SU1679339A1 - Device for measuring gas content of a gas-liquid flow - Google Patents

Abstract

The invention relates to the measurement of the hydrodynamic parameters of gas-liquid flows in the chemical-technological, metallurgical, food and other industries, for example, in the cultivation of microorganisms in fermenters. The purpose of the invention is to improve the measurement accuracy. A point electrode (FC) is supplied with direct current voltage and stabilizes the value of the supply current, constantly determining the current value of the voltage across it while it is in the liquid phase. Two different increment threshold voltages are set and, summing each value of these increments with the current value of the voltage on the FC, get two current values of the threshold voltages, which are then compared with the current value of the voltage drop across the TE Determined measured gas content corresponding to each value threshold voltage, and calculate the actual value of the gas content by mathematical dependence. 5 il. (Ls

Description

The invention relates to the measurement of gas content of gas-liquid flows in chemical engineering, metallurgy, food and other areas of science and technology in the study of hydrodynamics of processes occurring in multiphase flows in relevant types of technological equipment and structures, for example, in the processes of deep cultivation of microorganisms in fermenters.

The aim of the invention is to improve the accuracy of measuring the gas content of gas-liquid flows.

Fig. 1 shows a functional block diagram of an apparatus for measuring the gas content of gas-liquid flows; on

Fig. 2 shows a sequence of 1mpulse voltage on a point electrode; Fig. 3 and 4 show a sequence of rectangular pulses generated by this device; Fig. 5 shows a voltage pulse on a point electrode that is formed by means of a device when powered. point electrode voltage of direct current with a stabilized value of the current (also specifies the specified increments of threshold voltages (DiP1 and AUn2); the current values of threshold voltages (Unl and Un2), as well as the pulse elements necessary to derive the formula the actual value of the gas content measured by the device).

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A device for measuring gas content (Fig. 1) has a series-connected DC power source 1 with a stabilized current value, a load resistance 2, a point and a reference electrode 3 and 4, respectively, as well as a 5-meter measuring unit of the current voltage value on a point electrode 3 being in the liquid phase. The output of block 5 is connected to two parallel branches of blocks consisting of blocks 6 and 7 of summation, blocks 8 and 9 of comparison, blocks 10 and 11 of forming rectangular pulses, blocks 12 and 13 of gas content measurement, the outputs of which are connected to the inputs of block 14 arithmetic operations connected by its output to the input of the indicator 15 of the gas content.

These branches include two blocks 16 and 17 of setting increments of threshold voltages, the outputs of which are connected to the inputs of blocks 6 and 7 of the summation and the inputs of block 14 of arithmetic operations, while the input of block 5 measuring the current voltage value is connected in parallel with the inputs of blocks 8 and 9 comparisons.

The device works as follows.

A point electrode 3 fed from a constant voltage source 1 providing a stable value of the power supply to the electrode 3 is placed in the gas-liquid flow under study. As the reference electrode 4, the wall of the apparatus or pipeline in which the gas-liquid flow moves can be used. The current value of the voltage U is applied to the electrode 3 and simultaneously to three blocks: voltage measuring unit 5 Oh, blocks 8 and 9 of the comparison. In block B, continuously with a small averaging time, in the order of a few seconds, the current value of voltage Al is determined, which corresponds to the voltage on electrode 3 when it is about the liquid phase.

The voltage IC from the output of block 5 is input continuously into blocks B and 7 of the summation. In blocks 1G and 17, the specified values of the increments of threshold voltages AUni and AUn2 are respectively formed and continuously entered into blocks G and 7.

In blocks 6 and 7, the voltages AUni and AUn2 are added to the current value Al, the current values of the threshold voltages Uni and 11H2I are formed and continuously entered into the blocks 8 and 9 of the comparison, where the current value of the voltage U on the electrode 3 is continuously compared.

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five

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five

During periods of time when the voltage on the electrode 3 is greater than the corresponding current threshold voltage Un, a control signal is generated in blocks 8 and 9, which is fed to the inputs of blocks 10 and 11 of the formation of rectangular pulses. The rectangular pulses from the output of blocks 10 and 11 arrive into blocks 12 and 13 of measurement of gas content, where they are summed by duration for a given time of one measurement cycle T and the obtained sums 2 Tn and T2i are divided by the value T according to the formula

 T, A (1)

i 1

where TI is the residence time of the point electrode in the 1st gas bubble, s;

T is the total measurement time (it should be large enough compared to TI), s;

n is the total number of bubbles suspended on the point electrode during the measurement T.

The output signal from blocks 6 and 7, corresponding to the measured values of raSo contents Јh and (pr, is fed to the input of block 14 arithmetic operations, in which calculations are made using the formula Q (2) and the output signal is generated, fed to the pointer 15 and the corresponding actual gas content jon

5 (1Ü Yu

where pk is the actual value of the gas content at the measuring point, fraction of a unit; AUni is the first specified value of the threshold voltage increment, V;

0A Un2 - second setpoint

increments of threshold voltage, B, AUni-fAlW;

f is the measured value of the gas content at the measuring point obtained when

5 increments of the threshold voltage AUni from the ratio / 2 TC / T, the fraction of a unit;

p2 is the measured "gas content value at the measuring point obtained when

0 increment of the threshold voltage AUn2 from the ratio (pz-, Tai / T, fractions of a unit.

As can be seen from Figures 2-5, the voltage pulse shape on the electrode 3 when it is powered

5, the constant current of a stable value in this device differs significantly from the shape of the voltage pulses on a known FC.

When powering the electrode 3 with a constant current of a stable value, the steepness of the leading edge of the pulses remains constant, and the pulse has the shape of a right-angled triangle.

It follows from the diagrams shown in figs 2-5 that, when measuring the actual value of the gas content in this device, the relation (2) is realized, and not (1). In this case, the error in measuring the actual gas content and the effect of the change in the conductivity of the liquid phase and the resistance of the electrode 3 on the value of the error are significantly reduced.

Claims (1)

Formula - a device for measuring the gas content of gas-liquid flows, containing a DC power source, a point and reference electrodes, a branch of blocks containing a threshold voltage setting unit, a comparator unit, a rectangular pulse shaping unit, a gas content measurement unit, and a gas content value indicator characterized by that, in order to improve the measurement accuracy, a source with a stabilized value of current strength was used as a source of direct current power, In addition, a unit for measuring the current voltage value on a point electrode in the liquid phase, a summation unit, a second block branch, including summation units, setting threshold voltage, comparing, forming rectangular pulses, measuring gas content and arithmetic operations unit, are introduced into the device. In this way, the input of the measuring unit of the current voltage value on the dot electrode in the liquid phase is connected in parallel with the inputs of the comparison units, and its output is connected to the inputs of the summation blocks of the first and second branches there are blocks including summation blocks, setting threshold voltage increments, comparing, generating square pulses and measuring gas content, the outputs of the summing blocks are connected to the inputs of the comparison blocks, the outputs of the threshold voltage setting blocks are connected to the inputs of the summing blocks and the inputs of the arithmetic operations, the outputs of the gas content measurement units are connected to the inputs of the arithmetic operations unit, and the output of the arithmetic operations unit - to the input of the gas content indicator. 15 1 I P I U and 5 Editor N.Lazarenko Compiled by Y. Klevkov Tehred M. Morgental Proofreader A.Osaulenko