RU2782937C1 - Flow separating device on swirling flow - Google Patents

Abstract

FIELD: flow separating technology.

SUBSTANCE: invention relates to a technology for separating a liquid or gaseous dispersion system into dispersed phases having differences in substance density. The invention can be used in the oil and gas and petrochemical fields, in energy and mechanical engineering for cleaning oil, oil products, oils from water, from solid impurities and gas bubbles, for drying and dedusting compressed gas and air. The flow separating device is a pipe 1 with multi-start smoothly conjugated spiral protrusions 2 and grooves 3 on the inner wall. The pipe channel 1 has an inlet section in the form of a confuser 4, an average working section 5 and an outlet section in the form of a diffuser 6. The helix angle on the confuser 4 does not decrease towards the working section 5. The helix angle on the diffuser 6 does not increase in the direction from the working section 5. The working section 5 of the pipe 1 has a cylindrical shape with a constant along the length of the angle of the helix.

EFFECT: increasing separation efficiency due to ultra-high separation factor by reducing turbulence and negative overdispersion, increasing productivity by creating a high-speed swirling flow of the dispersion system.

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Description

The invention relates to a technology for separating a liquid or gaseous dispersion system into dispersed phases having differences in substance density. The invention can be used in the oil and gas and petrochemical fields, in energy and mechanical engineering for cleaning oil, oil products, oils from water, from solid impurities and gas bubbles, for drying and dedusting compressed gas and air.

Apparatus for separation and purification of liquids and gases from solid, liquid and gas inclusions are the most important part of technological processes in oil and gas production and processing, in the energy sector, in the chemical, metallurgical, agro-industrial and food sectors and in other industries with related processes for the separation of liquid and gas mixtures.

Traditional oil and gas separators based on trapping the liquid phase with a developed mass transfer surface and laminar flow of the phase into the sediment zone under the action of gravity have low productivity, low efficiency and large dimensions.

Higher performance centrifugal flow separators with a high flow rate created by the external pressure of the formation or pumping station. Existing centrifugal separators use flow swirling with inserts in the flow channel in the form of local impellers, screws or streamlined bodies with spiral fins, which makes it possible to accelerate the separation of phases of different densities. However, the imperfection of such technical solutions does not allow in practice to achieve a high quality of phase separation and separation performance of complex two-, three- and four-phase finely dispersed systems, such as, for example, well water-and-gas fluids with mechanical impurities, moistened field hydrocarbon gases or dusty air.

The existing centrifugal flow separators that use local swirling inserts fixed in the flow channel have the following negative phenomena.

1. Overlapping the flow area increases the pressure loss in the channel.

2. Direct averaged streamlines at the inlet of the flow channel abruptly change their direction in the cavities of the impeller, separated and reverse flows are formed, which increases the initial dispersion of the system and reduces the separation factor

3. A viscous sublayer, which is formed not only on the inner surface of the channel, but also on the surface of the swirling device itself, slows down and distorts the velocity field

4. Behind the impeller, the swirl is retarded, the separation factor is reduced. The processing time of the flow in the cavities of the impeller, where the centrifugal force develops, is not enough to carry out the separation.

As a result, the separation efficiency decreases, and the separation factor does not exceed 600 gravity forces in a liquid dispersed system.

The present invention eliminates the noted shortcomings of existing technical solutions.

A known method of low-temperature gas separation (options) (patent RU 2272973 and its analogues EA 010564, WO 2006032139), which uses a fixed swirling impeller at the inlet, a Laval nozzle at the outlet, where supersonic speed of the gas hydrocarbon system develops with a decrease in temperature to the dew point of individual fractions, which allows you to condense and separate natural or associated petroleum gas into separate liquid hydrocarbon fractions at the outlet. This solution applies only to gas and gas condensate media and cannot separate water-gas liquids.

A cyclone separator is also known according to patent EP 1458490 B1 dated April 19, 2006, in which a stationary modernized impeller is used as a swirling device - a local streamlined “torpedo” insert on the surface of which ribs swirling the flow are fixed at an angle to the channel axis. The device is applicable both to the separation of liquid and gaseous dispersed media. Its disadvantage is the use of a local swirling insert that disperses the inlet flow, blocks the flow section of the flow channel and increases pressure losses. Immediately behind the "torpedo", due to the viscosity of the working media, the azimuth velocity, the degree of swirl and the separation factor decrease downstream. As a result, the separation proceeds at a low separation factor, is accompanied by additional harmful mixing of the phases and has a low efficiency.

Closest to the proposed invention is the decision taken as a prototype according to the European patent EP 2429714 B1 dated 12/21/2016, where in one of the variants of the swirling device for separating the heavy fraction from the liquid in Fig. 4 shows a spiral-shaped pipe with slots that does not overlap the flow section of the channel (Fig. 4 of the patent). The prototype is applicable to both the separation of liquid and gaseous dispersed media. Its disadvantage is that the entry of an untwisted high-speed flow into the spiral part of the channel leads to separation and return flows on the ledges and in the grooves, which leads to turbulence and mixing - a process that is the reverse of phase separation. For this reason, it is not possible to increase the flow rate and achieve a high separation factor and a high separator capacity. The placement of slots in the high-speed flow path to remove the heavy phase also leads to additional turbulence and mixing of already separated phases. As a result, this solution can only be used at lower speeds with a low split factor and low efficiency.

The proposed invention solves the problem of increasing the separation efficiency and increasing the separation productivity.

The technical result of the invention, which allows solving this problem, is that the increase in separation efficiency is achieved due to the ultra-high separation factor by reducing turbulence and negative overdispersion, and the increase in productivity is achieved by creating a high-speed swirling flow of the dispersion system.

The technical result is achieved by a flow separating device, which is a pipe with multi-start smoothly conjugated spiral protrusions and grooves on the inner wall, in which, according to the invention, the pipe channel has an inlet section, a working section and an outlet section, the inlet section has the form of a confuser, on which the helix angle does not decrease in the direction of the working section, the outlet section has the shape of a diffuser, on which the helix angle does not increase in the direction from the working section, and the working section of the pipe has a cylindrical shape with a constant helix angle along the length.

In addition, the device may have smooth sections on the inner wall of the pipe between sections with helical projections and grooves.

It is possible to perform a device in which a cylindrical insert with multi-start spiral protrusions and grooves on its outer surface is coaxially located inside the working channel of the pipe with a constant along the length angle of the spiral, while an annular channel is formed between the pipe and the insert, the direction of twist and the angle of elevation of the spirals of the protrusions and grooves of the insert coincide with the corresponding parameters of the protrusions and grooves on the inner surface of the pipe, and in each cross section the top of the spiral groove of the pipe lies on the same radius as the top of the spiral protrusion of the insert.

In this case, the insert can be made in the form of a pipe with closed ends or in the form of a rod.

The invention is illustrated in the drawings.

In FIG. 1 shows a general view of a flow separation device with a partial longitudinal section.

In FIG. 2 is a cross-sectional view of the middle section of the device shown in FIG. one.

In FIG. 3 - the middle section of the embodiment of the device.

In FIG. 4 is a cross-sectional view of the middle section of the embodiment of the device shown in FIG. 3.

The principle of the invention consists in centrifugal separation of phases in a high-speed flow separation device, which eliminates the negative effects of turbulence and dispersion of the dispersion system, which reduce the quality of separation, caused by flow stalls at the swirler, as well as at the inlet and outlet devices.

The flow separating device is a pipe 1 having a spiral-profile inner surface formed by multi-start smoothly conjugated helical protrusions 2 and grooves 3 on the inner surface (Fig. 1, 2). The channel of the pipe 1 contains three sections with a spiral-shaped inner surface of the pipe 1: the inlet section in the form of a confuser 4, the middle working section 5 and the outlet section in the form of a diffuser 6. The angle α of the helix on the confuser 4 can be constant along its length or can increase in the direction of the working section 5. The angle α of the helix on the diffuser 6 may be constant along its length or may decrease in the direction from the working section 5. The working section 5 of the channel of the pipe 1 has a cylindrical shape with a constant along the length angle α of the helix.

As pipe 1, either a pipe with a smooth outer surface or a spiral-shaped pipe with multi-start helical corrugations can be used (see, for example, patents RU 2331493, RU 2386096)

The narrow end of the confuser 4 is connected to the working section 5, and the diameter of the wide part of the confuser 4 corresponds to the diameter of the supply device. The diffuser 6 is also connected with the working section 5 by its narrow end, and the diameter of its wide part corresponds to the diameter of the receiving device. Thus, the flow is swirled not locally, but throughout the entire flow channel of the pipe 1 of the total length required to complete the phase separation process.

The pipe 1 may have smooth sections on the inner surface between sections with a spiral-profile surface.

A variant of the device (Fig. 3) is possible, in which, inside the middle working section 4 of the pipe 1, an insert 7 of a cylindrical shape with multi-start spiral protrusions 8 and grooves 9 on its outer surface is coaxially located, which have a constant along the length angle of the helix. The direction of twist and the angle of elevation of the spirals of the protrusions 8 and grooves 9 coincide with the corresponding parameters of the protrusions 2 and grooves 3 on the inner surface of the pipe 1. At the same time, in each cross section, the top of the spiral groove 3 of the pipe 1 lies on the same radius as the top of the spiral protrusion 8 of the insert 7 formation of a multi-entry spiral channel between pipe 1 and insert 7. Insert 7 can be made either in the form of a solid rod, as shown in FIG. 4, or in the form of a spiral-profile pipe. Insert 7 is attached inside the pipe 1, for example, using jumpers (not shown in the drawing).

Flow separating device operates as follows.

In FIG. 1 shows a general view of the device when the flow moves from left to right.

At the inlet section in the form of a confuser 4, under the influence of swirling protrusions 2 and grooves 3, a gradual increase in speed and swirl of the flow occurs due to the narrowing of the pipe 1 by a cone or due to this and an increase in the helix angle (swirl angle), which makes it possible to prevent or minimize the formation of tear-off and return turbulent flows.

At the inlet section, the axial and angular velocities increase gradually due to the confuser 4 and the spiral-profile geometry, preventing flow separation and excessive phase dispersion. The geometry of the channel at the outlet of this section, namely, the depth of the grooves (height of the protrusions) and the angle of elevation of the spirals, must match the geometry of the channel at the inlet to the middle working section 5, which does not impair the quality of the dispersed system when the flow passes from the confuser 4 to the working section 5. The criterion for the quality of separation is the equality of axial and angular velocities at the outlet of the confuser 4 and the entrance to the working section 5.

The middle working section 5 is the narrowest and is designed to separate phases in the field of centrifugal mass forces with a maximum effect - heavy phases to the periphery, light to the center along the axis due to a higher flow rate than at the inlet to confuser 4 and at the outlet in diffuser 6 , and with the helix elevation angle the same as the elevation angles at the inlet of the diffuser 6 and at the outlet of the confuser 4. The length of the working section 5 is determined by the necessary processing time of the dispersion system to obtain the desired separation quality.

At the outlet section, the axial and angular velocities, due to the expansion of the diffuser channel 6 or due to this and a decrease in the helix angle (swirl angle), gradually decrease, which provides the output of the separated phases without mixing them into a low-speed receiving device or through the perforation of the wall of the heavy peripheral phase or through the device selection of separated phases for further use. The geometry of the channel at the exit from this section, namely, the depth of the grooves (height of the protrusions) and the angle of elevation of the spirals, must match the geometry of the channel at the exit from the middle working section 5, which does not impair the quality of the separated phases at the transition from the working section 5 to the diffuser 6 The separation quality criterion at the outlet section is the equality of the axial and angular velocities at the outlet of the working section 5 and the inlet to the diffuser 6, as well as the minimum angular velocity at the outlet of the diffuser 6. Further trapping of the separated phases can be carried out through the perforation of the walls, through the selection devices, braking systems and multi-phase sedimentation tanks.

In FIG. 2, on the example of the middle working section 5, a section of its spirally profiled inner surface is shown. In FIG. 1-3 shows the following parameters:

L - length of the middle working section 5 of pipe 1

Z - number of spiral starts (in the example Z=6)

α - the angle of the helix relative to the axis of the pipe 1

r ₁ - radius of the ledge 2

r ₂ - groove radius 3

h - height of protrusion 2 (groove depth 3)

These geometry parameters are subject to calculation when designing a separation device for specific dispersion systems, taking into account their rheological properties, the required performance of the separation device, the allowable pressure drop and the required separation factor (separation quality).

The speed and efficiency of separation is determined by the difference in the densities of the separated phases, the degree of smallness of the size of the dispersed phase and the centrifugal separation factor, determined by the formula:

f = (ω ² ⋅r)/g,

where ω is the angular velocity of rotation, 1/s;

r - average radius of flow rotation, m;

g is the acceleration due to gravity.

In the proposed invention, f reaches a value of 1,000 or more for a liquid system and 20,000 or more for a gaseous dispersion system.

In the embodiment of the device shown in FIG. 3, the inlet flow is directed into the annular gap formed by the inner spiral-shaped surface of the pipe 1 and the outer spiral-shaped surface of the insert 7. In the annular gap, the flow is swirled with a separating centrifugal effect, stronger than in the variant without the inner insert 7 due to the increased swirling radius of the flow while maintaining a smooth unseparated flow of the separated medium.

EFFECT: invention makes it possible to increase the separation efficiency due to an ultra-high separation factor in the absence of inserts in the flow channel, with minimal turbulence and negative overdispersion, as well as to increase productivity due to the high-speed swirling flow of the dispersion system.

Separator performance can also be increased due to the diameter of the channel or due to the number of channels connected in parallel.

Claims (4)

1. A flow separating device, which is a pipe with multi-start smoothly conjugated spiral protrusions and grooves on the inner surface, characterized in that the pipe channel has an inlet section, a working section and an outlet section, the inlet section has the shape of a confuser, on which the helix angle does not decrease in direction to the working section, the outlet section has the shape of a diffuser, on which the helix angle does not increase in the direction from the working section, and the working section of the pipe has a cylindrical shape with a constant helix angle along the length. 2. The device according to claim 1, characterized in that the inner wall of the pipe has smooth sections between sections with helical protrusions and grooves. 3. The device according to claim 1, characterized in that inside the working channel of the pipe there is a coaxial insert of a cylindrical shape with multi-start spiral protrusions and grooves on its outer surface with a constant along the length of the angle of elevation of the spiral, while an annular channel is formed between the pipe and the insert, direction the twist and the helix angle of the helixes of the protrusions and grooves of the insert coincide with the corresponding parameters of the protrusions and grooves on the inner surface of the pipe, and in each cross section the top of the spiral groove of the pipe lies on the same radius as the top of the corresponding spiral protrusion of the insert. 4. The device according to claim 3, characterized in that the insert is made in the form of a pipe with closed ends or in the form of a rod.

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