WO2014044473A1 - Method and device for determining properties and/or ingredients of a suspension - Google Patents

Description

 Method and device for determining properties and / or ingredients of a suspension

The present invention relates to a method and a device for the quantitative detection of properties and / or ingredients of a suspension, in particular a pulp suspension for paper, tissue or board web production. For paper, tissue or also cardboard web production, a fiber suspension is prepared in a pulp preparation, then applied by means of a headbox to a sieve belt and dewatered or dried so that it results in a fibrous web. For optimum production control and quality assurance, the most accurate knowledge possible of the ingredients of the fiber suspension is essential.

Pulp suspensions also contain various fillers, such as clay, calcium carbonate, etc., and various chemicals, e.g. for bleaching the fibers or flocculating between the various suspended substances. In the pulp and paper industry, in particular, the concentration measurement of pulp density and ash content of the pulp suspensions is of central importance.

An inline measurement can be done in different ways. Various measuring methods for measuring concentrations in a pulp suspension are known from the prior art.

For the determination of the ingredients, among other things, optical measuring methods are used. Essentially, there are two optical methods for measuring consistency and ash content of a suspension in a machine for manufacturing and / or finishing a fibrous web known.

In one method, properties of the suspension are measured with transmitted light, in the other method with scattered light.

In the transmitted light measurement is usually measured monochromatically. The transmitter and the receiver are about 1, 5 to 3mm apart so that the suspension in between can be measured. In the transmitted light method, casually, "shadows" of particles in the suspension are measured. The transmitted light measurement is independent of the particle type. Due to a small measuring window, the light beam has a diameter between 0.2mm and 0.5mm, the transmitted light measuring method is strongly dependent on the flocculation and the flow of the suspension, which can lead to measurement errors.

The scattered light measurement measures the light scattered back from particles in the suspension of a large but undefined volume range. The scattered light measurement is highly dependent on the particle type and its scattering intensity. For example, sensors based on the scattered light measurement are known with which the total material density can be measured up to a substance density of up to approx. 4.5%. Separate determination of individual components in the suspension, however, is limited. Depending on the concentration of the ingredients, the measurement must be done in a bypass. In addition, the aging of the light sources affects the measurement.

However, sensors based on transmitted light measurement and / or scattered light measurement, as disclosed for example in DE 10 2004 051 960 A1, also react sensitively to air bubbles and fiber flakes contained in the suspension (accumulation of many small particles / fibers). EP 1 653 214 A1 discloses a method and a device which combines these two measuring methods with one another and thus leads to a better measurement result. However, it has been shown that the measurement still does not meet the requirements.

In addition to optical methods, measuring devices for bypass or Linemessung known that measure the consistency in a suspension stream by means of mechanical devices. Such a device is described for example in EP 1 331 480 A1.

Further embodiments are known from the publications EP 0 740 783 A1 and EP 2 108 1 13 A1. Here, the consistency in the suspension stream is determined by means of a shear force measurement.

These measurements do not meet the requirements since only the so-called total material density, ie fiber density plus ash content, can be measured here.

The object of the invention is to propose a method and a device which is suitable for in-line measurement of pulp density and ash content of a pulp suspension.

The object is achieved by means of a method having the features of claim 1 and the device having the features of claim 9.

A method is proposed in which light is introduced into the suspension to be measured by means of a measuring device comprising at least one light source and a light measuring device and the light reflected by the suspension is recorded and the quantity of light received is determined quantitatively and / or qualitatively.

According to the invention, the light is coupled into the suspension selectively via a first channel at an injection point and the light reflections of the resulting halo are decoupled, measured and analyzed via at least two detection channels.

Here is exploited that a selectively introduced into a suspension light radiation propagates in this and forms a halo or halo. The amount of light reflected by the particles in the suspension decreases as the distance from the coupling point increases. The decrease depends on the nature and the number of particles. The measurable amount of reflected light thus has a different intensity value around the first channel at all points. The detection channels can therefore be arranged arbitrarily around the coupling-in point of the light radiation, the first channel. In a preferred embodiment, the detection channels are arranged at different distances around the coupling-in point of the light radiation. To improve the measurement result, the light transmission cross sections of the detection channels can be adapted to the light intensity of the reflected light with increasing distance to the coupling-in point.

Alternatively, the measuring device can be adapted to the deteriorating lighting conditions. The light measuring device may be a spectrometer system, by means of which at least one property and / or an ingredient is measured and analyzed by spectrometric analysis of the coupled-out light reflections.

In this case, the, by the detection channels, coupled-out light reflections can be directed by a light guide system on the spectrometer, which may consist of several spectrometers, which are each coupled to a detection channel.

The spectrometer system comprises an evaluation electronics or is connected to a corresponding computer for the evaluation of the measurement results.

From the measurement results of the reduced scattering coefficient and / or the spectral absorption coefficient can be determined or calculated.

The calculated values can be approximated by algorithms to the measurement results so that absolute values for the reduced scattering coefficient and / or the spectral absorption coefficient can be determined.

The measured distribution curve is thus compared with a simulation simulated from calculations. By numerically changing the reduced scattering coefficient and the spectral absorption coefficient, the calculated course is approximated to the measured course. If the curves are approximately congruent, it is assumed that the value pair for the reduced scattering coefficient and the spectral absorption coefficient is found. From the values of these coefficients, or from their change over the measured spectrum, the pulp density and / or the ash content can be determined.

The device according to the invention comprises a measuring probe, at least one light source, for coupling light into the suspension to be measured, and a light measuring device, by means of which the light reflected by the suspension is recorded and the quantity of light received can be quantitatively and / or qualitatively determined. The probe has a mask with a first channel, for coupling the light into the suspension at a coupling-in point, and at least two detection channels for coupling out light reflections from the fiber suspension.

In one embodiment, the detection channels are arranged at different distances around the coupling-in point of the first channel. Thus, the detection channels can also be arranged radially to the coupling-in point of the first channel or radially on a line starting from the coupling-in point of the first channel.

For better light absorption, the detection channels can also have larger light transmission cross sections with increasing distance.

Furthermore, a machine for producing a fibrous web is claimed with a corresponding device. The measuring probe is preferably inserted into a pipeline through which a suspension stream flows, and / or into a fabric chest.

The invention makes use of the effect of the spatially spectrally resolved light scattering in an advantageous manner in order to determine in-line pulp density and ash content in pulp suspensions. Further features and further advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawing.

In these show: Figure 1 schematic diagram of the measuring system

Figure 2 Structure of the probe and function of the measurement method

Fig. 3a / b Construction Front side of the probe with cover mask

FIG. 1 shows a schematic diagram of the measuring system. The aim is to determine the contents of the suspension 7, in particular the pulp density 1 1 and the ash content 12. For this purpose, light, e.g. the light of a halogen lamp 2, initiated. The light of the light source 2 is preferably conducted via a light guide 3 and an optical system 15 in the suspension. Through the optics there is a strong focus, so that the suspension 7 is punctiform illuminated at the coupling point 4 or the light is selectively coupled into the suspension.

As a result of the selective illumination, an atrium or a halo 10 forms in the suspension 7. That is, the light propagates hemispherically around the light exit point 9 or the light entry point 4 in the suspension 7. In the suspension 7, the light is both scattered by the ash particles 12 and fiber particles 1 1 present and absorbed and reflected.

With the light measuring device, the reflections are resumed and directed into a spectrometer system 5. The quantitative and / or qualitative determination of properties and / or ingredients of the suspension 7 then takes place with the aid of the spectrometer system of the light measuring device.

FIG. 2 shows the structure of a measuring probe 1, which is connected to the spectrometer system 5 and a light source 2. The measuring probe 1 consists of an encapsulated housing 8, which has at least three passage channels 19, 20 on the front side, wherein the light beam can exit through one of them and the reflected light radiation can reenter through the others. The channels, the first channel 19 and the detection channels 20, are formed by openings in a mask. As shown in FIG. 3, the end face of the measuring probe consists of a sapphire glass pane 22 and the covering mask 21 applied thereto. The sapphire glass 22 has a thickness of at least 0.1 mm. The inner side of the sapphire glass pane 22 is coated black in order to reduce back reflections, and the mask 21 is made of black material, which is applied as a metallic mask directly onto the sapphire glass pane 22. This mask can be made very thin via a galvano impression. In addition, this method allows to very precisely define the structures for the channels 19, 20 via a photo-exposure. The mask can be well coated with so-called camera paint, so that the surfaces have a very low reflection.

The light of the light source 2 is directed via an optical waveguide 3 to an optical system 15 and focused by the latter, so that the light is irradiated through the first channel 19, or the coupling-in point 4, at points into the suspension 7. The light spot may have a diameter of 0.1 mm to 2 mm at the coupling-in point.

By the detection channels 20, the reflected light is picked up and coupled via a sensor head 16 in light guide 3a and passed to the spectrometer system. The light entry points 17 and the detection channels 20 are, as can be seen in Figure 3, arranged such that the reflected light is recorded at different distances to the coupling point 4 and each directed via separate optical fibers 3a to the spectrometer 5.

Since the amount of reflected light decreases sharply as the distance increases, the passage openings become larger and larger with increasing distance to the first channel 19.

One or more spectrometer units are accommodated in the spectrometer system 5, so that the light coming from the optical waveguides 3a can each be measured with respect to the distance to the coupling-in point 4 and analyzed in the evaluation electronics. The spectrometer units can have different sensitivities.

Several spectrometer systems 5 are known from the prior art, all embodiments can alternatively be used.

For the quantitative detection of properties and / or ingredients, the measuring probe 1 is immersed in the suspension at least to the extent that at least the Sapphire glass plate 22 is immersed in the suspension. Thus, the measuring probe 1, for example, in a pipe 18 or a chest, for the treatment or storage of a suspension, be installed. The measuring probe 1 is thus installed directly at the desired measuring point in the process, so that an inline measurement is made possible.

The measured data can be forwarded to the machine control so that the process control or regulation of the pulp web production is improved.

LIST OF REFERENCE NUMBERS

probe

 light source

 optical fiber

 coupling point

 Spektrometersystenn

 evaluation system

 suspension

 casing

 light output

 Halo / halo

 fibers

 ash particles

 Connection to machine control lens

 sensor head

 light entry

 pipeline

 first channel

 detection channel

 mask

 Sapphire glass

25

Claims

Patent claims 1 . Method for the quantitative detection of properties and/or ingredients of a suspension (7), in particular a fiber suspension for paper, tissue or cardboard web production, by means of a measuring device which comprises at least one light source (2) and a light measuring device (5), wherein light is introduced into the suspension (7) to be measured and the light reflected by the suspension (7) is recorded and the amount of light recorded is determined quantitatively and/or qualitatively, characterized in that that the light is coupled into the suspension (7) at a point at a coupling point (4) via a first channel (19) and the light reflections of the resulting halo (10) are coupled out, measured and analyzed via at least two detection channels (20). . 2. Method according to claim 1, characterized, that the detection channels (20) are arranged around the coupling point (4) of the light radiation. 3. Method according to claim 2, characterized, that the detection channels (20) are arranged at different distances around the coupling point (4) of the light radiation. 4. Method according to claim 3, characterized, that the light transmission cross sections of the detection channels (20) are adapted to the light intensity of the reflected light as the distance to the coupling point (4) increases. Method according to one of the preceding claims, characterized, in that the light measuring device comprises a spectrometer system (5), by means of which at least one property and/or an ingredient is measured and analyzed by spectrometric analysis of the coupled-out light reflections. Method according to claim 5, characterized, that the light reflections coupled out through the detection channels (20) are guided to the spectrometer system (5) by means of a light guide system. Method according to one of the preceding claims, characterized, that the reduced scattering coefficient and/or the spectral absorption coefficient is determined from the measurement results. Method according to claim 7, characterized, that calculated values are approximated to the measurement results using algorithms, so that absolute values for the reduced scattering coefficient and/or the spectral absorption coefficient can be determined. Device for the quantitative detection of properties and/or ingredients of a suspension (7), in particular a fiber suspension for paper, tissue or cardboard production, comprising a measuring probe (1), at least one light source (2), for coupling light into the measuring suspension (7), and a light measuring device, by means of which the light reflected by the suspension (7) is recorded and the amount of light recorded can be determined quantitatively and/or qualitatively, characterized, that the measuring probe (1) has a cover mask (21) with a first channel (19) for coupling the light into the suspension (7) at a coupling point (4), and at least two detection channels (20) for coupling out light reflections from the Fiber suspension. 10. Device according to claim 9, characterized, that the detection channels (20) are arranged at different distances from the coupling point (4) of the first channel (19). 1 1 . Device according to claim 10, characterized, that the detection channels (20) are arranged radially on a line starting from the coupling point (4) of the first channel (19). 12. Device according to claim 1 1, characterized, that the detection channels (20) have larger light transmission cross sections as the distance increases. 13. Device according to claim 9, characterized, that the light measuring device comprises a spectrometer system (5). 14. Device according to claim 13, characterized, in that the spectrometer system (5) comprises several spectrometer units, each spectrometer unit being assigned a detection channel and the detection channels (20) being connected to the spectrometer units via light guides, which guide the reflected light from the detection channels (20) to the spectrometer units 5. 15. Machine for producing a fibrous web comprising a device according to one of claims 9 to 14. 16. Machine according to claim 13, characterized, that the measuring probe (1) is inserted into a pipeline (18) through which a suspension stream (7) flows, and/or into a fabric chest.