RU2581630C1 - Vortex jet apparatus for degassing liquids - Google Patents

Abstract

FIELD: processes.

SUBSTANCE: invention relates to apparatus for vacuum or combined thermal and vacuum degassing of liquids, including water, with a centrifugal effect. Swirling jet apparatus for degassing liquids comprises a body of cylindrical shape with a neck between confuser and diffuser, one or more tangential nozzles attached to it by means of tubing pump for degassed liquid, the ratio of the larger and smaller diameters confuser and the diffuser is in the range 3-7, diameter ratio of the larger diameter confuser tangential nozzle is in the range of 4-6, the apex angle of 28-32° confuser, angle at the apex of the cone is 10-14°, wherein the ratio of length to diameter of the neck is in the range from 5-15, in the diffuser set separator liquid and gaseous phases containing a rigidly mounted in the diffuser, and coaxially to it a conical divider with a central tube, wherein the tube is axially movable, and annular space between the divider cone and contains one or more blades, the ratio of the height to the height of a diffuser which is in the range 0.3-0.7.

EFFECT: degassing liquids efficiency and reduction in energy costs of the process.

2 cl, 2 dwg

Description

The present invention relates to devices for vacuum or combined thermal and vacuum degassing of liquids, including water, using the centrifugal effect and can be used for water treatment processes in the power system, including deaeration of feed water for steam boilers and make-up water, heating networks, desorption of gases from liquids in the chemical, pharmaceutical, food and other industries.

A known apparatus for degassing liquids, RF patent No. 2476767 (IPC F22D 1/50), comprising a housing with a nozzle for supplying deaerated water, nozzles for removing deaerated water and vapor, and a nozzle of variable cross section attached to the outlet of the nozzle for supplying deaerated water connected to the body of the deaerator and consisting of consecutively located confuser, cylindrical and diffuser sections, characterized in that the superheated water deaerator is additionally equipped with a reflective screen installed in the deaerator body on the path of movement of a nozzle of a variable cross-section emerging from a diffuser section of a stream of boiling deaerated water.

The known apparatus allows to increase the efficiency of deaeration of superheated water by increasing the surface of the emission of gases dissolved in water into the vapor phase due to crushing of the stream into small droplets due to the installation of a reflective screen in the deaerator body along the flow path of boiling deaerated water. However, in the known apparatus, only the kinetic energy of the water jet is used, which, after hitting the reflective screen, is transformed into the surface energy of the droplets. To achieve the required degree of deaeration, the water must be additionally heated in order to increase the partial vapor pressure. This leads to significant energy costs and reduces the overall efficiency of the installation.

A known apparatus for thermal degassing of liquids, RF patent No. 2473009 (IPC F22D 1/50), including a deaeration column mounted on a deaerator tank, equipped with a nozzle for supplying water, and a low-pressure water distribution device - a jet nozzle, characterized in that the deaeration column is made in the form water intake chamber, while the body of the jet nozzle is built into the partition and has an inlet for water, located above the fitting for supplying water to the water intake chamber.

The initial flow of water to be deaerated, enters the water distribution device - the jet nozzle of the deaeration column through the nozzle. The jets and drops of water flowing out of the nozzle outlet openings are crushed, breaking up into thinner jets and smaller drops. Then the water enters the deaerator tank, where it goes through the following processing stages. The known invention allows to prevent the ingress of steam from the deaerator into the pipelines for supplying water to the deaerator, to exclude the possibility of the occurrence of water hammer in them, and thereby ensure reliable operation of the water distribution device and the deaerator as a whole under all deaerator operating modes. The disadvantages of the known apparatus include the need for pre-heating water in order to increase the partial vapor pressure and provide a given level of deaeration. The costs of heating water due to its high specific heat are extremely high, which leads to insufficiently high energy efficiency in the degassing process.

A known device for thermal and vacuum degassing of liquids is a jet vortex deaerator, RF patent No. 2392230 (IPC C02F 1/20), comprising a vertically placed housing with a side nozzle for supplying heated water, a swirl with spiral channels, mounted coaxially in the upper part of the housing, and a cowl mounted coaxially in its lower part, characterized in that the spiral channels on the outer surface of the swirl have a variable cross-section, tapering from entrance to exit, and at the entrance to the housing between the outer surface of the swirl An annular receiving chamber is formed on the lower surface of the casing wall, while the swirl is hollow with an axial channel to remove the vapor, the entrance to which has a bell-shaped shape and is shifted downward relative to the outlet edges of the spiral channels so that the outer surface of the bell and the inner surface of the casing wall form an annular chamber sudden expansion, tapering towards the fairing, and the fairing is fixed in the housing by means of a support with holes for discharging water so that between the outer surface la and the inner surface of the housing is formed an annular diffuser, the swirler between the lower edge and the upper edge of the fairing is formed by rotating cylindrical chamber with a profiled inner surface.

In the known apparatus, water heated to a temperature of 70-90 ° C, through the pipe enters the prechamber and is evenly distributed over the entrances to the spiral channels. As the speed increases, the static pressure in the channels decreases. In the outlet section of the channels, water acquires maximum speed and minimum pressure. When leaving the canals, water enters the chamber of sudden expansion, where the flow boils instantly. A gas-liquid vortex with a complex structure is formed in the rotation chamber. In the known apparatus, the conditions of convective mass transfer in the core of the water flow are improved, the mass transfer coefficient between the liquid and gaseous phases is increased, the efficiency of separation of liquid droplets from the vapor stream is increased, and mechanical pulsations of the vortex inner boundary are eliminated.

The disadvantages of the known apparatus include: 1) narrow spiral channels significantly increase the hydraulic resistance of the apparatus, resulting in reduced vacuum depth; 2) in the zone of sudden expansion there are additional energy costs that also reduce the efficiency of the apparatus; 3) the fluid flow in the annular chambers is associated with friction on the surface of both the external and internal walls, which increases energy consumption; 4) the apparatus does not use the effect of increasing the depth of the vacuum when moving from a larger radius of rotation to a smaller one, i.e. the kinetic energy of the fluid is not sufficiently transformed; 5) the axial channel to remove the vapor has a too large bore, which does not allow creating a deep vacuum in the center of the vortex.

Closest to the claimed device is a vortex jet apparatus, RF patent No. 2296007 (IPC B01J 19/26), including a device for introducing a dispersed phase, a tank, a circulation pump, circulation pipelines, control valves and fittings, a device for introducing a dispersed phase includes a housing in in the form of a Venturi pipe, consisting of a cylinder-conical confuser, a neck and a diffuser, a nozzle installed coaxially with it, ending in a dispersed phase inlet pipe, which is equipped with inlet pipes in the form of a bend dy of which is designed as a knee, and is pivotally mounted about the axis, wherein the lead-in pipes are connected to the supply line of the liquid continuous phase, and the nozzle is axially movable relative to the housing and connected to the supply line of the dispersed phase.

The invention allows efficient mass transfer processes in heterogeneous systems with an increase in the degree of dispersion of the dispersed phase, to achieve a longer phase contact time, and in general allows to intensify the reaction and mass transfer processes. Although a certain rarefaction is achieved in the neck of the known device, the level of rarefaction is insufficient to achieve acceptable indicators for the degassing of liquids, in particular water. The neck length is too short, and the mass transfer processes do not have time to complete while the liquid is in the apparatus. In addition, the known apparatus does not provide measures for the separation of the liquid and gas phases, which leads to almost instant gas resorption by the liquid. This significantly reduces the efficiency of the apparatus and makes it unsuitable for use in liquid degassing processes.

The objective of the invention is to increase the efficiency of degassing liquids and reduce energy costs for the process.

The problem is solved in that in a vortex jet apparatus for degassing liquids, comprising a cylinder-conical body with a neck between a confuser and a diffuser, one or more tangential nozzles, a pump for supplying a degassed liquid connected to them with tubes, the ratio of the larger and smaller diameters of the confuser and diffuser lies in the range 3 ÷ 7, the ratio of the larger diameter of the confuser to the diameter of the tangential nozzle lies in the range 4 ÷ 6, the angle at the top of the confuser is 28 ÷ 32 °, the angle at the diffuser bus is 10 ÷ 14 °, according to the invention, the ratio of the neck length to its diameter lies in the range from 5 ÷ 15, a liquid and gas phase separator is installed in the diffuser, containing a conical divider rigidly fixed in the diffuser and aligned with the central tube, the tube made with the possibility of axial movement, and in the annular space between the divider and the diffuser one or more blades are installed, the ratio of the height of which to the height of the diffuser is in the range of 0.3 ÷ 0.7.

The problem is also solved by the fact that an axial nozzle is installed in the confuser, a rarefaction sensor is installed on the axial nozzle, and a gas concentration in the liquid is installed at the outlet of the diffuser, the outputs of the sensors are connected to the controller connected to the axial position of the central tube.

The inventive vortex jet apparatus for degassing liquids allows you to take advantage of thermal and vacuum degassing of liquids, increase the efficiency of vacuum degassing of liquids, reduce energy costs for the process, increase the compactness of the equipment for degassing.

The claimed technical solution is new, has an inventive step and is industrially applicable.

In FIG. 1 a is a diagram of a vortex jet apparatus for degassing liquids, FIG. 1 b, c - sections aa and bb, respectively, in FIG. 2 is a diagram of a vortex jet apparatus for degassing liquids with a system for automatically adjusting the position of the central tube.

The vortex jet apparatus for degassing liquids (Fig. 1) contains a cylinder-shaped confuser 1, a diffuser 2 and a neck 3 between them, one or more tangential nozzles 4 connected to a wide part of the confuser 1. A pump for supplying a degassed pump is connected to the nozzles 4 by means of tubes fluid (Fig. 1 and 2 conventionally not shown). The ratio of the larger and smaller diameters of the confuser 1 and the diffuser 2 lies in the range 3 ÷ 7, the ratio of the larger diameter of the confuser 1 to the diameter of the tangential pipe 4 lies in the range 4 ÷ 6, the angle at the top of the confuser 1 is α = 28 ÷ 32 °, the angle at the top of the diffuser 2 is β = 10 ÷ 14 °. In addition, the ratio of the length of the neck 3 to its diameter lies in the range from 5 to 15, in the diffuser 3 there is a separator 5 of liquid and gas phases containing rigidly fixed in the diffuser 2 and conically to it a conical divider 6 with a central tube 7, and the tube 7 is made with the possibility of axial movement relative to the diffuser 2, and in the annular space between the divider 6 and the diffuser 2 one or more blades 8 are installed, the ratio of the height of which to the height of the diffuser 2 is in the range of 0.3 ÷ 0.7.

The vortex jet apparatus for degassing liquids (Fig. 2) further comprises an axial nozzle 9 installed in the confuser 1, a rarefaction sensor 10 is installed on the axial nozzle 9, and a gas concentration in the liquid sensor 11 is installed at the outlet of the diffuser 2, the output of the sensors is connected to the controller 12 connected to the actuator 13 of the axial position of the Central tube 7.

The proposed device operates as follows.

When the degassed liquid is pumped through the tangential branch pipe (s) 4 to the confuser 1, the flow swirls, acquiring the initial speed of movement w ₁ , the tangential component of which is equal to w _t1 , axial w _z1 and radial w _r1 . Moving from a cylindrical zone with a radius of R ₁ to the tapering region of the confuser 1 adjacent to the neck 3 with a radius of R ₂ , the workflow is accelerated. Two components of speed increase - both axial and tangential. From the continuity equation written for the wide and narrow sections of the confuser 1, taking into account the fact that the remaining velocity components lie in the plane of these sections:

we find the axial component of the velocity in the neck

To estimate the tangential component, we use the ideal fluid approximation. In accordance with the law of conservation of angular momentum (kinetic moment)

where m is the mass of the elementary volume of the liquid,

the tangential component of the velocity at the entrance to the neck is

those. w _t2 > w _t1 .

Thus, an increase in the axial component of the velocity with a decrease in the radius occurs in the degree - 2, and the tangential - in the degree - 1.

Integrating the continuity equation

we estimate the change in the radial velocity component.

Given that at the confuser height h, the axial velocity varies from w _z1 to w _z2 , the derivative with respect to the axial coordinate can be estimated as

and the derivative with respect to the angular coordinate under the assumption of the presence of axial symmetry ∂u _φ / ∂φ = 0.

Then the approximate integration of the continuity equation, taking into account the approximate relation following from the mean value theorem

gives

or, after simplification

For the case of zero speed w _r1 we find

Here is an example of speed estimation using geometric data for a laboratory setup and typical velocity values. Let R ₁ = 25 mm, R ₂ = 5 mm, water is supplied with a speed w ₁ = w _t1 = 5 m / s, the pressure in the inlet pipe obtained in our experiments is p ₁ = 0.2 MPa (g) .

By integrating the Bernoulli equation for a fluid flow without friction in a vortex tube, [Fedyaevsky KK, Voitkunsky Y.I., Faddeev Yu.I. Hydromechanics. L .: Shipbuilding, 1968. S. 177-180; Domansky I.V. Hydraulics and Hydraulic Machines: Textbook / LTI them. Lensoviet. L., 1989. P. 73-75] ratio for calculating the dependence of pressure on radius r

where p ₁ is the pressure of the working stream at the point of its entry into the confuser, i.e. on a radius of R ₁ ;

ρ is the density of the fluid in the working stream.

From formula (11) it follows that with decreasing radius r, the pressure decreases and, for example, at the entrance to the neck (r = R ₂ ), the pressure near its walls will be

whence it follows that p ₂ <p ₁ , i.e. the average pressure at the inlet of the neck (at a radius of R ₂ ) is significantly lower (and on the axis of the neck, i.e. at the center of the vortex — even lower) than in the cylindrical part of the confuser (at a radius of R ₁ ).

When a working stream (water with a density ρ = 1000 kg / m ³ ) is supplied to the tangential pipe 8 with a speed w _t1 = 5 m / s, in accordance with formula (12), a pressure drop arises in the vortex jet device

The pressure at the entrance to the neck will be

p ₂ = p ₁ -Δp _p = 0.2-0.3 = -0.1 MPa.

Thus, theoretically, with the indicated parameters, values close to absolute vacuum are attainable in the neck.

This allows you to completely or almost completely abandon the use of the stage of thermal desorption, and therefore, significantly reduce energy costs for the processes of degassing liquids, including deaeration of water.

Thus, by using the transformation of the kinetic energy of a liquid into a deep vacuum, a high driving force of the degassing process is achieved in the apparatus proposed.

Due to the fulfillment of the ratio of the neck length to its diameter in the range from 5 ÷ 15, the necessary residence time of the liquid in the zone of maximum vacuum (minimum absolute pressure) is achieved with a rather deep vacuum in the neck. Studies have shown that when the ratio of the neck length to its diameter is less than 5, the vacuum is deep (85-98 kPa), but the residence time is not enough to significantly reduce the oxygen concentration in water (from 6 mg / l to 5.4 mg / l), t .e. on 10%. When the ratio of the neck length to its diameter is greater than 15, due to a significant increase in the hydraulic resistance of the apparatus, the vacuum depth decreases and reaches only 55-60 kPa, as a result of which the driving force of the degassing process decreases and the oxygen concentration in the water decreases from 6 mg / l to 5, 2 mg / l), i.e. by 13.3%. When fulfilling the ratio of the neck length to its diameter in the range from 5–15, the vacuum reaches 92–97 kPa, and the oxygen concentration in the water decreases from 6 mg / l to 0.7 mg / l, i.e. by 88.3%.

The installation in the diffuser of the separator 5 of the liquid and gas phases, containing a conical baffle 6 with a central tube 7, allows immediately after the degassing of the liquids to separate the gas and liquid flows and to exclude their repeated contact, and hence gas resorption. The execution of the tube 7 with the possibility of axial movement allows you to adjust its position to the optimal depending on the flow rate and the amount of gas released. The installation in the annular space between the divider 6 and the diffuser 2 of one or several blades 8 with a ratio of the height of the blades 8 to the height of the diffuser 2 in the range 0.3 ÷ 0.7 allows you to transform the remainder of the kinetic energy of the rotational movement of the liquid at the outlet of the diffuser into pressure energy and restore the pressure in the apparatus to atmospheric, preventing the suction of liquid and gas through the outlet cross section of the diffuser into the apparatus. The outer edges of the blades 8 are installed near the level of the diffuser outlet or flush with it, while maintaining the ratio of the height of the blades 8 to the height of the diffuser 2 in the range of 0.3 ÷ 0.7 in the neck 3, a vacuum level of 97-98 kPa is reached.

Studies have shown that when the height of the blades decreases less than 0.3 from the height of the diffuser, the vacuum level decreases from 98 kPa to 20 kPa, the same thing happens when the height of the blades exceeds 0.7 from the height of the diffuser.

The use in the proposed apparatus additionally of an automatic control system for the position of the tube 7, including an axial nozzle 9 with a rarefaction sensor 10, a sensor for gas concentration in the liquid 11 and a controller 12 with a drive 13 for the axial position of the central tube 7 allows you to automatically set the cutoff position of the central tube depending on the operation of the apparatus for the flow of fluid and the associated vacuum at the entrance to the neck 3 and the concentration of oxygen in degassed water.

Examples of specific performance. Examples of specific performance will be considered on the most common example of water deaeration in a device with thermal deaeration and in the proposed device.

An example of a specific implementation 1. The apparatus of thermal degassing.

Let us determine the temperature increment Δt, at which it is necessary to heat water to reduce the concentration of dissolved oxygen in water during a single pass through the apparatus, i.e. δC [O ₂ ] ₀ = 0.6 mg / L, for comparison with a similar result for a vortex jet apparatus. The temperature of the treated water was 21 ° C, i.e. lay in the temperature range t = 20 ÷ 30 ° C, for which the magnitude of the change in concentration is ΔC [O ₂ ] = 9.1-7.5 = 1.6 mg / l [Hammer M. Technology of natural and waste water treatment. M.: Stroyizdat, 2013.401 p.]. We perform the calculation using linear interpolation. The change in the concentration of oxygen in water for every degree in the temperature range t = 20 ÷ 30 ° C is

Then, a change in the concentration of oxygen in water by δC [O ₂ ] ₀ = 0.6 mg / L corresponds to the heating of water at a temperature:

The amount of energy required to heat the liquid at a temperature Δt is calculated by the formula:

Q _TD = CmΔt,

where C is the specific heat of the liquid, J / (kg · K);

m is the mass of the heated fluid, kg

The amount of energy required to heat water with a mass of m = 0.25 kg (that is how much water is in the vortex jet apparatus during processing) at a temperature of Δt = 3.75 ° C is Q _TD = 3928 J.

An example of a specific implementation 2. Vortex jet apparatus.

In a laboratory setup including an apparatus, the circuit of which is shown in FIG. 1, tested the degree of deaeration of distilled water. The ratio of the neck length to its diameter was 2. The oxygen concentration was measured using a dissolved oxygen analyzer of the OXICON-02P type. The initial concentration of oxygen in water was 5.65 mg / L; the concentration at the outlet of the apparatus was 4.95 mg / L, i.e. the decrease in oxygen concentration in water was 0.60 mg / L.

Let us determine the energy expenditures for decreasing the concentration of dissolved oxygen in a vortex jet apparatus. Power dissipated in a vortex jet apparatus:

N = qΔp,

where q is the volumetric flow rate of the liquid, m ³ / s;

Δр - pressure loss in the apparatus, kPa.

The residence time of the liquid in the apparatus is:

where V _a is the volume of liquid in the apparatus, m ³ , V _a = 0,00025 m ³ (the total volume of the apparatus was 0,0005 m ³ );

water flow q = 1.82 m ^{3 /} h = 5.05·10 ^-4 m ³ / s.

The hydraulic resistance of the apparatus averaged Δp = 200 kPa. Then the energy consumption in the ICA to reduce the oxygen concentration by 0.6 mg / l in one pass through the apparatus is:

From the results obtained, it can be concluded that the energy consumption for reducing the amount of dissolved oxygen in water using the ICA is 3928/50 = 78.6 times less than for the process of thermal desorption to a similar concentration.

Thus, the proposed vortex jet apparatus for degassing liquids can significantly increase the efficiency of degassing liquids and reduce energy costs for the process up to 78.6 times.

Claims (2)

1. A vortex jet apparatus for degassing liquids, comprising a cylinder-conical body with a neck between the confuser and the diffuser, one or more tangential nozzles, a pump for supplying the degassed liquid connected to them with tubes, the ratio of the larger and smaller diameters of the confuser and diffuser is in the range of 3 -7, the ratio of the larger diameter of the confuser to the diameter of the tangential pipe lies in the range of 4-6, the angle at the top of the confuser is 28-32º, the angle at the top of the diffuser is 10-14º, distinguishing in that the ratio of the neck length to its diameter lies in the range from 5-15, a liquid and gas phase separator is installed in the diffuser, containing a conical divider rigidly fixed in the diffuser and coaxially with the central tube, the tube being made with the possibility of axial movement, and in the annular space between the divider and the diffuser one or more blades are installed, the ratio of the height of which to the height of the diffuser is in the range of 0.3-0.7. 2. The vortex jet apparatus for degassing liquids according to claim 1, characterized in that an axial nozzle is installed in the confuser, a rarefaction sensor is installed on the axial nozzle, and a gas concentration sensor is installed at the outlet of the diffuser, the outputs of the sensors are connected to a controller connected to drive axial position of the central tube.

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