SU1664359A1 - Method and device for degassing a liquid - Google Patents

Abstract

The invention relates to a method for degassing a liquid and a device for carrying it out. The aim of the invention is to increase the efficiency of fluid degassing and energy consumption, as well as simplify the design of the device. A sealed gas chamber is placed in the liquid and oscillations are excited in the liquid periodically and at a certain frequency. The device comprises a container in which a toroid-shaped gas-filled elastic chamber is freely mounted on a vertical rod. On the surface of the fluid is placed floating perforated disk. The exciter is made in the form of a pulsator. 2 sec. f-ly, 4 ill.

Description

The invention relates to methods and devices for the degassing of liquids and can be used in the chemical, petrochemical and aeronautical industry, as well as in water preparation systems.

The aim of the invention is to increase the efficiency of liquid degassing and energy consumption, as well as simplify the design of the device for degassing.

The essence of the method is that a pressurized gas chamber is placed in the liquid and oscillates periodically in it with frequency

-fewHz

where n is the adiabatic coefficient for gas;

P is the pressure above the free surface of the liquid, dyn / cm;

S is the cross-sectional area of the gas chamber. cm2;

Q is the volume of the gas chamber, cm;

I is the height of the liquid column above the gas chamber, cm;

p is the density of the liquid, g / cm, while limiting the mobility of the surface of the liquid through the cellular plate.

Figure 1 shows the general scheme of the device; figure 2 - section aa in figure 1; fig.Z - node I in Fig 1; figure 4 - node II in figure 1.

The device contains a vertical cylindrical container 1 with nozzles of the inlet 2 and outlet 3 of the liquid. In the upper part of the tank there is a sealed cover 4 with a nozzle 5 connected to a vacuum pump or ejector. In the lower part of the tank 1, a vertical rod 6 is placed along its center and a gas-filled toroidal elastic chamber covering it with a gap, made of elastic elastic, for example rubber, film 8. providing good dynamic gas contact with the liquid poured into the container. The vertical rod 6 is fixed on the bottom of the chamber, and on its upper end there are fixed radial ribs 9 installed in a horizontal plane, the length of which is

with

oh

-N W

the next

The maximum size of the elastic is extended, the size 7.

On the outer surface of the container 1, near the upper end of the rod 6, a nozzle 10 is fixed, connecting the liquid part of the container with a liquid oscillation pathogen - pulsator 11. Inside the container there are freely floating cylindrical perforated disk 12 made of material having a density lower than the density of which is degassing fluid. The holes 13 of the disk 12 have a concave extension 14 in the lower part.,

A separator 15 is installed on the liquid line between the tank 1 and the pulsator 11 (FIGS. 1 and 4), which is a disk chamber divided into two hermetic cavities by a flexible membrane fixed in the chamber by its perforated part. When the separator 15 is installed horizontally (FIG. 4), gas is freely released from the separator cavity when it is filled with liquid. With the vertical installation of the separator (figure 1) in the upper part of this cavity it is necessary to provide a device for the removal of gas when it is filled with liquid. A perforated disk 12 is placed in the container 1 with a small annular gap (1-1.5 mm), allowing it to float freely when the container is filled with liquid and held on the surface of the liquid. The disk can be made, for example, of wood or finely cellular foam and have a protective lacquer layer or other more resistant coating on the outside.

The device works as follows.

At first, the tank 1 through the nozzle 2 is filled with a degassed liquid with the valve closed at the nozzle 3 of the liquid outlet. At the same time, the gas-filled toroidal chamber 7 floats up and presses against the lower part of the ribs 9 attached to the end of the rod 6, which limits the level of the torch to rise. A perforated disk 12, placed loosely with a small gap in the container 1, also floats and is on the surface of the liquid. Through pipe 10, it is filled with liquid and the cavity of separator 15 communicated with container 1. A variant of horizontal installation of separator 15 (Fig. 4) is preferable, since in this case, when filling with liquid, the gas leaves the separator cavity free through pipe 10. At the end of filling The tank 1 is turned on with a vacuum pump or an ejector to create through the nozzle 5 the required vacuum over the surface of the liquid. Then, the pulsator 11 is turned on, communicating the liquids in the tank through the separator 15 and the fitting 10 with periodic pressure pulsations with a predetermined frequency TB, exciting a variable (hydrodynamic) pressure in the fluid. The pressure pulsations of the fluid through the elastic walls 8 of the toroid-shaped chamber 1 are transmitted to the gas found therein, which begins to pulsate, compressing and expanding with the frequency of change in the hydrodynamic pressure tv. In this case, a liquid-gas oscillatory system occurs in the tank 1, in

5 of which the gas is an elastic element and the liquid is inertial. According to the experimental data obtained, the natural frequency of oscillations of such a system is

0

five

, lI P S g.

gngpgr hz)

Where n is the adiabatic coefficient for gas;

P is the pressure above the free surface of the liquid, dyn / cm;

S is the cross-sectional area of the gas chamber placed in the liquid, cm;

Q is the volume of the gas chamber in the liquid.

cm3;

 (- height of the liquid column above the gas

0 camera, cm;

p is the density of the liquid, g / cm. At the same time, the oscillating liquid – gas system formed in the tank has a high sensitivity, since the gas enclosed in an elastic shell has a very high elastic properties. Since the frequency of the external vibration of the liquid fB is set equal to f, the liquid-gas system immediately goes

0 to the resonant oscillation mode, characterized by a sharp increase in the intensity of gas pulsations (toroidal chamber) and an increase in the amplitude of the hydrodynamic pressure in the liquid by 6-8 times,

5, as its turbulence increases, powerful turbulent pulsating fluid flows through the entire fluid volume. The hydrodynamic instability of a liquid during resonant pulsations of the liquid – gas system decreases sharply. At the same time, in negative half-periods of the hydrodynamic pressure values, the negative pressure in the liquid becomes significantly lower than the partial pressure of the gases dissolved in the liquid, which leads to the evolution of gas from the liquid. Allocated gas connections in the conditions of the resonant mode of the pulsations of the system coalesce, combining into a gas

conglomerate or swarm, which is a local cluster of dynamically very actively interacting gas bubbles.

The gas conglomerate is located inside the liquid and is held there in the vicinity of the gas-filled elastic chamber. This is related to that. that in a pulsating liquid, gas bubbles act directed

 on the bottom., the vibration force, the magnitude of which is directly proportional to the magnitude of the hydrodynamic pressure. At high values of this pressure, which takes place in the resonant mode of the pulsations of the liquid-gas system, the vibrational force may exceed the Archimedes force permanently acting on the bubbles, as a result of which the bubbles move down to the position of a stable equilibrium (where Archimedes force is greater) and there in the conglomerate.

When the vibratory action on the liquid is stopped (the pulsator 11 is turned off), the resonant pulsations of the system cease, the hydrodynamic pressure in the liquid disappears and the gas conglomerate floats to the surface of the liquid, passes through the holes of the perforated disk 12, and leaves through the nozzle 5 from the tank.

After that, the pulsator is turned on again. In the vessel, a resonant mode of turbulent pulsations of the gas-liquid system occurs again and a gas conglomerate is formed again in the liquid (usually 2-5 seconds after switching on the pulsator). After the formation of a gas conglomerate, the regime is maintained for 5-10 s and again

briefly turn off the pulsator. After a pause necessary for the conglomerate to ascend (2-3 seconds), a pulsator, etc., is turned on. At the same time, the resonant pulsations of the gas-liquid system cause intense oscillations of the free surface of the liquid, with the liquid trapping bubbles from the gas cavity of the container. which are driven down by the action of the vibration force. To eliminate this undesirable phenomenon, in the proposed degassing method, the mobility of the free surface of the fluid is limited by the cellular structure, i.e. break it into many small cells separated one from another. In small cells, the influence of surface tension and viscosity on the mobility of the surface of the liquid increases dramatically. Therefore, even under the conditions of the resonant pulsations of the system, the fluctuations of the surface of the liquid in the cells are insignificant and the gas does not trap by it. At the same time, cells do not prevent gas from escaping from a liquid when it is degassed.

In the proposed device, this problem is solved by using a perforated disk freely floating on the surface of a liquid with a small annular gap relative to the vessel walls. When the diameter of the perforation holes (cells) of the disk is 3-4 mm, experiments have shown that gas capture from the liquid surface (water, kerosene, alcohol) during the system’s resonant pulsations is completely eliminated, and at 50% disk perforation conglomerate into the gas chamber cavity. Performing a conical expansion in the lower part of the perforation holes of the disk (Fig. 3) makes it possible to further improve the conditions for the gas to exit from the liquid.

Thus, the alternation of the excitation cycles of the resonant pulsations of the liquid-gas system, which cause fluid turbulization and the formation of a gas conglomerate, with pauses in the vibration action for the conglomerate to float into the gas cavity of the tank allows efficient liquid degassing of the fluid. the degree of degassing of the liquid

At the same time, the execution of the degassing tank vertical and cylindrical is optimal, since with this form the best conditions are provided for the dynamic interaction between the elements of the oscillating system liquid-gas and the maximum quality factor (sensitivity) of the system is achieved. With this shape of the container, a constant gap is also provided between its walls and the perforated disk, which is important for the normal implementation of the degassing process. The toroidal shape of the elastic gas-filled chamber is also optimal for improving the quality factor of the oscillatory system, since it provides the maximum surface of the dynamic contact of gas and liquid. Placing the torus with a gap on a vertical rod while limiting its height to ascend allows the torus to freely perform intense resonant pulsations (expansion and contraction) with the frequency of change of hydrodynamic pressure in the liquid. In this case, the torus also makes intense oscillating motions, which contribute to the enhancement of cavitation processes near its surface, and

A powerful pulsating fluid flow is formed in the center of the torus, in addition to the turbulizing volume of the degassed liquid. This intensifies the process of gas evolution from the liquid.

Thus, the proposed technical solution due to the realization in the liquid volume of the resonant mode of the pulsations of the liquid-gas system allows to significantly intensify the degassing process. At the same time, the high sensitivity of the oscillatory system makes it possible to carry out a resonant mode with minimal energy expenditure — as compared with the prototype, they are reduced by a factor of 8-10. The degassing time of the fluid is also significantly reduced. It was established experimentally that a degassing degree of 98% is achieved with 4-6 cycles of vibration effect on the liquid, while the duration of the degassing process is less than 3 minutes. The design and operation of the degassing device is also greatly simplified.

Claims (2)

1. A method of degassing a liquid, which includes exciting oscillations in it and evacuating the evolved gas, characterized in that, in order to increase the efficiency of the degassing process and reduce energy costs, a pressurized gas chamber is placed in the liquid and the oscillations are excited periodically with frequency f 1 In-P S ir-Fp where n is the adiabatic coefficient for gas; P — pressure over the free surface of the liquid, dyne / cm; S is the cross-sectional area of the gas chamber, cm2; Q - the volume of the gas chamber, cm f- height of the liquid column above the gas camera, cm; p is the density of the liquid, g / cm3, while limiting the mobility of the surface of the liquid through a cellular plate. 2. A device for degassing a liquid. containing a sealed container with nozzles for supplying and discharging liquid and gas and a liquid oscillation pathogen, characterized in that, in order to increase the efficiency of the degassing process and reduce energy consumption while simplifying the design of the device, the container is made vertical and cylindrical and provided with a gas-filled toroidal elastic chamber placed in the lower part , a vertical rod fixed on the bottom of the tank and having radial ribs in the upper part, and a perforated floating disk installed with a gap relative to the inner wall of the tank, while the toroidal chamber is freely mounted on the rod, and the exciter of the fluid oscillations is in the form of a pulsator connected through a separator to bottom of the camera. ЈJl Physical Center