RU2371712C1 - Method of determining dispersion composition in "water in hydrocarbon" type emulsions and device to this end - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device for determining dispersion composition in "water in hydrocarbon" type emulsions has a tared container 2 and a measurement module for determining volume of water extracted this container at a given point in time. The measurement module consists of a variable frequency generator 3 and a standard resistance 4 with a voltmetre 5, which are connected in parallel to an electrode 7 which is in the tared container 2 and located in the extracted water 6 and a vertical electrode 8 in dielectric coating 9. Dielectric coating 9 is released on the entire thickness of the emulsion 1 and pre-tared for similar composition of extracted water at the frequency on which measurement is done, which gives the relationship between voltage on standard resistance and height of the part of the dielectric coating moistened by water.

EFFECT: increased accuracy of determining distribution of droplets on size with reduction of subjective factor using readily available and cheap components.

2 cl, 4 dwg

Description

The invention relates to measuring equipment designed to determine the dispersed composition of liquid emulsions and can be used in the oil, refining and chemical industries to control the quality of separation or preparation of liquid emulsions.

Known sedimentation analysis of determining the distribution of particles of the dispersed phase of the emulsion by size (p.150 in the book: Schukin E.D., Pertsov A.V., Amelina E.A. Colloid chemistry. - M .: publishing house of Moscow State University, 1982). Its essence is as follows: a calibrated container is taken (for example, a cylinder or a laboratory sedimentation tank), in which at a height H a Figurovsky weighing cup is placed. Then, a weighed portion of the dispersion under investigation (suspension, emulsion) is neatly poured. Then register in time t the change in the weight P of the sediment accumulating on the Figurovsky weighing cup during settling of the particles of the dispersed phase, which were initially uniformly distributed over the height. The particle size distribution f (r) is found using formula (1):

where r is the particle radius;

ρ is the density of the dispersed phase;

ρ ₀ is the density of the dispersion phase;

g is the acceleration of gravity;

η is the viscosity of the dispersion medium;

H is the filling height of the calibrated capacity;

P _max - the maximum weight of the sediment.

The disadvantages of sediment analysis are the limited application of diluted emulsions and the complexity of the measurement.

Known conductometric method and device (counter Coulter) for determining the distribution of particles of the dispersed phase of the emulsion by size (p.62 in the book: Belyakov VL Automatic control of the parameters of oil emulsions. M .: Nedra, 1992). The counter consists of two electrodes, one of which is placed inside the ampoule filled with a clean dispersed medium. The ampoule has a micro-hole communicating with a vessel with a controlled fluid in which another electrode is placed. A constant voltage is applied to the electrodes. When a particle passes through a microhole, the resistance between the electrodes increases. In this case, the current decreases and a voltage pulse is removed from the load resistance, the amplitude of which is proportional to the volume of the particle passing through the micro-hole. Impulses are amplified, sorted by a discriminator, and read by a counter. The discriminator transmits pulses only if their amplitude exceeds a threshold value. Introducing several counting cycles at different thresholds of discrimination, we obtain an integral particle size distribution curve.

The method is not applicable to emulsions, the continuous phase of which is a non-conductive medium. In addition, to obtain high-quality measurement results, a high degree of dilution of the emulsion is required.

Recently, to determine the particle size distribution of the dispersed phase of an emulsion, digital microscopes equipped with appropriate software, for example, the KRUSS MBL 2100 brand with the software of Video Test, St. Petersburg, have been used. But practice has shown that the program is not able to correctly recognize microobjects with fuzzy borders and produces erroneous size distributions of droplets.

The closest in technical essence and the achieved results to the proposed are the method and device described in the book: Tronov V.P. Oil field preparation. - M .: Subsoil. - 1977, see p. 153-154. The method is as follows. Samples of the emulsion are taken, which settles under conditions simulating production, and then graphs are plotted in coordinates the amount of released water (W) - time (T). The determination of droplet size and evaluation based on the deposition curves of the rate of separation of the emulsion in the settling apparatus for oil and water is carried out using formulas (2) and (3):

where φ is the density distribution of the volume of the dispersed phase along the radii of the droplets;

W is the volume of the precipitated dispersed phase at time t;

a and b are the coefficients determined by the least squares method;

The main disadvantage of the method and device is that the sludge process is fixed visually, which in the presence of an intermediate layer leads to a large error in determining the value (W) and low accuracy in calculating the distribution of droplets by size. In commercial emulsions, the droplets of the dispersed phase of which are protected by shells, the thickness of the intermediate layer can be significant and not taking into account the intermediate layer does not allow to obtain reliable results. In addition, the vagueness of the border “emulsion - released water” enhances the role of the subjective factor in measuring the volume of released water.

The technical task of the proposed method and device is to increase the accuracy of determining the distribution of droplets by size with a decrease in the subjective factor using available, not expensive components.

The problem is solved by the described method for determining the dispersed composition in water-in-hydrocarbon emulsions, including measuring the volume of water released at a particular point in time in a calibrated tank, followed by processing the results depending on the time of determining the size distribution of water droplets in the emulsion.

What is new is that the volume of water released at a certain point in time is measured by registering the voltage at the reference resistance with an electrode installed in parallel with the electrode and a vertical electrode in the dielectric coating, deflated to the entire thickness of the emulsion and pre-calibrated for a similar composition of the released water at a frequency of which measure, giving the dependence of the voltage at the reference resistance on the wetting height of the dielectric coating with this water.

The problem is solved by the described device for implementing the method, including a calibrated tank and a measuring module for determining the volume in this tank of water released at a certain point in time.

What is new is that the measuring module is made up of a variable frequency generator, a reference resistance with a voltmeter connected in parallel to a calibrated container and located in the separated water electrode and a vertical electrode in a dielectric coating, deflated to the entire thickness of the emulsion and pre-calibrated for a similar composition water at the frequency at which measurements are made, giving the dependence of the voltage at the reference resistance on the height of the wetted part of this water th dielectric coating.

Figure 1 shows a diagram of a device for implementing the method.

Figure 2 shows the calibration curves.

Figure 3 shows the curves of sludge.

Figure 4 shows the density distribution of droplets by size.

The device for determining the dispersed composition in emulsions 1 (see figure 1) of the type "water in hydrocarbon" (hereinafter emulsion), including a calibrated tank 2 and a measuring module. The measuring module consists of a variable frequency generator 3, a reference resistance 4 with a voltmeter 5 connected in parallel to a calibrated container 2 and located in the water 6 separated from the emulsion 1 to the electrode 7 and to the vertical electrode 8 in the dielectric coating 9, deflated to the entire thickness of the emulsion 1 and pre-calibrated for a similar composition of the released water 6 at the frequency at which measurements are made, giving the dependence of the voltage measured by a voltmeter 5, at a reference resistance of 4 on the height of the wetted the second part 6 of the water dielectric coating 9.

The electrode 7 located in the released water 6 can be made in any way, for example: firstly, in the form of a conductor hermetically inserted into the lower part of the calibrated container 2 through its wall (not shown in Fig. 1); secondly, in the form of a conductor 7, lowered from above the tank 1, insulated from the outside, for example, by a vertical electrode 8 (see figure 1). In the first embodiment, the manufacture of electrodes 7 and 8 is simpler, but a specially prepared calibrated tank 2 is required, and in the second case, any calibrated tank 8 can be used, for example, a laboratory graduated sump. In this case, the role of the vertical electrode 8 (see Fig. 1) can play: in the first case, a thin conductor (not shown in Fig. 1) in a sealed braid, which is a dielectric coating 9 (see Fig. 1); and in the second case, an aqueous solution of NaCl, placed in a sealed chamber (for example, a polypropylene capillary with a diameter of 2 mm), which is a dielectric coating 9 located on the outside of the insulator 10 of the electrode 7.

The method is carried out in the following sequence.

An emulsion of the “water in hydrocarbon” type is poured into the calibrated tank 8 (for example, a laboratory graduated sedimentation tank), which consists of the released oil 11 and the intermediate layer 12 released during the sedimentation of distilled water 6 and an electrode 8 with a dielectric coating 9 installed vertically along the axis of the calibrated tank 2. Then collect the electrical circuit of the measuring module, consisting of a variable frequency generator 3 (for example, sound) and connected in parallel to the electrodes 7 and 8 of the reference resistance 4, digital volt 5, the oscilloscope 13 (to control the frequency of the generator 3 and the resulting interference) and ground 14 (to minimize the induced interference). After that, the device is calibrated at a certain frequency of the variable frequency 3 signal supplied by the generator. The frequency is selected based on the maximum approximation to the linear calibration curves (see figure 2) [the dependence of the volume of water 6 in the calibrated tank 2 (see figure 1) to the readings (voltage) from the reference resistance 10]. Why, in a calibrated container 2 at a given frequency, a measured NaCl aqueous solution is sequentially poured with a density close to the produced water 6 emitted from the emulsion 1, and calibration curves 1 and 2 are constructed (see FIG. 2) at different frequencies supplied from a variable generator frequency 3, with sequential readings (voltage) from the reference resistance 10, varying depending on the height of wetting with water 6 of the dielectric coating 9 of the vertical electrode 8. Select a frequency to reduce measurement errors at which cal calibration curve 1 (see figure 2) is closest to a linear relationship. This signal frequency is fixed, measurements are taken and a detailed calibration curve 1 is constructed for a given frequency (see Fig. 2). During the tests, a signal was used from a variable frequency generator 3 (see Fig. 1) with a frequency of n = 3-16 kHz. Then the laboratory sump 2 is filled with the emulsion 1 under study and, at selected time intervals, the readings of the digital voltmeter 5 are recorded. Using the calibration curve 1 (see Fig. 2), compiled during the calibration of the measuring module, the readings of the voltmeter 5 (see Fig. 1) are converted into volume water released 6. During the measurement process, the output signal is monitored using an oscilloscope 13. If the original waveform (sinusoid) changes, then the measurement is stopped. They search for the cause of signal distortion and eliminate it. Then fill the laboratory sump 2 with a new sample of the test emulsion and repeat the same measurements. At the end of the measurements, the density distribution of the dispersed phase (carbon droplets in water) is calculated by size using formulas (1), (2) for this.

An example of experimental execution. The electrical circuit of the measuring module is being assembled. The electrodes 7 and 8 are installed along the axis of the laboratory settler 2. The measurement module is calibrated and a calibration curve is constructed (see figure 2). The measurement results are presented in FIG. 2, where 1, 2 are calibration curves for volume and voltage at different frequencies (5 and 10 kHz, respectively) produced by a variable frequency generator 3 (see FIG. 1) (along the X axis (see FIG. 2) the true volume values, ml; are plotted; along the Y axis, the readings of a digital voltmeter 5 (see Fig. 1), taken from a reference resistance of 4, mV). Selected and fixed the frequency of the variable frequency generator 3, equal to 5 kHz and corresponding to the calibration curve 1 (see figure 2).

Then an artificial emulsion of the water-in-hydrocarbon type 1 is prepared, where transformer oil was used as the hydrocarbon. The choice of transformer oil in the composition of the emulsion 1 is due to the proximity of its properties to the properties of the oil and the difference from the latter in optical properties, namely, the emulsion 1 of water 6 in the transformer oil is optically less dense than the emulsion 1 of water 6 in oil 11, which allows a more accurate visual to fix the presence of an intermediate layer 12 in the process of sludge, thereby reducing the subjective factor. The emulsion sample is poured into a calibrated container 2 and measurements are carried out as described above at a frequency of 5 kHz. The results are shown in figure 3, where 1, 2 are the values found at the boundary of the intermediate layer 12 (see figure 1) with water 6 and transformer oil 11, respectively, determined by visual means; 3 (see figure 3) - according to the sensor. + and - is the scatter for curve 1, due to the lack of a clear phase boundary determined by different observers. This scatter reached 20% of the average reading. On the graph depicted in figure 3, the axis X shows the time, min, and the axis Y the volume, ml. The proposed method, in contrast to the visual one, began to control the separation of the emulsion with an average of 2 minutes earlier, the readings, especially at the initial stage, differed to 300% and gave readings more consistent with reality with a spread of no more than 10%. Moreover, the proposed device for implementing the method can be connected to automation systems, including computers, which almost completely excludes a person from the method implementation system, including for calculations, which almost completely eliminates the subjective factor.

After that, the density distribution of droplets by size is calculated by formulas (1) and (2). The density and dynamic viscosity of transformer oil at 20 ° C, equal to 885 kg / m ³ and 19.5 MPa · s, respectively, were taken into account. The results are shown in figure 4, where the value of the radius of the droplets in centimeters is plotted along the X axis, and the size distribution of the volume along the Y axis.

From the graphs in figure 3 it is seen that the proposed method, in contrast to the visual one, began to control the separation of the emulsion on average 2 minutes earlier, the readings, especially at the initial stage, differed up to 500% and gave them more corresponding to reality with a spread of no more than 10%. Moreover, the proposed device for implementing the method can be connected to automation systems, which may include computers, which almost completely excludes a person from the system of the method, including for calculations, which almost completely eliminates the subjective factor. To implement the method does not require the use of expensive components and specialized equipment.

The effectiveness of the method is even greater in the study of emulsions, where oil was used as the "hydrocarbon". The accuracy of the proposed method from visual at the initial stage was higher to 700%.

Using the proposed method and device for measuring the dispersed composition of oil emulsions can provide reliable information on the development of new fields and increase the efficiency of existing ones.

The method will allow the use of a hardware measurement method with subsequent data processing using available, low-cost components and without human intervention, providing a measurement accuracy of 2-3 times the accuracy of the visual measurement method.

Claims (2)

1. The method of determining the dispersed composition in emulsions of the type "water in hydrocarbon", including measuring the volume in a calibrated tank of water released at a certain point in time, followed by processing the results depending on the time of determining the size distribution of water droplets in the emulsion, characterized in that the volume measurement water released at a certain point in time is produced by registering a voltage at a reference resistance with an electrode and a vertical elec cathode in a dielectric coating, lowered over the entire thickness of the emulsion and pre-calibrated for a similar composition of the released water at a frequency at which measurements are made that give the dependence of the voltage at the reference resistance on the wetting height of the dielectric coating with this water. 2. A device for determining the dispersed composition in water-in-hydrocarbon emulsions, including a calibrated tank and a measuring module for determining the volume of water released at a certain point in time in this tank, characterized in that the measuring module is made up of a variable frequency generator, a reference resistance with a voltmeter connected in parallel to a calibrated container and located in the released water electrode and a vertical electrode in a dielectric coating, deflated for the entire thickness of the emulsion and pre-calibrated for a similar composition of the released water at the frequency at which measurements are made, giving the dependence of the voltage at the reference resistance on the height of the wetted part of the dielectric coating with this water.

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