RU2768664C2 - Method of ultrasonic dispersion of demulsifier in oil-water emulsion - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to treatment of water-oil emulsions, in particular to methods providing separation of water-oil emulsions using dispersion of demulsifier under action of ultrasonic action. Invention relates to a method for ultrasonic dispersion of a demulsifier in an oil-water emulsion, involving supply of a demulsifier and treatment of the emulsion with ultrasound. Multi-frequency spectrum of the acoustic wave in the water-oil emulsion after the demulsifier introduction is created by the formation of forced oscillations of the cylindrical main pipe through which the oil-water emulsion flows, and to create forced vibrations of the pipe, the wetting perimeter is preliminarily determined by the liquid phase, the frequency spectrum of the pipe with the flowing oil-water emulsion, selecting resonance frequencies of the pipe and the corresponding vibration modes of the pipe in the wetting perimeter zone, determining the location of antinodes on the wetting perimeter, in which ultrasonic oscillation sources are installed, having operating frequency equal to resonance frequency, and the length of the ultrasonic action pipe section is determined by the formula: L_p=υ×t_US, where: L_p is the length of the pipe section, m; υ is the average actual flow rate of the water-oil emulsion at the ultrasonic treatment section, m/s; t_US is the empirically derived time of ultrasonic action, determined by the given water separation index for the given type of emulsion and the type of the demulsifier used with the input rate, s. Invention also relates to an apparatus for implementing the method.

EFFECT: reduced fraction of introduced demulsifier, reduced effect of emulsion temperature on oil-water separation process and reduced time of phase separation.

5 cl, 8 dwg

Description

The invention relates to the field of processing water-oil emulsions (WOE), in particular to methods for separating water-oil emulsions using dispersion of a demulsifier using ultrasonic (US) exposure.

Demulsifiers are widely used for the separation of water-oil emulsions, in particular, in combination with heating and stirring, to improve the distribution of the demulsifier in the bulk of the emulsion. In many areas of technology, ultrasound is widely used for mixing and dispersing substances in a liquid phase; one of the most effective and widely used is the acoustic cavitation mode.

There is a method "Method of ultrasonic desulfurization of fossil fuels in the presence of dialkyl ethers" (patent for invention RU No. 2287551, published on November 20, 2006, IPC: C10G 29/22 and G 32/00), according to which the processed multiphase medium is passed through an ultrasonic chamber in continuous flow mode in which ultrasound acts on a multi-phase reaction medium for a time sufficient to cause the conversion of sulfides in liquid fossil fuel containing sulfides to sulfones.

An analysis of the materials of this analog shows that in order to obtain an effective reaction, relatively high temperatures (from 50 degrees and above), a fairly accurate dosage of mixed chemicals, and the presence of catalysts are required. For processing large volumes of water-oil emulsions in field conditions, the use of this method is very difficult and requires large capital and cost costs.

Also known is a method for the destruction of an oil-water emulsion using ultrasonic exposure (patent RU No. 2535793, published on December 20, 2014, IPC: C10G 33/02), which includes the process of processing the emulsion with a demulsifier, ultrasound, the settling process, as well as a preliminary determination of the optimal level of specific acoustic power of ultrasound. Common features with the claimed method are the treatment of the water-oil emulsion with a demulsifier and ultrasound. However, the application of the method requires the initial determination of a number of frequencies that act on water globules of different sizes and the sequential processing of the water-oil emulsion at the found frequencies, while the settling of the emulsion occurs during ultrasonic exposure, which leads to a significant increase in the total processing time, and is not effective enough when processing large volumes of water-oil emulsions.

An important proven result of this method is the substantiation of the effectiveness of multi-frequency exposure for the separation of emulsions, but since the processing uses rod ultrasonic vibration exciters, which are linear (that is, devices operating at the same frequency) resonant systems [4, 5, 8], sequential processing of the emulsion is required for different frequencies. The increase in time up to 120-240 min is facilitated by the fact that the ultrasonic effect occurs at the stage of gravitational settling. This requires the presence in the technological chain of settling tanks of the RVS type of large volume.

Therefore, this solution requires a significant increase in equipment costs and a long time of ultrasonic processing, which limits the application of this method in practice.

The closest to the claimed technical solution is a Method for separating an oil-water emulsion using ultrasonic exposure (patent for invention No. 2568980, published on May 20, 2015, IPC B01D 17/04, C02F 1/36, C10G 33/00), which includes preliminary determination of the optimal frequencies of ultrasonic exposure depending on the size of water droplets in the emulsion, allowing to achieve the minimum proportion of water in oil, and the emulsion is processed with a change in the optimal frequency of ultrasonic exposure, depending on the change in the size of water droplets during processing.

This method is a development of the patent-analogue RU No. 2535793 in that the preliminary selection of the optimal frequencies of ultrasonic exposure made it possible to reduce the settling time from ~120 min to ~55 min with stage-by-stage processing of the emulsion at different frequencies. Processing steps start at high frequencies (~1000 kHz) and progressively decrease to frequencies (~32 kHz), which leads to successive enlargement and precipitation of water droplets.

The technical result of the invention is to increase the efficiency of the separation of the water-oil emulsion and accelerate the separation of the water-oil emulsion in comparison with gravity settling.

The disadvantages of this method is the need for large volumes of gravity sedimentation tanks (RVS tanks), high heating temperatures of the oil-water emulsion, a large proportion of the introduced demulsifier to obtain the effect. The sequential process of ultrasonic treatment of an emulsion (from higher frequencies to relatively low ones), associated with the coagulation of water globules, requires additional hardware (rod ultrasound emitters) and time.

The technical problems to be solved by the present invention are to reduce the proportion of introduced demulsifier, to reduce the influence of the emulsion temperature on the oil-water separation process, and to reduce the time of phase separation.

To do this, in the claimed method, the formation, in the process of transporting the water-oil emulsion, is carried out, simultaneous multi-frequency ultrasonic exposure after the introduction of the demulsifier, for a given time, which is determined empirically, which leads to the solution of the technical problems indicated above.

These technical problems are solved by using a method for separating a water-oil emulsion using ultrasonic action, including the supply of a demulsifier and processing the emulsion with multi-frequency ultrasound with a preliminary selection of the action spectrum and the necessary time interval to obtain the optimal size of water droplets, while the multi-frequency spectrum of the acoustic wave in the water-oil emulsion after the introduction of the demulsifier is created due to the formation of forced vibrations of a cylindrical main pipe through which an oil-water emulsion flows, and to create forced vibrations of the pipe, the wetting perimeter for the liquid phase is preliminarily determined, the frequency spectrum of vibrations of the pipe with the flowing oil-water emulsion, one main and several lateral resonant frequencies are selected, and the corresponding vibration modes of the pipe in the area of the wetting perimeter determine the location of the antinodes for the established vibration modes, where the ultrasonic sources are placed. sonic vibrations having operating frequencies equal to the frequency of the main and side harmonics, and the length of the section of ultrasonic exposure is determined by the specified water separation indicator for a given type of emulsion and demulsifier and is determined by the established formula to set the required coagulation time of water globules.

The technical result achieved is to create forced vibrations of a cylindrical main pipe through which the emulsion flows, due to the formation of a multi-frequency spectrum with nonlinear vibrations of the main pipe and the required time of ultrasonic exposure.

The present invention allows for multi-frequency ultrasonic treatment of the emulsion on infield and main pipelines, pipelines of oil treatment facilities, while gaining the necessary time interval for the production and precipitation (coagulation) of water droplets, and the multi-frequency spectrum of the acoustic wave in the water-oil emulsion is created due to the formation of forced vibrations of the cylindrical the main pipe through which the oil-water emulsion flows, that is, in dynamics, and not at the settling stage, as proposed in the prototype, while the properties of nonlinear oscillations of the main pipe itself are used to form a simultaneous multi-frequency spectrum with point forced oscillations /1-3/.

The physical basis of this patent lies in the effective dispersion of the introduced demulsifier due to the action of a multi-frequency acoustic field in the liquid phase of the emulsion during its transportation through the pipeline. The amplitude of the acoustic wave, as in the prototype, should not exceed the threshold for the formation of stable direct emulsions.

The essence of the invention is illustrated by drawings, where in Fig. 1 shows an example of verification calculations (SCAD program) of natural vibrations of an unfilled cylindrical shell, freely supported on the ends (1 mode of vibration), in Fig. 2 - calculated and real multi-frequency spectrum of nonlinear vibrations of the pipe, in Fig. 3 - real multi-frequency spectrum of pipe oscillations in the frequency range up to 300 kHz (pre-cavitation mode of oscillations), in Fig. 4 - the location of the exciters of ultrasonic vibrations in the zone of the perimeter of the wetting of the main pipe, in Fig. 5 - dependence of the kinetics of water precipitation W (%) on the time of ultrasonic exposure in laboratory experiments when reaching the level of separation of the emulsion W \u003d 93% (W / H \u003d 67%, T \u003d 40 ° C, input rate DE \u003d 50%), in FIG. 6 - dependence of the kinetics of water precipitation W (%) under the action of ultrasonic treatment of various durations and without ultrasonic treatment (W/H=67%, DE=50%, T=35°C), in Fig. 7 - the stage of work associated with the simulation of WNE demulsification in the main pipe (one of the possible models of a laboratory installation), in Fig. 8 - dependences of the specific consumption of the reagent-demulsifier Emalsotron R2601 (A) and DEM 0840 during the pilot test (DNS-2 of the Taylakovskoye field of Slavneft-Megionneftegaz PJSC).

For example, in Fig. Figure 1 shows a verification example of calculation (SCAD program) of the 1st eigenmode of an unfilled cylindrical shell freely supported at the ends (steel, wall thickness 2.5 mm, pipe radius 76 mm, length 305 mm). The frequency range for such dimensions of a cylindrical shell lies from ~354 Hz (1st mode) to ~2832 Hz (150 mode). This pipe diameter is typical for cluster pipelines.

The main pipes at the fields and oil treatment facilities have, as a rule, a diameter of >400 mm, and the filling of the liquid phase of the water-oil emulsion is ~ 50% over the pipe section. For such conditions, the theoretical calculation of frequencies is extremely difficult, given the real dynamics of fluid motion. In practice, the most reliable is the experimental method for determining resonances and vibration frequencies. By analogy with the prototype, you can select the upper frequency range up to ~1 MHz. Studies have shown that the upper frequency range significantly decreases to the lower part of the spectrum with an increase in water cut to 60-80%. To obtain harmonics of the oscillation spectrum (up to ~500 kHz), it is necessary to use forced point oscillations of the main pipe.

Piezoelectric or magnetostrictive oscillation exciters and supply generators can be used as sources of ultrasonic energy [4, 5, 8].

Thus, the mass of a typical piezoelectric oscillation exciter is 0.5-0.7 kg, which creates a force load at a frequency of 22 kHz with an amplitude of 5 μm, equal to ~6.8 kilonewtons. A short action of a force load does not cause irreversible deformations of the pipeline, but local deflections occur at the place of application of the force with a nonlinear dependence of the elastic restoring force on the deflection, that is, resonance conditions arise in nonlinear oscillations [6, paragraph 29].

In this case, a multi-frequency spectrum of oscillations of the main pipe arises. On FIG. Figure 2 shows the theoretical and experimental spectrum of pipe oscillations in the case of nonlinear local resonance in the mode of small oscillation amplitude (1-2 μm). With a given power load, the spectrum is limited to a frequency of ~100–120 kHz.

The frequency with the maximum amplitude of oscillations is called the main (main), subharmonics - side. The theoretical calculation corresponds to the cubic dependence of the elastic force on the deflection (odd harmonics appear [6]). With the quadratic law "elastic force - deflection", even harmonics arise. In practice, Fig. 3, spectra are recorded with a fairly wide frequency range, which physically confirms the real picture of the dynamics of deformations in time - as the force increases, a consistent process of the transition of the elastic force from deflection with approximation according to the linear law (Hooke) to quadratic, cubic, etc. takes place. The real experimental spectrum corresponds to vibrations of a pipe with a diameter of 426 mm (wall thickness 7 mm) under the action of a force with a frequency of 20.8 kHz from a piezoelectric exciter of ultrasonic vibrations with a supplied power of 70 W. Oscillations were recorded using Brüel and Kjær equipment on a VellemanPCSU1000 digital oscilloscope; acoustic emission sensors had a linear frequency response in the frequency range up to ~400 kHz. To increase the amplitude of side harmonics in the range of 100-300 kHz, additional ultrasonic vibration exciters with the required frequencies are used.

If additional ultrasonic side harmonic exciters are not used, then, in practice, 90-95% of the oscillation energy is concentrated in the first 3-4 harmonics, including the main one (Fig. 2B) in the upper frequency range ~100-120 kHz.

For optimal placement of ultrasonic vibration exciters, the following technique is used.

Initially, the profile (wetting perimeter) of the WNE flow in the pipe is determined, that is, the definition of the “liquid-gas” phase boundary.

This procedure is necessary in order to ensure the passage of acoustic energy from the exciter of ultrasonic oscillations into the liquid phase of the VNE. In the presence of a gas cap on the inside of the pipe, due to the laws of reflection and the small thickness of the pipe compared to the wavelength, intense spall phenomena occur, which disable the oscillation exciters. No such effects were observed when an acoustic wave passed through the pipe wall into a liquid medium.

The wetting perimeter is determined using standard ultrasonic flowmeters, for example AKRON-01, where this procedure is described in the operation manual [7, paragraph 13].

The optimal frequency spectrum of ultrasonic exposure is determined similarly to the prototype to obtain the minimum time of precipitation of water globules (coagulation). In the field, an additional check is carried out on a laboratory installation (a variant is presented), figure Fig. 7. The set of frequencies is determined by the spectrum of forced oscillations and the amplitude of the main and side harmonics. To do this, a set of ultrasonic vibration exciters with different exposure frequencies is used and the frequency dependence of the amplitude A(f) of the main harmonic oscillations in the wetting perimeter zone is obtained. It is recommended to use the lower section of the pipe, which is guaranteed to be filled with the VNE liquid phase. The frequency f is selected (range 15-25 kHz), where the amplitude A will be maximum at a fixed power supplied to the exciter of ultrasonic vibrations. The vibration meter is located at a distance of 20-25 cm from the exciter of ultrasonic vibrations. The zone of action of the exciter of ultrasonic vibrations is estimated by the wavelength at the selected frequency:

where L is the zone of action of a single ultrasonic vibration exciter, m;

C is the velocity of longitudinal waves in the pipe material, m/s;

f - operating frequency, Hz.

So for the frequency f=15000 Hz (main harmonic), the velocity of longitudinal waves C=6000 m/s, the length of the action zone will be 0.4-1.2 m, which is the location step of the exciters of ultrasonic oscillations having their own frequency coinciding with main. In this case, both the main and side harmonics will be observed in the calculated zone. To amplify the amplitude of the side harmonics, if necessary, it is possible to similarly calculate the installation step of ultrasonic vibration exciters having frequencies coinciding with the side harmonics. Their installation must be carried out in places defined as antinodes of vibration modes that have equal frequencies with side harmonics. To do this, when the ultrasonic vibration exciter operates on the main harmonic, the contact method (broadband vibration probe) [8] is used and places with the maximum vibration amplitude corresponding to the selected lateral vibration harmonic in the wetting perimeter zone of the main pipe are found. Thus, the layout of the placement of vibration exciters is done.

In Fig. 4 shows the practical implementation of the placement of piezoelectric ultrasonic vibration exciters on the main pipe of the BPS-2 facility of the Taylakovskoye field of PJSC Slavneft-Megionneftegaz. The emitters are located in the lower semicircle of the pipe with a diameter of 426 mm, which is identified with the wetting perimeter.

To determine the required time of ultrasonic sounding, a diagram of the kinetics of water precipitation W (%) is preliminarily determined for a specific VNE, the demulsifier used, temperature, water content, etc. You can use the methods described in the prototype.

On FIG. Figure 5 shows the dependence of the kinetics of water separation W(%) on the time of ultrasonic exposure in laboratory experiments when reaching the level of separation of the emulsion W => 93% (W/H=67%, T=40°C, DE=50%). The input rate of the demulsifier is DE=50% of the input rate, when the VNE is not affected by ultrasonic vibrations.

This time was limited by the time of passage through the settling tanks of the BPS, that is, without the use of RVS tanks, and is up to 40 minutes. Modeling was carried out in model cylindrical channels with ultrasonic impact based on real main pipes, figure Fig. 8. It was determined on a real emulsion from the object that with the introduction of 50% of the demulsifier from the norm (the norm was 180 g / ton), with the existing water cut indicators (W / H = 67%,) and temperature T = 40 ° C, the time of ultrasonic sounding should be ~60 sec. Similar results were obtained at the Priobskoye field [9].

In Fig. 6 shows the dependence of the kinetics of water precipitation W(%) under the action of ultrasonic treatment of various durations and without ultrasonic treatment (W/H=67%, DE=50%, T=35°C). Comparing the dependencies of Fig. 5 and FIG. It can be seen from Fig. 6 that a decrease in the WHE temperature from 40°C to 35°C has practically no effect on the water separation time with a threshold W(%) => 93%, while the separation time with the variant without ultrasonic sonication is reduced by 3 times, from 90 min at 100% input of DE without US), up to 30 minutes with the duration of US 60 seconds and the rate of input of DE=50%. Such indicators make it possible to radically reconsider the structure of oil treatment facilities in terms of capital costs, to make them compact and efficient.

The turbulence of the WNE flow in the main pipe improves water separation and reduces the time of ultrasonic sounding. At a set flow rate of WNE in a pipe of ~1 m/s, this method requires the installation of ultrasonic exciters in a pipe section Ltr ~60 meters long, which was implemented:

where Ltr is the length of the main pipe, m;

υ - average actual flow rate of water-oil emulsion, m/s;

t _US - empirically obtained time of US exposure during the flow of water-oil emulsion, s.

When implementing this method in the course of pilot field tests (PTI) at the BPS-2 of the Taylakovskoye field of PJSC Slavneft-Megionneftegaz, the following data were obtained on reducing the demulsifier input rate (Fig. 8. The tests were carried out on two types of demulsifiers - Emalsotron R2601 and DEM 0840. Since the actual operation of objects has periods of instability, when it was necessary to turn off the action of ultrasonic exciters, such periods are marked with circles.

Of those shown in Fig. 8 data shows that the use of the claimed method of dispersion of the demulsifier provides a significant reduction in the input rate of the demulsifier (-35%), which is recorded in the Test Report.

When using this method, the influence of the WOE temperature on the oil-water separation process is significantly reduced, fully confirming laboratory tests. At the start of the pilot test and until mid-October 2019, the WHE temperature gradually decreased from ~37°С to 32°С. With the onset of winter operating conditions, the WHE temperature dropped to ~23°C-25°C, but this did not lead to an increase in the demulsifier input rate. Laboratory studies also showed that under ultrasonic exposure lasting 60 seconds, the temperature can drop to 10°C from the norm (without ultrasonic exposure) without worsening the dynamics of phase separation, while additionally there is a decrease in the demulsifier input rate by 25% -40%.

Increasing the time of ultrasonic exposure makes it possible to further reduce the consumption of chemicals, accelerate the process of phase separation when using the claimed method of ultrasonic dispersion of the demulsifier.

Thus, when using the method of ultrasonic dispersion of a demulsifier in a water-oil emulsion, an effective distribution of the demulsifier throughout the entire volume of the emulsion is ensured, which leads to more efficient and faster phase separation, and also allows to reduce the amount of demulsifier used, reduce the effect of the emulsion temperature on the phase separation time.

Sources of information

1. Birger I.A., Panovko Ya.G. Strength, stability, fluctuations. Handbook in three volumes. Volume 3. Moscow. Mashinostroenie, 1968, p. 437.

2. Volmir A.S. Shells in liquid and gas flow. Problems of hydroelasticity. Moscow, Nauka, 1979.

3. Bobkov G.V., Getalov A.A., Rukhman A.A., Rukhman E.P., Sargin B.V., Pisarev V.N. Technology of ultrasonic cavitation impact on liquid media. International scientific conference "Technical acoustics: developments, problems, prospects". Vitebsk State. Tech. University, September, 2016.

4. Bergman L. Ultrasound and its application in science and technology. Moscow. Publishing House of Foreign Literature, 1957.

5. Agranat B.A., Dubrovin M.N., Khaevsky N.N., Eskin G.I. Fundamentals of physics and technology of ultrasound. Moscow, Higher School, 1987.

6. Landau L.D., Lifshits E.M. Mechanics. Volume 1. Theoretical physics. Moscow, FIZMATLIT, 2019.

7. Ultrasonic flow meter with attached emitters AKRON-01. Manual. ATsPR.407154.011 RE. 2009

8. Khmelev V.N., Slivin A.N., Barsukov R.V., Tsyganok S.N., Shalunov A.V. Application of high intensity ultrasound in industry. Biysk, Altai State Technical University Publishing House. I.I. Polzunova, 2010.

9. Dengaev A.V., Verbitsky B.C., Mishchenko I.T., Getalov A.A., Sargin B.V., Grekhov I.V., Bogdanov A.V., Tarasevich S.A. Prospects for the use of ultrasonic treatment in the process of oil preparation at the Priobskoye field / Oil Industry, March 2020, pp. 28-30.

Claims (13)

1. The method of ultrasonic dispersion of a demulsifier in a water-oil emulsion, including the supply of a demulsifier and sonication of the emulsion, characterized in that the multi-frequency spectrum of the acoustic wave in the water-oil emulsion after the introduction of the demulsifier is created due to the formation of forced vibrations of a cylindrical main pipe through which the water-oil emulsion flows, and for creating forced vibrations of the pipe, preliminarily determine the wetting perimeter in the liquid phase, the frequency spectrum of vibrations of the pipe with a flowing oil-water emulsion, select the resonant frequencies of the pipe and the corresponding vibration modes of the pipe in the area of the wetting perimeter, determine the location of the antinodes on the wetting perimeter, in which the sources of ultrasonic vibrations are installed, having an operating frequency equal to the resonant frequency, and determine the length of the section of the ultrasonic treatment pipe according to the formula: Ltr \u003d υ × t _US , where: Ltr is the length of the pipe section, m; υ - the average actual flow rate of the water-oil emulsion in the area of ultrasonic treatment, m/s; t _US - empirically obtained time of ultrasonic exposure, determined by a given indicator of water separation for a given type of emulsion and the type of demulsifier used with the input rate, s. 2. The method of ultrasonic dispersion of the demulsifier according to claim 1, in which the wetting perimeter is determined using standard ultrasonic flow meters. 3. The method of ultrasonic dispersion of the demulsifier according to claim 1, in which the main and several side resonant frequencies are distinguished. 4. The method of ultrasonic dispersion of the demulsifier according to claim 3, in which the sources of ultrasonic vibrations have operating frequencies equal to the frequency of the main and side harmonics. 5. The installation for implementing the method according to claim 1, which is a section of the main pipe, on which ultrasonic emitters are installed at the antinodes of the resonant frequency of the main pipe on the wetting perimeter, having an operating frequency equal to the resonant frequency of the pipe, while the length of the pipe section is determined by formula: Ltr \u003d υ × t _US , where: Ltr is the length of the pipe section, m; υ - the average actual flow rate of the water-oil emulsion in the area of ultrasonic treatment, m/s; t _US - empirically obtained time of ultrasonic exposure, determined by a given indicator of water separation for a given type of emulsion and the type of demulsifier used with the input rate, s.

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