SU894528A1 - Method and device for monitoring paper web humidity profile - Google Patents

Description

(54) METHOD FOR CONTROLLING A PAPER WEIGHT MOISTURE PROFILE AND DEVICE FOR ITS IMPLEMENTATION

one

The invention relates to technical physics, namely to measuring the moisture content of sheet materials, and can be used, for example, in pulp and paper industry in the production of paper, cardboard and similar materials as a device for continuously monitoring the humidity profile of a moving paper or other sheet on a paper machine.

A known method for measuring the moisture profile of a paper web is intended to measure the humidity of a plurality of local areas of a paper web in which a series of moisture meters are used. Scanning the exits with a moisture meter and processing the scan results allows judging the moisture profile of the paper web 1.

The use of electronic scanning when measuring the moisture profile of a paper web on high-speed papermaking machines significantly increases the measurement speed and, consequently, their informativeness, but due to the complexity and the large number of elements, the question remains about the reliability of this system.

The closest to the present invention is a method for determining the fat and milk content of milk, based on the measurement of dielectric permeability by a capacitive sensor. According to this method, the contour of the shock excitation 10 is excited by rectangular pulses and, by the duration of the first impulse at the exit of the contour, the controlled parameter 5 is judged.

However, this method and the device implementing it do not provide the necessary and sufficient degree of reliability when using them to measure the moisture content of sheet materials directly on a papermaking machine.

20

The purpose of the invention is to increase the reliability and speed of control of the moisture profile of a paper web on high-speed paper-making machines with maximum information.

The goal is achieved by the fact that in the known dielectric method of controlling physicochemical parameters, including polarization

30 monitored material and determination of the parameter being monitored, the paper web is polarized by spreading the constant speed with a single polarization impulse; the polarization charge is removed from the paper web with a speed corresponding to the propagation speed of the polarization impulse; In the i-th polarization zone in the direction of the propagation of a polarizing pulse, the humidity in 1 2 ... i-th is measured directly from the measured capacitance by the amplitude of the polarization current; Eat from the moment of supplying the polarizing impulse to the other moment of moisture measurement in 1,2 ... i -th polarization zones, then directly determine the moisture profile of the paper web.

In a dielectric measuring device for measuring physicochemical parameters, including a unit carrying out the polarization of the test material, connected to the excitation devices.

The unit performing the polarization is designed as an unshielded delay line.

The drawing shows the block diagram of the device that implements this method.

The dielectric device contains a generator of 1 rectangular voltage pulses, an unshielded 2-delay line controlled material 3, a passive electrode 4, a polarization current amplifier 5, a recording device b. The generator 1 of rectangular pulses is connected to an unshielded delay line 2 located in close proximity to the paper web 3, the passive electrode 4, connected to the recording device b through the polarization current amplifier 5, is likewise located.

The device works as follows.

The -1 rectangular voltage pulse generator supplies the input of the delay line 2 to a rectangular impulse, a paper web 3 located in close proximity to the top of the unshielded delay line 2 and the passive electrode 4, is polarized as the front of the rectangular pulse moves along the delay line 2 . The passive electrode 4 removes the polarization current through the polarization current amplifier 5, and supplies data about it to the recording device 6.

Example. A model of the device for measuring the moisture profile along the capacity profile is fabricated.

As an active electrode, a set of 10 delay lines of the LZM-600-1.0 type is used, i.e. - 100 cells of 0.1 MKS for a total delay time T of 10 MKS, the output of each cell is connected to its electrode of size 8 X 60 mm. The total capacity of 100 cells relative to the passive electrode, set at a distance of 8 mm from the active surface, is 530 pF. The amplitude of the polarization voltage is 6 V on L1}. The amplitude of the current is 0.33 mA.

Since the dependence of the dielectric constant on humidity W is unambiguous, although non-linear, the humidity profile is read directly, for example, using an oscillogram of a capacitance profile, which is directly measured by the proposed method,

In the plant model, in order to obtain a low pulse propagation rate, in order to study in detail the processes occurring there, delay lines with lumped parameters are used, but in Industrial plants, unshielded lines with distributed parameters — for example, feeder lines containing only two parallel conductors, and the scanning time is reduced, and the design is simplified to such an extent The range of what consists of three conductors arranged in parallel, with two wires being used as a feeder through which a pulse propagates, the third as a passive signal electrode.

The invention can be used in a device for measuring the moisture profile of a paper machine on a paper machine and provides, in comparison with the known, high measurement accuracy, informativeness, and reliable operation of the measuring device at maximum speed. For example, to remove a moisture profile profilogram of paper web width m 100 µs with a resolution of 2% width, which, in contrast to the known devices, provides control of 100% of the area of the paper web. The use of the proposed method leads to a simplification of the design of the device, while the cost of the device is at least an order of magnitude lower than the cost of devices of the same value produced by the industry.

Claims (2)

1. A method of controlling a paper web's moisture profile, including the polarization of a controlled material and determining a controlled parameter, characterized in that, in order to increase the reliability and speed of monitoring a moisture profile, the paper web will polarize a single polarization pulse propagating with a constant speed J remove the polarization charge from the paper web with a speed corresponding to the speed of propagation of the polarization pulse, measure the capacitance in the 1.2 ... 1st polarization zones in the direction of propagation roubleshooting polarizing pulse current amplitude by directly floor robe; tion determined humidity 1,2 ... i-th areas and the measured capacitance, both measured from the time of the filing of polarizing pulse to the moment of moisture measurement in 1,2 ... i-th polarization zones, then the moisture profile of the paper web is then directly determined. 2. An apparatus for carrying out the method of claim 1, comprising a unit for carrying out the polarization of the monitored material and connected to the excitation unit, characterized in that the unit for carrying out the polarization is in the form 0 delay lines. Sources of information taken into account in the examination 1. The patent of France 2059612, cl. b 01 N. five 2. USSR author's certificate number 379865, cl. G 01 N 15/02, 1971 (prototype).