2}

OH YOU

a / 2 = arc cos (1 - 2h, / d) gives h, = 25.3 mm, α = 181.4 ° and then with the following relationship and with the density p _Q = 2,5kgm " ^{3 of} the gas stream 3rd

Pi - (h "/ d) p _fl ^Pt0" h./d

the average density pt = 417 kgm " ^{3 of} the gas-solid flow, α is the chord angle of the segregated grain layer 2 in the conveyor tube 1. With the electrode pairs 6, 7 a speed u, = 6.3 ms" ^{1 is} measured, so that the solid mass flow too

m, = u, ITi ₁₀ · A ₅ · 3600 = 18600kgh "'

 The measuring length of the speed u is 20mm. The measuring arrangement is housed on a pipe section of 500mm.

Claims (2)

1. A method for measuring the mass flow of solids rh ₈ a segregated gas-solid mixture in a conveying pipe for fine-grained bulk materials with known methods for speed, density and concentration measurement, taking into account the demixing effect of flowing media, wherein 'the solid mass flow rh _a according to the Koritinuitätsgleichung with m ₈ = u ₈ · p _f0 · A ₈ for the segment and ring flow and m ₈ = U ₈ · p (o · A · Ip / I = U ₈ · Pf · A) for the plug flow is calculated, characterized that with the measured values of the concentrations K _{f of} the gas-solid mixture and Kfo of the segregated grain layer, the densities Pf of the gas-solid mixture and P (o the segregated grain layer according to the following relationships, the shape of the segregated gas-solid Flow as a basis for the calculation of the flow cross-section As, A _R or the plug length I _P
- Pf <Pro or Kf <Kfo mean in the horizontal promotion segment flow of the grain layer with the segment height h "and in the vertical promotion a ring flow of the Grain layer with the ring internal diameter dj and -outside diameter d -Kf »Kfo means plug conveying, if Pf ^ 0.6 · pm, or demixing-free flow promotion, if pf> 0.6 Pf ₀ , whereby p _(D the characteristic, with Aufwirwirung of a bulk material is determined, and that the significant value * As, Ar or I _P by means of the proportions h ₈ Pf _Λ dj Pf Ip qi
,1 d pro d pfo 'I ς As Kf Ar Kf I _P Kf A Kfo A Kfo I Kfo be calculated as follows, which yields for
- the - ^c flow cross section π · (d / 2) ² · α / d _t \ d α
- = arc cos - the density Pfo using the radiometrically measured mean density pf at the Segment flow: p, ₀ = - τ -% -. - h _s / d _Ring flow: p _f0 = - ^ -; Plug flow: Pf ₀ = Pf · 7- «Pro ip - The flow velocity u _s in all flow forms without a necessary correction as a direct measurement. 2. A measuring arrangement for carrying out the method according to claim 1 by combination of capacitive and radiometric measuring devices, which are located in a narrow axial flow area with constant property characteristics and wherein the radiation source and the detector of the radiometric measuring device is arranged diametrically on the outer wall of the conveying tube so that the collimated beam is parallel with radial segregation and perpendicular to the mixing direction with axial segregation, characterized in that the two pairs of capacitive electrodes (6; Measurement of the grain layer velocity U ₈ and the capacitive electrode pair (5) for the measurement of the concentration Κκ> or the density of the segregated grain layer (2) on the inside of the tube wall (1) are arranged with contact to the grain layer at an angle <180 ° and that the radiation source (8) and the detector (9) are arranged at the conveyor tube circumference at an angle <180 ° and the radiator / detector axis forms a secant of the conveyor tube cross-section. For this 1 page drawings Field of application of the invention The invention relates to a method and a measuring arrangement for measuring the solids mass flow of fine-grained bulk materials during conveying and dosing in technological reaction chambers, containers and other aggregates. Characteristic of the known technical solutions The measurement of the solid mass flow rti, a gas-solid flow of fine-grained bulk materials by means of radiometric and capacitive measuring isi known from a variety of sources of information and belongs to the prior art. Fundamentals of radiometric density and thickness measurement as well as capacitance measurement are explained in / 1 / and / 7 / for homogeneous media. In 121 a correlation velocity measurement system in combination with a concentration measurement based on capacitive sensors is presented for two-phase flows and especially for the gas-solid flow. The electrodes of the measuring electrode pairs are located on the pipe circumference and are diametrically opposite. The measuring systems described take into account in the determination of the measured value no unequal distributions of the flowing solid over the delivery pipe cross-section. This unequal distribution and the highly variable measuring sensitivity along the Meßstrocke in capacitive sensors lead to density and Geschwindigkeitsmeßwerten that are not significant for the related to the Gesamtförderrohrquerschnttt mass flow calculation. Capacitive sensors also have the disadvantage that the Konzentrationsmeßwerte depend heavily on the moisture content of the dielectric, ie the moisture content of the bulk material. The use of the capacitive measuring device for density measurement is thus severely limited. In 131, page 53, these problems are referred to, without demonstrating solutions to averting the problem addressed. In contrast, in / 3 / method for marking the gas-solid flow for the purpose of increasing the safety of the Geschwindigkeitsmeßwerterfassung and in IAI and / 5 / method of continuous Injektionsgaszuführung in the gas-solid flow for the purpose of a targeted density change for enabling a mass flow calculation, the Although using radiometric Dichtemeßeinrichtungen, but no solutions for the metrological detection of the significant flow cross-section of a segregated flow can be seen. With a combined direct transmission and scattered radiation method, a so-called four-point measuring technique was developed for / 6 / for the local density determination of air-water mixtures in large process cross-sections. The net-like Mehrfachdurchstrahlung of the process cross-section or the need for quasi-continuous rotation of the measuring device and the time-consuming evaluation of the measured data do not allow this method of measurement for fast process control and monitoring to use. Object of the invention The object of the invention is a method and a measuring arrangement for measuring the solid mass flow of flowing gas-solid mixtures in the promotion and dosage in technological reaction chambers and other aggregates, in which regardless of the flow shape of the gas-solid mixture, the mass flow is determined in order to ensure a precise control and safe monitoring of the mass flow rh, adapted to the process taking place in the reaction space. Explanation of the essence of the invention The object of the invention is to eliminate the resulting from the segregation measurement problems in the solid mass flow measurement of gas-solid flows of fine-grained bulk solids with known in the measurement and control capacitive and radiometric measuring devices. The surprising effects for the solution of the problem are the detection of the segregation processes of gas-solid flows and the behavior of the segregated, flowing grain layer in the delivery pipe and in overcoming the matching problems of sensor sensitivity to the geometry of the segregated gas-solid flow. In fine, flowing gas-solid mixtures at a density of the mixture p /> 0.6 x p _{r D} a quasi-homogeneous flow promoter exists. The cross section of the delivery tube is filled with the flowing grain layer. The