DE102010060131A1 - Apparatus for determining three-dimensional spatial velocity profile of rheological medium in e.g. large microscale reactor, has measuring lance that is moved in three-dimensional space of process vessel - Google Patents

Abstract

The apparatus has a process vessel (1) that accommodates a measuring lance (4) with local detector units (5-9) that are connected with an external evaluating unit. The measuring lance is moved in the three-dimensional space of the process vessel. The measuring lance is moved around the own axis. The two-dimensional space detectors are arranged at preset gap with respect to each other and with respect to a planar unit. An independent claim is included for method for three-dimensional spatial velocity profile of rheological medium.

Description

Technical application area:

The invention relates to an arrangement for detecting the spatial velocity profile and the residence time spectrum of rheological media in industrial processes, especially in large-scale reactors and in biogas digesters. Furthermore, the method for the use of these arrangements will be described.

About the spatial velocity profile in reactor vessels, as they are operated in the chemical, environmental, bio and energy process technology, can be directly derived information about the flow conditions in the process and thus on the effectiveness and the local effect of the stirring devices used.

The residence time spectrum of the process media in reactors is a highly meaningful parameter that allows conclusions to be drawn about the efficiency of the entire system. With the help of the global residence time spectrum, for example, statements about the degree of mixing, the average residence time of the substances and existing dead zones or short-circuit currents can be made.

State of the art

Known methods for detecting spatial velocity profiles can be classified into non-invasive and invasive methods. Non-invasive optical methods such as 3D particle image velocimetry (PIV) or videometry are usually not applicable because of the nature of the process media (opacity and inhomogeneity). Radiation-based methods such as 3D process tomography (positron emission tomography, X-ray tomography or gamma computed tomography) are unsuitable due to the size of the reactors.

Invasive measuring methods such as impedance needle probes DE 10 2005 046 662 B3 and conductivity grating sensors DE 19 649 011 A1 . EP 1 990 612 B1 Measure locally or in a very limited local area and are therefore not suitable for a spatial detection on an industrial scale. In addition, in the last-mentioned electrical methods, the speed measurement is linked to existing phase transitions (liquid gas) or contrasts of the electrical impedance in one phase, which is not permanently guaranteed in every process. Furthermore, due to the size and structure of the metering devices, these invasive techniques run the risk of damage or clogging due to the presence of solid matter in the process medium. In EP 2 028 474 B1 it will discuss the detection of the velocity of metallic tracer particles in a tube cross-section, but the detection of the spatial velocity distribution in the reactor itself is not taken into account.

Known methods for acquiring residence time spectra are based on chemical, biological and physical properties of tracers, such as salts. Their detection requires manual sampling at the measuring point of the reactor with subsequent analysis to determine the concentration in the laboratory, which leads in addition to the high staffing time to delays in the measurement result. Furthermore, the data density is determined by the intervals of sampling, which are usually chosen relatively long for cost reasons. For online acquisition of color and fluorescence tracers such as rodamine or uranine, in addition to optical access to the measuring point, the sufficient optical clarity of the process medium is a prerequisite that is not given in the vast majority of processes. The use of radiotracers is questionable because of the safety aspect and because of a possible negative influence biochemical processes in reactors not desirable. The disadvantages of the above-mentioned methods is that with them the detection of the flow rate on an industrial scale of a reactor is possible only with great difficulty and with great technical effort.

With the use of ferromagnetic or magnetic tracers and a suitable electrical detection principle, the automatic event-dependent online acquisition of the residence time spectrum and the speed of the tracer is enabled. Exemplary methods for local detection of magnetic tracers are in EP 2 028 474 B1 . DE 2 029 337 or WO 2004 104 561 A1 disclosed. It addresses applications in which particle sizes in the submillimeter range are used for detection in rather small tube cross sections of less than 100 mm. When used in large-scale reactors, a detection in pipe cross-sections of up to 1000 mm is necessary. In addition, the large reactor volumes lead to a high dilution of the tracers. For the measurement of residence time spectra on large-scale reactors is therefore the detection of very low tracer concentrations up to the single detection of particles required in large pipe cross sections. Furthermore, the processes mentioned in the application in sufficiently homogeneous rheological process media such as lubricating oils, plastic melts or aniline. The detection in electrically highly conductive and highly inhomogeneous media has not been considered in detail.

Brief description of the invention

Tasks solved with invention

The object of the invention is to provide an arrangement for detecting the three-dimensional spatial velocity profile of rheological media in technological processes, especially for large-scale process container, which avoids the above-mentioned disadvantages of known solutions and in a broad and especially security-relevant application, in particular with regard to the composition and the Properties of the process medium, the flow rates and the equipment used in the reactor (process vessel), can be used. Another object is to specify the use of this arrangement for detecting the spatial velocity profile and for further optional detection of the residence time spectrum.

Technical solution

The object is achieved by the arrangement described in claim 1 and the use of this arrangement according to claim 7. Advantageous embodiments are specified in the dependent claims.

The task is solved by using tracers, which are added to the process. These tracers move smoothly with the process medium. The tracers are continuously recorded in an event-oriented manner at the measuring points in the medium.

The inventive arrangement consists of one or more detector units, which are arranged on one or more measuring lances, wherein the measuring lances are arranged to be movable. When using several detector units on a measuring lance a simultaneous evaluation in a spatial coordinate is possible.

Advantageous effect

The use of one or more movable measuring lances enables a distributed measurement of the local velocity vectors in the process vessel. The three-dimensional flow profile of the process container is imaged by fusion of the speed data collected sequentially with the lance. The prior art allows only one- or two-dimensional measurement in pipe sections or large-scale reactors. Due to the mobility of the individual measuring lance, the technical installation effort in the reactor is kept low. This measurement can be combined by using the tracers with a downstream residence time measurement at the outlet of the reactor.

Short description of the drawing figures

shows the basic structure of the example of a cylindrical process container with a stirrer.

shows the basic embodiment variant with multiple measuring lances.

shows the embodiment with a detector unit and a measuring lance.

shows the construction of a detector unit.

shows possible arrangements of the detector unit on a measuring lance.

represents the coordinate system for the process container.

shows the basic structure when using flat detector elements on a measuring lance in conjunction with the measured result.

shows the basic structure when using liquid tracers on flat detector elements.

Description of the embodiments

arrangement

The arrangement according to the invention consists of one or more measuring lances 4 entering the medium to be examined in the process container 1 be immersed. Along the measuring lance 4 are several detector units 5 ... 9 mounted at defined intervals.

The measuring lance 4 is attached at one end to a traversing device. With the help of this traversing device, the measuring lance 4 in the radial direction r, in the circumferential direction in the reactor Φ and / or additionally in the immersion direction h either by means of a manual drive or by means of electric motors.

In an arrangement according to the invention, the detector units attached to the measuring lance are made 5 ... 9 from at least one detector 25 . 26 . 27 and are connected to an evaluation unit (computer). The connection between the detector or detector unit and evaluation can be done with cables and / or wireless, in the latter case signals must still be evaluated outside of the process container and under certain circumstances appropriate safety requirements, such as explosion protection, are observed.

The detector unit 5 ... 9 can rotate on the measuring lance 4 be arranged. This is useful if less than three detectors are used.

The measuring lance 4 itself can additionally rotatable on a traversing device 10 be attached. In this case, the coordinates (r, Φ, h) of the measuring probe do not change with respect to the process container, but the position of the detector units on the measuring probe changes. In order to perform an optimal three-dimensional measurement, three detectors are mounted orthogonally as a detector unit on the measuring lance. In this case, a rotation of the detector unit on the measuring lance is not necessary.

The connection cables are guided along the measuring lance and the displacement device in an inventive arrangement along the measuring lance. In a further advantageous arrangement, the cables are guided inside the measuring lance, wherein the snagging of substances that move in the process container is excluded. A twisting of the cables is to be excluded by appropriate control of the movement and guidance of the cables.

The individual detector itself is constructed so that the local flow velocity in all direction components (v _r , v _φ , v _h ) is detected. At every detector position 5 ... 9 The lance is mounted three orthogonal coil arrangements along the three spatial axes. Each of these coil arrangements is formed around a pipe section with a much smaller diameter d than the process vessel ( 2r ) and protected from the process medium. The diameter of the pipe section or the detector must be large enough so that solid suspended matter does not get caught in it or damage the detector.

In a further embodiment, planar detector units, such as the surface sensors, are used. For this purpose, two sensors arranged orthogonally to one another or a rotatable sensor are to be used in order to detect the flow vector locally completely. In the planar arrangement, two detectors are arranged side by side (see. ) or juxtaposed and offset from one another. If liquid tracers are to be determined and if the liquid tracer is mixed with the process medium, it makes sense to inject the liquid tracer in the vicinity of the detectors. In this case, the arrangement may consist of an excitation electrode, in the vicinity of which, preferably at the center, the liquid tracer is injected into the process medium. Around this excitation electrode several sensors are arranged at a fixed distance and at an equal angle to each other.

The use of only one detector unit 5 is possible. In order to be able to create a speed profile, this detector unit must be movably attached to the lance and at the same time the measuring lance must move in space at time-defined intervals.

method

For local speed measurement at the detectors 5 ... 9 Different tracers can be used.

In the current process mode, a defined amount of tracers 13 with the process mixture or together with individual input materials, eg. B. starting materials (substrates in Biogasfermentern), by the inlet 2 introduced into the process container. The time of tracer addition is defined for the measurement as a time reference point t = 0 s. It is important that the tracers are distributed as homogeneously as possible in the template and this is introduced in as short a time as possible in order to obtain a pulse-shaped addition of tracer. If this is not feasible, it is recommended to record the time course of the tracer addition. This can be done either via an additional detector at the inlet or with homogeneous mixing of the template over a defined time specification of the feed (pump or screw conveyor). Based on the individual tracer function, the normalized impulse response can later be determined from the measured residence time spectrum as the sum or concentration curve.

According to the invention, once tracers are used which respond to inductive measuring methods, such as tracers consisting of ferromagnetic substances, containing or sheathed. Eddy current based inductive measuring methods or combined inductive proximity probes determine the type of tracer used. The tracers must have a Stoke number less than 1, so that they do not move too sluggishly in the process medium. Since the diameter of the detectors is much smaller than the diameter of the process container, tracers with a size smaller than 7 mm can be used. The diameter of the detector and the size of the tracers are linearly proportional.

As an alternative variant for speed measurement via metal tracers, liquid tracers such as deionized or NaCl solutions can be used. These can be detected by electrical surface sensors or flat scattered light sensors. Due to the dilution effect, this is more advantageous to inject locally near the detectors. One possible arrangement is in specified.

The tracers are distributed with the surrounding process medium in the reactor and represent the prevailing flows. During the passage of the tracer particles through the detectors at the positioned measuring probe, the local velocity vectors (v _n, v _.phi..sub.i, v _hi, with i = 1 ... N) is detected and, together with a time stamp and the position data of radius r, rotational angle Φ and Height h stored. This is repeated for each interpolation point to be detected in the process vessel (r _i , Φ _i , h _i ). In this way N support points for the velocity field of the reactor are detected. By three-dimensional interpolation between the measured field points, the velocity field can then also be determined for the non-measured spaces.

Optional residence time determination

At the exit 3 of the process container, the particles are then from a downstream detector 11 detected in the pipe cross-section. Each detected particle is assigned a time stamp, whereby a dwell time spectrum with event-dependent time resolution is formed. As a result, the data density of the residence time spectrum is automatically adapted to changes over time in the tracer concentration.

To record the residence time of the metal-based tracer is a residence time detector 11 at the pipe cross-section of the reactor outlet 3 , which is mostly realized as a dip tube with horizontal overflow used. The residence time detector 11 consists of a coil arrangement, which can be used especially for large pipe cross sections> 100 mm to 1000 mm. The exit 3 passing tracers are detected by the coil assembly and evaluated the resulting measurement signal in real time. In this case, each tracer particle including possibly parallel tracers is taken into account with an individual time stamp. The residence time spectrum can thus be recorded directly automated, eliminating the need for laborious laboratory analysis. Detecting each tracer at the exit increases the data density of the residence time spectrum over conventional residence time detection methods. Fluctuations in the level in the pipe have a negligible influence on the measuring signal due to the low frequency of the carrier signal. The size of the distance is determined by the type and size of the tracer used.

When the ferromagnetic-based tracer is the detector 11 These can happen through an electromagnetic filter 12 separated from the process medium and recovered.

Generated advantages or improvements over the prior art:

A major advantage is the low instrumentation and installation effort when using moving measuring lances compared to a variety of existing in the process vessel measuring instruments and the detection of a spatial flow profile. The local speed can be determined with fixed positioning of a measuring lance.

Another advantage is the possible online recording of the residence time spectrum without the need for sampling at the outlet of the process vessel and subsequent laboratory analysis. The data density of the residence time spectrum is event-oriented, and thus more precise correlations to retention time models than with the sampling methods based on fixed and usually long measurement intervals can be achieved.

The use of tracers with different particle sizes allows a separate determination.

The determination of several particles passing through the detector at the same time by corresponding signal analysis (multiple thresholds and / or local maxima) is possible.

When discrete tracers are used, they can be filtered at the output from the process medium and recovered. The discrete metal particles are chemically inert and have no dilution effect like other tracers. Therefore, they can also contribute individually to the residence time spectrum. The carrier signal is low-frequency, preferably with frequencies below 10 kHz, so that the measurement is not disturbed by inhomogeneities in the process media and level fluctuations in the detector cross-section.

Advantageous further embodiments:

By modifying the measuring lance technology, a stationary recording of the local speed by means of permanently installed lances is also possible. This is particularly conceivable when measuring near the action radii of agitators or in potential dead zones / short-circuit currents.

The design of the local speed measurement can be done alternatively to the metal detection via liquid tracers and electrical surface or scattered light sensors. A modification of the grating sensor is the surface conductivity sensor, which would be suitable in connection with a locally injected liquid tracer (deionized) for a local speed measurement. Similarly, optical scattered light sensors can be used locally. List of reference numbers 1 reactor vessel 2 Inlet with feed and inlet at the bottom of the container 3 Sequence / outlet 4 Measuring lance with detector units 5 . 6 . 7 . 8th . 9 local detector units 10 Track with linkage 11 Dwell detector at the exit 12 Filter for tracers 13 tracer 15 . 16 . 17 Measuring lance with detector units 20 stirring unit 25 . 26 . 27 Detectors for the three spatial axes 28 Holder for the detectors on the measuring lance (4) S _i with i = 1 ... 10 Detectors on the surface detector unit I _i with i = 1 ... 3 injection nozzle A _i with i = 1 ... 3 excitation electrodes E _i with i = 1 ... 8 receiving electrodes

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102005046662 B3 [0005]
• DE 19649011 A1 [0005]
• EP 1990612 B1 [0005]
• EP 2028474 B1 [0005, 0007]
• DE 2029337 [0007]
• WO 2004104561 A1 [0007]

Claims (14)

Arrangement for determining the spatial velocity profile of rheological media, which are located in a process vessel, characterized in that a. in the process container 1 at least one measuring lance 4 with at least one local detector unit 5 , which are connected to an external evaluation, is introduced and b. this measuring lance (s) 4 can be moved in the three-dimensional space of the process container. Arrangement according to claim 1, characterized in that the measuring lance 4 additionally movable around its own axis. Arrangement according to claim 1, characterized in that the movement of a measuring lance 4 on traversing units 10 done manually or with the help of a controller. Local detector unit 5 for use in the arrangement according to one of claims 1 to 3, characterized in that the detector unit can detect the local velocity vector by a. from at least three arranged individual detectors, which are preferably arranged orthogonal to each other, or b. a detector movably arranged in three spatial axes, or c. is constructed of at least two arranged individual detectors, which are preferably arranged orthogonal to each other, and the two individual detectors are arranged movably in space. Local detector unit 5 for use in the arrangement according to one of claims 1 to 3, characterized in that the detector unit consists of a flat unit, on the two-dimensional space a plurality of detectors in at least two columns next to each other or side by side and partially offset from one another. Local detector unit 5 for use in the arrangement according to one of claims 1 to 3, characterized in that the detector unit are applied from a flat surface, on which a plurality of receiving electrodes are arranged around an excitation electrode, and in the vicinity of the excitation electrode, preferably in the center, the tracer injected into the process medium. Method for detecting spatial velocity profiles using the arrangement according to one of claims 1 to 3 and local detectors according to one of claims 4 or 6, characterized in that a. tracers are added to the process medium at a fixed time t ₀ or within a time interval, b. the tracers move in the process medium and are detected by the detectors in the process medium and the position of the detectors is stored in the process medium, c. Since the detectors are connected to an evaluation unit, the signal is sent to them and then evaluated. A method according to claim 7, characterized in that the measuring lance 4 to another point on the track 10 is moved at the time t _φv , and the measurement is continued. A method according to claim 7, characterized in that the arrangement of the measuring lance 4 is changed in height at the time t _h and the measurement is continued. A method according to claim 7, characterized in that the measuring lance 4 at time t _M is rotated about its longitudinal axis, and the measurement is continued. A method according to claim 7, characterized in that the rotatably loaded detector unit 5 ... 9 at the time t _Φ at the measuring lance 4 is rotated, and the measurement is continued. A method according to claim 5, characterized in that one or all or all detectors i of the detector unit are rotated individually in space and the measurement is continued. A method according to claim 7, characterized in that in the vicinity of the measuring lance a tracer, preferably a liquid tracer, is injected into the process medium. Method according to one of claims 7 to 13, wherein subsequent to the determination of the velocity profile at the output of the process container, the dwell time spectrum can be determined with the tracers for determining the velocity profile by the tracers are counted when passing the exit.

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