RU2535515C2 - Humid gas consumption determining method - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: humid gas consumption determining method is based on a relationship between a dilution degree of an indicator substance and a value of consumption of the measured substance at known consumption and initial concentration of indicator substance. With that, as the indicator substance, paramagnetic marks are used, and as an applied method, an electron paramagnetic resonance (EPR) method is applied.

EFFECT: improving accuracy of determination of percentage content of water and gas condensate in humid gas and correction of a reading of dry gas consumption converters as per analysis results of spectrum performance of samples taken from a humid gas flow.

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Description

The invention relates to measuring technique and can be used in gas production and other industries for accurate measurement of gas flow rate, containing up to 10% (by volume) of water and gas condensate (hereinafter - wet gas) during its transportation through the pipeline.

Known concentration methods for measuring the flow of liquids and gases. They are based on the dependence of the degree of dilution of the indicator or impurity on the flow rate of the measured substance Q ₀ at a known initial concentration of the indicator C _u and its flow rate q _u . After sufficient mixing of the indicator with the measured substance, a sample of a fixed volume is taken downstream of the stream, in which the concentration of the indicator C _x is measured. The flow rate of the measured substance can be determined from the balance equation of the indicator:

$$Q_0{\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="00000005.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+q_u{C}_u=\left(Q_0+q_u\right)C_x,\left(\mathrm{one}\right)$$

where C ₀ is the possible initial concentration of the indicator in the measured substance.

If C ₀ = 0 and C ₀ << C _u , then

. $${\mathrm{<figure-callout\; id="0"\; label="Q"\; filenames="00000005.png"\; state="\{\{state\}\}">Q</figure-callout>}}_0=q_u\frac{C_u}{C_x}\left(2\right)$$

.

The method is given in the international standard ISO 2975-1 [1]. Its essence is described in more detail in many articles, for example [2].

Thus, to measure the flow rate of liquids and gases, it is necessary to determine with high accuracy the concentration of the indicator in the stream after mixing it. For gases containing up to 10% (by volume) of water and gas condensate in their composition, it is proposed to first determine the flow rate of the liquid phase in the above manner, and then correct the readings of the gas flow transducers.

Depending on the indicator substance, the methods are based on the following physical principles and research methods: chemical, colorimetric, fluorometric, refractometric, conductometric. These methods are designed for one-time or periodic measurements of flow rate during calibration / calibration of standard constricting devices and other gas flow transducers.

For the first time, paramagnetic labels of two different types were used as an indicator substance. Due to its chemical structure and properties, one type of label is soluble only in water, and the other type of label is soluble only in gas condensate. The intensity of the EPR signal, proportional to the number of paramagnetic labels, decreases with a decrease in their number in the selected sample, and for a fixed volume of the sample is proportional to the concentration of the indicator, C _x after mixing [3]. By analyzing the EPR spectra of paramagnetic labels in the selected samples, it is possible to determine the flow rate of wet gas in this stream.

The technical result of the invention is to increase the accuracy of the results of measurements of the flow rate of wet gas, the possibility of simultaneously determining the content of water and gas condensate in the wet gas, reducing the amount of the indicator substance required for measurements compared with the methods described previously [1, 2, 4].

The goal is achieved due to the high sensitivity of the EPR method when determining the concentration of paramagnetic labels in the sample. Figure 1 shows the dependence of the intensity of the EPR signal of various types of paramagnetic labels on their concentration. Also, due to the high sensitivity of the EPR method, it is sufficient to introduce solutions with a low initial concentration of paramagnetic labels into the wet gas stream, which can reduce its costs during measurements.

This method of simultaneously determining the content of water and gas condensate in a wet gas is very simple and obvious due to the fact that the EPR signals from various types of paramagnetic labels are “spaced” (occur at different values of the constant magnetic field induction).

The flow of wet gas in a horizontal pipeline is layered. At the bottom of the stream is the liquid phase of the wet gas, consisting of water and gas condensate. The invention is illustrated by the drawing shown in Fig.2. Paramagnetic label solutions with a known initial concentration are injected into the wet gas stream flowing through a pipe 1 with a diameter D and passing through a dry gas flow converter 2 using injection systems 3 at a constant flow rate from a container 4. After the flow has passed a distance of at least 100-D, which ensures its necessary mixing, a sample of the liquid phase of the wet gas is taken from the pipeline using a sampling system 5.

The sample taken is placed in the microwave cavity of the EPR spectrometer, and its EPR spectrum is recorded. The intensity of the obtained spectrum determines the concentration of both types of paramagnetic labels introduced upstream. The flow rate of the liquid phase present in the wet gas stream is found from the balance equation of the indicator according to the formula (1).

The operability of the method was determined in laboratory experiments using an Elexsys 500 EPR spectrometer from Bruker at a frequency of 9.5 GHz (which corresponds to a wavelength of 3 cm, X-band), the modulation amplitude is 0.5 G, and the temperature is 300 K.

In experiments, copper sulfate (copper sulfate), soluble in water, and a spin label based on TEMPON nitroxyl radicals, soluble in kerosene, were used as paramagnetic labels in the experiments. The required concentration of labels in water and kerosene was achieved by mixing in an ultrasonic bath, the mass of the components was controlled by weighing on a Vibra NT scale (abs. Heating - 1 mg).

Samples of the spin label dissolved in kerosene were placed in a glass capillary with an inner diameter of 1 mm using a thin long pipette. The total sample volume did not exceed 5 μl, which made it possible to maintain the quality factor of the microwave cavity at an acceptable level.

Copper sulfate samples dissolved in water were placed in a glass capillary with an inner diameter of 4 mm; the total volume of the sample did not exceed 0.5 ml.

Also, experiments were conducted in which samples of copper sulfate in water and spin label samples in kerosene were simultaneously placed in a microwave cavity of the spectrometer in different quantitative proportions. The EPR spectra (Figure 3) simultaneously contain signals from both types of labels, the intensity of these signals varies in accordance with the quantitative ratio of the two solutions in the resonator. EPR signals from various types of paramagnetic labels occur at magnetic fields of 3150 and 3450 G, respectively. The integrated signal intensity decreases with a decrease in the number of paramagnetic labels in the selected sample. By comparing the EPR spectrum of a sample of unknown concentration with these “calibration” spectra, one can determine the concentration of both types of labels in the sample and, therefore, determine the liquid flow rate based on equation (2), and then correct the readings of the gas flow transducers, i.e. determine the flow rate of wet gas.

Information sources

1. ISO 2975-1 “Measurement of water flow in closed channels. Vaccination methods. "

2. P.P. Kremlin. "Flowmeters and counters of quantity", St. Petersburg:

Polytechnic, 136-152 p. (2004).

3. R. S. Alger, Electron paramagnetic resonance: techniques and applications, New York, pp. 201-221 (1971).

4. H. de Leeuw, Wet gas flow measurement by means of a Venturi meter and a tracer technique, North Sea Measurement Workshop (1994).

Claims (1)

A method for determining the flow rate of wet gas, based on the dependence of the degree of dilution of the indicator substance on the flow rate of the measured substance, at a known flow rate and initial concentration of the indicator substance, characterized in that the paramagnetic labels act as the indicator substance, and the electron paramagnetic resonance method is used as the used method (EPR), which allows you to accurately determine the percentage of water and gas condensate in wet gas and adjust the readings azovateley flow of dry gas according to the analysis of the spectral characteristics of samples taken from the wet gas stream.

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