FI61964C - FOERFARANDE FOER MAETNING AV KONSISTENS I EN MASSA - Google Patents

Description

[\ δτ * Ι [B] (11) ANNOUNCEMENT Q

l J '' utlAggningsskrift o I? 64 C granted 11 10 1932, ¾¾¾ ^ Patent meddelat ^ ^ (51) Kv.lk?/lnt.CI.3 G 01 K 15/02

FINLAND —FINLAND (21) P «t * ntUI» kwwi »-P« t «» »eiuanf 79310U

(22) HkkamlipAivf - AnaMutlnpdaf 08.10.79 '* (23) Alkupllvt — Glhlghatsdaf 08.10.79 (41) Interpreters | ulklMk «l - BIMt off * ntll | 09.Ot. 8l

rakifMrllullitu · (M

Patent- och registerstyralaan '' AmMcm uthfd och utLskrUtMi pubUnnd 30.06.82 (32) (33) (31) Requested atuoUcaut — B «| ird priorhat (71) Kajaani Oy, Nuaskatu 11, 87 ^ -00 Kajaani ** 0, Finland -Finland (FI) (72) Juha Rapeli, Oulu, Finland-Finland (FI) (7 * 0 Papula Rein Lahtela Oy (5 * 0 Method for measuring the turbidity of pulp - Förfarande för mätning av konsistens i en massa

The invention relates to a method for measuring the consistency of a pulp containing pulp and / or ground fibers.

The object of the invention is to enable fast and accurate measurement of solid components from various processes, etc. This is necessary, for example, for process control and monitoring of the amounts and properties of substances present at different stages of the process.

Numerous methods are known for carrying out the measurements referred to in the invention. On the other hand, there are methods based on laboratory processing and examination of liquid samples that are not suitable for continuous process measurement. On the other hand, there are measurements based on various physical phenomena, such as those based on optical, mechanical, acoustic phenomena or X-rays. However, all of these are limited by the narrow range of application, inaccuracy, or suitability for measuring only certain types of ingredient-liquid combinations. Likewise, they are generally limited to measuring only one property, such as consistency.

For aspects of the invention, reference is made to the claims section.

The method according to the invention achieves the following advantages compared to the prior art: - the information obtained by the measurement method is versatile and the measurement applicable to the current situation is continuous in all conditions and the result is immediately available. The measurement result can be performed at the desired process point. for quantities such as pressure, flow rate and temperature, the measuring sensor can be constructed to be durable and of the desired size.

The method according to the invention is based on the behavior of the dielectric properties of substances. It is known theoretically and experimentally that there is a certain dependence between the permittivity and dielectric losses of the substance and the frequency and polarization mechanism of the electric field.

In a homogeneous substance, the mechanisms influencing the above dependence are space charge, molecular, atomic and electron shell polarizations. When the frequency is increased, the polarization disappears in a certain frequency range. At the same time, the permittivity drops rapidly from one level to another and a peak is observed in dielectric losses. For homogeneous substances, the above-mentioned transition frequency range is outside the frequently used frequencies, for space charge polarization fractional Hertz and for molecular, atomic and electron shell polarization, Gierehertz.

3 61964

In addition to the above-mentioned polarization mechanisms, mixtures of liquids and solids contain so-called rajapintapolarisaatio.

This means the transfer of an electric charge bound to the particle along the interface between the particle and the liquid. Po. the bound charge is created by the particle donating or receiving the charge into the liquid. At low frequencies, the polarization caused by the external field in each particle reaches equilibrium in a very short time compared to po. frequency so that the polarization losses remain small.

At high frequencies again due to po. due to the small mobility of the surface products with respect to the particle dimension, polarization does not take place, whereby the losses also remain small. In the frequency range typical of a particle, on the other hand, a considerable loss of polarization is observed, in which case, figuratively speaking, the surface charges with the external field essentially move from one side of the particle to the other.

It is theoretically justified that a substantially diatomic layer is formed at the liquid-particle interface so that the surface charge density at the interface is constant. It is also theoretically justified that the mobility of electrons in the above-mentioned biatomic layer is constant. It follows that the critical frequency range of polarization depends on the particle dimensions and also the shape. The total losses in the liquid in said frequency range depend on the number of particles.

In principle, the measurement event is as follows. Dielectric losses are measured at different frequencies in the frequency range characteristic of the particles in question. The amount of losses at different frequencies represents the number of particles with corresponding specific frequencies in the liquid. Thus, the size distribution of the particles can be calculated, as can the total number of particles in the liquid.

Em. the measurement event requires a calibration corresponding to the shape of the particles. However, it is now possible to obtain statistically sufficient information on the shape of the particles for both calibration and possible other process control purposes by performing measurements on a substantially single particle scale (small size sensor, dilution).

4,61964

By performing permittivity (i.e., capacitance) measurements at the interfacial polarization loss at lower frequencies and in a liquid with a permittivity substantially greater than the solid being measured, a strong increase in permittivity is observed at low solids concentrations due to interfacial polarization before permittivity of the substance, for example the so-called loqaritmi.1 ain. The phenomenon cannot be used unambiguously for the determination of sakcude or the like over a wide range, but it is very suitable for measuring small consistencies, for example less than 1%.

In practical measurements, the following measurement results have been obtained with pulp / ground fibers in water. In the consistency range of 0.1 ... 10%, the conductivity changed in a ratio of 1: 5 ... 1:10 depending on the frequency.

The dependence on this range was almost linear between 0.5 ... 10%. The conductivity represents the dielectric losses in question in the measurement.

There was some noticeable difference in the behavior of the pulp and the groundwood, which was apparently due precisely to the different fiber properties. The phenomenon was most preferably detected in the frequency range 10 ... 100 MHz.

Permeability increases in the consistency range 0.1 ... 0.5% almost linearly by 20% and reaches a gentle peak at a consistency of 1 ... 5%.

The sensor used was a so-called thick film technology. sormikuviokondensaattori.

The scope of the invention is defined in the appended claims. Implementations falling within the scope of equipment technology are known technology, incl. certain sensor structures and the necessary electronic calculation equipment.

The method according to the invention can be applied in a wide variety of fields, e.g. in the wood processing, ceramic, paint and textile industries, as well as e.g. in the measurement of wastewater.

61964 5

The invention will now be described in detail by means of an exemplary embodiment with reference to the accompanying drawing.

Example 1

The conductivity of the washed pulp was determined at a pulp consistency of 0-5% at frequencies: (1) 5 MHz, (2) 10 MHz, (3) 20 MHz, (4) 50 MHz, and (5) 80 MHz.

The measurement results are shown graphically in the attached figure. The dc conductivity of the mass was 3-5 juS.

The measurement results clearly show the relationship between conductivity and pulp consistency.

Claims (4)

61 964 6 A method for measuring the consistency of a pulp containing pulp and / or ground fibers, characterized in that the conductivity of the pulp and / or an electrical quantity proportional to the conductivity is determined in a certain frequency range of the measuring voltage, preferably 10-100 MHz, and the consistency of the measured mass is determined by comparison from the measurement result obtained with the corresponding measurement results obtained with a mass of known consistency. Method according to Claim 1, characterized in that the consistency of the mass to be measured is 0.1 to 10%. Process according to Claim 1 or 2, characterized in that the consistency of the pulp is 0.5 to 5%. Method according to one of Claims 1 to 3, characterized in that the permittivity of the pulp is determined in the method.