RU2355462C2 - Method of direct-flow separation of gas flows from solid and liquid impurities - Google Patents

Abstract

FIELD: treatment facilities.

SUBSTANCE: invention is designed for purifying gas flows from solid and liquid impurities in industrial systems and installations. The method implies passing a gas flow with impurities through a channel, separating it into the purified gas which is removed to the channel periphery and a concentrated bundle of impurities which is withdrawn from the channel through an offtake branch. Two or more convergent nozzle insertions are fitted in the channel sequentially, their configuration, size and relative position are defined on the basis of a gas-dynamic calculation of the flow passage made with the help of the application package for computer simulation of two-phase media flow FLUENT according to the required separation efficiency for different types and sizes of the impurities. A slope angle of the convergent nozzle entries amounts to 10°-30°. The nozzle insertions are coaxial to the channel or set with sequentially cross shift from the axis to the periphery.

EFFECT: it is provided for the purification of gas flows with wide range of initial gas flow parametres almost without speed and pressure losses, and basing on the method the development of devices to be integrated into the existing continuous manufacturing lines without the process flowchart alteration.

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Description

The present invention relates to methods for cleaning gas streams in channels from impurities in the form of solid particles, droplets and a liquid film flowing along the channel walls. It can be used in industrial systems and gas purification devices used in the oil, gas, engineering, food industries, in the production of powder materials and other industries.

A known method of aerodynamic cleaning of air from dust, aerodynamic dust removal module and installation of aerodynamic cleaning of air (hereinafter referred to as the "Method of aerodynamic cleaning ...") (RF patent No. 2100052, class B01D 45/04). "The method of aerodynamic cleaning ..." is intended for cleaning air dust. It includes the supply of polluted air to the cavity of the aerodynamic dust concentrator, into which the dust separation unit is coaxially mounted in the form of a conically or wedge-shaped converging system of round or ruled elements, through the lateral gaps between which the purified air is discharged, the dust particle paths bend towards the axis of symmetry and repeatedly dust particles are quantized from layer to layer within each adjacent pair of elements, then the dust is sent to the hopper, the air entering the hopper place the dust is removed in a flue, following the dust separation unit. The considered "Method of aerodynamic cleaning ..." has the following disadvantages:

“The Method ...” is considering the implementation of air purification from solid impurities (dust) and does not consider the cleaning of drops and liquid impurities flowing along the walls of the tract in the form of a film.

- “The method ...” is based on excessive schematization of the flow and speculative ideas about the behavior of a two-component mixture (carrier gas (air) and particulate matter impurities) in a tapering dust bag. The proposed geometry of the annular inserts, shown in figure 2 and 3 in the "Description of the invention", is a poorly streamlined configuration, which will inevitably lead to separation of the flow and the emergence of an extended zone of a highly swirling back-circulation flow between the elements of the dust separation unit. With the turbulent nature of the flow in the pipeline, which is almost always realized under real conditions, the geometry of the separation zone will be unstable, as a result of which the separated impurities will be ejected through the gaps between the inserts into the “cleaned” part of the gas stream, and this process will be repeated along the entire length of the dust collector. When implementing the described method, the degree of purification of the air environment substantially depends on the size of the dispersed inclusions, which makes this method inefficient and practically not applicable to many practical problems.

- “Method ...” does not provide for the possibility of cleaning high-speed flows of technical gases moving in main pipelines or technological devices at high pressures.

There is also known a method implemented in the invention "In-line separator" (RF patent No. 2079342, class B01D 45/04), in which the separation is carried out by passing a gas stream with an impurity suspended in it through a pipe with one coaxial nozzle, followed by the direction of the impurity stream into the separation bent pipe. The main disadvantages of the In-Line Separator are:

- With the proposed single-stage separation system, along with impurities, a significant part of the gas to be cleaned is removed from the motion channel (about a quarter, as follows from the ratio of the inlet section of the nozzle to the inner section of the separator body given in the description of the “Direct-flow separator”), which in some cases is unacceptable , for example, when cleaning combustible or explosive gas moving in main pipelines under high pressure, as well as in most continuous technological processes s.

The absence of an aerodynamic calculation of the flow of a dusty stream in the separator and the proposed “by eye” configuration of the nozzle and nozzle do not allow us to estimate the size and proportion of particles separated by the dust collector and, therefore, to judge the effectiveness of the separator for significantly higher velocities that occur in real gas pipelines, and particles whose size is beyond the very narrow range given in the description.

The closest analogue of the proposed method is a direct-flow separation of gas streams from solid and liquid impurities, described in patent GB 1101062, class. B01D 45/04, "Apparatus and Method for Separating Particles from Flow of Fluid" ("Device and Method for Separating Particles from a Flow"). Separation is carried out by passing a gas stream with impurities through a narrowing and expanding nozzle with coaxial inserts (separating elements) located in it, separating the purified gas and bringing it to the periphery of the stream without changing the main direction of movement and focusing the impurity stream in the center of the nozzle with its subsequent discharge through a special tap, while the inserts in the flow direction have a sharp narrowing and smooth expansion, each of the inserts is inside the other (Figs. 4, 7 and 12 in the patent description), o The cleaned gas is discharged into the gaps between the inserts, which are extended annular channels. As can be concluded from the descriptions and specifications given in the patent, the method has the following disadvantages:

- A sharp narrowing of the nozzle at the inlet (the angle of inclination of the contour of the inlet to the axis of the nozzle reaches 80-90 degrees) and a significant decrease in the cross-sectional area in the inlet (several times) will result when using the method for separating high-speed flows (10 m / s or more ) to the reflection of a large fraction (up to 75%) of particles from the walls of the tapering part of the nozzle and the appearance of intense transverse and even opposing particle flows, which in turn will entail a substantially uneven distribution of their velocity vectors at the entrance to the expanding a portion in which there are separating elements greatly reducing the separation efficiency as a result of contact with particles in the annular channels between rates.

- The location of the inserts, when each insert is inside the other, and between them there are narrow annular channels, can lead to significant unevenness of the gas flow at the outlet of the device and significant friction losses in the channels. This is not so important if the purpose of the separation is to collect the impurity for its subsequent use. However, this is a significant drawback if the goal is to clean the high-speed gas stream with the least energy loss.

Descriptions of all named patents of the Russian Federation are given in the attached copies. For patent GB 1101062 attached copies of figures 4, 7 and 12.

The task of the invention was to develop a method for separating a gas stream moving in a channel with high speed and various impurities contained therein (solid particles, droplets and a liquid film flowing along the walls of the channel), followed by removing a concentrated stream of impurities outside the channel and without changing the main direction of gas flow after cleaning it. The developed method is technological and efficient in terms of purification and is suitable for gaseous media with any properties, including aggressive, combustible and explosive (for example, hydrogen).

The essence of the proposed method for direct-flow separation of gas streams from solid and liquid impurities consists in passing a gas stream with impurities through channel 1 (see Figs. 1-4), in which specially profiled tapering nozzle inserts 2 (separating elements) that ensure focusing of inertial impurities into a narrow beam inside the channel (compression of the cross section of the flow with impurities to less than 1% of the area of the original path is achieved) and the gas on the periphery of the channel. The focused impurity stream is discharged through the side wall of the channel using a special branch pipe 3. In and after the separator, the gas stream retains its original direction of movement. A feature of the shape of the nozzle inserts is a smooth narrowing of the input parts of their internal channels and a sharp expansion of the output parts. The exact shape of the nozzle inserts, their size, number and relative position are determined as a result of gas-dynamic design of the separator path, which takes into account the size of the original channel and the characteristics of the movement of gas and impurities (density, viscosity, gas temperature; flow regime: laminar or turbulent; size and physical properties dispersed inclusions, flow rate). The gas-dynamic calculation of the path is carried out using the well-known universal application package for flow modeling FLUENT. The design goal is to provide specified technical requirements, which, in particular, include:

- minimizing the overall dimensions of the separator;

- providing the required degree of purification of the gas stream from particles from a given size range;

- minimization of the volume of gas discharged from the stream along with the impurity;

- minimization of gas velocity and pressure losses during the passage of the separator.

The proposed method is confirmed by detailed calculations of the parameter fields of a two-phase flow, as well as experimentally. It is envisaged to ensure separation of the liquid film flowing along the channel walls with crushing into droplets.

Profiling of the contours of the nozzle inserts 2, as well as the selection of their sizes, relative position and quantity, is based on the condition of preventing the formation of extended separation zones with the back-circulation movement of the gas phase, as well as the effective removal of the purified gas into the peripheral part of the channel without intensive vortex formation. This is ensured by giving the contours of the nozzle inserts a well streamlined shape, the choice of entry and exit angles for the gas flow with admixture, and the inclination angles of the external parts of the circuits to the main flow direction. The authors calculated the movement of impurities (particles and liquid droplets) of various fractions, different physical densities of the material of the particles and droplets with a gas stream and with profiled nozzle inserts. It is shown that the proposed method provides a high degree of focusing of the impurity flow and, accordingly, the high efficiency of the proposed separation method. Illustrative calculation results are presented in figures 1-3, which show the trajectories of particles of various sizes (respectively, diameters of 20, 100 and 1000 μm) in a cylindrical channel (pipe diameter of 100 mm) with nozzle inserts. It can be seen that this method provides effective focusing of the impurity in a very wide range of particle sizes. In the gas-dynamic design of the separator flow path that implements this method for various input data (geometric dimensions of the initial channel, flow rates, sizes of dispersed inclusions, densities of inclusion substances), it turned out that there is no universal solution for the configuration and location of the nozzle system that would be the same effective for any impurities. The calculation of the separator nozzle system for each technological process should be made depending on the specific geometric and gas-dynamic parameters of the initial flow (transverse channel size, speed, pressure, density) and impurities (density, size, concentration, etc.). A simple linear scaling of the optimally designed channel and nozzle inserts at constant parameters of the two-phase flow leads to a noticeable decrease in the effect of focusing the impurity and the degree of purification of the gas stream, which necessitates a substantial adjustment of all geometric characteristics of the separator path. The proposed method can be implemented both in the form of a coaxial system of sequential nozzle inserts (Figs. 1-3), and in the form of a sequence of inserts with a gradual lateral displacement (Fig. 4). In all cases, focusing of the impurity flux is ensured regardless of the geometry of the initial channel. The focused impurity flow can be evacuated from the channel using a special outlet 3, which also requires aerodynamic calculation in order to avoid its “clogging” by particles and to reduce the erosive effect of the removed impurities on the outlet walls.

The geometrical dimensions and location of the nozzle inserts along a properly designed separator satisfy the following proportions:

- the minimum internal diameter of the first stage of the separator is selected from a ratio of 1 / 2-2 / 3 of the diameter of the initial channel of gas movement;

- the minimum internal diameters of subsequent steps are reduced exponentially with a coefficient of 1.3-1.5;

- the angle of inclination of the inlet of the channels of the nozzle inserts is in the range of 10-30 °;

- the distance between the nozzle inserts decreases in proportion to the minimum diameter of the nozzle and is 0.3-0.5 of the diameter of the subsequent nozzle.

The exact configuration of the nozzle insert contours is determined by a sequence of calculations using the FLUENT package. The specific values of the given proportionality coefficients are selected depending on the process parameters (gas type, flow rate, pressure, size range of the separated impurities), as well as additional requirements for the separator (restriction on overall dimensions, compression ratio of the impurity stream, etc.).

The proposed separation method allows you to:

- provide gas-dynamic focusing of the flow of impurities of a given range of particle sizes into a narrow "bundle" with a very small cross section, less than 1% of the cross-sectional area of the original channel;

- to ensure the evacuation of the flow of impurities from the gas flow channel without disrupting the process;

- minimize pressure loss in the separator;

- eliminate the influence of the state of the channel surface on the separation process.

The outlet pipe 3 is made in the form of a tube bent along a special curve and excluding particles from “clogging” the tube. In the above illustrative examples, four stages of compression of the impurity stream are used. The number of steps can be reduced or increased depending on the requirements and restrictions.

Figures 1, 2 and 3 show patterns of movement of impurity particles with diameters of 20 μm, 100 μm and 1000 μm, respectively, in a pipe through a nozzle insert system. As can be seen, the smallest particles with a diameter of 20 μm are noticeably deflected by the gas flow. The patterns of motion paths of larger particles (100 and 1000 microns) qualitatively differ from the patterns of motion of small ones. Between collisions with the surfaces of nozzle inserts, these particles move along almost straight paths. At the same time, in the illustrated example, particles from the entire considered range of their sizes are effectively focused by nozzle inserts.

The implementation of the method is as follows.

When a gas stream with dispersed particles of impurities passes through a system of profiled nozzle inserts 2 installed in the motion channel 1, the impurity stream is compressed until a specified minimum cross-sectional size is reached, and the concentration of impurities in this stream increases. The impurity stream is evacuated outside the gas-dynamic path using a special outlet channel 3. The carrier gas is discharged to the periphery of the stream through the gaps between the nozzles as it moves through the nozzle system. Disposal of impurities is carried out depending on the requirements of a particular process and production conditions. If necessary, it can be ensured that the carrier gas returned to the bypass channel is returned after its preliminary treatment to the inlet of the first stage of the separator.

The technical effect of the invention lies in the fact that this separation method allows to solve a wide range of problems arising in various industries when cleaning gas flows (including in high-speed main pipelines) in a wide range of initial flow parameters (speed, pressure, temperature, geometry and operational requirements). Devices developed on the basis of the proposed method can fit into the existing process (including continuous) with virtually no change in the technological scheme.

Claims (1)

A direct-flow method for separating gas streams from solid and liquid impurities, including passing a gas stream with impurities through the channel, separating it into purified gas discharged to the periphery of the channel, and a focused beam of impurities discharged from the channel through an outlet, characterized in that the channel nozzle inserts in an amount of two or more, the configuration, dimensions and relative position of which are determined on the basis of gas-dynamic calculation of the flow channel using the application package software for computer simulation of flows of two-phase fluids FLUENT, based on the requirements of efficient separation of various types and sizes of impurities, while the angle of inclination of the inlet part of the tapered nozzle inserts is 10 ÷ 30 °, and the nozzle inserts of the pine with a channel or are arranged with a sequential transverse offset from the axis to the periphery.

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